CN112601801A - Method for maintaining high solubility of recycled solvent in upgrading process of steam cracked tar - Google Patents

Abstract

A process for improving the compatibility of a hydrocarbon feedstock is provided. More specifically, the method of producing a liquid hydrocarbon product includes heat soaking a tar stream to produce a reduced reactivity tar, and blending the reduced reactivity tar with a working fluid including a recycled solvent to produce a lower viscosity, reduced reactivity tar. The process also includes hydrotreating the lower viscosity, reduced reactivity tar at a temperature greater than 350 ℃ to produce a total liquid product containing liquid hydrocarbon product and recycled solvent. The method further includes separating the recycle solvent from the total liquid product and flowing the recycle solvent to the reduced reactivity tar for blending to produce a lower viscosity, reduced reactivity tar, wherein the recycle solvent has S_BNIs greater than 110.

Description

Method for maintaining high solubility of recycled solvent in upgrading process of steam cracked tar

Priority

This application claims priority and benefit from U.S. provisional application No. 62/724,949 filed on 30.8.2018 and european patent application No. 18209046.4 filed on 29.11.2018, the disclosures of which are incorporated herein by reference in their entirety.

FIELD

Embodiments are generally directed to improving hydrocarbon feedstock compatibility. More particularly, embodiments relate to processes that include combining a hydrocarbon feed and a working fluid comprising a recycle solvent to separate components of the feed into separable fractions, to hydrocarbon products of such processes, and to apparatus useful in such processes.

Background

Pyrolysis tar is a form of tar produced from the pyrolysis of hydrocarbons. One form of pyrolysis tar, steam cracker tar ("SCT"), contains a variety of component materials, including high molecular weight molecules such as asphaltenes that are produced during the pyrolysis process and that typically boil above 560 ° F. These asphaltene molecules have a low H/C and a high sulphur content, which contributes to the high viscosity and high density of SCT.

Solvent Assisted Tar Conversion (SATC) is an SCT upgrading process that involves mixing SCT with a working fluid and upgrading the mixture to a less viscous and less dense product that includes hydrotreated tar and solvent. At least a portion of the solvent may be recovered and recycled to the process, and the working fluid may comprise recycled solvent. Upgrading may include cracking and hydrotreating, such as one or more of thermal cracking, hydrocracking, and hydrogenation. The process is typically carried out under pressure and weight hourly space velocity ("WHSV") conditions selected to optimize one or more of SCT conversion, hydrotreated tar yield/quality, and solvent yield/and quality. The operating temperature is also an important process parameter that can be adjusted to maintain the desired solvent quality. Although hydrogenation of aromatic molecules is favored when hydrotreating at lower temperatures (e.g., about 300 ℃), less cracking occurs. This will increase the partially and/or fully hydrogenated molecules in the product, which will eventually be present in the recycled solvent after distillation. The increase in the amount of hydrogenated molecules in the recycled solvent reduces the solvency of the recycled solvent, which in turn reduces the ability of the recycled solvent to dissolve tar components. Another feature of SATC is the recycling of fractions from the product formed as solvent. The amount of recycled solvent used as the working fluid is typically from about 20% to about 60% by weight, for example about 40% by weight. The solvent recovered from the SATC process typically has a desirably high solvency, such as a significant solubility blending value (S) of the solvent_BN) As indicated. If S of the solvent is recovered_BNLess than 100, e.g., about 80 or about 90, the recycled solvent has a reduced tar dissolving capacityAnd is therefore less desirable for use as a working fluid or working fluid component.

Additional conditions such as start-up at lower temperatures (fresh catalyst) and adjustments (slower feed rates) can also lead to accumulation of hydrogenated/naphthenic molecules in the solvent of the middle distillate recycle. In addition, entrainment of smaller naphthenic molecules in the recycled solvent due to less efficient distillation can also affect solvent quality.

There remains a need to further improve the hydroprocessing of pyrolysis tars while improving the quality of the recycled solvent, for example by reducing the accumulation of hydrogenated molecules in the recycled solvent.

SUMMARY

Embodiments provide a process comprising maintaining a high solvency of a recycled solvent such that the recycled solvent can be used as a working fluid or working fluid component blended with an SCT. The method uses at least one reactive ("R") having a reactivity, e.g., as indicated by a bromine number ("BN") of no more than 28_T") pyrolysis tar as feed. Such pyrolysis tar (which may be SCT) is referred to as "reduced reactivity tar". The reduced reactivity tars are combined with a working fluid comprising a recycled solvent to produce a tar-fluid mixture, which is also referred to herein as "lower viscosity, reduced reactivity tars". Greater than 110, such as from about 115, about 120, or about 130 to about 133, about 135, about 138, about 140, about 145, or about 150S_BNResulting in the high solvency expected when the recycled solvent is used as the working fluid or working fluid component_。It has been found that the recovered recycled solvent has desirably high solvency when the lower viscosity, reduced reactivity tar is hydrotreated at a temperature of greater than 350 ℃ to about 500 ℃, e.g., about 400 ℃ to about 450 ℃.

In one or more embodiments, the method of producing a liquid hydrocarbon product includes providing a reduced reactivity tar (e.g., an SCT having greater reactivity by thermal soaking) and blending the reduced reactivity tar with a working fluid comprising a recycled solvent and/or a working fluid comprising a different solvent having properties substantially the same as those of the recycled solvent, thereby producing a lower viscosity,Reducing the reactivity of tar. The process also includes hydrotreating the lower viscosity, reduced reactivity tar at a temperature greater than 350 ℃ to produce an overall liquid product (TLP) at the hydrotreater outlet comprising (i) a solvent that can be recovered and recycled for use as a working fluid or a working fluid component and (i i) a liquid hydrocarbon product comprising hydrotreated tar. Certain aspects of the method further include separating the TLP having S_BN>110 and flowing the recycled solvent to the reduced reactivity tar for blending to produce a lower viscosity, reduced reactivity tar.

In one or more examples, the working fluid has S_BNIs 115 or more, and the method further comprises S if the solvent is recycled_BNLess than 115, increases the temperature of the lower viscosity, less reactive tar during hydrotreating. The lower viscosity, reduced reactivity tar may be hydrotreated at a temperature of greater than 350 ℃ to about 500 ℃, for example, about 400 ℃ to about 450 ℃. S of recycled solvent_BNCan be greater than 110 to about 160, such as greater than 120 to about 150 or about 130 to about 150.

In other examples, the process further includes centrifuging the lower viscosity, reduced reactivity tar to remove solids therefrom prior to hydrotreating. After solids removal (e.g., by centrifugation), the lower viscosity, reduced reactivity tar is completely or substantially free of solids having a size greater than 25 μm.

The recycled solvent may be or include an aromatic compound, such as a 2-ring aromatic compound, a 3-ring aromatic compound, a 4-ring aromatic compound, or any combination thereof. In some examples, the recycle solvent can be or include one or more solvents, such as benzene, ethylbenzene, trimethylbenzene, xylene, toluene, naphthalene, alkylnaphthalenes, tetralins, alkyltetralins, or any combination thereof.

In one or more examples, hydrotreating the lower viscosity, reduced reactivity tar may include heating the lower viscosity, reduced reactivity tar to a temperature of about 260 ℃ to about 300 ℃ in a preconditioner containing hydrogen gas, then heating the pretreated lower viscosity, reduced reactivity tar to a temperature of about 325 ℃ to about 375 ℃ in a first reactor containing hydrogen gas, and then heating the lower viscosity, reduced reactivity tar to a temperature of about 360 ℃ to about 450 ℃ in a second reactor containing hydrogen gas.

In another embodiment, a method of producing a liquid hydrocarbon product includes heat soaking a pyrolysis tar to produce a reduced reactivity tar, blending the reduced reactivity tar with a working fluid including a recycle solvent to produce a lower viscosity, reduced reactivity tar, and centrifuging the lower viscosity, reduced reactivity tar to remove solids therefrom. Thereafter, the process includes hydrotreating the lower viscosity, reduced reactivity tar at a temperature greater than 350 ℃ to produce a TLP containing liquid hydrocarbon products and recycled solvent. The method further includes separating the recycled solvent (S the recycled solvent has) from the TLP_BNGreater than 115) and flowing recycled solvent to the reduced reactivity tar for blending to produce a lower viscosity, reduced reactivity tar. In one or more examples, the method includes S if the solvent is recycled_BNLess than 120, increases the temperature of the lower viscosity, less reactive tar during hydrotreating.

In other embodiments, a method of producing a liquid hydrocarbon product includes heat soaking a tar stream to produce reduced reactivity tars, blending the reduced reactivity tars with a working fluid including a recycle solvent to produce lower viscosity, reduced reactivity tars, and hydrotreating the lower viscosity, reduced reactivity tars at a temperature greater than 350 ℃ to produce a TLP containing the liquid hydrocarbon product and the recycle solvent. The method further includes separating the recycled solvent from the TLP, measuring S of the recycled solvent_BNIf S of the solvent is recycled_BNLess than 115 deg.f raising the temperature of the lower viscosity, reduced reactivity tar during hydrotreating, and flowing a recycle solvent to the reduced reactivity tar for blending to produce a lower viscosity, reduced reactivity tar.

In one or more embodiments, a method of producing a liquid hydrocarbon product includes thermally treating (e.g., heat soaking) a tar stream to produce a tar stream having a reactivity R_CTar composition of 28BN or less (reduced reactivity coke)Oil). The method also includes blending the first process stream including the reduced-reactivity tar with a working fluid including a recycle solvent to reduce the viscosity of the first process stream and produce a second process stream containing solids and reduced-reactivity, lower-viscosity tar. The method also includes centrifuging the second process stream to produce a third process stream containing reduced reactivity, lower viscosity tars and having a solids concentration less than the second process stream, and hydrotreating the third process stream at a temperature of greater than 350 ℃ to about 450 ℃ to produce a fourth stream containing liquid hydrocarbon product and recycle solvent. The process further includes separating the recycled solvent (S the recycled solvent has) from the fourth stream_BNFrom about 130 to about 150) and flowing a recycle solvent to the first process stream for blending to produce a second process stream.

In other embodiments, the hydrocarbon product of any of the foregoing processes, and mixtures containing any such hydrocarbon product and a second hydrocarbon, particularly mixtures substantially free of precipitated asphaltenes, are provided.

These and other features, aspects, and advantages of the methods will become better understood with regard to the following description, appended claims, and accompanying drawings.

Brief description of the drawings

FIG. 1 depicts an exemplary process flow of a tar disposal method according to one or more embodiments.

FIG. 2 depicts a more specific illustration of a tar treatment process according to one or more embodiments.

FIG. 3 depicts an alternative cold tar recycling arrangement that may be used to heat soak a tar feed, where tars produced by two different upstream processes may be treated, according to one or more embodiments.

FIG. 4 depicts a configuration of a preconditioner and several reactors that may be used in a hydroprocessing process according to one or more embodiments.

Detailed description of the invention

Embodiments provide methods including the discovery of preferentially maintaining high solubility of recycled solvent used as a working fluid or working fluid component for use with reduced reactivity(tar) are blended to produce a lower viscosity, reduced reactivity tar. A solubility blend value (S) greater than 110, for example from about 115, about 120, or about 130 to about 133, about 135, about 138, about 140, about 145, or about 150_BN) Resulting in high solvency of the recycled solvent and the working fluid that typically contains the recycled solvent. In some embodiments, the methods are based, in part, on the discovery that by hydrotreating a lower viscosity, reduced reactivity tar at temperatures greater than 350 ℃ to about 500 ℃, e.g., about 400 ℃ to about 450 ℃, helps produce a recycled solvent with high solvency, among other products.

Definition of

The term "pyrolysis tar" means a mixture of (a) hydrocarbons having one or more aromatic components and optionally (b) non-aromatic and/or non-hydrocarbon molecules derived from hydrocarbon pyrolysis, wherein at least 70% of the mixture has a boiling point at atmospheric pressure ≧ about 550 ° F (290 ℃). Some pyrolysis tars have an initial boiling point of 200 ℃. For some pyrolysis tars, greater than or equal to 90 wt% of the pyrolysis tar has a boiling point at atmospheric pressure greater than or equal to 550F (290℃). The pyrolysis tar may contain, for example, 50 wt% or more, such as 75 wt% or more, such as 90 wt% or more, hydrocarbon molecules (including mixtures and aggregates thereof) having (i) one or more aromatic components and (ii) a number of carbon atoms of about 15 or more, based on the weight of the pyrolysis tar. Pyrolysis tars typically have a metal content of ≦ 1.0x10³ppmw, based on the weight of the pyrolysis tar, is much less than the amount of metals found in a crude oil (or crude oil component) having the same average viscosity.

By "olefin content" is meant the portion of the tar that contains hydrocarbon molecules having olefinic unsaturation (at least one unsaturated carbon that is not aromatic unsaturation), wherein the hydrocarbon may or may not also have aromatic unsaturation. For example, vinyl hydrocarbons such as styrene (if present in the pyrolysis tar) would be included in the olefin content. Pyrolysis tar reactivity was found to be strongly correlated with the olefin content of the pyrolysis tar. The tars, such as pyrolysis tars, e.g., SCT, have a bromine number reactivity ("R") of 28 or less (R)_T28BN or less). Having reactivity R_T>The 28BN tar may be subjected to one or more heat treatments (e.g., at least one heat soak) to produce a tar having a reactivity R_CA pyrolysis tar composition of 28BN or less. Having R_TTar of < 28BN and having R_CCombinations of tars of 28BN or less are each "reduced reactivity tars".

Typically, the tar is hydrotreated in the presence of a specified working fluid, for example as a mixture of tar and specified working fluid ("tar-fluid" mixture). Although it is usually determined to contain R having reactivity_CReactivity ("R") of tar-fluid mixture of thermally treated pyrolyzed tar compositions_M") but the pyrolysis tar self-reactivity (R) was determined_TAnd/or R_M) Are within the scope of the invention. The working fluid typically has a much lower reactivity R than the pyrolysis tar reactivity_U. Thus, R of the pyrolysis tar composition_CR derivable from tar-fluid mixtures containing pyrolysis tar compositions_MUsing the relation R_M～[R_CWeight of Tar) + R_U(weight of working fluid)]/(weight of tar + weight of working fluid), and vice versa. For example, if the working fluid has R_UIs 3BN and the working fluid is 40% by weight of the tar-fluid mixture, and if R_C(reactivity of the neat pyrolysis tar composition) is 18BN, then R_MIs about 12 BN.

"heavy tar" (TH) is a hydrocarbon pyrolysis product having an atmospheric boiling point of not less than 565 ℃ and containing not less than 5% by weight, based on the weight of the product, of molecules having multiple aromatic nuclei. TH is typically a solid at 25 ℃ and typically comprises n-pentane: a fraction of SCT insoluble in SCT. TH typically includes asphaltenes and other high molecular weight molecules.

By insoluble content ("IC") is meant the amount in weight% of the components of the hydrocarbon-containing composition that are insoluble in a mixture of 25 volume% heptane and 75 volume% toluene. The hydrocarbon-containing composition may be one or more of: asphaltene-containing compositions, such as pyrolysis tar; thermally treating the pyrolysis tar; hydrotreated pyrolysis tar; and a mixture containing a first hydrocarbon-containing component and a second component including one or more of a pyrolysis tar, a heat-treated pyrolysis tar, and a hydrotreated pyrolysis tar.

The equivalent isothermal temperature ("EIT") is the weighted average of the temperatures of the multiple catalyst beds in the reactor. EIT can be used as a reactor temperature, a hydrotreating temperature, or a temperature in a reactor or other type of vessel or chamber in which one or more materials (e.g., tars or hydrocarbons), products, or streams are hydrotreated and/or heated.

Overview of the method

Figure 1 shows an overview of certain aspects of the present method. The tar stream to be treated A is heat treated to reduce reactivity during transport to centrifuge B. Recycled solvent J, which serves as a working fluid, which can act as a solvent for at least a portion of the tar hydrocarbon compounds, can be added to the tar stream to reduce viscosity. The recycled solvent can be recovered from the process for recycling as shown. A filter (not shown) may be included in the transfer line to remove relatively large insolubles, such as relatively large solids. The thermally treated tar stream is centrifuged to remove insolubles (e.g., solids) having a size of 25 μm or greater. In one or more examples, after centrifugation, the heat-treated tar stream (e.g., lower viscosity, reduced reactivity tar) is substantially free of insoluble or solids having a size greater than 25 μm. The "clean" liquid product tar stream is fed to the guard reactor, in this illustration through a pretreatment manifold C, which directs the tar stream between an on-line guard reactor D1 and a guard reactor D2, which may be maintained off-line, for example, for maintenance. The guard reactor is operated under mild hydrotreating conditions to further reduce tar reactivity. The effluent from the guard reactor is transported through an outlet manifold E to a pretreatment hydrotreating reactor F for further hydrotreating with more active catalyst under slightly more severe conditions. The effluent from the pretreatment hydrotreatment reactor is passed to an intermediate hydrotreatment reactor G for further hydrotreatment under even more severe conditions to obtain a total liquid product ("TLP") of blended quality, but typically still somewhat higher sulfur content. The recovery facility H includes at least one separation, such as fractionation, for separating from the TLP (I) a light stream K suitable for fuel use, (ii) a bottoms fraction I including heavier components of the TLP and (iii) a middle fraction. At least a portion of the middle distillate fraction can be recycled (as recycle solvent) to the tar feed via line J for use as a working fluid or working fluid component. The bottoms fraction I is fed to a stage 2 hydroprocessing reactor L for additional hydroprocessing to provide desulfurization. The effluent stream M from the stage 2 hydroprocessing reactor has a low sulphur content and is suitable for blending into fuels meeting ECA standards.

Pyrolysis tar

Representative tars, such as pyrolysis tars, will now be described in more detail. Embodiments of the present disclosure are not limited to the use of these pyrolysis tars, and this description is not meant to exclude the use of other pyrolysis tars within the broader scope of the present invention, such as tars derived from the pyrolysis of coal and/or the pyrolysis of biological materials (e.g., biomass). Pyrolysis tar is a product or byproduct of hydrocarbon pyrolysis, such as steam cracking. The effluent from pyrolysis is typically in the form of a mixture containing unreacted feed, unsaturated hydrocarbons produced from the feed during pyrolysis, and pyrolysis tar. Pyrolysis tar typically contains 90% by weight or more of molecules of the pyrolysis effluent having an atmospheric boiling point of 290 ℃ or more. In addition to hydrocarbons, the feed to the pyrolysis optionally also contains diluents (diluents), such as one or more of the following: nitrogen, argon, water, aqueous solutions, or any combination thereof.

Steam cracking to produce SCT is a form of pyrolysis that uses a dilution containing appreciable amounts of steam. Steam cracking will now be described in more detail. Embodiments of the invention are not limited to SCT processing and this description is not meant to exclude the processing of other tars, such as other pyrolysis tars, within the broader scope of the invention.

Steam cracking

A steam cracking plant may include furnace facilities for producing steam cracking effluent and recovery facilities for removing various products and byproducts, such as light olefins and pyrolysis tar, from the steam cracking effluent. Furnace facilityA boiler typically includes a plurality of steam cracking furnaces. Steam cracking furnaces typically include two main sections: a convection section and a radiant section, which typically contains fired heaters. Flue gas from the fired heater is passed from the radiant section to the convection section. The flue gas flows through the convection section and is then conducted away, for example, for removal of combustion byproducts such as NO_xOne or more processes of (a). The hydrocarbon is introduced into a tubular coil (convection coil) located in the convection section. Steam is also introduced into the coils where it combines with the hydrocarbons to produce a steam cracking feed. The combination of indirect heating by flue gas and direct heating by steam results in vaporization of at least a portion of the hydrocarbon components of the steam cracking feed. The steam cracked feed containing the vaporized hydrocarbon components is then transferred from the convection coil to tubular radiant tubes located in the radiant section. The indirect heating of the steam cracking feed in the radiant tubes results in cracking of at least a portion of the hydrocarbon components of the steam cracking feed. Steam cracking conditions in the radiant section may include, for example, one or more of the following: (i) a temperature in the range of 760 ℃ to 880 ℃, (ii) a pressure in the range of 1 bar to 5 bar (absolute), or (iii) a cleavage residence time in the range of 0.10 seconds to 2 seconds.

The steam cracking effluent is conducted from the radiant section and quenched, typically with water or quench oil. The quenched steam cracking effluent ("quench effluent") is conducted away from the furnace facility to a recovery facility for separation and recovery of the reacted and unreacted components of the steam cracking feed. The recovery facility typically comprises at least one separation stage, for example for separating one or more of the following from the quench effluent: light olefins, steam cracker naphtha, steam cracker gas oil, SCT, water, light saturated hydrocarbons, molecular hydrogen, or any combination thereof.

The steam cracking feed typically contains hydrocarbons and steam, e.g.,. gtoreq.10 wt.% hydrocarbons, e.g.,. gtoreq.25 wt.%,. gtoreq.50 wt.%, e.g.,. gtoreq.65 wt.%, based on the weight of the steam cracking feed. While the hydrocarbon may be or include one or more light hydrocarbons (e.g., methane, ethane, propane, butane, pentane, or any combination thereof), it may be particularly advantageous to include a significant amount of higher molecular weight hydrocarbons. While doing so generally reduces feed costs, steam cracking such feeds generally increases the amount of SCT in the steam cracked effluent. One suitable steam cracking feed contains ≥ 1 wt.%, such as ≥ 10 wt.%, such as ≥ 25 wt.%, or ≥ 50 wt.% (based on the weight of the steam cracking feed) hydrocarbon compounds which are in the liquid and/or solid phase at ambient temperature and atmospheric pressure.

The hydrocarbon portion of the steam cracking feed typically contains 10 wt% or more, such as 50 wt% or more, such as 90 wt% or more (based on the weight of the hydrocarbon) of one or more of: naphtha, gas oil, vacuum gas oil, waxy residue, atmospheric residue, residue blend, or crude oil; including those containing ≧ about 0.1 wt.% asphaltenes. When the hydrocarbon comprises crude oil and/or one or more fractions thereof, the crude oil is optionally desalted prior to being included in the steam cracking feed. Crude oil fractions may be produced by separating atmospheric pipestill ("APS") bottoms from crude oil followed by reduced pressure pipestill ("VPS") processing the APS bottoms. One or more gas-liquid separators may be used upstream of the radiant section, for example to separate and conduct away any non-volatiles of the crude oil or a portion of the crude oil components. In certain aspects, such separation stages are integrated with a steam cracker as follows: the crude oil or its fractions are preheated in the convection section (and optionally by addition of dilution steam), the bottoms steam containing non-volatiles is separated and then the overhead stream of the main gas phase is conducted off as feed to the radiant section.

Suitable crude oils include, for example, high sulfur straight run crude oils such as those rich in polycyclic aromatics. For example, the hydrocarbons of the steam cracking feed may include ≧ 90 wt% of one or more crude oils and/or one or more crude oil fractions, such as those obtained from atmospheric APS and/or VPS; a waxy residue; atmospheric residue; naphtha contaminated with crude oil; various residuum mixtures; and SCT.

SCT is typically removed from the quench effluent in one or more separation stages, for example as a bottoms stream from one or more tar drums. Such bottoms streams typically contain ≧ 90 wt.% SCT, based on the weight of the bottoms stream. The SCT can have, for example, a boiling point range of greater than or equal to about 550 deg.F (290 deg.C) and can contain carbonMolecules having an atomic number greater than or equal to about 15, and mixtures thereof. Typically, the quench effluent includes ≧ 1 weight% C₂Unsaturates and 0.1 wt% or more TH, based on the weight of the pyrolysis effluent. It is also typical for the quench effluent to contain 0.5 wt.% or more TH, for example 1 wt.% or more TH.

Representative SCTs will now be described in more detail. The present invention is not limited to the use of these SCTs and this description is not meant to exclude the treatment of other tars, such as other pyrolysis tars, within the broader scope of the invention.

Steam cracker tar

Conventional separation equipment may be used to separate SCT and other products and byproducts from the quenched steam cracking effluent, such as one or more flash drums, knock-out drums, fractionators, water quench towers, indirect condensers, or any combination thereof. Suitable separation stages are described, for example, in U.S. patent No. 8,083,931. SCT may be obtained from the quench effluent itself and/or from one or more streams that have been separated from the quench effluent. For example, SCT can be obtained from a steam cracker gas oil stream and/or a bottoms stream of a primary fractionator of a steam cracker, from flash drum bottoms (e.g., bottoms of one or more tar knock-out drums located downstream of a pyrolysis furnace and upstream of a primary fractionator), or a combination thereof. Some SCTs are mixtures of primary fractionator bottoms and tar knock-out drum bottoms.

A typical SCT stream from one or more of these sources typically contains ≥ 90 wt.% SCT, based on the weight of the stream, e.g. ≥ 95 wt.%, e.g. ≥ 99 wt.%. The balance of the weight of the SCT stream greater than 90 wt% (e.g., the portion of the stream that is not SCT, if present) is typically particulate. SCT typically comprises 50 wt.% or more, such as 75 wt.% or more, such as 90 wt.% or more of the TH of the quench effluent, based on the total weight of TH in the quench effluent.

TH is typically in the form of aggregates comprising hydrogen and carbon and having an average size in the range of 10nm to 300nm in at least one dimension and an average number of carbon atoms ≧ 50. Typically, TH contains > 50%, such as > 80%, such as > 90% by weight of aggregates having a C: H atomic ratio in the range of 1-1.8, a molecular weight in the range of 250 to 5,000 and a melting point in the range of 100 ℃ to 700 ℃.

Representative SCTs typically have (i) a TH content in the range of 5.0 wt.% to 40.0 wt.%, based on the weight of the SCT, (ii) an API gravity (measured at a temperature of 15.8 ℃) of ≦ 8.5 API, such as ≦ 8.0 API or ≦ 7.5 API, and (iii) a viscosity at 50 ℃ of 200cSt to 1.0x10⁷cSt, e.g. 1x10³cSt to 1.0x10⁷cSt, as determined by a.s.t.m.d 445. SCT can have, for example>0.5% by weight, or>A sulfur content of 1 wt.% or more, for example in the range of 0.5 wt.% to 7 wt.%, based on the weight of SCT. In aspects where the steam cracking feed does not contain an appreciable amount of sulfur, SCT may contain 0.5 wt.% or less of sulfur, such as 0.1 wt.% or less, for example 0.05 wt.% or less, based on the weight of SCT.

The SCT can have, for example, (i) a TH content in the range of 5 wt% to 40 wt%, based on the weight of the SCT; (ii) density at 15 ℃ of 1.01g/cm³To 1.19g/cm³In the range of, for example, 1.07g/cm³To 1.18g/cm³Within the range of (1); and (iii) a viscosity at 50 ℃ of 200cSt or more, for example 600cSt or more, or between 200cSt and 1.0x10⁷cSt in the range. The defined hydrotreatment is particularly advantageous for SCT having a density of ≥ 1.10g/cm at 15 ℃³E.g.. gtoreq.1.12 g/cm³、≥1.14g/cm³、≥1.16g/cm³Or more than or equal to 1.17g/cm³. Optionally, the SCT has a kinematic viscosity at 50 ℃ of ≥ 1.0x10⁴cSt, e.g.. gtoreq.1.0 x10⁵cSt, or ≥ 1.0x10⁶cSt, or even ≧ 1.0x10⁷cSt. Optionally, SCT has I_N>80 and>70 weight percent of SCT molecules have atmospheric pressure boiling point of more than 290 ℃. Typically, SCT has an insoluble content ("IC)_T") of not less than 0.5% by weight, such as not less than 1% by weight, such as not less than 2% by weight, or not less than 4% by weight, or not less than 5% by weight, or not less than 10% by weight.

Optionally, the SCT has a normal boiling point of > 290 ℃ and a viscosity of > 1x10 at 15 ℃⁴cSt and density not less than 1.1g/cm³. The SCT can beA mixture comprising a first SCT and one or more additional pyrolysis tars, for example a combination of the first SCT and one or more additional SCTs. When SCT is a mixture, it is typical that at least 70 wt% of the mixture has a normal boiling point of at least 290 ℃ and includes olefinic hydrocarbons that contribute to tar reactivity under hydroprocessing conditions. When the mixture contains first and second pyrolysis tars (one or more of which is optionally SCT), optionally, greater than or equal to 90 wt% of the second pyrolysis tar has a normal boiling point of greater than or equal to 290 ℃.

It was found that an increased reactor fouling occurred during the hydroprocessing of tar-fluid mixtures containing SCT with excess olefinic hydrocarbons. In order to reduce the amount of reactor fouling it is advantageous for the SCT in the tar-fluid mixture to have an olefin content of 10 wt. -% (based on the weight of SCT), such as 5 wt. -%, such as 2 wt. -%. More specifically, it has been observed that less reactor fouling occurs during hydrotreating when the SCT in the tar-fluid mixture has (i) an amount of vinyl aromatic compounds of ≦ 5 wt.% (based on the weight of the SCT), such as ≦ 3 wt.%, such as ≦ 2 wt.%, and/or (ii) an amount of aggregates incorporated into the vinyl aromatic compounds of ≦ 5 wt.% (based on the weight of the SCT), such as ≦ 3 wt.%, such as ≦ 2.0 wt.%. It was also observed that fouling to protect the reactor and/or preconditioner occurred less when the heat treated tar (e.g., hot-dipped SCT) was subjected to a prescribed insolubles removal treatment (e.g., using filtration and/or centrifugation). Reduced fouling in the guard reactor and pretreater is advantageous because it results in longer guard reactor and pretreater run lengths, e.g., run lengths comparable to the run lengths of reactors G and L (fig. 1). This reduces the need for additional protection of the reactor and preconditioner reactors that would otherwise be required, for example, to replace the preconditioner reactor offline for regeneration while reactors G and L continue to operate. See, e.g., guard reactor 704B, which may be brought on-line while guard reactor 704A undergoes regeneration (e.g., by stripping with molecular hydrogen).

Working fluid

Typically, the working fluid comprises an aromatic hydrocarbon having S _BN100, such as 110, 120, or 140, and has a true boiling point distribution with an initial boiling point of 130 deg.C or more (266 deg.F) and a final boiling point of 566 deg.C or less (1,050 deg.F). To dilute (flux) the tar and produce the tar: the viscosity of the fluid mixture, the working fluid, should be less than the viscosity of the hydrotreated tar. For example, the working fluid may have a viscosity of 0.9 times or less tar: the viscosity of the tar component of the fluid mixture is, for example, 0.5 times or less, or 0.1 times or less, or 0.05 times or less, or 0.01 times or less. The working fluid may comprise (or consist essentially of or even consist of) a recycled solvent, and typically contains a mixture of polycyclic compounds. The rings may be aromatic or non-aromatic and may contain various substituents and/or heteroatoms. For example, the working fluid can contain the ring compound in an amount of ≧ 40 weight percent, ≧ 45 weight percent, ≧ 50 weight percent, ≧ 55 weight percent, or ≧ 60 weight percent, based on the weight of the working fluid. In certain aspects, at least a portion of the working fluid is obtained as a recycle solvent from the hydrotreater effluent, for example, by one or more separations. This may be done as disclosed in U.S. patent No. 9,090,836, which is incorporated herein by reference in its entirety.

Typically, the recycled solvent contains aromatic hydrocarbons, such as ≥ 25 wt.%, ≥ 40 wt.%, or ≥ 50 wt.%, or ≥ 55 wt.%, or ≥ 60 wt.% aromatic hydrocarbons, based on the weight of the recycled solvent. The aromatic hydrocarbon may include, for example, one, two, and three kinds of cyclic aromatic hydrocarbon compounds. For example, the recycled solvent may contain ≥ 15 wt.% 2-ring and/or 3-ring aromatic compound, e.g. ≥ 20 wt.%, or ≥ 25 wt.%, or ≥ 40 wt.%, or ≥ 50 wt.%, or ≥ 55 wt.%, or ≥ 60 wt.%, based on the weight of the working fluid. The use of recycled solvents containing aromatic hydrocarbon compounds having 2-rings and/or 3-rings as working fluids or working fluid components is advantageous because these compounds generally exhibit significant solvency, e.g., S_BNIs more than or equal to 100. In one or more examples, S of the solvent is recycled_BNCan be ≧ 110, ≧ 115, ≧ 120, or ≧ 125 to about 130, about 133, about 135, about 138, about 140, about 145, about 150, about 155, or about 160. In some examples, S of the solvent is recycled_BNMay be equal to or greater than 100 to equal to or greater than 160, equal to or greater than 110 to equal to or greater than 155, equal to or greater than 110 to equal to or greater than 150, equal to or greater than 110 to equal to or greater than 145, equal to or greater than 110 to equal to or greater than 140, equal to or greater than 110 to equal to or greater than 135, equal to or greater than 115 to equal to or greater than 130, equal to or greater than 120 to equal to or greater than 160, equal to or greater than 120 to equal to or greater than 155, equal to or greater than 120 to equal to or greater than 150, equal to or greater than 120 to equal to or than 145, equal to or greater than 115 to equal to or greater than 135, equal to or greater than 115 to or greater than 130, equal to or greater than 110 to or greater than 130, equal to or greater than 115, equal to or greater than 115, equal.

In another embodiment, S if the solvent is recycled_BNReduced and less than a predetermined desired value (e.g., 110, 115, 120, 125, or 130) during the treatment, the temperature of the fluid or tar (e.g., lower viscosity, reduced reactivity tar) during the hydrotreating process is increased to increase the solvency of the recycled solvent to have S equal to or greater than a predetermined value_BN. For example, if S of the solvent is recycled_BNReduced to a value of 115 or less during the treatment, the temperature of the fluid or tar (e.g., a lower viscosity, reduced reactivity tar) is increased to a temperature of greater than 350 ℃ to about 500 ℃ or about 400 ℃ to about 450 ℃, or 410 ℃ to 440 ℃, or 420 ℃ to 430 ℃ during the hydrotreating process to increase the solvency of the recycled solvent to have an S of equal to or greater than 115_BN。

Such recycled solvents typically contain significant amounts of 2 to 4 ring aromatics, some of which are partially hydrogenated. In one or more examples, the recycled solvent can be or include one or more solvents such as benzene, ethylbenzene, trimethylbenzene, xylene, toluene, naphthalene, alkylnaphthalenes, tetralin, alkyltetralins, or any combination thereof.

Under the specified process conditions, the recycled solvent typically has an A.S.T.M.D8610% distillation point ≥ 60 ℃ and a 90% distillation point ≤ 425 ℃, e.g. ≤ 400 ℃. In certain aspects, the recycled solvent has a true boiling point profile with an initial boiling point ≥ 130 ℃ (266 ° F) and a final boiling point ≤ 566 ℃ (1,050 ° F). In other aspects, the recycled solvent has a true boiling point distribution with an initial boiling point ≥ 150 ℃ (300 ° F) and a final boiling point ≤ 430 ℃ (806 ° F). In still other aspects, the recycled solvent has a true boiling point distribution with an initial boiling point ≥ 177 ℃ (350 ° F) and a final boiling point ≤ 425 ℃ (797 ° F). The true boiling point distribution (distribution at atmospheric pressure) can be determined, for example, by conventional methods such as the method of a.s.t.m.d 7500. When the final boiling point is greater than the boiling point specified in the standard, the true boiling point distribution can be determined by extrapolation. Particular forms of recycled solvent have a true boiling point distribution with an initial boiling point of 130 ℃ or more and a final boiling point of 566 ℃ or less and/or contain 15% by weight or more of 2-ring and/or 3-ring aromatic compounds.

The tar-fluid mixture is produced by combining pyrolysis tar, such as SCT, with a sufficient amount of a working fluid containing a recycle solvent (along with a sufficient amount of recycle solvent in the working fluid) for the tar-fluid mixture to have a viscosity sufficiently low for the tar-fluid mixture to be delivered to hydroprocessing, such as a 50 ℃ kinematic viscosity of the tar-fluid mixture of ≦ 500 cSt. To achieve such viscosities when the working fluid contains greater than or equal to 50 wt% of the recycled solvent, such as greater than or equal to 75 wt%, such as greater than or equal to 90 wt%, or greater than or equal to 95 wt%, or 50 wt% 99 wt%, the amount of working fluid and pyrolysis tar in the tar-fluid mixture is typically in the range of about 20 wt% to about 95 wt% pyrolysis tar and about 5 wt% to about 80 wt% working fluid, based on the total weight of the tar-fluid mixture. For example, the relative amounts of the working fluid and the pyrolysis tar in the tar-fluid mixture may be in the range of (i) from about 20 wt% to about 90 wt% of the pyrolysis tar and from about 10 wt% to about 80 wt% of the working fluid or (ii) from about 40 wt% to 90 wt% of the pyrolysis tar and from about 10 wt% to about 60 wt% of the working fluid. Working fluid: the pyrolysis tar weight ratio is typically ≧ 0.01, such as in the range of 0.05 to 4.0, such as in the range of 0.1 to 3.0 or 0.3 to 1.1. In certain aspects, particularly when the pyrolysis tar contains representative SCT, the tar-fluid mixture may contain 50 wt.% to 70 wt.% pyrolysis tar, with the balance of the tar-fluid mixture being 90 wt.% or more containing a specified working fluid, e.g., 95 wt.% or more, e.g., 99 wt.% or more. While the working fluid may be combined with the pyrolysis tar within the hydrotreating stage to produce a tar-fluid mixture, they are typically combined upstream of the hydrotreating, such as by adding the working fluid to the pyrolysis tar.

In one or more embodiments, the working fluid can be or include one or more recycle solvents or fluids, such as streams from line J depicted in fig. 1 and/or line 56 in fig. 2 and 3. The working fluid may be combined with tar treated during a hot soak process that reduces tar reactivity, as depicted in fig. 2 and 3 at line 56 ("optional diluent" inlet). In some embodiments, a working fluid is added to the tar after the heat soaking process is applied to the tar and before the process stream is fed to the solids removal step, as depicted by line J in fig. 1.

Typically, tar is combined with a working fluid to produce a tar-fluid mixture. Mixing hydrocarbon-containing compositions can result in the precipitation of certain solids, such as asphaltenes, from the mixture. Hydrocarbon compositions that produce such precipitates upon mixing are referred to as "incompatible". The generation of incompatible mixtures can be avoided as follows: mixing the composition alone such that the "solubility blend value" S of all components of the mixture_BNGreater than the "insolubility value" I of all the components of the mixture_N. Measurement of S_BNAnd I_NAnd thus determine compatible mixtures of hydrocarbon compositions, is described in U.S. patent No. 5,997,723, incorporated herein by reference in its entirety.

In certain aspects, the process comprises treating (e.g., by mild hydrotreating) the tar-fluid mixture in a guard reactor and then pretreating under pretreatment hydrotreating conditions, wherein the feed to the pretreater comprises at least a portion of the guard reactor effluent, e.g., a substantial amount of the guard reactor effluent, e.g., substantially all of the guard reactor effluent. These aspects are generally characterized by one or more of (i) the working fluid has S _BN120 or more, such as 125 or more, 130 or more, 135 or more, or 140 or more, (ii) the pyrolysis tar has I_N70 or more, e.g. 80 or more, and (iii) present in the composition>70% by weight of pyrolysisThe tar has an atmospheric boiling point of 290 ℃ or higher, for example 80% by weight or higher or 90% by weight or higher. The tar-fluid mixture may have, for example, S _BN110, such as 120 or 130. It was found that when the tar feed had I_N>110, provided that after combination with the recycle solvent or working fluid, the feed has S_BN150, 155 or 160 or more, reactor plugging is advantageously reduced, especially in a protected reactor and/or preconditioner. Pyrolysis tars can have relatively large I_NE.g. I_N>80, in particular>100 or>110, provided that the working fluid has a relatively large S_BNFor example, 100, 120, or 140.

The SCT upgrading process will now be described in more detail with reference to fig. 1-3. Although the process is described in terms of SCT, the description is not meant to exclude the use of other tars as an alternative or supplement to SCT, such as other pyrolysis tars. Conventional SCT (SCT produced by a conventional steam cracking process) may be used, but the present invention is not limited thereto.

The upgrading process comprises a step of SCT hydrotreating, typically such that a subsequent hydrotreating step is carried out under conditions similar to or more severe than the preceding hydrotreating step. Thus, at least one hydrotreating stage under "pretreatment hydrotreating conditions" is used to reduce the reactivity of the tar or tar-working fluid mixture. Pretreatment hydrotreating is typically performed after hydrotreating in one or more guard reactors (D1 and D2 in fig. 1) but before hydrotreating stages (G in fig. 1) that are performed at intermediate hydrotreating conditions. Intermediate hydrotreating typically achieves a major portion of hydrogenation and some desulfurization reactions. The pretreatment hydrotreating conditions are less severe than the "intermediate hydrotreating conditions". For example, the pretreatment hydrotreating conditions use one or more of a lower hydrotreating temperature, a lower hydrotreating pressure, a greater tar + working fluid feed weight hourly space velocity ("WHSV"), a greater SCT WHSV, and a lower molecular hydrogen consumption rate than the intermediate hydrotreating conditions. The particular hydrotreating conditions may be selected to achieve the desired 566 c + conversion, typically in the range of 0.5 wt% to 5 wt%, for at least ten days substantially continuously, within the parameters specified for the pretreatment hydrotreating conditions (T, P and/or WHSV).

Optionally, the process includes at least one further hydrotreating stage (L in fig. 1), in particular to further reduce the sulfur content of the intermediate hydrotreated tar. The reprocessing hydrotreatment is carried out after at least one hydrotreatment stage under intermediate hydrotreatment conditions under "reprocessing hydrotreatment conditions". Generally, reprocessing hydroprocessing is performed with little or no use of working fluid. The reprocessing hydrotreating conditions are typically more severe than the intermediate hydrotreating conditions.

When temperatures are indicated for particular catalytic hydrotreating conditions in the hydrotreating zone, such as pretreatment, intermediate, and retreatment hydrotreating conditions, this refers to the average temperature of the catalyst bed of the hydrotreating zone (half the difference between the inlet and outlet temperatures of the bed). When the hydroprocessing reactor contains more than one hydroprocessing zone (such as shown in fig. 2), the hydroprocessing temperature is the average temperature in the hydroprocessing reactor, e.g. (half the difference between the inlet temperature of the most upstream catalyst bed and the outlet temperature of the most downstream catalyst bed).

The total pressure in each hydroprocessing stage is typically adjusted to maintain flow from one hydroprocessing stage to the next, e.g., using little or no interstage pumping, of SCT, SCT composition, pre-treated tar, hydrotreated tar, and reprocessed tar. Although it is within the scope of the invention for any hydroprocessing stage to operate at significantly higher pressures than other stages, for example to enhance hydrogenation of any thermally cracked molecules, this is not essential. The present invention can be carried out using a stage-to-stage (from stage-to-stage) total pressure sequence sufficient to (i) achieve a desired amount of tar hydrotreating, (ii) overcome any pressure drop across the stages, and (iii) maintain tar flow to, within, and out of the process.

A heat treatment

The formation of coke precursors during SCT hydrotreating leads to increased fouling of the hydrotreating reactor. Coke precursor formation is observed to be primarily caused by two reactions: insufficient hydrogenation of the thermally cracked molecules and polymerization of the highly reactive molecules in the SCT. Although never fully hydrogenated by increasing the reactor pressure, the polymerization of highly reactive molecules depends not only on pressure, but also primarily on other conditions such as temperature and weight hourly space velocity ("WHSV"). Accordingly, certain aspects of the present invention relate to SCT hydrotreating with less reactor fouling by (i) thermally treating tar, which produces a tar composition having less reactivity, (ii) hydrotreating the thermally treated tar in the presence of a working fluid comprising a recycle solvent to form a preconditioner effluent, and (iii) hydrotreating the preconditioner effluent to produce a hydrotreated tar.

Found to be reactive, e.g. SCT reactive R_TSCT composition reactive R_CAnd reactivity R of tar-fluid mixtures_MClosely related to the olefin content of the tar, especially the styrene and diene content. While not wishing to be bound by any particular theory, it is believed that the olefinic compounds of SCT (i.e., the olefinic components of tar) have a tendency to polymerize during hydrotreating, leading to the formation of coke precursors that can clog or otherwise foul the reactor. In the absence of hydrogenation catalyst, fouling is more prevalent, for example in the dead volume zones of the preheater and the hydrotreating reactor. It was found that certain measures of the olefin content of the tar, such as BN, were closely related to the reactivity of the tar. Reactivity such as R_T、R_CAnd R_MBromine (as Br) in grams, which can thus be expressed in BN units, i.e. consumed (e.g. by reaction and/or adsorption) by a tar sample of 100 grams₂) The amount of (c). Bromine index ("BI") may be used as an alternative or supplement to BN measurement, where BI is Br in mg consumed by 100 grams of tar₂The amount of mass.

SCT reactivity can be measured using SCT samples withdrawn from SCT sources such as bottoms of flash drum separators, tar storage tanks, or any combination thereof. The sample is combined with sufficient working fluid to achieve a predetermined kinematic viscosity at 50 ℃ in the tar-fluid mixture, typically ≦ 500 cSt. Although BN measurements can be made at elevated temperatures using tar-fluid mixtures, the tar-fluid mixture is typically cooled to a temperature of about 25 ℃ prior to making the BN measurements. The method of measuring BN of heavy hydrocarbons can be used to determine SCT reactivity, or SCT reactivity of tar-fluid mixtures, but the invention is not limited to the use of these. For example, the BN of a tar-fluid mixture can be determined by extrapolation from conventional BN methods as applied to light hydrocarbon streams, such as electrochemical titration (e.g., as specified in a.s.t.m.d-1159), colorimetric titration (as specified in a.s.t.m.d-l 158), and Karl Fischer titration. The titration may be performed on a tar sample having a temperature ≦ ambient temperature, e.g., ≦ 25 ℃. Although the cited a.s.t.m. standards apply to lower boiling samples, they have also found application in the measurement of SCT BN.

Certain aspects of the method include thermally treating the tar to produce a thermally treated tar (tar composition, e.g., SCT composition), combining the tar composition with a working fluid, e.g., a working fluid comprising a recycled solvent, to produce a tar-fluid mixture, hydrotreating the tar-fluid mixture at pretreatment hydrotreating conditions to produce a preconditioner effluent, and hydrotreating at least a portion of the pretreated effluent at intermediate hydrotreating conditions to produce a hydrotreater effluent containing hydrotreated tar. For example, a method can include thermally treating an SCT to produce an SCT composition, combining the SCT composition with a specified amount of a defined working fluid comprising a recycle solvent to produce a tar-fluid mixture, hydrotreating the tar-fluid mixture in a pretreatment reactor under pretreatment hydrotreating conditions to produce a preconditioner effluent, and hydrotreating at least a portion of the preconditioner effluent under intermediate hydrotreating.

In addition to its high density and high sulfur content, tar (particularly pyrolysis tars such as SCT) is very reactive because it contains significant amounts of reactive olefins such as vinyl naphthalene and/or acenaphthylene (acenaphthalene). In some embodiments, uncontrolled oligomerization results in fouling in the preheater and/or reactor when the tar is heated, e.g., to a temperature greater than 250 ℃. The higher the temperature, the more severe the fouling. In the present process, the tar feed is subjected to an initial controlled thermal soak step to oligomerize the olefins in the tar and thereby reduce the reactivity of the tar during further processing. Certain aspects of the thermal treatment (e.g., thermal soaking) are described in more detail below with respect to representative SCTs.

Thermally treating the tar to reduce its reactivity may be accomplished with some minor modifications in the cold tar recycling process, for example, by reducing the flow of cold tar back into the process, as described further below. The heat treatment kinetics suggest that reaction temperatures of 200 ℃ to 300 ℃ with residence times of a few minutes, e.g., 2min to >30min, are effective in reducing tar reactivity. The higher the heat treatment temperature, the shorter the heat treatment reaction time or residence time may be. For example, a residence time of 2-5min at 300 ℃ may be sufficient. At 250 ℃, a residence time of about 30min produced a similar decrease in reactivity. Pressure has little effect on the heat treatment kinetics and therefore the heat treatment can be carried out at ambient pressure or at the exit pressure of the tar separation process feeding the tar upgrading process.

Typically, the tar reactivity is ≧ 30BN, e.g., in the range from 30BN up to 40BN or more. The target reactivity for reduced reactivity tars is 28BN or less in order to reduce (or even minimize) fouling in the guard reactor and/or pretreater, which typically uses hydrotreating temperatures in the range of 260 ℃ to 300 ℃. Providing a heat-soaked tar in the form of a reduced-reactivity tar (reactivity R)_CTar composition of (a) as a guard reactor feed operating within a specified guard reactor temperature range for guard reactor hydroprocessing, typically results in little, if any, fouling of the guard reactor during typical hydroprocessing operations. Dilution of the tar with a working fluid (as a solvent or diluent) should be minimized prior to or during heat soaking. In some cases it may be necessary to inject a working fluid to improve tar flow characteristics during and after heat soaking. However, excessive dilution with working fluids, particularly those containing recycled solvent, results in much slower reduction of tar reactivity during thermal treatments such as thermal soaking, as indicated by the BN of the tar. Therefore, it is desirable that the viscosity reduction will be used during heat treatment (heat soaking)The amount of working fluid used is controlled to be 10 wt% or less based on the total weight of the tar and the working fluid.

FIG. 2 includes an exemplary cold tar recirculation system (e.g., elements upstream of centrifugal element 600). FIG. 3 shows an alternative arrangement of a cold tar recycling system in which tar streams from two separate upstream processes are separately recycled and then may be combined for solids removal and subsequent downstream processing.

The cold tar recycle is designed to reduce tar residence time at elevated temperatures, such as at tar knock-out drum temperatures, which are typically about 300 ℃. In prior tar processing, cold tar recycle was implemented to base small oligomerization to minimize asphaltene content increase, which required the addition of expensive diluents such as steam cracked gas oil for blending into HSFO. To heat soak the tar to reduce tar BN, cold tar recycle is minimized, for example, by reducing the recycle tar flow rate to increase tar temperature and also increase residence time. The heat soaking is carried out at a temperature ranging from 200 ℃ to 300 ℃, generally from 250 ℃ to 280 ℃ for a heat soaking time ranging from 2 to 15 minutes by reducing the flow rate of the cold tar recycled to 0 to 100 tons/hour. Additional heat soaking, wherein the tar is held at an elevated temperature, e.g., 150 ℃ or higher, for an extended period of time, e.g., 0.5 hours-2 hours, should reduce the BN even further, e.g., to 25 or 23 or less, but may result in increased IC for certain tars, e.g., certain SCTs. In certain aspects, the heat treatment is carried out at a temperature in the range of 20 ℃ to 300 ℃, or 200 ℃ to 250 ℃, or 225 ℃ to 275 ℃ for a time in the range of 2 to 30min, such as 2 to 5min, or 5 to 20min, or 10 to 20 min. At higher temperatures, thermal soaking may be suitably carried out for a shorter period of time.

For a representative tar, e.g. a representative pyrolysis tar such as a representative SCT, a defined heat treatment, e.g. a defined reduction R of thermal soaking by cold tar recycling, is observed_T、R_CAnd R_MOne or more of the above. Generally, a reactive R is used_TIs subjected to a heat treatment to produce a SCT feed having less reactivity R_CThe SCT composition of (1). Conventional heat treatment is suitable for heat treatmentSCT, including thermal soaking, but the invention is not limited thereto. While reactivity can be improved by blending SCT with a second pyrolysis tar having a lower olefinic content, R is more typically improved by thermal treatment of SCT_T(and thus R)_M). The specified heat treatment is believed to be particularly effective in reducing the olefin content of the tar. For example, combining a heat treated SCT with a specified working fluid in specified relative amounts generally results in a composition having R_M18BN or less. If substantially the same SCT is combined with substantially the same working fluid in substantially the same relative amounts in the absence of heat treating the tar, the tar-fluid mixture will typically have R_MIn the range of 19BN-35 BN.

One representative pyrolysis tar is SCT ("SCT 1") having the following: r_T>28BN (based on tar), e.g. R_TIs about 35; the density at 15 ℃ is more than or equal to 1.10g/cm³(ii) a The kinematic viscosity at 50 ℃ is more than or equal to 1.0x10⁴cSt in the range; i is_N>80; wherein 70 wt.% or more of the hydrocarbon component of SCT1 has an atmospheric boiling point of 290 ℃ or more. SCT1 can be obtained from an SCT source, for example, from the bottoms of a separator drum (e.g., a tar drum) located downstream of the steam cracker effluent quench. The heat treatment may include maintaining SCT1 to T₁-T₂Temperature duration in the range of t or more_HS。T₁At 150 ℃ or higher, e.g.160 ℃ or higher, e.g.170 ℃ or higher, or 180 ℃ or higher, or 190 ℃ or higher, or 200 ℃ or higher. T is₂Is 320 ℃ or less, e.g. 310 ℃ or less, e.g. 300 ℃ or 290 ℃ or less, and T₂≥T₁. In general, t_HSIs ≥ 1min, e.g. ≥ 10min, e.g. ≥ 100min, or generally in the range of 1min-400 min. Let T be₂At 320 ℃ or lower, t of 10min or more, e.g. 50min or more, e.g. 100min or more is used_HSUsually with less t than processed_HSThose of better properties.

Although the present disclosure is not so limited, heating may be performed in the lower section of the tar drum and/or in SCT piping and equipment associated with the tar knock-out drum. For example, it is common for the tar drum to receive a quenched steam cracker effluent containing SCT.Although the steam cracker operates in pyrolysis mode, SCT accumulates in the lower section of the tar drum where SCT is continuously withdrawn. Can reserve part of extracted SCT for measuring R_TAnd R_MOne or more of the above. The balance of the SCT can be withdrawn from the tar drum and divided into two separate SCT streams. At least a portion of the first stream (recycle portion) is recycled to the lower region of the tar drum. At least a recycled portion of the second stream is also recycled to the lower region of the tar drum, e.g., alone or with a recycled portion of the first stream. Typically, greater than or equal to 75 wt% of the first stream is present in the recycle portion, e.g., greater than or equal to 80 wt%, or greater than or equal to 90 wt%, or greater than or equal to 95 wt%. Typically, greater than or equal to 40 wt% of the second stream is present in the recycle portion, such as greater than or equal to 50 wt%, or greater than or equal to 60 wt%, or greater than or equal to 70 wt%. Optionally, the storage portion is also derived from the second stream, e.g., for storage in a tar tank. Typically, the storage portion is ≧ 90 wt.% of the balance of the second stream after removal of the recycle portion. The heat treatment temperature range and t can be controlled by adjusting the flow rate of the tar drum of the first and/or second recycle stream_HS。

Typically, the recycled portion of the first stream has an average temperature that is no more than 60 ℃ lower than the average temperature of the SCT in the lower region of the tar drum, such as no more than 50 ℃ lower, or no more than 25 ℃ lower, or no more than 10 ℃ lower. This can be accomplished, for example, by thermally isolating the piping and equipment that transfers the first stream to the tar drum. The second stream, or a recycled portion thereof, is cooled to an average temperature that is (i) less than the average temperature of the recycled portion of the first stream and (ii) at least 60 ℃, such as at least 70 ℃, such as at least 80 ℃, or at least 90 ℃, or at least 100 ℃ less than the average temperature of SCT in the lower region of the tar drum. This can be accomplished, for example, by cooling the second stream using one or more heat exchangers. A working fluid may be added to the second stream as a diluent if desired. If a working fluid comprising recycled solvent is added to the second stream, the amount of working fluid added is considered when additional working fluid is combined with SCT to produce a tar-fluid mixture to achieve a desired tar within a specified range: fluid weight ratio.

Typically by adjusting (i) the recycle portion of the second stream: the weight ratio of the withdrawn SCT stream and (ii) the recycled portion of the first stream: the weight ratio of the recycled portion of the second stream controls the heat treatment. It was found that controlling one or both of these ratios for maintaining the average temperature of SCT in the lower region of the tar drum at T₁To T₂Is within a desired range for a processing time t_HSIs effective for 1 minute or more. A greater SCT recycle rate corresponds to a longer SCT residence time in the tar drum and associated piping at elevated temperatures and generally increases the level of the tar drum (the level of liquid SCT in the lower region of the tar drum, e.g., near the pilot (boot) region). Typically, the ratio of the weight of the recycled portion of the second stream to the weight of the withdrawn SCT stream is ≦ 0.5, such as ≦ 0.4, such as ≦ 0.3, or ≦ 0.2, or in the range of 0.1 to 0.5. Typically, the recycled portion of the first stream: the weight ratio of the recycled portion of the second stream is 5 or less, such as 4 or less, for example 3 or less, or 2 or less, or 1 or less, or 0.9 or less, or 0.8 or less, or in the range of from 0.6 to 5. Although it is not necessary to maintain the average temperature of the SCT in the lower region of the tar drum at a substantially constant value (T)_HS) But this is usually done. T is_HSMay be, for example, in the range of 150 ℃ to 320 ℃, e.g., 160 ℃ to 310 ℃, or ≧ 170 ℃ to 300 ℃. In certain aspects, the heat treatment conditions comprise (i) T_HSRatio T₁At least 10 ℃ and (ii) T_HSIn the range of 150 ℃ to 320 ℃. E.g. normal T_HSAnd t_HSThe range includes T being more than or equal to 180 DEG C_HSNot more than 320 ℃ and not more than 5 minutes_HSLess than or equal to 100 minutes; for example 200 ℃ T ≦ T_HST is less than or equal to 280 ℃ for 5 minutes_HSLess than or equal to 30 minutes. Let T be_HSAt 320 ℃ or lower, t of 10min or more, e.g. 50min or more, e.g. 100min or more is used_HSUsually at a smaller t_HSThose that are produced in the next step are better treated tars.

The specified heat treatment is effective in reducing R of the representative SCT_TThereby realizing R_C≤R_T0.5BN, e.g. R_C≤R_T-1BN, e.g. R_C≤R_T-2BN, or R_C≤R_T-4BN, or R_C≤R_T-8 BN. Because R is_CLess than or equal to 18BN, so R_MIn general<18BN, e.g.. ltoreq.17 BN, e.g. 12BN<R_MLess than or equal to 18 BN. In certain aspects, the heat treatment results in the tar-fluid mixture having R_M<17BN, e.g.. ltoreq.16 BN, e.g.. ltoreq.12 BN, or. ltoreq.10 BN, or. ltoreq.8 BN. At T₁To T₂Is carried out at a temperature within a predetermined temperature range for a predetermined time t_HSTar (SCT composition) which is advantageous for processing for more than 1 minute has insoluble content (' IC)_C") is less than the insoluble content of the treated tar obtained by the heat treatment carried out at the greater temperature. When T is_HSIs 320 ℃ or less, such as 300 ℃ or less, such as 250 ℃ or 200 ℃ or less, and t_HSThis is particularly the case for > 10 minutes, for example > 100 minutes. Advantageous IC_CThe content, for example ≦ 6 wt% and usually ≦ 5 wt%, or ≦ 3 wt%, or ≦ 2 wt% increases the suitability of the heat-treated tar for use as a fuel oil, for example a transportation fuel oil, such as bunker fuel oil. It also reduces the need for solids removal prior to hydroprocessing. In general, ICs_CAbout and IC_TIs the same or not significantly larger than IC_T。IC_CUsually not exceeding IC_T+ 3% by weight, e.g. IC_C≤IC_T+ 2% by weight, e.g. IC_C≤IC_T+ 1% by weight or IC_C≤IC_T+ 0.1% by weight.

Although SCT heat treatment is typically carried out in one or more tar drums and associated piping, the invention is not so limited. For example, when the thermal treatment comprises thermal soaking, the thermal soaking can be performed at least in part in one or more thermal soaking drums and/or vessels, conduits, and other equipment (e.g., fractionators, water quench towers, indirect condensers) associated with, for example, (i) separating SCT from the pyrolysis effluent and/or (ii) passing SCT to hydroprocessing. The location of the heat treatment is not critical. The thermal treatment may be performed at any convenient location, such as after separation from the pyrolysis effluent tar and prior to hydroprocessing, such as downstream of the tar drum and upstream of the mixing of the thermally treated tar with the recycle solvent or working fluid.

In some aspectsThe heat treatment is carried out as schematically illustrated in fig. 2. As shown, quench effluent from the steam cracker furnace facility is conducted via line 60 to tar knock-out drum 61. Cracked gas is removed from the drum via line 54. SCT condenses in the lower region of the drum (the directing region as shown) and the withdrawn SCT stream is directed away from the drum via line 62 to pump 64. A filter (not shown) for removing large solids, e.g.,. gtoreq.10,000 μm diameter, from the SCT stream can be included in line 62. After pump 64, the withdrawn stream is divided into a first recycle stream 58 and a second recycle stream 57. The first and second recycle streams are combined for recycle to drum 61 via line 59. One or more heat exchangers 55 are provided for cooling the SCT in lines 57 (shown) and 65 (not shown), for example with water. Line 56 provides an optional diluent for the working fluid, if desired. Valve V₁、V₂And V₃The amount of draw streams directed to the first recycle stream, the second recycle stream, and the stream conducted to solids separation via line 65 (represented here by centrifuge 600) is adjusted. The lines 58, 59 and 62 can be insulated to maintain the temperature of the SCT within a desired temperature range for thermal processing. Can be increased by passing through the valve V₁And V₂To increase the heat treatment time t_HSThis brings the SCT level in drum 61 from an initial level, e.g. L₁Towards L₂And (4) rising.

Passing the heat treated SCT through valve V₃And conducted via line 65 to a solids removal facility, here centrifuge 600, and then the liquid fraction from the centrifuge is passed via line 66 to a hydroprocessing facility containing at least one hydroprocessing reactor. Solids removed from the tar are directed away from the centrifuge via line 67. The aspect illustrated in FIG. 2 using a representative SCT, such as SCT1, in the lower zone of the tar drum (below L)₂) Average temperature T of SCT during Heat treatment_HSIn the range of from 200 ℃ to 275 ℃, and heat exchanger 55 cools the recycled portion of the second stream to a temperature in the range of from 60 ℃ to 80 ℃. Time t_HSCan be, for example, ≧ 10min, for example in the range from 10min to 30min or from 15min to 25 min.

In continuous operation, the SCT conducted via line 65 typically contains ≧ 50 wt.% SCT, such as SCT, e.g., > 75 wt.%, such as ≧ 90 wt.%, available for processing in drum 61. In certain aspects, substantially all of the SCT available for hydroprocessing is combined with a specified amount of a specified working fluid to produce a tar-fluid mixture that is conducted to hydroprocessing. Depending on, for example, hydrotreater capacity limitations, a portion of the SCT in line 65 or line 66 can be diverted, for example, for storage or further processing, including hydrotreating after storage (not shown).

FIG. 3 shows an alternative arrangement in which tars from two separate pyrolysis processes may be heat soaked in separate recycle processes and then combined for solids removal. The first process A includes separation in a tar knock-out drum 60A. As shown, lights are removed at the top of the drum, for example for further separation in at least one fractionator. A bottoms fraction containing pyrolysis tar is removed from a tar knock-out drum 60A located downstream of the steam cracker. The bottoms fraction is removed via line 62A through filter 63A for removal of solids large for pump 64A, e.g., > 10,000 μm diameter. After pump 64A, the withdrawn stream is divided into a first recycle stream 13 and a second recycle stream 57A (which bypasses the heat exchanger in stream 58A). The first recycle stream passes through heat exchanger 55a1 and optionally one or more additional heat exchangers 55a2, and is then recombined with stream 57A via lines 12 and 13 as recycle to drum 61A via line 59A. The heat exchanger(s) 55a2 may be bypassed via appropriate configurations of lines 11 and 13 and valves V5 and V6. Both heat exchangers 55a1 and 55a2 may be bypassed and the heat treated tar stream may be conducted to downstream process steps via line 10 and appropriate configuration of valves V4, V5, and V6. The heat treated tar from process a may be transported via line 65A to downstream process steps and/or to storage (in tank 900A) through appropriate configuration of valves V8 and V9. The proportion of recirculation through the heat exchanger and bypassing them can be adjusted by appropriate configuration of valves V1A and V2A. Line 56A and valve V7A may be configured to provide an optional diluent for the working fluid, if desired. The second process B includes a pyrolysis step that includes separation by fractionation, for example, in a primary fractionator 60B. As shown, lights are removed overhead from the primary fractionator, for example to a secondary fractionator. The bottoms of the still 60B containing pyrolysis tar are removed from the primary fractionator 60B via line 62B through filter 63B for removal of solids large to pump 64B, e.g., > 10,000 μm diameter. After pump 64B, the withdrawn stream is divided into a first recycle stream 59B and a second recycle stream 57B (which bypasses the heat exchanger in stream 58B). The first recycle stream is recycled via heat exchanger 55B and optionally one or more additional heat exchangers (not shown) via line 59B to the bottoms collector of fractionator 60B through valve V2B. The second recycle stream is recycled to the fractionator via valve V1B. The proportion of recycle through the primary fractionator and through the fractionator bottoms collector is adjusted by appropriate configuration of valves V1B and V2B. Line 56B and valve V7B can be configured to provide an optional diluent for the working fluid, if desired. Valve V3 controls flow from the thermal treatment process to the solids removal facility (here centrifuge 600) via line 65B and/or to storage (in tank 900B).

In the heat treatment of the tar produced in method A, the temperature T1 was shown, and the heat treatment temperature of the tar produced in method B was shown as T2. T1 and T2 may be the same or different, and T1 and T2 are suitably selected for the particular tar to be heat treated and the desired residence time of the heat treatment. For example, T1 may be around 250 ℃ for pyrolysis tar obtained from a tar knock-out drum, and T2 may be around 280 ℃ for pyrolysis tar obtained from the primary fractionator bottoms.

In fig. 3, lines 58A, 58B, 59A, 59B, and 62A and 62B can be insulated to maintain the temperature of the SCT within the desired temperature range for thermal processing. Downstream of the junction of lines 65A and 65B, valve V10 regulates the amount of heat treated tar fed to the solids removal step; where the solids are removed by centrifuge 600.

B, centrifugal separation

Tars such as SCT contain insolubles in the form of particulate solids in amounts of from 1,000ppmw up to 4,000ppmw or even greater. The particles are believed to have two sources. The first source is coke powder produced by pyrolysis. The coke powder from pyrolysis usually has a very low hydrogen content, e.g.. ltoreq.3% by weight and a density of.gtoreq.1.2 g/ml. The second source is from tar oligomeric or polymeric coke. There are multiple points in the steam cracking process where polymer coke can form and enter the tar stream. For example, some steam crackers have significant fouling problems in the primary fractionator. The source of this fouling is believed to result from polymers formed by oligomerization of vinyl aromatic compounds at temperatures ≦ 150 ℃ in the fractionator column. While it is conventional to periodically remove foulants from fractionator trays by hydro-blowing, some foulants are entrained in the tar stream by quench oil recycle. Such foulants (designated herein as polymer coke) are richer in hydrogen content than pyrolytic coke powder, e.g., >5 wt%, and typically have a lower density, e.g., < 1.1 g/ml.

In addition to the two main sources of coke powder, a third source of powder is believed to result from a specified heat soak. It is within the scope of the present invention to conduct the heat soaking under relatively mild conditions (lower temperature, shorter duration) within the specified heat soaking conditions. The solids produced during tar heat soaking are considered to have a relatively large hydrogen content (e.g., >5 wt%) and are considered to have a much lower particle size, e.g.,. ltoreq.25 μm, than the solids produced by other routes.

In certain aspects, centrifugation (typically with the aid of a working fluid) is used for solids removal. For example, a centrifuge may be used to remove solids from a tar-fluid mixture at temperatures in the range of 80 ℃ to 100 ℃. Any suitable centrifuge may be used, including those commercially available from Alfa Laval. The feed to the centrifuge may be a tar-fluid mixture containing a working fluid comprising recycled solvent and a tar composition (thermally treated tar). The amount of working fluid is controlled such that the density of the tar-fluid mixture at the centrifugation temperature (typically 50 ℃ to 120 ℃, or 60 ℃ to 100 ℃, or 60 ℃ to 90 ℃) is substantially the same as the desired feed density (1.02 g/ml to 1.06g/ml at 80 ℃ to 90 ℃). Typically, the working fluid contains, comprises, consists essentially of, or even consists of recycled solvent recovered from a middle distillate stream separated from the tar hydroprocessed product. The amount of working fluid in the tar-fluid mixture is typically about 40% by weight for various pyrolysis tars, but may vary, for example, from 20% to 60%, to provide a feed at a desired density that may be preselected.

With continued reference to FIG. 2, the heat treated tar stream is directed to centrifuge 600 via line 65 through valve V3. The liquid product is stored and/or subjected to defined hydrotreating via line 66. At least a portion of the solids removed during centrifugation are conducted away via line 67, e.g., for storage or further processing.

Similarly in FIG. 3, the heat treated tar stream from process A via line 65A and the heat treated tar stream from process B via line 65B are combined in line 65AB and conducted to centrifuge 600 via valve V10. The liquid product is conducted to downstream hydroprocessing facilities via lines 66 and 69. Solid product is removed via line 67 and may be conducted away. Line 68 carries the centrifuge liquid product for storage. The dispensing of centrifuge liquid product to storage or to further downstream processing is controlled by the configuration of valves V11 and V12.

The centrifuge effectively removes particles from the feed, particularly those greater than or equal to 25 μm in size. The amount of particles ≧ 25 μm in the centrifuge effluent is typically less than 2% by volume of the total particles. Tars such as pyrolysis tars such as SCT typically contain a relatively large concentration of particles having a size <25 μm. For a representative tar, the amount of solids typically ranges from 100ppm to 170ppm with a median concentration of about 150 ppm. The majority of the solids in each tar were in the form of particles having a size <25 μm. Particles of such size are carried through the process without significant fouling.

After solids removal, the tar stream is subjected to additional processes to further reduce the reactivity of the tar prior to hydrotreating at intermediate hydrotreating conditions. These additional processes are collectively referred to as "pretreatment" and include pretreatment hydroprocessing in a guard reactor and then further hydroprocessing in an intermediate hydroprocessing reactor.

C, protecting the reactor

Use protectionReactor 704 (e.g., 704A, 704B in fig. 2) to protect downstream reactors from fouling from reacting olefins and solids, for example, by reducing tar reactivity and reducing fouling by any particles in the centrifuge effluent. This reduces the amount of fouling in the pretreater and other hydroprocessing stages located downstream of the guard reactor. When further reduction of tar reactivity such as R is desired_C<27BN this may be advantageous. In one or more configurations (illustrated in fig. 1 and 2), the two guard reactors are operated in an alternating mode — one online and the other offline. When one of the guard reactors exhibits an undesirable increase in pressure drop, it is taken off-line so that it can be serviced and restored to conditions for continued guard reactor operation. The recovery while off-line may be performed, for example, by replacing the reactor packing and replacing or regenerating the internals of the reactor, including the catalyst. Multiple (in-line) guard reactors may be used. Although the guard reactors (not shown) may be arranged in series, it is more common for at least two guard reactors to be arranged in parallel, as in fig. 2 and 3.

Referring again to FIG. 2, the thermally treated tar composition with substantially >25 μm solids removed is conducted via line 66 for treatment in at least one guard reactor. This composition is combined with the recovered working fluid comprising recycled solvent supplied via line 310 to produce a tar-fluid mixture in line 320. Optionally, a supplemental recycle solvent or working fluid may be added via conduit 330. The first preheater 70 preheats the tar-fluid mixture (which is typically primarily in the liquid phase) and conducts the preheated mixture to the supplemental preheating stage 90 via conduit 370. The supplemental pre-adder stage 90 may be, for example, a fired heater. Recycled process gas is taken from conduit 265 and, if necessary, mixed with fresh process gas supplied through conduit 131. The process gas is conducted through a second preheater 360 via conduit 20 before being conducted to the supplemental preheater stage 90 via conduit 80. Fouling in line 110 and in the intermediate hydroprocessing reactor can be reduced by increasing the feed preheater duty in, for example, preheaters 70 and 90.

With continued reference to fig. 2, the preheated tar-fluid mixture (from line 380) is combined with the pretreated treatment gas (from line 390) and then conducted to the guard reactor inlet manifold 700 via line 410. A mixing device (not shown) may be used for combining the preheated tar-fluid mixture with the preheated process gas in the guard reactor inlet manifold 700. The guard reactor inlet manifold directs the combined tar-fluid mixture and treatment gas to an in-line guard reactor, e.g., 704A, via a suitable configuration of guard reactor inlet valves 702A (shown open) and 702B (shown closed). An offline protective reactor 704B is illustrated that may be isolated from the pretreatment inlet manifold by a closed valve 702B and a second isolation valve (not shown) downstream of the outlet of reactor 704B. While reactor 704B is brought online, online reactor 704A may also be taken offline and isolated from the process. Reactors 704A and 704B are typically taken off-line in sequence (one after the other), with one 704A or 704B on-line and the other off-line, e.g., for regeneration. The effluent from the in-line guard reactor(s) is conducted to further downstream processes via guard reactor outlet manifold 706 and line 708.

The guard reactor is operated under guard reactor hydrotreating conditions. Typically, these conditions include a temperature in the range of 200 ℃ to 300 ℃, more typically 200 ℃ to 280 ℃, or 250 ℃ to 270 ℃, or 260 ℃ to 300 ℃; the total pressure is in the range of 1,000psia to 1,600psia, typically 1,300psia to 1,500psia, and the space velocity, e.g., weight hourly space velocity ("WHSV"), is 5hr^-1To 7hr^-1Within the range. The guard reactor contains a catalytically effective amount of at least one hydrotreating catalyst. Typically, the upstream bed of the reactor comprises at least one catalyst having demetallization activity (e.g. a relatively large pore catalyst) to capture the metals in the feed. The bed located further downstream in the reactor usually contains at least one catalyst having olefin saturation activity, for example a catalyst containing Ni and/or Mo. The guard reactor generally receives a reactive R_M<18BN tar-fluid mixture as a feed, on a feed basis, wherein the tar component of the tar-fluid mixture has R_TAnd/or R_C<30BN, e.g.<28BN, based on tar.

Pretreatment hydrotreater

A pretreatment hydrotreater can be used downstream of the guard reactor to reduce fouling buildup in the intermediate hydrotreatment reactor. As shown in fig. 1, when the preconditioner effluent, such as the effluent of preconditioner F in fig. 1, has a reactivity of 17BN, then reactor G exhibits a significant dP in about 20 days. When the reactivity of the effluent of reactor F is in the 12BN-15BN range, the run length of reactor G increases from 20 days to more than 3 months.

Some forms of pretreating a hydroprocessing reactor will now be described with continued reference to fig. 2. In these aspects, the tar-fluid mixture is hydrotreated under the prescribed pretreatment hydrotreating conditions described below to produce a pretreated hydrotreater (preheater) effluent. The invention is not limited to these aspects and the description is not meant to exclude other aspects within the broader scope of the invention.

Pretreatment hydrotreating conditions

The SCT composition is combined with a working fluid comprising a recycle solvent to produce a tar-fluid mixture that is hydrotreated in a preconditioner hydrotreater in the presence of molecular hydrogen under pretreatment hydrotreatment conditions to produce a preconditioner hydrotreater reactor effluent. The pretreat hydrotreating is typically carried out in at least one hydrotreating zone (415, 416, 417) located in at least one pretreat hydrotreating reactor 400. The pretreatment hydroprocessing reactor can take the form of a conventional hydroprocessing reactor, but the invention is not so limited.

The pretreatment hydroprocessing is conducted under pretreatment hydroprocessing conditions to further reduce the reactivity of the tar stream (tar-working fluid stream) after the thermal treatment (e.g., by heat soaking) step and the initial pretreatment stage in the guard reactor. The pretreatment hydrotreating conditions include a temperature T_PTTotal pressure P_PTAnd space velocity WHSV_PT. One or more of these parameters are generally different from those of the intermediate hydrotreatment (T)_I、P_IAnd/or WHSV_I). Pretreatment ofThe hydrotreating conditions typically include one or more of the following: t is_PT150 ℃ or more, for example 200 ℃ or more but less than T_I(e.g. T)_PT≤T _I10 ℃ C, e.g. T_PT≤T_IAt 25 ℃ C, e.g. T_PT≤T_I-50 ℃) of total pressure P_PTIs more than or equal to 8MPa and less than P_I，WHSV_PT≥0.3hr^-1And is greater than WHSV_I(e.g., WHSV_PT>WHSV_I+0.01hr^-1E.g.. gtoreq.WHSV_I+0.05hr^-1Or not less than WHSV_I+0.1hr^-1Or not less than WHSV_I+0.5hr^-1Or not less than WHSV_I+1hr^-1Or not less than WHSV_I+10hr^-1Or greater), and a molecular hydrogen consumption rate of 150 normal cubic meters of molecular hydrogen per cubic meter of pyrolysis tar (S m)³/m³) -about 400S m³/m³(845SCF/B to 2250SCF/B) but less than the molecular hydrogen consumption rate of the intermediate hydrotreatment. The pretreatment hydrotreating conditions generally include T_PTIn the range of 260 ℃ to 300 ℃; WHSV_PTAt 1.5hr^-1-3.5hr^-1E.g. 2hr^-1To 3hr^-1Within the range; p_PTIn the range of 6MPa-13.1 MPa; molecular hydrogen supply rate of about 600 standard cubic feet per barrel of tar-fluid mixture (SCF/B) (107S m³/m³) To 1,000SCF/B (178S m)³/m³) And a molecular hydrogen consumption rate of 300 standard cubic feet per barrel of tar-fluid mixture (SCF/B) (53S m)³/m³)-400SCF/B(71S m³/m³) Within the range.

The pretreatment hydroprocessing is performed in the presence of hydrogen gas, such as by (i) combining molecular hydrogen with the tar-fluid mixture upstream of the pretreatment hydroprocessing and/or (ii) conducting the molecular hydrogen to the pretreatment hydroprocessing reactor in one or more conduits or lines. While relatively pure molecular hydrogen may be used for hydroprocessing, it is generally desirable to use a "treat gas" that contains sufficient molecular hydrogen for pretreatment hydroprocessing and optionally other materials (e.g., nitrogen and light hydrocarbons such as methane) that generally do not adversely interfere with or affect the reactions or products. The treat gas optionally contains greater than or equal to about 50 volume percent molecular hydrogen, such as greater than or equal to 75 volume percent, such as greater than or equal to 90 volume percent, based on the total volume of the treat gas conducted to the pretreatment hydroprocessing stage.

Typically, the pretreatment hydroprocessing in at least one hydroprocessing zone of a pretreatment hydroprocessing reactor is conducted in the presence of a catalytically effective amount of at least one catalyst having hydrocarbon hydroprocessing activity. Conventional hydroprocessing catalysts can be used for pretreatment hydroprocessing, such as those specified for use in the hydroprocessing of resids and/or heavy oils. Suitable pretreatment hydrotreating catalysts include bulk (bulk) metal catalysts and supported catalysts. The metal may be in elemental form or in the form of a compound.

Typically, the tar-fluid mixture in the guard reactor effluent fed to the pretreatment hydroprocessing reactor is predominantly in the liquid phase during the pretreatment hydroprocessing. For example, not less than 75 wt% of the tar-fluid mixture is in the liquid phase during hydrotreating, such as not less than 90 wt%, or not less than 99 wt%. The pretreatment hydroprocessing produces a preconditioner effluent comprising, at the outlet of the pretreatment reactor, (i) a major gas phase portion comprising unreacted treatment gas, such as major gas phase products derived from the treatment gas and tar-fluid mixture during the pretreatment hydroprocessing, and (ii) a major liquid phase portion comprising the pretreated tar-fluid mixture, unreacted recycle solvent or working fluid, and products of the pyrolysis tar and/or working fluid, such as cracked products, which may be produced during the pretreatment hydroprocessing. The liquid fraction (i.e., the pretreated tar-fluid mixture containing the pretreated pyrolysis tar) also typically contains insolubles and is reactive (R)_F) 12BN, for example 11BN, for example 10 BN.

Certain aspects of the pretreatment hydroprocessing will now be described in more detail with respect to fig. 2. As shown in the figure, the guard reactor effluent flows from the guard reactor to the pretreatment reactor 400 via line 708. The guard reactor effluent may be mixed with additional process gas (not shown); additional process gases may also be preheated. A mixing device (not shown) may be used for combining the guard reactor effluent with the preheated process gas in the pretreatment reactor 400, such as a gas-liquid distributor of the type conventionally used in one or more fixed bed reactors.

The pretreatment hydrotreating is conducted in the presence of hydrotreating catalyst(s) located in at least one catalyst bed 415. Additional catalyst beds such as 416, 417 may be connected in series with catalyst bed 415, optionally with intermediate cooling (not shown) provided between the beds using process gas from conduit 20. The preconditioner effluent is conducted away from pretreatment reactor 400 via conduit 110.

In certain aspects, the following pretreatment hydrotreating conditions are used to achieve the target reactivity (in BN) in the pretreater effluent: t is_PTAt a temperature in the range of 250 ℃ to 325 ℃, or 275 ℃ to 325 ℃, or 260 ℃ to 300 ℃, or 280 ℃ to 300 ℃; WHSV_PTAt 2hr^-1-3hr^-1Within the range of P_PTIn the range of 1,000psia-1,600psia, e.g., 1,300psia to 1,500 psia; and total pressure; the process gas rate is in the range of 600SCF/B to 1,000SCF/B, or 800SCF/B to 900SCF/B (on a feed basis). Under these conditions, the reactivity of the preconditioner effluent is generally<12BN。

E: intermediate hydroprocessing

Referring again to fig. 1, the intermediate hydroprocessing reactor G is used to perform most of the desired tar conversion reactions, including hydrogenation and first desulfurization reactions. The intermediate hydroprocessing reactor adds molecular hydrogen of about 800SCF/B to 2,000SCF/B to the feed, for example about 1,000SCF/B to 1,500SCF/B, the majority of which is added to the tar rather than the recycle solvent or working fluid.

The first set of tar conversion reactions may be used to reduce the molecular size of the tar, particularly the TH. Doing so resulted in a significant reduction in the 1,050 ° F + fraction of tar. Hydrodesulfurization (HDS) may be used to remove tar. For SCT, few alkyl chains survive steam cracking-most molecules are dealkylated. As a result, sulfur-containing molecules such as benzothiophenes or dibenzothiophenes often containExposed sulfur. These sulfur-containing molecules are readily removed using one or more conventional hydrotreating catalysts, although the invention is not so limited. Suitable conventional catalysts include those on a support such as an aluminate (Al)₂O₃) Those containing one or more of Ni, Co and Mo. Additional tar conversion reactions may be used, and these typically include ring opening after hydrogenation to further reduce the size of the tar molecules. Aromatic saturation reactions may also be used. It was found that adding hydrogen to any of the products from these reactions improved the quality of the hydrotreated tar.

In certain aspects, intermediate hydrotreating of at least a portion of the pretreated tar-fluid mixture is carried out in reactor G at intermediate hydrotreating conditions, e.g., to achieve at least hydrogenation and desulfurization. This intermediate hydrotreatment will now be described in more detail.

Intermediate hydroprocessing of pretreated tar-fluid mixtures

In certain aspects not shown in fig. 2, liquid and vapor portions are separated from the preconditioner effluent. The vapor portion is upgraded to remove impurities such as sulfur compounds and light paraffins, and the upgraded vapor may be recycled as a treat gas for use in one or more of the hydroprocessing reactors 704A, 704B, 400, 100, and 500. The separated liquid portion may be conducted to a hydrotreating stage operating at intermediate hydrotreating conditions to produce hydrotreated tar. Additional treatment of the liquid portion, such as solids removal, may be used upstream of the intermediate hydrotreatment.

In other aspects, as shown in fig. 2, the entire effluent of the preheater is directed from reactor 400 via line 110 for intermediate hydroprocessing of the entire pretreated hydrotreated effluent in intermediate hydroprocessing reactor 100 (reactor G in fig. 1). Those skilled in the art will appreciate that for a wide range of conditions within the pretreatment hydroprocessing conditions and for a wide range of tar-fluid mixtures, sufficient molecular hydrogen will remain in the pretreatment hydroprocessing effluent for intermediate hydroprocessing of the tar-fluid mixture pretreated in the intermediate hydroprocessing reactor 100 without the need for additional treat gas to be supplied, for example, from conduit 20.

Typically, the intermediate hydroprocessing in at least one hydroprocessing zone of the intermediate hydroprocessing reactor is carried out in the presence of a catalytically effective amount of at least one catalyst having hydrocarbon hydroprocessing activity. The catalyst may be selected from the same catalysts specified for use in the pretreatment hydroprocessing. For example, the intermediate hydrotreating is conducted in the presence of a catalytically effective amount of hydrotreating catalyst(s) located in at least one catalyst bed 115. Additional catalyst beds such as 116, 117 may be connected in series with catalyst bed 115, optionally with intermediate cooling (not shown) provided between the beds using process gas from conduit 60. The intermediate hydrotreated effluent is conducted away from the intermediate hydrotreating reactor 100 via line 120.

The intermediate hydroprocessing is carried out in the presence of hydrogen, for example by one or more of: (i) combining molecular hydrogen with the pretreated effluent upstream of the intermediate hydrotreatment (not shown), (ii) conducting molecular hydrogen to the intermediate hydrotreatment reactor in one or more conduits or lines (not shown), and (iii) using the molecular hydrogen in the pretreated hydrotreated effluent (e.g., in the form of an unreacted treat gas).

Typically, the intermediate hydrotreating conditions include T_I>400 ℃, e.g., in the range of 300 ℃ to 500 ℃, e.g., 350 ℃ to 430 ℃, or 350 ℃ to 420 ℃, or 360 ℃ to 410 ℃; and WHSV_IAt 0.3hr^-1-20hr^-1Or 0.3hr^-1To 10hr^-1Based on the weight of the pretreated tar-fluid mixture subjected to the intermediate hydrotreatment. It is also typical for the intermediate hydroprocessing conditions to include a molecular hydrogen partial pressure during hydroprocessing of 8MPa or more, or 9MPa or more, or 10MPa or more, although in some aspects it is 14MPa or less, such as 13MPa or 12MPa or less. For example, P_ICan be in the range of 6MPa to 13.1 MPa. In general, WHSV_IIs not less than 0.5hr^-1E.g.. gtoreq.1.0 hr^-1Or alternatively less than or equal to 5hr^-1E.g.. ltoreq.4 hr^-1Or less than or equal to 3hr^-1. Supplied to operation at intermediate hydroprocessing conditionsThe molecular hydrogen weight of the hydroprocessing stage is typically about 1,000SCF/B (standard cubic feet per barrel) (178S m³/m³)-10,000SCF/B(1780S m³/m³) In the context, where B refers to the barrel conducted to the intermediate hydrotreated pretreated tar-fluid mixture. For example, it may be at 3,000SCF/B (534S m)³/m³)-5,000SCF/B(890S m³/m³) Molecular hydrogen is provided within the range. The molecular hydrogen content of the pretreated pyrolysis tar component supplied with the hydrotreated pretreated tar-fluid mixture is generally less than if the pyrolysis tar component had not been pretreated and contained a greater amount of olefins such as C₆₊Olefins, such as vinyl aromatics. The molecular hydrogen consumption rate during intermediate hydroprocessing conditions is typically at 350 standard cubic feet per barrel (SCF/B, which is about 62 standard cubic meters per cubic meter (S m)³/m³) From about 1,500SCF/B (267S m)³/m³) In which the denominator represents barrel pretreated pyrolysis tar at about 1,000SCF/B (178S m)³/m³) To 1,500SCF/B (267S m)³/m³) Or about 2,200SCF/B (392S m)³/m³) To 3,200SCF/B (570S m)³/m³) Within the range of (1).

Within the parameter ranges (T, P and/or WHSV) specified for the intermediate hydroprocessing conditions, the particular hydroprocessing conditions are typically selected for a particular pyrolysis tar to (i) achieve the desired 566 deg.C + conversion (typically ≧ 20 wt%) for at least ten days substantially continuously, and (ii) produce TLP and a hydroprocessed pyrolysis tar having desired properties, such as a desired density and viscosity. The term 566 deg.C + conversion means the conversion during hydroprocessing of pyrolysis tar compounds with a normal boiling point ≧ 566 deg.C into compounds with a boiling point <566 deg.C. The 566℃ + conversion includes a high conversion rate of TH, resulting in a hydroprocessed pyrolysis tar having the desired properties.

Hydrotreating can be carried out under intermediate hydrotreating conditions for a significantly longer duration without significant reactor fouling (e.g., as evidenced by no significant increase in reactor dP during the desired duration of hydrotreating, such as a pressure drop of 140kPa or less, typically 70kPa or less or 35kPa during a hydrotreating duration of 10 days) than under substantially identical hydrotreating conditions for an unpretreated tar-fluid mixture. The duration of hydrotreating without significant fouling is typically at least 10 times, such as 100 times or more, such as 1,000 times greater than for a tar-fluid mixture without pretreatment.

In certain aspects, the intermediate hydrotreating conditions include T_IAt a temperature in the range of 350 ℃ to 500 ℃, 350 ℃ to 475 ℃, 350 ℃ to 450 ℃, 350 ℃ to 425 ℃, 350 ℃ to 400 ℃, 380 ℃ to 500 ℃, 380 ℃ to 475 ℃, 380 ℃ to 450 ℃, 380 ℃ to 425 ℃, 380 ℃ to 400 ℃, or 400 ℃ to 450 ℃; p_IIn the range of 1,000psi to 1,600psi, typically 1,300psi to 1,500 psi; WHSV_IAt 0.5hr^-1-1.2hr^-1Usually 0.7hr^-1To 1hr^-1Or 0.6hr^-1To 0.8hr^-1Or 0.7hr^-1To 0.8hr^-1Within the range; and a treat gas rate in the range of 2,000SCF/B to 6,000SCF/B, or 2,500SCF/B to 5,500SCF/B, or 3,000SCF/B to 5,000SCF/B (feed basis). The feed to the intermediate hydroprocessing reactor is generally reactive<12 BN. Tar in the feed to the intermediate hydroprocessing reactor: the weight ratio of the working fluid is typically in the range of 50-80:50-20, typically 60: 40. Typically, intermediate hydrotreating (hydrogenation and desulfurization) adds molecular hydrogen (feed basis) of 1,000SCF/B to 2,000SCF/B to the tar and can reduce the sulfur content of the tar by 80 wt% or more, such as 95 wt% or more, or in the range of 80 wt% to 90 wt%. In other aspects, first a T at a first temperature, e.g., less than 350 ℃_IIntermediate hydrotreating conditions are carried out. Then, for example, if the recycled solvent (e.g., middle distillates) recovered exhibit undesirable S_BNE.g. S_BN<110, T can be increased_ITo a second temperature of 350 ℃ or higher. E.g. T_ICan be increased from a first temperature in the range of 320 ℃ to 349 ℃, e.g., 325 ℃ to 445 ℃, or 330 ℃ to 440 ℃, to a second temperature of ≧ 350 ℃ to recover S of the recycled solvent_BNFrom S_BN<110 to S_BN≥110. Such as 115, such as 120, or 140. It has surprisingly been found that T can be increased without significantly altering other intermediate hydroprocessing conditions_ITo realize such S_BNAnd (4) improving.

In one or more embodiments, fig. 4 depicts a configuration of a preheater 420, a preheater 422, and several reactors 424, 426 that may be used in the hydroprocessing processes discussed and described herein. In one or more examples, hydrotreating the lower viscosity, reduced reactivity tar may include heating the lower viscosity, reducing the reactivity tar to a temperature of about 250 ℃ to about 275 ℃ in a preheater 420 and then heating the lower viscosity, reduced reactivity tar to a temperature of about 260 ℃ to about 300 ℃ in a hydrogen containing preheater 422. Hydrogen can be flowed into the preheater 420 at about 500 standard cubic feet per barrel (SCFB) to about 1,500SCFB, 700SCFB to about 1,200SCFB, or about 800SCFB to about 1,000SCFB, e.g., about 900 SCFB. Thereafter, the lower viscosity, reduced reactivity tar may be heated to a temperature of about 325 ℃ to about 375 ℃ in a first reactor 424 containing hydrogen. Hydrogen can be flowed into the first reactor 424 at about 800SCFB to about 2,000SCFB, 1,200SCFB to about 1,800SCFB, or about 1,400SCFB to about 1,600SCFB, for example about 1,500 SCFB.

Thereafter, the lower viscosity, reduced reactivity tar may be heated to a temperature of about 360 ℃ to about 450 ℃ in a second reactor 426 containing hydrogen. Hydrogen can be flowed into second reactor 426 at about 200SCFB to about 1,000SCFB, 400SCFB to about 800SCFB, or about 500SCFB to about 700SCFB, for example about 600 SCFB. In one or more examples, the lower viscosity, reduced reactivity tar is heated to a temperature of about 270 ℃ to about 280 ℃ in preheater 422, then heated to a temperature of about 340 ℃ to about 360 ℃ in first reactor 424, and then heated to a temperature of about 375 ℃ to about 400 ℃ in second reactor 426.

F, recovering the intermediate hydrotreated pyrolysis tar

Referring again to fig. 2, the hydrotreater effluent is directed away from the intermediate hydrotreatment reactor 100 via line 120. When the second and third preheaters (360 and 70) are heat exchangers, the hot hydrotreater effluent in conduit 120 can be used to preheat the tar/working fluid and treat gas, respectively, by indirect heat exchange. After this optional heat exchange, the hydrotreater effluent is conducted to separation stage 130 for separation of the total vapor product (e.g., heteroatom vapors, gas phase cracking products, unused treat gas, or any combination thereof) and the TLP from the hydrotreater effluent. The total vapor product is conducted via line 200 to an upgrading stage 220, which typically includes, for example, one or more amine columns. Fresh amine is conducted to stage 220 via line 230, with rich amine being conducted away via line 240. The regenerated treat gas is directed away from stage 220 via line 250, compressed in compressor 260, and conducted via lines 265, 20, and 21 for recycle and reuse in intermediate hydroprocessing reactor 100 and optionally in 2 nd hydroprocessing reactor 500.

The TLP from separation stage 130 typically contains hydroprocessed pyrolysis tar, e.g., > 10 wt.% hydroprocessed pyrolysis tar, e.g., >50 wt.%, or > 75 wt.%, or > 90 wt.%. The TLP optionally contains non-tar components, such as hydrocarbons having a true boiling point range substantially the same as the true boiling point range of the working fluid (e.g., unreacted recycle solvent or working fluid). TLPs can be used as diluents (e.g., diluents) for heavy hydrocarbons, particularly those having a relatively high viscosity. Optionally, all or a portion of the TLP may replace the more expensive conventional dilution. Non-limiting examples of blended feedstocks suitable for blending with TLPs and/or hydrotreated tars include one or more of the following: marine fuels; a burner oil; heavy fuel oils, such as fuel nos. 5 and 6; high sulfur fuel oil; low sulfur fuel oil; common sulfur fuel oil (RSFO); gas oils and the like that may be obtained from the distillation of crude oil, crude oil components, and hydrocarbons derived from crude oil (e.g., coker gas oil). For example, TLP may be used as a blending component to produce fuel compositions containing <0.5 wt% sulfur. While TLP is an improved product relative to pyrolysis tar feed and is a "as-is" useful blended feedstock, it is often beneficial to do further processing.

In the aspect illustrated in FIG. 2, the TLP from separation stage 130 is conducted via line 270 to further separation stage 280, such as for separating one or more of the following from the TLP: hydrotreated pyrolysis tar, additional steam, and at least one stream suitable for recycling as a working fluid or a component of a working fluid. Separation stage 280 can be, for example, a distillation column with a side-stream draw, although other conventional separation methods can be used. An overhead stream, a side stream, and a bottoms stream are separated from the TLP in stage 280, listed in order of increasing boiling point. An overhead stream (e.g., vapor) is conducted away from separation stage 280 via line 290. Typically, the bottoms stream conducted away via line 134 contains >50 wt.% of hydrotreated pyrolysis tar, e.g., > 75 wt.%, e.g., > 90 wt.%, or ≧ 99 wt.%; and typically constitutes about 40 wt% of the TLP in the main reactor (reactor 100), and typically about 67 wt% of the tar feed.

At least a portion of the overhead and bottoms streams may be conducted away, e.g., for storage and/or for further processing. The bottoms stream in line 134 can desirably be used as a diluent (e.g., diluent) for heavy hydrocarbons such as heavy fuel oil. When desired, at least a portion of the overhead stream 290 is combined with at least a portion of the bottoms stream 134 for further improvement in properties. Optionally, the separation stage 280 is adjusted to alter the boiling point profile of the side stream 340 such that the side stream 340 has the desired properties of the recycled solvent or working fluid, e.g., (i) an actual boiling point profile having an initial boiling point ≧ 177 ℃ (350 ° F) and a final boiling point ≦ 566 ℃ (1,050 ° F) and/or (ii) S _BN100, such as 120, such as 125, or 130. Optionally, trim molecules (trim molecules) may be separated and added to the sidestream 340, for example, in a fractionator (not shown) from the bottoms and/or overhead of the separation stage 280, as desired. A side stream (middle distillate) is conducted away from separation stage 280 via conduit 340. At least a portion of side stream 340 may be used as a working fluid and conducted via pump 300 and conduit 310. Typically, the side stream composition (middle distillate stream) of line 310 is at least 10 wt.%, such as ≧ 25 wt.%, such as ≧ 50 wt.% of the recycle solvent or working fluid.

Hydroprocessed pyrolysis tar products from intermediate hydroprocessing have desirable properties, for exampleThe density as measured at 15 ℃ is generally at least 0.10g/cm less than the density of the heat treated pyrolysis tar³. For example, the hydrotreated tar may have a density that is at least 0.12, or at least 0.14, or at least 0.15, or at least 0.17g/cm less than the density of the pyrolyzed tar composition³. The 50 ℃ kinematic viscosity of hydrotreated tars is generally ≦ 1,000 cSt. For example, the viscosity may be 500cSt or less, such as 150cSt or less, such as 100cSt or less, or 75cSt or less, or 50cSt or less, or 40cSt or less, or 30cSt or less. Generally, the intermediate hydroprocessing results in a significant viscosity improvement relative to pyrolysis tars conducted to the thermal treatment, pyrolysis tar compositions, and pretreated pyrolysis tars. For example, when the kinematic viscosity at 50 ℃ of the pyrolysis tar (e.g., obtained as feed from a tar knock-out drum) is ≧ 1 × 10⁴cSt, e.g.. gtoreq.1 x10⁵ cSt、≥1x10⁶cSt or ≥ 1x10⁷cSt, the 50 ℃ kinematic viscosity of hydrotreated tars is generally<200cSt, e.g.<150cSt，<100cSt、<75cSt、<50cSt、<40cSt or<30 cSt. Particularly when a given heat treated pyrolysis tar feed has a sulfur content of 1 wt.% or more, the hydrotreated tar typically has a sulfur content of 0.5 wt.% or more, for example in the range of about 0.5 wt.% to about 0.8 wt.%.

G working fluid recovery

An advantage of the specified process is that at least a portion of the working fluid can be obtained from the recycle stream. Typically,. gtoreq.50 wt%, such as 60 wt% to 90 wt%, for example 70 wt% to 85 wt%, of the middle distillate stream from fractionator 280 is recycled as recycled solvent for use as a working fluid or working fluid component. In certain aspects, the working fluid comprises ≧ 50 wt% recycle solvent, such as ≧ 60 wt%, such as in an amount ranging from 60 wt% -90 wt% or 70 wt% to 85 wt%, based on the weight of the working fluid. When the amount of recycled solvent in the working fluid is in the range of about 50 wt% to about 100 wt%, the amount of working fluid in the tar-fluid mixture is typically about 40 wt%, based on the weight of the tar-fluid mixture, but may range from 20 wt% to 50 wt%, or from 30 wt% to 45 wt%.

Can useOne or more distillation columns to recover a product having a defined S_BN(usually S)_BN110. gtoreq.110, for example 115. gtoreq.120, for example 140) is used as recycle solvent. Surprisingly, it has been found that the recovered recycle solvent can exhibit improved S relative to the working fluid used to perform the intermediate hydroprocessing_BN. For example, when the working fluid used to perform the intermediate hydrotreatment has S_BNIn the range of about 100 to 109, S of the recycled solvent recovered_BNGenerally exhibit S _BN110, such as 115, 120, or 140. This effect is achieved over a wide range of defined intermediate hydroprocessing conditions and for a wide range of steam cracker tars. In this manner, the addition (or substitution) of at least a portion of the recovered recycled solvent can be used to improve the process of making a product having less desirable S_BN(e.g. S)_BN<110) E.g. to realize working fluid S _BN110, such as 115, 120, or 140. Advantageously, this effect is achieved even when the boiling point range of the recovered recycle solvent is substantially the same as the boiling point range of the working fluid used in the intermediate hydroprocessing that produces the recovered recycle solvent. Any separation method (e.g., fractional distillation) that can provide a recycled solvent having a desired composition can be used. Conventional separations may be used, but the invention is not limited thereto. An additional about 20 weight percent of recycled solvent is produced in each cycle (based on the total weight of recycled solvent used as the working fluid), mostly as a result of conversion during the hydroprocessing of tar fractions having a normal boiling point ≧ 1,050 ° F (566 ℃). Additional recycle solvent produced by the process is used to supplement any over-hydrogenated recycle solvent or working fluid that may be purged from the process along with the light stream in a distillation fractionator located downstream of the first stage main reactor. The recovered light stream contains significant amounts of 1-or 2-ring aromatics. Generally, the molecule is in<Boiling at 400 ° F, with most of the composition boiling at 350 ° F. About 2 kbars/day (kbd) of middle distillate may be withdrawn from the fractionator(s). Recycled solvent that can be stored for recycle without recycling to tar upgrading processOther uses, such as blending into refinery diesel streams. The light stream may also be recovered and stored or transported for further processing or other uses.

Reprocessing of the reactor to further reduce sulfur

When it is desired to further improve the properties of the hydrotreated tar, such as by removing at least a portion of any sulfur remaining in the hydrotreated tar, the upgraded tar may be produced by optional reprocessing the hydrotreated tar. Some forms of reprocessing hydrotreating will now be described in more detail with respect to fig. 2. Reprocessing hydrotreatments are not limited to these forms and the description is not meant to exclude other forms of reprocessing hydrotreatments that are within the broader scope of the invention.

Referring again to FIG. 2, the hydrotreated tar (line 134) and the treat gas (line 21) are conducted to the retreatment reactor 500 via line 510. The reprocessing reactor 500 is generally smaller than the intermediate hydroprocessing reactor 100 (corresponding to reactor G in fig. 1). Generally, the reprocessing hydrotreatment in at least one hydrotreatment zone of the intermediate reactor is carried out in the presence of at least one catalyst having hydrocarbon hydrotreating activity. For example, the reprocessing hydrotreating is conducted in the presence of a hydrotreating catalyst located in one or more catalyst beds 515. Additional catalyst beds such as 516, 517 may be connected in series with catalyst bed 515, optionally with intermediate cooling (not shown) provided between the beds, for example using process gas from conduit 20. The reprocessor effluent containing upgraded tar is directed away from reactor 500 via line 135.

The description in this application is intended to be illustrative and not restrictive. Those skilled in the art will recognize that variations in the materials and methods used in the present invention and variations in the embodiments of the invention described herein are possible without departing from the present invention. It is to be understood that some embodiments of the invention may not exhibit all of the advantages of the invention or achieve each of the objects of the invention. The scope of the invention is limited only by the following claims. Certain embodiments and features have been described using a set of numerical upper limits and a set of numerical lower limits. It will be appreciated that ranges including any combination of two values, e.g., any lower value with any upper value, any combination of two lower values, and/or any combination of two upper values, are encompassed unless otherwise indicated. Certain lower limits, upper limits and ranges appear in one or more claims below.

Claims (26)

1. A process for producing a liquid hydrocarbon product comprising:

providing a reduced reactivity tar;

blending the reduced reactivity tar with a working fluid to produce a lower viscosity, reduced reactivity tar;

hydrotreating a lower viscosity, reduced reactivity tar at a temperature greater than 350 ℃ to produce a Total Liquid Product (TLP) comprising liquid hydrocarbon products and recycled solvent;

separating recycled solvent from the TLP, wherein the recycled solvent has a solubility blend value (S) greater than 110_BN) (ii) a And

the recycled solvent is flowed to the reduced reactivity tar for blending to produce a lower viscosity, reduced reactivity tar.

2. The process of claim 1, if recycling S of solvent_BNLess than 115, the method further comprising increasing the temperature of the lower viscosity, reduced reactivity tar during hydrotreating.

3. The method of claim 1 or 2, wherein the lower viscosity, reduced reactivity tar is hydrotreated at a temperature of greater than 350 ℃ to about 500 ℃.

4. The method of any of claims 1-3, wherein the lower viscosity, reduced reactivity tar is hydrotreated at a temperature of about 400 ℃ to about 450 ℃.

5. The method of any one of claims 1-4, wherein the working fluid comprises a recycled solvent, and wherein S of the recycled solvent_BNFrom greater than 110 to about 160.

6. The method of any one of claims 1-5, wherein S of solvent is recycled_BNFrom greater than 120 to about 150.

7. The method of any one of claims 1-6, wherein S of solvent is recycled_BNFrom about 130 to about 150.

8. The method of any of claims 1-7, further comprising treating the lower viscosity, reduced reactivity tar to remove solids therefrom prior to hydrotreating.

9. The method of any of claims 1-8, further comprising centrifuging the lower viscosity, reduced reactivity tar to remove substantially all solids having a size greater than 25 μ ι η.

10. The method of any one of claims 1-9, wherein the working fluid comprises a 2-ring aromatic, a 3-ring aromatic, a 4-ring aromatic, or any combination thereof.

11. The method of any one of claims 1-10, wherein the working fluid comprises a solvent selected from the group consisting of: benzene, ethylbenzene, trimethylbenzene, xylene, toluene, naphthalene, alkylnaphthalenes, tetralins, alkyltetralins, and any combination thereof.

12. The method of any of claims 1-11, wherein hydrotreating a lower viscosity, reduced reactivity tar further comprises:

heating the lower viscosity, reduced reactivity tar in a hydrogen-containing preconditioner to a temperature of from about 260 ℃ to about 300 ℃; then the

Heating the lower viscosity, reduced reactivity tar in a first reactor containing hydrogen to a temperature of about 325 ℃ to about 375 ℃; then the

The lower viscosity, reduced reactivity tar is heated in a second reactor containing hydrogen to a temperature of about 360 ℃ to about 450 ℃.

13. A process for producing a liquid hydrocarbon product comprising:

heat soaking the tar stream to produce reduced reactivity tar;

blending the reduced reactivity tar with a working fluid to produce a lower viscosity, reduced reactivity tar;

centrifuging the lower viscosity, reduced reactivity tar to remove solids therefrom; then the

Hydrotreating a lower viscosity, reduced reactivity tar at a temperature greater than 350 ℃ to produce a Total Liquid Product (TLP) comprising liquid hydrocarbon products and recycled solvent;

separating recycled solvent from the TLP, wherein the recycled solvent has a solubility blend value (S) greater than 115_BN) (ii) a And

the recycled solvent is flowed to the reduced reactivity tar for blending to produce a lower viscosity, reduced reactivity tar.

14. The process of claim 13 if recycling S of solvent_BNLess than 120, the method further comprising increasing the temperature of the lower viscosity, reduced reactivity tar during hydrotreating.

15. The method of claim 13 or 14, wherein the lower viscosity, reduced reactivity tar is hydrotreated at a temperature of greater than 350 ℃ to about 500 ℃.

16. The method of claim 15, wherein the temperature is from about 400 ℃ to about 450 ℃.

17. The method of any one of claims 13-16, wherein the working fluid comprises a recycled solvent, and wherein S of the recycled solvent_BNFrom greater than 120 to about 150.

18. The method of claim 17, wherein S of the solvent is recycled_BNFrom about 130 to about 150.

19. The method of any of claims 13-16, wherein the lower viscosity, reduced reactivity tar is substantially free of solids having a size greater than 25 μ ι η after centrifugation.

20. The method of any one of claims 13-16, wherein the working fluid comprises a 2-ring aromatic, a 3-ring aromatic, a 4-ring aromatic, or any combination thereof.

21. The method of any one of claims 13-16, wherein the working fluid comprises a solvent selected from the group consisting of: benzene, ethylbenzene, trimethylbenzene, xylene, toluene, naphthalene, alkylnaphthalenes, tetralins, alkyltetralins, and any combination thereof.

22. A process for producing a liquid hydrocarbon product comprising:

heat soaking the tar stream to produce reduced reactivity tar;

blending the reduced reactivity tar with a working fluid to produce a lower viscosity, reduced reactivity tar;

hydrotreating a lower viscosity, reduced reactivity tar at a temperature greater than 350 ℃ to produce a Total Liquid Product (TLP) comprising liquid hydrocarbon products and recycled solvent;

separating the recycled solvent from the TLP;

measurement of solubility blending value (S) of recycled solvent_BN)；

If recycling S of the solvent_BNLess than 115, increasing the temperature of the lower viscosity, reduced reactivity tar during hydrotreating; and

the recycled solvent is flowed to the reduced reactivity tar for blending to produce a lower viscosity, reduced reactivity tar.

23. The method of claim 22, wherein the temperature of the lower viscosity, reduced reactivity tar is from about 400 ℃ to about 450 ℃.

24. The method of claim 22 or 23, wherein the working fluid comprises a recycled solvent, and wherein S of the recycled solvent_BNFrom about 130 to about 150.

25. A process for producing a liquid hydrocarbon product comprising:

heat soaking the tar stream to produce a first process stream comprising reduced reactivity tars;

blending the first process stream with a working fluid to reduce the viscosity of the first process stream and produce a second process stream comprising solids and reduced-reactivity, lower-viscosity tars;

centrifuging the second process stream to produce a third process stream comprising reduced reactivity, lower viscosity tars and having a solids concentration less than the second process stream;

hydrotreating the third process stream at a temperature of greater than 350 ℃ to about 450 ℃ to produce a fourth stream comprising liquid hydrocarbon product and recycle solvent;

separating the recycled solvent from the fourth stream, wherein the recycled solvent has a solubility blend value (S) of about 130 to about 150_BN) (ii) a And

the recycled solvent is flowed to the first process stream for blending to produce a second process stream.

26. A process for producing hydrotreated tar, the process comprising:

(a) providing a process stream comprising reduced reactivity tars;

(b) mixing a process stream with a blend value (S) having solubility_BN)<110 to produce a tar-fluid mixture;

(c) catalytically hydroprocessing the tar-fluid mixture to produce a Total Liquid Product (TLP) comprising liquid hydrocarbon products and a working fluid;

(d) separating a recycle solvent and a hydroprocessed tar from the TLP, wherein the recycle solvent has a true boiling point range substantially the same as the true boiling point range of the working fluid and has a solubility blend value (S)_BN) More than or equal to 110; and

(e) replacing the working fluid in step (b) with at least a portion of the recycled solvent.

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