CN107557069B

CN107557069B - Method and system for hydro-conversion of coal tar raw material

Info

Publication number: CN107557069B
Application number: CN201610514028.6A
Authority: CN
Inventors: 李猛; 王蕴; 王卫平; 吴昊; 黄放
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2016-06-30
Filing date: 2016-06-30
Publication date: 2020-03-24
Anticipated expiration: 2036-06-30
Also published as: CN107557069A

Abstract

The invention relates to the field of coal tar processing, and discloses a method for hydro-conversion of a coal tar raw material and a system for hydro-conversion of the coal tar raw material, wherein the method comprises the following steps: carrying out water and/or impurity removal pretreatment on a coal tar raw material; in the presence of hydrogen and a slurry bed catalyst, carrying out mild hydrotreating on the obtained material; carrying out gas-liquid separation and fractionation on the obtained materials in sequence; throwing out part of the heavy fraction; and recycling part of the first middle fraction and the remaining heavy fraction to the slurry bed reactor; and subjecting the light fraction, the second middle fraction and the remaining first middle fraction to a hydrofining reaction; carrying out gas-liquid separation and fractionation on the effluent in sequence; resulting in a naphtha fraction, a diesel fraction and a wax oil fraction. The invention effectively combines the slurry bed and the fixed bed, realizes the clean and efficient utilization of the coal tar resource, improves the liquid yield and the utilization rate and the utilization value of the coal tar resource to the maximum extent, and prolongs the running period of the device to a certain extent.

Description

Method and system for hydro-conversion of coal tar raw material

Technical Field

The invention relates to the field of coal tar processing, in particular to a coal tar raw material hydro-conversion method and a coal tar raw material hydro-conversion system.

Background

With the continuous and high-speed development of social economy, the demand of China on petroleum products is increasing day by day.

However, petroleum is an irrenewable energy source and is facing a crisis of increasing exhaustion. In contrast, Chinese coal reserves are abundant, and therefore, the preparation of liquid fuel from coal has become a fundamental direction for coal processing and utilization.

With the rapid growth of the international and domestic steel industry, the coking industry has a high growth trend, the yield of coal tar is larger and larger, and the clean processing and effective utilization of the coal tar are more and more important. At present, the conventional coal processing method is to cut various fractions with concentrated components through pretreatment distillation, and then treat the various fractions by methods such as acid-base washing, distillation, polymerization, crystallization and the like to extract pure products; and part of the coal tar is directly combusted as inferior fuel oil after being subjected to acid-base refining, or is directly combusted as emulsified fuel after being directly emulsified. Impurities such as sulfur, nitrogen and the like in coal tar are changed into oxides of sulfur and nitrogen in the combustion process and released into the atmosphere to cause atmospheric pollution, and a large amount of sewage is generated in the acid-base refining process to seriously pollute the environment. Therefore, from the viewpoint of environmental protection and comprehensive utilization of the environment, an effective chemical processing way is expected to be found, so that the coal tar is upgraded, and the utilization value of the coal tar is expanded. How to effectively utilize coal tar resources and make the coal tar resources meet the requirement of environmental protection is always the research direction of all countries.

CN1766058A discloses a coal tar whole fraction hydrotreating method, and specifically discloses that coal tar whole fraction directly enters a suspension bed hydrogenation device, or enters the suspension bed device after being uniformly mixed with a homogeneous catalyst for hydrotreating and lightening reaction, water, fraction below 370 ℃ and tail oil above 370 ℃ are cut from a material flow generated after the reaction by a distillation device, wherein the fraction below 370 ℃ enters a fixed bed reactor for hydrofining reaction, gasoline below 150 ℃ and diesel oil at 150 and 370 ℃ are cut from the refined product, and the tail oil above 370 ℃ is circulated back to the suspension bed reactor for further conversion into light oil. After the light oil fraction at the temperature of less than 370 ℃ in the prior art enters a fixed bed for hydrofining, the property of the diesel oil product is still poorer, the density is higher and the cetane number is lower, and a deep dearomatization reactor is added for further improving the property of the diesel oil product, so that the method in the prior art increases the investment of a device and complicates the process, and requires harsh reaction conditions for deep dearomatization, which inevitably causes the loss of the liquid product. Therefore, the method provided by the prior art has complex flow and low liquid yield.

CN101885982A discloses a coal tar suspension bed hydrogenation method of a heterogeneous catalyst, which comprises the steps of coal tar raw material pretreatment and distillation separation, coal tar heavy fraction suspension bed hydrocracking and light distillate oil fixed bed upgrading. Most of the tail oil containing the catalyst after the light oil is separated from the hydrogenation reaction product is directly circulated to the suspension bed reactor, and a small part of the tail oil is subjected to catalyst removal treatment and then is circulated to the suspension bed reactor, so that the light oil is further lightened, and the heavy oil is completely or maximally circulated, so that the aims of maximally producing the light oil from the coal tar and recycling the catalyst are fulfilled. In fact, the prior art cracks heavy fraction at more than 370 ℃ through hydrocracking in a suspension bed to obtain light fraction at less than 370 ℃, and the suspension bed reactor is inevitably required to have higher conversion depth, and the higher conversion depth increases the byproducts of dry gas, liquefied gas and coke, thereby influencing the yield of liquid products.

CN103059973A discloses a coal tar full-fraction hydrogenation slurry bed and fixed bed coupling method, which mainly comprises five units of coal tar raw material pretreatment, slurry bed hydrocracking, primary hydrogenation product fractionation, fixed bed hydrofining and product rectification. The coal tar full distillate oil is pretreated by dehydration, dust removal and the like, is mixed with a hydrocracking catalyst and is preheated, then enters a slurry bed reactor for hydrocracking reaction, the light component obtained by fractionating the reacted primary hydrogenation product enters a fixed bed hydrofining unit, the middle fraction and the catalyst circulate back to the slurry bed hydrogenation reactor, and the heavy component is filtered to remove part of the catalyst and coke generated by cracking returns to the tar pretreatment unit for circular hydrogenation. The light component is rectified to obtain gasoline and diesel oil products after conventional hydrofining. The light components in the prior art enter a fixed bed hydrogenation unit, and the middle distillate and the heavy distillate are recycled to a slurry bed hydrogenation unit, so that the slurry bed hydrogenation reactor is required to reach a higher conversion depth, and the higher conversion depth increases the byproducts of dry gas, liquefied gas and coke, thereby influencing the yield of liquid products.

In the prior art, slurry bed coal tar hydrogenation mainly refers to the concept of slurry bed hydrogenation of petroleum-based heavy raw materials such as atmospheric residue, vacuum residue and the like, and the main purpose of the slurry bed coal tar hydrogenation is to realize the lightening of the heavy raw materials. Specifically, the heavy components are converted into light fractions at the temperature of less than 370 ℃ through a slurry bed reactor, and then the light fractions at the temperature of less than 370 ℃ are sent to a subsequent fixed bed hydrogenation unit for further hydrogenation and upgrading to produce clean fuel and the like.

However, the method of the prior art is easy to coke to form coke or deposit to block the inner components of the reactor, which is one of the main reasons that the prior coal tar slurry bed hydrogenation device cannot operate stably for a long period.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a method for hydro-conversion of a coal tar raw material so as to improve the liquid yield to the maximum extent, reduce the yield of coke and improve the utilization rate and the utilization value of coal tar resources.

In order to achieve the above object, in a first aspect, the present invention provides a method for hydroconversion of a coal tar feedstock, the method comprising:

(1) introducing a coal tar raw material into a pretreatment unit for water removal and/or impurity removal pretreatment;

(2) introducing the material obtained in the step (1) into a slurry bed hydrogenation reactor of a slurry bed hydrogenation unit for mild hydrogenation treatment in the presence of hydrogen and a slurry bed catalyst;

(3) carrying out gas-liquid separation and fractionation on the material obtained in the step (2) in sequence to obtain a light fraction, a first middle fraction, a second middle fraction and a heavy fraction, wherein the final boiling point of the first middle fraction is smaller than the initial boiling point of the second middle fraction;

(4) throwing out part of the heavy fraction; recycling part of the first middle fraction and the rest of the heavy fraction to the slurry bed hydrogenation reactor for mild hydrogenation treatment; and introducing the light fraction, the second middle fraction and the remaining portion of the first middle fraction into a finishing reactor of a fixed bed hydrogenation unit for a hydrofinishing reaction;

(5) sequentially carrying out gas-liquid separation and fractionation on the effluent of the refining reactor; resulting in a naphtha fraction, a diesel fraction and a wax oil fraction.

In a second aspect, the present invention provides a system for hydroconversion of a coal tar feedstock, the system comprising:

a pre-processing unit;

the slurry bed hydrogenation unit comprises a slurry bed hydrogenation reactor, and the material treated by the pretreatment unit enters the slurry bed hydrogenation reactor for hydrogenation conversion;

a first separation unit having a light fraction transfer line, a first middle fraction transfer line a, a first middle fraction transfer line B, a second middle fraction transfer line, a first heavy fraction transfer line, and a second heavy fraction transfer line, in which the material from the slurry bed hydrogenation unit is sequentially separated and fractionated to obtain a light fraction, a first middle fraction, a second middle fraction, and a heavy fraction, a portion of the heavy fraction being thrown out through the first heavy fraction transfer line, a portion of the first middle fraction and the remaining portion of the heavy fraction being recycled to the slurry bed hydrogenation reactor through the first middle fraction transfer line a and the second heavy fraction transfer line, respectively;

a fixed bed hydrogenation unit comprising a finishing reactor into which the second middle distillate, the light fraction and the remaining part of the first middle distillate from the first separation unit are introduced through the second middle distillate conveying line, the light fraction conveying line and the first middle distillate conveying line B, respectively, to perform a hydrofining reaction; and

a second separation unit in which the material from the fixed bed hydrogenation unit is sequentially separated and fractionated to obtain a naphtha fraction, a diesel fraction and a wax oil fraction.

The method utilizes the characteristic of strong raw material adaptability of the slurry bed hydrogenation reactor, firstly performs mild hydrogenation pretreatment on the inferior coal tar raw material with high metal content and high mechanical impurity content to remove metal, mechanical impurity and the like in the raw material, and recycles part of fractions back to the slurry bed hydrogenation reactor to inhibit asphaltene deposition or generate coke to influence the liquid yield and the stable operation of the device, thereby achieving the purposes of improving the liquid yield to the maximum extent, prolonging the operation period of the device and providing proper feeding for a subsequent fixed bed hydrogenation unit, and then finally obtaining a clean product with high added value by utilizing the subsequent fixed bed hydrogenation reactor.

The method provided by the invention realizes the clean and efficient utilization of the coal tar resource by utilizing the effective combination of the slurry bed and the fixed bed, improves the liquid yield to the maximum extent, improves the utilization rate and the utilization value of the coal tar resource, and prolongs the running period of the device to a certain extent.

The method for hydro-conversion of the coal tar raw material not only solves the problem that the operation period of the coal tar hydrogenation device of the prior fixed bed is seriously influenced due to the high content of metal, mechanical impurities and the like in the coal tar whole fraction raw material, but also achieves the purposes of removing the metal and the mechanical impurities from the coal tar raw material through mild hydrogenation pretreatment, avoiding the generation of byproducts and ensuring higher liquid yield by effectively controlling the hydro-conversion depth of a slurry bed reaction unit under the optimal condition.

On the other hand, the method can more effectively inhibit the asphaltene in the coal tar from precipitating and depositing or coking to generate coke by recycling part of the distillate to the slurry bed hydrogenation reactor, which is beneficial to further improving the liquid yield of the device and ensuring the long-period stable operation of the device.

The method provided by the invention not only solves the problem of low liquid yield in the prior art, but also effectively solves the problems that the fixed bed coal tar hydrogenation device in the prior art has short running period and asphaltene is precipitated and deposited or coked to generate coke during slurry bed hydrogenation.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a process flow diagram of the method of hydroconversion of the coal tar feedstock of the present invention.

Description of the reference numerals

1. Coal tar raw material 2, pretreatment unit 3, water and mechanical impurities

4. A slurry bed catalyst 5, a slurry bed hydrogenation reactor 6, a first separation unit

7. A first hydrogen-rich gas 8, a first recycle hydrogen compressor 9, and fresh hydrogen

10. First recycle hydrogen 11, first separated water 12, first fractionating tower

13. A tower top reflux tank 14, a first tower top gas 15 and second separated water

16. Light fraction 17, first middle fraction 18, heavy fraction

19. External throwing heavy fraction 20, refining reactor 21, refining effluent

22. Second separation unit 23, second separation water 24, second liquid hydrocarbon stream

25. A second hydrogen-rich gas 26, a second fractionating column 27, and a second overhead gas

28. Naphtha fraction 29, diesel fraction 30, wax oil fraction

31. Cracking reactor 32, cracked effluent 33, third separation unit

34. A third liquid hydrocarbon stream 35, a third hydrogen rich gas 36, a second recycle hydrogen compressor

37. Second recycle hydrogen 38, second middle distillate

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

In a first aspect, the present invention provides a method for hydroconversion of a coal tar feedstock, the method comprising:

(4) throwing out part of the heavy fraction; and recycling a portion of said first middle fraction and a remaining portion of said heavy fraction back to said slurry bed hydrogenation reactor for mild hydrotreating; and introducing the light fraction, the second middle fraction and the remaining portion of the first middle fraction into a finishing reactor of a fixed bed hydrogenation unit for a hydrofinishing reaction;

In the present invention, "a part of the heavy fraction" means a part of the entire heavy fraction obtained in step (3); the "remaining part of the heavy fraction" means the remaining part of the entire heavy fraction obtained in step (3) except for "part of the heavy fraction". In other words, said "part of said heavy fraction" and said "remaining part of said heavy fraction" constitute the entire heavy fraction obtained in step (3). And for "part of said first middle fraction" and "the remaining part of said first middle fraction", there are explanations similar to those described above, and the present invention will not be described in detail here.

The method for hydro-conversion of the coal tar raw material has the characteristics of high liquid yield, good product quality, long device running period and the like.

The aforementioned naphtha fraction and diesel fraction of the present invention can be discharged as a product from the apparatus.

The method of the invention has no special limitation on the specific operation mode of the water removal and/or impurity removal pretreatment of the pretreatment unit, as long as the purpose of primarily removing water and mechanical impurities in the coal tar raw material can be achieved. For example, the pretreatment for water removal and/or impurity removal may be performed by settling and/or centrifugation.

The method of the present invention has no particular requirement for the specific operation method of the gas-liquid separation and the fractionation, and for example, the gas-liquid separation may be carried out in a conventional gas-liquid separation apparatus, and the fractionation may be carried out in, for example, a fractionation column.

Preferably, the final distillation point of the light fraction is 150-200 ℃; the final boiling point of the first middle distillate is 330-400 ℃; the final boiling point of the second middle distillate is 460-510 ℃; more preferably, the final distillation point of the light fraction is 160-190 ℃; the final boiling point of the first middle distillate is 360-390 ℃; the final boiling point of the second middle distillate is 480-500 ℃. In the present invention, it is to be noted that a fraction having a distillation range of not more than the endpoint of the light fraction is the light fraction; similarly, the fraction having a distillation range of more than the end point of the light fraction and not more than the end point of the first intermediate fraction is the first intermediate fraction; the distillation range of the fraction which is greater than the final distillation point of the first intermediate fraction and less than or equal to the final distillation point of the second intermediate fraction is the second intermediate fraction; the heavy fraction is a fraction having a boiling range greater than the endpoint of the second middle fraction.

Preferably, the portion of the first middle distillate recycled to the slurry bed hydrogenation reactor accounts for 10 to 35 wt%, more preferably 15 to 25 wt%, of the total amount of the first middle distillate obtained after step (3). The inventor of the invention finds that when the part of the first middle distillate recycled to the slurry bed hydrogenation reactor accounts for 10-35 wt%, more preferably 15-25 wt% of the total amount of all the first middle distillates obtained after the step (3), asphaltene precipitation or coking in coal tar can be effectively inhibited to generate coke, which is beneficial to further improving the liquid yield of the device and ensuring the long-period stable operation of the device.

The slurry bed catalyst can be a homogeneous slurry bed catalyst or a heterogeneous slurry bed catalyst, and the slurry bed catalyst is preferably a heterogeneous slurry bed catalyst in the invention. More preferably, the slurry bed catalyst is a highly dispersed heterogeneous slurry bed catalyst. The highly dispersed heterogeneous slurry bed catalyst may be at least one selected from the group consisting of iron-based catalysts, iron-based compounds, and iron-based carbon-based supported catalysts. The iron catalyst is selected from at least one of pyrite, hematite and red mud; the iron-based compound is selected from Fe₂S、Fe₂O₃And Fe₃O₄At least one of; the iron-based carbon-based supported catalyst comprises a carrier and an active metal element loaded on the carrier, wherein the carrier is a carbon-based material selected from at least one of coal dust, activated carbon, graphite and carbon black, and the active metal element is selected from at least one of W, Mo, Ni, Co and Fe.

Preferably, the average particle size of the iron-based catalyst is 10 to 200 μm.

Preferably, the amount of the slurry bed catalyst is 0.1-3.5 wt%, preferably 0.15-2.5 wt%, calculated by active metal elements contained in the slurry bed catalyst, based on the total weight of the coal tar raw material. To explain more specifically, when the slurry bed catalyst is an iron-based catalyst and/or an iron-based compound, the slurry bed catalyst is used in an amount based on the content of an iron element contained therein; when the slurry-bed catalyst is an iron-based carbon-based supported catalyst, the slurry-bed catalyst is used in an amount based on the content of an active metal element (e.g., W, Mo, Ni, Co, and Fe) contained therein.

Preferably, the thrown-out part of the heavy fraction accounts for 30-70 wt% of the total weight of the whole heavy fraction obtained after the step (3); preferably, the content of the heavy fraction is 40 to 60 wt% based on the total weight of the heavy fraction obtained in the step (3).

Preferably, the conditions of the mild hydrotreating in the step (2) are controlled so that the conversion rate of the heavy fraction obtained in the step (3) is 35 to 65 wt% based on the coal tar raw material; the conversion rate of the heavy fraction is (mass fraction of the heavy fraction in the coal tar raw material fed into the slurry bed hydrogenation reactor-mass fraction of the heavy fraction in the liquid hydrocarbon product at the outlet of the slurry bed hydrogenation reactor x liquid hydrocarbon yield%/100)/mass fraction of the heavy fraction in the coal tar raw material fed into the slurry bed hydrogenation reactor x 100. The liquid hydrocarbon product at the outlet of the slurry bed hydrogenation reactor is a liquid phase product obtained by gas-liquid separation of all materials at the outlet of the slurry bed hydrogenation reactor. The inventor of the invention discovers in research that when the conversion rate of the heavy fraction obtained in the step (3) is controlled to be 35-65 wt%, the asphaltene in coal tar can be obviously and effectively prevented from being precipitated and deposited or coked to generate coke, which is beneficial to further improving the liquid yield of the device and ensuring the long-period stable operation of the device.

Preferably, the conditions of mild hydrotreating in the slurry bed hydrogenation reactor are controlled so that the solid content of the light fraction, the second intermediate fraction and the mixed oil of the remaining first intermediate fraction is not more than 0.01 wt% and the metal content is not more than 10 μ g/g.

Preferably, the conditions for mild hydrotreating in said slurry bed hydrogenation reactor comprise: the reaction temperature is 360-440 ℃, the hydrogen partial pressure is 8.0-15.0 MPa, and the volume space velocity is 0.5-2.0 h^-1Hydrogen oil bodyThe product ratio is 500-1500; more preferably, the conditions under which the mild hydrotreating is carried out include: the reaction temperature is 380-420 ℃, the hydrogen partial pressure is 8.5-12.0 MPa, and the volume space velocity is 0.6-1.5 h^-1The volume ratio of hydrogen to oil is 600-1200.

The hydrofinishing reaction may be carried out in the presence of a hydrofinishing catalyst.

Preferably, the hydrofining catalyst contains a carrier, an active component loaded on the carrier and an optional active auxiliary agent; the metal element of the active component is selected from at least one of VIB group metal elements and VIII group metal elements. The optional coagent is meant to include a coagent or not.

Preferably, in the hydrorefining catalyst, the carrier is silica-alumina, the group VIB metal element is molybdenum and/or tungsten, and the group VIII metal element is cobalt and/or nickel.

According to a preferred embodiment, in the hydrorefining catalyst, the carrier is silica-alumina, the group VIII metal element is nickel, the group VIII metal element is cobalt and/or nickel, and the hydrorefining catalyst contains a co-agent, the co-agent being phosphorus; based on the total weight of the hydrofining catalyst, the content of nickel calculated by oxide is 1-10 wt%, the sum of the contents of molybdenum and tungsten calculated by oxide is more than 10 wt% and less than or equal to 50 wt%, the content of phosphorus calculated by oxide is 1-9 wt%, and the balance is carrier. The sum of the contents of molybdenum and tungsten calculated by oxides is more than 10 weight percent and less than or equal to 50 weight percent, and if molybdenum and tungsten are contained simultaneously, the sum of the contents of molybdenum and tungsten calculated by oxides is more than 10 weight percent and less than or equal to 50 weight percent; if only one of molybdenum and tungsten is contained, the content of molybdenum or tungsten is more than 10% by weight and 50% by weight or less in terms of oxide.

Preferably, in the carrier of the hydrorefining catalyst, the content of silica is 2 to 45% by weight and the content of alumina is 55 to 98% by weight.

Since the mixed oil of the light fraction and the middle fraction still contains a small amount of impurities such as metals, in order to avoid the activity of the hydrofining catalyst from being affected by the impurities such as metals and prevent the bed pressure drop of the refining reactor from rising too fast, it is preferable to fill a small amount of hydrogenation protection catalyst at the top of the refining reactor. More preferably, the loading volume ratio of the hydrogenation protection catalyst to the hydrofining catalyst is 0.05-0.2: 1.

in the refining reactor, the hydrogenation protection catalyst is preferably graded and filled by a plurality of hydrogenation protection catalysts, and is preferably graded and filled by five hydrogenation protection catalysts. The hydrogenation protection catalyst grading mode is that a hydrogenation protection catalyst I, a hydrogenation protection catalyst II, a hydrogenation protection catalyst III, a hydrogenation protection catalyst IV and a hydrogenation protection catalyst V are sequentially filled along the direction of reactant flow; the active metal elements in the hydrogenation protection catalyst I, the hydrogenation protection catalyst II, the hydrogenation protection catalyst III, the hydrogenation protection catalyst IV and the hydrogenation protection catalyst V are selected from at least one of VIB group metal elements and/or VIII group metal elements.

Preferably, the hydrogenation protection catalyst I is a hydrogenation protection catalyst which is in a shape of a porous cylinder and takes silicon oxide or aluminum oxide as a carrier, and the average particle diameter of the hydrogenation protection catalyst I is 15-17 mm. The hydrogenation protection catalyst I has higher porosity and a super-large pore structure, and can contain solid particles carried in coal tar raw materials and the like.

Preferably, the hydrogenation protection catalyst II is a hydrogenation protection catalyst which is in a honeycomb cylindrical shape and has an average particle diameter of 9-11 mm. The total weight of the hydrogenation protection catalyst II is taken as a reference, the hydrogenation protection catalyst II contains 0.05-0.2 wt% of nickel oxide, 0.5-1.0 wt% of molybdenum oxide, and the balance of a carrier. The hydrogenation protection catalyst II has high porosity and macroporous structure, and can contain impurities such as particles, metals and the like carried in the coal tar raw material.

Preferably, the hydrogenation protection catalyst III is a hydrogenation protection catalyst which is in the shape of Raschig ring and has an average particle diameter of 5.6-6.5 mm. The hydrogenation protection catalyst III contains 0.1-0.5 wt% of nickel oxide, 0.5-2.5 wt% of molybdenum oxide and the balance of silicon oxide or aluminum oxide used as a carrier. The hydrogenation protection catalyst III has high porosity and macroporous structure, can contain impurities such as metal in the coal tar raw material, and can perform hydrogenation saturation on olefin and diene.

Preferably, the hydrogenation protection catalyst IV is a hydrogenation protection catalyst which is in the shape of Raschig ring and has an average particle diameter of 2.5-3.5 mm. The hydrogenation protection catalyst IV contains 0.1-1.0 wt% of nickel oxide, 1.0-5.5 wt% of molybdenum oxide and the balance of silicon oxide or aluminum oxide used as a carrier. The hydrogenation protection catalyst IV can remove impurities such as metals in the coal tar raw material.

Preferably, the hydrogenation protection catalyst V is a hydrogenation protection catalyst which is clover in shape and has an average particle diameter of 2.5-3.5 mm. The hydrogenation protection catalyst V contains 0.5-1.5 wt% of nickel oxide, 1.5-6.5 wt% of molybdenum oxide and the balance of silicon oxide or aluminum oxide serving as a carrier. The hydrogenation protection catalyst V can remove impurities such as metals in the coal tar raw material.

Preferably, the conditions under which the hydrofinishing reaction is carried out in the refining reactor include: the hydrogen partial pressure is 8.0 to 20.0MPa, and more preferably 10.0 to 19.0 MPa; the reaction temperature is 340-420 ℃, and more preferably 350-400 ℃; the volume ratio of the hydrogen to the oil is 600-1800; the hourly space velocity of the raw material liquid is 0.1-1.5 h^-1。

There is no particular requirement for the packing volume ratio between the various hydroprocessing protecting catalysts described above, and one skilled in the art can use the packing volume ratios conventional in the art to pack the various hydroprocessing protecting catalysts described above.

Preferably, the method of the present invention further comprises: introducing the wax oil fraction obtained in the step (5) into a cracking reactor of the fixed bed hydrogenation unit for carrying out hydrocracking reaction.

Preferably, the method of the present invention further comprises: and fractionating a liquid product obtained by carrying out gas-liquid separation on the effluent obtained from the cracking reactor and a liquid product obtained by carrying out gas-liquid separation on the effluent obtained from the refining reactor.

The hydrocracking reaction may be carried out in the presence of a hydrocracking catalyst.

Preferably, in the fixed bed hydrogenation unit, the packing volume ratio of the hydrofining catalyst to the hydrocracking catalyst is 8-1: 1.

preferably, the hydrocracking catalyst contains a carrier and a non-noble metal element loaded on the carrier, the carrier is a mixture of amorphous silica-alumina and a molecular sieve, and the non-noble metal element is at least one selected from a group VIB metal element and a group VIII metal element. Preferably, the amorphous silica-alumina is selected from at least one of silica, alumina, amorphous alumina-silica.

According to a preferred embodiment, the hydrocracking catalyst contains 30-72 wt% of alumina, 10-52 wt% of amorphous aluminum silicate, 1-15 wt% of molecular sieve, 15-35 wt% of group VIB metal element calculated as oxide and 2-8 wt% of group VIII metal element calculated as oxide.

Preferably, the molecular sieve is selected from at least one of faujasite, mordenite, L-type zeolite, omega zeolite, Beta zeolite.

Preferably, the conditions under which the hydrocracking reaction is carried out in the cracking reactor include: the hydrogen partial pressure is 8.0 to 20.0MPa, and more preferably 10.0 to 19.0 MPa; the reaction temperature is 300-400 ℃, and more preferably 320-390 ℃; the volume ratio of hydrogen to oil is 500-1200, and the hourly space velocity of the raw material liquid is 0.5-5.0 h^-1。

The coal tar refers to coal tar produced in coal pyrolysis or coal gas making or other processes, for example, the coal tar may be low-temperature coal tar fraction produced in the coal gas making process, and may also be at least one of low-temperature coal tar, medium-temperature coal tar and high-temperature coal tar produced in the coal pyrolysis process (including low-temperature coking, medium-temperature coking and high-temperature coking processes). In the invention, the distillation range of the low-temperature coal tar can be 50-450 ℃; the distillation range of the medium temperature coal tar can be 50-600 ℃; the distillation range of the high-temperature coal tar can be 50-650 ℃.

a pre-processing unit;

The pretreatment unit may contain dewatering and/or mechanical impurity removal devices for settling, centrifugal separation.

Preferably, the first separation unit and the second separation unit respectively comprise a gas-liquid separation device and a fractionating tower which are sequentially connected through a pipeline; in the first separation unit, an inlet of a gas-liquid separation device is connected with an outlet of the slurry bed hydrogenation unit through a pipeline, and an outlet of a fractionating tower is connected with an inlet of the fixed bed hydrogenation unit through a pipeline; in the second separation unit, an inlet of the gas-liquid separation device is connected with an outlet of the fixed bed hydrogenation unit through a pipeline, and an outlet of the fractionating tower leads the product out of the system through a pipeline.

Preferably, the system further comprises a recycle hydrogen unit, and the first separation unit and the second separation unit are respectively connected with the recycle hydrogen unit through pipelines, so that the gas-phase materials obtained from the first separation unit and the second separation unit enter the recycle hydrogen unit.

In the first separation unit, a material at an outlet of the slurry bed hydrogenation unit is introduced into a gas-liquid separation device of the first separation unit through a pipeline for gas-liquid separation, an obtained gas-phase material enters the recycle hydrogen unit for further impurity removal to obtain a hydrogen-containing material flow, and a liquid-phase material obtained by gas-liquid separation through the gas-liquid separation device enters a fractionating tower of the first separation unit through a pipeline for fractionation to obtain intermediate products with different distillation ranges. And the product obtained at the outlet of the fixed bed hydrogenation unit enters a gas-liquid separation device of the second separation unit through a pipeline for gas-liquid separation, the obtained gas-phase material enters the circulating hydrogen unit for further impurity removal to obtain a hydrogen-containing material flow, the liquid-phase material obtained by gas-liquid separation through the gas-liquid separation device enters a fractionating tower of the second separation unit through a pipeline for fractionation to obtain products with different distillation ranges, and the obtained products are led out of the system through a pipeline.

Preferably, the recycle hydrogen unit is connected with the slurry bed hydrogenation unit and the fixed bed hydrogenation unit through pipelines respectively to supplement hydrogen-containing streams to the slurry bed hydrogenation unit and the fixed bed hydrogenation unit respectively.

Preferably, the recycle hydrogen unit comprises at least one recycle hydrogen compressor. In particular, the first separation unit and the second separation unit are connected by means of lines to one or more recycle hydrogen compressors in the recycle hydrogen unit, respectively, to obtain hydrogen-containing streams in the gas phase feed resulting from the first separation unit and the second separation unit.

Preferably, the second separation unit has a wax oil fraction transfer line therein, and the fixed bed hydrogenation unit further comprises a cracking reactor therein, and the wax oil fraction from the second separation unit is introduced into the cracking reactor through the wax oil fraction transfer line to perform a hydrocracking reaction.

Preferably, the system further comprises a third separation unit having a liquid product transfer line, in which the effluent from the cracking reactor is subjected to gas-liquid separation to obtain a cracked liquid product, which is introduced into the second separation unit through the liquid product transfer line for fractionation.

According to a preferred embodiment, the present invention provides a process route as shown in FIG. 1 for coal tar hydrogenation, wherein some auxiliary equipment such as heat exchangers, preheating furnaces, etc. are not shown, but are well known to those skilled in the art, and the specific process route is as follows:

the method comprises the steps that a coal tar raw material 1 is subjected to sedimentation and centrifugal separation through a pretreatment unit 2 to remove water and mechanical impurities 3, then is uniformly mixed with a slurry bed catalyst 4 and then enters a slurry bed hydrogenation reactor 5 of a slurry bed hydrogenation unit together with first recycle hydrogen 10 to be subjected to mild hydrogenation treatment, the effluent flow of the slurry bed hydrogenation reactor 5 enters a gas-liquid separation device of a first separation unit 6 to be subjected to gas-liquid separation, first separation water 11, a first hydrogen-rich gas 7 and a first liquid hydrocarbon flow are separated, and the first hydrogen-rich gas 7 is pressurized through a first recycle hydrogen compressor 8 and then is mixed with new hydrogen 9 to serve as the first recycle hydrogen 10 of the slurry bed hydrogenation unit. The first liquid hydrocarbon material flow separated by the first separation unit 6 enters a first fractionating tower 12 for distillation and cutting to obtain a light component, a first middle fraction 17, a second middle fraction 38 and a heavy fraction 18, the light component enters an overhead reflux tank 13 of the first fractionating tower 12 for oil, water and gas separation, second separated water 15, a first overhead gas 14 and a light fraction 16 are separated, and the first overhead gas 14 is used as fuel gas out of the system. Wherein part of the first middle distillate 17 is circulated back to the slurry bed hydrogenation reactor 5 for further hydrogenation, part of the heavy distillate 18 is thrown out of the system as an external throwing heavy distillate 19, and the rest part of the heavy distillate is circulated back to the slurry bed hydrogenation reactor 5 for mild hydrogenation treatment. The light fraction 16, the remaining part of the first middle fraction 17 and the second middle fraction 38 are mixed and then enter the refining reactor 20 of the fixed bed hydrogenation unit together with the second recycle hydrogen 37 to contact and react with the hydrofining catalyst. The refined effluent 21 of the refined reactor 20 enters a gas-liquid separation device of a second separation unit 22 for gas-liquid separation, second separated water 23, a second liquid hydrocarbon material flow 24 and a second hydrogen-rich gas 25 are separated, the second liquid hydrocarbon material flow 24 enters a second fractionating tower 26 of the second separation unit for distillation and cutting, the obtained second overhead gas 27 serves as fuel gas to be discharged out of the system, naphtha fraction 28, diesel fraction 29 and wax oil fraction 30 are cut out, wherein the naphtha fraction 28 and the diesel fraction 29 serve as product discharge systems, the wax oil fraction 30 and second recycle hydrogen 37 enter a cracking reactor 31 of a fixed bed hydrogenation unit together to be in contact with a hydrocracking catalyst for reaction, a cracked effluent 32 of the hydrocracking reactor enters a gas-liquid separation device of a third separation unit 33 for gas-liquid separation, and the separated third hydrogen-rich gas 35 and the second hydrogen-rich gas 25 separated by the second separation unit are pressurized by a second recycle hydrogen compressor 36 and then are pressurized by the second recycle hydrogen compressor 36 The fresh hydrogen 9 is combined to form the second recycle hydrogen 37 for the fixed bed hydrogenation unit. The third liquid hydrocarbon stream 34 separated by the third separation unit 33 is fed into the second fractionation column 26 together with the second liquid hydrocarbon stream 24 separated by the second separation unit for distillation and cutting. That is, fixed bed hydrofining and hydrocracking share a single fractionation system.

The method of the invention has the following specific advantages:

(1) the slurry bed hydrogenation reactor provided by the invention adopts a mild hydrogenation treatment method, can effectively remove metals, mechanical impurities and the like in the coal tar raw material, can meet the feeding requirement of a subsequent fixed bed hydrogenation unit, and ensures the long-period stable operation of a fixed bed hydrogenation device.

(2) The slurry bed hydrogenation unit adopts a mild hydrogenation treatment method, so that the problem that the operation period of a coal tar fixed bed hydrogenation device is seriously influenced due to the high content of metal, mechanical impurities and the like in the coal tar whole fraction raw material is solved, and under the optimal condition, the mild hydrogenation condition is adopted and a certain hydrogenation conversion depth is controlled, so that the purposes that the coal tar raw material can be subjected to mild hydrogenation treatment in the slurry bed to remove the metal and the mechanical impurities, avoid the generation of byproducts and ensure higher liquid yield are achieved.

On the other hand, by controlling the hydroconversion depth of the slurry bed and circulating part of fractions back to the hydrogenation reactor of the slurry bed, the problem that the asphaltene is precipitated and deposited to block the internal components of the slurry bed can be solved more effectively, the long-period stable operation of the hydrogenation reactor of the slurry bed is effectively ensured, and the liquid yield of the device is further improved.

(3) The combined method of mild hydrotreating in the slurry bed and hydrogenation upgrading in the fixed bed is adopted, so that the advantages of strong adaptability of raw materials in the slurry bed and good quality of products in the fixed bed can be taken into consideration, and clean and efficient utilization of coal tar resources is realized.

The present invention will be described in detail below by way of examples. In the following examples, various raw materials used were commercially available unless otherwise specified.

The properties of the coal tar feedstock used below are shown in table 1.

A hydrogenation protection catalyst and a hydrogenation refining catalyst are filled in a refining reactor of a fixed bed hydrogenation unit, the hydrogenation protection catalyst is filled at the top of the reactor and is filled in five hydrogenation protection catalysts in a grading way, a hydrogenation protection catalyst I, a hydrogenation protection catalyst II, a hydrogenation protection catalyst III, a hydrogenation protection catalyst IV and a hydrogenation protection catalyst V are sequentially filled along the direction of a reactant flow, the trade marks are RGC-20 and RGC-30E, RGC-30A, RGC-30B, RGC-1 respectively, and the filling volume ratio of the hydrogenation protection catalyst I, the hydrogenation protection catalyst II, the hydrogenation protection catalyst III, the hydrogenation protection catalyst IV and the hydrogenation protection catalyst V is 1: 2: 1.5: 1.5: 2.

the hydrofining catalyst is sold under the trade designation RTC-2, and based on the total weight of the hydrofining catalyst, the content of nickel in terms of oxide is 2.4 wt%, the content of molybdenum in terms of oxide is 8.3 wt%, the content of tungsten in terms of oxide is 16.7 wt%, the content of phosphorus in terms of oxide is 2.0 wt%, and the balance is a carrier, silica-alumina, and based on the carrier, the content of silica is 20.0 wt%, and the content of alumina is 80.0 wt%.

A high-dispersion heterogeneous slurry bed catalyst is adopted in a slurry bed hydrogenation reactor of a slurry bed hydrogenation unit, and the high-dispersion heterogeneous slurry bed catalyst is a high-dispersion iron-based carbon-based supported catalyst and comprises the following components: the active carbon is used as a carrier, and the active metal components are Fe and Mo. And the weight ratio of Fe and Mo in the high-dispersion iron-based carbon-based supported catalyst is 1: 0.2.

the cracking reactor of the fixed bed hydrogenation unit is filled with a hydrocracking catalyst, and the commercial brand of the hydrocracking catalyst is RHC-3. The composition is as follows: based on the total weight of the hydrocracking catalyst, 50.7 wt.% of alumina, 17.0 wt.% of amorphous alumino-silicate, 4.5 wt.% of molecular sieve, 8.2 wt.% of molybdenum, 14.6 wt.% of tungsten and 5 wt.% of nickel, calculated as oxides.

The commercial-grade catalysts are all produced by Changling catalyst factories of China petrochemical catalyst division.

In the following examples and comparative examples, the loading volume of the hydrogenation protection catalyst was 10% of that of the hydrotreating catalyst based on the hydrotreating catalyst, unless otherwise specified; the filling volume of the hydrocracking catalyst is 30 percent of that of the hydrofining catalyst.

Example 1

The amount of the slurry bed catalyst based on the total weight of the coal tar raw material was 1.5% by weight in terms of the active metal element contained therein. The coal tar raw material in the table 1 and the high-dispersion heterogeneous slurry bed catalyst are uniformly mixed, then the mixture and hydrogen enter a slurry bed hydrogenation reactor for mild hydrogenation treatment, the effluent of the slurry bed hydrogenation reactor enters a first separation unit for gas-liquid separation, water is separated, the separated liquid hydrocarbon product enters a first fractionating tower, and the liquid hydrocarbon product is distilled and cut into light fraction, first middle fraction, second middle fraction and heavy fraction. And controlling the conversion rate of the heavy fraction in the coal tar raw material to be 52% by taking the corresponding heavy fraction in the coal tar raw material entering the slurry bed hydrogenation reactor as a reference. Wherein 50 wt% of the heavy fraction distilled and cut out by the first fractionating tower is thrown out of the device; the residual heavy fraction is recycled to the slurry bed hydrogenation reactor for further conversion. And 20 weight percent of the first middle distillate distilled and cut out by the first fractionating tower is circulated back to the slurry bed hydrogenation reactor for further conversion.

And mixing the light fraction cut by distillation in the first fractionating tower, the rest part of the first middle fraction and all the second middle fraction with hydrogen, and then entering a fixed bed hydrofining reactor to contact and react with a hydrofining catalyst. And the effluent of the refining reactor enters a second separation unit for gas-liquid separation, water is separated, and the separated liquid hydrocarbon product enters a second fractionating tower and is distilled and cut into naphtha fraction, diesel fraction and wax oil fraction. The naphtha fraction and the diesel fraction are taken as products to be discharged out of the device, the wax oil fraction enters a cracking reactor of a fixed bed hydrogenation unit to be in contact reaction with a hydrocracking catalyst, the effluent of the hydrocracking reactor enters a third separation unit to be subjected to gas-liquid separation, the separated liquid hydrocarbon product and the liquid hydrocarbon product separated by the second separation unit enter a second fractionating tower together to be fractionated and cut, and namely the fixed bed hydrofining and the hydrocracking share one fractionating system.

The specific reaction conditions are shown in Table 2, and the properties of the product after slurry bed mild hydrotreating are shown in Table 3. The properties of the naphtha product and the diesel product are shown in Table 4.

As can be seen from Table 3, after mild hydrotreating in a slurry bed, the metal content in the coal tar is less than 10 μ g/g, and the mechanical impurity content is less than 0.01 wt%, which can meet the feeding requirement of the subsequent fixed bed hydrogenation device.

In the embodiment, the slurry bed hydrogenation reactor adopts relatively mild hydrogenation conditions, and by controlling the appropriate conversion rate of the heavy fraction, the generation of byproducts such as dry gas, liquefied gas and coke is effectively reduced, the yield of liquid is correspondingly increased, the utilization rate and the utilization value of the coal tar which is an inferior and cheap raw material are improved, and the economic benefit of the device is improved to a certain extent.

As can also be seen from Table 3, in this example, part of the first middle distillate was recycled to the slurry bed hydrogenation reactor, and there was no problem of plugging the reactor internals by deposition of asphaltene, and the continuous operation period of the slurry bed hydrogenation apparatus of this example exceeded 5000 h. The method can effectively inhibit the deposition of asphaltene and the formation of coke to generate coke, further improve the liquid yield and ensure the long-period stable operation of the device.

As can also be seen from Table 4, the diesel oil product of the embodiment has the sulfur content of less than 10 mug/g, the condensation point of-16 ℃ and the cetane number of 45.7, and can be used as a blending component of low-sulfur clean diesel oil. The naphtha fraction has a sulfur content of less than 10 mu g/g and an aromatic hydrocarbon content of 68.7, and can be used as a high aromatic hydrocarbon reformate.

Comparing the results of this example with those of comparative example 2, it can be seen that comparative example 2 adopts the technical route commonly adopted in the prior art, and as can be seen from table 3, the yield of dry gas and liquefied gas in this example is 3.44%, the yield of coke is 3.27%, and the yield of liquid is 6.10%.

Example 2

This example was carried out in a similar manner to example 1, except that:

the amount of the slurry bed catalyst based on the total weight of the coal tar raw material was 2.0 wt% in terms of the active metal element contained therein. The coal tar raw material and the high-dispersion heterogeneous slurry bed catalyst are uniformly mixed and then enter a slurry bed hydrogenation reactor together with hydrogen for mild hydrogenation treatment.

And controlling the conversion rate of the heavy fraction in the slurry bed hydrogenation reactor to be 65% by taking the corresponding heavy fraction in the coal tar raw material entering the slurry bed hydrogenation reactor as a reference. Wherein, 60 weight percent of heavy fraction cut out from the first fractionating tower is thrown out of the device, and the rest heavy fraction is recycled to the slurry bed hydrogenation reactor for further conversion.

And (3) circulating 25 wt% of the first middle distillate distilled and cut out by the first fractionating tower to the slurry bed hydrogenation reactor for further conversion, mixing the rest first middle distillate, all light distillate and all second middle distillate with hydrogen, entering a refining reactor of a fixed bed hydrogenation unit, and carrying out contact reaction with a hydrofining catalyst. The other main conditions were the same as in example 1.

It can also be seen from Table 4 that the diesel product of example 2 has a sulfur content of less than 10 μ g/g, a pour point of-14 deg.C and a cetane number of 47.1, and can be used as a blending component for low-sulfur clean diesel. The naphtha fraction has a sulfur content of less than 10 mu g/g and an aromatic hydrocarbon content of 66.5, and can be used as a high aromatic hydrocarbon reformate.

Comparing the results of this example with those of comparative example 2, it can be seen that comparative example 2 adopts the technical route commonly adopted in the prior art, and as can be seen from table 3, the yield of dry gas and liquefied gas in this example is 2.65 percentage points lower, the yield of coke is 2.70 percentage points lower, and the yield of liquid is 4.86 percentage points higher.

Example 3

This example was carried out in a similar manner to example 1, except that:

the amount of the slurry bed catalyst based on the total weight of the coal tar raw material was 0.3 wt% in terms of the active metal element contained therein. The coal tar raw material and the high-dispersion heterogeneous slurry bed catalyst are uniformly mixed and then enter a slurry bed hydrogenation reactor together with hydrogen for mild hydrogenation treatment.

And controlling the conversion rate of the heavy fraction in the slurry bed hydrogenation reactor to be 37% by taking the corresponding heavy fraction in the coal tar raw material entering the slurry bed hydrogenation reactor as a reference. Wherein 40 weight percent of heavy fraction cut out from the first fractionating tower is thrown out of the device, and the rest heavy fraction is recycled to the slurry bed hydrogenation reactor for further conversion.

The other main conditions were the same as in example 1.

The specific reaction conditions are shown in Table 2, and the properties of the product after mild pretreatment by slurry bed hydrogenation are shown in Table 3. The properties of the naphtha product and the diesel product fractionated out by the second fractionation system are shown in Table 4.

As can also be seen from Table 4, the diesel oil product of the embodiment has the sulfur content of less than 10 mug/g, the condensation point of-16 ℃ and the cetane number of 44.0, and can be used as a blending component of low-sulfur clean diesel oil. The naphtha fraction has a sulfur content of less than 10 mu g/g and an aromatic hydrocarbon content of 70.3, and can be used as a reformate having a high aromatic hydrocarbon content.

Comparing the results of this example with those of comparative example 2, it can be seen that comparative example 2 adopts the technical route commonly adopted in the prior art, and as can be seen from table 3, the yield of dry gas and liquefied gas in this example is 3.99 percentage points lower, the yield of coke is 3.56 percentage points lower, and the yield of liquid is 6.66 percentage points higher.

Comparative example 1

This comparative example was carried out in a similar manner to example 3, except that:

compared with the example 3, the middle distillate separated from the first fractionating tower is not recycled to the slurry bed hydrogenation reactor in the comparative example, and other main operation conditions are the same as the example 3.

The specific reaction conditions of this comparative example are shown in Table 2, and the properties of the product after hydrogenation in a slurry bed are shown in Table 3. The properties of the naphtha product and the diesel product are shown in Table 4.

As can be seen from table 3, although the mild hydrotreating conditions are also adopted in this comparative example, the metal content in the coal tar after hydrogenation in the slurry bed is less than 10 μ g/g, and the mechanical impurity content is less than 0.01 wt%, and the subsequent fixed bed hydrogenation feeding requirement is also met, because the middle fraction separated from the first fractionating tower is not recycled to the slurry bed hydrogenation reactor, part of asphaltenes are still coked to a certain extent to generate coke, so that the coke yield is 0.6 percentage point higher than that in example 3 under the same process conditions, and the continuous operation period of the slurry bed device in the method of this comparative example is only 2560 hours.

Comparative example 2

This comparative example was carried out in a similar manner to example 1, except that:

in the comparative example, the fraction of more than 370 ℃ in the hydrogenation product of the slurry bed is completely circulated back to the hydrogenation reactor of the slurry bed for further hydrogenation conversion, the hydrogenation reactor of the slurry bed adopts harsher process conditions, and the fraction with lighter initial distillation point, namely the fraction of more than 370 ℃ is circulated back to the hydrogenation reactor of the slurry bed instead of the heavier fraction, for example, the fraction of more than 500 ℃, and the technical route commonly adopted in the prior art is adopted. As can be seen from Table 3, the conversion was 60% for the fraction > 370 ℃ and up to 85% for the heavy fraction > 500 ℃.

In the comparative example, the fraction of the coal tar raw material with the temperature higher than 370 ℃ is completely circulated back to the slurry bed hydrogenation reactor, so that only the fraction with the temperature lower than 370 ℃ is used as the feed of the subsequent fixed bed hydrogenation unit. The subsequent fixed bed hydrogenation unit is provided with only a finishing reactor because the light fraction at the temperature of < 370 ℃ is processed. This is also a commonly used technical route in the prior art.

As can be seen from table 3, compared with examples 1 to 3, in the present comparative example, since the slurry bed hydrogenation reactor adopts the technical route commonly adopted in the prior art, the hydrogenation depth of the slurry bed hydrogenation reactor is large, although the metal content in the coal tar after hydrogenation in the slurry bed is less than 10 μ g/g and the mechanical impurity content is less than 0.01 wt%, the feeding requirement of the subsequent fixed bed hydrogenation apparatus is satisfied, the yield of dry gas, liquefied gas and coke in the product distribution is high, the yield of dry gas and liquefied gas is 2.65 to 3.99% higher than that in examples 1 to 3, the yield of coke is 2.70 to 3.56% higher, the liquid yield of the comparative example is 4.86 to 6.66% lower than that in examples 1 to 3, and the continuous operation cycle of the slurry bed of the comparative example 2 is only 1040 hours.

TABLE 1

	Coal tar feedstock
		Density (20 ℃ C.)/(g/cm)³)	1.0570
Carbon residue/weight%	7.05
		Nitrogen content/(μ g/g)	6500
Sulfur content/(μ g/g)	2300
		C content/weight%	81.73
H content/weight%	8.37
		Asphaltene content/weight%	14.0
Distillation Range ASTM D-1160/. degree.C
		IBP	179
50％	386
		95％	507
Metal content/(μ g/g)
		Fe	96.3
Ni	＜0.1
		V	＜0.1
Na	13.5
		Ca	63.9
Al	12.1

TABLE 2

Item	Example 1	Example 2	Example 3	Comparative example 1	Comparative example 2
						Slurry bed hydrogenation reactor
Partial pressure of hydrogen/MPa	9.0	10.5	8.5	8.5	12.0
						Reaction temperature/. degree.C	400	420	390	390	420
Hydrogen to oil ratio/(Nm)³/m³)	800	1000	800	800	1000
						Volume space velocity/h^-1	1.0	0.6	1.5	1.5	0.6
Fixed bed hydrorefining reactor
						Partial pressure of hydrogen/MPa	17.0	15.0	18.0	18.0	15.0
Reaction temperature/. degree.C	380	390	395	395	375
						Hydrogen to oil ratio/(Nm)³/m³)	1500	1200	1800	1800	1200
Volume space velocity/h^-1	0.5	1.5	0.3	0.3	0.5
						Fixed bed hydrocracking reactor
Partial pressure of hydrogen/MPa	17.0	15.0	18.0	18.0	-
						Reaction temperature/. degree.C	360	370	380	380	-
Hydrogen to oil ratio/(Nm)³/m³)	800	1000	1200	1200	-
						Volume space velocity/h^-1	2.0	1.5	3.5	3.5	-

TABLE 3

TABLE 4

The results show that the method provided by the invention has the advantages of long device operation period, high liquid yield and the like, can give consideration to the advantages of strong raw material adaptability of the slurry bed hydrogenation reactor and good product quality of the fixed bed reactor, improves the utilization rate and the utilization value of coal tar resources, and provides an effective utilization way for the coal tar which is a cheap and poor resource.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims

1. A method for hydroconversion of a coal tar feedstock, the method comprising:

(3) sequentially carrying out gas-liquid separation and fractionation on the material obtained in the step (2) to obtain a light fraction, a first middle fraction, a second middle fraction and a heavy fraction, wherein the final boiling point of the first middle fraction is smaller than the initial boiling point of the second middle fraction, and the final boiling point of the light fraction is 150-200 ℃; the final boiling point of the first middle distillate is 330-400 ℃; the final boiling point of the second middle distillate is 460-510 ℃;

(5) sequentially carrying out gas-liquid separation and fractionation on the effluent of the refining reactor; obtaining naphtha fraction, diesel fraction and wax oil fraction;

wherein the mild hydrotreating conditions in step (2) are controlled so that the conversion rate of the heavy fraction obtained in step (3) is 35 to 65 wt% based on the coal tar feedstock;

and (3) the thrown-out part of the heavy fraction accounts for 30-70 wt% of the total weight of all the heavy fractions obtained after the step (3).

2. The method according to claim 1, wherein the light fraction has an end point of 160 to 190 ℃; the final boiling point of the first middle distillate is 360-390 ℃; the final boiling point of the second middle distillate is 480-500 ℃.

3. The process according to claim 1, wherein the portion of the first middle distillate recycled to the slurry bed hydrogenation reactor comprises 10 to 35 wt% of the total amount of the first middle distillate obtained after step (3).

4. The process according to claim 3, wherein the portion of the first middle distillate recycled to the slurry bed hydrogenation reactor is 15 to 25 wt% of the total amount of the first middle distillate obtained after step (3).

5. The process of any one of claims 1 to 4, wherein the slurry bed catalyst is a heterogeneous slurry bed catalyst selected from at least one of iron-based catalysts, iron-based compounds, and iron-based carbon-based supported catalysts;

the iron catalyst is selected from at least one of pyrite, hematite and red mud;

the iron-based compound is selected from Fe₂S、Fe₂O₃And Fe₃O₄At least one of;

the iron-based carbon-based supported catalyst comprises a carrier and an active metal element loaded on the carrier, wherein the carrier is a carbon-based material selected from at least one of coal dust, activated carbon, graphite and carbon black, and the active metal element is selected from at least one of W, Mo, Ni, Co and Fe.

6. The method according to claim 5, wherein the average particle diameter of the iron-based catalyst is 10 to 200 μm.

7. The method according to claim 5, wherein the slurry bed catalyst is used in an amount of 0.1 to 3.5 wt% in terms of active metal elements contained therein, based on the total weight of the coal tar feedstock.

8. The method according to claim 7, wherein the slurry bed catalyst is used in an amount of 0.15 to 2.5 wt% in terms of active metal elements contained therein, based on the total weight of the coal tar feedstock.

9. The process according to claim 1, wherein the thrown-out portion of the heavy fraction accounts for 40 to 60 wt% of the total amount of the heavy fraction obtained after step (3).

10. The process of any one of claims 1-4, wherein the conditions for mild hydrotreating in the slurry bed hydrogenation reactor comprise: the reaction temperature is 360-440 ℃, the hydrogen partial pressure is 8.0-15.0 MPa, and the volume space velocity is 0.5-2.0 h^-1The volume ratio of hydrogen to oil is 500-1500.

11. The process of claim 10, wherein the conditions for mild hydrotreating in the slurry bed hydrogenation reactor comprise: the reaction temperature is 380-420 ℃, the hydrogen partial pressure is 8.5-12.0 MPa, and the volume space velocity is 0.6-1.5 h^-1The volume ratio of hydrogen to oil is 600-1200.

12. The process of any of claims 1-4, wherein the hydrofinishing reaction is carried out in the presence of a hydrofinishing catalyst; the hydrofining catalyst contains a carrier, an active component loaded on the carrier and an optional active auxiliary agent; the metal element of the active component is selected from at least one of VIB group metal elements and VIII group metal elements.

13. The process of claim 12, wherein in the hydrofinishing catalyst, the carrier is silica-alumina, the group VIB metal element is molybdenum and/or tungsten, and the group VIII metal element is cobalt and/or nickel.

14. The process of claim 13, wherein the group VIII metal element is nickel and the coagent active element is phosphorus.

15. The process of claim 14, wherein the nickel content on an oxide basis is from 1 to 10 wt.%, the sum of the molybdenum and tungsten contents on an oxide basis is from greater than 10 wt.% to 50 wt.%, the phosphorus content on an oxide basis is from 1 to 9 wt.%, and the balance is a support, based on the total weight of the hydrofinishing catalyst.

16. The method as claimed in any one of claims 13 to 15, wherein the silica is present in an amount of 2 to 45 wt% and the alumina is present in an amount of 55 to 98 wt% in the support.

17. The method of any one of claims 13-15, wherein the top of the polishing reactor is loaded with a hydrogenation protection catalyst, and the loading volume ratio of the hydrogenation protection catalyst to the hydrogenation polishing catalyst is 0.05-0.2: 1.

18. the process of any of claims 1-4, wherein the conditions under which the hydrofinishing reaction is carried out in the refining reactor comprise: the hydrogen partial pressure is 8.0-20.0 MPa; the reaction temperature is 340-420 ℃; the volume ratio of the hydrogen to the oil is 600-1800; the hourly space velocity of the raw material liquid is 0.1-1.5 h^-1。

19. The method of claim 18, wherein the conditions under which the hydrofinishing reaction is carried out in the refining reactor comprise: the hydrogen partial pressure is 10.0-19.0 MPa; the reaction temperature is 350-400 ℃.

20. The method of any of claims 1-4, wherein the method further comprises: introducing the wax oil fraction obtained in the step (5) into a cracking reactor of the fixed bed hydrogenation unit for carrying out hydrocracking reaction.

21. The process according to claim 20, wherein the liquid product obtained after separation of the effluent obtained from the cracking reactor is fractionated together with the liquid product obtained after separation of the effluent from the finishing reactor.

22. The method of claim 20, wherein the hydrocracking reaction is carried out in the presence of a hydrocracking catalyst, and the loading volume ratio of the hydrofining catalyst to the hydrocracking catalyst is 8-1: 1.

23. the method of claim 22, wherein the hydrocracking catalyst comprises a carrier and a non-noble metal element supported on the carrier, the carrier is a mixture of amorphous silica-alumina and a molecular sieve, and the non-noble metal element is at least one selected from group VIB metal elements and group VIII metal elements.

24. The method of claim 23, wherein the amorphous silica-alumina is selected from at least one of silica, alumina, amorphous alumina-silica.

25. The process of any one of claims 22 to 24, wherein the hydrocracking catalyst comprises 30 to 72 wt% of alumina, 10 to 52 wt% of amorphous aluminum silicate, 1 to 15 wt% of molecular sieve, 15 to 35 wt% of group VIB metal element calculated as oxide and 2 to 8 wt% of group VIII metal element calculated as oxide.

26. The method of claim 25, wherein the molecular sieve is selected from at least one of faujasite, mordenite, L-type zeolite, omega zeolite, zeolite Beta.

27. The process of claim 25, wherein the conditions under which the hydrocracking reaction is carried out in the cracking reactor comprise: the hydrogen partial pressure is 8.0-20.0 MPa; the reaction temperature is 300-400 ℃; the volume ratio of hydrogen to oil is 500-1200, and the hourly space velocity of the raw material liquid is 0.5-5.0 h^-1。

28. The process of claim 27, wherein the conditions under which the hydrocracking reaction is carried out in the cracking reactor comprise: the hydrogen partial pressure is 10.0-19.0 MPa; the reaction temperature is 320-390 ℃.

29. The process of claim 1, wherein the coal tar feedstock is selected from at least one of low temperature coal tar, medium temperature coal tar, and high temperature coal tar.

30. A system for hydroconversion of a coal tar feedstock, the system comprising:

a pre-processing unit;

31. A system according to claim 30, wherein the second separation unit has a wax oil fraction transfer line therein, and the fixed bed hydrogenation unit further comprises a cracking reactor therein, the wax oil fraction from the second separation unit being introduced into the cracking reactor through the wax oil fraction transfer line for hydrocracking reactions.

32. The system of claim 31, further comprising a third separation unit having a liquid product transfer line, wherein the effluent from the cracking reactor is subjected to gas-liquid separation to obtain a cracked liquid product, which is introduced into the second separation unit through the liquid product transfer line for fractionation.