CA1209944A - Method of supplying soot-free products from the partial oxidation of hydrocarbon fuel to the fuel stream of the acr process - Google Patents

Abstract

THE METHOD OF SUPPLYING SOOT-FREE PRODUCTS
FROM THE PARTIAL OXIDATION OF HYDROCARBON
FUEL TO THE FUEL STREAM OF THE ACR PROCESS

ABSTRACT
An energy efficient method for providing a soot-free gaseous fuel for an Advanced Cracking Reactor which is produced by partial oxidation of a hydrocarbon fuel to form gaseous products and non-gaseous products. The gaseous products are separated from the solid materials with minimum heat loss and can then be utilized as fuel for the ACR.

Description

12~ 4~

THE ~ET~OD OF S~PPLYING SOOT-FREE PROD~CTS
FRO~ THE PARTIAL OXIDATION OF HYDROCARBON
FUEL TO THE FUEL STREAM OF THE ACR PROCESS

TECHNICAL FIELD
This invention is concerned with a process for a~vantageously practicing the Advanced Crac~ing Reactor ~ACR) process. Vtilizing this invention, a fuel oil ~uch as a heavy residual fuel oil, and preferably the atmospheric vacuum residue fractions from tbe distillation of crude oil, is partially o~idized to produce a gaseous mi~ture of hydroaen and carbon monoxide ~hereinafter termed "synthesi 5 gasn) and solid materials ~uch as soot and metal o~ides. The gaseous products are ~eparated from the 601id material6 and are ~ed to the combustion zone of an ACR where they are mixe~ with oxygen and steam. The gaseous products act as the fuel for effecting the combustion reaction in the ACR. The product~ of tbe combustion reaction are thereafter contacted with a liquid stream of hydro¢arbon feedstock and the combination of the two are fed tbrough a throat portion of the ACR into the diverging diffuser/reactor ~ection ~f tbe ACR. The hydrocarbon feedstream i~ therein converte~ into the desired composition of cracked product~ wbich contains a lar~e fraction of ethylene.
BACRGRO~ND ART
U. S. Patent No. 4,134,824, to Kamm, et al., patented January 16, 1979, describes the integration of some of the features of the partial o~idation process into the ACR process. In the prGcess ~e~cr~bed by Kamm, et al., the a6phaltic residue ~f O ~rude oil feedstock whirh supplies a crude oil di~tillate fraction stream for the ~ZQ9~4 reaction, is fed as a fuel to the combustion step of the ACR process. In the combustion step, the asphaltic stream is combined with a "fluid fuel" and o~ygen to be partially combusted in the presence of super-beated ~team to form a reducing stream of hot combus~ion product~. The partial combu~tion product~ are tber~after passed through the combustion zone and during the course of such passage, a crude oil distillate fraction stream is injected into the partial combustion products stream. The combination of hot partial combustion products and the crude oil distillate fraction flow at high velocities througb a converging zone, the typical throat section of the ACR reactor, into a diverging zone in which the streams increase in velocity an~ cracking of the crude oil distillate frac~ion occurs. The crac~ing ste~ is followed by ~uenching and product recovery~
~ he Advanced Cracking Reactor (ACR) process is e~plained in detail in UO S. Patent No.
4,136,015. It is described therein as involving the production of a hot gaseou~ combustion product stream in a first-sta~e combustion zone in the presence of ~uper-heated steam. The hydrocarbon feedstock to be cracked is then injected and mi~ed with the bot gaseous combustion product ~tream.
That ~i~ture is then ~ed into a crackinq zone. T~e effluent from the reaction zone CQntainS a stream whicb is rich in etbylene and contains varying concentrations of acetylene, propylene and butadiene~ The typical ACR process will produce hydroaen, methane, acetylene, ethylene; ethane, propylene, propane, butenes, 1,3-butadienef butanes, carbon monoxide, carbon dioxide methyl acetylene, ~Z~P9944 propadiene, and similar gaseous products. Typical liquid products are pyrolysis gasoline, benzene, toluene, xylenes, C8non-aromatics, tars and pitches, and tbe like.
U. S. Patent ~o. 4,134,824 describes the utilization of the partial oxidation proces~ to produce a product stream containing hydrogen, carbon mono~ide, carbon dioxide, steam, sulfur compounds, and other minor components, ~ometimes referred to as synthesis gas. The partial oxidation reaction mechanis~ is therein described as involving an exothermic partial combustion of a portion of a hydrocarbon feedstream which supplies heat to the endothermic steam cracking of the balance of the feed. Besides carbon mono~ide, hydrogen, carbon dioxide, hydrogen sulfide and other trace impurities, partial o~idation produces soot in non-equilibrium amounts. The composition of the products, particularly hydroqen/carbon monoxide ratio, sulfur and soot are generally determined by the type of feedstock, the oxygen/fuel ratio and the amount of steam used~ The process of U. S. Pa~ent No. 4,134,824 utilizes the asphaltic fraction of a fuel oil as part of ~he feed to the combustion reaction that is utilized for generating tbe temperature necessary ~or cracklng of tbe distillate portion of the feedstock into the desired products of tbe cracki~g reaction, as described above.
Con6e~uently, U. S. Patet No. 4,134,824 effects in situ in the combustion zone, a partial oxidation reacticn to thereby generate synthesis gas which is carried through the ACR reactor. Indeed, the ~ynthesi~ gas in U. S. Patent No. 4,134,824 is u~ilized as a beat carrier gas for transporting the ACR feedstock into tbe eeaction zone and for supplyin~ the endothermic heat of reaction.
U. S. Patent Nol 4,264,435 is essentially the ~ame process as U. S. Patent No. 4,134,824. The alleged diffecence in U. S. Patent No. 4,264,435 resides in the sug~estion that a substantial amount of ~uper-heated steam which is injected into the combustion gases allegedly effects a shift in the reaction resulting in a product with a ~ore desirable composition having a temperature of 1200 to 1800C. This stream is thereafter contacted with the hydrocaebon feed in the typical ACR manner. The process of U. S. Patent No. 4,264,435, as i~ the case with U. S. Patent No. 4,134,824 effects the partial o~idation reaction in situ in the combustion zone and the synthesis gas formed thereby serves to carry tbe heat of the combustion reaction to the cracking reaction downstream.
~ V. S. Patent No. 4,321,131, to Lower patent~d March 23, 1982, describes a reforming step in which ~team is combined with a fuel and fed to a reforming catalyst sucb as a metal catalyst of GrouP
VIII, see column, lines 30 to 37 of Lowe, and the ~yntbesi~ gas product formed is fed to the combustion zone of the ACR reactor with oxygen in ~he presence of steam to produce the com~ustion products stream, a~ defined previously.
In the proce~ses of Kamm, et al., U. S.
Patent Mo. 4,264,435 and the Lowe patent, one problem reoccurs. In each of tbe~e processes, the technology that is utilized and with which synthesis gas formation is involved, qenerates a carbonaceous material which in one form or another must be t~eated during the overall oper3tion of the ACR

processD For e~ample, in U.S. Paten~ No. 4,134,824 and V. S. Patent No. 4,264,435 processes, the partial oxidation process within the ACR process causes the formation of soot which will be carried through the reactor and deposited along the cracking reactor zone wall6. Even though the typical ~CR
process will generate some carbonaceous de~osit, the partial oxidation process will generate an increased concentration of sucb carbonaceous deposits and will tbereby necessitate a greater frequency of carbon removal treatment in order to effectively operate the ACR process. The Lowe process on the other band, causes steam and fuel to be reformed within a catalytic reaction step in which there ~ill be generated a certain amount of carbonaceous material and such carbonaceous material, instead of going to the ACR reaction, will fcrm within the reforming catalyst. This will necessitate a frequent treatment of tbe catalyst ~eds in order to restore their activity resulting from carbon deposits which cause~ the catalyst to be deactivated.
Another problem ~hat is associated with the DroCesS of ~. S. Patent No. 4,264,435 and U.S.
Patent No. 4,134,824 is that by virtue of starting with an untreated crude oil product, the combu~tion products will con~ain ash which will eventually contaminate the ceramic linina of the ACR reactor.
Such ash can create an acid flu~ on the wall and could therefore result in breakaqe of the ceramic as well as corrosion.

SUM~ARY OE THE INVENTION
-The process o~ this invention avoids tbe aforementioned problems which are associated with ~2Q9944 pa~tial oxidation in the combustion portion of the ACR or which are effected by a reforming process over a reformin~ catalyst.
The process of this ivention provi~es a two-~tep process in whicb any ~aseous, liquid, or ~olid hydrocarbon fuel can under~o a partial o~idation step whereby the synthesi~ ~as product is phy~ically ~eparated from ~he ~oot and ash which are generated in ~uch a way as to retain much of its sensible heat and such synthesis gas product is thereafter fea to the combustion zone of the ACR
process and i~ utilized as a fuel to generate the desired heat for tbe cracking reaction. Neither U.S. Patent No. 4,134,824 nor U. S. Patent No.
4,264,435 utilize~ ~ynthesi~ gas as a fuel for producing the de6ired temperature of the cracking reaction, whereas the Lowe patent does describe a proce6s which utilizes synthesi6 gas for that purpose.
DETAILED DESCRIPTION OF THE INVENTION
There is a substantial body of art directed to the manufacture of ~ynthe~is gas by the partial oxidation of bydrocarbon fuels. Illustrative of prior art is the followin~: British Patent 1,390,590; British Patent 1,445,549; British Patent 1,458,448: U. S. Pa~ent No. 2,698,830: U. S. Patent No. 3,705,108: U~ SO Patent No. 3,743,606: U. S.
Patent No, 3,816,332; U. S. Patent No. 3,945,942t U.
S. Patent No~ 3,989,444; U. S. Patent No. 4,081,253:
U. S. Patent ~o. 4,007,018: U. S. Patent No.
4,007,019: U. S. Patent No. 3,990,865: U. S. Patent No. 4,318,712 and U. S. Patent No. 4,282,010 and the like.

These patents variously describe the partial oxidation of a gaseous liquid or solid hydrocarbon fuel by reaction with oxygen in the presence of ~team at a temperature ranging from about 800C up to 2000C, preferably at a temperature of about 1000 to about 1~00C, more particularly at a tempera~ure ran~ing from about 1200C to about 1600C to produce a stream which contains carbon monoxide, bydrogen~ water and carbon dioxide as the gaseous products and soot and ash as the solid products. These well-known methods for producing syntbesis gas may be used in the present invention.
There is also a substantial body of art directed at quenching processes. IlIusteative of this prior art are the following: U. S. Patent No.
3,719,029, U. S. Patent No. 3,576,519, U. S. Patent No. 3,671,198, ~. S. Patent No. 3,~85,847, U. S.
Patent No. 3,907,661, U~ S. Patent No. 4,150,716 and the like.
Since the hydrocarbon stream has not been treated in advance to remove sulfur products, the gas stream that comes from the reaction also contains hydrogen sulfide and carbonyl sulide. The hot gaseous effluent plu~ the soot in the ash are ~ed to a se~aration system whereby tbe soot and ash are removed from the gaseous stream. T~is can be accomplished by a number of procedures.
In the present invention, the qaseous effluent from the partial oxidation process passes directly from the reaction zone to a ~uencher. It is here that the bulk of tbe soot is removed by dir2ct contact with this hydrocarbon quench liquid.
In this quenching step, just enou~h heat i5 removed to stop the partial oxidation ~,Q99~4 reaction and lower the temperature of the gaseous fuel to a point where it can be transported and handled by normal equipmentr This is in contrast to the common quenching processes for partial oxidation reactions, whereby the temperatures of the gases are lowered considerably further ~o that the ~ases are suitable for other processing steps, such as acid gas removal or compre~sion. Since the gases of the instat invention are to be used directly for fuel, the temperatures are lowered ~ust to the point ~hat the gases are usable in practical equipment. Thus, the process does not entail the energy losses and inefficiencies tbat are part of conventional quenching steps, and whicb waste part of the heat produced by tbe exothermic partial oxidation reaction.
The quenching is done most conveniently by direct contact with a recirculating heavy hydrocarbon quench liquid. Several ty~es of quenching apparatus whicb are direct liquid contact are ~nown and are in use. Quenchers in which the quencb liquid is ~prayed into the ~as stream would be especially suitable: those in which the gas stream flow~ through a body of quench li~uid (immersion quenchers) are also suitable. However, other types of quencher wbich would also be suitable can be conceived of, and could be used to practice this invention.
Some procedures utilize water to extract the solid ~oot and ash from the ~aseous stream and other techniques utilize a hydrocarbon oil to effect tbe same results. The advantage of utilizing a hyarocarbon oil iE that the oil plus the soot and D-1355~

~2Q9944 g ash products therein may be recycled directly back to tbe feed of`the partial oxidation step and when water is used to effect quenching, another separation step ~u t be introduced.
When tbe solid products are separated from the qaseous products, ~ome heat is removed by the quench fluid, thus lowering the temperature of the product gase6. As little of this sensible heat as pos~ible sbould be removed so that ~uch heat can add to the heat production by the combustion reaction of the ACR. Therefore, the quenching and soot extraction is carried out in a manner such that the qases e~it at a fairly high temperature, while still removing the bulk of the soot.
The gaseous effluent which is taken off from ~be ~eparation ~tep is typically a bot stream at a temperature ranging from about 300C up to about 1200C, preferably at a temperature from about 600C to about 1000C. That stream will contain hydrogen, carbon monoxide, carbon dioxide, water, hydrogen sulfide, and carbonyl sulfide. Usually, users of synthesis gas do not want hydro~en sulfide and carbonyl sulfide in the products of that stream and will take steps to remove them. However, in the ~ractice of the instant invention, hydrogen sulfide and carbonyl sulfide do not adversely affect the operation of the ACR process. Consequently, those products may be left in the effluent comin~ from the soo~/ash removal step. This provides the advantage of using a hot ~ynthesis gas ~tream as a feedstream to the ACR combustion step. Consequently, a savings in fuel costs and oxy~en are provided.
The ~ynthesis~gas-containing steeam whicb is obtained from the partial oxiBation reaction is 12~9!~44 fed while hot to the burner of the combustlon zone of the ACR wherein it is mixed with oxygen in an amount sufficient to effect essentially complete combustion of the hydrogen and carbon monoxide values within the synthesis gas. Utilizing the ratio of one-half mole of oxygen for each mole of hydrogen and one-half mole of oxygen for each mole of carbon monoxide, one should select an amount of oxygen which will leave the gas stream with a residual amount of synthesis gas still present.
The oxygen can be preheated to temperatures of up to approximately 80ooc before it is fed into the ACR
combustion zone. In the typical operation of the process of the invention, approximately 90 per cent or more of the ~ynthesis gas is converted to combustion products. Since the usual synthesis gas whlch will be obtalned will contain about a one-to-one molar ratio of hydrogen to carbon monoxide, then one will utilize approximately one-half mole of oxygen for each mole of synthesis gas.
The remainder of the ACR process is practiced exactly as is descrlbed in the prior art. The feedstock which is fed to the ACR reaction may be shrouded in steam as described ln U.~. Patent No. 4,136,015 and U.S.
Patent No. 4,142,963. The steam can be preheated to a temperature of 300C-1200C before i~ is fed into the Advanced Cracking Reactor combustion zones. The combustion product stream and the hydrocarbon feedstock can be thereafter fed to the cracking zone (termed in the priQr art as the diffuser/reactor zonej wherein cracking takes place to produce the desired products of the ACR proce~s.

, . ,~

lzl~994~

~ he con~entional ACR ic characterized in U.
S. Patent No. 4,136,015. In particular the concept of a throated region through which the gas streams are passed at sonic velocity to obtain ~uper-sonic velocities in a diverging difuser/reactor zone is a preferred ~y~tem ~or carrying out tbe ACR prccess~
_ Quenching below the reactor zone as described in U.
S. Patent No. 4,136,015 and U. S. Patent No.
4,142,963 is a preferred method of operation as well as tbe further quenching of the product streams as described in U. S. Patent No. 4,150,716.
The feed of hydrocarbon feedstream into the combustion chamber to ~e admixed with the combustion product ~tream can be carried out in an angular direction as described in U. S. Patent No.
3,855,339, utilizing the ~team ~hroud principal described in U. S. Patent No. 4,142.963.
In the preferrea embodiment a steam shroud can also be injected along the diffuser/reactor wall~ by virtue of an inlet located at about the end of the throate~ section.
Though this invention has ~een described witb respect to a substantial number of 6pecific embodiment~ it is not intended that the invention should be ~o limited.
EXAMPLES

EXAMPLE I
A partial oxidation process produces a product gas consi6ting of 50 mole percent hydro~en and 50 mole percent carbon monoxide. This ~aseous fuel is burned in essentially pure oxy~en, with a~ded steam, to produce a beat carrier for the ACR

~2~9~4 process. ~he temperature of the heat carrier is 2000C, and the heat carrier i5 produced at the rate of 7.5 lb.~moles/100 lbs of feed. Oxygen is used at 95 percent of tbe stoichiometric amount.
After it~ production by partial oxidation, the fuel gas i5 quenched and cooled to 100C and fed to the ACR burner. Oxygen is fed to the ACR burner at 25C and ~team at 350C. With these temperatures, the flow rates necessary to produce the desired heat carrier at the requisite temperature, and the resulting composition of the heat carrier is illustrated in Table A.
Example I indicates how fuel can be produced for the ACR, using a partial o~idation process under the present ~tate of the art.

EXA~PLE II
A fuel gas for the ACR process is produced and used in an identical way to EYamPle I, e~cept that the gas is only partially quenched to 800C.
With the fuel gas at this temperature, the flow rates necessary to produce the desired heat carrier at the requisite temperature and the resulting composition of the heat carrier are illustrated in Table A.
Example II illustrates the results that can be achieved when practicinq the process of this invention. By reducing the quench temperature to a range of appro~imately 600C-1900C, less fuel and oxygen are needed to generate a heat of eeaction temperature of 2000C. In Example II the quench temperatuee was 800C, and there were fuel 6a~ings of 3.06 lbs/100 lbs feed, and a 3.12 lbs/100 lbs - ~L2~99~4 feed reduction in the amount of oxygen utilized~Not only has a significant fuel and oxygen savings been realized, but additionally the amounts of carbon dio~ide and carbon monoxide in the ACR
effluent have ~een reduced. This allows for ~avings in subse~uent acid-gas removal processeC.
_, D-l 3 5 50 . , -~2Q9944 Tabl~ A

_ AMPLE I EXA~PLE II
Temperature of Heat Carrier2000C 2000C
~uench Temperature 100aC 800C
Flow Rates Necessary to Produce ~eat Carrier at 2000C~
Fuel 51b/100 lbs feed)35.75 32.69 Oxygen (lb/100 lbs feed)36.44 33.32 Steam (lb/100 lbs feed)80.61 84.2 Resultinq Composition of Heat C3 rrier:
Hydrogen llbs/100 lbs feed) 0.15 0.15 Oxygen (lbs/100 lbs feed)0.36 0.33 Carbon ~onoxide (lbs/100 lbs feed)1.18 1.01 Carbon Dioxide (lbs/100 lbs feed)50.57 46.36 ~team (lbs/100 lbs feed)112.07 113.99 ~-13550

Claims (5)

-15-

1. A method for providing gaseous fuel for an Advanced Cracking Reactor, which involves partially oxidizing a hydrocarbon fuel and quenching the gaseous products of such partial oxidation process to remove the bulk of the solid products while removing a minimal amount of the sensible heat of the partial combustion products, and feeding the remaining high-temperature gaseous products of said partial oxidation, usually at 300°C-1200°C to the combustion zone of the Advanced Cracking Reactor wherein such is combusted with oxygen and mixed with a hydrocarbon feedstream and then fed through the throat portion of the Advanced Cracking Reactor into the diffuser/reactor portion of said reactor wherein cracking of the hydrocarbon feedstream is effected.

2. The method of Claim 1 wherein the gaseous products of the partial oxidation process are quenched with a heavy oil or water.

3. The method of Claim 1 wherein the oxygen is preheated to a temperature of up to approximately 800°C before it is fed into the Advanced Cracking Reactor combustion zone.

4. The method of Claim 1 wherein the steam can be preheated to a temperature of approximately 300°C-1200°C before it is fed into the Advanced Cracking Reactor combustion zone.

5. The method of Claim 1 wherein the feedstock of the partial oxidation process is any gaseous liquid or solid hydrocarbon fuel.