US2557748A

US2557748A - Process for hydrocarbon conversion

Info

Publication number: US2557748A
Application number: US152383A
Authority: US
Inventors: George E Liedholm
Original assignee: Shell Development Co
Current assignee: Shell Development Co
Priority date: 1950-03-28
Filing date: 1950-03-28
Publication date: 1951-06-19
Anticipated expiration: 1968-06-19

Description

June 19, 1951 G. E. LIEDHOLM PROCESS FOR HYDROCARBON CONVERSION 2 Sheerls-Sheet 1 Filed March 28, 1950 k @w Lo fimcmmou ll J a jay-gs E. Lied helm His%orneg June 19, 1951 e. E. LIEDHOLM 2,

PROCESS FOR HYDROCARBON CONVERSION Filed March 28, 1950 2 Sheets-Sheet 2 Coke High Pressure Read-or Aemfion Gas Fig. 1b

G450?! Slur-r1. Oi! clcgji-Fied I Inven+or': Geor E. Liealholm 5L, a a- Hi AHor'neq 2. Co oils as charging stocks for the process. There a hot mixture of gas and Oil vapors and sus- Patented June 19, 1951 I UNITED STATES. PATENT OFFICE 2,557,748 PROCESS FOR HYDROCARBON CONVERSION George E. Lledholm, Berkeley, Calif., assignor to Shell Development Company, San Francisco, Calif.', a corporation of Delaware Application March 28, 1950, Serial No. 152,383

Claims. (Cl. 196-49) 2 The present invention relates to an improveproduces a relatively clean charging stock and ment in the art of converting heavy hydrocar an asphaltic residue. The second method is to bon oils into more useful products including vacuum flash the oil. This method, also in curcatalytic and non-catalytic hydrocarbon coninto low grade fuel oil. The third method, version steps carried out under special conditions which, as far as I am aware, is not used comto obtain a better utilization of the heavy hydromercially, is to subject the oil to a catalytic carbon oil in a practical manner. decarbonization treatment. This method has Reduced crude petroleum and similar residual not been developed sufliciently. The fourth nite, oilsand, representa large part of the'availa hot inert SOlld such as pebbles, sand, pumice able hydrocarbon oil supply and much eiiort or coke- This method is being developed at has been given to improve the utilization of such present.

the demand. It has therefore been the past catalytic hydro na ion, eg., the I. G. Destrucgested. The first is to thermally crack such 115 wasteful but far less costly removal of carbon.

leave a so-called black oil which is still suitable method by a novel Combination of process ps coke, Th e m th d b th of which are in process of this invention to be described has the present use, produce low quality gas oil and gascadvantages of t s p ty and low cost of line which require extensive refining with high thermal methods while at the same time achievprocesses, e. g., the Fluidized Catalytic Cracking x gen or hydrogen. 7

Process. There are numerous technical articles Broadly Speaking. the Process f t s invention d patents relating t t catalytic cracking comprises an integration of flashing, catalytic processes Many of t patents State that the cracking, and an operation which is in itself a process may be applied to such oils, but as will composite of "Contact flashing. a on" be seen from thetechnical literature, the use The feeds for these'operations' this is also borne out by many of the patents 1. Pumping the oil to be converted to a preswhich are directed to ways and means for prosure of at least 300 p. s. i. g.

ntacting said oil under said pressure with ing treatment. This method, in current use, ure oi. unconverted and partially converted liqconverted oil, and

commin 3 uid hydrocarbons containing suspended coke and a partially cooled vapor traction.

3. Releasing the pressure on said liquid fraction and iractionating the same at a pressure below 100 p. s. i. g. into a gasoline traction, an intermediate distillate traction of unconverted and partially converted oil, and a residue fraction of unconverted and partially converted oil containing the suspended cokel' 4. Bubiecting said intermediate fraction to eataiytic cracking.

5. I'ractionating the product oi said catalytic cracking into a gasoline. traction, an intermediate distillate fraction or unconverted and partially a residue traction.

ling at least a part of the product catalytic cracking heavier than gasoline with the above said residue traction unconverted and partially converted oil and'suspended coke.

'I. Pumping said last-mentioned mixture to a pressure of at least 300 p. s. i. g.

8. Heating said last-mentioned mixture.

9. Compressing the gases from step 5.

10. Beating the gases from step 9.

ll. Contacting said heated mixture from step sandsaidgasiromstep withafluidiaedmass orcokeatapressureoiatleastiwopai. g. thereby to produce a hot vaporized product of normal liquid hydrocarbon and gases con coke, and to deposit coke in the fluidined mass of coke.

12. Withdrawing coke from the said fluidised mass of coke.

13. Contacting the total vaporous products or step ii including said suspended coke with the tndoilasspeciiiedinstepz In a specific modification the coke withdrawn in step 12 is calcined at a graphitising temperature by partial combustion with air and the hot combustion gases are indirectly heat exchanged with the coke in step 11.

In another specific modification the coke withdrawn in step 12 is combusted under pressure; part of the hot combustion products is heat exehangedwiththehotcokeinstepllandtheremainder is utilized in a hot gas turbine.

Theprocesswillbeiurtherdescribedandexplained with reference to the accompanying drawings wherein a ilow diagram or a typical operation is illustrated. This flow diagram is shown in two parts which are given in Figs. Ia andIb. Reierringtothe drawingFlg.Ia.the feed which may, for example. be flasher pitch, thelike,entersvialine i. A small amount of coke or catalyst, to be later deto the feed from hopper I. The teed is pumped to a pressure or at least 300 p. s. i. g., e. g., 700 p. s. i. g., by pump I and is forced into the scrubbing tower I. The pumpability of the feed may be insured by preheating it or by adding a distillate traction (not shown). In scrubber l the teed passes downward countercurrent to a vapor stream oi-gas and oil containing suspended coke and in so doing it scrubs out the suspended coke and a substantial part or the less volatile constituents of the vapor stream and becomes itseli preheated. The vapors leavingthescrubbervialinelarecooledincoolerl and passed to a separator I from which the unoondensed gas is withdrawn overhead. This uneondensed gas, after expanding somewhat. e. g. to 300 p. s. i. g., is passed via line I to the absorber ll (Fig. 1b). The liquid product from the scrub- 8. from said I orten advantageous in the to the iractionator I. The feed to fractionator s. it will be noted, consists of the original reed plus gasoline. partially converted oil. heavy residual oil, and coke from a subsequent operation to be described. This mixture is separated in iractionator 8 into a gasoline plus gas fraction which is withdrawn overhead and Md to the absorber II: also. a rdlux condensate tractionwhichiswithdrawnthroughsidestrlpper ll; also a residue fraction containing suspended cokewhichiswithdrawniromthebottomvialine' ii. The reflux condensate traction heavier than gasoline withdrawn through side stripper II is an excellent feed stock for catalytic cracking and is catalytically cracked in reactor II. In the iiow illustrated. the catalytic cracking feed oil is iniected directly into the bottom of the cataly i cracking reactor by a seriu of nozzles. While this has distinct advantages over the conventional method ior introducing the teed into the catalytic cracking zone. it is to be understood that the invention is not limited to this feature, nortotheuseoiany typeoicatalytie cracking plant. The catalytic cracking operation maybecarriedoutwithanyoneottheknown catalysts. Particularly suit ispassed ing catalyst, and the catalyst which are special During use the catalyst gradually taminated with small amounts oi iron (Ll-0.2% iron, irom traces of iron in m y likewise be process 0! the invention to include a small amount oi iron oxide. e. g.

In the system illustrated, the spent cracking catalystiromthereactor llispassedtoaneievatedhopperflvialineflinastreamotstrip- Pin ga .e.g.steam.toremoveheavydifliculty volatilixable by his Thus stripped products with the strippin as pass via' line ll to the iractionator 0. The heavy stripped roducts are therefore combined with the bottom product in line ii. The stripped catalyst passes, to the regenerator 20 via line 21, and alter regeneration it is then to further use.

The vapors from the catalytic cracking reactorpassvialine II to aconventionalrractionator M (Fig. Ib) wherein separation is made between a asoline plus gas traction which is cooled and. passed to a separator II; also a gas oil traction which is withdrawn through the side stripper II; also a residue fraction which is withdrawn iron the bottom. The gasoline fraction is passed via line II to the absorber ii. The gas oil is preier-' ably combined with the residue traction from, iractiomtor but some or all of it may be withdrawn via line is it desired. The residue traction from iractionator It is preferably separated in the conventional mannerJnto a slurry oil eontainlng asmallamountotcatalystandaelariiled oil. Anydesiredproportionorthisoilmaybo combined with the residue fraction from m. tionatortormaybewithdrawnvialine ll 4. as well as the condensate from separator I, or II.

The uncondensed gases from seperator II are compressed to a pressure above 300 p. s. i. 8., e. g. 700 p. s. i. g., and after passing through a catchpot 2| they are preheated in furnace 22.

The residue fraction fromfractionator 9 contains most of the original feed stock plus a considerable amount of partially converted products and unconverted oil from the other described operations. It also contains suspended coke. The coke is finely divided, e. g. passing a 20 mesh sieve. The amount of suspended coke may vary from a minimum of about 1 lb./bbl. up to the maximum concentration affording a pumpable suspension. While concentrations near or at the minimum may be used it is preferred to operate with concentrations toward the maximum end of the applicable range. amount of coke in the recommended.

In preheater 22 the gases from the catalyst cracking operation and the composite residual material are preheated. oil is raised to substantially the maximum tem-' perature which can be employed with the particu- 3311 oil in question without coking the preheater tubes. This temperature is in the order of 850-950 F. The maximum allowable preheat temperature is increased by the presence of the suspended coke and may also be further increased Thus, for example, an order of 100 lbs./bbl. is

duced via line 28. In general, however, it is preferred to preheat part of the catalytic cracking gas separately to a higher temperature than the oil. Thus, in the fiow illustrated, part of the cracking gas is passed via line 29 through separate coils in the furnace.

:l1t1on.

The coke withdrawn advantageous method is to pass the coke into a lower vessel 33 wherein it is blown with air introduced via line 34. The coke is maintained in a fluidized state and by partial combustion its temperature is raised to a graphitizing temperature in the order of 2500 dry, graphitized coke suitable for use in the production of electrodes may be produced by this method. The hot calcined coke is then passed to a cooling chamber 35 and is finally withdrawn via line 37.

In order to insure proper calcination of all of the coke it is desirable to provide the calcination vessel with one or more refractory grid plates 38; such plates, even if of quite open structure, substantially decrease top-to-bottom mixing and thereby insure a more uniform residence time in the vessel.

This method of handling the coke is particularly advantageous from two standpoints. In the first place, a valuable another advantageous variation 18 to operate the it will be seen, is catalytic cracking is involved. The process is designed and intended to be also applicable with existing catalytic cracking plants. Conventional catalytic cracking plants are invariably provided with a suitable absorber. In general, a rectified absorption syscracking plant. If the gases from the catalytic cracking portion were passed to the absorber in the usual way, not be sumcient to handle F. A substantially pure,

7 material which would normally be removed in the absorption system.

fluidized bed in Numerous attempts to operate such a fluidized bed have failed due to the particles of coke agglomerating into large masses. This difllculty is overcome in the present method by maintaining a large fluidized bed of coke so that the residence time of the coke in the reactor is at least several minutes. Other features of the described process which cooperate in preventing difflculty due to the agglomeration with coke particles are as follows:

1. Coke is cycled with the feed oil through the preheating coils. This allows a greater amount of heat to be supplied with the oil without coking the preheater tubes.

2. A portion of the catalytically cracked gas may be preheated with the coil and coke in the preheater tubes. This gas creates turbulence in the tubes and increases the amount of heat which may be supplied with the oil without coking the preheater tubes.

3. Part of the catalytically cracked gas may be separately preheated to a higher temperature than the oil and coke mixture thereby further increasing the amount of heat which may be supplied to the reactor 30 with the feed streams. This is possible since the heavier less refractory hydrocarbons, such as butane and pentane, are largely removed from the catalytically cracked gas through the substantial comprcssion and separation in vessel 2|.

4. Sensible heat in the combustion gases from the calcination step may be used to supply additional heat to the coke without changing the pressure.

5. Such larger particles as may be produced by agglomeration tend to collect at the bottom of vessel 30 and are removed substantially as soon as formed.

6. The preheated catalytically cracked gas is introduced in part at a lower level in vessel 80 than the mixture of oil and coke. Thus, in the plant illustrated, the mixture of oil and coke is passed to the reactor 30 via line 28, whereas the catalytically cracked gas (or a part of it) is introduced at lower points via lines 42 and II This tends to hasten the va orization of the oil, to dry the coke particles beyond the point of sticking, and to prevent sticking by considerable agitation.

I claim as my invention:

1. The process for the conversion of hydrocarbon oils to lower boiling hydrocarbon oils which comprises the steps of (1) pumping the of at least 300 p. s. i. g., (2) contacting said oil under said pressure with a hot mixture of normally gaseous and normally liquid hydrocarbons and coke produced as hereinafter specified thereby to obtain a partially heated liquid fraction of a mixture of unconverted and partially converted hydrocarbons containing suspended coke and a partially cooled vapor fraction, (3) releasing the pressure on said liquid fraction and fractionating the same at a pressure below 100 p. s. i. g. into a gasoline fraction, an intermediate distillate fraction of unconverted and partially converted oil and a residue fraction 01' unconverted and partially converted oil containing the suspended coke, (4) subjecting said intermediate fraction to catalytic cracking, (5) separately fractionating the product of said catalytic cracking into a gaseous fraction, a gasoline fraction, an intermediate distillate fraction of unconverted and partially converted oil and a residue traction, (6) commingling at least a part of said fraction from the catalytic cracking heavier than gasoline with the above said residue fraction of unconverted and partially converted oil and containing suspended coke thereby to produce a mixture of unconverted and partially converted oil and suspended coke, (7) pumping said lastmentioned mixture to a pressure of at least 300 p. s. i. g., (8) heating said last-mentioned mixture, (9) compressing said gaseous fraction from step 5 to at least 300 p. s. i. g., (10) heating said gaseous fraction from step 9, (11) contacting said heated mixture from step 8 and said gas of step 10 with a fluidized mass of coke at a pressure of at least 300 p. s. i. g. thereby to produce a hot vaporized product of normally liquid hydrocarbons and gases carrying suspended coke and to deposit coke in the fluidized mass of coke, (l2) withdrawing coke from said fluidized mass of coke, (13) contacting the total vaporous product of step 11 including said suspended coke with the feed oil as specifled in step 2.

2. Process according to claim 1 in which the coke withdrawn in step 12 is withdrawn to a separate calcination zone operating at substantially atmospheric presure in which the coke is heated to a graphitizing temperature by partial combustion with air, and the hot combustion gases resulting therefrom are heat exchanged with the coke in step 11.

3. Process according to claim 1 in which the heating of the gaseous fraction in step 10 is carried out in two portions, one portion being commingled with the oil plus coke in step 8, and the other portion being separately preheated to a higher temperature.

4. Process according to claim 1 in which the catalytic cracking in step 4 is carried out with a siliceous cracking catalyst containing between 0.5 and 1% of iron oxide (F8203).

5. Process according to claim 1 in which the coke is withdrawn in step 12 without substantial reduction in pressure and the hot gases of combustion are utilized in part to heat the coke in step 11 and in part to produce energy.

GEORGE E. LIEDHOLM.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS

Claims

1. THE PROCESS FOR THE CONVERSION OF HYDROCARBON OILS TO LOWER BOILING HYDROCARBON OILS WHICH COMPRISES THE STEPS OF (1) PUMPING THE OIL TO BE CONVERTED TO A PRESSURE OF AT LEAST 300 P.S.I.G., (2) CONTACTING SAID OIL UNDER SAID PRESSURE WITH A HOT MIXTURE OF NORMALLY GASEOUS AND NORMALLY LIQUID HYDROCARBONS AND COKE PRODUCED AS HEREINAFTER SPECIFIED THEREBY TO OBTAIN A PARTIALLY HEATED LIQUID FRACTION OF A MIXTURE OF UNCONVERTED AND PARTIALLY CONVERTED HYDROCARBONS CONTAINING SUSPENDED COKE AND A PARTIALLY COOLED VAPOR FRACTION, (3) RELEASING THE PRESSURE ON SAID LIQUID FRACTION AND FRACTIONATING THE SAME AT A PRESSURE BELOW 100 P.S.I.G. INTO A GASOLINE FRACTION, AN INTERMEDIATE DISTILLATE FRACTION OF UNCONVERTED AND PARTIALLY CONVERTED OIL AND A RESIDUE FRACTION OF UNCOVERTED AND PARTIALLY CONVERTED OIL CONTAINING THE SUSPENDED COKE, (4) SUBJECTING SAID INTERMEDIATE FRACTION TO CATALYTIC CRACKING, (5) SEPARATELY FRACTIONATING THE PRODUCT OF SAID CATALYTIC CRACKING INTO A GASEOUS FRACTION, A GASOLINE FRACTION, AN INTER MEDIATE DISTILLATE FRACTION OF UNCONVERTED AND PARTIALLY CONVERTED OIL AND A RESIDUE FRACTION, (6) COMMINGLING AT LEAST A PART OF SAID FRACTION FROM THE CATALSTIC CRACKING HEAVIER THAN GASOLINE WITH THE ABOVE SAID RESIDUE FRACTION OF UNCONVERTED AND PARTIALLY CONVERTED OIL AND CONTAINING SUSPENDED COKE THEREBY TO PRODUCE A MIXTURE OF UNCOVERTED AND PARTIALLY CONVERTED OIL AND SUSPENDED COKE, (7) PUMPING SAID LASTMENTIONED MIXTURE TO A PRESSURE OF AT LEAST 300 P.S.I.G., (8) HEATING SAID LAST-MENTIONED MIXTURE (9) COMPRESSING SAID GASEOUS FRACTION FROM STEP 5 TO AT LEAST 300 P.S.I.G., (10) HEATING SAID GASEOUS FRACTION FROM STEP 9, (11) CONTACTING SAID HEATED MIXTURE FROM STEP 8 AND SAID GAS OF STEP 10 WITH A FLUIDIZED MASS OF COKE AT A PRESSURE OF AT LEAST 300 P.S.I.G THEREBY TO PRODUCE A HOT VAPORIZED PRODUCT OF NORMALLY LIQUID HYDROCARBONS AND GASES CARRYING SUSPENDED COKE, AND TO DEPOSIT COKE IN THE FLUIDIZED MASS OF COKE, (12) WITHDRAWING COKE FROM SAID FLUIDIZED MASS OF COKE, (13) CONTACTING THE TOTAL VAPOROUS PRODUCT OF STEP 11 INCLUDING SAID SUSPENDED COKE WITH THE FEED OIL AS SPECIFIED IN STEP 2.