US2885350A - Hydrocoking of residual oils - Google Patents

Description

May 5, 1959 J. W. BROWN ET AL HYDROCOKING OF RESIDUAL OILS Filed Jan. 20. 1954 2 SheetsSheet 1 1 I5 FRACTIUNATOR com\ l 4 "1 -7-vmh-- 2 5 4O I x 1 1 TRAgUSIfig LINE C IN}: 151212;; R

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ACTIVATOR COKE PRODUCT 6 FEED s45 36 'srm CHARLES EJAHNIG JAMES W. BRCDWN 'NVENTORS HOMER z. MARTIN av Eda H- 53 AITORNEY May 5, 1959 J. w. BROWN ET AL 5,

- HYDROCOKING OFRESIDUAL OILS Filed-Jan. 20, 1954 Y 2 Sheets-Shet 2 FRAGTIOII A TOR /I2I nEcYcLE,

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CHARLES E.\JAHN|G JAMES W. BROWN INVENTORS HOMER Z.MAR I'INv b Kim H S ATTORNEY is to improve hydrogen consumption in by using activated coke as the contact solids, andl'to in- United States Patent HYDROCOKING OF RESIDUAL OILS James W. Brown, Elizabeth, Homer Z. Martin, Cranford,

and Charles E. Jahnig, Red Bank, Esso Research and Engineering Company, a corporation. of Delaware Application January 20, 1954, Serial No. 405,066 2 Claims. (CL 208F127) "This invention relates to a process for" producing improved yields of liquid distillate from heavy hydrocarbons. More specificallyit relates to a process wherein a heavy hydrocarbon such as residuum is cracked in the presence of activated coke and hydrogen under pressure, and wherein the production of the required activated coke and hydrogen both form an integral partof the process.

The upgrading of heavy petroleum fractions by various forms of coking has been receiving increasing attention in recent times. However, in general such processeshave tended to produce relatively large amounts of gas and coke, at the expense of more valuable liquid products. Furthermore, in view of the nature of the feed-, the quality of both the desired liquid distillate and the coke product has left much to be desired, particularly with respect to sulfiur content. a

It is the main object of the present invention to increase the yield andquality of the liquid distillate obtainable from heavy hydrocarbons. A more specific object is to suppress coke formation and-to obtain desulfurization or the products with the'aid of cheap hydrogen produced in the process. A still more specific object the coking zone tegra tethe required hydrogen production and cokeacti-. vation with the residuum conversion step- These and other objects, as well as the: nature andsscope: of the invention, will become more clearly apparentfirom the sub-.

sequent: description In the drawing- Figure 1 is a schematic illustration or an. embodiment of the invention according to which the residuum: converand. accompanying drawing.

sion as well as the hydrogen: generation and coke activaare carried outin the presence of a. dense turbulent bedoffluidized solids; :and

Figure 2is an illustration: of an alternative embodiment wherein the residuum: conversion is carried. out. in". liquid phase;

The essence. of. the invention: is: that: the heavy hydrocarbons feed. is cracked-m the presence or activatedv coke and? hydrogen. under pressure, while the: required: activated. coke as: well as: the hydrogen. are obtained as an integrab part of: the: process by reacting: steam withr coke.

In a separate reactor- Surplus hydrogen in the gas may be used for further hydrogenation or desultun'zation or other after-treatment of the; products withldawn: from the process.

The hydrocarbon. feed may be any stock which eon-.

tains a major or at least a. substantial fiact'ion whicmcannot be vaporized: at atmospheric pressure withoutxextensivevdecomposition. Such. stocks may; beiofi virgin: nature such as atmospheric residua, vacuum residua, whole crudes, tar or clarified oil. obtained: asbottoms upon fractionation of catalytieal-ly cracked gas oil, shale oil, and so. one In generalstocksused as" feeds in the present invention. will be: characterizedby aboilingrange extending well. above 1000 F. or even 1300 F., e.g.. they .mayhaveaninitial or they may be cycle stocks such asviss-breaher.

velocity of about 0.5 to 3 ,ft/sec.

2 boiling point of about 700 to 1100 F., a gravity of about --l0 to 20 API, and a Conradson carbon content of about 5 to 40 weight percent.

"The feed stock is converted at a temperature of about .900 to 1100 R, either in a fluid bed or in a liquid phase slurry, in: the presence of activated coke and hydrogen. The fresh activated coke may be added to the conversion zone at a rate of about 0.1 to 5 lbs. per lb. of residual feed. Hydrogen is maintained in the conversion zone at a partial pressure of about 100 10500 psi, and the total pressure may accordingly be about 200 to 1.000 pus-.ig. The converted products will be withdrawn from the conversion zone and processed in an otherwise conv'cntional manner such as by char adsorption or low temperature product recovery. For instance, the temperatureof the products may be reduced to about F. prior to recovery. Further processing or the products may include factionation, additional desulfurization of the totalxefiiuent or of selected fractions, catalytic cracking, and so on.

Cokewill also be continuously Withdrawn from theconversion zone and then passed to a generator. There hydrogen and activated coke will be produced by reacting the coke with steam at a temperature between about 1400 vto 2000 F., e.g. 1700 to 1900 F., preferably under a pressure substantially equal to the conversion zone pres sure. Norm-ally about 2 to 5 lbs. of steam will be added to the generator per pound of coke converted, so as to .produce about 0.01 to 0.05 'lb.. of hydrogen. per pound of residuum feed going to the conversion zone. .However, if alarger proportion of hydrogen is desired, a fuel gas such as methane may also be fed to the generator with the steam so as to make hydrogen not only from coke but from the added hydrocarbon gas as well. The resulting hydrogen-containing gas and activated coke will then be passed from the generator to the conversion zone either in the form of a gaseous suspension or separately, dependingon the particular system used.

Heat may be conveniently supplied to the process by heating a. portion of the coke which circulates within the process. For instance, some coke may be withdrawn from the hydrogen generator and mixed with air or'sim-ilar oxygen-containing gas so as' to bring about partial combustion of. the Withdrawn coke. Such combustion may be carried out either in a transfer line reactor at relatively high. gas velocities, e.g. at 10- to 60 ft./ sec., or it. may be carried out in a. fluid combustion reactor Where the coke is maintained as a dense turbulent bed the gas which may pass upwardly therethrough at a In any event such combustion is regulated so as to heat the unburnt coke residue to about 1600 to 2200 'F., that is, hot enough to maintain the desired temperat re for steam conversion in the hydrogen generator and in the other parts of the process to which the reheated coke is returned. The coke may be circulated to the combustion vessel at a rate of about .5 to 20 lbs. per pound of liquid feed passing'to the conversion zone. Instead of feeding coke to the combustion vessel from the hydrogen generator, it is also 60:

possible to feed the coke directly from the residuum coking zone to a burner operated at atmospheric pressure and elevated a: substantial height above the coking zone, using'a shot heating system of the type described, for instance, in copending application Serial No. 236,782, filed on Iuly 14, 1951, byB urnsidecfal. now US. Patent "2,736,687, granted February 28, 1956. As still another alternative, an extraneous fuel, either gaseous, liquid, or

solid, may be fed to the combustion vessel and'the circulating coke may then be reheated either by direct con- ..tact with zth'e hot combustion gases or by indirect heat exchange therewith, avoiding the necessity of carrying out. the combustion at elevated pressure.

vated coke. The latter may be passed to the coking zone either by controlling the level in the activator so as to assure entrainment of the required amount of coke in the hydrogen gas passing to the coker, or the hot activated coke may be circulated to the coker separately. All hot coke from the burner is preferably passed to the activator rather than directly to the coker, so as to assure that the coke supplied to the coker has the highest activity available.

Since coke is continuously being'formed in the process, a net surplus of coke is usually available in excess of that consumed in the combustion and activation steps. This net surplus may be drawn off as product from any convenient point of the process, depending primarily on the intended end use. For instance, if an activated coke ,product is desired, it may be withdrawn from the hydrogen generator. If simply a dry coke of low volatile content is required, this may be recovered from the combustion vessel. Or if the excess coke is to be used as fuel, it may be recovered from the conversion zone. This may be done either directly, if the conversion zone is operated essentially in vapor phase with a fluid bed, or after filtration or other separation of the conversion zone efliuent, if the conversion zone is operated in liquid phase. Some of the circulating coke also may be continuously or at least intermittently ground in any convenient manner so as to maintain the particle size distribution substantially constant despite the tendency of the particles to grow as more and more liquid feed is coked thereon.

A specific example illustrating the present invention will now be described with reference to the embodiment shown in Figure 1. In this example a South Louisiana residuum of 107 API, 17 Conradson carbon and initial boiling point of about 1100 F. is introduced into the system through line 1, preheated to about 700 F. in fired coil 2, and sprayed through nozzles 3 into reactor 10 at a feed rate of about 40,000 gallons per hour. Reactor 10 preferably is a cylindrical vessel of about 5 to foot diameter and in its lower portion contains a dense turbulent mass of finely divided coke particles which are fluidized by gases and vapors flowing upwardly through the reactor at a velocity of about 1 to 4 ft./ sec. The particles preferably may range in size principally from about 40 to 300 microns, though minor amounts of particles even as large as 1000 microns may also be present. The depth of the dense mass of fluidizai particles in reactor 10 may be about 50 feet from the upper bed level 4 to the bottom of the vessel. Above level 4 is a dilute phase containing only a comparatively small amount of solids suspended in the gases leaving the reactor. The reaction temperature in vessel 10 is ad-' vantageously kept at about 950 to 1000 F. The reaction pressure may be about 500 p.s.i.g., with a hydrogen partial pressure of about 200 p.s.i.g. The cracked hydrocarbon vapors and other gases associated with them are withdrawn from an upper part of reactor 10, preferably after passage through a dust separating device such as cyclone 11, and passed through line 12 to a conventional fractionating tower 13. In tower 13 the withdrawn vapor phase may be fractionated into various cuts such as a fixed gas stream 14 rich in hydrogen and light hydrocarbons ranging from methane to propane, a naphtha cut 15 ranging from butanes up to materials boiling at about 430 F., a gas oil out 16 having a boiling range from about 430 to 1015 F., and a residual fraction 17 boiling above 1015" F. As an example, the conversion may produce about 8 weight percent of C -C fixed gas, 50 volume percent of C -430 F. naphtha, 30 volume percent of 430-650" F. gas oil, and 5 volume percent of feed introduced into the reactor. In addition, about 19 4 weight percent of solid carbonaceous residue or coke are produced in the conversion.

By comparison, a run carried out under similar oncethrough conditions but in the absence of hydrogen and activated coke, gave the following yields: C -C gas 10 wt. percent; C -430 naphtha 21.5 vol. percent; 430-650 gas oil 28.1 vol. percent; 650+ residue 23.2 vol. percent; coke 26 wt. percent. The importance of the invention in terms of increased liquid distillate, and particularly naphtha, as well as the greatly reduced coke and gas formation, are self-evident, and while recycling of liquid residue in the conventional coking operation can be used to reduce the amount of liquid residue to the same level as that obtained in accordance with the invention, it must be remembered that the resulting increase in liquid yields is obtained at the cost of still further increasing the wasteful formation of coke and fixed gas.

Coke is withdrawn from reactor 10 and passed through lines 5 and 6 to vessel 30 at a rate of about 1 lb. per pound of residuum feed. Net coke product may be withdrawn from the system through'lines 7 at a rate of about 0.07 lb. per pound of residuum feed.

In vessel 30 the coke is activated by reaction with steam, which at the same time produces the hydrogen required for the conversion zone. For this purpose superheated steam is introduced into vessel 30 through line 31 at a rate of about 14 lbs. per pound of hydrogen produced. The coke is activated to produce a surface area of at least 5 m.*/ g. A hydrocarbon gas may also be introduced into vessel 30 through line 32 at a rate of about I 10 lbs. per pound of hydrogen produced, so as to raise the hydrogen partial pressure. This hydrocarbon gas may be methane or other C to C hydrocarbon gases or the like. For instance, as mentioned before, an especially convenient source of hydrocarbon gas is the hydrogen-rich tail gas stream 14 separated in fractionator 13. Recycling of this stream 14 to vessel 30 thus permits both more complete utilization of the hydrogen present as well as formation of additional hydrogen by reaction of the light hydrocarbon gases with steam. A1- ternately, some advantage can also be obtained by recycling hydrogen-rich stream 14 directly to coking reactor 10. The preferred activation conditions in vessel -30 include a temperature of about 1800 F., pressure of about 500 p.s.i.g., and an average coke residence time of about 1 minute. The coke in vessel 30 is maintained as a dense turbulent mass by the fluidizing action of the gases which pass upwardly therethrough at a rate of about 1 to 4 ft./second.

The activated coke and the hydrogen-rich gas produced in vessel 30 may be transferred therefrom to conversion zone 10 in any convenient manner. For instance, the activated coke and the hydrogen-rich gas both may be removed from vessel 30 through overhead line 35 in the form of a solid-in-gas suspension which may contain about 1.0 lb. of coke per cu. ft. of gas. Or coke may be circulated from generator 30 to reactor 10 separately through a bottom draw-off, thereby offering an additional means for controlling reactor temperature. The activated coke is passed to the conversion vessel 10 at a rate of about 0.6 lb. per pound of liquid feed.

'Heat of reaction may be supplied to the system by withdrawing a portion of the coke from activator 30 through line 36 and passing it through a heater, where the coke is reheated to the desired temperature in an otherwise well known manner. For instance, the withdrawn coke may be mixed with an oxygen-containing gas 30 to reactor 10 is 'insuflicient to maintain the desired temperature in. the latter, a portion of the reheated partieles may also be passed iromeyelone 41 directly to reactor 10" through line "45. Alternately', to avoid the need for compressing the combustion air to process pressure, the circulating coke may be heated by indirect heat exchange with hot line gases which may be conveniently obtained in a burner operated at atmospheric pressure and a temperature of, say, about 2000 F.

Of course, instead of circulating the coke in the sequence just described, it may be preferred to pass the coke from the coker directly to the burner, and then the hot coke from the burner to the activator and finally back to the coker, rather than consuming any part of the activated coke in the burner.

Furthermore, in view of the hydrogen present in the coker, the invention makes it attractive to recycle considerable proportions of the cracked bottoms stream 17 from tower 13 to coker 10, since the hydrogen aids in converting this heavy fraction into valuable distillate in a manner not attainable in conventional coking.

Hydrogen consumption in the cracking zone may also be further increased by adding a metal-containing hydrogenation catalyst such as cobalt molybdate to the activated coke.

Figure 2 shows an alternative embodiment in which high yields of middle distillates are obtained by liquid phase cracking, rather than by fluid coking. According to this modification a residuum stream 101 of the type previously described is mixed with activated coke passing through line 102 so as to form a slurry containing about 5 pounds of finely divided activated coke per 100 pounds of liquid hydrocarbon. The activated coke again should have a specific surface area of at least 5 or m. /g. This liquid slurry may be preheated to about 800 F. in fired coil 103 prior to feeding into conversion vessel 110. In reactor 110 the slurry is kept at a tem perature of about 850 F. and a pressure of about 500 p.s.i.g. so as to form a predominantly liquid phase having an upper level 111, above which may be a vapor phase. Hydrogen mixed with carbon monoxide and dioxide and steam is produced in a later described step of the process and introduced at the bottom of reactor 110 through nozzles 115. In this manner the hydrogen-rich gas is intimately contacted with the feed slurry for the purpose of reacting therewith and also provides agitation which, in view of the added coke particles, assures that undesirable coke deposition on the reactor wall is avoided.

Reaction products are flashed from. the top of reactor 110 through line 112 into a still 120. Alternatively, reaction products may be removed from the liquid phase of reactor 110 through line 113. Still 120 may produce any desired combination of usual fractions, erg. a gas stream, naphtha, gas oil and bottoms containing unconverted residuum. As mentioned in connection with Figure 1, the hydrogen-rich gas stream may be recycled from the still overhead either to the later described hydrogen generator 140 or directly to the reactor 110. The largely unconverted bottoms from still 120 may be recycled to reactor 110 through lines 121 and 102 and coil 103. This recycle may amount to about 50 weight percent of the fresh feed.

A minor side stream equal to about 10 to 50 weight percent of the coke-containing still bottoms or slurry is removed from line 121 and passed through line 123 to separator 130 where the required amount of coke is separated from the hydrocarbon liquid and passed through line 131 to activator 140 while the net excess of coke formed in the process may be recovered through line 132. The amount of coke separated for activation may be about 0.05 lb. per pound of residuum feed. Separator 130 may be a filter though other devices capable of separating finely divided solids from a liquid may be used likewise. For instance, instead of a filter it is possible to use a fluid vaporizer wherein the slurry is fed into a hot dense turbulent bed of coke fluidized by an tupflowing gas such as steam orthe overhead stream from vessel 140. The temperature in such a fluid vaporizer is preferably kept at about 900 so that the liquid portion of the slurry is transformed into vapors, partly by evaporation and partly by cracking, and these vapors may then be returned to still 120. However, higher temperatures can be used similarly for evaporating the slurry. In fact, if the ratio of liquid to coke in the cycle bottoms is relatively small, the entire slurry side stream 123 may be injected directly'into activator 140 where the liquid :is quickly driven olf. Where zone is a filter, the filtrate may be passed through line and combined with the main slurry stream 121 for return to the conversion zone.

The coke introduced into vessel from separator 130 is activated at about 1600 F. and a pressure of 100 to 1000 p.s.i.g., preferably 500 p.s.i.g., in the presence of steam introduced through line 141, substantially as described in connection wtih Figure 1. The resulting activation gas comprises about 40 volume percent hydrogen admixed mainly with steam and carbon oxides. This gas passes through line 142 to liquid phase reactor 110, if desired after passage through a dust-separating device such as cyclone 145. Hydrogen may thus be fed to reactor 110 at a rate of about 2 weight percent based on fresh residuum feed. The activated coke may be removed from activator 140 through standpipe 147 and added to the recycle stream 121 at a rate of about 5 Weight percent based on fresh residuum fed to the process. Where the withdrawn activated coke is not fine enough, it may be advantageous to grind it in any convenient manner to a particle size range of about 40 microns before it is mixed with the recycle stream.

Heat to the process may be supplied in substantially the same manner as described in connection with Figure 1. Thus, some of the coke from the activator 140 or from separator 130 may be circulated through a heater or burner 150 where it is heated to the desired temperature, e.g. to 1900? F.

Having described specific examples as well as the general nature of the invention, it will be understood that the scope of the invention is not to be limited thereto except as particularly pointed out in the appended claims.

We claim:

1. A process for converting a heavy hydrocarbon oil boiling predominantly above 900 F. into lighter hydrocarbon products comprising a substantial gas oil fraction boiling predominantly below 900 R, which comprises preheating said heavy oil to a temperature between about 500 and 800 F., introducing the preheated oil into a coking zone containing a mass of finely divided activated coke at a temperature of about 900 to 1100 F., a total pressure of from 200 to 1000 p.s.i.g. and under a partial hydrogen pressure of about 100 to 500 p.s.i., passing a hydrogen-containing gas from an activation zone, referred to hereinafter, upwardly through said coking zone at a velocity suflicient to maintain said mass of activated coke in a dense, fluidized condition, removing converted hydrocarbon vapors ovenhead from said coking zone, removing spent coke particles from said coking zone, passing at least a portion of said removed spent coke particles to said activation zone, passing an activating gas consisting essentially of steam upwardly through said activation zone at a temperature between about 1700 and 1900 F., a pressure of about 100 to 1000 p.s.i.g. and at a. fluidizing velocity adapted to maintain said spent coke particles in the form of a dense, turbulent fluidized mass, thereby producing hydrogen and activated coke particles having a surface area of at least 5 m. /g., passing said activated coke particles to said coking zone at a rate of bout 0.1 to 5 lbs. of coke per lb. of heavy oil feed, feeding hydrogen-containing gas produced in said activation zone into said coking zone at a suflicient rate to maintain the aforesaid hydrogen partial pressure, supplying part of the heat of coking by the introduction of the-hot hydrogen-containing gas from said activation zone and the balance of the heat of coking by the hot activated coke particles, circulating some coke from-said activation zone through an external burning zone so as to reheat the circulating coke and then circulating it back to said activation zone to maintain said activation zone at the required activation temperature, removing excess coke ascoke product from said coking zone and utilizing all of said activated coke from said activation zone as the coke fed to said coking zone.

2. A process according to claim 1 wherein the hydrogen-containing gas produced in said activation zone and 1,933,435 -Kafier Oct. 31, 1933 2,527,575 Roetheli Oct. 31, 1950 2,600,430 RibIett June 17, 1952 2,606,862 Keith Aug. 12, 1952 2,738,307

Beckberger Mar. 13,, 1956

Claims (1)

1. A PROCESS FOR CONVERTING A HEAVY HYDROCARBON OIL BOILING PREDOMINANTLY ABOVE 900* F. INTO LIGHTER HYDROCARBON PRODUCTS COMPRISING A SUBSTANTIAL GAS OIL FRACTION BOILING PREDOMINANTLY BELOW 900* F., WHICH COMPRISES PREHEATING SAID HEAVY OIL TO A TEMPERATURE BETWEEN ABOUT 500* AND 800* F., INTRODUCING THE PREHEATED OIL INTO A COKING ZONE CONTAINING A MASS OF FINELY DIVIED ACTIVATED COKE AT A TEMPERATURE OF ABOUT 900* TO 1100* F., A TOTAL PRESSURE OF FROM 200 TO 1000 P.S.I.G. AND UNDER A PARATIAL HYDROGEN PRESSURE OF ABOUT 100 TO 500 P.S.I., PASSING A HYDROGEN-CONTAINING GAS FROM AN ACTIVATION ZONE, REFERRED TO HEREINAFTER, UPWARDLY THROUGH SAID COKING ZONE AT A VELOCITY SUFFUCIENT TO MAINTAIN SAID MASS OF ACTIVAED COKE IN A DENSE, FLUIDIZED CONDITION, REMOVING CONVERTED HYDROCARBON VAPORS OVERHEAD FROM SID COKING ZONE, REMOVING SPENT COKE PARTICLES FROM SAID COKING ZONE, PASSING AT LEAST A PORTION OF SAID REMOVED SPENT COKE PARTICLES TO SAID ACTIVATION ZONE, PASSING AN ACTIVATING GAS CONSISTING ESSENTIALLY OF STEAM UPWARDLY THROUGH SAID ACTIVATION ZONE AT A TEMPERATURE BETWEEN ABOUT 1700* AND 1900* F., A PRESSURE OF ABOUT 100 TO 1000 P.S.I.G. AND AT A FLUIDIZING VELOCITY ADAPTED TO MAINTAIN SAID SPENT COKE PARTICLES IN THE FORM OF A DENSE, TURBULENT FLUIDIZED MASS, THEREBY PRODUCING HYDROGEN AND ACTIVATED COKE PARTICLES HAVING A SURFACE AREA OF AT LEAST 5M.2/G., PASSING SAID ACTIVATED COKE PARTICLES TO SAID COKING ZONE AT A RATE OF ABOUT 0.1 TO 5 LBS. OF COKE PER LB. OF HEAVY OIL FEED, FEEDING HYDROGEN- CONTAINING GAS PRODUCED IN SAID ACTIVATION ZONE INTO SAID COKING ZONE AT A SUFFICIENT RATE TO MAINTAIN THE AFORESAID HYDROGEN PARTIAL PRESSURE, SUPPLYING PART OF THE HEAT OF COKING BY THE INTRODUCTION OF THE HOT HYDROGEN-CONTAINING GAS FROM SAID ACTIVATION ZONE AND THE BALANCE OF TAHE HEAT OF COKING BY THE HOT ACTIVATED COKE PARTICLES, CIRCULATING SOME COKE FROM SAID ACTIVATION ZONE THROUGH AN EXTERNAL BURNING ZONE SO AS TO REHEAT THE CIRCULATING COKE AND THE CIRCULATING IT BACK TO SAID ACTIVATION ZONE TO MAINTAIN SAID ACTIVATION ZONE AT THE REQUIRED ACTIVATION TEMPERATURE, REMOVING EXCESS COKE AS COKE PRODUCT FROM SAID COKING ZONE AND UTILIZING ALL OF SAID ACTIVATED COKE FROM SAID ACTIVATION ZONE AS THE COKE FED TO SAID COKING ZONE.

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