US2906689A - Two-stage residuum coking conversion process - Google Patents

Description

p 1959 J. F. MOSER, JR 2,906,689

TWO-STAGE RESIDUUM coxmc CONVERSION PROCESS Filed March 18, 1955 T0 msnum RE J E RY 1 CHEMICAL PRODUCTS l4 RECOVERY SEPARATOR- I ousncn 4 I -so MR I3 runs a T0 BURNER com- -|o a REHEATED COKE 6 I -0HENIOALS OOKER men NITROGEN q comm AM HEAVY on V l2 3 MFA u Sm" acumen COKE T0 aumnzn- Q JOHN F. MOSER. JR. INVENTOR BYX'. 64M ATTORNEY United States PatentO 2,906,689 TWO-STAGE RESIDUUM CoKING coNvERsioN PROCESS John Frederick Moser, .lr., Baton Rouge, 1121., 'assignor to Esso Research and Engineering Company, a corporation of Delaware Application March is, 1935, Serial No. 493,179

3 Claims. c1. z'0s-- 'ss The present invention relates to the art "of residuum conversion. More particularly it pertains to a fluidized solids process for upgrading heavy oils, particularly oils of high nitrogen content, to hydrocarbon distillates suitable for use as fuels, and to hydrocarbons suitable for use as chemicals or chemical intermediates.

In its 'more specific aspects, this invention proposes a two-stage combination process for converting high nitrogen content heavy oils such as reduced 'crudes, shale oils, tars, and asphalts, into lighter and more valuable products.

The present process comprises the steps of converting a heavy oil in a fluidized solids fuels coking zone operating at a temperature in the range of 900 to l-100 F. to vapors and coke which is deposited on the fluidized solids. The vapors so produced are then separated to obtain light distillate products and a distillate gas oil boiling in a range within the limits of 700 to 1000 F. This gas oil is then converted in a transfer line chemicals coking zone at a temperature in the range of 1200 to 1600" 'to .light unsaturates desirable as chemicals or chemical intermediates. The heavy ends of the fuels coker 'efilue'r'it are recycled substantially to extinction. A common heating system may be used to supply the necessary heat for the pyrolysis in the form of high temperature solids to both the fuels and the chemicals coking zones.

This invention has particular applicability to the treatment of heavy oils which upon being pyrolytically upgraded yield a gas oil which, by reason of its high nitrogen content, 'ash content, or aromaticity, is decidedly unsuitable as a catalytic cracking feed stock. -As examples of typical heavy oil feed stocks, there maybe indentioncd California residua such as Zaca, Santa Maria and Los Angeles Basin, shale oils and coal tars, etc.

A'p'rincipal object of 'this invention is to devise a combination fuels and chemical coking :process that can economically process such heavy oil feeds that normally produce gas oils of unsatisfactory or poor catalytic cracking quality. Another object of this invention is 'to develop a fluid solids process that will satisfactorily up gr'ade heavy oils such as reduced crude's, a major portion of which boils above 900 -F., characterized by API gravities of -10 to 20, Conradson carbons of 5 to 50 wt. percent, and nitrogen contents of over 0.6 wt. percent.

The following description of the attached drawing will serveto make this invention more clear. The attached drawing depicts schematically a preferred embodiment 'of the two-stage combination process of this invention. The major items of equipment shown are a fluid coking reactor operated primarily to produce lighter distillate products from heavy oils, and a transfer line reactor Patented Sept. 29, 1959 2 saturates.- Adjunctive e'qiiipniem such as cyclonic separato'rs, fractionation zones and a solids heating zone or zones also form elements 'of the process.

The heavy oil to be upgraded which may be suitably preheated is introduced into the process via li-he 1 and is introduced in the fuels coker 10 via manifold injection system 2. The fuels coker 'c zi'aiitaiii's a nine bed of sanstantially fc'atalytically inert solids, preferably coke particles produced bythe process, having a particle size iii.- the range of 0 to 1000 microns and atfa coking temperature in the range of 900 to 1100" R, the fluidity at the bed being accomplished by injection of a fluidizin'g gas, e.g., steam, into the vessel via line 3 in amounts sufficient to secure fluidizing gas velocities in the range of 0.1 to 5 ft./sec., all of which is conventional and known in the art.

Upon contact with the hot solids, the heavy oil is partially vaporized and partially coked, the vapors being withdrawn overhead via line 4 after having entrained solids removed. Relatively cool solids with fresh 'd'e posits of coke are removed from the fuels coker via line 5 after being stripped of occluded hydrocarbons in stripping zone 10a and are circulated to a heating zone, e.g.,.a fluid burner, wherein the solids are reheated by partial combustion. Reheated solids are returned to the fuels coker via line '6 at a temperature 100 to 300 F. above the coking temperature. Solid/oil circulation ratios are maintained Within the range of 5/1 to 30/1 wt./wt.

A fluid bed reactor is preferred for carrying out this fuels coking reaction as a relatively long time must 'be allowed for the coking reaction. Average solids holding times in the order of 4 to 30 minutes are maintained in the fuels coker.

The vaporous eflluent from the fuels coker in line '4 is passed to separation zone, ,e.g., a serubber fractiona tor30, wherein at least a light distillate fraction-is recovered and removed as product via line 7 and a gas oil fraction boiling above about' 700 F. -is separated and removed via line 8. The heavy high boiling ends, boil: ing above "about 1000" to 1150 P}, that have approxi.

mately the same coking and vaporization characteristics 20 operated 'to produce .primarily light hydrocarbon unas the fresh feed, are recycled to the fuels coker via line 9 substantially toextinction. V p p The initial boiling .point of gas oil fraction in -linej is adjusted so that it will contain all, or substantially of the deleterious compounds such as nitrogen that would adversely affect the quality of the products removedby line 7;. It has previously been suggested to recycle this gas oil which is not amenable to catalytic cracking to the fuels coker in order to reduce it completely to lighter distillates. As conversion of this mat'er iatl must take place in the vapor phase because of its low boiling range, such recycle operation is not attractive. Because the coking temperature in the fuels coker is relatively low, high conversions of the gas oil which is refractory are diflicult to obtain. This results, then, in excessive recycle rates. This difficulty cannot economically be circumvented by increasing the coking temperature in the fuels coker because this results in an excessive thermal iieg-rada tion and loss of the light distillate products,

This invention proposes that this gasoil material be converted to useful chemical raw materials. This is done by injecting it into -a transfer line chemicals coker 20. Thus the former onerbasfrec eie "operation to reduce gas oil is obviated.

The initial boiling point of the gas on traction can an be adjusted, if it be desired, to balance the amount of the fresh feed converted to distillate fuels and to chemicals. In normal operations, it is preferred to maintain 430 F. conversions 1 in the fuels coker in the range of 30 to 60 vol. percent, and to maintain C conversions 2 in the chemicals coker in the range of 50 to 80 wt. percent. In this manner approximately 40 to 60 vol. percent of the fresh feed will be upgraded to light distillates, and the remainder, excluding coke, will be converted to chemical raw materials including light unsaturates such as ethylene, propylene, butenes and butadienes and aromatic tars.

The gas oil fraction in line 8 introduced into a transfer line chemicals coker 20 is admixed with freshly heated solids, preferably coke particles produced by the process having a size in the range of to 1000 microns. The solids are at temperatures in a range of l300 to 1800 F., and are admixed with the gas oil in amounts in the range of 2 to 20 lbs. per lb. of gas oil sufiicient to obtain a reaction temperature in the range of 1200 to 1600 F.

The transfer line reactor comprises a narrowly confined vertically disposed elongated conduit, suitably lined with a refractory material, and terminates in a cyclonic separator 11. The length of the reactor is such that reaction times before quenching in the order of 0.1 to 3 see. are achieved. A conveying gas, e.g., steam, light hydrocarbon gases, nitrogen or flue gases, is admitted to the base of the reactor via line 12 in amounts sufficient to achieve solids velocities in the transfer line reactor above 10 ft./sec., e.g., 60 ft./sec. The density of suspension in the transfer line reactor will range from 1 to 20 lbs/cu. ft.

The entrained solids are separated from the conversion products in separator 11 and are transferred by line 13 to a heating zone to be reheated. The conversion products removed from the cyclone by line 14 may be met with a quench supplied by line 15 to be cooled to a temperature below about 900 F. whereby further thermal reaction is arrested. This quench may comprise liquid, e.g., water, or cool oils, solids, e.g., cool coke particles, or gases, e.g., cool light hydrocarbons or steam. The conversion products are then subjected to further processing (not illustrated) to recover the desired chemicals. This further processing may include by way of illustration, fractionation, sorption, crystallization, extraction, extractive or azeotropic distillation and polymerization. The higher boiling material recovered from the chemicals coker effluent may conveniently be recycled to the fuels coker and/or the chemicals coker depending upon the boiling range of the material or may be marketed directly as specialty tars.

Heat for the process may be generated by burning a portion of the coke produced by the cracking reactions. In cases where the value of the coke is greater than other extraneous liquid or gaseous fuels the latter may be burnt to supply part or all of the required heat to the circulating coke particles. The contact solids used in the fuels and chemicals cokers may traverse essentially separate circuits or a common heating zone may be used. Fluid gravitating or moving bed burners or transfer line burners may be used to accomplish the heating of the solids. Also other direct or indirect heat exchange means may be used such as systems wherein heavy heatcarrying inert particles, e.g., shot, are mixed with the contact solids.

Example A heavy oil feed may comprise a California residuum having the following inspections: 4.3 API gravity, 908 F. initial boiling point, 24.2 wt. percent Conradson carbon, 1.3 wt. percent sulfur, 0.08 wt. percent ash at 1742 1 430 F. conversion is defined as 100 vol. percent of fresh feed to the fuels coker less vol. percent of products from fuels coker boiling above 430 F., excluding coke,

C3- conversion is defined as 100 vol. percent of gas 011 feed to the chemicals coker less vol. percent of products hav ing more than 3 carbon atoms. excluding coke.

F., 1.2 wt. percent nitrogen, and a viscosity at 275 F. of 317 SSF. The feed, preheated to a temperature of 500 F., is injected into the fuels coker maintained at a pressure of 6 p.s.i.g. having a fluid bed of coke particles of a size range of 50 to 1000 microns (250 microns median particle size) and a temperature fo 950 F. A bed density of 38 lbs/ft. is maintained at an average superficial fluidizing gas velocity of about 1.5 ft./sec. (requiring a fluidizing steam rate of 12 wt. percent on fresh feed). Reheated coke particles are supplied to the fuels coker at a temperature of 1125 F. and at circulation rate of 10 lbs/lb. of fresh feed. Under these conditions, a 430 F. conversion of 48.5 vol. percent is obtained. The fuels coker effluent is separated to obtain a gas oil boiling in a range of 700 to 1000 F., amounting to 25 vol. percent on fresh feed, and heavy ends boiling above 1000 F., amounting to 15 vol. percent on fresh feed. The heavy ends are recycled to extinction to the fuels coker.

The 700 to 1000 F. gas oil is admixed with 6 lbs/lb. of gas oil of coke particles at an initial temperature of 1600 F. 60 wt. percent on gas oil feed of steam at a temperature of 1000 F. is admixed with this suspension, and the resulting mixture is passed through the transfer line reactor at a velocity of 30 ft./sec., a density of 3 lbs./ft. an average temperature of 1300 F., and an outlet pressure of 6 p.s.i. Reaction time before quenching is maintained at 1 see. sufficient to secure a C conversion of the gas oil of 40 wt. percent.

Approximately 26.6 wt. percent of the fresh heavy oil feed will be converted to coke in the fuels coker, and less than 1 wt. percent of the gas oil will be converted to coke in the chemicals coker. In all, approximately 27 wt. percent of the fresh feed to the process will be degraded to coke, of which 10 wt. percent on feed will be burnt to supply heat to the process, and the remainder is removed as product.

Under these conditions, the following product yields are obtained from the California residuum based on fresh feed:

Having described this invention, and a preferred embodiment, what is sought to be protected by Letters Patent is succinctly set forth in the following claims.

What is claimed is:

1. A two-stage combination fuels and chemicals coking process for converting heavy hydrocarbon oils boiling mostly above 900 F., and which produce gas oils of unsatisfactory catalytic cracking quality upon coking, which comprises coking a heavy oil boiling mostly above 900 F. in a dense fluidized solids fuels coking zone containing finely divided coke particles at a temperature in the range of about 900 F. to 1100 F., to produce vaporous conversion products and coke at a 430 F.- conversion in the range of 30 to 60 vol. percent and recovering from said vaporous conversion products light distillate hydrocarbon products boiling below about 700 F., heavy ends boiling above about 1000 F. and a gas oil fraction boiling in a range of about 700 F. to 1000 F., then cracking said gas oil fraction by contact with finely divided coke at a higher temperature than said first stage and in the range of about 1200 F. to 1600 F. for a relatively short time in a separate upfiow vertically arranged chemicals transfer line coking Zone to produce normally gaseous unsaturated hydrocarbons suitable as chemicals and chemical intermediates at a C conversion in the range of 50 to 80 wt. percent and circulating said finely divided coke from each of said coking zones to a heating zone wherein the particles are reheated by partial combustion and back to maintain the respective reaction temperatures in said zones.

2. The process of claim 1 wherein said heavy hydrocarbon oil is typified by inspections in the following ranges: -lO to 20 API gravity, 5 to 50 wt. percent Conradson carbon and a nitrogen content over 0.6 wt. percent.

3. The process of claim 1 wherein said heavy ends boiling above about 1000 F. are recycled to said fuels coking zone substantially to extinction.

References Cited in the file of this patent UNITED STATES PATENTS Kimberlin et a1. Apr. 28, 1953 Adams et a1. Oct. 5, 1954 Jahnig et a1. Jan. 17, 1956 Kimberlin et a1 Oct. 23, 1956 Boston Nov. 19, 1957

Claims (1)

1. A TWO-STAGE COMBINATION FUELS AND CHEMICALS COKING PROCESS FOR CONVERTING HEAVY HYDROCARBON OILS BOILING MOSTLY ABOVE 900*F., AND WHICH PRODUCE GAS OILS OF UNSATIFACTORY CATALYTIC CRACKING QUALITY UPON COKING WHICH COMPRISES COKING A HEAVY OIL BOILING MOSTLY ABOVE 900*F. IN A DENSE FLUIDIZED SOLIDS FUELS COKING ZONE CONTAINING FINELY DIVIDED COKE PARTICLES AT A TEMPERATURE IN THE RANGE OF ABOUT 900*F. TO 1100*F., TO PRODUCE VAPOROUS CONVERSION PRODUCTS AND COKE AT A 430* F. CONVERSION IN THE RANGE OF 30 TO 60 VOL. PERCENT AND RECOVERING FROM SAID VAPOROUS CONVERSION PRODUCTS LIGHT DISTILLATE HYDROCARBON PRODUCTS HOILING BELOW ABOUT 700* F., HEAVY ENDS BOILING ABOVE ABOUT 1000*F. AND A GAS OIL FRACTION BOILING IN A RANGE OF ABOUT 700* F. TO 1000*F., THEN CRACKING SAID GAS OIL FRACTION BY CONTACT WITH FINELY DIVIDED COKE AT A HIGHER TEMPERATURE THAN SAID FIRST STAGE AND IN THE RANGE OF ABOUT 1200* F. TO 1600*F. FOR A RELATIVELY SHORT TIME IN A SEPARATE UPFLOW VERTICALLY ARRANGED CHEMICALS TRANSFER LINE COOKING ZONE TO PRODUCE NORMALLY GASEOUD UNSATURATED HYDROCARBONS SUISTABLE AS CHEMICALS AND CHEMICAL INTERMEDIATES AT A C3- CONVERSSION IN THE RANGE OF 50 TO 80 WT PERCENT AND CIRCULATING SAID FINELY DIVIDED COKE FROM EACH OF SAID COOKING ZONES TO A HEATING ZONE WHEREIN THE PARTICLES ARE REHEATED BY PRTIAL COMBUSTION AND BACK TO MAINTAIN THE RESPECTIVE REACTION TEMPERATURE IN SAID ZONES.

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