US2742410A - Continuous coking process - Google Patents

Description

April 17, 1956 A. H. scHuTTE CONTINUOUS COKING PROCESS Original Filed March lO INVENTOR \OO O AT'roN CONTINUOUS COKING PROCESS August H. Schutte, Hastings-on-Hudson, N. to The Lummus Company, New York, N. ration of Delaware Original application March 10, 1951, Serial No. 214,948, now Patent No. 2,658,031, dated November 3, 1953. gidgg and this application April 8, 1953, Serial No.

Y., assgnor Y., a corpoz claims. (ci. 2oz- 14) This invention relates to the continuous conversion of liquid hydrocarbon to coke and vaporous material in the presence of a continuously moving gravity packed column of coke particles which serve to supply the required heat for the reaction and become coated with the residual carbon, the-vaporous materials being separately withdrawn for further treating as desired. It is aspecic improvement on the method shown in my patent No. 2,561,334, issuedluly 24, 195i, of which I am co-inventor, and is a division of my co-pending application Serial No. 214,948, iiled March 10, 1951, which has now issued as Patent 2,658,031.

It has been pointed out that the use of moving columns of -gravity packed granular material serve as an excellent heat transfer medium for carryingout various physical and chemical conversions. Such systems can be and are being used for catalytic reactions particularly in vapor phase operations. The liquid phase operation raises a further complication however, for it is indispensable to most reactions that a uniform charge be given a uniform heat treatment. it is important that deviations from the average temperature at any one region be avoidedand every effort is made to have the contact material move through the reaction zone at a uniform rate.

My present invention is primarily concerned with a unique iiow control apparatus and the method of drying the coke particles to more eifectively obtain a continuous coking operation. l

Another principal object of my invention is to provide an improved apparatus for continuous Coking of heavy hydrocarbon oils, such apparatus being easily controlled, simple in construction, and relatively small in comparison to structures heretofore available.

Further objects and advantages of my invention will appear from the following description of a preferred form of embodiment thereof, taken in connection with the attached drawing, in which: i

Fig. 1 is an elevational View with parts in section of a continuous colting apparatus.

FigfZ is a detailed central vertical section of `the lower part of a reactor Vand as more specifically taken on the line 2-2 of Fig. l.

v Fig. 3 lis a horizontal cross section taken'on the line 3-.3 ofFig. 1.

yThe continuous coking cycle in accordance with the invention disclosed in Patent No. 2,561,334, above noted, includesV a pre-heating of granular petroleum coke particles as ultimately made in the system, such particles being fed to a reactor l0 from hopper 12 by gravity through line 14. The heavy hydrocarbon charge primarily in liquid phase and preheated to a temperature of about 800 F. but below the temperature of incipient cokng and not above the desired temperature ofthe reaction is applied to this hot coke by feeding the liquid through conduit 16 to one or more feed nozzles 18 which distribute the oil on the coke before it reaches the main body of the reactor 10. The reactor is preferably of such depth and the particles contain suflicient heat so that a predetermined 2,742,410 Patented Apr. 157, 1956 ICC reaction'temperature is maintained between about 850 F. and about 1050 F. so that the applied liquid will go to dryness before the particles are drawn 0E at 20. At least live minutes coke travel time and as much as forty minutes may be necessary between the fuel injection and ycoke draw off points based onseveralffactors hereinafter described in order that the coke may be removed in a dry unagglomerated condition. The hydrocarbon vapors are removed at 22.

In order to vsupply the heat requirements in the reactor the coke particles are passed through a reheater 24 in which the particles may be suitably heated by fuel gas and air entering at 26 or by partial combustion the coke is usually heated therein to about 1000 to 1050" F. The

products of combustion are removed at 28. l

The reheated coke particles are next passed alternatively through pressure drums 30 and 32 suitably controlled by inlet'valves 34a and 34h and by outlet valves 36a and 36h and thence into the blow case 38. By suitable controls Y not shown, a minimum particle level can be maintained in blow case 38 and with the application of a gas or stream lifting medium through line 40, a constant ilovv'of particles can be obtained through lift line 42. Discharge is into vapor separator 44 from which the heated vparticles continuously flow by gravity into hopper 12 through line 46 to complete the cycle.

It will. be understood that various flow control elements, valves and regulators will be used. In general, a circulation of one hundred tons per hour of granular coke: of from mesh to l/2v inch average particle size wiil be sufficient to reduce about 1000 barrels per day of a 10 API reduced crude having a Conradson carbon content of 13%. The net make of coke will be drawn off at 50 or other suitable location.

A particular feature of my present invention is the boti tom drawpotf for solids in the reactor 10 as more specifically shown in Fig. 2. Conveniently and preferably, the bottom 10a is conical shaped having anvangle of about 45 with the vertical. Within this section I provide a series of vertical splitter plates 52 and as shown in Fig. 3, I provide increasing numbers of plates as the cross section increases. In the lowermost bank for example, twelve are used. In the next higher bank, twenty-four will be used, and in the higher banks, the number will be correspondingly greater. Generally, I find three banks sufficient in addition to the bank at the draw off pipe 20 which of course establish the uniform draw off characteristics of the entire column.

Surmounting these splitter plates 52 is an inverted cone 54 which may in turn support the vapor draw o assembly. This includes a central pipe S6 in communication through slots 56a with the lateral vapor outlet 22. A vapor collecting cone 58 is. mounted above the central pipe 20.

The lower cone thus produces an annular flow to the splitter plates 52. The flow is then subdivided by the splitter plates into independent streams which uniformly supply the draw'ol pipe 20 which is of sufficient length distance between the two cones is adequate to insure the flow of particles therebetween, usually at least 6 to 8 particle diameters. By this means it is possible to insure a positive ow and to prevent any dead spaces in the vessel above the cone 58.

I may also use a grid of radial rods 60 to further subdivide the column of particles and to prevent the passage of any particle which would cause jamming in the outlet 20. These rods 60 may be mounted on the concentric grid of rods 61 and the steam sparger pipe 62. The steam sparger is fed by steam inlet 64 and serves to dry out the coke below the vapor draw olf.

It has been my experience that the vapor outlet 22 is most effective when it is not more than 1/3 and preferably A of the distance betweenrthe feed inlet and the particle draw off, above the outlet. Not only do I obtain adequate time for conversion of the liquid charge to vapors and dry coke, but I can also obtain an essentially vapor-free steam stripping zone below the vapor draw oi during which I obtain complete drying with the aid of steam introduced at 64.

The steam from the stripping zone serves to seal the reactor against Vegress of oil vapors (resulting from the conversion of the oil on the coke particles) with the coke thru draw off pipe 20. In passing up thm the stripping zone the steam becomes highly superheated by heat transfer with the coke and, upon entering draw olf cone 58 and mingling with the oil vapors from the upper reactor, this steam prevents dew-point condensation of heavy ends and resulting coking of the vapor drawoff system.

While I have shown and described a preferred form of embodiment of my invention, I am aware that modilcations may be made thereto which are within the scope and spirit of the disclosure herein and of the claims appended hereto.

I claim:

l. In a closed continuous and cyclic method of converting residual hydrocarbons into colte and hydrocarbon vapors, the steps comprising passing through a sealed reaction zone and a sealed reheating zone solely by the force of gravity a continuous gravity packed column of discrete particles of coke, spreading on the particles of said column Within the reaction zone a charge of the residual hydrocarbons substantially in liquid phase, the heat content and temperature of the particles entering the reaction zone being sufficient to raise the charge to the reaction temperature, said spreading of liquid phase hydrocarbons being such that the unvaporized portion wets the particles and is carried downwardly therewith, maintaining the movement of the wetted particles in the reaction zone for at least five minutes and for a period suflicient to convert the wetted portion of the particles to hydrocarbon vapors and a dry coke, passing the released hydrocarbon vapors downwardly through the column in the reaction zone and to a central particle free vapor collecting space in the lower portion of said column, introducing drying steam into the column below the hydrocarbon vapor collecting space for passage to said collecting space and mingling with hydrocarbon vapors from the upper portion of the reaction zone, whereby to prevent condensation of hydrocarbon vapors and coking in said collecting space, withdrawing all the released hydrocarbon vapors from the vapor collecting space to outside the reaction zone, removing the dry coke particles from the bottom of the reaction zone through a seal zone to prevent the escape of vapors therewith, the point of introduction of drying steam with respect to the point of withdrawal of the hydrocarbon vapors being such that the drying steam passes upwardly through from not more than one-quarter to one-third of the column of coke particles in said reaction Zone, passing said particles through a reheating zone and subjecting them to sufficient heat at such a temperature to raise their temperature to a point sufficient for reuse, and returning the reheated particles to the reaction zone.

2. The method of converting residual hydrocarbons into dry carbon residue and lower boiling hydrocarbon vapors in the presence of a particle form solid contact mass, which comprises preheating the particles of said contact mass, continuously moving the contact mass in said preheated condition uniformly downwardly through a sealed reaction zone as an unagitated gravity packed column, preheating the residual hydrocarbon charge to a temperature of about 800 F., but below the temperature of incipient coking and not above the desired temperature of reaction, applying the preheated charge comprising residual hydrocarbons substantially in liquid phase to said particles in the upper part of said reaction zone so that the initially unvaporized portion of the charge will move in a direction concurrent with the direction of column movement, mutually adjusting the inlet temperature of said contact particles to the reaction zone, the temperature of said preheated hydrocarbon charge, the rate of application of said preheated hydrocarbon charge and the rate of flow of said column of contact particles to maintain a predetermined reaction temperature of between about 850 F. and about 1050 F. in said reaction zone below the point of application of said charge, retaining the particles of said moving column in said reaction zone after said application of charge and without other addition of heat or further charge application for at least five minutes and for a time suicient to complete conversion of the said charge to lower boiling hydrocarbon vapors and nonagglomerating column particles having a dry carbon deposit thereon, passing said lower boiling hydrocarbon vapors downwardly through said column in the reaction Zone and to a central particle free vapor collecting space in the lower portion of said column, introducing drying steam into the column below the hydrocarbon vapor collecting space for passage to said collecting space and mingling with hydrocarbon vapors from the upper portion of the reaction zone, whereby to prevent condensation of hydrocarbon vapors and coking in said collecting space, withdrawing said hydrocarbon vapors from the vapor eollecting space to outside said reaction zone, the point of introduction of drying steam with respect to the point of withdrawal of the hydrocarbon vapors from the vapor collecting space being such that the drying steam passes upwardly through :from not more than one-quarter to onethird of the height of column particles in said reaction zone, continuously and uniformly withdrawing the solid contact mass `asfree llowing discrete particles from the reaction zone by a controlled gravity flow without agitation or application of mechanical force, and sealing the removal of the particles from the reaction zone against loss of hydrocarbon vapors therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 2,432,344 Sinclair Dec. 9, 1947 2,482,137 Schutte Sept. 20, 1949 2,546,625 Bergstrom Mar. 27, 1951V 2,558,769 McKinney July 3, 1951 2,561,334 Bowles et al. July 24, 1951 2,624,696 Schutte Ian. 6, 1953 2,643,216 Findlay Tune 23, 1953

Claims (1)

1. IN A CLOSED CONTINUOUS AND CYCLIC METHOD OF CONVERTING RESIDUAL HYDROCARBONS INTO COKE AND HYDROCARBON VAPORS, THE STEPS COMPRISING PASSING THROUGH A SEALED REACTION ZONE AND A SEALED REHEATING ZONE SOLELY BY THE FORCE OF GRAVITY A CONTINUOUS GRAVITY PACKED COLUMN OF DISCRETE PARTICLES OF COKE, SPREADING ON THE PARTICLES OF SAID COLUMN WITHIN THE REACTION ZONE A CHARGE OF RESIDUAL HYDROCARBONS SUBSTANTIALLY IN LIQUID PHASE, THE HEAT CONTENT AND TEMPERATURE OF THE PARTICLES ENTERING THE REACTION ZONE BEING SUFFICIENT TO RAISE THE CHARGE TO THE REACTION TEMPERATURE, SAID SPREADING OF LIQUID PHASE HYDROCARBONS BEING SUCH THAT THE UNVAPORIZED PORTION WETS THE PARTICLES AND IS CARRIED DOWNWARDLY THEREWITH, MAINTAINING THE MOVEMENT OF THE WETTED PARTICLES IN THE REACTION ZONE FOR AT LEAST FIVE MINUTES AND FOR A PERIOD SUFFICIENT TO CONVERT THE WETTED PORTION OF THE PARTICLES TO HYDROCARBON VAPORS AND A DRY COKE, PASSING THE RELEASED HYDROCARBON VAPORS DOWNWARDLY THROUGH THE COLUMN IN THE REACTION ZONE AND TO A CENTRAL PARTICLE FREE VAPOR COLLECTING SPACE IN THE LOWER PORTION OF SAID COLUMN, INTRODUCING DRYING STEAM INTO THE COLUMN BELOW THE HYDROCARBON VAPOR COLLECTING SPACE FOR PASSAGE TO SAID COLLECTING SPACE AND MINGLING WITH HYDROCARBON VAPORS FROM THE UPPER PORTION OF THE REACTION ZONE, WHEREBY TO PREVENT CONDENSATION OF HYDROCARBON VAPORS AND COKING IN SAID COLLECTING SPACE, WITHDRAWING ALL THE RELEASED HYDROCARBON VAPORS FROM THE VAPOR COLLECTING SPACE TO OUTSIDE THE REACTION ZONE, REMOVING THE DRY COKE PARTICLES FROM THE BOTTOM OF THE REACTION ZONE THROUGH A SEAL ZONE TO PREVENT THE ESCAPE OF VAPORS THEREWITH, THE POINT OF INTRODUCTION OF DRYING STEAM WITH RESPECT TO THE POINT OF WITHDRAWAL OF THE HYDROCARBON VAPORS BEING SUCH THAT THE DRYING STEAM PASSES UPWARDLY THROUGH FROM NOT MORE THAN ONE-QUATER TO ONE-THIRD OF THE COLUMN OF COKE PARTICLES IN SAID REACTION ZONE, PASSING SAID PARTICLES THROUGH A REHEATING ZONE AND SUBJECTING THEM TO SUFFICIENT HEAT AT SUCH A TEMPERATURE TO RAISE THEIR TEMPERATURE TO A POINT SUFFICIENT FOR REUSE, AND RETURNING THE REHEATED PARTICLES TO THE REACTION ZONE.

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