US3158566A - Combination fluid coking and calcining - Google Patents

Description

Nov. 24, 1964 c. w. TYSON COMBINATION FLUID coxzuc AND CALCINING Filed Jan. 3. 1961 Inventor Charles W. Tyson By w Patent Attorney United States Patent 3,158,566 COMBENATIQN FLUID CURING AND CALCINDIG Charles W. Tyson, Summit, NJ., assignor to Essa Research and Engineering Company, a corporation of Delaware Filed Jan. 3, 1961, Ser. No. 80,196 10 tClaims. (Cl. 208-427) This invention relates to a novel integrated coke calcining process. More particularly, it relates to an integrated coke calcining process wherein the coke is heated at a high velocity for a short contact time in the form of one or more confined streams prior to the calcining operation.

In the coking of heavy hydrocarbon oils such as heavy crudes, atmospheric and vacuum still crude residua, tars, pitches, etc., either for the production of fuel products, such as gasoline and gas oils, or for the production of chemical raw materials, such as aromatics and olefins, one of the major lay-products is petroleum coke. Typically, such feeds can have an initial boiling point of about 700 F. or higher, an A.P.I. gravity of about 0 to 20, e.g., 1.9, and a Conradson carbon content of about 5 to 40 wt. percent, e.g., 30 wt. percent. The amount of coke formed depends on the character of the materials being processed and, to some extent, upon the coking conditions. In the case of high Conradson carbon stock, such as residuum from Hawkins crude, the coke yield can be 20 wt. percent or higher on the residuum. Gther stocks have been found wherein the yield can be as high as 35 wt. percent. The coking of other hydrocarbon feeds, both liquid and gaseous, may be accomplished in a similar manner.

Since the value of the coke as fuel alone detracts from a coking process, more attractive uses for the coke have been sought. One of the major uses to which the coke has been put has been the manufacture of electrodes. Carbon electrodes find their major use in the electrical refining of alumina to produce aluminum metal. For this purpose, petroleum coke, because of its low ash content, is preferred to metallurgical coke.

Green (uncalcined) petroleum coke contains volatile matter which must be removed before the material is suitable for electrode purposes. This. removal is accomplished by calcining the coke at a high temperature. This is done commercially at temperatures of 1800 F. to 2400 F. in rotary kilns, vertical retorts, ovens, and the like. The calcining operation reduces the volatile content of coke to 0.5% or lower of the final product, raises its true density, and reduces the electrical resistivity of the known as the fluid coking process. The fluid coking unit 7 consists basically of a reaction vessel or coker and 'a burner vessel. In a typical operation, the heavy oil to be processed is injected into the reaction vessel containing a fluidized bed of inert solid particles, preferably coke particles, maintained at a temperature in the range of 850 F. to 1200 F., and preferably at 900 F. to 1100 F., for the production of fuels, or at a higher temperature, e.g., 1200 F. to l600 F., for the production of chemicals, i.e., aromatics and olefins. Uniform temperature exists in the fluidized coking bed. Uniform mixing in the fluidized bed results in virtually isothermic conditions and eifects almost instantaneous decomposition of the feed stock. In the reaction vessel or coker, the feed stock is partially vaporized and partially cracked. Product vapors are removed from the coking zone and sent to a frictionator for the recovery of gas and light distillates therefrom. Any heavy bottoms is usually returned to the coking zone. The coke produced in the process remains in the bed coated on the solid particles thereof.

The heat for carrying out the endothermic coking reaction is generated in the burner vessel. A stream of coke or coke-coated, solid inert particles, if the latter are used, is transferred from the reaction vessel or coker to the burner vessel employing a standpipe and riser system; air being supplied to the riser for conveying the'solids to the burner. Heated coke is then returned to the reaction vessel, usually by means'for a standpipe and control valve, thereby completing the cycle.

Sufficient coke or carbonaceous matter is usually burned with an oxygen-containing gas in the burning ves sel to bring the solids therein up to a temperature sufficient to maintain the system in heat balance. The burner solids are maintained at a higher temperature than the solids in the reaction vessel. About 5% of coke on the feed is burned for this purpose. This amounts to approximately 15% to 30% of the coke made in the process. The unburned portion of the coke represents the net coke formed in the process. This coke is preferably, withdrawn from the burner, normally cooled and sent to storage. The coke normally contains about 86% to 94% carbon, 1.5% to 2% hydrogen, 0.5% to 7.5% sulfur, 0.6% to 1.5% volatile matter at 1100 R, up to 6% volatile matter at 950 (3., and approximately 0.1% to 1.0% ash.

A more complete description of this technique of fluid solids coking can be obtained by reference to Pfeiifer et al., Patent No. 2,881,130, granted April 7, 1959. The method of fluid solids circulation described above is well known in the prior art. This solids handling technique is described in greaterdetail in Packie Patent 2,589,124, issued March 11, 1952.

This invention provides an improved method for producing and for calcining of the coke in a fluidized coke process. The method in one form comprises treating a stream of hot coke particles from the coking process without substantial cooling for short periods of time and at high velocities while in the form of a confined elongated stream, i.e., a conduit, by burning a stream of combustible gases and oxygen-containing gases under conditions so as to minimize the reduction of carbon dioxide to carbon monoxide, and likewise, the reduction of water vapor to hydrogen and carbon monoxide. The thusheated coke is then separated from the accompanying gases and sent, without substantial cooling, to a moving bed calcining and desulfurizing operation wherein it is subjected to high temperature soaking in order to remove volatile material therefrom, to increase its true density, and to lower its electrical resistivity. The hot combustion gases are separated from the heated cokeparticles at the end of said conduit and then passed through the usual heater vessel on the coking unit where they serve to heat the stream of circulating coke particles sufficiently to carry out the coking operation when recycled to the reaction vessel or coking zone. This method provides In the drawing, 1 is a coking vessel constructed of suitable materials for operation at about 9001600 F. A bed of coke particles preheated externally of the coking vessel to a sufiicient temperature to effect the desired coking is made up of suitable particles in the range of about 70 to 600 microns. For example, the coke particles may be preheated to about 1200 F. to maintain an average bed temperature of about 1000 F. in the coking vessel. The bed of solid particles reaches an upper level indicated by the numeral 5. The bed is fluidized by means of a gas such as steam entering the vessel at the bottom thereof via pipe 3. The fluidizing gas passes upwardly through the vessel at a superficial velocity of about 2 ft. per second establishing the solids as a fluidized, liquidsimulating bed having the indicated level. The fluidizing gas serves also to strip vapors and gases from the coke which flows down into the vessel via pipe 9, as will be later described.

Oil to be converted is preferably preheated to a temperature not above its cracking temperature, e.g., 600 F. It is introduced into the bed of hot coke particles via line 2, preferably at a plurality of points in the system. The oil upon contacting the hot particles undergoes decomposition and the vapors resulting therefrom assist in the fluidizing of the solids in the bed and add to its general mobility and turbulent state. The product vapors pass upwardly through the bed and are removed from the coking vessel via line 4 after passing through cyclone 6 from which solids are returned to the bed via dipleg 7. A stream of solid particles is removed from the coking vessel via line or J-bend 8 and transported With the assistance of steam and/ or air or other free oxygen-containing gas from lines 9 through riser line 10 into heating vessel 11. In the heating vessel 11 the solid or coke particles are maintained as a dense fluidized bed 12 having a level 13 while they are heated as described hereinbelow to a temperature sufiicient to supply the heat required to carry out the endothermic reaction occurring in the coking vessel 1. The temperature of the solids in the heating vessel is usually 100 F. to 300 F. higher than that of the solids in the coking vessel, e.g., 1200 F. in this example. The bed of coke is in a dense turbulent fluidized condition in heating vessel 11 in much the same manner as the bed in coking vessel 1. The solids are fluidized by the incoming air and combustion gases as described below. Combustion gases leave the bed of hot particles, pass through one or more cyclones 14 and are vented via line 16. Any entrained solids are returned to the bed via dipleg 15. A portion of the hot solids is continually removed from heating vessel 11 via valved line 9' and introduced into vessel 1 at one or more points in order to maintain heat balance in the reaction or coking portion of the system.

The net make coke, in whole or in part, is removed from the heating vessel 11 via line 17 without substantial cooling and introduced into a transfer line preheater conduit 18. This transfer, line 18 is heated by the hot combustion products formed by the supply of air through inlet line 19 and fuel gas such as methane, natural gas, refinery make gas, or the like, through inlet line 20 to burner 21 in vessel 22. Temperatures in the gas burner or vessel 22 may be about 3000 F. to 3500 F. The hot combustion products containing about 040% of excess air, or even containing less than theoretical air, are discharged from the bottom of vessel 22 into preheater conduit 18 where they pass cocurrently with the coke particles heating the same to temperatures of about 2500 F. Coke is transported through the transfer line preheater 18 at high velocities, e.g., -60 ft. per second, so that the contact time is about 1-10 seconds. The transported preheated coke and the combustion gases are separated at the end of the transfer line preheater. The combustion gases are discharged through line 23 into the bottom of heating vessel 11 and thence through distribution grid 24 into the dense bed of coke particles 12 in order to heat the same by. transfer of the sensible heat in the gases. Additional heat may be provided in vessel 11 by the combustion of a small portion of the carbonaceous material by the small, residual amount of oxygen in the combustion gases. Additional oxygen-containing gas may be added to line 23 from line 23A. The temperature in the zone in vessel 11 below grid 24 may be lowered by allowing some of the coke above the grid in vessel 24 to flow into the zone below the grid. Or, as an alternate, circulating coke in line 10 may enter vessel 11 via line 23.

The preheated coke is discharged from the end of conduit 18 through line 25 into the calcining and dcsulfurizing vessel 26.

Calcining and desulfurizing vessel 26 is operated usually with a moving, nonturbulent bed of coke particles maintained at a temperature of from about 1800 F. to 2800" F. For some operations, when residence time is less important, a fluidized bed may be used in vessel 26. The coke particles are retained in the calcining vessel or soaker 26 for about 3 minutes, or up to 5 hours, or as long as necessary to reduce the volatile content at 950 C. to 0.3% weight or less and to increase the real density to the maximum obtainable, or reduce the sulfur content to the desired level. Temperatures in the upper portion of the above range, e.g., 2200 F. to 2800 F., are used when it is desired to produce a low sulfur coke product and in this case, adequate residence time must be allowed to achieve the desired desulfurization. The calcining vesse or soaker can be operated batchwise, using more than one vessel if desired. The product coke withdrawn from the soaker through line 27 can be cooled by indirect heat exchange in a waste heat boiler or it can be cooled by water quenching, or by any other suitable means.

The control of the system will be essentially as follows; however, there may be other methods to accomplish this end. The level in coking vessel 1 will be maintained by the rate of removal of solids from this vessel by actuating valve 28 or other suitable means. The temperature in vessel 1 will be controlled by the rate of addition of hot coke by valve and temperature sensing instrument 29. The level in heating vessel 11 will be controlled by'the rate of solids removal from the calciner-desulfurizer by level sensing instrument 30 and valve 31. The temperature in heating vessel 11 will be controlled by the temperature sensing instrument 32, actuating the air and gas supply to burner vessel 22. The auxiliary air added to line 23 will also provide a control to the temperature in vessel 11. The instrument 32 will also control the ratio of gas to air to insure the desired degree of combustion of the gas entering line 18. Additional control of temperature, as mentioned above, may be obtained by the air or oxygen-containing gas admitted from conduit 23A. The temperature in the calciner-desulfurizer 26 will be controlled by the rate of coke flow in line 17 as controlled by valve 33. Opening valve 33 will lower the temperature in line 18. Solids which flow in line 18 will fill conduit 25 leading into vessel 26 and any excess will flow through line 23 to the heating vessel 11. An alternate method for control of the temperature in vessel 26 would be to supply two or more inlets and control valves (not shown) from line 17 to line 18 at spaced intervals along line 18. By control of the flow among these spaced inlets, the temperature in vessel 26 may be controlled. This method of control depends on lengthening the exposure time of the solids to the hot combustion gases for heating to increase solids temperature and lowering the time of exposureto decrease solids temperature.

Under certain circumstances it is possible to simplify the coking-calcining process just described. In the more simplified form, soaker vessel 26 would be eliminated and the flow from line 18 would proceed through line 23 to vessel 11. In this modification the flow of coke through the transfer line 18, wherein calcination takes place, would be large in magnitude compared with the coke production. Hence, essentially all the coke in vessel 11 would have been calcined at least once and part of the coke would have been calcined many times. Since there are no disadvantages to multiple calcination and only a very minor fraction of the coke would not. have been calcined, the simplification mentioned ofiers great advantage. In this modification calcined coke would be withdrawn from vessel 11. The calcined coke so removed may be cooled as hereinbefore described.

In order to express this invention more fully, the following co-nditions or" operation of the various components are set forth as follows:

Conditions in Fluid Coker 1 Broad Preferred Range Range Temperature, F 850-1, 600 900-1,100 Pressure, p,s.i.g 1 -50 -15 Superficial Velocity of D ftJsee 0.2-5 0. 5-3

Conditions in H cater 11 Broad Preferred Range Range Su erficial Velocit of Fluidizing Gas iii sec 0. 2-5 0. 5-3 Temperatyre, F 1, 000-1, 800 1, 050-1, 300

Conditions in Transfer Line Preheater 18 Broad Preferred Range Range Temperature (gas), F 1, 600-4, 000 1, 800-3, 000 Pressure, p.s.i.g 0-50 o-40 Superficial Velocity of Fluidizmg Gas,

1't./sec -200 20-100 Contact Time (solids), sec 0.1-100 1-20 Conditions in Calciner 26 Broad Preferred Range Range Residence Time, hrs 0. 01-10. 0 0.1-4.- 0 Temperature, l" 1-. 1, 600-3, 000 1, 700-2, 800 Gas Velocity, it./sec 0-10 0.1-1.0 Pressure, p .s.i.g 0-50 3. 0-40. 0

electrodes or in graphite manufacture.

The advantages of this process stem from the fact that a higher yield of coke may be obtained at the expense of gaseous fuel due to the fact that the heat for the process is obtained by burning an extraneous gaseous fuel and.

not the product coke. In many situations the value of coke is considerably higher than that of natural gas or a refinery gas as a fuel source. The second advantage is that it makes it possible to combine in a single operation, in a simple, efiicient manner, the stepsof coking and calcining in a single, integrated system or unit.

It is to be understood that this invention is not limited d What is claimed is:

comprises the steps of coking hydrocarbons by contacting the same with hot coke particles in a coking zone wherein the hydrocarbons are converted to product vapors and carbonaceous solids are deposited on the coke particles, removing product vapors from the coking zone, continuously removing a portion of the coke particles from the coking zone and transferring them to a main heating zone, passing hot combustion gases through said main heating zone in order to increase the temperature of said coke particles, returning a portion of the heated coke particles from the main heating zone to the coking zone, passing a confined stream of coke particles without substantial cooling from said main heating zone through a transfer line heating zone, passing hot combustion gases obtained from the burning in a separate burning zone of an extraneous fuel in the absence of coke particles concurrently with said stream of coke particles through said transfer line heating zone in order to heat the coke particles to calcining temperature, separating at least a portion of the thus heated coke from the said combustion gases, supplying said combustion gases from said transfer line heating zone to the bottom of said main heating zone for passage therethrough and heating of the coke particles therein as specified above, passing the hot coke from said transfer line heating zone to a calcining zone, maintaining the coke particles in the calcining zone at a temperature in the range of 1600 F. to 3000 F. for from about 1 minute to 10 hours and removing calcined coke from the calcining zone.

2. An integrated coking and calcining process Which comprises the steps of coking a heavy hydrocarbon oil by contacting the same with a dense, fluidized bed of coke particles at a temperature of about 850 F. to 1600" F. in a coking zone wherein the oil is converted to product vapors and carbonaceous solids are deposited on the coke particles, removing product vapors from the coking zone, continuously removing a portion of the coke particles from the dense, fluidized bed in the coking zone and transferring them to a main heating zone, passing hot combustion gases through a bed of said coke particles in said main heating zone to increase the temperature of said coke particles to about 1000 F. to 1800 F., returning a portion of the heated coke particles from the main heating zone to the coking zone, passing a confined stream of heated coke particles from said main heating zone through a transfer line heating zone, passing combustion gases obtained from the burning in a separate burning zone of an extraneous fuel at temperatures of from 1600 F. to 4000" F. concurrently with said stream of coke particles through said transfer line heating zone to heat the coke particles to calcining temfor passage therethrough and heating said 'bed of cOke' therein as specified above, passing the so-heated coke particles separated from said hot combustion gases at the end of said transfer line heater into a calcining zone, maintaining the coke particles in the calcining zone at a temperature in the range of 1600 F. to 3000" F. for

to the specific examples which have been offered merely as illustrations, and that modification may be made without departing from the spirit of the invention.

to product vapors and carbonaceous solids are deposited on the coke particles, removing product vapors from the coking zone, continuously removing a portion of the 1 coke particles from the dense, fluidized bed in the coking zone and transferring them to a main heating zone, passing hot combustion gases through a bed of said coke particles in said main heating zone to increase the temperature of said coke particles to about 1000 F. to 1800 F, returning a portion of the heated coke particles from the main heating zone to the coking zone, passing a confined stream of heated coke particles from said main heating zone through a transfer line heating zone, burning extraneous fuel in a burning zone and passing the resulting hot combustion gases at a temperature between about 1600 F. and 4000 F. concurrently with said stream of coke particles through said transfer line heating zone to heat the coke particles to a temperature between about 1600" F. and 3000 R, separating at least a portion of the thus heated coke from said combustion gases at the end of the transfer line heater and supplying said separated combustion gases to the bottom of said main heating zone for passage therethrough and heating said bed of coke particles therein as specified above, passing the so-heated coke particles separated from said hot combustion gases at the end of said transfer line heater into a calcining zone, maintaining the coke particles in the calcining zone at a temperature in the range of 1600 F. to 3000 F. for from about 1 minute to hours and removing calcined coke from said calcining zone. I

4. The process as defined in claim 1 in which oxygencontaining gas is added to the combustion gases supplied to the bottom of the main heating zone to effect the combustion of a small portion of the carbonaceous material therein. 1

5. The process as defined in claim 2 in which oxygencontaining gas is added to the combustion gases supplied to the bottom of the main heating zone to eifect the combustion of a small portion of the carbonaceous material therein.

6. The process as defined in claim 3 in which oxygencontaining gas is added to the combustion gases supplied to the bottom of the main heating zone to etfect the combustion of a small portion of the carbonaceous material therein.

7. The process as defined in claim 1 in which the superficial velocity of the hot combustion gases in the transfer line heating zone is within the range of from 10 to 200 ft./sec. and the contact time of the coke solids with the combustion gases is in the range of from about 0.1 to 100 seconds.

8. The process as defined in claim 2 in which the superficial velocity of the hot combustion gases in the transfer line heating zone is Within the range of from 10 to 200 ft./=sec. and the contact time of the coke solids with the combustion gases is in the range of from about 0.1 to seconds.

9. The process as defined in claim 3 in which the superficial velocity of the hot combustion gases in the transfer line heating zone is Within the range of from 10 to 200 ft./ sec. and the contact time of the coke solids with the combustion gases is in the range of from about 0.1 to 100 seconds.

10. An integrated coking and calcining process which comprises the steps of coking hydrocarbons by contacting the same with hot coke particles in a coking zone wherein the hydrocarbons are converted to product vapors and carbonaceous solids are deposited on the coke particles, removing product vapors from the coking zone, continuously removing a portion of the coke particles from the coking zone and transferring them to a main heating zone, passing hot combustion gases through said main heating zone in order to increase the temperature of said coke particles, returning a portion of the heated coke particles from the main heating zone to the coking zone, passing a confined stream of heated coke particles from said main heating zone into a transfer line heating zone, burning fluid fuel in a burner zone in the absence of coke particles to provide hot combustion gases, passing said last mentioned hot combustion gases into said transfor line heating zone for admixture with said introduced coke particles, passing the resulting admixture through said transfer line heating zone in order to heat the coke particles to calcining temperature, separating the thus heated coke from the said combustion gases, supplying said separated combustion gases from said transfer line heating zone to the bottom of said main heating zone for passage therethrough and for heating the coke particles therein as specified above, passing the so-heated separated coke particles from said transfer line heating zone to a calcining zone, maintaining the coke particles in the calcining zone at a temperature in the range of 1600 F. to 3000 F. for from about 1 minute to 10 hours and removing calcined coke from the calcining zone.

References Cited in the file of this patent UNiTED STATES PATENTS

Claims (1)

1. AN INTEGRATED COKING AND CALCINING PROCESS WHICH COMPRISES THE STEPS OF COKING HYDROCARBONS BY CONTACTING THE SAME WITH HOT COKE PARTICLES IN A COKING ZONE WHEREIN THE HYDROCARBON ARE CONVERTED TO PRODUCT VAPORS AND CARBONACEOUS SOLIDS ARE DEPOSITED ON THE COKE PARTICLES, REMOVING PRODUCT VAPORS FROM THE COKING ZONE, CONTINUOUSLY REMOVING A PORTION OF THE COKE PARTICLES FROM THE COKING ZONE AND TRANSFERRING THEM TO A MAIN HEATING ZONE, PASSING HOT COMBUSTION GASES THROUGH SAID MAIN HEATING ZONE IN ORDER TO INCREASE THE TEMPERATURE OF SAID COKE PARTICLES, RETURNING A PORTION OF THE HEATED COKE PARTICLES FROM THE MAIN HEATING ZONE TO THE COKING ZONE, PASSING A CONFINED STREAM OF COKE PARTICLES WITHOUT SUBSTANTIAL COOLING FROM SAID MAIN HEATING ZONE THROUGH A TRANSFER LINE HEATING ZONE, PASSING HOT COMBUSTION GASES OBTAINED FROM THE BURNING IN A SEPARATE BURNING ZONE OF AN EXTRANEOUS FUEL IN THE ABSENCE OF COKE PARTICLES CONCURRENTLY WITH SAID STREAM OF COKE PARTICLES THROUGH SAID TRANSFER LINE HEATING ZONE IN ORDER TO HEAT THE COKE PARTICLES TO CALCINING TEMPERATURE, SEPARATING AT LEAST A PORTION OF THE THUS HEATED COKE FROM THE SAID COMBUSTION GASES, SUPPLYING SAID COMBUSTION GASES FROM

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