US3519553A

US3519553A - Coal conversion process

Info

Publication number: US3519553A
Application number: US719315A
Authority: US
Inventors: Edwin S Johanson; Seymour C Schuman; Harold H Stotler; Ronald H Wolk
Original assignee: Hydrocarbon Research Inc
Current assignee: HRI Inc
Priority date: 1968-04-08
Filing date: 1968-04-08
Publication date: 1970-07-07
Anticipated expiration: 1987-07-07

Description

y 7, 1970 E. $.JOHANSON ETAL 3,519,553

COAL CONVERSION PROCESS i Filed April 8, 1968 GASEDUS pnooucrs 46 42 20 28 WASH uouw P AD D U TS A8 L 1' 55 40 L r SEPARATION :4 STEP COAL LURRY 4 r J HIGH CONCENTRATION A 10 12 16 RESIDUUNSTREAM HYDROGEN men CA8 EDWARD S. JDHANSON SEYMOUR DSCHUNAN HAROLD H. STDTLER RONALD H/WDLK INVEN'IORS BY A; M

AGENT United States Patent O COAL CONVERSFON PROCESS Edwin S. Johanson and Seymour C. Schuman, Princeton,

Harold H. Stotler, Westfield, and Ronald H. Wolk, Lawrence Township, Mercer County, N.J., assignors to Hydrocarbon Research, Inc., New York, N.Y., a corporation of New Jersey Filed Apr. 8, 1968, Ser. No. 719,315 Int. Cl. Cltlg 1/04 US. Cl. 208- 19 Claims ABSTRACT OF THE DISCLOSURE A process for the catalytic hydrocracking of solid carbonaceous feed materials by passing an oil slurry of the particulated feed with hydrogen upwardly through a catalytic reaction zone such that the catalyst bed is in the ebullated state and removing gaseous and liquid products from the reaction zone along with solids. The liquid products are fractionated into light distillates, middle oils, re cycle and slurry oils and a residuum and solids containing bottoms material. A wash liquid is then mixed with the bottoms material after which the combined wash liquid and bottoms material are subjected to a separation step whereby the residuum and other valuable hydrocarbons in the bottoms material which were retained by the solids are preferentially attracted by the Wash liquid. The solids are then separated from the wash liquid solution and the residuum and hydrocarbon products may be easily recovered from said wash liquid.

BACKGROUND OF THE INVENTION This invention pertains to the field of conversion of a carbonaceous solid material to valuable hydrocarbon liquids and gases. More specifically, it pertains to the catalytic hydrogenation of coal and similar materials to liquid hydrocarbons of the nature of light distillates, middle oils and residuum.

Numerous processes for the conversion of solid carbonaceous materials, such as coal, anthracite, bituminous and sub-bituminous coals, lignite and peat are known to the art. Recently, substantial improvements in the catalytic hydrocracking of these materials to valuable liquid and gaseous hydrocarbons have been developed, particularly, as disclosed in the Johanson patent, Re. 25,770 and the Schuman et al. US. Pat. No. 3,321,393. In such processes, a feed material such as coal, is pulverized and dried and is then fed in a slurry oil upwardly with hydrogen through a catalytic bed at high temperatures and pressures. The velocity of the gas and the slurry feed are such that the catalyst is put in a random state of motion and the overall catalytic bed is expanded to a volume substantially greater than its original volume. Such liquid phase expanded beds have been given the designation ebullated. Typical conditions used for such processes are temperatures in the range from about 700 to about 900 F., hydrogen pressures in the range from about 1000 to about 4000 pounds per square inch and coal throughputs from about 10 to about 50 pounds per cubic foot or reactor. These contacting systems have demonstrated superior eifectiveness in the conversion of coal, specifically with respect to the yield of valuable products from the coal.

One of the products from such a hydrocracking process, is a material which has properties similar to that of a petroleum residuum, and experience has shown that increased distillate yields can be obtained from the feed material by recycling the residuum product such that a maximum residuum concentration is maintained in the catalytic reaction zone. Thus, it has been usual in such processes to fractionate the products from the reaction zone into light distillates, middle oils including recycle and slurry oils, and residuum bottoms material and to recycle the bottoms. In these bottoms materials, however, there exists in addition to the residuum, a significant amount of ash and unconverted coal, usually in a 1:1 ratio of liquid to solid, which make it necessary, before recycling the high residuum concentration stream back to the reactor, to remove the solid materials. While numerous separation procedures are available in the art and, indeed, relatively high conversion yields have been obtained by using these separation procedures, a significant amount of residuum and valuable liquid hydrocarbon products are retained in the separated solids material. These products are partially lost when the solids are subjected to subsequent treatment, e.g., coking, and such loss can represent as much as a 6% decrease in overall feed conversion.

Heretofore, there have been no practical methods for etficiently removing the last remnants of hydrocarbons from the solids material, whereby the hydrocarbons could be returned to the process for further conversion to valuable products. The increased conversion yields of anywhere between 2 and 6%, that could be obtained by the recovery of these retained materials, are quite significant relevant to the economic feasibility of the coal conversion process.

SUMMARY OF THE INVENTION We have discovered that by the addition of a wash liquid to that fraction of the reactor efiluent which contains the solids material, prior to the separation step, a substantial increase in the recovery of the residuum and valuable hydrocarbon liquid that would normally be retained with the solids after the separation step, can be effected.

Particularly, our invention applies to processes for converting carbonaceous feed materials to liquid and gaseous products by passing a hydrocarbon oil slurry of the dried particulate feed upwardly with hydrogen through a reaction zone which contains a bed of a particulate catalyst such that the bed is in the ebullated state. Gaseous and liquid products are removed from the reaction zone, the liquid product consisting basically of 2 components. The first component contains various hydrocarbon products plus residuum material and the second component consists of the solids from the hydrogenation step, i.e., ash and unconverted coal. The liquid product containing these 2 components is then introduced to a separation step, along with the wash liquid which has a preferential attraction for one of these components. In the separation step which may be any of the numerous type of systems known to the art, such as contacting systems, fractionating systems, centrifugal force type separation devices or settling and filtration operations, the wash liquid is separated along with substantial amounts of that component which has been preferentially attracted from the other component. This, thereby, allows increased recovery of the first component from the second component, since the separation is facilitated by presence of the wash liquid.

The wash liquid used may be any one of a number of substances that have preferential affinity either for the hydrocarbon and residuum containing component or for the solids component. Modifications of the particular process are required depending on the nature of the wash liquid and on which component it has the pref erential afiinity for. For example, the wash liquid may be water which is introduced with the liquid product into the separation step. Under particular conditions of temperature and pressure, the water may be removed containing substantially all of the solids component with only traces of the more valuable hydrocarbon and residuum materials. The major portion of the first component, i.e., the hydrocarbons and residuum, would include traces of water and possibly water vapor which can easily be separated by known fractionation processes.

Alternatively, the wash liquid may be an organic material, such as acetone or various liquid hydrocarbons including both aromatic and aliphatic compounds, which would have a preferential aflinity for the hydrocarbon and residuum component. In the separation step, substantial amounts of this first component would dissolve in the wash liquid. This solution would then be removed to any one of a number of type of fractionation devices wherein the wash liquid may be removed and, if desired, recycled for further use. The residuum and hydrocarbon fractions may then be further fractionated and/or used as a slurry oil, etc.

Any wash liquid that is retained with the solids component may be recovered by thermal or extractive treatment either alone or in combination. A major advantage of using this type wash liquid is that it, in effect, replaces the residuum material that would have been retained with the solids and, consequently, lost in the coking operation. The wash liquid, on the other hand, may be easily recovered either directly from the coking step or from an intermediate thermal fractionation.

In the case where the wash liquid is acetone, the solids component which is removed from the separation step would normally be introduced to a water wash step. The acetone will preferentially be absorbed by the water which is easily separated from the washed solids and then the acetone may be recovered from the water by simple fractionation or flashing.

If the wash liquid is an aliphatic or aromatic hydrocarbon, the solids material which would retain a portion of this hydrocarbon wash liquid, may be subjected to a liquid S wash. The S0 will preferentially absorb the hydrocarbon wash liquid and this solution may easily be separated from the solids material. S0 is a liquid at below 14 F., thus, only simple refrigeration would be required to maintain this liquid wash. After separation of the S0 solution, sulfur dioxide may be easily separated from the hydrocarbon and residuum component by allowing the solution to warm to a temperature above 14 F., in which case the S0 will vaporize.

Thus, by the use of our invention, increased recovery of valuable hydrocarbons and residual materials can be achieved from the solids produced from a carbonaceous fuel conversion process. This results ultimately in an overall increased conversion yield.

DESCRIPTION OF THE DRAWING The drawing is a schematic flow diagram of a coal conversion process.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawing, a carbonaceous fuel material such as bituminous or sub-bituminous coal, lignite or peat, which has been pulverized and dried is introduced at line 10, along with a hydrogen rich gas at 12 and a high concentration residuum stream from the process at 16 through line 14 into the reaction zone 18. The slurry is normally about a 1:1 mixture of solids and oils. As described heretofore, the reaction zone contains a particulate catalyst which is in an ebullated state due to the velocity of the gas and liquid feed materials, upwardly through it. Gaseous products are removed through line 20 and proceed into separator 32, wherein they are flashed at a pressure somewhat lower than the reaction pressure to produce a light vapor product in line 30 and a liquid in line 36. The liquid products from the reaction zone are removed through line 24. A portion of said liquid products may be recycled to the reactor through line 22, if desired. The liquid products proceed to separation step 26 wherein they are separated to produce a vapor overhead in line 28, which is combined with the vapor products overhead from separator 32 in line 30. The liquid from 4 separation or flash stage 26 is removed through line 34 and combined with the liquid from flash step 32 in line 36. Separation stage 26 may consist of any number of combination of flash steps, fractionation steps and physical separation steps known to the processing art. For example, the liquid product in line 24 may first be flashed and the liquid and solids from the flash introduced to a liquid cyclone or solids separation unit. Most of the liquids with minimal amounts of the solids are separated and may be utilized as the recycle stream. This stream would consist essentially of residuum and heavy and middle gas oils. The remaining solids and retained residuum and oil may then be introduced to the process as shown and would be represented by stream 34. If desired, however, the solids and retained residuum material and oil may be put through an additional fractionation step. The bottoms from this step would then constitute stream 34. Regardless, however, of the series or combination of steps employed, one will always end up with a stream containing most of the solids and retained products. Thus, this invention is directed basically towards a method for recovering those retained products. The final result, however, of this increased recovery is an overall increase in the yield of distillate products from the coal conversion.

This liquid product now consists essentially of two components. The first component is a combination of light and middle hydrocarbon products and a residuum material i.e., materials boiling above 975 F. The second component is a solids material which consists essentially of ash and unconverted coal. A wash liquid is added to the liquid product through line 38 and the mixture of the wash liquid and the liquid product proceeds to separation step 40. While not specifically shown, a step to allow a finite amount of contact time is required so that the wash liquid may attract or absorb that component for which it has the preferred affinity. It is inherent in the design of the process that proper time for mixing, extracting, etc., be provided. For purposes of clarity, such mixing will be considered to take place in the step designated as the separation step.

The wash liquid has a particular affinity or attraction for one of the components in preference to the other and depending upon the nature of this attraction, the nature of the separation step is determined. Therefore, there are two modes of operation for treatment of the mixture of wash liquid and liquid products as follows:

MODE I Wash liquid aflinity for first component Wash liquids which would typically have an attraction for the first or hydrocarbon liquid and residuum component of the liquid product would include materials such as acetone, linear and cyclic aliphatic compounds containing from three to fourteen carbon atoms and monocyclic and fused aromatic and alkyl aromatic compounds such as benzene, toluene, the Xylenes, ethyl benzene, naphthalene, Tetralin, phenanthrene, etc.

The amount of wash liquid added to the liquid product depends on the nature of the wash liquid with respect to its affinity for the first component and the proportions of solid to liquid in the liquid product. We have found that it is most preferable to add about one to three volumes of wash liquid per Volume of liquid in the liquid product. If the volume of added Wash liquid is too little, the amount of recoverable first component attracted will be decreased whereas equipment size considerations limit the maximum volume of wash liquid that can practicably be used. In any event, the optimum relative amounts of wash liquid to liquid product may be easily determined by experimentation. In the case of this type of wash liquid, separation step 40 is preferentially a centrifugal force type device, such as a hydro-cyclone or a liquid centrifuge, although fractional distillation or flashing may also be used. From this separation step, a solution of the first component hydrocarbon liquid and residuum in the wash liquid is removed in line 42. The solution is introduced to fractionator 44 wherein the wash liquid is recovered in line 46 and the hydrocarbon and residuum products are removed through line 48. Fractionation step 44, of course, may consist of several fractionations, such that a variety of distillate cuts from the hydrocarbon and residuum product are obtained. The wash liquid recovered in line 46 may be recycled back to line 38, such that it will not be necessary to add large amounts of additional wash liquid from an external source. From the various distillate cuts from fractionation step 44, and product removal line 48, a high concentration residuum stream is removed through line 16 and recycled to the reactor. As has been pointed out, the purpose of this recycle is to maximize the residuum concentration in the coal reactor in order to increase overall conversion yields.

Dry coal feed, lb./hr./[ Distillate recycle, lb./lb. eoal Reactor slurry:

Residuum, wt. percent Solids, wt. percent Pressure, p.s.i.a Percent H2 in vent gas Percent ash in feed Yields of liquids, wt. percent dry coal:

Total C4+liquid 62.3 63. 9 64. 7 C4400 F 22. 4 23. 4 25. 400650 F 15. 9 16. 8 18. 1 650975 F 1. 2 11. 7 12. 4 975 F.+residuu.m 22. 8 12.0 9. 2 Unconvegted iash-lreegoaL- 10. 2 4. 5 3. 0

O4+liqui s a ter res uum r l is. 48.0 55.0 58.6 py 0 YB 14. 6 16. 3 17.0 None None 0) 1 Mixture of light aliphatic and aromatic hydrocarbons.

Example I illustrates the improvement that is obtained by use of our invention with respect to increased coal conversion and distillate yields. The operating conditions for each run were the same except that in run A, the recycle stream contained only distillate materials, i.e., low residuum concentration, while in run B, the separation step designated 40 was carried out without the wash liquid modification of the invention and the amount of residuum recycled was only that recovered from said step. Run C showed the same process as run B except that additional residuum has been recovered as a result of using the wash liquid modification of the invention. As shown, not only is the distillate yield and coal conversion increased by use of our invention, but also recovery of liquids from the residuum pyrolysis or coking step is increased.

A bottoms material from the centrifugal force device is removed through line 50. This consists essentially of the second component solids material with some retained wash liquid. If it is desired, the entire bottoms material may be removed in line 52 for further downstream treatment, e.g., a coking step. Alternately, the bottoms may be treated in an intermediate separation stage 56 which may consist of either thermal treatment, e.g., atmospheric or vacuum fractionation steps or solvent extraction. It is possible, of course, to use both thermal treatment and extraction procedures in combination.

The type solvent extraction step used depends on the nature of the wash liquid. If the wash liquid is acetone, the bottoms in line 50 would be mixed with water introduced through line 54, and this admixture would then proceed to an intermediate separation stage 56, wherein the water and bottoms are contacted for a sufiicient length of time and in such a manner whereby the acetone will be preferentially absorbed in the water. Such contacting procedures are well known in the art. The water acetone fraction is then removed through line 58 and the acetonefree solids with a small amount of water are removed through line 60. The acetone-water mixture in line 58 is then fractionated and the acetone is recovered and reused as wash liquid.

EXAMPLE II Recovery of acetone wash liquid Ratio acetone to liquid product 3:1 Composition of liquid product (wt. percent) Residuum and oil 62 Unreacted coal 18 Ash 20 =Residuum and oil removed by acetone (wt. percent) 84 Original acetone remaining in solids after separation treatment (wt. percent) 10 Original acetone remaining in solids after extraction with 2:1 wt./wt. water and fractionation 0.1

Example II illustrates the recovery of residuum and 011 that can be aifected by the use of acetone as the wash liquid. If further shows the amount of recovery of the acetone from the solids that can be achieved with water.

If, on the other hand, the wash liquid is an aromatic hydrocarbon, the extraction would be carried out by mixing the bottoms material in line 50 with an extraction solvent in which the wash liquid has substantial solubility such as liquid sulfur dioxide introduced through line 54. In this case, a refrigeration step, not shown, is required to maintain the stream below the boiling point of S0 i.e., 14 F. The liquid SO -bottoms mixture then proceeds to intermediate separation step 56 wherein most of the wash liquid preferentially dissolves in the liquid S0 It is a simple expedient then to separate the wash liquid-free solids which is removed in line 60 and the SO -WEISh liquid solution which is removed in line 58. This wash liquid solution is then warmed up to temperatures above 14 F., whereby the S0 vaporizes and is easily recovered by known methods. The SO -free wa'sh liquid is then recovered and used as a product eflluent.

If desired, of course, the pressure of the intermediate separation step may be so controlled such that the S0 is maintained in the liquid phase without refrigeration below ambient. The S0 would then be vaporized upon releasing the pressure.

MODE 11 Wash liquid affinity for solids component In this case, the wash liquid is Water and it is introduced through line 38 to the liquid product in an amount corresponding to about 1 to 10 parts of water by weight per part of unconverted coal and ash. The mixture is then introduced to separation step 40, operated in the range from about to about 600 F. and at a pressure in the range from about 30 p.s.i.g. to about 3000 p.s.i.g., the particular combination of temperature and pressure being such that a substantial portion of the added water remains in the liquid phase. In the operation of said separation step, pressure is released from the separation zone in such a manner that at least 10 standard cubic feet of gas per hour per cubic foot of volume of the separation zone is bled oif from the separation zone. In this case, the line designated as 42 may actually consist of several take-offs for various fractions, such as a gaseous stream containing water vapor, dissolved light and middle-weight hydrocarbons, a stream containing just hydrocarbons, without water, a residuum stream, etc. It is a simple engineering technique to further separate said hydrocarbon products from the water. The bottoms from the separation step in line 50 would consist essentially of water, unconverted coal and ash, i.e., the solids component, with minimal amounts of hydrocarbons soluble in benzene at less than F. Since 7 it is unnecessary with regard to the economics of the process to recover the water used as the wash liquid, this mixture may then be sent directly to further processing or released as plant Waste.

It is possible, also in this mode, to include additives such as caustic, wetting agents and other known types of surface active agents with the water to facilitate the separation of the two components.

As previously mentioned, the fractions removed in line 42 are directed to fractionation step 44 to produce various distillates and product fractions, one of which would include a high concentration residuum stream for recycle to the coal hydrogenation unit.

Obviously, many modifications and variations of the invention as hereinabove set forth may be made without departing from the spirit and scope thereof, and, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A process for conversion of solid carbonaceous feed materials to valuable liquid and gaseous products of the type wherein a slurry of the dry particulate feed in a hydrocarbon oil is passed upwardly with hydrogen at high temperatures and pressures through a reaction zone containing a bedof particulate catalyst which is expanded and in a state of random motion and wherein the liquid product contains a residuum and hydrocarbon liquid product first component and a solids second component and wherein the liquid product is subjected to a separation step wherein some of the first component is removed from the second component and wherein at least a portion of a high concentration residuum stream derived from the removed first component is recycled to the reaction zone, the improvement which comprises introducing a wash liquid, which has a preferential attraction for one of the components to the separation step and therein contacting the wash liquid with the liquid effluent for a time sufiicient to allow substantial attraction of the preferred component, and then removing the Wash liquid, including substantial amounts of the preferentially attracted component from the separation step.

2. The process as claimed in claim 1 wherein the solid carbonaceous feed is a fuel selected from the group consisting of bituminous and sub-bituminous coals anthracite, lignite and peat.

3. The process as claimed in claim 2 wherein the second component consists essentially of ash and unconverted feed material.

4. The process as claimed in claim 3 wherein the wash liquid has a preferential attraction for the first component and is a material selected from the group consisting of acetone, linear and cyclic aliphatic hydrocarbons containing from three to fourteen carbon atoms and monocyclic and fused aromatic and alkyl-aromatic compounds.

5. The process as claimed in claim 4 wherein the separation step utilizes a centrifugal force type device.

6. The process as claimed in claim 4 wherein the separation step is a fractionation process.

7. The process as claimed in claim 4 wherein the wash liquid after the separation step contains substantial amounts of the first component and which further includes the steps of:

(a) recovering the wash liquid from the first component; and (b) fractionating the wash liquid-free first component into product fractions, one of which is the high concentration residuum stream. 8. The process as claimed in claim 7 wherein the wash liquid is acetone.

9. The process as claimed in claim 7 wherein the wash liquid is a material selected from the group consisting of 8 linear and cyclic aliphatic hydrocarbons containing from three to fourteen carbon atoms and monocyclic and fused aromatic and alkyl-aromatic compounds.

10. The process as claimed in claim 7 which further includes the steps of (a) removing the second component including retained wash liquid from the separation step; and then (b) separating the retained wash liquid from the second component.

11. The process as claimed in claim 10 wherein the retained wash liquid is separated from the second component by fractionation.

12. The process as claimed in claim 10 wherein the retained Wash liquid is separated from the second component by solvent extraction of the wash liquid using a solvent in which the wash liquid has a high solubility and wherein the wash liquid is recovered from the solvent.

13. The process as claimed in claim 12 wherein the Wash liquid is acetone and the solvent is water.

14. The process as claimed in claim 12 wherein the wash liquid is a material selected from the group consisting of monocyclic and fused aromatic and alkyl-aromatic hydrocarbons and wherein the solvent is liquid sulfur dioxide.

15. The process as claimed in claim 12 wherein about one volume of wash liquid is added for each volume of liquid product in the separation step.

16. The process as claimed in claim 3 wherein the Wash liquid is Water.

17. The process as claimed in claim 16 which further includes:

(a) removing most of the water from the separation step along with substantially all of the second component; and

(b) fractionating the second component-free first component into water-free product fractions, one of the fractions being the high concentration residuum stream.

18. The process as claimed in claim 17 wherein the amount of Water used as wash liquid is in the range from about one to about ten parts by weight per part of ash and unconverted feed material and wherein the separation zone is operated at a temperature in the range from about F. to about 600 F. and at a pressure in the range from about 30 p.s.i.g. to about 3000 p.s.i.g., the combina tion of temperature and pressure being such that a substantial portion of the Water remains in the liquid phase and wherein pressure is released from the separation zone at a rate equivalent to at least 10 standard cubic feet of gas per hour per cubic foot of separation zone volume and wherein fractionated streams containing water vapor and light and middle-weight hydrocarbons, water free hydrocarbons, residuum and a stream containing water, unconverted feed material, and essentially free of hydrocarbon soluble in benzene at below F. are removed from the separation zone.

19. The process as claimed in claim 18 wherein additives selected from the group consisting of caustic, wetting agents and surface active agents are added to the water prior to its introduction to the liquid product.

References Cited UNITED STATES PATENTS Re. 25,770 4/1965 Johanson 20810 3,321,393 5/1967 Schurnan et a1. 208-l0 3,030,297 4/1962 Schroeder 208-8 S.N.700,485 4/ 1969 Hemminger et al 20810 DELBERT E. GANTZ, Primary Examiner V. OKEEFE, Assistant Examiner