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Publication numberUS3503867 A
Publication typeGrant
Publication dateMar 31, 1970
Filing dateMar 4, 1968
Priority dateMar 4, 1968
Publication numberUS 3503867 A, US 3503867A, US-A-3503867, US3503867 A, US3503867A
InventorsLudlam Leslie L, Skripek Milan, Whitehead Kenneth E
Original AssigneeAtlantic Richfield Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Process and system for producing synthetic crude from coal
US 3503867 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

lPROCESS AND SYSTEM FOR PRODUCING SYNTHETIC CRUDE FROM COAL Filed March 4. 1968 United States Patent O 3,503,867 PROCESS AND SYSTEM FOR PRODUCING SYNTHETIC CRUDE FROM COAL Leslie L. Ludlam, Garden Grove, Milan Skripek, Anaheim, and Kenneth E. Whitehead, Fullerton, Calif., assignors to Atlantic Richfield Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Mar. 4, 1968, Ser. No. 710,036

Int. Cl. Cg 1 00 U.S. Cl. 208-10 8 Claims ABSTRACT OF THE DISCLOSURE A process is disclosed for producing synthetic petroleum crude from coal, for use in a petroleum refining system, which includes low temperature carbonization of dried pulverized coal, hydrocracking of the combination of middle oil, tar and naphtha, vacuum distillation and secondary hydroheating of the low volatility components derived from the hydrocracking process and fractionation of the high volatility hydrocarbons from the hydrocracking unit and the secondarily hydrogenated low volatility components derived from the hydrocracking process.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a process and apparatus for producing liquid hydrocarbon products from coal. More specifically, this process relates to methods for producv ing synthetic petroleum crude by carbonization of coal and hydrotreating of coal tar products.

Description of the prior art There has -been a continuing interest in utilizing coal as a source of liquid hydrocarbon products since the advent of the internal combustion engine. Several processes have been developed which have attained technical importance to countries having limited access to petroleum reservoirs. A number of processes were developed in Germany to offset shortages in petroleum during World War II.

Of recent years, there has been a revival of interest in several processes for producing synthetic petroleum crude from coal, Researchers Disclose Cost of H-Coal Gasoline, Oil and Gas Journal, May 16, 1966, p. 155; Coal Knocks at Refinery Door, Chemical Week, Feb. 11, 1967. p. 29-35. While numerous processes have been proposed for producing liquid hydrocarbon synthetic petroleum crude from coal and the technical feasibility of a substantial number of these processes has been proved, no commercially feasible process of this type has been put into operation. Accordingly, it is an object of this invention to provide a commercially and a technically feasible process for producing synthetic petroleum crude from coal.

Processes for producing synthetic crude from coal range from the so-called topping processes wherein only a very minor fraction of the more volatile products produced by mild destructive distillation of coal is converted to liquid hydrocarbons, the remainder of the coal ybeing burned in the normal manner to produce steam, and those wherein an eiiort is made to convert essentially all of the carbon content of coal to liquid hydrocarbons. Exemplary of the latter class of processes are those described by Clark et al., Hydrogenation of Coal in a Fluidized Bed, Industrial and Engineering Chemistry, May 1961, p. 861-865; and Hellwig, et al., Make Liquid Fuels from Coal, Hydrocarbon Processing, vol. 45, p. 165-169, May 1966. In the former case, coal is carbonized in the dry 3,503,867 Patented Mar. 31, 1970 ICC state, the liquids and volatile components being carried out of a iluidized bed. In the latter case, coal is suspended in a liquid phase, which may consist of tar, along with a catalyst.

A number of processes have also been proposed wherein coal is subjected to a more severe carbonization or hydrogenation treatment to convert an intermediate fraction of the coal to liquid hydrocarbon material, leaving the more diicultly converted coal components for cornbustion in the normal manner; i.e., in coke-fired furnaces.

There is reason to believe that the most economical and commercially feasible process will be of this latter type wherein, by carefully balancing the energy requirements for converting coal fractions to liquid hydrocarbon materials against the value of the hydrocarbon materials produced, the value of the synthetic crude, plus the value of the less valuable combustible solid coal products and the by-products will substantially exceed the cost of treating the coal.

Since the most valuable of the products of the coal treatment process is the synthetic petroleum crude it will'ibe understood that the commercial feasibility of any such process is very largely dependent upon the quality, and hence the value, of the synthetic crude produced. For optimum value, the synthetic crude should be of such a quality that it can be lprocessed in a conventional petroleum refinery, along with petroleum crude, without substantial alteration of operating conditions. It has been suggested, however, that certain superior grades of fuel may be produced from synthetic petroleum crude derived from low temperature carbonization of coal. Accordingly, it as an object of the present invention to provide a method for producing synthetic petroleum crude which is, in its renery characteristics, substantially identical with high quality petroleum crude.

A large number of coal carbonizing processes are known; see e.g., Farr, Coal Carbonization New Methods and Objectives, Coal Age, December 1966, pp. 88-96, and hydrocracking of liquid hydrocarbons, most particularly petroleum crude, and hydrotreating of liquid hydrocarbon materials are well known in the prior art. The present invention constitutes an improved combination of such known treating steps and includes novel cycle and recycle steps.

SUMMARY OF THE INVENTION Without limiting the scope or applicability of the invention, the present process may be described, in its principal steps, as including the low temperature carbonization of coal for converting the more valuable carbonaceous components to liquid hydrocarbon materials, feeding the liquid `hydrocarbon materials and naphtha through a hydrocracking step, vacuum distilling the heavier components from the hydrocracking step and recycling the solid and low volatility components to the carbonizer, secondarily hydrotreating the volatile components from the vacuum distillation step and combining the more volatile components from the hydrocracking step and the secondarily hydrotreated components for fractionation to produce a synthetic petroleum crude for being handled according to conventional petroleum refining techniques. It is, accordingly, a principal object of the invention to provide an improved method for producing synthetic crude of a qualityk comparable to petroleum crude by low temperature carbonization and hydrocracking of coal components.

A more specific object of the invention includes the addition of naphtha components for combination with tar and middle oil components in the hydrocracking step of a process of the type disclosed.

A further specic object of the process disclosed includes the combination of phenols from the carbonizer in the secondary hydrotreating step for increasing the synthetic crude yield.

An additional object of the invention is the provision of a system for carrying out a process of the type described.

A further and more specific object of the invention iS the provision of a novel combination carbonization and hydrogenation system for extracting liquid hydrocarbon fractions from coal.

Other objects will be apparent from the specification which follows and from the drawings to which reference is now made.

BRIEF DESCRIPTION OF THE DRAWING The figure is an overall schematic diagram showing the system for carrying out the inventive process and illustrating the process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference is made now to the figure. The major components of the preferred system for carrying out the inventive process comprise a low temperature carbonizer 10, a hydrocracking unit 20, a vacuum still 30, a hydrotreater unit 40, and a fractionator 50. Auxiliary units which comprise important elements in the system include a char pulverizer 6i), a phenol extractor 70, an ammonia stripper 80, a naphtha recovery unit 90,*an acid gas removal unit 100, and a hydrogen generator 110.

The components of the system are, individually, known in the prior art and have been described. For example, the low temperature carbonizer may be of the type constructed by Lurgi Gesellschaft, Frankfurt am Main and described in the Lurgi Manual (1961). This process is also described by Peters, W. and Bertling, H., American Chemical Society Division of Fuel Chemistry Preprints, vol. 8, No. 3, pp. 77-88; (148th National American Chemical Society meeting, 1964). The carbonization unit consists of three main sections, carbonization, heat generation and volatiles collection, and utilizes hot char recycle to supply heat for the carbonization. Dried coal is fed by a double screw mixer, where it is mixed with hot recycle char, into the carbonization chamber. As the solids leave the mixer, they fall into the devolatilization vessel of the carbonizer at a temperature of from 800 to 1250 F., preferably about 1100 F. The devolatilization vessel is substantially free of air. Here slow devolatilization reactions are allowed to proceed, giving maximum yields of gas and liquids from the coal. This overall technique, which is termed flash carbonization, provides the Very rapid solid-solid heat transfer which is essential for maximum devolatilization of coal. This process gives higher liquid yields than gas-solid heat transfer yields. Char from the carbonization zone ows by gravity through a gas seal at the bottom of a lift pipe and the heat generation zone of the carbonizer and is conveyed upwardly by a high velocity mixture of flue gas and air where part of the char is consumed with the air to produce heat. Char at 1250 F. is collected in a bunker and allowed to flow by gravity for recycling into the inlet of the double screw mixer. Excess char is removed.

It should here be pointed out that the type of carbonizing unit just described has been used and found to be successful in the overall process; however, other carbonizers have been used as well with varying degrees of success and the description herein is simply exemplary of the preferred embodiment of the invention and the process is not limited to the use of the Lurgi-Ruhrgas (L-R) type carbonizer. The liquid output of the L-R carbonizer, as will be discussed in some detail hereinafter, comprises two streams, tar and middle oil, which are subsequently combined for treatment. Other carbonizers may produce only one output stream of tar which will be referred to herein as light tar to distinguishthis product from the heavier tar output stream of the Lurgi carbonizer described in the 4 exemplary embodiment. Light tar obviously can be produced simply by premixing the middle oil and tar prior to treatment if desired.

The hydrocracking unit is specifically designed to handle extremely heavy feed stocks. This unit may be of the type associated with the H-Oil process which has been described; e.g., Helwig, et al., Hydrocarbon Processing, supra; Chervenak, M. C., et al., H-Oil Process Treats Wide Range of Oils, Petroleum Rener, vol. 39, No. l0, pp. 151-156 (October 1960); Rapp, L. M., and Van Driesen, R. P., H-Oil Process Gives Product Flexibility, Hydrocarbon Processing/Petroleum Refiner, vol. 44, No. l2, pp. 103-108 (December 1965); and Prescott, J. H., Novel Route Upgrades the Bottom of the Crude Barrel, Chemical Engineering, vol. 72, No. 15, pp. 142-144 (July 18, 1966).

The aforementioned publications are incorporated by reference for the details of the process but the following brief description is given for completeness. The feed oWS upwardly through a reactor which contains a suspended catalyst to produce an ebullated catalyst bed. Isothermal conditions can be maintained in the bed even with highly exothermic reactions and the ebullated bed is capable of handling feed stocks which contain entrained solids or which tend to form coke readily.

The vacuum still 30, the secondary hydrotreater 40, and the fractionator 50 are all conventional units of the type used in petroleum rening. The char pulverizer 60 may be o-f any conventional typefand the phenol extractor 70 may be a Phenosolvan unit in which phenol-rich water is contacted contracurrently lwith isopropyl ether and the extract solvent is distilled to produce a crude phenol product. Units of this type and other phenol extraction units are in operation commercially, and are described in the Lurgi Manual, supra.

The amm-onia stripper is of conventional design and may be combined with a water treatment system, if desired.

The naphtha recovery unit is preferably of the type wherein the gases and highly volatile components from the carbonizer 10, the hydrocracking unit 20, the hydrotreater 40 and the fractionator 50 are combined and scrubbed with middle oil to remove the naphtha. The naphtha, carried by the middle oil or light tar, is then recycled as will be described.

In the acid gas removal unit 100, all of the HZS and most of the CO2 are removed by methanol extraction. The sulfur-containing gases are treated in the conventional manner to recover the sulfur values therein.

Hydrogen is generated, in the hydrogen generator unit 110, by reaction of carbon monoxide and steam to form CO2 and H2 according to known reactions. The gases are then catalytically reformed to convert the hydrocarbons and steam to CO, CO2 and H2. The CO in the gas reacts with residual steam to complete the conversion to CO2 and H2. Units of this type are also known commercially.

It will be apparent from the foregoing that most of the units of the invention are, individually, known in the prior art and are in general of the types commercially in use and which have been described in the literature. It is the novel combination of such units which comprises the present invention.

Referring now to the ligure, the process of this invention will be described.

Dried coal, which may include recycled hot char, passes from line 9 through a vapor lock into the lo'w temperature carbonizer 10. Non-volatilized coal components pass by gravity through a pressure seal to exit line 11. The tar components of the volatilized coal products comprise the heavier liquid fractions and entrained solid particulate matter and are transferred through line 12 to the hydrocracking unit 20. The middle oil fractions are also fed to the hydrocracking unit 20 through line 13. It will, of course, be remembered that in the inventive process using a different type of carbonizer only one liquid Stream, light tar, which may include entrained particles, will be produced or a light tar may be produced by c-ombining the tar and middle oil fractions from the Lurgi carbonizer described in the example.

The more volatile components, including the highly volatile hydrocarbons and xed gases produced or released by the low temperature carbonization process exit through line 14. The aqueous components are condensed and are withdrawn from the carbonizer through line 15 carrying the water soluble components, primarily phenols and arnmonia. Fractions of the flue gas from the carbonizer may be recycled through the coal dryer as shown at line 16 to conserve heat values.

The low vapor pressure liquids and entrained solids are removed from the hydrocracker 20 through line 21 to the 'vacuum still 30. The high vapor pressure hydrocarbons leave through line 22 to the fractionator as will be described more specifically hereinafter. Gaseous components and the very light hydrocarbons are carried through line 23 to the naphtha recovery system as will be described. Ammonia-rich waste water is condensed and is withdrawn through line 24 to the ammonia recovery and water treatment system.

The major portion of the synthetic crude hydrocarbon fractions exit through line 31 from the vacuum still 30 to the hydrotreater 40. The still bottoms, including the solid material, are recycled through line 32 to the low temperature carbonizer 10.

T he upgraded synthetic crude is transferred from the hydrotreater 40 through line 41 where it is combined with the high vapor pressure hydrocarbons exiting from the hydrocracking unit 20 through line 22 and fed to the fractionator 50 which separates the syncrude (synthetic petroleum crude) which exits through line 51 and may be transported to the renery, and the light hydrocarbons together with small quantities of the more highly volatile naphtha components which are returned through line 52 to the systemi Returning again to the rst steps in the process, the char from the low temperature carbonizer is removed through line 11 to the char pulverizer 60 and thence through a conveyor line indicated at 61 for recycling or for combustion as conventional coke.

Phenols from the phenol extractor 70 are conveyed through line 71 to the hydrotreater 40 for being upgraded, along with the hydrocarbon components from the vacuum still 30, to form the synthetic crude. The aqueous phase from the phenol extractor is combined with the aqueous phase from the hydrocracking unit 20 and from the secondary hydrotreater 40 and flows through line 72 to the ammonia stripper 80. Ammonia is removed through line 81 vto any desired type of ammonia recovery system for the production of fertilizer, industrial chemicals, etc. Waste water from the system exits through line 82 to a water treatment plant and is discharged.

The light hydrocarbons, naphtha and xed `gas streams are collected from the low temperature carbonizer 10 through line 14, the hydrocracking unit 20 through line 23, the hydrotreater 40 through line 42 and the fractionator 50 through line 52 and enter the naphtha recovery unit 90. As previously described, the naphtha is removed by scrubbing with middle oil and recycled through line 91 where it is combined with middle oil or light tar output of the low temperature carbonizer and fed to the hydrocracking unit 20. Recycling the naphtha in the manner described provides several importat advantages. The hydrocracking step .of the process may be more easily and eliciently conducted by recycling the naphtha in the manne; described and the quality of the synthetic crude is improved. It is entirely possible that the recycle step in the process described may make the difference between an economically practical system and a system which, while eing technically feasible, is not economically attractive.

The light hydrocarbons and fixed gases llow from the naphtha recovery unit through line 92 to the acid gas removal system. The sulfur-containing components are carried through line 101 to the sulfur recovery unit. The remaining gases, primarily carbon monoxide, hydrogen, and gaseous hydrocarbons, exit through line 102. Fuel gas for providing heat at the necessary points throughout the entire system and for distribution to public utility gas companies is drawn olf through line 103. Enough of the hydrogen-containing gas is drawn through line 104 to the hydrogen generator to operate the hydrocracking unit 20 and the hydrotreater 40. As previously described, the hydrogen generator converts substantially all of the gas components to carbon dioxide and hydrogen with only traces of methane remaining. The carbon dioxide is drawn olf at 111 for purication and sale as an industrial gas or solidifcation and sale for refrigeration purposes. The hydrogen, containing the traces of methane, is drawn olf through line 112 and distributed through lines 113 and 114 to the secondary hydrotreater 40 and the hydrocracking unit 20.

By careful control of the operating conditions of the system, especially the low temperature carbonizer, the hydrocracking unit, the secondary hydrotreater, the naphtha recycle system and the hydrogen generation and recycle system, the process' may be balanced so that the maximum quantity and quality of synthetic petroleum crude is produced with a minimum consumption of heat. Optimum 'operating conditions are achieved when the value of the synthetic crude components extracted exceeds the marketable heat value of the char, giving consideration to the market value of the byproducts. Deeper extraction of hydrocarbon values from the coal may result in a relative net loss.

Careful consideration of the economic factors which control the relative values of the products of the described process will suggest the very significant advantage the present process has over the processes of the prior art. If the heat value of char or coke and the value of synthetic crude, as well as the values of the minor byproducts were fixed, a single set of process conditions could be determined which would result in maximum economic benefit to the operator and lower costs to the public. As is Well known, however, the market values for each of the products of the process described fluctuate according, e.g., to seasonal and industrial demands, the political forces in operation at a given time and general economic conditions. It is, therefore, highly desirable to provide a system and a process which can be varied to produce maximum economic value as the values of the individual products of the process shift. In the present process, the only products which will have a substantial effect upon the process variables are, of course, the relative values of char as a fuel and of the synthetic crude. As previously pointed out, however, the value of the synthetic crude is very highly dependent upon its quality.

Taking into consideration current economic and techni- 'cal conditions the following operating conditions are given as exemplary of a preferred embodiment of the invention, on a small pilot plant scale.

Coal from the Last Chance Creek outcrop of coal beds in southern Utah, known as Kaiparowits coal, was crushed and screened to pass through a 1A inch mesh screen. This grade of coal contains about 6.4 percent moisture, 40 percent volatile matter, 7.3 percent ash, and 46.3 percent xed carbon. Of course, other sub-bituminous coals, Such as those known as .Black Mesa coals from northern Arizona, or any roughly equivalent grade of coal may be used. The coal was dried to 3 weight percent moisture by countercurrent contact with hot ue gases from the carbonizer. These ue gases are byproducts of the char of combustion in the heat generation portion of the carbonizer. Any type of dryer may be used but the dryers found effective in this embodiment were Vertical columns .for dilute phase contact between hot gases and the wet coal, electrostatic precipitators being used to remove solids from the water-saturated waste gases.

The crushed, dried coal was fed to the double screw mixer of the carbonizer where it was mixed with hot recycle char. Contact time in the mixer is only a few seconds but a large percentage of the devolatilization of the coal occurs during this interval. The coal-char mixture was conveyed into the carbonization vessel of the previously described carbonizer. The average temperature of the coal in the carbonizer vessel was 1100 F.

The tar and middle oil components were fed into an H-Oil hydrocracking unit of the type described. The tar and middle oil are pumped separately into the unit and are preheated by exchange with the hot reactor liquid and fed into the reactor countercurrently with the recirculating hydrogen stream. Light tar is similarly treated, except that only one liquid feed is required.

The mixed phase high pressure product is allowed to separate after leaving the catalyst bed. This physical separation may occur in the upper section of the reactor or in an external vapor-liquid separator. Subsequent cooling and flashing of both streams allows recovery of most of the hydrogen from the products. Butanes and lighter are stripped from the stream and the low pressure liquid product is sent to the vacuum still.

The vacuum still is operated at 900 F. and supplies a solids-free feed to the secondary hydrotreater 40. The vacuum bottoms, as previously described, are recycled to the carbonizer and coked.

The 900 F. end-point vacuum still overhead is preheated by exchange with the reactor eiuent and fed to the secondary hydrotreater reactor. Hydrotreating, in an exemplary embodiment, may be done over Cyanamid HDS-3A Ni-Mo catalyst at about 1750 p.s.i.g. hydrogen, 750 F., and a liquid hourly space velocity of about 1.0. The reactor efiiuent is cooled to about 100 F. and ashed to separate hydrogen-rich recycle gases from the liquid products. Water settles by gravity from the oil products and is sent to the waste water cleanup system.

Low-pressure flash vapors and the unstabilized hydrotreater oil product are combined and fed into the hydrotreater fractionator. Butanes and lighter hydrocarbons are stripped from the synthetic crude product in this tower and sent to the gas cleanup facilities at the hydrogen plant. The high-pressure component from the fractionator is the synthetic crude and is now ready for shipment to a renery. Desirably, but not necessarily, the coal liquefcation plant may be located adjacent a reinery so that the entire production and refining of syncrude may be carried out continuously. In the speciiic embodiment, however, the syncrude was collected for further refining.

The gases and high 'vapor pressure hydrocarbons produced in the several stages of the process are rst scrubbed with middle oil to remove the naphtha. The naphtha contains large quantities of oleiins and dioleiins and requires hydrogenation and, therefore, is absorbed in middle oil which also requires upgrading. This eliminates the need for a distillation column to regenerate a lean oil stream.

The high pressure gases from which the naphtha has been removed are fed to the acid gas removal unit, which may be a Rectisol extraction tower, described in the Lurgi Manual, where all of the HZS and most of the CO2 are removed by extraction with methanol. This unit also includes equipment for solvent (methanol) regeneration.

The scrubbed gases from the Rectisol plant are then sent to the hydrogen plant as required to produce hydrogen for the process.

The other auxiliary units operate under conventional process conditions which have been described.

Complete data on the composition of the syncrude resulting from the above process are not yet available; however, the product appears to be compatible with petroleum crude in all respects and may be processed in a conventional petroleum rening process. There is considerable evidence that the relative energy content of the syncrude produced by this process is substantially higher than the energy content of a comparable quantity of conventional petroleum crude. A There is considerable evidence to indicate that the vacuum distillation step is essential to the operability of the process although this was not `denitely established. The liquid tar products derived from the prior stages, if handled immediately without significant delay in transit or holdup time, could be processed with some difficulty. However, where there was any appreciable holdup time between one stage and the following, there was a tendency for the material to harden and become a thick black mass of apparently polymeric material which could not be handled by any conventional reiinery process. l

It was determined that the components which were causing the difficulty constituted only a small fraction of the total composition of the liquid tar material. Initialy it was believed that a vacuum distillation step might result in substantially reduced yields but, surprisingly, this did not result. Probably less than 15 percent of the total material was objectionable and caused the diicult handling problems. IUpon removal, by vacuum distillation, of this fraction and recycling it through the previous steps, substantially total potential yield was obtained and the end product was easily handled according to conventional reiining techniques.

On this basis, the vacuum distillation stepappears necessary at least for application in a commercially successful processing operation.

-Review of pilot plant operations indicates that improved tar quality may result from the carbonization process utilized but optimum values were not determined. It is to be emphasized, however, that any type of low temperature carbonization process may be utilized as an individual step in the inventive process without departing from the scope and spirit of the invention which iS defined in the claims.

It will be understood, also, that the embodiment given is merely exemplary of the invention and that the conditions given are not necessarily limiting but rather indicate a workable operating condition. With these considerations in mind there are several areas in Iwhich it is known and/or expected that certain operating conditions may be varied to improve either the quality of the product or to improve the overall efficiency of the process. For example, While complete `data are not available to coniirm these iindings, there is good reason to believe, based on preliminary data, that as the fraction of the coal which is liqueiied to produce synthetic crude is increased the overall quality of the crude tends to go down. That is, the hydrogen content and the energy content as well as the compatibility of the syncrude with petroleum crude, are reduced. Thus, the severity of the coking operation is, from an economic standpoint, dependent in part on the quality of the syncrude which is desired. Similarly, the percent of the tar which is converted in the H-Oil process may be varied by changing the operating conditions in that process. Initial indications are that between 60 and 80 volume percent of the tar is converted to raw syncrude but it is expected that higher conversions can be obtained through optimization of the process variables. The operating conditions in the secondary hydrotreater have, likewise, not been optimized and significant advances are to be expected from further experimentation. Obviously, modifications can be expected to result from operating experience based on known engineering principles and Ifrom the process described herein.

lFrom the foregoing speciiication it will be apparent that a highly useful and commercially valuable process has been disclosed and that while a particular embodiment of the invention has been disclosed in detail departures may be made from the exemplary embodiment without departing from the scope and the spirit of the invention as defined in the following claims.

9 We claim: 1. The process for producing synthetic petroleum crude from coal which comprises the steps of:

carbonizing coal at a relatively low temperature to produce a stream of highly volatile uids including naphtha and at least one additional stream of higher molecular weight normally liquid products;

hydrocracking the normally liquid products to produce a stream of highly volatile fluids including naphtha and a stream of normally liquid products;

vacuum distilling the normally liquid products to produce a stream of synthetic crude;

hydrotreating the synthetic crude from the distilling step to produce a stream of improved synthetic crude and a stream of highly volatile uid products including naphtha;

lfractionating the improved synthetic crude to produce a stream of synthetic petroleum crude having refining properties substantially equivalent to lnatural petroleum crude;

combining the naphtha-containing streams;

stripping the naphtha from said combined streams; and

recycling at least a portion of the naphtha by combining said naphtha with the normally liquid products from the carbonizing step prior to hydrocracking said products.

2. The process of claim 1 wherein the carbonizing step produces a normally liquid tar stream and a middle oil stream, at least a portion of each of said streams being separately fed to the hydrocracking step.

3. The process of claim 2 wherein the recycled naphtha is mixed with the middle oil prior to hydrocracking.

4. The process of claim 1 wherein the normally liquid feed from the carbonizer to the hydrocracker is light tar and the naphtha is premixed with said light tar prior to hydrocracking.

5. The process of claim 1 wherein a phenol containing stream is produced in the carbonizing step and further comprising the steps of:

extracting the phenols from said phenol containing stream; and

feeding said phenols to the hydrotreating step along with the synthetic crude from the distilling step.

6. In a process for converting coal into synthetic petroleum crude which, comprises carbonizing the coal, hydrocracking liquids produced in the carbonizlng step and separating the liquids produced in the hydrocracking step to produce said synthetic crude and naphtha, the improvement comprising: recycling at least a portion of said naphtha for being mixed with the liquids produced in the carbonizing step prior to hydrocracking.

7. The process of claim 6 wherein the separating step comprises vacuum distilling the liquids and hydrotreating at least a portion of the distilled liquids for producing an improved synthetic crude product.

8. The process of claim 7 :wherein a phenol containing stream is produced by the carbonizing step and further comprising the steps of: separating phenols from said stream and hydrotreating said phenols with said distilled liquids for including hydrotreated phenol derivative hydrocarbons in the improved synthetic crude.

References Cited UNITED STATES PATENTS 2,654,695 10/1953 Gilbert et al 208-10 2,738,311 3/1956 Frese et al 20S-8 3,107,985 10/1963 Huntington 208-10 2,913,397 11/1959 Murray et al 208-8 2,913,3 88 11/1959 Howell et al 208-8 3,247,092 4/ 1966 Huntington 208-10 3,018,242 l/1962 Gorin 208-10 3,117,921 1/1964 Gorin 208-10 2,600,430 6/ 1952 Riblett 2018-8 3,442,793 5/ 1969 Carson 208-108 3,321,393 5/1967 Schuman 208-10 3,157,589 11/1964 Scott 20S-108 2,982,717 5/1961 Waddill 208-108 3,207,688 9/ 1965 Van Driesen 208-108 DELBERT E. GANTZ, Primary Examiner V. OKEEFE, Assistant Examiner U.S. Cl. X.R. 20S-8, 108

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EP0024139A3 *Jul 28, 1980Aug 19, 1981Dut Pty LimitedProducing liquid hydrocarbon streams by hydrogenation of fossil-based feedstock
EP0330757A2 *Dec 20, 1988Sep 6, 1989VEBA OEL Technologie GmbHProcess for reprocessing waste materials or the like by pyrolysis, and subsequent further processing of the pyrolysis oil
EP0330757A3 *Dec 20, 1988Mar 7, 1990Veba Oel Entwicklungs-Gesellschaft MbhProcess for reprocessing waste materials or the like by pyrolysis, and subsequent further processing of the pyrolysis oil
Classifications
U.S. Classification208/412, 208/415, 48/197.00R, 208/108
International ClassificationC10G1/00
Cooperative ClassificationC10G1/002
European ClassificationC10G1/00B