US3755136A

US3755136A - System for removing solids from coal liquefaction reactor effluents

Info

Publication number: US3755136A
Application number: US00123510A
Authority: US
Inventors: M Fields; J Meyer
Original assignee: Steel Corp
Current assignee: Braskem America Inc
Priority date: 1971-03-12
Filing date: 1971-03-12
Publication date: 1973-08-28
Anticipated expiration: 1990-08-28
Also published as: CA972306A; DE2210954A1

Abstract

This is a process for separating liquid and solids from coal liquefaction reactions by vaporization with hot, hydrogen-rich gas.

Description

United States Patent 1 7 Fields et-al;

SYSTEM FOR REMOVING SOLIDS FROM COAL LIQUEFACTION REACTOR EFFLUENTS inventors: Marvin C. Fields, Wilkins Township,

Allegheny County; James L. Meyer,

Monroeville Borough, both of Pa.

United States Steel Corporation, Pittsburgh, Pa.

Filed: Mar. 12, 1971 Appl. No.: 123,510

[73] Assignee:

U.S. Cl. 208/8, 208/10 Int. Cl C10g 1/00 Field of Search 208/186, 8, 10;

References Cited UNlTED STATES PATENTS 3,505,201 4/1970 Hodgson et al 208/8 '60 5, Liquid, Sal/d Mixture From Cool Convener Slurry Fluid/zed Solids Treating Sect/an Shipping 605 46 950"? [111 3,755,136 Aug. 28,1973

3,117,921 1/1964 ,Gorin"; 208/8 3,523,886 8/1970 Gorin et a1 208/8 3,449,238 6/1969 sStockburgeretal. 208/186 I FOREIGN PATENTS OR APPLICATIONS 657,249 6/1965 Belgium 208/186 I P rimary Examiner-Delbert E. Gantz Assistant Examiner-S. Berger Attorney-John E. Callaghan 5 7] ABSTRACT This is a process for separating liquid and solids from coal liquefaction reactions by vaporization with hot, hydrogen-rich gas.

24 Claims, 2 Drawing Figures Vapors To Cooling and Condensation Cyc/one Section Solids To l Ouencn Leaders et 208/8 I Gas, Liquid, Sol/'0' 2 g Mixture From 2 Coal Converter 3 .900 F. U 4500 F814 PATENTEDAUGZBIQIS 3755136 snmaurz VoporsTo Cooling and Condensofion Fla. 2.

'Siurry :5 k 2. G 0 36 E u Vapors a and b k b Gases Q) t Fluid/zed Solids Treating Section Stripping Gas 46 950E //v l/E/V TORS. 80/148 /1 MARVIN c. FIELDS a Que JA MES 1.. ME YER A I forney SYSTEM FOR REMOVING SOLIDS FROM COAL LIQUEFACTION REACTOR EFFLUENTS BACKGROUND OF THE INVENTION Coal liquefaction is the rendering of coal into more useful organic liquids; these liquids have a higher hydrogen to carbon ratio than the original coal. Rendering proceeds by adding atoms of hydrogen to the reactive constituents in the coal; generally, two processes are used: Coal hydrogenation and coal solvation. In coal hydrogenation, crushed coal is mixed with a hydrocarbon oil. The resulting suspension is contacted with a gas, such as H or H and CO, which is considered to be the hydrogenation agent. In coal solvation, crushed coal is mixed with a hydrocarbon oil that not only has solvency power for the coal, but also a hydrogen content by which it can donate hydrogen to the coal. Hydrogen gas is also contacted with this suspension, however its purpose is primarily to replenish or supplement the hydrogenation action of the hydrocarbon oil. In some cases, a hydrocarbon extract from coal rather than the crushed coal is subjected to hydrogen addition. A further exlanation of these processes is given in Chem. Eng., Nov. I969, pp. 32ff.

In these liquefaction processes, the highest possible conversions and recoveries of fluids are desirable; as a corollary, the lowest possible solid residue and highest degree of separation between liquids and solid residue is desirable. Therefore, the separation of solids from fluids is a critical step in coal liquefaction processes, their efficient separation is one aspect of the present invention.

Effluents from the liquefaction reaction contain solids, liquids and gases. Because the original solids were usually crushed and partial conversions have taken place, these effluents contain a minor, yet substantial, amount of suspended solids comprising ash residues, unreacted coal residues, unreacted coal and catalyst, if a catalyst was used. Due to their size, entrained liquids, minor amounts and the suspension in the desired product liquids, removal of these solids is both important and difficult.

In the commercial coal hydrogenation practice in Germany prior to and during World War II, the common method of removing solids from the liquid products was by centrifugation of the slurry. This method invariably given incomplete separation, leaving both solids in the oil and substantial oil in the centrifuge refuse. Carbonization of the residue would subsequently give partial recovery of the oil but still giving about 4 percent loss of oil and no recovery of the asphalt which constitutes about 20 percent of the liquid product at a conversion level of 90 percent of the organic material in the coal. This same type of operation has been used for coal solvation or extraction processes.

The use of filtration was also investigated but no filtration units were ever used commercially.

Vacuum and flash distillation of the heavy liquids from coal liquefaction have been studied. In Germany, vacuum distillation was practiced at 50 mm of Hg, but this practice resulted in even higher losses of oil than the combination of centrifugation andcarbonization. Flash distillation in the presence of steam was some-, what more successful than the vacuum distillation for recovering oil but resulted in substantial coking problems in the equipment and still gave no recovery of asphalt. Both steam flash distillation and centrifugation to process heavy oil were used by the U. S. Bureau of Mines; although the distillation produced a cleaner distillate, the oil recovery was very poor apparently because of coking and polymerization in the distillation drum.

Another attempt for effecting fractionation of the products from coat liquefaction was a German investigation in which sludge from centrifugation was topped by countercurrent contact with either steam or hydrogenation by-product gas, a hydrogen-rich gas, to concentrate the solid in the sludge by 38 to 50 percent to a maximum .concentration of 60 percent of the topped sludge. This was followed by low temperature carbon ization to recover part of the remaining 40 percent volatile oil and asphalt content. There was also a French investigation concerning continuous co-current hydrogenation and light hydrocarbon fractionation.

All of the above practices are described and referenced in the U. S. Bureau of Mines Bulletin 633, Hy drogenation of Coat and Tar, (1968) Cf. pp. 37-38,

' 9l-l03 (hereinafter BM 633).

The invention comprises vaporization under reducing conditions of the volatile components in the liquefaction effluents by a hydrogen-containing gas to cause complete separation of the liquids and gases from the solids and a recovery of organic liquids having a more favorable distribution of desirable components than is obtained by filtration or centrifugation.

OBJECTS OF THE INVENTION Among the objects of this invention are:

a. to provide a method for the separation of liquids and solids by vaporization ofliquids in the presence of a hydrogen-containing gas,said liquids and solids including at least some of the products of coal liquefaction processes;

b. to provide for this separation under conditions of temperature and pressure such that coking or carbonization would occur but for the reducing atmosphere created by the hydrogen-containing gas;

c. to include high boiling hydrocarbons, such as as phaltenes, among the liquids separated by volatilization;

d. to provide maximum separation between the liquids and solid residues through the aforementioned method;

e. to increase yields of selected components, such as chemical oils, by use of the above method;

f. to perform this method as a batch process, as a con tinuous process or any combination of these;

g. to perform this method as an individual process, as a component of coal liquefaction processes, and as a component of a liquid gas recovery process;

h. to perform this method by contact of gas with liquids or solids or liquid-solid mixtures sufficient to cause separation of the ingredients without filtration or centrifugation;

i. to include steps in this method such that maximum recovery of heat values from the product streams are obtained.

SUMMARY OF THE INVENTION AND BRIEF DESCRIPTION OF THE DRAWINGS In accordance with the invention, liquid and solid components of coal liquefaction products are in contact with hydrogen-containing gases under reducing conditions at temperatures and pressures sufficient to vaporize the liquids and leave the solid residues as a remainder.

FIG. 1 is a diagrammatic illustration of the separation method in combination with a coal hydrogenator and fluid recovery system; and

FIG. 2 is a diagrammatic illustration of the separation method being performed continuously in a single vessel.

DETAILED DESCRIPTION OF THE INVENTION To summarize, liquid solid mixtures from coal liquefaction processes are separated through vaporization by contact with hydrogen-rich gases.

In common with other chemical reactions, coal liquefaction is a partially complete reaction. Therefore, the reactor effluent contains both coal conversion products and unconverted feed materials. As an example, coal hydrogenation may use coal with exgess hydrogen as reactants and hydrocarbon oil as a suspending agent for feed materials. The reactor effluent will contain as reaction products gases, liquids and solids form converted coal and as unreacted feed material, coal hydrogen gas and hydrocarbon oil. For the liquid-solid separation in coal liquefaction, all the liquids, whether conversion products or unconverted feed material, are desirably removed from the solids whether the solids are conversion products or unreacted feed material.

By mixtures of solids and liquids including at least some of the reaction products of coal liquefaction is meant that solids and liquids from converted coal are a portion of the mixture, as well as solids and liquids otherwise present in the coal reactor effluent. This effluent usually contains light hydrocarbons, liqht oil, middle oil, heavy oil, unreacted coal, ash residue, residual organic matter and catalyst if any is used. Gases from the reactor may or may not be present. Where liquid coal extract alone is used in the liquefaction, this invention may be used for the separation of those liquid-solid mixtures that may be present in such processes.

Coal to be used in liquefaction is crushed. Its size is determined by the balance between increased process efficiency and cost of size reduction; in liquefaction, this balance favors larger particle sizes. Pumping equipment limits the largest size to about one-fourth inch. Sizes of 30 mesh, 70 and 100 mesh, US screen size are common. Some processes may use a majority of particles below 200 mesh. After addition of hydrogen, particle size becomes further reduced; depending upon the degree of conversion. Conversions are usually at least 50 percent; 90, 95 percent and above are quite common. When the original crushed coal is very fine, circa 200 mesh, average particle sizes of 1.5 microns or smaller may be obtained in the converted solid. Should it occur, colloidal suspensions of the solids in the liquids is one factor which would make separations by prior art methods difficult.

Crushed coal is fed to the reactor in combination with a hydrocarbon oil, called pasting oil. Depending upon the kind of oil, this combination may be viewed as a mixture of oil and crushed coal or as a mixture of oil, partially solvated coal, and coal. The invention applies to both kinds of mixtures; it applies to coal liquefactor effluents that carry hard to remove solids. The coal/oil ratio is commonly from 1 to l to l to 4 or lower.

Complete separation of volatilizable components from the solid residue is of prime importance in the overall efficiency of the coal hydrogenation process. This relates to the recovery of the asphalts and asphaltenes as well as heavy oils mixed with the solids. For preparing the initial coal paste, various kinds of oils may be used, hence recovery of the particular pasting oil depends upon which kind was used. The oil is chosen for its hydrogen content, boiling point and solvation power for coal. Simply to form a slurry with the coal, aromatic oils are used, commonly these are middle oil or heavy oil or mixtures of both. For increased coal solvent power, cresol, tetralin and others boiling at least about C are more preferred; whichever pasting oil is used, the ability to recover it by the separation process of this invention is a valuable advantage.

Assuming complete reaction of coal and no catalyst, the dry solid residue from which the volatilizable components have been removed may be viewed as a mixture of fusane and ash. Fusane is an organic, benzene insoluble, non-hydrogenable component of coal, similar to charcoal. Ash is an inorganic mixture of metallic substances such as silicates and oxides that is present in coal. While allowing for catalyst and unreacted coal, when the solid residue about equals the fusane and ash content of the coal fed to the hydrogenator, complete separation of liquids and solids has occurred; this of course is an aspect of the invention. The removal of substantially all of the volatilizables, even including asphaltenes and pitches, from the solid residue may be shown in the alternative, by continued hydrogen stripping without appreciable change in weight of the residue. Ordinarily, the fusane will be about 0.5 to about 13 percent of the m.a.f. coal, according to the rank of coal, e.g. lignite, bituminous. Ash may be about 3 to about l3 percent by weight of the dry coal. Fusane to ash ratios of about I to l to about 1 to 3 are common. These percentages reflect the amounts of residue to be expected. By the practice of the invention virtually all the solid residues may be separated from the vaporizable components.

While it is an important aspect of the invention that the various vaporizable components be recovered as valuable chemical products, particular attention is directed to the mixture of heavy oils and solids. It is especially difficult to separate this fraction by prior art methods, because this mixture of solid and heavy oil is a highly viscous phase, which contains large proportions of asphaltenes, whose specific gravities of liquid and solid are very close, and is very sensitive to air oxidation with the resultant problem of coking. Moreover, these last fractions of heavy oil and solids from the overall liquefaction liquid-solid output contain significant amounts of the hydrocarbon oil used to form the coal paste. The entire economics of the liquefaction process depends upon the extent of the hydrocarbon oil recovery, p. 93, BM 633, supra; US. Pat. No. 3,535,224. Compositions of the heavy oil-solids mixture vary considerably, solids content of 20, 22, 27 and 36 percent having been obtained in practice with benzene soluble oils making up the balance. Where the solid/liquid mixture is obtained as sludge from centrifugation of heavy oil residue, the solids content is even higher.

For the purposes of this invention, hydrogencontaining gas for volatilization means a gas containing sufficient hydrogen to permit a reducing atmosphere in the process and has a temperature, pressure and concentration of components to permit volatilization from the liquid and solid mixture being treated; these may also be called hydrogen-rich stripping gases. The existence of a reducing atmosphere can be easily determined by reason of the absence of coking, it is in contradistinction to the presence of air or oxygen'or other oxidizing atmosphere that would cause coking during the processing. The ability to permit volatilization means that the partial pressure of the component to be vaporized is equal to or less than its saturation pressure at the temperatures and pressures of the process, which may be determined by analysis or by computation from standard references for the component in question. Examples of hydrogen-rich stripping gases include hydrogen, the hydrogen vapor mixture being generated in the process such as by countercurrent contact of hydrogen with the solid-liquid mixture, and a hydrogen containing stream recycled from the liquid processing as described below.

Gases from liquefaction include hydrogen, hydrogen sulfide, ammonia, light hydrocarbons and volatile oils. These may be separately removed from the solid-liquid mixture after liquefaction or may be removed along with the vapors from the separation process of this invention.

The purpose of coal liquefaction is to convert coal into liquid hydrocarbons of higher value than the coal. Material balances for coal and the products of liquefaction are available in the literature, e.g. Gasification and Liquefaction of Coal, American Institute of Mining and Metallurgical Engineers, N.Y., 1953, pp. 1 and 5. The liquid products are first identified according to boiling ranges as light oil, naptha and gasolines, middle oil and heavy oil; these fractions are then further identified as gasoline, benzenes, phenols, etct, p. 5, supra.

The atomic compositions of the liquefaction products indicate the chemical nature of the products, e.g. saturated hydrocarbons, aromatics, -phenols, etc. Tables and graphs for these compositions which are typical of the "materials recovered in the process of the invention are given on pp. 18 and 19 of Gasification and Liquefaction"; adetailed-description of the oil fractions and their respective constituents isgiven on pp. -27 of this book. Further descriptions of the typical liquidproducts recovered by the process of the'invention are alsogiven on pp. l46-l50 of BM633, supra.

Among the liquid products, that fraction which are chemicals usefulin themselves or are chemicals useful as precursors in other reactions are known as chemical oils. To a large extent these are synonymous with light oils, and have a'boiling range up to about 475 F. As examples of the per se useful chemicals, there are benzene, toluene and xylene, tar acids and tar bases. The precursors are those in which by hydrogenation, dehydrogenation or dealkylation, useful chemicals can be obtained; these include benzene precursors, indene precursors, naphthalene precursors. A typical analysis would be:

Cyclohexanes, B.T.X., Alkyl Benzene: Tetralin lndane Phenols, Cresols, Xylenols Tar Bases Pyridine, Aniline 2 One feature of the invention-is to increase the percentage of chemical oils among the liquids recovered. This increase may be caused by increased efficiency in separation or by further hydrogen addition during the practice of the invention; the improved recovery contributes to the overall success of the invention.

In addition to the nature of the feed material and products, the description of the invention includes physical conditions and modes of transporting the material being treated.

The operating temperature of the process involves operating within the region where coking of the liquidsolid material will be significant. At the lower range, temperatures below about 350 C, no significant coking occurs regardless of the presence of hydrogen. Above about 530 C, coking occurs no matter how much hydrogen is present. Higher operating temperatures within the aforesaid range are especially preferred because removal of vaporizable components having high boiling points is desirable. Moreover, the flowability of the liquid-solid mixture increases at higher tempera-' tures. It is particularly desirable to operate the separation stages at the same temperature as the coal liquefaction stage, 420-5l5 C. l

The pressure at which the separation is preformed is selected in part by the purpose of the vapors, in part by the materials handling aspects of the invention and in part by the status of the-separation in the overall liquefaction and recovery process.

First, the pressure must be such that sufficient hydrogen is present to prevent coking while the overall volume of gas must be able to carry off the vaporized components. For example, in a batch process, at'about 470 C and 3,000 psig, the process performs acceptably, although at about psig, coking becomes severe. The increased hydrogen content prevents the coking, and so in practice if the pressure is too low, increasing the hydrogen concentration will prevent coking when operating within the aforementioned temperature range.

Second, one aspect of the separation is that the vapors from it and from the liquefactor may be processed and recycled to the coal liquefactor and to the separator. To avoid costly recompression steps when recycling the vapors, the separation taken as a whole may be conducted at high pressures, it is desirable that the compression ratio be no greater than about 2:1. When the liquefaction is a coal hydrogenation operating at a pressure of from 2,000 to 10,000 psig, the separation is conducted at or not more than 2,000 psi below the hydrogenator pressure. Coal hydrogenation is commonly performed at 3,000-5,000 psig. When the liquefaction is a coal solvation operating at 200 to 1,000 psig, the separation is conducted at ZOO-3,000 psig.

Third, the separation may be carried out in separate gas/liquid and gas/solid contacting stages. The contacting may be either co-current or countercurrent. These stages may be at the same or different pressures. When different pressures are used, the vapors from each stage may be separately drawn off and processed as shown in FIG. 1. There is a particular advantage in operating the gas/solid contacting stage at pressures as low as 200 psi while the gas/liquid contacting stage is operating at or close to liquefaction pressure, e.g. l,000-l0,000 psig. The lower pressure in the gas/solid stage facilitates discharge of the dry solids into the atmosphere by air lock devices, while the bulk of the vapors, being associated with the gas/liquid stages, are at a pressure that is favorable for recompression and recycle as explained above.

The entire separation may be conducted in a single vessel or in a multiplicity of vessels. As well, in one vessel, separate compartments may be used for treating the liquid-solid mixture and for treating the solids, as shown in FIGS. 1 and 2.

Another advantage of the invention is that the liquidsolid separation may be carried out solely by contacting with the hydrogen-rich stripping gases. There is no need for centrifuges or filters to cause separation of the liquid and solids during the separation process. Although the liquid-solid product from the centrifuge or filter may be separated by the method of this invention,- the method itself does not require such equipment. This means that the process of the invention may be performed in liquid-solid contactors such as trays, e.g. disk and doughnut, baffle or perforated plate tray types.

As the liquid-solid mixture is being treated, its flow character as a liquid also changes. Removal of volatiles will be accompanied by a thickening of the mixture; eventually a solid will result. The solid will have an ap preciable volatile content. The solid may then be stripped with the hydrogen-containing gas in fluidized bed treating zones. The total through-put or liquidsolid mixture can be quite high because liquid-gas and solid-gas contacting equipment is characterized by high flow rate, simplicity and efficiency. This capability to perform the separation of liquids and solids in a combination of liquid and solid contacting equipment is a unique advantage of the invention more fully described in the drawings.

Returning now to FIG. 1 for an exemplification of the process of the invention in which there is shown the coal converter and the vapor recovery systems. Feed, consisting of one ton of high volatile bituminous coal mixed with 2.5 tons of slurry oil is fed by line 1 to the coal converter V-l. The coal converter is a coal hydrogenator operating at 4,500 psia with an outlet temperature of 900 F. In V-l, most of the coal is hydrogenated by the hydrogen introduced by line 23. The effluent in line 2 will contain solid unreacted coal, liquids formed by coal hydrogenation and slurry oil, gases formed by hydrogenation and unreacted hydrogen. This mixture flows to the cyclone separator V-2, where at a pressure slightly below that of the V-] it is separated into a gaseous stream, which leaves by line 9, and a liquid-solid slurry which leaves by line 3. This slurry, containing about percent solids, flows down into the stripping column V-3, where it is contacted countercurrently by the hot, hydrogen-rich stripping gas. Most of the volatile oils (including asphalt-like liquids) are vaporized into the stripping gas. The slurry, now containing about 50 percent solids, leaves the stripping column by line 5 and enters V4 for further separation of liquids. In V-4,' the slurry is again contacted with not hydrogenrich gas; the solids may become free flowing and V4 can be operated as a fluid bed in this condition. When all the volatiles have been removed, the solidresidue is removed by line 6 to be let down at ambient pressure in the air lock device V-S. About 340 pounds of solid residue leaves the system as stream 8.

The hot hydrogen-rich stripping gas at about 950 F enters V-4 by line 18 from the furnace F-l or from another source by line 18a into line 18. In V-4, the gas picks up volatiles from the slurry; it may then be introduced through line 7 into V-3 or sent to liquid processing via line 7a or recycled through 18a and 7a or combined with the vapors from V-3 for processing by line 7b. The hot hydrogen-rich stripping gas for V-3zmay enter by line 7 or from the furnace by line 17 or from another source by

lines

18 and 17. Again in V-3, this stripping gas picks up volatiles from the liquid-solid slurry. It may leave by line 4 for de-entrainment in V-2 by line 4a for processing into liquids or by line 4b for combination and processing with vapors from V-2 in line 9. I

Liquid recovery is illustrated in the next section of the process. It is preferred to operate this section at about the same pressure as the separation section, although lower pressures may be used. To the extent lower pressures are utilized, additional gas compression needs to be provided for recycling hydrogen-containing gas to the separation zone and/or to the hydrogenator.

All of the vaporizable components may thus be collected in stream 9. This stream flows to heat exchanger 13-] where it is cooled to 750 F. A large portion of high boiling liquids will'condense from the gas, about 3,320 pounds of liquid may be recovered by line 11. As the liquid condenses in' B1, the heat released during condensation, including both sensible heat and heat of condensation of the stream, may be used to heat the hydrogen-rich gas going to the separation vessels. While the figure shows reheating a gas recycled from 8-2, hydrogen-containing gas from any other source may be similarly heated. Recovering this heat released during condensation lowers the overall fuel and furnace requirements of the process. Through line 10, the vapors enter heat exchanger E-2 where they are cooled to 370 F; heat released during condensation may be used to produce 200 psia steam, which again conserves the thermal energy of the entire process. The liquids, 2,780 pounds of the medium boiling range, may be recovered through line 12.

The gas leaving E-2 in line 13 is sufficiently rich in hydrogen and depleted in liquids that it may be used as the stripping gas in V-3 and/or V-4. Therefore, a portion is sent by line 14 to compressor C-l, then to E1 where it is heated; through line 16 it goes to the furnace F-l, from which by

lines

17 and 18 respectively it can be used as stripping gas in V-3 or V4.

The remainder of the gas goes by line 15 to cooler E-3 where at 250 F and at 4,000 psia, all the components other than hydrogen will condense. This mixture of gas and liquid is passed by line 19 to separator V-7. The hydrogen gas is separated and compressed in C-2 whereafter by line 21 it is returned to the coal converter V-l. In line 23, make-up hydrogen (180 pounds) is also added to the recycled hydrogen, the make-up gas being compressed by C-3 to the converter pressure.

The liquid leaves V-7 by line 20, then it is throttled to psia and fed to separator V-8. In V-8, the mixture flashes into 490 pounds of gas and 250 pounds of liquid, which are recovered through

lines

25 and 24.

The liquids having been separated and recovered 7 may be further refined. Depending upon the kind of oil in the cone' 34, about 120,000 SCF. The baffle 35 deentrains liq-uid from the vapors. A distributor 35a promotes uniform flow of the slurry onto the trays 36. On the trays, liquid levels and flow rates are maintained for good contact between the upflowing hydrogen-rich stripping gas and the slurry. In receptacle 37', about 790 pounds of the slurry pass through the outlet 38 into the fluidized solids treating section where it contacts fresh hydrogen-rich stripping gas and may be fluidized. Ultimately, solids leave by lines 39 and 41', to be released through the air lock device 44; 370 pounds are recovered. The stripping gas, about 20,000 SCF, enters the fluidized solids treating section by line 40, it leaves the section through line 41 along with volatiles and entrained solids if any. In cyclone separator 43, the'gas leaves by line 42 for the vapor collector 45; about 1,000 SCF of.volatiles are removed from the solids;

Other hydrogen-rich stripping gas is taken from the main 46 through line 47 where it enters the liquid slurry treating section; this gas will be about 1,912 pounds and 114,000 SCF. This stripping gas flows upwardly through the trays where it contacts the downflowing slurry. Finally, about l20,000 SCF of vapor is collected in cone 34. Vapors collected in 45 may be processed into liquids and gases as described previously, in FIG. 1, or the vapors may be used as'such for feedstocks to chemical processes such as gasoline synthesis.

The following examples illustrate the practice of the invention when the separation is carried out by passing a continuous stream of the hydrogen-rich stripping gas through a mixture of liquid and solid efiluent from a coal hydrogenator. The vapors are condensed in a series of receiving vessels. These examples also illustrate a simple technique to determine routine operating conditions of the invention for contemplated changes'in feed composition, stripping gas composition, temperature, pressure and product recovery.

EXAMPLE 1 Crushed high volatile, bituminous B coal is mixed 5 with middle oil, and hydrogenated. 261 grams of the liquid-solid mixture from the reactor are added to an autoclave. While at 465 C and 3,000 psig, hydrogen is sparged into the mixture in the autoclave. This continues for 6 hours. Vapors from the autoclave are recov- 50 ered. Afterwards, the solid residue in the autoclave is removed. The vapors are condensed and analyzed for distillation range and chemical composition.

The following results are obtained:

Chemical-Oil, wt.

6.3, B? 220C at 5 torr [.5

Middle Oil, wt. I: Heavy Oil, wt.

The mixture of heavy oil, middle oil and chemical oil has 91.56 percent C, 7.70 percent H, 0.65 percent N,

0.07 percent S.

The above solid residue corresponds to the calculated ash and fusane content of the solid-liquid mixture. V

, This shows complete separation of vaporizable compo- EXAMPLE 2 Crushed high volatile, bituminous B coal is mixed with middle oil and hydrogenated. After 2 hours of stripping with hydrogen at 470 C and 3,000 psig, the following results are obtained:

Again, the residue corresponds to the amount of fusane and ash in the mixture, indicating complete separation of vaporizable components and solid residue.

For 2 hours of suction filtration, the corresponding results would be: 0 wt. percent gas,=8 l .1 wt. percent oil, 18.9 wt. percent residue, 02 wt. percent water-oil, 10.7 wt. percent chemical oil, 75.1 wt percent middle o il,' 14.0 wt. percent heavy oil.

As these examples demonstrate, the invention is a method of separating liquids and solids from the products of coal liquefaction which features complete separation between the liquid and solid, enhanced recovery of liquid products, minimal losses of liquid entrained insolids, improved distribution of liquid products, conducted in a relatively simple manner of liquid and soldgas contacting that can be used for high production rates. The invention includes not only the specific embodiments herein described but also contemplates the variations and substitutions of equivalent conditions and materials as being within the practice of the invention.

We claim:

1. In the recovery of organic liquids from coal liquefaction processes, the steps comprising:

a. as a first stage, introducing a mixture of solids and liquids into a hydrogen containing gas under gas liquid contacting conditions at a temperature in the range of about 350 C to about 530 C, at a pressure of about 200 to 10,000 psig, and under areducing atmosphere, to vaporize a major portion of said liquids, and

b. as a final stage, introducing said remaining liquids and solids into a hydrogen containing gas under solid-gas contacting conditions at a temperature in the range of about 350 C to about 530 C, at a pressure of about 200 to 10,000 psig, and under a reducing atmosphere, to further vaporize volatilizable components of said mixture until said solids are substantially free of such components, a major portion of said mixture of solids and liquids being the carbonizable reaction products of coal liquefaction.

2. The process of claim I wherein the amount of sol ids free of volatilizable components about equals the amount of ash, fusane, unreacted coal and catalyst content of the mixture of liquids and solids.

3. The process of claim 1 wherein the specific gravity of the liquid about equals the specific gravity of the solids.

4. The process of claim 1 wherein the contacting is at a temperature of about 420 to about 515 C.

5. The process of claim 1 wherein the solid-liquid mixture flows countercurrently with the hydrogencontaining gas.

6. The process of claim 1 wherein the gas-liquid contacting conditions are such that gas flows through continuous bodies of liquid, and the solid-gas contacting conditions are such that the solid flows through continuous bodies of gas.

7. The process of claim 6 wherein the continuous bodies of liquids are pools maintained by trays, and where the solid flows as a fluidized bed through the gas. 8. The process of claim 1 wherein the contacting is performed in a continuous manner.

9. The process of claim 1 wherein the final stage is conducted at a pressure substantially less than the initial stage.

10. The process of claim 1 wherein the vapors from the first and final stages are separated into their components by cooling the vapors until at least the middle oil fraction is removed from the vapor, and wherein at least the heat released during condensation of the heavy oil fraction is used to heat the hydrogencontaining gas for the first and final stages.

11. The process of claim 10 wherein at least a portion of the vapor from which the middle oil fraction has been condensed is reheated by the heat released during the condensation of the heavy oil fraction and recycled to the first and final stages as the hydrogen-containing gas.

12. The process of claim 10 wherein the heat released during the condensation of the liquid fractions is also used to produce steam.

13. The process of claim 10 wherein the vapors are further cooled until essentially all the chemical oils have been removed from the vapors.

14. A coal liquefaction process comprising: a. converting coal into its liquefiable components by causing hydrogen addition to coal in the presence of a hydrocarbon oil, b. separating the carbonizable mixture of liquids and solids in the effluent from the conversion by i. as a first stage, introducing said effluent into a hydrogen containing gas under gas-liquid contacting conditions at a temperature in the range of about 350 C to about 530 C, at a presence of about 200 to l0,000 psig, and under a reducing atmosphere, to vaporize a major portion of said liquids, and

ii. as a final stage, introducing said remaining liquids and solidsinto a hydrogen containing gas under solid-gas contacting conditions at a tem perature in the range of about 350 C'to about 530 C, at a pressure of about 200 to 10,000 psig, 5 and under a reducing atmosphere, to further vaporize volatilizable components of said mixture until said solids are substantially free of such components,

c. obtaining therefrom a solid residue substantially free of volatilizable components and vapors of the liquids and volatilized components, and

d. separating said vapors into preselected components.

15. The process of claim 14 wherein the separating 15 is at a temperature of about 420 C to about 515 C.

16. The process of claim 14 wherein:

a. converting coal is done with a hydrogen containing gas present as a hydrogen addition agent, said converting is performed at a pressure of about 2,000 to about 10,000 psi, and

b. said separating is done at a pressure about equal to or no more than about 2,000 psi less than said coal conversion.

17. The process of claim 14 wherein separating in said final stage is conductedat a pressure substantially below that of the separating in said initial stage.

18. The process of claim 14 wherein;

a. converting coal is done with a hydrogen donor oil present as a hydrogen addition agent, said converting is performed at a pressure of about 200 to 1,000 psi, and

b. said separating of such mixture is done at a pressure of about 200 to about 3,000 psi.

19. The process of claim 18 wherein separating in said final stage is conducted at a pressure of at least about 200 psi.

20. The process of claim 14 wherein said vapors are separated by cooling to condense preselected liquid fractions, and where a vapor fraction having at least one of said liquid fractions removed therefrom is recycled as the hydrogen-containing gas to said separating step.

21. The process of claim 20 wherein a further vapor fraction having all of said liquid fractions removed therefrom is recycled to said coal conversion step as a hydrogen addition agent therein, said vapor fraction being at a pressure no less than about one-half the pres sure of said coal conversion step.

22. The process of claim 20 wherein said heat released during condensation of said liquid fractions is conserved within said liquefaction process.

23. The process of claim 14 wherein said vapor separation is conducted at a pressure lower than said separating step.

24. The process of claim 14 wherein said vapor separation is conducted at a pressure equal to said separating step.

Claims

2. The process of claim 1 wherein the amount of solids free of volatilizable components about eQuals the amount of ash, fusane, unreacted coal and catalyst content of the mixture of liquids and solids.
3. The process of claim 1 wherein the specific gravity of the liquid about equals the specific gravity of the solids.
4. The process of claim 1 wherein the contacting is at a temperature of about 420 to about 515* C.
5. The process of claim 1 wherein the solid-liquid mixture flows countercurrently with the hydrogen-containing gas.
6. The process of claim 1 wherein the gas-liquid contacting conditions are such that gas flows through continuous bodies of liquid, and the solid-gas contacting conditions are such that the solid flows through continuous bodies of gas.
7. The process of claim 6 wherein the continuous bodies of liquids are pools maintained by trays, and where the solid flows as a fluidized bed through the gas.
8. The process of claim 1 wherein the contacting is performed in a continuous manner.
9. The process of claim 1 wherein the final stage is conducted at a pressure substantially less than the initial stage.
10. The process of claim 1 wherein the vapors from the first and final stages are separated into their components by cooling the vapors until at least the middle oil fraction is removed from the vapor, and wherein at least the heat released during condensation of the heavy oil fraction is used to heat the hydrogen-containing gas for the first and final stages.
11. The process of claim 10 wherein at least a portion of the vapor from which the middle oil fraction has been condensed is reheated by the heat released during the condensation of the heavy oil fraction and recycled to the first and final stages as the hydrogen-containing gas.
12. The process of claim 10 wherein the heat released during the condensation of the liquid fractions is also used to produce steam.
13. The process of claim 10 wherein the vapors are further cooled until essentially all the chemical oils have been removed from the vapors.
14. A coal liquefaction process comprising: a. converting coal into its liquefiable components by causing hydrogen addition to coal in the presence of a hydrocarbon oil, b. separating the carbonizable mixture of liquids and solids in the effluent from the conversion by i. as a first stage, introducing said effluent into a hydrogen containing gas under gas-liquid contacting conditions at a temperature in the range of about 350* C to about 530* C, at a presence of about 200 to 10,000 psig, and under a reducing atmosphere, to vaporize a major portion of said liquids, and ii. as a final stage, introducing said remaining liquids and solids into a hydrogen containing gas under solid-gas contacting conditions at a temperature in the range of about 350* C to about 530* C, at a pressure of about 200 to 10,000 psig, and under a reducing atmosphere, to further vaporize volatilizable components of said mixture until said solids are substantially free of such components, c. obtaining therefrom a solid residue substantially free of volatilizable components and vapors of the liquids and volatilized components, and d. separating said vapors into preselected components.
15. The process of claim 14 wherein the separating is at a temperature of about 420* C to about 515* C.
16. The process of claim 14 wherein: a. converting coal is done with a hydrogen containing gas present as a hydrogen addition agent, said converting is performed at a pressure of about 2,000 to about 10,000 psi, and b. said separating is done at a pressure about equal to or no more than about 2,000 psi less than said coal conversion.
17. The process of claim 14 wherein separating in said final stage is conducted at a pressure substantially below that of the separating in said initial stage.
18. The process of claim 14 wherein: a. converting coal is done with a hydrogen donor oil Present as a hydrogen addition agent, said converting is performed at a pressure of about 200 to 1,000 psi, and b. said separating of such mixture is done at a pressure of about 200 to about 3,000 psi.
19. The process of claim 18 wherein separating in said final stage is conducted at a pressure of at least about 200 psi.
20. The process of claim 14 wherein said vapors are separated by cooling to condense preselected liquid fractions, and where a vapor fraction having at least one of said liquid fractions removed therefrom is recycled as the hydrogen-containing gas to said separating step.
21. The process of claim 20 wherein a further vapor fraction having all of said liquid fractions removed therefrom is recycled to said coal conversion step as a hydrogen addition agent therein, said vapor fraction being at a pressure no less than about one-half the pressure of said coal conversion step.
22. The process of claim 20 wherein said heat released during condensation of said liquid fractions is conserved within said liquefaction process.
23. The process of claim 14 wherein said vapor separation is conducted at a pressure lower than said separating step.
24. The process of claim 14 wherein said vapor separation is conducted at a pressure equal to said separating step.