US3211643A

US3211643A - Production of oil from solid carbonaceous materials

Info

Publication number: US3211643A
Application number: US144954A
Authority: US
Inventors: Albert F Lenhart
Original assignee: Oil Shale Corp
Current assignee: Oil Shale Corp
Priority date: 1961-10-13
Filing date: 1961-10-13
Publication date: 1965-10-12
Anticipated expiration: 1982-10-12
Also published as: ES281791A1; DE1241021B; FR1343695A; GB966154A

Description

United States Patent Office 3,211,643 Patented Oct. 12, 1965 3,211,643 PRGDUCTION OF OIL FROM SOLID CARBONACEOUS MATERIALS Albert F. Lenhart, Playa Del Rey, Calif., assignor to The Oil Shale Corporation, New York, N.Y., a corporation of Nevada Filed Oct. 13, 1961, Ser. No. 144354 21 Claims. (Cl. 208187) This invention relates to the production of oil from solid carbonaceous materials and, more particularly, to a process for economically producing oil from solid carbonaceous materials which oil is characterized by a relatively low moisture content, thereby avoiding emulsification problems heretofore encountered.

Naturally occurring deposits of solid carbonaceous materials, and especially oil shales, peats, and the like, contain appreciable quantities of occluded water. In addition, some solid carbonaceous materials, and in particular oil shale, contain hydrocarbon values in the form of a substance known as kerogen which when heated to retorting temperatures yields substantial amounts of water. Hydrocarbon values resident in these solid carbonaceous materials usually are recovered by a process wherein these materials are subjected to a thermal treatment which provides an efiiuent vapor containing the desired values and the effluent vapor is subsequently condensed. Due to the nature of the solid carbonaceous materials, however, an effluent vapor produced by such pyrolytic treatments also contains a substantial proportion of steam which effects the formation of a relatively stable emulsion upon the condensation of the effluent vapor.

Oils derived from solid carbonaceous materials usually are recovered in the form of an oil-water emulsion which usually is not satisfactory for commercial utilization. The presence of emulsified water makes fractionation of the crude oil in subsequent refining operations highly difficult due to the explosion hazards presented thereby with such problems being aggravated by the extreme stability of the crude oil emulsions. Accordingly, the refining industry considers oils derived from such sources undesirable if characterized by a moisture content above about 2% by weight. In addition, the presence of emulsified water in such crude oils is undesirable due to the additional cost involved in refining, pumping, storing and the like handling operations of a volume of fluid which is greater than of commercial value. Such additional costs usually are of significant magnitude since deposits of solid carbonaceous materials generally are remote from population centers and low cost transportation facilities such as navigable waters. Consequently, the only economically practical means for conveying crude oils derived from such deposits to market is by pumping them over relatively long distances through pipe line networks.

The formation of emulsions attendant conventional processes for recovering oils from solid carbonaceous deposits is a phenomenon which is an ordinary occurrence in the processing of petroleum crudes. Consequently, the segment of the industry dealing with the recovery of oil from solid carbonaceous materials has attempted to utilize methods for resolving crude oil emulsions which are conventionally employed in the petroleum industry.

Although crude petroleum emulsions are considered to be relatively stable and hence ditficult to resolve, methods which are economically practical are available to separate emulsions of this type into the desired aqueous and organic components. Such methods which have gained commercial signficance usually employ a relatively expensive de-emulsifying agent which is incorporated into the emulsion to effect the desired resolution or else expensive electrostatic equipment must be employed.

Due to the difference in composition between petroleum crude oils and oils derived from solid carbonaceous materials, such as oil shale, oil or tar sands, lignites, coals and the like, and due to the fact that shale oil and the like generally are recovered by simultaneous con? densation of water and hydrocarbon vapors, the liquid resulting from this condensation usually occur-ring in the form of a stable emulsion, processes which are commercially successful when employed in the resolution of crude oil emulsions have been unsuitable when applied in the recovery of oils produced by thermally treating such solid carbonaceous materials. For example, the attempted use of de-emulsifying agents and electrostatic emul-. sion breaking equipment to break crude shale oil emulsions has been either completely unsuccessful or commercially prohibitive in terms of the costs involved in achieving the desired degree of separation. Therefore, industry has beenled to the development of alternative processes for achieving the desired removal of water from crude oils derived from solid carbonaceous sources.

An alternative method which has been suggested for use in conventional processes for recovering oils produced from solid carbonaceous materials involves the utilization of a centrifuging technique to resolve the emulsions. Such a method also has been unsatisfactory in achieving the desired separation and furthermore is impractical due to the power requirements incident thereto and the high investment and maintenance cost of the equipment involved.

In is naturally the prime concern of producers of crude oils derived from solid carbonaceous materials to recover products in the highest possible yields which satisfy the requirements of the refining industry in terms of the properties thereof such as moisture content.

The nature of the water recovered as a by-product from the solid carbonaceous materials, however, also may be of substantial importance for plant use. Deposits of the solid carbonaceous materials often are located in areas wherein the supply of naturally occurring water is limited. In some instances when the natural supply of water is plentiful, the water is of such a character that extensive treatment thereof generally is required to adapt the Water for utilization in recovery plant water systems. Consequently, the amount of suitable natural water available at the production sites often is not sulficient to satisfy the requirements of a commercial scale operation for recovering oil from solid carbonaceous materials. Accordingly, the commercial success of an operation for recovering oil from a particular solid carbonaceous deposit may be at least partly contingent upon the production of water in the oil recovery process which is in a form suitably adaptable for plant use.

Generally the quantity of water produced in a process for recovering oil from solid carbonaceous materials may be sufficient alone to meet the requirements of the recovery operation. Even in most instances whenthis is not the case, the amount of water which is recovered can be employed to augment the natural water supply to make available the requisite quantity of Water.

When a satisfactory separation is achieved between the water and oil produced in such recovery operations, the water is contaminated only by sour constituents such as hydrogen sulfide and other sulfur containing compounds which can be readily and economically removed therefrom by conventional means, such as steam stripping. Removal of the sour constituents is important since the presence of such materials in water employed in conventional process equipment gives rise to corrosion problems.

Water recovered from solid carbonaceous materials in prior art recovery methods, including those utilizing a centrifuging means, are also contaminated by an appreciable amount of the desired hydrocarbon values. Aside from the economics involved in such a product loss, the presence of hydrocarbons in the recovered water is undesirable since these substances economically cannot be tolerated in steam boilers and, in addition, substantially reduce the effectiveness of means employed for the desired removal of the sour contaminants. Therefore, the utilization in plant water systems of wa ter produced in an inefficient recovery process is essentially precluded since commercially prohibitive means are required to obtain water having the requisite degree of purity.

It has now been found that separation problems attendant the formation of emulsions in the prior art techniques for recovering oil from solid carbonaceous materials may be essentially eliminated by the recovery technique of the present invention, described hereinafter, wherein emulsion formation is avoided.

Accordingly, it is an object of the present invention to produce an oil which is characterized by a relatively low moisture content from a solid carbonaceous material.

It is an additional object of the present invention to provide a method for the production of an oil from a solid carbonaceous material wherein problems attendant heretofore available techniques for producing such oils are substantially eliminated.

It is still a further object of the present invention to provide a method for producing an oil from a solid carbonaceous material wherein the recovery of the oil substantially free of moisture is effected without emulsion formation.

It is another object of the present invention to provide a method for producing an oil from a solid carbonaceous material wherein the recovery of a substantially moisture free oil is achieved by economic means.

It is yet another object of the present invention to provide a method for recovering oil from a solid carbonaceous material wherein the utilization of relatively expensive de-emulsifying agents or equipment is unnecessary.

Still another object of the present invention is to provide a method for recovering oil from solid carbonaceous materials wherein the removal of water produced in the process is achieved with substantially no loss of hydrocarbon product.

An additional object of the present invention is to provide a method for recovering oil from a solid carbonaceous material wherein water adapted for utilization in recovery plant water systems is recovered as a by-product.

It is a particular object of the present invention to provide a method for recovering oil from oil shale wherein an oil is produced which is substantially free of moisture and water is recovered as a by-product in amounts and of such quality as to satisfy the requirements of the water systems of the oil shale recovery plant.

Broadly described, the present invention provides a method for treating eflluent vapor derived by thermal treatment of solid carbonaceous materials which comprises condensing hydrocarbon having a normal boiling point above about 650 F. from said effluent vapor in a first condensation zone to provide at least one oil fraction and a vapor fraction comprising steam, separating said vapor fraction from said oil fraction, condensing steam from said vapor fraction in a second condensation zone to provide a condensate which is autogenously separable into a water fraction and a liquid hydrocarbon fraction, separating said liquid hydrocarbon fraction from said water fraction, and combining at least a portion of said liquid hydrocarbon fraction with said oil fraction to obtain a final oil having a rel tively low mois ure con ent.

A preferred embodiment of the present invention is a method for treating effluent vapor derived by thermal treatment of solid carbonaceous materials which comprises condensing hydrocarbons having a normal boiling point above about 650 F. from said effluent vapor in a first condensation zone to provide at least one oil fraction and a vapor fraction comprising steam, separating said vapor fraction from said oil fraction, condensing steam from said vapor fraction in a second condensation zone to provide a condensate which is autogenously separable into a water fraction and a liquid hydrocarbon fraction, separating said liquid hydrocarbon fraction from said water fraction, recycling a portion of said liquid hydrocarbon fraction to said first condensation zone to contact said effluent vapor, and combining the remainder of said liquid hydrocarbon fraction with said oil fraction to obtain a final oil having a relatively low moisture content.

Composite oils formed by the combination of a portion of the liquid hydrocarbon fraction from the second condensation zone with the oil fraction from the first condensation zones are carried out at temperature and tents which preclude the formation of an emulsion. Preferably, the condensations in the first and second condensation zones are carried out at temperatures and pressure conditions requisite to the production of a liquid hydrocarbon fraction in the second condensation zone which, upon the combination of a portion thereof with an oil fraction from the first condensation zone, will provide a final composite oil having a B, S & W (bottoms, solids and water) content of below about 2% by weight and hence meet the moisture requirements of the refining industry.

By the utilization of the method of the invention for recovering oil from solid carbonaceous materials, water which is substantially free of hydrocarbon values also is obtained as a by-product of the oil recovery process. Therefore, in addition to producing a final oil having the desirable relatively low moisture characteristics, the method of the invention provides an economic means for furnishing water at the oil production site which is suitably adapted for utilization in the recovery plant water systems.

The carbonaceous materials from which the effluent vapor feeds employed in the process of the invention are derived include, without limitation, oil shales, bituminous sands, lignites, coals, such as brown coal, peat, and the like. The vapor contemplated for treatment by the method of the present invention is any moisture-containing vapor having an appreciable amount of hydrocarbons therein normally boiling above about 650 F. which is derived from these sources as opposed to pctroleum hydrocarbons. Efiduent vapors produced by thermal treatment of oil shale deposits found in the United States often contain up to about 20% by weight moisture and up to about 40% by weight hydrocarbons boiling above about 650 F. These efiluent vapors derived from oil shale are specially suited for treatment in accordance with the present invention.

In the method of the invention an effiuent vapor derived by thermally treating solid carbonaceous materials is condensed in a first condensation zone under tempera ture and pressure conditions requisite to elfect the fractional condensation of hydrocarbons in the vapor having a normal boiling point above about 650 F., preferably above about 500 F., without effecting the condensation of steam from the vapor.

The temperature and pressure conditions contemplated to be employed in the first condensation zone are such that the vapor in the first condensation zone ultimately is below the dew point of hydrocarbons desired to be. condensed but well above the dew point of steam. Ac-. cordingly, at least one oil fraction and a vapor fraction which con ains the steam initially present in the effluent;

vapor and hydrocarbons remaining in the vapor state are thereby obtained.

Of course, the dew point of a constituent present in a particular vaporous mixture is theoretically the temperature at which the vapor pressure of the pure liquid constituent is equal to the partial pressure of the constituent in the vaporous mixture and therefore depends upon the composition and the total pressure of the vaporous mixture.

The total pressure employed in the first condensation zone therefore naturally may be any pressure at which the desired fractional condensation of the heavier hydrocarbons from the effluent vapor may be effected. Although lower and higher pressures suitably may be employed, to preserve the economy of the process, pressures which are preferred are in the range of from about 1 to 3 atmospheres. More preferably, the pressure employed is the autogenous pressure.

For a particular pressure the temperature which suitably can be attained by vapor in the first condensation zone may be any temperature at which hydrocarbons normally boiling above about 650 F. are condensed While the condensation of steam is substantially averted. Preferably the minimum temperature attained by vapor in the first condensation zone is at least about 60 F., preferably about 100 F., above the dew point of steam in the vapor. When an effluent vapor produced from oil shale is treated in accordance with the method of the invention and the first condensation zone is maintained under a pressure which is in the preferred range set out above, the vapor temperature to the second condensation zone preferably is in the range of from about 180 to about 500 F. and more preferably is in the range of from about 220 to about 400 F.

Although any suitably expedient means may be employed to provide the conditions requisite for the desired fractional condensation of the heavier hydrocarbons in the first condensation zone, the condensation preferably is effected by recycling cooled portions of liquid hydrocarbon fractions, which may be recovered at various stages in the process, to the first condensation zone to contact the effiuent vapor, as hereinafter described in other preferred embodiments of the invention.

The vapor fraction obtained in the first condensation zone is then removed from this zone and charged to a second condensation zone where the temperature and/or pressure is adjusted to below the dew point of steam. The condensate thereby provided is collected in a separator. Any combination of temperature and pressure conditions which effects the condensation of steam from the vapor fraction suitably may be employed in the second condensation zone. Conditions which are preferred are those which cause the condensation and, therefore, the recovery of substantially all of the steam and substantially all of the normally liquid hydrocarbons present in the vapor fraction. The actual preferred conditions, therefore, depend upon the composition of the vapor fraction. Preferably the conditions in the second condensation zone are such that the vapor therein ultimately is at least about 0 F., preferably about 140 F., below the dew point of the steam in the vapor fraction initially introduced thereinto. When a previously untreated effiuent vapor produced by thermally treating oil shale is treated in accordance with the preferred embodiment of the method of the invention, the lowest temperatures economically obtainable are preferred for utilization in condensing steam from the vapor fraction. Generally such temperatures range from about 60 to about 180 F., more preferably from about 60 to about 120 F., and the preferred pressure is in the range of from about 0.5 to about 2.0 atmospheres. Lower and higher pressures naturally may be employed but the utilization thereof is unnecessary to achieve the desired results and may involve impractical additional operating expense. More preferably, the autogenous pressure is utilized.

The condensation of constituents from the vapor fraction in the second condensation zone provides an uncondensed light vapor fraction and a condensate which is autogenously separable into a water fraction and a liquid hydrocarbon fraction. The term autogenously separable as employed in the specification and claims is meant to refer to a condensate which is separable without the aid of external expedients. The condensate formed in the second condensation zone is so characterized due to the fact that essentially all of the constituents specifically resident in efliuent vapor produced by thermally treating solid carbonaceous materials which are sufficiently surface-active and characterized by requisite gravity to exhibit emulsion-forming properties previously were condensed and removed from the vapor in the first condensation zone.

The liquid hydrocarbon fraction obtained in the second condensation zone is then separated from the water fraction, and at least a portion thereof is combined with the oil fraction or fractions produced in the first condensation zone. The composite oil resulting thereby is characterized by a relatively low moisture content. Effluent vapors derived by thermal treatments of oil shale and treated in accordance with the preferred embodiment of the method of the invention provide liquid hydrocarbon fractions in the second condensation Zone composed primarily of hydrocarbons normally boiling in the naphtha and/or naphtha-kerosene range. The combination of these fractions with oils condensed in the first condensation zone produce final oils containing less than 2%, usually less than about 1% by weight water.

Although all of the liquid hydrocarbon fraction obtained in the second condensation zone may be combined with the oil fraction or fractions recovered in the first condensation zone, it is preferred to recycle a portion of this fraction to the first condensation zone wherein it contacts and cools the efiiuent vapor to aid in effecting the desired condensation of the heavier hydrocarbons therefrom. The proportion of the liquid hydrocarbon fraction which is so recycled naturally may vary. In the preferred embodiment of the method of the invention, the proportion which is recycled is in the range of from about 60% of about of the total liquid hydrocarbon fraction obtained from the second condensation zone.

The water fraction produced in the second condensation zone in accordance with the method of the invention is substantially free of hydrocarbon values. The actual amount of hydrocarbons present in the water depends upon the nature of the original efliuent vapor and the conditions employed in the first and second condensation zones. Conditions in the first condensation zone which provide vapor fractions having lower average molecular Weights favor the production of water fractions having lower amounts of hydrocarbon contaminants. When the method of the invention is carried out in accordance with the preferred embodiment thereof, indicated by preferred ranges recited hereinabove, a water fraction is obtained which is characterized by a hydrocarbon content of less than about 0.2%, usually less than about 0.1% by Weight.

The water fraction obtained from the second condensation zone may contain sour constituents dissolved therein such as hydrogen sulfide and other sulfur-containing components if such are present in the eifiuent vapor. Since this water is substantially free of hydrocarbons, the sour contaminants easily may be removed from the water by any suitable means such as steam stripping. The water thereby is rendered suitable for use in the recovery plant as a boiler feed, cooling water, and the like.

The light vapor fraction produced in the second condensation zone in accordance with the method of the present invention usually consists in large proportion of normally gaseous hydrocarbons. The actual nature of the light vapor fraction depends upon the composition of original efiiuent vapor and the conditions employed in the first and second condensation zones. As stated hereinabove, the condensation of the vapor fraction from the first condensation zone preferably is carried out in the second condensation zone under conditions which produce a light vapor fraction relatively free of moisture and normally liquid hydrocarbons. When effluent vapor derived from oil shale is treated in accordance with the Preferred embodiments of the method of the invention, a light vapor fraction which is recovered in the second condensation zone consists substantially of hydrocarbons having 3 or less carbon atoms and is characterized by an average molecular weight in the range of from about 28 to about 34 and a moisture content of less than about 15%, usually less than about 5%, by weight. The light vapor fraction recovered from the second condensation zone is suitable, per se, for utilization as a plant fuel gas. Generally, however, it is desired to subsequently treat the light vapor fraction to further reduce the moisture content thereof and to remove therefrom essentially all hydrocarbons having more than about 2 carbon atoms. Such a treatment of the light vapor fraction may be carried out by any suitable means, but more preferably is carried out by a method, described hereinafter, wherein the light vapor fraction is subjected to several cooling and compression steps and intermediate thereto is scrubbed with liquid hydrocarbons previously produced in the first and second condensation zones.

In accordance with another embodiment of the method of the present invention, more than one oil fraction can be obtained by the condensation of the eflluent vapor in the first condensation zone. This can be accomplished by any suitable expedient means such as by the utilization of multiple-plate columns and the like to provide the first condensation zone.

Alternatively, in a further embodiment of the method of the invention a single oil fraction may be obtained from the first condensation zone and subsequently divided into light and heavy oil fractions by suitable methods including, without limitation, distillation and solvent extraction.

A portion of each oil fraction obtained in the various embodiments of the method of invention may be cooled and recycled to the first condensation zone to contact the effluent vapor therein and aid in the desired condensation of the heavier hydrocarbons. Preferably, at least about and more preferably from about 10 to 40%, of any oil fraction obtained in the recovery process of the present invention which is normally totally vaporizable at about 750 F. is recycled to the first condensation zone.

In accordance with another embodiment of the present invention, a heavy oil fraction obtained directly from the first condensation zone or subsequently obtained from an oil removed from the first condensation zone suitably may be subjected to an intermediate treatment designed to improve a property of the final composite oil other than the moisture content. Such intermediate treatments include, without limitation, treatments for solids removal, viscosity lowering and pour point lowering.

As stated above, in accordance with another embodiment of the method of the invention, the light vapor fraction produced in the second condensation zone may be subjected to additional treatment to further remove moisture therefrom and to recover any hydrocarbon values present therein having more than about 2 carbon atoms. This further treatment is requisite to the production of a final oil product which contains substantial amounts of the lower molecular weight constituents and which consequently is an attractive product to the refining industry. The desired recovery of the lower molecular weight hydrocarbons suitably may be accomplished by any method conventionally employed to achieve such a separation.

In the method which is preferred for utilization in the method of the present invention to recover such lower molecular weight hydrocarbons from the light vapor fraction, the light vapor fraction initially is compressed and the resulting compressed vapor is cooled to a temperature below the dew point of steam where condensate is formed and sent to a first receiving zone. In the first receiving zone a condensate is collected which is autogenously separable into a water fraction and a light liquid hydrocarbon fraction containing hydrocarbons having more than about 2 carbon atoms. The lighter hydrocarbons remain in the vapor state, are removed from the first receiving zone and are taken out of the recovery system, per se, as a product or subsequently subjected to further treatment as hereinafter described.

Any temperature and pressure conditions which suitably effect condensation of essentially all of the steam from the lighter vapor fraction may be employed. The actual conditions utilized naturally depend upon the nature of the vapor fraction and, consequently, upon the conditions pre viously employed in the second condensation zone. Temperatures usually employed correspond to the temperatures utilized in the second condensation zone and, accordingly, usually are in the range of from about 60 to about 180 F., preferably from about 60 to about F. Pressures contemplated for utilization in condensing vapor collected in the first receiving zone are usually in the range of from about 20 to about 40, preferably from about 25 to about 35, p.s.i.g.

The water fraction collected in the first receiving zone is separated from the light liquid hydrocarbon fraction therein and preferably is combined with the water fraction produced in the second condensation zone to be treated and subsequently used in the plant water system.

The light liquid hydrocarbon fraction separated in the first receiving zone suitably may be combined with other hydrocarbon condensates obtained in prior steps of the method of the invention to provide a final composite oil. More preferably, the light vapor fraction separated in the first receiving zone consisting essentially of hydrocarbons having less than about 3 carbon atoms is compressed and then combined with the light liquid hydrocarbon fraction recovered from the first receiving zone. The mixture resulting thereby is cooled to a temperature usually in the range of from about 60 to about 180 F., preferably from about 60 to about 120 F., and contacted in an absorption zone with hydrocarbon condensates recovered from previous steps of the process.

The absorption zone is maintained under pressure with the pressure being provided by the compression of the light vapor fraction from the first receiving zone. Pressures contemplated for utilization in the absorption zone usually are in the range of from about to about 220, preferably from about to about 200, p.s.i.g. Proportionally higher pressures may be employed if greater recovery of light hydrocarbons in liquid form is desired.

Although any hydrocarbon condensates produced in accordance with the method of the invention suitably may be employed as absorbent liquid in the absorption zone, absorbent liquids which are preferred for utilization are those normally characterized by a final boiling point of about 650 F., preferably about 600 F. or lower. Such hydrocarbon condenates are preferred for use as absorbent liquids in the absorption zone since the pressure conditions employed in the absorption zone to achieve the desired recovery of relatively low molecular weight hydrocarbon values also provide convenient means for effecting a separation of moisture not removed from hydrocarbon fractions in previous steps of the process. By the utilization of absorbent liquids of the recited preferred type, liquid can be drawn from the absorption zone from which small amounts of water are autogenously separable. If absorbent liquids are employed in the absorption zone which contain the higher boiling hydrocarbon constituents, any small quantities of water present in the absorbate hydrocarbon liquid would be highly dispersed therein and would not autogenously separate therefrom. Accordingly preferred absorbent liquids include light oil fractions produced in the first condensation zone, liquid 9 hydrocarbon fractions produced in the second condensation zone, light liquid hydrocarbon fractions collected in the first receiving zone and, more preferably, combinations thereof.

The hydrocarbon condensates composing the absorbent liquid employed in the absorption zone usually are introduced thereinto at temperatures corresponding to the temperature of the light vapor fraction charged to the absorption zone or at any lower temperature economically feasible. Preferably, hydrocarbon condensates prior to being sent to the absorption zone are cooled to a temperature in the range of from about 60 to about 180 F., preferably from about 60 to about 120 F.

In the pressurized absorption zone essentially all hydrocarbons having more than about 2 carbon atoms are removed from the light vapor fraction obtained from the first receiving zone by the absorbent liquid.

Since some hydrocarbons having less than about 3 carbon atoms will also be absorbed by the hydrocarbon absorbent liquid, it is preferred that the enriched absorbate liquid obtained in the absorption zone be subjected to sufficient heating while under pressure to desorb C and C hydrocarbons therefrom. Such desorption preferably is effected by sufiic-iently heating a portion of the enriched absorbate liquid and recycling the hot liquid to the bottom of the absorption zone.

The mixture of absorbate and the absorbing oil then is combined with intermediately treated and/ or untreated oil fractions obtained from the first condensation zone which were not employed in the absorbent liquid to thereby provide the desired final composite oil.

Gases remaining in the vapor state in the absorption zone are then removed therefrom and may be taken out of the process system as a product stream, but preferably these gases are passed to a second receiving zone maintained at autogenous conditions wherein any absorbent liquid entrained from the absorption zone is removed. The gaseous product thereby obtained from the second receiving zone is essentially free of moisture and hydrocarbons having more than about 2 carbon atoms and is removed from the recovery process system as a product thereof.

While the oil to be treated in accordance with the process of this invention may be produced from solid carbonaceous material, including, without limitation, oil shales, tar sands, and the like, by any of the known processes, it preferably is produced by the process of co-pending Aspergren application Serial No. 645,139, now Patent No. 3,025,223. Pursuant to the Aspergren process, particulate oil shale or oil-bearing sand or similar material is pyrolyzed in a revolving drum. The heat for the pyrolysis is furnished in the revolving drum by solid-tosolid milling contact with heat-carrying bodies such as balls of refractory material less attritionable than the oilor kerogen-bearing feed. The heat-carrying bodies are separated from the pyrolysis residue and then preferably are reheated by combustion of the carbonaceous pyrolysis residue in a separate zone. The reheated bodies then are recirculated to the pyrolysis drum in solid-to-solid milling contact with fresh feed. Such process has been found more effective than any other known pyrolysis process for production of oil from solid carbonaceous material and particularly from oil shale.

The invention will be more fully understood by reference to the following detailed description of an example of the more preferred embodiment of the method of the invention and the accompanying drawing which represents a flow diagram of the method so described wherein an effluent vapor derived by thermally treating Colorado oil shale is employed as the feed stream.

As shown in the drawing, an effluent vapor produced from an oil shale pyrolysis unit 100 is fed at about 870 F. to the bottom of a first condensation zone 2 through line 1. The first condensation zone 2 employed here is in the form of a fractionating column. In first condensation zone 2 the effluent vapor is subjected to fractional condensation and oil fractions are provided which are withdrawn from first condensation zone 2 through

lines

5, 8, 13 and 18. A vapor fraction containing steam and vaporous hydrocarbons and having an average molecular weight of about 52 is taken overhead from first condensation zone 2 at a temperature of about 240 F. and passed through conduit 3 to a second condensation zone 4 wherein it is cooled to about 100 F.

A light oil fraction characterized by a gravity of about 30 API is removed from first condensation zone 2 at about 370 F. through line 5 and passed by pump 6 to cooler 7. In cooler 7 the temperature of the light shale oil fraction is lowered to about 100 F., and the thereby cooled light oil fraction is then passed via line 5 to the top of absorbing zone 70. A medium weight oil fraction having a gravity of about 18 API is removed from first condensation zone 2 at about 565 F. through line 8. A portion of the medium weight oil fraction is passed by means of line 10 and pump 11 to heat exchanger 12. In heat exchanger 12, the medium weight oil fraction is cooled to about 370 F. and thereafter is recycled through line 10 to first condensation zone 2 to aid in the desired fractional condensation of the effluent vapor. The rest of the medium oil fraction is sent by means of pump 9 through line 8 to a reboiler 74 of an absorption zone 70. A heavy oil fraction characterized by a gravity of about 11 API is removed from first condensation zone 2 via line 13 at about 725 F. A portion of the heavy oil fraction is recycled to first condensation zone 2 through line 15 and heat exchanger 17 by means of pump 16 to aid in the desired fractional condensation of the efilue-nt vapor. In heat exchanger 17 the temperature of the recycled heavy oil fraction is lowered to about 550 F. The remainder of the heavy oil fraction is directed by means of pump 14 to line 8 wherein it is combined with medium oil and the resulting mixture is passed to reboiler 74. A residual oil having a gravity of about 0 API is drawn from first condensation zone 2 through line 18 as a bottoms product at about 820 F. and subsequently passed to a solids removal zone 20 by pump 19 through line 18.

In solids removal zone 20 a concentrated slurry oil is produced which is removed from the system by means of line 22. A clarified oil representing the bottoms product from which solids hav been substantially removed is obtained from solids removal zone 20, passed via line 21 to line 13 wherein it is mixed with the heavy oil fraction from first condensation zone 2 to provide a heavy oil fraction having a gravity of about 8 API, and the resulting heavy oil fraction is passed to reboiler 74 via line 8.

In line 8 the heavy oil fractions from lines 13 and 21 are combined with medium weight oil to provide an oil having a temperature of about 635 F. and characterized by a gravity of about 14 API.

Steam and light hydrocarbons, mostly naphtha constituents, undergo condensation in second condensation zone 4 which is maintained at a pressure of about 10 p.s.i.a. The condensate thereby formed separates into a Water fraction and a liquid hydrocarbon fraction in separator 30 without the need of external expedients. The water fraction is removed from separator 30 through line 31 and sent by pump 32 to a treatment zone wherein sour contaminants are removed from the water to adapt it for use in the recovery plant water system. The liquid hydrocarbon fraction characterized by a gravity of about 46 API is collected in separator 30 and is removed therefrom at about F. through line 37. About 90% of the liquid hydrocarbon fraction is recycled to first condensation line 2 through line 38 by means of pump 39 wherein it enters condensation zone 2 at a point above line 1 to contact and aid in the condensation of the heavier hydrocarbons in the efiluent vapor feed. The remainder 1 1 of the liquid hydrocarbon fraction is sent through line 40 by pump 41 to absorption zone 70.

An uncondensed vapor fraction is recovered from separator 30 having an average molecular weight of about 31. The vapor fraction is removed from the separator 30 via line 33 and subjected to compression in compressor 34 whereby it is heated to a temperature of about 285 F. A portion of the compressed vapor fraction is recycled to second condensation zone 4 via

lines

42, 36, and 3. The remaining portion of the compressed vapor fraction is passed through line 42 to cooler 35 wherein its temperature is lowered to about 100 F. at a pressure of about 31 p.s.i.g., so that condensation of steam and hydrocarbon vapor occurs to provide a condensate which is autogenously separable in a receiver 50 into a water fraction and a light liquid hydrocarbon fraction consisting primarily of C hydrocarbons. The water fraction is withdrawn from receiver 50 through line 56 and passed by pump 32 through line 31 to water treatment zone 90.

The light liquid hydrocarbon fraction having a gravity of about 56 API is removed from receiver 50 through line 55 with pump 58 at about 100 F. An uncondensed light vapor fraction having an average molecular weight of about 30 is removed from receiver 50 by line 51 and passed to a compressor 52 wherein it is subjected to compression and thereby heated to about 300 F. In line 57 the compressed light vapor fraction is then combined with the light liquid hydrocarbon fraction separated in receiver 50. The light vapor-liquid mixture resulting thereby is then passed by line 57 through a cooler 53, wherein it is cooled to about 100 F., and then to absorption zone 70.

In absorption zone 70 which is maintained at a pressure of about 190 p.s.i.g. essentially all hydrocarbons having 3 carbon atoms and above are condensed or absorbed in the absorbent liquid provided by the naphtha and light oil streams entering through

lines

40 and 5, respectively. An enriched hydrocarbon liquid characterized by a gravity of about 42 API and having a temperature of about 285 F. is thereby produced which is removed from absorption zone 70 by means of line 72. A portion of the enriched absorbate is recycled to the bottom of absorption zone 70 through line 73 and reboiler 74. In reboiler 74 the enriched hydrocarbon liquid stream is contacted in heat exchange relationship with a diverted portion of the combination of hot medium weight and heavy oils from first condensation zone 2 which is passed through reboiler 74 by means of line.75 to raise the temperature of the enriched hydrocarbon liquid stream to about 440 F. The remainder of the enriched hydrocarbon liquid obtained from absorption zone 70 is combined in line 76 with the combination of heavier oils from first condensation zone 2 which was cooled to about 525 F. by passing through reboiler 74. The resulting mixture of oils is passed through a heat exchanger 77 and cooler 78 by means of line 76 and thereby cooled from 500 F. to 130 F. to prvoide a final composite oil having a gravity of about 22 API and a moisture content of about .0l% by weight.

A liquid hydrocarbon stream is removed from absorption zone 70 and sent to a water settling zone 110 through line 112. In water settling zone 110 a water fraction forms which is drawn away through line 111. The dewatered hydrocarbon stream is recycled to absorption zone 70 by line 113.

An uncondensed stream of light hydrocarbon gases is removed from absorption zone 70 and passed by means of line 71 to a second receiver 60 which is maintained at a pressure of about 185 p.s.i.g. and a temperature of about 105 F. In second receiver 60 any entrained absorption oil is collected and removed therefrom through line 62. A hydrocarbon gas which has an average molecular weight of about 25 is recovered as a product of the process from second receiver 60 through line 61.

The method of the invention is to be distinguished from prior art methods employed in the recovery of specifically desired hydrocarbon fractions, in particular gasoline, from cracked heavy petroleum vapors. Such prior art methods are exemplified by the process described in United States Patent No. 1,751,733 1. In contradistinction to the method of the invention for treating efiluent vapor derived from solid carbonaceous materials wherein substances which effect emulsion formation upon condensation of the untreated vapor are removed therefrom in the form of heavy condensates, such prior art methods for'recovering particular fractions from petroleum vapors separate emulsion-forming substances from the desired fractions in overhead, non-condensible vapor streams.

Since modifications of the method of the invention which do not depart from its scope will become apparent from the general description and specific embodiments appearing in the specifications, it is intended that this invention be limited solely by the scope of the appended claims.

What is claimed is:

1. A method for treating effluent vapor derived by thermal treatment of oil shale and like kerogenous materials which comprises condensing under conditions of temperature and pressure such that the temperature is above the dew point for water vapor at said pressure hydrocarbons having a normal boiling point above about 650 F. from said efliuent vapor in a first condensation zone to provide a heavy oil fraction, at least one light oil fraction and a vapor fraction comprising steam; separating said vapor fraction from said oil fractions; condensing steam from said vapor fraction in a second condensation zone to provide a light vapor fraction and a condensate which is autogenously separable into a Water fraction and a liquid hydrocarbon fraction; separating said fractions provided in said condensation zone; and combining at least a portion of said liquid hydrocarbon fraction with at least one of said oil fractions from said first condensation zone to obtain a final oil having a relatively low moisture content.

2. The method according to claim 1 wherein said efiluent vapor is derived by thermal treatment of an oil shale.

3. The method according to claim 1 wherein hydrocarbons having a normal boiling point above about 500 F. are condensed from said efiluent vapor in said first condensation zone.

4. The method according to claim 1 wherein steam is condensed from said vapor fraction in said second condensation zone at a temperature in the range of from about 60 to about 180 F.

5. The method according to claim 1 wherein said condensations in said first and second condensation zones are carried out at autogenous pressures.

6. The method according to claim 1 wherein a portion of said liquid hydrocarbon fraction from said second condensation zone is recycled to said first condensation zone to contact said efiiuent vapor therein.

7. The method according to claim 1 wherein hydrocarbons having more than about 2 carbons are recovered from said light vapor fractions and said recovered hydrocarbons from said light vapor fraction and at least a portion of said liquid hydrocarbon fraction are combined with said oil fraction to provide a final oil having a relatively low moisture content.

8. A method for treating efiluent vapor derived by thermal treatment of oil shale and like kerogenous materials which comprises condensing under conditions of temperature and pressure such that the temperature is above the dew point for water vapor at said pressure hydrocarbons having a normal boiling point above about 650 F. from said effluent vapor in a first condensation zone to provide a heavy oil fraction, at least one light oil fraction, and a vapor fraction comprising steam, separating said fractions provided in said first condensation zone, condensing steam from said vapor fraction in a second condensation zone to provide a light vapor fraction and a condensate which is autogenously separable into a water fraction and a liquid hydrocarbon fraction, separating said fractions provided in said second condensation zone, recovering hydrocarbons having more than about 2 carbon atoms from said light vapor fraction, recycling at least a portion of said liquid hydrocarbon fraction provided in said second condensation zone to said first condensation zone to contact said efiluent vapor therein, and combining the remainder of said liquid hydrocarbon fraction and said hydrocarbons recovered from said light vapor fraction with said oil fraction to provide a final oil having a relatively low moisture content.

9. The method according to claim 8 wherein said effluent vapor is derived by thermal treatment of an oil shale.

10. The method according to claim 8 wherein hydrocarbons having a normal boiling point above about 500 F. are condensed from said etfiuent vapor in said first condensation zone.

11. The method according to claim 8 wherein steam is condensed from said vapor fraction in said second condensation zone at a temperature in the range of from about 60 to about 180 F.

12. The method according to claim 8 wherein said condensations in said first and second condensation zones are carried out at autogeneous pressures.

13. The method according to claim 8 wherein said recovery of hydrocarbons having more than about 2 carbon atoms from said light vapor fraction provided in said second condensation zone is achieved in an absorption zone wherein said light vapor fraction is contacted with at least a portion of said light oil fraction to provide a hydrocarbon liquid absorbate rich in hydrocarbons having more than about 2 carbon atoms.

14. In a method for recovering shale oil from efiluent vapor derived by thermal treatment of oil shale the steps of: condensing under conditions of temperature and pressure such that the temperature is above the dew point for water vapor at said pressure hydrocarbons having a normal boiling point above about 500 F. from said efiiuent vapor in a first condensation zone to provide a heavy oil fraction, at least one light oil fraction, and a vapor fraction comprising steam, separating said fractions provided in said first condensation zone, condensing steam from said vapor fraction in a second condensation zone at a temperature in the range of from about 60 to about 180 F. to provide a light vapor fraction and a condensate which is autogenously separable into a water fraction and a liquid hydrocarbon fraction, separating said fractions provided in said second condensation zone, contacting in an absorption zone said light vapor fraction provided in said second condensation zone with at least a portion of said light oil fraction from said first condensation zone to provide a hydrocarbon liquid absorbate rich in hydrocarbon-s having more than about 2 carbon atoms, and combining said liquid absorbate and at least a portion of said liquid hydrocarbon fraction provided in said second condensation zone with said heavy oil fraction to provide a final oil having a relatively low moisture content.

15. The method according to claim 14 wherein a portion of said liquid hydrocarbon fraction provided in said second condensation zone is recycled to said first condensation zone to contact said efiluent vapor therein.

16. The method according to claim 14 wherein a portion of said light oil fraction provided in said first condensation zone is cooled and recycled to said first condensation zone to contact said efiiuent vapor therein.

17. The method according to claim 14 wherein at least a portion of said liquid hydrocarbon fraction provided in said second condensation zone is introduced into said absorption zone.

18. The method according to claim 14 wherein said condensations in said first and second condensation zones are carried out at autogenous pressures.

19. The method according to claim 14 wherein said light oil fraction is totally vaporizable at about 650 F.

20. The method according to claim 14 wherein said absorption zone is maintained under a pressure in the range of from about to about 220 p.s.i.a.

21. The method according to claim 14 wherein said light vapor fraction provided in said second condensation zone is compressed, subsequently cooled, and introduced into a first receiving zone maintained at an autogenous pressure wherein are separated a vapor fraction consisting substantially of hydrocarbons having less than about 3 carbon atoms and a condensate which is autogenously separable into a water fraction and a light liquid hydrocarbon fraction rich in hydrocarbons having more than about 2 carbon atoms, said fractions collected in said first receiving zone are separated, said vapor fraction provided in said first receiving zone is compressed and then combined with said light liquid hydrocarbon fraction provided in said first receiving zone, said combination of said compressed vapor fraction and said light liquid hydrocarbon fraction is cooled and subsequently introduced into said absorption zone to contact said light oil therein, and a vaporous hydrocarbon product consisting essentially of hydrocarbons having less than 3 carbon atoms is provided as an overhead stream from said absorption zone.

References Cited by the Examiner UNITED STATES PATENTS 1,811,654 6/31 Pyzel 208368 2,601,257 6/52 Buchan 20811 2,905,595 9/59 Berg 202-14 2,933,447 4/60 Walker et al 208187 3,051,644 8/62 Friedman et al 2081l FOREIGN PATENTS 469,771 11/50 Canada. 41,163 10/08 Sweden.

ALPHONSO D. SULLIVAN, Primary Exantiner.

Claims

1. A METHOD FOR TREATING EFFLUENT VAPOR DERIVED BY THERMAL TREATMENT OF OIL SHALE AND LIKE KEROGENOUS MATERIALS WHICH COMPRISES CONDENSING UNDER CONDITIONS OF TEMPERATURE AND PRESSURE SUCH THAT THE TEMPERATURE IS ABOVE THE DEW POINT FOR WATER VAPOR AT SAID PRESSURE HYDOCARBONS HAVING A NORMAL BOLING POINT ABOVE ABOUT 650*F. FROM SAID EFFLUENT VAPOR IN A FIRST CONDENSATION ZONE TO PROVIDE A HEAVY OIL FRACTION, AT LEAST ONE LIGHT OIL FRACTION AND A VAPOR FRACTION COMPRISING STEAM; SEPARATING SAID VAPOR FRACTION FROM SAID OIL FRACTIONS; CONDENSING STEAM FROM SAID VAPOR FRACTION COMPRISING STEAM; SEPARATING SAID VAPOR VIDE A LIGHT VAPOR FRACTION AND A CONDENSATE WHICH IS AUTOGENOUSLY SEPARABLE INTO A WATER FRACTION AND A LIQUID HYDROCARBON FRACTION; SEPARATING SAID FRACTIONS PROVIDED IN SAID CONDENSATION ZONE; AND COMBINING AT LEAST A PORTION OF SAID LIQUID HYDROCARBON FRACTION WITH AT LEAST ONE OF SAID OIL FRACTIONS FRONT SAID FIRST CONDENSATION ZONE TO OBTAIN A FINAL OIL HVING A RELATIVELY LOW MOISTURE CONTENT.