US2885338A - Process and apparatus for retorting of oil shale - Google Patents

Description

May 5, 1959 L P- EVANS 2,885,338

n PROCESS AND APPARATUS FOR RETORTING oF OIL SHALE Filed Dec. 4, 1953 s sheefs-sheet 1 c'afvDf/vsw HND HE/IT EKCHNE ZONE MIX/N6 ZONE May 5, P. EVAN$ PROCESS AND' APPARATUS FOR RETORTING OF OIL SHALE Filed Dec. 4, 1953 3 Sheets-Sheet 2 May 5, 1959 L .,P. EVANS 2,885,333

APROCESS AND APPARATUS FOR RETORTING OF' OIL SHAL Filed Dec. 4, 1953 3 Sheets-Sheet 3 Y [amis j? fz/m15 B United States Patent PROCESS AND APPARATUS FOR RETORTING F OIL SHALE Louis P. Evans, Woodbury, NJ., assignor to Socony Mobil Oil Company, Inc., a corporation of New York Application December 4, 1953, Serial No. 396,221

Claims. (Cl. 208-11) This invention relates to an improved method and apparatus for recovering valuable hydrocarbons from hydrocarbonaceous solids such as oil shales, coal, peat, lignite, tar sands and the like. It is more particularly concerned with an improved apparatus and process wherein a hydrocarbonaceous solid is retorted economically and efficiently, with a substantially complete recovery of heat and with internal fractionation of the liquid and gaseous products.

As is well known to those skilled in the art, normally l liquid and gaseous hydrocarbons have been recovered from hydrocarbonaceous solids by means of processes which include heating or roasting the solids at elevated temperatures suliicient to educt the desired hydrocarbons and to separate them from residual mineral matter. Commercial retorting operations which have been ernployed hereinbefore have been cumbersome, expensive and unsatisfactory for large scale operations. For example, commercial shale retorting methods have required enormous equipment installations with proportionately small recovery of shale oil. The methods have generally involved the use of vertical cast iron retorts through which lumps of shale pass by gravity, heat has ordinarily been supplied through the retort walls. In other methods rotary kiln retorts have been used and even tunnel-kiln retorts in which the shale is loaded into small carts and passed through heated tunnels. It will be appreciated by those skilled in the art that such methods entail disproportionate equipment and operating costs per unit of shale throughput. Major factors which contribute to such economical operation are poor heat recovery in the retorting system, poor heat utilization, and the need for expensive separation and fractionation equipment to separate the liquid product into utilizable hydrocarbons.

It has now been discovered that liquid products can be recovered from hydrocarbonaceous solids by means of a method and apparatus which permits eicient heat utilization and which provides a novel means for fractionating the reaction products.

Accordingly, it is an object of this invention to provide a method and apparatus for eliiciently retorting hydrocarbonaceous solids such as oil shale without excessive heat loss. Another object is to provide a method and apparatus wherein the amount of elort expended in recovery of the retorted products is greatly curtailed. A further object is to provide a method and apparatus for accomplishing the retorting of shale and similar materials with a relatively substantial reduction in the amount and cost of equipment required therefor. Other objects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description considered in conjunction with the drawings wherein:

Figure l presents a schematic drawing of the apparatus of the present invention;

Fig. 2 presents a more detailed embodiment of the apparatus set forth in Figure 1;

Fig. 3 presents a diagrammatic representation of a fce preferred embodiment of the apparatus and process of this invention; and

Fig. 4 presents a diagrammatic representation of still another embodiment of the present invention.

In the drawings, in so far as possible, like parts have been given the same reference number. Referring now more particularly to Figure l, the basic apparatus of this invention may be appreciated. In general, the apparatus comprises an elongated cylindrical vessel 2, provided with a seal leg 3, a conical shaped internal cover disposed at the lower extremity of the seal leg 3 and having a plurality of orifices 10 therein. In the upper, or condensing and heat exchange, zone of the reactor proper, there is provided a trap tray 4 disposed around the inner wall of the reactor. The trap tray 4 is provided with a pipe 7 to permit draw-off of liquid products. The design of the trap tray 4 provides an annular opening for constricted passage 35. In the lower region of reactor 2, there is provided a gas distributing device 23 and a series of baffle plates 26 and 27 having orices 28 and 29. Below the bales there is an air inlet 30 and a drawot' tube 24. In operation, raw crushed hydroccarbonaceous material, such as oil shale, is carried to the top of the reactor by means of a suitable lift device 1, e.g., a bucket elevator. The crushed shale thus fed into the top of the reactor gravitates downward in a substantially compact mass through the seal leg 3 and into the main portion of the reactor. Inert gases such as flue gas are introduced into the feed leg via pipe 9 to provide a seal u which prevents the escape of gaseous products from the reactor. As the cold shale gravitates through the condensing and heat exchange zone, it is contacted with the hot condensible and non-condensible vaporous products of the process. Upon contact with the hot vaporous products, the cold shale is heated and the condensible products are liquefied and gravitate downwardly through the b ed of shale. Due to'the restricted opening 3S a portion of the bed of shale, immediately above the trap tray 4, becomes substantially immobile. The .condensed liquid products gradually trickle through the zone of immobile shale and eventually reach the trap tray 4. The noncondensible hot gaseous products of the process are passed through openings 10 into an annular collecting zone 11. These gases are then withdrawn via pipe 13 through pump 12. A portion of the hot gases is sent to a gas recovery plant through pipe 14. The remainder of the hot gases is recycled through pipe 15 into the gas distributing device v23. By means of this operation, the heat requirements of the shale retorting are satisfied. The shale gravitating downwardly passes through a combustion zone and thence through the openings 28 and 29 in the baffles 26 and 27. Below the baes, a combustion-supporting gas, such as air or oxygen, is introduced into pipe 30, pressured by means of pump 18. As the combustion-supporting gas passes upwardly through the battled region, it is heat exchanged with the hot spent shale so that the gas attains a temperature sufficient to support combustion. Thereafter the spent shale is withdrawn through conduit 24. In order to provide a more eflicient distribution of the raw shale in the upper portion of the reactor, a conically-shaped baille 5 is positioned immediately below the opening of the seal leg 3.

In Fig. 2 there is set forth another embodiment or renement of the process described in Figure 1. As has been described hereinbefore, raw crush shale is introduced into the upper portion of the reactor where it is heat exchanged with the non-condensible and condensible vaporous products of the reaction. In the present embodiment, however, the trap tray 4 is provided with one or more baiiles 6 which divide the trap trays into 2 or more sections. Each section is provided with a separate drawot tube 7 and 8. By means of this arrangement, a rough 3. fractionation of the liquid product is achieved in the reactor itself. Accordingly, the amount of fractionation required externally is greatly diminished.

Another improvement in `the embodiment shown in Fig. 2 relates to the utilization of the recycled gas via pipe 15. The stream of recycle gas is split into two streams, one stream passes `through pipe 22 into gas distributing device 23. The remainder of the recycle gas passes through pipe 16, wherein it is mixed with a portion of the combustion-supporting gas supplied via pipe 20. The resulting mixture of combustion-supporting gas and recycle gas is then passed through a gas distributing device 21 into the bed of shale. As was described hereinbefore, the remainder of the combustion-supporting gas is passed into the lower portion of the reactor via pipe 3 0.V The remaining operations involved in the embodiment `f Fis 2 are Sbsfantiallr the Saale as those de' scribed in `conjunction with the discussion 4of Figure l.

Aps -was mentioned hereinbefore, the oxygen-containing gases absorbed heat from the spent shalev as they passed therethrough. The temperature of the gaseous mixture is thus raised to the ignition point at which the oxygen contained therein reacts with the combustibles present in the system, such as the combustible components of the gaseous mixture and the coke contained in the spent shale. The combustion thus initiated generates the required amount of heat to maintain the entire process in thermal balance. This is an important feature of the present process which serves to minimize heat loss. Since the heat recovery from the incoming and outgoing process is substantially complete, only a small amount of net combustion heat must be supplied to make up heat loss and heat reaction. The temperature required to achieve combustion is ordinarily within the range varying between about 1000 F. and about 1500 F. Accordingly, in order to utilize more effectively the heat evolving from the combustion zone, it is preferred to split the recycle gas stream into two or more streams as was illustrated in Fig. 2. Generally, the amount of recycle gas conducted to the retorting zone is between about 1 and about 3 unit weights per unit weight of shale charge. The temperature of the gas issuing from the combustion zone is adjusted by means of the tlow of residual cold recycle gas lead to the pipe 22 and gas distributor 23. Contact between the residual recycle gas and the gas from the combustion zone takes place in the mixing zone of the reaction vessel. The resulting gaseous mixture rises to the retorting zone. In general, the temperature of the gas entering the retorting zone varies between about 800 F. and about 1000 F. The temperatures in excess of the foregoing range are usually to be avoided in the retorting Zone, because excessively high temperatures promote undesired secondary distillation and/or cracking of the shale oil released in the retorting zone. In a typical operation, the volume and temperature of the gas conducted to the retorting zone varies between about 120 and about 160 pounds of gas per 100 pounds of shale charge at a temperature of about 1000 F.

Suiiicient air or other suitable combustion-supporting gas is supplied to the bottom of the reacting vessel for the purpose of burning combustibles and furnishing adequate heat to maintain the process at thermal balance. In addition to the quantity of air thus supplied, sufficient cold recycle gas is introduced in the lower portion of the reaction vessel to dilute the oxygen content of the com bustible gas and to cool the hot spent shale. A secondary stream of cold recycle gas is introduced into the reaction vessel at a point immediately overlying the combustion zone. This secondary'stream is contacted with the gaseous products of combustion in an amount suicient to adjust the volume and the temperature of the gaseous mixture conducted to the retorting zone.

During the passage of the crushed shale yfeed downwardly through the reaction vessel, the cold shale becomes heated by contact with the condensi'ole and non-` condensible products of the process which pass upwardly through the condensing and heat exchange zone. The temperature attained by the shale in this zone is generally in the range of about 500 to about 600 F. The temperature of the shale thus preheated which enters the retorting zone should be above the dew point of the vapor stream leaving the retorting zone. Condensation of the shale oil vapors is effected upon contact of the rising hot products of retortation with the downwardlymoving cold shale. This condensation is largely confined to a separate zone, partly by reason yof the design of this zone which permits drainage and withdrawal of the condensate as it is formed, and in part by the relatively high vapor velocity of gaseous products entering the condensing zone due to the constricted passage 35 in the trap tray section. This further counteracts any tendency for condensate to run down into the underlying ,retorting zone. The rsmall `amount of condensate which may find its way into the lretorting zone is revaporized therein, and again passed into the upper, condensing zene, wherein it is collected and removed as liquid shale oil.

In practice it may be desirable to recycle at least a portion of the liquid product in order to achieve better fractionation. Such operation is illustrated in Fig. 3 which shows only a portion of the reactor. A portion of the liquid product in the collecting tray 4 can be withdrawn through pipe 4G. Into pipe 41 is introduced a gaseous carrier medium which is commingled with the liquid product in a mixing zone 43. The mixture is then conducted through pipe 44 to a spraying device 45. The liquid product passes through the orifices 10 into the condensing and heat exchange zone. In this zone the recycled liquid product can be further vaporized and condensed and eventually pass into the collecting tray 4 with a better degree of fractionation. Preferably, in such operation there will be two or more baffles 6 which will serve to divide the collecting tray 4 into three or more sections.

In order to elect more efficient condensation of the liquid products, cooling may be supplied to a portion of the bed immediately above the collecting tray 4. Such an embodiment is illustrated in Fig. 4. Cooling coils 31 are disposed in the interior of the reaction vessel 2, positioned immediately above the trap trays 4. A cooling medium circulated through coils 31 serves to lower thc temperature of the shale and gaseous products immediately above the trap trays. In this manner there is effected a greater degree of condensation of condensible vaporous products in this section. Accordingly, it is a preferred aspect of the present invention to subject the vaporous products in the condensing and heat exchange zone to'cooling for the purpose of promoting condensation thereof.

As will be appreciated by those skilled in the art, the process and apparatus of this invention provides an eicient means for educting oil from hydrocarbonaceous fluids. By means of the method of this invention, substantially complete heat recovery is accomplished in the reaction vessel without the necessity for heat exchange from an external source, thereby eliminating excessive heat loss which has been encountered heretofore. All products of the instant process including the spent shale are withdrawn at substantially atmospheric temperatures. The internal fractionation of the total retorted products serves to greatly reduce the product recovery facilities ordinarily required in retorting process.

A construction of the apparatus of this invention affords numerous advantages. The crushed shale and gaseous products are passedthrough a gone of restricted crosssection wherein heat exchange takes place. Due to the restricted cross-section, the rate of upward gaseous fiow prevents, substantially, the downward ow of condensed liquid product into the retorting zone. The high vapor velocities restricted to the restricted cross-sectional area zone offers advantages of construction and of operation.

lSince high vapor velocities are not used throughout the reactor, adequate time for combustion and retorting is achieved without the necessity of making the apparatus unduly large, particularly in height. Likewise, erosion of the equipment and shale is minimized by the substantial elimination of high vapor velocities in the leg section.

The operation described herein had been directed particularly to the retorting of oil shale. It is to be strictly understood, however, that the process and apparatus of this invention are likewise applicable for effecting retortation of other oil-containing or oil-producing solids, such as coal, peat, lignite, tar sands and the like.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to, without departing from the spirit and scope of this invention, as those skilled in the art will readily understand. Such variations and modifications are considered to be within the purview and scope of the appended claims.

I claim:

1. In a method for producing shale oil from oil shale by heating a downwardly moving compact bed of cold, crushed oil shale and liowing the hot vaparous products so obtained upwardly through said downwardly moving bed, whereby condensation of released shale oil vapors is obtained upon contact with the counter-owing cold shale, the improvement which comprises internally collecting within said bed at least two separate fractions of liquid shale oil condensate of varying boiling points and thereafter withdrawing separate streams of each of said collected liquid shale oil fractions from contact with said bed.

2. In a method for producing shale oil from oil shale by heating a downwardly moving compact bed of cold,

lying said bed, condensable gas to said bed below the zone o f retortation therein, whereby hot spent shale descending from said zone is cooled and removing a stream of cold, spent shale from the bottom of said bed.

3. A process for the recovery of shale oil from oil shale, which comprises heating crushed oil shade to ignition ternperature, contacting a bed of the resulting hot shale with a stream of air to effect combustion of combustible matter present therein, owng hot vaporous products emitted from the heated shale through a constricted zone of high adjacent said restricted zone, withdrawing separate streams of each of said collected shale oil fractions, removing noncondensable gas at substantially atmospheric temperature overlying the bed of crushed oil shale, recycling a stream of said non-condensable gas to said bed below the zone of retortation therein, whereby hot spent shale descending from said zone of retortation is cooled and removing a stream of spent shale, at substantially atmospheric temperature from the bottom of said bed.

4. A process for the recovery of shale oil from oil shale, which comprises initiating a zone of combustion in the lower portion of an elongated bed of oil shale, flowing the hot vaporous products upwardly through said downwardly moving bed of oil shale, whereby shale oil vapors contained in said vaporous products undergo condensation upon contact with the counter-owing cold, crushed shale,

collecting within said bed of shale, a plurality of fractions of said condensed liquid shale oil having varying boiling points, withdrawing a stream of non-condensable gas overlying said bed, recycling a portion of said withdrawn gas to the lower portion of said elongated bed in an amount sucient to adjust the volume and temperature of the gas rising from the zone wherein shale is undergoing the aforementioned combustion, causing the aforementioned gaseous products of retortation to ow upwardly through said downwardly moving bed, withdrawing separate streams of said collected liquid shale oil fractions from contact with said bed, and removing spent shale substantially freed of combustible matter from the bottom of said bed.

5. A process for the recovery of shale oil from oil shale, which comprises heating crushed oil shale to ignition temperature, contacting a downllowing bed of resulting hot shale with a stream of air to elect combustion of combustible matter present therein, llowing hot vaporous products emitted from the heated shale upwardly through a constricted zone of high vapor velocity, internally cooling the downliowing shale at a point upward and outward of said constricted zone, condensing the vaporous products of retortation which pass upward and outward of said constricted zone upon contact with counter-owng cold shale, collecting a plurality of fractions of condensed liquid shale oil of varying boiling points within said bed of shale and non-condensable gas overlying the bed of crushed oil shale, recycling astream of said cold, non-condensable gas to the lower portion of .said bed, whereby hot spent shale is the bottom of said bed.

6. In a retorting apparatus for producing shale oil surface of said reaction vessel at varying distances from the center thereof for collection of a plurality of fractions of liquid shale oil condensate of differing boiling points, a series of outlet conduits, one of said conduits extending from each of said trays for effecting separate withdrawal therefrom of the collected fractions of liquid shale oil condensate, an outlet for removing non-con densable gas from the top of said reaction vessel, a conduit for recycling said non-condensable gas to the lower interior of said reaction vessel wherein it contacts downowing hot spent shale, thereby cooling the same, and a conduit in the bottom of said reaction vessel for electing removal of cold spent shale.

8. In a retorting apparatus for producing shale oil from oil shale, the combination of an elongated vertical reaction vessel, means for introducing crushed oil shale to the interior of said reaction vessel, means for heating said crushed oil shale, means, within said reaction vessel, for collecting a plurality of fractions of liquid shale oil condensate of diiering boiling points, means for cooling heated oil shale and vaporous products released therefrom immediately above the aforesaid collecting means, means for removing non-condensable gas from said reaction ves-- sel, means for cooling spent shale within said reaction vessel, means for withdrawing cooled spent shale, and means for separately withdrawing Vfrom the interior of said reaction vessel eachof the aforesaid condensed liquid shale oil fractions.

9. In a retorting apparatus for producing shale oil from oil shale, the combination of an elongated vertical reaction vessel, an inlet conduit for introducing crushed oil shale to the interior of said reaction vessel, means for initiating combustion of said crushed oil shale, a series of trays aixed to the interior of said reaction vessel for collecting a plurality of fractions of liquid shale oil condensate of differing boiling points, a series of outlet conduits, one of said conduits extending from each of said -trays for electing separate withdrawal therefrom of the collected fractions of liquid shale oil condensate, an outlet near the top of said reaction vessel for removing noncondensable gas, conduit for recycling said non-condensable gas to the lower interior of said reaction vessel wherein it cools downowing hot spent shale and an outlet conduit in the bottom of said reaction vessel for removing cold spent shale.

10. In a retorting apparatus for producing shale oil from oil shale, the combination of an elongated vertical reaction vessel, means for heating said crushed oil shale to retorting temperature, a series of contiguous trays positioned along the interior surface of said reaction vessel at varying distances from the center thereof for collecting a plurality of fractions of liquid shale oil condensate of ditfering boiling points, a series of cooling coils immediately overlying said trays, a series of outlet conduits, true of said outlet conduits extending from each of said trays a point outside ysaid reaction vessel for effecting separate withdrawal therefrom of the collected fractions of liquid shale oil condensate, an outlet for removing noncondensable gas from the top of said reaction vessel, a conduit for recycling said non-condensable gas to the lower interior of said reaction vessel wherein it contacts and cools dewnowing hot spent shale and an outlet conduit in the bottom of said reaction vessel yfor effecting removal of cold, spent shale.

References Cited in the le of this patent UNITED STATES PATENTS 1,781,934v Synder Nov. 18, 1930 2,637,683 Kassel May 5, 1953 2,640,019 Berg May 26, 1953 2,707,163 Thibaut Apr. 26, 1955 2,723,225 Elliott Nov. 8, 1955 OTHER REFERENCES UNITED STATES PATENT OFFICE CERTIFICATE OE CORRECTION May 59 Patent No., 2,885 ,1338

Louis P. Evahs` It is hereb3T certified that error appears n the printed specification of the above numbered patent requiring correction and that the Said Letters Patent should read as corrected below.

nhydroooarbohacefous read m hydro lines 22 and. 23j for vaparousY read wvaporous en;

column 5, line' 23, for

d Shale ne.

Column 2,

oarbonaoeous 1f-1; line 5C, for "Shade rea Signe (SEAL) Attest: KARL H @MNE ROBERT O. WATSON Commissioner of Patents Attesting Oicer

Claims (1)

1. 2. IN A METHOD FOR PRODUCING SHALE OIL FROM OIL SHALE BY HEATING A DOWNWARDLY MOVING COMPACT BED OF COLD, CRUSHED OIL SHALE AND FLOWING THE HOT VAPOROUS PRODUCTS SO OBTAINED UPWARDLY THROUGH SAID DOWNWARDLY MOVING BED, WHEREBY SAID OIL SHALE UNDERGOES RETORTATION AND THE RELEASED SHALE OIL VAPORS UNDERGO CONDENSATION UPON CONTACT WITH THE COUNTER-FLOWING COLD SHALE, THE IMPROVEMENT WHICH COMPRISES COLLECTING A PLURALITY OF LIQUID SHALE OIL FRACTIONS OF DIFFERING BOILING POINTS WITHIN SAID MOVING BED, WITHDRAWING SEPARATE STREAMS OF EACH OF SAID COL-

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