US3520795A - Retorting of oil shale - Google Patents

Description

United States Patent O M 3,520,795 RETORTING F UIL SHALE Bernard L. Schulman, Livingston, and Herbert l.

Dengler, Fair Haven, NJ., assignors to Esso Research and Engineering Company Filed Dec. 29, 1966, Ser. No. 605,890 Int. Cl. Clg 1/00 U.S. Cl. 208-11 10 Claims ABSTRACT 0F THE DISCLOSURE In the retorting of crushed oil shale in a retorting system having in a single vessel preheating, retorting, and cooling zones and the crushed shale flows serially therethrough, a temperature below carbonate decomposition and below shale oil cracking temperature is maintained by introducing vaporous 'water into said system adjacent or into the retorting zone and liquid water into the cooling zone, whereby introduction of cooling gas into the cooling zone is reduced, oil and gas yields are improved and gas heating value is enhanced.

The present invention is directed to control of temperatures in the retorting of oil shale. More particularly, the invention is directed to control of temperatures while eliminating the use of a substantial amount of recycle gas streams in oil shale retorting. In its more specific aspects, the invention is concerned With the use of liquid cooling streams in retorting of oil shale.

The present invention may be briey described as an improvement in the method of retorting oil shale in which crushed oil shale is introduced into a vertical retorting system and flows serially through a preheating zone, a retorting zone, and a cooling Zone in which the oil shale is contacted with a heated gasiform fluid at a temperature sutiicient to decompose kerogen in the oil shale to shale oil and where heat is removed from the oil shale in the cooling zone. The particular improvement of the present invention is introduction of liquid water into the cooling zone to remove heat and introducing vaporous lwater into said retorting system at a point at least adjacent said retorting zone to maintain a temperature within the retorting zone below carbonate decomposition temperature and below a temperature where substantial cracking of shale oil occurs. By using liquid and Vaporous water in accordance with the present invention, introduction of cooling gas into the cooling zone is substantially reduced, if not entirely eliminated; oil and gas yields are improved and the heating value of the noncondensable gas used in the process is enhanced.

The vaporous water is suitably supreheated steam at a temperature within the range of about 1100D to about l200 F. This superheated steam is generated by flowing a stream of liquid water through a combustion zone extraneous to said retorting system in which the oil shale containing a combustible amount of carbonaceous material is subjected to combustion conditions, The oil shale containing a combustible amount of carbonaceous material may suitably be spent shale removed from the cooling zone, or it may be oil shale containing a small quantity of carbonaceous material and which is unsuitable for recovery of shale oil. Rather than use spent shale containing a small amount of carbonaceous material or oil shale which contains only a small amount of carbonaceout material, it is contemplated that oil may be added to oil shale where the carbonaceous material is in insufficient amounts to provide a sufcient amount for combustion.

The water used in accordance with the present invention may be obtained from any source and may be fresh or salt water. Preferably, however, at least a portion of 3,520,795 Patented July 14, 1970 ICC the water used in accordance with the present invention is water obtained by separation from the shale oil recovered from the retorting system. lf the amount of water produced in the operation is insucient, water from an extraneous source may be used. The water produced in the retorting operation may be used to provide the liquid Water and the Vaporous water. It is contemplated in acordance with the present invention that the retorting system may include a combustion zone intermediate the retorting and cooling zones. ln such instances, a mixture of liquid water and air is introduced into a combustion zone in said retorting system between said retorting zone and said cooling zone to provide said heated gasiform uid which is used in the retorting operation and the vaporous water introduced into the retorting zone. In the instances where a combustion zone is part of the retorting system, the heated gasiform fluid is suitably iiue gas resulting from combustion of carbonaceous material in the oil shale.

In the practice of the present invention where superheated steam is generated extraneous to the retorting system, the retorting zone is maintained at a temperature within the range of about 950 to about 1050D F. This maintenance of temperature is provided by introduction of the vaporous and liquid streams of water and prevents the so-called temperature peaking which results in carbonate decomposition and which also results in cracking of shale oil. By avoiding temperature peaking, substantial economies inure to the present invention.

When a combustion zone is provided in the retorting sytem, the maximum temperature in the combustion zone is controlled to a temperature within the range of about 950 to 1050" F. by introduction of the mixture of air and water into the combustion zone along with the cooling effects of the cooling water introduced as a liquid stream into the cooling zone.

The present invention will be further illustrated by reference to the drawing wherein best modes and embodiments are set forth in which:

FIG. 1 is a flow diagram of one mode and embodiment wherein a combustion zone is provided in the retorting system; and

FIG. 2 is another mode and embodiment wherein a combustion zone is provided extraneous to the retorting systems.

Referring now to the drawing, and particularly to FIG. l, numeral 11 designates a vertical retorting system provided with a preheating zone 12, a retorting zone 13, a combustion zone 14, and a cooling zone 15. Into the top of preheating zone 12 there is introduced by way of line 16, raw crushed oil shale which may have particle diameters ranging from about 1A inch up to about 3 inches. Line 16 may include a suitable hopper device not shown for introduction of the crushed oil shale into preheating zone 12.

In preheating zone 12, the crushed oil shale is preheated to a temperature within the range from about 400 to about 800 F., suitably a temperature of about 600 F., by contact with the up-tlowing gaseous and vaporous products produced in the process.

The preheated oil shale then flows downwardly into retorting zone 13 wherein a temperature within the range of about 600 to about l050 F. prevails. A suitable temperature may be from about 950 to about 1050o F. The kerogen in the oil shale is converted by contact of up-flowing gases to oil shale which forms as a mist in the retorting system 1l, and together with the noncondensable gas, serves to preheat the oil shale in zone 12.

In retorting zone 13 and combustion zone 14 heretofore there has been a problem of controlling so-called temperature peaking which frequently has resulted in cracking of shale oil produced in the system and decomposition of carbonate. The present invention eliminates this problem' by introducing into the combustion zone 14 by way of line 17 and distribution means 18, a suitable quantity of combustion air which may be from about 2,000 to about 6,000 cubic feet of air or other free oxygen-containing gas per ton of oil shale. Admixed with this combustion air is liquid water introduced into line 17 by line 19, controlled by valve 20 from a source which will be described later.

As a result of the combustion operation in zone 14, ue gases and steam mixture are provided, which heats the shale oil by combustion of carbonaceous material thereon, and provides the heated gasiform medium for decomposition of kerogen in retorting zone 13.

The spent oil shale ows downwardly into zone where a temperature within the range from about 1400 to about 200 F. may prevail. The spent shale may not be discharged at this temperature and, therefore, it is necessary to cool spent shale, which in accordance with the present invention, is accomplished by introducing a stream of liquid water into zone 1S through distribution means 21, connected to line 20 and by opening valve 22 therein.

The products from the retorting operation just described are discharged from the top of the retorting system 11 by way of line 23 which contains a condensercooler 24 and, thence, into a collection or demisting vessel 2S wherein a separation is made among the products of the retorting operation. Noncondensable gas is discharged from vessel 25 by line 26, and may be used as a fuel as may be desired. The shale oil is recovered by line 27 while the liquid water formed and introduced into the system is discharged by line 28, controlled by valve 29. Preferably, however, at least a portion of this liquid water is introduced back into the system by line 30, controlled by valve 31 which connects by Way of branch line 32 with line 19 which provide the liquid water streams for introduction into zone` 14 and zone 15.

If the amount of water required in the retorting system is greater than the amount of water withdrawn by line 28, Water from an extraneous source may be obtained by opening valve 33 in line 30.

The amount of water employed in the retorting system is in the range from about 200 to about 300 pounds of water per ton of raw oil shale. A preferred amount of Water is from about 250 to about 280 pounds per ton of raw oil shale. Employing water in these preferred amounts allows the spent shale to be cooled, for example, from about 1200 F. to about 200 F. with much less vapor being involved in the bottom of the retorting system than when ue gas is used as is conventional. The liquid water forms 5,800 s.c.f. of vapor per ton of raw oil shale while 16,000 to 18,000 s.c.f. of recycle gas per ton of raw oil shale would be required otherwise to do the equivalent amount of cooling. Since heat transfer is a factor, it is preferred that at least about 6 to about 10 feet of shale `bed height should be between vaporous and liquid water injection points.

While the sole cooling is obtained with liquid Water, it may be desirable to return a small amount of recycle gas to the retorting system 11 to purge steam from the cooling oil shale. To this end, line 34, controlled by valve 35 connects to line 26 and allows from about 1,000 to about 2,000 s.c.f. per ton of raw shale, to strip the steam from the cooled shale, to be introduced into cooling zone 15. The cooled spent shale is then discharged from zone 15 by line 36.

The present invention will be further described by reference to FIG. 2 wherein a combustion zone extraneous to the retorting system is provided. Referring to FIG. 2, numeral designates a retorting system provided with a preheating zone 41, a retorting zone 42, and a cooling zone 43. Introduced into preheating zone 41 is raw oil shale by way of line 43. The raw oil shale is crushed to have particle diameters from about 1A up to about 3 inches, and line 43 may include a suitable hopper device.

The raw oil shale introduced into zone 41 is preheated therein by contact with up-flowing products of the retorting operation which includes condensable and noncondensable material. The preheated oil shale then flows downwardly into retorting zone 42 where it is contacted with superheated steam at a temperature from about 1100 to about 1200 F., introduced therein by line 44 through distribution means 45. The superheated steam is obtained from a source which will be described further, and provides a maximum temperature in the retorting zone 42 within the range from about 950 to about 1050 F., and decomposes the kerogen in the preheated oil shale to shale oil which rises upwardly through preheating zone 41 with the steam and noncondensables to contact the incoming raw shale and to preheat same.

The returned oil shale then ows downwardly into cooling zone 43 where it is contacted with liquid water which is introduced or sprayed into the bottom of cooling zone 43 about one to two feet above the bottom. This liquid water is introduced by line 46 from a source which will be described further.

The cooled spent shale is discharged from the system, at least in part, by line 47, controlled by valve 48.

The products from the retorting system 40 are discharged from the preheating zone 41 by line 49 containing a condenser-cooler I50, which reduces the temperature of the vaporous and gaseous product, for introduction into a demisting or collection zone 51 wherein a separation is made among the gas, oil, and water in the products leaving zone 41 by line 49. The gas is discharged by line S2 for use suitably as a fuel and the shale oil by line 53 for further refining as desired. The water may be discharged by line 54 and branch line 55, controlled by valve 56, but preferably valve 56 is closed and valve 57 in line 54 is opened allowing the Water to be introduced into line 46 for introduction into cooling zone 43 as has been described. If the amount of water separated in vessel 51 is insufficient to provide the necessary cooling, additional amounts of water may be introduced by opening valve S8 connecting to an extraneous source of water which may be fresh or salt water.

At least a portion of the spent shale which may contain about 2% carbonaceous material is suitably withdrawn from line 47 through line 59, controlled by valve 60 and introduced into line 61 and thence into a combustion zone 62 in combustion vessel 63. The carbonaceous material on the spent shale is burned in combustion zone 62 by introduction of air in zone 62 by way of line 64 through distribution means 65, which raises the temperature to a temperature within the range from about 1400D to about 1800 F. Liquid water is introduced into zone 62 by line 66 and passes through the lower portion of zone `62 wherein a bed 67 of hot burned shale has accumulated which causes Vaporization and superheating of the water. The superheated steam is withdrawn by way of line 68 and introduced thereby into line 69 and thence into line 44. Superheated steam from an extraneous source may be introduced by opening valve 70 in line 69 if desired.

The burned shale may be discharged to a waste pile by way of line 71.

The present invention is quite advantageous in that normally temperatures in the combustion zone of the oil shale retort ranging from about l to about 1500 F. result in substantial amounts of carbonate decomposition, which is a highly endothermic reaction, and allows some cracking of the oil shale. -In accordance with the present invention, the latent and sensible heat of the water, together with the endothermic heat of reaction serves as an effective heat sink for the combustion zone. Any products from this reaction will add to the heating value of the product gas. Another advantage of the present invention is that compression costs are lower than heretofore since the streams used for introduction as cooling uid are liquid rather than gas.

Still another advantage is that vaporous water provides an oi-gas with a high heating value of about SOO-1,000 B.t.u. per s.c.f. as contrasted with an off-gas having a B.t.u. value of only 50-150 B.t.u. per s.c.f. as obtained in the conventional gas combustion retort. The present invention thus produces another valuable by-product which may be used as a fuel or in the production of hydrogen. Likewise, eficient recovery of ammonia and H28 is possible where vaporous water is used which Serves to reduce air pollution.

To illustrate the practice of the present invention where water is used as a cooling medium, the following comparisons have been made.

Air (M s.e.f./ton shale) Recycle gas It will be seen from the foregoing comparison that the amount of combustion air has been reduced from about 4M s.c.f./ton shale to 3M s.c.f./ton shale while the recycle lgas has been reduced from 18 to 2, a nine- :fold decrease which is quite substantial.

The present invention is quite important and useful.

The nature and objects of the present invention having been fully described and illustrated and the best mode and embodiment contemplated set forth, what we wish to claim as new and useful and secure by Letters Patent 1s:

1. In the retorting of oil shale in which crushed oil shale is introduced into a retorting system having in a single vessel therein preheating, retorting and cooling zones and said oil shale ilows serially through said zones and wherein said oil shale is contacted with a heated gasiform fluid in said retorting zone at a temperature sucient to decompose kerogen in said oil shale to shale oil and heat is removed from said oil shale in said cooling zone, the simultaneous steps of introducing suiicient liquid water directly into said cooling zone to remove said heat and to cool said contacted shale flowing from said retorting zone to about 200 F. while separately introducing suiiicient vaporous water directly into said retorting system at a point at least adjacent or into said retorting zone'to maintain a temperature within the range from about 950 to about 1050 F. in said retorting zone below car bonate decomposition temperature and below a temperature where substantial cracking of shale oil occurs;

the amount of water introduced into said system being in the range between about 200 and about 300 pounds per ton of crushed oil shale introduced thereinto;

whereby oil and gas yields are improved, and the heating value of the gas is enhanced.

2. A method in accordance with claim l in which the vaporous water is superheated steam at a temperature within the range from about 1l00 to about l200 F.

3. A method in accordance with claim 2 in which the superheated steam is generated by flowing a stream of liquid water through a combustion zone extraneous to said retorting system in which spent oil shale containing a combustible amount of carbonaceous material is sub jected to combustion conditions.

4. A method in accordance with claim 3 in which at least a portion of the stream of liquid water is obtained by separation from shale oil recovered from the retorting system.

5. A method in accordance with claim 3 in which at least a portion of the spent shale is obtained outside the system.

6. A method in accordance With claim 3 in which at least a portion of the spent shale is obtained from the cooling zone.

7. A method in accordance with claim 1 in which a mixture of liquid water and air is introduced into a combustion zone in said retorting system between said retorting zone and said cooling zone to provide said heated gasiform fluid and said vaporous water in said retorting zone.

8. A method in accordance with claim 7 in which the heated gasiform fluid is ilue gas resulting from com- Ibustion of carbonaceous material in said oil shale.

9. A method in accordance with claim 7 in which the maximum temperature in the combustion Zone is controlled to a temperature within the range from about 950 and 1050 F. by introduction of said mixture.

10. A method in accordance with claim 1 in which at least a portion of the Water is obtained by separation from shale oil recovered from the retorting system.

References Cited UNITED STATES PATENTS 2,544,843 3/1951 Leffer 202-15 2,698,283 12/1954 Dalin 202-6 2,796,390 6/ 1957 Elliott 202-6 2,814,587 11/1957 Van Dijck 202-3 3,130,132 4/1964 Sanders 202-7 DELBERT E. GANTZ, Primary Examiner T. H. YOUNG, Assistant Examiner U.S. Cl. X.R. 201-29, 38

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