US3162583A - Shale distillation - Google Patents

Description

1964 c. E HEMMINGER ETAL 3,162,533

SHALE DISTILLATION Filed Nov. 1, 1960 souos our $42 SOLIDS IN Fig. I

GAS STEAM Fig. 2

Charles E. Hemminger Richard I. Bergman inventors W07 Patent Attorney United States Patent 3.162533 SHAKE EltaTlLLATlSN Qharles E. Hernminger, Westfield, and Richard I. llergman, Princeton, NJL, assignors to Esso Research and Engineering Qonrpany, a corporation of Delaware Filed Nov. It, 196%, Ser. No. 65,567 3 Qlairns. (Cl. 2102-33) through the retort countercurrent to the flow of the shale.

Distilled oil and gas are withdrawn from near the bottom and spent shale is taken off the top of the top of the retort. This type of retort requires a large amount of heat.

In another type of retort the oil shale moves down by gravity countercurrent to rising combustion gases. In this type some raw shale oil leaves the top of the retort as a mist. Also shale fines are formed and these are ob jectionaole as they cause packing of the solids in the retort and interfere with the proper flow of gases through the retort.

The present invention is concerned with improving the operation of the prior art processes associated with these prior retorts. According to the present invention coal and/ or coke is added to the oil shale to be distilled. The coke is preferably coke made by subjecting bottoms from the distillation of shale oil to fluid coking as this coke is generally produced at the shale minm where it has no value other than as fuel and is burned up during retorting to supply part of the heat of distillation or retorting. When using fluid coke and coal in a mixture with oil shale in distilling and retorting, higher yields of oil and better operability are obtained than when using a mixture of coal and shale alone. Delayed coke made by the commercial delayed coking process can also be used.

In another form of the invention fine oil shale and fine coal are sprayed with heavy oil, such as bottoms from a shale oil distillation, in a rotary kiln to form balls which are fed to the retort for admixture with the oil shale to be distilled.

In the preferred form of the invention the efiiciency of the underfed frusto-conical retort where the oil shale is fed into the bottom of the retort is increased by adding coal with or without fluid coke in admixture with the shale to be retorted or distilled. The coal to be added is bituminous coal or lignite, gilsonite, anthracite coal, peat and other carbonaceous materials.

In the drawing:

FIG. 1 represents a diagrammatic showing of an underfed retort and associated fractionating tower; and

FIG. 2 represents a detailed vertical sectional view of the underfed type retort shown in FlG. l.

Referring now to the drawing and FIG. 1, the reference character it) designates a retort into which oil bearing minerals such as shale mixed with coal or coal and coke are introduced through line 12 into the bottom of the retort. Spent shale is taken overhead from the retort as shown by arrow 14. Air alone or air and steam are passed through line 16 into the top of the retort for downllow through the retort countercurrent to the up Wardly moving shale solids. Combustion gases and oil vapors leave the retort through line 18 and pass to the fractionator 22 for separation into a bottoms fraction which is withdrawn through line 24 and lower boiling 33,162,583 Patented Dec. 22, 1964 hydrocarbons and gases which are withdrawn overhead through line 26. The liquid products may be further fractionated and the fractions treated as. desired.

FIG. 2 shows the underfed retort in greater detail but the drawing is more or less diagrammatic. For a more detailed showing of this type of retort see Lielfers et 21]., Patent No. 2,875,137, granted February 24, 1959. The retort 10, arrow 14, line 16, outlet line 18, tower 22, bottoms line 24 and gaseous outlet line 26 are designated by the same numbers in FIGS. 1 and 2.

Retort 1% has a frusto-conical upper portion 32 with the smaller end 34 being at the bottom. Extending from the bottom 34 is another frusto-conical section 36 which has a more sharply converging wall provided at its bottom portion with an opening 35. The frusto-conical section 36 is a disengaging section provided with two vertically spaced rows of openings 38. Surrounding the disengaging section 36 is a jacket 42 for receiving combustion gas and cracked hydrocarbon vapors and gases. The outlet conduit 18 extends from the jacket 42 and conducts gases and vapors to the fractionating tower 22. Preferably a pump or gas blower 43 is provided in outlet line 26 to remove the gaseous fraction from the retort 10 through line 18.

Gas such as air for combustion for supplying heat of retorting is introduced through line 16 or from the atmosphere into the upper portion of the :top section 32 of the retort 10. If desired, steam is introduced along with the air through separate line 43' into the upper portion of the section 32 of :the retort 10. The steam increases the gas production during the retorting.

In this type of retort the ground oil shale particles are introduced into the bottom of the retort 10 and forced upwardly therethrough by a hydraulic piston feeder mechanism 47 arranged below the retort 10 in a support or case 44 which has a curved top portion 45 in the form of a section of the circle. The casing 44 is provided with an opening 46 which coincides or alines with the opening 35 in the bottom of the frusto-conical section 36 of the retort 10.

Arranged within the casing or support 44 is the piston feeder 47 which is shown as vertically arranged in the drawing in the charging position and which is provided with arms or guard-s 48 which are in the form of a circular section and extends outwardly from the opening 46 in the piston feeder 47. These arms or guards contact and have a relatively close slidable fit with the underside of the top portion of the casing or support 44.

Vertical webs or supports 49 extend downwardly at right angles from the arms or guards 48 to the housing of the piston feeder 47. Attached to one web 49 is cylinder 50 which has its lower end pivoted at 52 to a bottom support 54 within the casing 44. Reciprocable in the cylinder 50 are a piston and piston rod 56 which is pivoted at its upper end at 58 to web 49. Arranged at one side adjacent the jacket 42 surrounding bottom section 36 of the retort is a hopper 62 which opens at the bottom at 63 into the top of the casing or support 44. The hopper 62 is used for feeding the oil shale and coal and/ or coke mixture to die bottom of the retort 10.

' Arranged within the piston feeder mechanism 47 is a double ended piston 64 which is used for feeding the oil shale mixture into the bottom of the retort 10. The piston feeder mechanism 47 is pivoted at its lower end at 66 to a base member 68 at the bottom of the casing or housing 44. Line 72 is provided to supply liquid under pressure below piston 73 for raising the double ended piston as upwardly. A second line 74 is provided about half way up the piston feeder 47 to introduce liquid under pressure to actagainst the top of piston 73 to force the double-ended piston 64 downwardly. Other means of operating the piston may be used as shown in the Patent No. 2,875,137 above referred to.

In the position shown in FIG. 2 the double-ended piston 64 is ready to discharge shale solids and push them up wardl'y'into the bottom of the smaller lower section 36 of the retort 10. actuated by admitting hydraulic liquid under pressure through line 72 to force piston 64 upwardly to discharge the shale solids into the lower portion of the retort 10. Abutments 78 are provided at the :top of the cylinder in piston feeder 47 to limit the upward movement of the piston .64. V Thereafter the pivoted cylinder 50 is actuated to draw the piston rod 56 downwardly and this moves the piston feeder 47 around its pivot 66 toward the left in FIG. 2 so that the opening 46 in the piston feeder 47 is lined up with the opening 63 in hopper 62. Then hydraulic liquid under pressure is introduced through line 74 to force the double-ended piston 64 downward to allow a charge of shale solids to enter the upper part of the piston feeder 47.

In this position the arm or guard 43 extending'toward the right in FIG. 2 moves across the opening 35 at the bottom of the retort to prevent shale solids from falling downwardly out of the retort 10. Then the pivoted cylinder 50 is actuated to force the piston rod 56 outwardly and this moves the piston feeder back to the position shown in FIG. 2. Thereafter the double-ended piston v64- is actuated to introduce more shale solids into the bottom of the retort. In this position the arm or guard 48 on the left in FIG. 2 has moved to close opening 63 in hopper 62. v

The air passing downwardly through the retort 10 flows countercurrent to the upwardly moving compact bed of shale solids so that within the retort 10 there is a top airpreheating ,zone where the air contacts the spent shale leaving the upper portion of the retort 10. Then there is .acombustion zone where residual carbon on the shale particles is burned. Below the combustion zone is a retorting zone where the oil is formed and freed and drawn off through jacket 42. At the bottom of the retort is a product cooling, shale preheating zone where the shale oil vapors are essentially condensed to liquid. The air passing downwardly is first heated by direct heat exv change with the burnt or spent shale cooling zone and .pheric to a maximum temperature of 2000-2400 F. and a then to 100+300 F. as it passes down the retort with the result that in the high temperature zone a high degree of carbonate decomposition of the inorganic portion The double-ended piston 64 is then shale.

of the shale is produced. With this type of retort a large from the shale itself is increased from to 105% of the Fischer assay of the shale.

Since the heat load in this type of retort is high and practically all of the carbonates are decomposed'there v is not sufiicient residual carbon in the shaleto provide a the necessary heat for the shale retorting and carbonate decomposition. As a result in the countercurrent flow of air in the retort, air for which there is not suflicient carbon for combustion passes down through the shalebed 5 in another type of' a retort oi-l shale'is fed at the top of a and consumes a portion of the retorted hydrocarbon 7 product,

By feeding hydrocarbon.

. By adding coal orcoke to the shale feed, the coke from the coal distillation and the added coke are burned and this provides the necessary carbon to burn this excess 'air and oxygen-free hot gasenters the distillation or re torting zone at a lower level in the retort Consequently there is a substantially'complete recovery of oil from the oil shale as well as that from the coal. The fluid coke supplies heat by being burned. The fluid coke will not fuse like coal being distilled and hence better operability of the retort is obtained. Because of the fusing property of coals, which causes uneven distribution of the air by blockingair passages, the amount of coal is limited to about 25% by weight of the shale. Coke does not have any limitation but it, in itself, gives little or no liquid However, more coal can be distilled if coke is added with the shale, the 25% maximum content of coal can be increased to 40% on shale if 30% of coke on shale is added to the feed mixture to the retort.

The amount of coal which is added should be at least suflicient to have 1-5 carbon in the ash or spent shale leaving the top of the retort. This is the minimum amount of coal and the amount will depend upon the richness of the shale, more coal being used for a 20 gallons per ton than a 40 gallons per ton shale. For a 30 gallons per ton shale about 25 Wt. percent coal is utilized in the coal-shale mixture. If too much coal is added with the mixture, channelling results in the retort due to the coking and fusion of the coke particles. When channelling occurs, there is ineflicient contacting of the solids and the gases. The maximum amount of coal to be used is in the order of about a 50-50 weight mixture of coal and With the present invention, lean shales can be employed by enriching them withcoal or coke so that the liquid hydrocarbon product per retort is the same as with a rich shale. V

With the present invention the yield of hydrocarbons is larger than when using only oil shale. On a Btu. basis, coal is mined at a cost less than shale. Further, large coal deposits are available in the same area as shale in a number of sections of the country. Ste-am added with the air increases the yield and quality of byproduct gases by forming water gas.

If it ,is desired to introduce more carbonaceous fuel to the oil shale it is preferred to add fluid coke particles.

' As above pointed out, if more than a maximum amount of coal is added to the retort above a 50-50 weight mixture of coal and shale, channelling results. With this 'so'lid. Also coking is advantageous with large, coal additions so as to give lighter products from the coal tar. The fluid coke may be obtained from any source but the preferred source is fluid coke obtained by coking the bottoms withdrawn through line 24 from the tower 22.

This bottom fraction contains metal and other impurities and would form a poor coke product for general usage but is sufficiently good to supply fuel to be used as an addition to coal in a shale retorting process. The use of coal and fluid coke in the retort results in an increased yield and better quality'of by-product gases from the rej 'tortirig operation. The retort gases separated from the retor-t products can :be collected and used as refinery or other fuel. Another advantage of the coal mixture is the diluent effect of the liquid hydrocarbons from coal distillation. on' the pour point of the shale oil, reducing it. about 20 'F..when 25% coal is added to a 30 gal/ton shale. 1

the retort and air is introduced at an intermediate section of the retort for upwardly flow countercurrent to the downwardly moving shale. Spent shale is withdrawn from the bottom of the retort. To improve the operation of a retort of this type, coal or coal and fluid coke are added to the oil shale. One disadvantage of this type of retort is that the retort temperature is relatively high and some of the carbonate in the oil shale is decomposed.

As the shale moves down through the retort the residual carbon from the shale is burned but there is not enough of the residual carbon to burn to produce the high tern perature and hence all of the carbon is burned out of the shale and dusting or fines formation results. By adding coal to the oil shale the coal is coked and the residual carbon from the coking of the coal provides the fuel for retorting. Thus all the carbon need not be burned out of the shale and the residual carbon in the shale gives it physical strength so that dusting of the oil shale is avoided.

A minimum amount of coal is added to avoid fines formation or dust formation from the retort and a maximum amount of coal is used to avoid channelling in the retort. The minimum amount of coal depends upon the richness of the shale. The best way to define the amount of coal is that the carbon in the spent shale is in the order of 1 wt. percent. When less carbon is prescut, the fine shale production is high because of the absence of carbon to bind the fine shale particles together. The maximum amount of coal may be defined as having a liquid oil yield of not over 50 gallons per ton of total charge of oil shale and coal. If more liquid or more tar is formed than the 50 gallons per ton there is a tendency for bridging and plugging of the moving bed in the retort.

The coal enriches the shale so that the maximum hydrocarbon oil yield per square foot of retort area is obtained. Thus a plant using 20 gallons of oil per ton of oil shale can produce as much hydrocarbon distillate when coal is added as when a 30 gallons of oil per ton oil shale is employed. By adding steam at the bottom of the retort, water gas is produced by reacting with the coal coke and a richer and greater volume of byproduct gas is available. Due to the benzene ring structure of coal, more aromatics are produced from the coal shale mixture than from shale alone and higher octane gasolines are made available when hydrocracking or processing the shale oil.

In the underfed type of retort and the gas combustion retort fine shale particles are undesirable and are rejected because they cause packing of the particles in the retort and this impedes the flow of gases. When coal is added to shale, fine coal is also undesirable. To make the fine material available for retorting the fines from the coal shale mixture are screened from the charge to the retort and coked with the heavy tarry portions of the retort product. This tarry portion may be obtained by distillation of the retorted products or partial condensation of the retorted products, for example, a tar knockout drum.

The fines are fed to a rotary type of kiln and the tar sprayed inside the kiln to form a semi-plastic mass. The ratio oi tar liquid to line solids is carefully controlled in the range of about 5 to 25% depending upon the character of the fines and the shale-coal ratio so that balls are formed as the solid moves through the retort. Heat can be added by internal combustion of retort gases to bake and dry the balls by raising the temperature to about 200300 F. exit temperature. The balls are then strong enough to be added to the retort coal-shale mixture as feed to the retort. As the temperatures increase in the retort the tar is carbonized and the fines do not separate and cause trouble.

An alternate operation is to include the fine coal and fine shale from screening along with any tarry pitch from distillation in a suspension in the feed to the fluid or delayed coker. These fine materials are coated with coke from coking the shale oil, preferably the shale oil bottoms, and are increased in size so that they give good operability to the shale retorts, either upflow or downflow.

In addition to aiding in the operation of the retort another advantage of the invention is that the heavy oil which is used in spraying the fine shale or fine coal is subjected to visbreaking and additional cracking.

As a general example, the oil shale-coal mixture as it passes up through the retort is preheated internally by downwardly moving oil vapors.

The shale-coal mixture then is passed up through the combustion-retorting zone beginning at the bottom of conical section 34 where it is countercurrently contacted with hot downfiowing shale oil vapors and combustion gases. The shale-coal mixture is progressively heated from atmospheric temperature to about 2000 F.-2400 F. thereby retor-ting the oil shalecoal mixture to oil product. Different temperatures may be used for different oil shales which have difierent oil contents.

The rate of passage of the oil shale-coal mixture upwardly through the retort 10 is selected to insure a sufficient residence time in the retort 10 to completely retort the oil shale-coal mixture. Generally, the residence time will vary from about 30 minutes to 150 minutes.

The shale mixture then is passed upwardly into the airpreheating zone in the upper portion of retort 10 where the air i heated to a temperature of about 400 F., at which temperature combustion with the shale is initiated and the shale mixture is cooled to about 1000 F.

In a 1000 ton unit containing about 15 wt. percent of bituminous coal, about 9,000 cu. ft. of air per ton of shale and coal is passed down through retort 10. The maximum temperature in the retort may vary between about 2000 F. and 2400 F.

The oil shale to be retorted is ground and screened to a particle size of about A to 4 inches. The bituminous coal to be mixed with the shale is ground and screened to about the same size. The fluid coke to be mixed with the shale has a particle size between about 100 and 1500 microns. The mixture of shale and coal passes through the retort as a compact moving bed and not as a turbulent fluid bed.

An illustrative operation in the apparatus of the type shown in the drawing is one using the following percentages of shale, coal and coke with the listed qualities.

Shale 60 wt. percent, less than 4 inch size, 30 gal/ton, Fischer assay. Coal 30 wt. percent, less than 2 inch size. Volatile matter, wt. percent 42. Carbon wt. percent 42. Ash wt. percent l2.

Moisture wt. percent 4 Coke 10 wt. percent, fluid coke from shale oil bottoms, less than inch size, 15% volatile m a t t e r, carbon.

Feed rate 1500 t./d.

Combustion gas temperature to retorting zone 2100 F.

Spent shale 775 F.

Oil from retort F.

Air rate 9000 c.f./ ton coal, coke and shale.

Steam 0-500 c.f./ton coal, coke and shale.

Product 31 gal. per ton coal, coke and shale.

Gravity 19.5 API.

70% 870. V 90% Cracked.

Conradson, carbon percent 5.2. Viscosity, S.S.U. at 100 F. 235.

If shale alone is used without the addition of'coal and coke, the air rate needed is much higher and the shale oil production would only be about 36,000 gal./day due to the lower yield and lower throughput with shale.

Using the mixture of shale and coal and coke of the present invention requires less air (about 9,000 cubic feet per ton of the mixture) than when using shale alone which requires between about 10,000 and 12,000 cubic feet of air per ton of shale. Thus with the present invention it is possible to have greater throughputs of the shalecoal mixture for a given air rate (which is the dictating flow rate) and this advantage is in addition to the greater .yield of shale oil per ton of shale-coal mixture, The advantages are obtained with the present invention because there is no carbonate decomposition of the oil shale.

What is claimed is: 1. In a process wherein shale solids are moved upwardly as a compact non-fluid moving bed through a retorting zone maintained at a temperature between about 2000 F. and 2400 F. and a burning zone countercurrent to downwardly flowing o'Xygen-containinggas and shale solids are retorted in said retorting zone to form shale oil and spent carbon-containing shale solids and the spent carbon-containing shale solids are burned in said burning :zone to provide the heat for the retorting zone and insufiicient residual carbon is provided by thespent shale solids to supply all the'heat for the retorting zone, the improvement which comprises admixing bituminous coal and=fluid coke particles with .said shale solids so that the mixture contains between about 25 and 50 wt. percent of coal and between about 15 and 25 wt. percent of fluid coke particles to increase the amount of burnable carbon available after retorting to be burned to provide heat for said retorting zone without substantially burning shale oil 0 product and to increase the yield of retorted hydrocarbon oil.

2. A process according to claim 1 wherein the retorted hydrocarbon'is fractionated into a bottoms fraction and a distillate fraction and the bottoms fraction is coked in afluid coking step and the resulting fiuid coke particles are the ones added to the shale-coal mixture.

3. In a process wherein shale solids are passed upwardly as a compact non-fluid moving bed through a retorting zone maintained at'a temperature between about 2000 F. and 2400 F. and a burning zone wherein spent shale solids formed in the process are burned and insuflicient residual carbon is provided by said spent shale solids to supply all the heat of retorting and all the resi dual carbon is burned from said spent shale solids which then lose their structure and strength by carbonate decomposition and form dust and retorted hydrocarbon product is burned and lost, the improvement which cornprises admixing bituminous coal and fluid coke particles with said shale solids so that the mixture which is introduced into said retorthig zone contains between about 25 and 50 weight percent of coal and between about 15 and 25 weight percent of fluid coke particles and the rest shale solids to supply added carbon to be burned in said burning zone in preference to residual carbon on said spent shale solids to supply sufi'icient heat for retorting in said retorting zone while leaving at least 1% of residual carbon on said spent shale solids being discharged from said burning zone to maintain the physical strength and to avoid dusting ofthe burned shale and to prevent carbonate decomposition of said shale solids and to increase the yield of retorted hydrocarbon liquid product by avoiding burning 'of the'retorted hydrocarbon product in said burning zone.

References (Iii-ed inthe file of this patent 'UNITED STATES PATENTS 2,875,137 Lieffers et al Feb. 24,

Claims (1)

1. IN A PROCESS WHEREIN SHALE SOLIDS ARE MOVED UPWARDLY AS A COMPACT NON-FLUID MOVING BED THROUGH A RETORTING ZONE MAINTAINED AT A TEMPERATURE BETWEEN ABOUT 2000* F. AND 2400* F. AND A BURNING ZONE COUNTERCURRENT TO DOWNWARDLY FLOWING OXYGEN-CONTAINING GAS AND SHALE SOLIDS ARE RETORTING ZONE TO FORM SHALE OIL AND SPENT CARBON-CONTAINING SHALE SOLIDS AND THE SPENT CARBON-CONTAINING SHALE SOLIDS ARE BURNED IN SAID BURNING ZONE TO PROVIDE THE HEAT FOR THE RETORTING ZONE AND INSUFFICIENT RESIDUAL CARBON IS PROVIDED BY THE SPENT SHALE SOLIDS TO SUPPLY ALL THE HEAT FOR THE RETORTING ZONE, THE

Images