US3562143A - Liquid disengaging system - Google Patents

Abstract

THE EFFICIENCY AND YIELD OF THE GAS COMBUSTION RETORTING PROCESS FOR RECOVERING VALUABLE HYDROCARBONS FROM OIL SHALE IS IMPROVED BY DISENGAGING A MIXTURE OF GAS AND OIL FROM THE DOWNWARDLY MOVING SHALE, SEPARATING THE OIL FROM THE GAS IN A SHALE-FREE AREA AND RETURNING THE

GAS TO THE SHALE BED AT A LEVEL ABOVE THAT AT WHICH SAID MIXTURE WAS DISENGAGED.

Description

Feb. 9, 1971 L JAGEL, JR ET AL 3,562,143

LIQUID DISENGAGING SYSTEM Filed May 27, 1968 2 Sheets-Sheet 1 /6(t?0t0ting Chute) /3 (Anti- Segregation Device) i8/Feed Pipes) /9 (Off-Gas Headers) I x I /0 i l v I 2 fig v 70p of Disengager 30 i i-1 32(0/7 Recovery Deck Plate) g n "jl Bottom of Disengager 30 E 50(C0n0'uits) .1 v ZSMirD/stributian Ports} 1. 26(Recyc/e 60's Header Outlet} I V 1/ lZ/Refractary Bria/r Liner) L v 20 (Diamond Distributor) g FA? v 22(R0// Feeder) jg f- /n|/ent0rs 24 Kenneth J0ge/, Jr

Conveyar) Dal/id L/ederman Lester J Skowrone/ I (Ratary 1i By 4;

Feeder)25\ Age Feb. 9, 1971 AG L, JR" ETAL 3,562,143

LIQUID DISENGAGING SYSTEM 2 Sheets-Sheet 2 Filed May 27, 1968 F/GZ Jam

dm 696M fl 0 0 mJ k m GM M V. I ,0 J m /f m U V AC ,0

m y M n w i w 5 M Q "6 M V 5/\ 5 MW /2V/ 2 6 M 5 United States Patent O1 3,562,143 Patented Feb. 9, 1971 US. Cl. 208-11 4 Claims ABSTRACT OF THE DISCLOSURE The efficiency and yield of the gas combustion retorting process for recovering valuable hydrocarbons from oil shale is improved by disengaging a mixture of gas and oil from the downwardly moving shale, separating the oil from the gas in a shale-free area and returning the gas to the shale bed at a level above that at which said mixture was disengaged.

BACKGROUND OF THE INVENTION The retorting or destructive distillation of oil shale to recover liquid and gaseous hydrocarbons is fundamentally a relatively simple operation that involves the steps of heating the oil shale to the proper temperature, and recovering the liquid products evolved. However, the commercial application of this process on a large scale requires a large capital investment in equipment, and the recovery of useful products is small in comparison with the volume of oil shale that is retorted.

To effectively handle the large volume of oil shale that is treated in a commercial installation, vertical carbon steel retorts are conventionally employed through which lumps of shale pass by gravity. The energy requirements for the process may be supplied by heating the walls of the retort. Alternatively, the heat required by the process can be obtained by combustion of the gaseous products of the distillation within the retort under conditions designed to insure maximum transfer of heat to the shale and maximum recovery of heat from the gaseous and liquid distillation products and from the solid distillation residue.

Economical and eflicient apparatus for the recovery of valuable hydrocarbons from oil shale is described in US. Pat. No. 2,885,338. Oil shale in particulate form is passed downwardly as a vertical column of material successively through a preheating zone, a distillation zone, a combustion zone and a residue cooling zone. A solid residue from the combustion zone is removed in a cool condition at the bottom of the column while the products of combustion and distillation including low boiling normally liquid products together with noncondensible gas relatively lean in combustibles are withdrawn above the preheating zone in a relatively cool condition. At least a portion of the noncondensible gas in a cool condition is recycled to the bottom of the column and passes upwardly through the downwardly moving residue from the combustion zone thus cooling the hot residue and itself becoming heated to a temperature that will support combustion. A combustion supporting gas such as air or oxygen is introduced into the combustion zone and reacts with the combustibles in the system such as the hydrocarbon 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. Condensation of the shale oil vapors is effected upon contact of the rising hot products of retortation with the downwardly moving cold shale. A series of contiguous hoe trays is positioned within the distillation zone at various distances from the center of the column to receive a plurality of fractions of liquid shale oil condensate of different boiling points which are withdrawn separately through conduits that extend from each tray.

SUMMARY OF THE INVENTION It has now been discovered that the operation of a counter-current retort for oil shale can be improved by reducing the refluxing and percolation in the bed. Local ized liquid accumulations in the bed form carbonaceous agglomerates which wedge in the air distribution assembly and burn in this hot oxidizing environment to form clinkers that interfere with retort operability. Removal of these liquid accumulations from the shale bed reduces the formation of carbonaceous agglomerates and vitreous clinkers.

Localized liquid accumulations in the bed may be initiated by pieces of rich oil shale or by locally high concentrations of fine shale in the shale bed. These fines are more heavily wet with oil by the impaction of mist or by the surface condensation of oil than are large shale pieces.

As liquid is vaporized and cracked from these local accumulations, a tarry, carbonaceous residue is left behind which binds pieces of shale and dust together to form cohesive masses. This occurs at a temperature of about 700 F. The cohesive masses of shale, dust, and tarry binder are converted to dry hard agglomerates at temperatures between 800 F. and 1200 F.

In accordance with the present invention, flooding is caused to occur in a controlled fashion at a section of the retort wherein liquid can be disengaged. This reduces the likelihood of uncontrolled localized liquid accumulations and thus breaks the chain leading to clinkering and retort inoperability.

BRIEF DESCRIPTION OF THE DRAWINGS Advantages of the invention will become apparent to those skilled in the art from the following detailed de scription considered in conjunction with the drawings wherein:

FIG. 1 is an isometric view cf a vertical shaft kiln type oil shale retort, fitted with a liquid disengaging device constructed in accordance with the present invention;

FIG. 2 is a sectional plan view showing two modules of the liquid disengaging device illustrated in FIG. 1;

FIG. 3 is a sectional view of the liquid disengaging device on the line 33 of FIG. 2;

FIG. 4 is an isometric view of a liquid disengaging device useful in the practice of the present invention; and

FIG. 5 is a fragmentary sectional view that illustrates one method of positioning the liquid disengaging device of FIG. 4 within a shale retort.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, in so far as possible, like part have been given the same reference number. Referring now more particularly to FIG. 1, the basic apparatus of this invention may be appreciated. In general, the apparatus is an elongated rectangular retorting vessel 10 lined with a heat resistant refractory material 12. A charge hopper 13 is positioned at the top of the retort. The charge hopper may be of any suitable construction but should be designed to maintain a continuous feed of oil shale particles into the top of the retort and at the same time maintain a gas seal to preserve the escape of gas and vapors from the retort through the charging mechanism. As shown in the drawing, a rotary feeder 14 above the hopper 13 provides a top gas seal and distributes oil shale in particulate form through the rotating chute 16 and feed pipes 18.

At the bottom of the retort, a discharging mechanism is provided consisting of a diamond distributor 20, roll feeders 22 and screw conveyor 24. A second rotary feeder 25 provides a gas seal at the bottom of the vessel.

Extending horizontally from one wall of the retort are a plurality of spaced header outlets 26 for recycle gas and directly thereabove are located a series of vertically opening distribution ports 28 for admitting an oxygen containing gas such as air, into a combustion zone 30.

An oil recovery deck plate 32 extends horizontally across the retorting vessel 10 and is sealed at its edges to a stainless steel liner 34. The position of this deck plate within the retort is important, as it should be at such a level that retorting of the shale and some condensation of high boiling fractions (without flooding) occur below the deck plate. An oil disengager 36 extends above the deck plate 32 toward the preheating zone and below the deck plate toward the combustion zone. The structure and operation of the disengager 36 will now be described with specific reference to FIGS. 2 and 3.

Each unit or module of the disengaging unit 36 is constructed with downwardly diverging baffles 38 and 39 that extend completely across the retorting vessel from openings 40 in the deck plate 32. The length of the opening 40 is equal to the internal dimension of the retort; and the width of the opening is related to the shale particle size range and is sufficient to establish the proper flow of shale through the retort. Upwardly diverging baffles 42 and 43 from openings 40 in the deck plate also extend completely across the retorting vessel. These baffles 42 and 43 are constructed with lower longitudinal slots 44 and 45 in the walls thereof. The slots 44 and 45 are positioned an equal distance above the deck plate 32 and communicate therewith. Upper longitudinal slots 46' and 46 also communicate with the deck plate and are symmetrically positioned in the walls of the baflles 42 and 43. As can be seen, the upwardly diverging baffles 42 and 43 of adjacent modules are capped by an inverted V shaped baffle having an apex 48 to form a deflector that effectively prevents solid material from flowing onto the deck plate. Conduits 50 extending from the deck plate through the wall of the vessel provide for the recovery of liquid products.

While the dimensions of the disengaging unit are not critical, the angle a should be at least about 50 to avoid the formation of a shale free surface at which liquid could accumulate. Angle a should not be greater than 90". Increasing this angle above 50 within the range indicated provides improved operation of the disengaging unit at an increase in construction cost. The angle ,6 is less than 90 and may be as small as 50 providing that the material passing through the retort will flow at that angle; preferably the angle ,8 is between 70 and about 90 to insure smooth shale flow with no inactive zone of shale between the opening 40 and the upper longitudinal slots 46 and 46'. When the width of the opening 40 is about 14 inches, these conditions are achieved, and the gas flow through A to /2 inch shale with low liquid loading is about 3 feet per second.

A disengaging system 51 useful in the practice of the present invention is illustrated in FIG. 4. This device may be constructed of stainless steel with a longitudinal series of gas and oil inlet orifices 52 separated by the surface 54 which functions as a shale chute from a parallel longitudinal series of gas outlet orifices 56. The disengaging device 51 is placed in the retorting vessel so as to prevent solid material flowing downwardly through the retort from entering the sluiceway 58. The oil entering the inlet orifices 52 is separated from the associated gases and flows from the disengaging system at the oil outlet 59. Another view of this device in a retort of the type illustrated in FIG. 1 is shown in FIG. 5, wherein: inlet orifices are shown as 52, 52' and 52", the surfaces are shown as 54, 54' and 54", gas outlet orifices are shown as 56, 56 and 56", and the sluiceways as 58 and 58'.

The operation of the retort as shown in FIG. 1 will now be described with particular reference to the retorting of oil shale and in accordance with a preferred embodiment of the invention. It is to be understood of course, that with or without modification, the process described may be applied to the destructive distillation of other hydrocarbonaceous solids, such as coal, lignite, peat, wood, etc., and that many variations are possible within the scope of the invention.

Oil shale crushed to a suitable particle size, i.e. A to /2 inch, is introduced into the top of the retort by means of hopper 13 and is continuously passed downwardly through the retort in an uninterrupted column. The incoming oil shale from hopper 13 is at room temperature. The shale particle size can vary within relatively wide limits both as to maximum and minimum particle size and particle size distribution, depending on the size of the retort and the operating conditions.

The shale moves downwardly through the retort by gravity as a bed of freely moving particles and passes successively through a solids-preheating and product-cooling zone, a distillation zone, a combustion zone, and a residue cooling zone. The products of combustion and of distillation pass out of the top of the retort through the offgas headers 19 and are conducted to the product recovery system.

A portion of the gas stream flowing from the headers 19 is withdrawn and recycled to the retort through header outlets 26. The gas stream recycled to the retort by header outlets 26 consists essentially of the flue gases resulting from combustion within the retort enriched by noncondensible hydrocarbon gases produced by thermal decomposition of the kerogenous material in the shale. As used in the specification and in the claims, the term noncondensible gas refers to gases which fail to condense to liquids at atmospheric temperatures and under ordinary pressures, including the light hydrocarbon gases (such as methane, ethane, propane, ethylene, propylene, etc.) produced during the destructive distillation of the hydrocarbonaceous material, and the flue gases resulting from combustion including carbon dioxide, carbon monoxide, and nitrogen.

This recycle gas, which is at a relatively low temperature (for example, to 200 F.) is introduced into the bottom of the retort by header outlets 26 and flows upwardly through the downwardly flowing residue from the combustion zone. In this portiton of the retort, herein termed the residue cooling zone, direct heat exchange is effected between the cold recycle gas and the hot residue; the cold recycle gas is preheated by recovering sensible heat from the hot shale which in turn is cooled and leaves the retort at a temperature approximately that of the incoming cold recycle gas.

An oxygen-containing gas, preferably air, preheated if desired, is injected into the combustion zone 30 through the distribution ports 28. The oxygen-containing gas is mixed with the preheated recycle gases rising through the shale and is distributed in a uniform manner throughout the cross-section of the retort.

The ratio of recycle gas admitted at the bottom of the retort to the air admitted into the combustion zone is an important variable since it determines other process variables such as the combustion zone temperature. While the recycle gaszair ratio may vary within relatively wide limits, in general an excess of air should be avoided since this leads to high combustion zone temperatures which in turn lead to excessive mineral carbonate decomposition (which would absorb large quantities of heat). A deficiency of air leads to undesirably low combustion ZOne temperatures resulting in failure to fully retort the shale, causing lower yields and decreased throughput. Generally speaking, in the case of oil shale, under normal operating conditions, and employing the ordinary types of shale, recycle gas to air ratios between about 2.5/1 and about 8/1 have been found to give the most satisfactory results. Using these ratios, moderate combustion zone temperatures, between about l300 and about 1700 F. have been found to give the most satisfactory results.

The heat developed in the combustion zone is derived both from burning the lean recycle gases and from burning some of the organic residue remaining on the shale descending from the distillation zone. This organic residue is chiefly carbon in a reactive state which will burn very readily.

Continuing to follow the gas and solids flow within the retort, the hot gas from the combustion zone rises countercurrently to the descending shale thus effecting direct solids-to-gas heat exchange. The hot gases give up their heat to the shale rapidly bringing the shale to dis tillation temperatures, causing decomposition of the organic material therein, and evolution of oil vapors and noncondensible hydrocarbon gases. These combustion and distillation products continue to rise counter-currently to the incoming cold shale and thus are cooled to the condensation temperature below the deck plate 32 so that flooding occurs at or immediately above the operating 40. As the shale descends between the converging baflles 42 and 43 it passes through a relatively quiescent isothermal region in which there is little gas flow. At the openings 40 it is exposed to sufficient gas flow so that any liquid which is associated with the shale will not flow downwardly. The gas velocity above the openings 40 conveys the condensed liquids upwardly and laterally, normal to the gas flow through the longitudinal slots 44 and 45. In the relatively low velocity shale free region 47 behind the baffles 42 and 43, oil is disengaged from the gas and is drained off through the conduits 50. The associated gas which is now relatively free of liquid is reinjected into the shale bed through the longitudinal slots 46 and 46, and goes overhead with the offgases for subsequent recovery. While the retorting method described is applicable in general to the destructive distillation of solid hydrocarbonaceous materials, including oil shale, coal, lignite, peat, wood, etc., it is particularly adapted for the destructive distillation of oil shale. The term oil shale, as employed in the specification and claims, is intended to refer to sedimentary rocks containing an organic material, usually termed kerogen, which upon heating yields a mixture of hydrocarbons and organic nitrogen, oxygen, and sulfur compounds, usually termed shale oil. Extensive deposits of oil shale are found in this country, particularly in Colorado, Utah, and Wyoming, of which the deposits found in the so-called Green River shale formation are typical. The invention has been found to be particularly applicable to the type of shale found in the United States.

It is to be understood that the above description, together with the specific examples and embodiments described, is intended merely to illustrate the invention, and that the invention is not to be limited thereto, nor in any way except by the scope of the appended claims.

What is claimed is: 1. In a process for producing liquid hydrocarbons from oil shale by passing a moving bed of said shale in particulate form downwardly through a gas combustion retort and flowing the hot gas and vaporous products from the combustion zone thereof upwardly through the retort whereby a high boiling fraction of said vapors in condensed upon contact with the counter-flowing shale; the improvement which comprises:

disengaging said high boiling fraction from the shale bed with hot gas by passage to an adjacent quiescent zone in the retort as the shale passes through an area of high gas velocity above the combustion zone;

separating said high boiling fraction from entrained gases in said adjacent quiescent zone which is a shale-free region of low gas velocity, and

a high boiling liquid fraction; the improvement which.

comprises:

confining the gas and vapor stream as it moves upwardly through the retort toward the condensation zone to increase in velocity and provied lateral movement of the high boiling liquid fraction into an adjacent shale-free region of low gas velocity wherein said liquid fraction is separated from gases associated therewith, and returning the associated gases from which liquid has been removed to the shale bed at a level about that at which said high boiling liquid fraction was removed. 3. A process for the recovery of shale oil from oil shale which comprises:

initiating a zone of combustion in the lower portion of a downwardly moving bed of oil shale in a gas combustion retort, flowing hot combustion product gases upwardly through said downwardly moving bed of shale whereby shale oil vapors are formed which undergo condensation upon contact with counter-flowing cooler shale particles in an upper portion of the gas combustion retort; disengaging from an upper portion of the moving bed of shale in a region of relatively high gas velocity a mixture of noncondensible gas and liquid shale oil; separating the disengaged liquid shale oil from noncondensible gas in a shale-free area within the retort, collecting the liquid shale oil, and returning the noncondensible gas the the shale bed at a level above that at which the liquid shale oil was disengaged. 4. 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, and means within said reaction Vessel above the heating means for disengaging gas and liquid fractions from the oil shale and reengaging the gas with the shale at a higher level comprising parallel and separated horizontal plates extending across said reaction vessel defining openings therebetween, downwardly converging bafl les terminating in the openings between said plates and characterized by upper and lower longitudinal slots in the walls thereof, and diverging bafiles extending below said openings.

References Cited UNITED STATES PATENTS 2,723,225 11/1955 Elliott ,201-29 2,885,338 5/1959 Evans 208-11 CURTIS R. DAVIS, Primary Examiner U.S. C1.X.R.

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