WO1991013948A1 - Multi-stage retorting - Google Patents

Abstract

A multi-stage process for the retorting of solid, hydrocarbon-containing materials is provided. The solid, hydrocarbon-containing feed material is partially retorted in a dilute phase first fluidized retorting stage at first retorting stage conditions with a temperature elevated relative to ambient conditions and achieved by a method of admixing solid heat carrier containing an active cracking catalyst with the solid, hydrocarbon-containing material. The partially retorted product from the first stage is then substantially completely retorted in a second fluidized retorting stage at second stage retorting conditions, with the second stage retorting temperature being greater than the first stage retorting temperature. Vapor products are removed at intermediate stages so as to avoid undesired degradation.

Description

MULTI-STAGE RETORTING

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of commonly assigned, copending U.S. Patent Application Serial No. 492,780, filed March 13, 1990 as a continuation-in-part of U.S. Patent Application Serial No. 303,731 , filed January 27,1989, now abandoned, all of whose disclosure is incorporated herein by reference.

BACKGROUND OF THE INVENTION This invention relates to the retorting of a hydrocarbon-containing material, and more particularly, to a fluid bed process and system for retorting solid, hydrocarbon-containing -material such as oil shale, coal and tar sand, for example.

Researchers have renewed their efforts to find alternate sources of energy and hydrocarbons in view of the recent instability of the price of crude oil and natural gas and as the uncertain nature of ready supplies and access to crude oil has become increasingly apparent. Much of these research efforts have been focused on recovering hydrocarbons from solid hydrocarbon-containing material such as oil shale, coal and tar sand by pyrolysis or gasification to convert the solid hydrocarbon-containing material into more readily usable gaseous and liquid hydrocarbons.

Vast natural deposits of oil shale found in the United States and elsewhere contain appreciable quantities of organic matter known as "kerogen" which decomposes upon pyrolysis or distillation to yield oil, gases and residual carbon. It has been estimated that an equivalent of 7 trillion barrels of oil are contained in oil shale deposits in the United States with almost sixty percent located in the rich Green River oil shale deposits of Colorado, Utah, and Wyoming. The remainder is largely contained in the leaner Devonian-Mississippian black shale deposits which underlie most of the eastern part of the United States.

As a result of dwindling supplies of low cost petroleum and natural gas, extensive efforts have been directed to developing retorting processes which will economically produce shale oil on a commercial basis from these vast resources. In addition, in view of ever increasing attention and consideration directed to health, safety and environmental concerns, useful and effective processes for the treatment or neutralization of hydrocarbon-containing waste materials such as used or slop oils, soils contaminated with a petroleum or a petroleum product, thermoplastics, elastomers, petroleum derivable polymers, oil-containing sludges and spent hydrocarbon-treating catalysts, for example, are being sought.

Generally, oil shale is a fine-grained sedimentary rock stratified in horizontal layers with a variable richness of kerogen content. Kerogen has limited solubility in ordinary solvents and therefore cannot be readily recovered by simple extraction. Upon heating oil shale to a sufficient temperature, however, kerogen can be thermally decomposed to liberate vapors, mist, or liquid droplets of shale oil and light hydrocarbon gases such as methane, ethane, ethene, propane, and propene, as well as other products such as hydrogen, nitrogen, carbon dioxide, carbon monoxide, ammonia, steam and hydrogen sulfide. After such a process, however, a carbon residue typically remains on the retorted shale.

As indicated above, shale oil is not a naturally occurring product, but may be formed, such as by the pyrolysis of kerogen in the oil shale. Crude shale oil, sometimes referred to as "retort oil," is the liquid oil product recovered from the liberated effluent of an oil shale retort. The upgraded oil product resulting from the hydrogenation of crude shale oil is referred to as "synthetic crude oil" (syncrude). The process of pyrolyzing kerogen contained in oil shale to liberate hydrocarbons, known as retorting, can be done in above-ground vessels known as surface retorts or underground in in situ retorts. In principle, the retorting of shale and other hydrocarbon-containing materials, such as coal and tar sand, comprises heating the solid hydrocarbon-containing material to an elevated temperature and recovering the vapors and liberated effluent.

Generally, as the thermal severity of a retort, i.e., time and temperature exposure of retort products, is increased, the retort products degrade and thus become more difficult and costly to upgrade. For example, if the retorting is conducted at an excessively high temperature or even if the retorting is conducted at an acceptable elevated temperature but the products are exposed for prolonged periods of time to such elevated temperatures, degradation of the retort products can occur and losses in both yield and product quality associated with such degradation realized.

Further, simply decreasing the temperature in the retort while reducing the effects of thermal severity on the retort can generally result in less efficient recovery of hydrocarbon from the shale, as lower retorting temperatures are not conducive to maximizing or increasing the extent of retorting of hydrocarbons from the shale.

Moreover, as medium grade oil shale yields approximately 20 to 25 gallons of oil per ton of shale, the expense involved in handling the relatively large masses of oil shale, as would typically be required for use in commercially sized facilities, is critical to the economic feasibility of any such commercial operation.

In order to obtain high thermal efficiency in retorting, carbonate decomposition should be minimized. Colorado Mahogany zone oil shale contains several carbonate minerals which decompose at or near the usual temperatures attained when retorting oil shale. Typically, a 28 gallon per ton sample of such oil shale will contain about 23 weight percent dolomite (a calcium/magnesium carbonate) and about 16 weight percent calcite (a calcium carbonate), or about 780 pounds of mixed carbonate minerals per ton. Dolomite requires about 500 BTU per pound and calcite about 700 BTU per pound for decomposition, a requirement that would consume about 8% of the combustible matter of the shale if these minerals were allowed to decompose during retorting. Saline sodium carbonate minerals also occur in the Green River formation in certain areas and at certain stratigraphic zones. The choice of a particular retorting method must therefore take into consideration carbonate decomposition as well as new and spent materials handling expense, product yield and process requirements.

In surface retorting, oil shale is mined from the ground, brought to the surface, crushed and placed in vessels where it is contacted with a hot heat transfer carrier, such as hot spent catalyst, shale, sand or gases, or mixtures thereof, for heat transfer. The resulting high temperatures cause shale oil to be liberated from the oil shale leaving a retorted inorganic material and carbonaceous material such as coke. The carbonaceous material can be burned by contact with oxygen at oxidation temperatures to recover heat and to form a spent oil shale relatively free of carbon. Spent oil shale which has been depleted in carbonaceous material is removed from the retort and recycled as heat carrier material or discarded. The liberated hydrocarbons and combustion gases can then be dedusted such as in electrostatic precipitators, filters, scrubbers, pebble beds, cyclones such as shown in U.S. Patent Nos. 3,252,886; 3,784,462 and 4,101 ,412, by dilution, centrifugation or other gas-solid separation systems. i

Some well-known processes of surface retorting are: N-T-U (Dundas Howes retort), Kiviter (Russian), Petrosix (Brazilian), Lurgi- Ruhrgas (German), Tosco II, Galoter (Russian), Paraho, Koppers-Totzek, Fushum (Manchuria), Union B, Chevron STB, gas combustion and fluid bed. Process heat requirements for surface retorting processes may be supplied either directly or indirectly.

Directly heated surface retorting processes, such as the N-T-U, Kiviter, Fusham and gas combustion processes, rely on the combustion of some form of fuel, such as recycled gas or residual carbon in the spent shale, with air or oxygen within the bed of shale in the retort to provide sufficient heat for retorting. Directly heated surface retort processes usually result in lower product yields due to unavoidable combustion of some of the products and product stream dilution with the products of combustion. The Fusham process is shown and described at pages 101- 102, in Oil Shales and Shale Oils, by H. S. Bell, published by D. Van Norstrand Company (1948). The other processes are shown and described in the Synthetic Fuels Data Handbook, by Cameron Engineers, Inc. (second edition, 1978).

Indirectly heated surface retorting processes, such as the Petrosix, Lurgi-Ruhrgas, Tosco II and Galoter processes, utilize a separate furnace for heating solid or gaseous heat-carrying material which is injected, while hot, into the shale in the retort to provide sufficient heat for retorting. In the Lurgi-Ruhrgas process and some other indirect heating processes, raw hydrocarbon-containing solid, e.g., oil shale or tar sand, and a hot heat carrier, such as spent shale or sand, are mechanically mixed and retorted in a screw conveyor. Such mechanical mixing often results in high temperature zones conducive to undesirable thermal cracking of vapor product as well as causing low temperature zones which result in incomplete retorting of the hydrocarbon-containing solid. Furthermore, in such processes, the solids gravitate to the lower portion of the vessel.

Thus, stripping the retorted shale with gas causes lower product yields due to adsorption of a portion of the evolved hydrocarbons by the retorted solids. Generally, indirectly heated surface retorting processes result in higher yields and less dilution of the retorted product than directly heated surface retorting processes, but at the expense of additional materials handling.

Surface retorting processes with moving beds are typified by the Lurgi coal gasification process in which crushed coal is fed into the top of a moving bed gasification zone and upflowing steam endoihermically reacts with the coal. In such a process, a portion of the char combusts with oxygen below the gasification reaction zone to supply the required heat of reaction. Moving bed processes are generally disadvantageous because the solids residence time is usually long, necessitating either reactors with very large contact or reaction zones or a large number of smaller reactors. Moreover, moving bed processes often cannot tolerate excessive amounts of fines.

Surface retorting processes with entrained beds are typified by the Koppers-Totzek coal process in which coal is dried, finely pulverized and injected into a treatment zone along with steam and oxygen. The coal is rapidly partially combusted, gasified, and entrained by the hot gases. Residence time of the coal in the reaction zone is only a few seconds. Entrained bed processes are disadvantageous because they require large quantities of hot gases to rapidly heat the solids and often require the raw feed material to be finely pulverized before processing.

Fluid bed surface retorting processes may, depending on the properties of the feed and the processing requirements, be particularly advantageous. The use of fluidized-bed contacting zones has long been known in the art and has been widely used in the fluid catalytic cracking of hydrocarbons. When a fluid is passed at a sufficiently high velocity, upwardly through a contacting zone containing a bed of subdivided solids, the bed expands and the particles are buoyed and supported by the drag forces caused by the fluid passing through the interstices among the particles. The superficial vertical velocity of the fluid in the contacting zone at which the fluid begins to support the solids is known as the "minimum fluidization velocity." The velocity of the fluid at which the solid becomes entrained in the fluid is known as the "terminal velocity" or "entrainment velocity." Between the minimum fluidization velocity and the terminal velocity, the bed of solids is in a fluidized state and it exhibits the appearance and some of the characteristics of a boiling liquid. Because of the quasi-fluid or liquid-like state of the solids, there is typically a rapid overall circulation of all the solids throughout the entire bed with substantially complete mixing, as in a stirred-tank reaction system. Such rapid circulation is particularly advantageous in processes in which a uniform temperature and reaction mixture is desired throughout the contacting zone. Typifying those prior art fluidized bed retorting processes, fluid catalytic cracking processes, and similar processes are the Union Carbide/Battelie coal gasification process, the fluid coker and flexicoking processes described at page 300 of the Synthetic Fuels Data Handbook. by Cameron Engineers, Inc. (second edition, 1978) and those found in U.S. Patent Nos. 2,471 ,119; 2,506,307; 2,518,693; 2,582,712; 2,608,526; 2,657,124; 2,684,931 ; 2,710,828; 2,793,104; 2,799,359; 2,807,571 ; 2,844,525; 3,039,955; 3,297,562; 3,501 ,394; 3,617,468; 3,663,421 ; 3,703,052; 3,803,021 ; 3,803,022; 3,855,070; 3,925,190; 3,976,558; 3,980,439; 4,001 ,105; 4,052,172; 4,064,018; 4,080,285; 4,087,347; 4,110,193; 4,125,453; 4,133,739; 4,137,053; 4,141 ,794; 4,148,710; 4,152,245; 4,157,245; 4,183,800; 4,199,432; 4,211 ,606; 4,226,699; 4,227,990; 4,243,511 ; 4,293,401 ; 4,336,127; 4,336,128. These prior art processes have met with varying degrees of success. Gas fluidized bed processes of the prior art usually have a dense paniculate phase and a bubble phase, with bubbles forming at or near the bottom of the bed. These bubbles generally grow by coalescence as they rise through the bed. Mixing and mass transfer are enhanced when the bubbles are small and evenly distributed throughout the bed. When large bubbles are formed, such as when many bubbles coalesce, a surging or pounding action results, leading to less efficient heat and mass transfer. A problem with many prior art fluidized bed processes arises from the use of long residence times at high temperatures which in turn may result in many secondary and undesirable side reactions, such as thermal cracking of oil vapors derived from the hydrocarbon solids, which usually increase the production of less desirable gaseous products and decrease the yield and quality of desirable condensable products. Therefore, in processes designed to produce the maximum yield of high quality condensable hydrocarbons, it is generally preferred that the volatilized hydrocarbons be quickly removed from the retorting vessel in order to minimize deleterious side reactions such as thermal cracking.

Another problem with many prior art processes, particularly with countercurrent fluidized bed flow processes, is that after the shale oil has been vaporized, it then comes in contact with countercurrent flowing solids which are at a much cooler temperature, which leads to condensation of a portion of the shale oil and adsorption of a portion of the vaporized shale oil onto the downward flowing shale. This condensation and adsorption leads to coking, cracking and polymerization reactions, all of which are detrimental to maximizing the yield of condensable hydrocarbons.

U.S. Patent No-. 2,573,906 relates to a multi-stage dense phase catalytic conversion of bituminous solids wherein the conversion of the solids is controlled by adjusting the rate at which the catalyst is advanced from one stage to another. As will be described in greater detail below, with dense phase operation, wherein the velocity of the solids of the system is substantially less than the velocity of the gas in the system, the extent and duration of contact between the solids and the gas is typically substantially and significantly greater than in the case of dilute phase operation. Consequently, dense phase operation of retorts typically results in significant and substantial readsorption of liberated vapors by the retorted solid (e.g., by the spent shale) and thus a reduction in the yield of condensable products. U.S. Patent No. 4,561 ,966 discloses a process and an apparatus for direct coking of tar sands using a fluid coking vessel having two unseparated, adjoining zones therein. Such adjoining zones typically lead to increased retorting thermal severity as the time and/or temperature that the retort product is exposed to is increased. As identified above, increasing the thermal severity of the retort generally results in undesired product degradation, with the concomitant reduction in the yield of condensable products.

U.S. Patent Nos. 4,404,083 and 4,511 ,434, the disclosures of which are incorporated herein by reference, disclose and claim a process and a system, respectively, for the fluid bed retorting of solid hydrocarbon- containing materials whereby the aforementioned problem of adsorption of oil vapors onto partially heated solids in countercurrent flow is substantially overcome. These patents teach methods for implementing efficient co-current flow of shale feed and heat carrier and realizing short vapor residence times in the retorting zone. In large scale (1 Bbl/day) pilot plant testing of such retorting processes and systems, conversions of organic carbon from the kerogen to condensable liquids in excess of 75 percent have been obtained over a broad range of retorting temperatures. Such yields are significantly greater than those disclosed by most previously reported retorting processes.

Furthermore, implementation of the process and system of U.S. Patent Nos. 4,404,083 and 4,511 ,434 have been found to result in liquid yields which are approximately constant over a broad range of retorting temperatures, e.g., retorting temperatures ranging from about 900°F to about 1050°F, while the yields of noncondensable gases, e.g., C1-C3 gases, and coke vary considerably. Thus, at the extreme of lower temperatures, the yields of gas and coke are about 5 percent and 20 percent on the basis of organic carbon, respectively. Moreover, at the extreme of higher temperatures, the yields of gas and coke are about 15% and 10% on the basis of organic carbon, respectively. Further, while the stripping of hydrocarbons from the shale may more efficiently be conducted at higher temperatures, it is difficult to avoid increased cracking of the vapors with the use of such higher temperatures, even when reasonable, practical efforts are made to reduce the vapor residence time in the retort.

In prior art fluidized bed retorting processes wherein heat carrier is introduced only at one point during the retorting process, the temperature of the shale tends to decline as the retorting progresses, as retorting reactions are generally endothermic in nature. In addition, many side reactions which occur during retorting, such as carbonate decomposition, are typically endothermic and, consequently, the significant occurrence of these reactions progresses rather than an increase in retorting temperature whereby increased stripping of hydrocarbons from the shale may be obtained.

U.S. Patent Nos. 4,318,798; 4,332,669; 4,366,046; 4,392,942; 4,515,679; 4,601 ,812; and 4,617,107 disclose the use of residual solids, e.g., hot, spent shale, as a heat carrier in the retort processing of hydrocarbon-containing solid materials such as shale.

U.S. Patent Nos. 2,733,193 and 4,561 ,966 directed to the recovery of hydrocarbons from oil-bearing sands, such as tar sands, disclose the use of a heat transfer paniculate such as a catalyst in the case of '966 and a cracking catalyst in the case of '193 to effect needed transfer of heat. U.S. Patent No. 3,844,929 disclose the retorting of oil shale with special heat-carrying pellets. While suitable pellet materials are identified as being found in cracking catalysts, it is stated that the retorting process of the patent is not to be considered as relying on active catalytic sites. U.S. Patent Nos. 2,627,499 and 3,976,558 disclose the use of cracking catalysts in the recovery of hydrocarbons from oil shale. Such processes do not exhibit the benefits obtainable through a multi-stage retorting process wherein successive stages of retorting are done at successively higher temperatures and wherein the temperatures are achieved by admixing a solid heat carrier of an active cracking catalyst to the solid hydrocarbon-containing material. Further, the benefits obtained through the use of USY sieve-containing cracking catalyst, as opposed to other types of cracking catalyst such as REY sieve-containing catalyst, are not shown or suggested by these patents.

U.S.. Patent No. 4,087,347 discloses a shale retorting process wherein shale is mixed with a solid heat transfer material. The shale and heat transfer material are entrained in a high velocity gaseous stream and conveyed upward in a vertical dilute phase lift pipe retorting vessel wherein only "a minor portion," i.e., "less than 50 weight percent, and preferably less than 30% of the total volatile hydrocarbons present in the raw shale is vaporized." The partially retorted solids are subsequently passed into a stripper vessel, wherein the partially retorted solids flow downward countercurrent to the flow of stripping gas, with the stripping gas entraining and transporting the vaporized hydrocarbons out of the downward moving bed of shale. The lift gas and stripping gas, which both contain entrained gaseous hydrocarbons, are passed as a combined stream for further separation processing and treatment.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome one or more of the problems described above.

For example, it is an object of the present invention to avoid the problem of oil vapor cracking at higher temperatures while concurrently obtaining the more efficient stripping of hydrocarbons at increased temperatures. Accordingly, the temperature of the solid hydrocarbon- containing feed is increased in two or more stages, while overheating and cracking of the retort vapors is minimized. Thus, according to one embodiment of the present invention, a hot active cracking catalyst- containing heat carrier is introduced at two or more feed points in the portions of the integrated retort where retorting occurs, with vapors being withdrawn so as to minimize their heating and cracking. In this way, the yields of condensable products are increased. In such a fashion, the feed hydrocarbon-containing material is continually heated as the retorting progresses while the vapors liberated thereby avoid being subjected to excessive heating.

According to the invention, a method for retorting solid hydrocarbon- containing material to increase the yield of condensable products includes the step of partially retorting the material in a dilute phase first fluidized retorting stage at first stage retorting conditions to yield hydrocarbon vapor products liberated from the material totaling at least 50 weight percent of the total amount of volatile hydrocarbons present in the material and to also yield a partially retorted product including at least some un retorted material. The first stage retorting is followed by separating at least some of the vapor products from the partially retorted product and without subjecting the separated vapor products to the retorting conditions of further retorting. Such separation occurs prior to substantially completing retorting of the material in a second fluidized retorting stage at second stage retorting conditions to yield additional hydrocarbon vapor products and a substantially completely retorted product. At least some of the additional vapor products are separated from the substantially completely retorted product. The first retorting stage conditions include temperature and solids and vapor residence times with the temperature being elevated relative to ambient conditions and being achieved by a method of admixing an active cracking catalyst-containing heat carrier with the solid hydrocarbon-containing material. The second stage retorting conditions include temperature and solids and vapor residence times with the second stage retorting temperature being greater than the first stage retorting temperature with the second stage retorting temperature being achieved by a method of admixing an additional quantity of active cracking catalyst- containing heat carrier material with the partially retorted product.

The invention also comprehends a method for retorting oil shale to increase the yield of condensable products, in such a method the oil shale is heated to a temperature in the range of about 250°F to about 650°F. The heated oil shale is retorted in a dilute phase first fluidized retorting stage at first stage retorting conditions including temperature and solids and vapor residence times to yield hydrocarbon vapor products liberated from the shale totaling at least 50 weight percent of the total amount of volatile hydrocarbons present in the shale and to also yield a partially retorted product including at least some unretorted oil shale. The first stage retorting temperature is elevated relative to ambient conditions and is achieved by a method of admixing an active cracking catalyst heat carrier to the oil shale. At least some of the vapor products are separated from the partially retorted product prior to subjecting at least some of the unretorted oil shale to further retorting and without subjecting the separated hydrocarbon vapor products to the retorting conditions of the further retorting. The unretorted oil shale of the partially retorted product is then substantially completely retorted in at least one successive fluidized retorting stage at successive retorting stage conditions including temperature and solids and vapor residence times to yield additional hydrocarbon vapor products and a substantially completely retorted product. The successive retorting stage temperature is a temperature that is elevated relative to the first stage retorting temperature and is achieved by a method of admixing an additional quantity of active cracking catalyst heat carrier to the partially retorted product. Additional vapor products are then separated from the substantially completely retorted product. The invention also comprehends a method of retorting oil shale to increase the yield of condensable products including the steps of heating the oil shale, retorting the heated oil shale, separating at least some of the vapor products from the partially retorted product, subsequently substantially completing the retorting of the unretorted oil shale and separating additional vapor products from the substantially completed retorted product. In such a method, the first stage retorting temperature is in the range of about 875°F to about 975°F, the first stage solids residence time is between about 5 seconds and 75 seconds and the first stage vapor residence time is between about 0.5 seconds and about 10 seconds. Also, the first stage retorting temperature is achieved by a method of admixing an active USY sieve-containing cracking catalyst heat carrier to the oil shale. Vapor products totaling at least 50 weight percent of the total amount of volatile hydrocarbons present in the shale are separated from the partially retorted product prior to subjecting at least some of the unretorted oil shale of the partially retorted product to further retorting and without subjecting the separated hydrocarbon vapor products to the retorting conditions of further retorting. The unretorted oil shale of the partially retorted product is subsequently substantially completely retorted in at least one successive fluidized retorting stage. Such successive retorting occurs at conditions including a retorting temperature of at least about 50°F greater than the first stage retorting temperature. Such an operating temperature is achieved by a method of admixing an additional quantity of active USY sieve-containing cracking catalyst heat carrier to the partially retorted product. The successive retorting is also conducted at a vapor residence time of less than about 5 seconds and a solids residence time between about 30 seconds and 300 seconds to yield additional hydrocarbon vapor products and a substantially completely retorted product. Subsequently, additional vapor products are separated from the substantially completely retorted product.

The invention also comprehends a method for the treatment of hydrocarbon-containing waste. In such a method, a waste material including at least some solids and some hydrocarbons is retorted in a dilute first fluidized retorting stage at first stage retorting conditions including temperature and solids and vapor residence times. Such retorting yields hydrocarbon vapor products totaling at least 50 weight percent of the total amount of volatile hydrocarbons present in the waste material and also yields a partially retorted product including at least some unretorted waste material. The first stage retorting is followed by separating hydrocarbon vapor products from the partially retorted product prior to and without subjecting the separated hydrocarbon vapor products to the conditions of further retorting. In a second fluidized retorting stage, retorting of the separated unretorted waste material at second stage retorting conditions including temperature and solids and vapor residence times is substantially completed to yield additional hydrocarbon vapor products and a substantially completely retorted product with at least some of the additional vapor products being separated from the substantially completely retorted product. The first stage retorting temperature is elevated relative to ambient conditions and is achieved by a method of admixing a solid heat carrier of active cracking catalyst with the waste material. The second stage retorting temperature is greater than the first stage retorting temperature and is achieved by admixing an additional quantity of active cracking catalyst-containing heat carrier with the partially retorted product.

As used throughout this specification, the terms "substantially completely retorted" product or "substantially completely retorted" shale and "completely retorted" product or "completely retorted" shale refer to a hydrocarbon-containing material or oil shale, respectively, which has been retorted to liberate hydrocarbons leaving a material from which no substantial, additional quantities of gaseous or liquid hydrocarbon can be evolved by thermal treatment, e.g., substantially all remaining carbon is in the form of coke. The term "spent" hydrocarbon-containing material and "spent" shale as used herein refers to retorted hydrocarbon-containing material or shale, respectively, from which essentially all of the carbon residue has been removed by combustion. The terms "condensable," "condensed," "noncondensable," "normally gaseous" or "normally liquid" are relative to the conditions of the subject material at a temperature of about 77°F (25°C) at a pressure of about 1 atmosphere. The terms "partially retorted" product and "partially retorted" shale refer to product and shale, respectively, which has been partially retorted to liberate a portion of the hydrocarbons thereof leaving a material containing some gaseous or liquid hydrocarbons which can be evolved with further thermal treatment. The term "heat carrier" as used herein means a solid heated in a device, such as a combustor, to provide heat such as to raise the heat of the hydrocarbon-containing material or oil shale, respectively, to the desired retorting temperature, e.g., combusted solids are typically heated to a temperature of at least 1100°F and preferably at least 1300°F and no more than about 1500°F and retorting temperatures in the general range of about 850-1100°F are attained in the retort.

The term "stage" or "retorting stage"' as used herein refers to a chamber, vessel or the like in which the temperature of raw or partially retorted hydrocarbon-containing solid, e.g., shale, is increased in the absence of oxygen and wherein partial retorting, at retorting conditions including temperature and residence times, of the hydrocarbon-containing solid is effected.

The terms "dilute phase" and "dense phase" as used herein refer to solid-gaseous (vapor) combinations and can generally be characterized by the average density of the combination, with dilute phases typically having an average solids-gaseous (vapor) density of less than about 10 pounds per cubic foot and dense phases typically having an average solids-gaseous (vapor) density of more than 20 pounds per cubic foot. Other objects and advantages of the invention will be apparent to those skilled in the art in the following detailed description taken in conjunction with the accompanying drawing and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified schematic flow diagram of a fluid bed retorting process and system in accordance with one preferred embodiment of the invention.

FIG. 2 is a simplified schematic flow diagram of a fluid bed retorting process in accordance with an alternative preferred embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1 , a fluid bed process and system, generally designated 10, is provided to retort hydrocarbon-containing material, such as oil shale, tar sand, uintaite (gilsonite), peat and oil-containing diatomaceous earth for use in making synthetic fuels. While the process of the invention is described hereinafter with particular reference to the processing of oil shale, it will be apparent that the process can also be used to retort other hydrocarbon-containing materials such as tar sand, uintaite (gilsonite), peat, oil-containing diatomaceous earth, etc. It is to be understood that the process and system of the invention are also applicable for the treatment and neutralization of hydrocarbon-containing waste materials. It is also to be understood that application of the invention to the treatment of feeds having relatively higher organic contents and which do not readily decompose, such as lignite and some coals, is also possible but that such feeds tend to result in increased solids agglomeration in the retort.

In the process and system 10, raw oil shale is treated to produce vapor products, such as represented by the streams 11 and 11 ^*. Preliminarily, raw oil shale is fed to a crushing and screening station 12. The oil shale preferably contains an oil yield of at least about 15 gallons per ton of shale particles in order to make the process and system self- sustaining in terms of energy requirements, so that the lift gas consists primarily of light hydrocarbons liberated from the oil shale and so the heat carrier material is largely made up of spent oil shale from the system.

At the crushing and screening station 12, raw oil shale is crushed to a top size of about 3 millimeters or less so as to be relatively easily fluidizable in the process. Oil shale particles over 3 millimeters in diameter should be avoided, if possible, because they do not attain the desired lift velocity for effective retorting. In the crushing and screening station 12, the raw oil shale is crushed and sized to the desired particle size by crushing and screening equipment, such as conventional crushing equipment, such as a jaw, gyratory or roll crusher or autogenous or semi-autogenous grinders and by conventional screening equipment such as a shaker screen or vibrating screen.

The crushed oil shale particles are conveyed to a preheating station 14 wherein the shale is preheated to a temperature in a range of about 250°F to about 650°F, more preferably between about 300°F to about 400°F, to rapidly evaporate moisture contained in the shaie. Higher preheating temperatures are generally to be avoided as such higher temperatures may result in premature retorting of the shale particles. It is to be understood that the preheating station 14 and the crushing and screening station 12 can, if desired, be combined.

The preheated, crushed oil shale particles are conveyed by a screw conveyor 16 or other conveying means such as a lift elevator, gravity flow from a lock hopper or conventional conveying means for fluidized mediums, through a feed pipe 18 into a first retorting stage, a mixing chamber 20, which is sometimes referred to as an "ejector," "mixing zone" or "mixer" wherein initial retorting, e.g., partial retorting, of the preheated, crushed oil shale is conducted.

During operation of the mixing chamber 20 in the practice of the invention, the conditions of a dilute phase (i.e., an average solids-gaseous (vapor) density of less than about 10 pounds per cubic foot) will preferably be realized in this first retorting stage. Dilute phase conditions will generally be preferred as a dilute phase, as compared to a dense phase, will typically result in reduced contact of vapors (e.g., released from the shale during the first retorting stage) with spent shale and unretorted shale and minimize adsorption of the vapors by the solids.

The dimensions of the mixing chamber 20 are set by the desired solids residence time (typically, in the range of about 5-75 seconds, preferably in the range of about 5-45 seconds), the gas velocity required for fluidizing the shale (generally in the range of about 1-4.5 feet per second), the density of the fluidized shale/heat carrier mixture (generally in a range of about 20 to 100 pounds per cubic foot) and the desired gas or vapor residence time (generally in a range of about 0.5-10 seconds, preferably less than about 5 seconds). Given these constraints, typical fluxes of solids in the mixing chamber 20 range from about 5 to 400 tons per square foot per hour, with fluxes above about 20 tons per square foot per hour being preferred. Typically, the height of the mixing chamber, exclusive of conical transition sections, is greater than the chamber's diameter, which is set by the capacity of the retorting unit in tons of raw, crushed shale per day. The ratio of heat carrier solid to shale feed is generally set by the desire to maintain a retorting temperature generally elevated relative to ambient conditions and less than 1000°F and, more preferably, in the range of about 875°F to about 975°F, in the mixing chamber 20. Normal weight ratios of heat carrier to shale feed range from about 2:1 to 10:1 but generally fall in the range of about 3:1 to about 5:1.

The heat carrier used in the practice of the invention will preferably be an active, fluidizable cracking catalyst such as a REY sieve-containing cracking catalyst such as HEZ-55 of Engelhard Corporation or, more preferably, a USY sieve-containing cracking catalyst such as OCTISIV PLUS 580 of Engelhard Corporation, for example. The preferred "ultrastable" forms of Y-type zeolite ("USY") typically have a silicon to aluminum atom ratio of about six to one as compared to the rare earth forms of Y-type zeolite ("REY") which have a silicon to aluminum atom ratio of about two to one to about two and one-half to one.

The use of active cracking catalysts as the heat carrier is at least in part preferred as such use will typically result in the product stream having a more desirable product distribution as the cracking catalyst will generally result in the "cracking" of at least some of the hydrocarbon vapors produced during retorting to form lighter oils. In this fashion relatively heavy, e.g., large, hydrocarbon molecules (e.g., those molecules having a molecular weight of more than 200) liberated during the retorting can be cracked to produce desired, lighter oils. "Overcracking," whereby increased gas and/or coke formation occur at the expense of condensable products, can be and preferably is minimized such as by limiting the extent and duration of the physical contact of the hydrocarbon vapors with the active catalyst material such as more fully described below and as will be apparent to those skilled in the art and guided by the teachings herein provided. Further, such use of a cracking catalyst will generally result in the product vapors and oils having reduced nitrogen levels, as compared to products produced when using an inert heat carrier, as nitrogen- containing organic compounds generally will adsorb onto cracking catalyst materials employed in such use. Further, relative to the use of such cracking catalysts in the practice of the invention, USY sieve-containing cracking catalysts will be preferred relative to REY sieve-containing catalysts as a USY sieve-containing catalyst will generally result in less catalytic coke formation and in increased oil yields (e.g., about a 5-8 volume percent increase in oil yield may be realized with the use of a USY sieve-containing cracking catalyst as compared to similar processing using a REY sieve-containing cracking catalyst). The reduction in coke formation and the increase in oil yield resulting from the use of USY sieve-containing cracking catalyst as compared to the use of REY sieve-containing cracking catalysts are believed, at least in part, to be as a result of the lower alumina content of USY sieve-containing cracking catalysts. In addition, in such use, USY sieve-containing cracking catalysts inhibit hydrogen transfer reactions and consequently generally result in a minimization or reduction in the: a) formation of coke precursors and b) conversion or loss of light olefin and naphthene hydrocarbons. Further, in a preferred embodiment of the invention, active cracking catalyst is added to each of several retorting stages in the retorting process. In such a fashion, fresh, active cracking catalyst is maintained in the stages of the process and a more complete realization of the benefits (e.g., a more desirable product distribution, reduction in nitrogen levels in the product vapors and oils, etc.) of the use of a cracking catalyst and in the case of the use of a USY sieve-containing cracking catalyst, benefits such as a reduction in coke formation and an increase in oil yield are attained.

If desired, other heat carrier materials can be used in place of or as a supplement to the use of active cracking catalyst. Such other heat carrier materials include spent hydrocarbon-containing material (e.g., spent shale), steam, an inert solid-such as sand, for example, or a combination thereof. These alternative heat carrier materials, however, are generally inferior in performance relative to the use of active cracking catalyst as the heat carrier. For example, spent hydrocarbon-containing material as a heat carrier will generally result in yield losses as the spent material would typically adsorb some finite amount of the carbonaceous material liberated during retorting. The use of steam as a heat carrier suffers as steam will typically effect decomposition of carbonates, as are commonly present in hydrocarbon-containing materials such as oil shale. As described above, carbonate decomposition is typically endothermic and, consequently, the significant occurrence of these reactions tend to reduce the temperature of the stream being processed. Thus, the heating value of the energy expended during the endothermic decomposition of carbonates is lost, i.e., the energy is used in effecting the endothermic decomposition reactions as opposed to the hydrocarbon-liberating retorting reaction.

Solid heat carrier, preferably an active cracking catalyst, as described above, is conveyed to the mixing chamber 20 through a pipe 24. The heat carrier preferably is at a temperature in the range of about I

1100°F to about 1500°F, more preferably in the range of about 1200°F to about 1350°F. Generally, higher temperatures are to be avoided, such as when decomposition of carbonate minerals in the shale is sought to be avoided. In turn, operation at lower temperatures is generally to be avoided as such operation would typically require high rates of recycle of solids.

A stream 26 of fluidizing gas may be used to aid the flow of heat carrier through the processing pipe 24, which may include an L-valve 27, as shown. In addition, the flow of solids to the mixing chamber 20 from the line 24 can be controlled using a slide valve or other fluidic device.

The contents of the mixing chamber 20 are mixed to obtain retorting through the action of the in-flowing shale, the vapor released upon retorting, and the addition of a fluidizing gas 28, such as a nonoxygen- containing gas or, preferably, a noncondensable process gas. It is to be understood, however, that steam, if desired, can be used as a fluidizing gas. Such use of steam, however, will generally suffer from the same types of disadvantages described above relative to the use of steam as the heat carrier, e.g., carbonate decomposition and the associated loss of the heating value of the energy expended during the endothermic decomposition of carbonates, and will thus not be preferred. Where carbonate decomposition is being sought to be avoided, the use of steam, either as a heat-providing medium or as a fluidizing gas, will also usually be sought to be avoided.

The fluidizing lift gas 28, such as recycled light hydrocarbon gases from the system 10, is injected by a lift gas injector or gas tube 29 into the bottom of the mixing chamber 20. The lift gas should not contain an amount of molecular oxygen sufficient to support combustion of the hydrocarbons contained in the chamber. Consequently, a molecular oxygen, combustion-supporting gas, such as air, should be avoided as a lift gas in the mixing chamber 20 because it could undesirably result in the combustion of liberated oil in the mixing chamber.

The fluidizing gas 28 may, if desired, be heated to the desired retorting temperature to promote the reaction, and preferably is at a maximum pressure of about 50 psig. In addition, the fluidizing gas 28 is metered into the mixing chamber 20 to provide an average gas velocity in the range of about 1 foot per second to about 4.5 feet per second through the mixing chamber 20, as previously described. Preferably, the lift gas is noncondensable product vapors containing, for example, methane, ethane, etc., and carbon dioxide, preferably in excess of 10 percent, which suppresses the endothermic reaction of carbonate mineral decomposition. It is to be understood that if desired, internals, such as vertical metal bars, may be positioned in the interior of the mixing chamber 20 to promote a more uniform and even retorting of the oil shale by promoting mixing and heat transfer as well as to serve to break bubbles which may form in the mixing chamber and to reduce slugging of solid materials that may result during retorting.

Solids from the mixing chamber 20 are transported up a lift pipe 30, it being understood that the transport of the solids-gas (vapor) combination through the pipe 30 will also preferably be under dilute phase conditions (i.e., an average solids-gaseous (vapor) density of less than about 10 pounds per cubic foot). Also, as the solids and vapor residence times in the lift pipe 30 will typically be relatively small as compared to the corresponding residence time in the mixing chamber 20, the lift pipe 30, in order to facilitate understanding of the invention, can be considered as a part of the "first retorting stage."

The cross-sectional area of the mixing chamber 20 is generally 3 to 20 times the cross-sectional area of the lift pipe 30 and preferably at least 5 times greater than the cross-sectional area of the lift pipe 30. This ratio of cross-sectional area of the mixing chamber 20 to the lift pipe 30 enhances retorting in the mixing chamber 20 and the conveyance of solids in the lift pipe 30, while minimizing the thermal cracking of the retort vapors. Thus, the velocity of the lift gas and entrained solids in the lift pipe 30 is at least 20 feet per second, and preferably more than 40 feet per second, but preferably should not exceed about 100 feet per second so as to prevent undue erosion in the lift pipe. Under these constraints, the vapor residence time in the lift pipe is generally less than about 5 seconds, and preferably less than about 3 seconds. The density of the solids in the lift pipe is typically between about 3 to 20 pounds per cubic foot, preferably between about 5 and 10 pounds per cubic foot.

The solids transported up the lift pipe 30 are passed into a second retorting stage, referred to as a stripping vessel or stripper 40. In such passage, the solids, vapor products and fluidizing gas are fed through a cyclone 41 , connected directly to the lift 30, so as to obtain very rapid gas- solids separation with the vapor products gas, represented by the stream 11^*, being separated from the solids which pass through the dip leg 42 of the cyclone 41 , which dip leg preferably extends below the solids level "A" in the stripping vessel 40. In this fashion, vapor products are separated from the shale (or other solid, hydrocarbon-containing material) subsequent to a "first" retorting stage and prior to a successive or "second" retorting stage and thereby minimizing or substantially eliminating the exposure of the vapor products from the first retorting stage to the more severe retorting conditions including, for example, higher temperature, of succeeding retorting stages and thereby minimizing deleterious side reactions such as thermal cracking, as described above. The ratio of cross-sectional areas of the mixing chamber 20 and the stripper 40 is generally in the range of about 1 :1 to 10:1 and preferably less than about 5:1.

It is to be understood that in the practice of the invention, the hydrocarbon vapor products separated from the partially retorted product subsequent to the first retorting stage and prior to further retorting will generally total at least about 50 weight percent and preferably at least about 60 to about 70 weight percent of the total amount of volatile hydrocarbons present in hydrocarbon-containing material being treated.

Generally, additional heat carrier, e.g., active cracking catalyst, may, if desired, be preferably mixed with the solids in the stripping vessel 40. The additional heat carrier may, if desired, be conveyed through one or more secondary lift pipes 43 into the stripping vessel 40 in order to selectively increase the temperature therein so as to accelerate the liberation of hydrocarbon vapors from the partially retorted solids and to avoid cracking of the liberated hydrocarbon vapors. Generally, this additional heat carrier may be fed to the secondary lift pipe 43 via a pipe 45 and is at a similar temperature and pressure as the heat carrier fed to the mixing chamber 20 via the pipe 24. The solids density in the line 45 is generally around 50 pounds per cubic foot while that in the lift pipe 43 is generally around 10 pounds per cubic foot, the lower density being obtained through the use of a fluidizing gas 31 , similar to that used in the streams 26 and 28.

Preferably, the additional heat carrier is mixed with the solids in the stripping vessel 40 in a fashion that minimizes additional heating of the retort vapors. A conical deflector 44 and a cylindrical skirt 46 adjacent and about lift pipe 43 are examples of some of the many devices that can be used to prevent intermingling of added heat carrier with the retort vapors. Providing additional heat carrier to the stripping vessel 40 in this way efficiently strips additional hydrocarbons from the spent shale, providing additional condensable products, while reducing the thermal cracking and degradation of the retort vapors.

Backflow from the stripping vessel 40 is avoided through the use of slide valves, fluidic devices, etc. The average temperature of the solids in the stripping vessel 40 is maintained at least about 50°F above the temperature in the mixing chamber 20, and is preferably more than about 75°F higher than the temperature in the mixing chamber 20. Thus, the ratio of solids fed through the lift pipe lines 30 and 43 is in the range of about 1 :2 to about 1 :8, with ratios below about 1 :3 being preferred. Also, if desired or necessary, additional fluidizing gas 47 can be provided in the stripping vessel 40, such as by injecting the fluidizing gas through injectors 48 provided in the bottom portion 49 of the stripping vessel 40.

Certain mechanical devices may, if desired, be added to the stripping vessel 40 to promote retorting therein. For example, cyclones 55 or a series of cyclone stages to prevent the entrainment of solids in the product vapors from the retort may be added to the stripping vessel 40. Additionally, an array of conical baffles 56 is staggered in generally the lower portion of the stripping vessel 40 to promote the desired mixing of solids. The underside of the conical baffles 56 provide an upward barrier against backflow. The top surfaces of the conical baffles 56 slope downwardly and thereby facilitate the downward direction of solid agglomerates, to minimize the formation of clusters thereby.

In addition to mechanical devices, additional gas (as described above), especially process gas containing C0 , may be added to fluidize the solids and to promote more uniform retorting thereof. Thus, the upward gas velocity in the stripping vessel 40 is maintained in the range of about 0.1 feet per second to about 3 feet per second, preferably less than about 1.5 feet per second. The dimensions of the stripping vessel 40 are further constrained to give an average solids residence time of between about 30 seconds to about 300 seconds, preferably less than 150 seconds; and the vapor residence time is generally held below about 5 seconds, and most preferably below about 2.5 seconds to prevent thermal cracking of the retort products. Fine solids emerging with the hydrocarbon products from the stripping vessel 40 may be removed using additional cyclones, filters, etc., before the hydrocarbon products are condensed or further processed. Retorted solids and used heat carrier are withdrawn from the stripping vessel 40 via gravity flow through a pipe 60. A stream 62 of fluidizing gas may be used to aid the flow of retorted solids through the processing pipe 60, which may include an L-valve 64 (as shown), a slide valve or other fluidic device. The retorted solids are then conveyed through a lift pipe 70 with air, oxygen-enriched air, or some air combustion gas mixture 72, injected into the pipe 70 by a lift gas injector or gas tube 73. The velocity of the gas mixture in the lift pipe 70 is generally maintained in the range of about 20 feet per second to about 100 feet per second, preferably below about 50 feet per second. Partial combustion of residual hydrocarbon on the spent material and used heat carrier cracking catalyst serves to maintain the temperature within the lift pipe 70 in the range of about 1000°F to about 1400°F and, in the case of the cracking catalyst, may preferably result in reactivation of the catalyst via removal of carbon deposits which may have formed on the catalyst material. The residence time of gases and solids in the lift pipe 70 is generally no more than about 10 seconds, but preferably is greater than about 3 seconds.

Solids are conveyed through the lift pipe 70 and enter a combustor 80 wherein heat for conducting retorting is derived by combusting residual hydrocarbons from the solids, e.g., hydrocarbons adsorbed by the cracking catalyst as well as hydrocarbons adsorbed by or remaining in the substantially completely retorted solids. These solids are deflected downward by a deflector 82 and further retained in the combustor 80 by an optional annular skirt 84 to deflect and direct the flow of retorted oil shale particles, heat carrier material and air combustion gas mixture into the lower portion 85 of the combustor 80. If desired or necessary, additional heat for retorting may be provided by burning other low-value hydrocarbons added to the combustor 80.

The ratio of cross-sectional areas of the lift pipe 70 and the combustor 80 are greater than about 1 :10, and preferably about 1 :5. The temperature in the combustor 80 is generally in the range of about 1100°F to about 1500°F, preferably between about 1200°F and 350°F. Solids residence times in the combustor 80 are generally less than about 600 seconds and preferably less than about 200 seconds, before the solids are recycled via the pipe line 24 to the mixing chamber 20 or withdrawn via a solids withdrawal line 86. Thus, for example, operation of the valve 87 in the line 86 permits withdrawal of solids from the combustor 80 by gravity flow. Also, if desired or necessary, additional fluidizing gas 88 can be provided into the combustor 80, such as by injecting the fluidizing gas through injector 89 provided in the bottom 90 of the combustor 80. Solids may be retained in the combustor 80 with the aid of devices such as one or more cyclones 92, for example. Because decrepitation of higher grade shales is severe, much of the spent shale is entrained in the combustion gas stream 93 ejected from the combustion 80 and may, if desired, be removed using devices (not shown) such as ceramic bag filters, electrostatic precipitators, additional cyclones, or the like.

When using a cracking catalyst heat carrier, the catalyst will generally become at least in part deactivated through the deposition of residual hydrocarbons on the catalyst. Preferably, the used heat carrier, e.g., the at least partially deactivated cracking catalyst, is treated to reactivate the catalyst, thereby allowing the use of the reactivated catalyst in the practice of the invention. Such catalyst reactivation can be effected by suitable treatment steps such as by separating the at least partially deactivated cracking catalyst-containing used heat carrier from the substantially completely retorted product and combusting sufficient residual hydrocarbons from the material being treated to result in the material having substantial catalytic activity. Catalyst reactivation and use thereof will generally be preferred by factors such as relatively high material costs for fresh catalyst and environmental concerns such as disposal of contaminated solids, for example. Of course, if desired or preferred, fresh catalyst can be used to supplement or replace the catalyst used, as needed. In FIG. 1 , the combustor 80 in addition to combusting residual hydrocarbons from the solids, also serves to separate the spent shale from the catalyst. The gas velocity in the "free board," i.e., the space within the combustor above the solids level "B", is preferably sufficient to effect the desired separation as the catalyst particles will preferably fall to the lower portion 85 of the combustor 80 while much of the spent shale will be entrained in the gas stream 93, ejected from the combustor. Of course, if the gas velocity in the free board is insufficient, adequate separation of catalyst and spent shale will not be realized and if the gas velocity is too great, undesired loss of catalyst via entrainment in the dusty combustion gases 93 will be realized, which losses may require the addition of fresh catalyst to replace that which had been lost. In general, a superficial gas velocity in the free board of the combustor will preferably be in the range of about 0.1 to about 1.0 feet per second and, more preferably, be in the range of about 0.1 to about 0.5 feet per second.

In one preferred embodiment, the major vessels 20, 40 and 80 have circular cross-sections, as do the lift pipes 30 and 70. The mixing chamber 20 has a conical top and bottom which provide uniform mixing and smooth flow of solids. The stripping vessel 40 and the combustor 80 have conical bottoms to assist the gravity flow of solids and have dome-shaped tops, an economical design feature for pressure vessels.

Referring now to FIG. 2, an alternative embodiment of the invention is shown wherein third and fourth stages are implemented in a fluid bed retorting process and system of the invention. A system, generally designated 110, similar to the system 10 of FIG. 1 , is shown. The system 110 includes components such as a crushing and screening station 12, a preheating station 14, a mixing chamber 20, a stripping vessel 40 and associated connections, as in the system 10 shown in FIG. 1. Moreover, it is to be understood that in FIG. 2, devices and connections internal to vessels therein, e.g., the stripping vessels 40 and 40', for example, such as cyclones 41 and 55, deflector 44, and baffles 56, for example, as shown in FIG. 1 , are present but are not shown in order to minimize the complexity of FIG. 2. The system 110, however, includes a second mixing chamber 20' and a second stripping vessel 40'. In the system 110, the temperature of the hydrocarbon-containing solid, e.g., oil shale, is raised in each of the four successive stages, i.e., the mixing chamber 20, the stripping vessel 40, the second mixing chamber 20' and the second stripping vessel 40', and may thus increase the yield of condensable hydrocarbons obtained from the hydrocarbon-containing solid. In addition, the stages of the system 110, as will later be described herein, are configured in a manner whereby the retort vapors obtained in each of the stripping vessels, 40 and 40', respectively, are not intermixed prior to condensation, thereby serving to further reduce the amount of thermal cracking to which the liberated hydrocarbons are subjected.

In the system 110, partially retorted solids are withdrawn from the stripper 40 via gravity flow through the pipe 60 and, rather than being fed to the combustor 80', are fed to the second mixing chamber 20'. Heat carrier, preferably active, cracking catalyst, as described above, is also conveyed to the second mixing chamber 20' from the combustor 80' through a pipe 24'. The contents of the mixing chamber 20' are mixed to obtain retorting through the action of in-flowing partially retorted shale, the vapor released upon further retorting,- and the addition of a fluidizing gas 28', such as noncondensable process gas or other nonoxygen containing gas, as described above. Thus, in the mixing chamber 20', further retorting of the partially retorted shale is conducted.

Further, solids from the mixing chamber 20' are transported up a lift pipe 30' and into the stripping vessel or stripper 40'.

Also, if desired, additional heat carrier may be conveyed through one or more secondary lift pipes into the stripping vessel in order to selectively increase the temperature therein so as to accelerate the liberation of hydrocarbon vapors from the partially retorted solids and to avoid cracking of the liberated hydrocarbon vapors.

Retorted solids are withdrawn from the stripping vessel 40' via gravity flow through a pipe 60'. The retorted solids are then conveyed through a lift pipe 70' with air, oxygen-enriched air, or some air combustion gas mixture 72', injected into the pipe 70' by a lift gas injector or gas tube 73'.

The solids are conveyed through the lift pipe 70' and enter the combustor 80' wherein heat for conducting retorting is derived by combusting residual hydrocarbons from the solids, e.g., hydrocarbons adsorbed by the cracking catalyst as well as hydrocarbons adsorbed by or remaining in the substantially completely retorted solids.

As described above, when used in combination with a cracking catalyst heat carrier, the combustor 80' will preferably be used to effect catalyst reactivation and separation of spent shale from the catalyst. Further, decrepitation of higher grade shales is severe and much of the spent shale is entrained in the combustion gas stream 93' ejected from the combustor 80' and may, if desired, be removed using devices (not shown) such as ceramic bag filters, electrostatic precipitators, additional cyclones, or the like.

In the system 110, the hydrocarbon retort vapors produced in stripper 40, shown as stream 11 , and the hydrocarbon retort vapors produced in retort 40', shown as the stream 1 V, are sent to a fractionator 94, such as a distillation column, wherein the vapors are separated to form a gas stream 95 which is cooled by a condenser 96 to form a stream 97 of cooled gas and condensed gas (liquid), a portion of which may, if desired, be recycled to the fractionator 94, shown as recycle stream 98. Additional fractions separated in the fractionator 94 include light oils, middle oils and heavy oils shown as being withdrawn from the fractionator 94 as streams 99, 100 and 101 , respectively.

As shown, the hydrocarbon retort vapors, 11 ^* and 11 ^*', from the first and second mixer, 20 and 20', respectively, and 11 and 11' from the first and second strippers, 40 and 40', respectively, are not intermixed prior to fractionation and condensation. Thus, further thermal cracking of the hydrocarbons produced is reduced as the retort vapors 11^* from the first mixer 20 are not directly exposed to the higher temperature hydrocarbon retort vapors 11 , 11^*', and 11 ' for excessive periods of time. Likewise the retort vapors 11 and 11*' are not directly exposed to the higher temperature hydrocarbon retort vapors 11^* and 11', respectively, for excessive periods of time, thereby reducing thermal cracking and degradation of the retort vapors. As described above, the process and system of the invention is applicable to the treatment and neutralization of hydrocarbon-containing waste materials.

In the practice of this aspect of the invention, the hydrocarbon- containing waste material will typically contain at least some solids with the balance being made of one or more liquids, in the form of a solution, emulsion or the like. The solids of the waste material may themselves be non-hydrocarbonaceous with some hydrocarbon-containing material disposed in or on the non-hydrocarbonaceous solid or be hydrocarbon- containing with or without additional hydrocarbon-containing material disposed in or on such hydrocarbonaceous solid.

Such hydrocarbon-containing waste materials treatable in the practice of the invention include, but are not limited to: a) used or slop oils such as, including for example, used motor oils, slop oils from oil refineries, fouled fuel oils, and crude and processed oils such as are reclaimed from spills and, for example, may at least in some circumstances be contaminated with various metals; b) oil-containing sludges including, for example, sludges produced in a typical refinery or petrochemical plant and which can come from many sources including API separator bottoms, slop oil emulsions, storage tank bottoms, sludge from heat exchangers, oily waste, MEA reclaimer sludges, and other waste materials produced in a plant (the typical refinery sludge will contain solids along with oil, liquid and aqueous material with the concentrations of each being dependent on the source of the sludge. Generally, sludges will be in the form of suspensions, emulsions, or slurries and contain large amounts of water.) c) soils which have been contaminated with petroleum or petroleum products; d) . thermoplastics, elastomers and petroleum derivable polymers (that is polymers which are or can be derived or produced from petroleum feedstocks); these include synthetic rubber such as used in tires, for example, polyethylenes, polypropylene and polyethylterthalate beverage or liquid containers, nylon or other synthetic hydrocarbon- based materials (such as can be used as carpet materials, for example), polystyrene (such as used in foam packaging materials, for example), plastics and plastic resins; e) paint mixtures (such as alkyd-based paints and latex paints, for example); and f) food and agricultural waste or refuse, especially those that contain significant quantities of fatty acids, including animal by-products, seeds and manure.

In addition, while waste materials such as grass and plant trimmings, and other yard wastes, as well as typical paper and cardboard products and production wastes, will typically yield only relatively small amounts of oil in the treatment process of the invention, these materials can find use in the practice of the invention as they can be fed, directly or indirectly, into the combustor to provide heat utilized in retorting. It is to be understood that while second or successive stage retorting temperatures greater than first stage retorting temperatures can be achieved by a method of admixing additional solid heat carrier material to the solid, hydrocarbon-containing material, such a method can be supplemented or supplanted by other methods, such as through the utilization of fluidizing gases of the required elevated temperature, for example. In addition, it is to be understood that the heat required to maintain first stage retorting temperatures elevated relative to ambient conditions can, in addition to heat carrier addition, be supplemented by similar methods. The following examples illustrate the practice of the invention. It is to be understood that all changes that come within the spirit of the invention are desired to be protected and thus, the invention is not to be construed as limited by these examples. EXAMPLES Experimental Apparatus and Procedure

In these examples, single stage and multi-stage retorting were simulated utilizing an experimental apparatus comprising a fixed, fluid-bed retort wherein solid oil shale feed was added continuously to a bed of solid heat carrier material.

For both the simulated single stage and multi-stage retorting, a 600 gram shale charge of 60 gallon per ton shale beneficiate produced by acid-treating a Mahogany Zone shale source rock was added over a 10 minute period to a bed of well-characterized sand, F-140 sand produced by Ottawa Sand Company having an inorganic chemical analysis showing 99+ percent Si0₂, with the retort bed having a temperature of about 870°F.

To simulate a single stage retort, the bed was maintained at a temperature of about 870°F for 15 minutes following the completion of the shale charge addition.

To simulate multi-stage retorting, the retort bed was heated to a temperature of about 960°F during the 15 minutes following the completion of the shale charge addition. Thus, multi-stage retorting was simulated with the "first stage" corresponding to the time period of the shale addition at a bed temperature of about 870°F and the "second stage" corresponding to the 15 minute time period following shale addition, during which time the bed was heated to a temperature of about 960°F.

For both the simulated single stage and multi-stage retorting, gaseous and liquid products produced or formed during the retorting were withdrawn continuously from the retort and analyzed, and the spent shale accumulated in the retort bed.

_

Experimental results of both the simulated single stage (control) and multi-stage retorting are presented in the following table:

TABLE

Simulated Multi-Stage

Control Retorting

Liquid Yield (weight percent Tosco 108 1 15

Modified Fisher Assay) Carbon Balance (weight percent 99.4 99.2 recovered)

Percent of Shale Kerogen Carbon Converted To:

Gas (C₃-) 3.1 3.3

Liquid (C₄+) 70.1 74.5

Coke 26.8 22.2

Liquid Fractions (weight percent) C₄-430°F 14.5 15.0 430-650°F 17.5 18.0 650°F+ 68.0 67.0

Nitrogen In Liquids (weight percent) 1.8 2.0

Discussion of Examples

As clearly shown in the above table, higher liquid yields and lower coke formation were obtained with the simulated multi-stage retort as compared to the single stage retort. In addition, the carbon balances presented are very good, e.g., within plus or minus 5 percent, attesting to the accuracy of the data. Further, it is noted that a commercial retort would be expected to have much shorter solids residence times than those identified in these examples. For example, in a commercial retorting process an average first stage solids residence time of less than about 1 minute and an average second stage solids residence time of up to about 5 minutes would be expected. Such shorter residence times in the first stage would be expected to yield further benefits in the multi-stage retorting of liquid yields as such shorter residence times would limit the extent of coking reactions. Further, while the table shows that the simulated multi-stage retorting resulted in oils with a higher nitrogen content, the difference in nitrogen contents for the two cases borders the experimental limits of detection, and thus, the significance of the reported differences is limited.

The foregoing detailed description is given for clearness of understanding only, and no unnecessary limitations are to be understood therefrom, as modifications within the scope of the invention will be obvious to those skilled in the art.

Claims

WHAT IS CLAIMED IS:

1. A method of retorting solid hydrocarbon-containing material to increase yield of condensable products, said method comprising the steps of: retorting a solid, hydrocarbon-containing material in a dilute phase first fluidized retorting stage at first stage retorting conditions including a retorting temperature in the range of about 875°F to about 975°F, a solids residence time between about 5 seconds and 75 seconds and a vapor residence time between about 0.5 seconds and about 10 seconds to yield hydrocarbon vapor products liberated from said material totaling at least 50 weight percent of the total amount of volatile hydrocarbons present in said material and to also yield a partially retorted product including at least some unretorted solid hydrocarbon-containing material, wherein said first stage retorting temperature is achieved by a method comprising admixing solid heat carrier comprising an active cracking catalyst to said solid hydrocarbon-containing material; separating at least some of the vapor products from said partially retorted product prior to subjecting at least some of said unretorted solid hydrocarbon-containing material to further retorting and without subjecting said separated hydrocarbon vapor products to the retorting conditions of said further retorting; substantially completing retorting of said at least some unretorted solid hydrocarbon-containing material of said partially retorted product in a second fluidized retorting stage at second stage retorting conditions including temperature and solids and vapor residence time^'s to yield additional hydrocarbon vapor products and a substantially completely retorted product, said second stage retorting temperature being greater than said first stage retorting temperature and being achieved by a method comprising admixing an additional quantity of solid heat carrier comprising an active cracking catalyst to said partially retorted product; and separating at least some of said additional vapor products from said substantially completely retorted product.

2. The method of Claim 1 wherein said solid, hydrocarbon- containing material is selected from the group consisting of oil shale, tar sands, uintaite, peat and oil-containing diatomaceous earth.

3. The method of Claim 1 wherein said hydrocarbon-containing material comprises a waste material.

4. The method of Claim 1 wherein said active cracking catalyst comprises a USY sieve-containing material.

5. The method of Claim 4 wherein said solid heat carrier consists essentially of active USY sieve-containing cracking catalyst.

6. The method of Claim 1 wherein said cracking catalyst heat carrier of said first and second retorting stages becomes at least partially deactivated during said retorting in said stages, additionally comprising the step of treating the used heat carrier comprising at least partially deactivated cracking catalyst to reactivate said catalyst.

7. The method of Claim 6 wherein said catalyst has been at least in part deactivated through residual hydrocarbon deposition on said catalyst during said retorting wherein said treatment step comprises: a) separating at least some of said used heat carrier from said substantially completely retorted product; and b) combusting sufficient residual hydrocarbons from said deactivated catalyst to result in a material having substantial catalytic activity.

8. The method of Claim 7 wherein said resulting material having substantial catalytic activity is recycled as heat carrier to said first retorting stage, said second retorting stage or both.

9. The method of Claim 1 wherein said second stage retorting temperature is at least about 50°F greater than said first stage retorting temperature.

10. The method of Claim 9 wherein said second stage retorting temperature is at least about 75°F greater than said first stage retorting temperature.

11. The method of Claim 9 wherein said second stage retorting conditions include a vapor residence time of less than about 5 seconds and a solids residence time between about 30 seconds and 300 seconds.

12. The method of Claim 11 wherein said second stage vapor residence time is less than about 2.5 seconds.

13. The method of Claim 11 wherein said second stage solids residence time is less than about 150 seconds.

14. The method of Claim 1 wherein said first stage vapor residence time is less than about 5 seconds.

15. The method of Claim 1 wherein said first stage solids residence time is in the range of about 5 seconds to about 45 seconds.

16. A method of retorting oil shale to increase yield of condensable products, said method comprising the steps of: heating oil shale to a temperature in the range of about 250°F to about 650°F; retorting the heated oil shale in a dilute phase first fluidized retorting stage at first stage retorting conditions including temperature and solids and vapor residence times to yield hydrocarbon vapor products liberated from said shale totaling at least 50 weight percent of the total amount of volatile hydrocarbons present in said shale and to also yield a partially retorted product including at least some unretorted oil shale, said first stage retorting temperature being elevated relative to ambient conditions and being achieved by a method comprising admixing an active cracking catalyst heat carrier to said oil shale; separating at least some of said hydrocarbon vapor products from said partially retorted product prior to subjecting at least some of said unretorted oil shale to further retorting and without subjecting said . separated hydrocarbon vapor products to the retorting conditions of said further retorting; substantially completing retorting of said at least some unretorted oil shale of said partially retorted product in at least one successive fluidized retorting stage at successive retorting stage conditions including temperature and solids and vapor residence times to yield additional hydrocarbon vapor products and a substantially completely retorted product, said successive retorting stage temperature being at a temperature elevated relative to said first stage retorting temperature and being achieved by a method comprising admixing an additional quantity of active cracking catalyst heat carrier to said partially retorted product; and separating at least some of said additional vapor products from said substantially completely retorted product.

17. The method of Claim 16 wherein said shale to be retorted contains an oil yield of at least about 15 gallons per ton.

18. The method of Claim 16 additionally comprising the step of crushing the shale oil to be retorted to a top size of no more than about 3 millimeters.

19. The method of Claim 16 wherein said active cracking catalyst comprises a USY sieve-containing material.

20. The method of Claim 16 wherein said successive stage retorting conditions include a successive stage retorting temperature at least 50°F greater than said first stage retorting temperature, vapor residence time of less than, about 5 seconds and a solids residence time between about 30 seconds and 300 seconds.

21. The method of Claim 20 wherein said first stage vapor residence time is less than about 5 seconds and said first stage solids residence time is in the range of about 5 seconds to about 45 seconds.

22. The method of Claim 20 wherein said successive stage retorting temperature is at least about 75°F greater than said first stage retorting temperature.

23. A method of retorting oil shale to increase yield of condensable products, said method comprising the steps of: heating oil shale to a temperature in the range of about 250°F to about 650°F; retorting the heated oil shale in a dilute phase first fluidized retorting stage at first stage retorting conditions including a retorting temperature in the range of about 875°F to about 975°F, a solids residence time between about 5 seconds and about 75 seconds and a vapor residence time between about 0.5 seconds and about 10 seconds, to yield hydrocarbon vapor products liberated from said shale totaling at least 50 weight percent of the total amount of volatile hydrocarbons present in said shale and to also yield a partially retorted product including at least some unretorted oil shale, said first stage retorting temperature being achieved by a method comprising admixing an active USY sieve- containing cracking catalyst heat carrier to said oil shale; separating at least some of said hydrocarbon vapor products from said partially retorted product prior to subjecting at least some of said unretorted oil shale of said partially retorted product to further retorting and without subjecting said separated hydrocarbon vapor products to the retorting conditions of said further retorting; subsequently substantially completing retorting of said at least some unretorted oil shale of said partially retorted product in at least one successive fluidized retorting stage at successive retorting stage conditions including a retorting temperature at least about 50°F greater than said first stage retorting temperature and achieved by a method comprising admixing an additional quantity of active USY sieve-containing cracking catalyst heat carrier to said partially retorted product, a vapor residence time of less than about 5 seconds and a solids residence time between about 30 seconds and 300 seconds to yield additional hydrocarbon vapor products and a substantially completely retorted product; and separating at least some of said additional vapor products from said substantially completely retorted product.

24. The method of Claim 23 wherein said successive stage retorting temperature is at least about 75°F greater than said first stage retorting temperature.

25. The method of Claim 23 wherein said successive stage vapor residence time is less than about 2.5 seconds and said successive stage solids residence time is less than about 150 seconds.

26. The method of Claim 23 wherein said first stage vapor residence time is less than about 5 seconds and said first stage solids residence time is in the range of about five seconds to about 45 seconds.

27. A method for the treatment of hydrocarbon-containing waste comprising the steps of: retorting a waste material comprising at least some solids and some hydrocarbons in a dilute first fluidized retorting stage at first stage retorting conditions including temperature and solids and vapor residence times to yield hydrocarbon vapor products liberated from said material totaling at least 50 weight percent of the total amount of volatile hydrocarbons present in the material and to also yield a partially retorted product including at least some unretorted waste material, wherein said first stage retorting temperature is elevated relative to ambient conditions and is achieved by a method comprising admixing a solid heat carrier comprising an active cracking catalyst with said waste material; separating at least some of said hydrocarbon vapor products from said partially retorted product prior to subjecting at least some of said unretorted product and without subjecting the separated hydrocarbon vapor products to the retorting conditions of the further retorting; substantially completing retorting of the separated unretorted waste material in a second fluidized retorting stage at second stage retorting conditions including temperature and solids and vapor residence times to yield additional hydrocarbon vapor products and a substantially completely retorted product, said second stage retorting temperature being greater than said first stage retorting temperature and being achieved by a method comprising admixing an additional quantity of solid heat carrier comprising an active cracking catalyst to said partially retorted product; and separating at least some of said additional vapor products from said substantially completely retorted product.

28. The method of Claim 27 wherein said first stage retorting conditions include a retorting temperature in the range of about 875°F to about 975°F, a solids residence time between about 5 seconds and 75 seconds and a vapor residence time between about 0.5 seconds and about 10 seconds.

29. The method of Claim 27 wherein said waste material comprises used or slop oils.

30. The method of Claim 27 wherein said waste material comprises a soil contaminated with a petroleum or a petroleum product.

31. The method of Claim 27 wherein said waste material comprises thermoplastics, elastomers or petroleum derivable polymers.

32. The method of Claim 27 wherein said waste material comprises an oil-containing sludge.

33. The method of Claim 27 wherein said waste material^' comprises spent hydrocarbon-treating catalyst.