COUNTERFLOW MILD GASIFICATION PROCESS AND APPARATUS

Abstract: Counterflow mild gasification process and apparatus (1) employing reverse combustion, with a carbonaceous reactant (11), which may be a solid fossil fuel or solid biological waste. The solid carbonaceous material (11) fills an elongated combustion chamber (10) where it is ignited (12) creating an advancing combustion front (13). An oxidant (15), usually air or pure oxygen, is introduced such that it flows in a direction opposite the advance of the combustion front (13). This reverse flow of the oxidant (15) allows for only partial combustion of the solid carbonaceous material (11) and at mild temperatures, resulting in a high quality hydrocarbon gaseous product (6) and a solid coke.

Description: DESCRIPTION COUNTERFLOW MILD GASIFICATION PROCESS AND APPARATUS Technical Field The present invention is broadly applicable to the processing of carbonaceous feed material to effect desirable chemical and physical changes, usually through elevated temperatures and increased pressures. More specifically, this invention relates to the drying and/or gasification of solid fossil fuels and solid biological wastes by thermal restructuring or pyrolization to produce usable solids as well as gaseous and/or liquid by-products. Additionally, this invention relates to contaminated soil sterilization through the oxidation of organic toxins, and to the devolitilization and oxidation of toxins absorbed on spent beds of activated carbon or other materials, including inorganic adsorbents. Background Art The fuel shortages of the mid-1970's and the projection of future shortages of such conventional energy sources as gas and oil have given rise to investigations into alternative energy sources, including solid fossil fuels, such as oil shales, brown coals, lignites, subbituminous coals and the like, and solid biological wastes, such as wood chips, saw dust, peat, sewage sludge and other carbonaceous sludges, bagasse, hulls, straw, cornstalks and the like. Although this present invention applies to both solid fossil fuels and solid biological wastes, most of the relevant discussion the prior art deals with coal conversion. For example, a summary of coal conversion is provided in "Coal Conversion Technology: Opportunities and Challenges", Energy, Volume II, Number 11/12, pages 1239-1247, 1986, by T. Y. Yan. In general, coal conversion processes fall into four groups: desulfurization, liquification, carbonization, and gasification. Desulfurization, which for most coals is only marginally achieved by this invention, is usually accomplished by chemical leaching. Liquification has been accomplished by mixing crushed coal with oil (often process derived) into a slurry and then reacting it with hydrogen under increased temperatures and pressures. Carbonization, or coal drying, which has traditionally been accomplished in the absence of air or other oxidants, involves a boiling away of the moisture contained within the coal, a thermal restructuring of the coal into a char, and the generation of gaseous and liquid by-products. In gasification, coal is reacted with oxygen and/or steam at increased temperatures and elevated pressures to form gaseous mixtures of hydrogen, carbon monoxide, and carbon dioxide. Typical of current technology in coal drying are several of the prior art patents of Koppelman, including U.S. Patent No. 4,052,168 and its two continuations-in-part, U.S. Patent No's. 4,127,391 and 4,129,420. The parent U.S. Patent No. 4,052,168 describes a process for upgrading lignite-type coal by a batch autoclave treatment at elevated temperatures and increased pressure to effect a thermal restructuring of the coal and to generate a gaseous by-product. The first continuation-in-part, U.S. Patent No.4, 127,391, utilizes this autoclave treatment for the agglomerating of bituminous fines into useful low-sulfur fuel. The second continuation-in-part, U.S. Patent No. 4,129,420, generates coke from heating cellulosic materials in the autoclave. Other Koppelman patents that are typical of current technology in gasification include: U.S. Patent No. 4,069,107, and its continuation-in-part U.S. Patent No. 4,106,999. These two patents describe a continuous pyrolyzing of a particulated carbonaceous feed material in which preheated pebbles are mixed with the carbonaceous feed forming a downwardly moving columnar reaction mass. These two patents further describe the introduction of an oxidant into a cylindrical reaction chamber through pores in a concentric annular wall within the chamber. Other prior art patents of interest include Murray, U.S. Patent No. 4,126,519, and two other Koppelman patents, U.S. Patent No. 4,477,257 and U.S. Patent No. 4,626,258, all of which describe a countercurrent flow of the gaseous by-product, not the oxidant, to achieve a pre-heating of the feed material in their pyrolysis drying methods. U.S. Patent No. 4,126,519 is a continuous drying method utilizing contiguous chambers for the preheating and thermal reacting of the feed material. U.S. Patent No. 4,477,257 is also a continuous drying method, which has broken the process down into a pre-heating, pressurized dewatering and reaction stage with a separate chamber for each. The last of these, U.S. Patent No. 4,626,258, which is also a continuous process, utilizes a multiple hearth reactor containing a plurality of annular hearths. These and other current methods of coal drying and gasification have been characterized by slow and difficult transfer of heat from the heat source into the interior of the coal particles, thus resulting in a slow and inefficient way to boil moisture from the coal. One approach, called low temperature drying, has partially overcome this slow heat transfer problem by placing the coal in intimate contact with the drying gas, thereby creating a turbulent fluidized bed. Disadvantages with this turbulent, fluidized bed approach include difficulties in controlling the fluidized beds, a narrow, confining range of operating conditions, and large equipment investments which afford only marginal economic returns. The most severe drawback, however, is that low temperature drying methods typically generate a pyrophoric dried coal, which ignites spontaneously when exposed to air. Consequently, this pyrophoric dried coal product requires chemical treatment, at added expense before it can be transported, handled or stored. An additional persistent problem with current coal drying and gasification methods is the production of waste products such as tar and ash. These waste products create special handling and disposal problems, the solutions of which can significantly increase costs. Disclosure of Invention Accordingly, it is a general object of this invention to provide a rapid, inexpensive method and apparatus for the drying of coal and other organic material, as well as the production of gas and liquids. An additional general objective of this invention is to provide a rapid, inexpensive method and apparatus for the sterilization of contaminated soils through the burning off of the organic constituents and for the regeneration of adsorbent beds containing combustible adsorbates. Another object of this invention is to allow lower drying temperatures while still maintaining high drying rates and thereby providing higher output capabilities for a given size of equipment as well as a lower consumption of the oxidant, leading to more favorable economics. A further object of the present invention is to produce a gas product that is of substantially higher quality than that produced in other drying or gasification processes. It is also an object of the present invention to produce a much wider range of product gases than presently achieved with other drying or gasification processes. It is a still further object of the present invention to provide a drying or gasification process for coal and other organic materials that produces very little, if any, tar and ash. Additional objects, advantages and novel features of the present invention in part, are set forth in the description that follows; in part, will become apparent to those skilled in the art upon examination of this disclosure; and in part, may be learned by the practice of the invention. The objects and the advantages of the invention may be realized and attained by means of the instrumentalities and in combinations particularly pointed out in the appended claims. To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the counterflow mild gasification process and apparatus of this invention may comprise an elongated combustion chamber filled with solid carbonaceous feed materials. An ignition device for igniting the solid carbonaceous material is positioned near one end of the combustion chamber. Depending upon the nature and type of the solid carbonaceous material, this combustion may occur from 400°F up to 3000°F, but typically occurs in the range of 600°F to 1500°F. In a batch process, the combustion of the carbonaceous material begins at the ignition end and progresses through the chamber toward the other end. At said other end of the chamber is an inlet point for a fluid oxidant, usually air or pure oxygen. A fluid outlet port is provided at or near the ignition end of the reaction chamber. Accordingly, the oxidant flows through the chamber in a direction opposite to the progress of the combustion zone. This reverse flow of the oxidants allows only a partial combustion of the solid carbonaceous material. This oxidant flow may be continuous or periodic and may further be pressurized from 0 psia to 5000 psia, but it typically ranges from 1 psia to 600 psia. A high quality hydrocarbon gaseous product, which is the result of the interaction of the oxidant with the combusting or oxidizing carbonaceous material is retrieved from the fluid outlet port at the ignition end of the chamber. A further product of the counterflow mild gasification process is partially combusted, solid, carbonaceous material, which can be a char, coke, or upgraded coal, depending upon the nature and type of carbonaceous feed material used and operating conditions. The process of this invention can also be operated as a continuous process in which the char, coke, or upgraded coal is removed from the ignition end of the combustion chamber continuously or periodically by gravity or by mechanical means, such as an augur or rotary screw conveyor, as the solid carbonaceous feed material is added simultaneously from the other end of the reaction chamber. The addition of the carbonaceous feed material may likewise be continuous or periodic, by gravity or by some mechanical means such as an augur or rotary screw conveyor. Brief Description of Drawings The accompanying drawings, which are incorporated herein and form a part of the specification illustrate preferred embodiments of the present invention, and together with the description, serve to explain the principles of the invention. In the drawings: Figure 1 shows a schematic layout of the batch, counterflow mild gasification process in accordance with the preferred embodiment of the present invention; Figure 2 shows a schematic of an intermittent, gravity feed counterflow mild gasification process according to this invention; and Figure 3 shows a schematic of the continuous auger feed counterflow mild gasification process according to this invention. Best Mode for Carrying Out the Invention A batch process apparatus 1 for the present invention, as shown in Figure 1, can include an elongated combustion chamber 10, an igniter 12 near one end of the chamber 10, an inlet 14 at the other end of the chamber 10, and a gas product outlet 17 at the end of the chamber 10 that is adjacent the igniter 12. Batch combustion chamber 10, as shown in Figure 1, is filled with a primarily solid, feed material 11 comprising volatile matter that is to be dried, gasified, or sterilized. Combustion chamber 10 is sealed and may additionally be pressurized. Solid material 11 contains a carbonaceous reactant, which may be a solid fossil fuel, such as oil shale, brown coal, lignite, subbituminous coal or the like; or may be solid biological wastes, such as wood chips, saw dust, peat, sewage sludge or other carbonaceous sludge, bagasse, hulls, straw, cornstalks, or the like; or may further be, soil or absorbent beds contaminated with organic toxins and other toxins which can effectively be neutralized through burning. A catalytic material, such as an alumina supported catalyst, or a purely inert material to aid in heat distribution, such as ceramic berl saddles can be mixed with carbonaceous feed material if desired. The addition of a catalyst promotes reactivity, selectivity or suppresses undesired reactions. Prior to the introduction of feed material 11 into chamber 10, feed material 11 may be pre-dried. Said pre-drying may be by any methods commonly known in the industry, including sun drying, air drying or squeeze drying. Pre-drying is useful when feed material 11 is a high moisture content coal or high moisture biological waste. With certain of the higher moisture content biological wastes, such as peat and sludge, some form of pre-drying may be a necessity. Peat and sludge can have up to 80 to 90% moisture contents which results in a negative heating value for the material. Accordingly, unless these higher moisture content feed materials, such as peat or sludge, are pre-dried, combustion in chamber 10 may be impossible. An ignition device 12, such as an electric coil igniter or other suitable ignition device, is positioned near one end 2 of the chamber 10. The ignition coil 12 ignites certain volatile matter within feed material 11 thereby creating a combustion zone 3 with a combustion front 13, which moves away from the ignition coil 12 as indicated by the arrows 4. Igniting the feed material 11 and causing it to burn generates a great deal of heat. This places the heat of drying at the particle level instead of at the system level as would be the case with some form of external heating. Heating at the particle level, wherein feed material 11 heats itself, is far more efficient than trying to transfer external heat to the interior of a conglomeration of feed material 11. Although temperature will be primarily a function of the type of volatile material contained within feed material 11, and certain other factors as will be discussed below, having the feed material dry itself, though the heat of combustion allows a much shorter drying period and accordingly, a much lower system teperature. An inlet port 14 at the other end 5 of combustion chamber 10, opposite ignition coil 12, is provided for injecting an oxidant 15 into chamber 10. This oxidant 15 may be, for example, pure oxygen, a mixture of oxygen and air, or just plain air. The oxidant 15, which may be pressurized, flows through the feed material 11 toward the advancing combustion front 13. This flow of oxidant 15 in a direction opposite the direction 4 of the advancing combustion front 13 gives rise to the name of this process, Counterflow Mild Gasification Process. As will be shown in the examples below, pressurizing oxidant 15 and having it flow in a direction opposite the direction 4 of the advancing combustion front 13 reduces oxidant consumption by as much as half over what other commercial coal gasification processes consume. The peak temperature range within combustion chamber 10 is from about 400°F to 3000°F and is preferably in the range of about 600°F to 1500°F when carbonaceous material 11 is a subbituminour or lignite-type coal typical of those found in Montana and Wyoming. These temperature ranges are milder than the 1500°F to 3000°F typical of other conventional coal gasification processes. The specific temperatures involved will vary depending upon the nature and type of solid reactant 11 and oxidant 15. Much to this inventor's surprise, utilizing oxygen, instead of air, as the oxidant increases the reaction rate and decreases the system temperature. The reason for this is a little complicated. Both oxygen and air have similar levels of heat released at the combustion front 13. This heat of combustion is carried back through combustion zone 3 by convection, as the oxidant flows in a direction opposite the advance of front 13. The only way for temperature to increase ahead of combustion front 13, is by conduction and radiation. The amount of preheating of feed material 11 by conduction and radiation is controlled by how quickly combustion front 13 advances. Oxygen, being a purer oxidant than air, allows for a more rapid reaction rate resulting in a quicker advance of combustion front 13. The reaction rate with pure oxygen, as measured by the advance of front 13, was found to be 7 to 20 times faster than the reaction rate with air. This quicker advance of front 13 leads to greater levels of output and significantly lower total system temperatures. Of course, when figuring the economics of production, the quantity of oxygen, which costs more than air, must be weighed against the increased output in calculating the costs of production. Still, this present invention achieves significantly lower temperatures and faster reaction rates than other conventional coal drying and/or gasification processes. This feature of the Counterflow Mild Gasification Process, whereby system temperature and reaction rate can be manipulated by adjusting the oxidant, also allows for a much wider range of products. As will be discussed below, an additional feature with this counterflow process is that system temperature, reaction rate, and the end products can also be manipulated the inlet temperature, pressure, composition, and flow rate of the oxidant. An outlet port 16 for draining off product gas 17 is located at the ignition end 2 of chamber 10, opposite the inlet port 14. The gas 17 is a product of the reaction of oxidant 15 with the combusting (oxidizing) material 11. Pressurization of chamber 10 can be achieved by a pressure control valve or regulator 18 attached at outlet port 16. Accordingly, the pressure in chamber 10 is a back pressure resulting from restriction of the oxidant gas flow. Product gas 17 contains both the liquid components and gaseous components of the end-products. Due to the high temperature of combustion in chamber 10, the components of gas 17 which are normally liquids at temperatures nearer room temperature, are removed in their gaseous state along with the normal gaseous components in product gas 17. Once removed, product gas ϊl may be cooled in a condensation chamber (not shown) to separate the liquid components from the gaseous components. Product gas 17 is composed of a wide range of constituents, including hydrocarbons, carbon dioxide, carbon monoxide, and hydrogen. Heretofore, gasification processes have tended to produce a predominance of carbon monoxide, hydrogen, and water vapor which has limited economic value, being utilized chiefly as a pre-heating agent in the same gasification process which generated it or in conjunction with ammonia plants. However, in this present process, by varying operating conditions, i.e., temperature, pressure, and type of oxidant, up to 80% or more of the heating value of product gas 17 can be as methane, oil and other valuable hydrocarbons on a carbon dioxide-water free basis. Methane and other hydrocarbons tend to be more marketable. Using air as an oxidant tends to discourage production of oil in product gas 17. Air tending to allow higher temperatures, as discussed above, burns off the oil. Oxygen, on the other hand, tends to favor the production of oil as the lower temperatures tend to burn a smaller amount of fuel. By the same token, lower temperatures also favor methane production, while higher temperatures tend to favor carbon monoxide and hydrogen production. In certain applications of this counterflow process, it will be desirable to obtain a complete combustion of the feed material 11. If feed material 11 is a soil or adsorbent bed comprising organic and other volatile toxins, then it would be desirable to completely burn off the toxins. Likewise, if feed material 11 is a biological waste whose chief economic value in being processed lies in the gaseous and liquid end-products 17, it may be desirable to have a complete or almost complete combustion of the volatile matter. However, if feed material 11 is coal, and in addition to the high quality gas product 17 it is desired to obtain a high quality solid product 6, then complete combustion of the coal is undesirable. Solid product 6 is the thermal restructured material that remains behind the combustion front 13. One of the significant advantages of having the oxidant 15 flow in a direction reverse to the advance of combustion front 13 is that it allows greater control over the level of combustion achieved. With the partial combustion feature of this counterflow process as much as 95% of all volatile material within feed material 11 can remain unburned. Partial combustion, as is preferable with coal drying, can be achieved through this reverse flow of oxidant by manipulation of the inlet temperature and by the type, quantity and pressure of the oxidant. The preferred conditions for partial combustion are decreased flow rate of oxidant (oxidant lean) ; use of oxygen as the oxidant, lower temperature, and increased pressure. Conversely, the preferred conditions for complete combustion are increased flow rate of oxidant (oxidant rich) , use of air as the oxidant, higher temperatures and decreased pressure flow rate. However, the factor which seems to have the greatest influence over the level of combustion achieved is the quantity of the oxidant used. This makes sense, because in the oxidant lean state, which favors partial combustion, there simply is not sufficient oxidant to achieve a complete oxidation or combustion of feed material 11. In the case of coal, partial combustion of material 11 results in a chemical and thermal restructing of material 11 into product 6 characterized as char, coke, or upgraded coal, depending upon the operating conditions and the type and nature of material 11 which is used as feed. As shown in the examples below, this partial combustion feature of the counterflow process results in a solid product 6 of greater quality than has been obtainable heretofore in comparable industrial processes. The pressurized flow of the oxidant 15 within the combustion chamber 10 can be in the range from 0 psia to 5,000 psi, and it is preferably in the range of about 0 psia to 600 psia. The specific pressures will vary depending both upon the nature and type of feed material 11 used in combustion chamber 10 and upon the desired quality and quantity of gas product 17. Higher pressures tend to favor production of more oil and methane, which are more stable at these higher pressures. This is due to a shift with pressure of the thermodynamic equilibrium between carbon, hydrogen and carbon oxides on the one hand and oil and methane on the other hand. However, the equipment necessary to handle higher pressures can be very expense, and even cost prohibative. In addition to which, in this batch process, every time chamber 10 is emptied or filled, pressure is lost and it requires repressuration for each subsequent combustion cycle. Accordingly, the decision as to what kinds of pressure to employ in production, often resolves to economics as opposed to the desirability of a given end-product. But, as discussed above, selection of specific end-products can also be made by manipulation of the nature and quantity of oxidant 15 used on a particular feed material 11. Batch combustion chamber 10 has a bottom 19, which may * be constructed in such a manner that it is capable of being opened by being swung or slid out of the way. Then when combustion front 13 has reached bottom 19, thereby completing the thermal restructioning of all the feed material 11 into combusted, or partially combusted, material 6, bottom 19 may be opened releasing material 6 into some receiving apparatus (not shown) , such as a hopper. Combustion chamber 10 in Figure 1 is illustrated in a vertical position; however, it may be operated at any angle, including horizontal. Further the ignition from ignition coil 12 can be from the top, from the bottom, or from either side, so long as it is opposite inlet ports 14 for the oxydizing agent 15. The feature of this counterflow mild gasification process, where the oxidant flow 15 is in a direction opposite the advance of the combustion front 13 and combustion zone 3, is not limited to a batch process, but is also applicable to a continuous process. Such a continuous process may for example be utilized with gravity feed apparatus 101 such as shown in Figure 2, or with an auger feed apparatus 201 such as that shown in Figure 3. Referring now to Figure 2, a primarily solid carbonaceous feed material 111, is fed into valved storage tank 120 by a receiving chute 121 and through a valve 122. Valve 122, which is positioned between the chute 121 and the storage tank 120, can be a high pressure valve for holding a pressure differential when a pressurized oxidation process is used. When storage tank 120 has been filled with feed material 111, valve 122 can be closed. Feed 111 can then be emptied into combustion chamber 110 by opening a valve 123 between the storage tank 120 and the chamber 110. Valve 123 can also be a high pressure valve so that pressure can be maintained in chamber 110 when valve 122 is opened to fill the storage tank 120, as described above. When the combustion chamber 110 is completely filled or when storage tank 120 has emptied, valve 123 can be closed. If it is desired to pressurize chamber 110, the pressure can be maintained by alternating the opening and closing of high pressured valves 122 and 123 such that they are not both open at the same time. In the initial start-up of the continuous process illustrated in Figure 2, an ignition device 112 located at or near the bottom of combustion chamber 110 is activated to ignite the solid feed material 111, thereby creating a combustion zone 103, which defines a combustion front 113 at its leading edge. Combustion front 113 advances upwardly in the direction indicated by arrow 104 away from ignition device 112 and through chamber 110. An inlet port 114 is located at the top end 105 of combustion chamber 110 for flowing the oxidant 115 into chamber 110. As in the batch process described above, oxidant 115 may be air, pure oxygen or a mixture of the two. An outlet port 116 is located at the bottom end 102 of chamber 110 for drawing off the gaseous product 117. The location of the inlet and outlet ports 114, 116, respectively, define an oxidant flow that is in a direction opposite the movement of combustion front 113. As in the batch process described above, this reverse flow of the oxidant 115 in the continuous process allows for only a partial combustion of the solid carbonaceous material 111. Once the combustion front 113 has moved upward a substantial distance, such as in the range of about 50 to 75 percent of the length of chamber 110, a valve 131 at the bottom of chamber 110 can be opened to allow the solid, partially combusted carbonaceous material 106 to fall into a storage tank 130. When about 25 to 50 percent of the solid combusted product has been removed from chamber 110, valve 131 can be closed. Another valve 132 at the bottom of storage tank 130 can be opened to empty the storage tank 130 through outlet chute 133 as desired. Valves 131 and 132 can be high pressure valves. Again, if it is desired to maintain pressure in chamber 110, this can be achieved by alternating the opening and closing of high pressure valves 131 and 132 such that they are never open at the same time. The flow of oxidant 115 and the related gaseous product removal 117, may be continuous or periodic. Periodic flow affords a temporary halt during the emptying and filling of combustion chamber 110. This continuous process does not necessarily have to be gravity fed, rather, it can be driven by some mechanical means, such as rotary screw conveyors or an augers, as shown in the mechanical-driven, continuous feed apparatus 201 illustrated in Figure 3. A primarily solid carbonaceous feed material 211 is fed into a valved storage tank 220 by a receiving chute 221 and through a valve 222. Valve 222 may be a high pressure valve so that once storage tank 220 has been filled with solid feed material 211, valve 222 may be closed to maintain a pressure in storage tank 220. Solid feed 211 is transferred from storage tank 220 to a combustion chamber 210 by way of a conveyance tube 224 with an auger 225 rotatably positioned therein. A valve 223, which may be a high pressure valve, is located at the bottom of storage valve 220 and allows the transfer of the solid feed 211 into tube 224. Alternating the opening and closing of high pressure valves 222 and 223 allows the operator to maintain pressurization of combustion chamber 210. Auger 225 in tube 224 is driven by a drive motor 226. Such augers and drive motors are commonly known to persons skilled in the art. The rotating motion of auger 224 moves the solid feed 211 along its length, depositing feed 211 into one end 105 of chamber 210. Combustion chamber 210 is also fitted with a large diameter auger 218, which is driven by a drive motor 219. The rotating motion of auger 218 transfers the solid feed material 211 along the length of chamber 210 in a direction toward an outlet conveyance tube 234 positioned at the other end 202 of chamber 210. At or near outlet end of chamber 210 is an ignition device 212, which when activated ignites the solid carbonaceous feed material 211 in chamber 210. Igniting feed material 211 causes combustion of the feed material 211 creating a combustion zone 203 defined by combustion front 213. Combustion front 213 will tend to advance in a direction away from the ignition device 212, as indicated by arrows 204. However, the actual direction that combustion front 213 moves depends on the speed of feed material 211 through chamber 210, as controlled by auger 218. Ideally the auger 218 is operated at a speed that moves the feed material 211 toward end 202 at the same rate as the combustion front 213 advances into the uncombusted feed material 211, thereby effectively keeping the combustion front 213 and combustion zone 203 stationary at about the midpoint along the length of chamber 210. At the solid material inlet end 205 of chamber 210 is an inlet port 214 for injecting the oxidant 215 into chamber 210. At the ignition end 202 of chamber 210 is an outlet port 216 for removing the gaseous product 217 from the chamber 210. Accordingly, oxidant 215 flows through the feed material 211 in a direction that is opposite the direction that combustion front 213 would progress if the auger 218 was stationary. At the ignition end 202 of chamber 210, auger 218 deposits the now partially combusted material 206, which may be char, coke, or upgraded coal, into a conveyance tube 234, which can contain an auger 235 rotated by a drive motor 236. Auger 235 propels the partially combusted material 206 out of chamber 210 along the length of tube 234, finally depositing material 206 into a receiving tube or area 237, which empties into a valved storage tank 230 through an open valve 231, which can be a high pressure valve. Likewise, storage tank 230 may be emptied of combusted material 211 through an outlet chute 233 by way of a valve 232, which may also be a high pressure valve. By alternating the opening of high pressure valves 231 and 232, an operator can maintain the pressurized environment in chamber 210. In a continuous operating mode, the receiving tube 237 would have to have sufficient capacity to hold the partially combusted material 206 produced in chamber 210 while valve 231 is closed long enough to empty storage tank 230 with valve 232 open, or some other alternate storage area (not shown) would have to be provided. As described herein, and as shown in Figure 3, valved storage tanks 220 and 230 depend upon gravity in the filling and emptying cycles and accordingly have a vertical orientation. However, valved storage tanks 220 and 230 may be fitted with augers or similar propelling devices, when it is desired to have their orientation other than vertical. Similarly, chamber 210, which in this embodiment is fitted with augur 218, is not restricted to the vertical orientation depicted in Figure 3. Numerous test runs have been made according to this invention using subbituminous coals, found typically in the western United States, in a batch process as described above in the preferred embodiment and shown in Figure 1. Several of these test runs are des.cribed in the examples below. Although these examples deal specifically with subbituminous coals this process is equally applicable to other solid fossil fuels and solid biological wastes. These examples are for illustrative purposes only, and are not intended to limit the scope of the invention as herein described or as set forth in the appended claims. EXAMPLE I A subbituminous C coal from the Powder River Basin of Wyoming was treated with a batch process. An analysis of the raw coal was as follows: TABLE 1-1 COAL ANALYSIS (Weight Moisture Ash Volatile Matter Fixed Carbon Total Heating Valve - 7839 Btu/lb This first test run was conducted at or near optimum operating conditions for this type of coal, as shown in Table 1-2 below. Of course, optimum operating conditions will vary from seam to seam and from mine to mine. The operating conditions used in this example are as follows: TABLE 1-2 OPERATING CONDITIONS Pressure 80-100 psi Peak Temperature 1490°F Oxidant pure 0 2 Oxidant Inlet flux 117 Lb/ft 2 hr Combustion Front Velocity 21.7 feet/hour Particle Size 1/4 inch minus The following Tables 1-3, 1-4, and 1-5 show the analyses of the processed solid coal or char, the gaseous product, and a material balance which resulted from this first test run. TABLE 1-3 CHAR ANALYSIS (Weight %) Moisture 5.08% Ash 9.64% Volatile Matter 26.76% Fixed Carbon 58.52% Total 100.00% Heating Valve - 11766 Btu/lb TABLE 1-4 GAS ANALYSIS (Mole %) EXAMPLE II A subbituminous coal of the WyoDak type was treated with a batch process. An analysis of the raw coal is as follows: TABLE II-1 COAL ANALYSIS Proximate Moisture Ash Volatile Matter Fixed Carbon Total Ultimate Carbon *Hydrogen +*0xygen Ash *The Hydrogen and Oxygen values include water in free moisture associated with the sample. +θxygen percentage figured by difference. This second test run was a batch process conducted under the following operating conditions: TABLE II-2 OPERATING CONDITIONS Pressure 500 psi Peak Temperature 1020°F Oxidant pure 0 2 Oxidant Inlet Flux 115 Lbs/ft 2 hr Particle Size 1/8 inch minus The following Tables I1-3, II-4, II-5, and II-6, show the analyses of the processed char, the gaseous product, a material balance and an energy balance which resulted from this second test run. TABLE II-3 CHAR ANALYSIS (Weight %) Proximate *The Hydrogen and Oxygen valves include water in free moisture associated with the sample. +0xygen percentage figured by difference. TABLE II-4 GAS ANALYSIS (Mole %) H 2 CO C0 2 CH 4 *C 2 H 6 +C 38 Total Heating Valve - 350 HHV *Ethylene is included with Ethane +Any Propylene and Butane were included with Propane. TABLE II-5 MATERIAL BALANCE Entering Leaving % (Lbs) (Lbs) Difference Proximate Coal/Char Gas Liquid Total Ultimate Carbon Hydrogen Oxygen TABLE II-6 ENERGY BALANCE (Btu's) Entering Heat of Combustion (Coal) 312,865.0 Leaving Heat of combustion (Char) 169,497.0 Sensible Heat in Char 5,602.0 Heating Value of Gas 103,530.0 Sensible Heat in Gas 4,697.0 Sensible & Latent Heat of Liquids 21.688.0 Net Heat Loss 7,851.0 % Heat Loss 2.5% EXAMPLE III A subbituminous coal of the WyoDak type was treated with a batch process. An analysis of the raw coal is as follows: TABLE III-l COAL ANALYSIS Proximate Moisture 30.1% Ash 6.1% Volatile Matter 32.4% Fixed Carbon 31.4% Total 100.0% ' Ultimate Carbon 47.27% *Hydrogen 6.75% +*Oxygen 38.33% Ash 6.12% Sulfur 0.97% Nitrogen 0.56% Total 100.00% Heating Valve - 8100 Btu/lb *The Hydrogen and Oxygen values include water in free moisture associated with the sample. +0xygen percentage figured by difference. This third test run was a batch process conducted under the following operating conditions: TABLE III-2 OPERATING CONDITIONS Pressure 500 psi Peak Temperature 1090°F Oxidant pure 0 2 Oxidant Inlet Flux 115 Lbs/ft 2 hr Particle Size 1/8 inch to 1/4 inch The following Tables III-3, III-4, III-5, and III-6 show the analyses of the processed char, the gaseous product, a material balance and an energy balance which resulted from this third test run. TABLE III-3 CHAR ANALYSIS (Weight %) Proximate Moisture Ash Volatile Matter Fixed Carbon Total 100.0% Ultimate Carbon 74.90% *Hydrogen 3.64% " +*Oxygen 7.85% Ash 11.36% Sulfur 1.32% Nitrogen 0.93% Total 100.00% Heating Valve - 12,240 Btu/lb *The Hydrogen and Oxygen valves include water in free moisture associated with the sample. +Oxygen percentage figured by difference. TABLE III-4 GAS ANALYSIS (Mole %) H 2 6.6% CO 20.7% C0 2 52.2% CH 4 17.2% *C 2 H 6 2.5% +C 3 H 8 0.8% Total 100.00% Heating Valve - 337 HHV *Ethylene is included with Ethane +Any Propylene and Butane were included with Propane. TABLE III-5 MATERIAL BALANCE Entering Leaving (Lbs) (Lbs) Difference Proximate Coal/Char Gas Liquid Total Ultimate Carbon Hydrogen Oxygen TABLE III-6 ENERGY BALANCE (Btu's) Entering Heat of Combustion (Coal) 344.234.0 Leaving Heat of combustion (Char) 267,579.0 Sensible Heat in Char 9,229.0 Heating Value of Gas 39,913.0 Sensible Heat in Gas 2,813.0 Sensible & Latent Heat of Liquids 21.745.0 Net Heat Loss 2,955.0 % Heat Loss 0.86% EXAMPLE IV A coal from the Rosebud Mine of Hanna, Wyoming, variously classified as a high volatile bituminous coal or a subbituminous coal was treated with a batch process. An analysis of the raw coal is as follows: TABLE IV-1 COAL ANALYSIS Proximate Moisture 10.5% Ash 7.2% Volatile Matter 38.3% Fixed Carbon Total Ultimate Carbon *Hydrogen +*Oxygen Ash Sulfur Nitrogen . Total Heating Valve - 11,170 Btu/lb *The Hydrogen and Oxygen values include water in free moisture associated with the sample. +0xygen percentage figured by difference. This fourth test run was a batch process conducted under the following operating conditions: TABLE IV-2 OPERATING CONDITIONS Pressure 500 psig Peak Temperature 1340°F Oxidant pure 0 2 Oxidant Inlet Flux 115 Lbs/ft 2 hr Particle Size 1/8 inch minus The following Tables IV-3, IV-4, IV-5, and IV-6 show the analyses of the processed char, the gaseous product, a material balance and an energy balance which resulted from this fourth test run. TABLE IV-3 CHAR ANALYSIS (Weight %) Proximate Moisture 4.7% Ash 10.1% Volatile Matter 30.1% Fixed Carbon 55.1% Total 100.0% Ultimate Carbon 70.57% *Hydrogen 4.45% +*Oxygen 12.82% Ash 10.10% Sulfur 0.84% Nitrogen 1.22% Total 100.00% Heating Valve - 11,810 Btu/lb *The Hydrogen and Oxygen valves include water in free moisture associated with the sample. +0xygen percentage figured by difference. TABLE IV-4 GAS ANALYSIS (Mole %) H 2 14.4 CO 16.0 co 2 50 5% CH, 13 6% *C 2 H 6 3 3% +C 3 H 8 2 2% Total 100.0% Heating Valve - 350 HHV *Ethylene is included with Ethane +Any Propylene and Butane were included with Propane. TABLE IV-5 MATERIAL BALANCE Entering Leaving % Proximate Coal/Char Gas Liquid Total Ultimate Carbon Hydrogen Oxygen TABLE IV-6 ENERGY BALANCE (Btu's) Entering Heat of Combustion (Coal) 454.384 Leaving Heat of combustion (Char) 376,629 Sensible Heat in Char 19,460 Heating Value of Gas 18,911 Sensible Heat in Gas 1,553 Sensible & Latent Heat of Liquids 11,526 Net Heat Loss 26,305 % Heat Loss 5.8% The foregoing is considered as illustrative only of the principles of the invention. Since numerous-modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction, operation and examples shown and described herein. Accordingly, all suitable modifications and equivalents may be resorted to falling within the scope of the invention as defined by the claims which follow.

Claims: CLAIMS The embodiment in which an exclusive privilege is claimed is: 1. A method of drying and gasifying a solid, carbonaceous feed material comprising the steps of: placing the feed material in an enclosed chamber; igniting the solid feed material in the chamber to create a combustion zone with a combustion front that advances through the feed material to achieve a thermal restructuring of said solid feed material; flowing an oxidant through said feed material in the chamber in a direction opposite to the advancing movement of the combustion front in the feed material. 2. The method of claim 1, where the solid feed material includes a solid fossil fuel. 3. The method of claim 1, where the solid feed material includes solid biological wastes. 4. The method of claim 1, where the solid feed material is a soil contaminated with volatile toxins. 5. The method of claim 1, where the solid feed material is an adsorbent bed contaminated with volatile toxins. 6. The method of claim 1, where the oxidant is air. 7. The method of claim 1, where the oxidant is oxygen enriched air. 8. The method of claim 1, where the oxidant is pure oxygen. 9. The method of claim 1, including the step of partially drying the solid fossil fuel prior to ignition. 10. The method of claim 1, including the step of adding a catalyst to the solid feed material. 11. The method of claim 1, including the step of maintaining including the step of maintaining the oxidant gas flow pressure in the chamber in the range of about 0 psi to 5,000 psi. 12. The method of claim 11, including the step of maintaining the oxidant gas pressure in the chamber in the range of about 0 psia to 600 psia. 13. The method of claim 1, including the step of maintaining the temperature of combustion in the range of about 400 λ F to 3,000'F. 14. The method of claim 13, including the step of maintaining the temperature of the combustion in the range of about δOO'F to 1,500'F. 15. The method of claim 12, where the temperature of combustion is controlled by the constituents of the solid feed material, the initial bed temperature, the type of oxidant, the quantity of oxidant, the oxidant flow rate, and the oxidant pressure. 16. The method of claim 14, where the temperature of combustion is additionally controlled by the addition of a catalyst. 17. The method of claim of claim 1, where a level of combustion of the solid feed material is in the range of about 5% to 100%, said level of combustion being controlled by adjustment of the type of oxidant, the constituents of the solid feed material, the type of oxidant, the quantity of oxidant, the oxidant flow rate, the oxidant pressure and the combustion chamber. 18. Apparatus for drying and gasifying organic materials, comprising: an elongated container forming an enclosed chamber; feed material inlet means for feeding said organic materials into said chamber; igniting means positioned in said chamber for igniting said organic material in said chamber to create a combustion zone with an advancing combustion front in the organic material; oxidant inlet means connected to said chamber a spaced distance from said igniting means for introducing an oxidant gas into said chamber in such a manner that the oxidant gas flows through the organic material to said combustion front; and gas removal outlet means connected to said chamber a spaced distance from said oxidant inlet means such that the combustion front is positioned between said oxidant inlet means and said gas remvoal outlet means. 19. The apparatus of claim 18, including solid material outlet means on said container for removing oxidized organic solid materials from said chamber, said solid material outlet means being positioned such that said combustion front is between said feed material inlet means and said solid material outlet menas. 20. The apparatus of claim 19, including feed means for moving said organic material through said chamber in a direction opposite the direction in which said combustion front advances through said organic material. 21. The apparatus of claim 20, wherein said feed means is coordinated in speed with the flow of oxidant gas into said chamber in such a manner that the combustion front effectively remains stationary in the chamber as the organic material advances through the chamber and the oxidized organic material is removed from the chamber. 22. The apparatus of claim 21, wherein said container is an elongated cylindrical vessel and said feed means includes an auger extending partially through said cylindrical vessel with its axis of rotation oriented parallel to the longtidunial axis of said cylindrical vessel. 23. The apparatus of claim 18, wherein said container is capable of holding an elevated pressure therein and said oxidant is flowed into said chamber under sufficient pressure to create a net flow of oxidant and combustion gas products through said container in a direction opposite the direction of advance of said combustion front through said organic material.

Inventors: GUNN ROBERT D, GUNN, ROBERT, D.
Applicants: GUNN ROBERT D, GUNN, ROBERT, D.
Application year: 1989
Main classification: F23G5
IPC codes: C10B49, C10B53, C10J3