Method of gasifying solid organic materials

Abstract

A heating system for producing heat by the gasification of solid, organic biomass materials. A mass of such materials is maintained on a grate in a primary oxidation chamber of the catalytic type, and materials in such mass are gradually heated in a deficiency of oxidation for full oxidation of such materials to produce a gaseous, combustible effluent. The gaseous combustible effluent is transferred through an insulated exit duct to a secondary oxidation chamber where it is further oxidized to a fully oxidized state by burning. In one embodiment, the insulated exit duct has a restricted inlet portion within the primary oxidation chamber to serve as a flame deflector. The gaseous effluent from the secondary oxidation chamber is used as a heat source for a water tube boiler. A storage hopper is provided to store the biomass feed materials for delivery to the primary oxidation chamber. The bottom of the storage hopper is inverted and reciprocating plates are provided along the bottom of the storage hopper. The reciprocation of the reciprocating plates helps to keep the biomass feed materials in the storage hopper from bridging or compacting to promote the smooth flow of feed materials through the hopper. Counterrotating helical chipping blades can be provided within the hopper near the outlet thereof to reduce the size of any oversized or agglomerated portions of the biomass feed materials. The inner wall surface of the primary oxidation chamber is provided with a plurality of inwardly projecting members spaced along the periphery thereof for establishing a recirculating gaseous flow path in the primary oxidation chamber.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method for gasifying solid organic materials to convert the chemical energy stored in such materials to thermal energy. More particularly, this invention relates to a method for gasifying biomass materials, such as wood chips, sawdust, corn cobs, bagasse, tobacco waste and the like. The invention utilizes a new and improved feed hopper with inclined reciprocating plates lying along the bottom of the feed hopper to prevent the feed material from jamming in the hopper, even when the feed stock is moist and/or irregularly or nonuniformly shaped, and it utilizes a domed catalytic oxidation chamber where the feed stock is partially oxidized at an elevated temperature. The high-temperature gases produced by the practice of the invention can be utilized to advantage, for example, as the thermal energy source for a conventional water tube boiler.

2. Description of the Prior Art

It has long been recognized that many industrial and agricultural solid organic by-products, such as wood chips, sawdust, corn cobs, bagasse, tobacco waste, and the like, contain large amounts of chemical energy. The substantial increases in the cost of traditional fuels, such as fuel oil and natural gas, which took place during the 1970's, have provided substantial economic incentive to try to develop effective and efficient techniques for recovering the energy in these organic by-products, energy that traditionally was not recovered to any substantial extent. Such organic materials, which are frequently referred to as "biomass" materials, are now successfully utilized to some extent as fuel in some very large industrial systems, for example, in firing the recovery boiler in a pulp or paper mill. However, the high capital cost which has heretofore been associated with biomass energy recovery systems has precluded their successful use in small or even medium size energy recovery systems. Medium size energy recovery systems, viz., of the size from about 4,000,000 to 8,000,000 BTU/Hr., are used in schools, nursing homes, and small industrial and commercial establishments and, to date, biomass fuels have not been satisfactorily utilized as fuel in heating systems for such facilities. Among the U.S. Patents that have been issued on inventions relating to the recovery of energy from wood chips or similar organic materials are U.S. Pat. No. 4,184,436, to Palm, et al.; U.S. Pat. No. 4,312,278, to Smith, et al.; U.S. Pat. No. 4,366,802, to Goodine; U.S. Pat. No. 4,321,877, to Schmidt, et al.; and U.S. Pat. No. 4,430,948, to Ekenberg. However, it is not known that any of the inventions described in these patents have been successfully adapted to recover biomass energy on a cost-effective basis in small and medium size energy recovery systems.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a relatively simple method and apparatus for the recovery of energy from biomass materials by the gasification of such materials. The method and apparatus according to the present invention can be utilized on a cost-effective basis, due to the relatively low capital cost of the apparatus, to cleanly and efficiently recover energy at medium rates of recovery, and even at low rates of recovery, for example, approximately 100,000 BTU/Hr., rates which typically are those needed in home heating units. The apparatus according to this invention utilizes a domed catalytic oxidation chamber where the biomass feed stock is partially oxidized slowly in a process in which it first chars, preferably in a deficiency of oxygen, producing a high temperature combustible effluent which is burned in a secondary oxidation chamber, and the effluent from the secondary oxidation chamber can be utilized as a thermal energy source, for example, in an otherwise conventional water tube boiler as a substitute for the effluent from the fuel oil or gas burner that is normally utilized in conjunction with a boiler of such type.

During normal operation, the biomass feed stock is mechanically fed to the domed catalytic oxidation chamber from a storage hopper by means of a screw feeding system, preferably automatically in response to the demand for energy from the system. The feed hopper has a generally inwardly and downwardly tapered bottom, and reciprocating plates extend along the inwardly and downwardly tapering bottom plates of the hopper to help feed the biomass feed stock into the screw feeding system and to help keep the feed stock from clogging up or "bridging" in the hopper due to the high moisture content of many of such biomass feedstock materials and/or the irregular or nonuniform shape of such materials. Counterrotating chipper blades may be provided within the hopper, near the outlet therefrom, to break up large items in the feed stock that passes through the hopper, for example, blocks of wood in a wood chip feed stock. The domed catalytic oxidation chamber is provided with a grate system for removing ash and non-combustible contaminants, such as sand, dirt, stones, and rocks from the chamber.

The biomass oxidation method according to the present invention can be utilized to particular advantage in remote Northern regions, where winters are long and cold, conventional fuels are expensive and occasionally scarce because of the long delivery distances from remote major population centers, and where biomass feed stocks are plentiful and inexpensive as a result of the agricultural and/or forest-based business activities that are frequently conducted in such regions.

Accordingly, it is an object of the present invention to provide an improved method for producing energy by the gasification of organic materials.

More particularly, it is an object of the present invention to provide an improved method for efficiently producing energy at relatively low rates by the gasification of organic materials.

It is a further object of the present invention to provide an improved hopper for feeding solid materials into a material handling system.

It is also an object of the present invention to provide an improved catalytic oxidation chamber for at least partially oxidizing solid organic materials.

For a further understanding of the present invention, attention is directed to the drawings and the following description thereof, to the detailed description of the preferred embodiment, and to the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view, partially in section, of an apparatus for gasifying solid organic materials according to the present invention;

FIG. 2 is a fragmentary elevational view, in section, of a portion of the apparatus depicted in FIG. 1;

FIG. 3 is a fragmentary elevational view, partially in section a at an enlarged scale, of a portion of the apparatus depicted in FIGS. 1 and 2;

FIG. 4 is a plan view of the apparatus depicted in FIG. 3;

FIG. 5 is a fragmentary elevational view, in section, of another portion of the apparatus depicted in FIG. 1;

FIG. 6 is a sectional view taken along lines 6--6 of FIG. 5;

FIG. 7 is a view similar to FIG. 5 of an alternative embodiment of a portion of the apparatus according to the present invention;

FIG. 8 is a sectional view taken on line 8--8 of FIG. 7;

FIG. 9 is a fragmentary view of an alternative embodiment of the portion of the apparatus that is shown in FIG. 3;

FIG. 10 is a plan view of the apparatus depicted in FIG. 9;

FIG. 11 is a fragmentary view of a modified embodiment of the apparatus that is shown in FIGS. 9 and 10;

FIG. 12 is a fragmentary plan view of the apparatus depicted in FIG. 11;

FIG. 13 is a fragmentary side elevational view of the apparatus depicted in FIGS. 11 and 12; and

FIG. 14 is a schematic view of the drive mechanism of the apparatus depicted in FIGS. 11, 12 and 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As is shown in FIG. 1, an apparatus for practicing the present invention utilizes a drive assembly, indicated generally by reference numeral 100, a storage hopper assembly, indicated generally by reference numeral 200, a feed assembly, indicated generally by reference numeral 300, which is driven by the drive assembly 100 and which feeds material from the storage hopper assembly 200 into a primary oxidation chamber of the catalytic type, indicated generally by reference numeral 400. The unoxidized or unburned portion of the feed material fed into the primary oxidation chamber 400 is withdrawn therefrom and transported away by a clean-out assembly, indicated generally by reference numeral 500 and, in the preferred embodiment of the invention, the material fed into the primary oxidation chamber 400 is only partially oxidized therein, and there is provided a secondary oxidation chamber, indicated generally by reference numeral 600, to complete the oxidation of the partially oxidized feed material, which is now in gaseous form, as it leaves the primary oxidation chamber 400. The fully oxidized gaseous material from the secondary oxidation chamber 600 is used as a source of heat energy in a device which requires heat energy, and in the preferred embodiment of the present invention this takes a form of an otherwise conventional water tube boiler, indicated generally by reference numeral 700.

The material which is to be oxidized in the apparatus of FIG. 1 is delivered to the storage hopper assembly 200 in any suitable manner, for example, manually from a pile of such material or by means of a conveyor, not shown, from a self-unloading truck body of an appropriate type, also not shown, or in any other suitable manner. In FIG. 1 the transfer of the material into the storage hopper assembly 200 is indicated generally by an arrow which is identified by reference letter S.

The feed material which is delivered into the storage hopper assembly 200 may be any of the wide range of solid, organic materials of a type which is frequently referred to as "biomass" materials, and suitable materials of this type include wood chips, sawdust, corn cobs, and bagasse. These materials are usually waste by-product materials from various agricultural or forest-based industrial processes, and contain substantial amounts of chemical energy which is capable of being converted to thermal energy by suitable oxidation processes. Such materials are, however, difficult to handle because they are usually moist and are nonuniform or irregular in shape, and heretofore it has been difficult to efficiently and effectively oxidize such materials because of their high moisture content, their nonuniform chemical composition, and their frequent contamination with non-oxidizable materials, such as sand, dirt, rocks, and stones.

As noted above, the feed material from the storage hopper assembly 200 is oxidized to a gaseous state in the primary oxidation chamber 400, preferably to a state which is not fully oxidized. The primary oxidation chamber 400 is defined by a wall 401, and the chamber which is defined by the wall 401 is in the shape of a vertically extending cylinder 402 which has a flat bottom 403 and which opens at its top into an open, downwardly facing hemispherical dome 404. As is shown in FIG. 5, the wall 401 is made up of a multiplicity of layers, the innermost layer 405 of which is a layer of a high-temperature catalytic refractory that is capable of withstanding the elevated temperatures that will develop within the primary oxidation chamber 400, for example, temperatures in the range of approximately 2300.degree. F. to approximately 2500.degree. F., and that is capable of catalytically promoting the oxidation of the biomass feed material that is delivered into the primary oxidation chamber 400. A cementitious plastic refractory consisting of approximately 48 to 51% silica (SiO.sub.2), 43 to 46% alumina (Al.sub.2 O.sub.3), 1 to 2% iron oxide (Fe.sub.2 O.sub.3), 0.3 to 0.9% lime (CaO), 0.2 to 0.7% magnesia (MgO), 1.5 to 2.5% titania (TiO.sub.2) and 0.8 to 1.3% alkalies (Na.sub.2 O+K.sub.2 O) on a calcined basis manufactured by A. P. Green Company of Mexico, Mo. under the trademark SUPER HYBOND has been found to be a satisfactory material for use in forming the innermost layer 405. In addition to the innermost layer 405 of catalytic refractory material, the wall 401 also includes an insulating layer 406 in back of the innermost layer 405 to reduce a loss of heat through the wall 401 of the primary oxidation chamber 400. The insulating layer 406 may be but a single layer of a suitable insulating material, for example, insulating brick or insulating fire brick, or it may be made up of a multiplicity of layers of similar or dissimilar insulating materials if it is desire to minimize the transfer of heat through the wall 401 to a degree that cannot be accomplished in a satisfactory manner by means of a single layer of insulating material, all of which is known in the art. In any case, the final layer in the multiplicity of layers in the wall 401 is a structural layer 407 of sheet metal, for example, plate steel, to provide the necessary strength and rigidity for the primary oxidation chamber 400.

The biomass feed material from the storage hopper assembly 200 is introduced into the primary oxidation chamber 400 through an opening 408 in the bottom 403 of the primary oxidation chamber 400, the center of the opening 408 preferably lying along the vertical central axis of the cylinder 402 of the primary oxidation chamber 400. An annular air distributor 409 surrounds the opening 408, and feed material is introduced upwardly through the opening 408 and the annular air distributor 409 by means of the feed assembly 300. During normal operating conditions, as is illustrated in FIG. 5, the feed material rises over the top of the annular air distributor 409 and it rests on an annular grate, indicated generally by reference numeral 420, until it forms a mass of such material, indicated generally by reference letter M, which is the normal or equilibrium condition of the primary oxidation chamber 400 when it is operational.

To bring the primary oxidation chamber 400 to an operational condition on start up, the feed assembly 300 is activated to develop the mass M of feed material on the annular grate 420. The mass M of feed material is then ignited, for example, manually, a portion 401a of the wall 401 of the primary oxidation chamber 400 being removable from the remaining portion of the wall 401 to facilitate the igniting of the mass M, and/or to permit the inspection and/or cleaning out of the chamber of the primary oxidation chamber 400 when it is nonoperational. To facilitate the removal of the removable portion 401a of the wall 401, the removable portion 401a is mounted on a swing-out arm assembly 410, as is shown in FIG. 1. To facilitate bringing the mass M of feed material up to its normal operating temperature, fuel oil or other readily combustible supplemental fuel can be added to it, and this can be done manually through the opening provided when the removable portion 401a is removed.

The oxidation of the feed material in the primary oxidation chamber 400 requires a source of oxygen, and ambient air has been found to be a suitable source for this purpose. An air blower 411 of standard construction is used to provide ambient air to the primary oxidation chamber 400, the air being introduced into the interior of the mass M of feed material through the annular air distributor 409.

As the feed material in the mass M in the primary oxidation chamber 400 moves from the bottom to the top of the mass, it will get hotter and hotter, and volatile ingredients in such material will begin to dissipate therefrom, being carried away by the air from the blower 411 which is rising through such material. As the feed material in the mass M of feed material loses more and more of its volatile ingredients it will char until, eventually, it is exposed to the full operating temperature inside the primary oxidation chamber 400, at which time all of the organic constituents of such feed material will gasify and will pass from the primary oxidation chamber 400 as an incompletely oxidized gaseous effluent, the effluent leaving the primary oxidation chamber 400 through an insulated exit duct 412.

The oxidation of the feed material in the mass M of the feed material proceeds more satisfactorily if the amount of feed material in the mass M of feed material is maintained at a relatively constant value. To accomplish this, a reciprocable probe 414 is provided extending downwardly into the primary oxidation chamber 400 through the wall 401 to determine the elevation of the top of the feed material in the mass M of feed material. Suitable instrumentation, not shown, is provided to control the rate of the delivery of the feed material into the primary oxidation chamber 400 by the feed assembly 300 as a function of the elevation of the top of the feed material in the mass M of feed material, as measured by the reciprocable probe 414, lo maintain such elevation at a substantially constant value, and thereby to contain the mass M of feed material at a substantially constant value. The reciprocable probe 414 is preferably internally cooled, by circulating air or water therethrough, to permit it to function satisfactorily in the high temperature environment of the primary oxidation chamber 400.

The air which is added to the primary oxidation chamber 400 through the annular air distributor 409 appears to repeatedly flow up and down through the mass of feed material M in the primary oxidation chamber 400, as is illustrated by the arrows A and B in FIG. 5, this continuous recirculation of air, which progressively changes in composition to the gaseous oxidized feed material, being facilitated by the hemispherical shape of the dome 404 of the primary oxidation chamber 400. The recirculating effect may be enhanced by channelizing the flow of gaseous material within the primary oxidation chamber 400 by providing a spaced-apart series of vertical, radially inward projections or flutes 413 in the wall 401 of the primary oxidation chamber 400. The flutes 413 can be advantageously formed out of metal pipe, for examples, 11/4 or 11/2 inches in diameter, and these pipes can be embedded in the innermost layer 405 at the time it is cast, preferably to the extent of approximately one-half of the outside diameter of each of the metal pipes. While the metal pipes that make up the flutes 413 are exposes to the high temperature conditions existing in the primary oxidation chamber 400, it is possible to utilize conventional, low-temperature steel pipe to form such flutes 413 by providing a blower or other means, not shown, to circulate a coolant, such as air or water, through the flutes when the primary oxidation chamber 400 is operational to thereby avoid the need for using expensive, special high temperature alloys in the construction of such flutes 413.

The gaseous effluent leaving the primary oxidation chamber 400 leaves through the insulated exit duct 412 and passes into the secondary oxidation chamber 600. The secondary oxidation chamber 600 is defined by an insulated wall 601 and, in the preferred embodiment, the insulated wall 601 is arranged to define a secondary oxidation chamber which is in the form of a cylinder whose longitudinal axis is coextensive with the longitudinal axis of the insulated exit duct 412 of the primary oxidation chamber 400. A secondary oxidant is added to the secondary oxidation chamber 600 to burn or completely oxidize gaseous materials flowing into the secondary oxidation chamber through the insulated exit duct 412 from the primary oxidation chamber 400. Again, ambient air is satisfactory for use as the secondary oxidant and may be provided to the secondary oxidation chamber 600 by means of a second blower 602, again of conventional construction. Preferably, the second blower 602 is arranged with its outlet 603 entering the secondary oxidation chamber 600 in a direction which is tangential to the wall 601 which defines the secondary oxidation chamber 600. A swirling or cyclonic action will develop within the secondary oxidation chamber 600 by virtue of the tangential admission of secondary air through the blower outlet 603, and any solid particles which are carried into the secondary oxidation chamber 600 will be driven to the outermost portions of the secondary oxidation chamber 600 by centrifugal force resulting from this swirling action and may be readily removed from the secondary oxidation chamber 600 by means of a radial port 604 at the bottom of the secondary oxidation chamber 600. Solid particles leaving the secondary oxidation chamber 600 through the radial port 604 are collected and taken away to a storage and disposal location, not shown, by means of a collector 605, shown fragmentarily and schematically. Sufficient air is added to the secondary oxidation chamber 600 by means of the second blower 602 to fully oxidize the partially oxidized gaseous materials entering the secondary oxidation chamber 600 from the insulated exit duct 412 of the primary oxidation chamber 400 and, preferably, excess air is added to the secondary oxidation chamber 600 to prevent excessively high temperatures from developing therein.

In the preferred operation of the apparatus according to the present invention, the temperature in the secondary oxidation chamber 600 should be limited to no more than approximately 2800.degree. F., and this can be done by utilizing total air added to the system, including the air added to the primary oxidation chamber 400 by the air blower 411 and the air added to the secondary oxidation chamber 600 by the second blower 602, in an amount which equals approximately 150% of that required for full oxidation of the feed material added to the primary oxidation chamber 400. The fully oxidized, high-temperature gaseous material from the secondary oxidation chamber 600 exits from the secondary oxidation chamber 600 as an effluent through a second insulated duct 606 and passes into the water tube boiler 700, which may be considered to be of otherwise conventional construction, to be used as the source of heat for water flowing through tubes in such water tube boiler 700, as a substitute for the effluent from an oil or gas burner that is usually used in conjunction with such water tube boiler 700 as the source of heat therefor.

The annular grate 420 of the primary oxidation chamber 400 is made up of a first annular plate member 421 and a second annular plate member 422, with the first annular plate member 421 being superimposed on the second annular plate member 422. The first annular plate member 421 is provided with a spaced-apart series of radially extending slots 423 and the second annular plate member 422 is provided with a spaced-apart series of radially extending slots 424. The radially extending slots 424 in the second annular plate member 422 are normally offset with respect to the radially extending slots 423 in the first annular plate member 421, as is shown in FIG. 6. In this condition, neither the feed material in the chamber 400 nor any contaminants therein will be able to exit from the primary oxidation chamber 400 through the radially extending slots 423 of the first annular plate member 421. However, the first annular plate member 421 is mounted so as to be rotatable through a limited arc with respect to the second annular plate member 422, and a handle 425 is provided to manually effect such rotation on a periodic basis, as desired. The rotation of the first annular plate member 421 with respect to the second annular plate member 422 by means of the handle 425 is effective to bring the radially extending slots 423 in the first annular plate member 421 into alignment with the radially extending slots 424 in the second annular plate member 422. When this happens, any nonoxidizable materials which were in the original feed material, and which normally work their way to the bottom of the mass M of such feed material as the oxidation process continues, can exit from the primary oxidation chamber 400 through the aligned radially extending slots 423 and 424, by gravity, assisted to some extent by the vibration resulting from the rotation of the first annular plate member 421. These withdrawn materials are received in the clean-out assembly 500 which is disposed beneath the primary oxidation chamber 400, and they may be automatically withdrawn from the clean-out assembly 500 by means of a screw conveyor 501 associated therewith, to be deposited on a take-out conveyor 502, shown fragmentarily. Where desired, of course, the periodic partial rotation of the first annular plate member 421 with respect to the second annular plate member 422 may be mechanically actuated, for example, by means of a hydraulic system or a pneumatic system, not shown, and the removal of the withdrawn materials from the clean out assembly 500 may be done manually rather than mechanically as illustrated.

The storage hopper assembly 200, which will subsequently be described in detail, has an elongate opening 201 in the bottom thereof, and the elongate opening 201 is longitudinally aligned with a horizontal screw member 301 of the feed assembly 300, with the horizontal screw member 301 being disposed immediately below the elongate opening 201 of the storage hopper assembly 200. The feed assembly 300 also includes a tubular housing 302 which surrounds the horizontal screw member 301, except the portion of the horizontal screw member 301 which is in communication with the elongate opening 201 of the storage hopper assembly 200. The horizontal screw member 301 of the feed assembly 300 is normally rotated by the drive assembly 100, which will subsequently be described in detail, to advance the feed material from the storage hopper assembly 200 through the tubular housing 302 to the primary oxidation chamber 400. Preferably, as is shown in FIG. 2, the feed assembly 300 also utilizes a second or vertical screw member 303, which is disposed in a vertical position and which serves to vertically transfer feed material from the end of the horizontal screw member 301 upwardly into the primary oxidation chamber 400. Preferably, the tubular housing 302 of the feed assembly 300 is rectangular in its cross-sectional configuration, so that the feed material being advanced therethrough by the horizontal screw member 301 is constantly experiencing a change in the thickness of the passage through which it is traveling. It has been found that this arrangement is useful in preventing the jamming of feed material within the tubular housing 302, a phenomenon which can occur if the feed material is unusually moist, or otherwise inclined by its shape or composition to "ball-up."

The horizontal screw member 301 has a horizontal screw 301a which is arranged on a shaft 301b. The shaft 301b is journalled in a first bearing 304 which is disposed outboard of the elongate opening 201 of the storage hopper assembly 200 and a second bearing 305 which is disposed at the juncture of the horizontal screw member 301 and the vertical screw member 303. The shaft 301b of the horizontal screw member 301 extends into the drive assembly 100 where it is rotatably driven by means of a hydraulic drive motor 101 that receives pressurized hydraulic fluid from a hydraulic reservoir 102 of conventional construction. The drive assembly 100 also includes a cam bearing 103 Which is caused to rotate eccentrically when the shaft 301b of the horizontal screw member 301 is rotated by the hydraulic motor 101, for purposes which will be subsequently described. If it is desired to prevent the imposition of excessive torque on the shaft 301b of the horizontal screw member 301, an outermost portion 301c of the shaft 301b may be separated from the remainder thereof, and the separated portions may be connected to one another by means of a torque-limiting coupling 104 of the drive assembly 100. Spaced-apart bearing members 105 and 106 are provided to rotatably support the outermost portion 301c of the shaft of the screw member 301. Another bearing member 107, which is spaced-apart from the bearing member 106, and a bearing member 108, which is spaced-apart from the bearing member 107, are provided to rotatably support the shaft portion 301b, in conjunction with the first and second bearings 304 and 305 of the feed assembly 300. As shown, the torque-limiting coupling 104 is mounted between the bearing members 106 and 107 and the cam bearing 103 is mounted between the bearing member 107 and the first bearing 304 of the feed assembly 300.

The storage hopper assembly 200 is defined by a sheet steel or similar wall 202 that forms an open top parallelepiped upper section 200a of the storage hopper assembly 200 and an upwardly facing inverted lower section 200b. The lower section 200b commences at the bottom of the upper section 200a and extends downwardly therefrom, terminating in the elongate opening 201 above a portion of the horizontal screw member 301 as previously described. The upper section 200a of the storage hopper assembly 200 is defined by an upper rectangular portion 202a of the wall 202, and the lower section 200b of the hopper assembly is defined by a series of trapezoidal portions 202b, 202c, and 202d arranged end to end in a U-shaped pattern, and by an end wall portion 202e. The end wall portion 202e closes the end between the trapezoidal portions 202b and 202d that is opposed to the end that is closed by the trapezoidal portion 202c.

The feed material from source S flows downwardly through the storage hopper assembly 200 by gravity, and exits into the feed assembly 300 through the elongate opening 201 to be carried into the primary oxidation chamber 400 by the feed assembly 300, as heretofore described. The flow of the feed material through the storage hopper assembly 200 is, however, subject to compaction or bridging within the storage hopper assembly 200 by virtue of the high moisture content which, at least occasionally, is characteristic of many biomass feed materials and/or by virtue of the irregular or nonuniform shape of many of such materials. When such compaction or bridging occurs, the flow of feed material through the storage hopper assembly 200 may no longer proceed properly, thereby disrupting the proper operation of the apparatus. Conventional anti-bridging techniques, such as vibrators mounted externally to the storage hopper assembly 200 on the wall 202 and vibrating rods extending through the storage hopper assembly 200, have been tried, but these were found to be unsatisfactory in their consistency and occasionally even appeared to aggravate the problem by further compacting the feed materials.

According to the present invention, bridging within the storage hopper assembly 200 is prevented by providing reciprocating plates 203, 204, and 205 that lie along the trapezoidal portions 202b, 202c, and 200d of the wall 202, respectively. The reciprocating plates 203, 204, and 205 are reciprocated in unison, by means which will subsequently be described more fully, in a first direction indicated by the arrows A in FIG. 4, and then in the reverse direction indicated by the arrows B. The stroke of the reciprocating movement in each direction is typically of the order of 15/6 inches for use in the processing of wood chips, and reciprocating movement of the reciprocating plates 203, 204, and 205 of this order of magnitude has been found to be quite effective in preventing bridging or compaction of wood chips within the storage hopper assembly 200.

The reciprocating plate 203 is mounted on a spaced-apart pair of support arms 206 and 207. The support arms 206 and 207 extend through the wall 202 and are pivotally connected, respectively, to the ends of first and second links 208 and 209 which are non-pivotally attached to a common drive shaft 210. The drive shaft 210 has a third link 211 non-pivotally attached to it, and the third link 211 is pivotally connected to a rod 212 which, in turn, is connected to the cam bearing 103 of the drive assembly 100. Thus, when the drive assembly 100 is operated, the cam bearing 103 will be rotated and this will impart generally reciprocatory movement to the rod 212. The generally reciprocatory movement of the rod 212 will cause the third link 211 to oscillate to and fro, and this will cause the drive shaft 210 to rotate for a part of a revolution in a first direction and then for a part of a revolution in the opposite direction. The rotation of the drive shaft 210, as described, will cause the first and second links 208 and 209 to oscillate to and fro, and this oscillating movement of the first and second links 208 and 209 will translate into reciprocating movement of the support arms 206 and 207, and thereby into reciprocating movement of the reciprocating plate 203.

The reciprocating plate 205 is mounted on a second spaced-apart pair of support arms 213 and 214. The support arms 213 and 214 also extend through the wall 202 and are pivotally connected, respectively, to fourth and fifth links 215 arid 216. The fourth and fifth links 215 and 216 are non-pivotally connected to a second drive shaft 217. The second drive shaft 217 has a sixth link 218, and the sixth link 218 is pivotally connected to an end of a connecting rod 220, the other end of which is pivotally connected to a seventh link 219 that is non-pivotally attached to the drive shaft 210. Thus, the rotation of the drive shaft 210, as heretofore described, will cause the seventh link 219 to oscillate to and fro, and this will result in to and fro oscillating movement of the sixth link 218 by virtue of the connection of the sixth link 218 to the seventh link 219 by means of the connecting rod 220. The to and fro oscillating movement of the sixth link 218 will cause the second drive shaft 217 to rotate for a part of a revolution in a second directions and this will cause the fourth and fifth links 215 and 216 to oscillate to and fro. The oscillating movement of the fourth and fifth links 215 and 216 will translate into reciprocating movement of the second spaced-apart pair of support arms 213 and 214, and thereby into reciprocating movement of the reciprocating plate 205. With the structure as described, the reciprocation of the reciprocating plate 205 will inherently be in unison with the reciprocation of the reciprocating plate 203.

The reciprocating plate 204 is mounted on a support arm 221 which extends through the wall 202 and is connected to an eighth link 222. The eighth link 222 is mounted on the drive shaft 210 and will oscillate to and fro when the drive shaft 210 rotates as previously described. The oscillation of the eighth link 222 will translate into reciprocating movement of the support arm 221, and thereby into reciprocating movement of the reciprocating plate 204. With the structure as described, the reciprocation of the reciprocating plate 204 will inherently be in unison with the reciprocation of the reciprocating plates 203 and 205. By using the cam bearing 103 of the drive assembly 100 to actuate the reciprocation of the reciprocating plates 203, 204, and 205, as described, the reciprocation of the reciprocating plates 203, 204, and 205 will inherently be at a rate which is proportional to the rate at which the drive assembly permits feed material to be withdrawn from the storage hopper assembly 200.

It is to be noted that it is contemplated that the storage hopper assembly 200, as heretofore described, can be used to advantage in the storage and dispensing of a wide variety of solid and semisolid materials, and that it is not limited in its utility to the feeding of biomass or solid organic materials. Specifically, it is contemplated that the storage hopper assembly 200 can be used to advantage in the storage and dispensing of coal, various metallic and nonmetallic ores, sand, and moist cement, particularly where any such material is prone to compacting because of its moisture content or otherwise.

In the practice of the present invention it has been found that a primary oxidation chamber 400 with an internal diameter in the cylinder 402 of 30 inches is satisfactory for a heating unit to be used to produce heat at the approximate rate of up to 1,000,000 BTU/hr., and that an internal diameter of 62 inches is satisfactory for a heating unit to be used to produce heat at the approximate rate of up to 8,000,000 BTU/hr. It has also been found that the wall 401 of the primary oxidation chamber 400 of the invention can be satisfactorily formed using a 1 inch thick innermost layer 405 of the catalytic refractory, a 4 inch thick insulating layer 406 of insulating brick, and a 1/8 inch thick steel plate structural layer 407.

While the invention has been described in reference to the use of the heat produced thereby to heat water in a water tube boiler 700, the heat produced by the invention can also be used in other ways, for example, in the generation of electricity.

FIGS. 7 and 8 illustrate an alternative embodiment of a primary oxidation chamber of the catalytic type, indicated generally by reference numeral 1400, which may be used in the practice of the present invention. The primary oxidation chamber 1400 is shown as receiving feed material from an alternative embodiment of a feed assembly, shown fragmentarily and indicated generally by reference numeral 1300. However, it is to be understood that the feed assembly 300 of the embodiment of FIGS. 1 through 6 may be used with the primary oxidation chamber 1400 and that the feed assembly 1300 may be used with the primary oxidation chamber 400 of the embodiment of FIGS. 1 through 6.

The primary oxidation chamber 1400 is defined by a wall 1401, and the chamber which is defined by the wall 1401 is in the shape of a vertically extending cylinder 1402 which has a flat bottom 1403 and which opens at its top into an open, downwardly facing hemispherical dome 1404. As is shown in FIG. 7, the wall 1401 has a portion 1401a which is selectively removable to facilitate the start-up of the primary oxidation process within the primary oxidation chamber 1400 and/or to permit the inspection and/or the cleaning out of the primary oxidation chamber. Further, the wall 1401 is made up of a multiplicity of layers including an innermost layer 1405 of a high-temperature catalytic refractory, an insulating layer 1406 in back of the innermost layer 1405, and a structural layer 1407 of sheet metal.

Biomass feed material is introduced into the primary oxidation chamber 1400 through an opening 1408 in the bottom 1403 of the primary oxidation chamber 1400, the center of the opening 1408 preferably lying along the vertical central axis of the cylinder 1402 of the primary oxidation chamber 1400. An annular air distributor 1409 surrounds the opening 1408, and feed material is introduced upwardly through the opening 1408 and the annular air distributor 1409 by means of the feed assembly 1300 which includes a horizontal screw member 1301 and a vertical screw member 1306 that is separately driven by a drive assembly 1307.

Oxygen is supplied to the primary oxidation chamber 1400 by means of first and second air blowers 1411a and 1411b, the first air blower 1411a which introduces air through the annular air distributor 1409 being the primary source of air for the primary oxidation chamber. The second air blower 1411b introduces air into the primary oxidation chamber 1400 through the wall at various levels above the flat bottom 1403 of the primary oxidation chamber 1400 to mix with the gasifying feed material in stages, based on the need for oxygen at various times during the primary oxidation process that is being performed in the primary oxidation chamber 1400.

Gaseous effluent leaves the primary oxidation chamber 1400 through an insulated exit duct 1412, which has a restricted entry portion 1412a that extends into the primary oxidation chamber 1400. The restricted entry portion 1412a, which has a plurality of spaced restricted openings 1412b thereinto, serves as a flame deflector to prevent the passage of any flame from the primary oxidation chamber 1400 and, further, ensures the thorough mixing and preheating of the gaseous effluent leaving the primary oxidation chamber 1400. The gaseous effluent that enters the insulated exit duct 1412 passes therethrough and enters a secondary oxidation chamber 1600. The secondary oxidation chamber 1600 is defined by an insulated wall 1601 and is in the form of a cylinder whose longitudinal axis is coextensive with the longitudinal axis of the insulated exit duct 1412 of the primary oxidation chamber 1400.

Secondary air is added to the secondary oxidation chamber 1600 by a secondary air blower 1602, to ensure that any incompletely oxidized gases it tie gaseous effluent that enters the secondary oxidation chamber will be further burned or oxidized therein. Further, a sufficient excess quantity of secondary air is added to the secondary oxidation chamber 1600 to prevent excessively high temperatures from developing therein. The fully oxidized high temperature gaseous material from the secondary oxidation chamber 1600 exits therefrom through a second insulated duct 1606, and passes into a device to use such high temperature gaseous material, not shown, which may be a water tube boiler, such as the water tube boiler 700 of the embodiment of FIGS. 1 through 6.

The primary oxidation chamber 1400 is provided with an annular grate 1420 which may generally be the same as the annular grate 420 of the embodiment of FIGS. 1 through 6. Nonoxidizable materials in the original feed material pass from the primary oxidation chamber 1400 into an ash pit 1400 that is located beneath the primary oxidation chamber 1400. The ash pit 1440. which is defined by a wall 1441 and which is in the shape of an inverted frustum of a cone or frustum of a pyramid, is provided with a removal auger 1442 at the bottom thereof. The removal auger 1442, which is driven by a motorized drive 1143, preferably a hydraulically driven drive, conveys the nonoxidizable materials to an ash clean out door 1444. Preferably, a hydraulic drive 1445 is provided for the operation of the annular grate 1420.

FIGS. 9 through 13 illustrate an alternative embodiment of a storage hopper assembly 1200 which may be used in place of the storage hopper assembly 200 of the embodiment of FIGS. 1 through 6. The storage hopper assembly 1200 has an elongate opening 1201 in the bottom thereof, and the elongate opening 1201 is longitudinally aligned with the horizontal screw member 1301 of the feed assembly 1300. The storage hopper assembly 1200 is defined by a wall 1202 and has an open top upper section 1200a, which has a parallelepiped shape, and a lower section 1200b which extends upwardly and outwardly from the elongate opening 1201 to the upper section 1200a. The upper section 1200a of the storage hopper assembly 1200 is defined by a rectangular portion 1202a of the wall 1202, and the lower section 1200b is defined by a series of trapezoidal portions 1202b, 1202c, and 1202d of the wall 1202, which are arranged end-to-end in a U-shaped portion, and by an end wall portion 1202e of the wall 1202. The end wall portion 1202e closes the end between the trapezoidal portions 1202b and 1202d that is opposed to the end that is closed by the trapezoidal portion 1202c.

Feed material is added to the upper section 1200a of the storage hopper assembly 1200 and flows downwardly through the storage hopper assembly 1200 by gravity, to exit through the elongate opening 1201 and to be carried to the primary oxidation chamber 1400 by the feed assembly 1300. To prevent bridging of feed material within the storage hopper assembly 1200, the storage hopper assembly is provided with reciprocating plate assemblies 1203, 1204, and 1205 that lie along the trapezoidal portions 1202b, 1202c, and 1202d, respectively, of the wall 1202. The reciprocating plate assembly 1203 includes a mounting rod 1203a that is caused to reciprocate along its longitudinal axis through tie down brackets 1203b, which are attached to the trapezoidal portion 1202b of the wall 1202, by means of a hydraulic drive unit 1203c. Further, the reciprocating plate assembly 1203 includes a series of spaced, elongate plates 1203d, 1203e, and 1203f which are attached to the mounting rod 1203a and which extend transversely thereof. Preferably, the leading edge of each of the elongate plates 1203d, 1203e and 1203f, that is, the edge which is closest to the elongate opening 1201, is thicker than the opposed or trailing edge thereof, so that each of such elongate plates 1203d, 1203e, and 1203f will push more material on the downward portion of its reciprocating stroke than on the upward portion thereof. Similarly, the reciprocating plate assembly 1205 includes a mounting rod 1205a that is caused to reciprocate along its longitudinal axis through tie down brackets 1205b, which are attached to the trapezoidal portion 1202d of the wall 1202, by a hydraulic drive unit 1205c, and a series of spaced, elongate plates 1205d, 1205e, and 1205f which are connected to the mounting rod 1205a and which extend transversely thereof. Again, preferably, the leading edge of each of the elongate plates 1205d, 1205e, and 1205f is thicker than the trailing edge thereof. Also, the reciprocating plate assembly 1204 includes a mounting rod 1204a that is caused to reciprocate along its longitudinal axis through tie down brackets 1204b, which are attached to the trapezoidal portion 1202c of the wall 1202, by a hydraulic drive unit 1204c, and a series of spaced, elongate plates 1204d, 1204e, and 1204f which are attached to the mounting rod 1204a and which extend transversely thereof. Again, preferably, the leading edge of each of the elongate plates 1204d, 1204e, and 1204f is thicker than the trailing edge thereof. A timer 1206 is provided to control the operation of the hydraulic drive units 1203c, 1204c, and 1205c of the reciprocating plate assemblies 1203, 1204, and 1205, respectively, to synchronize the reciprocation of each of such reciprocating plate assemblies and to ensure that the reciprocation thereof occurs at a suitable frequency. As is understood in the art, hydraulic connections, not shown, are provided between the timer 1206 and each of the hydraulic drive units 1203c, 1204c, and 1205c.

In the operation of a storage hopper assembly similar to the storage hopper assembly 200 of the embodiment of FIGS. 1 through 6 or the storage hopper assembly 1200 of the embodiment of FIGS. 9 and 10, it may be that the feed material that is added thereto will contain oversized or agglomerated portions which are too large to pass therefrom. This can occur, for example, in a feed supply of wood chips that may contain unchipped wood blocks or logs. If this is likely to be a problem, the storage hopper assembly, for example, the storage hopper assembly 1200 of FIGS. 9 and 10, can, as is shown in FIGS. 11 and 12, be provided with counterrotating helical chipping blades 1207 immediately above the elongate opening 1201 so that any oversized portions of feed material will be subjected to a reduction in size when they move downwardly within the storage hopper assembly 1200 to the level of the helical chipping blades. Each of the helical chipping blades 1207 has a shaft portion 1203 which extends beyond the storage hopper assembly 1200, and as is shown in FIGS. 13 and 14, each shaft portion is driven in unison and in opposite directions by a chain 1209 that is trained around a sprocket 1210, that is attached to each shaft portion 1208. The chain 1209 is also trained around an idler sprocket 1211, and the drive for the helical chipping blades 1207 is integrated with the drive for the horizontal screw member 1301 of the feed assembly 1300 by also training the chain 1209 around a sprocket 1309 that is attached to a shaft portion 1310 of the horizontal screw member 1301 that extends beyond the storage hopper assembly 1200. Motive power is imparted to the shaft portion 1310 of the horizontal screw member 1301, and thence by way of the sprocket 1309 and the chain 1209, to the sprockets 1210 by a motor 1311 which drives a chain 1312 which is trained around a second sprocket 1313 that is attached to the shaft portion 1310.

Having, thus, described the present invention by way of an exemplary embodiment, it will be apparent to those skilled in the art that many modifications may be made from the exemplary embodiment without departing from the spirit of the present invention or the scope of the claims appended hereto.

Claims

1. A method for gasifying solid organic materials to produce a gaseous effluent and solid residue, said method comprising the steps of:

providing a source of supply of solid organic materials;

providing a primary oxidation chamber having a converging upper portion and a bottom portion;

introducing solid organic materials from said source of supply into said primary oxidation chamber upwardly from said bottom portion of said primary oxidation chamber to provide a mass of said solid organic materials in said primary oxidation chamber;

heating said mass of solid organic materials in said primary oxidation chamber;

adding an oxidant to said primary oxidation chamber to gasify said heated mass of solid organic materials in said primary oxidation chamber and to initiate a flow of gaseous effluent within said primary oxidation chamber;

establishing a gaseous effluent flow path within said primary oxidation chamber whereby a portion of said gaseous effluent repeatedly flows in a recirculating upward and downward direction through said heated solid organic materials to enhance continuous oxidation of said solid organic materials, and a further portion of said gaseous effluent flow is advanced in a direction outward from said primary oxidation chamber; and

transferring said solid residue out of said primary oxidation chamber.

2. The method according to claim 1 wherein said method is a continuous method, wherein said solid organic materials are transferred to said primary oxidation chamber at a predetermined rate to maintain a mass of said solid organic materials in said primary oxidation chamber, and further wherein said oxidant is continuously added to said primary oxidation chamber to continuously gasify said solid organic materials in said mass, and still further wherein said solid residue is transferred out of said primary oxidation chamber.

3. The method according to claim 2 wherein said primary oxidation chamber is in the shape of a cylinder with a dome, said cylinder having a longitudinal axis which extends generally vertically, said dome of said cylinder being disposed at the upper end thereof.

4. The method according to claim 3 wherein said solid organic materials are transferred into said primary oxidation chamber at a location adjacent the lower end of said longitudinal axis of said cylinder.

5. The method according to claim 4 further comprising the steps of:

providing a grate within said primary oxidation chamber at a location adjacent the lower end of said longitudinal axis of said cylinder, said grate receiving said solid organic materials as said solid organic materials are transferred into said primary oxidation chamber; and

maintaining said mass of said solid organic materials on said grate during the oxidation of said solid organic materials in said primary oxidation chamber.

6. The method according to claim 5 further comprising the steps of:

sensing the elevation of the top of said mass of solid organic materials on said grate; and

controlling the rate at which said solid organic materials are transferred into said primary oxidation chamber to maintain said top of said solid organic materials on said grate at a substantially constant elevation.

7. The method according to claim 6 wherein non-combustible solid residue forms on said grate as a result of said oxidation of said solid organic materials, said method further comprising the step of periodically actuating said grate to remove said non-combustible residue from said primary oxidation chamber through said grate.

8. The method according to claim 2 wherein said solid residue is transferred to a device to recover the thermal energy therein.

9. The method according to claim 2 further comprising the step of controlling the rate at which said solid organic materials are transferred to said primary oxidation chamber to maintain a substantially constant mass of said solid organic materials in said primary oxidation chamber.

10. The method according to claim 2 wherein said oxidant is added to said primary oxidation chamber at a rate which is insufficient to fully oxidize said solid organic materials, said method further comprising the steps of:

providing a secondary oxidation chamber for receiving said further portion of said gaseous effluent that is transferred out of said primary oxidation chamber;

adding an oxidant to said secondary oxidation chamber to further oxidize said further portion of said gaseous effluent into said gaseous effluent; and

transferring said gaseous effluent out of said secondary oxidation chamber.

11. The method according to claim 10 wherein said oxidant that is added to said primary oxidation chamber consists essentially of ambient air.

12. The method according to claim 11 wherein said oxidant that is added to said secondary oxidation chamber consists essentially of ambient air.

13. The method according to claim 10 wherein said secondary oxidation chamber is generally cylindrically shaped, wherein said further portion of said gaseous effluent flows through said secondary oxidation chamber generally parallel to the longitudinal axis of said secondary oxidation chamber and wherein said oxidant that is added to said secondary oxidation chamber is added substantially tangentially to said secondary oxidation chamber to swirl around said further portion of said gaseous effluent that is flowing through said secondary oxidation chamber.

14. The method according to claim 1 wherein said oxidant that is added to said primary oxidation chamber consists essentially of ambient air.

15. The method according to claim 1 wherein said primary oxidation chamber is vertically disposed and said solid organic materials are transferred into said primary oxidation chamber at a location adjacent said bottom; and further wherein a part of said oxidant is added to said primary oxidation chamber at a location adjacent said bottom, and wherein a second part of said oxidant is added to said primary oxidation chamber at at least one location above said bottom to gasify said heated organic materials in stages.

16. The method according to claim 15 wherein said step of advancing said further portion of said gaseous effluent from said primary oxidation chamber occurs through an insulated exit duct that has a restricted entry portion to prevent the passage of flame from said primary oxidation chamber.