Gasifier

Abstract

The present invention provides an improved gasifier, consisting of two separate and functionally different combustion zones within a common insulated chamber. Solid carbonaceous fuel enters the gasifier through an input feed. A spindle assembly, which is affixed to one end of the chamber, rotates, causing a mixing of the fuel and facilitating its movement through the chamber. The portion of the chamber nearest the input feed acts as a first combustion zone, partially oxidizing the raw fuel and carbonizing the fuel particles. A second combustion zone completes combustion of the char produced in the first zone. One end of the spindle assembly, located between the first and second combustion zones, includes a gas collection device for removing combustible product gas from the gasifier. The gas collector is circumscribed by an auger which, rotating with the spindle, actively transports charcoal from the first to the second combustion zone.

Description

BACKGROUND OF THE INVENTION

Solid fuels, including coal, coke, wood, charcoal, and agricultural residues, may be converted to combustible gases by processes involving heating and/or partial burning of these fuels. Such combustible gases may be burned to produce heat in more or less conventional furnaces or boilers, or, if they are adequately cleaned of ash and other solid fuel residues and tars, they may be burned in internal combustion engines, such as diesel or gas engines, or gas turbines, to produce mechanical or electrical energy. The conversion of a solid fuel to a gaseous fuel is performed in a device called a gasifier.

Coal and coke gasifiers were widely used in the 19^th and early 20^th centuries to produce combustible gas for heating, cooking, and illumination in towns and cities and for industrial energy needs. Smaller vehicle mounted gasifiers were used in Europe during the First and Second World Wars to propel these vehicles using wood or wood charcoal as fuel. While powering vehicles with solid fuel gasifiers is not convenient by present standards, the increasing cost and environmental effects of burning petroleum fuels are encouraging people to reconsider solid fuel gasifiers for stationery applications, including boiler firing and the production of electricity. Low grade wood, agricultural residues and other forms of biomass are particularly attractive gasifier fuels because they are inexpensive, they are renewable, and their combustion does not contribute to global warming.

Gasifiers may be classified according to whether they have a fixed or fluidized fuel bed, and also as to whether they produce a relatively high calorific content tar containing gas, which may only be burned in furnaces and boilers, or a lower calorific content gas, which has a low tar content and may be used to fuel engines. The present patent covers a new type of fixed bed gasifier, intended to produce a lower calorific value gas that is suitable for powering engines. The patent provides solutions to a number of problems commonly encountered with this type of gasifier, particularly when burning biomass fuels of non-uniform particle size, or having high ash content.

One specific problem that is encountered with all types of gasifiers is that solid fuel residues, including carbon, ash, and fuel particles are transmitted into the product gas. All gasifiers require gas cleaning equipment to remove these impurities before the gas may be introduced into an engine. The service requirements of this cleaning equipment, the disposal of residues, and the service requirements and durability of the engine are nonetheless sensitively affected by the particulate content of the gas leaving the gasifier.

The problem of particle entrainment in the gas arises because the solid fuel particles are consumed during their conversion to combustible gas. In gasifiers designed to produce gas having a low tar content, suitable for engines, gas is typically removed from the gasifier at the end opposite to where the fuel is introduced. This is because tars are released during heating and charring of the raw fuel, and can only be broken down by passing through the charcoal bed of the gasifier, where charcoal particles are also consumed in the production of combustible gas. Passing the gas through a bed containing many fine particles inevitably causes many such particles to be transported out of the gasifier by the product gas. Ash particles or carbon particles that have been largely consumed and contain high ash content are particularly detrimental to engines because ash is an abrasive material.

Another issue associated with biomass gasifiers is the tendency of the charcoal bed of the gasifier, where the production of combustible gas principally occurs, to become choked with fine char and ash particles. Choking of the charcoal bed, which is typically located between the combustion zone of the gasifier and a gas collection screen or grate, interferes with the withdrawal of combustible gas from the gasifier. Reduced gas flow proportionally reduces the amount of air or oxygen that may be injected into the gasifier, causing it to drop in temperature below the temperature required for gas production. More fundamentally, the permeation of the charcoal bed with hot combustion gas (CO₂ and H₂O) is what causes that gas to be converted to combustible gas (CO and H₂). Choking or densification of the charcoal bed with fine char and ash particles inhibits production of combustible gas. Choking or densification of the charcoal bed is more severe with natural fuels having random particle size, containing dust, or having high ash content. Such fuel characteristics were carefully controlled by users of earlier biomass gasifiers.

In some embodiments the grates or screens are adapted to vibrate or move with the intent to minimize the densification or choking of the charcoal bed. These methods have not however been found to be effective, the charcoal quickly resealing itself due to fine char migration with the briefly established gas flow. Furthermore, vibration and grate motion discharge fine char and ash into the product gas stream, from which it must subsequently be removed.

A third problem, which is related to the problem of char bed densification, is that efforts to reestablish gas flow by increasing the force of gas suction or by moving or vibrating the char bed tend to create channels or gas vents through the charcoal bed. As before, fine particles are discharged into the product gas, but the result is a channel through the charcoal bed. In this case combustion gas (CO₂ and H₂O) bypasses the charcoal bed and passes directly into the product gas stream without conversion to combustible gas (CO and H₂).

There is therefore a need to provide a gasifier capable of providing a gaseous output nearly devoid of particles with high efficiency of conversion of solid fuel to combustible gas. Furthermore, there is a need to provide a gasifier capable of operating continuously without degradation caused by char and ash buildup within the charcoal bed. Problems with fixed bed gasifiers, as described above, in combination with cheap petroleum, have prevented their commercial application worldwide since World War II.

Much more practical and experimental progress has been made with fluidized bed gasifiers, in which the particles of biomass or other carbonaceous fuel are held in suspension by high gas flow rates. Such gasifiers are operationally complex, and often produce high loadings of fine particulates and tars in the product gas. They often require large electricity consumption to run the large blowers that provide the high gas velocity needed to keep the particles in suspension. They also tend to be very tall in order to maintain stratification of operating conditions.

In contrast with the above, the fixed bed gasifier has the potential to greatly simplify the process of biomass conversion to gaseous fuel, and to permit this to be done on a smaller, more decentralized scale. The present invention enables the potential promise of the fixed bed gasifier to be fully realized. The application of this technology to coal needs to be explored, and is included under the present invention. A second preferred embodiment involves enclosing multiple functional units within a common gasification chamber, thereby increasing the capacity of the device.

SUMMARY OF THE INVENTION

The problems with the prior art have been overcome with the present invention, which provides an improved gasifier. Briefly, the gasifier is fed with biomass through an input feed, such as an auger. A spindle assembly, which is affixed to one end of the chamber, rotates, causing a mixing of the biomass and facilitating its movement within the chamber. The portion of the chamber nearest the input feed acts as a first combustion zone, having a rotating grate, air nozzles, and rotating hearth mounted upon the spindle assembly. Air nozzles inject air into the newly added biomass, causing the biomass to partially burn and be substantially converted to charcoal before moving further into the chamber.

As the charcoal passes past the rotating hearth, it moves between the surface of a gas collection device and the insulated walls of the gasifier chamber. Gas can be drawn through the surface of the gas collection device into the interior of the spindle assembly through the action of a suction blower located outside the gasifier and communicating with the spindle assembly at its open end. The charcoal bed that occupies the volume between the gas collector and the surrounding insulated walls of the gasifier chamber is made to move gradually due to the rotation of one or more augers surrounding the cylindrical gas collector.

In the preferred embodiment, the gas collector comprises a set of adjacent vertically stacked concentric rings. Gases are able to pass between the rings into the collector along with only very small char particles. The rotary movement of alternate rings relative to adjacent fixed rings prevents the very narrow gaps that naturally occur between such rings from becoming clogged.

Once charcoal has moved past the gas collector, it enters a second combustion zone, where additional air is introduced. Thermal energy (heat), the combustion gases CO₂ and H₂O, and tars are generated in the first combustion zone, located upstream from the gas collector. Heat and CO₂ are generated in the second combustion zone, located downstream from the gas collector. Since the second zone is fueled by dry, already hot carbon, rather than raw biomass, very elevated temperatures are achieved in the second zone where air or oxygen is introduced. The very hot CO₂ gas produced in the second combustion zone is converted to the combustible carbon monoxide gas as it moves through the charcoal toward the gas collector.

Optionally, combustion gas consisting of CO₂ and H₂O, but also containing tar and other combustible substances, produced in the first combustion zone may be drawn from the gasifier and injected by a blower into the second combustion zone. This “vapor reinjection” has the effect of accelerating combustion in the first zone and thus increasing the rate of conversion of raw biomass into charcoal. This occurs both because of the removal of water vapor from the first combustion zone, and also because removing combustion gas from the fuel feed end of the gasifier causes a propagation of the flame toward the fuel feed. It also reduces the amount of tar and also noncombustible gases that may reach the gas collector. Injecting these gases into the second combustion zone, where temperatures are much higher than in the first zone, enables the noncombustible gases to be more effectively converted to combustible gas and also enables thermal cracking of the undesirable tar molecules.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a vertical sectional view of a first embodiment of the gasifier of the present invention;

FIG. 2 is an exploded view of the gas collector in accordance with the present invention; and

FIG. 3 illustrates a second embodiment of the gasifier of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a first embodiment of the gasifier in accordance with the present invention. While this embodiment comprises a preferred embodiment in which the biomass fuel is fed into the top of a vertically oriented chamber and the fuel descends into the chamber as it is burned, the invention is not so limited. Those skilled in the art will appreciate that it is within the skill in the art to configure the chamber in other ways. For example, the biomass fuel can be fed into the bottom of a vertically oriented chamber and moved upward during burning. In another embodiment, the chamber can be configured horizontally or at some angle, such that the biomass is fed into one end of the chamber and moved to the other end.

A spindle assembly 10 is located within an insulated chamber 12, preferably along the central vertical axis of chamber 12. The chamber 12 must withstand temperatures in excess of 2000° F., and thus its walls must be constructed of a suitable material capable of withstanding these high temperatures as well as providing thermal insulation, such as ceramic, lined with insulation, and surrounded by a steel shell. Input auger 16, or other suitable feeding device, is used to feed biomass fuel into the top of chamber 12, typically from a suitably designed hopper and in such a manner as to minimize air leakage into the chamber with the fuel.

The spindle assembly 10 is suspended from the top or cover of chamber 12 in such a manner as to be able to rotate about a vertical axis. In the first embodiment, the spindle 10 is suspended from the center of the chamber so as to be equally spaced from the walls of the chamber 12. A second embodiment will be described below in association with FIG. 3. Spindle 10 comprises an inner tube 56, which is preferably fixed in position, such as by clamp 58, and unable to rotate. Spindle tube 64 circumscribes inner tube 56 and rotates about a vertical axis. In the preferred embodiment, spindle tube 64 is in communication with gear 68, which is connected via a gear assembly to a motor (not shown). Air jacket tube 20 preferably surrounds spindle tube 64 in such a manner as to allow the flow of air to occur in the space between the two tubes. Preferably, this flow of air is supplied under pressure by primary air blower 22. Air damper 24 can be optionally used to control the flow of air entering the air jacket pipe 20. Air damper 24 also can be used to prevent admission of air into the pipe when the gasifier is inactive. Optionally, air can be drawn through the air nozzles 18 into the gasifier chamber by maintaining the chamber at a lower pressure than the outside air. In either case, air that is pushed through the air jacket pipe 20 is forced through the air nozzles 18 into the gasifier chamber 12. In the preferred embodiment, a circular grate 26 is affixed above air nozzles 18 and rotates with the spindle tube 64. Optionally, stirring fingers 28 which extend outwardly from the air jacket pipe 20 can also be included. Located below the air nozzles 18 is a rotating hearth 30, preferably constructed of refractory ceramic, or other high temperature resistant material. The rotating grate 26, hearth 30 and fingers 28 increase the lateral mixing of the fuel material, and facilitate the downward flow of fuel, while also promoting flame penetration of the fuel above the hearth 30 and between the hearth and gasifier walls. All of these components are attached to the spindle tube 64, causing them to rotate in unison.

Below the ceramic hearth 30 lies the gas collector 14. The gas produced by the gasifier is captured by the collector 14 and transferred out of the gasifier through gas tube 56. Gas tube 56 is prevented from rotating by its attachment to the top of the gasifier via clamp 58. FIG. 2 illustrates the preferred embodiment of the gas collector 14. The collector comprises an internal frame 54, which is attached, such as by locating pins, to inner tube 56, and therefore unable to rotate. At the base of the internal frame 54 is a ceramic heat shield 66. Fixed rings 50 and rotating rings 52 are placed about internal frame 54 in an alternating pattern. The rings are preferably produced from heat resistant steel alloy and fit over the internal frame. Fixed rings 50 have one or more, preferably two, internal protrusions 50a, each of which is configured to fit between adjacent supports of internal frame 54, thereby fixing them with respect to the internal frame. Rotating rings 52 do not have the above-mentioned protrusions and therefore are free to rotate relative to internal frame 54. Natural imperfections in the manufacturing process create sufficient gaps between adjacent rings to allow gas to flow between them. The capacity of the gas collector can be varied by a number of techniques; an increase in the number of rings used causes an increased number of gaps through which gas can flow. Similarly, an increase in the radius of the rings also increases the area through which the gas can flow. The rings may be deformed or machined to have slightly rippled upper and lower surfaces, that, being identical for all rings, cause the rings to move slightly toward and away from adjacent rings as they turn relative to adjacent rings. Atop the uppermost ring, which is preferably a fixed ring 50, is situated a hub 62. Hub 62 preferably has upward facing protrusions, which interlock with corresponding lower side indentations on the ceramic hearth 30 and has locating pins or other means to ensure its rotation with spindle tube 64. This interlocking mechanism, or any other similar interconnection, allows the hub 62, to move in concert with the ceramic hearth 30 and spindle tube 64. Auger 60 is attached to hub 62, as by welding, and circumscribes the stack of rings. In the preferred embodiment, the auger 60 is attached to all rotating rings 52 by welding, but not attached to fixed rings 50. In this way, the rotation of spindle tube 64 causes the rotation of the ceramic hearth 30, the hub 62, the auger 60, and the rotating rings 52.

Turning back to FIG. 1, a second combustion zone within the lower portion of chamber 12 includes nozzles 32 for the injection of air or oxygen into said combustion zone. In the preferred embodiment, air is injected by blower 38, controlled by damper 42, which, when the gasifier is inactive, may entirely prevent air leakage via nozzles 32 into chamber 12. Optionally, nozzles 34 reinject gases produced in the first combustion zone, principally CO₂, H₂O, and tars, into the second combustion zone, near the bottom of gasifier chamber 12. Such reinjection may be caused by a blower 40 and controlled by a damper 44, or by varying the blower speed. Ash auger 36 is located at the bottom of chamber 12, which is preferably conical in shape to require the ash to accumulate near the auger. Auger 36 enables ash and other noncombustible residues to be removed from chamber 12 to an ash receiver suitably designed to prevent air leakage into chamber 12.

Having described the physical components of the present invention, the operation of the gasifier will now be described. Referring to FIG. 1, biomass is fed into the gasifier via the rotation of input auger 16. The drive motor of the input auger 16 (not shown) is equipped with a means of detecting that the gasifier chamber 12 is full of biomass fuel. In practice this may be performed by a variety of mechanisms such as electrical or mechanical detection of the torque applied to the feed auger, or by a separate paddle wheel type sensor. As the biomass enters the chamber 12, the rotary action of fingers 28 and circular grate 26 serve to mix the biomass and ensure even penetration into the biomass of the flame originating at nozzles 18. Air nozzles 18 provide the combustion air necessary for the biomass to burn. Air is preferably blown into the space between air jacket pipe 20 and spindle tube 64 by primary air blower 22. Damper 24 controls the flow of air entering the air jacket pipe 20. Alternatively, air can enter the gasifier by maintaining a negative pressure differential between the inside of the gasifier and the outside environment. The region of chamber 12 located in the vicinity of circular grate 26, circular hearth 30 and air nozzles 18 comprises combustion zone I, where solid fuel is carbonized by vaporization and combustion of substantially all of its volatile combustible constituents.

The combustion process is initiated by manually igniting the raw biomass, such as by the use of a blowtorch, or an automatic ignition device. Once ignited, the combustion of the biomass becomes a continuous, self-sustaining process, where the injection of air and additional biomass are all that is needed to maintain combustion. Spindle assembly 10 is rotated continuously or intermittently during operation of the gasifier, but at a low speed, to ensure mixing and flow of the material, but so as to avoid unnecessary breakage of the fuel and charcoal particles. As additional fuel is added and carbonized within combustion zone I, this newly carbonized fuel descends deeper into the chamber 12. The rotation of the auger 60 ensures that the carbonized fuel continues to descend, despite the movement of gas toward the gas collector surface and the consequent migration of small char particles toward the gas collector surface. The close proximity of the surface of the gas collector to the walls of the gasifier chamber 12, which chamber is square in its plan view or otherwise designed to prevent rotation of the charcoal particles with the spindle assembly, assists in forcing the char particles to descend toward combustion zone II. The bottom of the gasifier chamber 12, denoted as combustion zone II, is thereby maintained full of char particles, despite the upward flow of gas from combustion zone II toward the gas collector. In a preferred embodiment of the gasifier, the outside diameter of the gas collector is approximately ten inches, while the distance between opposite walls of chamber 12 is eighteen inches, creating a distance of four inches between the gas collector surface and the nearest surfaces of the chamber 12.

The downward movement of charcoal particles in proximity to the gas collector is responsible for preventing the problem of charcoal bed choking or densification mentioned previously. This problem is caused by the rapid migration of small char and ash particles with the flow of gas toward the gas collector. These small particles remain mobile and continue to flow with the gas until their path is obstructed by somewhat larger particles, having void spaces slightly too small to allow further migration of these particles. In this way the charcoal bed acts like a filter, trapping particles that would otherwise reach the gas collector surface, the smallest of which would pass between the gas collector rings and enter the product gas. A stationery charcoal bed would necessarily and quickly clog with these smaller particles, as occurs in fixed bed gasifiers of conventional design. In the present invention, the clogging, densification, or aggregation of the charcoal bed is counteracted by the continuous or intermittent transport of the charcoal bed toward combustion zone II. In practice a very high rate of combustible gas production may be maintained by this method with a suction of less than 2.5″ water column (0.1 psi).

Actively transporting the char downward also helps ensure that channels do not develop through which oxygen or noncombustible gases can travel to the gas collector surface. Channeling is the formation of passages through the char bed by erosion, which allow unreacted combustion gas, such as carbon dioxide, water vapor and hydrocarbons, to bypass the char bed and pass directly into the gas collector. Channeling occurs in conventional fixed bed gasifiers when the openings in the gas collector or grate are large enough to allow the passage of both intermediate size and small char particles out of the charcoal bed. When the charcoal bed is vibrated or otherwise disturbed, these particles may discharge from a portion of the char bed especially when the gas suction is strong. The present invention prevents channeling by utilizing very small gasflow passages in the gas collector surface, these being the gaps between adjacent rings. In addition gas suction across the char bed is very weak because of the continuous renewal of the char bed due to its downward displacement. Newly produced char from combustion zone I, containing relatively large particles, presents relatively little resistance to the flow of gas, and continuously or intermittently replaces the partially densified bed as it is moved toward combustion zone II.

Since the area surrounding the gas collector contains mostly carbonized fuel, it reacts with the hot gases, such as carbon dioxide and water vapor, that are produced in combustion zone I, located above the gas collector, and combustion zone II, located below the gas collector. This endothermic reaction yields carbon monoxide and hydrogen gas. The region of chamber 12 below Combustion Zone I and above Combustion Zone II (which is described below) comprises the reduction zone, which is also a region wherein the temperatures are lower than in either of the combustion zones surrounding it.

Because the zone of the gasifier surrounding the gas collector is not fed with air and is involved in endothermic reactions, its temperature is lower than that of combustion zone I, or combustion zone II, which is located in the lower portion of the chamber 12. To protect the gas collector from the extreme temperatures both above and below it, ceramic materials are used in the production of the hearth 30 and the heat shield 66. The gas collector itself may be made from relatively less temperature resistant material, such as high temperature corrosion resistant alloy steel. The gas temperature exiting the gasifier typically has a temperature of 800 to 1000 degrees Fahrenheit.

As the carbonized fuel passes below the gas collector, it enters combustion zone II, where air or oxygen is injected, using blower 38, into chamber 12 through nozzles 32. As in the case of combustion zone I, the flow of air or oxygen can be controlled by damper or valve 42, and can be completely stopped when the gasifier is inactive. This injection of air allows for the complete combustion of the char particles that have been transported down by the auger 60. This process will typically yield carbon dioxide and completely consumed fuel, in the form of ash. The second combustion zone produces much of the energy required for the conversion of noncombustible carbon dioxide gas to combustible carbon monoxide gas as the gas travels upward through the charcoal bed and is captured by the gas collector. The reduction of carbon dioxide to carbon monoxide is accompanied by the oxidation of carbon in the charcoal to carbon monoxide, which consumes a portion of the charcoal before it reaches combustion zone II.

The nozzles 32 are configured to consume charcoal as completely as possible, allowing only noncombustible ash to reach the ash auger 36. Auger 36 is rotated intermittently or continuously in response to excess air pressure encountered by air blower 38. Excess air pressure indicates a buildup of ash interfering with the injection of air into combustion zone II.

Summarizing the operation of the gasifier, combustion zone I uses air to convert fresh biomass into carbon dioxide, water vapor and carbonized fuel. This partially burned fuel is moved downward through the chamber by the rotation of the auger 60. As the hot carbon dioxide and water vapor move away from combustion zone I, they continue to react with the partially burned fuel, yielding carbon monoxide and hydrogen gas, which are captured by the gas collector 14. The rotation of the auger 60 also continues to push this carbonized fuel downward. The unique configuration of the gas collector, in conjunction with the rotary action of the auger, serve to continuously clean the surface of the gas collector to prevent aggregation. As the remaining carbonized fuel reaches the lower portion of the chamber 12, it enters combustion zone II. In this zone, air is injected into the chamber and the carbonized fuel is completely combusted to yield hot carbon dioxide and ash. Hot carbon dioxide travels through the carbonized fuel up toward the gas collector. While traveling, it reacts with the fuel to create carbon monoxide, which is captured by the gas collector. Thus, the gas collector is capable of capturing gases produced in both Combustion Zone I and Combustion Zone II after reaction with the reduction zone.

The efficiency of the described gasifier can be further enhanced by the re-circulation of exhaust gases from combustion zone I. In this embodiment, gases are drawn from the top of chamber 12 by the action of exhaust gas blower 40 and injected into combustion zone II via nozzles 34. These exhaust gases, including steam, carbon dioxide, tars and other hydrocarbons, are injected to reduce their presence in the product gas and to control the relative temperatures of combustion zone I and combustion zone II. The quantity of gas recirculated may be controlled by damper or valve 42 or by varying the speed of blower 38.

The re-circulation of the exhaust gases serves several purposes. Pulling a high gas flow through the recirculation loop decreases the downward flow of combustion gas from Combustion Zone I toward the reduction zone and the gas collector. Since zone I has lower temperatures than zone II, these combustion gases are less likely to be converted to combustible gas than if they originated from zone II. Recirculation also increases the upward penetration of the flame from Combustion Zone I into the raw fuel located above Combustion Zone I, thereby increasing the rate of fuel to char conversion. At very high rates of gas recirculation, much of the heat required for fuel pyrolysis or fuel to char conversion, may come from the upward flow of a portion of the hot gases from Combustion Zone II and the reduction zone. At lower rates of gas recirculation, water vapor is withdrawn from the top of gasifier chamber 12 fast enough to prevent condensation of water in the newly added biomass fuel, which would otherwise hinder combustion in zone I. Such water vapor may be partially or wholly dissociated into hydrogen gas and oxygen where the oxygen combines with carbon under high temperatures in combustion zone II.

The gas that enters the gas collector travels up inner tube 56. This tube is preferably in communication with gas cleaning equipment and a gas suction blower, where the blower delivers gas to the end use application at a rate equal to the rate of gas consumption, thereby minimizing or obviating the storage of the low caloric value gas produced. Ideally, the gas suction blower is regulated to maintain a slightly negative pressure inside the gasifier, relative to air pressure. This eliminates the possibility of combustible and lethal gas leakage into the surrounding environment.

FIG. 3 illustrates a second embodiment of the gasifier of the present invention. In this embodiment, a plurality of spindle assemblies 10 is used in conjunction with a single insulated chamber. FIG. 3 shows a top view of the chamber 12, with several spindle assemblies 10. These spindle assemblies are mounted to the top of the chamber, as described in reference to FIG. 1. In the first embodiment, the gas collector is surrounded by the walls of gasifier chamber 12, which are square in plan or otherwise configured to inhibit rotation of the char with the spindle assembly. In the embodiment of FIG. 3, there is no chamber wall around many of the augers. However, the use of multiple augers having the same pitch direction and same direction of rotation such that proximate points on adjacent augers are moving in opposition yields the same result. Referring to FIG. 3, a configuration of nine augers is shown. Auger 300, like all other augers rotates in a counterclockwise direction. When viewed in relation to its immediate neighboring auger 301, it can be seen that augers 300 and 301 are moving in opposite directions at the point where these augers are the closest together. This opposite movement creates a powerful downward tractive force on the charcoal surrounding these augers. The same phenomenon exists with respect to auger 300 and its other neighboring augers 302, 303 and 304. Similarly, this exists between each pair of neighboring augers. Thus, each auger is surrounded by either a chamber wall 330, or an opposing auger. This embodiment ensures a uniform downward motion of charcoal surrounding the gas collectors, and allows the production of large amounts of combustible gas due to the large combined surface area of multiple gas collectors.

The fixed gas pipes leading from the multiple spindles of such multi-spindle gasifiers may be manifolded together such that the gas may be drawn from multiple gas collectors by a single blower.

The combustible gas may be then used in a number of ways; it can be burned to produce heat, it can be used to power internal combustion engines or turbines, or it can be used as feedstock for chemical production.

Claims

1. An apparatus for the production of combustible gases through the pyrolysis of carbonaceous fuel comprising: a chamber into which said fuel is fed, a rotating spindle assembly comprising air nozzles for introducing air into said fuel to facilitate burning, thereby defining a first combustion zone in said chamber, and a gas collector spatially separated from said first combustion zone for capturing gas produced by the gasification of said fuel, wherein the rotation of said spindle assembly assists the movement of said burned fuel across the surface of said gas collector.

2. The apparatus of claim 1, wherein said rotating spindle assembly further comprises at least one inclined surface affixed to said gas collector.

3. The apparatus of claim 2, wherein said gas collector comprises a plurality of adjacent vertically stacked concentric rings whereby each ring of said plurality moves relative to each of its adjacent rings, and the gas that passes between said rings is captured by said gas collector.

4. The apparatus of claim 3, wherein said plurality of concentric rings comprises a first set of alternating rings coupled to said at least one inclined surface, such that said first set rotates in concert with said inclined surface.

5. The apparatus of claim 4, wherein said plurality of concentric rings comprises a second set of alternating rings that are fixed in position, thereby resulting in relative motion between said first set and said second set of alternating rings.

6. The apparatus of claim 5 further comprising a fixed pipe located within and coaxial with said rotating spindle assembly, said fixed pipe adapted to transmit gas captured by said gas collector to the exterior of said gasifier chamber; said fixed pipe also providing a means of fixing said second set of alternating rings.

7. The apparatus of claim 2, wherein said inclined surface comprises an auger circumscribed about said gas collector.

8. The apparatus of claim 1, further comprising a second combustion zone, wherein the rotation of said spindle assembly facilitates the movement of said burned fuel from said first combustion zone to said second combustion zone where it is further burned.

9. The apparatus of claim 8, wherein said first combustion zone is at a temperature effective for converting said fuel into char material, and said second combustion zone is at a temperature effective for converting said char material into ash.

10. The apparatus of claim 8, further comprising at least one air inlet to introduce air into said second combustion zone.

11. The apparatus of claim 8, wherein a portion of said gas produced by said burning in said first combustion zone is not captured by said gas collector, and further comprising at least one gas inlet for introducing said portion into said second combustion zone.

12. The apparatus of claim 11, further comprising a duct into which said portion flows, and a blower to introduce said portion through said gas inlet.

13. The apparatus of claim 1, wherein said combustible gas produced by said gasification comprises carbon monoxide and hydrogen.

14. The apparatus of claim 1, further comprising an airtight device for removing said burned fuel from said chamber.

15. The process of creating and capturing combustible gas from carbonaceous fuel comprising: introducing said fuel into a chamber having a central rotating spindle assembly comprising air nozzles and a gas collector spatially separated from said air nozzles;

introducing air through said air nozzles to facilitate the burning of said fuel, thereby defining a first combustion zone in said chamber;

rotating said spindle assembly so as to move said fuel burned in said first combustion zone downstream of said gas collector; and

capturing in said gas collector the gas produced.

16. The process of claim 15, further comprising the step of removing residual burned fuel from said chamber without introducing air to said chamber from a location downstream of said gas collector.

17. The process of claim 15, wherein said rotating spindle assembly further comprises an inclined surface affixed to the surface of said gas collector, such that the rotation of said spindle assembly facilitates the movement of said burned fuel past said gas collector thereby removing fuel residue from the surface of said gas collector.

18. The process of claim 15, further comprising the step of further burning said burned fuel in a second combustion zone located downstream of said gas collector.

19. The process of claim 18, whereby air is introduced into said second combustion zone.

20. The process of claim 18, whereby a portion of said gas that is produced in said first combustion zone is not captured by said gas collector and is introduced into said second combustion zone.

21. An apparatus for the production of combustible gases through the pyrolysis of carbonaceous fuel comprising: a chamber in which said fuel is burned; a plurality of rotating spindle assemblies, each of said plurality of spindle assemblies comprising air nozzles for introducing air into said fuel to facilitate burning, thereby defining a first combustion zone, and a gas collector spatially separated from said first combustion zone for capturing gas produced by the gasification of said fuel, wherein the rotation of said spindle assemblies moves said burned fuel in said chamber downstream of said gas collector.

22. The apparatus of claim 21, wherein said each of said plurality of spindle assemblies comprises at least one inclined surface affixed to each of said plurality of gas collectors.

23. The apparatus of claim 22, wherein each of said plurality of gas collectors comprises a plurality of adjacent vertically stacked concentric rings whereby each ring of said plurality of rings moves relative to each of its adjacent rings, and the gas that passes between said rings is captured by said gas collector.

24. The apparatus of claim 23, wherein said plurality of concentric rings comprises a first set of alternating rings coupled to said inclined surface, such that said first set rotates in concert with said inclined surface.

25. The apparatus of claim 24, wherein said plurality of concentric rings comprises a second set of alternating rings that are fixed in position, thereby creating relative motion between said first set and said second set of alternating rings.

26. The apparatus of claim 25 further comprising a plurality of fixed pipes, each of said pipes located within and coaxial with each of said plurality of rotating spindle assemblies, said plurality of fixed pipes adapted to transmit gas captured by said plurality of gas collectors outside of said gasifier chamber; said plurality of fixed pipes also providing a means of fixing said second set of alternating rings.

27. The apparatus of claim 22, wherein said inclined surface comprises an auger circumscribed about said gas collector.

28. The apparatus of claim 21, further comprising a second combustion zone, wherein the rotation of said plurality of spindle assemblies facilitates the movement of said burned fuel from said first combustion zone to said second combustion zone where it is further burned.

29. The apparatus of claim 28, wherein said first combustion zone is at a temperature effective for converting said fuel into char material, and said second combustion zone is at a temperature effective for converting said char material into ash.

30. The apparatus of claim 28, further comprising at least one air inlet to introduce air into said second combustion zone.

31. The apparatus of claim 28, wherein a portion of said gas produced in said first combustion zone by said burning is not captured by said gas collector, and further comprising at least one gas inlet for introducing said portion into said second combustion zone.

32. The apparatus of claim 31, further comprising a duct into which said portion flows, and a blower to introduce said portion through said gas inlet.

33. The apparatus of claim 21, wherein each of said plurality of spindle assemblies rotates in the same direction.

34. The apparatus of claim 21, wherein said combustible gas produced by said gasification comprises carbon monoxide and hydrogen.

35. An apparatus for the production of combustible gases through the pyrolysis of carbonaceous fuel comprising: a chamber into which said fuel is fed; a first set of air nozzles for introducing air into said fuel to facilitate burning, thereby creating a first combustion zone in said chamber, a gas collector device for removing product gas from said chamber, located downstream from said first combustion zone, and a second set of air nozzles located downstream from said gas collector for introducing air into said fuel previously burned in said first combustion zone to facilitate further burning, thereby creating a second combustion zone in said chamber.

36. The apparatus of claim 35, further comprising a rotating spindle assembly to which said gas collector is affixed and at least one inclined surface affixed to said gas collector such that rotation of said spindle assembly facilitates movement of said burned fuel across the surface of said gas collector from said first combustion zone toward said second combustion zone.

37. The apparatus of claim 36, wherein said gas collector comprises a plurality of adjacent vertically stacked concentric rings whereby each ring of said plurality moves relative to each of its adjacent rings, and the gas that passes between said rings is captured by said gas collector.

38. The apparatus of claim 37, wherein said plurality of concentric rings comprises a first set of alternating rings coupled to said inclined surface, such that said first set rotates in concert with said inclined surface.

39. The apparatus of claim 38, wherein said plurality of concentric rings comprises a second set of alternating rings that are fixed in position, thereby creating relative motion between said first set and said second set of alternating rings.

40. The apparatus of claim 36, wherein said inclined surface comprises an auger circumscribed about said gas collector.

41. The apparatus of claim 36, wherein said inclined surface comprises at least one tilted paddle affixed to said gas collector.

42. A device for extracting a gaseous or liquid stream from solid particles comprising at least one inclined surface and a plurality of adjacent vertically stacked concentric rings, wherein said plurality of concentric rings comprises a first set of alternating rings coupled to said at least one inclined surface, such that said first set rotates in concert with said inclined surface and a second set of alternating rings that are fixed in position, thereby creating relative motion between said first set and said second set of alternating rings.

43. The device of claim 42 wherein said at least one inclined surface comprises an auger that circumscribes said plurality of concentric rings and is affixed to each of said first set.

44. The device of claim 42 wherein said at least one inclined surface comprises at least one tilted paddle affixed to each of said first set of concentric rings.