Gasification apparatus and method

Abstract

A gasification system is disclosed having a combustion or reaction vessel, a scrubber housing, and a filter housing. A carbonaceous fuel is partially combusted in the reaction vessel to generate a combustible gas. An improved ash support and removal system reduces clogging and other problems in the reaction vessel. The combustible gas passes through the scrubber housing to remove matter such as tar and oil, and the scrubbed gas passes through a hybrid blower to the filter housing. Wood chips are used in the filter housing to provide a relatively clean, dry gas. Wastewater and other waste products from the scrubber housing and filter housing are captured and returned to the reaction vessel.

Description

This application claims priority from U.S. Provisional Patent Application Ser. No. 60/492,363, filed on Aug. 4, 2003.

BACKGROUND OF THE INVENTION

This invention relates to gasification and, more particularly, to a flexible gasification apparatus and method that provides combustible gases having high heating values while avoiding pitfalls of prior attempts at gasification.

Gasification has generally been known for years. In gasification, a carbonaceous fuel source is partially combusted to produce a combustible gas, synthesis gas, or syngas. The combustible gas is then combusted to produce work. The combustible gases produced by gasification may find any number of uses, including but not limited to supplying heat, powering a motor, or producing electricity. Gasification provides many advantages, such as allowing fuels having relatively low heating values to be used, allowing waste products to be used to produce work, and, similarly, reducing the amount of waste material that must be sent to landfills. Despite these obvious advantages, gasification has met with only limited success, because gasification systems have typically been plagued by a number of disadvantages or difficulties. For example, the heating values of gases produced using prior art systems have tended to fluctuate to an undesirable degree, particularly when a variety of fuel sources or fuel sources of varying compositions have been used. Similarly, it has also proven difficult to consistently produce gases having sufficiently high heating values. Separating particulate matter from the produced gas has proven problematic. Similarly, it has proven difficult to produce sufficiently clean gases having sufficiently low amounts of particulate matter as well as sufficiently low amounts of pollutants such as such as sulfur dioxide (SO₂), nitrogen oxides (NO_x), carbon monoxide (CO) and volatile organic compounds (VOC), ammonia, hydrogen chloride (HCl), and chlorides. Environmentally sound disposal of wastewater generated by such systems has also presented difficulties. Further still, the presence of water or other liquids in the combustible gas has made it difficult or impossible to use blowers for moving the combustible gases without creating undesirable levels of wear and tear on the blowers.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a flexible gasification apparatus and method that provides combustible gases having high heating values while avoiding pitfalls of prior attempts at gasification.

It is a further object of the present invention to provide an apparatus and method of the above type that can easily handle a wide variety of carbonaceous fuel sources or combinations of fuel sources.

It is a further object of the present invention to provide an apparatus and method of the above type that produces a high value heating gas having low amounts of particulate matter and other pollutants.

It is a further object of the present invention to provide an apparatus and method of the above type that requires little or no wastewater disposal.

It is a still further object of the present invention to provide an apparatus and method of the above type that captures a relatively high fraction of the potential heating value of the fuel sources.

It is a still further object of the present invention to provide an apparatus and method of the above type that safely and cleanly consumes a wide variety of agricultural and industrial byproducts, including but not limited to animal waste and wood pulp sludge.

It is a still further object of the present invention to provide an apparatus and method of the above type that is less prone to clogging problems typically associated with ash removal.

It is a still further object of the present invention to provide an apparatus and method of the above type that may easily process a wide variety of combinations of solid and liquid fuels.

It is a still further object of the present invention to provide an apparatus and method of the above type that can safely and efficiently handle and dry relatively wet combustible gases.

It is a still further object of the present invention to provide an apparatus and method of the above type that uses a rugged, hybrid blower that can safely and efficiently handle both dry and relatively wet combustible gases.

Toward the fulfillment of these and other objects and advantages, the system of the present invention comprises a combustion or reaction vessel, a scrubber housing, and a filter housing. A carbonaceous fuel is partially combusted in the reaction vessel to generate a combustible gas. An improved ash support and removal system reduces clogging and other problems in the reaction vessel. The combustible gas passes through the scrubber housing to remove matter such as tar and oil, and the scrubbed gas passes through a hybrid blower to the filter housing. Wood chips are used in the filter housing to provide a relatively clean, dry gas. Wastewater and other waste products from the scrubber housing and filter housing are captured and returned to the reaction vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

The above brief description, as well as further objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of the presently preferred but nonetheless illustrative embodiments in accordance with the present invention when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a flow diagram of a system for practicing the present invention;

FIG. 2 is a side elevation, schematic view of a combustion or reaction vessel for practicing the present invention;

FIG. 3 is an overhead, schematic view of a blower for practicing the present invention; and

FIG. 4 is a side elevation view of an impeller for practicing the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, the reference numeral 10 refers in general to a gasification system for practicing the present invention. The system 10 will typically comprise a combustion or reaction vessel 12, a scrubber housing 14, and a filter housing 16, and may also include a recycle housing 18.

Referring to FIG. 2, the reaction vessel 12 has an upper, outer wall portion 20 and a lower base portion 22. The reaction vessel 12 is open at the top. A feed line or conduit 24 is disposed above the vessel 12 to provide a carbonaceous fuel source. Another feed line 26 may also be provided to return waste material from other portions of the system 10 as discussed in more detail below. Additional feed lines may also be used, for example, to provide different types of solid and liquid fuel sources. An inner wall 28 is disposed within the vessel 12 and is connected to the vessel 12 to form an inner chamber 30 and an outer chamber 32. A lower portion of the inner wall 28 defines an opening 34. An ash support member 36 is affixed to a lower portion of the inner wall 28 by rigid members 38 so that the ash support member 36 is disposed a distance below the opening 34. The outer periphery of the ash support member 36 is relatively free from obstructions about the vast majority of the outer periphery, providing relatively open side passageways between the inner wall 28 and the ash support member 36. This allows ash to spill from the ash support member 36 preferably over at least approximately 80 percent of the outer periphery of the ash support member 36, more preferably over at least approximately 90 percent of the outer periphery of the ash support member 36, and most preferably over at least approximately 95 percent of the outer periphery of the ash support member 36.

A gas injection ring 40 is affixed to the inner wall 28 and is disposed at a medial point of the inner chamber 30. Openings 42 in the inner wall 28 provide a flow path for gas, such as air or an air and fuel mixture, to pass from a plenum 44 formed by the ring 40 into the inner chamber 30. A conduit 46 extends through the outer wall 20 of the vessel 12 and is operably connected to the ring 40. The conduit 46 is connected to an air source and is preferably connected to a fuel source, such as a source of natural gas or propane. As seen in FIG. 1, a recycle line 48 may also be provided to return a portion of the combustible gas generated by the system 10. An igniter 50, such as a spark plug igniter, is disposed in the conduit 46 adjacent to the reaction vessel 12.

A fuel agitator, such as a fuel stirring member 52 is provided in the inner chamber 30. The fuel stirring member 52 is preferably disposed above the opening 34 and is more preferably disposed above the ring 40. Similarly, an ash agitator, such as an ash stirring member 54 is provided inside the vessel 12, below the ring 40 and above the ash support member 36. Another ash agitator, such as ash stirring member 55 is provided inside the vessel 12, below the ash support member 36. Coaxial shafts 56 and 58 extend upward from the stirring members 52, 54 and 55 to or above an upper portion of the reaction vessel 12. Motors 60 and 62 are operably connected to the shafts 56 and 58 for rotating the shafts and stirring members 52, 54, and 55.

The frustoconical, lower base portion 22 of the reaction vessel 12 extends below the ash support member 36. An opening is provided at the bottom of the lower base portion 22 to allow ash to pass from the reaction vessel 12 to an ash removal system 64, such as an auger drive for solids transfer. A conduit 66 is provided through the outer wall of the vessel 12 in an upper portion of the outer chamber 32 to provide a path for combustible gases generated within the reaction vessel 12 to pass from the reaction vessel 12.

A fuel level sensor 68 is provided in the inner chamber 30, preferably above the opening 34, more preferably above the ring 40, and most preferably above the fuel agitator 52. The fuel level sensor 68 is operably coupled with the feed line 24 to automate the process of maintaining fuel at a desired level within the inner chamber 30. An ash level sensor 70 is disposed within the reaction vessel 12, preferably below the opening 34, more preferably below the ash agitator 54, and most preferably below the ash support member 36. The ash level sensor 70 is operably coupled with the ash removal system 64 to automate the process of maintaining ash at a desired level within the reaction vessel 12. It is of course understood that the reaction vessel 12 may take any number of sizes, shapes, and configurations. It is also understood that the vessel 12 need not be open at the top and need not be a downdraft reaction vessel 12.

Conduit 66 connects the reaction vessel 12 with the scrubber housing 14, providing a flow path into a lower portion of the scrubber housing 14. A pump 72 is provided to pass a liquid such as water through a water feed line 74 into an upper portion of the scrubber housing 14 and through sprayers. A water return line 76 is connected to a lower portion of the scrubber housing 14 for returning water to the pump 72 for reuse within the scrubber housing 14. A feed line 78 may also be provided for providing a source of fresh water. Wash lines 80 may be provided for intermittent use as described below. Scrubbed gas exits through conduit 82 that is disposed at an upper portion of the scrubber housing 14. A skim line 84 is provided at a lower portion of the scrubber housing 14, and a blow down line 86 is provided at the bottom of the scrubber housing 14. A level sensor 88, such as a float switch is disposed in the scrubber housing 14 for maintaining liquid levels within the scrubber housing 14 at desired levels. It is of course understood that the scrubber housing 14 may take any number of shapes, sizes, and configurations.

Conduit 82 passes from the scrubber housing 14 to blowers 90. As best seen in FIG. 3, the blowers 90 are heavy duty hybrids that combine desirable features of blowers designed for moving gases and pumps designed for moving liquids. Walls forming the impeller housing 92 preferably have a wall thickness of approximately ¾ inch. A sealing member 94, such as an O-ring is used to create an airtight and watertight seal between the walls forming the impeller housing 92. Referring to FIG. 4, the impeller blades 96 are curved and are thicker than impeller blades of common blowers designed for moving gases, preferably approximately 50 percent thicker. A packing gland 98, similar to a packing gland used in a water pump is used to provide a shaft 100 seal. Additional sets of bearings 102 are also used in connection with the impeller shaft 100. It is preferred to use at least three sets of bearings 102 and it is more preferred to use at least four sets of bearings 102. Conduit 104 passes from the blowers 90 to the filter housing 16, providing a flow path into a lower portion of the filter housing 16. It is of course understood that the blowers 90 may be disposed at any number of locations in the system 10 and that the blowers 90 may take any number of different sizes, shapes, and configurations. It is also understood that, although not preferred, conventional blowers may be used.

The filter housing 16 is preferably packed with wood chips. Conduit 106 passes from an upper portion of the filter housing 16 to provide a flow path for the scrubbed and filtered combustible gas. Additional conduits 108, 48, and 110 are also provided for passing the scrubbed, filtered combustible gas to flare, to recycle, and for further uses. A conduit 112 passes from a lower portion of the filter housing 16 for removing wastewater and other matter that condenses or is removed from the gas as it passes through the filter housing 16. It is understood that the filter housing 16 may take any number of shapes, sizes, and configurations and that any number of different filter media or combinations of filter media may be used.

Conduits 84, 86, 112, and 114 connect the scrubber housing 14 and filter housing 16 to a recycle housing 18, providing a flow path into an upper portion of the recycle housing 18. Return line or conduit 116 passes from a lower portion of the recycle housing 18 to pump 118 and line 26 passes from pump 118 to reaction vessel 12. A recirculation line 120 is provided for diverting a portion of the liquid from the return line 26 back to the recycle tank 18. A level sensor 122, such as a float switch, is disposed in the recycle housing 18 for maintaining liquid levels within the recycle housing 18 at desired levels. It is understood that the recycle housing 18 may take any number of different shapes, sizes, and configurations.

In operation, feed line 24 provides a solid carbonaceous fuel to the reaction vessel 12. The solid fuel drops through the inner chamber 30, accumulates on the ash support member 36, and builds up within the inner chamber 30 to a level above the ring 40 and then above the fuel stirring member 52. An oxygen source, such as air, is provided via conduit 124 , and an alternate fuel source is provided via conduit 126. The air and alternate fuel are mixed, ignited by igniter 50, and pass through the ring 40 and into the inner chamber 30. The burning air and alternate fuel mixture ignites the carbonaceous fuel within the inner chamber 30. As the carbonaceous fuel sources pass downward within the inner chamber 30, the carbonaceous fuel sources are at least partially combusted to produce, among other things, ash and a combustible gas. Fuel stirring member 52 keeps the different fuel sources blended and reduces or prevents channeling and similar problems.

Ash passes through opening 34 and collects on ash support member 36. The ash stirring member 54 prevents ash build up by moving the collecting ash outward so that the ash spills or passes from the outer periphery of the ash support member 36 down to the lower base portion 22 of the reaction vessel 12. Other than the ash stirring member 54 and support members 38, the area between the opening 34 of the inner wall 28 and the ash support member 36 is substantially unobstructed to provide a ready path for ash removal free from obstructions and sources of clogging such as grates or mesh materials. In that regard, the support members 38 connect the ash support member 36 to the inner wall 28 in a manner that allows ash to spill from the ash support member 36 preferably over at least approximately 70 percent of the outer periphery of the ash support member 36, more preferably over at least approximately 80 percent of the outer periphery of the ash support member 36, and most preferably over at least approximately 90 percent of the outer periphery of the ash support member 36.

Ash that accumulates in the lower base portion 22 of the reaction vessel 12 passes through an opening in the bottom of the reaction vessel 12 and is removed by an ash removal system 64, such as by an auger or screw drive. The auger drive 64 is operably coupled with ash level sensor 70 to maintain the ash in the reaction vessel 12 below a desired amount. The ash removed from the reaction vessel 12 will typically be a salable product.

The fuel level sensor 68 is operably coupled with the solid fuel feed line 24 to maintain solid fuel within a desired height range within the inner chamber 30. The desired height range will vary depending upon a number of factors, including but not limited to the properties of the solid fuel. It is typically desirable to maintain the solid fuel level within the inner chamber 30 at the lowest possible level while still maintaining an adequate seal to prevent products of combustion from escaping through the top of the reaction vessel 12. The level desired will vary with factors such as the density and moisture content of the solid fuel. For example, the desired level for a solid fuel comprised primarily of chicken litter will be higher than the desired level for a solid fuel comprised primarily of wood pulp or paper mill sludge, and the desired level for a solid fuel comprised primarily of wood pulp sludge will be higher than the desired level for a solid fuel comprised primarily of sanding dust. In a typical operation in which the solid fuel is comprised primarily of chicken litter, the level of solid fuel within the inner chamber 30 is preferably maintained at a height of approximately 8 inches to approximately 10 inches above the ring 40. Similarly, in an operation in which the solid fuel is comprised primarily of wood pulp sludge, the level of solid fuel within the inner chamber 30 is preferably maintained at a height that is only slight above the ring 40. Also, in an operation in which the solid fuel is comprised primarily of sanding dust, the level of solid fuel within the inner chamber 30 is preferably maintained at a height that is approximately even with or slightly below the ring 40.

The blowers 90 draw gaseous products of combustion downward through the reaction vessel 12 so that they pass through the opening 34 in the inner wall 28 and upwardly through the outer chamber 32 before passing through conduit 66. Combustible gas from the reaction vessel 12 enters a lower portion of the scrubber housing 14 and passes upward toward conduit 82. Pump 72 circulates water to the scrubber housing 14. Water enters the scrubber housing 14 through conduit 74, passes through sprayers, and contacts the combustible gas. The water cools and scrubs the combustible gas, removing matter from the combustible gas including tar, oil, and particulate matter. The water level in the scrubber housing 14 is maintained at a desired level so that tar, oil, and similar matter may be removed from the scrubber housing 14 via the skimmer line 84. Particulate matter and other components that settle to the bottom of the scrubber housing 14 are periodically removed via blow down line 86. Valves 128 are also opened periodically so that the pump 72 may circulate water through wash lines 80 and through conduits 66, 82, and 104 for cleaning. From time to time, valve 130 may be opened so that the water in scrubber housing 14 may also be drained through line 86 and replaced with fresh water from line 78.

The scrubbed combustible gas exits the scrubber housing 14 through line 82, passes through blowers 90 and is driven through filter housing 16. As it exits the scrubber housing 14, the gas may also be passed through a filter/knock-out pot, before being passed to the blowers 90. Wood chips in the filter housing 16 dry the gas and remove additional amounts of particulate matter and other pollutants. Wastewater and other matter that are removed from the combustible gas and that are not absorbed by the wood chips fall to the bottom of the filter housing 16 and are removed via line 112. Scrubbed, filtered combustible gas exits the filter housing 16 via line 106. From there the combustible gas is flared, returned to the reaction chamber, or sent to other uses. During initial start-up phase, the combustible gas is flared until it is determined that gas is being produced at a desired quantity and quality. Once the start-up phase is complete, the combustible gas will primarily be passed via line 110 to produce work elsewhere. For example, the combustible gas might be combusted to supply heat to a process or might be combusted within a motor or turbine to produce work or to generate electricity. As additional examples, the combustible gas produced by the system 10 may be used in brooder heaters in poultry houses, in internal combustion engines, and in boilers. In fact, the combustible gas generated by the present system 10 compares quite favorably with natural gas, often being cleaner while having comparable or higher heating values. The heating values of the combustible gas produced will vary depending upon a number of factors, such as the type, composition, and moisture content of the carbonaceous fuel provided, but the heating values of the combustible gas produced will typically be at or near 550 BTU per cubic foot. Accordingly, combustible gas produced using the present system 10 is a good candidate for use in any situation that currently uses natural gas or propane.

Depending upon the properties of the carbonaceous fuels being supplied to the reaction vessel 12, such as the moisture content, a portion of the combustible gas may be returned to the reaction vessel 12 via line 48 to supply additional fuel to aid in the partial combustion of the carbonaceous fuel. The combustible gas supplied via line 28 may serve as a complete or partial replacement for the alternate fuel source supplied to the reaction vessel 12 via line 126. Returning the combustible gas to the reaction chamber 12 offers a number of advantages. For example, it saves on fuel costs that might otherwise be required to maintain the desired combustion in the reaction vessel 12. The combustible gas will typically burn at higher temperatures than natural gas, and the higher temperatures are often desirable in the reaction vessel 12. For example, natural gas may burn at a temperature of approximately 1400° F., whereas a typical combustible gas produced using the present system 10 may burn at a temperature of approximately 2200° F.

Lines 86, 84, 112, and 114 pass from the scrubber housing 14 and the filter housing 16 to recycle housing 18. These lines 86, 84, 112, and 114 pass wastewater, excess water from wet fuel components, tar, oil, particulate matter, and other removed substances to an upper portion of the recycle housing 18. These components pass from the recycle housing 18 via line 116, and pump 118 passes these components via line 26 back to the reaction chamber 12, where they are fed into an upper portion of the reaction vessel 12. A portion of these components is diverted via line 120 and returned to the recycle tank 18 to help stir or agitate the contents of the recycle tank 18. Returning the wastewater and other components to the reaction vessel 12 provides a number of advantages. For example, the wastewater scavenges additional, residual carbon from the ash as the water is broken down. This provides for better recovery of the heating value from the carbonaceous fuel and eliminates or drastically reduces the need to dispose of wastewater.

The system 10 may be used to process a wide variety of carbonaceous fuels, as well as combinations thereof. The spacing between the ash support member 36 and the opening 34 of the inner wall 28, as well as the relatively unobstructed side openings there, allow a wide assortment of solid fuels to be used without fear of clogging. Possible carbonaceous fuels include but are not limited to things such as chicken litter, other animal waste, municipal solid waste, glued woods (such as plywood and press board), paper mill or wood pulp sludge (including sludge with a moisture content of 65% or higher), wood or yard waste, and shredded tires. Liquid carbonaceous fuels may also be added, including but not limited to waste motor oil and cooking oil. Adding these liquid carbonaceous fuels can markedly increase the heating value of the combustible gas produced.

The following emissions test examples illustrate that the gasification system 10 of the present invention can produce combustible gas that is environmentally friendly while dispensing with solid carbonaceous fuels that previously posed serious landfill issues.

EXAMPLE 1

An emissions test was conducted on combustible gas generated by the system 10 while combusting chicken litter. A sample run of 60 minutes in duration was performed. Testing was performed in accordance with the methods detailed in 40 C.F.R., Part 60, Appendix A. The flow, based on the lowest recordable flow, had a velocity of 6.77 feet per second, and the sample collected had a volume of 41.42 dry standard cubic feet. The results of the emissions testing are summarized in Table 1 below.

TABLE 1
                                 Emissions
Substance                        (lbs/hr)
Particulate Matter (based on lowest detectable flow rate) 0.003
VOC as Propane (corrected for moisture) 0.137
Nitrogen Oxides as NO2           0.001
Carbon Monoxide                  0.003
Sulfur Dioxide                   0.096
Ammonia                          0.033
HCl                              0.008
Chloride                         0.005

EXAMPLE 2

An emissions test was conducted on combustible gas generated by the system 10 while combusting paper mill sludge. A sample run of 60 minutes in duration was performed. Testing was performed in accordance with the methods detailed in 40 C.F.R., Part 60, Appendix A. The flow, based on the lowest recordable flow, had a velocity of 6.53 feet per second, and the sample collected had a volume of 40.60 dry standard cubic feet. The results of the emissions testing are summarized in Table 2 below.

TABLE 2
                                 Emissions
Substance                        (lbs/hr)
Particulate Matter (based on lowest detectable flow rate) 0.0014
VOC as Propane (corrected for moisture) 0.014
Nitrogen Oxides as NO2           0.013
Carbon Monoxide                  0.051
Sulfur Dioxide                   0.017

Other modifications, changes and substitutions are intended in the foregoing, and in some instances, some features of the invention will be employed without a corresponding use of other features. For example, the configuration of the ash support member 36 may be used in combination with any number of different gasification systems, regardless of whether such systems also use other features of the present invention, and may also find uses in systems other than gasification systems. Similarly, the wastewater return features of the present invention may be used in combination with any number of different gasification systems, regardless of whether such systems also use other features of the present invention, and may also find uses in systems other than gasification systems. Further, the wood chip filtering of the present invention may be used in combination with any number of different gasification systems, regardless of whether such systems also use other features of the present invention, and may also find uses in systems other than gasification systems. Further still, the hybrid blower 90 design of the present invention may be used in combination with any number of different gasification systems, regardless of whether such systems also use other features of the present invention, and may also find uses in systems other than gasification systems. Of course, quantitative information is included by way of example only and is not intended as a limitation as to the scope of the invention. Accordingly, it is appropriate that the invention be construed broadly and in a manner consistent with the scope of the invention disclosed.

Claims

1. A method, comprising:

(1) at least partially combusting a carbonaceous fuel to produce a combustible gas;

(2) passing said combustible gas through sprayed water to produce a scrubbed gas;

(3) passing said scrubbed gas through wood chips; and

(4) after step (3), combusting said scrubbed gas.

2. The method of claim 1, wherein step (1) comprises:

at least partially combusting said carbonaceous fuel to produce said combustible gas, said carbonaceous fuel comprising chicken litter.

3. The method of claim 1, wherein step (1) comprises:

at least partially combusting said carbonaceous fuel to produce said combustible gas, said carbonaceous fuel comprising wood pulp sludge.

4. The method of claim 1, wherein:

step (1) comprises at least partially combusting said carbonaceous fuel in a reaction vessel to produce said combustible gas; and

step (2) comprises passing said combustible gas through said sprayed water in a scrubber housing to produce said scrubbed gas; and further comprising

passing wastewater from said scrubber housing to said reaction vessel.

5. The method of claim 1, wherein:

step (1) comprises at least partially combusting said carbonaceous fuel in a reaction vessel to produce said combustible gas; and

step (3) comprises passing said scrubbed gas through said wood chips in a filter housing;

and further comprising

passing wastewater from said filter housing to said reaction vessel.

6. The method of claim 4, wherein:

step (3) comprises passing said scrubbed gas through said wood chips in a filter housing;

and further comprising:

passing wastewater from said filter housing to said reaction vessel.

7. The method of claim 1, wherein:

step (1) comprises at least partially combusting said carbonaceous fuel in a reaction vessel to produce said combustible gas;

step (2) comprises passing said combustible gas through said sprayed water in a scrubber housing to produce said scrubbed gas; and

step (3) comprises passing said scrubbed gas through said wood chips in a filter housing;

and further comprising:

passing wastewater from said scrubber housing to a recycle tank;

passing wastewater from said filter housing to said recycle tank; and

passing said wastewater from said scrubber housing and said wastewater from said filter housing from said recycle tank to said reaction vessel.

8. A method, comprising:

(1) at least partially combusting a carbonaceous fuel in a reactor vessel to produce a combustible gas;

(2) passing said combustible gas to a scrubber housing;

(3) spraying a liquid on said combustible gas within said scrubber housing; and

(4) passing a first portion of said liquid from said scrubber housing to said reactor vessel.

9. The method of claim 8, wherein step (3) comprises:

spraying said liquid on said combustible gas within said scrubber housing, said liquid comprising water.

10. The method of claim 8, wherein step (3) comprises:

spraying said liquid on said combustible gas within said scrubber housing to remove matter from said combustible gas, said matter comprising tar and oil; and further comprising:

passing said tar and oil from said scrubber housing to said reactor vessel.

11. The method of claim 8, further comprising:

passing said combustible gas from said scrubber housing to a filter housing; and

passing a waste liquid from said filter housing to said reaction vessel.

12. The method of claim 8, wherein step (4) comprises:

passing said first portion of said liquid from said scrubber housing to a recycle housing; and

passing said first portion of said liquid from said recycle housing to said reaction vessel.

13. The method of claim 12, wherein step (3) comprises:

spraying said liquid on said combustible gas within said scrubber housing to remove matter from said combustible gas, said matter comprising tar and oil; and further comprising:

passing said tar and oil from said scrubber housing to said recycle housing; and

passing said tar and oil from said recycle housing to said reactor vessel.

14. The method of claim 13, further comprising:

passing said combustible gas from said scrubber housing to a filter housing;

passing waste liquid from said filter housing to said recycle housing; and

passing said waste liquid from said recycle housing to said reaction vessel.

15. A combination, comprising:

a reaction vessel having an upper outer wall portion and a lower base portion;

an inner wall disposed within said vessel, an upper portion of said inner wall being connected to said vessel to form an inner chamber and an outer chamber, a lower portion of said inner wall defining a first opening within said vessel;

an ash support member disposed within said vessel below said first opening, said ash support member being affixed within said vessel so that ash may spill from said ash support member over at least approximately 80 percent of an outer periphery of said ash support member.

16. The combination of claim 15, wherein said ash support member is affixed within said vessel so that ash may spill from said ash support member over at least approximately 90 percent of said outer periphery of said ash support member.

17. The combination of claim 15, further comprising:

a first agitating member disposed within said reaction vessel above said opening; and

a second agitating member disposed within said reaction vessel below said opening.

18. The combination of claim 15, further comprising:

a scrubber housing, said scrubber housing being operably connected to said reaction vessel to provide a flow path from said outer chamber of said reaction vessel to said scrubber housing;

a filter housing, said filter housing being operably connected to said scrubber housing; and

wood chips disposed in said filter housing.

19. The combination of claim 15, further comprising:

a blower disposed downstream from said reaction vessel and operably connected to said reaction vessel for withdrawing a combustible gas from said reaction vessel, said blower comprising:

an impeller housing;

an impeller disposed within said impeller housing; and

an O-ring, said O-ring disposed to provide a seal between portions of said impeller housing.

20. The combination of claim 19, said blower further comprises:

a shaft affixed to said impeller; and

at least three sets of bearings operably connected to said shaft.