System & Method for mixing and distributing air and steam in a gasifier

Abstract

A gasifier system for converting biomass to biogas includes a reaction chamber with a biomass supply port for receiving a biomass volume, a waste outlet port for discharging biomass conversion by-products, a gas inlet for receiving heated oxidizing gas, a gas outlet for discharging generated biogas and a burner manifold for distributing oxidizing gas within the chamber to react the biomass. The burner manifold includes primary tubes and secondary tubes, positioned in a vertically lower part of the chamber and configured with multiple openings or ports for dispensing the oxidizing gas, where the secondary tubes extend into, inject and evenly distribute the oxidizing gas into the biomass volume to optimize conversion to biogas.

Description

BACKGROUND OF THE INVENTION

The present invention broadly relates to gasifier technology and, more particularly relates to a gasifier system configured for energy-efficient generation of an oxidizing air/steam mixture and distribution of same within the gasifier chamber to optimize a biogas production.

Gasification is a high-temperature thermal decomposition process for converting a fuel or feedstock, such as solid coal, petroleum coke, biomass, and/or solid waste, or liquid feedstock, such as black liquid oil, or a gaseous feedstock, into a fuel gas, consisting primarily of hydrogen (H₂) and carbon monoxide (CO), with lesser amounts of carbon dioxide (CO₂), water (H₂O), methane (CH₄), higher hydrocarbons and nitrogen (N₂) using reactants such as air, steam and oxygen, either alone or in any combination thereof.

Thermal gasification processes are highly endothermic chemical reactions. The general methods for supplying heat for the gasification use either of the following: a) an external source, e.g. sensible heat from hot char recirculation, and/or sensible heat from a heated gasification agent, b) reaction heat from oxidization of a part of the feedstock (incoming carbonaceous materials), and c) exothermal reaction heat from a non-carbonaceous material such as calcined lime and CO₂.

FIG. 1 depicts a known biomass gasifier 10, comprising a combustion or reaction chamber 15. Biomass fuel (or bio fuel) 20, e.g., wooden chips, wooden pellets, various by-products from naturally growing and bioengineered crops and flora, etc., without limitation, is fed into an opening or chute 25 disposed in an upper surface of the reaction chamber 15. Air, or a mixture of air and steam 30, is fed into the reaction chamber via a gas inlet port 35 to facilitate decomposition or oxidation of the biomass. A shutter or shutter pair 22 regulates the feed of the biomass fuel 20 into the reaction chamber 15 and prevents communication of outside air into the chamber, or the exit of chamber gases into the environment.

The heated air/steam mixture 30, which contains oxygen, may be said to “roast” the biomass fuel 20 in pyrolysis and gasification zones in the lower part the reaction chamber 15. That is, the biomass fuel 20 is partially combusted using the oxygen in the air/steam mixture 30. Partial combustion and pyrolysis result in the production of heated biogas 45 (referred to interchangeably herein as produced gas or synthetic gas), which heated biogas exits from gas outlet port 50 and is captured by means known to the skilled artisan. Ash including carbon, charcoal, etc., and other combustion and pyrolysis by-products 55, such as burnt embers, exits the reaction chamber 15 though an opening or port 60 in a bottom surface.

Tar is an undesirable by-product which is produced when the partial combustion temperature drops from 1000 degrees Centigrade to below 800 degrees C. The temperature inside of the reaction chamber 15 is controlled by controlling the rate of combustion therein by adjusting the amount of air/steam supplied. Ideal reaction chamber temperatures for optimized biogas generation are as follows: bottom or combustion zone temperature: about 1000 degrees C. or greater; lower middle or gasification zone temperature: about 600 degrees C.; upper middle or pyrolysis zone temperature: about 200 degrees C.; and top or reheating zone temperature: about 60 degree C. Typically, the reaction chamber temperature is controlled so that it drops to a temperature in which tar is produced after the biogas exits the gasifier chamber 15 (see inventive system depicted in FIGS. 9a, 9B and 10).

Conventional gasifier constructions (such as shown in FIG. 1) render it difficult to control the heated air/steam distribution in the reaction chamber 15 and, therefore, pyrolysis, gasification and partial combustion to optimize gas generation. For example, hot areas such as hot area 40 can result outside of the preferred combustion, gasification and pyrolysis and zones within the reaction chamber 15. While the temperature varies throughout the reaction chamber 15 varies (the combustion zone temperatures can reach 1000° C.), the air and steam arrives to conventional gasifiers at much lower temperatures. While steam arrives in zone 40 at around 120° C., the temperature at zone 40 is likely only about 40° C. as the temperature of outside fresh air mixes with the steam and drops its temperature.

As the gasifier uses steam as an oxidant, it is quite difficult to maintain conditions that allow gasifier to properly crack the gas, typically resulting in a large mass of tar being unintentionally produced. When humidity of bio-mass at entry port 25 is more than 4%, more tar is produced. When tar is produced in the reaction chamber, it damages steam generator, hot air generator as well as any heat exchanger, requiring maintenance. Secondarily, the inability to effectively distribute the heated air/steam mixture results in limited biogas quality, for example, a diminished H₂ content.

FIG. 2 shows a known biomass gasifier 10 that utilizes a separate heating system to heat water 70 to generate steam for use as an oxidant in the air/steam mixture 30. That is, a water tank 65 supplies water 70 to a separate boiler 75 to generate the steam using heat source 80. There is an associated cost in capital equipment, space and fuel to operate the water tank 65, boiler 75 and heat source 80 to generate the steam and heated steam for the air/steam mixture. Gas is typically used as the fuel to heat the water 70 to steam in the boiler 75, the cost for which diminishes the energy return value for the generated biogas.

SUMMARY OF THE INVENTION

The present invention presents a gasifier system that overcomes the shortcomings of known gasification systems and methods.

The gasifier system of the invention does not need to use extra fuel to boil water and heat air as it reuses waste heat of the gasifier, resulting in cost savings in the generation of biogas and in view of the fact that extra burners for heating the air and water/steam are unnecessary.

The inventive gasifier system operates with Double-Decker tube manifold construction formed to effectively disperse oxidizing air/steam through the biomass/reactions chamber. The burner manifold comprising the Double-decker tubes is located on a water-cooled support bar such that the Double-Decker tubes may move with heat expansion independently of the gasifier wall structure to prevent lock up and damage to the structure or tubes.

In an embodiment, the invention provides a gasifier system for converting biomass to biogas includes a reaction chamber with a biomass supply port for receiving a biomass volume, a waste outlet port for discharging biomass conversion by-products, a gas inlet for receiving heated oxidizing gas, a gas outlet for discharging generated biogas and a burner manifold for distributing oxidizing gas within the chamber to react the biomass. The burner manifold includes primary tubes and secondary tubes, positioned in a vertically lower part of the chamber and configured with multiple openings or ports for dispensing the oxidizing gas, where the secondary tubes extend into, inject and evenly distribute the oxidizing gas into the biomass volume to optimize conversion to biogas.

The gasifier system may includes a water-cooled support system positioned in the reaction chamber to support and enable the burner manifold to expand and contract in response to changes in temperature without obstruction, and a controller. Preferably, the water-cooled support system is physically attached to a reaction chamber wall with a top surface that extends into the reaction chamber and is in sliding contact with the burner manifold.

In another embodiment, the invention provides a gasifier system converting biomass to biogas that includes a reaction chamber including a regulated input port for receiving a biomass volume, a waste outlet port for discharging biomass to biogas conversion by-products, a regulated gas inlet for receiving heated oxidizing gas, a regulated gas outlet for discharging generated biogas, a burner manifold and a water heating chamber. The burner manifold is included for distributing oxidizing gas within the reaction chamber that comprises primary and secondary conduits, is positioned in a vertically lower portion of the chamber and is configured with multiple outlets or ports for injecting the oxidizing gas into the biomass volume, substantially evenly distributing the oxidizing gas therethrough.

The water heating chamber is in fluid communication with the gas outlet for receiving a flow of hot biogas, exposing water to the hot biogas to heat the water to steam and supplying the steam to the gas inlet port as oxidizing gas. Preferably, the gasifier system further includes an air heating chamber in fluid communication with the gas outlet for receiving a flow of hot biogas, exposing air to the hot biogas to heat the air and supplying the heated air to the gas inlet port as oxidizing gas, where the heated air and steam are first mixed before being supplied as oxidizing gas.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can best be understood in connection with the accompanying drawings. It is noted that the invention is not limited to the precise embodiments shown in drawings, in which:

FIG. 1 is a system level representation of a known biomass gasifier;

FIG. 2 is a system level representation of a known biomass gasifier that utilizes a separate heating system to generate steam to mix with air as an oxidant;

FIGS. 3 depicts a gasifier configured with a Double-Decker tube-based oxidizing gas distribution manifold for controlling distribution of an air/steam mixture within the biomass/reaction chamber in accordance with the invention;

FIG. 4 depicts an Double-Decker tube-based oxidizing gas distribution manifold for use in a gasifier the invention;

FIG. 4A depicts the oxidizing gas distribution manifold of FIG. 4 with a grating structure to contain biomass volume;

FIG. 4B depicts the process of forming double-decker pipes/tubes, support plate and secondary tubes to configure an oxidizing gas distribution manifold of the invention;

FIG. 4C depicts an oxidizing gas distribution manifold in an exploded view;

FIGS. 5A and 5B together depict ill-effects of heat expansion and contraction in a gasifier wherein the double-decker based oxidizing gas distribution manifold is fixed to the chamber wall;

FIG. 6 depicts a gasifier embodiment configured with a water-cooled support system upon which the oxidizing gas distribution manifold and double-decker tubes can slide to accommodate for heat expansion and contraction;

FIGS. 6A and 6B depict operation of the FIG. 6 gasifier in heat expansion and contraction, respectively;

FIG. 7 depicts a gasifier system that includes an gasifier configured with a water-cooled support and oxidizing gas distribution manifold within a reaction chamber connected to a conventional steam heating system and air/steam mixing chamber;

FIG. 8 is a system level representation of a biomass gasifier system and water-cooled support oxidizing gas distribution manifold that includes structure for utilizing heat from the generated biogas to heat air and generate for use in the gasification process;

FIGS. 9A and 9B together depict a generator system which includes the gasifier system of FIG. 8; and

FIG. 10 depicts a controller which may be used in the gasifier system.

DETAILED DESCRIPTION OF THE INVENTION

The following is a detailed description of example embodiments of the invention depicted in the accompanying drawings. The example embodiments are in such detail as to clearly communicate the invention and are designed to make such embodiments obvious to a person of ordinary skill in the art. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention, as defined by the appended claims.

FIG. 3 depicts one embodiment of a cross-draft biomass gasifier 100 of the invention. The gasifier 100 is configured with oxidizing gas distribution manifold 82 comprising double-decker tubes or pipes 85, which is fixed within reaction chamber 15, i.e., fixed to the inner chamber walls for support. The oxidizing gas distribution manifold 82 is configured for effectively distributing an air/steam mixture 30 within a volume of biomass 20 delivered into the chamber 15 via opening or chute 25. While not shown in FIG. 3, shutter or shutter pair 22 regulates the feed the biomass fuel into the gasifier 10 reaction chamber 15 and prevents communication of outside air into the chamber, or the exit of chamber gases into the environment. The gasifier 100 is approximately 4 to 6 meters from top to bottom, and approximately 2 to 4 meters wide.

Air and/or steam 30 are supplied to the double-decker tubes 85 through a gas inlet port 35. As can be seen in the FIG. 3, the oxidizing gas distribution manifold 82 is arranged in the lower middle or lower portion of the reaction chamber 15. The double-decker tubes or pipes 85 are preferably formed from stainless steel material, for example, SUS 310S or 304 manufactured by Shin Nippon Steel, Japan. The manufacturer of the double-decker tubes is Kowa Kogyo Co., Japan.

The oxidizing gas distribution manifold 82 relies on the double-decker tubes 85 (comprising two main conduits) to function as primary conduits and further comprises a plurality of secondary tubes 88 that extend from the primary conduits or tubes 85. The surfaces of the secondary tubes 88 are configured with a distribution of small through-holes 86 to allow oxidizing gas, an air/steam mixture, to effectively distribute the air/steam mixture within the volume of biomass in the reaction chamber 15. For that matter, some part of the surfaces of the primary double-decker tube conduits also may be configured with through-holes 86 to disperse the air/steam mixture.

The air/steam mixture 30 is blown out via the small holes 86 of the secondary tubes 88, spouting in all directions, i.e., the upper direction, the side directions and the lower direction to evenly mix within and heat to decompose the bio fuel. This distribution mechanism, i.e., the oxidizing gas distribution manifold 82, results in a more effective dispersion of oxidant and heat throughout the biomass volume with the reaction chamber 15, thereby optimizing temperature control and gasification. Please note that while not shown, the double-decker tubes also may include through-holes to support air/steam dispersion.

The oxidizing gas distribution manifold 82, comprising double-decker tubes 85, secondary tubes 88 and through-holes 86, offers a significant advantage over the use of a single inlet to deliver oxidizing gas in known gasifier designs. For that matter, while double-decker tubes are preferred, single or triple-decker tubes may be used in place of double-decker tubes without deviating from the inventive scope. The arrangement of the secondary tubes 88 and through holes 86 for dispersing the oxidant throughout the biomass volume is of primary importance as same arrangement defines the effectiveness of the oxidizing mixture with the biomass and, therefore, the effectiveness of biogas generation.

FIG. 4 presents a detailed view of an oxidizing gas distribution manifold 82 for use in a gasifier 100 of the invention. The square or rectangular shape of the double-decker tube 85 arrangement defines the shape of the manifold 82, allowing it to conform to the square or rectangular shape of the gasifier 100 (or reaction chamber 15). The upper extending secondary tubes 88 are positioned about an outer perimeter that is furthest from an axial center of the reaction chamber. These outer secondary tubes 88 are of the greatest height (1 to 3 feet depending on the size of the reaction chamber in which the manifold with operate), where as the position of the secondary tubes moves closer to the axial center of the chamber 15, the respective heights decrease (as shown). This changing height of the secondary tubes 88 provides for a manifold that may be likened to an inverted quadrangular pyramid.

FIG. 4A depicts this oxidizing gas distribution manifold 82 in greater detail. As seen therein, a grating structure 89 actually forms the inverted quadrangular shape (with the double-decker tubes 85 and secondary tubes 88) that readily contains the bio-mass 20 piles within its respective contained space or volume. Preferably, the biomass fuel sits in a metallic mesh basket above the oxidizing gas distribution manifold 82.

As already mentioned, while the double-decker tubes 85 are preferred, a single layer or level of tubes (as distinguished from double-decker layer of tubes) may be used to form the oxidizing gas distribution manifold 82. A single (horizontal) tube layer formed in a rectangular shape is much more likely to be unstable, however, as there is at times an uneven weight distribution of biomass fuel across the oxidizing gas distribution manifold 82. Consequently, even where the single level (primary conduit) design is arranged in an inverted quadrangular pyramidal structure, same may nevertheless be unstable and more likely to twist and possibly topple over inside the chamber 15 when compared to the preferred oxidizing gas distribution manifold 82 formed with the double-decker tubes.

The formation or manufacture of the oxidizing gas distribution manifold 82 with double-decker tubes 85 and secondary tubes 88 is now described in cooperation with FIGS. 4B and 4C. FIG. 4B highlights the process of forming a pipe or tube 85, a support plate 89 and secondary tubes 88 using a laser cutting tool 91. Attachment holes 93 are made in the primary conduit (e.g., double-decker tubes 85) in order to receive the secondary tubes 88. Plate 89 is cut to form support structure, such as grating structure 89.

FIG. 4C depicts the oxidizing gas distribution manifold 82 with its components in an exploded view. Connecting tube portions 92 (also cut with a laser) are included to interconnect double-decker tube 85 layers, where necessary. After being cut to form though-holes 86, the secondary tubes are welded or otherwise attached to the double-decker tubes 85 (see FIG. 4B). During operation, an air/steam mixture is always passing through the double-decker tubes 85, secondary tubes 88 and out through-holes 88, which substantially prevents any clogging of the through-holes. During shutdown, however, biomass fuel particles may pass into the secondary tubes and clog the through-holes. But such clogs are temporary as when the gasifier again becomes operational the heat from combustion burns these particles whether within the secondary tube 88 volume or in the through-holes 88.

During gasifier system operation, biomass fuel is decomposed and burned in the gasifier chamber 15 at rates that change according to the amounts of available air and steam. When the burning rate changes, the temperature changes accordingly. For that matter, there are different zones within the reaction chamber, with ideal temperature ranges to optimize the process and therefore biogas generation. For example, in and around what may be described as a first or pre-heating zone A, the temperature is preferably maintained at or around 60° C. This pre-heating zone operates to remove moisture from the bio fuel. In the drying area, or zone A, the bio-mass dries as the temperature rises.

In a pyrolysis zone B, the temperature preferably is around 200° C., to which the biomass or bio fuel begins decomposition reacts to generate carbon (C) and volatiles. Vertically lower in the chamber is a gasification zone C. Gasification zone is preferably maintained at or around 600° C. to react carbon (C) compounds with H₂O and air (O₂) to realize carbon fuels (C_xH_y), carbon dioxide (CO₂), carbon monoxide (CO) and hydrogen (H₂). The simplest way to adjust the product (gas) is to select to bio-mass material. Woodchip is the best material, then rice husk and straw. Food residue is also available but it contains large amounts of water that precipitate tar formation.

In the pyrolysis zone, or zone B, the bio-mass material is thermally decomposed according to

CxHyO₂->Ch4,CO,CO₂,H₂,H₂O,Cs,Tar.

At reduction zone, or gasification zone C, gasification of solid carbon at heat decomposition according to C+H₂O->CO+H₂.

At oxidation zone, or zone D, heat is generated with controlled burning (oxidation).

C+½O₂->CO+29.4 kcal

C+O₂->CO₂+97 kcal

In gasifier 100 (FIG. 3), the oxidizing gas distribution manifold 82 comprising the double-decker tubes 85 and secondary tubes 88 is fixed to an inside surface of the reaction chamber 15. A plate or other structural means 90 is fixed or bolted to the inner surface of the reaction chamber to which a portion of the oxidizing gas distribution manifold 82 is fixedly attached. The oxidizing gas distribution manifold 82 and double-decker tubes 85 must be supported as it supports the weight of the biomass being processed. But as support for the oxidizing gas distribution manifold 82 and double-decker tubes 85 is necessary, the fixation can cause deformation in gasifier chamber structure in the case of extreme temperature fluctuation.

In more detail, the coefficient of thermal expansion for SUS 304S steel is 17.3×10⁻⁶/° C. The temperature of the incoming air/steam 30, for example, is likely less than or equal to 100° C. (212° F.), where the temperature of the biogas produced is in a range around 800° C. (1500° F.). As this temperature differential is about 700 Centigrade degrees, the steel comprising the double-decker tube 85 and secondary tubes 88 likely expands and contracts significantly over time. For example, the length of a 2 meter steel pipe will change in length with a 700 degree Centigrade increase in temperature (2×700° C.×17.3×10⁻⁶/° C., or 0.02422 m) This is about one inch over 2 meters.

As the stainless steel double-decker tubes 85 are fixed or locked to the inner chamber wall, expansion is limited and likely results in bending of the tubes and/or of the inner chamber wall to which the tubes are attached via plates 90. FIG. 5A depicts gasifier 100 (FIG. 3 embodiment where oxidizing gas distribution manifold 82 is fixed to the chamber wall) in a heated state where double-decker pipes 85 are expanded to the left in the direction of arrow 92. As the double-decker tubes 85 are fixed to the chamber wall, such expansion has the potential to deform the chamber structure (indicated by stars 94), particularly in and around attachment means 90.

If expansion is extreme, the deformation of the chamber walls may be irreversible, resulting in a need for shutdown and refurbishment. But even where the expansion is not so extreme, when the gasifier cools, the oxidizing gas distribution manifold 82 including the double-decker tubes 85 contracts in the direction of arrow 95′ shown in FIG. 5B. The buckling or deformation of the chamber walls that might result from contraction is highlighted by stars 94.

An embodiment depicted in FIG. 6 overcomes the shortcomings of the gasifier design depicted in FIGS. 5A and 5B. That is, gasifier 100′ (FIG. 6) includes a water-cooled support system upon which the oxidizing gas distribution manifold 82 and double-decker tubes 85 can slide to accommodate for heat expansion and contraction. The water-cooled support system comprises left-side and right-side support structures 105, positioned at the right and left sides of the gasifier chamber 15 proximate oxidation zone D. The left-side and right-side support structures 105 are identical, each including a respective water inlet 106, located outside of the reaction chamber 15, for feeding water (preferably at around room temperature or 25° C.) into each of respective left and right water support bars 107. Each water support bar 107 operates as a conduit facilitating water flow one way to a water outlet 109. The water conduit may be single or multiple layers.

Each water support bar 107 is fixed to and extends through the reaction chamber wall. The in-chamber portion of the water-support bars 107 contact and support the oxidizing gas distribution manifold 82 and double-decker tubes. Left and right sides of the double-decker tube 85 slidably rest upon the respective left and right water support bars at contact points 108, as shown. The water flow through the water-support bar 107 is controlled in order to limit the amount of heat captured. Under normal conditions, the water flow rate is maintained so that the water exiting outlets 109 is not greater that 50 to 95 Centigrade degrees, preferably 60° C. Means for monitoring water temperature and regulating the water flow rate (for example, where the left and right side flow rates are different) are known to the skilled artisan, and therefore, not directly represented in the figure.

Please note that the water cooled support system including water support bars 107 obviates a need for means for fixing or attaching 90 the oxidizing gas distribution manifold 82 to the inner chamber wall. The water support bars 107 allow the double-decker tube structure to slide and move with respect to the chamber wall during expansion and contractions resulting from changes of temperature. That is, the double-decker tubes 85 are supported by and essentially slide over the water-support bar 107 at contact points 108. While not shown in FIG. 6, the double-decker tube 85 may include an insulator at the opening in the chamber wall to prevent the outflow of heat/gas. The insulator is made of glass fiber and it is soft and flexible. The thickness of glass fiber insulator is between 4.7 inch and 6 inch and it is harder for the gas to enter or exit.

FIG. 6A highlights movement of the double-decker tubes 85 to the left in the direction of arrow 112 as they are heated to very high temperatures and expand. The left-most part of the double-decker tubes is seen to approach the left side inner chamber wall when the tubes have expanded, for example, as a result of a maximum (D zone) reaction chamber temperature. FIG. 6B highlights movement of the double-decker tubes to the right due to contraction resulting from cooling from an extreme high temperature in the direction of arrow 114. The left most part of the double-decker tubes 85 is seen much further to the right of the left side inner chamber wall when the tubes are cooled (FIG. 4B) that when they are at very high temperatures (FIG. 4A).

FIG. 7 depicts an embodiment of a cross-draft biomass gasifier system that includes gasifier 100′ (FIGS. 6, 6A, 6B) connected to an air and steam mixing chamber 120. Air and steam mixing chamber 120 mixes air and steam before it is delivered to the double-decker tubes 85 in the reaction chamber 15 via gas inlet 35. Air is pumped into the air and steam mixing chamber 120 though air conduit or line 125 under pressure from air blower 135. A hot air/backflow valve 130 is included in the air line 125 to control the volume and/or air flow rate, and to prevent a backflow of hot air.

A steam generator chamber 140 generates steam and provides sit to air and steam mixing chamber 120 via steam conduit or line 145. To generate steam, water from outside water tank 150 is heated in boiler tank 155 by burner 160. The heated water and steam passes within steam tubes 165, where it is further heated from the flames generated by burner 160, moving into the conduit 145 and to the air and steam mixing chamber 120. A steam back off/backflow valve 170 allows for the control of the steam flow and/or volume into the air and steam mixing chamber 120, and prevents backflow. Combustion products are exhausted from the steam generator via stack 175.

FIG. 8 depicts a preferred embodiment of a gasifier system of the invention. The FIG. 8 embodiment differs from the FIG. 7 gasifier system in that the FIG. 7 steam generator chamber 140 is replaced with a steam generator chamber 142, and the FIG. 7 air intake means is replaced with a hot air generator chamber 180, where both the steam generator chamber 140 and hot air generator chamber 180 are heated by the hot biogas generated in gasifier 100′.

In greater detail, water and steam are heated in steam tubes 165 within steam generator chamber 142 using heat supplied by the high-temperature biogas flowing from gas outlet 50. Like steam generator chamber 140 (FIG. 7), steam generator chamber 142 heats water from tank 150 to steam in boiler tank 155, which generated steam then passes into steam tubes 165. But unlike the steam generator chamber 140 (FIG. 7), steam generator chamber 142 (FIG. 8) does not require a separate source of heat or flame to generate the steam and super-heated steam. The heated biogas discharging from the gasifier 100′ both turns the water to steam and super heats the steam before the superheated steam is fed to the air and steam mixing chamber 170.

The biogas is further directed from steam generator chamber 142 to hot air generator chamber 180 via gas conduit/line 190. Therein, part of the heat remaining in the biogas is transferred to air within air heating tubes 185. The heated air then proceeds via conduit 125, under pressure by air blower 135, to air and steam mixing chamber 120. Using the heat from the generated biogas avoids the need for a separate heat source to heat the air prior to injection into reaction chamber 15. Using heat from the hot biogas to heat both the air and steam results in an energy cost reduction that is essentially twofold. Not only is the heat from the biogas used to generate and superheat steam, and heat air for mixing with the steam, but by transferring some of the heat from the biogas, less energy is required to cool the hot biogas to condense it for use.

FIGS. 9A and 9B together depict an engine or generator system which includes a gasifier system of the invention similar to those described above in order to supply biogas to operate the engine/generator 200.

FIG. 9A depicts gasifier 100′ including a biomass fuel conveyor system 24 driven by motor M1, for feeding fuel into the gasifier's reaction chamber 15 under control of shutter 22. Shutter 22 comprises double shutters or gate valves to feed the biomass and prevent air from entering the reaction chamber. Motor M2 controls a screw conveyor 26 at the bottom of chamber 15 to facilitate outflow of solid waste 55 via port 60, e.g., screw conveyor 26 scoops out the ash from the transformed biomass. The end of a screw blade comprising the conveyor is inside of the gasifier and there is not at the outlet of conveyer. Then there is always ash and ember which prevent air inflow at the exit opening.

A catalyzing chamber 210 is connected to gas outlet port 50 which removes tar-based constituents from the generated gas before it flows into the steam generating chamber 142 and the air heating chamber 180. Generated biogas flows out air heating chamber 180 via biogas outlet 192 to heat exchanger 215 (FIG. 9B), in which the biogas is cooled. Heat exchanger 215 includes water inlet 216 and water outlet 218, which together facilitate the flow of cooling water through water cooling coils 220. The hot biogas passes through water coils 200 and is thus cooled under force of blower 225.

A waste gas exhaust port 230 exhausts gases not suited for consumption by engine/generator 200. A gas analyzer 228 senses or identifies gas constituents. While not shown, a gas filter or separator may be included to distinguish and separate gases not suited for engine/generator consumption. A flare port 235 provides for burning the biomass at times when the engine/generator is not operational, ready to receive and burn the generated biogas. Burner 238 is controlled by a controller 300 (FIG. 10) to burn the biogas when necessary.

FIG. 10 depicts controller 300 that controls operation of a FIG. 8 gasification system and/or a FIG. 9 engine or generator system. The controller 300 receives and processes signals from various sensor devices, for example, signals from sensors and detectors that monitor temperature levels, biomass levels, water levels, biogas output levels, gas constituent levels, shutter open and closed states, etc. Where digital, the signals are directly processed by processor 315. Where analog, the signals are first converted to digital by analog to digital (A/D) converter 310, and then processed by processor 315. The controller outputs (signals) are directed to actuator 320 or various motors 325. The actuators and motor regulate air flow, steam flow and volumes, biomass feed, cooling water flow and volumes (and other flow rates), pyrolysis, oxidation, gas burn off, gas discharge, engine/generator operation and, therefore optimization of biogas generation and collection.

Any number of sensors, flow detectors, level detectors, etc. may be disposed throughout the engine/generator and gasifier system. For example, and as shown in FIG. 9A temperature sensors T1 and T2 are positioned in zones A and B, respectively, within gasification gasifier chamber 15. Temperature sensor T3 is positioned at the rotary conveyer 26 and motor M2, proximate waste outlet 60. Temperature sensor T4 is positioned at the biogas outlet 50 of gasifier 100′. Temperature sensor T5 is positioned at the heated steam outlet 170 of the steam generator chamber 142. Temperature sensor T6 is positioned at boiler tank 155, temperature sensor T7 is positioned at hot air outlet 130 and temperature sensor T8 is positioned at downstream chamber of heat exchanger 215 (FIG. 9A). A temperature sensor T9 is positioned at the water inlet 109 of the water-cooler support system.

Pressure sensor P1 is positioned at heated steam outlet 170 and pressure sensor P2 is positioned at hot air outlet 130. Level sensors L1 and L2 are positioned to detect the closed and open positions, respectively, of upper shutter 22. Level sensors L3 and L4 are positioned to detect the closed and open positions of lower shutter 22. Level sensor L5 is positioned at the halfway container of shutter 22. Signals generated by the level sensors L1-L5 are utilized to activate solenoid valves that are controlled to open and close the shutters during various stages of the gasification process. Level sensor L6 is positioned at an upper location within the gasifier chamber 15 (zone A) to detect a full level of biomass fuel, while level sensor L7 is positioned at a lower location within the gasifier chamber 15 (zone B) to provide a low fuel indication. Signals generated by level sensors L6 and L7 are used to control the amount of bio-fuel to be processed at any given time.

Level sensor L8 is positioned in water tank 150 outside steam boiler 155, to control solenoids that regulate water flow in. Similarly, level sensors are preferably positioned in the conduits comprising the water-cooled support system for supporting and cooling the oxidizing gas distribution manifold 82 in the gasifier 100′. The level sensors control solenoids which open and close to control the flow of water. Level sensors L9 and L10 are positioned at the respective open and closed positions of exhaust port 230, to control open and closing, and level sensors L11 and L12 are positioned at the respective open and closed positions of flare port 235. While not shown, flow sensors may be included to detect the air flow, biogas flow and the air/steam mixture flow at the respective air blower 135, biogas outlet 192 and gas inlet 35.

The controller 300 processes the sensor inputs (i.e., the sensor signals), and generates sensor outputs in the form of control signals to control gasification processes. The signal from every sensor go into input port and change the signal from analog to digital, if needed, and the Controller calculate using the algorism. And then it outputs the signal to actuators through output port. D/A converter will be used if needed. Actuators are for example, motors, solenoid valves for shutter cylinders and flare valves.

The process flow of the generator system depicted in FIGS. 9A and 9B is as follows. At the gasifier 100′ start up, when there is no bio-fuel, level sensors L6 and L7 sense zero, generating signals that upon processing cause the upper shutter 22 to open. Conveyer motor M1 is then controlled to operate and to load bio-fuel into the top of the gasifier. Where level sensor L6 senses a full bio-fuel level in the chamber (FIG. 9A), solenoids within solenoid valves proximate level sensors L1 and L3 are actuated to close the respective shutters 22. Level sensor L8 indicates whether or not there is sufficient water, i.e., where level sensor L8 indicates low water, the gasification process is control to stop.

When level sensor L5 senses that the bio-fuel level is full a signal is generated to control motor M1 to stop, and to close the upper shutter. At this time, the level sensor L1 should be “on,”, and solenoid valve at level sensor L2 should be in an open state. When level sensor L1 is on, the lower shutter is opened. When L3 is off and L4 is on, biomass is fed into the gasifier 100′. The procedure is repeated several times until L7 is on and then L6 is on. When L6 is on, the bio-mass is at full in the gasifier.

The controller 300 starts up blower 135 in order to add air into the gasifier 110′ and starts up blower 225 to suck the gas from the gasifier 100′. P2 senses the air pressure. Then, ignition is manually carried at an ignition port, which is closed and sealed upon ignition. As combustion occurs, temperature sensor T2 sensing the increasing temperature. When T2 senses that the desired temperature (around 800 to 1000 degree in centigrade) is reached, the speed of blower 9 is adjusted o decrease the amount of oxygen. When sensor T6 detects that the temperature reaches 100 degree C., vapor is released. When P1 senses the steam pressure, it blows out from the Double Decker tubes 85 in the gasifier.

The exhaust port is actuated, which sets the valve L9 in open position. The initial gas which does not contain fuel gas and not suited to engine fuel goes out to atmosphere. The controller 300 receives sensor data from gas analyzer G1. If the density of gas is low, the speed of blower 135 is decreased and bio-mass is added until the level sensor L6 generates an active signal. The operational speed of blower 225 is decreased to enlarge the burning zone in the gasifier 100′. When gas contains enough fuel (CmHn and Hydrogen and Carbon monoxide), the operational speed of blower 225 is increased

The biogas first leaving the reaction chamber through outlet 50 contains tar, which is reduced in catalyzing chamber 210. When the gas is found to contain a sufficient amount of CmHn, the flare port 235 and burner 238 are actuated, setting the valve L12 to its closed position. Then, the exhaust port 230 is actuated, setting valve L10 to its closed position. Biogas is the burned.

When engine is ready, the flare port 235 is actuated to close and valve L11 is opened to transfer Biogas to engine 200. A start signal is sent to the engine controller 240, which operates the engine. When engine speed is slower than the set value, it is receiving less biogas than required whereby the controller increases the operational speed of blower 225 and the operational speed of blower 210. When the engine speed is higher than the set value, the operational speed of the blower 225 and the blower 210 are decreased to decrease biogas.

In order to shut down operation, the upper and lower shutters are closed by setting level sensors L1 and L3 to an on state. Blowers 225 and 210 are stopped, flare port 225 is opened and burner 238 is ignited. For that matter, conveyer M1 must be stopped. As the temperature at sensor T4 is indicated as decreasing, the water supply is still maintained. When temperature T4 is sensed to be around 40 degrees C., the system is essentially shut down. Hence, the burner 238 at flare port 235 may be extinguished as there is no more biogas being generated. The level sensors L9 then open and exhaust any remaining gas to atmosphere. Only when the temperature sensor T2 is sensed to be below 30 degrees C. is the water supply stopped.

In the foregoing description, certain terms and visual depictions are used to illustrate the preferred embodiment. However, no unnecessary limitations are to be construed by the terms used or illustrations depicted, beyond what is shown in the prior art, since the terms and illustrations are exemplary only, and are not meant to limit the scope of the present invention.

It is further known that other modifications may be made to the present invention, without departing the scope of the invention, as noted in the appended claims.

Claims

1. A gasifier system that converts biomass to biogas, comprising: a reaction chamber including a biomass supply port for receiving a biomass volume, a waste outlet port for discharging biomass conversion by-products, a gas inlet for receiving heated oxidizing gas and a gas outlet for discharging generated biogas; anda burner manifold for distributing oxidizing gas within the chamber to react the biomass, the manifold comprising primary tubes and secondary tubes, positioned in a vertically lower part of the chamber and configured with multiple openings or ports for dispensing the oxidizing gas, where the secondary tubes extend into, inject and evenly distribute the oxidizing gas into the biomass volume to optimize conversion to biogas.

2. The gasifier system as set forth in claim 1, further comprising an air/steam mixing chamber for receiving and mixing at least two of the group consisting of air, heated air, steam and heated steam to create and air/steam mixture to generate the oxidizing gas, wherein the air/steam mixing chamber is in fluid communication with the gas inlet.

3. The gasifier system as set forth in claim 1, wherein the primary tubes are double-decker tubes and the secondary tubes extend from a surface of the double-decker tubes.

4. The gasifier system as set forth in claim 1, further comprising a water heating chamber in fluid communication with the gas outlet for receiving a flow of hot biogas, wherein the water heating chamber includes a coil in which water flows and which is arranged to be exposed to the flow of hot biogas in order to heat water flowing in the coil to steam.

5. The gasifier system as set forth in claim 4, wherein the coil and steam in the water heating chamber are in fluid communication with an air/steam mixing chamber or the gas inlet or both.

6. The gasifier system as set forth in claim 1, further comprising an air heating chamber in fluid communication with the gas outlet for receiving a flow of hot biogas, which includes an air duct in which air flows and which is arranged to be exposed to the flow of hot biogas in order to heat the air flowing in the air duct.

7. The gasifier system as set forth in claim 6, wherein the air duct and hot air therein are in fluid communication with an air/steam mixing chamber or the gas inlet or both.

8. The gasifier system as set forth in claim 1, further comprising a plenum within which a water/steam conduit and an air duct for providing heated air and steam to the gas inlet are positioned in order that a flow of hot biogas from the gas outlet is caused to flow over the conduit and air duct and heat same to generate steam and hot air.

9. The gasifier system as set forth in claim 1, further comprising a water-cooled support system positioned in the reaction chamber to support and enable the burner manifold to expand and contract in response to changes in temperature without obstruction.

10. The gasifier system as set forth in claim 9, wherein the water-cooled support system is physically attached to a reaction chamber wall with a top surface that extends into the reaction chamber and is in sliding contact with the burner manifold.

11. The gasifier system as set forth in claim 1, further comprising a controller.

12. The gasifier system as set forth in claim 11, wherein the controller controls a flow rate of hot biogas to the air carrying duct and water/steam carrying conduit in order to regulate the temperature of the hot air and steam delivered to the reaction chamber.

13. A gasifier system converting biomass to biogas, comprising: a reaction chamber including a regulated input port for receiving a biomass volume, a waste outlet port for discharging biomass to biogas conversion by-products, a regulated gas inlet for receiving heated oxidizing gas and a regulated gas outlet for discharging generated biogas;a burner manifold for distributing oxidizing gas within the reaction chamber that comprises primary and secondary conduits, is positioned in a vertically lower portion of the chamber and is configured with multiple outlets or ports for injecting the oxidizing gas into the biomass volume, substantially evenly distributing the oxidizing gas therethrough; anda water heating chamber in fluid communication with the gas outlet for receiving a flow of hot biogas, exposing water to the hot biogas to heat the water to steam and supplying the steam to the gas inlet port as oxidizing gas.

14. The gasifier system as set forth in claim 13, further comprising an air heating chamber in fluid communication with the gas outlet for receiving a flow of hot biogas, exposing air to the hot biogas to heat the air and supplying the heated air to the gas inlet port as oxidizing gas.

15. The gasifier system as set forth in claim 13, wherein the secondary tubes extend from a surface of the primary tubes in such away that the secondary tubes extend into the biofuel volume to facilitate oxidizing gas distribution therethrough.

16. The gasifier system as set forth in claim 13, wherein the tubes are double-decker tubes.

17. The gasifier system as set forth in claim 13, further comprising a water-cooled support system positioned in the reaction chamber to support and enable the burner manifold to expand and contract in response to changes in temperature without obstruction.

18. The gasifier system as set forth in claim 17, wherein the water-cooled support system is physically attached to a reaction chamber wall with a top surface that extends into the reaction chamber and is in sliding contact with the burner manifold.

19. The gasifier system as set forth in claim 14, further comprising a controller for controlling a flow rate of hot biogas to the air heating chamber and the water heating chamber in order to regulate the temperature of the air and steam delivered to the reaction chamber in the form of oxidizing gas.