Furnaces – Combined
Reexamination Certificate
2001-10-18
2003-09-09
Lazarus, Ira S. (Department: 3749)
Furnaces
Combined
C110S229000, C110S248000, C110S303000, C110S306000, C110S312000, C110S297000, C048SDIG008
Reexamination Certificate
active
06615748
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a method and an apparatus for gasification of combustible material.
BACKGROUND OF THE INVENTION
A frequent problem encountered with the harvesting, re-fining or processing of organic matter is the accumulation of waste by-products. In particular, in forestry, the harvesting and primary and secondary processing of cellulose material results in the accumulation of large quantities of biomass such as slash, twigs, branches, bark, sawdust, trimmings and scrap. In agriculture, each crop cycle and primary processing leaves substantial biomass such as bagasse, corn cobs and rice hulls that cannot be otherwise utilized. The cost of disposing of such bio-mass, the environmental damage in disposing of such materials and the waste and lost value incurred in the failure to productively utilize such materials all constitute substantial problems. The historical practice of landfilling or open-incinerator burning such organic waste is unpopular for environmental reasons and in many instances contrary to present laws and regulations. Current environmental standards in many countries preclude the use of any burners except sophisticated incinerators to bum waste.
Single purpose incinerators are viewed as inefficient and wasteful of resources. Consequently, considerable activity has been directed at developing systems, procedures and apparatus to either clean burn organic waste materials or, preferably, to convert organic waste materials into a gas, as an alterative energy source, that can be used for other purposes. One approach is shown in U.S. Pat. No. 5,666,890. The need to create a portable gasification system is also stated in U.S. Pat. No. 4,530,702 although the problem is not addressed within that art.
Many existing gasification systems require drying of the biomass in order to reduce water content (Sawyer et al; German patent DE3505329; Frohlich & Kleineindam). It is preferable for gasification equipment to be able to process wood wastes having a high range of moisture contents (e.g., 15-60%) since this is the way it is found in its natural state. Several systems, such as that described in U.S. Pat. No. 4,530,702 require operation with pellets or chips, where the biomass is pre-manufactured for combustion. Other systems, such as that described in U.S. Pat. No. 5,666,890 require a basic pre-processing of the biomass through particle size reduction in order to achieve a satisfactory conversion process. In addition to adding to the expense and the complexity of the system, these steps or requirements are often impractical for the efficient disposal of waste. It is preferred to operate a system that accepts and operates efficiently with biomass in its natural form regardless of the variance in water content without pre-processing or other additional preparation steps.
Gasification devices have been described in prior art which are suitable for individual mill or plantation operations. For example, U.S. Pat. No. 5,226,927 discloses a vertical axis, updraft reactor in which the partial oxidation of wood material is used to heat the remaining wood to a temperature of 2700 degrees Fahrenheit to produce synthesis gas—a mixture of carbon monoxide, hydrogen and methane. Similarly, U.S. Pat. No. 4,764,185 teaches the utility of a similar device in which the gases are moved through the system by fan or blower. In U.S. Pat. No. 4,309,195 it is disclosed that the producer gas (essentially the same as synthesis gas) formed from solid organic fuel in a gasifier apparatus is lead from the cooler/cleaner using a blower, and it is suggested that it can be used directly as a substitute for natural gas or used as a fuel for diesel or gasoline engines. A French patent (FR 2497819) discloses a gas generator which can burn damp wood or maize cobs to produce gas for use in diesel or petrol engines. Likewise, a German patent (DE 3505429) discloses a method of converting dried (15-20% moisture content) chopped wood into gas which, after cooling and scrubbing, is fed to a gas engine coupled to a generator.
In addition to the patents referred to above, there are several publications that describe devices for generating gases from cellulose waste, and for fueling an internal combustion engine which powers a generator.
Various problems are associated with all of the existing cellulose pyrolysis devices, with particular problems characteristic or specific designs. Other gasification equipment requires intricate mechanical devices to prevent bridging of the input material (e.g., U.S. Pat. No. 5,226,927; Rundstrom) but such devices consume energy, require maintenance and are not necessarily effective with all types of feedstock, for example stringy bark.
In some types of gasification equipment, the partial pyrolysis of cellulose or other hydrocarbon material results in the formation of breakdown products which are gaseous at the elevated temperature in or near the gasification zone but which condense in pipes, valves and chambers at lower temperatures, for example, at ambient temperature. Such complications occur with gasification equipment, for example, which operates in an updraft mode, that is in which pyrolysis product gases are removed from the top of the vessel.
The nominal mineral (ash) content of wood cellulose is in the 1 to 2% range but there is, in addition, the probability of the inadvertent inclusion of foreign materials, e.g., stones, nails owing to the conventional methods of handling large quantities of waste materials. Equipment used in the gasification of cellulosic waste must be able to handle such mineral contaminants with provision for removal from the pyrolysis enclosure and quenching to ambient temperature. U.S. Pat. No. 5,226,927 describes an elaborate movable, (reciprocating) grate device which could be rendered inoperative with certain sizes of inorganic materials and which, in any event, does not provide for the quenching of the ash.
It is necessary to ensure the continuous flow of gases—air into the gasifier and a mixture of fuel gases, combustion products and nitrogen—down through the gasifier and on into adjacent pipes and/or chambers. Much of the prior art does not address this issue at all. In some cases, however, the use of a motor driven fan at the gasifier outlet is specified (e.g., U.S. Pat. No. 4,764,185 Mayer; U.S. Pat. No. 4,309,195 Rotter). In addition, to the extra costs of operating and maintaining such a blower, it can result in the removal by suction of excessive amounts of fine particles (ash, carbon) from the gasification chamber causing serious contamination problems downstream.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method and apparatus for converting organic waste to usable fuel gas which is portable, which uses fewer mechanical parts and less maintenance demands than existing systems, which operates in an environmentally secure manner and which is self sustaining and, after startup, fuels itself.
It is a further object of the present invention to provide a method and apparatus that efficiently converts biomass to usable gas without the need to dry or pre-process the feedstock and which utilizes the water inherent in most biomass as part of the pyrolysis procedure regardless of the variance in quantity.
It is an additional object of the present invention to provide an efficient means by which ash is removed from the burn chamber without interruption in the bum/pyrolysis processes, and an efficient means by which the synthesis gas is removed from the gasifier without mechanical moving parts such as a blower or a fan.
Therefore, according to a first aspect of the invention, there is provided a gasifier comprising a feed hopper, a burn chamber disposed to receive feed material from the feed hopper, a gas supply operably connected to the burn chamber for supplying gas containing oxygen to the burn chamber, a water supply operably connected to the burn chamber for supplying water to the burn chamber and a burn chamber outlet conduit in the burn chamber for egress of gases p
Neufeld Jake
Sunter Richard
Wiles David
Lambert Anthony R.
Lazarus Ira S.
Malahat Systems Corporation
Rinehart K. B.
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