Gasifiers for Special Applications

Much of gasification research and commercial usage has focused on coal as a feedstock for electricity, liquid fuel, synthetic natural gas and hydrogen, or chemical production. The basic gasifier designs reflect this. Gasification technology can be used, however, with more than just coal and can be modified for many different, inventive applications.

Biomass and Municipal Solid Waste
Biomass and municipal solid waste (MSW) pose similar problems to gasification. The categories cover a wide range of types of feedstock, especially MSW which, unless sorted, can be a diverse mixture of waste types. Biomass gasifiers can be designed to use a specific type of biomass (wood chips or corn stover, for example), but because of variable characteristics like ash content, moisture content, and bulk density, gasifier options can be limited.

Black Liquor Gasification
The wood pulp and paper manufacturing industry uses the Kraft process to turn wood into wood pulp, which is primarily cellulose, for further processing into a variety of paper products. This process produces a byproduct called black liquor containing the non-cellulose wood residues (lignin, hemicellulose) and Kraft process chemicals (toxic inorganics like sodium hydroxide and sodium sulfide). Black liquor is conventionally burned in recovery boilers, but black liquor gasification provides an alternative capable of producing electricity, steam, and a full-slate of gasification products.

Hydrogasification
Hydrogasification is gasification in a hydrogen-rich environment. It has been used since the 1930s primarily for the production of synthetic natural gas (SNG) from coal or other carbonaceous feedstock. A variation on this technique is called steam hydrogasification which uses both steam and hydrogen for gasification.

Catalytic Gasification
Catalysts can be used to increase certain reaction rates to produce difficult or otherwise unattainable products. In catalytic gasification, catalysts are primarily used to lower the operation temperature of the gasifier which saves energy, wear on the reactor, and heat transfer losses between process units (like syngas clean-up). Catalysts can also be used to favor or suppress certain syngas component formation.

Oil and Gas Partial Oxidation
Partial oxidation of oil and gas involves reaction of the feedstocks with less oxygen than required for complete combustion, a process that is very similar to solid fuel gasification, but because of the fluid state of the oil or gas some gasification stages like pyrolysis and char gasification either do not take place or take place at a much less significant level.

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Underground Coal Gasification
Underground coal gasification is similar to that of surface gasification except that the coal seam itself becomes the reactor, with gasification taking place underground instead of in a manufactured vessel.

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