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. This page and its subsections will describe some of these special applications in more detail. In the upper right is a table of contents to this section.

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. The sub-section on biomass and MSW covers the choices of gasifier technology available.

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 gasification provides an alternative capable of producing electricity, steam, and a full-slate of gasification products. The sub-section on black liquor gasification covers this application of gasification technology.

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. This gasifier application is discussed further in the sub-section on hydrogasification.

Catalytic Gasification
Catalysts can be used to increase certain reaction rates to produce difficult or otherwise unattainable products. In 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. The sub-section on catalytic gasification discusses this special application in further detail.

Oil and Gas Partial Oxidation
Fluid feeds like oil (liquid) and gas (like natural gas, which is almost entirely methane) can be gasified similar to solid feedstocks like coal. Partial oxidation is the reaction of the feedstock with less oxygen than is required for complete combustion. The sub-section on oil and gas partial oxidation describes the history and technology used in this special application of gasification.

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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. This technology, its advantages and disadvantages, history and recent research and demonstration are discussed in the sub-section on underground coal gasification.

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