Gasification is a key process driving clean coal technology at the Kemper County Power Plant in Mississippi. The following information is from the Gasification Technologies Council:
Gasification is a flexible, reliable and clean energy technology that can turn a variety of low-value feedstocks into high-value products, help a country reduce its dependence on imported oil and natural gas, and can provide a source of baseload electricity, substitute natural gas, fuels, fertilizers, and chemicals needed for economic growth.
It is a manufacturing process that converts any material containing carbon-such as coal, petroleum coke (petcoke), biomass or waste-into synthesis gas (syngas). The syngas can be burned in a turbine to produce electricity or further processed to manufacture chemicals, fertilizers, liquid fuels, substitute natural gas, or hydrogen. The percentage of biomass and waste used as feedstock has been increasing in recent years. (See Global Syngas Output by Feedstock).
Gasification has been reliably used on a commercial scale worldwide for more than 60 years in the refining, fertilizer, and chemical industries, and more than 35 years in the electric power industry. It is now being used to convert municipal and hazardous waste into valuable products.
Gasification vs. Pyrolysis
Pyrolysis is the thermal decomposition of the volatile components of an organic substance, in the temperature range of 400-1,400°F (200-760°C), and in the absence of air or oxygen, forming syngas and/or liquids. An indirect source of heat is used. A mixture of un-reacted carbon char (the non-volatile components) and ash remains as a residual. Burned toast is an example of pyrolysis.
Gasification takes this to the next step. It occurs in a higher temperature range of 900-3,000°F (480-1,650°C) with very little air or oxygen. In addition to the thermal decomposition of the volatile components of the substance, the non-volatile carbon char that would remain from pyrolysis is converted to additional syngas. Steam may also be added to the gasifier to convert the carbon to syngas. Gasification uses only a fraction of the oxygen that would be needed to burn the material. Heat is supplied directly by partial oxidation of the carbon in the feedstock. Ash remains as a residual.