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Biomass gasification is the process in which biomass is converted into a product or fuel gas through carbonization using a gasification or oxidation agent (usually air, oxygen, carbon dioxide or water vapour). As wood is primarily used as biomass, both historically and currently, it is usually referred to as wood gasification.
Gasification can be used to convert the biomass available as a solid fuel into a gaseous secondary fuel that can be used in various ways, such as the generation of heat and electricity ( cogeneration) or as a fuel (fuel gas) or for use as synthesis gas for chemical synthesis more efficiently. Analogous processes also exist for other solid fuels, especially for the gasification of coal (coal gasification).
After all, every biomass combustion process is preceded by a gasification process, as it is not the biomass itself that is combustible, but only the gases emitted from the biomass.Gammel Engineering has developed the modular, highly efficient, fuel-flexible Kombi Power System®, which is built by ReGaWatt as a turnkey solution. The system type "biomass" uses a counterflow wood gasifier with downstream combustion chamber and externally fired gas turbine or gas cleaning and combustion engine. The energy plants can be upgraded to gas and steam ( CCGT ) or gas and ORC ( GuORC ) cogeneration plants and, in addition to electricity from natural biomass, supply heat in the form of warm or hot water, steam, hot air or thermal oil.
The gasification of biomass begins after drying at temperatures of 150 °C, with water vapor and oxygen escaping first. At higher temperatures, the solid components of the biomass, especially the lignin and cellulose, are gasified. This gas ignites as soon as secondary air is supplied; the flash point is 230 to 280 °C.
Technical biomass gasification is a partial combustion process using a gasifying or oxidizing agent (usually air, oxygen, carbon dioxide or steam) without ignition at temperatures of 700 to 900 °C, in which the biomass is not oxidized to carbon dioxide (CO2) as in combustion, but essentially to carbon monoxide (CO). Other components of the resulting gas are hydrogen (H2), carbon dioxide (CO2), methane (CH4), water vapor (H2O) and, depending on the biomass used and the gasification process, a range of organic substances in varying concentrations. Ash remains as a solid residue and, depending on the gasification quality, residues of charcoal. When the temperature of the process gas is lowered, the water vapor, mixed with organic components, condenses to form a tar or an organically contaminated wood gas condensate.
The combustible product gas can be further oxidized in a subsequent process by combustion (fuel gas) or chemical synthesis (synthesis gas) with the release of energy (exothermic process). If gasification is carried out with air, the product gas diluted with nitrogen is often referred to as low calorific value gas (LCV).>>>>>>>>>>>>>>>>>>>>>>>>>>>Hydrothermal gasification is a special case of biomass gasification in which wet biomass is converted into hydrogen and methane. The bioconversion takes place at temperatures of 400 to 700 °C and pressures of 200 to 300 bar through the reaction with supercritical water, whereby an almost complete conversion of the organic components of the biomass is achieved.
Sources
Wikipedia
http://de.wikipedia.org/wiki/Biomassevergasung
http://de.wikipedia.org/wiki/Hydrothermale_Karbonisierung