Gas
Gasification describes a chemical-physical process in which part of a solid or a liquid is converted into a gaseous end product. This is done by heating, if necessary under a special, low-oxygen atmosphere.
Procedure
In contrast to evaporation , gasification involves splitting up and rearranging existing chemical compounds through cracking or pyrolysis and / or reduction or partial oxidation . Gasification is therefore to be regarded as the generic term for a series of chemical processes that have in common the generation of a chemically modified gaseous end product. Gasifying can leave solid residue behind.
Coal gasification for the generation of urban gas achieved a high level of awareness . In a Winkler generator , lignite was first burned in a fluidized bed until a uniform ember bed was created. A mixture of water vapor and air was then blown in, producing carbon monoxide and hydrogen - the main combustible components of town gas. The generator gas then had to be largely freed from its non-flammable components (water vapor and carbon dioxide ) in order to achieve a satisfactory calorific value . A disadvantage is the high energy loss when converting lignite into town gas. Town gas itself has the disadvantage of its poisonous carbon monoxide content and its low calorific value and has therefore been replaced by natural gas .
Another application example is wood or biomass gasification . In the period after the Second World War, wood gasifiers were occasionally used in Germany to operate motor vehicle gasoline engines . For some years now, thermo-chemical biomass gasification has been increasingly used again and further developed to generate electricity and heat as well as to produce synthesis gas for the production of chemicals and fuels. Further processing of the biomass gasification products by methanation leads to natural gas compatible biogas ( Synthetic Natural Gas , SNG), which can be fed into the existing gas networks.
Gasification is of certain importance in diesel engines , especially when starting from cold with the aid of a glow plug, which gasifies part of the injected fuel on contact, creating reactive radicals . Not to be confused, the concept described here gasifying the term carburettor in terms of a mixture forming device in a gasoline engine whose principle exclusively to sputtering and evaporation is based.
Changed energy contents during gasification are expressed by the cold gas efficiency .
Individual evidence
- ↑ A. Vogel: Decentralized electricity and heat generation from biogenic solid fuels. A technical and economic evaluation of gasification compared to combustion. IE report 2/2007, Institute for Energy and Environment gGmbH, Leipzig, 2007 ISSN 1862-8060 .