Coal gasification

Laluque mines coal gasification plant under construction

Laluque coal gasification plant

Coal gasification is the conversion of carbon (C) into flammable gaseous compounds, especially water gas ( synthesis gas ), generator gas and town gas .

history

Antoine Laurent de Lavoisier was already using coal gasification to produce water gas. At the beginning of the 19th century the English coal gas industry developed processes for coal gasification. The first generator was built in 1840. 1854 a process was then introduced, the hydrogen obtained by the water gas shift reaction of carbon monoxide to separate by reacting the carbon monoxide with excess steam to carbon dioxide converted. Coal gasification became important at the beginning of the 20th century when the demand for synthesis gases increased. The Winkler process was developed in the 1920s and the Lurgi process in the 1930s, which was useful for the town gas industry . In the early 1950s, the first Koppers-Totzek reactor was put into operation, which allowed the gasification of coal dust with air. Considerations for the use of high-temperature nuclear reactors as a supplier of process heat for coal gasification were not implemented.

use

Town gas was mainly used for street lighting and for the interior lighting of large buildings in the 19th century. Numerous cities built gas works to produce town gas from coal. The coke produced by the coal degassing was re-used in the steel industry and also as fuel. It was not until the beginning of the 20th century that town gas was also used for heating and cooking. Starting in the 1960s, it was gradually replaced by natural gas . In addition to the earlier production of town gas, coal gasification was or is significant for use in power plants, for the chemical industry (synthesis gas) and for the iron and steel industry.

Water gas

About the endothermic reaction :

{\ displaystyle \ mathrm {C \ + \ H_ {2} O \ \ longrightarrow \ CO \ + \ H_ {2}} \ qquad \ Delta H_ {R} = + 131 \ \ mathrm {kJ / mol} \,}

From coal, which was previously heated by combustion in air, and water vapor, so-called water gas, a mixture of carbon monoxide and hydrogen, is created . It is an equilibrium reaction .

This reaction was discovered by Felice Fontana in 1780 .

The resulting gas is also known as synthesis gas or syngas, as it is suitable for the synthesis of various chemical substances such as methanol .

Generator gas (carbon monoxide)

Generator gas is produced by incomplete combustion of coke with air. Here, coal, which was previously heated by combustion in air, reacts with carbon dioxide in an equilibrium reaction ( Boudouard equilibrium ) to form carbon monoxide.

{\ displaystyle \ mathrm {C \ + \ O_ {2} \ \ longrightarrow \ CO_ {2}}}

{\ displaystyle \ mathrm {C \ + \ CO_ {2} \ \ longrightarrow \ 2 \ CO}}

The overall reaction results from:

{\ displaystyle \ mathrm {2 \ C \ + \ O_ {2} \ \ longrightarrow \ 2 \ CO}}

Carbohydrate

Hydrocarbons of different chain lengths are formed during carbohydrate hydrogenation :

{\ displaystyle \ mathrm {m \ C \ + \ n \ H \ \ longrightarrow \ C_ {m} H_ {n}}}

Depending on the chain length, the reaction products are gaseous ( methane , ethane , propane , butane ) or liquid (higher alkanes , which are used, for example, in gasoline and diesel fuel ). In the case of liquid products, one speaks of coal liquefaction .

Conversions

Here, gases are generated from the products of coal gasification in secondary reactions.

Conversion to hydrogen:

{\ displaystyle \ mathrm {CO \ + \ H_ {2} O \ \ longrightarrow \ CO_ {2} \ + \ H_ {2}} \ qquad \ Delta H_ {R} = - 42.3 \ \ mathrm {kJ / mol} \,}

Conversion to methane:

{\ displaystyle \ mathrm {CO \ +3 \ H_ {2} \ \ longrightarrow \ CH_ {4} \ + \ H_ {2} O} \ qquad \ Delta H_ {R} = - 206 \ \ mathrm {kJ / mol } \,}

Gasification process

Different gasification processes have been developed for the gasification of coal, which take into account the different requirements for the input materials (hard coal, lignite), for the granularity of the input materials and for the desired end products. In general, a distinction is made between fixed bed, fluidized bed and entrained flow gasifiers. These are:

the General Electric - entrained flow gasification (formerly Texaco )

the "Winkler gasification" or the "high temperature Winkler process" (HTW) for the use of lignite, peat, wood and sewage sludge. The Winkler generator was developed by the chemist Fritz Winkler at BASF from 1921 . It is a fluidized bed gasifier .

the Koppers-Totzek method or Krupp-Koppers-Totzek (~ 1952) (entrained flow gasifier)

the PRENFLO process from ThyssenKrupp Uhde GmbH ( entrained flow gasification)

Shell entrained flow gasification

the E-gas entrained flow carburetor from ConocoPhillips

the Sasol - Lurgi -Festbettdruckvergasung (development since ~ 1925)

"BGL", British Gas Lurgi pressure gasifier (slag bath gasifier), e.g. B. Black Pump Industrial Park

the GSP process (according to Georg Bilkenroth and Erich Rammler ), developed at the German Fuel Institute in Freiberg and in the Schwarze Pumpe gas combine (entrained flow gasifier, high-temperature lignite coke )
allothermic steam process (from 1980)

literature

Werner Peters, Hans-Dieter Schilling: The gasification of coal - basics and application, chemistry in our time , 10th year 1976, No. 1, pp. 11-20, ISSN 0009-2851

Web links

Coal gasification in the Vienna-Simmering gasworks

Individual evidence

↑ Edmond Marcotte: Chimie Industrielle - La carbonization des lignites a basse temperature aux Mines de Laluque (Landes). La Genie Civil, Samedi 13 Mars 1926.

[1] Edmond Marcotte: Chimie Industrielle - La carbonization des lignites a basse temperature aux Mines de Laluque (Landes). La Genie Civil, Samedi 13 Mars 1926.