Coal gasification technology, in the gasification furnace exit through circulating water cooling spray system to reduce the gas temperature, at the same time, carry the gas can dissolve in water or organic impurities, slightly soluble in water without decomposition of gasification agent (water vapor) and tar the cooling down, and the ash content of coal gas wash down, resulting in a large number of coal gasification wastewater.
The process of desulphurization, removal of ammonia and the extraction of benzol, naphthalene and crude pyridine in the process of gas purification can also produce a small amount of complex wastewater.
The coal gasification process is different, resulting in different amounts and types of pollutants.
Lurgi gasification process to the environment, for example, the pollution load of Texaco gasification process, with brown coal and bituminous coal as raw material to produce the pollution levels of pollutants is much higher than with anthracite coal and coke as raw material to produce pollutants.
Table 1 shows the basic water quality of wastewater from three domestic mainstream gasification processes.