Studies of the release rule of NOx precursors during gasification of coal and its char

This investigation involved the formation and release of precursors of NOx, which were HCN and NH3, during gasification of coal and its char. Gasification was carried out in a fixed bed reactor at atmospheric pressure. The reactor allowed coal particles to be heated up rapidly and held for a prespecified period of time at peak temperature. The influence of coal rank and coal particle size on the release of N-containing compounds during coal gasification with CO2 is discussed. Gasification agents and coal gasification temperature were two key factors on the amount of nitrogenous compounds released. Results showed that with an increase of reaction temperature a great amount of NH3 was formed during gasification with steam: The yield of NH3 was highest at 800 degreesC during gasification with CO2. The volatiles in coal played the key role in the formation of HCN and NH3 during coal gasification under steam atmosphere. Volatiles were the main source of the formation of HCN and NH3, mainly from the nascent char thermal cracking, whose procedure could be promoted by H2O(g): The yield of HCN during coal gasification had no strong relation with gasification agents and increased with an increase in gasification temperature. A reasonable mechanism for the formation of nitrogenous compounds during coal gasification was suggested in this study, which could explain some results in the literature on pyrolysis and gasification of coal. (C) 2003 Elsevier Science B.V. All rights reserved.