The influence of included minerals on the intrinsic reactivity of chars prepared under N2 and CO2 environment

摘要

Oxy-fuel technology could be successfully used to retrofit existing coal-fired power plants or alternatively be used to design and build new coalfired power plants with almost zero emissions.Char reactivity under oxy-fuel conditions will have a significant impact on the coal burnout. In this paper, two fractions,representing organic-rich particles and organic particles with included minerals,were separated from each of three Chinese coals of different rank. They were then devolatilized at 1450°C in a drop tube furnace (DTF) under N2 and CO2 environment,respectively. The chars were subjected to nitrogen adsorption study, thermogravimetric analysis and XRD analysis. It was found that char reactivity of all three pairs of chars were increased under CO2 environment as compared with that under N2 environment,but with differing trend.For the organic-rich samples the reactivity difference is increased with decreasing rank.On the contrary,for the samples of organic particles with included minerals, the reactivity difference is decreased with decreasing rank. Mechanism analysis showed that they are resulted not from gasification,but from a combination of changes in surface area and in the ordemess of carbon structure in the chars,both of which,in turn,are resulted from the higher heat capacity of CO2 and the interaction between metastable liquid phase and the included minerals..