Fundamental reaction characteristics of pulverized coal at high temperature

Abstract

In order to enhance the overall thermal efficiency in blast furnace system as well as coal gasifiers, it is necessary to elucidate fundamental reaction characteristics of pulverized coal at high temperature. The experiments were carried out using a horizontal pulverized coal reactor with a pre-combustor to produce vitiated air at high temperature and high-oxygen concentration. The reaction behavior of coal during combustion and/or gasification are elucidated by means of sampling and analyzing both reacting particles and reaction gases as well as optical measurement of the instantaneous particle temperature. Evolution rate of the volatile matter for various types of coal at high temperature is obtained from the Arrhenius plots. As a result, the volatile matter is rapidly evolved as soon as coal particles are introduced into the furnace since temperature of the vitiated air increases sufficiently. Result shows that the evolution rate of volatile matter does not depend on coal types. Activation energy and frequency factor of the evolution rate of volatile matter for various types of coal remain almost constant in the particle temperature range of 2200 to 2700 K, even when other experimental conditions were varied. In the char combustion region, char structure was found to affect the reaction rate of fixed carbon. It is observed that coal, which forms a network-type of char, indicated reaction rate of fixed carbon which did not always increase even when the vitiated air temperature was high enough. For a balloon-type char, on the other hand, the reaction rate of fixed carbon decreased with an increase of the vitiated air temperature.