A friction model for iron powder pressing: B.Wikman et al. (Lulea University of Technology, Sweden.)

Abstract

Maceral concentrates, extracted by selective sampling from the coal face, were burnt as pulverised fuel in order to obtain the temperatures of many hundred individual particles of pulverised coal at several combustion times by two-colour pyrometry.The concentrate having a 93.7% vitrinite-rich analysis generates chars of fine walled cenospheres, with openings in the walls, which burn at high temperature, whereas the concentrate with a 89.2% intertinite-rich analysis generates chars of lower porosity and higher density which burn at a lower, and more uniform, temperature. The vitrinite-rich concentrate also burns with an increasing spread in the population of particle temperatures, the inertinite-rich concentrate burns with a decrease in this spread. Due to higher char densities and lower reactivities the burning time of the inertinite-rich concentrate is estimated to be from 2.9 to 3.8 times that of the vitrinite-rich concentrate.Reactivity distributions are estimated from the temperature populations by fixing the activation energy of the chemical rate coefficient and allowing the pre-exponential factor to accommodate the reactivity spread. An increase in the spread of the estimated distributions is evident at high burnoffs.