Primary Fragmentation Characteristics in the Process of Coal Slime Combustion

Abstract

ABSTRACT As a by-product of coal washing, coal slime has a high moisture content and it will fragment during combustion. To explore the primary fragmentation characteristics of coal slime, tests on a single pellet of different coal types with different water contents are carried out on a visual weighing test bench. The primary fragmentation process of the pellets is recorded by a camera and analyzed in combination with a weighing device to investigate the influence of moisture and temperature on the fragmentation characteristics of coal slime. The results show that water in coal slime is the factor that drives fragmenting of coal slime, and there is only a little volatile release from the slime during the primary fragmentation. The fragmenting form of coal slime pellets is intermittently “broken off layer by layer.” The fragmenting process is caused by internal stress produced by water that is rapidly released under high temperature and acts on the outer dry shell of pellets. The initial time required for primary fragmentation of coal slime is shortened with increasing temperature and is prolonged with the increase in the water content. There is a critical water content value for primary fragmentation, and when the water content of coal slime is lower than this value, it will not fragment; different types of coal slime have different critical values.