Ash deposition characteristics in pulverized coal reaction under high temperature conditions

Abstract

Ash deposition characteristics under high-temperature pulverized coal reaction conditions were studied using a horizontal pulverized coal reactor with pre-combustor to produce high-temperature vitiated air. The ash deposition experiments were performed by inserting a water-cooled tube into the reactor. Burning two types of coal with different melting temperature and ash content, and the ash deposition phenomena were visually and quantitatively elucidated. As a result, the quantity of ash deposition on the tube surface increases with an increase of the surface temperature. This is because the burning particles in the upper stream of the tube are radiatively cooled down under low temperature condition of the tube surface. Both the structure and quantity of ash deposition depend on coal types such as melting temperature and ash content. The deposition rate at the beginning of deposition, obtained by the peripheral width of deposition layer on the tube surface, is correlated as an Arrhenius-type equation since viscosity of the molten ash can be correlated as an Arrhenius-type equation. Hence, it suggests that the ash deposition phenomena may relate to the viscosity of molten ash.