Effect of the ash melting behavior of a corn straw pellet on its heat and mass transfer characteristics and combustion rate

摘要

The effect of ash melting behaviors on the characteristics of heat and mass transfer and combustion rate for the corn straw pellet were investigated by experiment and simulation methods. Considering that the fusion temperature range of ash is from 1418 K to 1558 K, four temperatures (1193 K, 1326 K, 1465 K, and 1618 K) were chosen as the operating temperatures. Results show that the molten ash exists as the spherical particles. At operating temperature between the initial deformation temperature and flow temperature, the spherical particles sharply increase, which contributes to the increase in oxygen concentration at the pellet surface, but limits that inside the pellet. Molten ash delays the char reaction. The tendency reaches the maximum at this temperature range. When the operating temperature is higher than flow temperature, the molten ash peels off from the pellet surface, which exposes the part of the pellet covered by molten ash to the environment directly, thereby accelerating the increase in oxygen concentration inside the pellet.