Control of in-bed agglomeration by fuel blending in a pilot scale straw and wood fueled AFBC

Abstract

Bed agglomeration in a pilot scale atmospheric fluidized bed combustor was controlled by blending wood into rice straw in concentrations of 50% wood or more and stoichiometrically holding reaction temperature at or below 800°C. At higher straw concentrations, agglomeration of the bed occurred over run times inversely proportional to the straw concentration in the blend. Bed agglomeration was preceded by a characteristic decline in bed pressure drop most likely related to combustion air channeling through the bed. Blend ash composition was not substantially affected until straw concentration decreased to 50% or below because of the four-fold higher ash concentration in the straw compared to wood. Blend ash base-to-acid ratio also was not substantially affected above 50% straw concentration, remaining essentially constant at 0.3, compared to the wood ash base-to-acid ratio of 1.1. Initial deformation temperature, as measured by standard cone test of the blend ash, increased from a minimum of 880°C for a 75% straw blend to 1120°C for a 10% straw concentration in the blend.