Experiment and Kinetics Studies on Ash Fusion Characteristics of Biomass/Coal Mixtures during Combustion

Cofiring of biomass and coal significantly reduces carbon emissions and alleviates ash-related problems of biomass. This study investigates the effect of the biomass/coal blending ratio on ash fusion characteristics through the ash fusion test, X-ray fluorescence, and X-ray diffractometry. Meanwhile, kinetic analysis of the ash fusion process was conducted to provide a new method and reading benchmark for obtaining precise and repeatable initial deformation temperature (IDT). Results showed that the IDT decreased with the increase of the biomass blending ratio because of the decrease of alumina content and the increase of potassium content. When the biomass blending ratio increased, the content of orthoclase and diopside at the low melting point increased, while the content of andalusite, quartz, and anhydrite at the high melting point decreased, resulting in the decline of IDT. Kinetic analysis indicated that with increasing biomass blending ratio, the activation energy of ash fusion reaction decreased, which is the essential reason for the decrease of IDT. Coal ash had an activation energy of 1144.67 kJ.mol(-1), while it decreased to 145.89 kJ.mol(-1) with an increased biomass blending ratio to 100%. Compared with the larger error (up to 60 degrees C) caused by visual reading on the morphological change of the triangle ash cone, kinetics calculation gave precise prediction with less error between 2 and 7 degrees C. As an optimal recommendation, the average shrinkage rate of height at 41% could be used as a reading benchmark for the determination of IDT in further study.