Experimental study on the sintering characteristics of biomass ash

Abstract

The alkaline metal content in biomass is high, which leads to a low initial sintering temperature. Therefore, during the process of direct biomass combustion for power generation, there are serious problems such as ash deposition and slagging on the heating surface, which has become a technical bottleneck for the safe, stable and long-term operation of boilers. In industry, the melting characteristics of ash are commonly used to guide boiler design and operation. However, traditional measurement of ash melting temperature has a large subjective error, and the releasing of alkaline metals during the measurement process results bit higher value, which affects the accuracy of the measured characteristic temperature. Comparingly, the initial sintering temperature is lower than the deformation temperature of the ash. This article provides a device for measuring the sintering temperature of biomass ash by using the pressure drop method. A novel two ash chamber system was invented, in which the alkali element released from the first ash chamber was captured by the downstream second ash chamber to compensate the escaping of alkali element. The initial sintering temperature of the second ash chamber has more accuracy with lower value than that measured by the traditional single sample chamber. XRD was used to analyze the mineral composition and causes of sintering of the ash samples before and after sintering. The results show that the sintering mechanisms of different types of biomass are different. In addition, combined with SEM analysis of rice husk, fruit core, rapeseed straw, and corn straw, the results show that the initial sintering temperature of the ash samples measured by the double chamber measurement method is more accurate than that measured by the single chamber measurement method, further validating the reliability of the two ash column system.