Release and Transformation of Potassium during Combustion of Biomass

To investigate the release and transformation of fuel K during combustion of biomass, wheat straw and corn stalk are burnt in a fixed-bed reactor system during 400−1000 °C, and weight measurement, elemental composition analysis, and chemical fractionation analysis are performed. The influences of fuel type, combustion temperature, and water washing pretreatment are discussed. The results show that wheat straw has a higher K release ratio than corn stalk, especially when combustion temperature is above 500 °C. For both biomass fuels, the released K is far less than the water-soluble K. For wheat straw, some of the other occurrence modes of K turn into the insoluble K gradually. For corn stalk, the water-soluble and ion-exchangeable K turn into HCl-soluble and insoluble K. Water washing removes all the water-soluble K of corn stalk and reduces the K release from 3.26 to 0.27 mg g-1 at 1000 °C.