SINTERING BEHAVIOUR OF WHEAT STRAW ASH WITH ADDITION OF ADDITIVE UNDER ELEVATED TEMPERATURE

摘要

In this work, the use of one non-commercial additive to reduce the wheat straw ash sintering tendency was investigated at elevated temperatures. Sewage sludge was blended with wheat straw in different mass ratios. Laboratory sintering tests were performed on the wheat straw and mixtures in the temperature range from 550°C to 1000°C. The ash from the wheat straw and mixtures with sewage sludge addition were producted under different ashing temperatures and characterized with XRF, XRD and SEM/EDX analysis. Wheat straw ash has high sintering tendency with formation of alkali chlorides and alkali silicates at low ashing temperature, which presented as amorphous phase in large amount. SEM/EDX analysis showed that the wheat straw ash started to sinter and aggmolerate even at temperature for 750°C with presence of sylvite. Sewage sludge was proven to decrease the wheat straw ash sintering temperture in this work. The crystalline phases in wheat straw ash changed to potassium aluminum silicates and aluminum oxides with addition of sewage sludge. All of these phases have high melting points and contributed to the lower sintering tendency of wheat straw ash. The dilution effect from the sewage sludge is considered the other reason related with the decrease of sintering for wheat straw ash. In addition, adsorption of potassium chlorides and sulfates on the sewage sludge particle surfaces was also observed with SEM/EDX analysis. Results from the SEM/EDX analysis had good agreement with XRD analysis and offered more supporting information with BSE image and spot elements quantification.