Physico-Chemical Characteristics and Mineral Transformation Behavior of Ashes from Crop Straw

In this paper, the physicochemical characteristics and mineral transformation behavior of three crop straw ashes (rice straw, wheat straw, and cotton straw) were investigated using ICP-AES, XRF, SEM-EDS, XRD, and ash fusion point analyzer. It was found that these ashes had quite high content of alkali metals (especially K) and quite low fusion point (especially cotton straw ashes) and caused easily the corrosion, slagging, and fouling of equipments. These straw ash particles were uniformly distributed in the small, medium, and large size. As the ashing temperature increased, some amounts of K (in the form of KCl) were released into the gas phase, quartz transformed to cristobalite and then keatite, and sonic mineral components also occurred to transform. Up to 1088 K, K2O and Na2O separately reacted with Al2O3 and SiO2 to produce albite (K-Al-Si) and sanidine (Na-Al-Si). Above 1273 K, other alkaline earth oxides also participated in the above reactions to form amorphous matters like augite. Meanwhile, comprehensive utilization of crop straw ashes is also worth our attention, due to their special compositions.