Effect of biomass ratio on co-firing of biomass with coal on pozzolanic properties

Abstract

Recently, fly ash from the coal combustion process in power generation has been used in the cement industry as an additive to cement or as partial replacing binder in cement-based structural mortars. The use of fly ash can reduce costs in cement production, including a reduction in the environmental impact. Co-firing biomass with coal is one of the existing technologies for utilizing biomass energy in the power generation system. However, this technology also influences the quantity and quality of the ash produced. The present work, therefore, aims to investigate the pozzolanic properties of ashes obtained from the co-firing ofcoal with corncob. Pozzolanic and physical properties of such ashes were investigated by varying the percentages of corncob at 20, 30 and 40 during combustion. The Pozzolanic compounds (SiO2+ Al2O3+ Fe2O3) according to ASTM C618 were determined by using X-ray fluorescence spectroscopy (XRF). Scanning electron microscopy (SEM) was used to investigate the structure of ash samples. The results show that content of pozzolanic compounds in ashes produced from cofiring corncob with coal decreased when increasing ratio of corncob and became stable when ratio of corncob was higher than 30%. It is observed that the morphology of such ashes illustrated in the form of small spherically shaped particles which can improve rheological behavior, viscosity and flow performance. Considering the requirements for pozzolanic-cementitious material, it is found that the ashes produced in this study has lower content of pozzoolanic compounds than the standard specification for pozzolan class C.