Co-combustion of carbon-rich fraction from coal gasification fine slag and biochar: Gas emission, ash sintering, heavy metals evolutions and environmental risk evaluation

Abstract

Mixed combustion of carbon-rich fraction (RC) from coal gasification fine slag and corncob char (CC) is an effective way of energy recycling. In this paper, the co-firing performance and kinetics of RC and CC were studied, and gas emission pattern, ash sintering trend and the migration and transformation behavior of heavy metals during combustion were explored. The results showed that the combustion performance was enhanced and the reaction activation energy was reduced during the blends burning. The synergistic effect between co-combustion reactions decreased emissions of gaseous pollutants. With the increasing RC compounding ratio and combustion temperature, the ash sintering tendency weakened. Cr and Ni were mostly enriched in the bottom ash, whereas Cu, Zn, As, Cd, and Pb tended to migrate to fly ash and flue gas. Cu, Zn, As, and Pb were in the form of stable fractions. Temperatures accelerated the chemical forms of Cr, Ni, Cu, Zn, and Cd being transformed into stable fractions. The environmental evaluation index suggested that the potential environmental risks of Cr, Zn, Cd, and As were relatively high. The results of this study provide guidance for the synergistic combustion disposal of double solid waste.