Fly ash-CaO sorbents prepared via hydration for CO2 capture in municipal solid waste incineration

Municipal solid waste incineration (MSWI), a promising technology for managing MSWI capacity, has a large amount of CO 2 in its flue gas emissions, but lacks effective means of carbon reduction. Modification of CaO-based sorbents using fly ash, a solid waste from coal-fired power plants, is a potential application to improve CO 2 capture capacity. In this study, a cost-effective fly ash-CaO sorbent was developed by combining high-calcium and high-magnesium fly ash with CaO by hydration. The CO 2 capture capacity and carbonation conversion of fly ash-CaO sorbents were investigated at different temperatures, CO 2 partial pressures and doping ratios in a calcination/carbonation reaction system. Optimum carbonation reaction temperature (760℃) for CaO and optimum calcination temperature (850℃) for fly ash were obtained. In the experiment of CaO doped with fly ash, the novel sorbents prepared by CaO doped with fly ash at a mass ratio of 3:1 had the highest carbonation conversion (98.88 %). The hydration reaction promoted the transformation of CaO to Ca(OH) 2 , which improved the CO 2 capture capacity of the sorbents. The inert materials (Al 2 O 3 , SiO 2 ) in the fly ash were uniformly distributed as structural skeleton in the sorbents, enhancing the structural stability and anti-sintering ability. The S element contained in the fly ash competes with CO 2 for adsorption sites and produces stable CaSO 4 , which reduces the carbon capture capacity of the sorbents. A unique mineralization sequestration process for MSWI carbon capture is proposed that is economical and industrially viable. A promising route to improve CO 2 capture performance with waste reutilization is emphasized.