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 CO2 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 CO2 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 CO2 capture capacity and carbonation conversion of fly ash-CaO sorbents were investigated at different temperatures, CO2 partial pressures and doping ratios in a calcination/carbonation reaction system. Optimum carbonation reaction temperature (760 degrees C) for CaO and optimum calcination temperature (850 degrees C) 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 CO2 capture capacity of the sorbents. The inert materials (Al2O3, SiO2) 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 CO2 for adsorption sites and produces stable CaSO4, 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 CO2 capture performance with waste reutilization is emphasized.