Utilization of coal fly ash and bottom ash as solid sorbents for sulfur dioxide reduction from coal fired power plant: Life cycle assessment and applications

Feasibility of sulfur dioxide (SO2) reduction from a coal fired power plant using fly ash and bottom ash as solid sorbents is evaluated. The study integrates inventory data from experiments, process simulation, published studies, and real plant operation for comprehensive life cycle assessment (LCA). The experimental results exhibit the capability of free lime contained fly ash and bottom ash to react with SO2 under the least efficient conditions. The scenario-based LCA results show that fly ash/bottom ash utilization can lower the SO2 load of untreated flue gas by 3.7-4.7% before an existing wet limestone flue gas desulfurization (WFGD) system. The combined desulfurization process with SO2 reduction saves the annual energy consumption by 4.0-5.0%, the environmental impacts by 3.0-5.0%, and the annual operating cost by 3.1-4.5%, compared to the existing WFGD process. The uncertainty analysis evaluates the probability of scenarios, and the sensitivity analysis recommends the parameter variations to further improve the combined desulfurization process and possible applications of the post SO2 capture fly ash. The approach can also be applied in other coal fired power plants for more environmentally-benign WFGD operation and cleaner electricity production.