Carbonation of gypsum from wet flue gas desulfurization process: experiments and modeling

In this paper, waste gypsum from wet flue gas desulfurization (WFGD) mixed with NH₃·H₂O was applied for CO₂ absorption in the solid-liquid-gas phase system. The effects of operation temperature, CO₂ flow rates, and ammonia-to-gypsum ratio on carbonation process were discussed. Meanwhile, a model for CO₂ absorption in the suspension of WFGD gypsum and ammonia was established. The results indicate that higher temperature favors the reaction, and WFGD gypsum conversion can be achieved above 90% even at lower ammonia-to-gypsum ratio, while CO₂ conversion reaches 90% and ammonia utilization is up to 83.69%. The model fits well with the experimental results at various CO₂ flow rates and predicts the concentration distribution of the main species, including CO₂ absorbed, NH₂COO^-, and HCO₃^-.