Flue gas desulfurization gypsum mineralization in waste Lye medium at pilot scale

Abstract

Abstract CO2 capture, utilization and sequestration technology is currently a global research hotspot with increasing CO2 emission and rising atmospheric temperatures. Flue gas desulfurization gypsum (FGDG) was used to realize CO2 mineralization in waste NaOH lye in a pilot scale bubble tower. The effects of the ionic strength, CO2 flow rate, reaction temperature, and liquid level in the reactor on the properties of the mineralization products and the CO2 mineralization efficiency were investigated using thermogravimetric analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and particle size analysis. The experimental results indicated that ionic strength, reaction temperature and CO2 flow rate significantly influenced the CO2 mineralization efficiency of FGDG. The CO2 mineralization efficiency reached 92.15% under the optimized conditions (the ionic strength: 10−2 mol·L−1, CO2 flow rate: 20 L·h−1, reaction temperature: 60 °C, liquid level: 50 cm). The liquid level has a strong effect on the particle size distribution of mineralized products. A higher liquid level promotes the formation of mineralized products with smaller particle sizes. These products consist of a single cluster of crystals and the main component is calcium carbonate. The pilot scale results demonstrate optimized evidence for CO2 mineralization using FGDG in waste lye. Therefore, this approach enables the comprehensive utilization of three types of waste-gas, liquid, solid- generated produced in coal-fired power plants.