Development of highly reactive and durable copper oxide based regenerable sorbents for flue gas desulfurization

Regenerable Flue Gas Desulfurization (FGD) processes offer advantages over the once-through processes, which include elimination of large quantities of waste materials and conversion of captured sulfur to salable products. However, highly reactive and attrition resistant sorbents are needed to make these processes economically more attractive than the conventional once-through wet/dry (FGD) processes.; Highly reactive and attrition resistant alumina-supported regenerable copper-based sorbents were developed by a sol-gel method, which are about 4 times more attrition resistant than a commercial FCC catalyst. The sorbents are capable of removing the SO2 content of flue gases to below 100ppmv in the temperature range of 300°-450°C and can be completely and readily regenerated by a reducing gas (e.g., methane) at 450°C. The optimum copper content of the sorbent appears to lie in the vicinity of the 14%. The overall reactivity of the optimum sorbent gradually decreases in the cyclic process during the first 15 cycles, which appears to stabilize after about 20 cycles. An expanding grain model with two adjustable parameters was selected to describe the kinetics of the sulfation and regeneration reactions. The model was shown to be able to fit the experimental conversion-time data with excellent accuracy. The model-derived parameters, namely the product-layer diffusivity (Dg) and tortuosity parameter (alpha) were related to the physical/chemical characteristics of the CuO-based sorbents. The model suggests that during the cyclic process, the product layer porosity gradually increases, which results in reduction in the product layer diffusivity and the tortuosity parameter.; The preliminary assessment of the overall process economics indicates that the calculated fresh sorbent makeup rate is extremely sensitive to the way the physical properties of the sorbent are extrapolated. The results also suggest that for a very low rate of sorbent deterioration, where the fresh make-up rate is dictated by the rate of sorbent loss through physical attrition, the regenerative process may be economically viable (and probably superior) to the commercially available once-through FGD processes.