Regenerating flue-gas desulfurizing agents by bipolar membrane electrodialysis

An experimental study was carried out on the regeneration of a flue-gas desulfurizing agent by using bipolar membrane electrodialysis (BMED) with sodium sulfate (Na2SO4) as the supporting and rinsing electrolyte, and piperazine sulfate (Pz(.)H(2)SO(4)) as a model compound for the heat stable salt formed in the process of desulfurizing. The results indicate that the low energy consumption and high current efficiency are achieved when applying electrolyte solutions with a concentration range about 0.3 similar to 0.4 mol/L, piperazine sulfate solution with a concentration range about 0.08 similar to 0.13 mol/L, and BMED stack of BP-C-C configuration. The results also indicate that when applying a high current density to the BMED stack, it has a high current efficiency and energy consumption. The process cost is estimated to be $0.96/kg Pz for the regeneration of piperazine with the laboratory-scale experimental equipment, indicating that the process is not only scientifically novel but also economically feasible and attractive besides its potential environmental benefits. (c) 2005 American Institute of Chemical Engineers.