Regenerating Fuel-Gas Desulfurizing Agents by Using Bipolar Membrane Electrodialysis (BMED): Effect of Molecular Structure of Alkanolamines on the Regeneration Performance

Alkanolamine sulfates are the heat-stable salts formed in the fuel-gas desulfurization by using alkanolamines, and they can cause the deterioration of absorption performance and loss of absorbents. In this paper, a method was reported to regenerate three alkanolamines (monoethanolamine, MEA; diethanolamine, DEA; and N,N'-dimethylethanolamine, DMEA) by using BMED. The effects of operation parameters (electrolyte concentration, alkanolamine sulfate concentration, and current density) on regeneration were analyzed on the basis of ion dimensions and intrinsic transport velocities, ion concentration, Donnan dialysis, ion orientation, and the interaction between alkanolamines and membranes. The process cost is estimated to be 0.48, 0.32, and 0.30 $/kg for MEA, DEA, and DMEA, respectively. BMED is not only feasible for alkanolamine regeneration but also environmental-friendly and economically attractive, especially as the bipolar membrane cost decreases and pollution control is strengthened.