Electrodialysis with Bipolar Membrane Process Costs

2 Electrodialysis with Bipolar Membrane Process Costs 

The determination of the costs for the production of acids and bases from the corresponding salts follows the same general procedure as applied for the costs in electrodialysis desalination. The contributions to the overall costs are the investment-related cost and the operating costs. 

Investment costs in electrodialysis with bipolar membranes Investment costs include nondepreciable items such as land and depreciable items such as the electrodialysis stacks, pumps, electrical equipment, and monitoring and control devices. The investment costs are determined mainly by the required membrane area for a certain plant capacity. The required membrane area for a given capacity plant can be calculated from the current density in a stack that is in electrodialysis with a bipolar membrane not limited by concentration-polarization effects. The required membrane area for a given plant capacity is given by  

A is the required membrane area, i is the current density, p is the product volume flow, F is the Faraday constant, q is the current utilization and Cp is the concentration of the product. 

The required membrane area A refers actually to a unit cell area that contains a bipolar membrane, and a cation- and an anion-exchange membrane. Since in strong acids and bases the useful life of the bipolar membrane as well as the anion-exchange membrane is rather limited, the stack-related investment costs are dominating the total investment costs. 

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