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Verfahren zum Elektrodialysieren von Fluessigkeiten

Two stage, monopolar and bipolar electrodialysis process achieving reduced energy consumption - produces high degree of concentration in e.g. sodium hydroxide and lactic acid products using circuits batch-recycling electrodialysed dilutate, with raw feed under conductivity control.
: Boergardts, P.

Frontpage ()

DE 1996-19637870 A1: 19960917
DE 1997-19700044 A: 19970102
DE 19700044 C1: 19980205
Patent, Electronic Publication
Fraunhofer IGB ()

This new method is used for the electrodialysis of fluids, accompanied by water electrolysis. Fluid containing a salt undergoes monopolar electrodialysis. Concentrate flowing from this stage is then subjected to bipolar electrodialysis. A novel feature of this process is that the concentrate stream undergoing bipolar electrodialysis, is mixed with fluid which has been reduced in concentration by bipolar electrodialysis, i.e. resultant dilutate. Also claimed is the equipment to carry out the procedure. This includes monopolar and bipolar electrodialysis units (6, 11), each with one or more electrodialysis stacks, with a circuit (15, 10) for cyclic electrodialysis of the dilutate. The new feature is connection of the concentrate chamber (s) (9) of the monopolar dialysis to the dilutate circuit (15, 10). USE - To electrolyse salts, producing a high product concentration. ADVANTAGE - This process wins the acid and alkaline products in higher concentration, for lower energy consumption than required in comparable prior art. The dilutate concentration may be made very low. The example of sodium lactate processing is described, producing lactic acid and sodium hydroxide. In a process example included, graphs clearly illustrate the changes in dilutate and concentrate concentrations, with time and with total electrical charge passed.