Abstract
In separation and concentration of potassium chloride by electrodialysis with ion exchange membrane from “calcium chloride solution” mentioned in previous report, effects of flow rate of the solution in desalting compartments and of degree of desalting on the composition of concentrated solution were estimated. The electrodialysis cell used was of 9cm2 in effective membrane area and consists of 4 concentrating compartments and 5 desalting ones. Membranes used were of the same as those in previous report, univalent permselective membranes. Desalting solution was circulated and raw solution was feeded continuously to the solution in circulating system. Effect of flow rate found to be little at 0.5-2.0cm/sec and that of degree of desalting to be serious.
A bench scale test based on the above experimental results was done with a cell unit having 5 dm2-effective membrane area, 17-concentrating compartments and 18-desalting ones. Circulation system of desalting solution was also employed. Degree of desalting was set so that the concentration of calcium chloride in desalted solution may be rather high compared with that in raw solution. Current density, flow rate of the solution in desalting compartment and temperature employed were 1A/dm2, 3cm/sec and 11-13°C (equilibrated to the room temperature), respectively. Separation and concentration of potassium chloride were carried out satisfactorily. Volume of concentrated solution taken was about 1/10 of that of raw solution feeded, and recoveries of potassium chloride deposited from both of solutions by evaporation at the same conditions were calculated to be nearly equal. Electric power demand for electrodialysis was calculated to be about 1,100KWH/t-KCI.
