1973 Volume 26 Issue 5 Pages 244-264
Three kinds of membrane cells (a),(b) and (c), as shown in Fig. 1 and Fig. 2 were experimentally produced to improve the filterpress-type concentrator. The effective membrane area of these cells were expanded further than that of the old type without providing internal conduit holes to the surface of the membrane. As the result of experimental use of these cells in an industrial scale apparatus, the authors reached the following conclusions:
1. The cell (a) proved it difficult to produce its gasket, and its concentrating characteristics were not favorable.
2. The cell (b) proved it easy to produce its gasket, and its concentrating characteristics were favorable. However, it had such a defect as the spacer of flow-paths was fragile, and it could not prevent an increase in the flow-resistance resulting from the deposition of suspended matters of sea water.
3. The cell (c) which was of the simplest structure proved it easy to produce its gasket. In addition, the leakage of liquid was little, and flow-characteristics and concentrating characteristics were favorable. However, it was presumed that the leakage of the current increased a little due to its wider flow-path than the old type.
4. The use of a thickness-adjustment-gasket in the cells (b) and (c) did not make it difficult to assemble membrane packs. Therefore, the use of thickness-adjustment-gasket was judged to be the most appropriate way for making the effective membrane area larger.
5. The experiments demonstrated that such a most rational and desirable cell-structure as the cell (c) could be produced by combining the membrane having no conduit-holes with the thicknessadjustment-gasket and the plane gasket having wider (simplified) flow-paths.
6. Even when the sea water which had been filtrated by sand or diatomaceous earth filter was fed to the apparatus, a farily large amount of suspended matter of the sea water was found to stick to the surfaces of the membrane and the spacer. However, the cell (c) with its flow-path expanded showed a less increase in the flow-resistance caused by such deposits as compared to the cells (a) and (b).
7. When the pH of sea water was adjusted to 5-6 by addition of hydrochloric acid before the sea water was fed to the apparatus, or when the pH of circulating brine was adjusted to around 4 by addition of hydrochloric acid also, there was no deposition of calcium carbonate. This was also true of a long-run operation which was done under such conditions as 5 amp/dm2 0f current density, 30% recovery of sodium chloride, and 14-25°C temperature of seawater.
