Prevention of the scale trouble of multi-effects stacked desalination plant

New scale prevention method was studied in order to adapt the top sea water temperature of more than 100°C in the multiple effect distillation process. The experimental apparatus was so designed that the sea water flows down on the surface of the evaporation plate of 10 mm width and 220 mm length with falling film. It became clear through the test that the surface was prevented from scale precipitation by keeping pH value of the sea water 5.3 and keeping surface vaporization of the sea water without nuclear boiling at a temperature of 130°C. Even when scale precipitation was brought on the evaporation plate surface in mal-operation, the scale is easily removed from the surface by reducing pH value of the sea water to 1 ∼ 2 only for several minutes. It was certified by autoclave tests that titanium is suitable plate material against crevice corrosion and general corrosion in pH of the sea water 5.3 and top sea water temperature of 130°C. As a result, top sea water temperature of 130°C can be apply to the actual multiple effect distillation process.