| 摘要 |
PURPOSE:To prevent the lowering in operation efficiency, by supplying condensed water into the heat transfer element of a recirculation flow part to be washed to fill said heat transfer element with condensed water. CONSTITUTION:When the distillation capacity in a final recirculation flow part 7 is lowered by the adhesion of scale during distillation, the introduction of a conc. liquid from the adjacent partition chamber 3 to the partition chamber 4 of the recirculation flow part 7 is blocked. Then, the outer surface of the heat transfer element of the recirculation flow part 7 of the partition chamber 4 is washed with washing water or a low concn. process liquid. At the same time, the condensed water stored in a condensed water tank 22 is forcibly sent to the header 10 of the recirculation flow part 7 by a water feed pipe 23 to fill the heat transfer element of the recirculation flow part 7 with condensed water within a short time. During washing, distillation is performed in recirculation flow parts 5, 6 and the recirculation flow part 7 is subjected to the washing of the outer surface of the heat transfer element. By this method, the evaporation efficiency in the recirculation flow part can be enhanced.
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