| 摘要 |
PURPOSE:To remove deposits with the maintained operation state, by making an ammonia absorption system and ammonia distillation system respectively and independently operable and leading a dilute aqueous solution of caustic soda to a heat exchanger, contactor, distillation column condenser and distillation column one after another. CONSTITUTION:An absorbing solution consisting of a phosphoric acid solution is first taken out of an absorption column 2 into a blow tank 4, and the phosphoric acid solution in a reduced amount of the taken out solution is filled in the absorption column 2. The absorption system and distillation system are temporarily cut off by valves 16 and 17 to carry out the separate respective operation thereof. In the absorption system, the supply of steam 10 to the distillation column 9 is stopped to keep the distillation column 9 in the pressure holding and reduced pressure state. Caustic soda and water are then respectively fed from lines 13 and 14 into a washing tank 12 to adjust the concentration to 5%. The resultant washing solution is then passed through a heat exchanger 6, contactor 7, distillation condenser 8, distillation column 9, heat exchanger 6, and cooler 10 and then returned to the washing tank 12. The above-mentioned operation is repeated and the solution is partially blown from the tank 12.
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