| 配方類型： |
METALS AND THEIR TREATMENT |
| 配方說明： |
Boiler Cleaning- In-Service |
| 配方組成： |
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| 配制方法： |
The normal hydrochloric acid cleaning consists of a 5 per cent w/w solution of inhibited hydrochloric acid circulating in the boiler at a temperature of 90-95C for a period of approximately 6 hr. or at such time as the concentration of iron in solution levels off. Occasionally, up to 1 per cent ammonium bifluoride may be added to prove a more rapid removal of magnetite and silica deposits. The contents of the boiler are then drained out and the boiler refilled with a weak citric wash consisting of a solution of 0.2 per cent citric acid, the pH of this weak citric wash is then raised to between 8 and 9 by the addition of ammonia to the boiler. The boiler is then flushed out with demineralised water, opened up and any loose deposits removed. The cleaned boiler surfaces are then passivated using hydrazine at 300 ppm and ammonia at 30 ppm. The passivation process takes 24 hr. |
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