1. Selection of cleaning agent
At present, the choice of cleaning agent is pickling, which includes organic acid and inorganic acid. Organic acids mainly include oxalic acid, formic acid, etc. Inorganic acids mainly include hydrochloric acid, nitric acid, etc. According to the analysis of scale formation, process, material and scale composition of heat exchanger:
1) The flow area of heat exchanger is small, the internal structure is complex, and it is not easy to discharge the cleaning liquid if it produces precipitation.
2) The material of heat exchanger is nitinol alloy, and hydrochloric acid is used as cleaning fluid. It is easy to produce strong corrosion on plates and shorten the service life of heat exchanger.
Through repeated tests, it was found that formic acid was the best cleaning solution. Adding buffer and surfactant into formic acid cleaning solution, the cleaning effect is better, and the corrosion of cleaning solution to plate can be reduced. Through the chemical test of scale samples, it is shown that formic acid can effectively remove scale. Through the acid immersion test, it is found that formic acid can effectively remove the scale attached to the plate, and its corrosion effect on the plate of heat exchanger is also very small.