The plate heat exchanger should be cleaned according to the scaling situation.When the heat transfer effect cannot meet the process design requirements, it must be cleaned.From the point of view of energy saving and consumption reduction, if the heat transfer surface of the plate heat exchanger is attached with 0.2 to 2 mm of scale, the heat transfer efficiency will be reduced by 10 to 40%, and the 0.3 mm scale will reduce the heat transfer efficiency of the heat exchanger by 90%. What is the process requirement for the plate heat exchanger clean the scale？
(1) Pickling temperature: Increasing the pickling temperature is beneficial to improve the descaling effect. If the temperature is too high, the corrosion of the heat exchanger plate will be aggravated by the acid washing liquid. It is found through repeated tests that the pickling temperature is controlled at 60℃
(2) Pickling solution concentration: According to repeated tests, the pickling solution should be prepared according to the concentration of formic acid 81.0%, water 17.0% a, buffer 1.2%, surfactant 0.8%, and the cleaning effect is excellent.
(3) Pickling method and time: The pickling method should be carried out by a combination of static immersion and dynamic circulation. The pickling time is first static soaking for 2 h, then dynamic cycling for 3-4 h.In the pickling process, the pickling concentration should be sampled frequently. When the difference between the two adjacent assays is less than 0.2%, the pickling reaction is considered to be over.