In the process of using the plate heat exchanger, the calcium, magnesium and carbonate in the water will be decomposed into calcium carbonate and calcium hydroxide precipitates when they are heated, forming hard scale on the heated surface of the heat exchanger.Technical requirements for cleaning scale of plate heat exchanger
(1) Pickling temperature of heat exchanger. Increasing the pickling temperature is conducive to improving the descaling effect. If the temperature is too high, the corrosion of the heat exchanger plates by the pickling liquid will be exacerbated. The pickling temperature is preferably controlled at 60°C.
(2) The concentration of pickling liquid in plate heat exchanger. According to the test, the pickling solution should be prepared at a concentration of 81.0% formic acid, 17.0% water, 1.2% buffer, and 0.8% surfactant. The cleaning effect is excellent.
(3) Pickling method and time of heat exchanger: The pickling method should be carried out by a combination of static immersion and dynamic circulation. The pickling time is first static immersion for 2 hours, and then dynamic cycle for 3 hours to 4 hours. During the pickling process, the acid pickling concentration should be sampled frequently. When the difference between the two tests is less than 1.2%, the acid pickling reaction can be considered to be over.
(4) Passivation treatment. After the pickling, most of the scale and metal oxides on the surface of the plate heat exchanger are dissolved and peeled off, exposing brand new metals, which is very easy to corrode. Therefore, the heat exchanger plates should be passivated after pickling.