The stainless steel plate heat exchanger consists of highly efficient heat transfer corrugated plates and a frame. The plate is clamped between the fixed compression plate and the movable compression plate by bolts. Many flow channels are formed inside the heat exchanger, and the plates are sealed with rubber. What are the process requirements for cleaning scale of stainless steel plate heat exchanger?
(1) Pickling method and time. The pickling method should be performed by a combination of static immersion and dynamic cycling. Pickling time is static soaking for 2h, then dynamic cycling for 3-4 hours. During the pickling process, the acid pickling concentration should be sampled frequently. When the difference between the two adjacent test concentrations is less than 0.2%, the pickling reaction can be considered to be over.
(2) Passivation treatment. After the pickling, most of the scale and metal oxides on the surface of the plate heat exchanger are dissolved and peeled to expose brand-new metal, which is easy to corrode. Therefore, the stainless steel plate heat exchanger plate is passivated after pickling.
(3) Pickling temperature. Increasing the pickling temperature is beneficial to improve the descaling effect. If the temperature is too high, the corrosion of the plate heat exchanger by the pickling liquid will be exacerbated. Through repeated tests, it was found that the pickling temperature should be controlled at 60 degrees.
(4) Concentration of pickling solution. According to repeated tests, the pickling solution should be prepared at a concentration of 81.0% formic acid, 17.0% a water, 1.2% buffer, and 0.8% surfactant, so the cleaning effect is excellent.