The plate heat exchanger is composed of a group of corrugated metal plates. There are four corner holes on the plate for the two liquids for heat transfer to alternately exchange heat through their respective channels. After a certain period of time, the plate heat exchanger will adhere to a layer of white scale on the inner and outer walls. The main cause of scale formation is due to the relatively low solubility of calcium and magnesium salts in water. The solubility of this salt decreases with the rise of water temperature, and it becomes an incomprehensible salt. What is the principle of scale cleaning of plate heat exchangers?
(1) Dissolution. Acid solutions easily react with calcium, magnesium, and carbonate scales to form soluble compounds that dissolve scales.
(2) Air lift effect. After the acid solution reacts with calcium, magnesium and carbonate scale, a large amount of carbon dioxide is generated. During the overflow process of carbon dioxide gas, there is a certain lifting force for the scale that is insoluble or slow to dissolve, so that the scale can fall off the heated surface of the heat exchanger.
(3) Peeling effect. The acid solution can dissolve oxides on the metal surface. The combination with the scale is broken, so that the scale attached to the surface of the metal oxide is peeled off and falls off.
(4) loosening effect. For scales containing mixed silicate and sulfate, oxides of calcium, magnesium, carbonate and iron dissolve in the acid solution, and the remaining scale will become loose and easily washed away by the flowing acid solution.
When the plate heat exchanger is used to remove scale, the basic principle is different depending on the method. The process of reaction between scale and its acid solution is also very different. Everyone can depend on the situation when removing scale.