Cleaning preparation of plate heat exchanger

2.1 scaling analysis of plate heat exchanger

Plate heat exchanger can be divided into two ways: water water exchange and steam water exchange. In water water exchange mode, the cold and hot medium is water, and the temperature difference between cold and hot water is not big, about 70-90 ℃, and the scaling condition on both sides is the same; The heat medium of steam water exchange mode is steam, which is not easy to scale. The cold medium is water, and the temperature is about 90 ℃. The scale samples can be roughly divided into scale and dirt, especially scale. The scale is mainly caused by the decomposition of various salts dissolved in water, the decrease of solubility and the crystallization deposition on the heat transfer plate, usually carbonate, phosphate, sulfate and silicate. The crystal density of this kind of scale is relatively hard and difficult to remove. Dirt is generally composed of fine particles of sand, dust, insoluble salt mud, colloidal hydroxide, debris, corrosion products, oil, algae and so on. This kind of dirt is large, loose and easy to remove.

2.2 cleaning process selection plate heat exchanger cleaning method is divided into closed-circuit circulation cleaning and disassembly immersion cleaning two processes, before cleaning, according to the circulating water quality scale sample analysis, select the corresponding cleaning process according to the following table: