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Causes of scale in plate heat exchangers and cleaning principles
Source: Time: 2021-01-25 14:26:13 Hit:
Plate heat exchangers usually produce some scale-like things during use, which is caused by improper use of their products during use and treatment. Next, Jiangsu YOJO will introduce you to the causes of scale in the plate heat exchanger and the cleaning principle!
Stripping effect: The acid solution can dissolve the oxides on the metal surface of the plate heat exchanger and break the bond with the scale, so that the scale attached to the surface of the metal oxide can peel off and fall off.
Dissolution: The acid solution easily reacts with calcium, magnesium, and carbonate scale to form easily soluble compounds to dissolve the scale.
Loosening effect: For mixed scale containing silicate and sulfate, since the oxides of calcium, magnesium, carbonate and iron are dissolved in the acid solution, the remaining scale will become loose and easily washed away by the flowing acid solution .
Air lift effect: after acid solution reacts with calcium, magnesium, and carbonate scale, a large amount of carbon dioxide is produced. During the overflow process of the carbon dioxide gas of the plate heat exchanger, it has a certain lifting power for the insoluble or slow-dissolving scale layer, so that the scale will fall off the heated surface of the heat exchanger.
After the brazed plate heat exchanger is used for a long time, the surface of its heat transfer plate will produce different degrees of dirt or deposits, thereby increasing the flow resistance and reducing the heat transfer performance. This is mainly manifested in the increase in the pressure difference between the inlet and outlet pressure gauges and the decrease in the outlet temperature of the cold medium.
1. Blockage
Particles larger than 1.5~3mm in diameter can easily block the plate passage. The flow channel gap of the plate heat exchanger is small, which causes the equipment to be blocked and the heat exchange capacity is greatly reduced, which seriously causes the continuous production of the device to be interrupted. Therefore, a coarse filter or a backwash device can be installed at the inlet of the medium according to the needs, which can effectively prevent the blockage of the plate heat exchanger.
2. Scaling
The plate design of the plate heat exchanger has a large number of supporting points, and fouling can cause the heat transfer coefficient of the heat transfer equipment to decrease. It is designed to turbulent flow and pressure support to the medium. The side effect is that the fluid forms a local stagnation and generates dirt. The calcium and magnesium ions in the medium are easy to form honeycomb scales after precipitation at a suitable temperature.
Tag:Plate heat exchanger scale,plate heat exchanger runner gap
