Analysis of Causes of Scaling in Plate Heat Exchanger

Analysis of Causes of Scaling in Plate Heat Exchanger

1.The impurities dissolved in water are ionic or molecular states

Calcium salts: Calcium salts including Ca (HCO3) 2, CaCl2, CaSO4, CaSiO3, etc, are the main component that cause scaling of heat exchanger

Magnesium salts: After magnesium is dissolved in water, it is decomposed by heat to form Mg (OH) 2 precipitation, forming sludge or scale. Magnesium salt includes Mg (HCO3) 2, MgCl2, MgSO4, etc.

Sodium salts: Sodium salts are mainly composed of NaCl, Na2SO4, NaHCO3,etc.

NaCl does not form scale, but there is free oxygen in the water, which will accelerate the corrosion of metal wall. Too high content of Na2SO4 will cause salt deposition and affect safe operation. NaHCO3 in water will decompose into NaCO3, NaOH and CO3 under the action of temperature and pressure, which will damage the metal grain.

2. Impurities in colloidal state

Iron compounds: The main component of iron compounds is Fe2O3, which will form iron scale.

Microorganisms: Because the temperature of circulating water and dissolved oxygen provide conditions conducive to the reproduction of microorganisms, microorganisms will multiply in large numbers. When the temperature of circulating water is high, phosphate and other chemicals are added to the water, which is just the nourishment of microorganisms. Microbial propagation not only blocks the plate channel, but also sometimes blocks the pipeline, and also causes metal corrosion.

Sludge: Sludge in cooling circulating water, which comes from dust in the air and suspended solids in make-up water, is gradually deposited in the heat exchanger with low flow rate.

Sticky scale: It is mainly formed by the adhesion of microbial secretion with sediment, corrosion products ,bacteria and algae residues in the water. And it is often attached to the wall of the heat exchanger.

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