What are the causes of scaling in plate heat exchangers?

Plate heat exchanger in chemical production plays an important role in the heat exchanger unit scaling and corrosion leading to insufficient heat transfer, heat exchanger is forced to clean or replace, and seriously affect the safety of production, increasing the cost of business operations. The following author would like to introduce to you the reasons for the scaling of plate heat exchangers.

1. Particle dirt

The accumulation of solid particles suspended in the fluid on the heat transfer surface, generally composed of fine particles of silt, dust, insoluble salts, gums, oil, etc.

When water containing these substances flows through the surface of the heat exchanger, it tends to form fouling deposits that form subscale corrosion, providing a breeding ground for certain bacteria to survive and reproduce. When the anti-corrosion measures are not taken properly, they eventually lead to corrosion and perforation of the heat transfer surface and leakage.

2. Biofouling

Biofouling in general refers to microbial fouling with the exception of seawater cooling units. The most common microorganisms in circulating water systems are mainly iron bacteria, fungi and algae.

Iron bacteria can convert water-soluble Fe2+ into water-insoluble Fe2O3 hydrates, which produce large iron oxide precipitation in water and establish oxygen concentration difference corrosion cells that corrode metals.

Also, algae in circulating water systems often form metal surface differential corrosion cells in the water that cause corrosion under the sediment. The block also clogs the lines in the heat exchanger, reducing the flow of water and thus reducing the efficiency of the heat transfer.

3. Crystalline dirt

In the cooling water circulation system, as water evaporates, the concentration of dissolved salts (such as bicarbonates) in the water increases, some salts precipitate due to oversaturation, while some salts precipitate due to thermal decomposition when passing through the heat transfer surface of the heat exchanger. These scales are composed of inorganic salts, crystalline and dense, and are known as crystalline scale.

4. Solidification of dirt

Fouling caused by fluid solidification on the supercooled heat transfer surface. For example, when water is below freezing point and solidifies into ice on the heat transfer surface. Whether the temperature distribution is uniform or not has a big impact on this fouling.

These are the common causes of plate heat exchanger scaling introduced by the author for you, I hope to help you, if you have other aspects want to understand, you can come to consult us.