How to Address Fouling in Plate Heat Exchangers

Plate heat exchangers are widely used heat exchange equipment in the atmospheric and vacuum distillation units of refineries. Factories incur significant costs annually due to fouling treatment, and severe fouling can even disrupt production. According to the mechanisms of fouling layer deposition, foulants can be classified into particulate fouling, crystalline fouling, chemical reaction fouling, corrosion fouling, biological fouling, etc.

1. Particulate Fouling: Accumulation of solid particles suspended in the fluid on the heat transfer surface. This type of fouling also includes sediment layers formed by larger solid particles on horizontal heat transfer surfaces due to gravitational effects (known as sediment fouling) and the deposition of other colloidal particles.

2. Crystalline Fouling: Deposits formed by the crystallization of inorganic salts dissolved in the fluid on the heat transfer surface, typically occurring during supersaturation or cooling. Typical examples include calcium carbonate, calcium sulfate, and silica scaling layers on the cooling water side.

3. Chemical Reaction Fouling: Fouling generated by chemical reactions on the heat transfer surface, where the surface material does not participate in the reaction but may act as a catalyst for the chemical reaction.

4. Corrosion Fouling: Fouling resulting from the corrosion of the heat transfer surface by corrosive fluids or fluids containing corrosive impurities. The corrosion degree generally depends on the fluid composition, temperature, and the pH value of the treated fluid.

5. Biological Fouling: Except for seawater cooling systems, biological fouling generally refers to microbial fouling. It can produce slime, which in turn provides conditions for the proliferation of biological foulants. Under suitable temperature conditions, biological fouling can form a fouling layer of considerable thickness.

6. Solidification Fouling: Fouling formed by the solidification of fluids on subcooled heat transfer surfaces. For example, water freezing into ice on the heat transfer surface below 0°C. The uniformity of temperature distribution has a significant impact on this type of fouling.