Fouling in heat exchangers

Fouling by crystallization

This occurs, for example, during crystallisation processes of salts with weak solubility that are dissolved in the medium (carbonate precipitation) and during solidification of liquids due to temperature drop.

Particle fouling

Occurs as sedimentation of small particles such as sand or rust.

Corrosion fouling

Deposits such as iron oxide, which forms through a chemical reaction with the wall material

Reactive fouling

Chemical compounds formed by the influence of temperature, e.g. coking of exchangers in refineries and chemical plants.

Bio fouling

Biological growth in untreated water or algae formation in seawater

In practice, combinations of the different types often occur.

Practical recommendation in case of fouling

  • Surfaces and medium temperatures. High temperatures generally are beneficial for fouling
  • Flow rates.. High velocities reduce the fouling rate, while in “dead zones” fouling is boosted. This is especially true for cooling water and solids-laden gases.
  • Choice of material and design. The choice of the right material influences fouling due to corrosion. The use of finned tubes in the area of high fouling rates should be avoided.
    Product quality, pre-treatment. Filtering media or pretreating with additives, dosing chemicals.
  • Placing the media. Cleaning tubes is easier than cleaning the shell. There are fewer dead spots in the tubes where fouling can form. The medium that tends to get fouled should therefore be placed on the tube side.
  • Cleaning methods. The cleaning method (mechanical / chemical cleaning in operation / out of operation) should be determined in the design, i.e. appropriate installation or provision of cleaning nozzles.

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