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.
Occurs as sedimentation of small particles such as sand or rust.
Deposits such as iron oxide, which forms through a chemical reaction with the wall material
Chemical compounds formed by the influence of temperature, e.g. coking of exchangers in refineries and chemical plants.
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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