Causes and treatment of fouling in heat exchanger

In the operation of heat exchanger, the inner and outer walls of tube bundle may be scaling, and the thermal resistance of fouling layer is much larger than that of metal tube, which leads to the rapid decline of heat transfer capacity, and in serious cases, the flow channel of heat exchange medium will be blocked

So, the following is to explain the cause of scale inhibition and treatment methods for the lower heat exchanger.

1. Particulate fouling: accumulation of solid particles suspended in a fluid on a heat transfer surface. This kind of fouling also includes the deposition layer of larger solid particles on the horizontal heat exchange surface due to gravity, namely the deposition of the so-called precipitated dirt and other colloidal particles.

2. Crystal fouling: deposit formed by crystallization of inorganic salts dissolved in the fluid on the heat transfer surface, usually occurring during supersaturation or cooling. Typical fouling such as calcium carbonate, calcium sulfate and silica scale on the cooling water side.

3. Chemical reaction fouling: fouling produced by chemical reaction on the heat transfer surface. The heat transfer surface material does not participate in the reaction, but can be used as a catalyst for chemical reaction.

4. Corrosion fouling: the fouling caused by corrosive fluid or corrosive impurities in the fluid which corrodes the heat exchange surface. Generally, the degree of corrosion depends on the composition of the fluid, the temperature and the pH value of the fluid being treated.

5. Biological fouling: in addition to seawater cooling device, general biological fouling refers to microbial fouling. It may produce slime, which in turn provides conditions for the reproduction of biofouling, which is very sensitive to temperature. Under suitable temperature conditions, biofouling can form a fouling layer of considerable thickness.

6. Solidification fouling: fouling formed by the solidification of a fluid on a subcooled heat transfer surface. For example, when water is below freezing point, it solidifies into ice on the heat exchange surface. The uniformity of temperature distribution has a great influence on the fouling.