Causes of scaling in heat exchanger and methods of preventing scaling

At present, the heat exchanger has been applied in all walks of life, and the effect is obvious. Of course, the heat exchanger also has defects. For example, the heat exchanger is easy to scale, which is a common problem of the heat exchanger.

Now let's look at the cause of scaling in the heat exchanger. First of all, when the heat exchanger equipment is running, the environment is a big reason for scaling. For example, some heat exchangers are installed in the workshop, where there is a lot of dust, which will become scaling after a long time, and some heat exchangers are installed in the water, and the suspended matter in the water is easy to scale after a long time. Scales will be produced in similar situations. What are the common dirt?

1) Crystalline dirt: The deposit formed by the crystallization of inorganic salts dissolved in the fluid on the heat exchange surface, usually occurs in the process of supersaturation or cooling. Typical fouling such as calcium carbonate, calcium sulfate and silicon dioxide scaling layer on the cooling water side.

2) Particle fouling: accumulation of solid particles suspended in the fluid on the heat exchange surface. This kind of dirt also includes the deposition layer formed by the gravity of large solid particles on the horizontal heat exchange surface, namely the so-called deposition of sediment dirt and other colloidal particles.

3) Chemical reaction fouling: the fouling generated 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) Corrosive dirt: the dirt produced by corrosive fluid or fluid containing corrosive impurities that corrodes the heat exchange surface. Generally, the degree of corrosion depends on the composition, temperature and pH value of the fluid being treated.

4) Biological fouling: Except for seawater cooling devices, generally biological fouling refers to microbial fouling. It may produce slime, which in turn provides conditions for the propagation of biological fouling. This kind of fouling is very sensitive to temperature. Under appropriate temperature conditions, biological fouling can generate a considerable thickness of fouling layer.

5) Solidification dirt: dirt formed by fluid solidification on the supercooled heat exchange surface. For example, when water is below the freezing point, it will solidify into ice on the heat exchange surface. The uniformity of temperature distribution has a great influence on this kind of dirt.

The following points should be taken into account in the technology to prevent scaling:

1) Prevent scaling;

2) Remove deposits from heat transfer surfaces.

3) Prevent the adhesion between substances after scaling and the deposition on the heat transfer surface;

Measures taken to prevent scaling include the following aspects:

1) The heat exchanger is easy to clean and maintain (such as plate heat exchanger);

2) A small number of dead zones and low velocity zones should be taken;

3) After the heat exchange equipment is installed, the dirt can be cleaned at the work site without dismantling the equipment;

4) The velocity distribution in the heat exchanger shall be uniform to avoid large velocity gradient and ensure uniform temperature distribution (such as baffle zone);

5) The influence of heat exchange surface temperature on fouling formation shall be considered.

6) On the premise of ensuring a reasonable pressure drop and not causing corrosion, increasing the flow rate helps to reduce dirt.