Analysis of the causes of fouling in air compressor heat exchangers

Compressor Heat exchangers are widely used in petroleum, chemical, light industry, pharmaceutical, energy and other industrial production. However, after long-term operation of heat exchangers, dirt will form inside, and the accumulation of dirt to a certain extent will cause internal passages of heat exchangers. The cross section becomes smaller or even blocked, resulting in insufficient cooling water flow and pressure reduction, resulting in shutdown and production stoppage; and even safety accidents such as bulging, cracks, and pipe bursts.

First, let's list the common causes of dirt formation

1. Precipitation of dirt

Most of the heat exchangers are heat exchange systems with water as the heat carrier. When the temperature increases or the concentration is high, the Ca(HCO3)2 and Mg(HCO3)2 originally soluble in water will precipitate out slightly soluble CaCO3 and Mg(HCO3)2. MgCO3. The precipitated salts adhere to the surface of the heat exchange tube to form scale, which is tightly attached to the surface of the heat exchange tube.

2. Particulate dirt

Suspended solid particles in the fluid system, such as: sand, dust, carbon black, and fouling formed by the accumulation of heat exchange surfaces.

3. Chemical reaction dirt

Deposits form between the heated surface and the fluid as a result of auto-oxidation and polymerization, i.e. chemical reactions.

4. Corrosion and dirt

Because the fluid is corrosive or contains corrosive impurities, the heat exchange surface is corroded, and corrosion products are deposited on the heat exchange surface to form fouling.

5. Biofouling

It is a sticky deposit formed by the adhesion of microbial groups and their excrement, chemical pollutants, mud and other components on the wall surface of the heat exchange tube, which is called biological fouling.

6. Solidified dirt

On the supercooled heat exchange surface, the fouling formed by the solidification and deposition of the highly soluble components of the cleaning liquid or multi-component solution.

Common cleaning methods for heat exchangers

(1) Chemical cleaning

Chemical cleaning is a chemical reaction generated by a chemical cleaning solution to dissolve, fall off or peel off the scale and other deposits on the surface of the heat transfer tubes of the heat exchanger.

Chemical cleaning does not need to disassemble the heat exchanger, which simplifies the cleaning process and reduces the labor intensity of cleaning. The disadvantage is that when the chemical cleaning solution is not selected properly, it will corrode and damage the substrate of the cleaning object, resulting in losses.

Commonly used chemical cleaning agents:

1. Detergents (including water and organic solvents) that decontaminate by dissolving;

2. Surfactant cleaning agents that use surface activity to decontaminate (such as cationic, anionic, nonionic and zwitterionic surfactants);

3. Chemical cleaning agents (such as acids, alkalis, salts, oxidants, etc.) that use chemical reactions to decontaminate.

Common methods of chemical cleaning

4. Circulation method: use the pump to force the circulation of the cleaning solution to clean.

5. Impregnation method: Fill the equipment with cleaning liquid and let it stand for a certain period of time.

6. Surge method: Fill the equipment with cleaning liquid, discharge a part of the cleaning liquid from the bottom at regular intervals, and then put the discharged liquid back into the equipment to achieve the purpose of stirring and cleaning.

Heat exchanger chemical cycle cleaning process:

1. Isolate the equipment and drain the water in the heat exchanger.

2. Clean the pipeline impurities with high pressure water and close the system.

3. A ball valve is installed between the isolation valve and the heat exchanger, and the transfer pump and conduit are connected. The cleaning agent is pumped in from the bottom of the heat exchanger and flows out from the top.

4. Inject the required cleaning agent and repeat the cycle cleaning.

5. Exhaust gas at any time and inject appropriate water.

6. Use pH test paper to determine the effectiveness of the cleaning agent.

7. Recover the cleaning solution and rinse with clean water repeatedly until the pH is neutral.

Physical cleaning is to use various mechanical external forces and energy to smash, separate and peel off the dirt from the surface of the object, so as to achieve the effect of cleaning.

Physical cleaning methods all have one thing in common: efficient, non-corrosive, safe, and environmentally friendly. The disadvantage is that when cleaning the inside of the equipment with complex structure, the force sometimes cannot reach all parts evenly and there is a "dead angle".

Common methods include ultrasonic descaling, PIG pigging technology, and electric field descaling technology.