Reasons for the fouling of the plate heat exchanger:

    The use of plate heat exchangers is very frequent. In order to ensure its energy-saving performance, we require maintenance during the process of using plate heat exchangers. In many situations, the plate heat exchanger is easy to foul, which will seriously affect the heat exchange efficiency. Since most of the plate heat exchangers use water as the heat carrier, certain salts crystallize out of the water when the temperature rises, and adhere to the surface of the heat exchange plates to form scale.
    Adding a polyphosphate buffer to the cooling water can also cause scale precipitation when the pH of the water is high. The scale formed in the initial stage is relatively soft, but with the formation of the scale layer, the heat transfer conditions deteriorate, the crystal water in the scale gradually loses, and the scale layer becomes hard and adheres firmly to the surface of the heat exchange plate.
    In addition, when the working conditions of the heat exchanger are suitable for the precipitation of crystals from the solution, the surface of the plates of the plate heat exchanger can accumulate a scale layer composed of material crystals. When the fluid contains more mechanical impurities and organic matter, and the flow rate of the fluid is low, local mechanical impurities or organic matter will also accumulate in the plate heat exchanger, forming loose, porous or colloidal dirt.

    Cleaning method of plate heat exchanger:

    1. Circulating water cleaning: On-line cyclic cleaning of heat exchange equipment is completed in 3-5 hours for ordinary equipment, and no more than 12 hours for large systems.
    2. Soaking and cleaning: For some smaller condensers, soaking can be used for 4-6 hours.
    3. Spray cleaning: For plate heat exchangers with a large area of fouling on the surface, spray cleaning can be used.
    4. Pickling: Use pickling liquid and impurities such as scale to react, which is the stop of the subsequent process.
    5. Alkaline washing: The application of alkaline washing to remove organic compounds and oil stains and stop the softening of the scale makes it easier to remove. The time is between 10-24 hours and the temperature is usually 85 degrees Celsius. At the same time, some impurities are removed from the surface and taken away. 
    6. Rinsing: Use rinsing liquid to separate the iron ions remaining in the system to reduce the content and prepare for passivation to prevent the metal from returning to the plate heat exchanger.
    7. Neutralization passivation: Use passivating agent to present a passivation film on the metal surface.
    8. Rinse with water after alkaline washing: In order to remove the remaining alkaline cleaning solution, soluble substances are generated.
    9. Water rinsing after pickling: remove residual acid and scattered solid particles, and at the same time remove the secondary rust that appears during water rinsing.
    10. Water flushing and system pressure test: Water flushing and pressure test are used to remove ash, silt, scattered metal oxides and loose dirt in the system, and the flow rate is less than 0.3m/s.