Keeping the heat exchanger plates clean is one of the important conditions for maintaining a high heat transfer coefficient.Between the sheets, the medium moves along a narrow, meandering flow path. Even if a relatively thick scale layer is produced, it will cause a change in the flow path, significantly affecting the movement of the fluid, increasing the pressure drop, and decreasing the heat transfer coefficient. For example, a sugar mill uses a plate heat exchanger in heating. Because the secondary water is not well treated, the flow channel is blocked for only two months during use and cannot continue to operate.
Plate heat exchanger cleaning method
(1) Pickling: The reaction is carried out using impurities such as pickling liquid and scale to facilitate the subsequent steps.
(2) Alkali washing: alkali washing is used to remove organic compounds and oil stains and softening the scale so that it is more easily removed. The time is between 10 and 24 hours and the temperature is usually 85 degrees Celsius. At the same time, local impurities are removed from the surface and taken away.
(3) Rinsing. The rinsing liquid is combined with iron ions remaining in the system to reduce the [Fe2+/Fe3+] content, in preparation for passivation, thereby avoiding rusting of the equipment metal.
(4) Neutralization passivation; a passivation film appears on the metal surface using a passivating agent.
(5) Water washing after alkali washing: in order to remove the residual alkaline washing liquid to form a soluble substance.
(6) Water washing after pickling: To remove the residual acid and the fallen solid particles, and remove the secondary rust that occurs when the water is rinsed.
(7) Water rinsing and system pressure test: Water rinsing and pressure test is to remove the ash, sand, falling metal oxide and loose dirt in the system, and the flow rate is less than 0.3 m.