1、 Determination of scaling type (confirm before cleaning)

Salt scale: mostly white crystals (such as sodium chloride and sodium sulfate), with a hard texture, soluble in water or dilute acid, commonly found in high salt wastewater treatment equipment.

Calcium magnesium scale (carbonate/sulfate scale): gray white or yellow white, hard texture, insoluble in water but soluble in dilute acids (such as citric acid and hydrochloric acid), commonly found in wastewater with high hardness.

Organic scale: brownish or black, with a soft texture (such as oil or polymer), soluble in organic solvents or strong alkaline solutions, commonly found in food and chemical organic wastewater treatment equipment.

2、 Targeted cleaning methods

1. Physical cleaning (suitable for mild scaling or preventive cleaning)

High pressure water flushing: Use a 30-50MPa high-pressure water gun, with a specially designed slender nozzle inserted into the heat exchange tube, and use high-pressure water flow to impact and peel off the scale layer. ✅  Advantages: Simple operation, no chemical pollution, suitable for stainless steel heat exchange tubes. ❗  Attention: Avoid direct impact on the welding area to prevent damage to the pipe wall; The effect on hard scale (such as calcium magnesium sulfate scale) is limited.

Mechanical scraping: Use a specialized pipeline scraper (customized according to the pipe diameter) manually or mechanically driven to insert into the pipe, rotate and scrape off the inner wall scale layer, suitable for heat exchange pipes with larger pipe diameters (≥ 20mm). ✅  Advantage: Suitable for thick layers of hard dirt, thoroughly removed. ❗  Attention: Control the force to avoid scratching the pipe wall (especially soft metals such as titanium alloy).

2. Chemical cleaning (suitable for moderate to severe scaling, chemicals need to be selected according to the scale type)

For salt scale/calcium magnesium carbonate scale: Use 1-5% dilute citric acid solution (safe and mild, suitable for various materials) or 1-3% hydrochloric acid solution (strong stain remover, only suitable for stainless steel materials, avoid using for corrosive metals such as titanium and aluminum) for cyclic cleaning. Operation steps: ① Turn off the equipment and connect the heat exchange tube with the circulation pump and chemical tank to form a closed loop; ② At room temperature or heated to 40-60 ℃ (to accelerate the reaction), the circulation pump continuously pumps the reagent for 3-6 hours; ③ After discharging the waste liquid, rinse with clean water 2-3 times until the pH of the effluent is neutral (to avoid residual chemical corrosion).

For calcium magnesium sulfate scale (insoluble scale): a specialized chelating agent (such as EDTA sodium salt) solution (concentration 5-10%) is used, heated to 60-80 ℃ for 8-12 hours of cyclic cleaning, and the scale layer is dissolved through chelation.

For organic scale: Use 2-5% sodium hydroxide solution (suitable for oils and fats) or organic solvents (such as ethanol and acetone) for cyclic cleaning, operate at room temperature or low temperature (to avoid organic matter volatilization), and thoroughly rinse with clean water after cleaning to prevent residual chemicals from affecting subsequent evaporation.

3. Online cleaning (suitable for scenarios where shutdown is not possible and requires equipment support)

If the equipment is designed with an online cleaning interface, a small amount of descaling agent (such as citric acid) can be injected into the heat exchange tube regularly (such as weekly) through an automatic dosing device, using the temperature and flow flushing during equipment operation to achieve preventive descaling and reduce the frequency of shutdown cleaning.

3、 Inspection and protection after cleaning

Effect inspection: After cleaning, observe the inner wall of the heat exchange tube through an endoscope to ensure that there is no obvious residue of scale layer; Monitor the heat transfer efficiency during operation (such as the difference in inlet and outlet water temperature), and restore it to the design value to meet the standard.

Anti scaling measures:

Pre treatment: Before entering the evaporator, the wastewater is softened (to remove calcium and magnesium ions) and filtered (to remove suspended solids) to reduce scaling sources;

Regular maintenance: Perform preventive cleaning every 1-3 months based on water quality to avoid difficult removal of hardened scale layers.