How to Maintain and Clean Heat Exchanger Scaling in Evaporation Crystallization Systems

Gu Zhouying
18 hours ago
3 min read

Over time, a solid layer of fouling—comprising process materials, low-solubility salts, and macromolecular organics—can form on the inner walls of heat exchanger tubes. When this happens, even high-velocity flow inside the tubes becomes insufficient to remove the buildup. This scaling significantly reduces heat transfer efficiency and evaporation capacity. If left untreated, it can lead to decreased evaporation rates and increased pump load on the circulation system. To maintain system performance and prevent operational disruptions, regular and systematic cleaning is essential.

I Circulation Cleaning Methods

1. Clean Water Circulation Cleaning

At the early stage of scaling, clean water flushing is typically used. Water is introduced into the system using the feed pump and heated gradually to 80–90°C. The solution is circulated for 8–12 hours. TDS (Total Dissolved Solids) should be monitored throughout the process to assess cleaning effectiveness.

Standard Procedure:

Drain the existing process liquid from the system
Add tap water until reaching ~30% of the tank level
Start the MVR forced circulation pump
Gradually open the steam valve and raise the temperature to 80–90°C
Close the steam valve and maintain circulation for 8–12 hours
After cleaning, discharge the fluid via the MVR discharge pump to the feed tank or the drainage system

2. Acid Solution Circulation Cleaning

If water quality analysis indicates hardness-based scaling (e.g., from calcium or magnesium), citric acid or oxalic acid is commonly used. An acid cleaning solution with a pH of around 3 is introduced into the system and heated to 60–70°C. Circulate the solution for 8–12 hours while monitoring the pH level.

Standard Procedure:

Drain the process liquid from the system
Pump acid solution into the MVR separator until ~30% full
Start the MVR forced circulation pump
Gradually heat the system to 60–70°C
Circulate for 8–12 hours
If pH rises significantly, add more acid and continue cleaning for another 8–12 hours
Once clean, discharge the solution into a dedicated tank or chemical wastewater system
Neutralize the pH before recycling the water back into the system
Rinse thoroughly with clean water to avoid residual acid corrosion

3. Alkaline Solution Circulation Cleaning

If the fouling is suspected to be organic in nature, use caustic soda (sodium hydroxide) or a specialized cleaning agent. Prepare a solution with a pH of around 12 and heat it to 60–70°C. Circulate for 8–12 hours while monitoring pH changes.

Standard Procedure:

Drain the system
Pump alkaline solution into the MVR separator until ~30% full
Start the MVR forced circulation pump
Gradually heat to 60–70°C
Circulate for 8–12 hours
If pH drops, add more alkali and continue cleaning for another 8–12 hours
Discharge the used solution to a designated tank or cleaning pit
Neutralize the pH before recycling the water
Rinse thoroughly with clean water to prevent corrosion

II. High-Pressure Mechanical Cleaning

If chemical cleaning (acidic or alkaline) fails to remove the scaling, mechanical cleaning with high-pressure water is required. Disassemble the heat exchanger by removing the upper and lower end covers, then use a high-pressure water jet to clean the surfaces.

Standard Procedure:

Drain all process liquid
Disassemble the separator, heater, and other related equipment
Use high-pressure water to remove surface scaling from the inner walls of the heat exchanger

III. Safety and Operational Precautions During Cleaning

Handle with care: Acid and caustic solutions are hazardous and highly corrosive. Dilution releases heat. Check for leaks, valve failures, and pipe corrosion regularly during cleaning.
Avoid corrosion: Alkaline cleaning agents can damage heat exchanger tubes. Conduct periodic sampling and control concentration, and cleaning time carefully.
Maintain system integrity: Never open pipelines connected to the MVR forced circulation system during cleaning operations.
Wear protective gear: Workers must wear full PPE, including rubber boots, gloves, face masks, and safety goggles.
Ensure good ventilation: Cleaning areas should be well-ventilated, with an accessible and adequate water supply.
Use proper equipment: Corrosive chemicals should be transported with forklifts or designated tools. Avoid skin or eye contact. In case of exposure, rinse thoroughly with water and seek immediate medical attention.
Filter cleaning water: High-pressure cleaning units can use tap water or system cooling water. If using cooling water, ensure it is properly filtered to prevent debris from entering the equipment.