Evaporator Scale Cleaning

I. Causes and Hazards of Scaling in Evaporation Systems

Mechanism of Scale Formation:

Solubility changes: Precipitation of supersaturated solutes during concentration (e.g., calcium sulfate, silicon dioxide, sodium chloride, etc.);

Temperature effect: Elevated temperatures cause polymerization of heat-sensitive substances (such as proteins and polysaccharides);

Chemical reaction: Calcium and magnesium ions react with carbonate ions to form insoluble salts.

Scale Deposits:

Heat transfer efficiency decreases by 30-50%, and energy consumption increases by more than 20%.

Pipeline blockages cause shutdowns, resulting in annual losses reaching millions;

Product contamination risk;

II. Comparison and Selection of Cleaning Technologies

1. Chemical Cleaning Method

Acid Cleaning Process (for Calcium and Magnesium Scale): Employ nitric acid, amino sulfonic acid, and citric acid. Circulate the cleaning solution at a temperature of 40-60°C.

Alkali Cleaning Process (for Organic Scale): Clean using a solution of 3% sodium hydroxide + 0.5% surfactant.

2. Physical Cleaning Method

High-pressure water jet: Pressure 200-400 bar, using a rotating nozzle to perform high-pressure cleaning on tube bundles, but not suitable for thin-walled heat exchange tubes.

III. Maintenance Recommendations

1. Preventive Measures

Perform pretreatment on the water to reduce calcium and magnesium content, and add 0.1-0.5% scale inhibitor;

2. Cleaning Cycle Optimization

When the heat transfer coefficient of the shell-and-tube heat exchanger decreases by 20%, shut down the unit for cleaning. It is recommended to clean it once a month.