1、 Wastewater pretreatment: reducing scaling substances from the source

This is the most fundamental preventive measure, which is to remove or reduce the content of scaling components in wastewater through pretreatment.

Remove suspended solids and colloids

Before entering the evaporator, the wastewater is filtered through quartz sand, activated carbon adsorption, or precision filters (with a filtration accuracy of 5-10 μ m) to intercept sediment, impurities, and organic colloids in the water, preventing them from adhering to the pipe wall and forming an initial scale layer.

Softening treatment (for calcium and magnesium ions)

If the hardness of the wastewater is too high (total amount of calcium and magnesium ions>100mg/L), it is necessary to reduce the concentration of calcium and magnesium ions by using ion exchange resin or adding scale inhibitors (such as polyphosphate), and reduce the basis for the formation of carbonate and sulfate scales.

Adjust the pH value of wastewater

For acidic or alkaline wastewater, adjust the pH to a neutral range of 6-8 by adding acid (such as hydrochloric acid) or alkali (such as sodium hydroxide) to avoid accelerating metal ion precipitation in extreme pH environments (such as the formation of hydroxide precipitation of calcium and magnesium under alkaline conditions).

Separate high concentration salts/organic compounds

If the concentration of a certain type of salt (such as sodium sulfate) or organic matter in the wastewater is too high, it can be pre concentrated or separated through sedimentation tanks, centrifugal separation, and other methods to avoid rapid saturation and scaling in the evaporator.

2、 Equipment operation optimization: Inhibiting the adhesion and growth of scale layers

By adjusting operating parameters, create a working environment that is not conducive to the formation of scale layers.

Control evaporation rate and temperature

Avoid evaporating too quickly (such as suddenly increasing the heating power), and prevent solutes in water from instantly saturating and precipitating in large quantities due to rapid concentration. At the same time, stabilize the evaporation temperature within the design range (such as 40-80 ℃) to avoid temperature fluctuations that may cause repeated dissolution precipitation and accelerated adhesion of the scale layer.

Maintain an appropriate flow rate

Ensure that the flow rate of wastewater in the heat exchange tube is maintained at 1-2m/s (adjusted according to the pipe diameter), reduce the residence time of solutes on the tube wall through the flushing effect of water flow, and suppress the initial adhesion of scale layer.

Regular slag discharge and sewage discharge

After the daily or shift operation is completed, promptly discharge the concentrated liquid and sediment at the bottom of the evaporator to avoid the long-term retention of high concentration waste liquid and reduce the chance of scale accumulation.

3、 Regular maintenance: intervene in advance to prevent the hardening of the scale layer

Through periodic maintenance, timely removal of small scale layers can prevent them from developing into difficult to handle thick scales.

Preventive physical cleaning

Every 1-2 weeks (adjusted according to water quality), rinse the inner wall of the heat exchange tube with low-pressure water (5-10MPa) or manually clean it with a soft bristled brush (for small tube diameters) to remove newly formed thin scale.

Add corrosion and scale inhibitors

Install an automatic dosing device in the wastewater inlet pipeline, regularly and quantitatively adding specialized corrosion and scale inhibitors (such as organic phosphonates and polycarboxylates) to inhibit crystal growth, disperse solute particles, and prevent the formation of scale layers. Attention should be paid to selecting the appropriate type of scale inhibitor based on the composition of the wastewater, in order to avoid the formation of new impurities through the reaction between the agent and the solute.

Regular inspection and monitoring

Observe the surface condition of the heat exchange tube through the equipment sight glass every week, or monitor the heat exchange efficiency (such as the difference in inlet and outlet water temperature, changes in vacuum degree). If the efficiency drops by more than 10%, promptly investigate whether there is scale formation and take cleaning measures.