I. Initial Selection: Selecting a Circulation Pump with Sufficient Margin

Select the pump based on the equipment’s evaporation capacity, pipeline length, and heat exchange channel resistance. Allow for a margin of at least 20% in pump flow rate and head to prevent flow rate decline during full-load operation. For high-salt crystallization waste liquid, use corrosion-resistant magnetic drive pumps or non-clogging centrifugal pumps.

Assign separate pumps for raw liquid and concentrated liquid circulation; do not share a single pump to prevent concentrated liquid crystals from clogging the piping or diverting flow, which reduces flow rate.

Use variable-frequency drive (VFD) circulation pumps, which can automatically increase speed based on system pressure differentials to compensate for flow losses caused by blockages.

II. Prevent Pump Cavitation to Avoid Significant Flow Rate Drops

Control the minimum operating liquid level in the evaporator and set up a liquid level interlock; if the level is too low, the pump will draw in air, causing cavitation, a sudden drop in flow rate, and abnormal vibrations and noises.

Check the pump inlet flange, gaskets, and piping for air leaks; air ingress forms bubbles, which directly reduce water transfer efficiency.

Minimize upward bends in the liquid inlet piping to reduce the likelihood of air ingress and ensure the pump inlet remains continuously submerged.

III. Clear the Entire System Piping to Reduce Resistance and Flow Restriction

Install bag filters and safety filters at the front end to intercept suspended solids and salt crystal impurities, preventing them from entering the heat exchange plates and piping and causing reduced flow cross-sections.

Select large-diameter piping and minimize the use of small elbows and throttling reducers; avoid narrow, fine pipes in crystallization conditions to reduce fluid resistance.

Periodically disassemble ball valves and check valves, as salt sludge and crystals easily accumulate in valve chambers; even partial blockages can directly reduce circulation flow. Flush branch pipes monthly.

IV. Prevent Blockages and Narrowing of Flow Channels in Heat Exchange Units

Strictly control the concentration ratio and ensure the salinity of the waste liquid does not exceed the saturation point to prevent crystal precipitation and adhesion to heat exchange plates or coils, which can narrow the flow channels.

Regularly perform online freshwater flushing and acid/alkali cleaning of heat exchange components to remove scale, salt crystals, and sludge, ensuring unobstructed flow channels.

In high-crystallization conditions, prioritize the use of wide-channel plate evaporators; compared to narrow-channel designs, they are less prone to fouling and blockages, ensuring long-term stable circulation flow rates.

V. Optimize Operating Procedures to Stabilize Water Flow Velocity

Avoid prolonged intermittent operation at low loads, as low-velocity water flow readily promotes impurity deposition; maintain continuous circulation to flush the heat exchange surfaces.

Install inlet and outlet differential pressure gauges; a sustained increase in differential pressure indicates scaling or blockage of the heat exchange surfaces, requiring immediate initiation of a cleaning procedure.

Install a high-flow bypass flushing line and periodically activate forced circulation to flush out salt sludge deposits at the bottom of the reactor, preventing bottom blockages from affecting overall circulation.

VI. Perform Regular Pump Maintenance to Maintain Delivery Efficiency

Disassemble and inspect the pump impeller and casing quarterly. High-salt media can crystallize and coat the impeller, causing wear and resulting in reduced pump output and insufficient flow.

Check the motor’s operating condition. Phase loss, aging, or damaged bearings can reduce the pump’s power output; repair or replace parts promptly.

Clean the filter screens at the pump inlet and outlet. Clogged filter screens are a common yet often overlooked cause of reduced flow.