I. Proper pump selection to guarantee rated flow fundamentally

Calculate the head and flow rate of the circulation pump according to the equipment evaporation capacity, heat exchange chamber volume and total pipeline length, with a 20% margin reserved to avoid matching an undersized pump with a large-scale system. For high-salinity crystallizing wastewater, corrosion-resistant magnetic pumps and self-priming circulation pumps shall be adopted to prevent flow attenuation caused by pump corrosion.

Separate the raw liquid circulation pump and concentrated liquid circulation pump with independent configuration instead of sharing one pump, so as to avoid circulation flow occupation due to blockage by concentrated liquid crystals.

Regularly calibrate the power of the pump motor. Motor aging or phase loss will lead to insufficient pump output and continuous flow decline.

II. Eliminate pipeline blockage and reduce flow loss

Install multi-stage filters (bag filter + security precision filter) at the water inlet to intercept suspended solids and crystalline impurities, preventing impurities from entering circulation pipelines and heat exchange channels to cause flow restriction by pipe diameter shrinkage.

Adopt large-diameter straight-through structures for pipelines and valves, minimize elbows, reducers and small throttle valves. Wide flow channels shall be used under crystallization conditions to lower pipeline resistance.

Dismantle ball valves and check valves regularly; salt crystals and sludge easily accumulate inside valve cavities, and partial valve blockage will greatly reduce circulation flow. Flush branch pipelines monthly.

III. Prevent blockage and flow restriction of heat exchange units (the most common cause of flow drop)

Control the concentration ratio to avoid oversaturated salt crystallization adhering to heat exchange plates or coils. Crystal accumulation will narrow the medium passage and result in sharp drop of circulation flow.

Carry out regular online flushing and acid-alkali cleaning for heat exchange assemblies to remove scale on pipe walls and plates and keep flow channels unobstructed.

Select wide-channel plate heat exchange structure. Compared with narrow channels, it is less prone to crystal blockage and can maintain stable circulation flow for long-term operation.

IV. Optimize operation process to stabilize circulation flow velocity

Equip the pump with variable frequency control system: automatically adjust pump speed based on inlet-outlet pressure difference. Rising pressure difference indicates blockage, and the system will increase frequency to boost flow and scour heat exchange surfaces.

Forbid operation under low liquid level: excessively low liquid level inside the evaporation kettle will cause air suction and cavitation of the circulation pump, resulting in sudden flow drop and intensified vibration. Set interlock for minimum liquid level; automatic water replenishment and shutdown protection will be triggered below the threshold.

Avoid interruption of raw liquid supply. Feed cut-off will cause sharp rise of salt concentration and local crystallization inside the kettle, accompanied by pump idling cavitation and unstable flow. Automatic liquid replenishment system is required.

V. Daily operation & maintenance to prevent cavitation and performance degradation

Keep the pump inlet pipeline unobstructed and airtight. Air ingress forming bubbles will greatly reduce pump delivery capacity. Inspect flanges, sealing rings and packing for air leakage.

Check impeller and pump casing regularly. High-salinity wastewater abrades the impeller and wraps it with crystals, lowering pump efficiency. Dismantle and clean crystal deposits on the impeller quarterly.

Install pressure gauges on circulation pipelines to monitor inlet-outlet pressure difference in real time. Flush and remove scale immediately if the pressure difference keeps rising to prevent insufficient flow in advance.

VI. Auxiliary facilities to enhance circulation scouring

A bypass large-flow flushing pipeline can be installed. Turn on large-flow circulation regularly every day; high-speed water flow scours salt sludge deposited at the bottom of the heat exchange chamber and mitigates flow attenuation caused by blockage.