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Pumping, heating and vapour separation have distinct jobs. Review them as a connected circuit.
01 / CIRCULATION PUMP
The circulation pump is selected against the concentrated product, loop pressure losses and suction conditions.
The pump maintains the process-liquid flow through the heating circuit. In the common non-boiling heater design, pressure is kept high enough to limit vapour generation in the heater. The returning liquid carries added heat toward the separation vessel.
The separator operates at a lower pressure than the heated return. Part of the liquid flashes; vapour leaves through the overhead route while liquid remains in the circulating inventory. The vessel level affects separation volume and pump suction conditions.
Fresh feed replenishes the system and concentrated product is withdrawn at the required rate. The circulation flow may be much larger than either net stream. Do not label circulation-pump flow as feed capacity or evaporation capacity.
Heater pressure drop, suction geometry, return location, vessel inventory and withdrawal controls all affect operation. Use a process flow diagram and a common duty sheet before comparing individual pump or heater quotations.
Keep the loop moving. The circulation pump sets the flow through the heater. That flow is distinct from the incoming feed and from the mass of water evaporated. Selection must follow the concentrated liquid throughout the planned operating range, including start-up and restart after cooling.
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Add heat under pressure. In the common non-boiling heater arrangement, pressure in the circuit limits boiling within the heater. Heat is added before the liquid enters the flash zone. Tube or plate geometry is selected from product behaviour and pressure-drop constraints, rather than the circulation label alone.
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Release vapour and retain liquid. The pressure change at the separator enables part of the heated liquid to flash. The vessel provides space for vapour disengagement while maintaining liquid inventory for recirculation. Its level and geometry therefore affect both separation and pump suction.
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