Weekly Topic 10.11.08, Issue 2: What are the reasons why the pressure-fed reflux pump does not deliver liquid during methanol distillation (pressure drop)?

If the reflux is suddenly interrupted: Cause: ① The reflux pump trips； ②The level of the reflux tank is too low or even empty ； ③The pump inlet filter is clogged ； ④The cooling effect at the top of the tower is poor, resulting in a high temperature of the reflux liquid ； (For low-boiling reflux liquids, due to excessively high temperatures or insufficient pump output, the material vaporizes inside the pump and fails to flow upward. ) Handling: ① Start the backup pump; if it cannot be started, the plant should be shut down for maintenance ； ②Stop the extraction process, shut down the reflux pump, adjust the operations; once the liquid level in the reflux tank returns to normal, restart the reflux pump to establish reflux, and only then resume extraction once everything is satisfactory ； ③Switch to the backup pump and clean the pump inlet filter ； ④Increase the cooling water volume and appropriately raise the cooling water pressure.

The possible reasons for the sudden interruption of the reflux flow are: (1) The motor of the reflux pump tripped； (2) Evacuate the material in the reflux liquid tank ； (3) The reflux liquid pump cannot deliver fluid ； (4) For low-boiling reflux liquids, due to excessively high temperatures or insufficient pump output, the material vaporizes inside the pump and fails to flow upward.

1 The false level in the return tank has been evacuated. It generally doesn’t happen, because by the time it’s taken out when there’s no space left, there’s already no amount left. 2 There is a problem with the equipment (clogged filter, pump cavitation, motor issues). 3 There is a problem with the flow meter for backflow

1 The false level in the return tank has been evacuated. 2 Equipment problems such as clogged filters and pump cavitation.

Possible causes: (1) The return pump trips; (2) The liquid level in the return tank is too low or even empty; (3) The filter screen at the pump inlet is clogged; (4) All of the pump blades are damaged, etc

Problems with the pump impeller or seals can also result in no flow

Why does a fluctuation in steam pressure, which leads to large pressure swings in the pressurized tower, also cause the recirculation pump to fail to deliver fluid?

The liquid level in the pressurized reflux tank is too low; the reflux temperature is too high, resulting in poor condensation efficiency. The filter at the pump inlet is clogged, and there is a problem with the pressure gauge

Air leakage at the inlet of the recirculation pump, insufficient liquid level at the inlet, blockage.

The most likely cause is a clogged filter. If the system is being operated for the first time, reverse rotation of the motor, a faulty pressure gauge, and incorrect readings of the liquid level in the return tank also need to be considered. From a process perspective, issues such as the pump not being able to discharge air, high temperature of the return fluid, and low pressure in the return tank all need to be taken into account!