1、 Process condition faults (core impact on separation efficiency)

1. Liquid flooding (core fault of gas-liquid imbalance)

-Phenomenon: Sudden increase in tower pressure difference, sharp drop in product purity at the top of the tower, rapid decrease in tower kettle liquid level, and sudden rise in reflux tank liquid level; The tray tower exhibits liquid accumulation and gas phase channeling, while the packed tower shows excessive liquid holding in the packing layer and a sudden increase in gas phase resistance.

-Root causes: gas-liquid phase load exceeding the design upper limit, blockage of downcomer/tray (scale blockage/freezing blockage), sudden increase in heating steam volume, and excessive fluctuations in feed rate/components.

-Disposal: Emergency load reduction (reducing feed, decreasing heating capacity, increasing tower top extraction), segmented pressure measurement to locate blockages; Freeze blockage requires injection of thawing agent, while scaling blockage requires parking and cleaning of the tower internals.

2. Tower flooding (liquid phase accumulation fault)

-Phenomenon: Slow increase in tower pressure difference, continuous rise in tower kettle liquid level, low tower top temperature, and sudden drop in product yield; The gas phase cannot rise normally, and there is no condensate reflux at the top of the tower.

-Root cause: excessive feed volume, high reflux ratio, insufficient discharge from the tower kettle, and insufficient flow area of the downcomer.

-Disposal: Stop feeding, increase the output of the tower kettle to lower the liquid level, and reduce the reflux ratio; After the liquid level returns to normal, gradually resume feeding and heating, and strictly control the load.

3. Leakage (liquid phase loss fault)

-Phenomenon: The liquid level in the tower kettle drops too quickly, the purity of the product at the top of the tower is low, the gas velocity inside the tower is too low, and the tower pressure difference is too small; When the leakage of liquid in the plate tower is severe, there is no liquid accumulation in the tray, and mass transfer fails.

-Root cause: insufficient gas phase load (low gas velocity), abnormal tray opening rate, tower body tilt, and damaged float valve/sieve plate.

-Disposal: Increase the heating capacity, increase the gas-phase load, and adjust the levelness of the tower body; If the internal components are damaged, the tower plate needs to be replaced or the float valve needs to be repaired.

4. Mist entrainment (gas phase with liquid fault)

-Phenomenon: The product at the top of the tower carries liquid, there is a large amount of liquid accumulation in the reflux tank, the pressure at the top of the tower fluctuates, and the purity of the product is unstable; In severe cases, it may cause blockage of the subsequent condenser.

-Root causes: high gas phase load, small tray spacing, high tower top temperature, and high liquid viscosity.

-Disposal: Reduce heating capacity and gas phase load, adjust reflux ratio to control tower top temperature; If there are design defects, it is necessary to stop and renovate to increase the spacing between the tower plates or install a demister.

2、 Equipment structural faults (directly affecting operational safety)

1. Tower leakage

-Phenomenon: There is material leakage at the flange/weld of the tower body, abnormal decrease in tower pressure, and material odor on site; Flammable media may pose a risk of fire.

-Root cause: aging of flange gasket, corrosion and cracking of welds, fatigue of tower material, and operating pressure exceeding the design value.

-Disposal: Immediately reduce the load and pressure. If the leakage is minor, temporarily tighten the flange; If the leakage is severe, emergency stop the vehicle, replace the material and inspect the sealing gasket or repair the weld seam.

2. Damage to tower internals

-Phenomenon: Severe fluctuations in tower pressure difference, fluctuating product purity, and significant decrease in mass transfer efficiency; Specific manifestations include valve detachment (plate tower), packing breakage (packing tower), and distributor blockage.

-Root causes: material corrosion, gas-liquid phase load impact, installation deviation, long-term operation wear.

-Disposal: locate the damaged area through pressure difference curve and sampling analysis, clean the damaged internal components after parking, replace the corrosion-resistant tray or packing, and recalibrate the distributor.

3. Reboiler malfunction

-Phenomenon: Low temperature in the tower kettle, decreased heating efficiency, and insufficient mass transfer inside the tower; If there is a leak, steam condensate will be mixed into the tower kettle material, and the product quality will exceed the standard.

-Root causes: insufficient steam pressure, poor discharge of condensate, blockage of tube/shell side, and leakage of heat exchange tubes.

-Disposal: Check the steam system (for non condensable gas, unclog the condensate pipeline), and chemically clean the blocked heat exchange tubes; If there is a leak, stop and replace the heat exchange tube, and retest the pressure.

4. Condenser malfunction

-Phenomenon: High temperature at the top of the tower, poor condensation effect, low liquid level in the reflux tank, and increased tower pressure; In severe cases, the safety valve will trip.

-Root cause: Insufficient coolant flow/high temperature, scaling and blockage of condenser tube side, accumulation of non condensable gas, and leakage of heat exchange tubes.

-Disposal: Increase coolant flow rate, reduce coolant temperature, and discharge non condensable gas from the condenser; Clean the heat exchange tubes if scaling occurs, and shut down for maintenance and replacement if there is a leak.

3、 Auxiliary system faults (indirectly affecting working condition stability)

1. Pump malfunctions (reflux pump/feed pump/kettle liquid pump)

-Phenomenon: Pump outlet pressure is zero/fluctuating, flow rate is insufficient, motor is overloaded and overheating; Failure of the reflux pump can cause interruption of reflux and instantaneous disorder of tower operating conditions.

-Root causes: pump body cavitation, filter blockage, impeller damage, motor failure, material vaporization (high temperature).

-Disposal: Clean the filter, discharge the pump body gas, check the impeller and motor; If the material vaporizes, the temperature of the material will be reduced, and if necessary, the backup pump will be switched.

2. Instrument malfunction (temperature/pressure/level gauge)

-Phenomenon: Abnormal instrument display (such as sudden temperature rise and drop, no change in liquid level), malfunction of automatic control, leading to operational misjudgment and causing fluctuations in working conditions.

-Root cause: instrument probe blockage/corrosion, signal line failure, transmitter malfunction, instrument calibration deviation.

-Disposal: Switch to manual control, verify the instrument on site, and clean the probe dirt; If the instrument is damaged, replace it with a spare instrument and recalibrate it.

3. Valve malfunction (regulating valve/shut-off valve)

-Phenomenon: Valve jamming, inability to adjust opening, internal/external leakage; Malfunction of the regulating valve can lead to loss of control over the feed rate, reflux rate, and extraction rate, as well as an imbalance in tower operating conditions.

-Root cause: valve core wear, valve stem jamming, actuator failure, medium crystallization blocking valve chamber.

-Disposal: Manually operate the bypass valve to maintain working conditions, disassemble the valve to clean blockages, and replace worn valve cores; If the actuator fails, replace the backup valve.