The membrane separation device has few moving parts and a high degree of automation. The core of operation management is to stabilize the partial pressure difference on both sides of the membrane. The pressure difference is the driving force of the separation, the raw material side of the pressurized and permeable side of the vacuum of any one end of the fluctuation, the recovery rate immediately follow the change. Whether the device runs well or not depends on the trend without looking at the instructions-the three curves of pressure difference, vacuum degree and permeation side flow are stable, and the membrane is in a good state. The curve drifts, and the problem is mostly not in the membrane itself, but in the pretreatment or vacuum system. This article clearly explains where the pressure difference comes from, which figures to look at during patrol inspection and how to extend the membrane life according to the actual order of operation of the device. The personnel on duty can directly control the implementation, and it is also suitable as an introductory training material for new employees. They can get started by telling it once during shift change.
The pressure difference between the two sides of the membrane is jointly established by the two ends: the raw material side is pressurized by the compressor to press the mixed gas to the front of the membrane; The permeate side is sucked by a vacuum pump to maintain a low pressure environment, and the permeated rich gas is continuously pumped away. The greater the pressure difference, the greater the component penetration, but the greater the pressure difference is not, the better-the pressure in front of the membrane is limited by the pressure bearing of the component, and the high vacuum degree will increase the load and energy consumption of the pump. The balance point is found according to the medium and recovery target during configuration. The vacuum pump is the most critical auxiliary machine of the membrane device, and its state directly determines whether the driving force is online.
The membrane unit requires a smooth feed: violent fluctuations in gas volume will cause the flow rate of the membrane surface to rise and fall, and the separation efficiency will decrease. The sudden change of pressure is a mechanical impact on the separation layer, and long-term accumulation will accelerate the performance attenuation. For devices with large fluctuations in upstream operating conditions, a buffer tank is installed before pressurization; if the exhaust gas is entrained with droplets and particles, the filtration and dehumidification section is often not saved. Under high humidity conditions, the condensation of water on the membrane surface affects the separation, and the temperature in front of the membrane should be fixed at the high temperature in summer-all these are done in front of the membrane, which is to give the membrane life time.
The management of vacuum pump is separate: it is one of the few rotating equipment in the membrane device. The oil level, temperature rise and sound are checked solidly, and most driving force problems can be exposed in advance. The maintenance period of the pump shall be determined according to the operating hours, and do not wait for any failure to start again. Seals in spare parts are most frequently consumed, and a batch of them are always available, so replacement will not delay production. The recovery rate of the device that the vacuum degree runs against the lower limit for a long time must not look good. Instead of hard support, it is better to find out the root cause-mostly the problem of sealing or condensing load.
The effect of the device finally falls on the data at both ends: on the recovery side, the recovery amount of condensate or enriched gas is checked with the input amount on a monthly basis; On the emission side, the detected concentration is stable below the limit value before it is really up to standard. The data at both ends should be put into the same ledger-the recovery amount is lost and the emission concentration is raised, mostly due to insufficient driving force of the membrane section; If both ends are stable and the total amount is not matched, check the seal and bypass of the collection end. Where the data is not right is the problem, which is much faster than checking by feeling.
| Inspection item | Focus point | Abnormal direction |
|---|---|---|
| pre-membrane pressure difference | Steady trend | The rise is mostly blocked by the front filter material. |
| Vacuum degree | Rated interval | Lit down to check pump and seal |
| Penetration side flow | Match with differential pressure | Pre-treatment |
| emission concentration | Below limit | Check the over-standard film and working conditions |
| Pre-film temperature | Allowable interval | Check pre-cooling and dehumidification on the high side |
| Vacuum pump | Oil level temperature rise | Abnormal shutdown according to regulations |
The sequence is: filter material and dehumidification in the pretreatment section, pump performance and sealing of the vacuum system, pre-membrane temperature, and finally the membrane layer is evaluated. Most of the so-called membrane attenuation is actually the loss of pretreatment to allow pollutants to reach the membrane surface, the front section is restored, and the membrane performance is mostly followed back.
Check item by item: the state of the vacuum pump itself, the sealing of the pipeline and flange, and whether there is back pressure on the permeation side. Insufficient vacuum directly depresses the driving force, and the recovery rate decreases accordingly. This is an abnormality that the membrane device has the highest priority.
Short-term shutdown shall keep the system dry and purge regularly; long-term shutdown shall be sealed to prevent pollution according to the requirements of the membrane plant. Performance calibration shall be done before re-operation to confirm that the flux and separation effect are normal before parallel operation.
This article by LuoyangWohong PetrochemicalEquipment Co., Ltd. arranges that the company provides design, manufacturing and operation and maintenance services for condensation recovery, membrane separation recovery and complete solvent recovery devices for chemical and pharmaceutical enterprises. If you need process evaluation or scheme configuration, please contact and exchange.
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