How to determine if the surface of the membrane component is contaminated with oil mist? Direct answer: Focus on three sets of control parameters - pressure difference on both sides of the membrane, vacuum degree on the permeate side, and unit time recovery rate. Looking at the trend of the three sets of data together is more reliable than looking at one number alone. After the oil mist forms a layer on the surface of the membrane, the breathable channel narrows, manifested as an increase in pressure difference, abnormal vacuum degree on the permeation side, and a decrease in recovery rate; The synchronous failure of the three can basically be attributed to pollution rather than fluctuations in operating conditions. The judgment caliber is trend comparison: compare the current reading with the baseline of stable operation period, and arrange cleaning or pre-processing when the deviation reaches a certain degree. This article explains the signs, parameter comparison, and disposal of oil mist pollution.
Oil mist mostly comes from compressor lubricating oil, vacuum pump return oil, and liquid oil droplets carried in the feed. The membrane is sensitive to oil and gas molecules, and oil mist is more likely to layer on the membrane surface than gaseous molecules, forming a layer of adhesive that blocks the breathable channel. If the oil and mist removal in the feed pretreatment is not in place, the oil mist will enter the membrane core all the way. The common signs on site are a gradual decrease in the amount of recycling and rapid dirtiness of the vacuum pump oil, which often occur before the pressure difference significantly increases. Checking the source of oil mist in three stages: compressor, vacuum pump, and feed, is more convenient than washing after the membrane is dirty.
The pressure difference reflects the resistance of the membrane channel, and the pressure difference gradually increases after the oil mist layer is applied; The vacuum degree on the permeation side reflects the suction capacity, and when pollution worsens, the vacuum degree reading becomes abnormal or the suction becomes more difficult; The amount of recycling is a very intuitive result indicator, as pollution reduces the effective flux and the amount of recycling per unit time decreases accordingly. Three groups need to look at it together: only when the recovery volume decreases and the pressure difference is stable, first check the working conditions and instruments; If the pressure difference rises, the vacuum degree is abnormal, and the recovery amount drops, it shall be disposed of as pollution. Simply looking at the amount of recycling can easily be misled by fluctuations in feed concentration, so three comparisons are necessary.
When the feed concentration fluctuates and the temperature changes, the recovery amount also changes, which does not mean pollution. The differentiation method is to look at the pressure difference and vacuum degree: when the pure operating condition fluctuates, these two items fluctuate slightly around the baseline, and the recovery amount changes in the same direction as the concentration; When polluted, the pressure difference and vacuum degree go in the wrong direction, and the recovery amount decreases against the concentration. Put temperature, concentration, vacuum degree, pressure difference, and recovery amount on a trend chart, and distinguish pollution and fluctuations at a glance. Don't wash the film as soon as the recycling volume drops, first eliminate false signals.
After confirming that it is oil mist pollution, first check whether the feed oil and mist removal is ineffective. Replace the front-end filter and mist remover as needed, and wash the source repeatedly without clogging. Cleaning should be done according to the membrane material regulations, with physical rinsing and targeted treatment. After washing, three sets of parameters should be retested to compare the recovery amplitude with the baseline. The gradual decrease in recovery indicates that pollution is developing irreversibly and is being pushed forward according to the replacement plan. After disposal, include the pre-processing status and three readings in the normal record, and discover them early next time.
| parameter | Normal | pollution signal | Priority Action |
|---|---|---|---|
| differential pressure | Surrounding the baseline | Continuous upward trend | Pre processing check |
| Permeation vacuum degree | Stability | Abnormal or difficult | Synchronize membrane inspection |
| Recycling quantity | Move with concentration | Reverse concentration descent | According to the location of pollution |
| temperature | Design within | seasonal deviation | Revise and compare again |
| Feed oil mist | Filter up to standard | Defogging failure | Change filter material |
| Recovery amplitude | Near baseline | successive decrement | Press to replace |
Not necessarily: Fluctuations in feed concentration or temperature can also affect the recovery volume. First, check the pressure difference and vacuum degree. Only when these two factors also go in the wrong direction and the recovery volume decreases against the concentration, should it be treated as oil mist pollution. Do not blindly wash the film.
The early oil mist layer recovered significantly after washing, and the front-end oil and mist removal was repaired according to the membrane material regulations. The three parameters were retested and compared with the baseline; Repeated pollution often occurs when the source is not blocked, and only washing the membrane will result in more frequent washing.
Make a trend chart of five items: pressure difference, vacuum degree, recovery amount, temperature, and concentration. The rapid dirtiness of vacuum pump oil and the gradual decrease in recovery amount are early signals, much earlier than the bursting of the pressure difference gauge.
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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