How to determine the replacement of membrane components after cleaning? Direct answer: Conduct a flux recovery test - measure the flux and pressure difference under the same operating conditions before and after cleaning, compare the baseline during stable operation, and see the extent of recovery. Recovery close to baseline indicates reversible pollution and continued use; The significant decrease in recovery amplitude after two consecutive cleaning cycles and the inability to return to baseline pressure difference indicate an irreversible decline in membrane performance, and the replacement plan should be followed. Judging the caliber is based on comparison with the same working conditions, not on hand feel; The numbers measured at different feed rates and temperatures are not comparable. This article explains how to conduct tests, what to observe, and when to change them.
The membrane will lose its flux after a long time of use. The reasons for the loss are reversible and irreversible: the oil mist dust layer and gel pollution are reversible, and the cleaning can recover; Membrane material aging, pore compaction, and sealing failure are irreversible and cannot be washed off. The common misconception on site is that washing is enough, and the extent of recovery may be unpredictable, resulting in faster blockage and replacement of nodes next time all relying on luck. The value of recovery testing is to turn fuzzy data into comparable data, providing a basis for replacement decisions and avoiding the burden of replacement on the entire system.
Testing emphasizes the same operating conditions: select a stable operating window, record the feed concentration, temperature, vacuum degree, pressure difference, and flux as the reference before washing; After cleaning according to the regulations, measure again in the same window and under the same working conditions to obtain the cleaned data. The two intervals should be consistent, and comparisons with large temperature and concentration differences are invalid. The record should be recorded in the ledger as the exclusive baseline for the film core. For those without a historical baseline, starting from this round, take the average of two to three consecutive cycles as a temporary baseline and make up for it while using it.
The core focus is on two aspects: flux recovery amplitude and pressure drop rebound. If the flux returns to more than 90% of the baseline, it is considered to have recovered well; The synchronous return of pressure difference to the baseline indicates the release of channel resistance. Match the permeate side concentration and recovery rate, which reflect the membrane state in the same direction as the flux. Abnormal signals are when the flux only rebounds slightly, the pressure difference cannot decrease, or it drops back to its original state after washing for a few days, indicating irreversible damage. Judging from all three factors together, the flux is more stable than looking at it alone.
The criterion for replacement is trend rather than single time: after two consecutive cleaning cycles, the recovery amplitude gradually decreases, and the second cycle is significantly lower than the first cycle, the replacement should be promoted; The long-term inability of the pressure difference to return to baseline and the trend of increasing concentration on the permeate side also indicate irreversibility. Don't wait until the system becomes ineffective before replacing it, as it often hinders the later stages and meets the standards. Replace spare parts in advance according to the shutdown window, hand over the judgment data to the operation and maintenance, and continue across shifts. The fixed term is only a reference, and the recovery range and trend are the true basis.
| indicator | Recovering well | need attention | Replace signal |
|---|---|---|---|
| Flux recovery | More than 90% | 50-90% | Less than 50% |
| Differential pressure rebound | Near baseline | relatively high | Cannot go back |
| Osmolarity | Stability | Slightly increased | Trend increase |
| Restoration of diminishing returns | Single fluctuation | Twice decreasing | Gradually becoming apparent |
| Maintain after washing | long cycle | Easy to replicate | Quickly return to its original state |
| Basis for judgment | data comparison | observe | Trend determination |
Comparing with the same operating conditions: the flux returns to over 90% of the baseline and the pressure difference rebounds synchronously, indicating good recovery; Returning to its original state after only a slight rebound or a few days is a false recovery, indicating irreversible damage. Don't be fooled by a single number.
From this round of baseline construction: record the pre wash and post wash data for two to three consecutive cycles under the same operating conditions, take the average as a temporary baseline. The earlier the baseline is built, the more accurate the subsequent judgment will be. Don't wait until there is a fault to make up for it.
No need: The lifespan is only a reference, the real basis is the extent and trend of cleaning and recovery. If the recovery gradually decreases and the pressure difference cannot return to the baseline, the replacement plan will be followed. If the lifespan is not reached, it will easily drag down the system.
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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