What organic solvents can be recovered by membrane separation? Direct answer: Common hydrocarbons, ketones, esters, alcohols and halogenated hydrocarbon solvents have mature recovery performance-toluene, xylene, hexane and other hydrocarbons, acetone, butanone and other ketones, ethyl acetate, butyl acetate and other esters, methanol, ethanol, isopropanol and other alcohols, dichloromethane, trichloroethylene and other halogenated hydrocarbons, as well as the lithium battery industry NMP, are in the applicable list. The wide list does not mean that the difference in film compatibility, water solubility and boiling point of different media determines the difference in configuration. In this paper, the media list, boundary conditions and grouping recommendations are clarified at one time.
According to the characteristics of ethnic groups: hydrocarbons, with good dissolution and diffusion penetration and high recovery rate, are the most classic applicable objects. Benzene series and alkane tail gas in petrochemical and storage links belong to this category. Ketones and esters-good volatility and high recovery value. The tail gas of printing, packaging and coating industry is mainly composed of these two groups, and the recovery rate of film condensation combination can reach more than 90%. Alcohol-water solubility is the key word, the recovery of methanol and ethanol should solve the dehydration problem simultaneously, and the water content should be controlled before the condensate is remixed. Halogenated hydrocarbons-high recovery value but compatibility of membrane materials should be specially evaluated, and the tendency of hydrolysis to produce acid also upgrades materials and water control design. NMP -- lithium battery coating oven exhaust, high temperature and high humidity feed requires high pretreatment.
The three boundaries should be drawn first: the concentration boundary-the feed concentration is recommended to be above 1000 mg per cubic meter, the concentration is too low and the partial pressure difference is insufficient, so the membrane cannot be economically efficient; Cleanliness boundary-particulate matter, oil mist and liquid droplets are the natural enemies of the membrane. Pretreatment and grading under heavy dust conditions will lead to rapid flux attenuation. Compatibility boundary-strong oxidizing components and some active media have swelling risks to membrane materials. Special media should be verified by small tests before engineering, thousands of dollars of test fees block hundreds of thousands of transformation risks. If any one of the three boundaries is not satisfied, solve the boundary first and then talk about recycling.
Multi-medium mixed tail gas is grouped according to the principle of "compatibility, same path and homogeneity": compatible components can be collected and recycled in a unified way; Separate pipes with different recovery paths and condensate disposal; If the recovered solvent is to be reused, the quality shall be determined according to the purity requirements of the product. The light and heavy components in the mixed tail gas have different liquefaction temperatures in the condensation section, and the enrichment of the membrane section is also effective for the light components, and the combined process is naturally suitable for the mixing system. The grouping scheme is finalized in the exploration stage, and the grouping of pipelines and storage tanks is carried out accordingly. After being put into operation, the grouping is changed, and the cost is doubled.
Give the user a check action: list your own solvent list, concentration range and temperature and humidity conditions into a table, and hand it over to the supplier to check the applicability one by one-the "can accept" in the list and the "worth accept" under your working conditions are two different things.
| Clan | Representative medium | Configuration points |
|---|---|---|
| Hydrocarbon | Tylbenzene hexane | Classic application high recovery rate |
| Ketones | acetone butanone | Paint printing industry-oriented |
| Esters | ethyl acetate butyl ester | Film condensation combination 90% |
| Alcohols | Methanol Ethanol Isopropanol | Condensate dehydration pre-control water |
| Haloalkane | Dichloromethane Trichloroethylene | Compatible with small test material upgrade |
| Special | NMP lithium battery tail gas | High temperature and high humidity pretreatment |
The condensate of water-soluble solvents such as alcohols shall be tested for moisture and purity first, and then remixed according to batches after dehydration reaches the standard. Moisture control runs through both ends of recovery and storage, and the test data shall prevail before remixed.
The recovered liquid of different fractions can be obtained by stage condensation according to the liquefaction temperature of light and heavy components; the depth of separation is determined according to the purity requirement for reuse, and the mixed liquid that is not reused is disposed according to the standard caliber.
Three-step check: whether the concentration is in the applicable range, whether the cleanliness pretreatment is in place, and whether the medium has compatibility risk with the membrane material; If you are not sure, do a small test and use the test data instead of empirical judgment.
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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