The solvent tail gas of chemical and pharmaceutical enterprises is mixed with components and has a large concentration span: the concentration of the blending and reaction process is high but fluctuates, and the concentration of the drying and cleaning process is low but the air volume is large. Membrane separation plays the role of "selective gate" in these scenarios-organic vapors are preferentially enriched and recycled through the membrane, and air is trapped and discharged to the standard. It does not pick the medium, from alcohol ketone ester to aromatic hydrocarbons, halogenated hydrocarbons can be processed, combined with condensation of the recovery scheme, investment and operating costs of the account is good. How to match the membrane section, where to go the enriched gas and how much to put in the pretreatment, these issues that determine the success or failure of the scheme will be explained clearly one by one according to the process sequence. Operators who have been put into operation can also check whether there are any missing items in their own configuration against this article.
The gas through the membrane is a dissolution diffusion mechanism: organic molecules are first dissolved on the upstream side of the membrane surface, driven by the partial pressure difference, diffuse through the membrane body, and then desorb on the downstream side. The permeability coefficient is determined by both solubility and diffusion coefficient, while the rubber separation layer happens to have extremely high solubility for organic vapors-oil and gas with large molecules run faster than air, and the membrane penetration speed is several times to dozens of times that of air. The membrane is non-porous and compact structure, which does not rely on pore size screening, so it does not block, and the separation effect is only related to the material and working conditions of the separation layer.
The typical process is divided into four sections: the tail gas collection manifold enters the booster section, and the compressor presses the mixed gas to the front of the membrane; The configuration with condensation section collects the solvent of high temperature and high concentration first, and the uncondensed tail gas enters the membrane unit; The permeate side behind the membrane is maintained at low pressure by a vacuum pump, and the permeated enriched gas either returns to the compressor inlet for circulation or enters condensation and liquefaction for reuse. The clean air on the interception side meets the standard discharge. The direction of the enriched gas is determined by the value of the solvent-the liquefaction with high value is remixed, and the small amount is recycled without delay.
There are two pits that are easy to step on during the distribution process: first, pretreatment-the membrane surface is afraid of droplets and particles. The filtration and dehumidification section before pressurization looks simple, but it determines the long-term state of the membrane layer. Once it is cast, it must be cast frequently and cannot be used as an optional spare section. Second, the destination of the enriched gas should be determined in advance-return to circulation or liquefaction and distribution. The pipeline design and control logic are completely different, it will take a lot of trouble to change the movement and static after it is put into operation. In addition, the temperature before the membrane should also be managed. High temperature will change the permeability characteristics of the separation layer. In summer, under high humidity and high heat conditions, pre-cooling and dehumidification are often done together.
| system | Representative Media | Recycling destination |
|---|---|---|
| Alcohols | Methanol, ethanol, isopropanol | Redistribution of condensate after dehydration |
| Ketoesters | Acetone, butanone, ethyl acetate | Reuse after refining |
| alkane alkene | Hexane, solvent oil | Liquefied rematch or sell |
| Aromatic hydrocarbon | Toluene, xylene | Layered Dehydration Redistribution |
| Haloalkane | Dichloromethane, etc | Reuse after refining |
| mixed system | multi-component coexistence | Collect in groups or reuse by mix |
If the components are compatible and the condensate reuse caliber is consistent, it can be mixed; if the reuse indicators conflict with each other, the membrane section will calibrate the operating parameters according to the dominant components, and the whereabouts of each unit will be recorded separately in the ledger.
High concentration, reuse value of membrane separation or condensation membrane. In scenarios with high safety requirements, the membrane has more advantages-open handling, no static accumulation, and no risk of overheating of the carbon bed.
Two paths: return to the inlet for circulation treatment, or return to the condensation and liquefaction. According to the solvent value and process caliber, high value solvent liquefaction reuse is the most cost-effective, small amount of low price cycle treatment can be.
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.
Mr. Li 13526990215
Hotline
