How to treat dichloromethane waste gas in pharmaceutical plants is a well-recognized challenge in the industry. This solvent has a low boiling point and evaporates rapidly; it is classified as a halogenated hydrocarbon VOC. Traditional approaches have limitations:activated charcoalAdsorption saturation fast, frequent carbon exchange, saturated carbon as a hazardous waste disposal cost is not low, combustion method to treat halogen-containing waste gas, high temperature is easy to produce dioxin and other highly toxic by-products, while hydrogen chloride will cause corrosion to equipment.
The membrane condensation recovery scheme provides a technical route for physical separation. This process employs a combined “compression-condensation–membrane separation” approach. The exhaust gas is first pressurized by the compressor and then enters the condensation unit. Most of the dichloromethane is directly liquefied from gaseous to liquid at low temperature, and can be directly reused for production after being separated by the collection tank.
The condensed tail gas still contains a small amount of methylene chloride that is not liquefied, and this part of the gas enters the membrane separation unit.gas separation membraneTaking advantage of the difference in permeation rate between dichloromethane molecules and air molecules in the membrane material, dichloromethane preferentially permeates the membrane layer to form concentrated gas, which is sent back to the front end of the system for circulating treatment. The air is intercepted and discharged to the standard. Through this cycle design, the recovery rate of dichloromethane can reach more than 90%, and the concentration of tail gas after treatment can be controlled at a low level.
The advantage of this scheme is high security. Membrane separation is a purely physical process that involves no combustion or open flames, thereby eliminating the risk of dioxin formation at the source. The equipment does not have activated carbon consumables and does not produce hazardous waste. The daily maintenance is mainly to clean up the heat exchanger and check the pressure difference of the membrane module. The skid-mounted structure integrates each unit on the steel base, completes the assembly and debugging before leaving the factory, and can be put into operation only by connecting the power supply and gas circuit on site.
The concentration of recovered dichloromethane is higher than 90%, which can be directly reused in the production line to reduce the cost of raw material procurement. For the working conditions of dichloromethane waste gas in pharmaceutical plants that meet the applicable conditions, the membrane condensation recovery scheme is a mature choice to realize solvent resource utilization under the premise of ensuring safety.
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