Pharmaceutical fine chemical mother liquor recovery process, mother liquor storage tank, mother liquor transfer kettle, distillation feed buffer tank, vacuum desolvation unit will continue to produce VOCs waste gas, waste gas contains ethyl acetate, acetone, dichloromethane, tetrahydrofuran, various alcohols and other high-value pharmaceutical solvents. The composition of the mother liquor system is complex, containing intermediates, salts and colloidal impurities. The waste gas in the mother liquor recovery operation stage maintains a high concentration. At the time of mother liquor transfer, storage tank nitrogen replacement, batch switching and vacuum pressure breaking, the concentration of organic steam rises instantaneously, the concentration of tail gas in the storage tank static storage stage falls back, and the overall working condition fluctuates greatly. The waste gas flow is very easy to entrain mother liquor droplets, heavy sub-colloid, fine solid particles and saturated water vapor. Halogenated solvents react with water vapor to generate corrosive medium, which is easy to cause scaling and corrosion of collection pipelines and internal components of equipment. The mother liquor recovery area belongs to Class A explosion-proof control site. The solvent is flammable and explosive, and some materials are toxic. Very strict comprehensive requirements are put forward for the fog droplet colloid pretreatment capability, instantaneous concentration impact resistance, corrosion resistance, explosion-proof safety interlocking system and continuous operation capability under wide working conditions of the supporting VOCs organic solvent treatment equipment.
The traditional exhaust gas treatment process adapts to the mother liquid recovery exhaust gas operating conditions have obvious short boards. The incineration process can oxidize and decompose organic pollutants, but the organic solvent with recovery value in the waste gas is directly incinerated, resulting in large material loss. When the waste gas contains halogenated hydrocarbon components, hydrogen chloride and toxic by-products are easily generated under high-temperature working conditions, damaging the furnace body and pipelines. Complex flue gas post-treatment systems are also required, and equipment investment, fuel consumption and daily operation and maintenance costs remain high.activated charcoalAdsorption is a pollutant transfer treatment method, which cannot realize solvent recovery and utilization. Facing the exhaust gas with random high and low concentration switching in the mother liquor recovery process, the mother liquor mist droplets and colloidal impurities entrained in the intake air are superimposed, and the adsorption filler is easily cemented, quickly reaching adsorption saturation and undergoing penetration failure. Frequent shutdown and replacement of adsorption consumables are required. The output of hazardous waste is large, and the later operation and maintenance burden of the enterprise is heavy. The simple condensation process relies on low temperature to realize solvent liquefaction, and the recovery effect is better only under the working condition of mother liquor distillation treatment of high concentration intake air. The concentration of exhaust gas decreases during the static stage of storage tank and equipment standby stage, the partial pressure of organic vapor is insufficient, the recovery efficiency of solvent liquefaction is greatly attenuated, and a large number of organic components are emptied with the exhaust gas, which cannot realize stable resource treatment in the whole cycle. A large number of project practices show that a single process mode is difficult to adapt to the real operating conditions of complex components and fluctuating working conditions in the mother liquor recovery process. The equipment has insufficient processing capacity when the concentration impact is caused by material transfer and pressure breaking. The emission index is easy to exceed the standard under low concentration working conditions, and cannot meet the multiple demands of workshop safety production, environmental protection compliance and solvent recovery income at the same time.
The compression condensation film is coupled with a complete set of full physical treatment process, and there is no combustion and no chemical reaction in the operation process. It is very suitable for VOCs organic solvent treatment equipment for the recovery of pharmaceutical fine chemical mother liquor. The waste gas generated by the mother liquor storage tank, transfer kettle and desolvation unit is collected and transported through the closed negative pressure gas collecting pipeline network. The waste gas first enters the equipment pretreatment unit, and the mother liquor mist droplets, colloidal heavy components, solid particles and free moisture carried by the air stream are removed by the multi-stage filtration and defoaming structure to avoid impurities entering the back-end compressor, heat exchanger and membrane components, resulting in blockage, glue formation and irreversible pollution of membrane components. In view of the working conditions with high content of gum and fog droplets in the mother liquor recovery tail gas, the pretreatment unit adopts a hierarchical interception structure to complete filtration and purification step by step according to the particle size of impurities, effectively protecting the precision core components at the back end and prolonging the service life of the whole set of equipment. After undergoing preliminary purification, the waste gas enters the compression unit, where the partial pressure of organic vapors is increased to create favorable conditions for solvent liquefaction. The gas is then fed into a multi-stage gradient condensation module, which utilizes the boiling point differences among the components of the mixed solvent to achieve staged cooling. As a result, the majority of the organic solvents are condensed and separated, completing the initial solvent recovery process.
After condensation, the tail gas still contains some unliquefied organic components, which then enter the organic membrane separation unit. There, the difference in permeation rates between organic solvent molecules and air molecules through the polymeric membrane material is utilized to enrich and concentrate the organic components. The treated exhaust gas is discharged to the atmosphere, while the high-concentration organic gas stream enriched on the membrane side is recirculated back to the compressor inlet, forming a closed-loop system that further enhances the overall recovery rate of the multi-component solvent. The recovered liquid mixed organic solvent can be returned to the mother liquor distillation system for reuse after the quality meets the requirements of the mother liquor recovery process after precipitation filtration and index detection, so as to recover the solvent resources originally lost with the volatilization of the mother liquor recovery tail gas, reduce the amount of hazardous waste generated from the source, and reduce the solvent procurement cost and hazardous waste disposal expenditure of enterprises. The whole set of equipment can adopt the skid-mounted integration mode, the factory prefabrication is completed, the on-site installation work quantity is small, and the original negative pressure gas gathering pipe network of the mother liquor recovery section can be directly connected to the original negative pressure gas gathering pipe network of the mother liquor recovery section, so as to minimize the shutdown period of technological transformation and reduce the interference to the mother liquor recovery and rectification operation.
The entire system is designed in strict compliance with pharmaceutical and chemical explosion-proof standards. All pipelines, valves, and heat-exchange components that come into contact with the exhaust gas are fabricated from corrosion-resistant materials to withstand the acidic corrosion caused by hydrolysis of halogenated media, thereby ensuring long-term, continuous operation of the equipment. The equipment is fully equipped with overpressure, overtemperature, and combustible gas detection systems, as well as automatic interlock protection mechanisms, to handle the instantaneous concentration surges caused by mother liquor transfer, nitrogen purging, and vacuum relief, thereby mitigating various safety risks associated with flammable and explosive media. The intelligent variable-frequency control system dynamically adjusts the equipment’s operating load in real time based on the incoming air volume and concentration, accommodating the intermittent exhaust gas emissions characteristic of batch production involving mother liquor recovery. This prevents equipment overload or unnecessary no-load operation, thereby optimizing overall energy consumption. Based on field-measured flue gas flow rates, component compositions, concentration fluctuation ranges, mother liquor droplet and colloidal content, pipeline network layout, and site conditions of the mother liquor recovery area, we provide customized design—avoiding the use of standardized, off-the-shelf models. We offer end-to-end services covering process design, equipment manufacturing, on-site installation and commissioning, operator training, and subsequent operation and maintenance.Standardized manufacturing, standardized on-site construction, and routine inspection and maintenance ensure the long-term reliable operation of the complete VOCs organic solvent treatment system, achieving the dual objectives of compliant emission control for exhaust gases from the mother liquor recovery section in the pharmaceutical fine chemical industry and cost reduction through the resource recovery of organic solvents.
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