Dimethylformamide is a strong polar solvent commonly used in polyurethane, acrylic fiber and pharmaceutical industries. Its two characteristics directly determine that the recovery route is different from conventional solvents: first, the boiling point is high, volatilization is not violent at normal temperature, and the concentration of waste gas is often not high; Second, it is completely miscible with water, condensate cannot be stratified by static standing, and rectification purification is generally required for reuse after recovery. Therefore, the focus of DMF recovery is not on the condensation temperature, but on the collection efficiency and subsequent purification.
The conventional method is to collect and then condense, and then send the condensate to distillation for purification. Due to the high boiling point of DMF, most of the vapor can be liquefied by conventional refrigerant in the condensation section without deep cooling. The difficulty lies in that the concentration of the gas source may be low, and the collection link should be sealed to avoid unorganized emission of diluted gas source. Because the condensate is miscible with water, DMF must be separated from water by distillation, the purified DMF is used again according to the quality index, and the kettle residue is disposed of according to the management requirements of waste water or hazardous waste.
The key to convergence lies in concentration: low gas source concentration will enlarge the scale of equipment and reduce the unit recovery income, so the sealing degree of the collection link is more worthy of effort than the condensation temperature level. The scale of distillation purification is determined according to the amount of recovered liquid and the target purity, and should match the capacity of the condensation section to avoid backlog caused by large front-end recovery and back-end purification.
| Comparison item | DMF | Common solvents (such as toluene, ethyl acetate) |
|---|---|---|
| Boiling Point Level | High, with slow volatilization at room temperature | Moderate or low, volatile fast |
| water-soluble | Completely miscible with water | Most of them are insoluble in water |
| Condensate treatment | Reuse after rectification and purification | Allow it to stand until the layers separate. |
| Recycling Focus | Collection tightness and purification matching | Condensation temperature level and recovery degree |
Focus on the sealing effect of the collection system, the recovery of condensate and the quality stability after purification. The abnormally low gas source concentration is mostly related to the collection is not closed. The fluctuation of condensate composition should be checked back to the process batch. The fluctuation of purification quality needs to check the operation parameters of the distillation tower. If the records of recovery, purification and reuse are strung together, the problem location will be much faster.
DMF and water are completely miscible, standing will not stratify, must be through distillation and other ways to separate DMF and water, in order to get a reusable product.
Usually not needed. The boiling point of DMF is relatively high, and most of the vapor can be liquefied by conventional refrigerant. Whether to deepen the cooling should be judged according to the actual emission management requirements.
After distillation purification and sampling inspection, it can be used again after reaching the reuse quality index; the process with high purity requirements can adjust the distillation parameters to improve product quality.
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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