Compression condensation membrane separation, three-stage condensation plus membrane enrichment

The integrated process of compression and membrane separation is currently one of the more mature technological approaches for the recovery and recycling of VOCs. The process couples the two technical gradients of three-stage condensation and membrane separation, forming a division of labor mode of "three-stage condensation is responsible for main body recovery and membrane separation is responsible for cycle control.

The front end of the process consists of a three-stage condensation unit. After the exhaust gas is pressurized by the compressor, it is gradually cooled by the three-stage condensation system in turn: the first-stage condensation usually removes high boiling point components and water vapor in the range of 0 ℃ to 5 ℃, the second-stage condensation drops to -15 ℃ to -20 ℃ to recover medium boiling point solvent, and the third-stage condensation further drops to -30 ℃ or even lower, and deep trapping is carried out for low boiling point components. Through graded cooling, most of the organic matter in the waste gas is directly liquefied from gaseous to liquid solvent, with a purity of more than 90%, which can be directly reused in production.

The back end of the process is a membrane separation unit. The condensed tail gas still carries a small amount of unliquefied organic matter, which entersgas separation membraneComponent. The permeability of the polymer separation membrane to organic vapor is 10 to 100 times higher than that of air. Driven by the pressure difference between the two sides of the membrane, VOCs molecules preferentially penetrate the membrane layer to form concentrated gas, which is sent back to the compressor inlet and re-enters the three-stage condensation process for recycling treatment. The untreated purified gas is discharged up to standard.

This combination solves the short board of a single process: the condensation method can recover the solvent but the tail gas always remains, and the membrane separation can be concentrated efficiently but cannot be directly liquefied. The three-stage condensation and membrane enrichment are used together, and the system forms a closed cycle, and the overall recovery rate can reach more than 95%. The process operates with pure physical separation, does not involve combustion, and does not produce hazardous waste.