Compression condensation plus membrane separation, waste gas solvent recovery scheme

Compression condensation plus membrane separation, waste gas solvent recovery scheme

Process Principle

The combined process of compression condensation and membrane separation is a more mature technical route in the recovery of VOCs resources. The process combines three technical gradients of compression, condensation and membrane separation to form a closed-circuit recovery system.

Step 1: Compression and condensation. The exhaust gas enters the condensing unit after being pressurized by the compressor, and most of the organic matter is changed from gaseous to liquid through staged cooling. The research data show that for the VOCs exhaust gas with a concentration of 500-6000ppm, a higher condensation recovery rate can be obtained when the condensation pressure is 0.55MPa and the condensation temperature is -10 ℃ to -15 ℃.

Step 2: Membrane separation cycle. The condensed tail gas still contains a small amount of unliquefied organic matter and enters the membrane separation unit. The permeability of the polymer separation membrane to organic vapor is 10 to 100 times higher than that of air. VOCs preferentially pass through the membrane layer to form concentrated gas, which is sent back to the compressor inlet and re-enters the condensation process for circulation treatment. The untreated purified gas meets the discharge standard.

Advantages of the plan

High recovery efficiency. Using this combined process, the organic solvent recovery rate can reach more than 95%, and the exhaust emission concentration can be stably controlled below 40mg/Nm. For specific components such as propylene monomer, the membrane system can recover more than 90% from the tail gas.

Energy consumption is significantly reduced. Compared with traditional cryogenic technology, membrane separation pre-concentration can reduce the processing load of the condensing unit and reduce the overall energy consumption by 25% to 60%.

Wide scope of application. Suitable for ketones, esters, hydrocarbons, halogenated hydrocarbons, alcohols and other organic solvent waste gas, the recovery effect of medium and high concentration (above 1000 mg/m) waste gas is particularly obvious. Membrane separation is pure physical separation, no open flame, suitable for chemical, pharmaceutical, storage tank area and other explosion-proof places.

Process route selection

The single condensation method or membrane separation method has its own limitations: the condensation method has high energy consumption for treating high-concentration exhaust gas and low efficiency for treating low-concentration exhaust gas; although the membrane separation method has good concentration effect, it cannot directly liquefy the solvent. The combined design of compression condensation and membrane separation is a complementary scheme for the short board of the two-condensation is responsible for the main body recovery, and membrane separation is responsible for the cycle control, so as to realize the unity of efficient recovery and standard discharge.