Study On Choices Of Absorbent In Membrane-based Gas Absorption

In this paper, the aqueous solution of n-Formyl morpholine (NFM) was used as absorbent, the work studies physical properties and compatibilities with membrane of NFM aqueous solution, and Henry's law constant of benzene and toluene; The results show the aqueous solution of NFM have low viscidities and high surface tensions, better compatibilities with membrane, and benzene and toluene have great solubilities in NFM aqueous solution. So choosing the aqueous solution of NFM as absorbent disposed VOCs is appropriate. The work also focuses on a membrane based gas absorption process for the separation VOCs from N₂. Benzene was chosen as the target VOCs. Mass-transfer performance of separation benzene was studied in the hollow fiber polypropylene membrane (HFPPM), and packed tower as comparison. Effect of various factors, including flowrate of absorbent and feeding gas, concentration of absorbent and feeding gas, differences of membranes modules, temperature of absorbent on the efficiency of benzene absorption were investigated. The results show that the removal efficiency achieves 65.0 % - 99.6 % and the overall volume transfer coefficient achieves 0.0157 s^-1 - 0.08412 s^-1, when following conditions were used: concentration of feed gas, 10.2 mg·L^-1; flowrate of absorbent, 20 mL·min^-1 - 100 mL·min^-1; flowrate of feed gas, 40 mL·min^-1 - 300 mL·min^-1; In the same condition, the removal efficiency of benzene absorption in the HFPPM is evidently higher than in the packed tower. The characteristics of separation of VOCs/N₂ by membrane contactor are of quicker mass transfer velocity and higher efficiency of separation.