Wetting Of Polyvinylidene Fluoride Hollow Fiber Membrane During The Absorption Of CO₂ By Potassium Glycinate Solution

Compared with traditional absorption devices, the membrane contactors used in membrane gas absorption technology has the features of a high surface-area-to-volume ratio, operational flexibility, independent gas and liquid flow, a compact size, easy scale-up and modularity. But the mass transfer flux would be declined sharply when there just a little part of membrane pores were wetted, and the membrane resistance would be the controlling transfer resistance with the extension of operation time. Reveal the causes and development of membrane wetting has theoretical and practical valve.In the first part of this paper, we measured the membrane weight at different time when the PVDF hollow fiber membrane immersed into the PG and DEA aqueous solution. The increasing ratio of membrane weight was obtained under different temperature, concentration of solution. The result showed that, the ratio increased along with time and two-stage growth manifested:rapid growth and slow growth. The higher the concentration of PG, the ratio rise faster within 1000min and the lower the concentration of PG the higher degree of the wetting during 1600min-2600min. The higher the temperature of PG the higher degree of wetting and the faster of wetting. The average wetting rate of PVDF hollow fiber membrane in the PG aqueous solution is significantly less than in the DEA aqueous solution.In the second part the wetting during the absorption of CO2 using the hydrophobic Polyvinylidene fluoride (PVDF) hollow fiber membrane contactors by potassium glycinate (PG) aqueous solution was studied. The effect of absorbent concentration, temperature and operation time to wetting and the influence of wetting to membrane resistance, membrane coefficient were investigated; the regeneration of PG aqueous solution and the recovery of PVDF hollow fiber membrane were also studied. The results showed that, the lower of the concentration and the higher of the temperature of absorbent, the higher the degree of wetting was; membrane transfer resistance increased and coefficient decreased largely with a tiny fraction of membrane wetting. On the condition of the concentration of 0.5mol/L, the temperature of 308.15K, the average rate of wetting could reach to 0.181 and 88.33% decline in total mass transfer coefficient after 40 hours’running and the membrane transfer resistance was 2.501×105 kPa·S·m2/moL,10 times at the beginning of the experiment. Regeneration of PG aqueous solution using the method of heating and Recovery of the PVDF hollow fiber membrane using the method of purging and drying, membrane performance has greatly improved but the absorbent molecules remaining in the membrane can’t be completely removed, the broken structure of membrane will also not be able to restored.