Effect of absorbent vapor on stability of characteristics of a composite PTMSP membrane on nonwoven polyester support during regeneration of diethanolamine solution in membrane contactor
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The regeneration of a carbon dioxide-loaded aqueous solution of diethanolamine (DEA) in a membrane contactor-stripper at a temperature of 100°C, an absorbent pressure of 10 atm, and a varying absorbent feed flow rate has been studied. The membranes used were laboratory samples of composite membranes prepared by deposition of thin separation layers of poly[1-(trimethylsilyl)-1-propyne] (PTMSP) on a porous support. The support was MFFK-1 microfiltration membrane (Vladipor) with the filtering porous layer of fluoroplastic F-42 (tetrafluoroethylene-vinylidene fluoride copolymer) deposited on a nonwoven polyethylene terephthalate (PET) support. After the first 10 days of testing, the CO2 flux at the membrane contactor outlet was reduced by a factor of 3 and then stabilized at 2 m3/(m2 h) within the next 80 days. It has been found that along with CO2 transport through the membrane, the vapor of the absorbent solution components is transferred. The concentration of DEA in the condensate was 0.5 wt %, that corresponds to the composition of equilibrium vapor over a 30 wt % DEA aqueous solution at 100°C. Since PTMSP is chemically resistant to the DEA solution at the regeneration temperature, the deterioration of the transport properties of the PTMSP/MFFK(PET) composite membrane with time during the absorbent regeneration is associated with the chemical degradation of the nonwoven PET support by the action of penetrating DEA vapor at a temperature of 100°C. It has been concluded that more chemically and thermally resistant porous supports such as ceramic microfiltration membranes should be used.
Keywordscomposite membranes membrane contactor-stripper diethanolamine regeneration carbon dioxide
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