The Study Of Membrane Absorption Utilized For Acetylene Separation From The Mixture Gas Of Coal Pyrolysis By Plasma

Acetylene production from coal by plasma pyrolysis was simple process, low power consumption andzero emissions on the environment, so it was a highly competitive method in acetylene production.However, the output of acetylene contained a large number of H2, olefins (CH4, C2H4, C2H6, etc.), theacetylene separating from the mixed gas was the premise and key of downstream process. Membraneabsorption as a gas separation method has been studied extensively in many areas showing a goodadvantage. In this paper, for the acetylene from coal by plasma pyrolysis, membrane absorption method hadbeen used for acetylene separation. The main contents were as follows:(1) The absorption and desorptionperformance of absorbents were studied;(2) According to the nature of the absorbent and membranematerials the Chitosan had been screened as the membrane material, and the hydrophilic Chitosan hollowfiber membrane was prepared;(3) Acetylene was separated by Polyvinylidene fluoride (PVDF) hollowfiber membrane and Polytetrafluoroethylene (PTEF) hollow fiber membrane. The factors influencing on theacetylene absorption rate and the mass transfer rate, such as the gas flow rate, liquid phase flow rate andlength of membrane module were investigated. The research results as follows.(1) Methanol, acetone, N, N-dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) asabsorbent, the absorption and desorption performance of acetylene were studied. The results showed that: at100minutes, the mass fraction of acetylene were1.27%,2.04%,5.35%and4.93%in the methanol, acetone,DMF and NMP respectively; when the absorbent was heated, the desorption rate of acetylene were90.52%,74.97%,72.48%and77.29%in the methanol, acetone, DMF and NMP respectively. When the absorptivecapacity was considered, desorption amount of C2H2were as follows: methanol <acetone <NMP <DMF.(2) Chitosan hollow fiber membrane was prepared by phase inversion process, and effects of chitosanconcentration, pore-foaming agent concentration, and coagulation conditions on the structures andmechanical properties of chitosan hollow fiber membrane were studied. Experimental results revealed that:with increasing the chitosan concentration in the casting solution, the quantity of finger holes decreased;with increasing pore-foaming agent polyethylene glycol2000(PEG2000) content the quantity of fingerholes decreased; with increasing sodium hydroxide concentration in coagulation, the quantity of fingerholes decreased The hollow fiber membrane prepared had better pore structure and mechanical propertiesin the follow condition: sodium hydroxide concentration20%, chitosan concentration4%, PEG content10%. Using anhydrous alcohol-hexane-glycerol step by step liquid-liquid drying method was applied toavoid the chitosan hollow fiber membrane shrink and subsidence during dehydration process.(3) Membrane absorption was studied using PVDF hollow fiber membrane and methanol asabsorbent. The results showed that acetylene absorption rate decreased as gas flow rate increased, but themass transfer rate increased; acetylene absorption rate decreased and then changed to be steady as liquidflow rate increased, the mass transfer rate decreased then changed to be steady also; suspending the gas andliquid flow rate, acetylene absorption rate increased and the mass transfer rate decreased as the effectivelength of membrane module increased. The single-pass absorption rate reached23.37%, when followingconditions were used: liquid flow rate was1.660×10-5m/s, gas flow rate was0.5490m/s, the effectivelength of membrane module was30cm.（4）Membrane absorption was studied using PEFT hollow fiber membrane and NMP as absorbent.The results showed that acetylene absorption rate decreased as gas flow rate increased, but the masstransfer rate increased; acetylene absorption rate decreased as the liquid flow rate increased, the masstransfer rate increased as the liquid flow rate increased; suspending the gas and liquid flow rate, acetyleneabsorption rate increased and the mass transfer rate decreased as the effective length of membrane moduleincreased. When the liquid flow rate was4.9788×10-5m/s, gas flow rate was0.4244m/s and the effectivelength of membrane module was20cm, the acetylene cycle absorption rate maintained about74%.