Research On Pervaporation Treatment Condtion Of Wastewater Containing Coal Gasification Phenol

With the social progress and human needs increasing, the increase of demand for energy is rising sharply, so coal is used as the raw material for gasification by most countries. In gasification process, a large number of phenol wastewater with high concentration and difficult to be degraded was produced. Because phenolic compounds are important industrial materials, for high concentration of phenol wastewater, recovery of phenol is carried before wastewater is being treated by biochemical method. Membrane separation technology was developed gradually in recent decades,because this method showes environment friendly, simply operation, wide applicability,among which pervaporation have been noticed by the international researchers.In the experiment, PDMS membrane, ZSM type molecular sieve filling PDMS membrane and NaY type molecular sieve filling PDMS membrane were choosed as the experimental object, performance of pervaporation which was influenced by these membrane was investigated. Operating conditions of pervaporation technologies to treat coal gasification wastewater was studied. Due to turbidity of the actual wastewater is high, the waste water needs to be coagulated with PAC and PAM as coagulants in the experiments. After coagulation pretreatment, the SS of the wastewater was reduced from 1190 mg/L to 510 mg/L, removal rate of phenol was up to 20.09%.Temperature, flow rate and the membrane downstream pressure are main influencing factors for pervaporation. The relationship of flux and temperature meet Arrhenius equation.With the increase of temperature, flux of phenol was increased gradually and by increasing of the feed flow rate, the level of liquid turbulence on membrane surface was enhanced, and concentration polarization and temperature polarization phenomenon was reduced.The adsorption and dissolution of phenol in membrane was promoted, so the flux of phenol was improved. Reducing the membrane downstream pressure may increase the pressure differential and phenol concentration gradient on both sides of the membrane; the phenol mass driving force in membrane was improved, and the flux was improved.Membrane reaction pool effective diameter was 5 cm and area is 19.625cm². After coagulation pretreatment, phenol concentration of coal gasification wastewater was 1850 mg/L. Pervaporation experiment result shows that when the temperature was 50℃, liquid flow rate was 3.6 L/h, membrane downstream pressure was 1000 Pa , treatment effect was the best, and the pervaporation flux of PDMS membrane was 7714.98mg/h·m².Through pervaporation mass transfer model research, relationship formula among total mass transfer coefficient, liquid mass transfer coefficient and membrane mass transfer coefficient was deduced. And it is found that the liquid mass transfer coefficient was increased by changing liquid membrane surface feed flow rate. On the basis of experimental data, mass transfer coefficients of phenol in PDMS membranes was calculated, the total mass transfer coefficient being 2.87×10^-6, liquid mass transfer coefficient 4.40×10^-5, and membrane mass transfer coefficient 3.07×10^-6.In the best operation conditions, the adsorption and dissolution process of phenol was promoted by increasing of molecular sieve filling rate. But when the filling rate was higher than a certain degree, the pervaporation membrane flux was reduced. The experimental result shows that treatment efficience with membrane of ZSM molecular sieve 5%filling rate was better than that with 10% filling rate. Filling rate was 45% for NaY molecular sieve filling membrane flux was better than 30% and 60% of molecular sieve filling rate. Phenol membrane flux of 5% ZSM filling rate was 14325.42mg/h·m²; phenol concentration was reduced to 270.76mg/L and removal rate of phenol was reached to 85.33%.Membrane reaction pool with effective diameter 25 cm and area 490.625 cm² was used as amplification experiment of pervaporation and when the temperature was 50℃, liquid flow rate was 75L/h, membrane downstream pressure was 1000 Pa, the pervaporation flux of 5% ZSM filling rate membrane was 9901.72 mg/m²...