聚四氟乙烯中空纤维膜臭氧曝气的传质过程研究

发布时间：2018-03-12 07:45

本文选题：PTFE中空纤维膜　切入点：超声　出处：《西南石油大学》2017年硕士论文　论文类型：学位论文

【摘要】：曝气是实现臭氧在水中高效传递的关键,在整个曝气过程中臭氧的气液传质是以气泡为媒介发生的,因此气泡尺寸与气液传质过程有着密不可分的联系。论文采用具有微孔结构的聚四氟乙烯(PTFE)中空纤维膜对臭氧进行曝气,分别从气泡粒径分布和表观传质系数两方面对臭氧的气液传质过程进行了研究,且在原有体系中引入超声进行了强化传质研究,探讨了两种体系所对应的强化传质机制,并对模拟印染废水的处理效果进行考察。论文基于图像法对PTFE中空纤维膜曝气制造的气泡粒径分布进行了研究,结果表明:在进气流量为100L/h～500L/h的条件下,PTFE中空纤维膜所制造的气泡平均粒径在36.4μm到51.8μm之间;PTFE中空纤维膜的膜孔径不断增大时,形成的气泡粒径显著增加;气泡的尺寸与膜的亲疏水性有关,亲水性膜的平均气泡粒径小于疏水性膜;PTFE中空纤维膜所制造气泡尺寸小于微孔曝气;液相流体表面张力减小、黏度增加、矿化度增加,均会使气泡平均粒径减小,小气泡所占比例增加,这主要是由于水质特性的改变主要影响了气泡间的聚并作用。在PTFE中空纤维膜单独臭氧曝气效果的研究中得知:当进气流量为300L/h时,臭氧在水中的溶解浓度最高,且KLa值最高为0.438min-1;随着温度的升高,臭氧在水中的传质效果变差,其KLa值较常温操作降低了一倍。随着膜孔径的不断增大,臭氧在水中的浓度及表观传质系数均随之下降;疏水性PTFE中空纤维膜的曝气效果优于亲水性PTFE中空纤维膜;PTFE中空纤维膜曝气的臭氧传质效率明显高于微孔曝气,膜曝气所产生的表观传质系数约为后者的2.2倍。PTFE中空纤维膜强化臭氧的气液传质作用是通过压力的提升来实现的。此外,论文将超声作为一大强化手段引入臭氧体系,结果表明:当臭氧与超声联合时,液相饱和臭氧浓度相比于单独臭氧提高了 34.7%～54.4%;当臭氧和超声联合作用时,表观传质系数相比于单独臭氧提高了约38%左右。操作温度的提高不利于臭氧在水中的气液传质,与常温操作条件相比,液相臭氧饱和浓度与表观传质系数均随温度的降低幅度最高分别可达68%和71%。超声功率为1000W时,臭氧在水中的气液传质效果最佳,与单独臭氧处理方式相比,液相臭氧饱和浓度与表观传质系数分别提高了 58.6%和30.7%。模拟印染废水的处理研究得知,超声手段引入臭氧体系中废水脱色率可以快速达到100%,又可以节省50%的臭氧投加量;超声/臭氧联合体系和单独臭氧的脱色反应速率常数k分别为0.372min-1和0.253 min-1;在对模拟印染废水的降解中,超声引入臭氧反应体系可以强化臭氧的氧化能力和提高废水的降解速率。
[Abstract]:Aeration is the key to the efficient transfer of ozone in water. In the whole aeration process, the gas-liquid mass transfer of ozone takes place in the medium of bubble. Therefore, the bubble size is closely related to the gas-liquid mass transfer process. In this paper, the porous PTFE hollow fiber membrane is used to aerate ozone. The gas-liquid mass transfer process of ozone was studied from the aspects of bubble particle size distribution and apparent mass transfer coefficient, and the enhanced mass transfer mechanism of the two systems was studied by introducing ultrasound into the original system. The effect of simulated printing and dyeing wastewater treatment was investigated. The bubble size distribution of PTFE hollow fiber membrane aeration was studied based on image method. The results show that when the average diameter of the bubble produced by PTFE hollow fiber membrane is between 36.4 渭 m and 51.8 渭 m, the pore size of PTFE hollow fiber membrane increases obviously when the inlet flow rate is 100L / h and 500L / h. The size of the bubble is related to the hydrophobicity of the membrane, the average bubble diameter of the hydrophilic membrane is smaller than that of the hydrophobic membrane PTFE hollow fiber membrane, the bubble size is smaller than that of the microporous aeration, the surface tension of liquid phase decreases, the viscosity increases, and the salinity increases. Will decrease the average diameter of bubble and increase the proportion of small bubble. This is mainly due to the change of water quality characteristics which mainly affect the coalescence between bubbles. In the study of the ozone aeration effect of PTFE hollow fiber membrane alone, it is known that when the inlet flow rate is 300L / h, the dissolved concentration of ozone in water is the highest, and the concentration of ozone in water is the highest when the flow rate is 300L / h. With the increase of temperature, the mass transfer effect of ozone in water becomes worse, and the KLa value of ozone decreases twice as compared with normal temperature operation. With the increase of membrane pore size, the concentration and apparent mass transfer coefficient of ozone in water decrease. The aeration efficiency of hydrophobic PTFE hollow fiber membrane is better than that of hydrophilic PTFE hollow fiber membrane. The apparent mass transfer coefficient produced by membrane aeration is about 2.2 times that of the latter. The gas-liquid mass transfer of ozone enhanced by PTFE hollow fiber membrane is realized by increasing the pressure. The results show that when ozone is combined with ultrasound, the concentration of saturated ozone in liquid phase increases by 34.7% compared with that of ozone alone, and when combined with ozone and ultrasound, the concentration of saturated ozone in liquid phase increases by 34.7%. The apparent mass transfer coefficient is about 38% higher than that of ozone alone. The increase of operating temperature is not conducive to the gas-liquid mass transfer of ozone in water. The maximum decreases of liquid ozone saturation concentration and apparent mass transfer coefficient with temperature are as high as 68% and 71 respectively. When ultrasonic power is 1000W, the gas-liquid mass transfer effect of ozone in water is the best, compared with that of ozone treatment alone. The saturated concentration of liquid ozone and apparent mass transfer coefficient increased by 58.6% and 30.7 respectively. The treatment of simulated printing and dyeing wastewater showed that the decolorization rate of wastewater introduced into ozone system by ultrasonic method could be up to 100 quickly, and the ozone dosage of 50% could be saved. The decolorization rate constants k of ultrasonic / ozone combined system and single ozone system were 0.372min-1 and 0.253min-1, respectively. In the degradation of simulated printing and dyeing wastewater, the ability of ozone oxidation and the degradation rate of wastewater could be enhanced by introducing ozone reaction system.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703

【参考文献】