气泡循环流动型膜生物反应器流体力学特性研究

以气升式环流反应器和膜生物反应器为基础,提出气泡循环流动型膜生物反应器的概念.利用气液循环流动减缓膜污染,通过充压渗透的操作方式,降低水处理能耗与设备投资.实验研究了下降管内中空纤维膜填充率对反应器的平均气含率、循环液速等流体力学性能的影响,使用模拟体系考察膜分离性能. 研究结果表明:循环流动的气液两相能够明显缓解膜污染,提高膜渗透通量;利用充压渗透的操作方式可以实现膜分离过程,同时加压操作会导致平均气含率减小,循环液速降低.在理论分析基础上,导出平均气含率、循环液速随操作气速和压强的变化关系.     

外循环气升式膜反应器中的体积传质系数

传质系数是决定气升式反应器传质特性的主要参数之一,文中介绍了一种新型的将陶瓷膜曝气系统与外环流反应器耦合的外环流膜反应器,考察了不同曝气气量,曝气压力,曝气方式以及曝气位置条件下反应器中体积传质系数的变化情况。结果表明,曝气气量,曝气压力,曝气孔孔径都能影响体积传质系数,孔径的影响尤为显著,采用膜微孔曝气,体积传质系数相比曝气头曝气提高近2倍。将膜管曝气和曝气头曝气耦合起来,可在获得良好气液循环的条件下有较大的气液接触面,从而优化气液传质。     

基于多孔陶瓷膜的脱硫废水负压式膜蒸馏实验

目前采用多孔陶瓷膜进行膜蒸馏的技术已有不少研究，但由于膜本身的亲水特性，需要在使用前进行疏水改性，这增加了工序和成本，且疏水性随着使用过程逐渐减弱。因此，提出一种基于多孔陶瓷膜的脱硫废水负压式膜蒸馏方法，直接采用亲水性多孔陶瓷膜，通过泵的抽吸作用使膜内溶液形成负压，以防溶液渗出膜外。为探究负压式膜蒸馏的传热传质机理，通过实验对比了亲、疏水多孔陶瓷膜在不同工况下的传递特性。实验结果表明：当膜内负压值小于膜孔内溶液毛细力时，亲、疏水多孔陶瓷膜的膜孔内分别为溶液输运和水蒸气输运；当空气流量为22L/min、废水温度和流量分别为50℃和11L/h时，亲水膜的渗透通量在1.9～3.9kg/(m²·h)之间，而疏水膜的渗透通量仅为0.13～0.25kg/(m²·h)；亲、疏水多孔陶瓷膜的热效率分别在92%和55%左右，说明亲水性多孔陶瓷膜有着更高的热效率，陶瓷膜的较高热导率有利于提升亲水膜的膜蒸馏性能；脱硫废水流量对热质传递性能影响不大，随着空气流量或者废水温度的增加，膜渗透通量随之增加。     

反应与分离相耦合的钢铁酸洗液处理研究

采用反应与分离相耦合的途径,用19通道陶瓷膜元件构建了5L气升式膜反应器,并就其用于钢铁酸洗液的处理进行了研究.结果表明:在0.5～2.5 m~3/h曝气量范围内,稳定膜通量能维持在60L/(m~2·h)以上,且提高曝气量有利于提高循环液体流速.在稳定操作条件下,料液中氢氧化铁悬浮物浓度、温度(1～45℃)和膜两侧压差(0.025～0.1MPa)均与膜通量呈线性关系.当处理Fe~(2+)质量浓度为400ms/L的酸洗废液时,在溶氧度>70%、压差0.1 MPa、18～25℃、pH为6-9、HRT=2h条件下,出水浊度<2 NTU,pH符合国家排放标准.     

气升式陶瓷膜过滤装置处理油田含聚采出水

采用新型的气升式陶瓷膜过滤系统处理油田含聚采出水,通过气液两相流替代单一的液相流动,降低了陶瓷膜处理油田含聚采出水过程的能耗,系统考察了曝气孔大小、曝气量和跨膜压差对膜渗透通量的影响。结果表明,采用孔径为微米级的曝气头曝气使高压气体在多通道膜管内的分布更为均匀,进而有效抑制膜污染和浓差极化,延缓通量衰减。当曝气孔径为1 μm时,渗透通量达到最大,且曝气量从300 L·h^-1增加到600 L·h^-1时,通量显著增加。此外,跨膜压差对膜的渗透通量影响显著,当跨膜压差为0.4 MPa时,渗透通量最佳。陶瓷膜处理油田采出水的出水水质各方面指标数据较为稳定,达到5.1.1回注水标准。最后,计算讨论了气升式陶瓷膜过滤装置的吨水能耗。     

气升式陶瓷膜过滤装置处理油田含聚采出水

采用新型的气升式陶瓷膜过滤系统处理油田含聚采出水,通过气液两相流替代单一的液相流动,降低了陶瓷膜处理油田含聚采出水过程的能耗,系统考察了曝气孔大小、曝气量和跨膜压差对膜渗透通量的影响。结果表明,采用孔径为微米级的曝气头曝气使高压气体在多通道膜管内的分布更为均匀,进而有效抑制膜污染和浓差极化,延缓通量衰减。当曝气孔径为1μm时,渗透通量达到最大,且曝气量从300 L·h~(-1)增加到600 L·h~(-1)时,通量显著增加。此外,跨膜压差对膜的渗透通量影响显著,当跨膜压差为0.4 MPa时,渗透通量最佳。陶瓷膜处理油田采出水的出水水质各方面指标数据较为稳定,达到5.1.1回注水标准。最后,计算讨论了气升式陶瓷膜过滤装置的吨水能耗。     

弹状流对陶瓷膜超滤葡聚糖水溶液的影响

为降低膜污染和浓差极化需维持较高膜面流速,能耗较高。将气升式外循环引入膜过程,可有效降低浓差极化和能耗。实验考察了曝气量对渗透通量的影响,当曝气量为400 L·h^-1时,与相同液速条件下单相流错流过滤相比较,膜通量提升87%;进一步增大曝气量,膜通量增加趋势变缓。对气升式膜过滤过程的水力学特性进行了研究,在弹状流条件下,气液两相流可有效提高膜面剪切力,增强膜面传质。在较低流速下,曝气可有效降低膜污染阻力,提高膜通量。结合气液两相流理论和膜过滤阻力模型,分析了弹状流提升膜通量的机理。     

4nm孔径陶瓷膜去除水中钙离子研究

采用孔径为4 nm的陶瓷膜去除水中的Ca2+,考察了不同Ca2+含量、跨膜压差、溶液pH和温度对陶瓷膜渗透通量和Ca2+截留率随时间的变化情况。结果表明,溶液中的Ca2+含量越低,膜渗透通量越高,Ca2+截留率也越高;跨膜压差升高,膜渗透通量增大,Ca2+截留率降低;降低溶液pH及升高温度能够提高膜渗透通量及对Ca2+的截留率。对Ca2+的质量浓度为10 mg/L的水溶液,在TMP为0.1 MPa、溶液pH为3、温度为50℃时、孔径为4 nm陶瓷膜渗透通量稳定在80 L/(m2.h),Ca2+截留率为85%左右。研究结果可为金属离子微污染水的净化提供方法。     

气液两相流在炭膜微滤钛白悬浮液中的应用研究

采用平均孔径为1.0μm的管状多孔炭膜实验研究了炭膜微滤钛白悬浮液的过程中引入气体形成两相流的强化微滤过程.实验结果表明,在温度20℃、跨膜雎差0.04～0.16 MPa、料液流速0.85～1.56 m·s-1、气体流速0.29～2.02 m·S-1、悬浮液浓度0.1～1.0 g·L-1时,通入气体形成的气-液两相流可以大大强化微滤过程.两相流相对于单相流的最大稳定渗透通量可提高62%,而且达到稳定通量的时间也相应缩短.实验发现,在相同操作条件下膜组件竖直放置比水平放置时稳定渗透通量增加了12%;弹状流是有利的强化流型:两相流条件下随着跨膜压差的增加,稳定通量快速增加,在压力0.11 MPa 时通量达到最大值,然后随压力增加,渗透通量缓慢下降.     

气升式反应器在发酵工业中的应用研究进展

气升式反应器是一种用于气液两相或气液固三相过程的接触式反应装置,简要综述了气升式反应器在发酵工业中的应用研究进展,按照集成强化的思路开发的气升式膜生物反应器被重点介绍。     

Experiment and calculation of filtration processes in an external-loop airlift ceramic membrane bioreactor

Air sparging is recognized as an effective way to increase permeate flux in membrane filtration processes. The application of air sparging with an external-loop airlift ceramic membrane bioreactor was studied at different gas flow rates, biomass concentrations and suction pressures. A 180% increase in permeate flux was obtained while filtering a 2 g/L activated sludge wastewater suspension with the airlift cross-flow operation for U_g=0.21 m/s. The mechanism of flux enhancement in the case of slug flow in tubular membrane was discussed. The region near the gas slug was divided into three different zones: falling film zone, wake zone and remaining liquid slug zone. Air sparging significantly lowered cake thickness and consequently cake resistances for the wake region and the falling film region. A novel model combining hydrodynamic of gas-liquid two-phase flow and cake resistance was developed to simulate the process. The model was validated with experimental data with an error of 8.3%.     

Application of ultrafiltration hybrid membrane processes for reuse of secondary effluent

This study evaluates the factors affecting pretreatment conditions for hybrid UF membrane processes for reuse of secondary effluent from the sewage treatment plant. The experimental results obtained from the ultrafiltration (UF) membrane process showed that the particles of the size range between 0.2 and 1.2 μm caused a significant impact on membrane fouling in all cases even with or without the coagulation process. As pretreatment of UF membrane process, the coagulation significantly improved the permeate flux. Optimal flux improvement was seen at an alum dose of 50 mg/L. In addition, it was found that the permeate flux was least declined under the coagulation condition of charge neutralization (pH 5.0). Also, the powdered activated carbon (PAC) adsorption enhanced the permeate flux. Application of the direct filtration as a pretreatment of UF membrane process was also very effective in reducing the UF membrane fouling.     

Simultaneous recovery of phosphorus and nitrogen from liquid digestate by vacuum membrane distillation with permeate fractional condensation

A vacuum membrane distillation(VMD) process with permeate fractional condensation on membrane downstream has been developed for simultaneous recovery of phosphorus and nitrogen from liquid digestate. The polytetrafluoroethylene(PTFE) membrane flux could reach 6000 g·m~(-2)·h~(-1) with the rejection efficiency of total phosphorus(TP) over 0.99, under the condition of flowrate being 120 L·h~(-1) and temperature being 40°C. Membrane fouling occurred with a film of organics and microorganism deposited on the surface of the membrane. Membrane flux could be reversed after the membrane was rinsed by water. Higher feed temperature and flowrate could improve the membrane flux, while hardly affect the rejection efficiency of total phosphorus. The concentration of TP could reach 1600 mg·L~(-1) after membrane distillation, which is about 5 times of that in initial liquid digestate. On the downstream of the membrane, some of the permeate vapor was condensed under the vacuum condition and most of water was collected here. The remaining vapor enriched with total nitrogen(TN) was compressed and pumped to the atmospheric condition to condense. The TN concentration in atmospheric condensate was as high as 7000 mg·L~(-1) with the process separation factor for ammonia being enhanced to 114.     

纳米TiO_2复合膜光催化和膜分离的耦合作用

以微孔陶瓷管为载体,采用阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)辅助的溶胶-凝胶法制备了纳米TiO2复合超滤膜。以1 g/L聚丙烯酰胺(PAM)为料液(目标污染物),以膜截留率及膜通量为实验参数,研究了复合膜的光催化-膜分离耦合作用,耦合时的膜通量较单一膜分离的膜通量提高了60%;以0.5 g/L牛血清白蛋白(BSA)为模拟天然大分子料液,采用无光照料液过膜-紫外光照清水过膜的交替间歇运行方法,膜通量可恢复60%以上。     

往复旋转管式陶瓷膜超滤脱脂奶水溶液的研究

往复旋转管式陶瓷膜过滤系统通过膜组件往复旋转在膜表面反复产生高剪切率,达到减缓膜污染的效果。在相同操作条件下,与单向旋转过滤和死端过滤相比较,往复旋转过滤具有更好的减缓膜污染的作用。本实验利用往复旋转膜过滤装置超滤脱脂奶水溶液,考察了各种参数对该膜系统过滤特性的影响。实验结果表明,料液浓度增大,膜通量减小;过高的操作压差将会抑制膜通量增加;旋转速度增大,膜表面剪切强化作用增强,膜通量相应增大;膜稳态通量随往复旋转周期增大呈现先增大后减小的趋势。当料液速度达到膜组件转速时,瞬时反方向旋转膜组件,膜表面产生最大的剪切率,膜稳态通量也达到最大值。能耗分析表明,往复旋转过滤较单向旋转过滤单位通量能耗低。     

Application of Membrane Deliquoring Technology in Ginkgo Biloba Extract Production

To displace the original vacuum hypothermia triple effect evaporation technology, save energy, and enhance product activity, nanofiltration technology is applied in getting rid of most solvent of macro porous resin eluent, which is generated in producing Gingko biloba extract. Membrane K and membrane L are studied systematically in this experiment. The results indicate that permeate flux increases with the accretion of operating pressure, operating temperature, and recycle flux, and decreases with the increase of feed concentration. An increased operating pressure and recycle flux resulted in a decreased permeate concentration, and increased operating temperature and feed concentration lead to an increased permeate concentration. Active components content in permeate almost does not change with operating condition. However, the cutoff ratio is about 99%, which can meet the need of production. Optimized operating condition was assured and small field experiment was done. It was shown that nanofiltration membrane technology could effectively eliminate solvent of macro porous resin eluent. Elementary estimation indicates that nanofiltration membrane technology can reduce 90% energy and 70% cost over the original technology.     

Separation of Nitrocellulose-Manufacturing Wastewater by Bench-Scale Flat-Sheet Crossflow Microfiltration Units

Abstract

This paper reports laboratory-scale experiments for the separation of nitrocellulose fines from nitrocellulose manufacturing wastewater with crossflow microfiltration units. Results are reported in terms of the factors affecting permeate flux, membrane fouling, the effects of pulsating cleaning and chemical cleaning, and the optimum condition for operation. The separation process under steady operation is described mathematically with the aim of elucidating the transport mechanism and the effects of operating parameters on permeate flux.     

超声在陶瓷膜处理乳化含油废水中的作用研究

Ultrasonic field was applied in the treatment of oil emulsification wastewater by ZrO2 ceramic mem-brane. The permeate flux, rejection ratio in the filtration process and recovery ratio of flux in the membrane cleaning process were measured. Great improvement in the permeate flux and rejection ratio have been observed for the membrane process enhanced by the ultrasonic field. The permeate flux of water through the membrane was about 210L.m^-2.h^-1 and the oil rejection ratio was over 99.9% under the optimal ultrasonic treatment conditions, which were 8W of ultrasonic power, 7cm of ultrasonic probe length introduced into the membrane channel and the same ultrasonic radiation direction as the wastewater flow. The resistance of the membrane process was compared between the cases with and without ultrasound, and the total resistance was reduced 68% by the use of ultrasound, Four methods including water cleaning, water cleaning under sonication, chemical cleaning and chemical cleaning under sonication were used to recover membrane flux. It was found that the flux recovery ratio increased with the increase of ultrasonic cleaning power. In addition, the use of chemical agents combining with ultrasonic irradiation showed a synergistic effect, which resulted in the highest cleaning efficiency and the shorter cleaning time.     

聚丙烯中空纤维膜的应用与清洗方法

采用聚丙烯中空纤维微孔膜的减压膜蒸馏技术对氯化钠、氯化钙和硫酸镁等盐溶液进行脱盐处理，考察了料液温度、料液流量、料液浓度和冷测真空度对膜的渗透通量和去除率的影响。实验表明：随着真空度及料液流量、温度的提高，膜的渗透通量有增加的趋势。在相同条件下处理不同的盐溶液，膜的渗透通量相差不大，膜的去除率达到99％以上。使用0．5mol／L盐酸以及0．05mol／L EDTA清洗被污染的膜效果最明显，可迅速有效地将附着在中空纤维膜上的无机污染物去除，使膜渗透通量得到基本恢复。