1、1,1. Introduction,1.2 Advantages of Membr. Sep. No phase change; Lower energy cost; Ambient temperature operation; No need to add other components; Environmental friendly tech.;,2,1. Introduction,1.3 Membrane the heart A membrane may be defined as an interphase separating two phases and selectively

2、controlling the transport of materials between those phases.,3,1.4 Membrane classification,4,1.6 膜技術(shù)的應(yīng)用,分離 RO NF UF MF ED GS PV D MC LM,控制釋放 藥物 化肥 農(nóng)藥,膜反應(yīng)器 催化膜反應(yīng)器 酶膜反應(yīng)器 生物膜反應(yīng)器 移植免疫隔離,能量轉(zhuǎn)換 電池隔膜 燃料電池膜,5,無機(jī)分離膜的優(yōu)勢和特點(diǎn):,多孔膜 - 孔徑分布窄，分離系數(shù)高 耐高溫（ 100 1000 ） 化學(xué)穩(wěn)定性好， 可在惡劣環(huán)境下使用 機(jī)械強(qiáng)度大， 可高壓使用或反沖、反洗 經(jīng)久耐用，使用壽命長,6,PV

3、優(yōu)點(diǎn),高效，合適的膜，單級就能達(dá)到高的分離度 * 低能耗，一般比恒沸精餾節(jié)能1/3 2/3 * 過程不引入其它組份，產(chǎn)品和環(huán)境不受污染 * 便于放大及與其它過程耦合和集成 * 過程簡單，附加的處理少，操作方便,7,液膜的特點(diǎn)-與固體膜相比,(1) 傳質(zhì)速率高。溶質(zhì)在液體中的分子擴(kuò)散系數(shù)(10-610-5 cm2/s)比在固體中(10-8 cm2/s)高幾個數(shù)量級 (2) 選擇性好,8,2.1 Membrane material,Membrane,Inorganic,Organic,High thermal, mechanical, chemical and biologic stability

4、 Simple operation and control and reliable performance,Difficult in sealing of module in high temperature, low reproducibility and high cost Low membrane area,Good flexibility, high permeability, low-density,Low solvent resistance, corrosion resistance,不耐腐蝕 temperature resistance,9,The types of inor

5、ganic membrane,10,2.2 Membrane structure and its characterization,Membrane structure Morphology: cross section and surface structure Crystalline and Molecular: aggregation and polymer chain orientation on the membrane surface,Aim: find out the relationship between the membrane structure and performa

6、nce, development of methods and systems for membrane preparation and improve the membrane performance,11,2.2.1 Membrane Morphology,Asymmetry and symmetry membrane Dense and porous membrane Composite membrane,12,Pore diameter and Pore size distribution,Pore diameter: maximum, average, and minimum por

7、e size Pore size distribution: the ratio of the number of a given pore size to the total number of the pore size.,13,Pore density the number of pores per unit membrane area Membrane porosity () is the fraction of pore volume in the total membrane volume,Pore density and Porosity,14,2.2.3 Membrane st

8、ructure and its characterization,Scanning Electron Microscopy（SEM） Atomic Force Microscope （AFM） Membrane thickness Membrane porosity Pore diameter and Pore size distribution,15,Homogeneous membrane preparation,Solution casting 刮膜 Melt pressing 壓片,16,Symmetric porous membrane preparation,Irradiation

9、 放射 Stretching 拉伸 Template leaching,17,Precipitation of polymer solution to form membrane,Polymer precipitation by thermal gelation Solvent evaporation Polymer precipitation by absorption of water vapor Loeb-sourirajan process,18,Composite membrane preparation,The properties of both the dense separa

10、ting layer and the porous support layer can be individually optimized Thin and correspondingly delicate selective layer A highly permeable material, protect the membrane from damage,Composite membranes offer advantages,19,Preparation method:,Solution-coated Interfacial Polymerization Plasma polymeri

11、zation Dynamically Formed Water cast,20,2.5 Inorganic membrane preparation,Inorganic membranes are versatile. They can prepared from metal, ceramic, zeolite and glass inorganic materials. Nowadays, the growth rate of Inorganic membrane is higher than organic membrane.,Sol-gel technique Chemical etch

12、 method Thermal decomposition method Sintering Process,Preparation Methods:,21,2.4 Organic membrane forming process,Flat membrane Tubular membrane Hollow fiber membrane,22,Flat membrane,Used for Plate-and-frame modules and spiral wound modules. Use fabric materials to increase the strength of the me

13、mbrane, such as filter paper, non-woven polyester fabric.,23,Tubular membrane,Inside-out or outside-in tubular membrane Tubular modules are now generally limited to ultrafiltration applications, for which the benefit of resistance to membrane fouling due to good fluid hydrodynamics outweighs their h

14、igh cost.,24,Hollow fiber membrane,Easy to make and very large membrane areas (16000-30000m2/m3 ). Dense or microporous membrane, asymmetric membrane, composite membrane. Inner diameter: 25300m; Outer diameter:50600m. Solution spinning and Melt spinning,25,Solution spinning,Dry spinning：a hot polyme

15、r melt is extruded from an appropriate die and is then cooled and solidified in air. Wet spinning：polymer solution is extruded and precipitated into a nonsolvent. Dry-wet spinning: combination of the two spinning methods. The dense selective layer on either the outside or the inside surface.,26,Melt

16、 spinning,Hot polymer melt extruded from an appropriate die. Cooled and solidified in air prior to immersion in a quench tank. Denser and lower fluxes than solution-spun fibers. Used the polymer that not soluble in convenient solvents and are difficult to form by wet spinning. Used in high-pressure

17、reverse osmosis and gas separation applications,27,Preparation method Casting solution Sprinkler structure Spinning temperature Spinning and air stream speed,Effect of hollow fiber membrane performance:,The fluid of feed and permeate side has favorable flow state, e. g. no concentration polarization

18、, no back-mixing, favorable sealing, et. al. Higher membrane packing density (area of membrane per unit volume in membrane module). Low operation and manufacture cost. Adaption of operating conditions, safety and reliability, easy maintenance, et. al.,The requirement for membrane module,The characte

19、ristics of Plate-and-Frame Modules,First designed and exploited using traditional filter press as a model. Higher manufacture cost. Extremely strict requirement for sealing. Less application, mainly applied in special process, such as electrodialysis, pervaporation and ultrafiltration, reverse osmos

20、is in a small scale.,The characteristics of tubular modules,Very low membrane packing density. Higher manufacture cost. Replaced by spiral-wound modules and hollow fiber modules Better flow state of fluids, anti-fouling ability, still applied in some processes of ultrafiltration and nanofiltration,O

21、ne type of the tubular modules. There is no supporting materials in it, but self-support. The hollow fiber membrane is divided into two structures.1)一端開口一端封閉2)兩端都開口,Hollow fiber modules,Main factors considered for selecting membrane module,Manufacture cost Membrane packing density Anti-fouling abili

22、ty The limitation of membrane materials Suitability for special operating conditions,Main characteristics of various types of membrane module,34,Crystal Properties 1、純度 Purity (或生化活性指標(biāo)、效價、吸光值、澄清度) 2、超分子結(jié)構(gòu)(Supramolecularstructure) 的要求： 晶型 Crystal Shape(如晶系、晶格常數(shù)) 晶習(xí) Crystal Habit (晶形-即外觀形狀，如片狀、針狀、棒狀或晶

23、粒狀) 3、粒度分布 Crystal Size Distribution, CSD（堆密度或比容等）,一、結(jié)晶,35,結(jié)晶的基本過程 任何結(jié)晶過程發(fā)生的基本（必須）條件： 過飽和度 Supersaturate degree 決定過程的進(jìn)行速率 決定著什么過程發(fā)生 結(jié)晶過程的基本階段： 過飽和度產(chǎn)生 晶體的成核 Nucleation 晶體的成長 Growth,一、結(jié)晶,36,晶體成核（自發(fā)出現(xiàn)一個新相） 第一階段是形成過飽和溶液，體系處于非平衡狀態(tài)。 在下一階段（成核），溶解在溶液中的分子開始聚集（濃度推動） ，最終形成可以作為結(jié)晶中心的晶核。 晶核可以被界定為一個新相能夠獨(dú)立存在的最小粒度晶體

24、。,一、結(jié)晶,37,晶體成核 初級成核 存在臨界過飽和度 二次成核 機(jī)理復(fù)雜,均 相 非均相,流體剪應(yīng)力 磨損 接觸,一、結(jié)晶,Primary nucleation,secondary nucleation,homogeneous,heterogeneous,38,晶體生長 成長階段，緊接在成核之后，由兩個步驟組成的： 溶質(zhì)擴(kuò)散：待結(jié)晶的溶質(zhì)通過擴(kuò)散穿過靠近晶體表面的靜置液層，從溶液中轉(zhuǎn)移到晶體表面的質(zhì)量傳遞過程。 表面反應(yīng)：到達(dá)晶體表面的溶質(zhì)在濃度差的推動下進(jìn)入晶面的表面反應(yīng)過程，使晶體長大。,一、結(jié)晶,39,膜結(jié)晶VS 溶液結(jié)晶 （MCr）（Evaporation ，Anti-solven

25、t Crystallization）,溫度極化現(xiàn)象不如膜蒸餾明顯（操作溫度低30-40C ） 膜結(jié)晶過程可采用反滲透膜濃縮溶液，進(jìn)一步降低所需溫度。 生產(chǎn)時間長，膜材料熱阻有待降低（Both）。,操作溫度較低，過程溫和可控，晶體純度高，易于進(jìn)行多晶型選擇； 目前的材料跨膜阻力仍較大，跨膜通量受限制，操作時間、濃縮時間較長，僅適于對濃溶液（近飽和態(tài)）操作。 需注意晶體在膜表面快速生長，堵孔后傳質(zhì)效率驟降。,膜結(jié)晶VS 膜蒸餾 （MCr） （MD）,四、研究進(jìn)展,6.1 Introduction,Electrodialysis process is an electro -chemical sep

26、aration process with charged membrane. Ion in the solution gets through the membrane by the driving force of the electric potential difference, being separated from the solvent and no charged constituents. This progress is called electrodialysis。,40,6.2 Basic principles of electrodialysis,Cation tra

27、nsfer membrane and Anion transfer membrane are placed between two electrodes alternately. Cation transfer membrane choose cation to pass through, Anion transfer membrane choose anion. Ions with opposite charge of membrane passing through the membrane calls the counterion migration。,41,From the analy

28、sis above, the three basic conditions for Electrodialysis process are direct current electric field, Ion-selective membrane and the ion-containing solution to deal with.,42,Ion-exchange membrane is also known as ion-selective transmission membrane. It is the membrane with ion-exchange group, made of

29、 polymer material, and gradually develops with the research of Symmetric membrane. The permselectivity is mainly due to the porosity of the membrane and effects of the ionic groups on the membrane. The membrane is the key component of the electrodialyzer.,43,44,GOOD ELECTRODIALYSIS MEMBRANE high per

30、mselectivity for ions（離子選擇透過性） small amount of electrolyte dialysis（電解質(zhì)滲析量） small amount of penetration of water （滲水量） low resistance（膜電阻） high mechanical strength（機(jī)械強(qiáng)度） homogeneous structure low cost.,A number of process discussions in the following,Brackish water desalination Salt production Water

31、 dissociation Other industrial applications of electrodialysis process,45,Advantages: No phase change Simple device Less land occupation Lower energy consumption,Applications: Desalination of Seawater and brackish water Concentration in food and medical industry Ultrapure water treatment Boiler wate

32、r softening Municipal wastewater treatment Microorganism, bacteria and virus control,RO,Concentration polarization has a series of negative influences on RO process: 1. Increasing the solute permeability, decreasing the purity of product water; 2. Increasing the osmotic pressure on the high-pressure

33、 side of the membrane, reducing the driving force of the RO process; 3. Forming precipitate on the high-pressure side; 4. The real operating pressure is several times higher than the calculated osmotic pressure.,48,微濾膜多為對稱膜（symmetric membranes） 微濾膜孔徑范圍：0.0510m； 微濾膜厚：10150 m 微濾膜分離機(jī)理：篩分機(jī)理 微濾過程推動力：壓力差：

34、0.10.3MPa 微濾膜的種類： 1、陶瓷膜：Al2O3, ZrO2, TiO2 2、多孔玻璃：SO2 3、多孔金屬：不銹鋼 4、聚合物膜：PVDF、PTFE、PP、PES,微濾,在穩(wěn)定狀態(tài)下，被脫除（截留）組分濃度分布和易滲透組分的濃度分布情況。,（a）截留組分的濃度分布 （salt in desalination of water by reverse osmosis),（b）易滲透組分的濃度分布 （water in dehydration of ethanol by pervaporation),Impact of Concentration Polarization inevitable！,K傳質(zhì)系數(shù)； J膜通量,增加湍流，減小邊界層厚度以減小濃差極化,膜通量加大，濃差極化加大,膜濃縮加大，濃差極化加大,溶質(zhì)擴(kuò)散系數(shù)增大，濃差極化減少,湍 流 強(qiáng) 化 器,Flow dynamics around the spacer netting often used to promote turbulence in a membrane module and reduce concentration polarization,Water recovery and advanced treatment Oily wastewater Wa