電子教案與課件：《化工專業(yè)英語》Unit13

1、Unit 13 Membrane Separation TechnologiesHang XuHenan University of Science and TechnologyThere are five types of membrane processes, which are commonly used in water and wastewater treatment: electrodialysis, microfiltration, ultrafiltration, nanofiltration and reverse osmosis and . 電滲析、微濾、超濾、納濾和反滲透

2、是水處理和廢水處理中常用的五種膜過程。Through these processes dissolved substances or finely dispersed particles can be separated from liquids.通過這些過程，溶解的物質(zhì)或細微分散的顆?？梢詮囊后w中分離出來。 All five technologies rely on membrane transport, the passage of solutes or solvents through thin, porous polymeric membranes.所有這些技術(shù)都依賴于膜輸送，即溶質(zhì)或

3、溶劑通過薄而多孔的聚合物膜。A membrane is defined as an intervening phase separating two phases forming an active or passive barrier to the transport of matter. 膜被定義為分隔兩相形成主動或被動屏障以進行物質(zhì)運輸?shù)慕槿胂?。Membrane processes can be operated as dead-end filtration and cross-flow filtration.膜過程可以作為隔板過濾和錯流過濾。 Dead-end filtration r

4、efers to filtration at one end. A problem with these systems is frequent membrane clogging. 靜濾指的是一端過濾。這些系統(tǒng)的一個問題是頻繁的膜堵塞。Cross-flow filtration overcomes the problem of membrane clogging and is widely used in water and wastewater treatment.錯流過濾技術(shù)克服了膜堵塞問題，廣泛應(yīng)用于水處理和廢水處理。The membrane itself is a polymeric

5、 coating or extrusion with inverted conical shaped pores. 膜本身是聚合物涂層或具有倒錐形孔的擠出物。Membrane filters do not plug because the pore diameter is smaller at the top, which is the point of contact with the wastewater.膜過濾器不堵塞，因為在頂部的孔徑較小，這是與廢水的接觸點。 Material passing through the membrane passes unimpeded through

6、the membrane structure, therefore eliminating accumulation of material within the filter.材料通過薄膜不受阻礙地通過膜結(jié)構(gòu)，因此消除了材料在過濾器內(nèi)的積累。 Wastewater is pumped across the membrane surface at high flow rates.廢水以高流速被泵送到膜表面。This parallel fluid flow eliminates the cake-like build-up typical of conventional filters such

7、 as bags and cartridges which must be frequently replaced. 這種平行的流體流動消除了傳統(tǒng)過濾器典型的類似于錐形的積累，例如必須經(jīng)常更換的袋子和墨盒。Some wastewater contaminants slowly accumulate on the membrane surface, forming a thin film, during normal operating conditions. 在正常操作條件下，一些廢水污染物會慢慢積聚在膜表面，形成薄膜。This fouling process is normal and ca

8、uses the filtration rate to slowly decrease with time. 這種結(jié)垢過程是正常的，導致過濾速率隨時間緩慢下降。When membranes no longer produce clean water at the desired rate they are cleaned in place with soap and water and returned to service. 當膜不再以理想的速度產(chǎn)生清潔水時，它們就用肥皂和水進行清洗，然后重新投入使用。Membranes can be repeatedly cleaned for years

9、 of productive, dependable service prior to replacement.細胞膜可以進行多年的清潔工作，可靠的先決條件是更換。Most of these processes are often times used with chemical mechanical polishing (CMP), which is fast becoming the established technology for planarizing multi-level devices. 這些工藝中的大部分常常用于化學機械拋光(CMP) ，這種拋光技術(shù)為計劃中的多級裝置奠定了

10、基礎(chǔ)。This process requires large quantities of ultra pure water for rinsing slurry particles off the polished wafers. 這個過程需要大量的超純凈水來沖洗拋光晶圓片上的吸漿顆粒。Treatment by this method is generally needed in order to maintain an acceptable level of total suspended solids (TSS) in industrial wastewater effluent. 一般而

11、言，要維持工業(yè)廢水的可接受總懸浮固體水平，便需以這種方法處理。With large quantities of particles in the CMP wastewater stream, cross-flow filtration is the most economical method for TSS removal.由于CMP 廢水中含有大量顆粒，橫流過濾是去除 ss 最經(jīng)濟的方法。Eletcrodialysis電透析The principle of electrodialysis (ED) is that the potential gradient will allow char

12、ged molecules to gain a higher diffusion rate in a given medium.電滲析的原理是電位梯度使得帶電分子在給定介質(zhì)中獲得更大的擴散速率。 When a direct current is transmitted through a saline solution, the cations migrate toward the negative terminal, or cathode, and the anions toward the positive terminal, the anode.當直流電流通過鹽水溶液傳輸時，陽離子朝向負

13、極端或陰極遷移，而陰離子朝向正極端，即陽極遷移。By adjusting the potential between the terminals or plates, the electric current and, therefore, the flow of ions transported between the plates can be varied.通過調(diào)節(jié)端子或板之間的電位，可以改變在板之間傳輸?shù)碾娏饕约耙虼穗x子流的流動。Ultrafitration超濾 Suspended materials and macromolecules can be separated from a

14、 waste stream using a membrane and pressure differential, called ultrafitration (UF). 懸浮物和大分子可以從廢水中分離出來，使用膜和壓差，稱為超濾(uf)。This method uses a lower pressure differential than reverse osmosis and doesnt rely on overcoming osmotic effects.這種方法使用較低的壓差比反滲透，并不依賴于克服滲透影響。 It is useful for dilute solutions of

15、large polymerized macromolecules where the separation is roughly proportional to the pore size in the membrane selected.它適用于大型聚合大分子的稀溶液，其分離大致上與所選膜的孔徑成正比。Ultrafiltration membranes are commercially fabricated in sheet, capillary and tubular forms. 超濾膜在商業(yè)上以片狀、毛細管和管狀的形式制造。The liquid to be filtered is fo

16、rced into the assemblage and dilute permeate passes perpendicularly through the membrane while concentrate passes out the end of the media.待過濾的液體被擠入裝配體中，稀釋滲透垂直通過膜，濃縮液則從介質(zhì)端流出。 This technology is useful for the recovery and recycle of suspended solids and macromolecules. 這項技術(shù)有助回收和循環(huán)懸浮固體和大分子。This techn

17、ology is useful for the recovery and recycle of suspended solids and macromolecules. 這項技術(shù)有助回收和循環(huán)懸浮固體和大分子。Ultrafiltration equipment are combined with other unit operations. 超濾設(shè)備與其他單元操作相結(jié)合。The unique combination of unit operations depends on the wastewater characteristics and desired effluent quality,

18、 and cost considerations.單位行動的獨特組合取決于廢水的特性和期望的污水水質(zhì)，以及成本考慮。Microfiltration微濾膜In the case of microfiltration (MF), a more porous membrane is used than in the other membrane separation technologies, thus yielding a relatively higher flux. 在微濾的情況下，微孔膜比其他膜分離技術(shù)具有更多的孔隙，從而產(chǎn)生較高的通量。It is mainly useful in remo

19、ving turbid causing materials and can replace conventional granular filtration processes.主要用于去除造成混濁的物質(zhì)，可替代傳統(tǒng)的顆粒過濾工藝。 There have been only a few studies have evaluated membrane microfiltration of secondary wastewater effluent.目前國內(nèi)外對二級出水膜微濾技術(shù)的研究還很少。Microfiltration membranes might be used to achieve ve

20、ry low turbid effluents with very little variance in treated water quality.微濾膜可以用于處理低濁度的廢水，處理后的水質(zhì)變化很小。 Because bacteria and many other microorganisms are also removed, such membrane disinfection might avoid the need for chlorine and subsequent dechlorination.由于細菌和許多其他微生物也被除去，這種膜消毒可以避免對氯的需要和隨后的脫氯。 Me

21、tal salts of iron or aluminum may also be added to enhance membrane performance.還可以添加鐵或鋁的金屬鹽以提高膜的性能。Nanofiltration納濾膜Nanofiltration (NF) membrane process are receiving considerably more attention since they are efficient at removing the trihalomethanes (THM) and haloacetic acids (HAA). 由于納濾膜在去除三鹵甲烷(

22、THM)和鹵乙酸(HAA)方面具有很高的效率，因此納濾膜過程正受到越來越多的關(guān)注。NF systems usually operate in three stage system. NF系統(tǒng)通常在三級系統(tǒng)中運行。The first stage consists of three pressure vessels, which usually contain four to eight membrane elements; the second stage has two pressure vessels; and the final stage has one.第一級由三個壓力容器組成，通常包

23、含四到八個膜元件; 第二級有兩個壓力容器; 最后一級有一個。 In full scale plants, elements are approximately 1,000mm long and have a diameter of 200 mm.在大型植物中，元素大約1000毫米長，直徑200毫米。 Permeation is collected from each pressure vessel.從每個壓力容器收集滲透。The concentrate from the first stage serves as the feed to the second and concentrate f

24、rom the seconds tage serves as the feed to the third.從第一級到第二級的集中作為供給，從第二級到集中作為供給第三級。 Consequently, each successive stage of the array increases the total system recovery.因此，數(shù)組的每個連續(xù)階段都增加了總的系統(tǒng)恢復。Reverse Osmosis反滲透Reverse osmosis (RO) is a means for separating dissolved solids from water molecules in a

25、queous solutions.反滲透是一種從水溶液中分離出溶解固體的方法。 When pure water and a salt solution are introduced on opposite sides of a semipermeable membrane in a vented container, the pure water diffuses through the membrane and dilutes the salt solution.當將純水和鹽溶液引入通風容器中的半透膜的相對側(cè)面上時，純水通過膜擴散并稀釋鹽溶液。At equilibrium, the liqu

26、id level on the saline water side of the membrane will be above that on the freshwater side; this process is known as osmosis and is depicted in Figure 1.在平衡時，膜的鹽水側(cè)的液面將高于淡水一側(cè)，這個過程稱為滲透，如圖1所示。左邊的視圖說明滲透的開始，中心視圖呈現(xiàn)平衡條件。 The effective driving force responsible for the flow is osmotic pressure. 負責流動的有效驅(qū)動力是

27、滲透壓。By applying pressure to the saline water, the flow process through the membrane can be reversed. 該壓力的大小取決于膜特性、水溫、鹽溶液的性質(zhì)和濃度。When the applied pressure on the salt solution is greater than the osmotic pressure, fresh water diffuses in the opposite direction through the membrane and pure solvent is extracted from the mixed solution; this process is termed reverse osmosis (RO).當對鹽溶液施加的壓力大于滲透壓時，淡水沿相反方向通過