化學(xué)工程與工藝專業(yè)英語Unit15ReadingIonExchange

1、Unit 15 Reading Ion ExchangeIon exchange stands as a unit operation in its own right, often sharing theory with adsorption or chromatography but having its own special areas of application. Its oldest and most enduring application is for treatment, to soften or demineralize water before industrial u

2、se, to recover components from an aqueous effluent before it is discharged or recirculated. Ion exchange can be manufactured which catalyze specific reactions or which are suitable to use for chromatographic separations. 離子交換本身作為一個單元操作，常與吸附或色譜法有相同的理論，但離子交換在自己的特殊領(lǐng)域有著很多應(yīng)用。它的最古老和最持久的應(yīng)用是治療，在工業(yè)使用前軟化或生產(chǎn)去離

3、子水，在廢水排放或循環(huán)前將其處理。離子交換可以制造催化特定反應(yīng)催化劑或適合用于色譜分離。In the present consent, the exchange is that of equivalent numbers of similarly charged ions, between an immobile phase, which may be a crystal lattice or a gel, and a liquid surrounding the immobile phase. If the exchanging ions carry a positive charge, t

4、he ion exchange is termed cationic, and, if a negative charge, anionic. The rate at which ions diffuse between exchanger and liquid is determined not only by the concentration differences in the two phases, but also by the necessity of maintaining electroneutrality in both phase.現(xiàn)階段主流的觀點(diǎn)是，離子交換是固定相之間

5、同等數(shù)量的類似的帶電離子的交換，這個固定相可能是晶格、凝膠或周圍液體。如果交換離子帶正電荷,稱為陽離子交換；如果交換離子帶負(fù)電荷,則稱為陰離子交換。交換器和液體之間的離子擴(kuò)散的速度不僅取決于兩個固定相的離子濃度，還取決去兩個固定相保持電中性的必要性。Ion exchange process function by replacing undesirable ions of a liquid with ions such as H+ or OH- from a solid material in which the ions are sufficiently mobile, usually so

6、me synthetic resin. Eventually the resin becomes exhausted and may be regenerated by contact with a small amount of solution with a high content of the desired ion. Resins can be tailored to have selective affinities for particular kinds of ions.離子交換的運(yùn)作過程是用合成樹脂中移動性較好氫離子和氫氧根離子取代液體中不希望存在的某些離子。最終，這些樹脂達(dá)

7、到交換飽和狀態(tài)，并可以通過與少量高濃度離子的接觸再生。樹脂可以制作成對某些離子有選擇性的親和力。Commercial columns range from up to 6 m dia and bed heights from 1 to 6 m, most commonly 13 m. Freeboard of 50100 is provided to accommodate bed expansion when regenerant flow is upward. The liquid must be distributed and withdrawn uniformly over the c

8、ross section. Perforated spiders are suitable. The usual support for the bed of resin is a bed of gravel or layers of ceramic balls of graded sizes, balls sometimes are placed on top of the bed to aid in distribution or to prevent disturbance of the top level. Since the specific volume of the materi

9、al can change 50% or more as a result of water absorption and ion-ion exchange, the distributor must be located well above the initial charge level of fresh resin.商業(yè)離子交換柱范圍從高達(dá)6米直徑和高達(dá)1到6米的交換床，最常用的凈高1 3米的交換床。凈空50% 100%提供容納床再生劑流量時(shí)向上擴(kuò)展。液體必須均勻地分布在橫截面上，穿孔蜘蛛式結(jié)構(gòu)是理想的液體分布結(jié)構(gòu)。通常支撐樹脂床的是一張礫石床或一層層陶瓷球的床，這些球有時(shí)被放置在床上

10、的頂部，以幫助分配或防止頂部水平的干擾。由于材料的特定體積可以改變50%或更多的水吸收和離子交換的結(jié)果，材料必須位于遠(yuǎn)高于新鮮樹脂的初始電荷水平If the proposed process is similar to known commercial technology, a new design can be made with confidence. Otherwise laboratory work must be performed. Experts claim that tests on columns 2.5 cm dia and 1 m bed depth can be sc

11、aled up safely to commercial diameters. The laboratory work preferably is done with the same bed depth as in the commercial unit, but since the active exchange zone occupies only a small proportional to the bed height, and tests with columns 1 m high can be dependably scaled up. The laboratory work

12、will establish process flow rates, regenerant quantities and flow rates, rinsing operations, and even deterioration of performance with repeated cycles.如果目標(biāo)工程是類似于已知的商業(yè)技術(shù)，一個新的設(shè)計(jì)可以有信心的完成。否則，必須進(jìn)行實(shí)驗(yàn)室工作。專家稱，交換柱上直徑2.5厘米和1米床深度測試可以安全地規(guī)模商業(yè)直徑。同等深度的交換床，實(shí)驗(yàn)室的研究成果往往比實(shí)際工業(yè)單元操作更好,這是由于積極交流區(qū)僅占小比例的床層高度與柱高1米的測試可以可靠地?cái)U(kuò)大規(guī)模

13、。實(shí)驗(yàn)室的工作是要建立離子交換過程中的流速、流量的數(shù)量和再生劑，清洗操作，甚至反復(fù)循環(huán)性能惡化。Operating cycles for liquid contacting process such as ion exchange consist of these steps:液體接觸的方法如離子交換包括這些步驟的操作周期：(1) Process stream flow for a proper period.(2) A rinse for recovering possibly valuable occluded process solution.(3) A backwash to remo

14、ve accumulated foreign solids from the top of the bed and possibly to reclassify the particle size distribution.(4) The flow of regenerant for a proper period.(5) Rinse to remove occluded regenerant.（1） 適當(dāng)期間的工藝流程。（2） 一個沖洗有回收價(jià)值物質(zhì)的解決方案。（3） 反沖洗以清除從床上積累的固體雜質(zhì)和可能重新分類的粒度分布。（4） 一段再生流程。（5） 沖洗出去多余物質(zhì)從而再生。As co

15、mplex a cyclic process as this may demand cycle times of more than a few hours. Very high ion concentrations or high volumetric rates may require batteries of vessels and automatic switching of the several streams, or continuously operating equipment. Several continuous ion exchange plants are being

16、 operated successfully.這么復(fù)雜的循環(huán)過程可能需要超過幾小時(shí)的周期。非常高的離子濃度或高容積率可能需要電池和自動切換電流,或連續(xù)操作設(shè)備，這樣幾種連續(xù)離子交換設(shè)備正在成功運(yùn)行。1. Chromatographic Separations1. 色譜分離Chromatographic methods of separation are distinguished by their high selectivity, that is their ability to achieve separation between components of similar physica

17、l and chemical properties. Manymixtures which are difficult to separate by other methods can be separated by chromatography. The range of materials which can be processed covers the entire spectrum of molecular weights, from hydrogen t

18、o proteins.色譜分離方法具有高選擇性, 色譜分離可以分離具有相似物理和化學(xué)性質(zhì)的物質(zhì)。許多其他方法難以分離的混合物可以通過色譜分離。可分離的材料范圍涵蓋整個光譜的分子量,從氫到蛋白質(zhì)。Chromatographic techniques have been used routinely for chemical analysis since the 1950s, and for automated analysis of process streams in process control (process chromatography) since 1961. They have

19、also been extensively developed as rapid and accurate methods of measuring a great variety of thermodynamic, kinetic and other physico-chemical properties. We are concerned here with use as a commercial separation process. This is often called production or large-scale chromatography (or sometimes,

20、confusingly, process chromatography) to distinguish it from its smaller, laboratory-scale relative, preparative chromatography. Production chromatography is a relatively new entrant to the range of unit operations available to chemical engineers. Its use is increasing as the demand for high purity m

21、aterials grows.色譜技術(shù)1950年代以來經(jīng)常用于化學(xué)分析,，自1961開始用于控制過程中的過程流的自動分析（過程色譜）。色譜技術(shù)也被廣泛開發(fā)為快速、準(zhǔn)確的測量的各種熱力學(xué)、動力學(xué)等物理化學(xué)性質(zhì)的方法。我們擔(dān)心工業(yè)分離過程，這是通常被稱為生產(chǎn)或大規(guī)模層析(或有時(shí),令人困惑的是,過程層析)區(qū)別于其規(guī)模較小、實(shí)驗(yàn)室相對中制備色譜。生產(chǎn)色譜法對化學(xué)工程師來說是一種相對較新的可用的單元操作范圍，它的使用提高了對高純材料需求的增長。In production chromatography the components a mixture are separated as they pass

22、through a column. The column contains a stationary phase which may be a packed bed of solid particles or a liquid with which the packing is impregnated. The mixture is carried through the column dissolved in a gas or liquid stream known as the mobile phase, eluent or carrier. Separation occurs becau

23、se the differing distribution coefficients of the components of the mixture between the stationary and mobile phases result in differing velocities of travel.在生產(chǎn)色譜中，當(dāng)混合物穿過交換柱時(shí)，它們會被分開。這個交換柱包含一個固定相，該固定相可以是固體顆粒的填充床，也可以是用該填料浸漬的液體?；旌衔锿ㄟ^柱溶解在液體或氣體中的流稱為流動相，洗脫劑或載體。固定和流動相混合物的不同分配系數(shù)導(dǎo)致各個混合物的不同速度，所以分離才能得以進(jìn)行。Chro

24、matography methods are classified according to the nature mobile and stationary phases used. The terms gas chromatography (GC) and the liquid chromatography (LC) refer to the nature of the mobile phase.色譜方法的分類是依據(jù)流動相的固定相的使用性質(zhì)。氣相色譜（氣相色譜）和液相色譜（液相色譜法）是指流動相的性質(zhì)。Both GC and LC may be operated in one of sev

25、eral modes. The principal modes currently used for large-scale separations are elution, selective adsorption or desorption, and countercurrent chromatography. Elution is the most used and best developed form of the technique.氣相色譜法和液相色譜法都可以在幾種模式中進(jìn)行操作。目前用于大規(guī)模分離的主要模式是洗脫，選擇性吸附或解吸，和逆流色譜法。洗脫法是最常用和最發(fā)達(dá)的技術(shù)形式

26、。2. Membrane Separation Process2.膜分離過程Effective product separation is crucial to economic operation in the process industries. However, certain types of materials are inherently difficult and expensive to separate. Prominent examples include:有效的產(chǎn)品分離是過程工業(yè)中經(jīng)濟(jì)運(yùn)行的關(guān)鍵。然而，某些類型的材料的分離是困難的和昂貴的。突出的例子包括：(1) Fin

27、ely dispersed solids, especially those which are compressible, have a density close to that of the liquid phase, have high viscosity, or are gelatinous.(2) Low molecular weight, non-volatile organics or pharmaceuticals and dissolved salts.(3) Biological materials which are very sensitive to their ph

28、ysical and chemical environment.（1） 細(xì)分散的固體，尤其是可壓縮的，有一個密度接近的液相的粘度高，或是凝膠狀的。（2） 低分子量，非揮發(fā)性有機(jī)物或藥物和溶解的鹽。（3） 對物理化學(xué)環(huán)境非常敏感的生物材料。The processing of these categories of materials has become of increased importance in recent years, especi

29、ally with the growth of the newer biotechnological industries and with the increasingly sophisticated nature of processing in the food industries. When difficulties arise in t

30、he processing of materials of biological origin, there is one question which is well-worth asking-how does nature solve problem? The solution which nature has developed is likely to be both highly eff

31、ective and energy efficient, though it may be slow in process terms. Nature separates biologically active materials by means of membranes. A membrane may be defined as “an interphase separating two phases and selectively controlling the transport of materials between those phases”. It is an interpha

32、se rather than an interface because it occupies a finite, though normally small, element of space. Human beings are all surrounded by a membrane, the skin, and members control the separation of materials at all levels of life, down to the outer layers of bacteria and subcellular components.這類材料的處理已變

33、得日益重要，尤其是生物技術(shù)產(chǎn)業(yè)的發(fā)展更新和食品處理的日益復(fù)雜。當(dāng)生物材料加工出現(xiàn)困難時(shí)，有一個很值得問的問題是自然是如何解決問題的？自然發(fā)展的解決方案可能是高效和節(jié)能的，但它的過程可能是緩慢的。自然通過膜分離生物活性物質(zhì)。膜可以被定義為“相間分隔兩個階段，并有選擇地控制這些相之間的材料的運(yùn)輸”。它是一個相間，而不是一個接口，因?yàn)樗紦?jù)了一個有限的元素的空間，雖然通常是小的。人類都被一層膜-皮膚包圍著，在生活的各個層面上控制物質(zhì)的分離，到細(xì)菌和亞細(xì)胞組分的外層。Since the 1960s a new technology using synthetic membranes for proce

34、ss separations has been rapidly developed by materials scientists, physical chemists and chemical engineers. Such membrane separations have been widely applied to a range of conventionally difficult separations. They potentially offer the advantages of ambient temperature operation, relatively low c

35、apital and running costs, and modular construction.自20世紀(jì)60年代以來，材料科學(xué)家，物理化學(xué)家和化學(xué)工程師通過一個合成膜工藝的新技術(shù)使膜的工藝分離得到了迅速的發(fā)展。這樣的膜分離已被廣泛應(yīng)用于一系列常規(guī)難于分離物質(zhì)的分離。膜分離可能提供操作溫度，相對較低的資本和運(yùn)行成本，和模塊化建設(shè)的優(yōu)點(diǎn)。Industrial membrane process may be classified according to the size range of materials which they are to separate and driving fo

36、rce used in separation. There is always a degree of arbitrariness about such classification. The pressure driven process are microfiltration (MF), ultrafiltration (UF) and reverse osmosis (RO). These are already well-established large-scale industrial process. For example, reverse osmosis is used wo

37、rld-wide for the desalination of brackish water, with about 1,000 plants in operations. Plants capable of producing up to 10,000 m³/day of drinking water are planned. As a further example, it is standard practice to include an ultrafiltration unit in paint plants in the car industry. The resulting recovery of paint from wash waters can produce savings of 1030 per cent in paint usage, and allows recycling of the wash waters. The use of reverse osmosis and ultrafiltrat