化学工程与工艺专业英语Unit 15 Reading Ion Exchange_通信工程专业英语unit
化学工程与工艺专业英语Unit 15 Reading Ion Exchange由刀豆文库小编整理，希望给你工作、学习、生活带来方便，猜你可能喜欢“通信工程专业英语unit”。
Unit 15 Reading
Ion Exchange Ion 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 use, to recover components from an aqueous effluentbefore it is discharged or recirculated.Ion exchange can be manufactured which catalyze specific reactions or which are suitable to use for chromatographic separations.离子交换本身作为一个单元操作，常与吸附或色谱法有相同的理论，但离子交换在自己的特殊领域有着很多应用。它的最古老和最持久的应用是治疗，在工业使用前软化或生产去离子水，在废水排放或循环前将其处理。离子交换可以制造催化特定反应催化剂或适合用于色谱分离。
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, the 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 neceity of maintaining electroneutrality in both phase.现阶段主流的观点是，离子交换是固定相之间同等数量的类似的带电离子的交换，这个固定相可能是晶格、凝胶或周围液体。如果交换离子带正电荷,称为阳离子交换；如果交换离子带负电荷,则称为阴离子交换。交换器和液体之间的离子扩散的速度不仅取决于两个固定相的离子浓度，还取决去两个固定相保持电中性的必要性。
Ion exchange proce 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 some 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.离子交换的运作过程是用合成树脂中移动性较好氢离子和氢氧根离子取代液体中不希望存在的某些离子。最终，这些树脂达到交换饱和状态，并可以通过与少量高浓度离子的接触再生。树脂可以制作成对某些离子有选择性的亲和力。
Commercial columns range from up to 6 m dia and bed heights from 1 to 6 m, most commonly 1~3 m.Freeboard of 50％~100％ is provided to accommodate bed expansion when regenerant flow is upward.The liquid must be distributed and withdrawn uniformly over the cro section.Perforated spiders are suitable.The usual support for the bed of resin is a bed of gravel or layers of ceramic balls of graded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 material 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.商业离子交换柱范围从高达6米直径和高达1到6米的交换床，最常用的净高1 ~ 3米的交换床。净空50% ~ 100%提供容纳床再生剂流量时向上扩展。液体必须均匀地分布在横截面上，穿孔蜘蛛式结构是理想的液体分布结构。通常支撑树脂床的是一张砾石床或一层层陶瓷球的床，这些球有时被放置在床上的顶部，以帮助分配或防止顶部水平的干扰。由于材料的特定体积可以改变50%或更多的水吸收和离子交换的结果，材料必须位于远高于新鲜树脂的初始电荷水平
If the proposed proce 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 scaled 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 will establish proce flow rates, regenerant quantities and flow rates, rinsing operations, and even deterioration of performance with repeated cycles.如果目标工程是类似于已知的商业技术，一个新的设计可以有信心的完成。否则，必须进行实验室工作。专家称，交换柱上直径2.5厘米和1米床深度测试可以安全地规模商业直径。同等深度的交换床，实验室的研究成果往往比实际工业单元操作更好,这是由于积极交流区仅占小比例的床层高度与柱高1米的测试可以可靠地扩大规模。实验室的工作是要建立离子交换过程中的流速、流量的数量和再生剂，清洗操作，甚至反复循环性能恶化。
Operating cycles for liquid contacting proce such as ion exchange consist of these steps: 液体接触的方法如离子交换包括这些步骤的操作周期：
(1)Proce stream flow for a proper period.(2)A rinse for recovering poibly valuable occluded proce solution.(3)A backwash to remove accumulated foreign solids from the top of the bed and poibly to reclaify the particle size distribution.(4)The flow of regenerant for a proper period.(5)Rinse to remove occluded regenerant.（1）适当期间的工艺流程。
（2）一个冲洗有回收价值物质的解决方案。（3）反冲洗以清除从床上积累的固体杂质和可能重新分类的粒度分布。
（4）一段再生流程。
（5）冲洗出去多余物质从而再生。
As complex a cyclic proce as this may demand cycle times of more than a few hours.Very high ion concentrations or high volumetric rates may require batteries of veels and automatic switching of the several streams, or continuously operating equipment.Several continuous ion exchange plants are being operated succefully.这么复杂的循环过程可能需要超过几小时的周期。非常高的离子浓度或高容积率可能需要电池和自动切换电流,或连续操作设备，这样几种连续离子交换设备正在成功运行。
1.Chromatographic Separations 1.色谱分离
Chromatographic methods of separation are distinguished by their high selectivity,that is their ability to achieve separation between components of similar physical and chemical properties.Manymixtures which are difficult to separate by other methods can be separated by chromatography.The range of materials which can be proceed covers the entire spectrum of molecular weights, from hydrogen to proteins.色谱分离方法具有高选择性, 色谱分离可以分离具有相似物理和化学性质的物质。许多其他方法难以分离的混合物可以通过色谱分离。可分离的材料范围涵盖整个光谱的分子量,从氢到蛋白质。
Chromatographic techniques have been used routinely for chemical analysis since the 1950s, and for automated analysis of proce streams in proce control(proce chromatography)since 1961.They have 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 proce.This is often called production or large-scale chromatography(or sometimes, confusingly, proce 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 materials grows.色谱技术1950年代以来经常用于化学分析,，自1961开始用于控制过程中的过程流的自动分析（过程色谱）。色谱技术也被广泛开发为快速、准确的测量的各种热力学、动力学等物理化学性质的方法。我们担心工业分离过程，这是通常被称为生产或大规模层析(或有时,令人困惑的是,过程层析)区别于其规模较小、实验室相对中制备色谱。生产色谱法对化学工程师来说是一种相对较新的可用的单元操作范围，它的使用提高了对高纯材料需求的增长。
In production chromatography the components a mixture are separated as they pa 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 diolved in a gas or liquid stream known as the mobile phase, eluent or carrier.Separation occurs because the differing distribution coefficients of the components of themixture between the stationary and mobile phases result in differing velocities of travel.在生产色谱中，当混合物穿过交换柱时，它们会被分开。这个交换柱包含一个固定相，该固定相可以是固体颗粒的填充床，也可以是用该填料浸渍的液体。混合物通过柱溶解在液体或气体中的流称为流动相，洗脱剂或载体。固定和流动相混合物的不同分配系数导致各个混合物的不同速度，所以分离才能得以进行。
Chromatography methods are claified 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.色谱方法的分类是依据流动相的固定相的使用性质。气相色谱（气相色谱）和液相色谱（液相色谱法）是指流动相的性质。
Both GC and LC may be operated in one of several 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.气相色谱法和液相色谱法都可以在几种模式中进行操作。目前用于大规模分离的主要模式是洗脱，选择性吸附或解吸，和逆流色谱法。洗脱法是最常用和最发达的技术形式。
2.Membrane Separation Proce 2.膜分离过程
Effective product separation is crucial to economic operation in the proce industries.However, certain types of materials are inherently difficult and expensive to separate.Prominent examples include: 有效的产品分离是过程工业中经济运行的关键。然而，某些类型的材料的分离是困难的和昂贵的。突出的例子包括：
(1)Finely dispersed solids, especially those which are compreible, 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 diolved salts.(3)Biological materials which are very sensitive to their physical and chemical environment.（1）
细分散的固体，尤其是可压缩的，有一个密度接近的液相的粘度高，或是凝胶状的。
（2）
低分子量，非挥发性有机物或药物和溶解的盐。
（3）
对物理化学环境非常敏感的生物材料。
The proceing of these categories of materials has become of increased importance in recent years, especially with the growth of the newer biotechnological industries and with the increasingly sophisticated nature of proceing in the food industries.When difficulties arise in the proceing 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 effective and energy efficient, though it may be slow in proce 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 interphase 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.这类材料的处理已变得日益重要，尤其是生物技术产业的发展更新和食品处理的日益复杂。当生物材料加工出现困难时，有一个很值得问的问题是自然是如何解决问题的？自然发展的解决方案可能是高效和节能的，但它的过程可能是缓慢的。自然通过膜分离生物活性物质。膜可以被定义为“相间分隔两个阶段，并有选择地控制这些相之间的材料的运输”。它是一个相间，而不是一个接口，因为它占据了一个有限的元素的空间，虽然通常是小的。人类都被一层膜-皮肤包围着，在生活的各个层面上控制物质的分离，到细菌和亚细胞组分的外层。
Since the 1960s a new technology using synthetic membranes for proce 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 capital and running costs, and modular construction.自20世纪60年代以来，材料科学家，物理化学家和化学工程师通过一个合成膜工艺的新技术使膜的工艺分离得到了迅速的发展。这样的膜分离已被广泛应用于一系列常规难于分离物质的分离。膜分离可能提供操作温度，相对较低的资本和运行成本，和模块化建设的优点。
Industrial membrane proce may be claified according to the size range of materials which they are to separate and driving force used in separation.There is always a degree of arbitrarine about such claification.The preure driven proce are microfiltration(MF), ultrafiltration(UF)and reverse osmosis(RO).These are already well-established large-scale industrial proce.For example, reverse osmosis is used world-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 10~30 per cent in paint usage, and allows recycling of the wash waters.The use of reverse osmosis and ultrafiltration in the dairy industry has led to substantial change in production techniques and the development of new types of cheeses and related products.Electrodialysis is a purely electrically driven separation proce used extensively for the desalination or concentration of brackish water.There are about 300such plants in operation.However, economics presently favor reverse osmosis rather than electrodialysisfor such separations.It may have a future role in the desalination of protein solution.The major use of dialysis is in hemodialysis of patients with renal failure, where it is most appropriate to use such a gentle technique.Hemodialysis poses many interesting problems of a chemical engineering nature, but dialysis is a relatively slow proce not only really suited to large-scale industrial separations.工业膜的过程可以根据材料的大小范围进行分类，它们是分离和驱动力分离使用的材料。工业膜的分类有一定的随意性。压力驱动的过程是微滤（MF）、超滤（UF）和反渗透（RO）。这些都是已经成熟的大型工业过程。例如，全世界约有1000个工厂应用反渗透淡化海水，这些工厂计划生产高达10000米³/天饮用水。作为进一步的例子，汽车行业的油漆厂的超滤单元是标准的做法。由此产生的从洗涤水的油漆回收可以节省10至30 %油漆的使用，并回收洗涤水。在乳品行业的反渗透和超滤的使用导致了大量的生产技术的变化和新类型的奶酪和相关产品的开发。电渗析是纯电驱动分离过程，广泛用于海水淡化，大约有300个这样的工厂在运作。然而，经济学目前喜欢逆渗透而不是这种电渗析分离。电渗析在海水淡化的蛋白质溶液可能有一个未来。透析的主要用途是在血液透析患者肾功能衰竭，它是最适当的使用的温和的技术。血液透析的化学工程设计带来了许多的问题，但透析是一个相对缓慢的过程，不适合于大规模的工业分离。
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