化学工程与工艺专业英语unit14 reading

Plate Columns and Packed Columns

板柱和填充柱

1. Plate Columns

Cross-flow plates are the most common type of plate contactor used in distillation and absorption columns. In a cross-flow plate the liquid flows across the plate and the vapor up through the plate. The flowing liquid is transferred from plate to plate through vertical channels called “downcomers”. A pool of liquid is retained on the plate by an outlet weir.

1.板柱

十字板是蒸馏和吸收塔中使用的最常见的板式接触器类型。在一个横向流动板中，液体流过板和蒸气通过板。流动的液体从板通过垂直通道称为“容易”。通过一个出口堰在板上保留了一个液体池。

Other types of plate are used which have no downcomers (non-cross-flow plates), the liquid showering down the column through large openings in the plates (sometimes called shower plates). These, and, other proprietary non-cross-flow plates, are used for special purposes, particularly when a low-pressure drop is required.

其他类型的板用无降液管（非交叉流板），淋液下柱通过在板的大开口（有时称为淋浴板）。这些，和，其他专有的非交叉流板，用于特殊用途，特别是当一个低压降是必需的。

Three principal types of cross-flow tray are used , classified

according to the method used to contact the capor and liquid.

使用横流塔三种主要类型，根据使用的汽包和液体接触的方法分类。

(i) Sieve plate (perforated plate). This is the simplest type of cross-flow plate. The vapor passes up through perforations in the plate; and the liquid is retained on the plate by the vapor flow. There is no positive vapor liquid seal. And at low flow-rates liquid will “weep” through the holes, reducing the plate efficiency. The perforations are usually small holes, but larger holes and slots are used. These are much simpler in construction, with small holes in the tray. The liquid flows across the tray and down the segmental downcomer.

（I）筛板（多孔板）。这是最简单的一种十字流板。蒸气通过在板的穿孔；和液体的蒸气流保留在板。没有正的汽液密封。在低流速的液体会“哭”通过孔，降低了板的效率。穿孔通常是小孔，但使用更大的孔和槽孔。这些都是简单得多的建设，在托盘中的小洞。液体流经托盘下弓形降液管。

(ii) The bubble-cap plates. In which the vapor passes up through short pipes, called risers, covered by a cap with a serrated edge, or slots. The bubble-cap plate is the traditional, oldest type of cross-flow plate, and many different designs have been developed. Standard cap designs would now be specified for most applications.

The most significant feature of the bubble-cap plate is that the use of

risers ensures that a level of liquid is maintained on the tray at all vapor flow-rates.

（II）泡罩板。其中蒸气通过短的管子，称为立管，复盖的有锯齿状边缘，或槽。泡罩板是传统的，最古老的类型的横流板，和许多不同的设计已经研制出来的。现在将为大多数应用程序指定标准的盖设计。

泡罩板最显著的特征是，立管的使用使液位保持在托盘上所有的蒸汽流量。

(iii) Valve plates (floating cap plates). Valve plates are proprietary designs, they are essentially sieve plates with large-diameter holes covered by movable flaps, valve plates can operate efficiently at lower flow-rates than sieve plates: the valves closing at low vapor rates. Some very elaborate valve designs have been developed, but the simple type is satisfactory for most applications.

（iii）阀板（浮动盖板）。阀板是专有的设计，他们基本上是大孔筛板覆盖移动皮瓣，阀板能有效地运作比筛板流动率低：关闭的阀门在低蒸发率。一些非常精心设计的阀门设计已被开发，但简单的类型是令人满意的大多数应用。

Selection of Plate Type

The principal factors to consider when comparing the performance of bubble-cap, sieve and valve plate are: cost, capacity, operating range, efficiency and pressure drop.

板式选择

在比较泡沫盖、筛板和阀板性能时考虑的主要因素是：成本、容量、工作范围、效率和压降。

Cost. Bubble-cap plates are appreciably more expensive than sieve or valve plates. The relative cost will depend on the material of construction used; for mild steel the ratios, bubble-cap : valve : sieve, are approximately 3.0 : 1.5 : 1.0.

成本。泡罩板明显比筛或阀板更昂贵。相对成本将取决于所使用的材料；对于低碳钢的比率，泡沫帽：阀门：筛，约为3：1.5：1。

Capacity. There is little different in the capacity rating of the three types (the diameter of the column required for a given flow-rate); the ranking is sieve, valve, bubble-cap.

容量。有一点不同的容量等级的三种类型（所需的列的直径为一个给定的流量）；排名是筛，阀，气泡帽。

Operating range. This is the most significant factor. By operating range is meant the range of vapor and liquid rates over which the plate will operate satisfactorily (the stable operating range). Some flexibility will always be required in an operating plant to allow for changes in introduction rate, and to cover start-up and shut-down conditions. The ratio of the highest to the lowest flow rates is often referred to as the “turn-down” ratio. Bubble-cap plates have a positive liquid seal and can therefore operate efficiently at very low vapor rates.

经营范围。这是最重要的因素。按操作范围是指蒸汽和液体的范围内，该板将运行令人满意的范围（稳定的工作范围）。一些灵活性永远是经营工厂的要求允许在引进率的变化，并覆盖启动和停机条件。最高的最低流量的比率通常被称为“拒绝”的比率。泡罩板有一个正的液体密封，因此可以有效地在非常低的蒸气率。

Sieve plates rely on the flow of vapor through the holes to hold the liquid on the plate, and cannot operate at very low vapor rates. But, with good design, sieve plates can be designed to give a satisfactory operating range; typically, form 50 per cent to 120 per cent of design capacity. Valve plates are intended to give greater flexibility than sieve plates at a lower cost than bubble-caps.

筛板依靠蒸汽通过孔的流动来保持板上的液体，并不能以非常低的蒸气率操作。但是，有了良好的设计，可以设计筛板给一个令人满意的工作范围；通常情况下，形成50 %至120的设计能力%。阀板的目的是提供更大的灵活性比比泡沫板在一个较低的成本泡沫帽。

Efficiency. The Murphree efficiency of the three types of plate will be virtually the same when operating over their design flow range, and no real distinction can be made between them.

效率。这三种板Murphree效率将几乎相同的操作时，在他们的设计流量范围，并没有真正的区别他们。

Pressure drop. The pressure drop over the plates can be an important design consideration, particularly for vacuum columns. The

安装，和昂贵的。

Packed-Column Design Procedures 填充柱设计程序

The design of a packed column will involve the following steps: 填充柱的设计将涉及以下步骤： (i) Select the type and size of packing. （I）选择包装的类型和大小。

(ii) Determine the column height required for the specified separation.

（II）确定指定的分离所需的列高度。

(iii) Determine the column diameter (capacity), to handle the liquid and vapor flow rates.

（III）确定柱直径（容量），以处理液体和蒸汽的流速。 (iv) Select and design the column internal features: packing support, liquid distributor, redistributors.

（IV）选择和设计专栏内部特征：填料、液体分布器、再分布 Types of Packing 包装类型

Many diverse types of packing have been developed to satisfy these requirements . They can be divided into two broad classes:

许多不同类型的包装已被开发，以满足这些要求。他们可以分为两大类：

(i) Packings with a regular geometry: such as stacked rings, grids and proprietary structured packings.

（I）与常规的几何包装：如叠环，网格和专有规整。

(ii) Random packings: rings, saddles and proprietary shapes, which are dumped into the column and take up a random arrangement. （II）随机包装：戒指、鞍座和专有的形状，这倒进柱采取了随机安排。

Grids have an open structure and are used for high gas rates, where low pressure drop is essential; for example, in cooling towers. Random packings and structured packing elements are more commonly used in the process industries.

网格有一个开放的结构，并用于高气体率，其中低的压力降是必不可少的，例如，在冷却塔。随机包装和结构化包装元素在过程工业中更为常用。

Random packing. Raschig rings are one of the oldest specially manufactured types of random packing, and are still in general use . Pall rings are essentially Raschig rings in which opening have been made by folding strips of the surface into the ring. This increases the free area and improves the liquid distribution characteristics. Berl saddles were developed to give improved liquid distribution compared to Raschig rings. Intalox saddles can be considered to be an improved type of Berl saddle; their shape makes them easier to manufacture than Berl

saddles.

随机包装。拉西环是最古老的一个专门制造类型的随机包装，并仍在普遍使用。鲍尔环基本上是拉西环，开放已由表面折叠带到环。这增加了自由区域，并提高了液体的分布特性。贝尔鞍座来给改进的液体分布较拉西环。矩鞍可以被认为是一种改进的马鞍形式；它们的形状使它们比贝尔鞍座制造更容易。

Ring and saddle packings are available in a variety of materials : ceramics, metals, plastics and carbon. Metal and plastics (polypropylene) rings are more efficient than ceramic rings, as it is possible to make the walls thinner.

环形和鞍形填料的各种材料有：陶瓷、金属、塑料和碳。金属和塑料（聚丙烯）环比陶瓷环更有效，因为它有可能使墙壁更薄。 Raschig rings are cheaper per unit volume than Pall rings or saddles but are less efficient, and the total cost of the column will usually be higher if Raschig rings are specified. For new columns, the choice will normally be between Pall rings and Berl or Intalox saddles.

拉西环是每单位体积比鲍尔环或马鞍便宜但效率较低，且柱的总成本通常会较高，如果指定了拉西环。新的列，选择通常会在鲍尔环和贝尔或矩鞍。

The choice of material will depend on the nature of the fluids and the operating temperature. Ceramic packing will be the first choice for corrosive liquids; but ceramics are unsuitable for use with strong

alkalies. Plastic packings are attacked by some organic solvents, and can only be used up to moderate temperatures; so are unsuitable for distillation columns. Where the column operation is likely to be unstable etal rings should be specified, as ceramic packing is easily broken.

材料的选择将取决于流体的性质和工作温度。陶瓷填料将腐蚀性液体的首选；而陶瓷是不适合使用强碱性。塑料填料是由某些有机溶剂的攻击，只能使用到温度适中；所以不适合蒸馏塔。在塔的操作可能是不稳定的金属环应该指明，作为陶瓷填料容易破碎。

Structured packing. The term structured packing refers to packing elements made up from wire mesh or perforated metal sheets. The material is folded and arranged with a regular geometry, to give a high surface area with a high void fraction.

规整填料。结构包装是指由金属丝网或多孔金属板制成的包装材料。该材料被折叠并排列成具有规则的几何形状，以提供高的表面面积与高的空隙率。

Structured packing are produced by a number of manufacturers. The basic construction and performance of the various proprietary types available are similar. The advantage of structured packings over random packing is their low HETP(typically less than 0.5m) and low pressure drop (around 100Pa/m). They are being increasingly used in the following applications:

结构包装是由一些制造商生产的。各种类型的专有类型的基本结构和性能都是相似的。规整填料在填料的优点是低值（通常小于0.5m）和较低的压降（约100Pa／m）。他们正在越来越多地使用在以下应用：

(i) For difficult separations, requiring many stages: such as the separation of isotopes.

（I）为困难的分离，需要许多阶段：如分离同位素。 (ii) High vacuum distillation. （II）高真空蒸馏。

(iii) For column revamps: to increase capacity and reduce reflux ratio requirements.

（iii）柱改造：增加容量和降低回流比的要求。

The cost of structured packings per cubic meter will be significantly higher than that of random packings, but this is offset by their higher efficiency.

规整填料的每立方米的成本将显著高于随机包装，但这是以更高的效率抵消。

Selected from “Chemical Process Equipment, Stanley M. Walas, Butterworth Publishers, 1988”

选自“化工过程设备、Stanley M. Walas、巴特沃斯出版社，1988”

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