Valve trays
浮阀塔板
In valve trays,
perforations are covered by liftable caps. Vapour flows lifts the
caps, thus self creating a flow area for the passage of vapour. The
lifting cap directs the vapour to flow horizontally into the
liquid, thus providing better mixing than is possible in sieve
trays.
在浮阀塔板中，塔板孔上覆盖有可掀式泡罩。蒸气通过时，泡罩被掀开，从而为蒸气创造流动通道。被掀起的泡罩将蒸气水平引入液层，从而提供比筛板塔盘更佳的汽液混合效果。
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Sieve trays
筛板塔盘
Sieve trays are simply
metal plates with holes in them. Vapour passes straight upward
through the liquid on the plate. The arrangement, number and size
of the holes are design parameters.
筛板塔盘就是简单的带孔金属板。蒸气上升并直接通过塔板上的液层。设计参数包括孔的排列、数量和尺寸。
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Because
of their efficiency, wide operating range, ease of maintenance and
cost factors, sieve and valve trays have replaced the once highly
thought of bubble cap trays in many applications.
由于效率高、操作范围广、易于维护且成本低，筛板塔盘和浮阀塔板已经取代曾经广受欢迎的泡罩塔板，并且被应用在诸多行业中。
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Liquid
and Vapour Flows in a Tray Column
塔板塔中的气液流
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The next
few figures show the direction of vapour and liquid flow across a
tray, and across a column.
下列图片显示经过塔板和精馏塔内的气液流方向。
Each tray has 2 conduits,
one on each side, called ‘downcomers’. Liquid falls
through the downcomers by gravity from one tray to the one below
it. The flow across each
plate is shown in the above diagram on the right.
每个塔板都有两个导管，分别位于塔板两侧，被称为“降液管”。液体由于重力沿降液管从一个塔板流向下一个塔板。
A weir on
the tray ensures that there is always some liquid
(holdup) on the tray and is designed such that the the
holdup is at a suitable height, e.g. such that the bubble caps are
covered by liquid.
塔板上的溢流堰确保塔板上始终有一定量的液体（持液量），且液体高度足够浸没泡罩。
Being lighter, vapour
flows up the column and is forced to pass through the liquid, via
the openings on each tray. The area allowed for the passage of
vapour on each tray is called the active tray area.
由于质量较轻，蒸气沿塔上升，并通过每个塔板上的孔穿过液层。塔板上允许蒸气经过的区域称作有效塔板区。
As the hotter vapour
passes through the liquid on the tray above, it transfers heat to
the liquid. In doing so, some of the vapour condenses adding to the
liquid on the tray. The condensate, however, is richer in the less
volatile components than is in the vapour. Additionally, because of
the heat input from the vapour, the liquid on the tray boils,
generating more vapour. This vapour, which moves up to the next
tray in the column, is richer in the more volatile components. This
continuous contacting between vapour and liquid occurs on each tray
in the column and brings about the separation between low boiling
point components and those with higher boiling points.
由于蒸气较热，所以当通过上方塔板的液层时，蒸气将热量传递给液体，从而使一部分蒸气冷凝，变成液体并加入塔板上的液层。然而与蒸气相比，冷凝液中含有更多不易挥发组分。此外，由于获得来自蒸气的热量，塔板上的液体沸腾，生成更多蒸气。该蒸气含有更多易挥发组分，并沿塔向上层塔板上升。在精馏塔内，每个塔板上都在不断进行上述气液接触，并由此产生低沸点组分与高沸点组分的分离。
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Packings
填料
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There is
a clear trend to improve separations by supplementing the use of
trays by additions of packings. Packings are passive devices that
are designed to increase the interfacial area for vapour-liquid
contact. The following pictures show 3 different types of
packings.
为了提高分离效率，人们在塔板的基础上越来越多地采用填料作为补充。填料为被动元件，用于提高气液接触界面面积。下列图片显示了三种不同填料。
These strangely shaped
pieces are supposed to impart good vapour-liquid contact when a
particular type is placed together in numbers, without causing
excessive pressure-drop across a packed section. This is important
because a high pressure drop would mean that more energy is
required to drive the vapour up the distillation column.
这些填料看起来形状怪异，但是当同一种填料大量排列在一起时，便可以提高气液接触效率，并且不会引起填料区域压力大幅度下降。这一点很重要，因为如果压力下降太大，就意味着需要更多能量来推动蒸气上升。
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Packings versus Trays
填料vs 塔板
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A tray
column that is facing throughput problems may be de-bottlenecked by
replacing a section of trays with packings. This is because:
如果塔板塔存在物料通过问题，那么可以用填料代替一部分塔板来解决问题，这是因为：
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packings
provide extra inter-facial area for liquid-vapour contact
填料为气液接触提供更多界面面积
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efficiency of separation is increased for the same column
height 在相同塔高下，分离效率提高
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packed
columns are shorter than trayed columns
填料塔比塔板塔高度低
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Packed
columns are called continuous-contact columns while
trayed columns are called staged-contact columns
because of the manner in which vapour and liquid are
contacted.
由于气液接触方式不同，填料塔被称作连续接触塔，而塔板塔则被称作阶段接触塔。
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