The slab column is an extremely widely used gas-liquid mass transfer device consisting of a generally cylindrical casing and a number of trays arranged horizontally at a certain distance. When the plate column is working normally, the liquid passes through the trays from top to bottom and is discharged from the bottom of the column under the action of gravity; the gas is pushed by the pressure difference, and the openings uniformly distributed on the tray pass through from bottom to top. After the layer tray is discharged from the top of the column, a certain liquid is stored on each tray. When the gas passes through the liquid layer on the plate, the two phases are in contact with each other for mass transfer.

There are many types of plate columns, which can be classified as follows:

1 According to the tray structure, there are blister sheets, sieve plates, floating valve plates, mesh plates, tongue plates and the like. The earliest applications in history were blister columns and sieve tray columns. Around the 1950s, valve trays were developed. The most widely used are sieve rice and valve trays, and other types of trays are also used. Improvements in some new trays or conventional trays are also being developed and researched.

2 According to the flow pattern of gas-liquid two-phase, there are cross-flow trays and counter-flow trays, or there are downcomer trays and no downcomer trays. There are a wide range of downcomer trays, which have high mass transfer efficiency and wide operating range; counterflow trays without downcomers are also often referred to as through-flow trays, both gas and liquid phases are The tunnel on the tray passes. The tray structure is simple, and the entire tray area is utilized more fully. Commonly used are through-flow sieve plates, through-flow grid plates, through-flow corrugated plates and the like.

3 According to the liquid flow type, there are single manifold, double manifold, U-shaped manifold and other manifolds (such as quadruple, stepped, toroidal, etc.).

The single-flow tray is the most widely used, and its structure is simple, and the liquid flow stroke is long, which is beneficial to improve the efficiency of the tray. However, when the column diameter or liquid volume is too large, the liquid surface gradient on the tray will be large, resulting in uneven gas-liquid distribution or overloading of the downcomer, which will affect the efficiency and normal operation of the tray.

The double-flow tray should be used for large column diameter and large liquid flow. At this time, the liquid split is two strands, which can reduce the flow intensity and downcomer load of the weir, and also reduce the tray. The liquid level gradient on it. However, the downcomers of the trays should be placed in the middle or on both sides of the trays, which occupy more of the mass transfer area of the trays.

The inlet and outlet ports of the U-shaped manifold are placed on the same side of the tray. A separator above the liquid layer is placed therebetween. The flow is U-shaped to control the flow, thereby extending the flow stroke. This type of plate is used in small diameter columns and low liquid volumes.

The four-flow, stepped manifold is suitable for larger diameter columns and large liquid volumes.