Table of Contents
Overview
This page goes into detail regarding the equipment used for distillation, gas absorption, and stripping, as it is all very similar. More information on the separation processes themselves can be found on their respective pages.
Trayed Columns
As specified in the name, trayed columns have multiple trays with openings that allow vapor to travel up the column and water flows down through the column contacting the vapor. The three different types of trays are sieve trays, valve trays, and bubble-cap trays which all differ based on the openings they have. Sieve trays have perforations which are simply holes in the tray. Valve trays have multiple valves caps on them that allow vapour to escapee through the sides when the cap comes off. Bubble-cap trays have multiple bubble caps that work similar to valve caps although the vapour is directed downwards before escaping. [1]
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| Examples of a) Perforation b) Valve Cap c) Bubble Cap [1] |
| Tray Type | Relative Cost | Size (in) | Efficiency | Pressure Drop | Vapor Capacity |
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| Sieve Trays | 1.0 | 1/8-1/2 | Low | Low | High |
| Valve Trays | 1.2 | 1-2 | High | Intermediate | High |
| Bubble-cap Trays | 2.0 | 3/16, 2, 4 | High | High | Low |
| Tray Specifications [1] | |||||
Packed Columns
Packed columns have multiple levels of packing, similar to the multiple trays of a trayed column, where the liquid and gas come into contact. Droplets of the liquid flow down through the sections of packing while vapor travels upward through the packing contacting the the liquid in each packed section. Packed columns can operate with either random packing or structured packing. One type of random packing includes rings and saddles. In many old packed columns, ceramic Raschig rings and Berl saddles are used although these have mostly been replaced by metal and plastic Pall rings, metal Bialecki rings, and ceramic Intalox saddles in modern packed columns. Another type of random packing is through-flow random packing. Through-flow packing can offer many advantages including a low pressure drop rate and a higher mass transfer rate making them extremely efficient. Structured packing is a much more efficient type of packing although this increased efficiency comes at a higher cost. Old structured packing was often made as metal sheets while new types of structured packing are made of plastic and metal and are much cheaper to produce. [1]
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| Random Packing [2] |
Spray Towers
Although not as popular as packed and trayed columns, spray towers can also be used. Sprayed towers consist of an empty cylindrical where the liquid sprayed through novels contacting a gas. The gas is fed through the bottom of the vessel while the liquid is fed through into nozzles which is then sprayed inside the vessel. [2]
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| Figure 5: Spray Tower [3] |
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