Columns are regularly used to perform chemical and/or thermal separations. However, column requires some internal components to be installed in which help facilitate the separation process. In any column system, the best performance of packings is very important and it can be obtained when complemented with appropriate designed of tower distributors, collectors, supports and other column internals to get an optimum liquid-vapour distribution to the packed beds. Column internals also playing significant part for attaining greater throughput, lower pressure drops & better mass transfer efficiency.
The distributor in which it is installed above the packing beds in the columns is the key element to the packing and column efficiency. Distribution of the liquid onto the packed bed is provided by appropriate liquid distributors. To obtain an effective column and secure an intensive mass transfer between the phases, it is important to have an equal liquid distributor across the column area. The important characteristics of liquid distributor:
- low gas-side pressure drop
- low sensitivity to fouling
- low overall height
Support Grid & Hold-down Grid
Support grid is used to support the structure of tower packing bed in which it keep the packing in position. It is also used in certain column for distributing the gaseous phase. There are various type of support grid is available depending on the specific application and the column diameter. Support grids must be adapted to:
- Bed height
- Liquid holdup
- Type of packing
- Additional weight from fouling
- Design temperature for specific application
Hold-down grid are situated above the packed bed which it will hold the packed bed in position to prevent the movement or discharge of the packing. This grid is needed for some cases where packing can experience uplift because of high gas loading or sporadic pressure surges. In addition, intermixing within the column can be avoided by using the hold-down grid as it is used to separate packing of different sizes.
The collection of liquid between packed beds is frequently required. The liquid collector systems is important as it will improve cross mixing of the liquid and allow mixing of feed streams with the internal column liquid.
The liquid collector is used in the columns to achieve one or more of following purposes:
- Vapor distribution
- Liquid collection from above bed and conduction to below distributor
- Total or partial liquid draw-off