Description

The primary function of the packing support grids is to serve as a physical support for the tower packing plus the weight of the liquid holdup. In addition, the packing support grids must pass both the downwardly flowing liquid phase as well as the upwardly flowing gas phase to the limit of capacity of the tower packing itself. The primary function of bed limiters is to prevent expansion of the packed beds, as well as to maintain the bed top surface level. They also should prevent fluidization of the packed bed top surface. These devices are fastened to the column wall or restrained by the column internal located above it.

Support Grids & Limiters For the design of the specific grids, following points have to be considered with regard to the load of the grid:

• weight of packed bed
• liquid hold up during operation
• fouling
• pressure drop of gas flow in cases of parallel flow
• installation loads

The support grid has to be constructed in a way that it allows flowing of gases and liquids in the column as unrestricted as possible. Especially in the area between support grid and packed bed there is the danger of blocking the gas flow by an unsuitable packing support.

For the installation of a support grid, there is a support ring and – from case to case – one or more intermediate support beams necessary. Usually, it is sufficient to put the support grid on the support ring without fixing it. If, however, high gas velocities, pressures or flooding are to be expected it is necessary to fix the support grid at the support ring.