Grid packing, metal

In large-diameter columns, gas-injection support plates have the additional advantage of minimizing the number of midspan beams required for supporting the support plate or grid. In metallic application, alternative support t3q>es require two to three times as many support beams 2is the gas-injection plate (74). The author and others (74, 111, 166) recommend specifying gas-injection support plates whenever possible in metallic and plastic random packing applications. 

This is an open area packing with multiple layers of lattice-type panels. This grid, as described by the manufacturer s bulletin, consists of vertical, slanted, and horizontal planes of metal. The vertical strips have horizontal flanges oriented alternately right and left. Due to the random overlap, the vapor path must zig-zag through the bed. 

As an alternative to trays, especially at low volumetric liquid-to-vapor ratios, packing can be used to promote vapor-liquid contact. One approach is to dump specially shaped pieces of metal, glass, or ceramic material into the column, wherein they are supported on a grid. An example of dumped or random packing is shown in Fig. 7. 

Another topic related to the self-assembly of coordination cages in the solid state has been described by Harrison and coworkers [55]. Octaanionic cages 30a with four Ca2+ countercations form grids in the solid state and pack into porous materials resembling zeolites. The carboxylate groups on the four sides of cage 30a can bind to more than one metal ion. In particular, the calcium ions coordinate with carboxylates from two... 

Corrosion and oxidation. Due to the relatively thick metal, low specific surface area, and rugged construction of grids, their tendency to oxidize is low. Grids tend to degrade to a much lesser degree than either random or structured packings. 

The form and shape of the electrodes are tailored for the specific reactor configuration. Typical shapes include flat metal sheets, perforated or expanded metal grids, metal foams and meshes, and three-dimensional packed bed electrodes formed by stacking metal meshes, pressing catalyst powders, or by use of microporous carbon felts and cloths (three-dimensional electrodes are particularly attractive for low-current density reactions because the electrode surface per unit reactor volume can be made very large) [28]. 

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