Effect of Vapor Maldistribution on Packing Efficiency

Vapor is easier to distribute than liquid, but vapor maldistributioi can also be troublesome. The effects of vapor m distribution haw been investigated far less than those of liquid maldistribution. Tb following findings have been reported  

Vapor flow throu packings tends to be uniform if the initial liq uid and vapor distributions to the packings are uniform (15,66). 

Although vapor spreads radially through the packing quite rapidly 

The packed hei t throng which a nonuniform profile persists is a function of column diameter (156). In pilot-scale columns, vapor maldistribution was found to posist for abed he t of the order of 1 ft (155,157). In large-diameter columns, this maldiattibution persists to a much greater hei t (15,152,154). In a number of 15-ft-diameter absorbers (154), vapor maldistribution persisted throu a 50-ft bed the efficiency was about balf that encountered during good vapor distribution. 

Redistribution of vapor depends on a balance between the vertical and horizontal pressure gradients (157). The horizontal pressure gradient depends on column diameter, and diminishes rapidly as column diameter increases. This explains the strong effect of diameter in item 4 above. Another important factor cited by Porter and Ali (157) is vortex formation. This can cause downward flows of vapor in the bed. Downward flows were actually measured fay Kabakov and Rozen (154) and Porter and Ali (157). 

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