Weir-through liquid distributors

Several distributor types are available trough, orifice-rise, and perforated pipe. Examples of these types are shown in Fig. 14-64. The trough distributor provides good distribution under widely varying flow rates of gas and liquid. The liquid may flow through simple V-notch weirs, or it may flow throu tubes that extend from the troughs to near the upper level of the packing. Some deposition of solids can be accommodated. 

Weir distributors are prone to out-of-levelness more than any other distributor because the flow rate through a triangular notch is proportional to the liquid head raised to the power of 2.5 (flow rate through an orifice is only proportional to the liquid head raised to the 0.5 power). With weir distributors, an out-of-levelness of 1 or 2 in is sufficient to cause severe maldistribution (237, 436). One case was reported (436) in which a distributor in a 40-ft tower was installed to a level tolerance of Vie in to avoid this problem. Adjustable leveling screws are often provided and should always be specified with this distributor to enable an in situ level adjustment. The problem is most severe at low liquid rates and tumed-down conditions. 

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