Detection of Packed Column Maldistribution in the Field

Maldistribution in packed columns can be detected in the field by the following techniques 

Water testing prior to startup When possible, water can be run through the packed bed before startup, and the quantity reaching the bottom of the bed can be measured at different points. 

Temperature measurements around the circumference of the column at different vertical heights Maldistribution causes a variation in 

A surface pyrometer, often with an extension probe to penetrate through the insulation, can be used. Success with this technique was demonstrated in a couple of cases (34, 121). Temperature differences greater than 15°F are usually indicative of a maldistri-buted pattern temperature differences smaller then 5°F suggest no evidence for a maldistributed pattern. 

It is important to note that small temperature differences along the column circumference do not necessarily imply the absence of maldistribution. In column sections where temperature does not vary greatly along the column height (e.g., in sections where there is almost a pure product in the column, or in superfractionators where the boiling points of both products are close), temperatme may be insensitive to composition, and large composition differences may exist and still indicate the same temperature along the circumference. Also, when the maldistribution is between the side and center (e.g., excessive wall flow or excessive center flow), circumferential temperature measurements will be unable to detect maldistribution. 

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