Top and Bottom Level Control Combinations

Considerable controversy has existed on the question of whether to have the condensate receiver level adjust the r ux flow or the top-product flow. One well-known author argues strongly for the former. Controversy also exists as to whether it is better to have column-base level control bottom-product flow or the reboiler heating mediiun, usually steam. Another expert recommends the second. It is probably apparent that we cannot follow both reccnimendations at least one of the two levels must control a diawofir flow. 

Tliere are many columns operating today with condensate receiver level controlling reflux and base level controlling bottcHn-product flow. There are other columns in which condoisate receiver level adjusts top-product flow while base level manipulates steam flow. How do we choose between them, assuming that we cannot, for some reason, have both levels adjust drawoff flows  

It seems to us that it is largely a matter of convenience. In a supofoactionator, for example, the reflux flow may be ten or more times greater than the top-product flow. Inventory in the receiver may be regulated a little more readily by manipulation of the large flow than of the sm one. This does not mean that level control via the small flow is either impossible or impractical. It does 

Material balance signal flow diagram—vapor sidestream drawoff 

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