There is very limited flexibility to self adjust recirculation rates in the reboiler circuit if you have a thermosyphon reboiler. There may be slugging in the transfer line from the reboiler to the column, leading to poor product quality in the bottoms product. A simulation study may bear this out. Consider adding a recirc pump to enable forced recirculation.
Pls realise that in the case of a thermosyphon reboiler, do not try to turn down reflux rate during column turndown. The thermosyphon reboiler has limited flow turndown also and hence reflux rate must be kept constant. Keeping a constant reflux rate would help somewhat to maintain liquid traffic down the column, but in many cases, the bulk of the liquid traffic is from the fresh feed to the column.
