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I am looking to increase reboiling capacity for a column which already has four parallel thermosyphone reboilers. However, there is a space constraint for a new reboiler and also, since there are four reboilers, replacing each with high capacity could be a costly affair. Hence, i am looking for some alternative. Is it feasible to operate a column with four existing thermosyphoe reboilers plus a new forced circulation reboiler in parallel to existing thermosyphone which can be located at some distance from column and hence, there won't be issue of space constraint? could there be any operating difficulties because i have never seen this type of arrangement?
 
Answers
22/10/2014 A: Nagesh Bejgam, Reliance Industries Limited, nagesh.bejgam@ril.com
Just a small addition. Please ensure that the forced thermosyphon flow is not so large that the available static head for other four thermosyphon reboilers is reduced (lower circulation rate will yield high vapor fractions and same can be a concern if it is a fouling service, also check for flow regime at the reboiler return line).
05/04/2013 A: keith bowers, B and B Consulting, kebowers47@gmail.com
In addition to Mr Ragsdale's guidance, I suggest the following:
1) add nozzle and draw tray modifications to the column such that the new draw will not impact the existing thermo-siphon draw. Attention to hydraulics is essential. Get them right or weep a lot.
2) be sure the new return line is free draining and will not impinge on or disrupt the existing return line hydraulics.
05/04/2013 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
It should work well. Avoid pocketing the 2-phase flow line from the reboiler to the column. Design for less than 40% vaporization per pass.