Q & A > Question Details
In our Propylene Recovery Unit (PRU) why is reflux drum mounted above the condenser? It means condenser on ground floor and reflux drum above the condenser, but other distillation column generally condenser on top and reflux drum below the condenser.
11/05/2018 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
Or, if this is the propylene column, it may have a heat pump. In that case, the overhead vapor is compressed and the hot compressor discharge provides heat to one of the reboilers. The remainder of the vapor is condensed, and that condenser can be grade mounted or even with the reboiler.
10/05/2018 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
It is called a Flooded Condenser, a method of column pressure control. The method works well if properly designed. There can be no non-condensables in the overhead vapor. Installation is comparatively low due to the condenser being grade mounted.
10/05/2018 A: Peter Marsh, XBP Refining Consultants Ltd, peter.marsh@xbprefining.co.uk
For water-cooled partial condenser systems, the condenser is often located below the reflux drum to minimise capital cost, facilitate condenser maintenance and ensure adequate cooling water supply pressure at the tubeside inlet elevation. The condenser outlet line has to be carefully sized to avoid slug flow - this may constrain turndown operating range. The process-side pressure drop across this type of condenser is a little higher than that for a condenser mounted above the reflux drum but the difference is marginal in the context of typical PRU operating pressures.