We have a stripper installed used for treatment of process condensate. Stripper is equipped with valve trays with feed entering at 20 tray and some of the stripping steam exiting from 21st tray. Total of 26 trays are installed in the column.
This system has a chronic history of high quantity of over head condensate due to which we have to keep open the drains of pump installed at outlet of overhead condensate vessel to maintain the level with in the stripper.
Steam entering in the stripper in design was at 3.5 kg/cm2 (Saturated conditions) but due to higher loads currently it is at 5.6 kg/cm2 (Saturated Condition). We have desuperheated the steam by DMW injection and apparently have recovered around 50 % of water which was being drained earlier.
Problem is that now when we increase steam flow to stripper, level in the stripper starts increasing and column gets pressurize due to which we have to decrease the flow of steam and are unable to recover 30 % of drained condensate.
Kindly assist that what is the possible phenomenon happening with in the stripper?