I work in a Diesel Hydrotreater Unit. Currently the Naphtha Stabilizer of our unit has a suspected choking problem in the overhead line. The stabilizer top pressure (design value- 7.5 kg/cm2) suddenly increases, top temperature drops and reboiler outlet temperature starts dropping to low value. This happens especially at night or in very cold conditions.
To re-establish reboiling the stabilizer column is drained (both rundown and reboiler side) then after raising level in column reboiling is established again as usual.
The column overhead line has no tracing steam, so we have kept an external steam lancer to keep naphtha in vapor phase.