Plugging off of a SRU steam jacketed sulfur rundown can be caused by a number of things. The single most common cause for plugging of the rundown lines is from a tube or tubesheet leak in the condenser. The BFW comes through from the shell side to the tube side and will freeze off the liquid sulfur in the area of where the leak is. As the leak worsens, odd behaviour is noted in the rundown lookbox which looks like slugging of the liquid sulfur. The next stage of severity will require rodding either horizontally in the rundown legs or vertically up into the belly of the condenser outlet. Eventually the problem becomes so serious that the rundown will cease to flow, the condenser will flood with liquid sulfur and then the liquid sulfur will be carried over to the next stage or case of the final condenser, it will show up as a large emissions spike from the CSEM.
Another cause of rundown plugging is from corrosion of the steam jacketing which will allow steam into the sulfur side and again will allow for solidification of the sulfur which can be rodded to keep the unit running. Eventually, the leak will worsen and the rundown line cannot be made to flow sulfur.
Another cause can be catalyst fines or a type of sulcrete which is a mixture of catalyst fines and corrosion products that can plug up the seal leg at the bottom where the dip tube ends which will stop of restrict the flow of liquid sulfur.
The final cause can be a failure in the converter grating used to support the catalyst which is allowing alumina catalyst to fall down and be swept into the condenser which then allows for the migration of the catalyst to the bottom of the dip tube.
Consultation with operations should allow for determination of which mechanism is the most likely that is causing the problems at which time a proper fix can be scheduled.
(Per John O’Connell)