Q & A > Question Details
In a team discussion about the start up sequence of Naphtha Catalytic Reformer, everyone was wondering about the effect of prolonging the hot hydrogen circulation across the catalyst bed more than 12 hours.
The question rose from the fact that usually the Stabilizer (Debutanizer) Tower in the Reformer Unit is started parallel with reactor heating up, in such a way that when Reactor has reached the required temperature for charge in the liquid feed, the Stabilizer Tower has been ready to strip out the light ends. But it's not seldom that Stabilizer Tower is suffering from un-predicted prolonged problem --- such as very frequent bottom pumps' strainer blockage-- while reactor inlet temperature has reached the feed cut in temperature.
Under such situation, the start up team was in the pro-cons whether to keep the hot hydrogen circulating across the reactor for few more hours till the readiness of Stabilizer Tower, or to immediately cool down the reactor loop. The first opinion merely consider about the time efficiency, while the second group worried that alumina support of the catalyst will undergo a phase change due to hydrogen embrittlement on this alumina.
Has anyone here had the similar experience, and can give us more enlightenment on this matter?
 
Answers
27/12/2014 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
I am sorry for answering the question after long gap as I came across this question today.
In Semi regenerative CRU the catalyst is presulfided before feed cut-in. The feed cut-in is performed at about 440 to 460 degree C. The stabilizer is started in such way that it reaches the bottom temperature before feed cut in and may run under total reflux till it receives the reformate from separator.
Running the hot hydrogen circulation for the period specified by you before feed cut at about 460 degree C is not likely to change the phase of alumina. The only adverse affect could be that sulfur from the pre-sulfided S-R CRU catalyst would strip out to some extent resulting in a little loss in selectivity and cycle length of catalyst due to accelerated coke formation. There are methods available to overcome that situation too.