Strange case of hot tubes in the Primary Reformer....

[quickstepper]

Hi guys,
We had a situation of extremely hot tubes in the primary reformer. Our process is desulphurised natural gas and steam. Here's the problem...

After shutdown of the unit for mechanical repairs, the delta P on the reformer increased by 15 psi and the dropped by 5 psi. Subsequent surveys on the catalyst tubes revealed they were getting progressively hot. However not all the tubes were hot. Actually only 20% were hot, however the distribution was primarily on the extremes of the reformer near the ends.....

It was so bad we had to shutdown to vacuum the tubes and reload catalyst...

What on earth could have caused this? Preliminary inspection revealed the catalyst was not significantly damaged. Help solve this mystery!!!!!

P.S: A couple of weeks before we had a minor sulphur break thru which we took care of and got reaction back in the reformer....Could this impact in any way?

 

[rmw]

What kind of oxygen levels were you running in your flue gas? Is your reformer Balanced draft or Induced draft?

rmw

 

[unclesyd]

What type furnace do you have?
Did vacuuming the catalyst completely eliminate the problem?
Did the mechanical problem have anything that would affect the furnace operation?
Any work on the process steam supply?
Did you have any problems during the startup?

A little more information would help immensely.

 

[quickstepper]

rmw: Our reformer is induced draft and we usually run around 2% to 3% excess O2.

unclesyd: No problems during startup; yes vacuuming the affected tubes worked out fine. and there were no mechanical problems with the furnace.

During shutdown we ran the reformer for a long while; excess of 8 hrs with steam in the reformer before we began startup.