Q & A > Question Details
For part of a project, I am dealing with SR naphtha reforming reactors. The process is four reactors in series that use Pt-Alumina catalysts. Due to the high-temperature generation in the regeneration step, one of the reactors can not be in the service anymore.
I want to know does anyone have the same experience?
Is it possible to work with three reactors?
Could you please inform me to find some useful resources to find a similar study and situation?
16/12/2019 A: Jake Gotham, InSite Technical Services, jake.gotham@insitetechnical.com
Many reformers operate with only three reactors so, in principle, it is possible. It is reasonable to assume that capacity, product octane, run-length and yield will be lower – your catalyst vendor or licensor should be able to prepare estimates of the impact. Your reformer process engineer may also be able to make these calculations if access to a well-tuned process model is available.
If you can find an economic operating point with the reduced catalyst volume, the next challenge is engineering the modification safely. The Flixborough disaster was the result of a poorly-engineered attempt to bypass one reactor in a multi-reactor system. It was a long time ago and in a different type of process unit, but your design and management of change teams would be well-advised to review this case study before implementing any changes you intend to make.
You should also be focusing attention on your regeneration procedures and safeguards to minimise the likelihood of a temperature excursion at future regenerations.
16/12/2019 A: Peter Marsh, XBP Refining Consultants Ltd, peter.marsh@xbprefining.co.uk
I assume by “SR naphtha reforming” you mean fixed bed semi-regenerative naphtha reforming since you imply one of the reactors is at end of life? Also, you do not specify which reactor you would need to take out of the reaction circuit (or its metallurgy), but since most of the coke is laid down in the tail reactor I assume you would be taking out Reactor #4?

In principle it should be possible to bypass Reactor #4 and Interheater #3 safely, but if you bypass these major items of equipment you must take great care to properly design the necessary bypass pipework and positive isolation systems (different process, but remember Flixborough …?). Alternatively, you could simply remove the catalyst from Reactor #4 and operate it as a bubble in the line (empty) and blind off all fuel sources to Interheater #3 and close the stack damper (to minimise heat loss from the Reactor #3 effluent stream before it reaches the combined feed exchanger). The reduction in reaction system pressure drop resulting from bypassing Interheater #3 and Reactor #4 or from removing catalyst from Reactor #4 will help improve reformate and hydrogen yield per bbl of feed. However, Reactor #4 typically contains a disproportionately large volume of catalyst (up to 50%!), so it will be very difficult to meet the usual reformate octane target unless operating at significantly reduced throughput. Higher reactor temperature differences in Reactors #1 and #2 will increase the heat load on Interheater #1 and #2 which may further constrain throughput if these heaters are already running at firing or metallurgical limits. Also, a lower reactor system pressure will increase the risk of seal catalyst fluidisation which could potentially cause attrition of the catalyst and centrepipe screen blockage (assume a radial flow reactor).
16/12/2019 A: sagar dandekar, Bharat petroleum, sagar.girgaon@gmail.com
Due to high temperature in the regenerator, sometimes catalyst are agglomerated. In this case catalyst lumps are formed which affects catalyst circulation.