Q & A > Question Details
In our new octanizing unit (axens) we have gas dryer in catalyst regeneration section, but in some cases we need to bypass the dryer and we don't know can we do this without shutting down the regeneration section or not?
 
Answers
08/02/2016 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
The reasons for temporarily bypassing the regeneration gas dryer are not stated. The regeneration section has already appreciably high moisture content due to burning of coke and one can easily calculate the high moisture content in the environment of regenerator. It prompts that for certain small period of time one can do that bypassing subject to licensor recommendations and clearance. High HCl content in regeneration circulating gas becomes highly corrosive at certain temperature when moisture condenses in the pipe or vessel. Keep watch for this issue depending on metallurgy High temperature and high moisture add to platinum crystallite growth and alumina surface area loos. Platinum dispersion could be regained in oxychlorination step. Alumina surface loss is not recoverable
26/01/2016 A: Xavier Decoodt, Axens, Xavier.DECOODT@axens.net
Axens Octanizing Regeneration section can be maintained in service with the regeneration gas dryer being by-passed for a short period of time.
The potential issue of by-passing the gas dryer is to increase subsequently the regeneration gas moisture which will accelerate the catalyst surface area ageing and the catalyst chlorine elution with potential corrosion issue on regeneration section cold locations.
New “Symphony” catalysts are much more hydrothermal resistant compared to previous generations, thus making the above mentioned issues much less critical.
10/01/2016 A: Satyalal Chakravorty, Sr Consultant, satya1354@yahoo.co.in
If the dryer is at the suction of the Recycle Gas compressor , it would be possible to use Double-block & bleed valves( inlet/outlet) to enabling isolation of the dryer and bypass the same. Please carry out a Hazop for establishing all control measures.
10/01/2016 A: Rajesh Kumar Singh, IOCL, rkumarioc@gmail.com
In octanizing unit regeneration system there is two dryers one is regeneration gas dryer and the second one is reductor gas dryer. Regeneration gas dryer can not be bypassed. reduction gas dryer can be bypassed for few days till moisture in regeneration gas is wel within range.