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In our semi regenerative catalytic reforming unit we are facing problems of low recycle gas purity.70-72%. Octane has been in the range 92-93 as per design. Reformate yield is around 83% against design of 86.%.Our stabiliser off gas production has been incresed by 3-5 % and reflux control valve has been opened fully. Ratio of C1+C2/C3+C4 is higher 1.9. PCE dosing @1.5 ppm
 
Answers
04/11/2016 A: Mohan Shyam Pathak, UOP A Honeywell Company, mohanspathak@gmail.com
Based on your information and assuming that your team has not observed a significant change in required WAIT, otherwise you would have mentioned, the catalyst seems to be chloride deficient.
Suggest monitoring the HCl content in recycle gas. Increase the PCE injection until you observe nearly 5 ppm HCl in recycle gas.
Observing the trend of your complete data over longer time period will provide more clue.

08/02/2016 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
I hope you would have got response to your question from UOP as stated by Dr. Patrick Bullen of UOP. There are number of reasons for low purity of recycle gas associated with 3 % lower reformate yield and higher stabilizer gas production.
If the feed stock PNA and boiling range is same, primary cause is overchloriding of catalyst that could be due to number of reasons.
It is well known that higher paraffins content with lower naphthenes in feed give lower reformate yield at same octane. However, under such situation higher RIT is required.
You have not mentioned about chloride content, hydrogen sulfide content in recycle gas.
I assume that sulfur in feed is in limits.
If the feed has become lighter due to lower IBP, 5 % etc. you will also get lower yields at same octane.
Sometimes such phenomenon may be observed due to temporary failure of recycle compressor causing greater deactivation of metal functions.
13/01/2016 A: Yogesh Bhintade, Raffinerie Heide, bhintadeyogesh@gmail.com
Check for moisture content and H2S content 'in recycle gas. Also check for chloride on the catalyst as per requirements.
Check the separator pressure and temperature at the suction side of the RC GAS COMPRESSOR
Above stated are the major causes of low recycle gas purity.
12/01/2016 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
Sounds like hydrocracking is increasing while conversion to aromatics is decreasing. Low reactor delta T would indicate that. So would reduction in quantity of aromatics produced. Excessive chloride on catalyst can increase hydrocracking above desired level. Declining catalyst activity would also be a cause if you are increasing RIT faster than normal.
10/01/2016 A: Rajesh Kumar Singh, IOCL, rkumarioc@gmail.com
It happened because of undesirable reaction, hydrocracking. Due to hydrocracking reactions your reformate yield decreased and lighters production increased.
08/01/2016 A: Patrick Bullen, UOP, patrick.bullen@uop.com
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08/01/2016 A: Satyalal Chakravorty, Sr Consultant, satya1354@yahoo.co.in
Please examine whether Paraffin content in reformer feed has gone up? Find out the catalyst activity using corelations. It seems the catalyst reached towards the end-off run of the cycle.
08/01/2016 A: NS Murthy, Suez, murthy.ns.ext@suez.com
Its a semi regenerative design as per the query. Did you check how much life already utilized? Pr drop and delta T across bed can give good indication of happening. Further, there is no info on % N+A (some refiners use N+2A) in feed which too impact hydrogen purity and the resultant reformate yield. Last but not the least look into temp poisons like moisture, nitrogen, etc. ingress in feed. Good luck.