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What is minimum H2S level maintain in UOP naphtha hydrotreating reactor recycle gas? why naphtha hydrotreating reactor can not purge at what temp?
 
Answers
08/11/2018 A: Xavier Ruiz, Haldor Tops√łe, xerm@topsoe.dk
As long the reactor is fed with SR/cracked feed naphtha, there is not minimum level of H2S to maintain. In case of no feed scenario, 100 vol ppm H2S is required in order to avoid sulfided metal reduction.
29/10/2018 A: Ganesh Maturu, Self, maturu.ganesh@gmail.com
Typical Naphtha Hydrotreater Configuration is without Recycle Gas Scrubber and recycle gas compressor is designed for NACE service. Since there is no recycle gas scrubber, H2S level in recycle gas typically observed much higher i.e 0.5-1.5wt% depends on feed sulfur level. It turns out to be 15000 ppm and hence downstream compressor system is designed accordingly and also no issues with respect to H2S stripping from reactor catalyst system.
If there is a recycle gas scrubber available in Naphtha Hydrotreaters which is very rare, recycle gas compressor typically not designed for NACE. For these systems, downstream piping and compressor designed to handle max 50 ppm on continuous basis operation which otherwise increases the corrosion significantly (It was mentioned somewhere in NACE manual). Feed contains some sulfur content and it will be ensured to avoid H2S stripping from catalyst. If feed contains very less sulfur <100 wtppm, we may need to maintain some H2S in recycle gas at 50ppm levels.
26/10/2018 A: vijaykumar natarajan, BPCL, Mumbai Refinery, vijaykumarn@bharatpetroleum.in
Typical value is more than 100 ppm H2S. if you feed sulphur is more than > 200 ppm and you are not doing any purge.
200 ppm ensures you are away from risk of losing H2S even though NHDT feed sulphur reduces < 50 ppm. Also if you are doing regular purge maintain above 200 ppm H2S
16/10/2018 A: Dipankar Phukan, Indian Oil Corporation, dipankarphukan79@yahoo.com
500 ppm is what I know, but not very sure. We have a wax hydrotreating unit where feed Sulphur is 50 ppm and we need to inject DMDS to keep the catalyst in Sulphided form.
09/10/2018 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
The value is specified by catalyst supplier. It is necessary to keep catalyst active in sulfided state. At lower values sulfur from catalyst is depleted by hydrogen.