Q & A > Question Details
Naptha generated from Hydrocracker is having less then 5 ppm sulfur mainly of marcaptan type and the CRU feed demands for a sulfur level of less then 0.5 ppm. Existing NHDTs are having T'put limitations. Please recommend some other alternative for the removal of the marcaptan sulfurs so that it can be directly routed to the CRU feed pool.
05/01/2012 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
I agree with one of the respondents for the sulfur guard suggestion for hydrocracked heavy naphtha as a component of CRU. But you have to look for a good adsorbent in the guard as life of the adsorbent is also an issue. The location of the guard should be made based on a number of issues.
Good latest generation catalyst in NHDT can also operate at higher LHSV giving desired sulfur. However issues of other equipments etc in NHDT are also to be investigated.
Latest generation catalysts are now used as bottom beds in hydrocrackers to reduce the mercaptan sulfur in cracked products from hydrocracker.
04/01/2012 A: Sanjay Rajora, Essar Oil Ltd, sanjay.rajora@essaroil.co.in
Install sulphur guard bed at the bottom of the debutanizer in the hydrocracking unit.
04/01/2012 A: Rajkumar Chate, Sulzer, rajkumar.chate@sulzer.com
sulfer content is not related with your T'put. If sulfer content in feed to CRU exceeds the limit of 0.5 ppm then it is high chance of catalyst poisoning in CRU reactor. To reduce this sulfer content you have to look in to NHDT ractor and stripper. There are two possibilities of this your sulfer is not converting in to H2S in reactor for which you may need to look to the catalyst of NHDT ractor, H2 to feed ratio and reactor pressure temperature. second one is that your NHDT ractor is ok but your stripper column may not be able to stripout the sulfer from the NHDT ractor effluent.
if you feel the limitations in column then this can be easily soved by revamping the stripper column internals. Try increasing the bottom temperature of stripper column and rate of purge stream from stripper overhead reflux drum, this will help you to reduce the sulfer content. During this you have to check the pressure drop across the stripper column, if it is increasing then you have alimitation in column and column internals shall be replaced.