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In CCR unit we have 85% rich H2 coming from PSA as off gas. Currently we are using in the fuel gas mixing feeding our furnaces. I would like to ask whether it can be used in more fruitful ways?
Can it be combined in HGU at any stage as we already have 85% pure hydrogen??
 
Answers
14/11/2015 A: Rajesh Nandanwar, Bharat Oman Refineries Limited, Bina, rajesh.nandanwar@borl.co.in
Above the normal options suggested there are other methods also available which would be helpful for you to utilize this very high H2 content off gases.
1. If you are operating Hydrogen plant, this off gases can be feed to H2 plant along with NG/Naphtha. Hydrogen would take free ride while other higher Hc's would get converted. Need for recycle H2 which is normally pure product is not there as suffient H2 is available in the off gases. Only concern is H2S and Chloride content which would be required to be treated and gas is to be compressed to higher pressure of 35-40 kg/cm2g.
2. Cryogenic H2 separation is gaining importance. This technology provides higher purity H2 which can be directly use for hydrotreating requirement.
3. Best is to use this 85% hydrogen steam in hydrotreating which normally dont ask for very high purity H2 by providing dedicated header. Your purge quantities (diverted to fuel gas) would go up slightly to maintain recycle gas H2 purity but worth studing based on your configuration as there is no additional investment except a line from CCR H2 header to hydrotreating unit.
23/07/2015 A: J Sudeep, SATORP REFINERY, jsudeep81@gmail.com
Yes. All latest refinery have adopted two methods
First PSA(Pressure swing adsorption) Linde/UOP are pioneer in this field again you will end up with H2 product 99.99% and rest off gas which can be used in Fuel system
Second is membrane purification system where the hydrogen permeate through membrane and pure hydrogen and waste gas as produced , waste gas is used for fuel system
Both methods requires sufficient pressure in upstream and downstream it depends upon the requirement .
23/07/2015 A: Balasubramanian Iyer, Nexen CNOOC Limited, balasubramanian.n@aol.in
Yes, You can route the CCRU gas to the PSA inlet it is the efficient way of increasing your H2 yield but the important factor to be reminded is look for the composition of the H2 from CCRU for H2S, Chlorine content and also check with the PSA adsorbents that whether I can take care of the H2S and Chlorine if else we have to add an adsorbent bed for both H2S and Chlorine to prevent downstream issues because of these impurities. and also preventing corrosion issues in PSA due to localized HCL formation.