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We are going to commission a new refinery which includes Hydrogen Unit also. The Naphtha feed specication for the Hydrogen unit is <1ppm Sulfur and boiling range of IBP-95 degC. But during commissioning we cannot suppy the above naphtha spec. So it is agreed to supply naphtha with boiling range of IBP-160 degC and Sulfur <150 ppm for initial one month. The Feed Desulphurised catalyst vendor says it cannot handle beyond 30 ppm Sulfur. Can anyone share such experience and can advise how to manage the situation. Also what will be the Hydogen yield with changed specfication of feed Naphtha?
 
Answers
08/09/2013 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
Sulfur is very bad and irreversible poison for steam reformer catalyst. One month is very long period to sustain. Deactivation would be visible in hours. Once hydrogen is available pretreater would provide naphtha of desired quality.
24/08/2013 A: Rajesh Nandanwar, Bharat Oman Refineries Limited, Bina, rajesh.nandanwar@borl.co.in
Sulphur level >0.1 ppm is detrimental to the reformer catalyst. It is always preferable to operate with naphtha which is hydrotreated and desulphurized. HGU plant pre desulphurization section takes care of low level of sulphur where sulphur species gets converted to H2S in NIMO/COMO catalyst and downstream adsorbed in ZnO bed. Similarly, chloride contents gets adsorbed on Na2O bed. Risk with high sulphur naphtha is that, higher thiophenic contents and mercaptans in feed naphtah will not fully get converted in to H2S in COMOx. ALso it have limited capacity at normal operating temperature of 380C. If sulphur other than H2S is coming out from COMOx bed, it will pass on to reformer catalyst without any adsorption in ZnO bed. Immendiately reformer catalyst will get spoiled. I am strongly against using high sulphur naphtha as feed even for 1 week. Get this naphtha hydrotreated to at least 5 ppm sulphur in naphtha hydrotreated before thinking of using in HGU plant.
01/04/2013 A: HUSSEIN SAID, CLG-KUWAIT, HUSSAIN_SAID@YAHOO.COM
In Similar units there is always Zinc oxide guard up stream of the reformer to protect reformer from any slippage of sulphur <1ppm. High sulphur will affect the nickle catalyst as poisining material. However if you are able to control sulphur you may able to process heavier naphtha at low feed rate with higher steam to carbon ratio than design.
29/03/2013 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
I agree with the other responses. Don't do it. Normal procedure is to import low sulfur naphtha from another refinery to feed the cat reformer, which in turn produces both sweet naphtha for the hydrogen plant feed and the hydrogen needed to start the cat reformer pretreater. This all happens before running out of the imported sweet naphtha.
27/03/2013 A: Alan Goelzer, Jacobs Consultancy, alan.goelzer@jacobs.com
This may be a "Catch 22" situation. Usual practice has been to start up the catalytic reformer on purchased hydrotreated heavy naphtha and get the naphtha hydrotreater unit [bulk WSR or LSR and HSR separate NHTU] running so that there is internally available air-free / hydrotreated light naphtha AND cat reformer hydrogen to start up the hydrogen plant. Cat reformer hydrogen [preferably sent through chloride trap] serves temporarily as 'service hydrogen' for the Feed Vaporization & Pretreating System. Most of the sulphur species in straight-run naphtha will be a combination of mercaptans, thiophenes, and sulfides. These are not as well captured by the Zinc Oxide expendable sorbents as H2S. But the trim hydrotreater system after the fired vaporizer and ahead the Zinc Oxide sorbent beds which turns residual sulphur species in previously hydrotreated light naphtha feed requires some 'service hydrogen'.
Accumulation of sulphur and accelerated 'coke' formation from sending heavy naphtha into the reformer catalyst tubes may debit replacement life of the reforming catalyst and conversion selectivities.
Note that I remain an advocate for "super hydrotreating" of lightest possible naphtha as hydrogen plant feed.
26/03/2013 A: keith bowers, B and B Consulting, kebowers47@gmail.com
Feeding even low sulfur naphtha to the hydrogen unit will poison the catalyst, likely beyond recovery. You should purchase on-spec naphtha, put it in a clean tank, and feed on-spec naphtha to the hydrogen unit. Otherwise, no warranty on catalyst, no hydrogen make, big mess.