PTQ Q&A search: sulfur vs. sulphur (key word criticality)

“The question isn't who is going to let me; it's who is going to stop me.” -- Ayn Rand (Russian born American Writer and Novelist, 1905-1982)

The Technical Q&A feature on the ePTQ (www.eptq.com) Web is a rich resource.  But here’s a tip for key word searchers … be very specific.  For example, when searching for discussions pertaining to “sulfur,” search for “sulfur,” browse the results, and then search AGAIN for “sulphur.”  This will produce different results.

Here is one Question and Answer …

QuestionWe are going to commission a new refinery which includes Hydrogen Unit also. The Naphtha feed specication for the Hydrogen unit is less than 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 deg C and Sulfur less than 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

29/03/2013

Ralph Ragsdale, Ragsdale Refining Courses, ragsdales@juno.com

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

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

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.