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My question is related to arsenic and mercury contents in delayed coking products.
We were thinking of sending coker naphta ang gas to the olefins cracker without hydrotreating beforehand. Both arsenic and mercury could cause problems in this unit. I would like if somebody have had some similar experience or if somebody know the level of these contaminants in these feeds.
 
Answers
15/07/2013 A: Lindsay McRae, Pall Corporation, Lindsay_McRae@pall.com
Whether or not mercury or arsenic is an issue in your coker naphtha or not depends very much on the source of crude you are using. Mercury often follows naphtha and / or LPG cuts too. If mercury levels in naphtha are >1 ppm then you are going to have a problem selling to an ethylene plant and if that's the case you might want to consider installing a MRU to remove mercury. This is commonly done in some parts of Asia where the mercury content in crudes and condensates is quite high.
05/07/2013 A: Morgan Rodwell, Fluor Canada Limited, morgan.rodwell@fluor.com
I concur with Mr. Goelzer. To further answer your question, the arsenic content of coker naphtha depends very much on the crude feedstock. Some extra heavy crudes can produced coker naphtha containing 200-400 ppbw arsenic, although most coker naphthas are well below 100 ppbw, and many refiners have never even measure it or its build-up on naphtha hydrotreater catalyst.
04/07/2013 A: Alan Goelzer, Jacobs Consultancy, alan.goelzer@jacobs.com
My recommendation is strongly against sending RAW coker naphtha and RAW Coker Olefinic C3 + C4 LPG into Olefin Steam Cracker---regardless of whether admixing into saturated propane/butane feeds or saturated petri-naphtha feeds or sending into the "back end" of the Olefin Steam Cracker.
Organic Sulphur + Organic Nitrogen + Di-Olefins + Trace Arsenic + Trace Mercury can all trigger problems. Values for arsenic down in the modest weight parts per billion level are desirable. Best practice might be to send Coker Naphtha [with some of olefinic C4 LPG] to high performance Two-Stage Coker Naphtha Hydrotreater Unit, using perhaps "excess" hydrogen available from the Olefin Steam Cracker.