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The wash water quality standard from NACE and most articles I have read recommend using phenolic water in either desalters or crude overheads only. I have not found an example of any reuse of stripped sour water from a SWS with phenolic water (FCC or coker sour water) feeds for wash water on a hydrotreater effluent train wash water injections. I have read through articles on polymer fouling in the sour water stripper itself due to phenols and one corrosion book cited kerosene color issues with phenols. Other than that most articles just say phenolic water is recommended for desalter usage mainly but don't call out the specific issues of phenolic stripped sour water for hydrotreater wash water. Are the accompanying cyanides and HSS the main concern, concentrating up at the injection site, or are there concerns with the phenols themselves being injected downstream of the hydrotreater? Are there any examples of diluting phenolic stripped sour water with other streams and reusing it in hydrotreaters if you don't have enough sources of non-phenolic stripped sour water?
17/06/2019 A: Morgan Rodwell, Fluor Canada Limited, morgan.rodwell@fluor.com
There a numerous reasons to avoid using phenolic / cyanide containing sour water in a hydrotreater. Cyanide corrosion mechanisms, fouling due to the presence of polysulfide additives used to capture cyanides, filming amines that may have been injected into the CDU/VDU/Coker overheads, phenols transferring to the hydrocarbon phase and contaminating the hydrotreated product. Additionally, phenolic sour waters from CDU/VDU/Coker are often higher in chlorides, and coker waters may contain other trace species that could have negative impacts to your hydroprocessing unit from a corrosion, fouling or contamination perspective.
17/06/2019 A: Peter Marsh, XBP Refining Consultants Ltd, peter.marsh@xbprefining.co.uk
Stripped sour water from FCC, Coker, or Visbreaker units will contain residual phenolic compounds as these are not readily stripped from water. This water should preferentially be directed to the crude desalter since most of the residual phenolic compounds will be absorbed into crude oil. Stripped sour water from vacuum distillation units may contain residual oxygen (air ingress) and should not be used as wash water on high pressure hydroprocessing or hydrocracking units as it can cause oxidation of bisulphide compounds in low pH environments (bisulphides are oxidised to elemental sulphur which can cause fouling problems).