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What is the typical phenol content in FCC waste water?
18/03/2010 A: Robert Trou, Total, robert.trou@gmail.com
It's not really an answer but a question related to the one above: what is the typical phenol content in FCC gasoline? In our unit, the phenol content is quiet high and is leading to a high consumption of caustic in the downstream sweetening unit.
10/03/2010 A: Prakash Pimparkar, Environmental Consulting Services , prakash.pimparkar@yahoo.in
There could be two streams from FCC containing phenols a) phenolic spent caustic b) phenolic sour water.
a) spent caustic is the purge steam from caustic scrubbing of FCC products to remove sulphur.
b) sour water is the condensed steam from the main column overhead condensor.
Phenolic spent caustic can contain up to 2500-5000 mg/l of phenols. This spent caustic is either treated by acid to float napthanics (which can be sold) and then mixed with other waste water.Another way of treatment is wet air oxidation destroying all phenols before mixing with other refinery wastewaters.
For sour waters the standard practice is to first steam strip it to remove H2S and NH3 ( incidentals) and then use it as desalter makeup water.In the desalter the phenols in the stripped sour water (100-150 mg/l depending on the severity of cracking in FCC) are transferred to the crude due to their affinity to crude oil rather than waste water.The desalter effluent may contain from 30 to 50 mg/l of phenols.The desalter effluent can then be further stripped to remove Sulpides and Ammonia before sending to the wastewater treatment plant. No stripper is designed to remove phenols.
Now all these figures are for standard operating conditions for a normal crude and could vary and should be taken as a guideline. Hope this meets the requirement.