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Many of the operating plants inside a refinery complex use fresh caustic to sweeten the gases/Naphtha products. Almost all of this spent caustic is then transferred to Effluent Treatment Plant of this spent caustic. Are there processes available which may be utilised to regenerate this spent caustic?
 
Answers
22/08/2015 A: Sridhar Balakrishnan, Bharat Oman Refineries Limited , laksrid@yahoo.com
Oxidation of spent caustic can be performed in the presence of oxygen, but the rate of oxidation is found to be very low in the absence of a catalyst. Metal Pthalocyanine catalysts are used to enhance the rate of oxidation.
20/08/2015 A: S Banik, Centre for High Technology, sbdr@rediffmail.com
Extraction of lower mercaptans i.e. methyl-,ethyl-,propyl- and H2S from stream like LPG using caustic of 10-20% concentration is a standard practice. The caustic stream containing reaction products sodium mercaptide and sodium sulphide is regenerated using liquid catalyst e.g cobalt phthalocyanine ,proprietary catalyst .Air is also used in the process as oxidizing agent. Caustic used for mercaptans is fully regenerated and for H2S partially regenerated. Thus most of the caustic can be recycled and load of effluent treatment plant can be reduced.
Apart from above process licensors , Engineers India Ltd (EIL) also offers this technology. The Technology is in operation in many refineries.
18/08/2015 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
Also, if you are using a mixture of MEA and caustic for COS removal, the mixture must be discarded when spent.
17/08/2015 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
UOP and Merichem have extractive processes for removing mercaptans that are regenerable. If caustic is used to remove trace H2S, the caustic is not normally regenerable.