What is industrial practice of caustic dosing in desalted crude? And what should be optimum dosing in ppm?
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15/02/2017
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Apoorv Gupta, IOCL Haldia, apoorv.work19@gmail.com
Normally caustic dosing in post desalter is not recommended as same will increase Na content of Reduced crude oil/atmospheric residue & have deter mental effect on Coker furnaces & FCC Catalyst.
Caustic dosing is recommended in case sign of overhead corrosion ( Boot water chloride >20 ppm & Fe >0.5 ppm). Dosing rate of caustic in postdesalter circuit should be nearly equal to the post desalted crude salt content.
Caustic dosing in post desalter is not required if your desalter is working within design frame.
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15/02/2017
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Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
Approximately 50% of refineries worldwide inject caustic.
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14/02/2017
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Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
Spent caustic is not normally recommended due to potential contaminants and variability in actual caustic strength. Typically up to 3-6 ppm of NaOH is the maximum that most refiners will allow. Use of clean water source with low hardness/TDS is important to minimize fouling. Caustic is usually injected just downstream of the desalter and a 3-5wt% solution is typically recommended. The sodium all ends up in the resid so can cause problems with catalyst if resid is fed to a downstream catalytic unit like an RFCC or a resid hydroprocessing unit. If the resid goes to a coker, it can increase furnace fouling rates and hurt anode grade coke quality.
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14/02/2017
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Eric Hennings, Technip Stone & Webster, EHennings@technip.com
Usually, spent caustic is used at 1 pound per thousand barrels rate.
Note this practice will affect RFCC catalyst and possibly delayed coking furnace run length.
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