Q & A > Question Details
Why is sour water from the main fractionator O/H drum acidic in the FCC during initial catalyst circulation without feed but becomes neutral after introducing feed to the reactor? I am interested in the chemistry of the process leading to acidic sour water? Are there any ways to reduce the acidity of sour water by changing the operating conditions of the reactor or fractionator?
15/10/2019 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
My guess is that with no feed in the unit, entrainment of flue gas from the regenerator can be significant. This flue gas will have significant SOX but little ammonia to neutralize it, so you end up with acidic sour water. Once you get feed in the unit there is a lot of NH3 formed and NH3 and H2S will be present in roughly equal molar concentrations, so the pH is not neutral or basic.