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22/01/2020
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Joel Kaye, Retired from UOP & Tesoro, kaye13@gmail.com
Caustic while reducing the HCL formation has deleterious impacts. You can operate without caustic or chemical injection in the crude feed, but you will need to adjust for the higher chlorides in the overhead with additional neutralizers or filmers in the tower overhead.
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17/12/2019
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Berthold Otzisk, Kurita Europe GmbH, Berthold.Otzisk@kurita-water.com
Berthold Otzisk, Kurita Europe, berthold.otzisk@kurita.eu
The hydrolysis of MgCl2 and CaCl2 forms corrosive HCl, which will pass the crude distillation column, entering the overhead system. Caustic injection after desalting is a common old fashioned method to reduce the chlorides in the CDU overhead system by forming more NaCl, which will stay in the residue. Drawbacks are an increased fouling potential in the hot preheat exchangers and deactivation of downstream catalysts (e.g. at ARDS units, H-Oil units).
Kurita´s ACF Technology is a real alternative. It is a proven method and offers the options to stop the caustic injection completely or to reduce the sodium concentration in the atmospheric residue by lowering the required caustic injection to a minimum level. ACF products are based on a very strong organic amine, containing no metals. ACF directly reacts with chlorides and strong acids such as hydrochloric acid (HCl) or its ammonium salts (e.g. NH4Cl, NH4HS). When ACF is injected after desalting, the chloride concentration in the CDU overhead sour water is significantly reduced, while no additional sodium is added to the atmospheric residue.
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01/10/2019
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Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
Baker Hughes came out with a caustic alternative a few years ago, which I think was some sort of heavy amine that formed a non volatile amine chloride salt. I looked at using it in a refinery but the concern was that the molecule was not thermally stable and that the HCl would reform in the coker furnace that this particular refinery had. I'm not sure that the additive ever really caught on.
The only other alternative is to improve desalter performance to reduce the amount of chlorides leaving the desalter. Sometimes there are no or relatively low capital options that can make a significant difference in desalter performance.
Caustic doesn't really control chloride carryover. That is set by desalter performance. Caustic effectively suppresses HCl that would otherwise be produced when magnesium and calcium chloride salts that carryover from the desalter hydrolyze at elevated temperatures in the crude & vacuum unit. caustic is thought to react with HCl as it forms, thus making thermally stable sodium chloride.
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01/10/2019
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sam lordo, Becht Engineering, salordo@comcast.net
Over the years a number of caustic replacements have been tried with minimal success, typically not performing, or creating other downstream issues like fouling. in almost all cases , as long as caustics are used properly, dosages and injected correctly, it has little to no impact on downstream equipment. Na contribution increase is minimal. If the resid is going to a FCC then Na loading needs to be controlled to minimize catalyst impact. The amount of caustic used should be 0.5-1.5 ptb
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01/10/2019
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Mike Watson, Tube Tech International Ltd, mike.watson@tubetech.com
An alternative to chemicals (depending on operating pressure, flow and temperature) , is to modify small bespoke access points and mechanically clean whilst the unit is running. Effectively it’s not really cleaning so much as periodically removing the precipitation layer and thereby avoiding fouling build up and in equal measure reduce under same corrosion, improve throughout, run length etc etc. We’ve done this on furnaces @1000 deg C , Flare Lines whilst flaring, water cooled condensers/exchangers all while the unit continues to run. Regards Mike@tubetech.com
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01/10/2019
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Mike Watson, Tube Tech International Ltd, mike.watson@tubetech.com
An alternative to chemicals (depending on operating pressure, flow and temperature) , is to modify small bespoke access points and mechanically clean whilst the unit is running. Effectively it’s not really cleaning so much as periodically removing the precipitation layer and thereby avoiding fouling build up and in equal measure reduce under same corrosion, improve throughout, run length etc etc. We’ve done this on furnaces @1000 deg C , Flare Lines whilst flaring, water cooled condensers/exchangers all while the unit continues to run. Regards Mike@tubetech.com
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