We are currently using overhead sour water as wash water for the crude overhead system which is injected just before fin fan coolers. Neutraliser is injected into the vapor line before water injection point. Will injecting neutraliser in wash water line help reduce corrosion in crude column overhead system?
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07/03/2013
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Eugen Goudsmith, Nijhuis Industries, eugen@goudsmith.eu
In principle you would not need extra neutraliser in the WW to control corrosion. Salt deposition temperatures vs dewpoint calcs should be made and quantity of WW & chemical distribution should be checked.
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02/01/2013
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Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
Whether it helps or not depends on how well your current injection point is designed and how well your water wash is designed and operated. There is nothing inherently better about injecting neutralizer with water wash and there are some risks.
When you inject your corrosion control chemicals with the water wash, your whole corrosion control program is totallly dependent on the effectiveness of the water wash. An effective water wash requires adequate water rate and good distribution to scrub chlorides out of the overhead. I have seen problems with installation (installed wrong) and operation (plugged nozzles caused maldistribution) of well designed water wash systems render them totally ineffective.
If the neutralizer is all in the wash water and vapor phase chlorides get past the water wash, there is no neutralizer present when secondary condensation starts to occur downstream of the water wash. For this reason, I prefer to keep the water wash and neutralizer injections separate when at all possible. If neutralizer has been injected into the vapor phase, there is a good chance that poor scrubbing efficiency by the water wash will allow both chlorides and neutralizer to pass, thus reducing corrosion issues at secondary dewpoints. If neutralizer injection rate is high enough, there are some risks of salt formation upstream of the water wash injection, so there are no perfect solutions to the issue of where to inject neutralizer.
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02/01/2013
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Alan Goelzer, Jacobs Consultancy, alan.goelzer@jacobs.com
It is not clear from the question what is the "neutralizer" being employed in overhead condenser system for atmospheric tower within CDU+VDU and whether the overhead condenser system inclding the air cooler condenser is 'gravity flow' from 'tower top piping U' to associated overhead accumulator.
Generally speaking and subject to concurrence by metallurgists and chemicals supplier, "filming amine" chemicals should be injected directly into the overhead line from the tower via an injector in tee just after the U-bend.
Ammonia being employed as a "neutralizer" can be spiked into the sour water recirculated from the accumulator sour water boot to wash water injector(s) in tee(s) ahead of the overhead air cooler bays-----provided that the ammonia is injected via a controllable metering pump and pH of sour water is routinely monitored.
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02/01/2013
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keith bowers, B and B Consulting, kebowers47@gmail.com
I suggest you consult with your additive supplier. The type of corrosion and cause is often different 'in the column' and in different sections of the 'overhead system'. Different and /or additional chemicals may be necessary to completely mitigate corrosion and fouling.
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