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Post-Combustion Carbon Capture: Absorption Tower Capable of Dry Operation While Out Of Service?

Post-Combustion Carbon Capture: Absorption Tower Capable of Dry Operation While Out Of Service?

Post-Combustion Carbon Capture: Absorption Tower Capable of Dry Operation While Out Of Service?

(OP)
Hello again all,

This is a follow-up to my previous post on this topic.

I'm wondering if anyone can point me to resources about a design of amine absorption tower that, while not in operation, can or could tolerate subjection to gas temperatures of as high as, say, 540 °C...and yes, I've "Googled" the topic, but I'm likely not using the right search terms...

Background info: the two-over-one combined cycle plant I'm contemplating would employ a pair of once-through steam generators [OTSGs] that are normally started and shut down dry, in other words steam generation would not commence until the OTSG was fully warmed up, and would end before GT shutdown. As a consequence, absorption towers placed downstream of the OTSGs, if not provided with bypass ducting, would be subjected to full flow gas turbine exhaust at design full load temperature. Additionally, in the event the GTs were operated for extended periods with the OTSGs out of service, the absorption towers would have to be capable of withstanding extended operation at this temperature without damage or significant loss of design life.

Note that the dry start and shutdown of the OTSG design imposes no restrictions at all on gas turbine operation, meaning there would be no constraints at all on the rapidity of GT start-ups or shutdowns. As a result it would be preferable to not have the absorption tower design impose any such limits either, namely "temperature ramp rates" due to thermal concerns.

Plant start sequence would therefore be: gas turbine into operation, OTSG into operation and, once OTSG flue gas outlet temp and therefore amine absorption tower internals temp was back down to below 100° C, CO2 absorption could commence. Shut down would be in reverse order.

If anyone can say whether for the tower to operate dry it would be necessary to flush it with scavenging water to strip the "trays" / catalyst / absorption surfaces completely clean of amines so same would not be dissociated by subsequent high temps, I'd appreciate it.

Thanks for reading.

Carl

ps: Upon further reading, I've learned there would likely also need to be a water wash / reflux drum capable of withstanding the same conditions...

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Post-Combustion Carbon Capture: Absorption Tower Capable of Dry Operation While Out Of Service?

I suggest that you'd be looking at a corrosion nightmare if you operated a piece of equipment this way. You'd need nickel alloys to handle those conditions, since refractory-lined equipment wouldn't handle the rapid temperature changes you seem to be looking for. High carbon austenitics would be running in the sensitization region when running hot, and then you'd be cooling the equipment down and using it in corrosive aqueous service. Then there are the column packings or trays typically required for good gas-liquid mass transfer- none of them are going to like spending extended periods at high temperature. Even if you could get the entire internals of these piece of equipment completely free of the amine solution using water with a minimal residue of evaporation, you're still evaporating the water to dryness, concentrating corrosives in every nook and cranny and leaving behind some scaly residue each cycle. That might not matter if you used nickel alloys for everything, but the cost would be high.

RE: Post-Combustion Carbon Capture: Absorption Tower Capable of Dry Operation While Out Of Service?

(OP)
Thanks, molten; I knew there was a reason I asked this question here... smile

It seems fairly clear, then, that completely bypassing both the absorption tower and the subsequent water wash would be the better way to go...

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

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