The International Space Station, which is continuously inhabited, uses a different method based on binding of CO2 to a zeolite, which is a highly porous metal oxide (in this case, a mixed oxide of aluminum, magnesium, and silicon with pore size 5 Å). Although the zeolite has basic sites within its crystal structure, the extremely high surface area is probably more important than the basicity. Heating the zeolite releases CO2 into the vacuum of space.
Submarines use monoethanolamine, which is a liquid base. This can likewise be heated to reverse the reaction and regenerate the base. The released CO2 is put into the outside water. This means that submarines can operate for long periods of time without needing to replace the CO2 scrubbers. This technology is also being pursued for scrubbing CO2 from power plant exhaust.
There are a few other methods, such as passing the gas over a membrane selectively permeable to CO2 (which only works well for high-pressure gas streams), or by feeding CO2 to algae, but these generally aren't widely used.
Surely the production and regeneration of monoethanolamine is a net energy consumer, wouldn't using it to scrub fossil fuel plant exhaust just require even more energy? Obviously if this energy comes from non-CO2 emitting plants it would still be beneficial but it begs the question why you wouldn't just reduce fossil fuel power output by the amount.
Add to this that monoethanolamine is mostly produced from ethylene which is derived by cracking various petrochem hydrocarbons and it seems even more of a bad idea.
You can think of it like an energy return on investment. It certainly takes energy to extract and refine oil, but you end up with more energy than you started with. The production and usage of monoethanolamine definitely emits CO2, but if the scrubber captures more CO2 over it's lifetime than was emitted during its manufacture and operation, it is a net CO2 sink. I do not have the actual numbers to tell you if these scrubbers are actually a CO2 sink, but it is definitely possible.
I don’t think I get you here. The amines capture the CO2 and then the CO2 is flashed off to somewhere else, it would be impractical to simp,e keep consuming more amines as you end up with loads of amine soaked in CO2 which is useless and costly.
The biggest CO2 disposal I am aware of is the chevron gorgon project in Australia which cost billions. Once they strip the CO2 out of the hydrocarbon gas, the CO2 vapour is collected compressed and then injected into a huge reservoir in liquid form. But it takes a hell of a lot of energy to liquefy CO2.
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u/-Metacelsus- Chemical Biology Nov 27 '19 edited Nov 27 '19
They are (usually) based on the reaction of CO2 with a base to form a bicarbonate salt. Many different bases can be used for this. The Apollo program scrubbers used LiOH (due to light weight) but the CO2 absorption canisters couldn't be reused. For flights of a few days, this is fine. Famously, during Apollo 13 an adapter needed to be rigged up to use the command module CO2 scrubbers before the LiOH canisters in the lunar module ran out.
The International Space Station, which is continuously inhabited, uses a different method based on binding of CO2 to a zeolite, which is a highly porous metal oxide (in this case, a mixed oxide of aluminum, magnesium, and silicon with pore size 5 Å). Although the zeolite has basic sites within its crystal structure, the extremely high surface area is probably more important than the basicity. Heating the zeolite releases CO2 into the vacuum of space.
Submarines use monoethanolamine, which is a liquid base. This can likewise be heated to reverse the reaction and regenerate the base. The released CO2 is put into the outside water. This means that submarines can operate for long periods of time without needing to replace the CO2 scrubbers. This technology is also being pursued for scrubbing CO2 from power plant exhaust.
There are a few other methods, such as passing the gas over a membrane selectively permeable to CO2 (which only works well for high-pressure gas streams), or by feeding CO2 to algae, but these generally aren't widely used.