A machine that absorbs CO2? How?

[OhyesOhno]

I found this article: http://www.sciencedaily.com/releases/2008/09/080929123941.htm and it talks about a machine that absorbs CO2 invented by a professor from University of Calgary.

I'm thinking to make a feasible model of it for construction (it's actually a school project), but the machine itself is quite new and I don't know how to relate that to physics. Do you think it's a good idea? What can I talk about from a physics point of view if I am to do that topic? Does anyone know how it works (from a physics point of view)?

 

[Borek]

First of all - this article doesn't say a word about the principle on which the machine operate.

 

[mgb_phys]

It sprays KOH/NaOH in a fine mist to absorb CO₂ and then recovers the K/Na with Ti-oxide - main advantage is that it does it at low pressure so it's fairly low energy.

 

[f95toli]

So basically it is a energy efficient scrubber?

 

[OhyesOhno]

yeah i guess its a bit hard to make a model out of it.

Well i am thinking of making a photovoltaic cell using an organic material... maybe polycarbonate? It is bio-degradable right? Is it hard? How long will it take to make a solar panel?

 

[mgb_phys]

Making a model of this is easy - you need a beak of CaOH (slaked lime / lime water) and a straw, blow bubbles through the liquid and it will turn milky as CaC03 (chalk) is formed.

Don't suck, and wear goggles - CaOH isn't very nice.

 

[OhyesOhno]

Hmm what I actually mean by a model is a machine that can be used... I guess that works but I just need to work on a bigger scale. If I do make a bigger machine, how will I be able to make a machine that replaces the CaOH once it is used up?

 

[Enthalpy]

- Forget about making solar cells by yourself! The CO2 machine looks better.

- Spraying is one possibility, but I fear some carbonates (especially CaOH) or their impurities are insoluble and will clog the nozzles. I would rather let many disks rotate slowly, partly immersed in the liquid, partly blown gently with the air. Also requires less power usually.

- Recovering CO2 and CaO from CaCO3 is done industrially by heating a lot. This is how plaster is produced from chalk. Energy-hungry process. No idea if KOH or NaOH are better here.

- Wouldn't it suffice for your demonstrator that CO2 extraction is automatic, and that you recycle the alkali manually in your lab? Only the first part needs to be proven, the second is existing technology.

- However, if you can build a solar furnace to crack CaCO3, it'll be of interest to many people.

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Another nice possibility would be to combine CO2 with a mineral to store it as a stable solid: more secure than a compressed gas. Silicates +CO2 can transform to silica +carbonates.

 

[Borek]

some carbonates (especially CaOH)

Ca(OH)₂, and it is not carbonate but hydroxide.

 

[chemisttree]

It sprays KOH/NaOH in a fine mist to absorb CO₂ and then recovers the K/Na with Ti-oxide...

Any idea how this is done? One of the publications by Dr. Keith indicates that it is done using the same method as used in the Kraft alkali recovery process. My brief online search of this recovery process (black liquor recovery process) involves burning the liquor and isolating the alkali carbonate followed by calcination. NOT a very energy efficient process.

Dr. Keith's paper refers only to the energy required to move air and pump the alkali solution. Nothing significant is said about the alkali recovery process.

To assess the practical feasibility of air capture, example systems using current technology have been proposed (1, 2, 4). The proposals generally include a sodium hydroxide
(NaOH) or calcium hydroxide (Ca(OH)2) solution which absorbs CO2 and is regenerated using the kraft chemical recovery process, an industrial process to recover NaOH (caustic) from Na2CO3 used in pulp and paper mills and other industries (5).

(5) Adams, T. N. [/b]Lime Reburning[/b]. In 5 Alkaline Pulping, Chapter XXII,; Joint Textbook Committee of the Paper Industry: 1989; Vol. 1, pages 590–608..

Article http://www.ucalgary.ca/~keith/papers/97.Stolaroff.AirCaptureContactor.e.pdf"

The alkali recovery process is the real energy hog in this process. In black liquor recovery, the liquor is actually burned... it has enough of a BTU content to offset the energy requirement of drying the liquor. No such energy content will be available in Dr. Keith's process! The dilute solution must be evaporated to dryness and the residue heated to it's calcination point. No calculations are given for the energy requirements of this portion of the process.
A huge omission IMO.

 

[mgb_phys]

Presumably the recovery process is the 'secret sauce' so they aren't going to detail it until they are making money.