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enter image description here

This image is a CO2 scrubber I'm trying to optimize. It's 3 inch PVC with a fan to draw or force air over soda lime to extract CO2 out of the air. It presently drops the CO2 level a small amount, and I want to boost its performance. The first fan I tried is a USB computer fan powered from an Anker battery recharger.

Constraints:

  • it needs to work where there's no electric, so has to be battery powered

  • it should be able to run about 24-32 hours from a battery charge

I think the next logical step is to use a more powerful fan setup. That would move more air, and could move it over a larger amount of soda lime. What I'm thinking is to find a fan compatible with the 3 inch PVC that is powered by a 12v motorcycle battery.

What kind of fan should I look for to fit this application?

EDIT:

Considering Ed's advice, it may be that I need a new scrubber design. There are a couple options to try with this design, based on his comment that the air must be forced through a volume of the pellets.

In the following images, the purple area represents pellets in the scrubber. I've tried configuration 1 and 2, and intend to try 3 and/or 4 with the existing fan or stronger one, before scrapping the design.

Configuration 1: enter image description here

Configuration 2: enter image description here

Configuration 3: enter image description here

Configuration 4: enter image description here

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I have removed CO2 from breathing air (a rebreather for diving) the area of the absorbent is a big part of the systems ability to convert the CO2. The gas needs to be in contact with the media pushing it faster may actually reduce the efficiency where reducing the flow by increasing the area may be a better choice.

  • Thanks, makes sense. I've tried filling the bottom of the "U" partway and drawing the air over the top. Filling the bottom completely and drawing the air through that is something to try. That may need a stronger fan, or a good seal around the fan, at least, but I can start by trying that. – Don Branson Mar 28 '18 at 8:19
  • The air will take the path of least resistance, the pipe would need to blocked by the absorbent another important thing to note is the thickness of the granules needs to be uniform. the absorbent at the top of the bend would get the flow and the material at the bottom would get very little. You may want to rethink your scrubber design. When you say draw the air over the scrubber you need to be thinking force it through, it may sound counter intuitive but you need to pack the absorbent to get the best results. – Ed Beal Mar 28 '18 at 10:22
  • Yes, I'm thinking it has to be forced through, between the granules. – Don Branson Mar 28 '18 at 11:53

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