There was some talk about recycling absorbent, and I got a chance to ask someone who actually knows at the Rebreather Party 98

From: Paul Elliott
Subject: Recycling absorbent: The scoop
Sender: rebreather-request@nwdesigns.com

Lee, Scott,

I promised I would try to find out more about recycling absorbent, and I found the right guy to ask. A rep from O.C. Lugo (U.S. Sofnolime distributor) was at the party and I asked him about recharging absorbent. He gave me a good and proper "Are you nuts?" He did say it could be done, but it was stupid to do so. So I asked about the process used to make Sofnolime and here it is:

He said that in theory you could recharge absorbent, but the efficiency would be significantly compromised, and that the results would tend to be inconsistent. When I mentioned you were talking about Dragersorb, he literally laughed a big New York one in my face. I know it’s his job to sell new absorbent, but the guy knew what he was talking about and answered all my questions. Before I talked to him, recycling absorbent was something that I might try under controlled conditions once, just for kicks. Now I’d treat it like diving a closed circuit rig without an O2 sensor.

If you try it, do it in your living room and let me know how long it takes for you to pass out. I still think it’s interesting, but I’d be scared to try it.

Best regards,
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Paul Elliott | |Software Eng. Northwood Designs, Inc.
class Flames {public: Flames() {delete this ;} ; } ;

Some more words before the above was posted

Subject: Re: recycling absorbent
From: nssdiver@juno.com (Lee C Kresge)

On Sun, 25 Jan 1998 11:50:05 +1100 diver@chilli.net.au writes:
>Does anyone know what sort of temperature would be needed to 'bake'
>the CO2 back out of the absorbent so it could be re-used. Can this be done at
>all? Has anyone tried it?

To bake the CO2 out of your used absorbant, you would need to be able to attain a temperatue of 750-800 Celcius (~1380-1480F) for at least half an hour. This leaves you w/ Calcium and Sodium Oxide. You now have to be able to rehydrate it _uniformly_ to Ca/Na Hydroxide and replace the indicator (if your absorbant uses one) because it was just decomposed @ ~300C.

Presuming that you could find an oven that was both big enough and hot enough (most muffle furnaces are no more than a few 1/10's of a cubic ft.), you would need to be able to rehydrate the oxide accurately (balance) and uniformly to get even close to regenerating a useful scrubber matrerial. Also, see previous posts to "Anhydrides vs. Hydroxides" on Rebreathers, ie: if you did manage to get as far as the Oxide, DON'T put that in your scrubber!

Date: Tue, 27 Jan 1998 08:29:52 -0800
From: "John E. McKenney" <jmpi@ix.netcom.com>

Guys
When it really comes down to it. Why do you want to waste your time and worry on recycling it. Just throw it over board let it turn to rock, buy a new can of it. It's like aluminum cans how many of you out there take your cans in and get cash for them, c'mon. If you are going to the trouble of diving and maintaining a rebreather why don't you want to use the best supplies. I'll tell you what, I'll sell you my used absorbent for 50% of what you pay for new stuff. You can invest in a kiln, cook it, use it, and worry about its effectiveness while your using it. Its not fu----g worth it.

Date: Tue, 27 Jan 1998 11:44:20 -0800
From: heyydude@pipeline.com  (Mr. Dude)

I agree with John. Why would you want to go through the hassle, just to get Calcium Oxide (CaO) that you have to re-hydrate anyway? (BTW: If you DON'T re-hydrate the CaO, I guarantee that you'll melt your entire rebreather the first time you get in the water with it - CaO with JUST A FEW DROPS of water can generate temperatures that would astound you, just before your lungs turn into soup...).

I've been trying for a while to sell Dr. Heseltine the "goober-juice" that comes out of my hoses after a long dive - I figured he could use it to grow cultures of Ebola Virus, or something particularly toxic... So far, he says he has his own supply...

Kevin.

Date: Tue, 27 Jan 1998 18:15:13 -0500
From: nssdiver@juno.com  (Lee C Kresge)

Scott

If you REALLY want to try this and actually make it as far as the Oxide w/o destroying the physical charasitcs/mechanical integrity of the granuals, DON"T spray water on them. Calculate the amount of water you will need to add and place it in the bottom of a wide flat bottom bowl.  Set a glass/cup in there (upright) and a plate on top of that and spread the Ca/Na Oxide on the plate. In about 1 day, the oxide should suck all of the water from the bottom of the bowl. If you can't calculate how much water you need to add, you _probably_ shouldn't be doing this. . .

Lee

This page last updated: April 25, 2003