scrubber moisture

jasondrake · 29th June 2006, 01:05

Questions for the knowledgeable:

How much water do the various scrubber media produce. Is it a simple link between moisture produced and CO2 scrubbed? Does it vary with temperature? Does anyone have figures?

Also, has anyone ever measured the % humidity in a loop during a dive?
I know human exhalant is always about 6% Humidity. The scrubber will add to this, and temperature of the loop surfaces will affect condensation.

Seems to me better control of loop humidity may make o2 sensors more dependable.

Thanks for your thoughts,
Jason

**hoppyinca** · 29th June 2006, 01:39

Water temperature surely effects the amount of moisture produced... though in my specific example, the scrubber type may also play a role...

diving a Mk15 in Hawaii (74 degrees F -ish) for 2 hours using Dreager DiveSorb minimal moisture was produced, the absorbent pads were damp.

Diving in 60 degree F water in little mud holes in Texas using SodaSorb for 1 hour and 45 minutes, I can literally pour water out of my counter lung!

I think the temperature difference is probably the biggest factor in regards to the difference in moisture produced.

Hoppyinca

jhaaja · 29th June 2006, 07:59

I think that the relative humidity in the loop will reach 100% quite fast during the dive.

I dive mostly in cold 2-6 C water and get quite a lot of condensation water in to the exhale CL. Usually there is a few drops on the bottom of the scrubber also. I dive an YBOD.

JH

Dutchy · 29th June 2006, 10:19

To create water to need Hydrogen and Oxygen. The hydrogen isn't in your mixture (unless you do very specific dives deeper than 200m

) nor is it in the scrubber.

This leaves us with the only source of water -> YOU !

With the big difference being temperature it's most likely that your exhaled air condesates in the loop. As a consequence humidity of inhaled air once warmed up in your lungs is <100%. More water can evaporate and it starts again....

The remedy? Thermally Isolate your loop and you'll have less water in it.
Oh and btw stop spitting in it will help as well

jhaaja · 29th June 2006, 10:32

Isn`t there also some water in the slime granules? But most is coming from the diver for sure.

JH

plazma · 29th June 2006, 10:52

Quote: (Originally Posted by jhaaja)

Isn`t there also some water in the slime granules? But most is coming from the diver for sure.

JH

Scrubbing process produces heat and water.

-Pasi

jhaaja · 29th June 2006, 11:03

Quote: (Originally Posted by plazma)

Scrubbing process produces heat and water.

-Pasi

Also true!

JH

Dutchy · 29th June 2006, 11:28

Quote: (Originally Posted by jhaaja)

Isn`t there also some water in the slime granules? But most is coming from the diver for sure.

JH

Water in the granules is there for two reasons....a) To limit dusting. b) To act as a catalist medium for the reaction. CO2 is very soluable in water and forms the slightly accidic H2CO3. It is the H2CO3 that is scrubbed releasing the water again.
Noteworthy is the fact that it is only returned, no additional water is formed. Read your scrubber material datasheet, there's no hydrogen in any of the substances other than the few % of water that was deliberately added.

Quote: (Originally Posted by plazma)

Scrubbing process produces heat and water.

Even if there were the reasoning just isn't right. How in a closed loop would you explain where the water goes to in warmer water dives?

plazma · 29th June 2006, 11:38

CO2 + H2O <-> H2CO3

2H2CO3 + 2NaOH + 2KOH -> Na2CO3 + K2CO3 + 4H2O + Heat

So for every CO2 molecule absorbed it produces 2 molecules of H2O. Right?

-Pasi

Dutchy · 29th June 2006, 11:52

Right?

I'm not sure if that's where the reaction stops. If so you're certainly right. But I have my doubts and will check it tonight.
The most obvious problem I have with it is of course that it doesn't explain for the differences found depending on water temperature.

29th June 2006, 01:05	#1 (permalink)
jasondrake New Member Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: Nov 2005 Location: Completely homeless Posts: 74	scrubber moisture Questions for the knowledgeable: How much water do the various scrubber media produce. Is it a simple link between moisture produced and CO2 scrubbed? Does it vary with temperature? Does anyone have figures? Also, has anyone ever measured the % humidity in a loop during a dive? I know human exhalant is always about 6% Humidity. The scrubber will add to this, and temperature of the loop surfaces will affect condensation. Seems to me better control of loop humidity may make o2 sensors more dependable. Thanks for your thoughts, Jason
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29th June 2006, 01:39	#2 (permalink)
hoppyinca New Member Current Rebreather/s: MK 15.X Other Rebreather/s: Join Date: Jun 2005 Location: Laguna Niguel, CA USA Posts: 250	Re: scrubber moisture Water temperature surely effects the amount of moisture produced... though in my specific example, the scrubber type may also play a role... diving a Mk15 in Hawaii (74 degrees F -ish) for 2 hours using Dreager DiveSorb minimal moisture was produced, the absorbent pads were damp. Diving in 60 degree F water in little mud holes in Texas using SodaSorb for 1 hour and 45 minutes, I can literally pour water out of my counter lung! I think the temperature difference is probably the biggest factor in regards to the difference in moisture produced. Hoppyinca
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29th June 2006, 07:59	#3 (permalink)
jhaaja Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Mar 2005 Location: Finland Posts: 867	Re: scrubber moisture I think that the relative humidity in the loop will reach 100% quite fast during the dive. I dive mostly in cold 2-6 C water and get quite a lot of condensation water in to the exhale CL. Usually there is a few drops on the bottom of the scrubber also. I dive an YBOD. JH
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29th June 2006, 10:19	#4 (permalink)
Dutchy SK#007 Current Rebreather/s: Sport Kiss Other Rebreather/s: Join Date: Apr 2006 Location: Nieuwegein (The Netherlands) Posts: 699	Re: scrubber moisture To create water to need Hydrogen and Oxygen. The hydrogen isn't in your mixture (unless you do very specific dives deeper than 200m ) nor is it in the scrubber. This leaves us with the only source of water -> YOU ! With the big difference being temperature it's most likely that your exhaled air condesates in the loop. As a consequence humidity of inhaled air once warmed up in your lungs is <100%. More water can evaporate and it starts again.... The remedy? Thermally Isolate your loop and you'll have less water in it. Oh and btw stop spitting in it will help as well __________________ = This post is environmentally friendly. It is composed of 100% recycled electrons only. = SK #007
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29th June 2006, 10:32	#5 (permalink)
jhaaja Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Mar 2005 Location: Finland Posts: 867	Re: scrubber moisture Isn`t there also some water in the slime granules? But most is coming from the diver for sure. JH
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29th June 2006, 10:52	#6 (permalink)
plazma New Member Current Rebreather/s: Inspiration Classic Home Build Other Rebreather/s: Home Build Join Date: Feb 2005 Location: Oulu, Finland Posts: 104	Re: scrubber moisture Quote: (Originally Posted by jhaaja) Isn`t there also some water in the slime granules? But most is coming from the diver for sure. JH Scrubbing process produces heat and water. -Pasi
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29th June 2006, 11:03	#7 (permalink)
jhaaja Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Mar 2005 Location: Finland Posts: 867	Re: scrubber moisture Quote: (Originally Posted by plazma) Scrubbing process produces heat and water. -Pasi Also true! JH
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29th June 2006, 11:28	#8 (permalink)
Dutchy SK#007 Current Rebreather/s: Sport Kiss Other Rebreather/s: Join Date: Apr 2006 Location: Nieuwegein (The Netherlands) Posts: 699	Re: scrubber moisture Quote: (Originally Posted by jhaaja) Isn`t there also some water in the slime granules? But most is coming from the diver for sure. JH Water in the granules is there for two reasons....a) To limit dusting. b) To act as a catalist medium for the reaction. CO2 is very soluable in water and forms the slightly accidic H2CO3. It is the H2CO3 that is scrubbed releasing the water again. Noteworthy is the fact that it is only returned, no additional water is formed. Read your scrubber material datasheet, there's no hydrogen in any of the substances other than the few % of water that was deliberately added. Quote: (Originally Posted by plazma) Scrubbing process produces heat and water. Even if there were the reasoning just isn't right. How in a closed loop would you explain where the water goes to in warmer water dives? __________________ = This post is environmentally friendly. It is composed of 100% recycled electrons only. = SK #007
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29th June 2006, 11:38	#9 (permalink)
plazma New Member Current Rebreather/s: Inspiration Classic Home Build Other Rebreather/s: Home Build Join Date: Feb 2005 Location: Oulu, Finland Posts: 104	Re: scrubber moisture CO2 + H2O <-> H2CO3 2H2CO3 + 2NaOH + 2KOH -> Na2CO3 + K2CO3 + 4H2O + Heat So for every CO2 molecule absorbed it produces 2 molecules of H2O. Right? -Pasi
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29th June 2006, 11:52	#10 (permalink)
Dutchy SK#007 Current Rebreather/s: Sport Kiss Other Rebreather/s: Join Date: Apr 2006 Location: Nieuwegein (The Netherlands) Posts: 699	Re: scrubber moisture Right? I'm not sure if that's where the reaction stops. If so you're certainly right. But I have my doubts and will check it tonight. The most obvious problem I have with it is of course that it doesn't explain for the differences found depending on water temperature. __________________ = This post is environmentally friendly. It is composed of 100% recycled electrons only. = SK #007
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