How temperature affects sodalime?

[super scrubber]

I'm sure it's like most reactions in chemistry where it's sped up with heat, but was wondering if anyone had any research handy about how it's affected for dives of different temperatures? I'm diving in 82°F water and was just wondering if I should have more sodalime then.

Thank you!

 

[cathal]

Not an expert at all, but my understanding is that cold water temperatures reduces scrubber time as the gas in the loop is denser hence more gas molecules to be scrubbed. Scrubbers usually perform with longer scrubber times in warmer water because the gas in the loop is less dense and therefore there are less gas molecules to scrub. I expect I am wrong somewhere in that simple explanation and I look forward to being correced if so.

 

[broncobowsher]

I know the rEvo has 2 scrubber rating times, depending on temperature. And the difference between them is different depending on which sorb is used, 812 vs 797. So it also appears that some sorbs are more sensitive to temp than others.

 

[bletso]

You will get more time in warm water, not that the sorb will take more CO2 than it can. The efficiency appears to give you more time. A given quantity of sodalime will absorb just so much CO2 and that is physics. That being said the normal dwell time in the scrubber allows more efficient scrubbing and therefore more usable scrubber time.

At colder temps the normal dwell time may not be enough for efficient CO2 removal. Make sense?

In warm water say 25 C - 30 C I can get 40% or more dive time versus say 10 C. However towards the end of dive time if a large demand is put on the scrubber it will be bad juju. Efficiency all about dwell time, temperature and Amount of CO2 to be removed during the dwell time.

 

[mr_v]

The short answer: it depends.

Scrubber material contains 3 chemicals. The first is your accelerator. The accelerator can remove carbon dioxide fast, effectively, and it does not require heat to get started. Here is the catch: the accelerator is expensive and corrosive. That's why there is only a small amount of it. Typically, the accelerator is LiOH. When you start pre-breathing your unit, the accelerator kicks in first.

The second is you diesel engine. It can remove CO2 quite well but requires heat. The accelerator creates the heat and then the diesel engine kicks in. Good thing - this engine is quite cheap. It makes up most of the scrubber volume. Sodalime or Ca(OH)2 is your diesel engine. The chemical reaction produces heat, so at some point the engine is self-sustaining.

The third chemical is a binding agent - the duct tape.

In warm temperature, the diesel engine becomes effective quickly. In cold water, the accelerator has to warm up the environment quite well before the diesel engine can work effectively. As cold water removes heat from the scrubber cassettes, the conditions are less ideal for effective CO2 removal. Therefore, when diving cold water you must do two things: prebreathe well and cut your dive time. Prebreathing ensures that the accelerator kicks in and warms up sorb. Reduced dive time ensures that you're not diving with ineffective scrubber.

 

[inquis]

Never heard the diesel engine analogy, but it is genius! Thanks for that.