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Date: Mon, 4 Nov 1996 18:26:27 -0800
To: Richard Pyle <deepreef@bi*.bi*.ha*.or*>
From: heyydude@pi*.co* (Mr. Dude)
Subject: Re: CO2 Absorbency
Cc: techdiver@terra.net
At last, something I can definitively comment on...

Rich, scrubber is essentially granulated Calcium Hydroxide (CaOH2), the
hydrated version of Calcium Oxide (Quicklime - CaO).  Quicklime absorbs CO2
faster than Hydrated Lime, but is incredibly reactive in the presence of
water, and can generate enough heat to melt damn near any plastic, and some
metals when mixed with water.

Hydrated Lime absorbs ANY CO2 it comes in contact with, reacting with it on
the molecular level to become Calcium Carbonate (Limestone - CaCO3).
Limestone is what it starts out as, and Limestone is what it shall become.

Therefore, since the reaction takes place on the molecular level, there is
NO transfer of CO2 within the body of the granule, except via microscopic
holes in the granule itself.  Once a molecule of CO2 has reacted with a
molecule of CaOH2 it becomes, once again, CaCO3, the Hydrogen atom is
driven off, where is combines with O2 and becomes water vapor once again.

That is why you can throw you used Sofnolime in the ocean with no ill
effects.  It simply absorbs CO2 from the water until it becomes Limestone
again.

There is sooo much limestone in the world because of all the little
critters throughout time that have taken CO2 out of the water, mixed it
with Calcium and an Oxygen free-radical to produce nice little CaCO3
shells.  When these critters die, they sink to the sea floor, eventually to
get compressed over time, to form almost pure Calcium Carbonate.  Your
marble table started out that way.

An important fact about Calcium Carbonate (Limestone) is that Calcium is
the fourth most common element in the Earth's crust, comprising 3.2%.  Only
Silicon, Aluminium, and Iron are present in greater quantities.

Lime (Calcium Oxide, or Calcium Hydroxide) is never found in a natural
state, due to its inherent instability (it absorbs any CO2 present, and
converts back to Calcium Carbonate).  It is a manufactured product made by
"calcining" limestone.  Calcining is the process of heating a substance to
a high temperature below the melting or fusing point, in this case, between
1,800 and 2,400 degrees Fahrenheit, causing loss of moisture, and
oxidation.  The calcining process drives off molecules of CO2 from the
limestone, leaving pure CaO - Calcium Oxide, or "QuickLime".

Calcium Oxide is the 5th most produced chemical in the United States, and
is used for everything from Steel manufacturing, to rebreather divers.

I produced a documentary on Lime several years ago, so the above is your
lesson for the day...

Kevin "Mr. Science"
Heyydude.


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