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Cliff, Check this out: http://people.oregonstate.edu/~atwaterj/zeolite.htm From: owner- Greg A molecular sieve separates the CO2 gas stream from the
O2 and N2 gas stream by forcing the air mixture through an engineered
media ( zeolite ) that is sized to allow the larger O2 (3.5
angstroms) and Nitrogen (3.6 angstroms) molecules to pass and blocks
the smaller CO2 molecules (3.3 angstroms) from passing. So now
that you have a slip stream of pure CO2 you have to do something with this
like compress the CO2 and purge the gas out of the
hull for figure out something else to do with this concentrated CO2
stream. I personally think it is to complicated for a psub
and breaks the KISS rule. It is a better fit for a large nuclear
boat. Cliff
From: Greg
Cottrell <greg@precisionplastics.com> Hi Cliff, What do you think about using molecular
sieve for CO2 removal? Greg C From: owner- The easiest way to build a CO2
scrubber is to buy some SodaSorb HP (4/8 mesh) and use 2.2
lbs of this absorbent for every 8 hours per person in the boat. You
pack enough of this absorbent for your normal dive into canister or
any container with a fan and your good to go. If you follow ABS rules, you
carry some reserve absorbent to give you an additional 72 hours of bottom
time. For ABS rules this this means for say and 8 hour dive time
plus the 72 hours reserve, you would need about 22 lbs of Sodasorb
HP. As a check, the Deepwork 2000 carries 24 lbs of this absorbent. The 2.2 lbs for 8 hours comes from
http://www.sodasorb.com/English/downloads/Sodasorb_Manual.pdf, page 16 in
which is says "In a properly packed and well designed canister... for
8-hour capacity... a canister should hold approximately 1 kilogram of (2.2
pounds) of SodaSorb absorbent". On my boat, I picked a canister size to
meet my normal mission time and then played around with different fan motors
until I found a fan size that would circulate the cabin air through the
canister without pulling so much current that it would drain my emergency
battery bank before I reached the 72 hours limit. While this worked fine, I wondered about
what a "properly packed and well designed canister" meant. I
recently came across an excellent technical report that goes into a lot more
detail on this subject. It is titled "Design Guidelines for Carbon
Dioxide Scrubbers", (May 1983, revised July 1985) by M.L. Nuckols, A.
Purer and G.A. Deason of the Naval Systems Center , Panama city This goes into the impact of design
variables such as temperature, pressure, canister length and diameter, relative
humidity, CO2 concentration, flow rate through the canister and particle
size. The experimental work sited in the paper is for SodaSorb.
While this report was written for designing re-breather canisters
operating at elevated pressures that a diver would see, it does handle the
limiting condition of 1 atm that we would see in a 1-atm. psub. So if you need a little "light"
reading while your doing your business in the morning, you might want to have a
read. Now if we could just get someone to drop this into an excel
spreadsheet, we would be in business. Cliff |