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In this video I'm going to turn seashells into dry ice. Sea shells are
mostly made up of limestone - or Calcium Carbonate (CaCO3), which can be
decomposed into Calcium Oxide (CaO) and Carbon Dioxide (CO2) when heated
to around 900C. I used a 500W induction heater i built to heat a sealed
pipe full of sea shells to a hot enough temperature and collected the
CO2 gas into a beach ball by using a vacuum pump to extract it from the
pipe.
For limestone decomposition to occur at a reasonably fast rate, the
temperature really needs to be over ~1000C, so this process took several
hours (even for only ~50 grams of limestone) and required a vacuum pump
to pull off the CO2. I broke down the remainder of my sea shells by
dissolving them in vinnegar, and saved the Calcium Acetate biproduct for
later use as a solid fuel for camping/hiking.
Once I collected a decent volume of CO2, I used a refrigeration
compressor to pump it into a plate-stack heat exchanger and used a
propane-based vapor compression refrigeration system to chill the high
pressure CO2 down to about -30C, so it required only modest pressure to
liquify. The refrigeration system is actually the pre-cooler stage for
my joule-thomson cryocooler, which i borrowed for this video.
Once a decent mass of CO2 has been pumped into the heat exchanger and
liquified, it's discharged through a ~1mm diameter capillary tube into a
thermos with a glass wool baffle to stop high speed gases from carrying
away tiny particles of the ice.
With a little bit of improvement to the limestone furnace temperature,
and some minor tweaks to my refrigeration system, this could be an
extremely cheap way to make dry ice, assuming a limestone source is
available. With the right setup, costs could be as low as a few cents
per pound of ice.
Induction Heater Schematic:
https://drive.google.com/file/d/1WWGMMiXeocOpjPDXXiNxOdZxMykq30Rp/view?usp=sharing
Music Used:
Kevin MacLeod - George Street Shuffle
Kevin MacLeod - Groove Groove
Kevin MacLeod - Lobby Time