Refinery
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Drying CaCl2?
How to properly dry 77% Calcium chloride, preferably retaining it's granulated form?
If it's heated, it will liquefy in it's own water of hydration and form a monocrystalline solid block of salt.
Does slow oven drying produce desired dehydration?
Or is vacuum drying only option? What should be used as desiccant, or should the drying be completed with minor heating in a (distillation) apparatus
where the moisture absorbent(silica gel for ex) is placed in the other vessel?
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Junk_Enginerd
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Just put it in the oven, it's not a difficult substance to dry. If you absolutely want to keep the shape, then I suppose you'll just have to ramp up
the temperature slowly enough. Warm air should do it as well, again you'll need some way of controlling the temperature.
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Syn the Sizer
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I think it is almost inevitable that it will melt by heating in the oven. The melting point starts at 30oC for the hexahydrate and is
260oC for the monohydrate where it decomposes into the anhydrous form. I am pretty sure the product needs to melt in order to decompose to
the next lower hydrate form.
If you need it granular you could try grinding it after the fact. I know it's hard since it usually forms a hard sheet.
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Refinery
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It doesn't appear to be a problem if it is dried in thin enough sheets (2-3mm thick) in wide oven pans so it can just be cracked and stored as is.
AFAIK commercial CaCl2 flakes are made by rolling the sludge and heating it so it solidifies and crumbles during the process and it's sieved and
bagged.
I did not remember to ask as well how suitable is the 77% hydrated form as is for desiccant use? It does the job in ambient conditions, but if used in
vacuum desiccator, will it form equilibrium and stall due to being too hydrated already?
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Syn the Sizer
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That is 23% of the water removed, it will still dry just not much, honestly I would dry it more or you really won't be absorbing much water. The
tetrahydrate will only absorb 2 moles of H2O per mole of desiccant before fully hydrated to the hexahydrate form and the monohydrate 5
moles of H2O. It just won't be as successful as the lower hydrates. Also to note, I feel that drying to monohydrate is still very useful
and saves on time and energy heating from 175oC to 260oC just to lose 1 more mole of H2O.
Heat in the oven at ~175oC until it forms a thin hard layer of the monohydrate. As long as the temp is below 260oC it should
harden at the monhydrate form.
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RogueRose
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I can't remember it ever melting on me. If you are using ice melter then I think you should be fine as I've always thrown it in on a high heat IIRC.
As some others have suggested, I would slowly ramp the temp up and see if it melts. I'd try a small sample at 350 and see if it melts or not, if it
doesn't then you are good to do the rest.
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Syn the Sizer
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If the CaCl2 is in it's heptahydrate form it will melt at ~30oC, if it's the tetrahydrate form it will melt at ~45.5oC, the
dihydrate at ~175oC, and monohydrate ~260oC. It will take ages to evaporate H2O under 100oC so unless you
have the dihydrate form chances are it will melt. If it is the dihydrate form I wouldn't bother drying it because it will suck up 4 moles of water per
mole of CaCl2. Also I don't believe it will decompose to the next lower hydrate form unless it reaches and maintains at least it's melting point of
the current form long enough to dissipate the H2O
.
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