posted 13 years ago
I am picturing a 5 gal pocket rocket, with 1/4 inch or 3/8ths pipe wrapped around it, and somewhat high flow, so you get live steam just as it gets to the end of the pipe. The supply tank would be up relatively high, so you can run a loop of pipe down and back up without too much chance of steam-locking the pipe.
Then the steam gets put through a condenser (cold pipe, can be metal or glass, usually coiled up in an ice bath or cool water bath). In my version, that condenser would drip into an evaporation chamber on the stovetop, with another condenser that drips into your final collection beaker.
If I understand correctly, you are looking for a very fast way to distill water, and get the purest product you can. Some salts and minerals will only come out when the water is evaporated the second time, just boiling it can spit minerals into your distillate. If you are just looking to create drinkable water, you might be able to use the boiled-off results.
You might also look at prices for a reverse-osmosis filtration system. There are some on the market for under $100, but they might not meet the 30-minute deadline.
If you pre-filter all the guck with cheap materials you should have a much easier time with either distillation or osmosis.
(Cheesecloth, coffee filters, worn cotton; Erica remembers somebody suggesting 4 layers of an old cotton sari will remove most waterborne parasites in the Ganges if you don't have anything else).
As far as the pots, direct contact just above the flame path will give you good heat transfer, but if you are picturing an open-flame type rocket cookstove, you also have to keep the soot and smoke out of your setup. See if you can find Erica's illustration of the J-tube pocket rocket; it's a contained fire that gives good access to both high- and low-temperature heat without messing up your fire's burn by making the fire itself too cold.
A drip gives control; but it's slow. A big hot bath (maybe with a towel or something to speed evaporation) might be faster, but could give too much pressure unless your condenser is set up to accept all that steam at once. A pipe with fixed diameter, and controlling the flow by raising or lowering the source tank, lets you put a fair amount of material through quickly but stay within the limits of your condenser. You'd definitely have to pre-filter it though, or risk blowing the pipe.
Need more info?
Ernie and Erica
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