Commercial Desalination by Freezing

Freezing does work, but the reason why it's rarely used is because it's high energy inefficient, so it's going to be a very costly process. However, if you're still interested, the fresh water will float on the surface as ice, with the concentrated brine below.

You can try circulating LN₂ in metal pipes through the water. The intense cold of the LN₂ will cause the water to freeze up quickly. Take note that ice will form on the pipe. It's not a method I'll really recommend, but it will work. You may also want to consider using freon, methyl bromide, or some other similar refrigerant. FYI, I had actually studied it as a possibility to remove high TDS content from treated industrial effluent resulting from a flawed treatment process designed by another engineer, but I abandoned the idea because it would be too costly.

Comrade!

I would suggest "vapor compression distilation" instead. The inlet and outlet temperature is only 3 degrees, making it at least 200 times better...just saying...

Seaplanguy

It's not as attractive as evaporation in the first instance, and reverse osmosis [RO] in the second.

• Ships and platforms have, sometimes, an excess of low-grade heat that will make evaporation go like billy-o, which is why evaporation, less energy-effective than RO, will often be found there.
• If waste heat is not available then electricity is the fall-back position. At 2-4kWh per tonne of potable water delivered, RO wins over freezing every time.

The simple answer is that, while it could be done, other processes are more economic.

Well, I'm given to understand that, as an example, a RO seawater plant making 1,000,000 gallons per day needs about 53 megawatts over 24 hours--our plan will use electricity derived from solar, so the costs won't actually be astronomical [even at $65/MW that is only 0.003/gallon for electricity]--part of the plan is also about reusing the single-hull VLCC tankers and similar ships that are being phased out from petroleum hauling--another aspect is to get close to the places most in need, but far enough offshore to avoid most of the sewage spills and other pollution, plus directly drop the brine back into the sea [alternatively long pipes or hoses could be run for those purposes]

I'm also given to understand that a freezing method is LESS energy intensive [compared to Multi-Stage Flash for example] if only because it takes less energy to phase-change down in temperature that to shift up to boiling, even with vacuum. Plus there aren't the pipe scaling issues.

I mostly wanted to know if anyone was already doing this on any commercial scale.

No. Too costly.

I just found that a company is using ice to store AC cooling energy at night . This would be a good match to add desalination at the same time. Check this out http://www.calmac.com/benefits/general.pdf

The combination of those two technologies might be what you need to make this a commercial success. Their system seems already viable. All you need is to add the brine separator.

P.S. Don't forget who gave you this idea if you become rich...

This one even better: www.icesynergy.com

Ice Slurry floats.

Suggest tap your utility to give you off-peak rates normally at night operation. Make ice (fresh water) from seawater then thaw (sell the cool energy) by cooling a building then collect the fresh water.

This company developed technology for freezing desalination many years ago and is using it for snowmaking worldwide.

http://ide-tech.com/AllProducts.asp?id=1455&sid=1455&pid=1578

Sincerely,

Thanks for the input--I'm still years away from being able to do this but every bit helps...

I produce ice making equipment for fishing boats. Our seawater machine produces ice in a form about 80% frozen pure crystals and 20% concentrated brine which drains off by gravity leaving behind almost pure ice. See www.seaice.co.uk