Half a croissant, on a plate, with a sign in front of it saying '50c'
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Mixed Cycle Desalination

Reverse Brayton, Reverse Rankine hybrid
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This is a type of salt water distiller, that works well below the boiling point of water.

First, there's the salt water chamber, a thermally insulated, cylindrical chamber, with two heat exchanger coils in it, and an air bubbler at the bottom.

Salt water is pumped in at the bottom and is heated as it rises.

Dry air is pumped in at the bottom through the bubbler; the air bubbles become humid on their way up, partly because the air is dry to start with, and partly because the water is warm near the top.

The bubbles remove enough moisture that the salt water becomes a concentrated brine by the time it reaches the top.

The warm brine, upon reaching the top, then flows down through one of the two heat exchanger coils in the chamber, giving most of it's heat back to the unconcentrated salt water.

The air, upon reaching the top, passes through a baffle that ensures no saltwater is mixed with the air, and then is compressed.

The hot, compressed, humid, air is then sent through the other heat exchanger coil, giving it's heat to the salt water.

After the air reaches the bottom, it goes through an expander, which air pressure into mechanical energy, which reduces the energy needed to compress the air in the first place.

Not only will some water condense out of the humid compressed air due to cooling while in the heat exchanger, but more water will condense due to the cooling of the air when the air is expanded.

After expansion, the air goes through a gas/liquid seperator, and the distilled water is pumped away.

The cold air then goes through a heat exchanger, where the waste brine (which was still warm) heats the air back up to it's starting temp.

Then the air goes back to the bubbler.

goldbb, Jul 20 2009

Drawing of your idea https://docs.google...Po&authkey=CMnfwJYG
remarks are welcome [pashute, Nov 29 2010]

[link]






       Sounds good in paper form - would be nice to see it in diagram form!
Skrewloose, Jul 20 2009
  

       I would love to do so, but I lack the artistic skills.   

       If any HBer would like to illustrate this idea, feel free to do so.   

       But, for those with good imaginations... picture a cylinder full of water, drawn as blue at the bottom, and purple at the top. It's got two spirals within it, one labeled brine, one labeled compressed air. It's got a bubbler at the bottom, and baffles to seperate air from splashes of water at the top.   

       Outside of this cylinder, near the top of it, is a symbol indicating an air compressor, taking air from above the baffles and moving it to the compressed air coil.   

       Outside of the cylinder near the bottom, is a symbol indicating an air powered motor, with an incoming pipe from the compressed air tube, and a shaft connecting it to the air compressor.   

       Off to the side, is a rectangle representing a countercurrent heat exchanger, with a drawing of a pipe from the bottom of the brine spiral, and a pipe from the air powered motor. The brine output of the heat exchanger is labled "waste", and the air output of the heat exchanger is the bubbler at the bottom of the main tube.
goldbb, Jul 23 2009
  

       Sorry, did this without reading your instructions.
pashute, Nov 29 2010
  

       Brilliant and concise.   

       Where are all of its buns.   

       I can picture this mounted at the bottom of a high solidus wind pump. With a small flat solar thermal panel. Taking brackish ground water from the pump and giving drinking water.   

       Another use for this design would be as a still. Replace the salt water with ferment able augers and yeast. And use the carbon dioxide that is produced in place of the circulating air. The out put will be alcohol flavoured by the volatile components of the grain or grape that is fermented.
j paul, Jul 31 2011
  
      
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