Vapor distillation apparatus with two disparate compressors

A vapor compression system including in combination an evaporator vessel, heat exchange tube within said vessel, first and second ends of said heat exchange tube, a rotary positive displacement compressor, an outlet of said vessel, first conduit means communicating said outlet with said rotary compressor, a liquid ring compressor, interstage conduit means communicating said rotary compressor with said ring compressor, second conduit means communicating said ring compressor with said first end of said heat exchange tube, a distillate receiving vessel, and third conduit means communicating said second end of said heat exchange tube with said distillate receiving vessel.