{HEAD ~ A method} of distillation employing a heat pump using a vapor stream from within the distillation system as a heat source and a liquid stream from within the distillation system as {TAIL ~ a heat sink} 
{ HEAD ~ A method } of distillation employing a heat pump using a vapor stream from within the distillation system as a heat source and a liquid stream from within the distillation system as { TAIL ~ a heat sink }
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