Multi-stage processing and concentration of solutions

A process of concentrating a solution comprising the steps of:

• continuously heating a liquid body of the solution to be concentrated in a first vessel to drive off water vapor therefrom and maintain the said body at a high temperature in a first heating step;
• passing the overhead vapor from said first vessel to a counterflow gas-vapor-liquid direct heat exchange water heater as at least part of the heating medium thereto;
• passing the concentrated hot liquid bottoms from said first vessel as the overhead liquid input to a counterflow direct heat exchange cooling tower in gas-liquid contact with ambient air for further concentration thereof;
• withdrawing concentrated liquid bottoms from the cooling tower and passing a portion thereof out of the system as concentrated product;
• passing the gas-vapor overhead from the cooling tower to said counterflow water heater as another part of the heat exchanging medium thereto;
• continuously joining a continuous stream of new solution to be concentrated with the remaining of the concentrated liquid bottoms withdrawn from the cooling tower into a combined flow thereof,
• thereafter passing said combined flow in indirect liquid-liquid heat exchanging relationship with the liquid bottoms from the water heater prior to passing said combined flow to said first heating step to be concentrated therein,
• passing said combined flow after heat exchange with said water heater bottoms as a continuous feed to said first heating step to replace liquid evaporated therefrom, and
• passing said heat exchanged liquid bottoms to the overhead liquid input of the water heater as feed thereto.