Mechanical Vapour Recompression (MVR) Evaporation is an energy efficient process that produces pure distilled water from wastewater containing dissolved solids. With evaporation, pure water is boiled from wastewater and can be later condensed as distilled water. The dissolved solids remain in solution and are removed from the system as concentrated blowdown.

In an MVR Evaporator, a compressor is used to add the energy required to boil water. The feed water passes through two preheat exchangers where sensible heat is absorbed from the distillate and concentrate products leaving the system. The feed then passes through a de-aerator column where dissolved gases are vented. The feed then passes into a recirculation loop where concentrate circulates through an evaporator exchanger and a vapour / liquid separator. A portion of the concentrate is boiled to steam in the evaporator exchanger and separated from the liquid in the separator vessel. A compressor draws the steam off the separator and boosts the pressure, which results in an increase in temperature. The steam is driven through the opposite side of the evaporator exchanger where it condenses to distilled water, releasing its latent heat to the boiling concentrate. The distilled water is then pumped through the preheat exchanger where remaining sensible heat is transfered to the incoming feed. Concentrate is continually pumped from the recirculation loop out of the unit to prevent the solution from reaching saturation. The concentrate also passes through a preheat exchanger where remaining sensible heat is transferred to the incoming feed.

Producing distilled water from direct-fired distillate requires 1000 BTU/lb of heat energy. Due to the sophisticated heat exchanger configuration in MVR evaporation, distilled water can be theoretically produced with only 25-28 BTU/lb, 1/40th the energy.