Abstract: A double-effect evaporator comprises a first and a second effects and an external steam ejector, each of the effects having feed-liquid spray means, a bundle of heat-transfer tubes below the spray means and extending between headers, and a concentrated liquid collector. The first effect heat-transfer tubes extend perpendicularly to the second effect tubes. A suction port of the ejector opens into the second effect evaporation chamber. A diffuser of the ejector extends in parallel to the second effect heat-transfer tubes. A discharge port of the ejector opens into the inlet header of the first effect. The first effect evaporation chamber is connected with a duct straight to the inlet header of the second effect.

Abstract: A process for evaporation comprises the step of introducing high-temperature steam successively into separate bundles of horizontal heat-transfer tubes and spraying feed-liquid over the tubes. The number of the tubes in each bundle is smaller than that in the next lower bundle. The steam is first introduced into the tubes of the bottom bundle after cooled by subjection to condensate produced in the tubes of the middle bundle. An evaporator is also disclosed.