NOVELTY - The heat, of at least one of the streams of the permeate which is to be cooled, before the entry of the stream into a vaporizer (2), or another permeate stream upstream of pervaporation unit (6), is taken in the cooling phase of at least one of the streams of the permeate, and the heat taken is at least partially directed as secondary energy to the use for heating of the mixture of ethanol and water entering into the pervaporation unit, which is arranged to dewater the mixture of the ethanol and water by pervaporation.    USE - Dewatering of mixture of ethanol and water in pervaporation process for dewatering ethanol, to retentate, from water as enriching to permeate, for use as component in fuel containing 85% ethanol and 15% gasoline.    ADVANTAGE - The method increases ethanol content by volume of 80-96% to 99.7%. The method is energy-efficient, and efficiently restores heat in the pervaporation process of the mixture as secondary energy for heating mixture.    DETAILED DESCRIPTION - The heat, of at least one of the streams of the permeate which is to be cooled, before the entry of the stream into a vaporizer arranged to vaporize at least partially once processed ethanol-water mixture by the pervaporation process, or another permeate stream upstream of pervaporation unit, is taken in the cooling phase of at least one of the streams of the permeate, and the heat taken is at least partially directed as secondary energy to the use for heating of the mixture of ethanol and water entering into the pervaporation unit, which is arranged to dewater the mixture of the ethanol and water by pervaporation. INDEPENDENT CLAIMS are included for the following:    (1) apparatus for dewatering mixture of ethanol and water in a pervaporation process, consisting of heat exchanger (HEXI) for exchanging heat energy from at least one of the streams of the permeate from the pervaporation unit to the stream of mixture of ethanol and water entering into the pervaporation unit for dewatering the mixture via pervaporation;    (2) heat exchanger consisting of unit (I) for primary circulation of fluid for receiving heat to be transferred, and unit (II) for secondary circulation of fluid for giving heat received from the primary circulation fluid via an heat-exchanging surface. Unit (I) comprises a connection unit for connecting at least to a permeate flow and/or a distillation product flow as a primary flow. Unit (II) comprises a connection unit to connect to the pervaporation unit heating circuit for heating a membrane unit in the membrane unit topology;    (3) use of heat exchanger in ethanol rectification process for restoring secondary energy for membrane heating;    (4) pervaporation process for dewatering ethanol-water mixture using the heat exchanger in an ethanol rectification process for restoring heat and directing the heat as secondary energy to membrane heating;    (5) pervaporation unit comprising the heat exchanger integrated into the pervaporation unit; and    (6) utility unit for ethanol rectification using the heat exchanger in pervaporation process for dewatering ethanol-water mixture.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view explaining ethanol rectification by pervaporation process.    Vaporizer (2)    Stream of liquid phase mixture of ethanol and water (5)    Pervaporation unit (6)    Dewatered mixture of ethanol and water (7)    Vaporized mixture of ethanol and water (8)    Heat exchangers (HEX1,XEX6,HEX7,HEX9,HEX10,HEXI)    Membrane unit (MU)