Low-energy consumption method for dehydrating ethanol into ethylene

A process for dehydrating an ethanol feedstock to give ethylene, comprising:

• a) a stage for vaporizing a vaporization feedstock comprising said ethanol feedstock in an exchanger by means of a heat exchange with a dehydration effluent resulting from stage c), so as to produce a vaporized feedstock;
• b) a stage for heating said vaporized feedstock in an exchanger by means of a heat exchange with a thermal fluid, so as to produce a superheated feedstock having a temperature of greater than 400° C. and less than 550° C.;
• c) a stage for dehydrating said superheated feedstock so as to produce a dehydration effluent, wherein said stage for dehydrating comprises a reaction section comprising at least one multitubular reactor in which the dehydration reaction takes place, said multitubular reactor comprising a plurality of tubes having a length of between 2 and 4 m and a shell, said tubes each comprising at least one fixed bed comprising at least one dehydration catalyst, said superheated feedstock being introduced into said tubes at an inlet temperature of greater than 400° C. and less than 550° C. and at an inlet pressure of between 0.8 and 1.8 MPa,
• a heat transfer fluid circulating inside said shell at a mass flow rate such that the ratio of the mass flow rate of said heat transfer fluid in the shell relative to the mass flow rate of said superheated feedstock introduced into said tubes is greater than or equal to 10, said heat transfer fluid having a temperature at the inlet into the shell of said multitubular reactor of greater than 430° C. and less than 550° C.;
• d) a stage for separating the dehydration effluent resulting from stage c) into an effluent comprising ethylene at a pressure of less than 1 MPa and an effluent comprising water;
• and
• e) a stage for purifying at least a portion of the effluent comprising water resulting from stage d) and the separation of at least one stream of purified water and at least one stream of unconverted ethanol.