Method of and an apparatus for separating a liquid mixture

A method of separating a liquid mixture using an apparatus having at least two pervaporation membrane modules connected in multi-stage form, comprising the steps of:

• heating the liquid mixture;
• supplying the heated liquid mixture to a pervaporation membrane module of a first stage;
• circulating a portion of the non-permeated liquid through a circulation pipe into a liquid mixture feeding pipe before a heater and supplying the remaining portion of the non-permeated liquid to the pervaporation membrane module of a next stage;
• measuring the temperature of the liquid in the liquid mixture feeding pipe, in which the non-permeated liquid discharged from the pervaporation membrane module of the first stage has been mixed with the liquid mixture, or in the circulation pipe for the non-permeated liquid;
• and
• stopping a new supply of the liquid mixture to the first stage and/or extraction of the non-permeated liquid at a last stage when the measured temperature is out of a predetermined range.

A pervaporation separation apparatus which comprises:

• a pervaporation membrane module,
• a liquid mixture feeding pipe,
• a heater disposed in the liquid mixture feeding pipe,
• a circulation pipe for non-permeated liquid,
• a thermometer disposed in the liquid mixture feeding pipe, in which a circulation liquid has been mixed with the non-permeated liquid, or in the circulation pipe for the non-permeated liquid, and
• a controller for stopping new supply of the liquid mixture and/or extraction of the non-permeated liquid when the thermometer indicates a value which is out of a predetermined range.