Patent ID: 6336997
Filing Date: 2002-01-08
Classification: B01D,C07C,Y10S

Abstract:
A process for refining a heat-sensitive compound contained in a multi-component liquid mixture by distillation, comprising the steps of:(1) feeding a multi-component liquid mixture comprising a lower boiling temperature component and a higher boiling temperature component containing a heat-sensitive component, into a distillation column having a top outlet located in a top portion of the distillation column and a bottom outlet located in a bottom portion of the distillation column, the bottom outlet being connected to a falling-film reboiler having a plurality of heat-conductive vertical pipes spaced from each other and arranged in a heating chamber through which a heating medium passes; (2) distilling the multi-component liquid mixture in the distillation column to generate a vapor fraction comprising the lower boiling temperature component and a liquid fraction comprising the higher boiling temperature component, in such a manner that (A) the liquid fraction is withdrawn through the bottom outlet of the distillation column and introduced into the reboiler at a rate such that the introduced liquid fraction falls in the form of a film along inner surfaces of the vertical pipes at a Reynolds number (Re) of 700 to 10,000; (B) the film falling through the vertical pipes is heated by the heating medium passing through the heating chamber to a temperature lower than the heat-deterioration-starting temperature of the heat-sensitive compound but sufficient to evaporate a portion of the falling film liquid fraction wherein an evaporation rate of the falling film is controlled at 1% to 15% by weight of the flow rate of the liquid fraction introduced into the reboiler, per one pass of the liquid fraction through the reboiler; (C) the resultant evaporated and non-evaporated portions of the liquid fraction are withdrawn from the reboiler and returned into the distillation column through a returning inlet thereof located above the level of the liquid fraction accumulated in the bottom portion of the distillation column; and (D) the evaporated portion of the returned liquid fraction heat exchanges with the multi-component liquid mixture fed into the distillation column to evaporate the lower boiling temperature component; (3) delivering the resultant vapor fraction comprising the lower boiling temperature component through the top outlet of the distillation column while allowing the resultant liquid fraction comprising the higher boiling temperature component to be accumulated in the bottom portion of the distillation column; and (4) recovering a portion of the liquid fraction accumulated in the bottom portion of the distillation column and comprising the higher boiling temperature component containing the heat-sensitive compound from the bottom portion of the distillation column.