Abstract: The present invention provides a method for operating a rectification column (1000) for separating a mixture (S) containing a component A and a component B having a boiling point higher than that of the component A at an operating pressure of the rectification column (1000) which is lower than ambient pressure, wherein the method comprises a step for controlling the mass fraction of the component B in the product stream of the component A (P1) to a value within a first target range from 0.1% to 5.0% and the mass fraction of the component A in the product stream of the component B (P2) to a value within a second target range from 0.1% to 5.0%, wherein the control is carried out as a function of a controlling temperature (TC) for which a setpoint TCsetpoint is calculated according to the equation TCsetpoint=T2+F·(T1?T2), where F is a factor which is in the range from 0.1 to 0.

Abstract: The invention relates to a cascade tray suitable for use in a rectifying column and comprising openings in the weir-type cascade edge, to a rectifying column containing at least one cascade tray according to the invention, to a method for operating such a rectifying column, and to the use of a claimed rectifying column in the fractionation of specific substance mixtures.

Abstract: A distillation column for separating a multicomponent mixture into at least three fractions. The distillation column has at least one separating wall and at least one material exchange element (1) above the at least one separating wall. A device (10) for mixing the steam flows flowing upwards to the left and the right of the at least one separating wall is arranged between the at least one separating wall and the at least one material exchange element (1). The use of the distillation column for purifying isocyanates, in particular for toluene diisocyanate (TDI), is also described.

Abstract: The invention relates to a cascade tray suitable for use in a rectifying column and comprising openings in the weir-type cascade edge, to a rectifying column containing at least one cascade tray according to the invention, to a method for operating such a rectifying column, and to the use of a claimed rectifying column in the fractionation of specific substance mixtures.

Abstract: The present invention relates to a purifying apparatus for polycarbonate polyols, especially for removal of cyclic alkylene carbonates, comprising an evaporation unit (1) provided with a heater (10) and having an inlet (6) disposed at the top end thereof and a bottoms vessel (11), and a stripping column (2) connected downstream of the evaporation unit (1) and having a top (21) and a bottom (23), wherein a feed (5) for the polycarbonate polyol to be purified opens into the inlet (6) to the evaporation unit (1) and a gas outlet line (12) and a connecting line which opens into the top (21) of the stripping column (2) and is equipped with a pump (18) depart from the evaporation unit (1), and wherein a gas inlet line (24) for an inert gas opens into the bottom (23) of the stripping column (2) and a product line (27) for the purified polycarbonate polyol departs from the bottom (23) of the stripping column (2) and a gas outlet line (25) departs from the top (21) of the stripping column (2).

Abstract: The invention relates to a distillation column for separating a multicomponent mixture into at least three fractions. The distillation column has at least one separating wall and at least one material exchange element (1) above the at least one separating wall. A device (10) for mixing the steam flows flowing upwards to the left and the right of the at least one separating wall is arranged between the at least one separating wall and the at least one material exchange element (1). The invention likewise relates to the use of the distillation column according to the invention for purifying isocyanates, in particular for toluene diisocyanate (TDI).

Abstract: The present invention relates to a purifying apparatus for polycarbonate polyols, especially for removal of cyclic alkylene carbonates, comprising an evaporation unit (1) provided with a heater (10) and having an inlet (6) disposed at the top end thereof and a bottoms vessel (11), and a stripping column (2) connected downstream of the evaporation unit (1) and having a top (21) and a bottom (23), wherein a feed (5) for the polycarbonate polyol to be purified opens into the inlet (6) to the evaporation unit (1) and a gas outlet line (12) and a connecting line which opens into the top (21) of the stripping column (2) and is equipped with a pump (18) depart from the evaporation unit (1), and wherein a gas inlet line (24) for an inert gas opens into the bottom (23) of the stripping column (2) and a product line (27) for the purified polycarbonate polyol departs from the bottom (23) of the stripping column (2) and a gas outlet line (25) departs from the top (21) of the stripping column (2).