Method for controlling the reboiler section of a dual reboiler distillation column

Claim 1

A method for controlling heat input to the reboiler section of a distillation column comprising a reboiler section and a fractionation section, said column having two external heat-recovery reboiler heaters appurtenant thereto, which method comprises the steps of: a. withdrawing a liquid bottoms stream from said reboiler section; b. regulating the quantity of a first portion of said bottoms stream removed from said distillation column as a bottoms product, in response to the level of liquid in said reboiler section; c. introducing a second portion of said bottoms stream into a first of said external heaters, and therein heating and partially vaporizing said second portion via indirect contact therein with an external process stream; d. passing the heated, mixed-phase second portion of said bottoms stream into a substantially liquid-free area of said reboiler section, and therein disengaging liquid from said heated mixed-phase; e. introducing a third portion of said bottoms stream into the second of said external heaters, and therein heating and partially vaporizing said third portion; f. passing the heated, mixed-phase third portion of said bottoms stream into said substantially liquid-free area of the reboiler section, and therein disengaging liquid therefrom; g. measuring, within said reboiler section, the quantity of vapor passing upwardly from the reboiler section into said fractionation section of said distillation column; and h. regulating the heat input to said second external reboiler heater in response to a signal representative of the measured quantity of vapor passing into said fractionation section, thereby regulating the heat input to said reboiler section.

Claim 2

A method for controlling heat input to the reboiler section of a distillation column comprising a reboiler section and a fractionation section, said column having two external heat-recovery reboiler heaters appurtenant thereto, which method comprises the steps of: a. withdrawing a liquid bottoms stream from said reboiler section; b. regulating the quantity of a first portion of said bottoms stream removed from said distillation column as a bottoms product, in response to the level of liquid in said reboiler section; c. introducing a second portion of said bottoms stream into a first of said external heaters, and therein heating and partially vaporizing said second portion via indirect contact therein with an external process stream; d. passing the heated, mixed-phase second portion of said bottoms stream into a substantially liquid-free area of said reboiler section, and therein disengaging liquid from said heated mixed-phase; e. introducing a third portion of said bottoms stream into the second of said external heaters, and therein heating and partially vaporizing said third portion; f. passing the heated, mixed-phase third portion of said bottoms stream into said substantially liquid-free area of the reboiler section, and therein disengaging liquid therefrom; g. measuring, within said reboiler section, the quantity of vapor passing upwardly from the reboiler section into said fractionation section of said distillation column; and h. regulating the heat input to said second external reboiler heater in response to a signal representative of the measured quantity of vapor passing into said fractionation section, thereby regulating the heat input to said reboiler section.