Separation of fluid mixtures in multiple distillation columns
AssigneeAir Products and Chemicals, Inc.
InventorsRakesh Agrawal, Jianguo Xu
Life of this patent
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Abstract
A fluid mixture is separated by distillation in a two column system in which the feed is prefractionated in a first column having at least one separation stage above the feed and the prefractionator bottoms provides feed to a second column operating at a lower pressure. Cooling for condensing the overhead vapor of the first column is provided by heat exchange with flashed prefractionator bottoms or with an intermediate fluid in the second column. The two-column system is readily combined with a high pressure column in a three-column distillation system for separating air which is particularly useful for integration with a gasification combined cycle combustion turbine system. Optionally, three nitrogen products can be produced at three different pressures.
Claims35
A method for the separation of a fluid mixture containing at least one more volatile component and at least one less volatile component which comprises:
- a) introducing said fluid mixture at a first pressure as a first feed stream into a first distillation column having at least one separation stage above the feed point and withdrawing therefrom a first overhead vapor and a first bottoms liquid;
- b) flashing said first bottoms liquid to a second pressure, feeding the resulting flashed first bottoms stream to a second distillation column, and withdrawing therefrom a second overhead vapor enriched in said more volatile component and a second bottoms liquid enriched in said less volatile component;
- and
- c) condensing at least a portion of said first overhead vapor and returning at least a portion of the resulting first condensate to the first column as reflux, wherein the cooling duty for condensing said first overhead vapor is provided by indirect heat exchange with either (1) fluid at an intermediate point in said second column or (2) at least a portion of said resulting flashed first bottoms stream prior to said second distillation column;
- wherein either (1) the temperature at the bottom of said first column is equal to the temperature at the bottom of said second column and the temperature at any other point in said first column is between the highest and lowest temperatures in said second column or (2) the temperature at any point in said first column is between the highest and lowest temperatures in said second column.
A method for the separation of a fluid mixture containing at least one more volatile component and one less volatile component which comprises:
- a) introducing said fluid mixture at a first pressure as a first feed stream into a first distillation column having at least one separation stage above the feed point and withdrawing therefrom a first overhead vapor and a first bottoms liquid;
- b) flashing said first bottoms liquid to a second pressure, feeding the resulting flashed first bottoms stream to a second distillation column, and withdrawing therefrom a second overhead vapor enriched in said more volatile component and a second bottoms liquid enriched in said less volatile component;
- c) condensing at least a portion of said first overhead vapor and returning at least a portion of the resulting first condensate to the first column as reflux, wherein the cooling duty for condensing said first overhead vapor is provided by indirect heat exchange with either (1) fluid at an intermediate point in said second column or (2) at least a portion of said resulting flashed first bottoms stream prior to said second distillation column;
- and
- d) withdrawing one or more intermediate products consisting of a portion of said first condensate, a portion of said first overhead vapor, or portions of said first condensate and said first overhead vapor;
- wherein either (1) the temperature at the bottom of said first column is equal to the temperature at the bottom of said second column and the temperature at any other point in said first column is between the highest and lowest temperatures in said second column or (2) the temperature at any point in said first column is between the highest and lowest temperatures in said second column.
A method for the separation of a fluid mixture containing at least one more volatile component and at least one less volatile component which comprises:
- a) introducing said fluid mixture at a first pressure as a first feed stream into a first distillation column having at least one separation stage below the feed point, and withdrawing therefrom a first overhead vapor and a first bottoms liquid;
- b) condensing said first overhead vapor and returning at least a portion of the resulting first condensate to the first column as reflux, pumping the remaining portion of said first condensate to a second pressure, and introducing the resulting pressurized condensate into a second distillation column;
- and
- c) withdrawing from said second column a second overhead vapor enriched in said more volatile component and a second bottoms liquid enriched in said less volatile component;
- wherein either (1) the temperature at the top of said first column is equal to the temperature at the top of said second column and the temperature at any other point in said first column is between the highest and lowest temperatures in said second column or (2) the temperature at any point in said first column is between the highest and lowest temperatures in said second column.
Dependencies are inferred from the claim text.