Patent ID: 9410738
Filing Date: 2016-08-09
CPC Classification: C01B,F25J

Claim Text:
1. A method for producing carbon monoxide by cryogenic distillation using a system of distillation columns fed by a mixture comprising at least hydrogen, carbon monoxide and for at least part of the time nitrogen, the method comprising a first operation mode and a second operation mode, wherein in both the first operation mode and the second operation mode, the method comprises the steps of: cooling the mixture to be separated to a distillation temperature; purifying the mixture of hydrogen to produce a fluid, wherein the fluid comprises carbon monoxide and at least part of the time nitrogen, wherein the fluid has reduced amounts of hydrogen as compared to the mixture; introducing the fluid to a denitrogenation column under conditions effective to separate the carbon monoxide from the nitrogen in order to produce a carbon monoxide-rich liquid at the bottom of the denitrogenation column and a nitrogen-rich gas at the top of the denitrogenation column, wherein the nitrogen-rich gas is produced when nitrogen is present within the denitrogenation column; withdrawing the carbon monoxide-rich liquid from the denitrogenation column and a vaporized liquid from the system of columns; wherein in the first operation mode, the method further comprises the step of: condensing a portion of the nitrogen-rich gas in a condenser to form condensed nitrogen and returning at least a portion of the condensed nitrogen to the denitrogenation column; and regulating the pressure of the denitrogenation column by withdrawing a purge flow of nitrogen from the condensed nitrogen; wherein in the second operation mode, the method further comprises the step of: regulating the pressure of the denitrogenation column by withdrawing a carbon monoxide-rich gaseous flow from the denitrogenation column, wherein the method switches from the first operation mode to the second operation mode when the pressure of the denitrogenation column cannot be maintained by withdrawing the purge flow of the nitrogen from the condensed nitrogen.