Process for separating a mixture of CO2, NO2 and nitrogen by distillation
By expanding CO2-rich product to cool and liquefy it for use in the distillation column, the method addresses cooling and NO2 removal limitations, enhancing the efficiency of CO2, NO2, mercury, oxygen, and nitrogen separation.
Patent Information
- Application Number
- FR2025003695
- Authority / Receiving Office
- FR · FR
- Patent Type
- Utility models
- Current Assignee / Owner
- Filing Date
- 2025-04-08
- Publication Date
- 2026-03-06
- Estimated Expiration
- 2035-04-08
AI Technical Summary
Existing methods for separating CO2, NO2, mercury, oxygen, and nitrogen face limitations in cooling output due to restricted nitrogen flow rates and high-pressure constraints, which hinder effective NO2 removal and overall efficiency.
A method involving the expansion of a portion of CO2-rich product through a valve to cool and liquefy it, sending it to a distillation column as a reboiling gas substitute, and vaporizing the liquid at different pressures to enhance cold production.
Enhances cooling output and improves NO2 removal efficiency by optimizing the distillation process, addressing the limitations of previous methods.
Abstract
Description
Title of the invention: Method for separating a mixture of CO2, NO2 and nitrogen by distillation
[0001] The present invention relates to a method for separating a mixture of CO2, NO2, mercury, oxygen, and nitrogen by distillation. In particular, the invention provides a simple method for producing cold.
[0002] It is known from EP1869385A1 to separate the mixture by pressure-toggle adsorption, producing a gas enriched in CO2 relative to the mixture and a gas enriched in nitrogen relative to the mixture. The nitrogen-enriched gas is expanded in a turbine to provide cooling for the process. The CO2-enriched gas is compressed, cooled in a heat exchanger, and separated by scrubbing to remove NO2 and form an NO2-depleted overhead gas, as described in FR2988167A1. The overhead gas is compressed, purified of mercury, as described in FR3148642A1, and then sent to a distillation column that produces a CO2-depleted, oxygen- and nitrogen-enriched overhead gas and a CO2-enriched, oxygen- and nitrogen-depleted liquid in the tank. The liquid is vaporized by heat exchange with the CO2-enriched gas in the heat exchanger and then part of the vaporized liquid is compressed in a compressor preferably to a supercritical pressure.Part of the compressed gas in the compressor can be separated again in a scrubbing column to remove residual NO2. The cooling output is limited by the flow rate of nitrogen-enriched gas sent to the turbine, which is limited by the design of the adsorption unit, and by the pressure of the gas entering the turbine, which is limited by the pressure of the scrubbing column, the pressure of which cannot be too high if proper NO2 removal is to be desired.
[0003] This problem is solved by taking a portion of the CO2-rich product compressed in the compressor, expanding it through a valve to cool and liquefy it, and sending it to the distillation column, which acts as a gas-liquid separator. This produces gas in the column that can replace the reboiling gas normally sent to the distillation column's tank.
[0004] The liquid formed joins the column tank liquid and is vaporized at two different pressures with CO2 at 5 and 11 bars to supplement the required cold production.
[0005] According to one aspect of the invention, a process is provided for separating a mixture of CO2, NO2, mercury, oxygen and nitrogen by distillation in which: i. The mixture is separated by pressure-switching adsorption, producing a gas enriched in CO2 relative to the mixture ii. The CO2-enriched gas is compressed, cooled in a heat exchanger, separated by scrubbing to remove NO2 and to form a NO2-depleted overhead gas. iii. The overhead gas is compressed, purified of mercury, and then sent to a distillation column which produces a gas depleted in CO2 and enriched in oxygen at the top and a liquid enriched in CO2 and depleted in oxygen in the tank iv. The CO2-enriched liquid is vaporized by heat exchange with the CO2-enriched gas in the heat exchanger, and then the vaporized liquid is compressed in a compressor, forming a compressed gas and v. Part of the compressed gas is expanded and sent to the distillation column to separate.
[0006] Steps ii) and iii) can be reversed so that NO2 is removed after oxygen, as described in FR3127556A1 and EP4520416.
Claims
[Claim 1] Demands A process for separating a mixture of CO2, NO2, mercury, oxygen, and nitrogen by distillation in which a. The mixture is separated by pressure-toggle adsorption, producing a gas enriched in CO2 relative to the mixture. b. The CO2-enriched gas is compressed, cooled in a heat exchanger, separated by scrubbing to remove NO2 and to form a NO2-depleted overhead gas, c. The overhead gas is compressed, purified of mercury, and then sent to a distillation column which produces a gas depleted in CO2 and enriched in oxygen at the top and a liquid enriched in CO2 and depleted in oxygen in the tank d. The CO2-enriched liquid is vaporized by heat exchange with the CO2-enriched gas in the heat exchanger, and then the vaporized liquid is compressed in a compressor, forming a compressed gas and e. Part of the compressed gas is expanded and sent to the distillation column to separate.