Method and device for separating a mixture containing carbon dioxide by means of distillation
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Solution Overview
Problem
Current distillation methods for separating carbon dioxide from mixtures containing NOx are inefficient, particularly in oxycombustion processes, as they often require complex exchanger systems and lack effective NOx removal mechanisms, leading to sub-optimal energy usage and product purity.
Innovation Solution
The method involves a dedicated NOx removal column upstream of the distillation column, where the overhead gas is mixed with the carbon dioxide stream and heated in an exchanger, with the bottom liquid being vaporized and expanded through turbines, and the NOx-rich liquid returned to the boiler, optimizing energy transfer and separation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a dedicated NOx removal column is added upstream of the distillation column, then NOx content in the separated carbon dioxide is reduced, but device complexity increases
Solution Approach 1:
The separation process is divided into two distinct stages: first, a dedicated NOx removal column eliminates nitrogen oxides from the feed gas; second, a distillation column separates carbon dioxide from the purified gas stream. This segmentation allows each column to be optimized for its specific function, effectively removing NOx while maintaining manageable complexity through functional specialization.
2Use of energy by moving object
If the overhead gas is heated in the first exchanger and mixed with the carbon dioxide stream, then energy transfer is optimized, but device complexity increases
Solution Approach 1:
The overhead gas from the distillation column, which contains residual heat, is routed back through the first exchanger to preheat the incoming carbon dioxide-containing feed stream. This merging of the heating function with the existing exchanger infrastructure optimizes energy transfer by recovering waste heat, while avoiding the need for separate heating equipment.
Solution Approach 2:
The system uses its own overhead gas, which retains thermal energy after distillation, to provide the heating function for the incoming feed. This self-service approach allows the process to supply its own thermal requirements internally, improving energy efficiency without requiring external heating sources or additional complex equipment.
3Power
If the bottom liquid is vaporized and expanded through turbines, then energy management is improved, but device complexity increases
Solution Approach 1:
The bottom liquid from the distillation column undergoes phase transition from liquid to vapor in the reboiler, and then expands through turbines back to its original pressure. This phase transition process is harnessed to generate mechanical work and electricity through the turbines, converting thermal energy into useful power while managing the energy balance of the overall system.
Solution Approach 2:
The bottom liquid, which represents a waste stream containing residual heat and pressure energy, is converted into a useful energy source by expanding it through turbines. What would otherwise be discarded waste energy is transformed into beneficial mechanical work and electricity, improving overall energy management while utilizing existing process streams.
4Loss of energy
If sub-cooling is eliminated and liquefaction energy is optimized, then energy usage is reduced, but manufacturing precision of temperature control is required
Solution Approach 1:
The overhead gas is used to preheat the incoming feed stream in the first exchanger before the feed enters the distillation column. This preliminary heating action reduces the temperature difference that would otherwise require sub-cooling of the overhead gas, thereby reducing energy losses while maintaining adequate temperature control through process integration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the separation efficiency of carbon dioxide, reduces NOx content, and improves energy management by eliminating sub-cooling and optimizing liquefaction energy, resulting in higher purity products and reduced operational costs.
Implementation Method 1
heated in an exchanger
Implementation Method 2
bottom liquid being vaporized
Implementation Method 3
expanded through turbines
Implementation Method 4
separating a mixture containing carbon dioxide by distillation
Data Source
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AI summary
The invention relates to a method for separating a gas containing carbon dioxide by means of distillation. According to the method, the gas containing at least 50% of carbon dioxide is cooled in a first exchanger (43) so as to produce a cooled fluid, a liquid (23) derived from the cooled fluid is sent to a distillation column (25) to be separated therein, a head gas (6) is withdrawn from the distillation column and reheated in the first exchanger, a vat liquid (27), which is richer in carbon dioxide than the gas containing at least 50% of carbon dioxide, is withdrawn and at least a portion thereof is heated in the first exchanger, at least a first portion of the vat liquid is vaporized in the first exchanger in order to produce a vaporized portion, the vaporized portion (31) is sent back to the column and an NOx removal column is supplied with the liquefied cycle gas (155) produced by vaporizing and reliquefying the vat liquid from the column.