CO2 Gas Separation with NO2 Recycle for Higher Purity Capture
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Solution Overview
Problem
Current CO2 capture processes in power plants face challenges in achieving high CO2 purity and energy efficiency, particularly in oxycombustion techniques, where recycling of flue gases is energy-intensive and requires high-pressure storage, and existing methods do not effectively address the separation of CO2 from NO2 and other gases.
Innovation Solution
A process and apparatus that separates a gaseous mixture containing CO2, NO2, and other gases by producing a CO2 enriched stream and a NO2 enriched stream, with the NO2 stream being recycled upstream of the separation phase, utilizing methods such as distillation, phase separation, or adsorption to enhance CO2 purity and reduce energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If CO2 is captured directly from flue gas with low concentration (4-14% by volume), then the storage reservoirs would be filled quickly, but compressing the high volume flue gas to storage pressure (more than 100 bar abs) consumes excessive energy
Solution Approach 1:
The flue gas stream is segmented into multiple separation stages. First, a preliminary separation removes the bulk of CO2 at lower pressure, then subsequent separation stages further purify the CO2 stream. This segmentation allows progressive concentration of CO2 while minimizing the total compression energy required, as only the enriched streams need final compression to storage pressure.
Solution Approach 2:
The invention performs preliminary CO2 enrichment and purification actions before the final compression to storage pressure. By pre-concentrating CO2 from dilute flue gas through multiple separation stages, the volume to be compressed is dramatically reduced, and the compression process operates on a smaller, more energy-efficient scale.
2Productivity
If CO2 concentration in flue gas is increased by oxycombustion techniques with flue gas recycling, then CO2 recovery efficiency improves, but the process complexity and energy consumption increase
Solution Approach 1:
The invention extracts and removes NO2 from the flue gas stream in a dedicated removal step before the main CO2 separation process. This extraction of interfering components simplifies the subsequent CO2 separation by eliminating substances that would otherwise complicate the separation chemistry and reduce CO2 purity, thereby improving overall process efficiency without proportionally increasing complexity.
Solution Approach 2:
The invention utilizes temperature and pressure parameter changes to optimize the separation process. By controlling temperature profiles across different separation stages and adjusting pressure conditions, the process achieves high CO2 recovery efficiency while managing the complexity of flue gas recycling through thermodynamically optimized operating conditions.
3Manufacturing precision
If multiple separation steps are implemented to achieve high CO2 purity, then CO2 product purity increases, but the process complexity and capital costs increase
Solution Approach 1:
The invention applies different separation mechanisms and operating conditions to different stages of the process. Early stages use methods optimized for bulk CO2 enrichment, while later stages use different approaches for final purification. This local optimization of separation quality at each stage achieves high overall CO2 purity while avoiding the complexity of using a single overly complex separation system throughout.
Solution Approach 2:
The invention converts the presence of NO2 and other flue gas components from harmful impurities into beneficial process features. By designing separation stages that selectively remove or utilize these components, the process transforms what would be problematic contaminants into opportunities for process integration and energy recovery, achieving high CO2 purity without proportionally increasing complexity.
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 improves CO2 recovery efficiency and product purity, reduces energy consumption, and allows for more effective conversion of SO2 to sulfuric acid, making the process more economical and environmentally friendly.
Implementation Method 1
separating the carbon dioxide enriched stream to form a nitrogen oxides enriched stream and a carbon dioxide further enriched stream by distillation
Implementation Method 2
separating the carbon dioxide enriched stream to form a nitrogen oxides enriched stream and a carbon dioxide further enriched stream by phase separation
Implementation Method 3
separating the carbon dioxide enriched stream to form a nitrogen oxides enriched stream and a carbon dioxide further enriched stream by adsorption
Implementation Method 4
mixing said recycle stream with a portion of said incoming gaseous mixture
Implementation Method 5
converting SO2 to sulfuric acid for efficient flue gas treatment
Data Source
AI summary
A process for separating carbon dioxide from a fluid containing carbon dioxide, NO2, and at least one of oxygen, argon, and nitrogen comprises the steps of separating at least part of the fluid into a carbon dioxide enriched stream, a carbon dioxide depleted stream comprising CO2 and at least one of oxygen, argon, and nitrogen and a NO2 enriched stream and recycling said NO2 enriched stream upstream of the separation step.