Gas Mixture Separation with NO2 Recycle for High-Purity CO2
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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 complex and energy-intensive, and the separation of CO2 from NO2, oxygen, argon, and nitrogen is not efficiently addressed.
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 enriched 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 volume of gas requiring compression and storage is excessive, but achieving high purity CO2 stream requires significant energy consumption for compression to more than 100 bar abs
Solution Approach 1:
The patent applies preliminary action by performing chemical reactions (oxidation of SO2 to SO3 using NO2, and absorption of SO3 in water to form H2SO4) before the main CO2 compression and storage process. This pre-treatment removes impurities that would otherwise require additional energy for separation and compression, thereby reducing the overall energy consumption while maintaining high CO2 purity
Solution Approach 2:
The patent introduces NO2 as an intermediary substance to facilitate the oxidation of SO2 to SO3. This intermediary enables the conversion of harmful SO2 into a form (SO3) that can be easily removed through absorption in water, thus purifying the CO2 stream without requiring excessive compression energy
2Reliability
If flue gas is compressed to more than 100 bar abs for storage to avoid CO2 emissions, then CO2 can be stored, but the high volume of flue gas means storage reservoirs would be filled quickly
Solution Approach 1:
The patent extracts and removes SO3 from the flue gas stream through absorption in water, converting it to H2SO4. This extraction of impurities increases the concentration and purity of CO2 in the remaining gas stream, thereby reducing the total volume of gas that needs to be stored while maintaining the same amount of CO2 capture
3Object-affected harmful factors
If SO2 is present in flue gas during CO2 capture, then it pollutes the atmosphere, but removing SO2 requires additional processing steps that increase system complexity
Solution Approach 1:
The patent merges the SO2 removal process with the existing CO2 capture system by using NO2 (already present or introduced) to oxidize SO2 to SO3, which is then absorbed in water. This combined approach eliminates the need for separate, complex SO2 removal equipment while effectively reducing atmospheric pollution
Solution Approach 2:
The patent converts the harmful SO2 pollutant into a beneficial process intermediate (SO3) that can be easily removed through water absorption. The NO2, which could be considered a pollutant itself, is utilized as a reagent to transform SO2 into a removable form, effectively converting harmful substances into useful process components
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 cost-effective and environmentally friendly.
Implementation Method 1
recycling NO2, which aids in converting SO2 to sulfuric acid
Implementation Method 2
enhanced CO2 enrichment and purification through distillation, phase separation, or adsorption
Implementation Method 3
enhanced CO2 enrichment and purification through distillation, phase separation, or adsorption
Implementation Method 4
enhanced CO2 enrichment and purification through distillation, phase separation, or adsorption
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.