CO2 Purification Membrane Separation for NO2 Removal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current CO2 purification methods from flue gas face challenges such as increased energy consumption, equipment sizing issues, and CO2 losses due to the recycling of NO2-enriched fluids or the use of wash columns, and the technical difficulty of reducing NOx in burner flames, leading to unsatisfactory NOx removal efficiency.
Innovation Solution
A process and apparatus that separates NO2 from CO2 without recycling NO2-enriched fluids or using wash columns, involving a fluid separation membrane with a selective separation layer, a stripping column, and a pervaporative separation membrane to produce a high-purity CO2 stream with reduced NOx content, utilizing materials like cross-linked polysiloxane copolyether and poly(ether) block copolymers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NO2-enriched fluid is recycled to the compressor inlet, then NOx removal efficiency is improved, but energy consumption increases by 5-10% and equipment size must be increased
Solution Approach 1:
The patent extracts and removes the NO2-enriched liquid stream from the process before it can be recycled to the compressor inlet. This is achieved through a De-NOx column that separates NO2 from CO2, producing a NO2-enriched liquid bottom stream that is diverted to a wash column or other treatment rather than being recycled. This extraction eliminates the harmful recycle loop while maintaining NOx removal efficiency.
Solution Approach 2:
The patent converts the harmful NO2-enriched liquid stream, which would otherwise cause acid gas condensate formation and increased energy consumption if recycled, into a beneficial separated stream that can be treated independently. The wash column uses this stream to generate nitric acid as a useful byproduct while preventing the harmful effects of recycling.
2Object-affected harmful factors
If reflux liquid flow rate to the De-NOx column is decreased to reduce NO2 recycle, then compressor acid attack is reduced, but distillation efficiency becomes unsatisfactory due to exceeding wettability limit
Solution Approach 1:
The patent introduces a wash column as an intermediary device between the De-NOx column and the rest of the system. This wash column receives the NO2-enriched liquid bottom stream and processes it to remove NO2 through absorption, generating nitric acid as a useful byproduct. This intermediary solution allows the De-NOx column to operate at optimal reflux rates for distillation efficiency while preventing NO2 from being recycled to the compressor.
3Reliability
If wash column is used to remove NO2 from liquid bottom, then CO2 losses are avoided compared to burning, but significant CO2 losses occur if washed stream is not recycled to CPU inlet
Solution Approach 1:
The patent extracts and removes the washed stream from the process entirely rather than recycling it to the CPU inlet. The wash column processes the NO2-enriched liquid bottom stream to remove NO2, and the resulting washed stream is discharged or treated separately. This extraction approach eliminates CO2 losses that would occur from burning while avoiding the need to recycle the stream, thus preventing any CO2 dilution or loss.
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 reduces energy consumption, minimizes equipment size requirements, and effectively lowers NOx content in the CO2 product, enhancing the reliability and efficiency of CO2 purification without the drawbacks of existing methods.
Implementation Method 1
a fluid separation membrane (operated under pervaporative conditions) that separates the NO2-enriched liquid from the rectifying column into a NO2-enriched gaseous permeate stream and a liquid non-permeate stream
Implementation Method 2
a pervaporative separation membrane that separates the NO2-enriched liquid from the rectifying column into a NO2-enriched gaseous permeate stream and a liquid non-permeate stream
Data Source
Figure 1
Figure 2
Figure 3
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.