Auto-Refrigerated CO₂ Capture Using Compression and Gas Recycling
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Solution Overview
Problem
Current carbon dioxide capture processes from mixed gas streams in fossil fuel and industrial plants are inefficient due to high energy requirements, complex systems, and high capital and operation costs, particularly in handling lower carbon dioxide concentrations and requiring external refrigeration.
Innovation Solution
A system utilizing multiple compression stages with intercooling and condensate separation, combined with gas recycling and auto-refrigeration, where the energy in the compressed gas is used to cool the incoming stream and recycle a portion of the gas back to the compressor, reducing overall energy demand and eliminating the need for external refrigeration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional carbon dioxide capture processes are used, then carbon dioxide can be separated from mixed gas streams, but high energy requirements and high capital and operation costs occur
Solution Approach 1:
The patent combines multiple compression stages with intercooling and auto-refrigeration into an integrated system. The compression and cooling functions are merged, where the compressed gas itself provides the cooling effect through intercooling between stages and auto-refrigeration at the expansion device, eliminating the need for separate external refrigeration systems and reducing overall energy consumption.
Solution Approach 2:
The system uses the compressed carbon dioxide-rich gas to cool itself through intercooling between compression stages and through auto-refrigeration at the expansion device. The gas serves its own cooling needs without requiring external refrigeration, thereby reducing energy requirements and operational costs.
2Temperature
If external refrigeration is used to cool incoming gas streams, then carbon dioxide separation can be achieved, but system complexity and capital costs increase
Solution Approach 1:
The system achieves cooling of the incoming gas stream through auto-refrigeration, where the compressed gas is expanded through a valve or expander that causes self-cooling. This eliminates the need for external refrigeration equipment, reducing system complexity and capital costs while maintaining the required temperature for carbon dioxide separation.
Solution Approach 2:
The patent utilizes phase transitions during the compression and expansion process. The intercooling between compression stages condenses some carbon dioxide, and the auto-refrigeration during expansion causes further cooling and potential phase change, enabling separation without external refrigeration systems.
3Productivity
If multiple compression stages with intercooling are used, then carbon dioxide separation efficiency improves, but system complexity increases
Solution Approach 1:
The patent merges the compression and cooling functions into a single integrated process. Multiple compression stages are combined with intercooling, where the cooling function is provided by the compressed gas itself rather than separate refrigeration equipment. This reduces system complexity while maintaining high separation efficiency.
4Loss of energy
If gas recycling is implemented, then energy consumption is reduced, but system complexity increases
Solution Approach 1:
The system implements gas recycling where a portion of the processed gas is fed back to the compressor inlet or intermediate stages. This feedback loop allows the system to recover and reuse energy contained in the recycled gas, reducing overall energy consumption. The recycling is integrated into the existing compression and separation process, adding minimal 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 enables efficient separation of carbon dioxide with high purity (>94%) from gas streams with concentrations as low as 30% to 90% without external cooling, reducing energy consumption and system complexity, resulting in a cost-effective and compact carbon dioxide capture system.
Implementation Method 1
cooling the incoming stream using the energy in the compressed gas
Implementation Method 2
compression to the inlet gas streams in multiple stages
Implementation Method 3
cooling and forms condensates that can be removed in condensate separator vessels
Implementation Method 4
throttling the liquid carbon dioxide stream to provide cooling to earlier stages
Data Source
AI summary
A system and method for capturing and separating carbon dioxide from mixed gas streams. The gas stream is processed in a structure including a compression module comprising a plurality of compressors, intercoolers and inter-stage condensate separators. The flow path from the compression module includes a plurality of flow separators, gas stream splitters, heat exchangers and at least a first mixer and a first expander. The gas stream is sequentially compressed and cooled to form process condensate and separate it from the compressed gas stream. The gas stream is further dried and cooled to liquefy carbon dioxide and separate it from the non-condensable portion. Selective expansion of liquid carbon dioxide streams provides cooling for the system, and further energy efficiency is achieved by selective recycling of portions of gas streams, allowing for compact equipment and economical operation, while providing for high purity product streams of carbon dioxide.