Cryogenic Air Separation with Adiabatic Compression Heat Recovery
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Solution Overview
Problem
Current cryogenic air separation systems require significant shaft power for compression and refrigeration, and there is a need for more efficient methods to integrate air separation with power production processes, particularly for providing high-pressure oxygen and utilizing heat of compression effectively.
Innovation Solution
The process involves adiabatic compression of air in multiple stages without intermediate cooling, followed by heat transfer to a working fluid stream, such as a CO2 stream, to produce a high-pressure oxygen stream with a molecular oxygen concentration of 99.5% to 97% and to provide heat for power production processes, eliminating the need for a dedicated oxygen compressor and optimizing energy use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional multi-stage compression with inter-cooling is used, then the air temperature is controlled to ambient levels, but the heat of compression is rejected to the environment causing energy loss
Solution Approach 1:
The patent converts the previously harmful heat of compression into a beneficial resource by directing it to preheat the working fluid (CO2) in the power generation cycle. The heat exchanger captures this waste heat and transfers it to the working fluid, transforming an energy loss into a useful heating function that improves overall system efficiency.
Solution Approach 2:
The patent merges the air separation process with the power generation process by integrating the compression heat into the power cycle. Instead of separate systems, the air compressor and power generation working fluid share a common heat transfer pathway, allowing the air compression heat to directly contribute to power generation.
2Stress or pressure
If a second multi-stage air compressor is used to compress air to high pressure for oxygen production, then high-pressure oxygen can be obtained, but additional shaft power is required increasing energy consumption
Solution Approach 1:
The patent enables the air separation system to serve the power generation system's heating needs using its own compression heat. The air compressor's waste heat automatically becomes the heat source for the working fluid, creating a self-sufficient arrangement where one process's byproduct fuels another process's requirement without external energy input.
3Loss of energy
If the air compression heat is transferred to the working fluid stream, then the working fluid is heated for power production, but the air must be cooled requiring additional cooling infrastructure
Solution Approach 1:
The air compressor serves multiple functions: it compresses air for the separation process and simultaneously generates heat for the power generation cycle. This multi-functionality eliminates the need for separate heating systems and reduces overall equipment complexity by making one piece of equipment serve dual purposes.
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 by preserving heat of compression for later use, enables high-pressure oxygen production without additional compressors, and integrates efficiently with oxy-fuel power generation systems, enhancing overall cycle efficiency and reducing energy losses.
Implementation Method 1
The process involves adiabatic compression of air in multiple stages without intermediate cooling
Implementation Method 2
followed by heat transfer to a working fluid stream, such as a CO2 stream, to produce a high-pressure oxygen stream
Implementation Method 3
Known cryogenic air separation units achieve the low distillation temperatures required through use of a refrigeration cycle
Data Source
AI summary
The present invention relates to a cryogenic air separation process that provides high pressure oxygen for an oxy-fired combustion of a fuel (e.g., a carbonaceous fuel). The air separation process can be directly integrated into a closed cycle power production process utilizing a working fluid, such as CO2. Beneficially, the air separation process can eliminate the need for inter-cooling between air compression stages and rather provide for recycling the adiabatic heat of compression into a process step in a further methods wherein an additional heat supply is beneficial.