Cryogenic Air Separation Column Feed for Higher Oxygen Recovery
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Solution Overview
Problem
Current air separation methods in distillation column units face limitations in oxygen and argon recovery due to the liquid to vapor ratio in the lower pressure column, which can be enhanced by increasing the liquid to vapor ratio below the liquid feed location, but existing methods do not achieve optimal subcooling to maximize oxygen and argon extraction.
Innovation Solution
A cryogenic rectification process that involves producing two liquid streams with different oxygen and nitrogen content, where the second liquid stream is subcooled through indirect heat exchange and introduced above the crude liquid oxygen in the lower pressure column, increasing the liquid to vapor ratio and enhancing oxygen and argon recovery by reducing oxygen in the column overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If liquid air is introduced into the lower pressure column above the crude liquid oxygen introduction location, then the liquid to vapor ratio below the introduction point increases and oxygen recovery improves, but the subcooling effect is insufficient to maximize oxygen and argon extraction
Solution Approach 1:
The liquid air stream is subcooled before introduction into the lower pressure column through indirect heat exchange with the crude liquid oxygen stream. This preliminary subcooling action maximizes the refrigeration effect and enhances the liquid to vapor ratio below the introduction point, thereby improving oxygen recovery beyond what would be achieved by simple liquid air introduction alone.
Solution Approach 2:
The temperature parameter of the liquid air stream is changed through subcooling before introduction into the column. By reducing the temperature of the liquid air stream through heat exchange with crude liquid oxygen, the system achieves enhanced refrigeration effects and improved separation efficiency for both oxygen and argon.
2Productivity
If the liquid to vapor ratio below the liquid feed location is increased, then oxygen and argon extraction is enhanced, but the complexity of the heat exchange system increases
Solution Approach 1:
The subcooling of liquid air and the cooling of crude liquid oxygen are combined into a single indirect heat exchange operation. The liquid air stream and crude liquid oxygen stream exchange heat through a heat exchanger, simultaneously achieving subcooling of the liquid air and pre-cooling of the crude oxygen without requiring separate cooling systems, thereby enhancing extraction while limiting complexity increase.
Solution Approach 2:
The crude liquid oxygen stream serves as the cooling medium for subcooling the liquid air stream. The crude oxygen, which requires cooling anyway, is used to pre-cool the liquid air, creating a self-service heat exchange system that achieves enhanced oxygen and argon extraction with minimal additional system 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 process increases oxygen production and recovery by reducing oxygen in the column overhead and increases argon accumulation in the lower sections, leading to improved overall recovery of both oxygen and argon.
Implementation Method 1
the second liquid stream is subcooled through indirect heat exchange with the first liquid stream
Implementation Method 2
distilling compressed and purified air into at least a nitrogen-rich fraction and oxygen-rich fraction within a distillation column unit
Implementation Method 3
a cryogenic rectification process is conducted that comprises distilling compressed and purified air
Implementation Method 4
a crude liquid oxygen stream composed of crude liquid oxygen column bottoms produced in the higher pressure column is subcooled and introduced into and further refined in the lower pressure column
Data Source
AI summary
A cryogenic air separation method and apparatus in which first and second liquid streams are produced. The first liquid stream has a higher oxygen content than air and can consist of a higher pressure distillation column bottoms and the second liquid stream, for instance, air, has a lower oxygen content than the first liquid stream and an argon content no less than the air. The second liquid stream is subcooled through indirect heat exchange with the first liquid stream and both of such streams are introduced into the lower pressure column. The second liquid stream is introduced into the lower pressure column above that point at which the crude liquid oxygen column bottoms or any portion thereof is introduced into the lower pressure column to increase a liquid to vapor ratio below the introduction of the second liquid stream and therefore, reduce the oxygen present within the column overhead.