Cryogenic Air Separation With Split-Pressure Argon Recovery
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing air separation processes by cryogenic distillation struggle to produce oxygen at high purities (>99%) and argon simultaneously, with previous methods either not producing argon or achieving low oxygen purity when attempting to inject significant low-pressure air into a low-pressure column.
Innovation Solution
A system of columns with a first column operating at a higher pressure and a second column at a lower pressure, where a significant portion of air is compressed to a third pressure for purification and sent to the first column, and a smaller portion to a fourth pressure for purification before being sent to the second column, allowing for the production of oxygen-enriched and argon-enriched streams with high purity and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a significant portion of air is compressed to high pressure and sent to the first column, then oxygen purity is improved, but energy consumption increases due to compression requirements
Solution Approach 1:
The air stream is divided into two separate flows: a first air flow (75-98% of total air) compressed to high pressure (5-6 bar) for the first column, and a second air flow (2-25% of total air) compressed to intermediate pressure (1.2-2 bar) for direct injection into the second column. This segmentation allows optimization of compression energy by avoiding excessive compression for the portion of air that only needs to reach the lower-pressure column.
Solution Approach 2:
Different pressure parameters are applied to different air flows based on their destination. The first air flow is compressed to a third pressure (5-6 bar abs) suitable for the first column operation, while the second air flow is compressed only to a fourth pressure (1.2-2 bar abs) sufficient for direct injection into the second column, reducing unnecessary compression energy consumption.
2Use of energy by moving object
If low-pressure air is injected directly into the low-pressure column, then energy consumption is reduced, but oxygen purity deteriorates
Solution Approach 1:
The second air flow (purified at intermediate pressure) is merged with the oxygen-enriched liquid from the first column in the second column. This combination allows the direct-injected air to contribute to oxygen production without requiring full high-pressure compression, maintaining energy efficiency while achieving the desired oxygen purity through the distillation process in the second column.
Solution Approach 2:
The first column acts as an intermediary that pre-concentrates oxygen from the high-pressure air flow before the mixture enters the second column. This intermediary step ensures that even though some air bypasses full compression, the final oxygen purity is maintained through the combined distillation processes in both columns.
3Device complexity
If a single adsorption unit is used for air purification, then device complexity is reduced, but purification effectiveness deteriorates due to inability to handle multiple pressure streams
Solution Approach 1:
Two separate adsorption units are employed: a first adsorption unit for purifying the first air flow at high pressure, and a second adsorption unit for purifying the second air flow at intermediate pressure. This segmentation allows each adsorption unit to be optimized for its specific pressure condition, ensuring effective removal of water and carbon dioxide from both streams before they enter their respective columns.
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 configuration achieves oxygen purity greater than 99.5% and an oxygen yield greater than 95%, while also producing an argon-rich fluid with a high argon content, reducing energy consumption by optimizing the air injection into the second low-pressure column.
Implementation Method 1
compressed to a third pressure between 5 and 6 bar abs and above the first pressure, cooled and sent at the third pressure to a first adsorption unit to be purified of water and carbon dioxide
Implementation Method 2
compressed to a fourth pressure between 1.2 and 2 bar abs and above the second pressure but below the third pressure, preferably cooled by direct contact in an air cooling tower, sent at the fourth pressure to a second adsorption unit to be purified into water and carbon dioxide
Implementation Method 3
Air separates in the first column to form an oxygen-enriched liquid and a nitrogen-enriched gas
Implementation Method 4
Method and device for air separation by cryogenic distilling
Implementation Method 5
pressurized and then vaporized by heat exchange with at least part of the first airflow
Implementation Method 6
An argon-enriched gas is sent from the second column to a third column, and an argon-rich fluid is drawn off at the top of the third column
Data Source
Figure 1
Figure 2
AI summary
In a cryogenic distillation air separation process using a column system consisting of a first column (101) operating at a first pressure and a second column (102) operating at a second pressure, a first air flow (1) constituting between 75 and 98% of the air sent to the column system compressed to a third pressure above the first pressure, is sent to the first column, a second air flow (33) constituting between 5 and 25% of the air sent to the column system is compressed to a fourth pressure above the second pressure but below the third pressure, is sent to the second column, a third column (103) separates an argon-enriched flow and the air (20) sent to the second column constitutes between 10 and 25% of the total air sent to the column system.