Method and apparatus for producing high-purity nitrogen and low-purity oxygen
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Solution Overview
Problem
Conventional air separation methods for producing low-purity oxygen result in high energy consumption and inefficient equipment investment, as they rely on two-column rectification and additional nitrogen compression, which is not economically viable for producing high-purity nitrogen and low-purity oxygen simultaneously.
Innovation Solution
A three-column rectification system is introduced, where air is cooled and separated into high-purity nitrogen and low-purity oxygen using a high-pressure column, a medium-pressure column, and a low-pressure column, with a main heat exchanger and subcoolers, eliminating the need for a nitrogen compressor and optimizing energy usage by employing internal-compression procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional two-column rectification is used for low-purity oxygen production, then oxygen can be produced, but energy consumption is high and additional nitrogen compression equipment is required
Solution Approach 1:
The rectification system is divided into three independent columns operating at different pressure levels (high-pressure, medium-pressure, and low-pressure columns). Each column performs specific separation functions, with the high-pressure column producing high-purity nitrogen, the medium-pressure column serving as an intermediate stage, and the low-pressure column producing low-purity oxygen. This segmentation allows direct production of both products without additional compression equipment.
Solution Approach 2:
The system introduces a pressure dimension by operating columns at different pressure levels rather than a single pressure. The high-pressure column operates at higher pressure to produce compressed nitrogen directly, while the low-pressure column operates at lower pressure for oxygen production. This pressure differentiation eliminates the need for nitrogen compression equipment and reduces overall energy consumption.
2Quantity of substance
If high-purity oxygen is mixed with air to produce low-purity oxygen, then the required concentration is achieved, but this is still conventional two-column rectification with high energy consumption
Solution Approach 1:
The system changes the operational parameters by using three columns at different pressure levels instead of mixing products from conventional two-column rectification. The medium-pressure column operates at an intermediate pressure level, and the low-pressure column produces oxygen at the desired concentration directly through rectification, eliminating the need for energy-intensive mixing operations.
3Ease of operation
If a nitrogen compressor is added to convey low-purity nitrogen, then nitrogen can be transported, but equipment investment increases
Solution Approach 1:
The high-pressure column produces high-purity nitrogen at compressed pressure directly from the rectification process. This self-service approach generates the compressed nitrogen product as a direct output of the separation process, eliminating the need for separate compression equipment and reducing overall system complexity and investment.
4Use of energy by moving object
If three-column rectification is used for simultaneous production, then energy consumption is reduced, but the system complexity increases
Solution Approach 1:
The three-column system performs multiple functions simultaneously: the high-pressure column produces high-purity nitrogen, the medium-pressure column serves as an intermediate rectification stage, and the low-pressure column produces low-purity oxygen. Each column is multi-functional, handling both separation and pressure regulation, which reduces the need for additional auxiliary equipment despite the increased number of 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 approach reduces energy consumption by over 15% compared to conventional two-column methods, enhances oxygen extraction rates, and eliminates the need for additional nitrogen compression, achieving a higher product value while promoting a circular economy.
Implementation Method 1
feedstock air is cooled in a main heat exchanger and led into a rectification system for nitrogen/oxygen separation
Implementation Method 2
nitrogen and oxygen undergo rectification in different columns, with high-purity nitrogen and low-purity oxygen being separated out of air simultaneously
Implementation Method 3
a lower region of the low-pressure column has a low-pressure condensing evaporator
Implementation Method 4
the rectification system comprises at least two subcoolers, specifically a high-pressure subcooler and a low-pressure subcooler
Implementation Method 5
feedstock air passing through a first pressurizer is pressurized to a first pressure air
Implementation Method 6
a first portion of the second pressure air is cooled in the main heat exchanger and collected from a middle position of the main heat exchanger, and then passes through an expander to obtain the third pressure air
Data Source
Figure 1
AI summary
A method for producing high-purity nitrogen and low-purity oxygen uses three-column rectification, nitrogen and oxygen undergo rectification in high pressure, medium pressure and low pressure columns, with high-purity nitrogen and low-purity oxygen being separated out of air simultaneously, in which a nitrogen stream (10) is collected from an upper region of the medium-pressure column (25), undergoes a pressure increase in the liquid state, passes through a subcooler (21) and is led into the top region of the high-pressure column (24).