Cryogenic Air Separation Column Layout for Nitrogen Purity and Energy
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Solution Overview
Problem
Current air separation technologies using double columns with medium and low pressure configurations face inefficiencies in energy usage and nitrogen production, particularly when operating under pressure, as they either waste nitrogen or require excessive energy to produce pure oxygen.
Innovation Solution
Implementing a hybrid system that combines pressure diagrams with low-pressure schemes across multiple air separation units, allowing nitrogen production and purification across different pressure levels, and utilizing waste gases for regeneration to optimize energy usage and nitrogen production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If air separation units operate under pressure (greater than 2 bar abs) to save energy, then energy consumption is reduced, but nitrogen purity deteriorates and all nitrogen must be used
Solution Approach 1:
The system divides air separation into multiple independent trains with different pressure configurations. Some trains operate under pressure (greater than 2 bar abs) to optimize energy consumption, while other trains operate at low pressure to produce high purity nitrogen. This segmentation allows each train to be optimized for its specific function, resolving the contradiction between energy efficiency and nitrogen purity.
Solution Approach 2:
Different parts of the multi-train system have different operational characteristics. Pressure trains are configured with specific column arrangements and pressure levels optimized for energy efficiency, while low pressure trains are configured for nitrogen purity. Each local unit has tailored quality characteristics matching its production goal.
2Manufacturing precision
If multiple air separation units operate in parallel at low pressure to produce pure nitrogen, then nitrogen purity is improved, but energy consumption increases
Solution Approach 1:
The system merges multiple air separation trains into a single integrated multi-train system. By combining pressure trains and low pressure trains, the system achieves both energy efficiency (from pressure trains) and nitrogen purity (from low pressure trains) simultaneously, rather than having to choose one approach over the other.
Solution Approach 2:
The multi-train system serves multiple functions within a single integrated configuration. Pressure trains provide energy-efficient oxygen production, while low pressure trains provide high purity nitrogen production. The system universally handles both production goals through its multi-functional design.
3Use of energy by moving object
If all nitrogen produced by pressure diagrams is used, then energy efficiency is improved, but operational flexibility deteriorates
Solution Approach 1:
The low pressure trains serve the pressure trains by providing purification services. The low pressure trains produce high purity nitrogen that can be used to purify the nitrogen stream from pressure trains, allowing the pressure trains to operate at optimal pressure for energy efficiency while still meeting purity requirements through the self-service purification capability of the low pressure trains.
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 average production energy by 10% and ensures the desired nitrogen purity while leveraging energy gains from pressure diagrams for oxygen production across some trains.
Implementation Method 1
the head of the medium pressure column being thermally connected with the tank of the low pressure column by means of a reboiler-condenser
Implementation Method 2
Process for separating air by cryogenic distillation
Implementation Method 3
the head of the first column being thermally connected to the tank of the second column by means of a reboiler-condenser
Data Source
Figure 1~2
AI summary
A process comprises a first set of distillation columns (1) and a second set of distillation columns (2), a low-pressure column (5) of the first set being connected to a column operating at higher pressure (3') of the second set by means of a gas (15) arriving from the top of the column operating at a higher pressure and/or by means of a fluid (17) arriving from the low-pressure column.