Cryogenic Air Separation with Transient Heat Exchange Lines
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Solution Overview
Problem
Air separation devices face challenges in achieving flexibility and efficiency in producing gases at varying pressures and flow rates, particularly during transient phases when large volumes are required, as existing systems are not optimized for these conditions and rely heavily on liquid storage which has limited capacity.
Innovation Solution
The implementation of a double-column cryogenic distillation apparatus with dedicated heat exchangers allows for flexible production of gases by using transient exchange lines, where nitrogen and oxygen are produced under different conditions, optimizing energy efficiency and compactness by eliminating the need for a third fluid in the exchanger, thereby reducing volume and maintaining normal production settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If liquid storage is used to improve flexibility during transient phases, then the ability to meet varying gas demands is improved, but the storage capacity is limited and cannot meet large volume requirements over several days
Solution Approach 1:
The system is divided into normal operation mode and transient mode with dedicated exchange lines for each mode. The transient exchange line is specifically designed for transient operations, while the normal exchange line handles regular production, allowing the system to switch between modes without compromise
Solution Approach 2:
The system dynamically switches between different operating modes (normal and transient) by activating or deactivating specific exchange lines. This dynamic reconfiguration allows the system to adapt to varying demands while maintaining optimal performance in each mode
2Productivity
If the main exchanger is sized to meet transient phase requirements, then the gas production capability during transient phases is improved, but the exchanger deviates from technical and economic optimum for normal operation
Solution Approach 1:
The heat exchange function is segmented into two separate systems: a main exchanger optimized for normal operation and a dedicated transient exchange line for transient phases. Each component is sized and designed for its specific purpose, avoiding the need to oversize the main exchanger
Solution Approach 2:
The transient exchange line is designed as a dedicated, simpler component specifically for transient operations. It can be a more economical solution for temporary/high-demand phases without requiring the main exchanger to be oversized for these occasional conditions
3Use of energy by moving object
If a third fluid is used in the exchanger to improve heat exchange efficiency, then the energy efficiency is improved, but the volume and complexity of the exchanger increases
Solution Approach 1:
The third fluid (waste nitrogen) is removed from the transient exchange line, simplifying the system to only two fluids (HP air and LIN). This extraction eliminates the need for complex three-fluid heat exchange while maintaining effectiveness for transient operations
Solution Approach 2:
The HP air from the booster discharge serves as the heat exchange medium in the transient line, replacing the need for a third fluid. The HP air provides both the heat transfer function and the pressurization function, eliminating the need for additional intermediate substances
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 solution enables the production of gases according to specific customer demands during transient phases without degrading normal operation efficiency, achieving substantial energy savings and compactness gains by redistributing flows and adjusting production accordingly.
Implementation Method 1
The nitrogen is pumped from the first column (MP column) and vaporized through a dedicated exchanger line (here called transient exchange line) against high pressure (HP) air coming from the discharge of a booster possibly driven by a turbine; simultaneously, the pumped oxygen is vaporized through another dedicated line of exchangers against HP air coming from the discharge of the same booster or a second booster
Implementation Method 2
Method for producing a first gas under pressure as well as a second gas on an ad hoc basis by cryogenic distillation of air in a double column comprising a first column and a second column
Implementation Method 3
a pressurized liquid vaporizes in the third exchanger, a pressurized liquid flow is sent from the double column to vaporize in the third exchanger, The transient nitrogen is pumped from the first column (MP column) and vaporized through a dedicated exchanger line
Data Source
Figure 1
AI summary
In a method for producing a first pressurised gas and a second gas on a one-off basis by cryogenic distillation of air, according to a first step, no fluid heats up or cools down in a second heat exchanger (2), and according to a second step, a flow of pressurised liquid (19) from the double column heats up and vaporises in the second exchanger to form a gas required on a one-off basis, a flow of air (9) at the second pressure cools in the second exchanger.