Method for regulating a device for separating air by cryogenic distillation
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Solution Overview
Problem
Air separation devices with cryogenic distillation face challenges in rapidly regulating argon production, leading to instability in the argon bulge and potential column shutdowns due to nitrogen rushes, which result in significant losses and prolonged operation in degraded mode.
Innovation Solution
Implementing a regulation strategy that uses lead-lag filters to manage liquid flow rates in air separation units, allowing for rapid mode changes of at least 1% per minute by adjusting the flow rates of liquids entering the low-pressure column, and managing argon hold-up through denitrogenation, storage, or venting during mode changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the flow rate of air feeding the device is rapidly increased or reduced (at least 1% per minute), then the productivity and flexibility of the air separation unit is improved, but the stability of the argon bulge deteriorates, leading to nitrogen rushes and potential column shutdowns
Solution Approach 1:
The regulation strategy applies preliminary action by anticipating the effects of rapid mode changes before they occur. When the air flow rate is rapidly increased or reduced, the control system proactively adjusts the liquid flow rates entering the low-pressure column in advance to compensate for the expected nitrogen rush or argon depletion, preventing column shutdown before it happens
Solution Approach 2:
The regulation strategy employs feedback mechanisms by continuously monitoring the argon bulge composition and using this information to dynamically adjust the liquid flow rates. The control system measures the actual state of the argon bulge and compares it with the desired state, then applies corrective adjustments to maintain stability during rapid mode changes
2Reliability
If conventional regulation strategies are used to maintain argon bulge stability, then the reliability of continuous operation is improved, but the speed of mode change is limited to around 0.3-0.5%/min, reducing the adaptability to intermittent energy resources
Solution Approach 1:
The regulation strategy applies dynamics by making the control system adaptable to varying operating conditions. The liquid flow rates are dynamically adjusted based on the rate and direction of mode changes, allowing the system to rapidly respond to intermittent energy resources while maintaining argon bulge stability through continuous, real-time control adjustments
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 strategy ensures stability of the oxygen content in the argon bulge, prevents excessive oxygen loss, and avoids column shutdowns, enabling continuous operation and efficient argon production during rapid changes in air flow rates.
Implementation Method 1
a device for separating air by cryogenic distillation
Implementation Method 2
Because of the differences in relative volatility between argon, nitrogen and oxygen, virtually pure nitrogen is formed at the top of the second column, virtually pure oxygen is formed at the bottom of the second column, and argon-rich gas is formed in the middle of the second column
Implementation Method 3
This argon mixture is sent to a denitrogenation column in order to remove the nitrogen by reboiling
Implementation Method 4
a device for separating air by cryogenic distillation
Implementation Method 5
The crude argon is rectified to give an oxygen-rich reflux at the bottom of the third column and a very argon-rich stream... at the top of the third column
Data Source
AI summary
In a method for regulating a device for separating air by cryogenic distillation, during the change from a low-flow mode to a high-flow mode, two flow rates of reflux sent to the low-pressure column of a double column are increased more rapidly than the flow rate of gaseous air sent to the medium-pressure column of the double column in order to ensure the stability of the oxygen content in the argon bulge of the low-pressure column during the mode change.