Air Separation Waste Gas Control for Regeneration Flow Balance
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Solution Overview
Problem
Pressure fluctuations in the regeneration gas pipes of an air separation unit can lead to flow imbalances and require operator intervention to maintain flow rates, especially when gases with small pressure differences are used, potentially causing one gas not to be supplied due to lack of pressure and affecting the process balance.
Innovation Solution
An air separation unit with first and second waste gas control valves and flow rate control units that adjust valve openings based on measured and set flow rates to maintain a stable flow rate of nitrogen waste gas without operator intervention, ensuring a balanced process even with small pressure differences between regeneration gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If two types of gases with small pressure difference are used as regeneration gas, then energy efficiency is improved, but flow imbalance occurs and process stability deteriorates
Solution Approach 1:
The patent implements feedback control by measuring the actual flow rates of both waste gases and comparing them with target flow rates. The control unit automatically adjusts the valve openings based on this feedback to maintain balanced flow rates, thereby stabilizing the process balance while using gases with small pressure differences.
Solution Approach 2:
The control system automatically regulates the flow rates of both waste gases without operator intervention. The control unit independently adjusts each valve based on measured flow rates and target values, enabling the system to self-correct flow imbalances and maintain process stability.
2Ease of operation
If manual valve adjustment is used to maintain flow rates, then operator control is improved, but operational complexity and response time worsen
Solution Approach 1:
The control system automatically monitors flow rates and adjusts valve openings without operator intervention. The control unit continuously compares measured flow rates with target values and independently modifies valve positions, eliminating the need for manual operation and enabling immediate response to flow rate deviations.
Solution Approach 2:
The patent replaces manual mechanical valve adjustment with an automated control system that uses sensors to measure flow rates and electronically controls valve openings. This substitution of mechanical/manual operation with an automated control system improves response time and eliminates operational delays.
3Stability of the object's composition
If valve openings are increased to maintain flow rate during pressure rise, then flow rate stability is improved, but pressure control becomes difficult and one gas may not be supplied
Solution Approach 1:
The control system uses feedback from flow rate measurements to adjust valve openings appropriately. When pressure rises cause flow rate deviations, the control unit detects these changes and modifies valve positions to restore target flow rates, preventing both flow instability and excessive pressure buildup that could block gas supply.
Solution Approach 2:
The control system dynamically adjusts valve openings based on real-time flow rate measurements and changing pressure conditions. Rather than using fixed valve positions, the system continuously adapts valve openings to maintain optimal flow rates under varying pressure conditions, preventing supply blockage while ensuring flow stability.
Data Source
AI summary
An air separation unit comprises: a first waste gas control valve which is provided in a first waste gas pipe; a first waste gas flow rate control unit which measures a gas flow rate in the first waste gas pipe and adjusts a degree of opening of the first waste gas control valve so that a measured value which has been measured reaches a preset first waste gas flow rate set value; a second waste gas control valve which is provided in a second waste gas pipe; a regeneration gas flow rate control unit which measures the gas flow rate in a regeneration gas pipe and outputs a first output value based on a measured value which has been measured and a preset regeneration gas flow rate set value; and a control unit which uses, as a target set value of the flow rate of a second waste gas, a value obtained by subtracting the first waste gas flow rate set value of the first flow rate measuring unit from the flow rate set value of the regeneration gas flow rate, compares the first output value with a second output value based on a value obtained by subtracting the measured value of the first flow rate control unit from the measured value of the regeneration gas flow rate control unit, controls the degree of opening of the second waste gas control valve on the basis of the lower of the values, and adjusts the second waste gas flow rate.