Method and device for oxygen production by low-temperature separation of air at variable energy consumption
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Solution Overview
Problem
Existing methods for air separation, such as the classic Linde double-column system, are inefficient in managing variable energy costs, leading to suboptimal energy storage and increased operational disruptions when energy prices fluctuate.
Innovation Solution
The main condenser is reconfigured as an intermediate evaporator, allowing for varying the amount of nitrogen compressed to heat the low-pressure column, which adjusts the evaporation capacity and reflux ratio, thereby optimizing energy use and reducing the outlet pressure of the main air compressor, especially in a secondary operating mode where energy efficiency is critical.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the main condenser is reconfigured as an intermediate evaporator and the amount of nitrogen compressed is varied, then energy efficiency is improved and total energy consumption is reduced, but the device complexity increases due to additional control mechanisms and variable operating modes
Solution Approach 1:
The system implements variable operating modes where the amount of nitrogen compressed by the cold compressor can be dynamically adjusted between a first amount (first operating mode) and a second amount (second operating mode). This dynamic adjustment allows optimization of energy efficiency by adapting the compression ratio to varying operational requirements, resolving the contradiction between energy efficiency and device complexity through controlled variability rather than fixed design
Solution Approach 2:
The invention changes the operating parameters of the distillation column system by varying the amount of nitrogen compressed in the cold compressor. This parameter change enables the system to switch between different operating modes, where the second operating mode achieves approximately 14% energy savings compared to the first mode, while managing the complexity through defined parameter ranges rather than uncontrolled variation
2Productivity
If the evaporation capacity of the low-pressure column is adjusted by varying nitrogen compression, then the reflux ratio is optimized and energy use is reduced, but the control difficulty increases
Solution Approach 1:
The system employs feedback control mechanisms to monitor and adjust the evaporation capacity of the low-pressure column. By measuring the actual evaporation rate and comparing it to the target rate, the control system can adjust the nitrogen compression amount accordingly, maintaining optimal reflux ratio and oxygen production efficiency while managing control difficulty through closed-loop regulation
Solution Approach 2:
The invention implements periodic switching between first and second operating modes, allowing the system to cycle through different evaporation capacities. This periodic action enables optimization of oxygen production efficiency during high-demand periods while reducing energy consumption during low-demand periods, with the understanding that control difficulty increases during transition phases
3Loss of energy
If the outlet pressure of the main air compressor is reduced in the second operating mode, then energy consumption is decreased, but the separation performance may be affected
Solution Approach 1:
The invention applies local quality changes by reducing the outlet pressure specifically at the main air compressor while maintaining appropriate pressure levels in other critical sections of the system. This localized pressure reduction allows energy consumption to decrease by approximately 14% in the second operating mode, while the separation performance is preserved through compensatory adjustments in other parts of the distillation system
Solution Approach 2:
The system dynamically adjusts the outlet pressure of the main air compressor based on the operating mode. In the first operating mode, higher pressure maintains optimal separation performance, while in the second operating mode, reduced pressure decreases energy consumption. The dynamic adaptation allows the system to balance between energy efficiency and separation reliability depending on operational requirements
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 configuration enables significant energy savings by effectively utilizing the separation work and liquefaction costs, reducing the total energy consumption by approximately 14% in the secondary operating mode while maintaining oxygen production efficiency.
Implementation Method 1
The main condenser is reconfigured as an intermediate evaporator, allowing for varying the amount of nitrogen compressed to heat the low-pressure column
Implementation Method 2
Methods and devices for the low-temperature decomposition of air are known, for example, from Hausen/Linde, Tieftemperaturtechnik, 2nd edition 1985, Chapter 4 (pages 281 to 337)
Implementation Method 3
A 'condenser-evaporator' refers to a heat exchanger in which a first, condensing, fluid stream enters into indirect heat exchange with a second, evaporating fluid stream
Implementation Method 4
The condensation (liquefaction) of a first fluid stream is carried out in the liquefaction chamber, and the evaporation of a second fluid stream is carried out in the evaporation chamber
Data Source
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AI summary
The method and the device serve to produce oxygen by the low-temperature separation of air at variable energy consumption. A distillation column system comprises a high-pressure column (34), a low-pressure column (35) and a main condenser (36), a secondary condenser (26) and a supplementary condenser (37). Gaseous nitrogen (41, 42) from the high-pressure column (34) is liquefied in the main condenser (36) in indirect heat exchange with an intermediate liquid (43) from the low-pressure column (35). A first liquid oxygen stream (70) from the bottom of the low-pressure column (35) is evaporated in the secondary condenser (26) in indirect heat exchange with feed air (25b) to obtain a gaseous oxygen product (72). The supplementary condenser serves as a bottom heating device for the low-pressure column (35) and is heated by means of a first nitrogen stream (44) from the distillation column system, which nitrogen stream was compressed previously in a cold compressor (45). In a second operating mode of lower energy consumption, less feed air (1) is compressed in the main air compressor (3) of the installation to a lower pressure compared to a first operating mode of higher energy consumption, less liquid oxygen (70) from the low-pressure column (35) is passed into the secondary condenser (26) and more nitrogen is compressed in the cold compressor (45). Furthermore, in the second operating mode, a second liquid oxygen stream (73) is additionally passed into the secondary condenser (26).