Cryogenic Air Separation with Nitrogen Recycle Amplification Cycle
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Solution Overview
Problem
Current air separation plants face challenges in producing nitrogen with high purity at elevated pressures while also delivering impure oxygen efficiently, as existing methods either require pure nitrogen or result in suboptimal energy usage and product purity.
Innovation Solution
A method involving a double-column system with a high-pressure column and a low-pressure column connected via a condenser evaporator, where impure nitrogen from the low-pressure column is heated, compressed, and returned to the high-pressure column, allowing for efficient production of nitrogen and oxygen products at elevated pressures without additional compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If nitrogen is recycled from the top of the low-pressure column to the high-pressure column using a boosting cycle, then nitrogen purity is improved, but energy consumption increases due to additional compression
Solution Approach 1:
The patent merges the nitrogen recycling function with the existing distillation column system by integrating the amplification cycle into the high-pressure column. The recycled nitrogen from the low-pressure column is combined with feed air and fed into the high-pressure column, eliminating the need for separate compression infrastructure and reducing overall energy consumption while maintaining high nitrogen purity.
Solution Approach 2:
The patent changes the operational parameters of the high-pressure column by introducing an amplification cycle that adjusts the nitrogen flow rates and pressure levels. By optimizing the compression ratio and recycle ratio, the system achieves high nitrogen purity without excessive energy consumption, transforming the parameter optimization problem into a solved contradiction.
2Manufacturing precision
If the high-pressure column operates at elevated pressure to produce high-purity nitrogen, then nitrogen purity is improved, but the ability to deliver impure oxygen efficiently deteriorates
Solution Approach 1:
The patent segments the air separation process into distinct functional zones within the double-column system. The high-pressure column is optimized for nitrogen production with elevated pressure operation, while the low-pressure column handles oxygen delivery. This segmentation allows each column to operate at optimal pressure levels for its specific product, resolving the contradiction between nitrogen purity and oxygen delivery efficiency.
Solution Approach 2:
The patent introduces an intermediary amplification cycle that acts as a mediator between the low-pressure column (oxygen side) and the high-pressure column (nitrogen side). This amplification cycle transfers nitrogen from the low-pressure column to the high-pressure column without disrupting the oxygen delivery process, allowing both products to be produced efficiently simultaneously.
3Loss of energy
If a double-column system is used with condenser evaporator connection, then energy consumption is reduced, but device complexity increases
Solution Approach 1:
The patent makes the condenser evaporator serve multiple functions: it acts as both a heat exchanger for energy recovery and a connection point for the amplification cycle. This multi-functionality reduces overall energy consumption without adding separate dedicated components, thereby limiting the increase in device complexity while achieving energy savings.
Solution Approach 2:
The condenser evaporator performs self-service by using the cold nitrogen from the low-pressure column to cool the feed air entering the high-pressure column. This internal heat exchange eliminates the need for external cooling systems, reducing energy consumption without significantly increasing system complexity.
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 enables the production of nitrogen with high purity and impure oxygen at 9.5 bar pressure, optimizing energy consumption and product purity by utilizing an amplification cycle within the high-pressure column, enhancing the efficiency of air separation processes.
Implementation Method 1
a condenser evaporator (5) in which liquid from the high-pressure column (11) is heated and evaporated by heat exchange with the low-pressure column (12)
Implementation Method 2
liquid from the high-pressure column (11) is heated and evaporated
Implementation Method 3
compressed in a compressor (8)
Implementation Method 4
cooled again in a main heat exchanger (4)
Data Source
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AI summary
The invention relates to a method for a low-temperature air separation in which an air separation unit (100, 200) with a distillation column system (10) is used that has a high-pressure column (11) operated at a first pressure range and a low-pressure column (12) operated at a second pressure range below the first pressure range. A first sump liquid which has a higher content of oxygen and a lower content of nitrogen than atmospheric air and a first head gas which has a lower content of oxygen and a high content of nitrogen than atmospheric air are formed in the high-pressure column (11) using a low-temperature rectification process; a second sump liquid which has a higher content of oxygen and a lower content of nitrogen than the first sump liquid and a second head gas which has a higher content of nitrogen and a lower content of oxygen than the first sump liquid are formed in the low-pressure column (12) using a low-temperature rectification process; and the second head gas or a component thereof is drawn from the low-pressure column (12) in the form of unpurified nitrogen. A fraction of the unpurified nitrogen, in the form of a return quantity, is heated, compressed to a pressure level in the first pressure range, cooled, and fed to the high-pressure column (11) one after the other. The invention likewise relates to an air separation unit (100, 200).