Process for the low-temperature separation of air in an air separation plant and air separation plant
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Solution Overview
Problem
Air separation plants, particularly those with mixing columns, face inefficiencies in energy consumption and power usage, necessitating improvements to enhance overall efficiency and reduce power consumption.
Innovation Solution
A method involving a two-column system with a first separating column operating at a high-pressure and a second separating column at a lower pressure, where cooled air is separated into nitrogen-enriched and oxygen-enriched fractions, and the oxygen-rich fraction from the first column is further processed in a mixing column, with the nitrogen-enriched top fraction from the second column being cooled and recycled to optimize energy usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a mixing column is used in the air separation plant, then energy consumption for material separation is reduced, but the purity of the gaseous oxygen product deteriorates
Solution Approach 1:
The invention divides the air separation process into multiple stages: a first distillation column for initial separation, a mixing column for energy-efficient mixing, and a second distillation column for final purification. This segmentation allows the system to achieve both energy savings and high product purity by performing separation in steps rather than a single stage.
Solution Approach 2:
Different sections of the process are optimized for different functions: the first distillation column operates for initial separation, the mixing column operates at different pressure conditions for energy-efficient mixing, and the second distillation column operates specifically for achieving high purity. Each section has locally optimized conditions suitable for its specific function.
2Productivity
If high-pressure compression is used in the air separation plant, then separation efficiency is improved, but power consumption increases
Solution Approach 1:
The invention employs periodic pressure changes and alternating operation modes in the distillation columns, where columns are switched between compression and expansion phases. This periodic action allows the system to maintain high separation efficiency while recovering energy during expansion phases to offset compression power consumption.
Solution Approach 2:
The system dynamically changes operating parameters including pressure, temperature, and flow rates between different columns and operational phases. By optimizing these parameters periodically and adapting them to current operating conditions, the system achieves high separation efficiency while minimizing power consumption through energy recovery during pressure changes.
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 reduces the energy required for air separation by minimizing the need for high-pressure compression, resulting in energy savings of up to 10% compared to conventional methods, while maintaining oxygen product purity between 80 and 98%.
Implementation Method 1
Through intensive contact, some of the more volatile nitrogen from the air stream migrates into the oxygen-rich stream
Implementation Method 2
The oxygen-rich stream is vaporized in the mixing column and drawn off at the upper end as gaseous, so-called impure oxygen
Implementation Method 3
The air stream in turn is liquefied, enriched to some extent with oxygen, and can be withdrawn at the bottom of the mixing column
Data Source
Figure 1
AI summary
The invention relates to a process for the separation of air (AIR), in which cooled air (AIR) at a first separation pressure is separated in a first separation column (S1) at least into a nitrogen-enriched top fraction and an oxygen-enriched bottom fraction, and in which further cooled air (AIR) in a mixing column (M) is liquefied at a mixing column pressure by means of direct heat exchange against a liquid oxygen-enriched stream, which is at least partly obtained from the oxygen-enriched bottom fraction from the first separation column (S1), to form a mixing column bottom fraction. According to the invention further cooled air (AIR) at a second separation pressure is likewise separated in a second separation column (S2) into a nitrogen-enriched top fraction and an oxygen-enriched bottom fraction, wherein the nitrogen-enriched top fraction from the second separation column (S2) is at least partly cooled by using the mixing column bottom fraction from the mixing column (M). To this end, the nitrogen-enriched top fraction from the second separation column (S2) is at least partly guided through the liquefaction chamber of a top condenser (E2) of the second separation column (S2), which is constructed as a condenser evaporator and the evaporation chamber of which is operated at an evaporation chamber pressure which lies between the mixing column pressure and a third separation pressure, at which the liquid oxygen-rich stream is obtained in a third separation column (S3), and in which at least part of the mixing column bottom fraction from the mixing column (M) is fed in in liquid form at the evaporation chamber pressure. The invention further relates to a corresponding air separation plant.