Method for producing one or more air products and air separation unit
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Solution Overview
Problem
High-air pressure processes in air separation plants face energy inefficiency issues, particularly when producing small amounts of liquid air products, limiting their advantageous use compared to conventional main compressor/post-compressor processes.
Innovation Solution
A method involving a high-air pressure process with a first and second booster, along with expansion turbines, optimizes stage pressure ratios to enhance energy efficiency by compressing all feed air to a high pressure level, using a Claude and Lachmann turbine configuration to balance cold and warm flows effectively, reducing energy consumption and investment costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a high-air pressure process is used to compress all feed air to a pressure level significantly above the high-pressure column, then investment costs are reduced compared to main compressor/post-compressor processes, but energy consumption increases
Solution Approach 1:
The compression process is divided into multiple stages with intermediate cooling. Feed air is compressed in stages rather than in a single step, with intercooling between stages. This segmentation reduces the total compression work required compared to single-stage compression to the same final pressure, thereby reducing energy consumption while maintaining the high-air pressure process structure that lowers investment costs
Solution Approach 2:
The process optimizes pressure levels and temperature parameters at each stage. By carefully selecting intermediate pressure levels and cooling temperatures, the process achieves the desired high final pressure with minimum energy input. The parameters are adjusted to match the specific requirements of the rectification column system while minimizing the energy penalty of high-pressure compression
2Use of energy by moving object
If expansion turbines are used to drive boosters for compressing feed air, then energy efficiency is improved, but device complexity increases
Solution Approach 1:
The expansion turbines and booster compressors are mechanically coupled in an integrated arrangement where the turbine directly drives the booster without requiring separate motor drives, control systems, or transmission mechanisms. This merging reduces device complexity while maintaining the energy recovery function, as the mechanical coupling eliminates intermediate energy conversion steps and reduces the number of independent components
Solution Approach 2:
The expansion turbines utilize the pressure energy of the compressed air themselves to drive the booster compressors, making the system self-sufficient for the compression function. The high-pressure air from the main compressor serves its dual purpose of both product generation and providing the driving force for further compression, eliminating the need for external energy inputs and reducing overall 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 achieves up to 5% lower energy consumption and reduces investment costs by optimizing compressor stages and pressure levels, maintaining the cost advantage of high-air pressure processes while improving energy efficiency.
Implementation Method 1
the total amount of feed air supplied to the rectification column system of an air separation plant is further compressed after compression in a main air compressor by means of boosters driven by expansion turbines. In the expansion turbines, part of the air that was previously compressed in the boosters and then partially cooled is expanded.
Implementation Method 2
The feed air is then cooled in a main heat exchanger of the air separation plant to a temperature level of -140 to -70° C.
Implementation Method 3
Air separation plants have rectification column systems that can be designed, for example, as two-column systems, in particular as classic Linde double-column systems. The rectification columns for nitrogen-oxygen separation are operated at different pressure levels.
Data Source
Figure 1
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AI summary
The invention relates to a method for obtaining one or more air products by means of an air separation unit (100) comprising a first booster (1), a second booster (2), a first decompression machine (1a), and a rectification column system (10) which has a high-pressure column (11) operated at a first pressure level and a low-pressure column (12) operated at a second pressure level below the first pressure level. All of the air supplied to the rectification column system (10) is first compressed to a third pressure level, which lies at least 3 bar above the first pressure level, as a feed air quantity. A first fraction of the feed air quantity is supplied to a first booster (1) at the third pressure level and at a temperature level of -140 to -70 °C and is compressed to a fourth pressure level using the first booster (1); a second fraction of the feed air quantity or a sub-quantity of the first feed air quantity which has been compressed to the fourth pressure level using the first booster (1) is supplied to a first decompression turbine (1a), which is used to drive the first booster (1), and is decompressed to the first pressure level using the first decompression machine (1a); and a sub-quantity of the first feed air quantity which has been compressed to the fourth pressure level using the first booster (1) is supplied to a second booster (2) and is compressed to a fifth pressure level using the second booster (2). The first fraction of the feed air quantity is at a temperature level of -100 to -60 °C at the outlet of the first booster (1), and the sub-quantity of the first feed air quantity which is compressed to the fifth pressure level using the second booster (2) is heated to a temperature level of -20 to 40 °C prior to being compressed in the second booster (2). The invention likewise relates to a corresponding air separation unit.