Cryogenic Air Separation Using Parallel Compressors and Async Motors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current air separation technologies face challenges in scalability, energy efficiency, and reliability, particularly in high-power applications where synchronous motors are required, leading to increased costs and limited spare parts compatibility across machines.
Innovation Solution
The use of multiple small air compressors driven by asynchronous motors, each compressing air to a standardized pressure range, and routing the compressed air through a single purification unit and cold box for cryogenic distillation, eliminating the need for expensive start-up devices and allowing for flexible power distribution across compressors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single large high-pressure air compressor is used to introduce all necessary energy, then investment costs are significantly reduced, but the machine becomes difficult to achieve at very high powers and requires complex and expensive start-up devices called dimmers
Solution Approach 1:
The single large compressor is divided into multiple smaller compressors (typically 3-10 units). Each compressor handles a portion of the total air flow requirement, eliminating the need for complex start-up devices while maintaining the economic benefits of standardized equipment. This segmentation allows each compressor to be started directly without expensive dimmers.
2Power
If synchronous motors are used for high-power compressors beyond 25 MW, then the power requirement is met, but the number of additional manufacturers is extremely small and spare parts availability is limited
Solution Approach 1:
The power rating of each compressor is changed from above 25 MW to below 25 MW by dividing the total compression load among multiple smaller units. This parameter change enables the use of asynchronous motors with direct-on-line starting, which have widespread manufacturer support and excellent spare parts availability, thereby improving system reliability.
3Reliability
If multiple small compressors are used instead of a single large compressor, then asynchronous motors can be used with better reliability and spare parts availability, but the number of compressors increases to between 3 and 10 units
Solution Approach 1:
Multiple small compressors are merged into a single integrated compression system that feeds a common purification train and distillation column. The compressors share common infrastructure including purification units, heat exchangers, and control systems, which reduces the overall complexity despite having multiple compression units. This merging approach maintains reliability benefits while managing 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 configuration reduces costs and enhances reliability by allowing for the use of asynchronous motors, simplifies start-up procedures, and standardizes spare parts, making the system more efficient and adaptable to varying customer needs while avoiding the limitations of high-power synchronous motor technologies.
Implementation Method 1
each of the N compressors compresses the air to a first pressure greater than 12 bar absolute and less than 35 bar absolute
Implementation Method 2
the purified air is cooled in the purification unit before being sent to a single column system in a single cold box where the air is separated by cryogenic distillation
Data Source
Figure 1
Figure 2
AI summary
An apparatus for separating air by cryogenic distillation comprises N air compressors (C1, C2, C3), which are connected so that they receive air at ambient pressure and which are designed to produce air at a first pressure higher than 12 bar abs, N being at least equal to 3, each of the compressors being driven by a single asynchronous motor (M1, M2, M3), the total power of the compressors being at least equal to 10 MW.