Cryogenic Air Separation Turbine-Compressor Coupling for Cooling Power
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Solution Overview
Problem
Existing air separation units (ASUs) using cryogenic distillation face inefficiencies and high costs due to the need for additional means to generate cooling power, as current methods like oil brakes, compressor brakes, and generators are limited in power output and suffer from friction losses and high implementation costs.
Innovation Solution
A method where two compressed air flows are generated using a single-stage compression process driven by a cryogenic expansion turbine, with the first compression step producing work outside the cold box and the second step being cryogenic, allowing for the same rotational speed for all turbine and compressor wheels, reducing investment costs and maintaining thermodynamic efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a cryogenic expansion turbine is coupled to a generator to extract work, then electrical energy is generated, but the system requires expensive reduction gearboxes and signal processing systems, and is limited in generated power (approx. 250 kW)
Solution Approach 1:
The patent merges the expansion turbine with two compressor stages on a common shaft, combining power extraction and gas compression functions into a single integrated system. This eliminates the need for separate generators, reduction gearboxes, and signal processing systems, thereby reducing device complexity while maintaining adequate power generation for the air separation unit's cooling needs
2Power
If a cryogenic expansion turbine is coupled to a compressor brake and refrigerant system, then cooling power is generated, but additional assemblies with multiple turbines and compressors are required, increasing system complexity
Solution Approach 1:
The expansion turbine is designed to perform multiple functions simultaneously: it drives the first compressor stage for ambient temperature compression, drives the second compressor stage for cryogenic compression, and generates the necessary cooling power for the air separation unit. This multi-functionality eliminates the need for separate brake systems and additional refrigerant assemblies, reducing overall system complexity
3Power
If an oil brake is used to extract work from the cryogenic expansion turbine, then work is extracted, but the work is lost to friction heating and requires external cooling, limiting extracted power (approx. 100 kW)
Solution Approach 1:
Instead of using an oil brake that dissipates work as waste heat requiring external cooling, the patent converts the expansion turbine's work output into useful compression work by directly coupling it to drive the compressor stages. The energy that would have been lost to friction is now productively used to compress the gas flows, eliminating energy loss and increasing extracted power capability
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 investment costs and maintains acceptable thermodynamic efficiencies, enabling higher cooling power generation without the need for additional power extraction methods, thus addressing the limitations of existing technologies.
Implementation Method 1
a cryogenic expansion turbine with a single wheel, having an inlet temperature lower than -100°C
Implementation Method 2
cooled in a heat exchanger and then separated in a system of columns, liquid oxygen is vaporized in the heat exchanger
Implementation Method 3
separating air by cryogenic distillation
Data Source
AI summary
A method for separating air by cryogenic distillation, wherein air is compressed in a first compressor, cooled in a heat exchanger and then separated in a system of columns, liquid oxygen is vaporized in the heat exchanger countercurrent to a flow of pressurized gas which pseudo-condenses, a flow of gas which is air or a gas delivered from the system of columns is expanded in a cryogenic expansion turbine having a single wheel, the turbine having an inlet temperature lower than −100° C., a gas which is air or a gas delivered from the system of columns is compressed in a first booster compressor having a single wheel, with an inlet temperature higher than −50° C., a gas which is air or a gas delivered from the system of columns.