Cryogenic air separation method for producing oxygen at high pressures
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Solution Overview
Problem
Current methods for producing high-pressure oxygen are limited to approximately 100 bar, which is insufficient for high-flow rate applications such as power generation systems requiring oxygen at pressures up to 200 bar to 500 bar.
Innovation Solution
A cryogenic air separation process utilizing a pumped liquid oxygen cycle integrated with an adiabatic air compressor and expansion turbines, along with a compact heat exchanger, to efficiently produce high-pressure gaseous oxygen streams suitable for power generation systems, leveraging waste heat from carbon dioxide recycle compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If conventional air separation methods are used, then oxygen can be produced at pressures up to 100 bar, but the pressure is insufficient for high-flow rate power generation applications requiring 200 bar to 500 bar
Solution Approach 1:
The air separation process is divided into multiple pressure stages: a low-pressure distillation column operating at approximately 1.25 bar and a high-pressure distillation column operating at approximately 5-8 bar, with intermediate pressure boosting stages. This segmentation allows oxygen to be produced at progressively higher pressures suitable for power generation applications requiring 200-500 bar.
Solution Approach 2:
The invention utilizes hydraulic pumping of liquid oxygen and adiabatic compression of air streams to achieve the required pressure levels. Liquid oxygen is pumped to high pressures and then vaporized, while air is compressed adiabatically to intermediate pressures before entering the distillation columns, enabling efficient production of oxygen at 200-500 bar.
2Loss of energy
If adiabatic compression is used to increase air pressure, then heat can be recovered for power cycle efficiency, but the compressed air temperature increases requiring additional cooling
Solution Approach 1:
The invention converts the harmful effect of high temperature compressed air into a beneficial resource by recovering the compression heat in heat exchangers to preheat feed streams and generate power in expansion turbines. The hot compressed air from adiabatic compression ( reaching temperatures above 150°C) is used to heat working fluids in power cycles, transforming the thermal burden into useful energy recovery.
Solution Approach 2:
The compressed air stream serves multiple functions: it provides the oxygen feed for separation, generates power through adiabatic expansion in turbines, and its compression heat is recovered to preheat process streams. This multi-functionality maximizes the utility of each compression stage while managing temperature effects.
3Ease of manufacture
If liquid oxygen is heated to ambient temperature using external heat sources, then high pressure gaseous oxygen can be produced, but the process becomes less efficient and more costly
Solution Approach 1:
The invention uses internal heat integration where hot compressed air streams and other process streams within the system provide the heating required to vaporize liquid oxygen. The heat exchangers are arranged so that waste heat from compression and process streams is used to heat the liquid oxygen product, eliminating the need for external heat sources and reducing both energy consumption and production costs.
Solution Approach 2:
The heating of liquid oxygen is merged with the cooling of hot compressed air streams in heat exchanger networks. These two thermal processes are combined in a way that simultaneously achieves both objectives using the same heat transfer equipment, improving overall thermal efficiency and reducing the number of separate heating operations required.
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 method enables the production of high-pressure oxygen streams at 200 bar to 500 bar with reduced costs and increased efficiency, optimizing heat exchange and oxygen production for power generation processes.
Implementation Method 1
compressing an inlet air stream in an adiabatic air compressor
Implementation Method 2
transferring at least a portion of the adiabatic heat of compression of the pressurized air to heat a working fluid stream
Implementation Method 3
expansion turbines
Implementation Method 4
separating a partially liquefied air stream into at least a product liquid oxygen stream and a low pressure nitrogen stream in a Linde double column distillation system
Implementation Method 5
increasing the pressure of the liquid oxygen to between about 200 bar and 500 bar in a liquid oxygen pump
Implementation Method 6
heating the high pressure liquid oxygen stream to near ambient temperature in a high pressure heat exchanger using waste heat from carbon dioxide recycle compression
Data Source
AI summary
The present invention relates to a cryogenic air separation process that provides high pressure oxygen for an oxy-fired combustion of a fuel (e.g., a carbonaceous fuel). The air separation process can be directly integrated into a closed cycle power production process utilizing a working fluid, such as C02. Beneficially, the air separation process can eliminate the need for inter-cooling between air compression stages and rather provide for recycling the adiabatic heat of compression into a process step in further methods wherein an additional heat supply is beneficial.