Cryogenic Air Separation With Warm Expander for High-Pressure Oxygen
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Solution Overview
Problem
Current methods for producing high-pressure gaseous oxygen at moderate pressures through air separation are inefficient, particularly in terms of power consumption and product recovery, as they often vent a portion of the air feed and rely on complex 'lost air' processes.
Innovation Solution
A method involving the cryogenic separation of air using a warm expander, which splits the air into multiple fractions, fully cools and rectifies certain fractions in a double column system, and utilizes a warm expander to power a booster, optimizing the process to produce high-pressure oxygen and nitrogen with reduced power consumption and increased product recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional air separation methods are used to produce high-pressure gaseous oxygen, then oxygen production is achieved, but power consumption increases and product recovery decreases due to venting air feed
Solution Approach 1:
The air feed is divided into multiple fractions (first air fraction, second air fraction, third air fraction) that are processed through different pathways in the column system. This segmentation allows each fraction to be optimized for specific purposes, with all fractions ultimately contributing to product recovery rather than venting, thereby reducing energy loss and increasing overall productivity.
Solution Approach 2:
The invention utilizes pressure changes throughout the system, with the main air feed at 15-30 bara and different columns operating at different pressures. The warm expander recovers energy from pressure differential, and the system maintains high-pressure oxygen product (20-60 bara) without requiring additional high-energy compression steps, thus reducing power consumption while maximizing product recovery.
2Ease of manufacture
If complex 'lost air' processes are used for high-pressure oxygen production, then oxygen can be produced, but process complexity increases
Solution Approach 1:
The warm expander is driven by the pressure differential within the system itself, using the energy from the third air fraction expansion to drive the second warm booster compressor. This self-service mechanism eliminates the need for external complex compression systems and simplifies the overall process while maintaining efficient high-pressure oxygen production.
Solution Approach 2:
The column system is designed to handle multiple air fractions and produce multiple products (gaseous oxygen, gaseous nitrogen, liquid oxygen, liquid nitrogen) simultaneously through a unified process. The heat exchanger serves multiple functions including cooling air fractions, condensing vapors, and warming products, reducing the need for separate dedicated systems and simplifying the overall process design.
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 enables the production of high-pressure oxygen between 20 and 60 bara with up to 10% savings in power consumption and increased product recovery, while simplifying the process by ensuring all main air feed is utilized for separation rather than being vented.
Implementation Method 1
fully cooling the first air fraction in a heat exchanger to a temperature suitable for rectification of the first air fraction
Implementation Method 2
rectification of the cooled air feed into low pressure gaseous nitrogen (LP GAN), liquid oxygen (LOX), liquid nitrogen (LIN), and high pressure gaseous nitrogen (HP GAN)
Implementation Method 3
expanding the first portion of the boosted second air fraction in a cold turbine to form an expanded second air fraction
Implementation Method 4
expanding the third air fraction using a warm expander to create an expanded third air fraction, wherein the warm expander powers the second warm booster
Implementation Method 5
warming the LP GAN, LOX, and HP GAN in the heat exchanger
Implementation Method 6
boosting the second air fraction in a warm booster to form a boosted second air fraction
Data Source
AI summary
A method is provided for production of gaseous oxygen at high pressures by splitting a main air feed into at least three separate streams, with the first stream being fed to a heat exchanger and then a column system for rectification; the second stream being further compressed in a warm booster, partially cooled in the heat exchanger, expanded in a turbine coupled to the warm booster and then fed to the column system; the third stream being expanded in a warm expander before being introduced to the heat exchanger and introduced to the column system. In certain embodiments, substantially all of the main air feed is eventually introduced to the column system for rectification, resulting in reduced sizing of a main air compressor and improved product recoveries.