Three-Column Cryogenic Air Separation with Cold Compressor Integration
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Solution Overview
Problem
Current air separation systems for gasification processes using cryogenic distillation are inefficient due to suboptimal thermal integration between columns, leading to high energy consumption and reduced oxygen separation efficiency.
Innovation Solution
A process involving a set of columns operating at different pressures, with thorough thermal integration and a cascade effect using a cold compressor to reduce pressure in the first column, enhancing energy savings and efficiency by recycling refrigerating capacity and optimizing heat exchange.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If traditional cryogenic distillation columns are used with standard thermal integration, then the system can separate air into oxygen and nitrogen, but energy consumption is high and thermal integration efficiency is suboptimal
Solution Approach 1:
The patent merges multiple distillation columns operating at different pressures (first column at first pressure, second column at second pressure lower than first, third column at third pressure lower than second) into an integrated system. The columns are thermally coupled through heat exchangers where nitrogen-enriched gas from one column is condensed in vaporizer-condensers of other columns, creating a cascading thermal integration that recovers and reuses refrigerating capacity across the entire system, thereby reducing overall energy consumption.
Solution Approach 2:
The patent changes the operating parameters by introducing a cascade of pressure levels across multiple columns (first pressure > second pressure > third pressure). This parameter variation enables optimized thermal integration at each pressure level, allowing nitrogen condensation and oxygen vaporization to occur at different temperature-pressure conditions that maximize heat exchange efficiency and minimize energy loss.
2Manufacturing precision
If a single pressure column is used for air separation, then the device complexity is low, but oxygen separation efficiency is reduced
Solution Approach 1:
The patent segments the air separation process into multiple independent columns operating at different pressure levels. The first column operates at first pressure, the second column at second pressure, and the third column at third pressure. Each column is optimized for its specific pressure level and separation requirements, with nitrogen-enriched gas from one column being condensed in vaporizer-condensers of other columns. This segmentation allows each column to be tuned for optimal separation efficiency at its operating conditions.
Solution Approach 2:
The patent adds the pressure dimension to the traditional single-column or two-column system by operating columns at three distinct pressure levels (first pressure > second pressure > third pressure). This dimensional expansion enables enhanced thermal integration and improved oxygen separation efficiency, as each pressure level provides a different temperature-entropy profile for heat exchange and phase change processes.
3Use of energy by moving object
If refrigerating capacity is not recycled, then the system operation is simple, but energy efficiency is reduced
Solution Approach 1:
The patent recovers refrigerating capacity that would otherwise be discarded by using nitrogen-enriched gas from one column as a cooling medium in vaporizer-condensers of other columns. The nitrogen-enriched gas condenses in these vaporizer-condensers, releasing refrigerating capacity that is used to cool and condense oxygen-enriched liquid streams. This recovery and reuse of refrigerating capacity across multiple columns significantly improves overall energy efficiency.
Solution Approach 2:
The patent implements a feedback loop where nitrogen-enriched gas from the distillation process is fed back into the system through vaporizer-condensers to provide cooling. The condensed liquid from these vaporizer-condensers is then returned to the distillation columns, creating a closed-loop thermal integration system where heat and mass are continuously exchanged and reused, maximizing energy efficiency.
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
The proposed solution significantly reduces energy consumption and improves oxygen separation efficiency by cascading pressure in the first column, allowing for substantial energy savings and enhanced oxygen purity.
Implementation Method 1
compressed, purified and cooled air is sent to the first column where it is separated in order to form an oxygen-enriched liquid and a nitrogen-enriched gas
Implementation Method 2
a portion of the nitrogen-enriched gas from the first column is condensed in a bottom vaporizer-condenser of the second column
Implementation Method 3
a nitrogen-enriched gas is sent from the top of the second column to a first vaporizer-condenser of the third column where it is condensed
Implementation Method 4
a liquid containing at least 85% oxygen is withdrawn from the bottom of the third column, pressurized and vaporized in order to form a gaseous product containing at least 85% oxygen
Implementation Method 5
a nitrogen-enriched gas from the second column is compressed in a compressor having an inlet temperature below ambient temperature
Data Source
AI summary
The invention relates to a method for separating air by cryogenic distillation in a set of columns including a first column operating at a first pressure, a second column operating at a second pressure which is lower than the first pressure, and a third column operating at a third pressure, which is lower than the second pressure, wherein the third column includes first and second evaporator-condensers, and nitrogen from a cold compressor is sent to one of the evaporator-condensers.