Cryogenic Air Separation Exchanger With Integrated Nitrogen Reflux
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Solution Overview
Problem
The existing air separation apparatus for nitrogen production by cryogenic distillation is constrained by the need for a bath condenser-reboiler, which increases investment costs and complicates liquid recirculation, impurity concentration, and purge level maintenance, posing safety and operational challenges.
Innovation Solution
Integrating the vaporization-condensation function in the main exchanger, using its coldest part as a dephlegmator to condense nitrogen, eliminating the need for a separate deconcentration purge and associated equipment, and optimizing the heat exchange process to reduce cooling capacity consumption and operational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a bath condenser-reboiler is used for nitrogen condensation and liquid recirculation, then nitrogen separation efficiency is maintained, but investment cost increases and operational complexity increases
Solution Approach 1:
The patent merges the condensation function and recirculation function into a single integrated column structure. The condensation column serves both to condense nitrogen vapor and to provide natural recirculation of liquid nitrogen, eliminating the need for separate bath condenser-reboiler equipment and associated purge systems.
Solution Approach 2:
The condensation column performs multiple functions simultaneously: it acts as a condensation unit for nitrogen, a recirculation system through natural liquid flow, and a purification system. This multi-functionality reduces the number of separate components needed while maintaining separation efficiency.
2Temperature
If a bath condenser-reboiler with liquid recirculation is used, then nitrogen condensation is achieved, but investment cost increases due to additional equipment
Solution Approach 1:
The patent combines the condensation function and recirculation function into a single integrated column structure. The condensation column serves both to condense nitrogen vapor and to provide natural recirculation of liquid nitrogen, eliminating the need for separate bath condenser-reboiler equipment and associated purge systems.
3Object-generated harmful factors
If a separate deconcentration purge system is used, then impurity removal is achieved, but device complexity and safety monitoring requirements increase
Solution Approach 1:
The patent extracts and eliminates the separate purge system (pebble pit, bubblers, level gauges, impulse ports) by incorporating impurity removal functionality directly into the main distillation and condensation process. The natural recirculation and phase separation within the column inherently handle impurity management without requiring dedicated purge equipment.
4Manufacturing precision
If liquid recirculation is implemented through a bath condenser, then nitrogen purification is maintained, but cooling capacity consumption increases
Solution Approach 1:
The system uses natural recirculation driven by density differences and phase separation within the column. Liquid nitrogen naturally flows from the condensation zone back into the distillation column without requiring external pumping or additional cooling, making the system self-sustaining and reducing energy consumption.
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 results in a simplified and safer operational setup with reduced liquid nitrogen consumption, lower operating costs, and a more compact apparatus design, while maintaining effective separation efficiency.
Implementation Method 1
The exchange line comprises a conventional heat exchange section 3A and a dephlegmation section 3B. Air 1 is cooled in the exchange line to the cold end of section 3A
Implementation Method 2
Air 1 is cooled in the exchange line to the cold end of section 3A, then leaves the exchange line to be sent to the base of a simple distillation column 7
Implementation Method 3
The air separates into a flow 11 enriched in oxygen and a flow enriched in nitrogen. The oxygen-enriched flow 11 is withdrawn in liquid form from column 7
Implementation Method 4
The nitrogen condenses in part: the condensed part falls back by gravity into the column to serve as reflux
Implementation Method 5
The nitrogen-enriched gas leaves directly from the head of the column in the passages of section 3B
Implementation Method 6
the condensed part falls back by gravity into the column to serve as reflux
Data Source
Figure 1
AI summary
The invention relates to an air separating device by means of cryogenic distillation for producing nitrogen, comprising an exchange line (3), a simple distillation column (7) containing plates and/or structured packings, a supply line for delivery of compressed purified air (1) to the exchange line, a supply line for delivery of the compressed purified and cooled air from the exchange line to the distillation column, a line for withdrawal of a liquid (11) enriched in oxygen from the distillation column for delivery to the exchange line, said exchange line having two sections, a rectifying section (3B) and a heat exchange section (3A), the rectifying section being connected to the column and the line for the enriched liquid and the heat exchange section is connected to the air supply line and the rectifying section.