System and method for enhanced recovery of liquid oxygen from a nitrogen and argon producing cryogenic air separation unit
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Solution Overview
Problem
Moderate pressure air separation units face challenges in achieving high nitrogen and argon recovery while efficiently producing liquid oxygen, often requiring oxygen compressors that are costly and operationally complex, and are limited by refrigeration duties and penalties in existing air separation cycles.
Innovation Solution
A cryogenic air separation unit with a distillation column system comprising a higher pressure column, a lower pressure column, and an argon column, where the argon column uses a mixture of oxygen enriched streams and liquid nitrogen for condensation, optimizing pressures to achieve high nitrogen and argon recovery without the need for oxygen compressors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high purity liquid oxygen is used as refrigerant in the argon condenser, then argon recovery is improved, but the argon column and other columns must operate at higher pressures which increases device complexity and operating costs
Solution Approach 1:
The patent introduces a heat exchanger as an intermediary device between the oxygen production system and the argon condenser. This heat exchanger recovers cold energy from the oxygen product stream and uses it to refrigerate the argon condenser, eliminating the need to use high purity liquid oxygen as direct refrigerant and allowing the argon column to operate at lower pressures
Solution Approach 2:
The system uses its own oxygen product stream to provide refrigeration duty for the argon condenser through the heat exchanger. The cold oxygen stream self-services the cooling requirement of the argon condenser without requiring additional external refrigeration or high pressure operation
2Adaptability or versatility
If oxygen compressors are installed to deliver oxygen product at sufficient pressure, then oxygen delivery capability is improved, but capital cost and operating costs increase significantly
Solution Approach 1:
The heat exchanger acts as an intermediary that transfers pressure energy from the oxygen stream to the argon condenser system. By using the oxygen stream's pressure and cold energy in the heat exchanger, the system achieves oxygen delivery without requiring a separate oxygen compressor
Solution Approach 2:
The patent replaces the mechanical oxygen compressor system with a thermal-based heat exchanger system. Instead of using mechanical compression to achieve the required oxygen delivery pressure, the system uses thermal energy transfer and pressure exchange through the heat exchanger to accomplish the same goal
3Use of energy by moving object
If moderate pressure operation is implemented for nitrogen production, then nitrogen compression power is reduced, but liquid oxygen production is limited by refrigeration duties
Solution Approach 1:
The heat exchanger enables continuous refrigeration duty by continuously exchanging thermal energy between the oxygen stream and the argon condenser. This continuous thermal coupling allows the system to maintain moderate pressure operation for nitrogen while simultaneously supporting liquid oxygen production without interruption
Solution Approach 2:
The patent changes the thermal parameters of the oxygen stream by using it as a refrigerant source in the heat exchanger. This parameter change (using oxygen's cold energy instead of its pressure alone) enables the system to produce liquid oxygen at moderate pressures by effectively managing the refrigeration duty through thermal energy transfer
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 system achieves nitrogen recovery of 98% or greater and argon recovery of 30% or greater, with efficient liquid oxygen production, reducing operational costs and complexity by eliminating the need for oxygen compressors and minimizing refrigeration penalties.
Implementation Method 1
a distillation column system having a higher pressure column and a lower pressure column linked in a heat transfer relationship via a condenser-reboiler and configured to separate an incoming feed air stream
Implementation Method 2
The argon condenser is configured to condense the argon-enriched overhead against a mixture of a first portion of the oxygen enriched stream from the lower pressure column and a stream of liquid nitrogen from an external source
Implementation Method 3
a higher pressure column and a lower pressure column linked in a heat transfer relationship via a condenser-reboiler
Data Source
AI summary
A moderate pressure, argon and nitrogen producing cryogenic air separation unit and air separation cycle having a higher pressure column, a lower pressure column and an argon column arrangement is disclosed. The moderate pressure, argon and nitrogen producing cryogenic air separation unit is configured to take a first portion of an oxygen enriched stream from the lower pressure column, which together with an external source of liquid nitrogen is used as the boiling side refrigerant to condense the argon in the argon condenser. Use of the external source of liquid nitrogen in the argon condenser allows a second portion of the oxygen enriched stream from the lower pressure column to be taken as a liquid oxygen product stream.