Air separation method and air separation apparatus
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Solution Overview
Problem
Conventional air separation apparatuses face a decrease in argon recovery when collecting high-pressure nitrogen gas, liquefied oxygen, and liquefied nitrogen, and existing methods only marginally improve argon recovery.
Innovation Solution
The air separation method involves a series of low-temperature distillation steps and indirect heat exchanges in a multi-column system, including a low-pressure column, an argon column, and a high-pressure column, to efficiently separate and liquefy nitrogen and oxygen gases while maintaining argon recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large amount of middle-pressure nitrogen gas, high-pressure nitrogen gas, liquefied oxygen, and/or liquefied nitrogen is collected, then the yield of nitrogen and oxygen products is improved, but the argon recovery decreases
Solution Approach 1:
The invention divides the air separation system into multiple pressure levels (high-pressure column, middle-pressure column, low-pressure column) with separate distillation zones. Each column operates at a specific pressure range and produces specific products, allowing independent optimization of nitrogen, oxygen, and argon recovery without mutual interference. This segmentation enables simultaneous high yield of nitrogen/oxygen products and high argon recovery.
Solution Approach 2:
The invention adds a pressure dimension to the traditional air separation system by implementing multi-column distillation at different pressure levels. This dimensional expansion allows the system to produce multiple product streams (high-pressure nitrogen, middle-pressure nitrogen, liquefied oxygen, liquefied nitrogen) while maintaining efficient argon separation in dedicated zones, resolving the trade-off between product yield and argon recovery.
2Productivity
If the flow rate of liquefied oxygen, middle-pressure nitrogen gas, or liquefied nitrogen is increased, then the productivity is improved, but the argon recovery decreases
Solution Approach 1:
The system segments argon separation into dedicated zones within each pressure-level column, with specific trays or sections optimized for argon concentration. This allows high flow rates of other products (liquefied oxygen, nitrogen gases) to be withdrawn from different sections without disrupting the argon separation zones, maintaining high argon recovery alongside high productivity.
Solution Approach 2:
The invention uses intermediate pressure-level columns as mediators between the high-pressure and low-pressure systems. These middle-pressure columns provide buffer zones for product withdrawal and heat exchange, allowing flexible adjustment of flow rates for nitrogen and oxygen products while preserving the argon separation efficiency in connected columns.
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 allows for the collection of a larger amount of high-pressure nitrogen gas and liquefied oxygen while inhibiting a decrease in argon recovery, enhancing the overall yield of nitrogen and oxygen products.
Implementation Method 1
a low-pressure oxygen separation step in which a mixed fluid containing oxygen, nitrogen, and argon, which is a low-pressure feed supplied into a low-pressure column, is distilled at low temperatures, and the mixed fluid is separated into low-pressure nitrogen gas, low-pressure liquefied oxygen, and liquefied feed argon
Implementation Method 2
a first indirect heat exchange step in which, by indirect heat exchange between the argon gas and the low-pressure liquefied oxygen, the argon gas is liquefied, and liquefied argon is produced while a part of the low-pressure liquefied oxygen is vaporized
Implementation Method 3
an argon separation step in which the liquefied feed argon is distilled at low temperatures, and separated into argon gas and middle-pressure liquefied oxygen
Implementation Method 4
a second indirect heat exchange step in which, by indirect heat exchange between middle-pressure nitrogen gas supplied from a middle-pressure column and the low-pressure liquefied oxygen, the middle-pressure nitrogen gas is liquefied and middle-pressure liquefied nitrogen is produced
Data Source
AI summary
One object of the present invention is to provide an air separation method and an air separation apparatus which can collect a larger amount of nitrogen gas, liquefied oxygen, and liquefied nitrogen which have higher pressure than the operating pressure in the low-pressure column while inhibiting a decrease of the argon recovery, and the present invention provides an air separation method comprising a step in which the low-pressure liquefied oxygen at the bottom part of the low-pressure column is reboiled by the argon gas at the top part of the argon column and the middle-pressure nitrogen gas at the top part of the middle-pressure column, and a step in which the middle-pressure liquefied oxygen at the bottom part of the argon column is reboiled by the high-pressure nitrogen gas at the top part of the high-pressure column.