Nitric Acid Tail Gas Separation for Lower-Energy Argon and Nitrogen
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Solution Overview
Problem
Current air fractionation processes for producing high-purity argon and nitrogen are costly and energy-intensive due to the close boiling points of argon and oxygen, leading to difficulties in separation and the presence of impurities in nitrogen streams.
Innovation Solution
A process that utilizes the tail gas from the synthesis of nitric acid, involving NOx absorption, NOx removal, and cryogenic separation treatment to produce high-purity argon and nitrogen streams, eliminating the need for large distillation columns and compressors, thereby reducing capital and energy costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If large-size distillation columns with a large number of plates are used to separate argon and nitrogen, then separation efficiency is improved, but plant design cost and energy consumption increase
Solution Approach 1:
The invention removes oxygen and other impurities from the air feed stream before the argon-nitrogen separation step. This preliminary purification action reduces the burden on the distillation columns, allowing for smaller column sizes with fewer plates while achieving the same separation efficiency, thereby reducing both capital cost and energy consumption.
Solution Approach 2:
The invention divides the air separation process into distinct stages: first removing oxygen and impurities in a preliminary purification step, then performing argon-nitrogen separation in a dedicated column. This segmentation allows each unit to be optimized independently, reducing the overall complexity and energy requirements compared to a single large-scale distillation system.
2Manufacturing precision
If multiple distillation columns are used to separate argon and nitrogen, then separation efficiency is improved, but device complexity increases
Solution Approach 1:
By performing preliminary removal of oxygen and impurities before the argon-nitrogen separation, the invention eliminates the need for additional distillation columns that would otherwise be required to achieve the same purity levels. This reduces the number of columns from three to two, simplifying the overall device complexity.
3Manufacturing precision
If adsorption beds are installed downstream of distillation columns for further purification, then product purity is improved, but device complexity and cost increase
Solution Approach 1:
The invention performs preliminary removal of oxygen and impurities at the beginning of the process, which prevents these contaminants from interfering with the argon-nitrogen separation. This upfront action eliminates the need for downstream adsorption beds or additional purification stages, reducing device complexity while maintaining high product purity.
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 process achieves high-purity argon and nitrogen production at lower costs and energy consumption, utilizing the previously discarded tail gas, enhancing operational safety and adding value to nitric acid plants by providing a profitable byproduct.
Implementation Method 1
subjecting a process gas containing NOx to a NOx absorption stage in a suitable absorption means, obtaining nitric acid and a tail gas containing nitrogen, argon and residual NOx
Implementation Method 2
subjecting at least a portion of said conditioned tail gas to a separation treatment, obtaining a first product stream containing argon and a second product stream containing nitrogen
Implementation Method 3
separates argon, nitrogen and oxygen, making use of their different boiling points
Data Source
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AI summary
A process comprising: subjecting a process gas (22) containing NOx to a stage for absorption of NOx in a suitable absorption means (23), obtaining nitric acid (24) and a tail gas (25) containing nitrogen, argon and residual NOx; subjecting said tail gas (25) to a treatment which comprises at least one NOx removal stage, obtaining a conditioned tail gas (26); subjecting at least a portion (26b) of said conditioned tail gas to a separation treatment, obtaining a product stream (40) containing argon and a product stream (37) containing nitrogen.