Multi-Layer Catalyst Pre-Purification for Cryogenic Air Separation
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Solution Overview
Problem
Current pre-purification systems for cryogenic air separation units are costly and inefficient in removing hydrogen, carbon monoxide, water, and carbon dioxide from feed air streams, as they rely on expensive catalytic materials and multiple layers with limited effectiveness.
Innovation Solution
A multi-layer pre-purification system comprising a first catalyst layer of manganese and copper oxides to remove carbon monoxide and hydrogen, followed by an adsorbent layer to remove water and carbon dioxide, and a second catalyst layer, preferably with a noble metal-based catalyst, to further purify the stream, reducing impurities to low concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional catalytic pre-purification techniques are used to remove hydrogen and carbon monoxide, then the removal effectiveness is improved, but the system cost increases due to expensive noble metal catalysts
Solution Approach 1:
The pre-purification system is divided into multiple sequential stages: a first catalytic stage using inexpensive manganese and copper oxides for initial hydrogen and carbon monoxide removal, followed by a second catalytic stage using noble metal catalysts for final trace removal. This segmentation allows the expensive noble metal catalysts to process only the reduced impurity load from the first stage, significantly reducing the required catalyst quantity and system cost while maintaining high removal effectiveness.
Solution Approach 2:
The first catalytic stage using manganese and copper oxides performs preliminary removal of the bulk of hydrogen and carbon monoxide before the gas stream enters the second catalytic stage. This preliminary action reduces the impurity concentration to low levels, allowing the subsequent noble metal catalyst stage to operate more efficiently with lower catalyst loading, thereby reducing overall system cost while maintaining high removal effectiveness.
2Manufacturing precision
If multiple layers of adsorbent materials are used to remove water and carbon dioxide, then the purification precision is improved, but the device complexity increases
Solution Approach 1:
The system combines catalytic removal and adsorptive removal mechanisms into a unified pre-purification process. The catalytic stages remove hydrogen and carbon monoxide through chemical reactions, while the adsorbent layers remove water and carbon dioxide through physical adsorption. This merging of different purification mechanisms achieves high purification precision for all four impurities without requiring excessive complexity, as each mechanism targets specific impurities efficiently.
Solution Approach 2:
Different sections of the pre-purification system are designed with locally optimized properties: the catalytic sections use specific catalyst compositions (manganese-copper oxides followed by noble metals) optimized for hydrogen and carbon monoxide removal, while the adsorbent sections use materials optimized for water and carbon dioxide removal. This local quality optimization achieves high purification precision for each impurity type without requiring the entire system to be overly complex.
3Productivity
If conventional single-stage catalytic systems are used, then the device complexity is reduced, but the productivity decreases due to limited removal effectiveness for trace impurities
Solution Approach 1:
The catalytic pre-purification system is segmented into two sequential stages: a first stage using manganese and copper oxides for bulk impurity removal, and a second stage using noble metal catalysts for trace impurity removal. This segmentation enables the system to achieve high removal effectiveness for both high-concentration and trace-level impurities, significantly improving productivity compared to single-stage systems while maintaining manageable device complexity through modular design.
Solution Approach 2:
The system changes the catalytic parameters between stages by using different catalyst compositions (manganese-copper oxides vs. noble metals) and operating conditions optimized for different impurity concentration ranges. This parameter change allows the first stage to efficiently remove bulk hydrogen and carbon monoxide, while the second stage is optimized for removing trace amounts, thereby achieving high overall removal effectiveness and productivity.
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 effectively reduces hydrogen, carbon monoxide, and carbon dioxide concentrations to below 500 ppb and 50 ppb, respectively, while maintaining low water and carbon dioxide levels, offering cost advantages and improved performance over prior art methods.
Implementation Method 1
passing the gas stream substantially free of carbon dioxide and water through a first catalyst layer comprising a mixture manganese and copper oxides configured to remove at least some of the carbon monoxide and hydrogen from the gas stream
Implementation Method 2
passing the first intermediate effluent through an adsorbent layer disposed downstream of the first catalyst layer, the adsorbent layer configured to remove water and carbon dioxide from the intermediate effluent
Implementation Method 3
passing the second intermediate effluent through a second catalyst layer disposed downstream of the adsorbent layer, the second catalyst layer configured to remove at least hydrogen from the second intermediate effluent
Data Source
AI summary
A system and method of pre-purification of a feed gas stream is provided that is particularly suitable for pre-purification of a feed air stream in cryogenic air separation unit. The disclosed pre-purification systems and methods are configured to remove substantially all of the hydrogen, carbon monoxide, water, and carbon dioxide impurities from a feed air stream and is particularly suitable for use in a high purity or ultra-high purity nitrogen plant. The pre-purification systems and methods preferably employ two or more separate layers of hopcalite catalyst with the successive layers of the hopcalite separated by a zeolite adsorbent layer that removes water and carbon dioxide produced in the hopcalite layers. Alternatively, the pre-purification systems and methods employ a hopcalite catalyst layer and a noble metal catalyst layer separated by a zeolite adsorbent layer that removes water and carbon dioxide produced in the hopcalite layer.