Method for cryogenic purification of a feed stream comprising hydrogen, methane, nitrogen and argon
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Solution Overview
Problem
Current ammonia production plants face inefficiencies and high costs in the cryogenic purification processes for recovering hydrogen, nitrogen, and argon from synthesis gas, particularly due to complex and capital-intensive conventional methods.
Innovation Solution
A method integrating cryogenic purification with nitrogen rectification and liquefaction, involving pressure management, stream conditioning, and recycling, to produce a hydrogen-nitrogen synthesis gas, a methane-rich fuel gas, and nitrogen products, utilizing a nitrogen rectification column operated at low pressure and incorporating hydrogen and nitrogen recycling and liquefaction systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional argon recovery processes are used from ammonia tail gas, then argon, hydrogen and nitrogen can be recovered, but the process becomes complex involving multiple columns, vaporizers, compressors, and heat exchangers with additional capital and operating costs
Solution Approach 1:
The patent combines the cryogenic purification process with argon recovery into a single integrated system. The synthesis gas rectification column simultaneously performs hydrogen-nitrogen separation and argon concentration, while the nitrogen rectification column handles both nitrogen purification and argon recovery. This merging eliminates the need for separate argon recovery equipment such as dedicated columns, vaporizers, compressors, and heat exchangers, thereby reducing device complexity while maintaining recovery efficiency
Solution Approach 2:
The rectification columns in the patent serve multiple functions: the synthesis gas rectification column performs both H2-N2 separation and argon concentration, while the nitrogen rectification column simultaneously purifies nitrogen and recovers argon. This multi-functionality allows a single integrated system to achieve what previously required multiple separate processes, reducing both capital and operating costs while maintaining comprehensive gas recovery
2Quantity of substance
If a single stage of refrigerated rectification is used in the Braun Purifier, then the overhead synthesis gas stream is substantially free of unconverted methane and argon is rejected into the fuel gas stream, but the process cannot recover nitrogen as a separate product
Solution Approach 1:
The patent divides the single rectification stage into two separate rectification columns: the synthesis gas rectification column that removes methane and produces H2-N2 synthesis gas, and the nitrogen rectification column that separates nitrogen from argon-rich bottom streams. This segmentation enables independent optimization of each separation function and allows nitrogen to be recovered as a separate product while maintaining effective removal of methane and argon from the synthesis gas stream
Solution Approach 2:
The patent adds a new dimension to the process by introducing a second rectification column operating in series. This dimensional expansion from single-stage to two-stage rectification creates additional separation capability, enabling nitrogen recovery as a distinct product stream while maintaining the original function of methane and argon removal from the synthesis gas
3Ease of manufacture
If the feed gas stream is cooled and expanded to near saturation and partially condensed, then the cryogenic purification can proceed, but additional energy is consumed in cooling and expansion processes
Solution Approach 1:
The patent applies preliminary cooling and expansion of the feed gas stream to near saturation conditions before entering the rectification columns. This preliminary action prepares the gas for efficient cryogenic separation by achieving the necessary temperature and pressure conditions upfront, enabling the rectification process to proceed effectively while minimizing subsequent energy requirements for additional cooling stages
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 enhances the recovery of hydrogen, nitrogen, and argon with reduced capital and operating costs, improving the efficiency of ammonia synthesis gas production and fuel gas recycling, while producing high-purity nitrogen products.
Implementation Method 1
The feed gas stream is then partially cooled and expanded to a lower pressure
Implementation Method 2
The nitrogen rectification column is configured to separate a nitrogen and argon enriched bottom stream from a hydrogen and nitrogen containing overhead stream
Implementation Method 3
All or a portion of the warm gaseous nitrogen stream is directed to a nitrogen liquefaction system to produce a liquid nitrogen product stream
Data Source
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AI summary
A system and method for cryogenic purification of a hydrogen, nitrogen, methane and argon containing feed stream to produce a methane free, hydrogen and nitrogen containing synthesis gas and a methane rich fuel gas, as well as to recover an argon product stream, excess hydrogen, and excess nitrogen is provided. The disclosed system and method are particularly useful as an integrated cryogenic purifier in an ammonia synthesis process in an ammonia plant. The excess nitrogen is a nitrogen stream substantially free of methane and hydrogen that can be used in other parts of the plant, recovered as a gaseous nitrogen product and/or liquefied to produce a liquid nitrogen product.