Green Ammonia Plant Integration With Nitrogen Recycle and Waste Heat
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Solution Overview
Problem
Current ammonia production methods, such as steam methane reforming and the Haber-Bosch process, contribute significantly to carbon dioxide emissions, and there is a need for improved process efficiency and integration of plant units, particularly in large-scale ammonia production using renewable energy sources.
Innovation Solution
A method and plant design that integrates hydrogen production via electrolysis and cryogenic air separation, utilizing a nitrogen recycle stream to optimize energy usage, heat management, and storage, allowing for flexible operation and reduced energy consumption by using waste heat and renewable energy sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional steam methane reforming and Haber-Bosch process are used for ammonia production, then large-scale ammonia production is achieved, but carbon dioxide emissions increase significantly
Solution Approach 1:
The patent changes the fundamental parameter of hydrogen production from fossil fuel-based (SMR) to electrolysis-based, transforming the chemical process from carbon-intensive to carbon-free. This parameter change in the feedstock source eliminates CO2 emissions while maintaining large-scale production capability through industrial electrolysis units
Solution Approach 2:
The air separation unit serves multiple functions: providing nitrogen for ammonia synthesis, generating oxygen for electrolysis, and producing liquid nitrogen for storage and transport. This multi-functionality consolidates previously separate processes into one integrated unit, maintaining productivity while reducing overall carbon footprint
2Object-generated harmful factors
If electrolysis is used for hydrogen production, then carbon footprint is reduced, but operating costs increase due to high energy consumption
Solution Approach 1:
The patent merges the air separation unit with the ammonia production unit, creating an integrated system where the air separation unit provides both nitrogen for synthesis and oxygen for electrolysis. This integration shares infrastructure and energy resources, reducing overall energy consumption and operating costs compared to separate units
Solution Approach 2:
The air separation unit operates continuously to pre-produce and store liquid nitrogen and oxygen in advance. This preliminary action allows the electrolysis unit to receive oxygen on-demand without requiring continuous high-energy operation, enabling flexible energy consumption patterns that reduce costs during high-tariff periods
3Reliability
If air separation unit operates continuously at full capacity, then nitrogen supply for ammonia synthesis is ensured, but energy consumption increases during peak periods
Solution Approach 1:
The air separation unit pre-produces and stores large quantities of liquid nitrogen and oxygen in storage tanks during low-energy-cost periods. This preliminary production ensures reliable nitrogen supply for ammonia synthesis while allowing the unit to operate at reduced capacity during high-energy-cost peak periods, reducing overall energy consumption
4Productivity
If electrolysis and air separation are integrated, then process efficiency is improved, but plant complexity increases
Solution Approach 1:
The patent combines the air separation unit and ammonia production unit into one integrated plant, sharing common infrastructure such as compressors, heat exchangers, and control systems. This merging reduces the total number of separate units required, simplifying plant complexity while improving overall process efficiency through better resource utilization and energy integration
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 significantly reduces operating costs and carbon footprint by efficiently utilizing renewable energy, maximizing power consumption during low-tariff periods, and minimizing it during high-tariff periods, while enabling large-scale green ammonia production with improved operational flexibility.
Implementation Method 1
hydrogen produced by water electrolysis
Implementation Method 2
production of air products in liquid or gaseous state by cryogenic separation of air
Implementation Method 3
rectification column systems... for the recovery of nitrogen and/or oxygen in liquid and/or gaseous state
Implementation Method 4
waste heat from the ammonia synthesis reactor
Implementation Method 5
both feed streams are subjected to a compression
Implementation Method 6
catalytically reacting hydrogen provided in a first feed stream and nitrogen provided in a second feed stream
Data Source
AI summary
A method for producing ammonia by catalytically reacting hydrogen provided in a first feed stream and nitrogen provided in a second feed stream is proposed, the hydrogen in the first feed stream being at least in part formed by water electrolysis and the nitrogen in the second feed stream being at least in part formed by cryogenic air separation, wherein said cryogenic air separation is performed using an air separation unit comprising a rectification column system, a recycle stream being formed in the air separation unit from a gas stream at least predominantly comprising nitrogen which is withdrawn from the rectification column system, the recycle stream being, in the order indicated, compressed, cooled, expanded and reintroduced into the rectification column system, and wherein waste heat from said catalytically reacting hydrogen and nitrogen is transferred to a steam system providing steam.