Ammonia Cracking in Retrofitted SMR Reactor Tubes
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Solution Overview
Problem
Existing hydrogen production technologies face challenges such as high costs, carbon footprint, and inefficiencies in scaling up CO2-free methods like water electrolysis, and decarbonization of steam methane reforming processes is hindered by low CO2 concentration and infrastructure limitations, while ammonia cracking in existing facilities is hampered by high nitrogen content affecting PSA unit performance.
Innovation Solution
A method and apparatus for producing hydrogen in a retrofitted steam methane reformer using ammonia cracking, which involves preheating ammonia, cracking it in the reformer tubes, and using water washing to reduce unreacted ammonia levels before introducing the stream into a PSA unit, optimizing conditions like temperature and catalysts to achieve high conversion rates and efficient hydrogen production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If ammonia cracking is performed at higher pressures to save hydrogen compression energy, then compression efficiency is improved, but conversion rate decreases due to Le Chatelier's principle
Solution Approach 1:
The patent applies parameter changes by adjusting temperature to compensate for pressure effects. Higher pressures are used to reduce compression energy, but temperature is increased accordingly to maintain favorable conversion rates despite the pressure disadvantage according to Le Chatelier's principle
2Productivity
If ammonia cracking is performed at higher temperatures to improve conversion rate, then productivity is improved, but energy consumption increases
Solution Approach 1:
The patent merges the ammonia cracking process with the existing steam methane reforming process by utilizing the same reactor tubes and furnace. The high-temperature environment required for ammonia cracking is achieved by combining it with the thermal field of the SMR process, thereby sharing energy requirements rather than creating a separate energy-intensive system
Solution Approach 2:
The patent makes the SMR reactor tubes multi-functional by enabling them to perform both steam methane reforming and ammonia cracking reactions. This universal utilization of the same equipment for multiple purposes optimizes energy use and avoids the need for dedicated high-temperature ammonia cracking facilities
3Ease of manufacture
If existing SMR facilities are retrofitted for ammonia cracking, then investment cost is reduced, but nitrogen content in product stream increases affecting PSA performance
Solution Approach 1:
The patent extracts and removes nitrogen from the product stream by routing it through a PSA unit specifically designed or configured for nitrogen removal. This separation step isolates the harmful nitrogen component from the hydrogen product, protecting the PSA unit's performance while maintaining the cost benefits of using existing SMR facilities
Solution Approach 2:
The patent introduces a PSA unit as an intermediary component between the ammonia cracking reactor and the final hydrogen product. This intermediary device mediates the conflict by selectively removing nitrogen from the product stream, thereby protecting downstream equipment and ensuring product quality without requiring complete redesign of the base facility
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 enables efficient hydrogen production with high conversion rates (95-99.8%) and reduced ammonia levels in the PSA feed, overcoming bottlenecks in existing PSA units and allowing for the use of existing infrastructure, thereby reducing costs and carbon emissions.
Implementation Method 1
cracking an ammonia stream in the SMR tubes to produce a crude stream comprising nitrogen, hydrogen, and unreacted ammonia
Implementation Method 2
Ammonia can be cracked into hydrogen and nitrogen at ambient pressure and moderate temperatures (450-600° C.) in the presence of a catalyst
Implementation Method 3
removing the unreacted ammonia from the crude stream using the means for water washing to produce a washed crude stream and an aqueous ammonia stream
Implementation Method 4
introducing the washed crude stream into the PSA unit to produce a hydrogen product stream and a PSA off-gas
Data Source
AI summary
An apparatus is provided for producing hydrogen in an existing steam methane reformer (SMR) via ammonia cracking, the apparatus comprising: an ammonia storage vessel; a furnace having a plurality of reactor tubes and a plurality of burners, wherein the reactor tubes and the burners are in fluid communication with the ammonia storage vessel, such that the reactor tubes and the burners are configured to receive a flow of ammonia gas sourced from the ammonia storage vessel, and catalytically crack the ammonia within the reactor tubes to produce a crude process gas and a flue gas; a plurality of waste heat recovery sections; a boiler feed water preparation system; means for treating the crude process gas in order to reduce the amount of the unreacted ammonia in the crude process gas, thereby resulting in an aqueous ammonia stream and a washed crude stream; and a pressure swing adsorption (PSA) unit disposed downstream the means for treating the crude process gas.