Ammonia Sweep Gas in Membrane Reactors for Hydrogen Separation
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Solution Overview
Problem
Existing ammonia cracking processes for hydrogen production face challenges in efficiency, infrastructure requirements, and corrosion issues due to the use of steam or nitrogen as sweep gases, which also necessitate additional processing and infrastructure.
Innovation Solution
Using ammonia as a sweep gas in a membrane reactor to facilitate hydrogen production, allowing for continuous recycling and reducing infrastructure needs, while minimizing corrosion and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If steam or nitrogen is used as sweep gas to remove hydrogen from the permeate side, then hydrogen permeation through the membrane is increased, but infrastructure requirements and system complexity increase
Solution Approach 1:
Ammonia serves multiple functions: it acts as both the feed material for hydrogen production and as the sweep gas to remove hydrogen from the permeate side. This eliminates the need for separate sweep gas generation and processing infrastructure, reducing system complexity while maintaining high hydrogen permeation rates
Solution Approach 2:
The ammonia sweep gas that contacts the permeate side is continuously recycled back to the retentate side after separation from permeated hydrogen. This recovery and reuse of ammonia eliminates waste and reduces the need for continuous ammonia supply infrastructure
2Productivity
If steam is used as sweep gas to enhance hydrogen removal, then hydrogen permeation is improved, but corrosion issues arise due to traces of ammonia crossing over and generating corrosive mixtures
Solution Approach 1:
Instead of using steam that creates corrosive conditions when mixed with ammonia traces, the patent uses ammonia itself as the sweep gas. This converts the potentially harmful interaction into a beneficial one, eliminating corrosion while maintaining effective hydrogen removal
Solution Approach 2:
The ammonia sweep gas creates an inert atmosphere on the permeate side that prevents corrosive reactions. Since ammonia is chemically compatible with the system materials and does not form corrosive mixtures like steam does, it provides a protective environment
3Productivity
If vacuum is used to reduce hydrogen partial pressure on the permeate side, then hydrogen permeation is increased, but system complexity and energy consumption increase
Solution Approach 1:
The ammonia sweep gas automatically maintains low hydrogen partial pressure on the permeate side through continuous flow and recycling, eliminating the need for vacuum systems. The system self-regulates hydrogen removal through the chemical and physical properties of ammonia
4Productivity
If additional sweep gas infrastructure is implemented, then hydrogen production efficiency is improved, but costs and energy consumption increase
Solution Approach 1:
The ammonia sweep gas is continuously separated from permeated hydrogen and recycled back to the retentate side, eliminating the need for continuous ammonia consumption and reducing energy requirements for gas generation and processing
Solution Approach 2:
Ammonia serves dual purposes as both feed material and sweep gas, eliminating the need for separate infrastructure and reducing overall energy consumption compared to using dedicated sweep gases like steam or nitrogen
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 achieves high ammonia conversion to hydrogen and nitrogen with reduced greenhouse gas emissions, simpler implementation, and lower costs by leveraging ammonia's recyclability and avoiding steam-related corrosion.
Implementation Method 1
a membrane selectively permeable to hydrogen
Implementation Method 2
The difference in partial pressure of hydrogen between the retentate side of the membrane and the permeate side of the membrane drives the permeation of hydrogen through the membrane
Implementation Method 3
The ammonia sweep gas can be liquefied at relatively non-severe pressures and moderate sub-ambient temperatures, thereby making it relatively easy to separate the ammonia sweep gas from the produced hydrogen
Implementation Method 4
Ammonia cracking to form hydrogen and nitrogen is a highly endothermic process
Data Source
AI summary
The disclosure relates to systems and methods for the production of hydrogen (H2) from ammonia (NH3) in a membrane reactor that include using ammonia as a sweep gas. Ammonia is converted to hydrogen and nitrogen (N2), and the hydrogen is separated from the nitrogen and unreacted ammonia by passing the hydrogen through a hydrogen-permeable membrane while using ammonia as a sweep gas. The ammonia sweep gas can be separated from the permeated hydrogen and continuously recycled.