Ammonia Cracking Hydrogen Recovery via Membrane Separator
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Solution Overview
Problem
Current processes for producing hydrogen from ammonia are inefficient in terms of energy consumption and hydrogen recovery, and they often require the combustion of fossil fuels, which is undesirable, especially when aiming for 'green' hydrogen production.
Innovation Solution
A method involving pressurizing and heating liquid ammonia, using a furnace to crack it into hydrogen and nitrogen, followed by purification in a Pressure Swing Adsorption (PSA) device, and further processing with a membrane separator to recycle and recover hydrogen, where the fuel for the furnace can include PSA tail gas, hydrogen, and methane, promoting heat integration and high hydrogen recovery rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PSA is used to purify cracked gas to recover hydrogen, then hydrogen purity is improved, but hydrogen recovery is reduced due to PSA tail gas venting
Solution Approach 1:
The patent recovers hydrogen from the PSA tail gas that would otherwise be vented to atmosphere. By integrating a membrane separator or combustion system, the hydrogen in the tail gas is either separated and recycled or combusted to provide heat for the cracking process, thereby recovering what would have been lost and improving overall hydrogen recovery while maintaining product purity.
Solution Approach 2:
The patent converts the harmful venting of PSA tail gas (which contains valuable hydrogen) into a beneficial heat source by combusting it in the furnace. This eliminates the hydrogen loss while providing thermal energy for the endothermic cracking reaction, transforming a waste stream into a useful resource.
2Temperature
If furnace is used to heat reactor tubes for ammonia cracking, then cracking temperature is improved, but energy consumption increases due to fossil fuel combustion
Solution Approach 1:
The patent converts the previously wasted PSA tail gas into a beneficial fuel source by combusting it in the furnace. This provides the necessary heat for ammonia cracking while eliminating the need for external fossil fuel combustion, thereby maintaining cracking temperature while reducing energy consumption from non-renewable sources.
Solution Approach 2:
The system uses its own process byproduct (PSA tail gas containing unreacted ammonia and hydrogen) as the fuel source for heating the cracking reactor. This self-service approach eliminates the need for external energy inputs and achieves thermal self-sufficiency within the hydrogen production process.
3Device complexity
If PSA tail gas is vented to atmosphere, then process simplicity is maintained, but hydrogen loss occurs
Solution Approach 1:
The patent merges the PSA tail gas stream with the furnace combustion process, combining what would have been a separate venting operation with the thermal processing step. This integration eliminates hydrogen loss by utilizing the tail gas as fuel while adding minimal complexity to the overall process flow.
Solution Approach 2:
Instead of discarding the PSA tail gas to atmosphere, the patent recovers the valuable hydrogen content by combusting it in the furnace. This recovery approach eliminates hydrogen loss while maintaining operational simplicity through a straightforward modification to the existing process.
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 method achieves high hydrogen recovery rates, approaching 99%, while reducing energy consumption and eliminating the need for fossil fuel combustion, making it suitable for producing 'green' hydrogen efficiently.
Implementation Method 1
combusting a fuel in a furnace to heat catalyst-containing reactor tubes
Implementation Method 2
supplying the heated ammonia to the catalyst-containing reactor tubes to cause cracking of the ammonia
Implementation Method 3
purifying the cracked gas in a PSA device to produce a hydrogen product gas and a PSA tail gas
Implementation Method 4
separating the PSA tail gas, or a gas derived therefrom, using a membrane separator to discharge a nitrogen-rich retentate gas and recycle a hydrogen-rich permeate gas
Data Source
AI summary
Recovery of hydrogen from an ammonia cracking process in which the cracked gas is purified in a PSA device is improved by using a membrane separator on the PSA tail gas.