Ammonia Engine Exhaust Aftertreatment for N2O and Ammonia Slip
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing ammonia-fueled internal combustion engines produce significant amounts of nitrous oxide (N2O), a greenhouse gas, especially under lean conditions, and the use of N2O reduction catalysts is uneconomical and requires inefficient combustion parameters.
Innovation Solution
An internal combustion engine system with a combination of SCR and three-way catalytic converters, an ammonia slip catalyst, and oxygen injection, controlled by an engine control device to manage lambda values and oxygen supply, reducing N2O and residual ammonia in the exhaust gas without the need for specialized catalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a special catalyst is used to reduce N2O content in exhaust gas, then N2O emissions are reduced, but the device complexity and cost increase significantly
Solution Approach 1:
The patent extracts the N2O reduction function from the specialized expensive catalyst and transfers it to the existing SCR or three-way catalytic converter by optimizing combustion parameters (lambda control). This removes the need for the difficult-to-produce and expensive specialized N2O reduction catalyst while maintaining N2O reduction capability.
Solution Approach 2:
The existing SCR or three-way catalytic converter is made to perform the additional function of N2O reduction by itself through proper combustion control, without requiring a separate specialized catalyst. The system uses its own components more effectively to achieve multiple functions.
2Object-affected harmful factors
If high temperatures are used in combustion to enable N2O reduction catalyst function, then N2O is converted, but combustion efficiency decreases
Solution Approach 1:
The patent changes the combustion parameter (lambda value) to a specific range (0.95-0.999) that simultaneously achieves efficient combustion and creates conditions for N2O reduction in the existing catalyst, eliminating the need for inefficient high-temperature combustion parameters.
Solution Approach 2:
The combustion process is preliminarily optimized by controlling lambda values before the exhaust reaches the catalyst, creating the right conditions for the existing catalyst to reduce N2O effectively without requiring additional high temperatures during catalysis.
3Productivity
If lean combustion conditions (lambda > 1) are used, then fuel efficiency improves, but N2O formation increases massively
Solution Approach 1:
The patent optimizes the lambda parameter to a specific range (0.95-0.999) that balances fuel efficiency with N2O formation control, finding the optimal point where fuel efficiency is maintained while N2O formation is minimized and subsequently reduced by the catalyst.
Solution Approach 2:
The system uses feedback control to manage the lambda value and oxygen supply, adjusting combustion parameters based on exhaust composition to maintain the optimal balance between fuel efficiency and N2O emissions while coordinating with the catalyst function.
4Object-affected harmful factors
If SCR or three-way catalytic converter is used to reduce NOx, then NOx emissions are reduced, but residual ammonia increases
Solution Approach 1:
The patent introduces an oxygen intermediary by controlling oxygen supply to the catalyst, which enables the oxidation of residual ammonia to nitrogen and water, thereby removing the harmful ammonia byproduct while maintaining NOx reduction function.
Solution Approach 2:
The system uses controlled oxygen supply (strong oxidant) to the catalyst to accelerate the oxidation of residual ammonia, converting it into harmless nitrogen and water, thereby eliminating the ammonia slip problem while preserving NOx reduction.
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
Significantly reduces N2O emissions and residual ammonia by controlling lambda values and oxygen supply, maintaining efficient combustion parameters, thus minimizing greenhouse gas emissions without the need for expensive N2O reduction catalysts.
Implementation Method 1
selective catalytic reduction (SCR) converters and three-way catalytic converters are used for reduction of nitrogen oxides (also referred as NOx) with the aid of catalytic materials into diatomic nitrogen (N2), and water (H2O)
Implementation Method 2
ammonia slip catalysts (also named ASC) are used for reduction of ammonia into diatomic nitrogen (N2), and water (H2O)
Implementation Method 3
at least one oxygen injection device to inject oxygen from an oxygen source upstream or into the at least one ammonia slip catalyst to provide oxygen to the at least one ammonia slip catalyst
Implementation Method 4
combustion of an under-stoichiometric air-ammonia mixture generating an exhaust gas containing NOx, N2O and residual ammonia
Data Source
Figure 1a~1c
Figure 2a~2b
Figure 3
AI summary
Internal combustion engine, comprising: - a plurality of piston-cylinder units (2) comprising a main combustion chamber, - an engine control device (9) for controlling the operation of the internal combustion engine (1), the engine control device (9) and the piston-cylinder units (2) being configured for combustion of an under-stoichiometric air-ammonia mixture generating an exhaust gas containing NOx, N20 and residual ammonia, - an exhaust gas aftertreatment device (10) for aftertreatment of the exhaust gas generated during operation, wherein the exhaust gas aftertreatment device (10) comprises • at least one SCR converter (4) or at least one three-way catalytic converter (5) to reduce at least the amount of NOx in the exhaust gas, • at least one ammonia slip catalyst (6) downstream the at least one SCR catalytic converter (4) or the three-way catalytic converter (5) to reduce the amount of residual ammonia in the exhaust gas, • at least one oxygen injection device (13) to inject oxygen from an oxygen source upstream or into the at least one ammonia slip catalyst (6) to provide oxygen to the at least one ammonia slip catalyst (6), wherein the engine control device (9) is configured to: - control at least one actuator (15) to provide an air-ammonia mixture with a lambda value less than one to the at least one main combustion chamber to create a relatively low amount of the N20 in the exhaust gas, and - control the amount of oxygen provided to the at least one ammonia slip catalyst (6) depending on the lambda value of the under-stoichiometric air-ammonia mixture to decrease the amount of residual ammonia in the exhaust gas.