Hydrogen Generation Catalyst for Ammonia Slip Control
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Solution Overview
Problem
Current fuel cell systems face limitations in maximizing NOx purification rates due to ammonia slip, leading to increased costs from excessive precious metal use in ammonia oxidation catalysts, as existing systems struggle to efficiently utilize ammonia as a reducing agent.
Innovation Solution
A hybrid vehicle system incorporating a hydrogen fuel cell system and internal combustion engine, where ammonia is used as both a fuel and reducing agent in the SCR system, with a hydrogen supply system generating high-purity hydrogen and an exhaust system utilizing ammonia to enhance SCR efficiency, including a hydrogen generation catalyst, fuel cell stack, and SCR/AOC devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ammonia injection amount is increased to maximize NOx purification rate, then NOx removal efficiency is improved, but ammonia slip increases and system cost increases due to need for larger AOC device
Solution Approach 1:
The patent introduces a hydrogen generation catalyst device as an intermediary component between the ammonia storage container and the exhaust system. This device catalytically converts ammonia to hydrogen, which then serves as the reducing agent for NOx purification. This intermediary conversion process eliminates ammonia slip while maintaining effective NOx reduction, as hydrogen is more precisely controllable and does not cause the same environmental issues as ammonia slip.
Solution Approach 2:
The patent changes the chemical form of the reducing agent from ammonia (NH3) to hydrogen (H2) through catalytic conversion. This parameter change in the chemical composition allows for more precise control of the reducing agent dosage and eliminates the ammonia slip problem while maintaining or improving NOx purification efficiency. The hydrogen generation catalyst device enables this transformation by facilitating the chemical reaction NH3 → H2.
2Object-generated harmful factors
If ammonia injection amount is limited to prevent ammonia slip, then ammonia emission is reduced, but NOx purification rate cannot be maximized
Solution Approach 1:
The hydrogen generation catalyst device acts as an intermediary that converts ammonia to hydrogen before the reducing agent reaches the SCR catalyst. This allows the system to use ammonia as the storage form (which is stable and easy to store) while delivering hydrogen to the SCR system (which provides better purification efficiency without ammonia slip). The intermediary conversion resolves the contradiction between limiting ammonia emission and maximizing NOx purification.
Solution Approach 2:
The patent replaces the direct mechanical injection of ammonia into the exhaust stream with a chemical conversion process. Instead of mechanically controlling ammonia injection to balance between purification and slip prevention, the system uses catalytic conversion to transform ammonia into hydrogen, which then chemically reacts with NOx. This substitution of the delivery mechanism enables more precise control and eliminates the trade-off.
3Object-generated harmful factors
If AOC device is enlarged to remove ammonia slip, then ammonia emission control is improved, but system cost increases due to increased precious metal amount
Solution Approach 1:
The patent extracts the ammonia-to-hydrogen conversion function from the AOC device and places it in a dedicated hydrogen generation catalyst device. This separation allows the AOC device to be minimized or eliminated, as the hydrogen generation catalyst device handles the ammonia conversion before the exhaust reaches the SCR system. By taking out the ammonia management function to a separate component, the system reduces the size and precious metal content of the AOC device while still controlling ammonia slip.
Solution Approach 2:
The hydrogen generation catalyst device serves as an intermediary that prevents ammonia from reaching the AOC device in the first place. By converting ammonia to hydrogen upstream, the system eliminates the need for a large AOC device to handle ammonia slip. This intermediary conversion reduces the burden on the AOC device, allowing for a smaller, less expensive configuration with reduced precious metal content.
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 configuration efficiently uses power from the fuel cell system, increases SCR system efficiency, and reduces ammonia slip, thereby minimizing costs and environmental impact by optimizing ammonia utilization and NOx reduction.
Implementation Method 1
a hydrogen generation catalyst device connected to the NH3 storage container and configured for generating high purity hydrogen from the solid NH3 using a hydrogen separation catalyst
Implementation Method 2
an oil circulation circuit that communicates with an engine oil circuit and is provided in the NH3 storage container to circulate a solvent that heats the solid NH3
Implementation Method 3
electricity is generated by an electrochemical reaction between hydrogen as a fuel and oxygen in the air
Implementation Method 4
a selective catalyst reduction (SCR) device, and an ammonia oxidation catalyst (AOC) device
Data Source
AI summary
A vehicle may include a fuel cell system configured for generating electrical energy used in the vehicle using hydrogen, an engine system including an engine and configured for generating power of the vehicle using hydrogen, an exhaust system that purifies exhaust gas discharged from the engine, and a hydrogen supply system connected to the fuel cell system, the engine system and the exhaust system, and configured for supplying the hydrogen used in the fuel cell system and the engine system, and ammonia (NH3) used in the exhaust system.