Urea Electrolyser Ammonia Injection for Cold SCR
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Solution Overview
Problem
Current systems for reducing nitrogen oxides in engine exhaust gases are inefficient in cold conditions due to the freezing of urea, which prevents the injection of liquid urea into the exhaust line, and existing solutions that use solid ammonia storage are complex and require maintenance.
Innovation Solution
A system that includes a liquid urea tank, an electrolyser for converting urea into gaseous ammonia, and an absorber with alkaline-earth salts that can absorb and desorb ammonia, allowing for the injection of gaseous ammonia into the exhaust line even in cold conditions, enabling continuous nitrogen oxide reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid urea is used for SCR catalyst supply, then nitrogen oxide reduction efficiency is improved, but the system fails in cold conditions below -11°C due to urea freezing
Solution Approach 1:
The invention changes the physical state parameter of ammonia from liquid (urea solution) to gas phase. By using gaseous ammonia instead of liquid urea, the system eliminates freezing issues while maintaining SCR catalyst supply functionality, thus resolving the contradiction between reliability and cold-temperature adaptability
Solution Approach 2:
The invention introduces an intermediary substance (gaseous ammonia) that mediates between the urea storage system and the SCR catalyst. The gaseous ammonia serves as a carrier that can be stored in solid form (ammonium carbamate) and then converted to gas for catalyst supply, enabling operation in cold conditions while maintaining reduction efficiency
2Adaptability or versatility
If solid ammonia storage materials are used to enable cold operation, then operational capability in cold conditions is improved, but device complexity increases due to salt block handling and maintenance
Solution Approach 1:
The invention extracts the problematic solid salt block handling and maintenance functions from the system. By using gaseous ammonia generated from a liquid storage tank, the system eliminates the need for solid ammonia storage materials, thereby reducing device complexity while maintaining cold-temperature operational capability
Solution Approach 2:
The invention enables the system to self-regulate ammonia supply through pressure differential control. The gaseous ammonia is automatically supplied to the catalyst based on exhaust gas flow conditions without requiring complex control systems or manual intervention, thus reducing device complexity while maintaining versatility
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
Enables efficient reduction of nitrogen oxides in exhaust gases by providing gaseous ammonia during cold starts, eliminating the need for complex salt block handling and maintenance, and allowing continuous operation of the SCR catalyst.
Implementation Method 1
an electrolyser for transforming liquid urea into gaseous ammonia
Implementation Method 2
an absorber with alkaline-earth salts capable of absorbing gaseous ammonia
Implementation Method 3
capable of absorbing and desorbing gaseous ammonia
Data Source
Figure 1~2
AI summary
The invention particularly relates to an assembly for reducing the nitrogen oxides circulating in an exhaust line (9) of an internal combustion engine, said assembly comprising: - a liquid urea tank (1) having one or more outputs and one input supplied by at least one fill pipe (13) and said tank (1) being connected to a distribution pump (12); - a first supply duct (31) connecting said tank (1) to said exhaust line (9), said assembly being characterised in that it further comprises: - an electrolyser means (14) for converting at least some of the liquid urea into gaseous ammonia; and - a second supply duct (32) for introducing said gaseous ammonia into said exhaust line (9).