Ammonia Generation System for SCR Emission Control
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Solution Overview
Problem
Conventional diesel exhaust fluid systems for selective catalytic reduction (SCR) catalysts face challenges such as urea decomposition requirements above 180°C, system complexity, and urea deposition, especially in cold environments, necessitating improved reductant delivery systems for efficient NOx emission control.
Innovation Solution
An ammonia generation system utilizing ammonium hydroxide as the ammonia source, which can produce gaseous ammonia for direct injection into the exhaust gas stream, eliminating the need for urea decomposition and reducing system complexity, with a refillable reservoir and heating mechanism to control ammonia injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If diesel exhaust fluid (urea) is used as the ammonia source for SCR catalyst, then the system can provide necessary reductant for NOx reduction, but the system requires high temperatures (180°C or higher) for urea decomposition and has increased complexity
Solution Approach 1:
The patent changes the chemical parameter from urea-based diesel exhaust fluid to ammonium hydroxide solution, which fundamentally alters the temperature requirement. Ammonium hydroxide can decompose at lower temperatures compared to urea, eliminating the need for high-temperature operation while maintaining the SCR catalyst's reductant supply function
Solution Approach 2:
The patent extracts and eliminates the complex urea decomposition process from the system by using pre-formed ammonium hydroxide solution. This removes the need for high-temperature heating and complex mixing channels required for urea decomposition, simplifying the overall system while maintaining effective ammonia delivery to the SCR catalyst
2Reliability
If diesel exhaust fluid systems are used for SCR catalyst, then ammonia can be provided for NOx reduction, but urea deposition occurs particularly during low temperature operation
Solution Approach 1:
The patent changes the chemical composition parameter from urea-based to ammonium hydroxide-based solution. This parameter change eliminates urea deposition because ammonium hydroxide does not undergo the same deposition issues as urea, particularly during low-temperature operation, thereby improving system reliability without harmful byproducts
3Productivity
If conventional SCR systems with diesel exhaust fluid are used, then NOx reduction can be achieved, but long mixing channels and high turbulence mixing area are required
Solution Approach 1:
The patent changes the reductant delivery parameter from urea solution requiring long mixing channels to ammonium hydroxide solution that can be injected more directly. This parameter change reduces the required mixing channel length and turbulence mixing area while maintaining effective NOx reduction efficiency
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 ammonia generation system enables efficient NOx conversion at lower temperatures, reduces system complexity, and operates effectively in cold environments without the need for high pressurization or long mixing channels, improving overall emission control efficiency.
Implementation Method 1
a heating mechanism to control ammonia injection
Implementation Method 2
The SCR process uses catalytic reduction of nitrogen oxides with a reductant (e.g., ammonia) in the presence of atmospheric oxygen, resulting in the formation predominantly of nitrogen and steam
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
The invention provides an emission control system for treatment of an exhaust gas stream of an engine, including an engine producing an exhaust gas stream; an SCR catalyst unit downstream from the engine and in fluid communication with the exhaust gas stream; and an ammonia generation system comprising a reservoir containing ammonium hydroxide and an ammonia injector, wherein the reservoir is in fluid communication with the ammonia injector and the ammonia injector is in fluid communication with the exhaust gas stream upstream of the SCR catalyst unit. A method of treating an exhaust gas stream of an engine is also provided, including the steps of heating ammonium hydroxide to produce gaseous ammonia and transferring the gaseous ammonia through an ammonia injector into the exhaust gas stream such that the gaseous ammonia disperses within the exhaust gas stream upstream of a SCR catalyst unit.