Compact SCR System with Vaporizer Module for Uniform Ammonia Distribution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing SCR systems for reducing NOx in engines face space constraints and inefficiencies due to long urea injection ducts and uneven ammonia distribution, leading to reduced NOx conversion and potential precipitation issues, particularly in smaller engines like those in marine and power generation sectors.
Innovation Solution
A compact SCR system with a vaporizer module and inlet flow system that uses hot treated exhaust gas to decompose urea into ammonia, providing a longer residence time and uniform distribution across the SCR reactor, eliminating the need for an ammonia injection grid and reducing system size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If long injection ducts are used to provide sufficient residence time for urea decomposition, then ammonia generation is improved, but system size and space requirements increase
Solution Approach 1:
The patent increases the temperature parameter in the vaporizer module (using hot exhaust gas at 150-450°C) to accelerate urea decomposition kinetics, allowing sufficient residence time (0.5-5 seconds) to be achieved in a much shorter duct length compared to lower temperature systems
Solution Approach 2:
The patent divides the exhaust flow into two separate streams: one passing through the vaporizer module for urea decomposition, and another bypassing it. These streams are then recombined, allowing the decomposition process to occur in a dedicated small-volume zone rather than requiring a long common duct for all exhaust
2Volume of stationary object
If urea is injected directly into exhaust gas without sufficient decomposition time, then system size is reduced, but precipitation on reactor walls and catalyst occurs
Solution Approach 1:
The patent performs preliminary decomposition of urea in the vaporizer module before the exhaust enters the SCR reactor. The hot exhaust gas pre-heats and decomposes urea in advance, ensuring complete vaporization and conversion to ammonia before catalyst contact, preventing precipitation
Solution Approach 2:
The patent introduces hot exhaust gas as an intermediary medium in the vaporizer module to transfer thermal energy to urea, facilitating its decomposition. This intermediary approach allows controlled decomposition in a dedicated zone before mixing with the main exhaust stream
3Device complexity
If ammonia is directly introduced into exhaust flow without uniform distribution, then system complexity is reduced, but temperature unevenness leads to precipitation and corrosion
Solution Approach 1:
The patent segments the ammonia introduction process into two stages: (1) decomposition in the vaporizer module where hot exhaust gas creates turbulent mixing, and (2) recombination of the decomposed stream with the bypass stream, achieving uniform distribution without complex injection grids
Solution Approach 2:
The patent utilizes turbulent flow (a form of mechanical motion) in the vaporizer module to enhance mixing of urea decomposition products with exhaust gas. The chaotic eddies and vortices in turbulent flow promote uniform ammonia distribution, preventing localized cold spots
4Manufacturing precision
If long ducts with large diameter are used for SCR systems in 500-4500 kW engines, then NOx conversion is improved, but space constraints in marine and power generation applications are worsened
Solution Approach 1:
The patent changes the temperature parameter in the vaporizer module to optimize urea decomposition rate, achieving high conversion efficiency in a compact volume. The controlled temperature range (150-450°C) ensures complete decomposition without requiring long residence times
Solution Approach 2:
The patent combines multiple functions into integrated components: the vaporizer module serves both as a heating zone and decomposition reactor, while the flow distribution system combines separation and recombination functions, reducing overall system volume compared to conventional separate components
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 achieves efficient NOx reduction with a more compact design, ensuring uniform ammonia distribution and longer decomposition time, thereby enhancing NOx conversion efficiency and reducing space requirements for installation.
Implementation Method 1
a stream of hot treated exhaust gas is used to provide for decomposition of the urea into its active components including ammonia
Implementation Method 2
The inlet flow system is located adjacent to at least four sides of the SCR reactor and is configured to provide an approximately uniform flow of the exhaust gas through the catalyst
Implementation Method 3
The flow of exhaust gases through flow ducts around the SCR provides additional heat to the vaporizer module to volatilize a solution of urea
Implementation Method 4
Nitrogen oxides formed in the combustion process of fossil and renewable fuels are reduced with a reductant, such as ammonia, on a catalytic surface
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A Selective Catalytic Reduction (SCR) system comprises an SCR reactor (3), comprising at least one SCR catalyst and is in communication with the inlet flow system (1) and the vaporizer module, an inlet flow system (1), comprising one or more entrances for exhaust gases from an engine, wherein the flow of gases through at least one flow duct (11, 12) is located around the SCR reactor (3) and provides heat to the vaporizer module and is introduced into the SCR reactor after the introduction of an ammonia-laden gas stream and after passing through a plurality of baffle plates to provide an uniform gas concentration profile across the cross section of the SCR reactor (3), and a vaporizer module, comprising a means for introducing urea into a heated pre-reactor in which it is at least partially decomposed and prior to introducing the exhaust gas stream to the SCR reactor (3).