Ceramic Baffle Plate Mixing for Shorter SCR Exhaust Pipes
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Solution Overview
Problem
Existing systems for mixing reducing agents in exhaust gas streams require significant installation space and suffer from high wear due to the chemical and thermal stress of the baffle plates, leading to increased maintenance costs and limited efficiency.
Innovation Solution
A ceramic baffle plate with irregularly arranged ceramic hard bodies and pores, positioned downstream of a mixing nozzle, is used to atomize and evaporate the reducing agent droplets efficiently, minimizing contact with pipe walls and reducing wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a straight exhaust pipe more than 1.5 m long is used to ensure complete evaporation of the reducing agent, then the evaporation completeness is improved, but the installation space requirement increases
Solution Approach 1:
The exhaust pipe is segmented into multiple sections with baffle plates inserted at intervals. This segmentation creates multiple evaporation zones along the exhaust path, allowing complete evaporation of the reducing agent within a shorter overall pipe length by distributing the evaporation process across several localized zones rather than requiring a single long continuous path.
Solution Approach 2:
Baffle plates are introduced as intermediary elements within the exhaust pipe. These baffle plates serve as mediators that disrupt the exhaust flow, forcing it to pass around and through the plates, thereby increasing the effective path length and providing additional surface area for evaporation without requiring the entire exhaust pipe to be excessively long.
2Productivity
If conventional baffle plates are used to mix the reducing agent, then the mixing efficiency is improved, but the wear on baffle plates increases due to chemical and thermal stress
Solution Approach 1:
The baffle plates are constructed from composite materials that combine materials with complementary properties. This composite structure provides both the mechanical strength and chemical resistance needed to withstand the harsh exhaust environment while maintaining the flow disruption capability required for efficient mixing of the reducing agent.
Solution Approach 2:
The material parameters of the baffle plates are specifically changed to match the harsh exhaust environment. The plates are made from materials with high temperature resistance and chemical inertness, allowing them to operate reliably in the high-temperature, chemically aggressive environment without significant wear or degradation.
3Device complexity
If the reducing agent is injected directly into the exhaust stream, then the system complexity is reduced, but the mixing efficiency decreases
Solution Approach 1:
The injection system is segmented into multiple injection points along the exhaust pipe rather than a single injection point. This segmentation allows the reducing agent to be introduced at multiple locations, improving mixing efficiency by distributing the injectant throughout the exhaust stream more effectively, while each individual injection point remains relatively simple.
Solution Approach 2:
Baffle plates serve as intermediary elements that enhance the mixing process. When the reducing agent is injected, the baffle plates disrupt the exhaust flow and force the injectant to mix more thoroughly with the exhaust gas, thereby improving mixing efficiency without requiring complex injection mechanisms.
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 system requires less space, reduces wear on components, and enhances mixing efficiency while maintaining high chemical reaction effectiveness.
Implementation Method 1
The disordered, porous surface of the impact plate is advantageous because the impacting liquid molecule chains are effectively atomized
Implementation Method 2
a reducing agent is added and vaporized in the exhaust gas stream
Implementation Method 3
The combustion system being equipped typically has an exhaust pipe that carries the hot exhaust gases from the combustion process to the SCR unit
Implementation Method 4
The chemical reactions taking place in SCR systems reduce the nitrogen oxides
Implementation Method 5
These catalysts can have different designs and preferably utilize materials with large effective surface areas
Data Source
Figure 1
Figure 2
AI summary
The invention relates to an arrangement for mixing a reducing agent into an exhaust gas stream. For this purpose, the arrangement has an exhaust gas guide pipe (04) with a central axis into which nitrogen oxide-containing combustion gases are introduced via an exhaust gas inlet to form an exhaust gas stream. Furthermore, a reducing agent feed (05) is provided, which is located in the exhaust gas guide pipe (04) and comprises a mixing nozzle (06) to which compressed air and reducing agent are supplied via supply lines (07) to spray a mist into the exhaust gas stream. A ceramic baffle plate (23) is arranged downstream with a fanning distance (lA) upstream of the mixing nozzle (06) so that the spray mist emitted by the mixing nozzle (06) directly impacts the baffle plate (23). The baffle plate (23) consists of rigidly connected, irregularly arranged hard bodies.Pores remain between the hard bodies; the strong bond between the hard bodies is created by an added binder. The softening temperature of the binder is chosen relative to the melting temperature of the pore-forming agent such that stable glass bonds are formed between the hard bodies during the ceramic firing process before the pore-forming agent burns off.