Exhaust Aftertreatment Partial Flow Ammonia Oxidation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing exhaust gas aftertreatment systems for internal combustion engines face challenges in simultaneously reducing nitrogen oxide emissions and fine particle emissions, particularly due to issues with SCR catalytic converters, particle filters, and the handling of ammonia and its by-products, which can lead to corrosion and inefficient operation.
Innovation Solution
An exhaust gas aftertreatment system with partial flow hydrolysis that uses a branched exhaust gas flow to recirculate ammonia and its by-products through an oxidation catalytic converter, followed by an SCR catalytic converter, to achieve efficient nitrogen oxide reduction while preventing backflow and corrosion, and includes a hydrolysis catalytic converter to optimize ammonia release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If an SCR catalytic converter is used to reduce nitrogen oxide emissions, then nitrogen oxide conversion is improved, but ammonia slip and corrosion of engine parts occur
Solution Approach 1:
The oxidation catalytic converter is positioned upstream in the exhaust flow to oxidize ammonia and reducing agent by-products before they can reach and corrode engine parts. This preliminary oxidation action prevents the harmful backflow of ammonia to the engine while maintaining the nitrogen oxide reduction function of the SCR catalyst downstream.
Solution Approach 2:
The oxidation catalytic converter acts as an intermediary component between the SCR catalytic converter and the engine. It mediates by converting ammonia and by-products into less harmful substances (nitrogen, water, carbon dioxide) before they can cause corrosion, thus protecting the engine while allowing the SCR system to function effectively.
2Object-generated harmful factors
If a particle filter is used to reduce fine particle emissions, then particle removal is improved, but the filter becomes clogged with oil ash and requires complex regeneration
Solution Approach 1:
The oxidation catalytic converter enables the particle filter to regenerate itself by providing oxidized nitrogen species that react with accumulated soot particles. This self-service mechanism converts harmful deposits into harmless gases (CO2, N2, H2O), eliminating the need for complex external regeneration systems and reducing maintenance requirements.
Solution Approach 2:
The oxidation catalytic converter accelerates the oxidation process by catalytically converting carbon monoxide and hydrocarbons to carbon dioxide, and generating oxidized nitrogen species. These strong oxidizing conditions enable the particle filter to burn off accumulated soot and oil ash more efficiently, preventing clogging without complex regeneration equipment.
3Productivity
If the exhaust gas flow is recirculated to optimize ammonia release, then ammonia conversion efficiency is improved, but ammonia and by-products can backflow to the engine
Solution Approach 1:
The oxidation catalytic converter is positioned to act preliminarily on the recirculated exhaust gas, oxidizing ammonia and by-products before they can backflow to the engine. This ensures that even when exhaust gas is recirculated to optimize ammonia release and conversion, the engine is protected from corrosive substances.
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 system effectively converts nitrogen oxides to nitrogen and water, prevents ammonia backflow and corrosion, and optimizes the conversion of nitrogen oxides, while minimizing the risk of ammonia slip and maintaining efficient engine operation.
Implementation Method 1
there is an oxidation catalytic converter which oxidizes ammonia and/or reducing agent decomposition products flowing back under engine operating conditions in which the flow of exhaust gas is reversed
Implementation Method 2
an SCR catalytic converter which reduces the nitrogen oxides contained in the exhaust gas flow with the aid of the ammonia split off by means of selective catalytic reduction to nitrogen and water vapour
Implementation Method 3
a hydrolysis catalytic converter arranged downstream of the feed point for the reducing agent and in the exhaust gas flow to promote the splitting of ammonia from the reducing agent
Data Source
Figure 1~2
Figure 3~4
AI summary
Exhaust aftertreatment system with nitrogen oxide reduction for internal combustion engines operated with excess air, wherein the nitrogen oxide reduction is effected by means of an SCR catalyst (6, 6") and wherein - upstream to the SCR catalyst (6, 6') an exhaust gas partial flow (11, 11') branches off from the exhaust gas flow (10, 10'), - a storage container (8) for a reducing agent and a metering device (9) for the reducing agent are provided and wherein the metering device (9) adds the reducing agent to the exhaust gas partial flow (11, 11'), - the reducing agent is a substance that releases ammonia downstream of the supply point through the hot exhaust gas or the reducing agent is ammonia, - the exhaust gas partial flow (11, 11') is returned downstream to the supply point and upstream to the SCR catalyst (6, 6') in the exhaust gas flow (10, 10'), - the SCR catalyst arranged downstream of the recirculation point (6,6') the nitrogen oxides contained in the exhaust gas stream are reduced to nitrogen and water vapor by means of selective catalytic reduction using the separated ammonia, - in the exhaust gas partial stream (11, 11') upstream of the supply point for the reducing agent, an oxidation catalyst (16, 16') is arranged, which oxidizes backflowing ammonia and/or backflowing reducing agent decomposition products during engine operating conditions in which there is a reversal of the exhaust gas flow towards the internal combustion engine.