Exhaust Gas Heating for NO2-Based Particle Filter Regeneration
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Solution Overview
Problem
Current particle filter regeneration methods in internal combustion engines face challenges such as clogging, increased exhaust back pressure, and inefficient soot oxidation, particularly at low temperatures, leading to unreliable filter function and high carbon monoxide emissions, due to limitations in NO2 formation and thermodynamic constraints.
Innovation Solution
The method decouples thermal energy from the heating device and directs it to the NO oxidation catalyst, maintaining an optimal temperature range of 250°C to 380°C for NO2 formation, and couples thermal energy upstream of the NO oxidation catalytic converter to enhance NO2 production and soot oxidation, combining active and passive regeneration techniques to ensure reliable and efficient filter operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the exhaust gas temperature is increased to improve soot oxidation, then the regeneration efficiency is improved, but the risk of thermal damage to the particle filter and downstream catalysts increases
Solution Approach 1:
The exhaust gas flow is divided into two separate flows: one passing through the NO oxidation catalytic converter and another through the heating device. This segmentation allows independent temperature and composition control of each flow, enabling the heated flow to be mixed with the NO2-enriched flow to achieve effective regeneration temperature without exposing the entire system to excessive temperatures that could cause thermal damage.
Solution Approach 2:
A mixing section is introduced as an intermediary between the heating device and the particle filter. This mixing section combines the hot exhaust gas from the heating device with the cooler exhaust gas containing NO2 from the NO oxidation catalytic converter, achieving a balanced temperature that is sufficient for soot oxidation but safe for the particle filter and downstream catalysts.
2Productivity
If an NO oxidation catalytic converter is arranged upstream of the particle filter to enable passive regeneration, then soot oxidation is improved, but the construction volume and system complexity increase
Solution Approach 1:
The NO oxidation catalytic converter and the particle filter are merged into a single structural unit, with the entry area of the particle filter serving as the NO oxidation catalytic converter. This integration eliminates the need for a separate upstream catalytic converter, reducing construction volume while maintaining the ability to generate NO2 for passive regeneration.
Solution Approach 2:
The particle filter structure is designed to serve multiple functions: it acts as both the particle filtration medium and the NO oxidation catalytic converter. The filter material or coating is equipped with both filtration capabilities and NO oxidation activity, allowing a single component to perform what would traditionally require separate devices.
3Productivity
If a catalytic coating is applied to the particle filter for NO oxidation, then passive regeneration is enabled, but the filter cake blocks access of NO2 to soot particles, reducing regeneration effectiveness
Solution Approach 1:
The system is segmented into two independent flows: one that generates NO2 through NO oxidation and another that provides thermal energy through hydrocarbon oxidation. This segmentation allows the NO2 to be introduced downstream of the filter cake formation zone, ensuring that NO2 can reach soot particles for oxidation without being blocked by the filter cake.
Solution Approach 2:
A mixing section serves as an intermediary that combines the NO2-enriched exhaust flow with the thermally activated flow. This mixing occurs downstream of the particle filter, ensuring that NO2 is available in the exhaust gas after it has passed through the filter medium, allowing NO2 to access and oxidize soot particles that have been trapped in the filter cake pores.
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 approach allows for functionally safe and reliable particle filter regeneration with reduced fuel consumption, lower thermal load, and minimized platinum requirements, while maintaining optimal operating temperatures for both the NO oxidation catalytic converter and the particle filter, thereby shortening regeneration time and reducing the risk of thermal damage.
Implementation Method 1
an oxidation catalytic converter arranged upstream of the particle separator or particle filter oxidizes the nitrogen monoxide (NO) in the exhaust gas with the help of the residual oxygen (O2) that is also contained to form nitrogen dioxide (NO2)
Implementation Method 2
the reducing agent is metered into the exhaust gas stream upstream of the heated catalyst, by means of which an exothermic reaction is triggered in the heated catalyst, as a result of which the exhaust gas flow is heated
Implementation Method 3
the carbon is completely oxidized up to oxidation level +4 in the form of carbon dioxide, with two NO2 molecules per carbon molecule being required for this oxidation
Data Source
Figure 1
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Figure 3~4
AI summary
The invention relates to a method for regenerating a particulate filter arranged in the exhaust gas tract of an internal combustion engine, having at least one NO oxidation catalytic converter arranged upstream of the particle filter for the oxidation of NO, in particular to form NO2, and having at least one heating device for raising the temperature of an exhaust gas stream. According to the invention, by means of the at least one heating device (8), a defined quantity of thermal energy is produced, with which the temperature of the NO oxidation catalytic converter (4) is set in a defined temperature range, wherein the temperature range is preferably predefined as a function of a level of loading of the particulate filter (6) with carbon black and/or of an efficiency of the NO2-based regeneration of the particle filter (6) by means of the quantity of NO2 formed at the at least one NO oxidation catalytic converter (4).