Electrically Heated Catalyst for Exhaust Gas Treatment
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Solution Overview
Problem
Internal combustion engine exhaust gas treatment systems face challenges in efficiently reducing NOx emissions, particularly during cold starts, due to the need for initial heating of catalysts like SCR and OC devices, which affects the oxidation and reduction of NOx and HC species.
Innovation Solution
An exhaust gas treatment system incorporating an oxidation catalytic device (OC), a selective catalytic reduction device (SCR), and an electrically heated catalyst (EHC) with platinum group metal and metal oxide catalysts, along with storage materials, is used to oxidize and store NOx and HC species, and the EHC is strategically placed between the OC and SCR to facilitate simultaneous heating and reduce NOx breakthrough.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional catalyst heating methods are used during cold starts, then the catalysts can reach operating temperature, but the system requires multiple heating zones and complex control mechanisms
Solution Approach 1:
The patent combines multiple heating functions into a single EHC unit located in the exhaust conduit. This single heater simultaneously heats the OC device, SCR device, and exhaust gas, eliminating the need for multiple separate heating zones and reducing system complexity while ensuring all components reach their activation temperatures.
Solution Approach 2:
The EHC serves multiple functions: it heats the exhaust gas to promote catalytic reactions, heats the OC and SCR devices to their light-off temperatures, and enables earlier reductant injection. This multi-functional approach replaces traditional multiple heating systems with a single versatile heater.
2Reliability
If reductant injection is delayed until SCR reaches operating temperature, then NOx reduction efficiency is maintained, but emission control during cold starts deteriorates
Solution Approach 1:
The patent enables preliminary reductant injection before the SCR device reaches its normal operating temperature by using the EHC to preheat the exhaust gas and SCR. This allows the reductant to be injected and begin decomposing earlier, improving emission control during cold starts while maintaining efficiency through the heated environment.
3Reliability
If multiple catalysts are used for oxidation and reduction functions, then catalytic performance is improved, but system cost and complexity increase
Solution Approach 1:
The patent places the EHC in close proximity to both the OC and SCR devices, creating an integrated thermal management system. This single heater serves all catalytic components, reducing the number of separate heating systems while maintaining the performance benefits of having both OC and SCR catalysts.
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 enhances the efficiency of NOx reduction and HC oxidation, ensuring effective emissions performance by optimizing the heating of OC and SCR, minimizing NOx and HC breakthrough, and allowing for earlier reductant injection and decomposition, thus improving the overall performance of the exhaust gas treatment system.
Implementation Method 1
The heating element can include one or more second oxidation catalyst materials disposed on an outer surface of the heating element and capable of oxidizing CO, HC, and one or more NOx species
Implementation Method 2
The catalytic composition can include one or more first oxidation catalyst materials capable of oxidizing carbon monoxide (CO), hydrocarbons (HC), and one or more nitrogen oxide (NOx) species, and one or more storage materials individually or collectively capable of storing NOx and HC species
Implementation Method 3
The EHC can include a heating element having an outer surface including one or more second oxidation catalyst materials
Data Source
AI summary
Exhaust gas systems include an oxidation catalyst (OC) capable of receiving exhaust gas and oxidizing one or more of combustible hydrocarbons (HC) and one or more nitrogen oxide (NOx) species, a selective catalytic reduction device (SCR) disposed downstream from and in fluid communication with the OC via a conduit, and an electrically heated catalyst (EHC) disposed at least partially within the conduit downstream from the OC and upstream from the SCR. The EHC comprises a heating element having an outer surface including one or more second oxidation catalyst materials capable of oxidizing CO, HC, and one or more NOx species. The OC includes one or more storage materials individually or collectively capable of storing NOx and/or HC species. Exhaust gas can be supplied by an internal combustion engine which can optionally power a vehicle.