Exhaust Control Device Sulfur Release Sensor Poisoning
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Solution Overview
Problem
In internal combustion engine exhaust systems, sulfur components adhere to catalysts, leading to catalyst deterioration and potential poisoning of downstream gas sensors, particularly when hydrogen sulfide is generated during sulfur release processing, causing detection issues.
Innovation Solution
A control device that includes a catalyst in the exhaust passage for releasing sulfur components using rich components and a gas sensor downstream, which performs sulfur release processing by controlling the catalyst temperature and air-fuel ratio to minimize hydrogen sulfide generation and prevent sensor poisoning, using a reaction suppression process when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sulfur release processing is performed to remove sulfur components from the catalyst, then catalyst performance is improved, but gas sensor poisoning occurs due to hydrogen sulfide generation
Solution Approach 1:
A selective catalytic reduction (SCR) catalyst is introduced as an intermediary component between the sulfur release catalyst and the gas sensor. This SCR catalyst specifically converts hydrogen sulfide (the harmful intermediate) into less harmful substances, thereby protecting the downstream gas sensor from poisoning while allowing the upstream catalyst to perform sulfur release processing effectively.
Solution Approach 2:
The system converts the harmful hydrogen sulfide generated during sulfur release processing into a beneficial situation by using the SCR catalyst to transform it into less harmful substances. The harmful byproduct of sulfur release is thus converted into an opportunity to demonstrate the protective function of the SCR catalyst, resolving the contradiction between catalyst maintenance and sensor protection.
2Productivity
If rich components are used to release sulfur components from the catalyst, then sulfur removal efficiency is improved, but hydrogen sulfide generation increases causing sensor detection issues
Solution Approach 1:
The SCR catalyst serves as a mediator that processes the hydrogen sulfide generated during high-efficiency sulfur removal. By positioning this intermediary component in the exhaust flow path, the system can maintain aggressive sulfur release processing while the SCR catalyst continuously converts the resulting hydrogen sulfide into less harmful substances, preventing sensor detection issues.
Solution Approach 2:
The system transforms the harmful hydrogen sulfide generated during efficient sulfur removal into a beneficial demonstration of the SCR catalyst's protective function. The high productivity sulfur removal process that would normally cause sensor poisoning instead becomes an opportunity to showcase the harm-conversion capability of the SCR catalyst, resolving the contradiction between removal efficiency and harmful factor generation.
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
Effectively minimizes sensor poisoning by suppressing reactions between oxygen and sulfur components, allowing for continued detection and maintaining catalyst performance by efficiently releasing sulfur components without generating hydrogen sulfide.
Implementation Method 1
a catalyst provided in an exhaust passage of an internal combustion engine, having adhered thereto sulfur components in the exhaust gas and releasing the adhered sulfur components using rich components contained in the exhaust gas
Implementation Method 2
the gas sensor has a solid electrolyte, an exhaust side electrode provided on the exhaust side of the solid electrolyte, and a reference side electrode provided on the reference chamber side, and detects a specific gas component by causing migration of oxygen ions in the solid electrolyte by applying a voltage to the exhaust side electrode and the reference side electrode
Data Source
AI summary
The present invention is applied to an exhaust system provided with a three-way catalyst and a NOx catalyst which are provided in an exhaust passage of an engine and to which sulfur components in exhaust adhere and release the attached sulfur components by rich components in exhaust, and NOx sensors provided downstream of the catalysts. The NOx sensor is a limiting current type sensor. It is determined whether a sulfur release state is present in which a sulfur component is released from the three-way catalyst and the NOx catalyst. When it is determined that it is in the state of sulfur release, reaction suppression processing for suppressing the reaction between oxygen and sulfur components in the pump cell electrodes and the monitor cell electrodes of the NOx sensors is performed.