Three-Chamber Gas Sensor for Hydrocarbon-Resistant H2O and CO2 Measurement
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Solution Overview
Problem
Existing gas sensors struggle to accurately measure water vapor (H2O) and carbon dioxide (CO2) concentrations when the measurement gas contains a significant hydrocarbon (H/C) component, leading to inaccurate readings and potential sensitivity changes due to Au evaporation in noble metal electrodes.
Innovation Solution
A multi-gas sensor with a sensor element comprising an oxygen-ion conductive solid electrolyte structure, including adjustment and measurement pump cells, and a controller to oxidize and reduce gas components, allowing for accurate measurement of H2O and CO2 concentrations by controlling oxygen flow and electrode temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a three-chamber configuration gas sensor is used to measure H2O and CO2 concentrations, then parallel measurement capability is achieved, but measurement accuracy deteriorates when hydrocarbon gas components are present due to oxidation interference
Solution Approach 1:
The sensor divides the measurement process into three distinct chambers, each performing a specific function: the first chamber reduces H2O and CO2 to H2 and CO, the second chamber selectively oxidizes H2, and the third chamber oxidizes CO. This segmentation allows independent control of each measurement step, preventing hydrocarbon oxidation interference from affecting the accuracy of H2O and CO2 measurements.
Solution Approach 2:
Each chamber is equipped with electrodes having specific local properties tailored to their function. The first chamber uses electrodes suitable for reduction reactions, while the second and third chambers use electrodes with catalysts optimized for selective H2 and CO oxidation respectively. This local quality differentiation ensures that hydrocarbon oxidation does not interfere with the measurement of target gases.
2Measurement precision
If Au-based noble metal electrodes are used to improve selective H2 oxidation property, then H2 oxidation selectivity is enhanced, but electrode stability deteriorates due to Au evaporation at high temperatures
Solution Approach 1:
The patent changes the material parameter of the electrode from pure Au or Au-based noble metal alloys to Pt-based catalysts. Pt has a much lower vapor pressure at operating temperatures compared to Au, eliminating the evaporation problem while maintaining catalytic activity for H2 oxidation. This parameter change resolves the contradiction between selectivity and stability.
Solution Approach 2:
The patent employs composite catalyst materials, specifically Pt-based alloys or Pt supported on suitable substrates, in the second chamber electrodes. These composite materials provide both the selective H2 oxidation capability and thermal stability required for long-term reliable operation, overcoming the limitations of Au-based materials.
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 sensor effectively measures H2O and CO2 concentrations even in the presence of hydrocarbons, maintaining long-term reliability and reducing sensitivity changes, ensuring precise readings.
Implementation Method 1
a sensor element having a structure formed of an oxygen-ion conductive solid electrolyte
Implementation Method 2
the adjustment pump cell pumps oxygen into the internal chamber from an external space so that, when the measurement gas having reached the adjustment electrode contains a hydrocarbon gas component, the hydrocarbon gas component is oxidized
Implementation Method 3
the first measurement pump cell pumps oxygen out of the measurement gas having reached the first measurement electrode so that substantially all water vapor and carbon dioxide contained in the measurement gas are reduced
Implementation Method 4
the second measurement pump cell pumps oxygen into the internal chamber to selectively oxidize hydrogen generated by reduction of water vapor and contained in the measurement gas having reached the second measurement electrode
Implementation Method 5
a heater heating the sensor element
Data Source
AI summary
A sensor element includes first to third chambers communicating sequentially from a gas inlet, an adjustment pump cell pumps oxygen into the first chamber so that an H/C component is oxidized, a first measurement pump cell pumps out oxygen from the second chamber so that all H2O and CO2 contained in the measurement gas are reduced, a second measurement pump cell pumps oxygen into the third chamber to selectively oxidize H2 generated by reduction, a concentration of H2O is identified from values of currents generated by pumping-in by the adjustment pump cell and the second measurement pump cell, and a concentration of CO2 is identified based on the identified concentration of H2O, the value of the current generated by pumping-in by the adjustment pump cell, and a value of a current generated by pumping-out by the first measurement pump cell.