CO2 Sensor with Segmented Electrolyte for High-Pressure Measurement
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Solution Overview
Problem
Existing methods for measuring CO2 concentration in gas streams, particularly in high-pressure and high-temperature environments, face challenges such as limited sensitivity, slow response times, and corrosion issues, as well as difficulties in maintaining pressure balance and preventing electrolyte migration, which are critical for accurate and robust CO2 monitoring in applications like downhole measurements and CO2 injection projects.
Innovation Solution
A sensor assembly using a eutectic mixture of Li2CO3 and K2CO3 as the electrolyte, housed in alumina with separate pathways for sample and reference gases, and incorporating a diffusion controlling communication channel to measure Nernst electrochemical potential, allowing for rapid and robust CO2 concentration measurement by maintaining pressure balance and preventing electrolyte migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing CO2 sensors are used in high-pressure environments, then measurement capability is provided, but pressure balance maintenance and electrolyte migration prevention become difficult
Solution Approach 1:
The sensor is divided into two separate compartments (reference compartment and sample compartment) that are physically isolated but electrochemically connected through the electrolyte. This segmentation allows independent pressure control in each compartment while maintaining electrochemical functionality, solving the pressure balance and electrolyte migration issues in high-pressure environments
Solution Approach 2:
A porous plug or membrane acts as an intermediary between the two compartments, allowing ionic conduction through the electrolyte while preventing direct gas mixing and electrolyte migration. This intermediary enables the sensor to function reliably under pressure differential conditions
2Productivity
If response time is reduced for rapid measurement, then productivity improves, but measurement precision may be compromised
Solution Approach 1:
The sensor operates at elevated temperatures (above the melting point of the carbonate electrolyte) to increase ionic conductivity and accelerate the electrochemical response. This parameter change enables rapid equilibrium to be reached while maintaining measurement precision through the Nernst equation relationship
3Measurement precision
If sensor sensitivity is increased for trace CO2 detection, then measurement precision improves, but device complexity increases
Solution Approach 1:
The electrode surfaces are selectively coated with materials that enhance CO2 sensitivity locally at the electrolyte-gas interface. This local quality enhancement provides high sensitivity for trace CO2 detection without requiring complex overall sensor architecture
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 solution enables rapid and accurate measurement of CO2 concentrations in mixed-gas streams, achieving equilibrium potential within seconds and maintaining sensor integrity, even at high temperatures, thus addressing the limitations of existing technologies.
Implementation Method 1
measuring a Nernst electrochemical potential generated by the electrolyte in response to different partial pressures of carbon dioxide
Implementation Method 2
a diffusion controlling communication channel between the two compartments
Data Source
AI summary
Described herein is an apparatus and methods for characterizing a fluid composition including exposing electrolyte to one fluid mixture, collecting a signal from an electrode in contact with the electrolyte, and simultaneously exposing the electrolyte to a second fluid, collecting a signal from a second electrode in contact with the electrolyte exposed to the second fluid, and comparing the signal difference between the electrodes with the Nerst equation wherein the temperature of the electrolyte is above 488° C. Carbon dioxide, nitrogen, and/or oxygen may be present in the fluid and/or the second fluid.