Thermal Analysis Gas Detection Using Ambient CO2 Subtraction
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Solution Overview
Problem
Conventional thermal analysis apparatuses are inadequate for accurately analyzing large samples (e.g., several kilograms) due to variations in mixing ratios of components and increased gas desorption, leading to inaccurate qualitative analysis of CO2 in concrete samples.
Innovation Solution
A thermal analysis apparatus with a heating furnace, carrier gas flow paths, and gas detectors, utilizing outside air as a carrier gas, and employing flow rate adjustment and subtraction of ambient gas detection to accurately measure CO2 and H2O from large samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sample size is increased from several milligrams to several kilograms, then the homogeneity of component mixing ratio is improved, but the amount of gas desorbed from the sample increases
Solution Approach 1:
The gas detection process is segmented into multiple measurement stages: first measuring the baseline gas composition with carrier gas alone, then measuring the gas composition after sample heating, and finally calculating the difference to determine the actual desorbed gas amount. This segmentation allows accurate measurement of large gas volumes by comparing differential changes rather than attempting to measure the total absolute amount directly.
Solution Approach 2:
A carrier gas (such as nitrogen or air) is introduced as an intermediary substance to transport the desorbed gases from the heating furnace to the detection device. The carrier gas acts as a medium that dilutes and conveys the large volume of desorbed gas, making it manageable for detection while maintaining the integrity of the gas composition information for analysis.
2Adaptability or versatility
If conventional thermal analysis apparatus specifications are used for minute samples, then the apparatus is suitable for small sample detection, but it cannot achieve highly accurate qualitative analysis for large samples with varying component ratios
Solution Approach 1:
The detection parameters of the apparatus are changed to accommodate large samples. Specifically, the detection device is configured to handle larger gas flow rates and volumes, and the measurement methodology is changed from direct absolute measurement to differential measurement (comparing baseline carrier gas composition with post-heating gas composition). This parameter adaptation enables accurate analysis of large samples weighing several kilograms.
3Reliability
If a large amount of gas is desorbed from large samples, then complete analysis of all desorbed gas is required, but this increases the complexity of gas detection
Solution Approach 1:
The actual desorbed gas signal is extracted from the total gas flow by subtracting the baseline carrier gas composition (measured before sample heating) from the post-heating gas composition. This extraction method isolates the relevant analytical information (the desorbed gas components) from the large volume of carrier gas, simplifying the detection requirement while maintaining complete analysis of all desorbed gases.
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
Enables quick and accurate detection of large amounts of CO2 and H2O from large samples, preventing dew condensation and maintaining thermal analysis stability, thus ensuring precise qualitative analysis.
Implementation Method 1
a heating furnace for heating a sample placed therein
Implementation Method 2
analyzing a state change when a sample is heated, and analyzing gas desorbed from the sample due to heating
Implementation Method 3
a carrier gas flow path for carrying the component gas desorbed from the sample inside the heating furnace to the component gas detector by a carrier gas
Implementation Method 4
a specific gas detection sensor that is provided in the component gas detector and detects a specific component gas desorbed from the sample
Implementation Method 5
an air-containing specific gas detection sensor for detecting the same gas as a specific component gas to be detected by the specific gas detection sensor from the air taken into the carrier gas flow path by the air intake unit
Data Source
AI summary
A configuration is provided in which outside air is taken as a carrier gas into a carrier gas flow path (A, B). A CO2 sensor (specific gas detection sensor) (71) for detecting a CO2 gas desorbed from a sample is installed in a component gas detector (70). A CO2 sensor (air-containing specific gas detection sensor) (54) for detecting a CO2 gas contained in air taken into the carrier gas flow path by a blower fan (51) is installed separately. A CO2 gas detection amount detected by the air-containing specific gas detection sensor (54) is subtracted from a CO2 gas detection amount detected by the specific gas detection sensor (71) to calculate a detection amount of the CO2 gas desorbed from the sample.