Overview
The percentage-level (%) thermal conductivity analyzer (TCD) utilizes the physical differences in gas-specific thermal conductivities to measure the concentration of a target gas in binary or quasi-binary mixtures. Operating as a non-depleting, non-destructive physical measurement tool, it serves as the golden standard for high-conductivity gases (such as H2 and He) while remaining highly effective for low-conductivity gases (such as CO2, Ar, and SF6). This versatile analyzer is widely deployed in air separation, electronic specialty gas blending, biochemical fermentation off-gas analysis, metallurgical shielding atmosphere control, and power plant purging, making it a rugged and low-maintenance cornerstone of industrial process automation.
Principle
When the sample gas enters the thermal conductivity cell, and a thermistor is used above the film to maintain a constant temperature. In this way, a small cavity is formed below and above the membrane, and the measurement gas can diffuse into it. In this way, the heat loss caused by the thermal conductivity of the sample gas is compensated by heating, and the power required to maintain a constant temperature of the membrane is a measurement of the thermal conductivity of the measured gas.
Application
• Industrial Air Separation & Noble Gas Refining
Helium Recovery and Purification: Monitoring high-concentration He (0% to 100%) during cryogenic separation or recovery from natural gas, leveraging helium's high thermal conductivity (second only to H2).
Argon Purity in Steelmaking: Verifying the concentration of Argon shield gas (Ar in N2 or O2 mixtures) used in metallurgy, as Argon has a significantly lower thermal conductivity than air.
Neon and Krypton Extraction: Real-time purity tracking during the extraction of rare gases from bulk air streams.
• Bioprocessing, Food & Agriculture (CO2 Applications)
Fermentation Off-Gas Analysis: Monitoring percentage-level carbon dioxide (CO2 typically 0% to 20%) in the exhaust of industrial bioreactors to analyze microbial respiration rates without consuming sterile process gases.
Modified Atmosphere Packaging (MAP) Quality Control: Checking the mixing ratios of CO2 and N2 gas flushes in food packaging systems to inhibit bacterial growth and extend food shelf-life.
• Electric Power Generation & Infrastructure
Generator Casing Purging: Tracking the multi-stage gas displacement process (Air→CO2→H2) in large power-generating turbines to avoid explosive mixtures.
SF_6 Gas Insulated Switchgear (GIS): Monitoring the purity of Sulfur Hexafluoride (SF_6) insulating gas in high-voltage electrical equipment, where SF_6 has an extremely low thermal conductivity compared to leaking air.
• Metal Processing & Advanced Heat Treatment
Shielding Gas Mixing (N2/H2 or Ar/He): Online measurement of binary gas mixing ratios used in welding, bright annealing of copper, and sintering of powder metals to ensure consistent atmospheric composition.
Carburizing Furnaces: Monitoring carbon-carrying carrier gases where CO2 or hydrocarbon percentages affect metal hardening depth.
• Chemical Synthesis & Acid Production
Sulfuric Acid Converter Feeds: Analyzing high-concentration sulfur dioxide (SO_2) gas percentages in air before catalytic conversion to sulfur trioxide (SO3).
Syngas and Ammonia Synthesis Loops: Continuous balancing of the H2/N2 reactant ratio in ammonia synthesis loops.
For detailed introduction, please refer to Thermal Conductivity Gas Analyzer.