Principles and Types of Gas Analysis Instruments

Gas analysis is the process of determining the composition of mixed gases by using the differences in gas physics and chemical properties, and the core tool is gas analysis instruments, and its measurement principle is divided into three categories: physics, physical chemistry and chemistry. Physical methods such as thermal conductivity instruments use the difference in thermal conductivity of gases, and infrared instruments rely on the selective absorption of specific infrared light by gases. Physical and chemical methods such as Conductivity Analyzer change the conductivity of the solution after gas absorption; The chemical laws are analyzed through changes in volume or weight after gas is absorbed, and these principles provide the core basis for instrument design.

Introduction to core gas analysis instruments

Infrared carbon-sulfur analyzer

As an important equipment for carbon and sulfur detection of industrial materials, infrared carbon and sulfur analyzer has been widely used in steel, non-ferrous metals and other fields since the 80s of the 20th century. The working principle is based on the selective absorption of 4.4μm and 4.0μm infrared light by carbon dioxide and sulfur dioxide, and the target gas is generated by burning the sample at high temperature, and then the light energy change is detected by the infrared absorption cell, and finally the carbon and sulfur content is converted. The instrument is composed of three parts: heating and combustion (including high-frequency induction furnace, heating up to more than 1700 °C), detection (infrared analyzer as the core) and result processing (microprocessor and printer), which is divided into two categories: single test and joint test.

Gas chromatograph

The gas chromatograph is suitable for the analysis of inorganic gases such as hydrogen and oxygen and most organic gases such as methane and propylene, and the core is composed of a gas circuit system, a chromatographic column, a Detector and a data processing system. Through the difference in the partition coefficients between the gas phase and the stationary phase of different gases, the mixed gas is separated by the chromatographic column, and then the gas composition is converted into a measurable signal by Detectors (such as thermal conductivity Detector and hydrogen flame ionization Detector), and finally the concentration analysis is completed. When using, it is necessary to adjust the column temperature, carrier gas flow rate and other parameters according to the characteristics of the gas to be measured, and establish an exclusive analysis method to ensure the separation effect and detection accuracy, which is widely used in petrochemical, environmental monitoring and other fields.

Electrochemical Gas Analyzer

Electrochemical Gas Analyzers rely on the redox reaction of gas on the electrode, and common three-electrode systems (working electrode, pair electrode, and reference electrode) can stabilize the detection signal. The target gas releases or acquires electrons when the working electrode reacts, forming a current signal proportional to the gas concentration, which is converted into a concentration value after being processed by an amplifier. The instrument has high sensitivity (can detect ppm or even ppb gases), fast response speed (usually results within a few seconds), and is compact and easy to use, often used for real-time monitoring of toxic and harmful gases such as carbon monoxide and hydrogen sulfide, and is indispensable in mine safety, indoor air quality testing and other scenarios.

Thermal conductive Gas Analyzers

The thermal conductivity Gas Analyzer is designed based on the difference in thermal conductivity of different gases, and the core component is a thermal conductivity cell, which is equipped with temperature-sensitive heat-sensitive elements (such as platinum wires). When the mixed gas to be measured and the pure reference gas (such as air) flow through the measuring arm and reference arm of the thermal conductivity cell respectively, if the concentration of the target component in the mixture changes, it will lead to a change in the temperature distribution in the thermal conductivity cell, which will cause the resistance value of the thermistor to be different. The instrument has a simple structure, good stability and long service life, especially suitable for the detection of hydrogen, helium and other gases with significant differences in thermal conductivity and air, and is often used as a process control instrument in fertilizer production and gas separation and purification processes.

summary

Gas analysis instruments are based on physics, physical chemistry, and chemical principles, and have derived various types such as infrared carbon and sulfur analyzers and gas chromatographs, and various instruments have unique advantages and applicable scenarios due to different principles - infrared carbon and sulfur instruments focus on the detection of industrial material elements, gas chromatographs are good at multi-component gas separation and analysis, electrochemical instruments focus on rapid monitoring of trace toxic gases, and thermal conductive instruments perform stably in the detection of specific gas constants. These instruments are widely used in industrial production, environmental protection, safety protection and other fields, and are key equipment to ensure production quality, environmental safety and human health. With the iteration of technology, instruments are developing in the direction of higher precision, more intelligence, and more portability, and will further expand the application boundaries in the future to provide more efficient and reliable solutions for gas analysis needs in various fields.