Difficulties in the application of oxygen analyzers and online gas analyzers

Gas analyzer is a tool used for gas composition analysis and testing, with the help of which data on the types and contents of certain components can be obtained. However, gas analyzer is not a simple tool. It is neither as simple in structure as flowmeters and pressure gauges, nor as easy to operate and use as various thermal instruments. It is a kind of tool with complex structure and high technical difficulty in use. Using gas analyzer is a relatively complex and difficult-to-master specialized technology.

Generally speaking, the application of gas analyzer itself is a unique technical work, and it is a research-based work. However, this point is not recognized and understood by outsiders.

1. Analysis of Difficulties in the

Application of Gas Analyzers About the difficulties in the application of gas analyzers, we can roughly understand one or two from the following aspects. 2.1 Gas analysis is the realization of a series of chemical processes

A gas analyzer or a gas analysis system is equivalent to a complete set of chemical process equipment. Therefore, the working process of the gas analysis instrument system is to realize a series of chemical processes. If you want to get correct data through gas analysis, you must understand the situation and changes in each stage of this series of chemical processes, carefully study and grasp the laws in them, and only in this way can you achieve the purpose of correct measurement. It should be pointed out that not only does a gas analysis instrument have the same conditions and conditions as a set of chemical process, but sometimes the sample gas pretreatment part (including sampling system) at the front stage of the instrument is also a set of chemical process. If more complex and special process technology conditions are encountered, the chemical process reflected by the sample gas pretreatment system is still very complex, equivalent to the purification process of a small chemical plant. It can be seen that the process of gas analysis is to strictly control various factors that affect the measurement conditions under the condition of understanding and grasping the conditions of the entire chemical process system, so as to obtain the correct data required by the process and management personnel.

2.2 It is difficult to control the influencing factors and eliminate the interference factors during the application process

. In the process of instrument application, there are many types of influencing factors and the changes are more complex, and it is more difficult to effectively control these influencing factors and eliminate the factors that interfere with the measurement. For example, for the determination of trace oxygen, not only the system material and sealing must be strictly controlled, but also many factors such as the cleanliness of the system must be solved one by one, otherwise, the oxygen component analysis will not get the correct measurement results. For the determination of trace water content in gas, in addition to considering the various influencing factors mentioned above, the adsorption equilibrium of water in the sample gas in the pipeline must also be considered. The proper handling of this problem must rely on repeated experiments, understanding its changes and laws, and mastering the manipulation techniques in order to obtain correct results. Of course, the factors to be considered and controlled when using gas chromatograph to determine the ppm-ppb level impurity content in high-purity gas are more complicated.

2.3 The influencing factors of trace gas component analysis are more complicated

. The microscopic changes that occur when gas components move in pipelines and equipment are complex and changeable. Many influencing factors that can be ignored in the analysis of constant gas components cannot be ignored in the analysis of trace gas components. Instead, they must be taken seriously. At this time, these factors have become the main contradictions that affect the correct results of trace gas component analysis. They must be eliminated and resolved one by one to enable the trace gas analysis instrument to work smoothly. These influencing factors mainly include the following aspects:

① Repeated mixing of gas in the sampling pipeline;

② Physical and chemical effects between the pipe wall and gas components;

③ Pipeline material;

④ Pipeline connection method;

⑤ Pipeline cleanliness.

2.4 Instrument and method verification is one of the keys to obtaining correct data. As a measurement and detection tool, the data given by the instrument under normal operation are mostly relative values. The instrument itself cannot provide or verify whether the measured data is correct and the degree of correctness (accuracy). It must be completed by peripheral technical work, which is the verification of analytical data.

(1) Verification of instrument linearity. First of all, in order to ensure the normal operation of the instrument, the analytical instrument, as a kind of measurement instrument, must be tested by the authoritative measurement department in accordance with the regulations formulated by the state every year before it can be used. At the same time, it is necessary to use a series of standard gases every year to check whether the linear relationship of the instrument in the entire linear range remains normal. Otherwise, blindly believing in the integrity of the analytical instrument (even if it is an imported instrument) will definitely lead to wrong data and mistakes in production management and quality management.


(2) Error analysis. In the application process of analytical instruments, error analysis must be conducted for each measurement result to determine the authenticity, reliability and credibility of the data analysis. A qualified analyst will not and should not report or publish the results of each analysis and measurement carelessly. Generally, after the measurement results are obtained, after error analysis, when it is determined that the sum of the errors of the analytical data is less than the specified allowable error, this one (or a group of) data will be considered as the correct measurement result and reported or published. Otherwise, incorrect data will bring serious adverse consequences to production managers.

(3) Instrument calibration commonly used in quantitative analysis. As a quantitative analysis instrument, the gas analyzer must be calibrated (or calibrated) with standard gas before quantitative analysis. Standard gas is generally purchased from the national metrology department or a legitimate factory. In special circumstances, it can also be configured by itself (but it must have the qualifications and ability to configure standard gas and related equipment). The shelf life of standard gas is one year. When using standard gas to calibrate analytical instruments, it is also necessary to have a deep understanding of normal procedures and usage rules. If standard gas that does not meet the requirements is purchased and used, it will lead to great deviations in the analysis data. If the use requirements of standard gas are not well understood, it will also cause trouble to air separation production due to the failure to obtain correct data results.

2.5 Analytical engineers should strive for excellence and improve analytical detection technology. A qualified analytical engineer needs to constantly learn and study new technologies of analytical instruments and new instrument analysis technologies, and apply them to his job in a timely manner to achieve the purpose of striving for excellence and improving analytical detection technology. An analytical engineer should not only be able to make the best use of existing equipment, but also absorb foreign and domestic advanced analytical technologies at any time on the basis of a deep understanding of the principles, structures and performance of the instruments currently used, continue to innovate technology, further improve and improve the detection level of existing instruments, and not just be satisfied with simple operation.

2. Conclusion

In short, trace gas analysis is a specialized technology and a research-based work, which determines the application effect and level of gas analysis instruments. Trace gas analysis technology is also a practical science. It must go through a lot of experimental practice to explore the regularity of the chemical, to master it well, and to satisfactorily solve various specific trace gas analysis topics. This is also the experience summary of the first generation of gas analyzers in my country when they began to develop high-purity gases in the 1960s and 1970s. This conclusion drawn from their decades of gas analysis should attract the attention of future generations. We hope that gas analysis technicians can achieve faster and greater development under the new situation of rapid development of air separation. Shanghai Shuangxu Electronics Co., Ltd. is willing to work with all colleagues to make due efforts for domestically produced gas analyzers and promote their qualitative leap and move towards a higher level. (end)