Challenges in the application of oxygen analyzers and online gas analyzers

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Challenges in the application of oxygen analyzers and online gas analyzers: Gas analysis instruments are tools used for analyzing the composition of gases, enabling the acquisition of data on certain types of components and their concentrations. However, gas analysis instruments are not simple tools; they are neither as simply structured as flow meters or pressure gauges, nor are they as easy to operate as various thermal instruments. It is a type of tool with a complex structure and high technical requirements; using gas analysis instruments is a complex and difficult-to-master specialized technique. Generally speaking, the application of gas analysis instruments is a unique technical task, as well as a task of a research nature. However, this is not recognized or understood by outsiders. Analysis of the challenges in the application of gas analysis instruments: The difficulties associated with using gas analysis instruments can be roughly understood by examining them from the following aspects. 1. Gas analysis is used to carry out a range of chemical processes: A gas analyzer or a gas analysis system functions as a complete set of chemical processing equipment; therefore, the operation of such gas analysis instrument systems involves carrying out various chemical processes. To obtain accurate data through gas analysis, it is necessary to understand the conditions and changes at each stage of these chemical processes, to study them carefully and grasp the underlying patterns; only in this way can accurate measurements be achieved. It should be noted that not only is there an identical set of chemical process conditions within a gas analysis instrument, but sometimes the sample gas preprocessing section prior to the instrument (including the sampling system) also constitutes a chemical process. In the case of more complex and specialized process technical conditions, the chemical processing involved in the sample gas pretreatment system becomes extremely complex, akin to the purification processes in a small chemical plant. It can be seen that the process of gas analysis involves, on the basis of understanding and mastering the conditions of the entire chemical process system, strictly controlling various factors that affect the measurement conditions, in order to obtain accurate data required by process and management personnel. 2. It is difficult to control influencing factors and eliminate interfering factors during application: During the use of the instrument, there are many types of influencing factors, and their variations are complex; therefore, it is quite challenging to effectively control these influencing factors and remove those that interfere with accurate measurements. For example, in the determination of trace amounts of oxygen, it is not only necessary to strictly control the material and sealing of the system, but also various factors such as the cleanliness of the system must be addressed properly; otherwise, accurate results for oxygen content analysis cannot be obtained. For the determination of the trace water content in gases, in addition to considering the various influencing factors mentioned above, it is also necessary to take into account the adsorption equilibrium of water in the sample gas within the pipes. Proper handling of this issue requires repeated experiments to understand its variations and patterns, as well as to master the relevant operational techniques, in order to obtain accurate results. Of course, when using a gas chromatograph to determine the content of impurities at the ppm-ppb level in high-purity gases, the factors that need to be considered and controlled become even more complex. 3. The influencing factors for the analysis of trace gas components are more complex: the microscopic changes that occur as gas components flow through pipes and equipment are complex and variable. Many factors that can be ignored in the analysis of constant gas components must not only not be ignored but also taken seriously when analyzing trace gas components. At this point, these factors become the main obstacles to obtaining accurate results in such analyses, and they must be eliminated and addressed one by one in order to ensure the proper functioning of the instruments used for trace gas analysis. These influencing factors mainly include ① the repeated mixing of gases within the sampling pipeline, ② the physicochemical interactions between the pipe walls and the gas components, ③ the material of the pipeline, ④ the way the pipeline is connected, and ⑤ the cleanliness of the pipeline. 4. Instrument and method validation is one of the keys to obtaining accurate data: As a measurement tool, an instrument yields relative values in most cases when operating properly; it is unable to provide or verify whether the measured data are accurate and to what extent (i.e., the precision). It must be accomplished through peripheral technical work, which is the verification of analyzed data. (1) Verification of the linear relationship of the instrument. Firstly, to ensure the proper operation of the instruments, analytical instruments, as a type of measuring instrument, must be tested annually by authorized metrology agencies in accordance with **established procedures before they can be approved for use. At the same time, it is also necessary to use a series of standard gases each year to check whether the linear relationship of the instrument remains normal across the entire linear range. Otherwise, blindly trusting the integrity of analytical instruments (even imported ones) will certainly lead to erroneous data, resulting in mistakes in production and quality management. (2) Error analysis. In the use of analytical instruments, an error analysis must be conducted for each set of measurement results in order to determine the authenticity, reliability, and credibility of the data analysis. A competent analytical technician will not and should not casually report or publish the results of each analysis. Generally, only after the measurement results are obtained and an error analysis is conducted, and it is confirmed that the total error of the analytical data is below the specified allowable error, is this one (or set of) data considered a correct measurement result to be reported or published. Otherwise, inaccurate data can have serious negative consequences for production managers. (3) Calibration of instruments commonly used in quantitative analysis. As a quantitative analysis instrument, a gas analyzer must be calibrated using standard gases before performing quantitative analysis. Standard gases are generally purchased from **metrology departments or legitimate manufacturers; in special cases, they can also be prepared in-house (but one must have the qualifications and capabilities to do so, as well as the appropriate equipment). The shelf life of standard gases is one year. When using standard gases to calibrate analytical instruments, it is also necessary to have a thorough understanding of the proper procedures and usage guidelines. Using standard gases that do not meet the required standards can lead to significant deviations in analytical data. If there is a poor understanding of the requirements for using standard gases, inaccurate data results will be obtained, which in turn can cause problems in air separation production. 5. Analysis engineers must continuously improve and enhance analysis and testing techniques: A competent analysis engineer needs to keep learning about and researching new technologies related to analytical instruments as well as new approaches in instrumental analysis, and apply these advancements in their work in order to continually improve analysis and testing techniques. An analysis engineer must not only be able to make the best use of existing equipment, but also, based on a thorough understanding of the principles, structure, and performance of the instruments in use today, continuously adopt advanced analysis techniques from both domestic and international sources. Through technological innovation, such engineers can further improve the testing capabilities of these instruments, rather than settling for simple operations alone. In short, trace gas analysis is a specialized technique as well as a research-oriented field; it determines the effectiveness and quality of gas analysis instruments. Trace gas analysis technology is also a practical science; it requires extensive experimental work in order to discern the underlying patterns, to master it effectively, and to successfully address various specific tasks related to trace gas analysis. This is also a summary of the experience of China’s first generation of gas separation experts, gained during the development of high-purity gases in the 1960s and 1970s. The conclusion drawn from their decades of gas analysis should attract the attention of future generations. We hope that those working in gas analysis technology can achieve faster and greater progress amid the rapid development of air separation technology.