Abstract This paper examines the sample processing system technology of online analyzers from the perspective of cutting-edge 21st-century technology. Sample processing system technology is the core and key technology of process analyzer engineering application systems (hereinafter referred to as online analysis systems). Establishing this technological concept is of profound significance and will greatly incentivize and promote the application of online analysis systems. This paper focuses on reviewing the system architecture of sample gas processing systems, the targeted design of sample gas processing system technology, and the engineering application technology of online analysis systems in industrial furnaces and chemical fields. It affirms the latest efforts and progress in the research and development of sample processing system technology. Keywords Sample processing system technology Online analyzer Online analysis system Sample processing components 1 The Position of Sample Gas Processing System in Online Analysis Systems If the sample processing system is limited to the field of process gas analysis systems, it should be called a sample gas processing system. However, in the online analysis engineering technology industry, the sample gas processing system described in this paper has historically been called a sampling pretreatment system, pretreatment system, sample gas pretreatment system, sampling and pretreatment unit, etc. Because it has long carried the word "pre," it seems to be merely an additional part of the online analyzer and has not received the attention it deserves. The national standard GB/T 19768—2005, "Performance Representation of Sample Processing Systems for Online Analyzers," and the Ministry of Machinery standard JB/T 6854—1993, had already removed the word "pre-" before "processing system," inevitably implying the technical concepts and terminology of sample gas processing systems and components. Regrettably, this has long been neglected and unrecognized by industry professionals. The sample gas processing system technology discussed in this article possesses relative independence, rigor, and systematicity, as evidenced by the self-control function and software of the PLC programmable controller. The fact that dozens of H&B's 60S dry high-temperature sampling probes are sold separately in the Chinese market, with the highest price reaching 1.35 million yuan, serves as further compelling evidence. To advance the engineering application technology of online analysis systems, we should adopt a new technological perspective: online analysis faces numerous extremely challenging and complex technical problems, and sample gas processing system technology is the core and key technology of online analysis systems. We expect that sample gas processing system technology will henceforth embark on a path of comprehensive improvement and development. 2. The Dependence and Requirements of Online Analyzer Engineering Applications on Sample Gas Processing System Technology 2.1 Before 1986, online analyzers from domestic professional analyzer manufacturers were almost entirely sold as standalone units. However, approximately two-thirds of the online analyzers from the German company H&B were sold as online analysis systems (including analysis cabins). At that time, the term "pre-" in sample gas processing systems was not unjustified. Taking the introduction of three technologies, including infrared technology, from Sichuan Instruments, as an opportunity, and simultaneously importing online analysis system technology from H&B, and conducting two training sessions for system design and engineering application personnel, Sichuan Instruments inadvertently played the role of a pioneer in the engineering application of online analyzers, resulting in significant progress in design level, application level, and production scale. 2.2 The Key Issues and Optimal Approaches to Online Analyzer Engineering Applications The long-term, continuous, and timely detection and analysis of online analyzers inevitably requires continuous sampling and rigorous sample gas processing technology. It demands that the sample gas be authentic and transmitted quickly, and that the sample gas reach near-standard gas quality when entering the analyzer. The reliability and security of online analysis systems during long-term continuous operation, as well as their near-maintenance-free ease of maintenance, all depend entirely on the targeted design of the sample gas processing system technology. Based on the specific field application and sampling conditions of each online analysis system, specialized, standardized, and tailored online analysis systems must be employed. These high-quality online analysis systems are manufactured by professional manufacturers with extensive engineering experience, who also provide comprehensive technical services throughout the process. For comprehensive process gas analysis, the decisive factor is ensuring that the sample gas processing system is appropriately matched and perfectly integrated with the diverse production process conditions and environmental application conditions. This absolute dependence of online analyzers on sample gas processing systems makes the supply of online analyzers as online analysis systems both an inevitable development in online analysis engineering technology and a logical choice for all parties in the industry. 3. Complex Sample Gas Conditions and Dry Sample Gas Processing Technology 3.1 Complex sample gas conditions are the biggest challenge in process gas analysis: high or low temperature, high dust, high moisture or liquid mist, high pressure/negative pressure, corrosiveness and explosiveness hazards; high degree of automation, requiring minimal or even near-maintenance operation; stringent protection and safety requirements in terms of dustproofing, waterproofing, corrosion prevention, and explosion prevention; fast reaction speed, with a lag time generally required to be <60s; ensuring necessary detection accuracy, etc. 3.2 The Necessity of Dry Sample Gas Processing Technology Dry sample gas processing technology helps to effectively maintain the authenticity of the sample gas, thereby ensuring the necessary detection accuracy. Dry sample gas processing technology can dry and clean the sample gas, achieving a quality close to that of standard gases, and greatly reducing the potential for corrosivity. All of these factors contribute to ensuring the continuous, stable, reliable, and accurate operation of online analyzers, extending their service life. I have seen an infrared analyzer used by a petrochemical company for over 20 years. Dry sample gas processing technology has become the absolute mainstream technology. Of course, wet gas processing technology has not been completely eliminated. For example, in coke oven gas O2 analysis systems, wet processing is more effective at dealing with tar. 4 Systemic Characteristics of Gas Processing System Technology If we remove the online analyzer and certain application support components from the online analysis system, we get the gas processing system. A systematic description of the gas processing system is as follows: 4.1 The sampling probe, usually called the sampling probe, is the most important gas processing component in the gas processing system. Depending on the sampling conditions, there will be different highly targeted probes. The most commonly used is the medium-temperature general-purpose probe below 650℃. The sampling probe should also include a compressed air heating (180℃) backflush unit and its programmed backflush technology. 4.2 The gas delivery pipeline usually uses Φ6×1 stainless steel pipe. To avoid condensation, heat tracing and insulation technology (120℃) is often used. Self-regulating electric heating tape is the most economical and practical heat tracing method. 4.3 Filters In terms of their applications, the following three types of filters are representative: First, probe filters, which filter dust at the sampling point to avoid the risk of dust accumulation and clogging later. The current advanced level is 0.3μm 99%. Second, post-stage high-precision membrane filters, primarily for the protection of the analyzer. The current advanced level is 0.05μm 99%. Third, micro-filters inside the analyzer, for the self-protection of the online analyzer, and are not part of the sample gas treatment system. 4.4 Sample Gas Condensers These condense the sample gas to a low dew point, aiming to dry the sample gas. Compressor-type sample gas condensers can cool the sample gas from 140℃ to a dew point of 2℃, offering the best effect but also the highest cost; semiconductor-cooled sample gas condensers generally have an inlet sample gas temperature of only 45℃; eddy current-cooled sample gas condensers can reduce the sample gas temperature by more than 20℃, with the biggest advantage being the use of compressed air and intrinsic safety and explosion-proof properties; water-based sample gas coolers (i.e., exchangers) also have many applications. 4.5 Sampling pumps, often called suction pumps, can provide the analyzer with the specified sample gas flow rate even when the sample gas pressure is negative or slightly positive. Diaphragm suction pumps are commonly used. Peristaltic pumps are also commonly used to discharge condensate. 4.6 Gas-Liquid Separators Gas-liquid separation is often a very challenging technical problem. Cyclone self-cleaning separators are effective at separating dust and liquid mist >5μm, equivalent to gravity separation of particles larger than 70μm. Condensation separators can handle even smaller liquid mist particles. Gas-liquid separation for specific projects (such as ethylene cracking) is a highly complex and technically demanding process. The simplest gas-liquid separator is simply a cylinder with a tube inside. Research is now underway on using polymer membranes to filter liquid mist. 4.7 Sample Gas Flow Measurement and Control Sample gas flow is generally measured using a spherical rotor flow meter, and flow control is achieved using a needle valve. Various valves are used to switch and shut off the gas path, with the "five-way switching valve" being the most important. 4.8 Sample Gas Pressure Measurement and Regulation: Pressure reduction, stabilization, and regulation of high-pressure samples are challenging tasks, and the selection of various valve principles and specifications requires considerable expertise. Local pressure reduction at the root valve of the sampling point is essential to avoid slowing the reaction rate. 4.9 Correct Selection of Component Materials: Taking O-ring material selection as an example: the order of continuous operating temperature from highest to lowest is: fluororubber-coated PTFE, fluororubber, silicone rubber, and nitrile rubber. 4.10 Equipment Housing and Protection: The cabinets generally used are called instrument panels, and after assembly, they are called analysis (instrument) cabinets; cabinets that can be entered by personnel are called analysis cabins; the protection level of the cabinet against dust and water is expressed as IPXX; the explosion-proof rating of the cabinet against flammable gases and vapors is dⅡCT6. 4.11 Cabinet Climate Control: Cabinet climate control can be divided into three main aspects: cooling, heating, and ventilation. 4.12 The continuous, stable, and near-maintenance-free operation of the automatic control unit sample gas processing system, as well as various alarms, all rely on the automatic control unit with a PLC programmable controller as its core. 4.13 Standard substances, i.e., standard gases, are the metrological standards for online analyzers; currently, 99.999% high-purity nitrogen is used as the zero-point gas. 4.14 Fast loop design improves the response speed of the analysis system. 4.15 Safe discharge of tail gas and condensate. 4.16 Data processing and remote transmission. 4.17 Construction design for on-site installation. 5 Dry High-Temperature Sampling Probe System for Cement Kiln Tail 5.1 Furnace Negative Pressure Sample Gas Processing System For negative pressure or slightly positive pressure sample gases, as long as the pressure does not exceed 0.01 MPa, a certain principle-based air pump is often required as a key component to meet the specified sample gas flow rate requirements. (Some negative pressure online analysis systems for furnaces and kilns also require explosion-proof protection, such as those for coke oven gas.) 5.2 Normal Sampling Conditions for Cement Kiln Tail: Sample gas temperature < 1300℃; Sample gas dust volume < 2000g/m³. 5.3 Key Technical Characteristics of the Dry High-Temperature Probe: High-precision dust filtration technology (0.3μm 99%), airflow resistance < 6mmH₂O; Applicable sample gas temperature ≤ 1300℃; Temperature-controlled closed-loop water cooling (outlet water temperature < 85℃); Filter heating to 180℃, internal and external programmed backflushing; Backflushing cycle, can be set or modified on-site as needed; Probe length 3m; Comprehensive automatic control and safety alarm technology; On-site installation and commissioning technology. 5.4 LKP 101S Dry High-Temperature Probe System. 5.5 The dry high-temperature sampling probe is actually a complex system, complete set of equipment, or complete device integrating various technologies, hence the name "high-temperature probe system." It is one of the technological high points of online analysis systems. 6. Explosion-proof Analysis Cabin 6.1 Sample gases from the chemical and petrochemical industries are generally under positive pressure and have strict explosion-proof requirements. Therefore, a positive pressure explosion-proof sample gas processing system should be used. Of course, the online analyzer must also be strictly selected as explosion-proof, and the sample gas processing components must also be explosion-proof. 6.2 Explosion-proof Analysis Cabin. Explosion-proof rating: dⅡCT4. Specifications: 2.7m high, length and width can be selected when ordering. Structure: Steel plate structure, 50mm thick, filled with flame-retardant, heat-insulating centrifugal vacuum insulation cotton; exterior walls are polished and brushed stainless steel plates, interior walls are galvanized and powder-coated steel plates, and the top is 304SS; outward-opening door, explosion-proof viewing window, emergency escape lock; built-in standard gas cylinders and carrier gas cylinders, as well as mounting brackets; overall grounding protection; "ground" is a herringbone steel plate, δ=5; fully enclosed safety manifold discharge system with a safety vent cover equipped with a flame arrester. Electrical equipment: Explosion-proof air conditioner (1.5P), explosion-proof exhaust fan, explosion-proof lighting, explosion-proof power supply junction box, explosion-proof signal junction box, explosion-proof and corrosion-resistant switch, explosion-proof alarm light, explosion-proof CO alarm, etc. Technical features: Professional and standardized fully enclosed explosion-proof system. 6.3 The explosion-proof analysis cabin is another technological high point of the online analysis system. 7. Development Trends of Sample Gas Processing System Technology 7.1 Driving Forces of Sample Gas Processing System Technology Development Online analyzers, especially those from foreign companies, have seen rapid development and progress in recent years, such as the 19″ standard chassis six-component online analyzer. Due to the long-term national industrial orientation towards energy conservation, environmental protection, resource conservation, and high technology, the domestic online analysis system market exhibits characteristics of rapid growth and openness. These have become the two main driving forces for the development of sample gas processing system technology. 7.2 Certain Trends in Sample Gas Processing System Technology Development The concept of continuous improvement is very suitable for the development of sample gas processing system technology: for example, the eddy current cooling sample gas condenser from Chengdu Beicheng Analytical Technology Research Institute has been improved to the fifth generation, and the company's explosion-proof analysis cabin represents the advanced level in this field domestically. Impacting the commanding heights of sample gas processing system technology: Sichuan Branch's dry high-temperature probe has occupied nearly 80% of the domestic market share for several consecutive years. Miniaturization is one of the inherent laws of technological development: Swagelok in the United States has developed a new type of "integrated" sample gas treatment system resembling a string of candied hawthorns. While its overall size is very small, its price is high, and its technological adaptability is limited, making widespread adoption difficult. Sifmei in the United Kingdom uses a Φ2 welded three-way gas path for its zirconia backflush system, and its zirconia sensor is smaller than a thumb. Widespread improvement in advanced sample gas treatment system technology still requires time: while probe filters and post-filters have reached advanced levels of 99% (0.3μm) and 99% (single-stage) respectively, other companies, including some foreign companies competing in the domestic market, remain at the conservative levels of around 2μm and 0.5μm respectively. The research and development of sample gas treatment system technology is showing signs of deepening: combined sample gas treatment components (such as water-washing separators); high-efficiency sample gas treatment components (such as high-efficiency water-cooled separators); and self-cleaning, maintenance-free sample gas treatment components (such as cyclone self-cleaning filters). High-safety sample gas treatment components (such as detachable chemical sampling probes); sample gas treatment components based on new principles (such as high-efficiency self-cleaning integrated filters); intrinsically safe sample gas treatment system technology that does not use sample gas electronic condensers and peristaltic pumps is under development; specialized sample gas treatment component R&D companies and marketing websites are beginning to emerge. 8. Analysis of Utility Model (Patent Technology) of New Sample Gas Treatment Components: High-Efficiency Self-Cleaning Integrated Filters. Current filters are all designed for dust, and are not only ineffective against liquid mist, but also often clog or damage the filter membrane, causing membrane filter failure. Some manufacturers have had to adopt moisture alarm type membrane filters. There is a polymer membrane material with nano-characteristics that has very unique properties: filtration accuracy of 0.3μm can reach 99.9999%, and 0.05μm can also reach 99%; oil mist filtration rate of 0.0001% (water mist filtration rate should also be this technical data); hydrophobic properties (like lotus leaves to water); the polymer membrane will not be affected by water even when soaked. Airflow resistance ≤7mmH2O (at 60L/h, Ф50 diaphragm). It has good tensile strength and is not easily damaged. The new high-efficiency self-cleaning integrated filter can filter 99% of 0.05μm dust and 99% of 0.05μm liquid mist. The filtered dust and liquid mist are self-cleaning and then discharged through a bypass, greatly reducing maintenance. 9 Expectations for the Development of Sample Gas Processing System Technology 9.1 The development of sample gas processing system technology cannot be driven solely by the development of analyzers and market expansion. Innovation in online analysis engineering technology theory and the technology of sample gas processing systems themselves are also strong driving forces for the development of sample gas processing system technology. 9.2 Through this international forum on cutting-edge technologies, we expect the development of sample gas processing system technology to have a new development direction that adheres to the concept of "continuous improvement and continuous innovation".