Common knowledge of gas pretreatment system in Dongri Yingneng gas analysis system

With the integration of instrumentation into various applications, normal working conditions can no longer meet market demand, so how do we solve it in special environments? The following editor collects some common knowledge about the gas pretreatment system in the gas analysis system
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If the sample handling system is limited to the field of on-line gas analysis systems, it should be called a sample (gas) handing system
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In the on-line analysis engineering technology industry, the sample gas treatment system described in this article has been called sampling pretreatment system, or pretreatment system, sample gas pretreatment system, sampling and pretreatment unit, etc.
in the past
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Because the word "pre" has been carried for a long time, it seems that it is only a trivial part of the online analyzer, and it is far from being given due attention.
This kind of irrational "technical discrimination" has seriously hindered its healthy development
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The national standard of GB/T 19768-2005 "Online Analyzer Sample Processing System Performance Representation", in fact, the earlier JB/T 6854-1993 Ministry of Machinery standard has long cancelled the word "pre" before the pre-processing system.
The most important core technical concepts and terms are inevitably derived from it: sample gas processing system and sample gas processing components
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Note that technical concepts and their normative use are also technical
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Regrettably, it has not received the attention and approval of professionals for a long time, and it still refers to "sampling pretreatment device", and the sample gas processing part is called "functional part"
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The sample gas treatment system technology that this paper focuses on expounds has its own relative "independence", rigor, systematicness, and strict normativeness in the application of on-line analysis engineering.
It cannot be overstated
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The automatic control function of PLC programmable controller and its software is a proof
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In order to promote the development of on-line analysis engineering technology, we should believe in and adhere to a brand-new "dian coverage" technical concept: on-line analysis faces many very difficult and complex technical problems, "Sample gas processing system technology is the core of the on-line analysis system.
and key technologies", we look forward to the comprehensive improvement and healthy development of the sample gas processing system technology
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The crux of the engineering application of the online analyzer and the best way for the long-term continuous and timely detection and analysis of the online analyzer, the continuous sampling and strict sample gas processing technology are inevitably required, and the sample gas is required to be undistorted and quickly transmitted.
When the sample gas enters the analyzer , it is required to achieve high quality close to the standard gas, such as dust content <0.
3um <10ug/m3, unfortunately, some famous professional factories at home and abroad have not been able to achieve this uncompromising control standard
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The reliability and safety of the long-term continuous operation of the online analysis system, as well as the near maintenance-free ease of maintenance, this kind of integrity guarantee for engineering applications completely depends on the specialized and targeted design of the technical specifications of the sample gas processing system
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According to the field application conditions and sampling conditions of each on-line analysis system, a specialized on-line analysis system with standardized and targeted design shall be adopted, and these high-quality on-line analysis systems shall be produced by professional manufacturers with long-term engineering practice experience.
And undertake the whole process of technical services
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This special type of on-line analysis system must and must have a sample gas processing system as the core and key technology
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For perfect on-line gas analysis, the decisive role is to make the sample gas treatment system properly matched with the widely different production process conditions and environmental application conditions, the combination is perfect, and the coordinated operation can be continuous, stable, accurate and reliable, and almost maintenance-free
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The dependence of the online analyzer on the sample gas processing system, that is, the dependence on the entire system and the process, the online analyzer is being (or has been) breakthrough and surpassed by the online analysis system, so that the online analyzer can be On-line analysis system form to engineering application has become an inevitable trend of on-line analysis engineering technology development, both domestic and foreign has become the mainstream of irreversible technology development
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 The most important definition of the sample gas processing system technology is the sample gas processing system technology.
From the technical logic analysis, it should be composed of the sample gas processing system and the sample gas processing technology.
The former is hardware technology and the latter is software technology
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Sample gas processing system technology: sample (gas ) handing engineering The ultimate definition of sample gas processing system: through the specialized design of the specifications for the on-line analyzer engineering application conditions and sample gas conditions, the realized sample gas processing components and on-line analysis The reasonable matching and perfect combination between the analyzers, and the continuous and stable, reliable preparation, almost maintenance-free coordinated operation, and the sum of the complete and systematic sample gas processing components that can be used for the strict requirements of one or more on-line analyzers for engineering applications
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In short, the sample gas handling system provides the perfect connection between the analyzer and the sampling point, the discharge point and the utility
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Sample gas processing system: sample (gas) handing sistem The ultimate definition of sample gas processing system technology: a highly comprehensive technology that closely combines the specialization of sample gas processing system specifications, targeted design technology, and professional engineering application and maintenance technology.
It should also be understood to include hardware technology and software technology
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Sample gas handling component: sample (gae ) handing component Analysis system, and successfully realize all the hardware technology, software technology and professional technology concept of online analysis engineering application, which are closely integrated and highly comprehensive technology
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 Complex sample gas conditions and dry sample gas processing technology Complex sample gas conditions are the biggest difficulties faced by on-line gas analysis: high temperature (maximum 1400°C) or low temperature, high dust (maximum ≤ 2000g/m3), high Moisture (maximum 12000ppm or more) or liquid mist, high pressure (maximum greater than 50MPa) or negative pressure, corrosive and explosive hazards, etc.
; high degree of automation, less maintenance or even close to maintenance-free application requirements; dustproof and waterproof , anti-corrosion, anti-explosion and other aspects of extremely harsh protection and safety requirements; faster response speed, the total system lag time generally requires <60s; to ensure the necessary detection accuracy,
etc.

The above difficult application requirements are highly summarized by Zhu Lao as "sampling system, reliability, less maintenance, software technology"
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Necessity of dry sample gas treatment technology Dry sample gas treatment technology is conducive to effectively maintaining the authenticity of the sample gas, that is, the sample gas is not distorted, thereby ensuring the necessary detection accuracy
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The dry sample gas treatment technology can make the sample gas dry and clean, that is, after high-efficiency "dust removal" and "water removal", to achieve a high quality close to the standard gas, and at the same time, the possible corrosiveness is also greatly reduced
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All of these are beneficial to ensure continuous stable, accurate and reliable, low maintenance coordinated operation of the online analyzer and prolong its service life
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Dry sample gas treatment technology has become the mainstream technology of the company
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Of course, the wet sample gas treatment technology has not been completely eliminated.
For example, the coke oven gas O2 analysis system is more effective to deal with tar by the wet method
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 Systematic features of sample gas treatment system technology The online analysis system is the sample gas treatment system if the online analyzer and some application guarantee conditions and public works are removed.
The sample gas treatment system is briefly described as follows: 1.
Called sampling probe, it is the most important and critical sample gas treatment component of the sample gas treatment system.
According to the sampling conditions that differ greatly in different industrial production processes, there must be different targeted sampling probes.
The most commonly used one is Medium temperature general purpose sampling probe below 650°C
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The sampling probe should also include compressed air heating (180°C) backflushing unit and its program-controlled backflushing technology
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The design of the backflushing unit must meet the requirements of fluid mechanics, which is a very critical design technology to ensure the backflushing effect
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The sampling probe can realize the continuous sampling of the process sample gas in the industrial production process
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Sampling probes are recognized from the practical point of view, and should be called sampling probe systems to be more accurate
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It is important to technically achieve physical separation when sampling
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2.
The sample gas transmission pipeline usually adopts Φ6×1 stainless steel pipe.
In order to avoid condensation, the heat tracing and heat preservation technology (≥120℃) is often used
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If a transmission pipeline larger than Φ6×1 is used, the technically necessary reaction speed of the system will exceed the specification requirement, that is, the requirement of <60s will not be met
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It is a very careless and low-level mistake to think that the pipeline is thick or the pressure is high and the reaction speed is fast
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3 Filters For their uses, the following three types are more representative: First, the probe filter, which filters the dust at the sampling point to avoid the risk of dust precipitation and blockage.
The current advanced level is 0.
3um 99%
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The second is the post-stage high-precision membrane filter, the main purpose of which is to protect the analyzer.
The current advanced level is 0.
05um 99%
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The third is the micro filter inside the analyzer, which is for the purpose of self-protection of the online analyzer.
It does not belong to the sample gas processing system, and is generally made relatively small
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4 The sample gas condenser condenses the sample gas to a low dew point (eg about +2°C) for the purpose of drying the sample gas
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Compressor-type sample gas condenser: It can cool the sample gas from 140 °C to +2 °C dew point, with good effect, but the cost is also high; semiconductor refrigeration sample gas condenser, the inlet sample gas temperature is generally only allowed to be 45 °C; eddy current causes The cold sample gas condenser can reduce the sample gas temperature by more than 25 °C.
The biggest advantage is that it uses compressed air, which is an intrinsically safe explosion-proof type; the sample gas cooler (ie, heat exchanger) that uses a water source also has many applications
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The simple structure of the sample gas cooling pipe can be used as a useful supplementary means
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5 The sampling pump is usually called the suction pump.
When the sample gas pressure is negative pressure or slightly positive pressure, it can also be driven by the suction pump to provide the analyzer with the specified sample gas flow.
The diaphragm suction pump is used more
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In addition, peristaltic pumps are often used to discharge condensate, which is not limited by the suction pump and negative pressure, and can continuously discharge condensate in the state of being isolated from the main gas path of the sample gas
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6 Gas-liquid separator Gas-liquid separation is often a very difficult technical problem.
Cyclone self-cleaning separator is more effective for separating dust and liquid mist >5μm, which may be equivalent to gravity separation of dust with particle size above 70μm; condensation separator is suitable for dealing with Micro liquid mist with smaller particle size, cyclone condensation separation filter is very useful in positive pressure analysis system
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Gas-liquid separation for specific projects (such as ethylene cracking) is a comprehensive technology with high technical content; 7 Sample gas flow measurement and control of sample gas flow generally use spherical rotor flowmeter, flow control is adjusted with needle valve, and online analyzer The required flow rate is generally 30-60l/h
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Various valve parts are used to switch and shut off the gas path, and the five-way switching valve is the most important
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8.
Sample gas pressure measurement and adjustment Decompression, pressure stabilization and adjustment of high-pressure sample gas are difficult tasks, and the selection of principles and specifications of various valves is also very professional
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It is necessary to decompress the high-pressure sample gas at the root valve of the sampling point in order to avoid reducing the reaction speed and to ensure the safety of the sample gas processor part of the subsequent stage
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9 The correct selection of component materials takes the selection of O-ring seals as an example: the order of continuous use temperature is, fluorine rubber coated PTFE (260 ℃), fluorine rubber (180 ℃), silicone rubber (200 ℃), Nitrile rubber (100℃)
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The above is not only the order of long-term use temperature, but also the order of resistance to chemical substances, anti-aging, and length of service life
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The maximum operating temperature of the non-metallic O-ring seal is 327°C.
It is the perfluoroelastic O-ring Kalrez of Dubang Company, and its unit price of more than 200 yuan is prohibitive
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10 The cabinet generally used for equipment shell and protection is called the instrument panel, and it is called the analysis (instrument) cabinet after assembly; the cabinet that people can enter is called the analysis cabin; the protection level of the cabinet against dust and water is represented by IPXX; Explosion proof rating for gases and vapours
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Such as dⅡCT4 dⅡBT6 and so on
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11 Cabinet climate regulation Cabinet climate regulation can be divided into three major aspects: cooling, heating, and ventilation
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12 Automatic control unit The continuous, stable and almost maintenance-free operation of the sample gas processing system and various alarms are inseparable from the automatic control unit with the PLC programmable controller as the core
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13 The standard material or standard gas is the measurement standard of the online analyzer, and now 99.
999% high-purity nitrogen has been used as the zero point gas.

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Significantly different from other majors, standard gas is not as "standard" as imagined.
The accuracy of constant standard gas is <0.
5%, while the accuracy of trace standard gas can only reach 2%
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The above is the common knowledge of the gas pretreatment system in the gas analysis system.
I hope it can help you, Dongri Yingneng, the gas detection expert around you!