氣體分析儀應(yīng)用指南 
氣體分析儀應(yīng)用指南
 
    一般地說(shuō)，氣體分析儀器應(yīng)用本身是一門*的技術(shù)工作，而且是一種具有研究性質(zhì)的工作。但是，這一點(diǎn)是不為行外人所認(rèn)知和理解的。目前為止，國(guó)內(nèi)空分行業(yè)器應(yīng)用的技術(shù)水平與石化行業(yè)及化工化肥行業(yè)相比，仍然停留在初級(jí)階段，難以快速提高和發(fā)展，主要原因正在于此。
    （本文專指為微量氣體分析用的儀器）是一種用來(lái)進(jìn)行氣體成分分析檢驗(yàn)的工具，借助它能得到某些成分種類和含量的數(shù)據(jù)。但是，器不是一種簡(jiǎn)單的工具，它既不像流量計(jì)、壓力表那樣結(jié)構(gòu)簡(jiǎn)單，也不像各種熱工儀表那樣易于操作使用。它是一類結(jié)構(gòu)復(fù)雜、使用技術(shù)難度較大的工具，使用器是一項(xiàng)較復(fù)雜且不易掌握的專門技術(shù)。
    
二 器應(yīng)用難點(diǎn)分析
    關(guān)于器應(yīng)用的難點(diǎn)，從以下幾方面分析可以概略地了解一二。
    2．1 氣體分析是實(shí)現(xiàn)一系列的化工過(guò)程
    一臺(tái)或一套氣體分析系統(tǒng)相當(dāng)于一套完整的化工工藝設(shè)備，因此，器系統(tǒng)工作過(guò)程就是在實(shí)現(xiàn)一系列的化工過(guò)程。若想通過(guò)氣體分析得到準(zhǔn)確數(shù)據(jù)，就必須了解這一系列化工過(guò)程中各階段的情況及變化，認(rèn)真研究并掌握其中的規(guī)律，只有這樣才能達(dá)到準(zhǔn)確測(cè)定的目的。應(yīng)當(dāng)指出，不僅在一臺(tái)器內(nèi)部具備一套化工工藝過(guò)程的同樣情況和條件，而且，有時(shí)在儀器前級(jí)的樣氣預(yù)處理部分（含取樣系統(tǒng)）也同樣是一套化工工藝過(guò)程。如遇到較復(fù)雜、較特殊的工藝技術(shù)條件的話，那么樣氣預(yù)處理系統(tǒng)所體現(xiàn)的化工過(guò)程還是非常復(fù)雜的，相當(dāng)于一個(gè)小化工廠的凈化處理工藝過(guò)程。由此可見，氣體分析的過(guò)程就是在了解并掌握整個(gè)化工過(guò)程系統(tǒng)條件的前提下，嚴(yán)格控制各種影響測(cè)定條件的因素，從而得到工藝及管理人員所需要的準(zhǔn)確數(shù)據(jù)。
    2．2 應(yīng)用過(guò)程中控制影響因素和排除干擾因素困難較大
    在儀器應(yīng)用的過(guò)程中，影響因素種類較多且變化較復(fù)雜，而要想有效地控制這些影響因素及排除干擾測(cè)定的因素則困難比較大。例如微量氧的測(cè)定，不但要嚴(yán)格控制系統(tǒng)材質(zhì)和密封，而且系統(tǒng)的潔凈等諸多因素也必須逐一解決好，否則，氧成分分析不會(huì)得到準(zhǔn)確的測(cè)定結(jié)果。而對(duì)于氣體中微量水含量的測(cè)定，除了考慮以上提到的各種影響因素外，還必須考慮到樣氣中的水在管道內(nèi)的吸附平衡問(wèn)題，而這一問(wèn)題的妥善處理必須依靠反復(fù)試驗(yàn)，了解其變化情況和規(guī)律，掌握其中的操作技術(shù)，以便得到準(zhǔn)確無(wú)誤的結(jié)果。當(dāng)然，使用氣相色譜儀測(cè)定高純氣體中ppm—ppb級(jí)雜質(zhì)成分含量要考慮和控制的影響因素就更加復(fù)雜了。
    2．3 微量氣體成分分析的影響因素更復(fù)雜
    氣體成分在管道及設(shè)備中流動(dòng)時(shí)發(fā)生的微觀變化是復(fù)雜的、多變的。在常量氣體成分分析時(shí)可以忽略的諸多影響因素，在微量氣體成分分析時(shí)不僅不能忽略，反而必須認(rèn)真對(duì)待，此時(shí)，這些因素已經(jīng)成為影響微量氣體成分分析正確結(jié)果的主要矛盾，必須逐一排除和解決才能使微量器工作順利完成。這些影響因素主要包括以下幾個(gè)方面：①取樣管路內(nèi)氣體多次的反復(fù)混合；②管壁與氣體成分的物理化學(xué)作用；③管路材質(zhì)；④管路連接方式；⑤管路潔凈程度。
    2．4 儀器和方法驗(yàn)證是獲得準(zhǔn)確數(shù)據(jù)的關(guān)鍵之一
    儀器作為一種計(jì)量檢測(cè)工具，在正常運(yùn)行情況下，給出的數(shù)據(jù)絕大多數(shù)都是相對(duì)量值，測(cè)定數(shù)據(jù)是否準(zhǔn)確及準(zhǔn)確的程度（精度），儀器本身是無(wú)法提供的，也是無(wú)法證實(shí)的。必須依靠外圍技術(shù)工作完成，這就是分析數(shù)據(jù)的驗(yàn)證工作。
    （1）儀器線性關(guān)系的驗(yàn)證。首先，為確保儀器的正常運(yùn)行，分析儀器作為計(jì)量?jī)x器的一種，必須每年經(jīng)過(guò)*按照國(guó)家制訂的規(guī)程進(jìn)行檢測(cè)，方能許可使用。同時(shí)，每年還需要用系列標(biāo)準(zhǔn)氣體檢查儀器在整個(gè)線性范圍內(nèi)的線性關(guān)系是否保持正常的狀態(tài)。否則盲目相信分析儀器（即使是進(jìn)口儀器）的完好程度肯定會(huì)使錯(cuò)誤的數(shù)據(jù)導(dǎo)致生產(chǎn)管理及質(zhì)量管理上的失誤。
    （2）誤差分析。在分析儀器的應(yīng)用過(guò)程中，對(duì)于每一次測(cè)定結(jié)果的數(shù)據(jù)，必須作出誤差分析，以確定數(shù)據(jù)分析的真實(shí)性、可靠性和可信程度。一個(gè)合格的分析工作者是不會(huì)也不應(yīng)該隨隨便便地把每次分析測(cè)定的結(jié)果上報(bào)或公布的。一般是在測(cè)定結(jié)果得出后，經(jīng)過(guò)誤差分析，在確定分析數(shù)據(jù)的誤差總和小于規(guī)定的允許誤差時(shí)，才將這一個(gè)（或一組）數(shù)據(jù)視為正確測(cè)定結(jié)果上報(bào)或公布。否則，不準(zhǔn)確的數(shù)據(jù)會(huì)給生產(chǎn)管理者帶來(lái)嚴(yán)重的不良后果。
    （3）定量分析常用的儀器校正。作為一種定量分析儀器，在做定量分析前必須使用標(biāo)準(zhǔn)氣進(jìn)行校正（或標(biāo)定）。標(biāo)準(zhǔn)氣一般是從國(guó)家*或合法工廠購(gòu)買的，在特殊情況下，也可以自行配置（但要具有配置標(biāo)準(zhǔn)氣的資格和能力以及相關(guān)的設(shè)備）。標(biāo)準(zhǔn)氣保質(zhì)期為一年，在使用標(biāo)準(zhǔn)氣校正分析儀器時(shí)，還必須深入了解正常手續(xù)和使用規(guī)律。如果購(gòu)買和使用不合乎要求的標(biāo)準(zhǔn)氣，會(huì)導(dǎo)致分析數(shù)據(jù)的極大偏差。如果對(duì)標(biāo)準(zhǔn)氣的使用要求不甚了解，也會(huì)因得不到準(zhǔn)確數(shù)據(jù)結(jié)果，給空分生產(chǎn)帶來(lái)麻煩。
    2．5 分析工程師要不斷改進(jìn)和提高分析檢測(cè)技術(shù)
    一個(gè)合格的分析工程師需要不斷學(xué)習(xí)和研究分析儀器的新技術(shù)及儀器分析新技術(shù)，并及時(shí)將其應(yīng)用到本職工作中，以達(dá)到不斷改進(jìn)和提高分析檢測(cè)技術(shù)的目的。一個(gè)分析工程師不但要能夠盡可能搞好現(xiàn)有設(shè)備的應(yīng)用，而且還應(yīng)當(dāng)在對(duì)現(xiàn)今使用的儀器原理、結(jié)構(gòu)及性能深入了解的基礎(chǔ)上，隨時(shí)吸收國(guó)外及*分析技術(shù)，不斷技術(shù)創(chuàng)新，進(jìn)一步完善并提高現(xiàn)有儀器的檢測(cè)水平，而不只是滿足于簡(jiǎn)單操作。
Gas analyzer application guide
Gas analyzer application guide
Generally speaking, the gas analysis instrument itself is a unique technology application, and it is one kind has the nature of the job. But, this is not for people who have cognitive and understand it. So far, the technology level of domestic gas analysis instrument application of air separation industry are compared with the petrochemical industry and chemical fertilizer industry, still stays in the primary stage, it is difficult to quickly improve and development, the main reason.
Gas analyzer (this article specifically for trace gases analysis instrument) is a kind of used for gas composition analysis inspection tools, using it to get some component types and content of data. Gas analysis instruments, however, is not a simple tool, it is neither simple structure as flowmeter, pressure gauge, also don't like all kinds of thermal instrument is easy to operate. It is a kind of complex structure, using the technology difficult tool, using the gas analysis instrument is a complex and not easy to master the specialized technology.
Two gas analysis instrument application difficulty
Difficulties with applications of gas analysis instrument, can be roughly know a thing or two from the following several aspects.
2.1 gas analysis is to implement a series of chemical process
A gas analyzer, or a gas analysis system is equivalent to a complete set of chemical process equipment, as a result, the working process of the gas analysis instrument system is in the implementation of a series of chemical process. If you want to get the accurate data through the analysis of the gas, you have to understand this situation in each stage of a series of chemical process and change, serious study and master the law of only in this way can achieve the purpose of accurate determination. It should be pointed out that not only within a gas analysis instrument has a set of chemical processes in the same situation and conditions, and sometimes in the sample gas pretreatment section of the level before the instrument (including sampling system) is a chemical process as well. If more complex, the special technology condition, so gas pretreatment system embodies the chemical process is very complex, the equivalent of a small chemical purification treatment process. Gas analysis, therefore, is in the understanding and grasp the process of the whole system in chemical process conditions under the premise of strict control of all kinds of factors that influence the determination conditions to get the accurate data of technology and management are required.
2.2 application process control influence factors and is difficult to eliminate interference factors
In the process of instrument application, factors affecting species changes more and more complex, and to effectively control these factors and difficult to rule out the factors of interference measurement is relatively large. The determination of trace oxygen, for example, not only should strictly control system and sealing material, and the system is clean, and many other factors must also be addressing is good, otherwise, the oxygen composition analysis will not be accurate determination results. As for the determination of trace amounts of water content in the gas, in addition to consider the various factors affecting the above mentioned, the water in the sample gas must also be taken into account in the pipe of adsorption equilibrium problems, and properly handle the problem must rely on trial and error, to understand the changes and regularity, grasp the operation technology, in order to obtain accurate results. , of course, using gas chromatography determination of PPM - PPB level of impurities in high purity gas component content to consider and control factors are more sophisticated.
2.3 trace gas composition analysis of influence factors is more complex
Gas composition in the microscopic changes of flow in pipeline and equipment is complicated and changeful. Can ignore when constant gas composition analysis of many influence factors, not only can't be ignored when trace gas composition analysis, it must be taken seriously, at this point, these factors has become the influence of trace gas composition analysis results of the principal contradiction correctly, must resolve to make one by one, exclusion and trace gases analysis instrument work finished smoothly. These factors mainly include the following aspects: (1) the sample gas in the pipeline for many times repeatedly mixed; (2) the wall with the physical chemistry of gas composition; (3) the pipe material; (4) connection way; (5) line clean degree.
2.4 instrument and method validation is one of the keys to obtain accurate data
As a kind of measuring instruments detection tools, under normal operating conditions, the data given the vast majority are relative values, the extent of the measurement data are accurate and precise (precision), and is unable to provide the instrument itself, is also unable to confirm. Must rely on the peripheral technology work, this is the analysis of the data validation work.
(1) instrument validation of linear relationship. First of all, in order to ensure the normal operation of the instrument, analytical instruments as a kind of measuring instrument, must through measuring authorities every year according to the country to develop procedures for testing, to licensing. Every year at the same time, also need to use series of standard gas inspection equipment within the scope of the whole linear whether to keep the linear relationship between the normal state. Otherwise blindly believe analysis instrument (even imported instrument) in good level will surely make the wrong data lead to the errors in the production management and quality management.
(2) the error analysis. In the process of analysis of the application of the instrument, data for each determination results, error analysis, must be made to determine the authenticity of the data analysis, reliability and trust. The analysis of a qualified workers is not and should not be casually to each analysis report or released the results of determination. Is generally after the determination results obtained through the error analysis, in determining the analysis data of the total error is less than the specified margin of error, to this one or a set of data as a correct determination results submitted to or published. Otherwise, the inaccurate data will have serious adverse consequences for production manager.
(3) the quantitative analysis of commonly used equipment calibration. Gas analyzer as a kind of quantitative analysis instrument, before taking a quantitative analysis of calibration must be conducted using a standard gas (or calibration). Standard gas purchased from national metrology department or legal factory, under special circumstances, can configure itself (but with standard gas of qualification and ability as well as relevant equipment). Gas standard warranty is one year, when using standard calibration gas analysis instruments, also must deeply understand the normal procedure and use regularly. If the purchase and use unsuited to the requirements of the standard gas, can cause great deviation analysis data. If the use of standard gas requirements don't know much, will be not accurate data as a result, bring trouble to the production of air separation.
2.5 engineers to continuously improve and improve analysis testing technology
A qualified engineers need to keep on learning and research analysis instrument of new technology and new technology of instrument analysis, and apply it to the job in time, in order to achieve the purpose of continuous improvement and improve the analysis detection technology. An analysis engineers as much as possible not only to be able to do well the application of the existing equipment, but also should be in on today's use of the instrument principle, structure and performance, on the basis of deep understanding, ready to absorb the foreign and domestic advanced analysis techniques, technical innovation constantly, further perfect and improve the level of detection of existing instruments, not just satisfied with simple operation.