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    Home > Coatings News > Paints and Coatings Market > What do you love? Vocs.

    What do you love? Vocs.

    • Last Update: 2020-12-13
    • Source: Internet
    • Author: User
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    In all levels of increasing attention to VOCs, the country from top to bottom have introduced a lot of VOCs on the rectification program, VOCs included in the total control indicators of the voice constantly, so that we have to pay attention to him, but a closer look at the study, but found that there are several problems.
    focus on VOCs may be due to the fact that VOCs are a major cause of smog, but the cause of the haze is still unclear.
    is the bottom number of VOCs, if you want to reduce emissions, where does the underlying data come from?
    is voCs emission standard construction problem, where are the industry and comprehensive standards?
    is VOCs' monitoring method scientific and reasonable?
    a management indicator is proposed, is to have a set of standard system, if in the immature conditions, eager to launch the management of VOCs, it is not good to say, Guangdong Province's strict waste management is a former car .
    (a)
    of organic exhaust gas is very deep and speaks for a long time.
    in the EIA, both to judge the current situation and forecast comparison, but also to meet the emission standards. However, the early EIA indicators for the quality and emission evaluation of organic emissions are different.
    the current situation of environmental air quality evaluation is generally used TVOC, emission standards are used in non-methane total hydrocarbons.
    TVOC indicators in the Environmental Air Quality Standards (GB3095-2012), which refer to indoor air quality standards. Non-methane total hydrocarbons are used in a combination of standards or industry standards, such as the Guangdong Provincial Local Standard "Atmospheric Pollutant Emission Limits" (DB44/27-2001) and the "Synthetic Resin Industrial Pollutant Emission Standard" (GB31572-2015).
    later, haze is a well-known demon, VOCs as an important source of haze, gradually attracted people's attention, out of the game.
    a variety of VOCs standards have emerged, such as Guangdong, Tianjin, Shanghai and other industries out of voCs standards.
    Guangdong in 2010 on the introduction of the shoe industry, furniture manufacturing industry, surface coating (automotive manufacturing), printing industry volatile organic compound emission standards, can be said to be in the forefront of the country.
    these standards as soon as they come out has become a new favorite, many wind cattle and horses do not match the industry is also implemented by reference. VoCs emission standards for the plastics industry in many regions, for example, refer to furniture.
    I always feel a bit of a, but there is no way, after all, environmental management has a principle of compliance, no strict. There is no international saying, who has mastered the standard of discourse, who has mastered wealth!
    (ii)
    , what is TVOC, what is VOCs, and what is non-methane total hydrocarbons?
    concept is like this.
    TVOC: Using Tenax GC or Tenax TA sampling, non-polar columns (polarity index less than 10) are analyzed to preserve volatile organic compounds between positive hexane and positive hexane. The Indoor Air Quality Standard (GB/T18883-2002)
    TVOC indicator appears in the Indoor Air Quality Standard (GB/T18883-2002), which is not an indicator of all VOC additions, but an indicator of the add-on of all VOCs commonly found indoors.
    because TVOC has been unanimously agreed as a quality criterion, we can leave him talking about two other organic emissions indicators: VOCs and non-methane total hydrocarbons.
    VOCs: Volatile contaminants are organic compounds with boiling points below 260 degrees C, which have high vapor pressure in the air and are prone to evaporation in gaseous form in ambient air - Air and Exhaust Gas Monitoring Methodology (Fourth Edition)
    Vapor pressure greater than or equal to 10 degrees Celsius under 293.15K conditions, or all organic compounds (excluding methane) with corresponding volatility under certain applicable conditions, VOCs. Tianjin Industrial Enterprise Volatile Organic Emission Control Standard (DB12524-2014)
    Non-Methane Total Hydrocarbons: Gas Chromatography (HJ/T38-1999) defines non-methane total hydrocarbons (mainly C2-C8) as "general terms other than methane".
    (pictured online)
    is messy, but we can simplify and catch the point: conceptually, TVOC is C6-C16, non-methane total hydrocarbons are C2-C8, voCS basically contains all volatile organic pollutants.
    so from the above concept, non-methane total hydrocarbons should be contained in VOCs. Paradoxically, however, the measurement of non-methane total hydrocarbons is often higher than voCs, and according to empirical data, it is 4 or 5 times less, and more than 10 times higher.
    simple reason, monitoring methods are different.
    (iii) what
    monitoring methods are there? Simply put, it's all gas chromatography, but there's a big difference.
    Measurement methods for non-methane total hydrocarbons:
    Air and exhaust gas monitoring and analysis methods (fourth edition) There are three methods for determining non-methane total hydrocarbons, namely, total hydrocarbon and non-methane total hydrocarbon determination method I, total hydrocarbon and non-methane total hydrocarbon determination method II, and gas chromatography to determine non-methane hydrocarbons (method III).
    methods I and II were used to determine the content of total hydrocarbons and methane hydrocarbons in the air with the hydrogen flame ionization detector of gas chromatography, the difference between which is the content of non-methane hydrocarbons. method
    3 using GDX-102 and TDX-01 adsorption sampling tube to collect air samples at room temperature, non-methane hydrocarbons are adsorbed sampling tube adsorption, heating and desorption, imported into the gas chromatography, with flame ionization detector determination, the results are calculated with positive penane.
    The Gas Chromatography Method (HJ/T38-1999) for the determination of non-methane total hydrocarbons in fixed pollution source exhaust provides for the determination method of non-methane total hydrocarbon emissions from fixed source organization and non-tissue emissions, mainly using a two-pillar dual hydrogen flame ionization detector gas chromatography instrument, direct injection of syringes, respectively, to determine the total hydrocarbon and methane content in the sample, and to obtain the total non-methane hydrocarbon content by the difference between the two.
    VOCs: "Solid adsorption-thermal de-adhesion phase chromatography-mass spectrometry" and "sample tank sampling gas chromatography-mass spectrometry" were used to determine VOCs in
    Air and Exhaust Gas Monitoring and Analysis Methodology (Fourth Edition).
    The sampling method of "sampling gas chromatography-mass spectrometry with sampling tank" requires high precision and high cost, which is rarely used in the actual monitoring work, and most of the actual work uses "solid adsorption-thermal desorption gas chromatography-mass spectrometry" to monitor VOCs.
    The method generally adopts a combination of adsorption agents, often using the following three adsorption agents to combine: 30mm Tenax GR plus 25mm Carbopack B composition, the middle with 3mm of unsilaneized glass or quartz cotton separated, the tube is suitable for compounds in the C6-C20 range;
    35mm Carbopack B-10mm Carbosieve SIII. and Carboxen 1000, separated in the middle by unsilane glass or quartz cotton, the tube is suitable for compounds in the C3-C12 range;
    13mm Carbopack C, 25mm Carbopack B and 13mm Carbosieve SIII. or Carboxen 1000 for compounds above C4.
    different sampling methods in VOCs monitoring, reflecting different characteristics of pollutants. In testing, absorption tubes for the C6-C20 range are commonly used.
    We can also use one sentence to explain the difference between the two: usually non-methane total hydrocarbon sampling air bags or syringes, the measurement is mainly from C2-C8, VOCS sampling adsorption agent, the measurement is generally from above C6.
    because ethylene, acetylene, propane, butane and other hydrocarbons that are not normally measured in methane total hydrocarbons are gases at room temperature and are not absorbed by absorbers in VOCS monitoring methods. As a result, VOCS is often measured much lower than non-methane total hydrocarbons in general.
    (iv)
    To this point, it can be concluded that, conceptually, the total non-methane hydrocarbon is C2-C8, VOCs basically contain all volatile organic pollutants;
    , non-methane total hydrocarbons are more mature than VOCs in both standard systems and testing methods.
    VOCs one is not yet a unified national standard, industry standards and local comprehensive standards are also lacking, and the second is that the detection method is not scientific.
    you want to abandon non-methane total hydrocarbons and push VOCs, how to solve it?
    , we should unify the standards. The concept of VOCs and non-methane total hydrocarbons should be clear, but to establish the same analytical evaluation system, especially the testing standards, do not because of the different testing standards and produce the two who is big and who is small.
    since we want to push the management of VOCs and reduce emissions, then voCs as the criterion, hastened to establish VOCs of the entire evaluation standard system, including emission standards, testing methods and so on.
    there's another problem at home. Take the industry rectification, pollution problem equivalent, multi-replacement, is to have a home base. What was the amount of VOCs before and now?
    no, the opportunity has come, the pollution source census work has been carried out in full swing. If the estimates are correct, VOCs statistics will be one of the most important tasks in the country's second survey of pollution sources.
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