1.The hazards of volatile organic compounds

  The harm of VOCs is mainly manifested in the atmospheric environment, which is specifically manifested in two points: First, VOCs has photochemical characteristics, and N0x and VOCs will form different photochemical oxidants by sunlight and thermal conditions。Because ozone accounts for more than 90%, ozone has become the most typical substance in photochemical oxidants。The presence of ozone will oxidize SO2, NOx, VOCs in the atmosphere, and the substances formed after oxidation will be secondary PM2.5 provides the necessary anions, and after combining with cations in the atmosphere, can form inorganic secondary PM2.5. Fusion with organic aerosols will form secondary PM2.5;Second, VOCs and photochemical products are toxic substances, and contact with the human body will harm health。

2. Problems existing in VOCs management and control of modern coal chemical enterprises

  2.1 LDAR work is progressing slowly

  LDAR work is a systematic engineering to control material leakage in the whole process of industrial production。The use of fixed or mobile testing instruments, quantitative detection or inspection of valves in the production unit easy to produce VOCs leakage sealing points, and within a certain period of time to take effective measures to repair the leak point, so as to control the loss of material leakage, reduce the pollution caused by the environment。At present, the main problems in the development of LDAR in coal chemical industry are as follows:

2.1.1. Leakage control is not systematically carried out

  The dynamic/static sealing point of the equipment exists both in the production plant and in the public auxiliary facilities such as storage, loading and unloading, sewage treatment plants, and circulating water plants, and its VOCs emissions are related to the system control level of process configuration, planning and design, investment and construction, and operation management。The control measures for VOCs emissions should include source control, process control and end treatment to achieve whole-process control。At present, most enterprises do not carry out leakage control from the source, process, end and other whole processes。

2.1.2 Data authenticity is difficult to guarantee

  LDAR basic information statistics and field testing involve a lot of human labor，Limited by the level of the operator, the scope of application of statistical methods and the complexity of sealing points and other reasons，It is difficult to guarantee the quality of LDAR basic information statistics，It brings great difficulty to ensure the authenticity of LDAR field test data。Coupled with the lack of effective supervision and management mechanism and reward and punishment means at the national level, the authenticity of the LDAR work process and results in the modern coal chemical industry is difficult to guarantee。

2.1.3. Large investment in manpower and material resources

  The LDAR basic information statistics link requires that each sealing point of the device be documented, and the field test link should find each sealing point corresponding to the device site and test it against the archives。According to the statistics of dynamic/static sealing points installed in research enterprises, the number of dynamic/static sealing points in modern coal chemical enterprises is basically tens of thousands, so the workload of LDAR basic information statistics and on-site testing is relatively large。In addition, the instruments and software platforms needed to carry out this work are expensive。Therefore, LDAR has invested a lot in manpower and material resources。

2.2. Inaccurate accounting of VOCs emissions

2.2.1 Source item identification error or omission

  Various forms of VOCs emissions, coupled with insufficient understanding of the Petrochemical Industry VOCs Pollution sources Investigation Guide, often lead to source item identification errors or omissions。For example, enterprises or third-party testing units will not involve VOCs material air separation devices, gasification and thermoelectric units of dynamic/static sealing points into the test and accounting;The underground waste oil tank and organic material intermediate tank are not included in the accounting;Periodic start-stop source item is not identified;The emission of flare source item is not paid enough attention，The operation status of the enterprise torch is not continuously monitored，Some enterprises did not collect flare gas，Because of frequent driving and stopping，The emission of torch source term is large，However, due to the lack of necessary supervision in the daily management process of enterprises，This portion of emissions is not accounted for。

2.2.2 The selection of accounting parameters is not accurate

  The VOCs emission calculation process involves the selection of a large number of calculation parameters，Organic liquid storage and blending of volatile source terms is the most obvious，It involves the physical and chemical properties of the storage materials (such as: red vapor pressure, storage temperature, etc.), equipment parameters (such as: tank type, floating disk type, edge seal form, etc.), meteorological parameters (such as: daily average maximum ambient temperature, daily average minimum ambient temperature, average wind speed, solar radiation intensity, etc.)。Actual VOCs emissions calculation process，There may be cases where estimates of some parameters are used for accounting，For example, a modern coal chemical enterprise has not obtained diesel red vapor pressure，Estimate at 7kPa，There is a certain deviation from the actual situation;In addition，The key parameters involved in the accounting do not reflect the characteristics of modern coal chemical industry，Parameters are not localized，Such as oil physical and chemical properties，Most refer to the petrochemical industry，No database has been developed for the modern coal-to-oil industry。

2.2.3. Large error of monitoring and analysis data

  In the calculation of VOCs emissions, the source items such as process organized emissions and combustion flue gas emissions need to be sampled, monitored and analyzed for the concentration of non-methane main (or real matter) at the discharge port, and the accounting results are obtained by combining the emission gas volume and other parameters。In the process of sampling and analysis, due to the influence of the level of sampling and analysis personnel, sampler and analysis instrument, the analysis results of non-methane total monster are not accurate, and some errors are larger than the actual ones。This interference is particularly pronounced for emission sources with very low non-methane total mass concentration (about 1mg/m3), such as combustion flue gas。

2.3 VOCs governance is difficult to carry out

  The treatment of VOCs emission sources in modern coal chemical industry can not only reduce VOCs emissions, reduce environmental pollution, but also reduce material losses and improve economic benefits;Reduce flammable material leakage and reduce safety hazards;Reduce environmental odor and ensure the occupational health of employees。However, at present, the modern coal chemical industry has not yet systematically carried out VOCs governance, the main reasons are as follows:

2.3.1 Lack of VOCs emission standards for modern coal chemical industry

  National, local and industry standards are the basis and criteria for the legitimate operation of enterprises。Without specific VOCs emission standards, there is a lack of mandatory requirements and specific guidance for the modern coal chemical industry。In the absence of specific VOCs emission standards, if modern coal chemical enterprises blindly carry out VOCs governance work, it is likely to cause problems such as technology selection errors or emission standards that cannot keep up with subsequent environmental requirements。

2.3.2 VOCs emissions have not been calculated clearly

  Most enterprises in modern coal chemical industry have not yet carried out VOCs accounting work，Although some modern coal chemical enterprises have carried out VOCs accounting work，However, due to the large deviation of accounting data, inaccurate accounting parameters, inadequate source item identification and other reasons，There is a large deviation in the accounting results，As a result, the modern coal chemical industry can not clarify the focus of VOCs governance，Therefore, VOCs governance can not be effectively carried out。

2.3.3 VOCs governance technology is in urgent need of improvement

  Combustion is the cheapest and most thorough way to deal with VOCs，But there are some security risks;Regenerative catalytic oxidation (RCO) and regenerative combustion (RTO) are costly，Tens of millions of dollars;It is difficult for activated carbon adsorption method to guarantee long period qualified discharge，And produce hazardous waste;Tank roof connectivity can significantly reduce the amount of VOCs exhaust gas produced，But there are security risks。In short, due to the flammable and explosive characteristics of VOCs and the current increasingly stringent environmental protection standards, the current VOCs governance technology still needs to be improved and improved。