New RTO incinerator, RTO professional manufacturer Moranz Environmental Protection, April 9, 2019: Abstract: Volatile Organic Compounds (VOCs) emissions from chemical enterprises account for a large proportion in the industrial production process, as an important precursor of PM2.5 and O3, have a serious impact on the atmospheric environment and human health. In this paper, the characteristics of VOCs emission from chemical enterprises in Jiangxi Province, the status quo of VOCs control and existing problems are analyzed and analyzed. The corresponding countermeasures and suggestions are put forward from the comprehensive renovation of VOCs in chemical parks, providing technical support for the prevention and reduction of VOCs in chemical parks
With the sustained and rapid development of China's economy, the total amount of volatile organic compounds (VOCs) discharged from industrial sources has increased year by year, and environmental pollution has become increasingly prominent. VOCs (volatile organic compounds) are organic compounds whose saturated vapor pressure is greater than 133.32 Pa at room temperature, boiling point is below 50-260 C at normal pressure, or any organic solid or liquid that can volatilize at normal temperature and pressure. Most VOCs are highly toxic and are one of the important precursors of photochemical smog and PM2.5, which have important effects on regional atmospheric ozone, PM2.5 pollution and human health. Jiangxi Province organized a survey on the status of volatile organic compounds in industrial enterprises. The results of five key industries, including organic chemical industry, medicine, surface coating, plastic products, packaging and printing, showed that VOCs emissions from organic chemical industry ranked first, accounting for more than 90%, and equipment allocation rate of treatment facilities was less than 50%. Especially, there is a big gap between the present situation of VOCs prevention and control in chemical industrial parks with centralized chemical enterprises and the requirements of "Ten Articles of Atmosphere" and "Detailed Rules for the Implementation of Action Plan for the Prevention and Control of Atmospheric Pollution in Jiangxi Province". Therefore, to promote the high-quality development of chemical enterprises and enhance the chemical industrial parks in Jiangxi Province, it is necessary to carry out comprehensive treatment of atmospheric volatile organic pollutants in industrial enterprises and establish a The level of green development is of great significance to further improve atmospheric quality.
2. Current situation of volatile organic compounds control in industrial enterprises
2.1 Investigation of Volatile Organic Compounds Control in Industrial Enterprises
In 2014, the Department of Environmental Protection of Jiangxi Province investigated the prevention and control of volatile organic pollutants in the first batch of 475 industrial enterprises (excluding shutdown and construction enterprises), involving 112 sub-industries in five key areas: organic chemical industry, medicine, surface painting, plastic products and packaging and printing. According to the analysis of VOCs production in five industries, most of VOCs come from organic chemical industry, accounting for 91.66%, followed by pharmaceutical industry, surface painting, plastic products manufacturing and packaging printing industry, accounting for 5.55%, 1.92%, 0.63% and 0.23%, respectively. The VOCs emission of enterprises shows that organic chemical industry still occupies the absolute dominant position, and its emissions amount is 178.8 million t/a, accounting for 89.47%. From the analysis of VOCs processing efficiency of five industries, the processing efficiency of all industries is at a low level. The average processing efficiency of the first batch of 475 industrial enterprises is only 48.3%. Among them, the average treatment efficiency of organic chemical industry is 49.6%, which does not meet the requirements of national and local environmental protection standards.
2.2 Status of Volatile Organic Compounds Control in Chemical Industry Park
At present, there are about 90 industrial parks in Jiangxi Province. Among them, the main parks involved in chemical industry are sparkling silicone industrial park, Leping fine chemical industry park, Dingnan fine chemical industry base, Wannian fine chemical industry park, Pengze County Jishan chemical industry park, Ruichang wharf chemical industry park, Guixi vulcanization industry park, Jinxi spice chemical industry park and so on. The main parks are new silicone materials, petrochemical and fine chemical industry, new materials. Industrial clusters. The main chemical enterprises in our province are concentrated in chemical industry parks. The top ten industries with the largest VOCs emissions are organic chemical raw material manufacturing and chemical pharmaceutical raw material manufacturing in turn. Among them, chemical industry VOCs emissions accounted for 87%. The disposal situation of the top ten industries shows that the overall coverage and average disposal efficiency of the industry treatment facilities are at a low level. Among them, the coverage rate of treatment facilities in organic chemical industry, which accounts for nearly 90% of emissions, is only 38.46%, and the average treatment efficiency is only 48.76%. Some enterprises have not yet established any VOCs treatment facilities, which has a serious impact on the surrounding air quality. Therefore, there is a big gap between VOCs control in chemical industry park and national standards and control requirements such as "Standards for Emission of Pollutants from Synthetic Resin Industry" (GB 31572 - 2015) and "Comprehensive Treatment Plan for Volatile Organic Compounds in Petrochemical Industry" (Environmental Development  177). In addition, the VOCs unorganized emission control is not in place, and odor complaints are frequent. Because of the illegal discharge of chemical enterprises, especially VOCs, many times in the chemical industry parks in the province, serious odors have been complained by the surrounding residents, and even repeatedly exposed in important media such as CCTV, which exposes the shortcomings of environmental protection management and the inadequate ability of pollution prevention and control in some chemical industry parks in our province.
Main Problems in VOCs Prevention and Control in Chemical Industry Park
3.1 Serious inadequacy of VOCs governance facilities
At present, the overall development of VOCs governance industry is still in its infancy. Some chemical enterprises are indifferent to VOCs pollution prevention and control and lack of comprehensive control ability. According to incomplete statistics, the VOCs treatment facility in chemical enterprises has less than 50% commissioning rate, which only concentrates on the volatile pollutants in the treatment process and solvent use. VOCs non-organized emission is more common.
3.2 VOCs governance technology is single and backward
The types and components of VOCs are very complex. Different technologies and combinations are needed for different components and concentrations of VOCs. At present, most enterprises in chemical industry parks adopt activated carbon adsorption process, which has low removal efficiency, fast activated carbon failure, short effective operation cycle and can not meet the long-term emission requirements. In 2014, the average VOCs processing efficiency of the first batch of industrial enterprises in the province was only 48.6%. Some enterprises have the phenomenon of untreated direct row because VOCs treatment facilities can not be put into use normally.
3.3 Insufficient monitoring and supervision capacity of VOCs
Most enterprises and chemical parks do not have VOCs monitoring capability. Enterprise VOCs are usually organized and unorganized. Organized emissions mainly include the organic process exhaust gas in material production process, loading and unloading and transporting. Most enterprises have not established a perfect VOCs monitoring and supervision system, and have not carried out leak detection and repair (LDAR) work. Due to the limitation of VOCs monitoring ability, VOCs pollutant monitoring has not been carried out regularly, so a large number of VOCs have not been effectively treated and directly discharged.
Comprehensive renovation technology and Countermeasures of VOCs in Chemical Industry Park 4
4.1 Establishment of VOCs Monitoring and Supervision System
Taking key chemical enterprises as monitoring objects, VOCs characteristic pollutants are monitored to find out the types and emissions of pollutants. At the same time, combined with the geographical location and meteorological data of the park, VOCs emission status, pollution level, fixed-point traceability and cause mechanism are analyzed. Establishment of monitoring, monitoring and early warning system. Three-dimensional remote leak monitoring and organic pollutant emission monitoring are carried out for key monitoring enterprises. The monitoring and monitoring of VOCs with high toxicity and high hazard, such as benzene and formaldehyde, as well as the monitoring and early warning of catastrophic sudden exhaust gas leakage accidents are increased.
4.2 Implementing the whole process of VOCs pollution prevention and control
4.2.1 Leak detection and repair (LDAR)
Leak detection and repair (LDAR) technology is an effective method to control VOCs unorganized emission in chemical enterprises. The management system of leak detection and repair is established. According to the requirements of "Discharge Standards for Pollutants in Petroleum Refining Industry" and "Discharge Standards for Pollutants in Synthetic Resin Industry", portable VOCs detectors are equipped. The key elements such as working procedures, detection methods, detection frequency, leakage concentration limits and repair requirements are defined. The number and identification of sealing points for dynamic and static equipment are found out. If there is no organization leak point, the leak over-standard sealing point should be repaired in time; the leak point information should be comprehensively analyzed, and the leak-prone links should be improved; the number and leakage status of dynamic and static equipment in enterprises should be found out by LDAR, the equipment leak management account should be established, and VOCs emissions should be accounted for.
4.2.2 Source Control of VOCs Emissions
Continuous promotion of cleaner production, optimization and improvement of production technology, focusing on source control of VOCs emissions. Chemical enterprises should implement the concept of cleaner production into the whole process of production management, combine the production link of VOCs with the source of exhaust gas, adopt the combination of source reduction, process control and end treatment to realize the control and emission reduction of VOCs, strengthen the identification of environmental factors and risks in operation and equipment maintenance, strengthen the recovery of process materials, and ensure the closed purge and condensate recovery. Measures such as putting in place to prevent VOCs from being discharged into the atmosphere, paying attention to the elimination of equipment defects and the improvement of process methods, and synchronously implementing schemes and technical regulations, standardizing maintenance management, and preventing leakage and random discharge of process materials.
4.2.3 Implementing VOCs Terminal Management
Efficient control of VOCs organized emission from chemical enterprises is the key measure to reduce VOCs total emission in the park. The "one enterprise, one policy" approach is adopted to strengthen the management of organized process exhaust gas. According to the actual situation of the emission characteristics and types of organized process exhaust gas, each enterprise formulates the technical route of end-treatment. By optimizing the production process, the waste gas can be recycled and reused to minimize the emission of the organized process. For the waste gas which is difficult to be recycled, catalytic combustion and thermal incineration can be used to treat and discharge the waste gas, and the treatment efficiency should not be less than 95%. The waste gas and odor of the wastewater system should be strengthened so as to eliminate VOCs and produce odor in the process of wastewater collection, storage and treatment. Effective sealing measures such as capping and sealing should be adopted in the links, and technical routes should be determined according to different working conditions for treatment, so as to achieve emission standards and effectively control odor generation and emission.
4.2.4 Controlling pollution under abnormal working conditions
Chemical enterprises should formulate operating rules, emergency plans and emergency cards for abnormal working conditions such as start-up and shutdown of plant or equipment maintenance process, leakage of circulating water cooling system, flare combustion flue gas, etc. Enterprises take the initiative to file with the environmental protection department before the implementation of equipment overhaul, carry out environmental monitoring during the implementation process, and carry out environmental impact post-assessment afterwards; unplanned operation should perform relevant procedures in accordance with the provisions, and timely assess and report to the local environmental protection department. The measures of preventing and dealing with sudden VOCs leakage should be incorporated into the enterprise emergency plan system; the monitoring system should be established for normal and abnormal conditions respectively, and the environmental protection management rules for reporting and filing such as shutdown maintenance should be formulated. The CEMS monitoring system of organized exhaust gas (such as combustion flue gas, VOCs treatment facility exhaust gas, etc.) should be installed step by step.
4.3 Selection of VOCs Governance Technology
VOCs are of various types and concentrations, which make it difficult to control. At present, three kinds of technologies or processes are widely used in the industry to control VOCs organized emission. The first type is recovery technology. For high-concentration VOCs exhaust gas over 10,000 ppm, selective absorbent and selective osmosis membrane should be used to enrich and separate organic pollutants and recycle them, mainly including absorption, adsorption, condensation and membrane separation technology. The recovered VOCs can be reused directly or after simple purification, or centralized separation and purification to reduce the consumption of raw materials. The second type is destructive technology. For VOCs exhaust gas with 1000 ppm to 5000 ppm concentration, heat, light, catalysts or microorganisms should be used to convert VOCs into carbon dioxide and water, mainly including catalytic combustion, high temperature incineration, biological oxidation and low temperature. Temperature plasma and photocatalytic oxidation technology, etc., are characterized by high removal rate, up to 99%, especially for the treatment of toxic pollutants such as benzene and sulfide. The third type is combination technology, which combines recovery technology and destruction technology, and can achieve the treatment effect that is difficult to achieve by single treatment technology. For low concentration VOCs below 1000ppm, the combination technology can be used. Waste gases should be treated by adsorption concentration-combustion technology, or by biological treatment technology.
Organized VOCs emissions mainly include the production process of process materials, waste gas from sewage treatment plant, discharge from loading and unloading, and discharge through exhaust canister during transporting. For example, VOCs and H2S on the top of acid water tank in a chemical enterprise are produced by a combined process of "low temperature diesel oil absorption + alkali washing + incineration". The design and treatment scale is 300 m3/h, including low temperature diesel absorption tower, liquid ring compressor and other equipment. It is mainly used to recover and treat acid water tank, oil tank VOCs and odor exhaust gas. The core technology is to absorb the exhaust gas with VOCs concentration of 1-10*105mg/m3 and organic sulfur of 200-500 mg/m3 by low temperature diesel oil, recover about 75% of VOCs, then send it to the desulfurization reactor to remove H2S by alkali absorption, and finally purify the desulfurized gas into the sulfur incinerator through the liquid separator and flame arrester for incineration treatment. The exhaust gas meets the requirements of non-methane total hydrocarbons less than 120 mg/m3 and removal. Requirements for 97% division rate.
Waste gas treatment of sewage treatment plant in chemical enterprises. At present, low temperature catalytic oxidation technology is widely used in waste gas purification and treatment of sewage treatment plant. The principle of this technology is that VOCs undergo oxidation reaction at 250-450 C and under the action of catalyst to produce water and carbon dioxide, so as to achieve the purpose of destroying treatment. The catalysts used include noble metal catalysts, such as honeycomb Pt/Pd noble metal catalysts. After catalytic oxidation, the removal rate of VOCs in waste gas is more than 97%, benzene concentration is less than 4 mg/m3, toluene concentration is less than 15 mg/m3, xylene concentration is less than 20 mg/m3 and VOCs concentration is less than 120 mg/m3.
VOCs emission during loading and unloading. Because the concentration of VOCs is over 200 000 mg/m3 in the initial stage of loading, VOCs must be treated. For example, when benzene products are loaded on Railway in a chemical enterprise, VOCs treatment adopts the combined process of "low temperature diesel oil absorption + membrane separation + activated carbon adsorption". Low temperature diesel oil was used as absorbent, and the temperature of diesel oil was not more than 30 C. Membrane separation was carried out through treatment.
More than 80% of VOCs can be recovered and reused when the mixture of oil, gas and air is discharged and the organic waste gas is returned to the tank. The basic principle is that the VOCs concentration in the exhaust gas is less than 120 mg/m3 and benzene concentration is less than 4 mg/m3 by selective permeation of organic gas/air mixture driven by a certain pressure difference, taking advantage of the preferential permeability of special polymer membranes to organic chemicals.
4.4 Enhancing Environmental Monitoring Capability
At present, VOCs environmental monitoring capability is one of the shortcomings in the management of chemical industry parks. It is urgent to strengthen the environmental monitoring team and capacity building. First, each park should set up VOCs monitoring posts, equipped with a certain number of laboratories and portable VOCs analysis instruments, so as to facilitate VOCs monitoring and monitoring in the production links of chemical enterprises; second, enterprises should strengthen the operation and maintenance management of online monitoring equipment, regularly calibrate and compare online instruments, timely maintenance of abnormal data, timely upload of relevant vouchers, and ensure the validity of data. Transmission. Third, we should improve the capacity building of emergency monitoring and gradually equip environmental monitoring UAV and other atmospheric emergency monitoring instruments to achieve emergency monitoring of key enterprises and sensitive points inside and outside the park.
4.5 Strictly Control Environmental Access of Enterprises in Park
Strictly implement the environmental assessment of chemical park planning and accelerate industrial transformation and upgrading. In the design and construction of new, reformed and expanded petrochemical projects, enterprises should select advanced clean production and sealing technology, improve design standards, realize the sealing of equipment, devices, pipelines and sampling, reduce VOCs leakage from the source, and adopt efficient VOCs recovery and treatment technology to improve the efficiency of waste gas emission reduction in process, storage, loading and unloading, waste water, liquid and slag treatment to meet the requirements. The National Pollutant Discharge Standards for Petrochemical Industry and the Pollutant Discharge Standards for Synthetic Resin Industry have effectively improved the environmental quality around the park.
4.6 Step by step to promote VOCs information declaration
Chemical enterprises should regularly report VOCs and toxic and harmful substances emission information to the park management committee and local environmental protection departments. Organized emission should specify the number and location of exhaust cylinders, pollutant types, emissions, concentrations and estimation methods, and unorganized emission should specify the emission location, emission rules and emission estimation methods. The basic information of annual operation, treatment efficiency, emission concentration and emission reduction of VOCs treatment facilities should be clarified.
5 Concluding remarks
(1) Chemical enterprises should incorporate VOCs monitoring into their daily production management system. Establish dynamic files of basic data and process management, operating accounts of VOCs pollution prevention and control facilities, regularly carry out LDAR work, formulate measures to prevent and deal with sudden VOCs leakage, and incorporate them into the enterprise emergency plan system.
(2) Establish VOCs monitoring and monitoring system in chemical industry park, which accords with VOCs emission characteristics of the park. Enterprises are urged to carry out annual monitoring of import and export of VOCs waste gas treatment facilities and concentration monitoring of factory boundaries in order to achieve VOCs control.
(3) According to the types and concentration of VOCs, the reliable and stable combination technology and equipment for VOCs treatment can effectively reduce the total VOCs emissions in chemical industry parks and the pollution of volatile organic compounds to the environment.
(4) Comprehensive renovation of VOCs in chemical industry parks highlights the project as an important grasp of total VOCs emission reduction, speeding up the construction of VOCs treatment facilities, increasing the assessment of smooth operation rate and compliance rate of treatment facilities, and improving the ambient air quality around the park.