Pollution Status and Control Countermeasures of VOCs in China's Printing Industry
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The printing industry is a typical source of volatile organic compounds (VOCs). Summarized the pollution control regulations and policies of VOCs in the printing industry of the United States, the European Union, and Japan, as well as pollution control technologies, and studied the pollution status of VOCs in China's printing industry. On the basis of the above, some suggestions for the pollution control of VOCs in the printing industry in China were put forward.
In recent years, China's printing industry has maintained a steady growth trend, and has become the world's fourth largest printing market after the United States, Japan, and the European Union, and has made tremendous contributions to the rapid development of China's economy. At the same time, printing materials such as printing inks, adhesives, and cleaning agents are consumed in large quantities, and many VOCs are emitted during the production process. Among them, ethyl acetate, toluene, xylene, acetone and other substances are toxic, causing great harm to the human respiratory system, liver and nervous system. At the same time, these substances also have strong photochemical activity, which can cause photochemical smog, organic aerosols and excessive ozone concentration in the near-surface layer, leading to deterioration of regional ambient air quality.
The pollution problem of VOCs in the printing industry is gradually attracting the attention of the government and industry sectors. During the "Twelfth Five-Year Plan" period, China will launch the prevention and control of such pollution for the first time in key areas. At present, there are still many problems in the prevention and control of pollution in the industry, including insufficient control of the quantity, types and main sources of pollution of VOCs, lack of control measures such as standards, management systems and strategies, and related clean production and end-of-pipe technology development. behind. Compared with China, the printing industry in the United States, the European Union and Japan has developed and implemented a series of laws and regulations on pollution prevention and control of VOCs in the printing industry, which promoted the development and application of advanced processes and end-of-pipe treatment technologies, and achieved the reduction of VOCs pollution. According to reports, the total amount of VOCs released by Japanese printing inks decreased from about 130,000 tons in 2000 to 73,000 tons in 2008 [6]. The emissions of VOCs in the US printing industry decreased from 330,000 tons in 1980 to 130,000 tons in 2009, with an average annual reduction rate of 3.2%. The emissions of VOCs in the 27 member states of the European Union during the period of 1999-2009 have remained at the level of 20-255,000 tons, basically achieving the containment of pollution growth trends.
The experience of reducing emissions in Europe, America and Japan can provide valuable experience for China's future prevention and control of VOCs in the printing industry. The author summarizes the pollution control measures and control technologies of VOCs in the printing industry in the United States, the European Union, Japan and other developed countries, analyzes the pollution status of VOCs in the printing industry of the country, and proposes countermeasures for pollution control in light of the actual situation in China, with a view to comprehensive prevention and control of the industry. Provide a certain reference.
1 Foreign printing industry VOCs pollution control measures and technology
1.1 pollution control measures
1.1.1 United States
The United States was the first developed country to conduct pollution control of VOCs. In order to effectively control the pollution sources of industrial VOCs including the printing industry and promote the national standard of ozone concentration in the whole federal state, the US Air Pollution Control Law [Clean Air Act] stipulates that the Environmental Protection Agency (EPA), state and local environmental protection departments must Develop and promulgate RACT regulations, pollution source emission standards, NewSource Review and Permits.
The RACT regulations are technical regulations for existing sources of pollution in ozone-deficient areas. RACT refers to reasonably feasible control technologies and is a general term for a type of technology that EPA chooses for its technical and economic considerations.
The RACT technology is designated by the EPA and is published to the State and Regional Environmental Protection Agency in the form of a Control Technical Guide. The State and Regional Environmental Protection Agency's Reference Guide identifies the RACT regulations in the region. In 1978, the EPA first published the "Technical Guide for Control of Flexible Packaging Printing Industry". In 1993, it released another "Technical Guide for Offset Printing and Stamping Control", which became the direct basis for most state and regional RACT regulations. As of 2006, when the EPA revised the above guidelines to improve the reduction requirements, there were 17,34 state and regional agencies in the Commonwealth, which issued the RACT regulations for the offset/emboss printing industry and the RACT regulations for the flexible packaging printing industry. The regulations mainly stipulate the VOCs content of printing consumables and the purification efficiency of exhaust gas from printing facilities. The regulations in some regions are shown in Table 1.
Compared with existing pollution sources, the United States has stricter control over new sources. From 1982 to 1984, the EPA introduced two new pollution source implementation standards—“Emission Standards for Gravure Coating Printing of Flexible Vinyl and Polyurethane Products” and “Emission Standards for Gravure Printing of Publications”. The VOCs emissions of the relevant equipment are required to be less than 1kg/kg solids use and 16% solvent use, and the requirements for VOCs emissions detection methods, procedures, cycles, data records and reporting are specified. In 1996, the EPA established the “Determination of Hazardous Air Pollutants in the Printing and Publishing Industry”, which targets harmful air pollution based on VOCs such as toluene, xylene, ethylbenzene, methyl ethyl ketone, methanol, ethylene glycol and glycol ethers. (HAP), which stipulates the emission limit based on BACT, the relevant units must adopt BACT technology, so that the HAP emissions of flexible packaging printing and publication gravure printing process are less than 5% of their raw material usage. And 8%.
The new source review is similar to China's environmental impact assessment system. When new or rebuilt a fixed source is used, it must first analyze the new source emissions and report it to the environmental authority for archival purposes. However, the new source review is accompanied by technical regulations requiring that the ozone emission source should be installed with the lowest emission rate (LAER) control technology and the BACT technology installed in the ozone compliance zone.
The sewage permit system is a new management system of the Clean Air Act Amendment in 1990. For major pollution sources (annual emissions greater than 25t), the fixed emission source projects for new, modified and expanded enterprises must meet the new source review and new pollution sources. Construction permits, such as standards and hazardous air pollutant emission standards, can be obtained.
In addition to the above regulations, the United States has also established incentive policies and support programs to encourage and guide corporate pollution control.
1.1.2 EU
The two important control regulations affecting the emission of VOCs in the EU printing industry are the Comprehensive Pollution Prevention and Control Directive (1996/61/EC) promulgated by the Council of the European Union in 1996 and the Solvent Directive (1999/13/EC) of 1999, in which comprehensive prevention and control The requirements of the instructions are more stringent than the solvent instructions.
The Integrated Pollution Prevention and Control Directive requires each member state to implement an emission permit system based on Best Available Technology (BAT) for the printing industry. BAT information is submitted by each member country and is finally released by the EU Council to the member states by reference. [18]. The BAT file contains control technologies for soft-pack gravure and flexo printing, publication rotary gravure, and thermoset web offset printing. The Solvent Directive specifies the emission VOCs emission concentration limits and total solvent escape limits for rotary gravure, thermoset rotary offset printing, rotary screen, composite, etc., and also proposes a new standard of compliance, ie implementation and emission standards. Equivalent reduction plan [19]. After the promulgation of the directive, each member country successively converted it to the national laws and regulations, and issued supporting implementation documents.
Similar to the United States, some EU member states have also established relevant assistance agencies, such as the German Cleaner Production Center, which provides information on clean production technologies and environmental management in the industrial sector. In addition, the EU countries headed by Germany have also strengthened pollution control and control of raw materials and production processes through environmental management system certification, environmental protection equipment certification, and industry initiatives.
1.1.3 Japan
The early VOCs pollution control in Japan began with restrictions on photochemical oxidants and malodorous substances in the Environmental Basic Law and the Odor Prevention Act. In 1994, the "Stench Prevention Law" set the boundary concentration limit for eight substances such as toluene, xylene, ethyl acetate and isobutanol discharged from the printing workshop. In April 2006, the control regulations for industrial VOCs emission facilities were officially implemented. The emission concentration of the drying equipment and gravure drying equipment for rotary offset printing must be less than 0.04% C and 0.07% C (in terms of carbon atoms) [20]. The regulations also encourage other unrestricted facilities to implement independent emission reductions. The planned reduction of VOCs through regulatory regulation and autonomous actions by 2010 should reach the target of 10% and 20% reduction respectively based on 2000. In order to promote the realization of this goal, the Ministry of Economy, Trade and Industry, the Ministry of the Environment and other government departments and the Printing Industry Federation (Emission Reduction Leadership Agency) exchanged industry-wide reduction targets and action plans, issued guidelines for corporate emission reduction actions and conducted “VOCs processing technology demonstrations”. "project.
In addition, the printing industry has developed a series of environmentally friendly ink standards, which have realized the limitation of aromatic hydrocarbons, petroleum solvents and VOCs in inks, and promoted the development and application of soy inks and low-mineral oil solvent inks. Since 2001, the printing industry has successively introduced standards such as "Offset Printing Service", "Gravure Printing Service", "Sticker Printing Service" and "Screen Printing Service", including environmental protection in materials procurement, process and management. The regulations are based on the evaluation of the “Green Printing Factory” certification.
1.2 Control Technology
The United States, Japan, and the European Union mainly treat process waste gas using solvent-based inks and adhesives, such as thermoset rotary offset printing, flexible packaging gravure printing, flexible packaging flexographic printing, publication gravure printing and flexible packaging composite processes, and pollution control technologies including source control. And end governance 2 classes.
In terms of source control technology, the first step is to adjust the raw material formula or adopt an environmentally friendly product replacement. The US EPA has specifically proposed formulation recommendations in the RACT Technical Guide. For example, the alcohol content in the fountain solution for offset printing should be less than 1.6%; when the alcohol content is higher than 3%, it must be stored at 15.5 °C; or 5 % content of glycol ether substitute or alcohol-free fountain solution; cleaning agent requires a vapor pressure of less than 10 mm Hg at 20 ° C or a VOCs content of less than 70% [21]. Another source control measure is process technology improvement. Update related equipment to clean production technology equipment such as water-based flexographic printing, waterless offset printing, digital printing, or sealed storage solvent equipment, solvent pipeline transportation system, automatic ink delivery system, fountain solution circulation purification system and automatic cleaning system To improve the automation and sealing of equipment components, thereby reducing the escape of VOCs.
In terms of end treatment technology, mainstream technologies include combustion method (catalysis, heat, heat storage), activated carbon adsorption, biological method and adsorption-distillation, adsorption concentration-storage combustion, adsorption concentration-catalytic combustion, and other combined process technologies. Generally more than 90% [21-23]. The choice of various VOCs treatment technologies is related to parameters such as exhaust gas composition, concentration, and air volume. For organic waste gas with high concentration but difficult to recycle, thermal combustion and catalytic combustion method can be adopted; organic waste gas with high concentration and single solvent type, such as toluene and ethyl acetate solvent exhaust gas discharged from publication gravure printing and flexible packaging composite process It can be recycled by activated carbon adsorption-distillation purification method; for low-concentration and high-volume printing waste gas, adsorption method, biological method, adsorption concentration-storage combustion or adsorption concentration-catalytic combustion method is suitable.
2 Pollution Status and Control Countermeasures of VOCs in China's Printing Industry
2.1 Pollution status
Since the reform and opening up, China's printing methods are mainly offset printing and gravure printing technology. The application of advanced environmentally friendly flexographic printing and digital printing technologies is very small. Therefore, there is inevitably a problem of large amount of organic solvents volatilizing in traditional printing methods. In addition, the lack of regulations, policies, and technologies for the long-term supervision and control of pollution sources has led to the pollution of VOCs emitted by most printing companies. A survey of printing companies in Guangdong Province found that only a small number of companies use low-VOCs inks at the source to prevent pollution, or install end-technology equipment such as catalytic combustion and adsorption recovery to treat the emissions of VOCs emitted by the production, and about 70%. ~80% of most companies have not taken any waste prevention and treatment facilities. The results of the exhaust gas monitoring of these enterprises show that the total VOCs concentration in the printing workshop and in the shop exhaust is tens to hundreds of milligrams per cubic meter, as shown in Table 2, in which flexible packaging printing and metal packaging printing are used due to the use of solvent-based raw materials. Large, its pollution level is more serious than other printing methods, and exceeds the "Guangdong Province printing industry VOCs emission standards" (DB44/815-2010).
In terms of VOCs emissions, domestic and foreign research scholars mainly use the emission factors of the EU or the United States. The emission factors of various types of printing processes range from 300 to 800 kg/t. The estimation results show that the printing industry in China emits dozens of VOCs per year. Ten thousand tons. Wei Wei and other scholars studied the VOCs content and corresponding product structure ratio information of the main varieties of printing technology inks in China, and took the weighted average of VOCs content and product structure ratio as the VOCs emission coefficient of various inks, and then combined with various types. The apparent consumption of ink was estimated, and the VOCs emissions from the ink use process in China's printing industry in 2005 were about 388,000 tons [24]. Compared with the direct use of foreign emission factors, the uncertainty of the research results is relatively low.
Based on the research methods of Wei Wei and other scholars, the VOCs content of the main varieties of inks, thinners, adhesives and other consumables were collected [25-26], the proportion of product structure and the apparent consumption of various consumables. Volume [27-31], estimated that in 2009 China's printing industry did not consider the control level of VOCs emissions is about 895,000 tons, see Table 3.
Among them, the sector that contributes the most to VOCs emissions is flexible packaging composite adhesives, accounting for 32.49%, followed by ink cleaning agents, ink thinners, gravure inks, other adhesives, offset inks and other inks; The composite process, printing equipment cleaning activities, gravure printing process and thermosetting offset printing process are the most important sources of pollution and should be controlled.
2.2 Control Countermeasures
2.2.1 Conducting investigation and monitoring of VOCs pollution in the printing industry
At this stage, although China has attached importance to VOCs pollution, VOCs have not been included in the daily environmental monitoring and environmental statistics work of China's environmental protection departments, and there are few investigations and studies on VOCs pollution in China's printing industry, which directly affects the industry and government departments. Master the pollution discharge status of VOCs and formulate effective emission reduction measures in a timely manner. Therefore, it is necessary to first conduct extensive investigation and monitoring of VOCs pollution in the printing industry. Master the detailed data and information on the quantity and scale of relevant process types, the VOCs content of raw and auxiliary materials, the types of VOCs emitted, the concentration and pollution control status, etc., in order to formulate relevant emission reduction policies and regulations, and establish a national And lay the foundation for the VOCs emissions inventory of the printing industry at the local level.
2.2.2 Formulate emission standards and compliance technology systems for printing industry VOCs
In recent years, Beijing, Guangdong and other places have issued VOCs emission standards specifically for the relevant printing process, but most of the other regions have not yet developed relevant standards. Faced with the rapid development trend of the printing industry, we should formulate emission standards for VOCs in the printing industry at the national or local level on the basis of the advanced experience of relevant domestic and international standards.
The emission standards should cover important pollution sources such as solvent-based compounding process, gravure printing process, offset printing process and equipment cleaning, and comprehensively stipulate the VOCs content limit of ink, dampening solution, adhesive and cleaning agent, and the organized emission limit of process exhaust. Solvent escape limit, at the same time strengthen the management requirements of the company's production process, to minimize the volatilization of VOCs; it is recommended to add detailed instructions on the standard compliance procedures in the standard, to guide enterprises to implement VOCs emissions estimates, various raw materials VOCs content detection, exhaust emission concentration monitoring, operational efficiency monitoring of pollution control equipment, and data record reporting are conducive to cultivating corporate awareness of compliance, improving the ability of enterprises to control pollutants, and promoting compliance management of environmental protection departments; Most of them are based on technologies such as RACT and BACT. This ensures that the company can meet the standard requirements by adopting the corresponding level of control technology, thus improving the feasibility of the standard. It can be appropriately used for reference. Development situation, unified by the environmental protection department and standards Set of technical guidelines or norms, guide enterprises to cut back on technology.
2.2.3 Construction of long-term management and control mechanism for VOCs pollution sources
Developed countries have a sound management system for the emission control of VOCs in the printing industry, and have promoted the effective implementation of VOCs pollution prevention regulations and policies. The management ideas of VOCs in the printing industry should be appropriately incorporated into the existing environmental management system. The long-term control mechanism of VOCs pollution sources including environmental impact assessment, pollutant discharge declaration and pollutant discharge permit system can be gradually constructed to achieve effective supervision of polluting enterprises and ensure that enterprises meet the standards.
When constructing a long-term management system, it may be considered to supplement the VOCs pollution assessment indicators in the environmental impact assessment system regulations, and to require the VOCs monitoring analysis, prediction and evaluation, and the best when it is required to newly, reform or expand the environmental impact assessment of printed pollution facilities. Prevention and reduction of technical measures; sewage declaration and discharge permit system are important means of supervision and management of pollution sources. In view of the fact that the two systems in China have little practical experience, we can first choose to conduct pilot discharge declaration systems in qualified parks and enterprises. After the trial of the licensing system and successful experience, it will be gradually promoted to the whole country. The discharge declaration is implemented by the printing company to provide the original data, which proves that the VOCs emissions concentration, emissions, pollution equipment control efficiency and other data are true and reliable, and the environmental protection department is responsible for strict verification. The VOCs sewage permit system must follow the principles of certification, evidence-based discharge and total amount control. Based on the identification of existing sources and accurate estimation of emissions, the local VOCs total control targets and distribution reduction targets can be determined. Issue a sewage permit in accordance with legal procedures.
2.2.4 Design incentive policies and support projects
The majority of the printing industry is small and medium-sized enterprises, whose production technology is relatively backward, and it is difficult to raise funds for pollution control, resulting in low governance. In order to encourage the pollution prevention and control behavior of these enterprises, we can refer to foreign experience and design effective VOCs prevention and control policies and support projects. For example, it provides: financing channels, financial subsidies and tax incentives for enterprises that introduce advanced clean production and end-of-pipe treatment equipment, research and development of new technologies, new processes, and new materials, and environmental protection; priority is given to environmentally friendly government procurement activities. Enterprises; increase the penalties for illegal sewage companies, and the government departments organize other departments to carry out support projects, such as consultation and recommendation of pollution prevention technical information.
2.2.5 Develop advanced VOCs pollution control technology
The overall level of pollution control technology in China's printing industry is relatively backward, which is reflected in the weak research and development capabilities of environmentally friendly raw materials, green printing technology and organic waste gas treatment technology. To this end, in the future, we should strengthen cooperation between the printing industry and research institutes, printing equipment manufacturing, ink manufacturing, organic waste gas treatment and other departments, integrate the advantages of all parties, and enhance the R&D and innovation capabilities of advanced clean production technologies and end-of-pipe treatment technologies. On the other hand, it is important to vigorously promote the VOCs pollution prevention technology equipment that is relatively mature at home and abroad, such as adsorption, adsorption concentration-catalytic combustion, adsorption concentration-storage catalytic combustion method.
2.2.6 Promote environmental certification work
Environmental certification can improve the quality of products and environmental management within the certification company. By standardizing the certification process of printing industry environmental labeling certification and ISO14000 environmental management system certification, enterprises are encouraged to carry out certification work, and promote the integration of environmental protection and circular economy ideas into the decision-making of production, operation and management of enterprises, in product procurement and design. VOCs pollution prevention and control in all aspects and processes of processing, transportation, sales and waste disposal.
3 Conclusion
The experience of Europe, America, Japan and other countries proves that the prevention and control of VOCs pollution in the printing industry is a long-lasting and arduous system engineering, and also an important opportunity to promote the long-term healthy development of the industry. China should carry out systematic and in-depth industry VOCs emission investigation and monitoring, focus on formulating a set of comprehensive emission standards and technical assistance systems for compliance, and gradually improve management, policies, projects, technologies, certifications and other means to actively promote the pollution of VOCs in the printing industry. Prevention and control work to promote sustainable development of the industry.