The Status Quo of Pollution and Control of VOCs in Printing Industry in China
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In recent years, the printing industry in China has maintained a steady growth. During the “12th Five-Year Plan” period, the average growth rate of the printing industry reached 9.2%. With the rapid progress of China's printing industry, printing has become one of the major sources of VOC emissions from industrial sources.
1 Status Quo of VOCs Pollution and Control in Printing Industry in China
1.1 Pollution Status of VOCs in Printing Industry in China
The printing industry includes various types of printing processes (printing paper, printing, printing, etc.). There are various kinds of printing inks. According to printing methods, they can be divided into lithography, gravure printing, letterpress printing, and orifice printing. At present, China mainly uses lithography and gravure printing, and the proportion of using green printing technology is relatively low.
From the perspective of printing methods, the VOCs emissions in the field of gravure printing and printed metal cans are the largest: In gravure inks, solvent inks are the mainstream because gravure inks must maintain a good printability and must be added to a large proportion. The organic solvent, so when the print is dry, there will be a large number of VOCs emitted from the ink. Iron products are mainly used in three-piece cans (canned foods, milk powder cans, etc.) and metal lids (easy-opening lids, unscrewing lids, etc.), and conventional printing ink inks have a solid content of 40% to 60%, that is, about 40% in Indian iron inks. The solvent will volatilize to the atmosphere.
Yang Lijun and others investigated the printing enterprises in Guangdong Province: Only a small number of printing companies use environmentally-friendly inks, while more than 70% of companies did not take any control measures for exhaust gases containing VOCs . Through monitoring, the emission concentration of VOCs in the exhaust pipes of some enterprises' workshops is greater than 200 mg/m3 , which is a serious excess discharge.
Through the investigation of 8 printing companies in an industrial park in Chengdu, it was found that 6 of them did not adopt any exhaust gas prevention and control facilities, and only collected organic waste gas from the workshop and then discharged them through the exhaust pipe. After the other two companies collected printing waste gas, The water used to absorb and discharge the emissions can't meet the requirements of relevant emission standards.
Based on the above analysis, printing is one of the major sources of industrial-source VOC emissions and should be controlled with emphasis. However, at present, environmental protection inks are not widely used in the printing industry in China, and most printing companies in China have not adopted effective organic waste gas pollution control measures.
1.2 Status Quo of VOCs Pollution Control Technology in Printing Industry in China
In the source control technology, the domestic mainly through the use of environmentally friendly ink printing process to replace the pollution of the printing process, such as the use of alcohol-soluble ink flexo printing instead of the traditional gravure printing process. In terms of end-of-pipe treatment technology, domestically, granular activated carbon adsorption recovery and honeycomb activated carbon adsorption and concentration-catalytic combustion technology are used for treatment. The use of granular activated carbon adsorption recovery, the recovered mixture contains alcohol and other water-soluble organic compounds, the need for distillation purification, waste gas treatment costs are higher, which has become a bottleneck restricting the adsorption of printing waste gas recovery.
Through the investigation on the status quo of VOCs treatment in printing enterprises in Sichuan Province: A printing company in Shifang, Sichuan Province, was put into operation in 2013. It mainly produces wine labels, wine boxes, printing and processing water pine paper, bottle caps and other products. The organic waste gas from the printing process of the printing shop and carton production workshop and the drying process of the lidding workshop is discharged by the 15m exhaust pipe after being treated by “active carbon adsorption + catalytic combustion”. According to the company's environmental protection acceptance inspection data, the emission concentration of VOCs in the exhaust cylinder is 60 mg/m3, and the discharge rate is 0.255 kg/h. As the country has not yet established a complete emission standard for volatile organic compounds, reference is made to the control standards for volatile organic compounds emissions from industrial enterprises in Tianjin (DB12/524-2014). The company's printing production line VOCs emissions meet the requirements of the printing and packaging industry VOCs permitted in DB12/524-2014. The emission concentration is 100mg/m3 and the maximum allowable emission rate is 2.5kg/h.
A printing company in Chengdu, Sichuan, mainly prints periodicals and newspapers. The company adopts environment-friendly printing ink. VOCs discharged from the workshop are collected by the gas gathering hood. After being adsorbed by activated carbon, they are exhausted through the exhaust pipe of 15m. According to the enterprise's environmental protection acceptance inspection data, the emission concentration of VOCs in the exhaust cylinder is 12mg/m3. Far below the concentration required by the relevant emission standards for VOCs.
In summary, the use of environmentally friendly inks or the use of appropriate mature organic material recovery and processing technologies during the printing process makes it feasible to achieve VOCs compliance.
2 control measures and suggestions
2.1 Improving the Prevention and Control System of Volatile Organic Compounds in the Printing Industry
In May 2013, the Ministry of Environmental Protection issued the “Voice Organic Compounds (VOCs) Pollution Prevention and Control Technology Policy” announcement, which put forward guidance on VOCs pollution prevention and control for the printing industry.
In January 2014, the Sichuan Provincial People's Government issued a circular on the issuance of the Sichuan Province's Air Pollution Prevention Action Plan Implementation Guidelines, with VOCs as total control targets, and proposes that by the end of 2015, conventional ink production facilities with an annual output of 300 tons or less will be eliminated. All ink production facilities without VOCs collection, recovery (purification) facilities, banned the production of benzene-based solvent-based inks . In recent years, Guangdong, Shanghai, and Beijing have successively issued the “Air Pollution Emission Standards for Printing Industry”. However, China has not yet released the general printing industry emission standards. In the face of sustained and rapid development of the printing industry, national or local printing industry should be established as soon as possible. Organic pollutant discharge standards.
2.2 Source Prevention Measures
1) In order to solve the problem of volatile organic emissions in the printing industry, the “fixing” measures are to reduce the use of organic solvents in production. Therefore, the policy encourages the use of environmentally friendly inks certified by China's environmental labeling products such as water-soluble inks, high solid inks, and benzene-free inks.
2) In the printing process, it is recommended to replace the heavily-polluted printing process with a printing process using an environmentally-friendly ink. For example, flexographic printing using an alcohol-soluble ink instead of a conventional gravure printing process can greatly reduce the emission of VOCs.
2.3 End governance and comprehensive utilization
1) Improve the efficiency of waste gas collection and reduce the fugitive emissions of waste gas: Encourage the use of closed integrated production technologies, and collect and process waste gas generated during the printing production process.
2) According to factors such as production concentration of organic waste gas and nature of organic pollutants, adopt appropriate and mature organic waste gas treatment measures.
3) Recycling of VOCs: In the management of VOCs, it is first necessary to consider whether resources can be recycled. It is recommended that printing companies have more concentrated areas, implement unified production and enter the park, concentrate on the establishment of solvent recovery centers, and concentrate on the recovery of solvents.
With the rapid progress of China's printing industry, the pollution of VOCs in the printing industry should be controlled. However, at present, most printing companies in China do not adopt effective organic waste gas pollution control measures. Some printing companies adopt environmentally friendly inks or use appropriate mature organic material recovery and treatment technologies to achieve compliance with VOCs emission standards. China should improve recycling of volatile organic compounds in the printing industry, encourage the use of environment-friendly inks certified by China's environmental labeling products in print production, optimize printing production, adopt exhaust gas collection measures for printing production processes, and collect VOCs before considering recycling. The organic waste gas that cannot be recycled is treated by the exhaust gas treatment device and then discharged to the standard. It actively promotes pollution prevention and control in the printing industry and promotes sustainable development of the industry. The successful application of environmental protection inks to various printing processes and the strengthening of waste prevention and treatment for printing companies are the development goals of the printing industry in the near future.