Research On Control Of Volatile Organics Pollution For Typical Printing Enterprises

With the rapid development of science,technology and economic globalization,the printing industry in China has developed quickly.All of those have made China a leading position of printing industry in the world.Meanwhile,with the growth of the awareness of environmental protection,the pollution caused by organic solvents such as ink and thinners used in the printing process has also attracted the attention of the government and relevant departments.After the "Twelfth Five-Year Plan",the printing industry has become a key industry for the control of volatile organic compounds in China.However,the control of China on VOCs is still predominated by terminal emissions points and lack of overall awareness of environmental friendly production.Therefore,the research on the control of volatile organic pollutants in green printing enterprises has a positive significance on promoting the sustainable development of printing industry in China.This paper focuses on the VOCs emitted by the printing industry,and starts research on the control of VOCs in green printing enterprises from four aspects:Pollution Production,Process Control,Environmental Benefits of End-control Technology and Total Emissions.Taking comprehensive analysis on printing ink product formula and typical enterprise on-site sampling results can confirm the proportion of the discharge process on each process of printing.Under certain conditions,three-dimensional large eddy simulation was performed using aerodynamic CFD(computational fluid dynamics)software combined with the field measured data.Simulate the appropriate air volume of the external suction hood of a single color machine for solvent-based ink printing plants and water-soluble ink printing plants under specific conditions.This simulation can provides the data support for the placement of an external suction hood during the printing process control.Based on methods of the cross-media environmental benefit analysis,taking the exhausted?Gas condition and the power consumption of the end equipment as reference,the comprehensive environmental benefit evaluation and comparison of the VOCs end prevention technology was carried out to guide the end technology selection of the printing enterprise.From the perspective of emission standards,we calculate the total amount of pollutants produced by printing enterprises and take integral control over printing companies in conjunction with relevant national standards.The results show that the key process with pollution discharge of printing enterprises is the drying and the non-organized diffusion of ink trough.Moreover,the VOCs generated by gravure enterprises in the drying and printing sectors account for more than 80%.In the printing process,both solvent-based printing companies and water-soluble printing companies should install an external suction hood beside the ink tank of the printing press due to the volatilization characteristics of the ink.According to the three-dimensional large eddy simulation experiment,it is recommended to install a fan with 5000m3/h air volume next to the monochrome machine to collect the exhaust gas if the VOCs component of the ink in the monochrome machine is more than 0.35kg/m2 per unit time.In addition,since the density of the volatile organic compounds in the ink is high and there is a tendency that it will deposit in the air during the volatilization process,in order to collect the exhaust gas with no tissue diffusion in the ink tank,such external suction hood should be installed between the ground and the ink tank.Different ethnologies of end treatment have different environmental benefits according to various pollutant emissions situation of companies.Based on the theory of life cycle time,from the photochemical ozone point,this paper calculates that if a water-based flexographic printing uses catalytic combustion technology as the end treatment technology,the potential photochemical ozone generated by the untreated pre-exhaust gas and the end treatment facility itself is 254 kg/year.The potential photochemical ozone caused by power consumption is 1025 kg/year.The potential photochemical ozone generated by the end treatment facility itself is much larger than the photochemical ozone potential generated by the untreated pre-exhaust gas,which indicates that the end treatment technology does not improve the environmental benefits from the viewpoint of photochemical potential.Therefore,it is recommended that enterprises should pre-evaluate the environmental benefits according to their own production status before selecting the end treatment technology,as well as select the appropriate end treatment technology.In addition,it is suggested that the emission standards of China's printing industry should propose different emission limits in accordance with different processes in the future to achieve accurate supervision of VOCs pollution prevention and to control different printing processes in the whole industry.At the same time,it is found that both VOCs emission allowance calculation methods based on emission limits and material balance have mutual advantages and disadvantages.In the subsequent research,targeted improvement is needed to further improve the green printing enterprise standards.