Printing plant organic waste gas biological treatment technology

The discharge of organic waste gas from the printing plant during the printing process consists of two parts: the volatilization of the ink in the printing unit and the emission in the drying box. A large amount of volatile organic waste on the body of workers and the external environment harm, the country has not allowed casual emissions. With the haze hazards in recent years, at present our air pollution is already quite serious, so these emissions should be treated before discharge.

The organic waste gas discharged by the printing plant is characterized by large air volume and small concentration. At present, the treatment technologies mainly include catalytic combustion and adsorption-catalytic combustion. For the more concentrated industrial parks, adsorption and recovery technologies are also adopted. Compared with other organic waste gas treatment processes, the biological process has the advantages of higher treatment efficiency, lower processing cost, simple equipment configuration, secondary pollution, better safety and other characteristics, especially for microbial degradability Good organic matter shows its own superiority. The characteristics of the printing flue gas exactly match the characteristics of the biological flue gas treatment, so the biological oxidation method may become an effective treatment technology of the printing plant organic waste gas, of course, a large number of experimental and theoretical studies yet to be done.

1. The main composition of the printing plant organic waste and biological treatment of the basic principles

The printing machine laminating machine volatile emissions are mainly toluene and ethyl acetate, toluene and ethyl acetate is the use of a wider range of organic solvents exist in many dyes or other solvents, the printing of these two gases accounted for the main component . In addition, benzene, xylene, isopropanol or n-propanol, acetone, butanol, ethanol, butyl acetate, etc., these components are relatively small, but also can not ignore the long-term emissions caused by their harm.

Biological purification is the existence of a microbial oxidation and decomposition process, the growth of microorganisms in the packing layer of organic compounds in the exhaust gas as nutrients, through its own growth and metabolism, to convert them into useless meta-matter CO: and H: 0 Or the constituent substance of the cell. According to the biofilm theory recognized by most people, the decomposition of organic waste gas goes through the following three steps: (1) Organic waste gas enters into the packing layer and comes in contact with water and is continuously dissolved in water; (2) The organic waste gas is diffused into the biofilm with microorganisms under the promotion of concentration difference and captured by microorganisms. (3) The microorganisms make their own growth and metabolism with the diffused organic substances as carbon sources and oxidize and decompose them into CO2 and H2O.

2. Biological method of technology and equipment

The current biological treatment of organic waste gas main processes are biological filtration, bio-trickling and biological washing three processes. In recent years, bio-trickling filter technology in the treatment of organic waste gas is even won the hearts of all researchers, with a more systematic theoretical basis.

2.1 biological filtration process

Exhaust gas enters from the bottom of the tower, passes through the packing layer, and is trapped and digested and decomposed into CO2 and H2O by the microorganisms in the packing layer of Wanfang Data to achieve the purpose of purification. The packing layer of this device is mostly mixed with soil, sawdust, compost, etc. The top of the tower is sprayed with circulating water to provide the microorganisms with the water needed for their growth. Fillers provide a variety of nutrients for microorganisms.

2.2 biological trickling filter process

This treatment device is similar in structure to the filtration device, except that the composition of the packing layer and the spray is the nutrient solution required for the metabolism of the microorganisms. Its filler layer and more of inert materials, such as Raschig rings, gravel, ceramics and so on. Top of the sprinkler spray liquid nutrient solution, first in the filler layer on the formation of biofilm, and then continue to provide nutrients for the film's growth in the film, organic waste gas from the bottom into contact with and spread to the biofilm, by microorganisms Capture decomposition.

3. The latest progress of printing organic waste gas biological treatment

The two main organic waste gases from the printing plant organic waste are toluene and ethyl acetate. Studies by Liu Yonghui and Sun Yumei et al. Have shown that when the mixed gas of toluene and ethyl acetate stays in the filtration bed for 1min, Removal efficiency has reached 90%.

Hua Sulan, Wang Liping and others using toluene-specific strains of bacteria inoculation, the use of biotrickling method can effectively degrade toluene, ethyl acetate and other printing plants in the organic waste gas. When the pollution load to be treated daily is continuously supplied for 8-12h, the total removal efficiency is 85% -90% when the mass flow rate of exhaust gas is 8400L / h, one-week supply is 7d and the total VOC is kept at 550-750mg / m3.

Wu Weijun Experimental study on the use of biofilter to study the mixture of triphenylbenzene showed that the dominant microorganisms degraded by triphenyltetrabromide mixture were used as degrading bacteria and the decontamination efficiency decreased with the increase of inlet concentration and vice versa . When gas residence time was 84.8s, benzene inlet concentration was lower than 132.2mg / m3 and toluene concentration was 418.2mg / m3, the purification efficiency of benzene and toluene for irregular shaped ceramic packing column was also 100%.

SUN Yu-Mei Studies on the Treatment of Mixed Toluene and Ethyl Acetate by Biofilters The results show that the high concentration of ethyl acetate and isopropanol can significantly inhibit the removal efficiency of toluene. Too high concentration of isopropanol can significantly inhibit the biofilter Ethyl acetate removal efficiency.

LI Yun-lu Trituration of Toluene-Containing Exhaust Gas with TITLE Filtration The results showed that the performance of biotrickling filter decreased significantly when the content of N was low, but too much N source did not obviously improve the removal ability. C: N at 17.5 or less microbial toluene removal efficiency was basically stable at 90%.

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