Microwave Catalytic Combustion VOCs Exhausting From Printing And Packaging By Pilotscale And Field Test

Emission of volatile organic compounds（VOCs）is one of the major contributors to haze,photochemical smog,ozone layer depletion and greenhouse effect,and seriously harm to both the environment and human health.At present,VOCs are mainly emitted from different industrial sources that including petroleum refining,chemical synthesis,oil storage and transportation,printing and packaging and industrial coating.The Ministry of Ecology and Environment has issued the"Comprehensive Treatment Plan for Volatile Organic Compounds in Key Industries"to reduce VOCs emission and implement end-of-pipe treatment simultaneously.Catalytic combustion has been considered as one of the most promising methods for the elimination of VOCs with different concentration and flow rates and has the advantages of non-selectivity and highly reduction rate.Microwave is a kind of electromagnetic energy.Dipoles of polar substance are polarized in an electromagnetic field,which converted electromagnetic energy into thermal energy.Microwave catalytic combustion is a new catalytic combustion technology that combining microwave irradiation with microwave-absorbing catalyst closely.Based on the development of microwave catalytic combustion device and the exploitation of monolithic honeycomb catalysts of both Pt-CuMnCeO_x/cordierite and Pt-CuMnCeO_x/nano ceramic,the pilotscale experiment was carried out in the laboratory to investigate the oxidation effect of two catalysts on multi-component VOCs and this new technology was applied to treat volatile organic compounds（VOCs）exhausting from a printing and packaging factory.Subsequently,surface morphology,specific surface area and crystal structure of the catalysts were characterized in this study.On the basis of pilotscale and field test,the following results are obtained:（1）The SEM micrographs and BET data indicated that the existence of Mn₃O₄/Mn₂O₃,Ce O₂/Ce₂O₃,Cu Mn₂O₄ and Pt O spinels reduced reaction temperature and improved oxygen reserving-releasing ability and catalytic activity of the catalysts greatly.The mesoporous structure and abundant specific surface area of the catalysts were beneficial to the diffusion of pollutants in the inner pores and could prolong the retention time of targets on the surface of the catalysts simultaneously.（2）The catalytic oxidation of toluene,acetone and ethyl acetate mixture over Pt-CuMnCeO_x/cordierite and Pt-CuMnCeO_x/nano ceramic catalyst were studied in the laboratory,then the following order was established:ethyl acetate>toluene>acetone for Pt-CuMnCeO_x/cordierite,and toluene>ethyl acetate>acetone for Pt-CuMnCeO_x/nano ceramic catalyst,respectively.In addition,when the bed temperature was at 400℃,the order of catalytic activity of acetone in the binary mixture（toluene and acetone）was slightly lower than in the ternary mixture（toluene,acetone and ethyl acetate）for Pt-CuMnCeO_x/cordierite,and Pt-CuMnCeO_x/nano ceramic showed the opposite order of acetone.However,the orders of catalytic activity of toluene in the binary mixture were slightly higher than in the ternary mixture for both two catalysts.（3）Field test showed that the initial concentration of VOCs was one of the most influencing factors in VOCs destruction,and VOCs exhaust with medium and high concentration exhibited the highest conversion,when the catalyst had sufficient active sites during reaction.More heat is released from higher-concentration VOCs exhaust,which can increase the bed temperature and improve VOCs removal rate.When the intake air volume was 565 m³/h,the removal rate could be stabilized at about 80%,however,when the air intake volume reached 600 m³/h and 712 m³/h,the removal rate was unstable,60%～80%and 40%～90%,respectively.This result indicates that the gas flow rate not only affects the stability of the removal rate,but also affects the level of the removal rate.The research work in the paper confirms that the new technology of microwave catalytic combustion is suitable for the treatment of VOCs with medium or high concentration while sufficient active sites are provided onto the surface of the catalyst.Simultaneously,heat release from VOCs combustion can maintain high temperature of catalyst bed so that additional energy do not need to be provided that saving energy and reducing cost in the operation.This study carves out a new way for the treatment of VOCs from printing and packaging industry.