Study On Analytical And Removal Method For Gas Emission In A Resin Plant

The environmental problems,especially the air pollutions have become a great concern due to the frequent occureances of fog in many Chinese cities.In addition to the emission from daily life,winter heating and transportation,industrial waste gas is one of the main causes of air pollution.In the paper,the exhaust gases from a resin plant are systematically tracked and tested.Chlorinated hydrocarbon volatile organic compounds are found in the exhaust components of the resin plant,which are difficult to degrade in the air and easy to accumulate causing serious harm to human beings.Therefore,it is urgent to detect and effectively deal with the volatile organic compounds in the process of resin plant.However,there are few literatures on the detection and treatment of volatile organic compounds in the vinyl chloride-vinyl acetate copolymer resin.In this paper,the volatile organic compounds in the production-process were tested based on the actual situation of the resin plant.And the trichloroethylene is chosen as the template molecule to study the removal technique of the waste gas from vinyl chloride-vinyl acetate copolymer resin plant and it is hoped that the new technique can create a good working environment for factory workers and reduce the waste gas emission.The main contents include the following aspects:（1）According to the production-process of the vinyl chloride-vinyl acetate copolymer resin,the possible volatile components in this resin company were identified and the simulative standard mixed gases were prepared.And the methods for sampling and determination are optimized by using the simulative standard mixed gases.It was concluded the PVF air bag sampling method was the most appropriate one,as which exhibited a high sampling efficiency（99%）and the gas samples can be stored at 25?C for 5 days.Analysis of the mixed gas was conducted on the Agilent OV-17 chromatographic column,with oven temperature at 110?C and vaporizing chamber temperature at 90?C,and negligible interference of acetic acid,acetaldehyde,and butanol were observed.The exhaust components of the resin plant were sampled and determinated in the optimized conditions.The results show that the main components are consist of chloroethylene,isopropanol,vinyl acetate and trichloroethylene in the gas stripping process,of which the concentration as high as 7280mg/m³ was detected for chloroethylene.The main components in the scrubbing-and-drying process are isopropanol,chloroethylene,vinyl acetate and trichloroethylene,of which the highest concentration of 168.9 mg/m³ was detected for isopropanol.（2）Based on the determination results,an absorption method was initially proposed for the removal of VOCs.The tricloroethylene was chosen as the model molecule for the lab scale experiments.The absorption of trichloroethylene was studied by using sodium dodecyl sulfate（SDS）,hydroxypropyl-β-cyclodextrin,polyethylene glycol-600（PEG-600）and surfactant PeregalO-25 solution.The results show the highest removal efficiency was obtained by using the surfactant PeregalO-25 solution.The effects of the peregalO-25concentration,temperature,the quantity of surfactant solution,and the concentration of trichloroethylene on the removal rate were comprehensively investigated.The increase of the peregalO-25 solution quantity was found to be effective for the increase of removal rate.A removal rate as high as 90%was achieved for 5374 mg/m³ of trichloroethylene by using more than 70 mL 0.07 mg/mL（5CMC）peregalO-25 solution（at≤4.29 liquid-gas ratio）.Moreover,the effect of same liquid-gas ratio at different gas velocity on the removal of trichloroethylene was studied.It is significative that the conclusion was abtained that the same liquid-gas ratio could result in the same removal rate for trichloroethylene.The appropriate equipment can be designed and the optimum absorbent quantity can be calculated for the specified emission velocity.The conclusion also reveal when 50 mL 0.07 mg/mL（5CMC）peregal O-25 solution was used（at 6 liquid-gas ratio）,a removal rate greater than 80%can be maintained for at least46 h for 300 mL/min 5374 mg/m³ trichloroethylene,suggesting that the method proposed in this work is promising for industrial application.（3）To overcome the possible secondary pollution from the absorption method,the catalytic combustion method for trichloroethylene was studied.According to the literature and pre-experiment,the catalyst RuO₂ supported by ceria–zirconia mixed oxide was prepared for the degradation of trichloroethylene,which were prepared by impregnation of Ru on the hydrothermally synthesized CeZrO_X at different molar ratio of Ce/Zr（12:0,8:4,6:6,4:8,0:12）and the quantity of Ru（0.5 w.t%,0.9 w.t%,1.4 w.t%）.The resultant products were systematically characterized by ICP,XRD,SEM/EDS,H₂-TPR,NH₃-TPD and XPS.XRD patterns of the catalysts revealed Zr ions were incorporated into CeO₂ lattice to form Ce/Zr solid solution.XPS results showed there were highest Ce³⁺（26.6%）and adsorbed O（40.1%）in0.9Ru/Ce₂Zr₁,which made contribution to the catalytic performance.It was proved by H₂-TPR and NH₃-TPD that the presence of Zr contributes to the increments of acid properties of catalysts,which was in favour of the adsorption of trichloroethylene.The effects of molar ratio of Ce/Zr mixed oxide,the quantity of Ru and the calcination temperature（200?C,300?C,400?C,500?C）on the catalytic performance were studied.The results showed that the trichloroethylene removal rate was enhanced by introduction of RuO₂,when the molar ratio of Ce/Zr was 8:4,the quantity of Ru was 0.9 w.t%,and the calcined temperature was at 400?C,the removal rate of 90%were reached for trichloroethylene.The sufficient RuO₂ were formed when the catalysts were calcined temperature was at 400?C,which contributed to Deacon reaction and enhanced the stability of catalysts.A removal rate of 90%was achieved at 250?C for 5374 mg/m³ trichloroethylene on the 0.9Ru/Ce₂Zr₁ and the stability of the catalysts was investigated on the condition.The results show this high removal rate can be maintained for at least for 90 h,and it is proved the highest stability for 0.9Ru/Ce₂Zr₁ compared with other catalysts in the recent literature for catalytic combustion of trichloroethylene.