| With the rapid progress of China’s urbanization and industrialization,human activities such as energy use,industry and transportation have released a large number of pollutants into the atmosphere.In addition to conventional atmospheric pollutants,the emission of volatile organic compounds(VOCs)has attracted growing attention.VOCs are key precursors of atmospheric ozone and secondary organic aerosol pollution,and an important cause of formation of haze and photochemical smog.VOCs also have high-risk biological toxicity,which is potentially harmful to human health and plant growth.Among the numerous emission sources,industrial emission is an important source of VOCs pollution in the environment.Therefore,the control of VOCs emission from industrial sources will be conducive to reducing the concentration of PM2.5 and O3,which is particularly important for the improvement of the regional atmospheric environment.China’s existing VOCs waste gas treatment mode is“one enterprise one policy”,that is,each enterprise is responsible for its own waste gas treatment.However,for some small enterprises with irregular VOCs composition and concentration,their waste gas treatment effect cannot be guaranteed because of their limited technical and economic capacity,and lack of effective supervision.If the VOCs waste gas can be centralized for unified treatment,it will not only reduce the economic burden of enterprisesbut also facilitate the supervision.In this thesis,we analyze the centralized treatment of VOCs waste gas with high air volume and low concentration in industrial concentration area from the perspectives oftechnical,environmental and economic feasibility.On one hand,life cycle analysis(LCA)is used to evaluate the environmental impact of VOCs processing systems with different technologies and materials;On the other hand,CBA is used to evaluate the economic performance of industrial VOCs centralized processing mode.Modeling and simulation based on different processing technologies and operation modes were carried out in this thesis.Comprehensive studies on VOCs centralized processing mode were conducted from multiple perspectives of technology,environment and economy.The results could provide theoretical supports for the selection of technology,auxiliary materials and centralized treatment scheme of VOCs exhaust gas treatment in industrial concentration area from the perspective of sustainable development of environment and economy.This study provides scientific basis for industrial VOCs exhaust gas centralized control and emission reduction,and has important social and economic benefits.This paper mainly contains the following four contents:1.Based on the investigation of theindustrial VOCs emission sources of China,three organic compounds such as toluene,ethyl acetate and acetone are selected as the typical volatile organic compounds.In order to simulate the VOCs waste gas with large air volume and low concentration,the total concentration of VOCs was set as 350mg/m~3,among which the initial steam concentration of toluene,ethyl acetate and acetone were 100 mg/m~3,140 mg/m3and 110 mg/m3,respectively.The air volumes of the four pollution sources were set as 50,000 m3/h,8,000 m3/h,5,000 m3/h and 3,000m3/h,respectively.Two integrated technologies,adsorption-catalytic oxidation and adsorption-condensation recovery,were selected as the technical schemes of the VOCs treatment system according to the comprehensive analysis of air volume,composition,properties,temperature and pressure.Activated carbon and zeolites were selected as adsorbents and CuOwas selected as the catalyst.According to the relevant national regulations and technical schemes,the equipment components in each stage of the treatment process are selected and designed,and the VOCs treatment model is constructed.2.In order to simulate the actual technological process of VOCs waste gas treatment,laboratory simulation was divided into the following units:VOCs generation unit,absorption/desorption unit,catalytic oxidation unit,condensationunit.In addition to the adsorption-desorption process,the production of activated carbon and zeolite were included in the absorption-desorption unit.And the production of catalyst was also included in the catalytic oxidation unit.The performance of four different processing systems was analyzed in detail,and the specific data of material flow and energy flow of four processing systems were summarized,which provides data support for the compilation of life cycle inventory.3.The VOCstreatment processes were analyzed by LCA software simapro8 based on the experimental simulation data and the Eco-invent database.The environmental impact and energy consumption were evaluated by ReCiPe Midpoint(H)V1.09/World Recipe H method and energy balance calculation.Three major categories and eight environmental impact categories of VOCs treatment system are determined according to pollutant emission:energy-related impacts(climate change,fossil energy consumption),health-related impacts(human toxicity,particulate matter formation,terrestrial ecotoxicity,freshwater ecology toxicity)and other effects(acidification,freshwater eutrophication).The results show that the environmental impact of VOCs integrated treatment is mainly reflected in human toxicity potential,particulate matter formation and fossil energy consumption.Among all impact categories,human toxicity showed the most serious impact in allscenarios,accounting for 63.9%,68.2%,67.5%and 71.8%of the total environmental impact,respectively.Power consumption,waste/by-products and material production have the greatest impact on climate change,fossil energy consumption,human toxicity,particulate matter formation,terrestrial ecological toxicity and freshwater ecological toxicity.Land acidification is mainly affected by material production,waste/by-products and equipment manufacturing,while freshwater eutrophication is mainly caused by material production and equipment manufacturing.Usually,it is equipment manufacturing and material production.The results show that the adsorption-condensation recovery process is superior to the adsorption-catalytic combustion process and the zeolite adsorbent is superior to the activated carbon adsorbent in terms of energy consumption and environmental impact.4.The technical and economic feasibility of VOCscentralized treatment in industrial concentration areas was explored in terms of the life cycle environmental impact assessment.Two centralized schemes,direct centralized and multi-split centralized,were designed.Three scenarios using different centralized schemes and technologies were established,namely baseline scenario(BS),energy cycle scenario(ERS)and material cycle scenario(MRS),respectively.The economic performance of each scenario was compared and analyzed by using the cost-benefit method.In ERS scenario,the operation cost was reduced by using multi-split centralized scheme,because of the optimizing of gas centralized mode and reducing of power cost of waste gas transportation.Its operation cost was 69%of that of direct centralized scheme and its economic performance was better.The operation cost of ERS multi-split centralized scenario was 11.8%lower than that of BS scenario and providing a cost advantage.The total cost of BS scenario was 17.6%and 24%higher than that of ERS and MRS as the multi-split centralized scheme was used in these two scenarios respectively when the expected revenues were included.And the total operation cost of MRS scenario was5.9%lower than that of ERS,indicating that the condensation recovery technology was more cost-effective than catalytic oxidation.The operation cost of adsorption unit was the highest in the BS and ERS scenarios,mainly due to the contribution of adsorbent replacement and power consumption.Next was the gas collection unit,mainly from the replacement of the cost of filter cotton.In MRS scenario,operation costs mainly come from adsorption unit and desorption unit. |
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