| Cooking oil fumes has become an important precursor of the air pollution in China,and a danger source to the human health.Thus,it is an urgent work to purify and control the cooking oil fumes.The high temperature cooking with Chinese characteristics makes the fumes with complex composition,including gas,liquid and solid.Especially,the cooking oil fumes pollution is tremendously serous in catering enterprises.At present,it is hard to achieve the desired effect with a single purification technology.Therefore,multiple purification technology and devices should thus be developed to treat with the cooking oil fumes.This dissertation aims to construct a purification treatment system of cooking oil fumes from the perspective of device design and material synthesis through technological innovation.Moreover,it is also trying to introduce gas sensing technology into the oil fumes purification system,and develop an intelligent purification mode of cooking oil fumes.The detail content and results were listed below.1.Design and application of a rotary grease separating filter(1)A monolayer rotary grease separating filter was desinged,and used for the separation of grease particulate matter in a home-made grease separation test system.Two important variables of pore diameter and rotate speed were investigated on grease separation and particulate matter interception.The results showed that grease separation was increased with the increase of rotate speed under the same pore diameter filter,and a high rotate speed was favor of the removal of PM10,PM2.5,PM1 and PM0.1.Moreover,reducing the bore diameter of the filter effectively increased the probability of physical collision between filter and particulate matter under a high rotate speed,and thus enhanced the grease separation and particulate matter interception.Significantly,the grease separation reached 96.5%with 1300 r/min rotate speed and 0.73 mm pore diameter.In addition,the grease particulate matter attached on the filter can easily be thrown out by centrifugal force,and thus keeping the filter clean and not blocked.(2)Numerical simulation of the oil and gas flow was carried out in a range hood with the rotary filter,and to observe the motion state of grease particulate matter.The simulation results showed that rotary filter effectively intercept the grease particulate matter,but a dead angle existed and caused the secondary escape of grease particulate matter.Therefore,the simulation results can be used to optimize the range hood.(3)A coaxial-heterodromous double layer rotary grease separating filter was designed through the cooperation of two pairs of gears.The filter with double layer structure further increased the probability of physical collision between filter and particulate matter,and made the particulate matter stay longer in the positive and negative airflow vortex,thus effectively intercepting the particulate matter.Moreover,by adding the spoke with oil groove structure into the filter and tilting the filter,the grease particulate matter attached on the filter can more easily be thrown out,and thus keeping the filter clean.2.Intensification of VOCs absorption by a co-current rotating packed bed and degradation of organic wastewater by Fenton-like catalysis(1)A co-current rotating packed bed was designed and applied for the removal of volatile organic compounds(VOCs)by sodium hypochlorite and sodium dodecyl benzene sulfonate from air stream.Xylene was used as the model VOC.The effect of different variables on xylene removal efficiency and overall mass transfer coefficient were investigated,and the obtained results were used to evaluate the treatment ability of the co-current rotating packed bed.The results showed that the xylene removal efficiency was increased with the decrease of pH and gas flow rate,and increased with the increase of liquid flow rate,NaClO concentration and rotational speed.In addition,the surfactant of SDBS effectively increased the removal efficiency.Moreover,a correlation for overall mass transfer coefficient of the co-current rotating packed bed was proposed by fitting the experimental data,which was in good agreement with the experimental data(the deviation?±30%).(2)Magnetic porous Fe3O4/carbon octahedra were constructed by a two-step controlled calcination of iron-based metal organic framework.Significantly,the porous Fe3O4/carbon octahedra showed efficiently heterogeneous Fenton-like reactions and good recyclability for decomposing the organics in wastewater.The good Fenton-like catalytic performance of the as-synthesized Fe3O4/carbon octahedra was ascribed to the unique mesoporous structure derived from MOF-framework,as well as the sacrificial role and stabilizing effect of graphitic carbon layer for preventing ?Fe2+ from oxidation.Moreover,the mesoporous structure was favor of the electron transfer,further enhancing the Fenton-like performance.3.Synthesis and application of ZnO-based gas sensing materials(1)Hierarchical hollow ZnO nanocages were synthesized by a facile strategy through the simple and direct pyrolysis of Zn-based metal-organic framework.The obtained hollow structure processed meso-/macro-porous channels and facilitated the diffusion and surface reaction of gas molecules.Moreover,the porous hollow structure was favor of the exposure of active sites and oxygen vacancies,thus enhancing the sensitivity of low-concentration VOCs.The results showed that the ZnO hollow nanocages perform sub-ppm level sensitivity with 2.3 ppm-1 towards 0.1 ppm benzene,and ppb level sensitivity with 15.3 ppm-1 towards 50 ppb acetone,respectively.(2)The hollow ZnO/ZnFe2O4 microspheres with heterogeneous structure are synthesized by direct pyrolysis of metal-organic frameworks.Interestingly,the hollow ZnO/ZnFe2O4 microspheres based gas sensors show interestingly temperature-dependent n-p-n type conductivity transition in detecting low-concentration VOC gases.This interestingly n-p-n transition phenomenon is mainly ascribed to the trade-off of highly separated electron-hole pairs originated from the in-shell ZnO-ZnFe2O4 hetero-interfaces,resulting in the down-shift and up-shift of the Femi level.This conductivity transition significantly improves the selectivity of gas sensors. |
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