Study On Photocatalytic Treatment Of Nitrogen-containing Odorous Gas By Microwave Discharge Electrodeless Lamps

In recent decades,nitrogen-containing odor emissions have been increasing globally,and gaseous ammonia（NH₃）is mainly decomposed from nitrogen-containing organic pollutants,which has a wide range of sources and is representative.It has a strong pungent odor,is extremely harmful to the human body,and has a major impact on the nitrogen cycle of the earth’s ecosystem,climate change,and other atmospheric reactions.The current ammonia treatment technology has complex procedures,long treatment cycle,secondary pollution,high treatment cost and low treatment capacity.Improving the treatment capacity of ammonia removal technology and reducing the secondary pollution in the process has become an urgent problem to be solved at this stage.problem.In this research,using microwave electrodeless lamp as the medium,coupling the microwave external field and photocatalytic technology,and combining experiment and CFD numerical simulation,the microwave electrodeless photocatalytic reaction device was independently built,and anatase titanium dioxide was selected as the photocatalyst,and the electrodeless lamp Then,by comparing the conditions such as luminous time length,reaction temperature,and ozone generation concentration,an electrodeless lamp with a length of 200 mm and a radius of 15mm was selected as the reaction light source.The software Ansys Fluent is used to simulate the reaction zone,and the visualized flow velocity distribution effect map and the temperature distribution effect map under different microwave powers are obtained.The gas inside the reaction zone is in a laminar flow state,and the flow velocity at the geometric center is large,and the flow velocity near the pipe wall is small.On the contrary,due to the fast gas flow rate,the geometric center temperature has a higher heat transfer rate than other regions.In order to improve the generation efficiency of reactive oxygen molecules in the reaction,the species and proportion of active oxygen generated under different influencing factors in the reaction were determined by oxidation extraction spectro-photometry.It was found that ¹O₂,O（¹D）and·OH were the main reactive oxygen species in the system,and the relationship between volumetric space velocity and active oxygen is negatively correlated,and the reaction temperature not only has a negative correlation with active oxygen,but also has a huge impact.Because most of the·OH is produced on the photocatalyst,the proportion of·OH in the microwave auroral-free catalytic system is higher than that in the microwave auroral-free oxidation system.Therefore,relative humidity has little influence on the microwave auroral-free oxidation system,while ROS in the microwave auroral-free catalytic system decreases at high humidity.The comparison shows that the active oxygen species in the system is the most when the temperature is90°C,the volume space velocity is 700h^-1,and the relative humidity is 68%.Finally,experiments of auroral-free microwave catalytic degradation of ammonia gas under different influencing factors show that the microwave auroral-free catalytic system has the best removal effect.Among the influencing factors,the volume space velocity and initial ammonia concentration are inversely proportional to the removal efficiency.Relative humidity has little effect on the degradation efficiency,but high humidity will have a negative effect on the removal effect.The photocatalytic dose was proportional to the reaction removal rate,but the removal efficiency could not be further improved when the loading was over 3g.It is obtained comprehensively that the catalyst load is 3g,and when the volume space velocity is 700h^-1,the relative humidity is 55%RH,and the initial concentration of ammonia gas is 100 ppm,it is the optimal parameter of the process,and the removal rate can reach 90.79%.The selectivity of NO_xin the product is 8.3%,the selectivity of NO₂^-is 0.5%,the selectivity of NO₃^-is 2.6%,and the selectivity of N₂is 88.6%.Because the 185nm high-energy ultraviolet light of the microwave electrodeless lamp breaks NH₃molecules in advance,a large amount of·NH₂is produced,and under the optimal process conditions,more OH and ¹O₂are produced,which promotes the conversion of the reaction to N₂,reducing the formation of NO_xand nitrate.