Effect of the Mixing Structure Parameters of a Self-reflux Burner on Combustion Characteristics and NO_(x)Emission

To solve the problem of low efficiency of NO_(x)emission reduction in self-reflux burners,this study is based on the concept of coordinated control of self-reflux burner structural and thermal parameters.After completing the structural design and optimization of thermal parameters,we continue to adjust the two key structural parameters:the nozzle axis distance and the length of the cylindrical section,to minimize NO_(x)emissions.These are the two parameters that chiefly affect the mixing of flue gas and fuel gas.The results show that increasing nozzle axis distance can delay the mixing of gas and air and create a more uniform oxygen concentration field for the combustion process.The maximum combustion temperature is reduced from 1973.65 K to 1935.88 K and the volume fraction of NO_(x)in the flue gas is reduced from 188.08×10^(–6)to 143.47×10^(–6).However,compared with the nozzle axis distance,the length of the cylindrical section of the burner has little effect on the mixing of the flow field.Under different cylindrical section lengths,the maximum combustion temperature does not change more than 3 K,and the volume fraction of NO_(x)in the flue gas changes within 5×10~(–6).

Full-scale application and performance of a new multi-self-reflow decentralized Wastewater treatment device: Impact of hydraulic and pollutant loads

Decentralized treatment of wastewater in rural areas usually has several challenges,which include large fluctuations in pollutant concentration and water quantity,complicated operation and maintenance of conventional biochemical treatment equipment,resulting in poor stability and a low compliance rate of the wastewater treatment process.In order to solve the above problems,a new integration reactor is designed,which uses gravity and aeration tail gas self-reflux technology to realize the reflux of sludge and the nitrification liquid,respectively.The feasibility and operation characteristics of its application for decentralized wastewater treatment in rural areas are explored.The results demonstrated that,under constant influent,the device showed strong tolerance to the shock of pollutant load.The chemical oxygen demand,NH_(4)^(+)-N,total nitrogen and total phosphorus fluctuated in the ranges of 95–715 mg/L,7.6–38.5 mg/L,9.32–40.3 mg/L and 0.84–4.9 mg/L,respectively.The corresponding effluent compliance rates were 82.1%,92.8%,96.4%and 96.3%,respectively.When the wastewater discharge was non-constant and the maximum single-day Qmax/Qmin reached 5,all indicators of the effluent met the relevant discharge standard.The integrated device also demonstrated high phosphorus enrichment levels in its anaerobic zone;the concentration of phosphorus reached a maximum of 26.9 mg/L,which created a good environment for phosphorus removal.The microbial community analysis showed that sludge digestion,denitrification,and phosphorus-accumulating bacteria all played an important role in pollutant treatment.