Cold Experimental Research On The Air-blast Spray Nozzles For Selective Non-catalytic Reduction System

Nitrogen oxides are atmospheric pollutants which have great harm to the nature and human health,the treatment of nitrogen oxides become an important part of environmental protection.Selective non-catalytic reduction(SNCR)is a technology for controlling nitrogen oxides emission which has been widely used in engineering,for which the spray nozzle for reductant is the key equipment.The flow rate and atomization characteristics of spray nozzle have obvious influence on the denitrification efficiency.In this thesis,all of research is based on air-blast spray nozzles.According to the principle of twin fluid nozzle,an internal-mixing spray nozzle and an effervescent spray nozzle were designed,and the spray test bench for SNCR spray nozzle was set up.The flow rate and atomization characteristics of SNCR spray nozzle were tested and studied;the experimental research shows that:The design method of internal-mixing spray nozzle is reasonable,while the design method of effervescent spray nozzle needs to be rectified.In addition,the flow characteristic curves of internal-mixing spray nozzle and effervescent spray nozzle shows the same change trend with the change in gas pressure or liquid pressure.Generally,compared to effervescent spray nozzle,internal-mixing spray nozzle is better in spray distance and atomization effects.Based on the internal-mixing spray nozzle with better atomization effects and longer spray distance,the influence of mixing chamber nozzle structure on the flow rate and atomization characteristics of spray nozzle was studied,and three types of mixing chamber nozzles were designed,including one circular hole,eight small hole and fan nozzle.The results shows that:The nozzle structure of mixing chamber has little influence on the quantity of flow;The droplet particles from fan nozzle have better particle size distribution which is favor for denitrification;The spray distance of spray nozzle with one circular hole nozzle is the farthest.Based on the internal-mixing spray nozzle,the influence of gas pressure,liquid pressure and gas-liquid ratio on the flow rate and atomization characteristics of spray nozzle was further studied.The design conditions of the SNCR internal-mixing spray nozzle were optimized.The results shows that:The liquid flow characteristic curve conforms to the exponential relationship of Qw?(Pw-P3)0.5;The better design conditions of spray nozzle are:the range of gas pressure is Pw?Pa?Pw+0.1 MPa,the range of gas liquid ratio is 0.10?ALR?0.24;Increasing the initial pressure of gas and liquid can not improve spray distance significantly.