Development Of Gas Generators With Stable Concentration For Ozone And Chlorine Dioxide

Objective:To provide the technical reference for further study on ozone and chlorine dioxide standard gas generator,two gas generators with stable concentration for ozone and chlorine dioxide were explored and developed based on the research about performance evaluation and effects of related factors.Methods:(1)The ozone generator was developed by irradiating the ambient air with the ultraviolet ray emitted by mercury lamp.The concentrations of ozone produced by the generator were monitored by ultraviolet photometry.The stability of the generator was evaluated based on the research about the stability of the intra-day and inter-day ozone concentrations,while the influence of applied voltage,environmental temperature and humidity on the concentrations of ozone was investigated in the environmental test chamber.(2)The gas generation method for chlorine dioxide used in the gas generator was selected by sustainability of the reaction,purity and stability of chlorine dioxide gas.A rapid detection method was explored to determine the concentrations of chlorine dioxide gas through the determination of absorption efficiency and precision.The stability,purity and uniformity were determined to evaluate the generator performance,while the environmental temperature and humidity were precisely controlled in the environmental test chamber to explore the influence of environmental factors on the concentrations of chlorine dioxide.Results:(1)The ozone generator developed in this study included three parts:the generator system,the concentration analysis system and the concentration signal feedback control system.In the stability experiment of the generator,the concentrations of ozone gas were in the range of 32.73mg/m3-33.83mg/m3 with the relative standard deviation(RSD)of 0.94%within 400 minutes of the generator operation,indicating that the intra-day stability of the generator was good.The average concentrations of ozone were in the range of 33.06mg/m3-33.33mg/m3 with the RSD of 0.29%,while the generator was turned on once a day for ten days,indicating that the inter-day stability of the generator was good.In the study on influencing factors,there were no statistically significant difference in the concentrations of ozone gas produced by the generator(P>0.05),when the environmental temperature was 15℃,22℃ and 30℃,and the environmental humidity was 10%,30%,and 60%,and the applied voltage was 200V,220V and 240V.(2)The chlorine dioxide generator was developed by adding hydrochloric acid to sodium chlorite solution with peristaltic pump.The large buffer flask was used to reduce concentration fluctuations for chlorine dioxide gas,while gas concentrations were controlled by adjusting the speed of the peristaltic pump.The detection method using the syringe was established to rapidly determine gas concentrations of chlorine dioxide,and the absorption efficiency of the method was over 97.75%.The RSD of detection results was in the range of 0.48%-6.88%when gas concentrations of chlorine dioxide were in the range of 125.78mg/m3-1386.46mg/m3.The concentrations of chlorine dioxide produced at the peristaltic pump speeds of 20rpm,60rpm and 100rpm(corresponding to dropping rate of hydrochloric acid of 0.38±0.01 mL/min,1.18±0.01mL/min and 2.07±0.04mL/min,respectively)were 132.50±12.17 mg/m3(low concentration),858.44±41.11mg/m3(medium concentration),and 1376.25±40.65mg/m3(high concentration),respectively.In the gas purity analysis experiment,both five-step iodimetry and N,N-Diethyl-p-phenylenediamine(DPD)spectrophotometry showed that the purity of chlorine dioxide was over 97.28%.In the stability experiment of the generator,the concentrations of chlorine dioxide gas produced by the generator in the large buffer flask declined less than 8.52%within 8h at the peristaltic pump speeds of 20rpm,60rpm,indicating that the intra-day stability of the generator was good.The concentrations of chlorine dioxide in each flask produced daily by the generator were consistent when the RSD was less than 5.20%,indicating that the inter-day stability of the generator was good.In the gas uniformity analysis,there was no significant difference in the concentrations of chlorine dioxide at different positions of large buffer flask for medium and high gas concentrations(P>0.05).In the study of influencing factors,environmental humidity(10%,30%,and 60%)had little effect on the stability of chlorine dioxide gas,while high temperature had strong effect.The concentrations of chlorine dioxide gas declined over 16.38%at the environmental temperature of 30℃,while chlorine dioxide declined less than 8.19%and remained stable within 8h at relatively low temperature(15℃ and 22℃).Conclusion:(1)The ozone generator was developed based on ultraviolet irradiation method.The experimental results showed that the generator was stable and could overcome the influence of applied voltage,ambient temperature and humidity on the concentrations.(2)The chlorine dioxide generator was developed based on the sodium chlorite-hydrochloric acid reaction.The experimental results showed that the chlorine dioxide gas produced by the generator was in high purity and uniformity,and the generator stability was good,which could overcome the influence of environmental humidity,but not environmental temperature.