Ozone Yield Limit In Low Temperature Plasmas And Temperature Effect

Ozone generation is a power-consuming process,the high energy consumption has been an obstacle for ozone further application.Currently,the energy efficiency of commercial ozone generator is usually less than 20%,and a large part of input energy is converted into heat,causing a temperature increase in discharge gap and therefore accelerating ozone decomposition.With the deep exploration of ozone generation mechanism,a good progress has been made in ozone yield,but it is still far less than theoretical value 1226 g/k Wh.In this paper,the classic thermodynamics is adopted to investigate energy conversion in ozone generation process,and the more practical ozone yield limits at specific conditions are proposed.In addition,the effect of temperature on ozone generation process was also investigated by combining simulation and experiment.The main conclusions are as follow:(1)A detailed thermodynamic model is developed for ozone generation process,and the ozone yield limit is investigated from the overall reaction and elementary reactions respectively.In the former case,the ozone yield limit increases with increasing oxygen ration in feed gas and oxygen conversion ratio,and decreases with increasing final gas temperature.Ozone yield limits are 921.22 g/k Wh and 487.54 g/k Wh in pure oxygen and in synthetic air respectively at final gas temperature of 400 K and oxygen conversion ratio of 10%.When elementary reactions are considered,the ozone yield limit increases with the increasing reduced field and the oxygen conversion ratio.Ozone yield limits are 238.92 g/k Wh and 191.14 g/k Wh in pure oxygen and in synthetic air at reduced field of 300 Td respectively.(2)The heat transfer simulation results of ozone generator indicate that: gas temperature in discharge gap increases along with gas flow direction,and reaches the maximum around the outlet.At small gas flow rate,gas temperature around the inlet is radially distributed,and gas temperature near the center line is obviously lower.Owing to the narrow discharge gap,the change of portrait gas temperature is less than 3 K.Moreover,the average gas temperature in discharge gap increases with the increasing inlet gas temperature and decreases with increasing gas flow rate,and the higher gas flow rate also influences the gas temperature distribution in discharge gap.(3)The average gas temperature in discharge gap has obvious effect on discharge power,ozone concentration and ozone yield.As average gas temperature increases,all discharge power,ozone concentration and ozone yield decrease.Besides,at high average gas temperature,the change of gas temperature has greater effect on ozone concentration and yield.