Characteristic of Thermal Decomposition of Ozone

Abstract

In general, dielectric barrier discharge (DBD) typed ozone generators are used for water treatment including drinking water and wasted water. Recently, it has been reported that composed ozone concentration by DBD type ozone generator decreases with time using high purity oxygen as a fed gas. The phenomenon is called “Ozone Zero Phenomenon”. As one of factors responsible for the occurrence of this phenomenon is speculated to be an influence from electrode surface, we have focused our investigation on electrode surface heating generated by electrical discharge. Rate of thermal decomposition of ozone by heated stainless steel (SUS) pipe and Pyrex glass pipe were evaluated by ozone concentrations at inlet and outlet of heated pipes. As a result, for temperature of heated both pipes below 120°C, thermal decomposition of ozone was not confirmed in each transit time (0.25-1.5s). However, when both heated pipes are over 160°C, thermal decomposition of ozone was found and the rate of ozone decomposition increased depend to transit time in heated pipes. It was thought that there were at the least 2 processes of decomposition of ozone: one is oxidation of surface of pipes, and another is thermal decomposition in gas phase. The former is enhanced at the stepwise increase of ozone concentration in stainless steel pipe below 160°C compare with Pyrex pipe. The temperature above 180°C, thermal decomposition is increased against the time in the both kind of pipes. This is considered decomposition of ozone in gas phase.