운전조건에 따른 O3/UV, TiO2/UV 및 O3/TiO2/UV 시스템의 BTEX 증기처리에 관한 비교 연구

Abstract

A multilayer tower-type photoreactor, in which <TEX>$TiO_2$</TEX>-coated glass-tubes were installed, was used to measure the vapor-phase BTEX removal efficiencies by ozone oxidation (<TEX>$O_3$</TEX>/UV), photocatalytic oxidation (<TEX>$TiO_2$</TEX>/UV) and the combination of ozone and photocatalytic oxidation (<TEX>$O_3/TiO_2$</TEX>/UV) process, respectively. The experiments were conducted under various relative humidities, temperatures, ozone concentrations, gas flow rates and BTEX concentrations. As a result, the BTEX removal efficiency and the oxidation rate by <TEX>$O_3/TiO_2$</TEX>/UV system were highest, compared to <TEX>$O_3$</TEX>/UV and <TEX>$TiO_2$</TEX>/UV system. The <TEX>$O_3/TiO_2$</TEX>/UV system accelerated the low oxidation rate of low-concentration organic compounds and removed organic compounds to a large extent in a fixed volume of reactor in a short time. Therefore, <TEX>$O_3/TiO_2$</TEX>/UV system as a superimposed oxidation technology was developed to efficiently and economically treat refractory VOCs. Also, this study demonstrated feasibility of a technology to scale up a photoreactor from lab-scale to pilot-scale, which uses (i) a separated light-source chamber and a light distribution system, (ii) catalyst fixing to glass-tube media, and (iii) unit connection in series and/or parallel. The experimental results from <TEX>$O_3/TiO_2$</TEX>/UV system showed that (i) the highest BTEX removal efficiencies were obtained under relative humidity ranging from 50 to 55% and temperature ranging from 40 to <TEX>$50^{\circ}C$</TEX>, and (ii) the removal efficiencies linearly increased with ozone dosage and decreased with gas flow rate. When applying Langmuir-Hinshelwood model to <TEX>$TiO_2$</TEX>/UV and <TEX>$O_3/TiO_2$</TEX>/UV system, reaction rate constant for <TEX>$O_3/TiO_2$</TEX>/UV system was larger than that for <TEX>$TiO_2$</TEX>/UV system, however, it was found that adsorption constant for <TEX>$O_3/TiO_2$</TEX>/UV system was smaller than that for <TEX>$TiO_2$</TEX>/UV system due to competitive adsorption between organics and ozone.