Effect of water spray on adsorbed toluene decomposition by nonthermal plasma flow

We have been investigating a technology for decomposing adsorbed volatile organic compounds (VOCs) using a nonthermal plasma flow, which is easily generated at low cost with a compact apparatus. In this study, we investigated the effect of water spray on the decomposition of adsorbed toluene that is achieved using nonthermal plasma flow. Spraying water upstream of the adsorbent should increase the amount of OH radicals, which form a strong oxidizing agent, and thereby enhance the toluene oxidation. Two different water spray conditions are tested: (I) spraying for 10 s after 30 min, spraying for 20 s after 60 min, and spraying for 10 s every 3 min from 90 min to 120 min; and (II) spraying for 10 s every 5 min. The decomposition efficiencies under conditions I and II are compared to that achieved without water spray. With no water spray and under condition I, the toluene conversion efficiency reaches a maximum of 98% in 105 min after the experiment starts. In contrast, the conversion efficiency is 76% under condition II. Excessive humidity is known to decrease ozone generation; therefore, the conversion efficiency decreases.