Temperature profile of packed-bed non-thermal plasma reactor and its effect on toluene decomposition

Abstract

This study aims to profile real plasma temperature inside the packed-bed (PB) non-thermal plasma (NTP) reactor using a fiber Bragg gratings (FBG) and its effect on toluene decomposition efficiency. PB reactor was designed and fabricated by packing some dielectric material of barium titanate (BaTiO3) pellets between two stainless steel electrodes. The FBG was embedded inside the reactor to measure the plasma temperature within the plasma stream. Plasma temperatures for four carrier gases, helium (He), argon (Ar), nitrogen (N2), and air were profiled at different applied voltages ranging between 4 and 16 kV based on their breakdown voltage to determine suitable gases for toluene decomposition process that has good temperature stability and no arc formation. For noble gases He and Ar, the plasma temperatures are in the range of 25-80°C and 60-170°C, respectively, while those of N2 and air are in the range of 28-200°C. Air was selected as carrier gas for toluene decomposition process due to higher plasma temperature, no arc formation and higher free oxygen radicals in the plasma stream. The results show that the plasma temperature increases with the increase in applied voltage, and with the decrease in flow rate and toluene input concentration. The average plasma temperature for toluene decomposition in air is in the range of 100-260°C when measured under applied voltage of 14-19 kV, carrier gas flow rate of 1.0-2.0 L/min and toluene input concentration of 500-8400 ppm. Complete toluene decomposition efficiency has been achieved under plasma parameters of 18 kV, 2.0 L/min and 500 ppm. From this finding, plasma temperature profiling using FBG sensor can be used as plasma diagnostic tool to replace Fourier Transform Infrared spectroscopy (FTIR) instrument and as indicator when toluene decomposition process is complete.