Characteristics of Secondary Emission Electron Gun and its Application to Decomposition of VOCs

Abstract

Summary form only given. VOCs are released into the atmosphere from various plants and cars. And they are very harmful to human body. Nonthermal plasma methods using electrical discharges or electron beam irradiation are some of the emerging technologies for the disposal of VOCs, and other toxic substances. Especially, electron beam processing is more energy-and cost-efficient than others. We have developed a low-energy secondary emission electron gun (SEEG) using a wire ion plasma source (WIPS) for VOCs treatment. The device has some inherent advantages compared to conventional ones such as compact in size, wide and uniform electron beam. The WIPS itself acts as an ion source for the SEEG. The WIPS generates helium ions. And the ions are extracted as an ion beam from the WIPS and accelerated in vacuum towards a negatively biased stainless steel cathode plate inside the SEEG by high accelerating voltage. Then the ions collide with the cathode plate and secondary emission takes place. The emitted electrons will form a relatively uniform electron beam and the beam penetrates into a gas treatment chamber at atmospheric pressure causing the treatment process of VOC. It offers better capability in high repetition rate pulse operation with easy control than that of glow discharge or field emission control cathode guns. In this work, distribution of electron team energy in the gas treatment chamber was measured with gafchromic film and enough energy to decomposition of VOC is confirmed. The removal ratio of benzene, toluene and trichloroethylene and removal efficiency were investigated in terms of gas flow rate, pulse repetition rate and cathode voltage, respectively. The experimental results indicate better benzene, toluene and tri-chloroethylene removal than other techniques such as electrical discharges.