Study On Key Techniques Of Multi-phase AC Arc Discharge Experiment Device

With the development of our country’s modernization, hazardous solid wastes(including medical waste and nuclear waste, etc.) gradually increased. If you cannot properly deal with these wastes, it would lead to great harm to the people’s health and living environment. Previous treatment methods for the high risk hazardous waste include incineration and landfill, which may result in the secondary pollution. For example, the incineration method will produce dioxins and furans; while dioxins is one of the most toxic organic compounds. Therefore, there exist some disadvantages, e.g., incomplete treatment, secondary pollution and resource waste, among the present methods. Thermal plasmas have the characteristics of high temperature, high chemical activity, etc., and is gradually employed for the treatment of the high risk hazardous solid wastes.Plasmas generated by AC arc discharge belong to thermal plasma. When the thermal plasmas operate under high pressures,the volume of the high temperature is usually small with a gas temperature and electron number density on the order of 10000 K and 1022 m-3, respectively; while with the decrease of the environmental pressure, the plasma volume will be expanded accompanied by a decrease of the gas temperature. In this thesis, a six-phase AC arc discharge device is designed with the thermal plasma waste treatment as the research background. In this system, the precise movement of the electrodes of the plasma generator is achieved with the servo motor controlled a,PLC; and a water-cooled constraint tube is employed to elongate the length and volume of the plasma jet. The major research is as follows:Firstly, a six-phase AC arc discharge plasma generator is developed. The influences of the plasma working gas flowrates and the corresponding gas entrance positions, and the power input on the characteristics of the plasma jets are studied experimentally. The results show that this six-phase AC arc discharge device can produce stable thermal plasma jet with a large high temperature volume, which makes an efficient treatment of the hazardous wastes be possible.Secondly, a power supply system capable of producing six-phase AC arc plasmas is designed. According to the working principle of single phase AC arc welding power source, the power supply of six-phase AC arc discharge is developed. The soft start circuit for starting the transformer and the high frequency arc starter for the non-contact arc ignition are also designed.Finally, a water-cooled constraint tube with a cold gas injection along the jet flowing direction is proposed to increase the length and volume of the plasma jets. A stable arc discharge thermal plasma jet with the length and volume of 35 and 13, respectively, is obtained operating at a medium pressure level. And the characteristics of the plasma jets under different operation conditions are studied experimentally.