Thermal pulsed-plasma technology for hazardous waste treatment

A new, efficient, and environmentally friendly pulsed-plasma technology for hazardous wastes treatment is presented. The waste material is decomposed using a high-energy pulsed-plasma jet produced in a confined discharge. Tests were successfully carried out in a modular, transportable laboratory. It comprises a pulsed power supply, confined plasma discharge injector, reactor, gas handling and monitoring systems. The 5-stage PFN designed for 5 million shots, provides up to 30kJ, 40kA, 0.3ms pulses at 1Hz. The plasma jet temperature is in the range of 2.5 to 5eV, with a density of 10^-3-10^-4 g/cm³ and velocity of about 10 km/s. The major technological challenge is the development of the repetitive plasma injector. An injector withstanding almost 1000 shots before replacement of a few consumable components has already been demonstrated. Experiments were performed using perchloroethylen and trichlroethylen as reference materials and real industrial waste comprising mono- and dichlorobenzene (30-70%). The tests were performed in several operation scenarios and under various operation parameters. It was found that complete destruction of about 2cc of waste per shot could be achieved by direct injection into the plasma injector. The energy needed was 7-9 kJ/shot - considerably below (at least by 50%) the amount of energy required in other thermal methods. It was found that the system could run without additional gases supply. The vapor pressure of the waste material was sufficient to starting the discharge while the waste itself formed the plasma. The test results proved the technical and economical feasibility of the technology. Further R&D is required in order to industrialize the components, especially the plasma injector, and to define the process for specific wastes of interest. This work was performed within the framework of the 4th European Brite Euram R&D Program.