3-D Modelling of DC Transferred arc Twin Torch for Asbestos Inertization

The aim of this work is to investigate by means of a 3-D numerical model the fluid flow and temperature distribution of a plasma transferred electric arc discharge generated between two suspended metallic electrodes. This twin torch device is used inside a plasma furnace for hazardous waste incineration and asbestos inertization. Flow and energy equations are solved for an optically thin plasma under conditions of LTE, while the electromagnetic field equations are solved in their scalar and vector potential form. Electrodes interfaces are taken into account using a simplified approach, imposing a current density distribution on the cathode surface. The anode and cathode regions are discretized in their detailed design, in order to better understand the effects of their geometries on the discharge behavior. Turbulence effects are taken into account into the model using a RANS approach, as well as the effect on the discharge characteristics of using different types of plasma gas (Ar and Ar/H2 mixtures), for various geometric and operating conditions. Results are presented in order to characterize the fluid flow and the temperature field of this kind of device. Simulations are performed using a customized CFD commercial code FLUENT°R , parallelized over a network cluster of double processor calculators in order to use the full capabilities of the 3-D modelling code.