Numerical Simulations of the Temperature and Velocity Fields in a Plasma-Arc System and Equilibrium Calculations of Steam Injected for Syngas Recovery from POPs

摘要

A direct current (DC) experimental facility of 30 kW with plasma-arc technology was set up to study the pyrolysis process in the laboratory. The temperature and velocity fields make a great impact on the transfer and reaction among the molecules, and so determining the destruction efficiency. It's difficult to directly measure the temperature of the arc region, therefore numerical simulation becomes a substitute method. According to the dimension of this facility, a magnetohydrodynamic model is used to simulate the temperature and velocity fields. The section drawings clearly exhibit the phenomenon of cathode jet and cathode spot. Furthermore, the treatment of Persistent Organic Pollutants (POPs) agents in a steam-plasma system for syngas recovery has been simulated. Based on the principle of Gibbs free energy minimum, the equilibrium product distribution versus steam content and temperature is calculated. Amount of syngas increases with the increase of temperature, the process acts as energy transformation - electrical energy is finally restored in the syngas. At the ideal temperature of POPs treatment, the energy recovered (Q_(re)) and the energy input (Q_(in)) both increase with the increase of steam content, but Q_(in) subtracted from Q_(re) gets to maximum while the molar ratio of oxygen to carbon (O/C) is near 1. The results show that the plasma-arc technology is an environmentally friendly and economically feasible for the disposal of POPs.