Study of electric arcs in an air-steam mixture in AC plasma torches

A review of existing plasma torches designed for steam plasma is presented in this paper. Together, they cover the following ranges of key technical parameters: efficiency from $51$ to $95\%$, enthalpy of the plasma from $12$ to $84$ MJ/kg, and the fraction of the steam in the plasma forming gas from $17$ to $100\%$. The advantages of alternating current to produce plasma is grounded. The problems of creating of a steam plasma torch are described. The description of the experiments carried out on the AC plasma torch, during which the total flow of the plasma forming steam-air mixture and the effective value of the current remained constant $\sim 6.7$ g/s and $\sim 28.4$ A, respectively, and the steam content ranged from $54$ to $85\%$, is given. With an increasing proportion of steam, the voltage increased from $1.03$ to $1.59$ kV, while the estimated temperature of the arc decreased from $11600$ to $10200$ K, which is caused by intensification of heat transfer. In all modes, there was a high efficiency of $94.3$–$95.3\%$ with a significant change in the specific energy input from $8.3$ to $12.4$ MJ per $1$ kg of plasma-forming gas.