Modeling of Coal Ignition in Plasma-Fuel Systems With an Electric Arc Torch

Results of numerical experiments on ignition of pulverized coal in a plasma-fuel system (PFS) are presented. PFS is designed for fuel oil-free startup of the boilers and stabilization of pulverized coal flame and represents a pulverized coal burner equipped with plasma torch. The calculations were carried out using the PlasmaKinTherm program. It combines kinetic and thermodynamic methods for calculating the processes of motion, heating, thermochemical transformations, and ignition of the fuel mixture in the volume of the PFS. The ignition conditions of the fuel mixture had previously been determined for two operating parameters of the PFS: the electric power of the plasma torch and the ash content of coal. Also, one of the main regime parameters of the PFS providing ignition of the fuel is the concentration of coal dust in the fuel mixture. It can vary within a wide range. Therefore, conditions for fuel mixture ignition in the PFS have been investigated, depending on the concentration of coal in the fuel mixture in the range from 0.4 to 1.8 kg of coal per 1 kg of air. Calculations were performed for cylindrical PFS of 0.2 m diameter and 3 m of length at fixed consumption of coal (1000 kg/h), the plasma torch power (60 kW), and three values of coal ash content (20%, 40%, and 70%). Nontrivial regularities of the process of plasma thermochemical preparation of fuel for burning were revealed.