Plasma ignition of dust-coal flame

Abstract

One of the promising power engineering technologies is the plasma thermochemical preparation of pulverized coal to burning using plasma-fuel systems (PFS). This technology allows increasing the efficiency of fuel use and environmental indicators of thermal power plants, as well as eliminating the use of fuel oil, traditionally used to start-up the boilers and stabilize the combustion of a pulverized coal flame. This paper presents the results of numerical experiments on ignition of pulverized coal in PFS. PFS is designed for fuel oil-free start-up of the boilers and stabilization of pulverized coal flame, and represents a pulverized coal burner equipped with plasma torch. Via PlasmaKinTherm software which combines kinetic and thermodynamic methods of calculating the processes of motion, heating, thermochemical transformations and fuel mixture ignition in the volume of PFS, impact of the power of the plasma torch and ash content of coal onto efficiency of fuel mixture ignition have been determined. Also one of the main regime parameters of PFS providing ignition of the fuel is concentration of coal dust in the fuel mixture which can vary within a wide range. Therefore, conditions for fuel mixture ignition in 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 2 m of length at fixed consumption of coal (1000 kg/h) and the plasma torch power (60 kW) for three values of coal ash content (20, 40 and 70%). The basic regularities of the process of plasma thermochemical preparation of fuel for burning were revealed.