Plasma ignition of solid fuels at thermal power plants. Part 1. Mathematical modeling of plasma-fuel system

One of the promising ignition technologies is the plasma thermochemical preparation of pulverized coal for combustion using plasma-fuel systems (PFS). This technology allows increasing the efficiency of fuel application and improving the environmental performance of thermal power plants, as well as eliminating fuel oil, used traditionally to ignite boilers and stabilize combustion of a pulverized coal flame. This paper presents the numerical results on ignition of a pulverized coal flame in a PFS. The plasma-fuel system is designed for oil-free start-up of boilers and stabilization of flame combustion and this is a pulverized coal burner equipped with a plasma torch. In addition to plasma torch electric power and ash content in coal, one of the main operating parameters of PTS, which ensures fuel ignition, is concentration of coal dust in the aeromixture, which can be varied over a wide range. The conditions of fuel mixture ignition in the PFS were determined for three above-mentioned operating parameters of PFS using the PlasmaKinTherm program, which combines kinetic and thermodynamic methods for calculating the processes of motion, heating, and thermochemical transformations. The calculations were performed for a cylindrical PFS with a diameter of 0.2 m and a length of 2 m. The coal consumption was 1000 kg/h. The conditions of fuel mixture ignition in the PFS were studied depending on the plasma-torch power (20–100 kW), coal concentration in the fuel mixture in the range from 0.4 to 1.8 kg of coal per 1 kg of air, and also for three different values of coal ash content (20, 40, and 70 %). The main regularities of the process of plasma thermochemical preparation of fuel for combustion have been revealed.