NUMERICAL MODELING OF PEAT BURNING PROCESSES IN A VORTEX FURNACE WITH COUNTERCURRENT SWIRL FLOWS

The paper presents the process of peat burning in a swirl furnace with countercurrent swirl flows and the results of a numerical study. The cyclone-vortex technology of solid fuel combustion allows the furnace volume of a boiler unit, its dimensions and weight to be reduced. The aim of the work is a numerical study of the combustion of pulverized peat in a cylindrical vortex furnace with countercurrent swirl flows. The results of computer simulation of the combustion of pulverized peat with a moisture content of 40%, an ash content of 6%, and a higher heat of combustion Q(H)(p) = 12.3 MJ/kg are presented. The results of the influence of the design parameters of the furnace and heat load (from 100-15%) are given as well. When the heat load is reduced to 15%, the entrainment of unburnt particles increases. The cooled and adiabatic furnace is studied. A significant entrainment of unburned particles is observed in a cooled furnace. The fields of temperature distribution, gas velocity, and particle trajectory in the volume and at the outlet of the furnace are determined. The 3-D temperature distribution in the furnace volume indicates the combustion of peat particles at temperatures (1300-1450 degrees C). Values of the tangential velocity of a swirl flow near the furnace outlet reach 150-370 m/s, which ensures the efficiency of separation of fuel particles and a reduction in heat loss due to mechanical underburning (up to 0.06%). The results of a numerical study show that the diameter of peat particles affects the combustion process, namely coke of particles with an initial diameter from 25-250 mu m burns out by 96%, and particles with a diameter of about 1000 mu m are carried away from the furnace and do not burn. The furnace provides a complete combustion of dust particles of peat by 99.8% and volatiles by 100%.