Use of pulverized coal fuel in low-shaft furnace smelting

Industry research on the issues of injection of pulverized coal particles into low-shaft furnaces to reduce solid fuel consumption is well known. A certain amount of practical experience has been accumulated and summarized. Despite the obvious positive effects, this method for low-shaft furnaces has not been fully explored. Due to the lack of a theoretical basis to calculate optimal parameters of coal injection when injected into the shaft of a low-shaft furnace, certain difficulties arise in achieving consistent results during smelting using units with varying productivity. Thus, development of a theoretical framework to calculate the optimal parameters of pulverized coal injection is a matter of current importance, as it will make it possible to provide practical recommendations for its application. A mathematical modeling method has been used to examine the thermal energy processes occurring in the low-shaft furnaces during pulverized coal injection. Calculations are based on heat and mass balance equations, gas-dust flow aerodynamics, and empirical relationships for various coal grades. A comparative analysis of the obtained data on the burnout of particles of various coal grades in low-shaft furnaces was carried out. It has been established that lean coals, ground to a particle size of 0,03–0,075 mm with a low ash content of 16 % on a dry basis should be used to prepare pulverized coal fuel. The low-shaft furnace must be equipped with three rows of tuyeres spaced 350–400 mm apart. Pulverized coal fuel should be optimally fed to the tuyeres of the bottom row with a constant flow rate for all tuyeres in the bottom row at the same rate for each tuyere. The results of the study make it possible to provide practical recommendations for the preparation and injection of pulverized coal fuel, and design of the low-shaft furnaces that ensures stable smelting process.