Substitution of Coke and Energy Saving in Blast Furnaces. Part 2. Study of influence on the Processes of Individual Charge Parameters

Abstract

The system of discrete material and thermal balances in the radial annular cross-sections for 12 vertical and 10 radial ring zones is used to describe the heat and mass transfer processes of iron ore reduction and melting in blast furnace with respect to the various degree of preliminary metallization of the metallic burden. It was found that with increase in preliminary metallization degree the heat demand on direct reduction and the ratio between material and gas flow heat capacities are reduced which leads to the decrease in intensity of a heat transfer in the bottom zones of the furnace. As a result, the height of the bottom zones of blast furnace is increased, while the height of the upper zones is decreased. The gas isotherms move upwards, increasing heat losses through the furnace top. The cohesive zone also moves up and increases in size. The influence of material distribution at the furnace top on parameters of blast furnace operation becomes weaker. Because of decrease in extend of direct reduction the effect of natural gas injection on coke rate is also reduced. As a result the reduction in coke rate associated with the preliminary metallization of the metallic burden could not be fully realized if the burden metallization degree is grater than 20%. The model makes it possible to determine the relationships that exist between processes which take place in the furnace and which affect the character of the smelting regimes and the final results.