Analysis of energy efficiency increase of cast iron smelting in NLMK blast furnaces

The analysis of effects and risks of the main measures aimed at reducing energy costs has shown that the change in any one parameter is ineffective. The greatest effect can be achieved by the joint change of several variables. Theoretical analysis made it possible to identify the main combinations of changes in the regime parameters, which provide the greatest effect on the particular activity factor. The influence of the granulometric composition of the agglomerate on the efficiency of blast furnace smelting was examined through the influence of average diameter of the pieces, both on the rate of recovery and on the gas dynamics of furnace upper zone. It is shown that the variations in heat costs are largely determined by the fluctuations in recovery work of gas flow, which, in turn, depends on granulometric composition of the agglomerate. It was established that when the FeO + CO = Fe + CO2 reaction is approached to balance, the heat loss reduction for cast iron smelting is achieved by increasing the melting intensity. The specific ways of reducing the heat costs for cast iron smelting in blast furnaces were analyzed on the example of PAO NLMK. It is shown that the main activities providing the reduction of heat losses in the plant conditions are: quality optimization of the iron ore materials due to the fraction decrease of +45 mm; increasing the intensity of the blast-furnace operation to relative production of 75 – 90 tons per day from square meter of the blast-furnace hearth; blast-furnace operation at the alarm pressure (according to the design of charging equipment); increasing the coke strength reactivity up to 60 – 62 %; pulverized coal injection up to 140 kg per ton of cast iron and optimization of the ore load distribution on the furnace’s radius. As a result of these measures implementation in 2013 – 2016, the coke rate reduction by more than 10 kg per ton of cast iron was achieved. In this case, not only the specific consumption of coke, but also the consumption of total carbon of fuel is reduced. © 2017, National University of Science and Technology MISIS. All rights reserved