PRINCIPLES OF IMPROVEMENT AND PRACTICAL RESULTS OF PIG IRON SMELTING TECHNOLOGY CHANGES AT PJSC SEVERSTAL

Abstract

The paper presents a rationale for searching for ways to reduce the cost of metal products by preserving and improving the elements of the pig iron production process chain. The article provides a description of the metallurgical process at Severstal PJSC. The consumption of dry skip coke was reduced by 15.7% (abs.) over the period 2014–2024. Key research areas and objectives for improving the modern blast furnace process are formulated. The definition of the technological ZBB (Zero Based Budgeting) potential is given as the difference between the quantitative description of the initial state and the theoretical limit value of the parameter under ideal conditions of technology implementation at the current moment in time. The actual value of the coke-to-natural gas replacement ratio is 0.81 kg of coke/m³ for a natural gas consumption range of 118.8–204.4 m³/t of pig iron under the conditions of PJSC Severstal in the period 2014–2024. The difference in the distribution of alkali elements in the structure of a piece of coke sampled at a height of 2/3 of the furnace shaft under conditions of a total alkali load (K₂O + Na₂O) in the range of 2.8–3.0 kg/t of pig iron is shown: the potassium content is maximum in the center of the piece and gradually decreases on the surface by 1.35 times, the sodium content is maximum on the surface and gradually decreases towards the center by 2.51 times. The limits of the possible reduction in the temperature of the smelted pig iron and its carbon content with an increase in the specific consumption of natural gas blown into the blast furnace in the range from 110 to 220 m³/t of pig iron have been established. Based on the processing of statistical data for the period 2014–2024, it was found that the temperature of the pig iron decreased by 1.0 °C and the content of [C] decreased by 0.005% for every 10 m³/t of change in natural gas consumption.