Adjustment of a technology of cast iron smelting in the blast furnace of jsc "ural steel" w ith a volume of 1232 см³ with charge h a v in g 95% share of Mikhailovskii GOK pellets

Abstract

To use effectively internal raw material base, JSC “Ural Steel” accomplished I category major overhaul of the blast furnace No. 2. The main purpose of the overhaul was to design a rational profile which could ensure an ability to operate with a charge containing 95 % of Mikhailovskii GOK (mining and concentrating plant) pellets having basicity of 0.5 by CaO/SiO2. The blast furnace No. 2 having useful volume of 1232 m3, was constructed by design of Danieli Corus, the Netherlands, and was blown in on December 30, 2020. In the process of guarantee tests, step-by-step increase of Mikhailovskii GOK pellets (Fetotal = 60.5 %, CaO/SiO2 = 0.5) content in the charge iron ore part was being accomplished from 55 to 95.1%. Charging of the blend containing pellets in the amount of 55% of iron ore part, was done by charging system 4OOCC + 1COOCC (Ore - Coke) with filling level 1.5 m. Under conditions of pellets part increase in the blend, the charging system was changed to decrease their content at the periphery, to increase it in the ore ridge zone and make it intermediate between periphery and the ore ridge. At the pellets share in the iron ore raw materials 0.75 the charging system was used as the following: 3OOCC + 1COOC + 1COOCC, while at the content 95.1% the following charging system was used: 2COOC + 2COOC + 1COOCC. It was noted that in the period of guarantee tests the furnace running was smooth. The average silicon content in the hot metal was 0.70% at the standard deviation 0.666. Sulfur content in the hot metal did not exceed 0.024%, the blowing and natural gas consumption figures were 2100 m3/min and 11000 m3/min correspondently, oxygen content in the blowing 26.5%, hot blowing and top smoke pressure figures were 226.5 and 109.8 KPa correspondently. The productivity of the furnace was reached as high as 2358 t/day at the specific coke rate 433 kg/t of hot metal. After guarantee tests completion, the pellets content in the iron ore part was decreased gradually from 95 down to 50%. The decreasing was made by 5% in every 6 hours of operation. Application of the mastered technology of the blast furnace No. 2 with the increased share of pellets will enable to stably supply the blast furnaces No. 1, 3 and 4 by iron ore raw materials in the proportion of 30-35% of pellets and 65-70% of sinter.