Experience in conducting pre-start tests on Severstal's blast furnaces during major repairs of the first category

The paper presents the experience of conducting pre-start-up studies on the blast furnaces of PAOSevers-talduring the first-category major repairs in the period 2020–2025.The importance of the blast furnace preparation stage, the need to configure and select rational operating modes for equipment and automated control systems, and the implementation of full-scale technical and information support for effective smelting modes have been identified. The article demonstrates the uniqueness of the parameters characterizing the distribution of the charge components on the surface of the fill, as well as the possibility of obtaining them once during the campaign during pre-launch studies. The article discusses the content of the pre-start-up research program for blast furnaces equipped with cone-free charging devices (CFDs), including the stages of research before loading the furnace, determining the trajectories of falling charge materials, and using sampling and laser 3D scanning to establish the actual distribution of materials in the furnace working space. The map shows the distribution of iron ore materials and coke in the working space of blast furnace No. 4 based on the results of unloading the volume of research feed with the thickness of the coke and iron ore mixture layers for each specified angle of the hopper tray, as well as the component composition of the iron ore mixture at each point of investigation. The article presents an algorithm for solving the problem of refining the distribution of iron ore materials that are homogeneous in terms of their physical conditions during the formation of a batch in a skip, a hopper of a load-ing device, and unloading into a blast furnace. By recalculating the chemical composition of the samples taken from the research feed, the authors obtained data on the percentage of each type of pellet in the specified areas of the filling surface, both for iron ore batches that contain agglomerate and those that consist solely of a mixture of pellets in various proportions. The results of the start-up and inflation of blast furnace No. 4 in forced mode are presented based on the data of pre-start-up studies. During the first month of operation (September 2025), the specific consumption of solid carbon fuel was 351.8 kg/t, natural gas was 198.6 m3/t, and the daily capacity of the furnace was 6500–7000 tons of pig iron per day.