Analysis of the blast furnace operations with a volume of 5000 m3 on tuyeres of different diameters from the positions of full mechanical energies of flows of combined blow and hearth gas

In the commissioning period of the development of pulverized coal injection technology (PCI) on a blast furnace No. 9 with a volume of 5000 m3 of PJSC “ArcelorMittal Kryvyi Rih”, frequent cases of burnout of refrigerators of the cooling system of the shoulders and air tyueres appeared due to the highly developed peripheral gas flow. An attempt to limit the gas flow at the periphery by controlling the distribution of charge materials on the top produced a short-term result. Based on the prevailing ideas, that to reduce the intensity of the peripheral gas flow, it is necessary to increase the speed of the blast and, accordingly, the kinetic energy of the blast flow, flowing out of the air tuyeres of a blast furnace, it was decided to reduce their diameter. As a result of analysis of the operation of the specified blast furnace using the technology of PCI on tuyeres with a diameter of 150 and 140 mm, increased peripheral gas flow with a smaller diameter was established. Based on the results of the analysis, conclusions were made by many researchers and it was shown that with constant kinetic energy of the blast, flowing from the tuyeres of different diameters, the dimensions of the combustion zone are always larger before the tuyeres of a larger diameter. This is explained by the fact that the kinetic energy of the gas flow is only a part of their total mechanical energy. It was shown that to analyze the change in the size of the combustion zones and the depth of penetration of the hearth gas, it is necessary to use the full mechanical energy of the flows of the combined blast on the cut of the tuyere and hearth gas. It was established that the transition to PCI in a blast furnace instead of natural gas, it always causes an increase in the peripheral gas flow. The main reason for this phenomenon is associated with a decrease in the total mechanical energy of blast and hearth gas. It was recommended on a blast furnace with a volume of 5000 m3 with a hearth diameter of 14.7 m and the PCI technology to maintain the total mechanical energy of the blast flow at least 2100–2600 kJ/s, and the full mechanical energy of the hearth gas flow at least 5100–5300 kJ/s.