Simulation of gas dynamics of oxygen flow and hydrodynamics of cooling water flow in tuyere tips with tangential optimized nozzles and results of their pilot tests.

Abstract

The blowing mode largely determines the technical and economic indicators of BOF smelting, which was confirmed during the technological audit of the BOF shop of Azovstal Iron and Steel Works, carried out in 2021. It was found that the blowing mode of the process using an oxygen lance of the basic design was noticeably shifted from the optimal one in the direction of “hard” blowing. In a significant number of melts this led to an increase in the specific consumption of metal sheets, deterioration of lime assimilation by slag, dephosphorization and desulphurization of the metal. Taking into account that adjustment of the blowing mode by changing the working height of blowing and oxygen consumption did not provide a stable positive result, changes were made in the design of the tuyere tip. The design of the head with tangential arrangement of nozzles is proposed to “soften” the blowing of melts. The advantages and dis-advantages of oxygen lances of this type are considered. Numerical modeling of the gas dynamics of the oxygen flow and the hydrodynamics of the flow of cooling water in a tip with a tangential arrangement of nozzles has been per-formed. On the basis of simulation results, two variants of an improved design of the tips of 350-t LD converters with five (variant 1) and four (variant 2) main peripheral tangentially oriented nozzles and a central nozzle of lower throughput were developed to use them mainly in the second and first periods of the campaign according to the lining of the converters, respectively. It is shown that the design parameters of the nozzle blocks provide an oxygen jet outflow regime close to the design one in the main range of oxygen operating flow rates and a “non-separated” outflow regime with a decrease in the off-design ratio down to 0.8. The design parameters of the cooling system provide both an acceptable loss of water pressure in the head (0.9 MPa), the absence of local low-speed vortex zones of water, and a fairly high average coolant flow rate along the most heat-stressed (the lower) surface of the tip (about 4.5 m/s). As a result of industrial testing of a pilot batch of experimental heads with five main peripheral tangentially oriented nozzles, manufactured at the plant’s own repair and mechanical base, an increase in the resistance of copper tips was found to be 1.2 times, the resistance of lances to removal for cleaning from accretion was found to be 6.8 times, reduction in the specific consumption of metal charge by 0.9–5.6 kg/t, an increase in the dephosphorization and desulfurization coefficients of metal in the converter by 0.7–1.5 and 1.3–3.2%, respectively.