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Influence of Bottom Blowing Gas Parameters on Erosion Rate of Purging Plug Brick

In order to study the effect of bottom blowing gas injection parameters (pressure, flow rate, orifice diameter, etc.) on the erosion rate of breathable bricks, the dissolution rates of salt, borax, sodium carbonate and mixtures of salt and sodium carbonate in different proportions in water were compared. Natural salt bricks were selected to simulate the material of breathable bricks for erosion water simulation test. Using water to simulate molten steel, blowing compressed air in a 1:10 plexiglass model, changing the blowing parameters (pressure, flow rate and blowing time), measuring the change in the size of the nozzle holes of the permeable bricks before and after blowing, and calculating the erosion of the nozzle holes conditions (radial erosion velocity, axial erosion velocity, and erosion angle), to construct the relationship between the gas injection parameters and the erosion velocity of the permeable brick. According to the size of the injection hole, the injection parameters of the gas and the dimensionless number (modified Froude number, Reynolds number and apparent Mach number, etc.) The equivalent volume and equivalent diameter, the height of the gas column formed during the injection process, the transition of the bubble flow and the jet flow, etc. The research results show that the axial erosion and radial erosion velocities of the permeable brick nozzle holes both increase with the increase of the bottom blowing air supply flow rate, and the erosion angle is little affected by the nozzle hole diameter and gas flow rate. , which can improve the stirring effect of the bottom blowing gas on the molten pool. The research results have reference significance for the improvement of re-blowing technology.

 

Through the material selection test, natural salt bricks are used to simulate the material of breathable bricks, water is used to simulate molten steel, and injection holes of different diameters are used to carry out injection tests under different pressure and flow conditions. After each injection, the erosion data of injection holes are measured. The corrosion damage of the vented bricks under different injection conditions can be obtained. The corrosion loss of the permeable brick spray hole is the dissolution process of water to the salt brick under the condition of gas agitation, not only the scouring of the brick by the gas, which is very similar to the actual melting loss of the permeable brick. According to the test data, the similar number calculation of the injection process is carried out, and the interaction between the injection gas and the molten pool is analyzed by using the calculation results.

(1) The axial erosion velocity and radial erosion velocity of the nozzle holes of the permeable brick increase with the increase of the bottom blowing air supply flow. The design of the permeable brick should prevent the two nozzle holes from overlapping too much in the direction of the erosion zone.

(2) The large erosion angle (about 80°) at the upper part of the nozzle hole of the permeable brick is caused by the upward suction of the bottom blowing airflow and the formation of a horizontal circulation at the outlet of the nozzle hole of the permeable brick. The erosion angle is little affected by the diameter of the orifice and the gas flow.

(3) The erosion of the lower part of the orifice is mainly caused by the water leaking down the wall of the orifice to dissolve the wall of the orifice, and the erosion angle is about 10°. It is similar to the expansion angle of the airflow, and is little affected by the diameter of the nozzle hole and the flow rate of the bottom blowing gas.

(4) The use of nozzle holes with a smaller diameter can enhance the stirring effect of the bottom blowing gas on the molten pool, but it is necessary to increase the gas source pressure for the re-blowing, which should be paid attention to in the construction of domestic converters or equipment renovation.

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