Model Study of Gas-liquid Momentum Transfer to Design Optimum Tuyere Dimension for Bottom and Top/Bottom Blown Converters

Abstract

Cold and hot model experiments on the gas-liquid momentum transfer have been carried out to optimize the relationship among gas flow rate (Q), diameter (d), and number (N) of tuyeres through which gas is blown into the steel melt. Cylindrical and converter-type vessels were used for cold model experiments, and 5t test converter in hot metal experiments. Particular attention has been paid to investigating the leakage of liquid into submerged tuyeres, swelling of bath surface, spitting and drilling of gas jet through bath.
Critical condition for the occurrence of leakage of liquid into the tuyere is given by constant Froude number, calculated from the critical cold and hot model data with temperature correction. The semiempirical equation for the swelling of bath surface is derived that involves energy dissipation rate and bath depth. A multiple regression analysis of the amount of spitting observed in cold model experiment has been done to find the influence of operational variables. A momentum balance between the dynamic pressure of the gas jet and the ferrostatic pressure of the bath has been examined to predict the drilling of gas jet through the bath.
From above observation, a region on Q/N vs. d coordinates where neither leakage of liquid nor drilling of gas jet occurs has been determined and also a method has been given to optimize the relationship among Q, N, and d for satisfactory bottom blowing operation.