Research On The Erosion Law Of Furnace Lining Based On The Calculation Of Molten Iron Flow Field And Temperature Field In The Hearth Of Blast Furnace

The longevity of a blast furnace is an important prerequisite for the long-term stable production of steel companies,and the erosion condition of the blast furnace hearth largely determines the service life of the blast furnace.The main erosion of the hearth in daily production includes molten iron scouring,thermal stress rupture of carbon bricks and molten iron dissolution,etc.Therefore,it is a key research direction for blast furnace researchers to systematically analyze the distribution of molten iron flow fields and temperature fields in the hearth during the molten iron production process,and provide reference suggestions for the daily maintenance of the hearth to achieve the purpose of improving the life of the blast furnace hearth in a comprehensive manner.In this study,a three-dimensional furnace model is established and numerical simulations of the molten iron flow fields and temperature fields are carried out based on the actual commissioning data of a blast furnace in a steel company(later referred to as“A” blast furnace).By correlating data such as shear stress and temperature distribution of the hearth wall with the actual erosion profile data of the hearth,relevant empirical equations were obtained so that key parameters such as molten iron flow velocity and hearth temperature could be used to estimate the degree of erosion of the hearth.The results of the study show that during the molten iron production process,the deadman in“A” blast furnace is in a sitting state in the hearth,which causes most of the molten iron entering the hearth to first flow into the coke-free zone(free flow space)formed between the deadman and the hearth sidewall,and then accelerates in the coke-free zone along the hearth circumferential direction towards the tophole.The area of high shear stress on the hearth sidewalls is mainly located within the 0-20° azimuthal degree of the tophole and1.0 m below the tophole.In contrast,the average molten iron flow velocity near the bottom of the hearth is very low and the corresponding shear stress is negligible.There is a significant temperature gradient near the inner surface of the hearth in contact with the molten iron,with the temperature gradient at the bottom of the hearth being greater than at the side walls of the hearth.The empirical expressions obtained by multiple linear regression show that the depth of erosion at the bottom of the hearth depends to a large extent on the temperature value and that the effect of shear stress on the depth of erosion at the bottom of the hearth is negligible;the depth of erosion at the side walls of the hearth depends more on the shear stress on the walls and the "contribution" of the wall temperature to the depth of erosion at the side walls is less than that of the shear stress,but its role is not negligible.On the basis of the conventional simulation study of “A” blast furnace,the influence of the operating parameters of the tophole(tophole depth,tophole diameter and tophole inclination),the suspension state of the deadman,the physical parameters of the deadman(deadman porosity,bottom angle of the deadman)and the structure of the refractory material on the molten iron flow field or the temperature field of the hearth was investigated using orthogonal analysis or the control variable method respectively,and the simulation results were used to propose corresponding optimisation recommendations for blast furnace production.The results show that increasing the tophole significantly reduces the shear stress on the side walls of the hearth,due to the fact that the highest velocity region of the hearth molten iron flow field is shifted from the vicinity of the mud ladle near the hearth wall to the tophole near the inside of the deadman.The order of magnitude of the effect of the operating parameters on the shear stress on the hearth wall is: tophole depth > tophole inclination > tophole diameter.According to the results of the range analysis,the lowest hearth wall shear stress peak corresponds to a tophole depth of 3.5 m,a tophole diameter of 60 mm and a tophole inclination of 11.5°.The shear stress of the bottom of the hearth is small when deadman is in the sitting state;after the deadman has changed from a sitting state to a suspended state,the average shear stress on the side walls of the hearth increases and then decreases as the suspension height increases,while the shear stress on the bottom of the hearth continues to increase.When the porosity of the deadman decreases,the distribution of shear stress on the side wall of the hearth is more or less the same,but the value of shear stress on the inner wall of the hearth increases slightly;when the bottom angle of the deadman decreases,the shear stress on the side wall of the hearth is approximately the same,but the shear stress in the inner wall of the hearth increases slightly;when the bottom angle of the deadman is reduced,the shear stress on the side wall of the hearth is also reduced.Compared with the traditional large block carbon brick furnace hearth structure,the 1423 K isotherm of the composite carbon brick structure combined with large block and small carbon brick is closer to the inner surface of the side wall of the hearth,which indicates that the heat dissipation of the composite hearth structure is better than that of the traditional hearth structure.