Diagnostic Model Of Blast Furnace Hearth With Double Inner Profile

Large-scale blast furnace is the development trend of iron and steel industry,and how to ensure the longevity and high productivity of large blast furnace is the focus of operators’ and researchers’ attention.Many years production practice shows that the loss of lining material is inevitable and irreversible in actual production process in the hearth that is located below the blast furnace.The basic way to prolong the service life of the hearth and keep the lining in a safe state for a long time is by forming "self-protection" skull on the hot surface of the hearthlining through reasonable cooling system and the introduction of excellent quality,good performance of thermal conductivity of refractory lining,in order to inhibit the 1150℃solidification isotherm of hot metal outside the hot surface of the carbon brick.However,it is not wise to blindly pursue the "self-protection" skull.The excessively thick skull will compress the inner volume of the blast furnace hearth and affect the productivity.Therefore,it is necessary to monitor and diagnose the erosion profile of blast furnace hearth in real time,and then make the corresponding production regulation operation,so as to ensure the long-term safe,stable and efficient operation of blast furnace.Considering that the traditional furnace hearth profile prediction model still has a large room for improvement in accuracy and efficiency,this study fully considers the fact that the hearth profile is double-contour,and based on the equivalent thermal resistance,finite element and Levenberg-Marquardt method(L-M method for short),an inverse-problem model for fixed grid is established to accurately and efficiently predict the inner profile of blast furnace hearth.The model is verified and applied in practice.Finally,an interactive interface is made by self-programming to realize the real-time monitoring and visual management of the hearth inner profile.The main conclusions of this study are as follows:(1)Among the three of L-M method,Newton method and gradient method,L-M method has the best inverse calculation results,having the minimum calculation relative error of 1.15%and the lowest calculation time of 4.3s.At the same time,an erosion sample featuring the elephant-foot shaped wear is used to verify the accuracy of the present model.(2)Based on the production data of a large-scale blast furnace from its blow-in to 341 weeks of operation,the evolutions of the hearth skull and remaining lining volumes are analyzed and three distinct periods are found.Before 150 weeks,a rapid loss period of refractory and a rapid formation period of skull are experienced,respectively.After 150 weeks,the hearth enters a dynamic equilibrium state of loss and buildup of the skull.In this"self-protection" period,the average erosion rate of the residual lining is only about 0.02m3/week,and the volume of the skull in the hearth fluctuates between 10 and 45m3.(3)Through monitoring the residual thickness of the hearth lining at three heights of eight directions of the hearth sidewall,it is found that the minimum residual lining thickness of the hearth sidewall is 1.246m after 341 weeks of operation,which is located at 10°circumferential direction of the hearth and at a height of 11.594m.The minimum residual lining thickness is greater than the minimum safe production thickness of 0.4m,so it is considered that the hearth is still in safe production state at present time.