Numerical Calculation Of Blast Furnace Hearth Tapping Model And The Thermal Design

The blast furnace is an important production equipment of steel smelting, and the cost of construction and maintenance is huge. With the rapid development of economy and the advancement of large-scale blast furnace of china, people pay more and more attention to the life of blast furnace. And the life of blast furnace hearth is an important effect factor of the blast furnace's overall life. So prolonging the life of blast furnace hearth can reduce the cost of smelting and make more economic benefits. The furnace bottom contacts with the high temperature iron directly in the process of tapping iron, and the erosion is an important factor of furnace hearth's breakage. So analyzing influencing factors of erosion and looking for reasonable and effective research methods to reduce the erosion have important significance to guide the design and process control of blast furnace.This paper gives an analysis of the blast furnace hearth's erosion boundary through the studies of heat transfer balance curve. Current studies usually takes the 1150? isothermal which is iron's solidification line as the estimate of erosion boundary. Controlling the 1150? isothermal in a certain position through the reasonable cooling and the protection of slag skin layer has certain practical value on the design and analysis on lifetime of furnace hearth.The overall structure of the furnace hearth is quite complex, as there are cooling pipes in the bottom and sidewall of it. Under the premise of guaranteeing accuracy, according to the principle of heat transfer, this paper equivalently converts the convective heat transfer coefficient of the sidewall and bottom of the hearth to greatly simplified the structure of cooling walls and improve the efficiency of the analysis and calculation.This paper established the calculation model of furnace hearth, focused on the research of the 1150? isothermal distribution during the calculation of the heat transfer balanced boundary. Use heat conduction theory and the method of lined unit and molten iron unit substituting mutually to simulate erosion boundary moving automatically. Taking the molten iron solidification line as the erosion criterion we get the erosion shape of the ideal tapping iron condition which is the operation model. In addition, we discussed the influence of lined thermal conductivity, convective heat transfer coefficient of furnace's sidewall and bottom, capacity utilization coefficient and the porosity of dead-man coke to the heat transfer balanced boundary of the operation model, and gives quantitative results at last, it has certain reference value to the design and operation of blast furnace.This paper analysed the safety thickness of the lined structure under internal pressure, the minimum thermal stability safety thickness of the cooling wall and the critical thickness which molten iron begin to solidfy, then discuessed a new criterion which based on the critical thickness is greater than the safety thickness.