| With the continuous improvement of ironmaking level,the longevity of blast furnace has become a common concern of ironmaking workers and researchers,and also an important guarantee for high efficiency and low consumption in iron and steel enterprises.The middle and lower part of BF mainly includes high heat load areas such as furnace belly and furnace waist directly washed by gas flow and furnace charge,as well as hearth and furnace bottom areas in direct contact with liquid molten iron.The life and safety of the lining in the middle and lower part of BF is the main limit of its service hours.How to prolong the service life of BF and realize a scientific furace blowing out under the premise of safety and ensuring certain smelting intensity and productivity are important issues related to safety andproduction cost.The basis and foundation of long life of BF mainly depends on the proper selection of refractory materials,reasonable lining masonry structure and size parameters,efficient lining cooling equipment and scientific and standardized heating-up system.This article mainly researches the above aspects,and in the process of simulating and analyzing thethermodynamic coupling characteristics under the conditionof furnace heating and opening inthe middle and lower part of BF,the basic long-life technology which is used to realize the longevity operation of BF,is analyzed and optimized as well.The main contents of this paper are as follows:(1)High-quality refractory is the most basic condition for a reasonable lining masonry structure.Therefore,a reasonable,accurate and true evaluation of the changing laws of thermophysical properties and mechanical properties of refractories for BF is not only of guiding significance for the preparation of refractories,but also provides security for the reliable and stable operation of refractories in the service process of BF.Based on the lack of data,this article conducts a multi-factor regular contacted experiment on the thermal properties and mechanical properties of unshaped refractory closely related to the thermodynamic coupling calculation of the furnace lining structure with professional instruments,and comprehensively describes the mechanical properties of carbon ramming material in an uncured state through the triaxial variable confining pressure cycle experiment,it can not only select high-quality refractory materials for new or overhaul blast furnaces,but also provide parameters that meet the actual state for the simulation calculation of coupling characteristics.(2)On the premise of selecting high-quality refractory materials,reasonable masonry structure and size parameters of hearth and bottom become the main factors that determine the service life of the furnace.This article firstly analyzes the heat transfer characteristics of different masonry structures of BF hearth,aiming at the problem of whether large or small carbon bricks are used in the masonry structure of BF hearth at present,and the characteristics of heat transfer characteristics of the two types of hearth masonry structures are obtained according to whether the furnace hearth tamping filler layer can reach the optimal solidification temperature in the furnace baking state and the difficulty of forming a stable slag iron protective layer on the brick lining hot surface in the furnace opening state;Secondly,the thermodynamic coupling characteristics of large carbon bricks wet hearth structure and dry hearth structure are analyzed,and the respective characteristics of the two brick-lined hearth masonry structures are obtained too;Finally,the calculation method of the remaining thickness of the carbon brick with no temperature measurement at the center of the blast furnace is improved.On the basis of this,the advantages and disadvantages of the heat transfer characteristics of the upper-mounted water pipe cooling and the bottom-mounted water pipe cooling bottom structure are discussed.(3)The safety and stability of the cooling stave is the foundation for the long campaign operation of the blast furnace.Firstly,This paper analyzes the heat transfer characteristics of the copper cooling stave,and obtains the influence of each parameter change on its heat transfer characteristics distribution rule;Secondly,the heat transfer model of the copper cooling stave structure of the profile tubes(oval,rectangle,double circle,triple circle and regular hexagon)that have appeared in recent years,the optimal selection of the cooling pipe type is made based on the heat transfer characteristics of the copper cooling stave;Finally,based on the optimal tube type selection of copper cooling stave,in order to reduce the risk of high temperature failure,the heat-structure coupling calculation was carried out by simulating the furnace belly heat transfer model of oval pipe copper cooling stave with brick hot surface uncovered with slag skin.From the safety of copper cooling stave temperature,based on the response surface method and Monte-Carlo simulation analysis method,the correlation degree between each parameter and the index parameter is quantitatively calculated by taking the thickness of the copper cooling wall body,the cooling specific surface area,the cooling water velocity and the cooling water temperature as the comparison sequence and the maximum temperature of the copper cooling wall body as the index.Then,the response surface model and NSGA-? genetic algorithm are combined to optimize the structure parameters and longevity technology of the furnce belly region with the maximum thermal stress of the copper cooling wall body as the optimization objective,and the furnace belly region structure models before and after optimization are compared and analyzed.Through comparison,it is found that the optimized structure of the furnace belly has been improved obviously in terms of heat transfer characteristics and mechanical properties,while reducing the cooling water flow rate and the thickness of the cooling wall body,reducing the iron-making cost of the enterprise.At the same time,it also verifies the effectiveness of the combination of response surface method and NSG A-? genetic algorithm in optimizing the structure of the furnace belly.(4)Furnace heating for new construction or overhaul of BF is an important technological process to improve the performance of refractory masonry structure of furnace body.Taking a 1750m3 BF as an example,this paper first uses CFD fluid software to establish a furnace gas flow model at the hearth and bottom of the furnace to analyze the characteristics of furnace gas flow in the hearth and bottom of the furnace,and discusses the relationship between the.comprehensive convection heat transfer coefficient between the furnace gas and the hot surface material at the hearth and bottom of the furnace with the changes of various factors during the furnace baking process;Secondly,the heat transfer characteristics of heat transfer model of the furnace hearth and furnace bottom under furnace heating conditions are analyzed,and the correlation formula of the temperature field of each layer structure of the furnace hearth and furnace bottom with the change of each factor is obtained;Finally,for the key links of the furnace heating:furnace temperature rise curve,furnace air volume curve and cooling water flow rate adjustment,based on the theoretical analysis and combined with the previous practical experience,a more scientific,reasonable and optimized furnace heating system is presented,which is proposed to make the furnace heating more efficient and energy saving. |
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