| The technical policy of modern blast furnace is"long life,high efficiency,low consumption,high quality and environmental protection",among which"long life"is the basis for realizing all technical objectives of blast furnace.In view of the damage of blast furnace lining and cooling stave,this paper takes the blast furnace of WISCO as the research object,firstly determines the research method of long-life technology of blast furnace lining and cooling stave,and then studies the damage mechanism of lining and cooling stave.On this basis,from the perspective of heat transfer,the research on hearth structure design and lining type selection is carried out,and the development and application of monitoring system for slag skin and heat flux intensity of copper cooling stave in high heat load area are discussed.Meanwhile,optimization measures for long campaign life of blast furnace in WISCO are put forward from the perspective of production practice.The main conclusions are as follows:The erosion characteristics of hearth and bottom of No.4 and No.5 blast furnaces in WISCO are mainly characterized by hearth girth zone erosion and hearth bottom elephant foot erosion.The former is caused by the joint action of thermal stress and harmful elements,which leads to the formation and propagation of cracks;the latter is mainly due to the shallow dead depth of dead man and molten iron circulation.In order to solve the problem of abnormal temperature rise at the bottom of the furnace in the middle of the service life,WISCO adopts titanium ore to protect the furnace.After the furnace is shut down,the analysis shows that there are Ti C,Ti N and Ti in the sediment,and the particles are wrinkled and stacked.When they are attached to the hearth side wall and bottom,the erosion process can be effectively alleviated.The production practice of WISCO shows that the titanium content of pig iron can reach 0.10-0.20%when the amount of vanadium titanium ore is 2%-3%,the fluidity of slag iron is acceptable,and the erosion rate of furnace lining is controlled.The damage investigation of No.5,No.1,No.7 and No.6 blast furnaces of WISCO was carried out.It was found that the wall cracking caused by longitudinal and transverse cracks was the main manifestation of the cast iron cooling stave,and the wall body was burnt or even dropped off in serious parts.The main damage reasons were the wall cracking caused by thermal stress and the oxidation and growth of cast iron matrix in blast furnace atmosphere.Based on the analysis of mechanical properties,chemical composition,SEM and EDS,the damage mechanism of copper cooling stave is carried out.When slag skull falls off,the gas flow and burden directly contact with the hot surface of copper cooling stave,so that the wall temperature increases,the mechanical properties decrease and thermal deformation occurs.The long-term accumulation of stress and strain makes micro cracks,and then the melting loss occurs under the penetration of slag iron and gas and fall off.The heat transfer calculation shows that the drying effect can be guaranteed only when the water supply is cut off.The calculation results show that cast iron cooling stave can meet the needs of hearth heat transfer.For the two hearth structures of"cast iron cooling stave+large carbon brick"and"cast iron cooling stave+composite carbon brick",the research shows that when the ceramic cup exists in the early stage of furnace service and the thermal conductivity of large carbon brick is 25W/(m·K),the hot surface temperature of the former carbon brick is 571?and the latter is 537?,which can basically prevent the occurrence of chemical reaction of harmful elements.When the hot surface of the lining is reduced to 1150?,the residual thickness of the former refractory is 850mm and the latter is 1060mm,which can meet the requirements of long service life of blast furnace.For the"cast iron cooling stave+large carbon brick"structure hearth,the increase of specific surface area of cooling stave has little influence on lining temperature.In addition,the characteristics of vertical and horizontal cooling staves are compared and analyzed.Considering the life cycle demand of hearth,the vertical cooling stave is recommended.Finally,the technical countermeasures for prolonging the life of BF hearth and the evaluation method of hearth safety status are put forward.WISCO adopts the method of analyzing cooling system data and furnace shell temperature measurement to comprehensively judge the hearth condition,and the effect is good.The characteristics of slag skull of copper cooling stave were studied.The main phases of slag skull are albite,spinel and carbon.The content of Al2O3in slag skin is high,and it is easy to form magnesia alumina spinel with high melting point.The results show that the fluidity temperature of slag skull is 1584.1?,the viscosity is 1000m Pa·s(1550?),and the thermal conductivity is about 1.5W/(m·K).The calculation method of slag skull thickness,heat flow intensity and furnace gas temperature of WISCO was determined.The monitoring system of slag skull thickness and heat flux intensity of copper cooling stave was developed.It can help researchers master the fluctuation law of blast furnace slag skin.In view of the damage problem of cast iron cooling stave in the bosh,the lower thickness of the stave is increased and the belly angle is reduced by using the abnormal shape of the cooling stave which is narrow at the top and wide at the bottom.Aiming at the problem of the bottom damage of the copper cooling stave,the inlet pipe is changed into the convex cover design to prevent the gas flow flowing into the water inlet pipe from the connection of the bosh and hearth.In daily production,WISCO takes measures to control harmful elements,stabilize material structure,maintain reasonable heat system and slagging system,and strengthen cooling system management to ensure reasonable slag skull thickness of cooling stave,so as to effectively extend the service life of cooling stave. |
PDF Full Text Request