As ironmakers are well aware, it was only a few decades ago that the blast furnace was viewed as a strange 'black box'. Recently, however, various in-furnace phenomena have become the subject of serious scientific study, largely as the result of the 'dissection' of dead furnaces, together with the development of advanced monitoring and control techniques. In this way, a new frontier has been opened within the venerable domain of metallurgy. In the light of these new developments, the Committee on Reaction within Blast Furnaces was set up in March 1977 by the Joint Society ofIron and Steel Basic Research - a cooperative research organization of the Iron and Steel Institute of Japan (ISIJ), the Japan Institute of Metals (JIM) and the Japan Society for the Promotion of Science (JSPS). Consisting of twenty-six members and advisors drawn from the fields of academia and industry, this committee collected, discussed, and evaluated numerous papers during its five- year commission.
Particular attention was paid to the interpretation of findings drawn from the autopsy of dead furnaces, in the context of the live furnace state, and the correlation of data regarding cohesive zone configuration, level, and furnace performance. The results of this intense research activity are presented here in the hope that they will serve not only as a source of enrichment to the professional knowledge of researchers and operators, but also as textual material for graduate students in the field of metallurgy.
I: Phenomena in the Blast Furnace.- 1 Dissection of Quenched Blast Furnaces.- 1.1 Introduction.- 1.1.1 Background to the present study.- 1.1.2 Methods of quenching and their effects.- 1.1.3 General in-furnace situations and peculiar phenomena.- 1.2 Relation Between Behavior of Descending Burden and State of Combustion Zone.- 1.2.1 Fundamental descent behavior of burden in the shaft.- 1.2.2 Asymmetrical descent of burden.- 1.3 Behavior of the Core.- 1.4 Situations in and Around the Combustion Zone.- 1.4.1 State in front of the tuyere nose.- 1.4.2 Formation of shell and movements at the lower part of the raceway.- 1.4.3 Conditions inside the furnace and the shape of the raceway.- 1.5 Shape of Cohesion Zone and Relation to Distribution and Movement of Burden.- 1.5.1 Formation of the cohesion zone.- 1.5.2 Relation between shape of the cohesion zone and operation conditions.- 1.6 Behavior of Circulating Elements.- 1.6.1 Effect of water quenching on the circulating elements.- 1.6.2 Behavior of circulating elements and amounts of circulation.- 1.7 Changes in Properties of Burden Materials.- 1.7.1 Macroscopic changes.- 1.7.2 Microscopic structural and composition changes.- 1.7.3 Effects of circulating elements on the behavior of the cohesion zone.- 1.8 Reactions in the Hearth.- 1.8.1 Slag formation reactions.- 1.8.2 Changes in the metal composition.- 1.9 Concluding Remarks.- 1.10 Addendum.- 1.10.1 Arrangement inside the furnace.- 1.10.2 Changes in properties of the burden.- 2 Measurements in Operating Blast Furnaces.- 2.1 Objectives of Blast Furnace Measurements.- 2.2 Development of Measurements for Clarification of Furnace Reactions.- 2.2.1 Standard instrumentation for blast furnaces a decade ago.- 2.2.2 Development of instrumentation since the introduction of blast furnace dissection.- 2.3 Relationship Between Furnace Measurement and Furnace Operation (Actual Examples).- 2.3.1 Relationship between measurements before blowing out of blast furnace and results of dissection.- 2.3.2 Measurements and estimations of the cohesive zone.- 2.3.3 Development and use of the latest sensors to study furnace interiors.- 2.4 Future Development of Blast Furnace Measurements.- II: Modelling of the Blast Furnace.- 3 Global Formulation.- 3.1 Review of Blast Furnace Models.- 3.1.1 Reichardt diagram.- 3.1.2 Operation diagram.- 3.1.3 Kinetic model.- 3.1.4 Control models.- 3.1.5 Models for estimating internal situations based on observed data.- 3.2 One-dimensional Static Model.- 3.2.1 Overall reaction rates.- 3.2.2 Overall material balance.- 3.2.3 Temperatures of gas and solid at the top of the furnace.- 3.2.4 Flow rate and composition of gas at tuyere level.- 3.2.5 Theoretical flame temperature.- 3.2.6 Temperature of gas and coke at tuyere level.- 3.2.7 One-dimensional mathematical formulation for internal state of blast furnace.- 3.2.8 Effect of various operating conditions on productivity and situation in blast furnace.- 3.2.9 Some applications of the model.- 3.3 Layered Structure Model.- 3.3.1 Radial distribution of flow rate of gas.- 3.3.2 Mathematical-kinetic model of blast furnace.- 3.3.3 Numerical analysis of blast furnace operation.- 3.3.4 Computed results.- 3.3.5 Steady-state two-dimensional modelling.- 3.3.6 Governing equations for cylindrical polar coordinates.- 3.3.7 Some auxiliary relations.- 3.3.8 Numerical solution of two-dimensional model.- 3.4 Two-dimensional Model for Gas Flow, Heat Transfer and Chemical Reactions.- 3.4.1 General concept of the radial distribution model.- 3.4.2 Momentum transfer.- 3.4.3 Mass transfer with chemical reactions.- 3.4.4 Heat transfer.- 3.4.5 Input conditions.- 3.4.6 Method of analysis.- 3.4.7 Simulation results.- 3.5 Two-dimensional Formulation by Finite Element Method.- 3.5.1 Flow analysis of gas.- 3.5.2 Computed results for gas flow.- 3.5.3 Simultaneous analysis of gas flow and heat transfer.- 3.5.4 Computed results on the simultaneous gas flow and heat transfer.- 3.6 Model for Estimating the Profile of the Cohesive Zone.- 3.6.1 General description of the mathematical model.- 3.6.2 Relation between indices estimated using the mathematical model and from blast furnace operation (cohesive zone analysis with 4000 m3 class blast furnace).- 3.6.3 Analysis of operation with decrease in production.- 3.6.4 Future direction.- 3.7 One-dimensional Dynamic Model.- 3.7.1 Outline of mathematical simulation model.- 3.7.2 Applications to blast furnace operations.- 3.8 Notation.- 4 Flow of Gas, Liquid and Solid.- 4.1 Flow of Solids During Charging and Control of Burden Distribution.- 4.1.1 Burden distribution of bell top furnaces.- 4.1.2 Burden distribution of bell-less top furnaces.- 4.2 Flow of Solids in the Upper Part of the Furnace.- 4.2.1 Information from dissected blast furnaces.- 4.2.2 Burden descent model.- 4.2.3 Decrease in angle of layer inclination with burden descent.- 4.2.4 Influence of some other factors.- 4.3 Flow of Solids in the Lower Part of the Furnace.- 4.3.1 Basic phenomena.- 4.3.2 Formation of mixed zone in the peripheral region near the wall.- 4.3.3 Movement of coke to the raceway.- 4.3.4 Movement of coke in dead coke zone and hearth.- 4.4 Theoretical Approach to the Flow of Burden Material in the Furnace.- 4.4.1 Stress distribution in the blast furnace.- 4.4.2 Inclination of the dead coke zone boundary.- 4.4.3 Notation (Sections 4.3 and 4.4).- 4.5 Numerical Simulation of Radial Gas Flow Distribution.- 4.5.1 Burden distribution model.- 4.5.2 Two-dimensional gas flow in the blast furnace.- 4.5.3 Outline of results of calculation.- 4.5.4 Concluding remarks.- 4.5.5 Notation.- 4.6 Flow of Gas and Liquid in the Dropping Zone.- 4.6.1 Counter-current flow region.- 4.6.2 Cross flow region.- 4.6.3 Concluding remarks.- 4.7 Flow of Slag and Metal in the Hearth During Tapping.- 4.7.1 State of coke bed in the hearth.- 4.7.2 Flow of slag during tapping.- 4.7.3 Flow of metal during tapping.- 4.7.4 Mathematical simulation of hearth flow.- 4.7.5 Concluding remarks.- 5 High Temperature Properties of Iron Ore Agglomerates.- 5.1 Reduction Behavior in Lumpy Zone.- 5.1.1 Estimation of reducibility in lumpy zone.- 5.1.2 Determination of reaction rate constant of reduction and comparison with blast furnace operation.- 5.2 Change of Mineral Phases in Blast Furnace.- 5.2.1 Change of mineral phases during reduction.- 5.2.2 Mineral phases in reduced iron ore agglomerates.- 5.2.3 Change of gangue minerals.- 5.3 Flow Resistance of Gas Through the Fused Packed Bed.- 5.3.1 Measurement of pressure drop in fused packed bed.- 5.3.2 Numerical calculation of gas flow resistance through a fused packed bed by use of an orifice model.- 5.3.3 Equation of pressure drop in fused packed bed.- 5.3.4 Quantitative determination of softening properties.- 5.4 Effects of High Temperature Properties of Burden on Blast Furnace Operation.- 5.4.1 Factors for evaluating high temperature properties of burden.- 5.4.2 Relationship between high temperature properties of burden and blast furnace operating performance.- 5.5 High Temperature Properties of Burden with Cohesive Zone Model and Direct Measurement of Cohesive Zone.- 5.5.1 Estimation of cohesive zone with theoretical models.- 5.5.2 Effect of softening properties on gas permeability.- 5.5.3 Evaluation of softening properties of sinter.- 5.5.4 Direct measurement of cohesive zone.- 5.6 Notation.- 6 The Raceway.- 6.1 Measurement and Observation of the Blast Furnace Raceway.- 6.1.1 Movement of coke particles in the raceway.- 6.1.2 Condition near the raceway.- 6.1.3 Reactions in the raceway.- 6.2 Mathematical Model of the Raceway.- 6.2.1 One-dimensional model.- 6.2.2 Two-dimensional model.- 6.3 Notation.- 7 The Lower Region of the Blast Furnace and the Slag-Metal-Gas Reaction.- 7.1 Reaction of Silicon.- 7.1.1 Introduction.- 7.1.2 Behavior of silicon in the blast furnace.- 7.1.3 Kinetics of silicon transfer.- 7.2 Other Reactions.- 7.2.1 Manganese.- 7.2.2 Titanium.- 7.3 Application of Reaction Models of Silicon to Blast Furnace Operation.- 7.3.1 Review of silicon reaction models.- 7.3.2 Partition reactions of Si, S and Mn.- 7.3.3 Mathematical model of silicon reactions in the blast furnace.- 7.4 Notation.- III: Flexibility and Adaptability of Blast Furnace.- 8 Blast Furnace Ironmaking Technology in the Near Future.- 8.1 Flexible Operation.- 8.2 Increase of Furnace Life.- 8.3 Mechanization of Cast-house Operation.- 8.4 Technology Development Related to Innovative Steelmaking Process.- 8.5 Use of Blast Furnace for Producing Other Metals.