Blast furnace model

For practical reasons, the blast furnace hearth is divided into two principal zones the bottom and the sidewalls. Each of these zones exhibits unique problems and wear mechanisms. The largest refractory mass is contained within the hearth bottom. The outside diameters of these bottoms can exceed 16 or 17 m and their depth is dependent on whether underhearth cooling is utilized. When cooling is not employed, this refractory depth usually is determined by mathematical models these predict a stabilization isotherm location which defines the limit of dissolution of the carbon by iron. Often, this depth exceeds 3 m of carbon. However, because the stabilization isotherm location is also a function of furnace diameter, often times thermal equiHbrium caimot be achieved without some form of underhearth cooling. 

EXAMPLE 2.1 MODELING AND OPTIMIZING BLAST FURNACE OPERATION... 

The next step in formulating the problem is to construct a mathematical model of the process by considering the fundamental chemical and physical phenomena and physical limitations that influence the process behavior. For the case of the blast furnace, typical features are... 

The flow pattern of gas through blast furnaces was studied by VDEh (Veren Deutscher Eisenhiittenleute Betriebsforschungsinstitut) by injecting Kr-85 into the air stream entering the tuyeres of the 688 m furnace. A sketch and listing of pertinent quantities for run 10.5 of 9.12.1969 is shown in Fig. P13.1. Assuming that the axial dispersion model applies to the flow of gas... 

Dynamic reactions like processes in blast furnaces, roasting processes or the solidification of liquid alloys can be simulated using the REACTOR MODEL... 

The last part of ionic electrochemistry, ionics, is about pure electrolytes. A few decades back this electrochemistry would have been all about high-temperature liquids (liquid common salt at 850 °C was the role model). However, this has changed, and the temperatures for eliminating the solvent have deaeased considerably. Some molten salts are now room temperature liquids. At the other end of the temperature scale are the molten silicates, where large polyanions predominate. These are important not only in the steel industry, where molten silicate mixtures form blast furnace slags, but also in the corresponding frozen liquids, the glasses. 

Model of Burden Distribution in Operating Blast Furnaces... 

The model has been applied on data from the blast furnace No 1 of Rautaruukki Steel in Raahe, Finland. This medium-sized bell-top furnace is equipped with movable armors with ten possible positions (MA=1,...,10), has a throat radius of Rt = 3.15 m and a radar that measures the burden level 0.6 m from the furnace throat wall. The furnace burden consists of sinter (S), pellets (P) and coke (C). The data evaluated are from two distinct periods where the furnace was operated with ten-dump charging sequences. The average burden-layer thicknesses, Azr, estimated from the radar signals, as well as the main characteristics of the charging programs are given in Table 1. 

A model for studying the formation of burden layers in the ironmaking blast furnace has been developed on the basis of a single-point measurement of the stock level by radar. The model, which, furthermore, makes use of geometrical conditions of the problem at hand, has been kept conceptually simple so it can be applied to track the burden distribution in operating blast furnace. The model has been tuned to data from a... 

Hinnela, J., Saxen, H. and Pettersson, F., 2002, Modeling of the Blast Furnace Burden Distribution by Evolving Neural Networks, submitted manuscript. 

Nikus, M., 2001, A set of models for on-line estimation of burden and gas distribution in the blast furnace. Doctoral dissertation. Heat Engineering Laboratory, Abo Akademi University, Finland. 

Omori, Y. Ed., 1987, Blast Furnace Phenomena and Modelling, The Iron and Steel Institute of Japan, Elsevier, London, UK. 

Saxen, H. and Hinnela, J., 2002, Model for burden distribution tracking in the blast furnace, accepted for Mineral Processing and Erxtractive Metallurgy Review, Special Issue on Advanced Iron Making. 

There have been a number of attempts to model the lead blast furnace, notably Lumsden (1971), MadeUn, Sanchez and Rist (1990), as well as descriptions of the prcxrss chemistry by Willis (1980) and Oldwright and Miller (1936). 

Madelin, B, Sanchez, G and Rist, A, 1990. Investigation and modelling of the non-ferrous blast furnaces of Metaleurop, in Proceedings Lead and Zinc 90 Symposium, pp 571-596 (The Minerals, Metals and Materials Society Warrendale and American Institute of Mining, Metallurgical and Petroleum Engineers Littleton). 

Kellogg, H H, 1990. A practical model of the imperial smelting zinc-lead blast furnace, in Proceedings Lead-Tine 90, pp 549-569 (The Minerals, Metals and Materials Society Warrendale). 

The deviation of the blast furnace from plug flow behavior can be described by the tanks-in-series model (Section 4.10.5) or by the dispersion model (Section 4.10.6). 

Tanks-in-Series Model Figure 6.5.23 shows the residence time distribution of the investigated blast furnace in comparison to a cascade of stirred tanks with 20, 30, and 50 tanks. The best fit is obtained for a number N of 30. For conversion of a gaseous reactant i in a blast furnace, we therefore have according to Eq. (4.10.32) with N=30 ... 

Standish, N. and Polthier, K. (1975) An interpretation of tracer results from an operating blast furnace by a dispersion model, in Blast Furnace Aerodynamics, Australian Institute of Mining Metallurgy, Melbourne, p. 99. 

The scale-up problems become much more difficult if the large scale reactor differs considerably from these ideal models. Notorious examples are fluidized bed reactors without internals, stirred tanks where the macro mixing is rate determining, and reactors filled with solid material where large temperature gradients exist, such as coke ovens and blast furnaces, and some catalytic gas-phase processes. 

It might be impossible to pinpoint a precise time of birth for chemical reaction engineering, but some milestones are worth noting. The central issue in chemical reaction engineering is to determine the residence time, which is needed to obtain the desired product with specified quality requirements. This idea has existed in the human mind since time immemorial, starting from food preparation over an open flame. An excellent example of an early developed chemical reactor is the empirical construction of a blast furnace for the treatment of iron ores a semibatch reactor with an optimized shape. The equipment was developed empirically throughout centuries, whereas today advanced mathematical modeling is applied to predict the behavior of iron production units. 

Jha, R., Sen, P.K., Chakraborti, N. Multi-objective genetic algorithms and genetic programming models for minimizing input carbon rates in a blast furnace compared with a conventional analytic approach. Steel Res. Int. 85(2), 219-232 (2014) Pettersson, F., Chakraborti, N., Saxen, H. A genetic algorithms based multiobjective neural net apphed to noisy blast furnace data. Appl. Soft Comput. 7(1), 387-397 (2007)... 

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