Application of the genetic algorithm to estimate the parameters related to the kinetics of the reduction of the iron ore
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Application of the Genetic Algorithm to Estimate the Parameters Related to the Kinetics of the Reduction of the Iron Ore, Coal Mixture AMIT KUMAR and G.G. ROY A novel methodology has been developed to calculate the kinetic parameters associated with reduction of ore-coal composite mixtures and to describe the time course of reduction of hematite to iron. The empirical parameters, namely, the three sets of activation energies and frequency factors, have been estimated by employing an evolutionary optimization tool, the genetic algorithm (GA). The model prediction matches well with the experimental literature data. The estimated activation energies are higher than the corresponding intrinsic values, indicating the role of heat transfer in the process.
The direct reduction of iron ore, coal composites is a cokefree and environmentally friendly process. Use of noncoking coal, unused iron-rich ore fines, coal fines, process integration (ore and coke preparation in one unit), less emission, and economic production are major driving forces toward studies evaluating prereduced ore-coal composites as a feed to the blast furnace and even in the steelmaking unit. Several fundamental studies have also been conducted on reduction kinetics of ore-coal composite pellets.[1,2] Several semiempirical models have also been put forward to determine the time course of the reduction of ore-coal composite pellets.[3,4] The validity of these models depends critically on accurate estimation of the parameters related to kinetics of the iron oxide reduction process. The present model
AMIT KUMAR, Undergraduate Student, and G.G. ROY, Associate Professor, are with the Department of Metallurgical & Materials Engineering, Indian Institute of Technology, Kharagpur 721 302, India. Contact e-mail: [email protected] Manuscript submitted March 18, 2005. METALLURGICAL AND MATERIALS TRANSACTIONS B
applies an evolutionary optimization tool, the genetic algorithm, to estimate these parameters for the first time. The reactions for the coal-based direct reduction actually take place in three steps by gaseous intermediates (CO, CO2), namely, hematite to magnetite, magnetite to wustite, and wustite to iron. Hematite to magnetite: 3Fe2O3 CO 2Fe3O4 CO2
[1]
Magnetite to wustite: Fe3O4 CO 3FeO CO2
[2]
Wustite to iron: FeO CO Fe CO2
[3]
The CO gas in turn is produced by gasification of carbon by CO2, as follows: C CO2 2CO
[4]
Assuming that the transition of hematite to magnetite, magnetite to wustite, and wustite to iron are first-order reactions, the production of these species may be given by the following mass balance equations:[3] EH dH Hk H expa b dt RT
[5]
EH EM dM xHk H expa b Mk M expa b dt RT RT
[6]
EW EM dW yMk M expa b Wk W expa b dt RT RT
[7]
EW dF zWk W expa b dt RT
[8]
Here, x, y, and z are the stoichiometric factors; kH, kM, and kW are the frequency factors; and EH, EM, and EW are the activation energies for the reduction of hematite to magnetite, magnetite to wustite, and wustite to iron, respect
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