Investigation into the role of the boudouard reaction in self-reducing iron oxide and carbon briquettes
- PDF / 308,899 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 1 Downloads / 191 Views
I. INTRODUCTION
UTILIZATION of iron oxide fines has significant benefits in the metallurgical industry, as they are present from the mining stage through to metal processing. Similarly, carbonaceous fines are also readily formed in all stages of processing. Through combining the iron oxide fines and the carbonaceous fines to produce a reduced oxide, or even metallic iron, utilization of what is essentially degraded resources presents an exciting prospect. This has both environmental and economic benefits. Haque and Ray[1] have shown that the mechanistic process of reaction between the two solids has generally been accepted as occurring via gaseous intermediaries (CO and CO2). That is, the iron oxide is reduced by CO and the carbon is oxidized by CO2. Iron oxide–carbon contact is not unimportant, as is evidenced by the catalysis of graphite oxidation (Boudouard reaction) by the presence of metallic iron. Autocatalysis has, however, generally been witnessed on very high grade carbonaceous materials (i.e., graphite).[2,3] Of the two broad solid-gas reactions, there is a large body of work to show that, kinetically, the Boudouard reaction displays a strong controlling influence on the carbothermic reduction. Early work by Rao[4] assumed this to be the case as reported rate constants for the Boudouard reaction were considerably higher than those of iron oxide reduction by CO. This assumption was supported by the carbothermic reduction rate being increased by decreased carbon particle size, increased carbon content, and the presence of known Boudouard reaction catalyzing agents. Fruehan[5] investigated the carbothermic reduction of iron oxide by comparing the Boudouard reaction rate (for 70 pct CO, 30 pct CO2, and 100 pct CO2) with the carbothermic reduction rate. It was found that the carbothermic reduction rates and activation energies were sufficiently similar to the oxidation of carbon and, accordingly, the Boudouard reaction JEREMY MOON, formerly Research Student, with the School of Materials Science and Engineering, University of New South Wales, Sydney, Australia, is Senior Engineer with Gorrad Masson Pacific, Melbourne, Australia. VEENA SAHAJWALLA, Professor, is Director of Sustainable Materials Processing Program, with the School of Materials Science and Engineering, University of New South Wales, Sydney, Australia, Contact e-mail: [email protected] Manuscript submitted May 15, 2004. METALLURGICAL AND MATERIALS TRANSACTIONS B
was the likely controlling reaction. This was also supported by the carbothermic reaction rate increasing with decreasing carbon particle size (inferring increased carbon surface area), and the rate increasing with increased carbon content. More recent investigations still indicate that the Boudouard reaction displays a strong degree of control for most of the carbothermic reductions of iron oxide.[6–11] However, as Srinivisan and Lahiri[12] indicate, there appears to be a transition away from the Boudouard reaction under certain conditions. Kinetic data based on instantaneous oxygen flux r
Data Loading...
