Kinetics of the solid-state carbothermic reduction of wessel manganese ores
- PDF / 1,811,983 Bytes
- 12 Pages / 603.28 x 783.28 pts Page_size
- 100 Downloads / 194 Views
I.
INTRODUCTION
M A N G A N E S E ore production in South Africa is estimated to be the second largest in the world after the former USSR. m Manganese ore deposits in South Africa that are situated in the Northern Cape Province include Wessel, Mamatwan, and Hotazel mines. Wessel type is a hydrothermally upgraded, carbonate poor, braunite, hausmannite, bixbyite, and braunite II bearing manganese ore. 12j Prereduction of manganese ore with carbon could be a promising route to increase cost-effectiveness of ferromanganese production, t31The prereduced material may then be smelted in an open-arc furnace to produce ferromanganese and slag. It was reported that the energy consumption has dropped from about 3000 kWh/ton FeMn to about 1600 kWh/ton FeMn when prereduced pellets were used instead of ore in the electric furnace, t41 Most of the investigators who studied the reduction of metal oxides by carbon assumed that the overall rate of reaction was controlled by the reaction between carbon dioxide and carbon at temperatures up to 1000 ~ At higher temperatures, this reaction (also known as Boudouard reaction) is quite fast, and hence, the ratecontrolling step of reduction of metal oxides could be different. [8] CO2 + C = 2CO At low temperatures up to 1000 ~ to 1050 ~
[1] the rate
GUVEN AKDOGAN, formerly Doctoral Student, Department of Metallurgy and Materials Engineering, University of the Witwatersrand, Johannesburg, is Lecturer with the Mining Engineering Department, Istanbul University, Turkey. R. HURMAN ERIC, Professor in the Chamber of Mines, Chair of Extractive Metallurgy, and Head of Department, is with the Department of Metallurgy and Materials Engineering, University of the Witwatersrand, Johannesburg, WITS 2050, South Africa. Manuscript submitted December 14, 1993. METALLURGICALAND MATERIALSTRANSACTIONS B
of Reaction [1] is dependent upon the temperature and is controlled by chemical reaction. At temperatures above 1100 ~ the rate is controlled by diffusion, tg-191 The kinetic studies on the C-CO2 reaction have not produced a generally accepted value for activation energy for Reaction [1]. The reported activation energies vary from 246.6 to 405.5 k J / k g / m o l , t6'l~ Kor I191 investigated the rate of reduction of MnaO4 to MnO by carbon between 900 ~ and 1200 ~ and concluded that the overall rate is controlled by the rate of oxidation of carbon in CO2; although, there is a considerable overlap between pore diffusion control and chemical reaction control for the Boudouard reaction in the range 1000 ~ to 1100 ~ t2~ Tereyama and Ikeda t231reduced MnO with carbon under helium atmosphere in the range 1100 ~ to 1200 ~ and reported that the overall rate seemed to be controlled by the rate of oxidation of carbon by carbon dioxide. Rankin and Van Deventer t241 developed a kinetic model for the reduction of MnO by graphite derived on the conclusion that the gasification of graphite was the rate-controlling step in the temperature range 1200 ~ to 1425 ~ for which an activation energy of 240.4 k J / k g / tool was
Data Loading...
