Effect of Sintering and Porosity Development on Direct Reduction of Manganese Ore Pellets
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https://doi.org/10.1007/s11837-020-04479-9 Ó 2020 The Minerals, Metals & Materials Society
SINTERING OF OXIDES AND CONCENTRATES
Effect of Sintering and Porosity Development on Direct Reduction of Manganese Ore Pellets XI LING
,1,2 RICHARD ELLIOTT,1,3 and MANSOOR BARATI1,4
1.—Department of Materials Science and Engineering, University of Toronto, 184 College Street, Toronto, ON M5S 3E4, Canada. 2.—e-mail: [email protected]. 3.—e-mail: [email protected]. 4.—e-mail: [email protected]
High manganese steels with > 10% Mn offer a combination of high tensile strength and good ductility, two critical properties for automotive steels. Conventional routes to produce the Mn units used for steelmaking are energyand capital-intensive. Therefore, a novel methane-based solid-state reduction process for manganese ore pellets is under investigation. It was found in preliminary tests that the reduction of ore pellets by methane was limited by gas transport to the pellet interior. To enhance the reducibility of Mn ore pellets, this study aimed at improving pellet porosity through adjustment of Mn ore powder particle size and the addition of limestone, which thermally decomposes to CaO and CO2. The change in compressive strength with an increase in pellet porosity was also studied. It was found that the increase in porosity as a result of limestone addition improves the reducibility of pellets and decreases the pellet strength. The effect of particle size on pellet reducibility was, however, more complicated because of the simultaneous change in the total surface area and sintering behavior of the particles.
INTRODUCTION Manganese is an essential alloying element in steelmaking with > 13 million metric tons of manganese alloys used in the steel industry annually.1 High content of manganese increases the strength of steels without sacrificing the ductility, two properties that cannot be improved simultaneously in the traditional hardening processes. Common manganese alloys, i.e., ferromanganese (FeMn) and silicomanganese (SiMn), are dominantly produced via carbothermal reductions of manganese ores by coke in submerged arc furnaces (SAFs). Several drawbacks are associated with this method including consumption of large amounts of energy, for example, 18,400 MJ to 24,000 MJ per ton of highcarbon ferromanganese (HC FeMn).1 Besides, high consumption of carbon, 300 to 360 kg/ton alloy, not only increases the cost of manganese production but also produces large amounts of greenhouse gases.1,2 As an attempt to address such issues, alternative reductants such as natural gas and hydrogen have been considered for direct reduction of Mn ores. As a (Received August 27, 2020; accepted October 27, 2020)
reductant with higher carbon activity,3 methane can reduce manganese oxides at a much lower temperature (Reactions 1 and 2) and generates smaller amounts of greenhouse gases. Natural gas, as the main source of methane, is also more economically competitive than coke in certain areas. MnO þ
MnO þ
10 1 C ¼ Mn7 C3 þ C
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