The purpose of this study is to explore the possibility of using industrial lignin instead of pulverized coal as a reducing agent for the production of direct reduced iron (DRI), thus reducing CO 2 emissions. The pyrolysis characteristics and kinetics of pulverized coal and industrial lignin were studied by nonisothermal thermogravimetry. In the three stages of pyrolysis, the weight loss rate of industrial lignin is higher than that of pulverized coal. The volatile matter of industrial lignin is easier to release than that of pulverized coal, but the coking process is longer than that of pulverized coal. The activation energies of pyrolysis of Lu'an anthracite (LA), Shen'mu bituminous coal (SM), alkali lignin (AL), and magnesium lignosulfonate (ML) were 71.10, 70.30, 55.20, and 37.34 kJ•mol −1 at the middle-temperature stage, and 133.64, 98.31, 57.78, and 46.68 kJ•mol −1 at the high-temperature stage, respectively. After pyrolysis, a few nanometer thick carbon film structure appears in alkali lignin coke, which is conducive to the reduction of iron ore powder.
Decreasing the MgO content can improve most of the metallurgical properties of sinter, but the low-temperature reduction disintegration index (RDI) property will be worse. In order to improve the RDI property of sinter under certain MgO contents, the effects of fine MgO-bearing flux on the strength of sintered samples before and after reduction in three systems (Fe 2 O 3 -MgO, Fe 2 O 3 -MgO-CaO, and Fe 2 O 3 -MgO-CaO-SiO 2 ) were investigated in the present work. The experimental results show that (1) in the three systems, the percentage of fine light calcined magnesite (LCM) increases from 0 to 100%, and the compression strength of the samples before reduction increases from 0.140 to 0.187 MPa, from 0.115 to 0.175 MPa, and from 0.121 to 0.164 MPa, respectively. The compression strength of the samples after reduction increases from 0.062 to 0.151 MPa, from 0.100 to 0.156 MPa, and from 0.099 to 0.151 MPa, respectively. (2) The fundamental reason is that the fine powders can increase the specific surface area and the surface energy of the interface. It is beneficial to promoting the mineralization of MgO-bearing flux. More formation of MgO•Fe 2 O 3 may increase the strength of samples before reduction. Less transformation from Fe 2 O 3 to Fe 3 O 4 may increase the strength of samples after reduction. The microstructures of samples are more compact and uniform. Therefore, fine LCM can improve the strength of sinter before and after reduction. The outcomes of the present work can improve the sintering quality by using the fine MgO-bearing flux in the sintering process.
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