Simulation of the Internal Temperature Field and Flow Field in a Double-Layer Sintering Bed.

To meet the requirements of Angang's blast furnace smelting for sintering output, improve the double-layer sintering process, and determine the appropriate parameters for the double-layer sintering process, this article established a mathematical model and simulated the temperature field in the burden bed and the changing trends of O2 and CO2 concentrations in the sintering tail gas during the single-layer and double-layer sintering processes of the sintering machine. The simulation results show that (1) compared with the sintering time of single-layer sintering in the baseline period, the error of the single-sintering model is only about 2.5%, and the model's accuracy is high. (2) Two combustion zones of double-layer sintering increase O2 consumption, and the O2 concentration in the tail gas decreases significantly. (3) The thickness of the upper and lower feeding layers of double-layer oxygen supplement sintering is 650 + 300 mm better than that of 600 + 350 mm. (4) The optimal secondary ignition time is 15 min.

Effects of Fine MgO-Bearing Flux on the Strength of Sinter before and after Low-Temperature Reduction.

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 (Fe2O3-MgO, Fe2O3-MgO-CaO, and Fe2O3-MgO-CaO-SiO2) 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·Fe2O3 may increase the strength of samples before reduction. Less transformation from Fe2O3 to Fe3O4 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.

Pyrolysis Characteristics of Industrial Lignin for Use as a Reductant and an Energy Source for Future Iron Making.

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 CO2 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.