Qingmin Meng

Preparation of Chromium-iron Metal Powder from Chromium Slag by Reduction Roasting and Magnetic Separation

Chromium slag (CS) has become one of the most hazardous solid waste containing chromium and iron. Based on its characteristics, the technology of reduction roasting and magnetic separation was employed to treat CS. The major impurity element of CS is magnesium and it exists in magnesium ferrite phase, which is hard to recover iron in the absence of additives. During reduction roasting, additives (Al2O3 and CaF2) could destroy the structure of magnesium ferrite and improve the iron grade and recovery. The final product, i. e. chromium-iron powder, contains 72.54% Fe and 13.56% Cr, with the iron recovery of 80.34% and chromium recovery of 80.70%.

Influence of microwave heating on the microstructures of iron ore pellets with coal during reduction

Iron ore oxidised pellets as the burden of blast furnace present many advantages, such as uniform size, high iron grade and high physical strength. A comparison of the iron ore oxidised pellets with coal (out-proportioning) by conventional heating and microwave heating was carried out in this paper. Microstructure transformations during reduction process were investigated by optical microscopy and scanning electron microscope with energy dispersive spectrometry analysis. Micro-hardness of metallic iron phase formed in the reduction was tested with digital micro-hardness tester. The influences of microwave heating on reduction degree, morphology, iron phase and gangues were investigated, respectively. The results show that reduction time can be greatly shortened by microwave heating even at lower temperatures. The fine cracks generated, as the pellets were heated by microwave, were irradiated due to the selectivity of microwave heating. Densification of the metallic iron phase and the separation of the iron and gangues were both found to be enhanced by microwave heating.

Mechanism of Selective Desulphurization in Iron Ore Sintering Process by Adding Urea

Abstract Iron ore sintering is an important part during the ironmaking process, and a large amount of SO2 is also generated. Our previous research shows that it is an effective way to reduce SO2 content of flue gas by adding urea to a special sintering material zone position. In this paper, the mechanism of selective desulphurization by adding urea during the iron ore sintering was carried out. The results show that 88.14 % desulphurization rate was obtained with the addition of 0.05 % urea particles at 100 mm height from the feed bottom. During the sintering process, when drying zone reached the added position of urea, large amounts of NH3 were generated by urea decomposition, and then reacted with SO2 to produce (NH4)2SO4 in the wetting zone. With the accumulated desulphurization reactions during the sintering, the low SO2 emission in the flue gas was achieved. Moreover, the addition of urea in the bottom zone avoided the ammonia present in the sintering ore and promoted the urea utilization efficiency.

A pilot-scale study of selective desulfurization via urea addition in iron ore sintering

The iron ore sintering process is the main source of SO2 emissions in the iron and steel industry. In our previous research, we proposed a novel technology for reducing SO2 emissions in the flue gas in the iron ore sintering process by adding urea at a given distance from the sintering grate bar. In this paper, a pilot-scale experiment was carried out in a commercial sintering plant. The results showed that, compared to the SO2 concentration in flue gas without urea addition, the SO2 concentration decreased substantially from 694.2 to 108.0 mg/m3 when 0.10wt% urea was added. NH3 decomposed by urea reacted with SO2 to produce (NH4)2SO4, decreasing the SO2 concentration in the flue gas.

Preparation of metallic iron powder from copper slag by carbothermic reduction and magnetic separation

Copper slag is a solid waste that has to be treated for metals recovery. In order to recover iron from copper slag, the technology of carbothermic reduction and magnetic separation was developed. During the reduction roasting, additive CaO reacted with Fe2SiO4 of copper slag, forming CaO·SiO2 and 2CaO·SiO2, which ameliorates the separation between iron and other minerals during magnetic separation. Meanwhile, additive CaF2 improved the growth of iron grains, increasing the iron grade and iron recovery. The metallic iron powder obtained contained 90.95 wt-% TFe at 91.87 wt-% iron recovery under the optimum conditions, which can be briquetted as a burden material for steel making by electric arc furnace to replace part of scrap.

Microscopic study on the interior and exterior reactions of coke with CO2 and H2O

The interior and exterior reactions of coke with H2O and CO2 were studied at 950–1250°C by self-made gas–solid reacting apparatus, including the particle diameter, apparent porosity, relative volume density distribution and pore structure of coke after reaction. It was obtained that the porcoke in the interior and exterior parts were all eroded after reacting with CO2 or H2O. However, compared with CO2, the reaction of coke with H2O occurred at the coke exterior more strongly, but in the coke interior occurred more weakly, indicating the reaction area of coke with H2O was much closer to the coke exterior. Therefore, injecting hydrogen fuel into blast furnace can increase the coke particle size, so as to make coke playing a better role as skeleton in blast furnace. In addition, increasing the temperature can reduce the amount of solution loss in the coke interior, in particular for the reaction with H2O.

Sticking behaviour and mechanism of iron ore pellets in COREX pre-reduction shaft furnace

ABSTRACT COREX is a clean process releasing lower pollution and consuming fewer cokes than the blast furnace process. However, serious sticking phenomenon often occurs in COREX shaft furnace, causing many problems to the normal operation. In this study, the loading reduction experiments of iron ore pellets were carried out under the simulating COREX reducing conditions. The influence of temperature and H2 content in the syngas on the sticking behaviour of the pellets was observed by scanning electron microscope, energy-dispersive spectrometer and X-ray diffraction. The results indicated that the sticking index increased from 6.7 to 90.43%, when the temperature increased from 750 to 950°C. The main composition of sticking material was metallic iron, and the sticking behaviour depended upon the amount and morphology of precipitated iron on the pellets’ surface. The sticking mechanism was the interpenetrating diffusion mechanism of iron atoms between the adjacent pellets.

Preparation of Direct Reduction Sponge Iron (DRI) Using Pyrite Cinder Containing Nonferrous Metals

Abstract Pyrite cinder is a solid waste generated by the sulfuric acid industry and is considered environmentally hazardous. It contains abundant iron, such as Fe2O3 and Fe3O4, and nonferrous metals, such as zinc, lead and copper. In order to try and recycle this material as a source of Fe units, preparation of direct reduction iron (DRI) using pyrite cinder was investigated by coal-based grate rotary kiln process. This process includes chloridizing and reduction roasting. The results show that 97 % lead was removed after the chloridizing process. Copper was only detached in chloridizing process with the removal rate of 78.49 %. Furthermore, the removal of zinc was carried out in both chloridizing and reduction process, and the removal rate of 96.76 % was achieved after reduction roasting. The final product representing a metallization degree of 93.36 % with compressive strength of 1,198 N/pellet was obtained after the oxidized pellets were reduced at 1,050 °C for 80 min.

Effects of Treated Cow Dung Addition on the Strength of Carbon-Bearing Iron Ore Pellets

It is of particular interest to use biomass as an alternative source of fuel in direct-reduction ironmaking to ease the current reliance on fossil fuel energy. The influence of cow dung addition on the strength of carbon-bearing iron ore pellets composed of cow dung, iron ore, anthracite, and bentonite was investigated, the quality of green and dry pellet was evaluated based on FTIR analysis, and the mechanism of strength variation of the reduced pellets was investigated by analysing the phase composition and microstructure using XRD and SEM. The results show that cow dung addition decreased the green pellet strength due to expansion of the amorphous region of the cellulose in the cow dung; however, the dry pellet strength increased substantially. In the process of reduction roasting, it was found that cow dung addition can promote aggregation of iron crystals and increase the density of the pellets, resulting in increased strength of the reduction roasted pellets, while excessive cow dung addition resulted in lower strength.

Influence of Basicity and MgO on Fluidity and Desulfurization Ability of High Aluminum Slag

Abstract The viscosity of experimental slag, which was mixed based on the composition of a practical blast furnace slag, was measured in this paper. The influence of Al2O3 and MgO content, basicity R2 = w(CaO)/w(SiO2) on the fluidity of slag was studied. The stepwise regression analysis in SPSS was used to reveal the relationship between sulfur distribution coefficient LS and slag composition as well as furnace temperature. The results show that increasing of MgO up to 12% can decrease the slag viscosity. The w(MgO) should be controlled below 8% when there is 20% Al2O3 in the slag. Temperature of hot metal and content of CaO in slag are the two dominant factors on the desulfurization capacity of slag.