Jiaxin Li

Emission reduction of dioxin in iron ore sintering by adding urea as inhibitor

Abstract Dioxins are a type of highly toxic persistent organic pollutant, and the sintering process has become one of the most important emission sources. In this paper, a detailed analysis of the waste gas from sintering pot experiments shows that when adding urea at 0·05, 0·1 and 0·5%, the dioxin emissions decrease by 63·1, 66·8 and 72·1% compared to zero urea. At 0·05%, the influence on the technical parameters of the sintering process is slight, and there is no emission of ammonia in the waste gas. However, at 0·1 and 0·5%, the sintering technical performance decreased and emissions of ammonia in flue gas at 0·07 and 0·11 mg m−3 occurred. It is concluded that an addition of 0·05% urea is the optimum amount to minimise dioxin without affecting sintering performance or the occurrence of secondary ammonia pollution.

Reduction kinetics of carbon containing pellets made from metallurgical dust

Abstract Reduction experiments of carbon containing pellets made from metallurgical dust were conducted under a weak oxidising atmosphere in the temperature range of 1348–1573 K. Analysis of kinetics and the reduction mechanism revealed that the rate determining step of the reduction of the pellets is the interfacial or local reaction with the activation energy 111·66 kJ mol−1. The reduction rate can be expressed by the McKewan equation 1−(1−R)1/3u200a=u200akt. In addition, temperature is an important factor influencing the reaction rate as dezincification and metallisation increase with the increased temperature. The amount of dezincification and metallisation could be up to 97·8 and 79·9% respectively at 1573 K compared to a minimum of 75·3 and 60·2% at 1348 K.

Alumina-Iron Separation of High Alumina Iron Ore by Carbothermic Reduction and Magnetic Separation

The carbothermic reduction of high alumina iron ore in the absence/presence of sodium carbonate (Na2CO3) was carried out for alumina-iron separation by wet magnetic separation. Sodium carbonate is found to be capable of improving the separation of alumina and iron, as well as increasing the particle size of metallic iron significantly. When the high alumina ore briquettes were reduced at 1050°C for 80 min, the average particle size of metallic iron was approximately 100 μm in the presence of sodium carbonate, which is bigger than the size of 50 μm in the absence of sodium carbonate. Compared with the absence of sodium carbonate, the Al2O3 content of iron concentrate decreased from 4.33% to 1.29%, while the Al2O3 removal rate increased from 43.70% to 83.37% with the addition of 9% sodium carbonate. Experimental evidence showed that Na2CO3 reacted with Al2O3 and SiO2 to form sodium silicate, aluminum silicate, and sodium aluminosilicate, and decreased the content of Fe in the slags, which improved the separation between the alumina and iron during the magnetic separation. Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/lsst.

Strength and consolidation mechanism of iron ore and coal pellets

Abstract The consolidation mechanisms of green and metallised iron ore and coal pellets (ICPs) using four kinds of inorganic binders and four organic binders were studied. The strength of wet ICPs mainly depends on capillary force. However, that of preheated ICPs mainly depends on chemical adsorption, followed by viscous force. The metallised pellet strength can be controlled as per the growth and spread of the iron joined crystals, and the strength of the metallised pellets increases with the iron crystal area. The adhesive properties of phenolic resin as a binder are significantly better than those of other binders, and it does not affect ICP reduction. With 2% phenolic resin, the compressive strength and drop strength of preheated ICPs improved to 312·5 N and by 15·1 times respectively, whereas the metallisation degree and compressive strength of metallised ICPs improved to 92·56% and 3505 N respectively (at 1473 K).

Grinding Kinetics of Vanadium-Titanium Magnetite Concentrate in a Damp Mill and Its Properties

The grinding behavior of the as-received (5xa0pct moisture) vanadium-titanium magnetite concentrates in a damp mill was investigated in this paper. A grinding kinetics equation was established based on a population balance model using size distribution data obtained from a laser diffraction technique. X-ray diffraction results show that a loss in crystallinity occurs when the grinding time is increased. The crystallite size of the materials decreased, whereas their structural microstrain increased with increasing grinding time. The wettability increased because the surface roughness increases with increasing grinding time. The moisture capacity of the solids increased during the first 3xa0minutes of grinding and then remained roughly constant with further increases in grinding time. The water transfer coefficient of the particles increased at grinding times of 3 and 6xa0minutes and then decreased at grinding times of 9 and 12xa0minutes. The compressive strength of oxidized pellets increased with increasing grinding time; longer grinding times can compensate for the effects of lower roasting temperature or shorter roasting time on the strength of the pellets. Lowering the roasting temperature and shortening the roasting time by grinding appeared to be possible.

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 88.14u2006% desulphurization rate was obtained with the addition of 0.05u2006% urea particles at 100u2006mm 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.

Mathematical simulation and experimental study on coke oven gas injection aimed to low carbon blast furnace ironmaking

Coke oven gas (COG) tuyere injection is recognised as one of effective measures to achieve low carbon blast furnace ironmaking. In this paper, simulation of blast furnace operation with COG injection was investigated by means of multi-fluid blast furnace model, and the softening-melting and dripping behaviours of mixed burden were studied on basis of simulation results. The model simulation shows that, with COG injection rate increasing, the concentration of inner-furnace hydrogen is enhanced obviously. Cohesive zone moves downwards and becomes thinner. The column permeability gets better. Hot metal productivity increases and CO2 emission reduces. Compared with conventional operation without COG injection, when COG injection rate is 152.34u2005Nm3/tHM, column pressure drop is decreased by 31.5% and hot metal productivity is increased by 26.36% and CO2 emission is decreased by 17.54%. Therefore, the simulation and experimental results reveal that it is achievable to improve blast furnace operation performance, such as hydrogen-enriched reduction, better column permeability, high efficiency, low carbon emission and so on.

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 90.95u2005wt-% TFe at 91.87u2005wt-% 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.

Optimization Method for Iron Ore Blending Based on the Sintering Basic Characteristics of Blended Ore

The basic characteristics of iron ore, including assimilation, fluidity, cohesive phase strength and the ability to produce calcium ferrite, are often used to evaluate the sintering properties of iron ore and guide the optimization of iron ore blending. Six kinds of common iron ore used in a steel company in China were selected in this work. The basic characteristics of the single iron ore and blended iron ores were studied, as well as the difference between weighted averages of basic characteristic index of single iron ores and the real value of basic characteristic index of blended iron ore under different ore blending ratios. The results shew that the liquid phase liquidity, cohesive phase strength and calcium ferrite formation ability had a significant linear positive correlation with SiO2 content. The weighted average of basic characteristic index of single iron ore cannot fully reflect the actual blended iron ore properties. The optimization of the blending ratio can be achieved through the detection of the basic characteristics of the mixed iron ore, combined with the basic characteristics of iron ores.

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.