Upgrading and dephosphorization of Western Australian iron ore using reduction roasting by adding sodium carbonate

The technology of direct reduction by adding sodium carbonate （Na2CO3） and magnetic separation was developed to treat Western Australian high phosphorus iron ore. The iron ore and reduced product were investigated by optical microscopy and scanning electron microscopy. It is found that phosphorus exists within limonite in the form of solid solution, which cannot be removed through traditional ways. During reduction roasting, Na2CO3 reacts with gangue minerals （SiO2 and A1203）, forming aluminum silicate-containing phosphorus and damaging the ore structure, which promotes the separation between iron and phosphorus during magnetic separation. Meanwhile, Na2CO3 also improves the growth of iron grains, increasing the iron grade and iron recovery. The iron concentrate, assaying 94.12wt% Fe and 0.07wt% P at the iron recovery of 96.83% and the dephosphorization rate of 74.08%, is obtained under the optimum conditions. The final product （metal iron powder） after briquetting can be used as the burden for steelmaking by an alactrie a.re furnace to rer）la,ce scrar） steel.

Detection of the assimilation characteristics of iron ores: Dynamic resistance measurements

Resistance in iron ore undergoes a sharp change of up to several orders of magnitude when the sintered solid phase changes to liquid phase.In view of the insufficiency of existing assimilation detection methods,a timing-of-assimilation reaction is proposed,which was judged by continuously detecting the changes in resistance at the reaction interface.Effects of pole position and additional amounts of iron ore on assimilation reaction timing were investigated.The results showed that the suitable depth of pole groove was about 2 mm,and there was no obvious impact when the distance of the poles changed from 4 to 6 mm,or the amount of iron ore changed from 0.4 to 0.6 g.The temperature of sudden change of resistance in the temperature-resistant image was considered to be the lowest assimilation temperature of iron ore.The accuracy of this resistance method was clarified by X-ray diffraction,optical microscope,and scanning electron microscope/energy dispersive spectrometer(SEM/EDS)analyses.

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

The iron ore sintering process is the main source of SO_2 emissions in the iron and steel industry. In our previous research, we proposed a novel technology for reducing SO_2 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 SO_2 concentration in flue gas without urea addition, the SO_2 concentration decreased substantially from 694.2 to 108.0 mg/m^3 when 0.10wt% urea was added. NH_3 decomposed by urea reacted with SO_2 to produce（NH_4）_2SO_4, decreasing the SO_2 concentration in the flue gas.

N-doped C-coated MoO_(2)/ZnIN_(2)S_(4)heterojunction for efficient photocatalytic hydrogen production

Designing a heterojunction photocatalyst to improve the separation efficiency of photogenerated electrons and holes is of great significance to improve the hydrogen production efficiency.In this work,we report a rational design to grow ZnIN_(2)S_(4)on Mo-MOF-derived N-doped C-coated MoO_(2)(MOZIS),and it has excellent photocatalytic hydrogen production with triethanolamine(TEOA)as sacrificial agent.N-doped C improves the electron transport efficiency between MoO_(2)and ZnIN_(2)S_(4)·The systematic study shows that MOZIS has good properties to promote the effective separation and transfer of photocatalytic charges,which is attributed to the tight contact interface and good energy band structure between MoO_(2)and ZnlN_(2)S_(4).The optimized nanocomposites have a high hydrogen production efficiency of 10.89 mmol·g^(-1)(4 h)under visible light.MOF-derived N-doped C-coated MoO_(2)is an effective strategy to improve the photocatalytic hydrogen production efficiency of ZnIN_(2)S_(4).

Application status and comparison of dioxin removal technologies for iron ore sintering process

The emission of dioxins from the iron ore sintering process is the largest emission source of dioxins, and the reduction in dioxin emission from the iron ore sintering process to the environment is increasingly important. Three approaches to control the emission of dioxins were reviewed： source control, process control, and terminal control. Among them, two terminal control technologies, activated carbon adsorption and selective reduction technology, were discussed in detail. Following a comparison of the reduction technologies, the terminal control method was indicated as the key technology to achieve good control of dioxins during the sintering process. For the technical characteristics of the sintering process and flue gas, multiple methods should be collectively considered, and the most suitable method may be addition of inhibitors ＋ ultra-clean dust collection （electrostatic precipitation/bag filter） ＋ desulphurization ＋ selective catalytic reduction to sufficiently remove multiple pollutants, which provides a direction for the cooperative disposal of flue gas pollutants in future.

Effect of metallurgical dust on NO emissions during coal combustion process

NO emissions from coal combustion are receiving significant attention in recent years. As a solid waste generated from metallurgical industry, metallurgical dust （MD） contains a large amount of metal oxides, such as Fe2O3, CaO, SiO2 and Al2O3, as well as other rare metal oxides. The influence of MD on the NO emissions and the mechanism of the coal com- bustion systems were analyzed. The results show that the peak values of NO emission decrease with the increase in MD mass percent, and the curve of NO emission can be divided into two stages including rapid generation （400-600 ℃） and slow release （800-900 ℃）. The reduction of NO is significantly affected by temperature, volatile components, 02 and CO. CO has a significant catalytic action which can deoxidize NO to N2. The results obtained by X-ray diffraction and scanning electron microscopy indicate that multiple components in MD, such as FegTiO15, Fe2O3 and TiO2, can react with NO to produce TiN. Besides, the alkali metals in MD, such as Na, K and Ca, may catalyze NO precursor to inhibit NO emission. These results indicate that MD is cheap and highly efficient in controlling NO emissions during coal combustion processes.

Determination method of high-temperature characteristics of iron-ore sintering based on n(Fe2O3)/n(CaO)

The high-temperature characteristics of iron ores play important roles in optimizing ore proportion of sintering,which are tested by using iron-ore fines and analytical reagent CaO as raw materials.Two calculation methods of CaO addition amount based on binary basicity(basicity method)and n(Fe2O3)/n(CaO)(mole ratio method),respectively,were employed to evaluate the liquid phase fluidity(LPF)and the capability of calcium ferrite formation(CCFF)of iron ores.The results show that the rule of LPF of iron ores under the mole ratio method is different from that with basicity method.The LPF measured by basicity method has a linear positive correlation with the SiO2 content,and there is no linear relationship between LPF and Al2O3 content or mass loss on ignition,which are inconsistent with the results of the previous study.And the results of CCFF with low SiO2 content(<3 wt.%)or high SiO2 content(>7 wt.%)based on basicity method cannot reflect the true CCFF.The mole ratio method could successfully solve this problem by reducing the effect of CaO addition amount changes caused by SiO2 content of iron ores.

Consolidation mechanism of fluxed hematite pellets

Fluxed pellets are becoming a popular burden for the blast furnace in China.The basicity(wCaO/wSiO_(2))ranging from 0.33 to 1.33 was prepared by adding CaO analytical reagent.The phase change of pellets during roasting was analyzed by the FactSage software,and the consolidation mechanism of fluxed hematite pellets was also investigated.The results show that the increase in basicity gradually increases the diameter,volume,and porosity of pellets.The diameter,volume,and porosity of pellets change slightly when the basicity is greater than 0.83.The increase in roasting temperature gradually decreases the volume and porosity of pellets.With the increase in pellet basicity,the compressive strength of pellets reaches the maximum at the basicity of 0.83.The higher the roasting temperature is,the more the slag phase is produced,thereby accelerating Fe^(3+)diffusion and promoting Fe_(2)O_(3) recrystallization.In addition,the consolidation effect of the slag phase after cooling improves the consolidation strength of fluxed pellets.When the basicity is higher than 0.83,the slag phase decreases with the increase in basicity,and the high-temperature solid solution,such as melilite and spinel,increases,thereby hindering Fe2O3 recrystallization.

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（Al2O3and 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%.

Effects of gangue compositions on reduction process of carbonbearing iron ore pellets

The influence of gangue compositions (mainly composed of SiO2,CaO,MgO and Al2O3)on the reduction kinetics of carbon-bearing iron ore pellets was estimated at 1373-1473 K in N2 atmosphere.The results showed that gangue content and each component distribution affected the pellets reduction process.The reduction rate was found to follow a linear correlation with quaternary basicity R4 [mass ratio of (CaO +MgO)to (SIO2 +Al2O3)]of the carbon-beating iron ore pellets;also,the content of SiO2 solid solution in iron oxide had a significant impact on the reduction rate.At the same reduction temperature,a higher R4 resulted in a lower SiO2 free content,weakening its inhibitory effect on the Boudouard reaction.The reduction temperature of Fe2SiO4 could be reduced by increasing the contents of CaO and MgO,improving the iron oxide reduction as well as the precipitation and growth of the iron grains.The g'angue content and .component distribution showed no effect on the rate-controlling step of the reduction;however,the apparent activation energy of reaction decreased with increasing quaternary basicity.When R4 increased from 0.15 to 0.67,the apparent activation energy decreased from 228.51 to 193.66 kJ/mol.