Improvement of carbothermic reduction of nickel slag by addition of CaCO3

The effect of CaCO3 addition on the carbothermic reduction of nickel slag was studied,and the mechanism of CaCO3 in improving the reduction was analyzed.The results showed that when the CaCO3 content added to the slag was increased from 0 to 8 wt.%,initiation temperature of the carbothermic reaction decreased from 1100 to 1000℃,the temperature reaching the maximum reduction rate decreased from 1150 to 1100℃,and the reduction degree of the nickel slag increased from 58%to 88%.The iron particles in the reduced nickel slag were coarsened and the X-ray diffraction intensity of metallic iron peaks increased,confirming that the addition of CaCO3 was beneficial to the reduction of nickel slag and recovery of iron.

Effect of aluminum oxide on the compressive strength of pellets

Analytical-reagent-grade Al2O3 was added to magnetite ore during the process of pelletizing, and the methods of mercury intru-sion, scanning electron microscopy, and image processing were used to investigate the effect of Al2O3 on the compressive strength of the pellets. The results showed that, as the Al2O3 content increased, the compressive strength of the pellets increased slightly and then decreased gradually. When a small amount of Al2O3 was added to the pellets, the Al2O3 combined with fayalite （2FeO＆#183;SiO2） and the aluminosilicate （2FeO＆#183;2Al2O3＆#183;5SiO2） was generated, which releases some iron oxide and reduces the inhibition of fayalite to the solid phase of consolidation. When Al2O3 increased sequentially, high melting point of Al2O3 particles hinder the oxidation of Fe3O4 and the recrystallization of Fe2O3, making the internal porosity of the pellets increase, which leads to the decrease in compressive strength of the pellets.

Reduction mechanisms of pyrite cinder-carbon composite pellets

The non-isothermal reduction mechanisms of pyrite cinder-carbon composite pellets were studied at laboratory scale under argon （Ar） atmosphere. The composite pellets as well as the specimens of separate layers containing pyrite cinder and coal were tested. The degree of reduction was measured by mass loss. The microstmctures of the reduced composite pellets were characterized by scanning electron mi- croscopy （SEM）. It is found that the reduction processes of the composite pellets may be divided into four stages： reduction via CO and H2 from volatiles in coal at 673-973 K, reduction via H2 and C produced by cracking of hydrocarbon at 973-1123 K, direct reduction by carbon via gaseous intermediates at 1123-1323 K, and direct reduction by carbon at above 1323 K. Corresponding to the four stages, the apparent activation energies （E） for the reduction of the composite pellets are 86.26, 78.54, 72.01, and 203.65 kJ.mol-1, respectively.

Effect of B_(2)O_(3) content on viscosity and structure of SiO_(2)−MgO−FeO-based slag

The effect of B_(2)O_(3) content on the viscosity of SiO_(2)−MgO−FeO-based molten slag system was investigated using the rotating cylinder method.The evolution process of the melt structure under different contents of B_(2)O_(3) was comprehensively studied via FTIR spectroscopy and a model for calculating the degree of polymerization was developed.The results showed that the viscosity of the molten slag decreased with the addition of B_(2)O_(3),which had a slight effect when its content exceeded 3 wt.%.As the addition of B_(2)O_(3) increased from 0 to 4 wt.%,the break temperature of the slags decreased from 1152 to 1050℃ and the apparent activation energy decreased from 157.90 to 141.84 kJ/mol.The addition of B_(2)O_(3) to the molten slag destroyed the chain silicate structure to form a more cyclic borosilicate structure.The Urbain model was improved to calculate the viscosity of the SiO_(2)−MgO−FeO-based slags,and the values were in good agreement with the experimentally measured values.

Phase transformation behavior of titanium during carbothermic reduction of titanomagnetite ironsand

The reduction of titanomagnetite（TTM） ironsand, which contains 11.41wt% TiO_2 and 55.63wt% total Fe, by graphite was performed using a thermogravimetric analysis system under an argon gas atmosphere at 1423–1623 K. The behavior and effects of titanium in TTM ironsand during the reduction process were investigated by means of thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. During the reduction procedure, the titanium concentrated in the slag phase, where the phase transformation followed this sequence： Fe O ＋ FeTiO_3 → Fe_2 TiO_4 → FeTiO_3 → FeTi_2O_5 → TiO_2. The calculated results for the reduction kinetics showed that the carbothermic reduction was controlled by the diffusion of ions through the product layer. Furthermore, the apparent activation energy was 170.35 k J·mol^（-1）.

Effect of different bottom blowing elements on stirring characteristics of molten bath in converter

The bottom blowing element is the key equipment to ensure the bottom blowing effect of the converter.Three types of bottom blowing elements,dispersive type(D1),double circular seam(D2)and straight cylinder type(D3),were built,and the effects of bottom blowing element type on molten bath flow,wall erosion and furnace bottom erosion were simulated.It was found that when the bottom blowing elements of dispersive type(D1)and double circular seam(D2)were used,the dead zone area in the lower part of the molten bath was smaller,and the high-speed zone area was larger;therefore,the stirring effect on the bottom melt was better.When the straight cylinder type(D3)bottom blowing element was used,the gas penetrated the molten bath at a faster rate to reach the surface of molten bath and failed to disperse in the bottom molten bath,and the wall shear stress near the nozzle outlet was larger.When argon was blown by three different bottom blowing elements,the area of the wall shear stress greater than 3 Pa was 4.8,5.6 and 8.7 cm2,respectively,within 0.2 m of the bottom blowing nozzle outlet.

Reduction of Pyrite Cinder Pellets Mixed with Coal Powder

Direct reduction of pyrite cinder in a rotary hearth furnace （RHF） was studied under the condition of labo ratory simulation. Effects of reduction temperature, reduction time, molar ratio of carbon to oxygen, .and CaO addition on metallization rate as well as compressive strength of the pellets after reduction were discussed. The results showed that the metallization rate and compressive strength were 93.9% and 2 160 N per pellet respectively under the conditions of the reduction temperature of 1 200 ℃, the reduction time of 16 min, and the molar ratio of carbon to oxygen （xc/xo） of 1. 0; adding 2.5% CaO was beneficial to sulfur enrichment in slag phase of pellet, and metal- lization rate increased slightly while compressive strength decreased.

Mechanisms of Swelling of Iron Ore Oxidized Pellets in High Reduction Potential Atmosphere

The influences of the time, temperature and atmosphere on the reduction swelling of oxidized pellets were investigated by single factor experiments. The mechanisms of reduction swelling of oxidized pellets were analyzed and investigated by SEM （scanning electron microscopy） and XRD （X-ray diffractometer） analysis. The results show that the change rules of reduction swelling index of oxidized pellets in different reduction atmospheres are very similar. With the increase of reduction time, the reduction swelling index moves up firstly and then down. When the reduction temperature is above 900 ℃, α-quartz turns into α-tridymite, and the transition generates additional volume expansion effect. The reduction swelling index changes faster in H2 atmosphere than in CO atmosphere. Increasing Ha content in the reduction atmosphere is useful to decrease the reduction swelling index, but it is also easy to cause oxidized pellets cracking.

Effect of mechanical activation on enhancement of carbothermal reduction of nickel slag

The effects of mechanical activation on particle size distribution,crystalline phase,morphology,and mechanical energy storage of nickel slag were studied.Then,the direct reduction experiments of mechanically activated nickel slag mixed with reducing agent graphite powder were performed under conditions of 873-1273 K and reduction for 30-70 min.The results show that after 12 h of activation,90%of the nickel slag has a particle diameter less than 1.05 pm,and the total energy storage is 1790.4 kJ mol^(-1).With the extension of the mechanical activation duration,the intensity of the dift'raction peaks of the main crystalline phases Fe_(2)SiO_(4) and Mg2SiO4 in the nickel slag decreases.Mechanical activation is also an effective means to enhance the reduction of nickel slag.With the extension of the activation time,the reduction effect of the nickel slag and metallization degree increase.After 12 h of mechanical activation,the nickel slag was reduced at 1273 K for 70 min,and the metallization degree of the reduced product could reach 83.12%.

Effect of BaSO_(4) on phase composition and sintering process of iron ore fines

Iron ore containing BaSO_(4) may have a series of effects on the quality of the sinter and performance of the blast furnace.Thus,the effect mechanism of BaSO_(4)(0-6.0 mass%)on the compressive strength,mineral composition,and microstructure of the sinter was investigated.The experimental results show that the compressive strength of the sintered samples initially increases and then decreases when the BaSO_(4) content increases from 0 to 6.0 mass%,reaching a peak value of 12.78 kN with a BaSO_(4) content of 1.0 mass%.Thermal analysis indicates that BaSO_(4) initially decomposes to produce BaO at 1468 K in the presence of iron ore.BaO combines with Fe_(2)O_(3) forming barium ferrite(Ba_(2)Fe_(6)O_(11)),which exists in the sintered sample with a granular form.BaO also dissolves in calcium ferrite and slag to promote the formation of calcium ferrite and barium glass,respectively.The content of needle-like calcium ferrite gradually increases and then decreases with the increase in BaSO_(4) content.Hematite exists in a plate-like form.The generation of dicalcium ferrite is promoted by increasing the BaSO_(4) addition from 2.0 to 6.0 mass%.

Effect of TiO_(2) and BaO on viscosity and potassium removal capacity of blast furnace slag

In order to increase the utilization rate of vanadium–titanium magnetite in blast furnace smelting,the viscosity and potassium removal capacity of CaO–SiO_(2)–Al_(2)O_(3)–MgO–BaO–TiO_(2) slag(CaO/SiO_(2)=1.05,1–5 wt.%BaO,2–20 wt.%TiO_(2))were studied for slag optimization using the cylinder method and slag–metal equilibrium technique,respectively.Also,the structural properties of the slag were characterized by Fourier transform infrared spectroscopy.The concept of“a ring structure of Ti–O–Si”was proposed to express the change in the viscosity of the blast furnace slag.The results showed that the viscosity of slag increased with the increase in BaO content while the potassium removal capacity decreased.Furthermore,an increase in TiO_(2) content from 2 to 20 wt.%resulted in a decrease in viscosity and an increase in potassium removal capacity.The Fourier transform infrared spectroscopy results showed that the charge compensation of Ba2+can form complex aluminosilicate structure and increase the viscosity of slag.Meanwhile,with the increase in TiO_(2) content,Ti4+ions replace Si4+in the silicon-oxygen tetrahedral structure,thereby reducing the degree of polymerization of the silicate network and decreasing the viscosity.

Identification of working conditions and prediction of FeO content in sintering process of iron ore fines

The iron oxide(FeO)content had a significant impact on both the metallurgical properties of sintered ores and the economic indicators of the sintering process.Precisely predicting FeO content possessed substantial potential for enhancing the quality of sintered ore and optimizing the sintering process.A multi-model integrated prediction framework for FeO content during the iron ore sintering process was presented.By applying the affinity propagation clustering algorithm,different working conditions were efficiently classified and the support vector machine algorithm was utilized to identify these conditions.Comparison of several models under different working conditions was carried out.The regression prediction model characterized by high precision and robust stability was selected.The model was integrated into the comprehensive multi-model framework.The precision,reliability and credibility of the model were validated through actual production data,yielding an impressive accuracy of 94.57%and a minimal absolute error of 0.13 in FeO content prediction.The real-time prediction of FeO content provided excellent guidance for on-site sinter production.