Magnetization Roasting Research Articles

Phase transition and magnetic properties of low-grade limonite during reductive roasting

Magnetization roasting and magnetic separation is an effective method of recovering iron from low-grade ores. The phase transformation mechanism of minerals is an important basis for optimizing technological parameters. In this study, biomass was used as a reducing agent to roast Baotou low-grade limonite in a high-temperature vacuum furnace. The phase transformation law and its influence on magnetic properties were studied via X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. The results show that roasting temperature is related to the magnetism of iron ore. With an increase in temperature, iron content increases gradually, and limonite magnetism also increases, at 700 °C reaching a maximum saturation magnetization of iron concentrate of 43.06 emu/g. It was also found that during vacuum roasting, S elements migrated and accumulated on the surface of limonite and distributed evenly on the surface of mineral particles in the form of FeS, forming ash shells.

An Novel Method for Iron Recovery from Iron Ore Tailings with Pre-Concentration Followed by Magnetization Roasting and Magnetic Separation

ABSTRACTIron ore tailing is currently one of the most important secondary mineral resources. Pre-concentration followed by magnetization roasting and magnetic separation process was well recognized to be very effective in recycling iron from iron ore tailings. An iron concentrate containing 66.35% Fe with a total recovery of 57.74% was produced under the optimal experimental conditions (i.e., roasting temperature, 540°C; CO concentration, 30%; roasting time, 15 min; total gas flow rate, 450 ml/min; grinding fineness 90% passing 25 μm for roasted products, and low-intensity magnetic separation magnetic field, 104 kA/m). Mechanisms of magentization roasting were studied using XRD, SEM, and VSM, which had showed that most of the hematite was transformed into magnetite with a porous and cracked structure after roasting, and the saturated mass magnetic moment and specific susceptibility of ore were also increased significantly.

Innovative utilization of refractory iron ore via suspension magnetization roasting: A pilot-scale study

In this study, an innovative suspension magnetization roasting (SMR) technology was developed and utilized for the recovery of iron from a typical refractory iron ore. The effects of the roasting temperature, CO reducing gas flow rate, N2 fluidizing gas flow rate, and feeding rate on the iron recovery were investigated. Under the optimal roasting conditions, a continuous and stable pilot scale SMR test was conducted for 72 h, and a staged grinding and staged low-intensity magnetic separation (LIMS) process was designed to upgrade the roasted product. The results showed that with the appropriate SMR conditions — a roasting temperature of 520 °C, CO flow rate of 4.0 m3/h, N2 flow rate of 2.0 m3/h, and feeding rate of 100 kg/h — an iron concentrate with a total iron grade (TFe) of 60.18% and iron recovery of 90.17% could be obtained. Compared to the traditional process of shaft furnace magnetization roasting (SFMR) followed by LIMS, the novel technique developed here could improve the TFe and iron recovery of the iron concentrate by 12–14% and 17–22%, respectively, with well-functioning equipment. During the SMR process, hematite and siderite were transformed into magnetite, which enhanced the magnetism of the iron minerals. The utilization of the SMR method has the potential to provide a significant technological advance in the field of refractory iron ore recovery in China and globally.

Development of Magnetic Processing Circuit for Oxidized Iron Ore after Magnetic Roasting

The process of wet magnetic separation of oxidized ore from the deposit of Abail, Republic of Kazakhstan, is studied. Kinetics of roasted product milling is analyzed, and the optimal size is recommended for the fist stage of milling as −0.071 mm at the content of 55–60%. The accomplished magnetic analysis of different size products shows that the decrease in size causes no increment of iron in the magnetic product and iron is at the level of 63.0 mass%. The scanning electron microscopy reveals that the roasted and magnetic products contain floccules of gangue and magnetite particles which transfer into magnetic fraction and worsen its quality. Two schemes are proposed for decomposition of floccules: multistage desliming with regard to sedimentation velocity in liquid medium and attrition with deffloculation agent. It is recommended to apply the two-stage circuit with milling, desliming and wet magnetic separation, which allows production of iron concentrate with iron content of 67% at recovery of 76.5%.

Development of Magnetic Processing Circuit for Oxidized Iron Ore after Magnetic Roasting

Development of Magnetic Processing Circuit for Oxidized Iron Ore after Magnetic Roasting

Test on Fluidized Magnetization Roasting of Donganshan Carbonate-Bearing Iron Ore

Test on Fluidized Magnetization Roasting of Donganshan Carbonate-Bearing Iron Ore

Oxidation Kinetics of Magnetite During the Cooling Process of Magnetization Roasting

Oxidation Kinetics of Magnetite During the Cooling Process of Magnetization Roasting

Oxidation mechanism and non-isothermal kinetic studies on carbonate iron ore by thermogravimetric analysis

Due to the uncertain and heterogeneous compositions of carbonate iron ore after magnetization roasting, an oxidation pretreatment was applied to increase the uniformity of the composition of the ore. The oxidation of carbonate iron ore was characterized using a thermogravimetric method over a temperature range of 723–948 K. It is shown that the oxidation process of carbonate iron ore is complicated and consists of multiple reactions that include the decomposition and oxidation of carbonates such as FeCO3, MnCO3, MgCO3 and CaMg(CO3)2. The main product that results from oxidation is Fe2O3. Because of the low content of other carbonates (MnCO3, MgCO3 and CaMg(CO3)2) in raw carbonate iron ore and the small change in the apparent activation energies during oxidation, the oxidation of carbonate iron ore can be treated as a single-step FeCO3 oxidation reaction. Based on the Ozawa–Flynn–Wall method, which is one of the model-free methods, the apparent activation energy for the oxidation of carbonate iron ore is 284.50 kJ mol−1. The most probable reaction model for the oxidation of carbonate iron ore is the Sestak–Berggren model as determined by the theoretical and actual master plot and eigenvalues of the Malek method. The reaction orders n and m are 1.317 and 0.0295, respectively. The pre-exponential factor is 2.628 × 1017 min−1.

Recovery and separation of iron from iron ore using innovative fluidized magnetization roasting and magnetic separation

In this investigation, a pilot-scale fluidized magnetization roasting reactor was introduced and used to enhance magnetic properties of iron ore. Consequently, the effects of roasting temperature, reducing gas CO flow rate, and fluidizing gas N2 flow rate on the magnetization roasting performance were studied. The results indicated that the hematite was almost completely converted into magnetite by a gas mixture of 4 Nm3/h CO and 1 Nm3/h N2 at roasting temperature of 540?C for about 30 s. Under optimized conditions, a high grade concentrate containing 66.84% iron with iron recovery of 91.16% was achieved. The XRD, VSM, and optical microscopy (OM) analyses revealed that most of the hematite, except some coarse grains, was selectively converted to magnetite, and that the magnetic properties were greatly enhanced. Thus, their separation from non-magnetic gangue minerals was facilitated.

Beneficiation of an iron ore fines by magnetization roasting and magnetic separation

The utilization of abundant low-grade iron ores is potentially important to many countries in the word, especially to China. These iron ores contain many detrimental impurities and are difficult to upgrade to make suitable concentrates for the blast furnace. In this paper, the beneficiation of a low-grade hematite ore fines containing carbonates with magnetization roasting and magnetic separation was proposed and studied. The hematite and siderite are almost completely converted into magnetite by 8wt% coal at roasting temperature of 800°C for 8min. Under the optimized conditions, a high grade magnetic concentrate containing 65.4wt% iron with an iron recovery of 92.7% was achieved. Meanwhile, the effects of roasting temperature, reaction time and coal to ore ratio on the magnetic properties of roasted materials were investigated using a vibration sample magnetometer (VSM). The results show that the magnetic susceptibility and magnetism saturation of hematite ore can be highly increased due to the selective conversion of hematite and siderite into magnetite caused by magnetization roasting which facilitates their separation from non-magnetic minerals.

Characterization and Exploitation of El-Gedida High-Mn Iron Ore, El-Bahariya Oasis, Western Desert, Egypt

Two strategies have been chosen for the exploitation of El-Gedida high-Mn iron ore containing 46.37 wt.% Fe and 7.53 wt.%Mn. The first one included magnetic roasting and subsequent low intensity magnetic separation. The second strategy involved a blend process of the El-Gedida high-Mn iron ore with the Um Bogma manganese ore. The magnetic separation failed to reduce the Mn content up to 4 wt.% and produced iron concentrate containing 52.15 wt.% Fe with a recovery of 94.47% and 6.45 wt.% Mn with a recovery of 71.95%. At this point, the magnetic separation is considered to be unsuitable process for upgrading the high-Mn iron ore. Moreover, this physical separation supported the microscopic prediction regarding the difficult liberation of iron minerals from manganese phase during the comminution process. On the other hand, blending the high-Mn iron ore with the Um Bogma manganese ore at weight ratio of 1/6 (El-Gedida sample/Um Bogma sample) produced a suitable mixture for making the ferromanganese alloys.

Research on the Magnetizing Roasting and Magnetic Separation of Blast Sludge

In the blast furnace production process, the high iron content in the sludge produced by collecting, Iron can be used as recycled raw materials. Experimental study found that the use of magnetic roasting - weak magnetic iron powder method of recovering technology is feasible. The optimum conditions are: the grinding fineness is 87%, calcination temperature is 750 °C, roasting time is 25min, magnetic current is 1.5A under conditions to obtain a grade of 59% recovery rate of 79.3% iron ore .

Suspended Magnetic Roasting Study of Fine Grained Iron Ore

Suspension roasting furnace was used as the reactor of magnetic roasting of fine grained siderite, and the N2 was used as the conveying gas. The results show that, the siderite ore be roasted at the conditions of gas velocity is 1.7m/s, and the roasted time is 12.35s, according to magnetic separation can obtained iron concentrate grade is 65.04%, and recovery rate is 93.03%.

Recovery of Gold and Iron from the Cyanide Tailings by Magnetic Roasting

Abstract The pretreatment of the cyanide tailing by roasting and its effect on the followed comprehensive recovery of valuable metals were investigated. The results indicate that the leaching rate of gold reaches 46.14%, the magnetic susceptibility of iron is up to 86.27% when the roasting temperature is 750 °C, the roasting time is 1.25 h, and the dosage of reductant is 6%. Combined with mineral structure and principle of magnetic roasting, the promoting mechanism of gold leaching by roasting was explored. The gold exposed through the magnetic roasting is the foremost improvement for high leaching rate of gold.

The Present Conditions of Micro-Fine Disseminated Refractory Oolitic Hematite and Expectation

Because of oolitic hematite micro-fine disseminated and complex structure and other characteristics, has been considered the world's mineral processing problems. This paper studies the use of its current situation in China and some traditional sorting techniques such as strong magnetic separation - reverse flotation, flocculation - intensity magnetic separation, magnetic roasting - magnetic, and discuss an efficient sorting technique - the deep reduction, which has important practical significance for oolitic hematite sorting.

Microwave Heating in Iron Ore Magnetization Roasting the Current Status

This template explains the principle of microwave heating and iron ore magnetization roasting principle. Moreover，it summary analysis microwave heating in the use of iron ore magnetization roasting and points out that we should strengthen the study on microwave heating mechanism.

Comparison Tests between Magnetic Roasting in a Fluidized Bed and Magnetic Roasting in a Fixed Bed

This paper discussed the roles of magnetic roasting and the main factors that affect magnetic roasting. Mechanism research of magnetic roasting shows that feed size, roasting temperature, reducing atmosphere and roasting time are the main four factors. Comparison tests of magnetic roasting in a fluidized bed or in a fixed bed have been done. The results show that the appropriate feed size and reducing atmosphere play an important role in roasting. The roasting temperature in a fluidized bed is lower than that in a fixed bed and the roasting time in a fluidized bed is much less than that in a fixed bed. As a result, roasting in a fluidized bed has a higher efficiency of heat and mass transfer than that in a fixed bed.

Characterization and technology of fast reducing roasting for fine iron materials

The features of the techniques of fast reducing roasting (FRR) and conventional magnetic roasting, as well as tremendous demands of iron ores in iron and steel industry of China, were briefly described. The test equipment suitable for FRR of fine-grained materials was introduced. Weakly magnetic materials with grain size of <0.30 mm were converted into strongly magnetic materials by FRR for several to dozens of seconds. In a weakly reducing atmosphere and at 740–800 °C, refractory powder iron material (<0.30 mm) which is rich in specularite, limonite and Mg-Mn siderite was subjected to FRR for a few seconds to 60 s. Concentrate with iron grade of 55.67%–55.21%, high contents of Mg and Mn in the ore is obtained and the yield of magnetic separation reaches 81.66%–86.57%. The results of X-ray diffraction (XRD) analysis and magnetism detection of the material before and after FRR indicate that weakly magnetic material is mainly converted into strongly magnetic material Fe3O4 with specific saturation magnetic moment. The efficiency of FRR is consistent with TFe recovery of magnetic separation; meantime, the specific saturation magnetic moment increases from 33 to 42 times after FRR. Calculations show that speeds of flash magnetic roasting are obtained from several dozen to two or three hundred times, compared with rotary kiln or shaft furnace. This indicates that it is practicable to use the fast reducing roasting technique to improve the comprehensive utilization of iron ore resources.

The Study on Microwave Magnetic Roasting Plus Magnetic Seperation and Acid Pickling to Enrich Nb of Low-Grade Niobium Minerals

In present article, the low intensity magnetic separation process was studied for the low-grade niobium minerals by microwave magnetic roasting. The influence of magnetic density, particle size of grinding and dispersant addition on the magnetic separation effect of sinter ore with the best magnetisability was investigated emphatically. The results show that the iron recovery was decreased and the iron grade increased gradually with decreasing the magnetic density and particle size of grinding. The magnetic separation result of sinter ore was optimal under the magnetic density of 80KA / m and the grinding grain-size of 33 μm. Fine grinding can effectively make Fe separated from Nb, especially when the dispersant(industrial alcohol) was used in the process of magnetic separation , resulting in the improvement of the grade of iron from 57.2% to 60.5% and enrichment of Nb in the tailing ore(the grade of Nb was 5.01%). After the acid pickling of tailing ore containing Nb, the grade of Nb in the extract was improved to 12.36%, which was enriched four times more than that of low-grade niobium ore before microwave magnetic roasting.

Experimental Study on Magnetic Roasting of Low Grade Specularite

Along with the continuously rose of the iron ore price and the Chinese iron ore quantity demanded, Iron ore self-sufficient rate has become the bottleneck of Chinese steel industry development. In order to increase Chinese ore self-sufficiency rate, the paper study the xinjiang region low grade specularite. When the crude ore grade is 35%, the mass percent of reducing agent pulverized coal is 12%, roasting temperature is 800°C，roasting time is 50 min, milling fineness is 90% passing 0.074 mm and the magnetic induction is 84kA/m, after a low intensity magnetic separation, the iron concentrate can be got whose yield is 42.83%, grade is 62.04% and recovery is 79.26%.