Reduction Roasting-magnetic Separation Research Articles

Effect of CaO on Fluorine in Spent Cathode Carbon during Nickel Laterite Reduction

Large amounts of solid waste-spent cathode carbon (SCC) was produced in aluminum electrolysis process. At present, landfill and storage methods are widely used, which will not only cause great harm to the environment, but also cause a lot of waste of resources. Nickel and iron were recovered from laterite nickel ore by reduction roasting-magnetic separation using SCC as reducing agent. The fluorine in SCC was fixed in roasted ore by adding CaO. The feasibility of the method was verified by thermodynamic analysis and experiments, and the optimum conditions for CaO addition were determined. The recovery of nickel and iron reached 91.23% and 89.63% respectively when the addition of SCC was 14 wt. % and CaO was 8 wt. %. Adding 8 wt.% CaO under the condition of SCC as reducing agent can change the viscosity of roasted ore and promote the aggregation of ferronickel particles. The concentration of soluble F- in roasted ore was reduced and fixed in roasted ore in the form of insoluble calcium fluoride. Under the condition of adding 8 wt.% CaO, the fluorine fixation rate was 95.99%, and the concentration of F- in roasted ore was only 31 mg·L−1.

Separation of Iron and Zinc Values from Blast Furnace Dust Adopting Reduction Roasting-Magnetic Separation Method by Sawdust Pyrolysis

Separation of Iron and Zinc Values from Blast Furnace Dust Adopting Reduction Roasting-Magnetic Separation Method by Sawdust Pyrolysis

Extraction of ferronickel concentrate from laterite nickel ore by reduction roasting-magnetic separation using spent cathode carbon

Laterite nickel ores are the most important raw materials in nickel production, but processing laterite nickel ores with a low nickel content is difficult. Annually, the aluminum electrolysis industry produces a large amount of spent cathode carbon containing toxic substances, such as fluorine and cyanide, but a considerable amount of it cannot be effectively utilized. The purpose of the present study is to prepare ferronickel concentrates by reduction roasting–magnetic separation using spent cathode carbon as a reducing agent. Different factors affecting the agglomeration and growth of metal particles are studied. The migration of fluorine and the aggregation behavior of iron and nickel after the addition of spent cathode carbon and CaO are studied. Results show that the nickel grade in the ferronickel concentrate is 5.4 wt%, the nickel recovery rate is 84.80%, the iron grade is 67.93 wt%, and the iron recovery rate is 89.91%. Efficient recovery and utilization of nickel and iron in laterite nickel ores are realized. Waste utilization of spent cathode carbon thus provides a new method for the treatment of spent cathode carbon.

Individual enrichment of titanium and iron from low-titanium beach titanomagnetite via preconcentration-reduction roasting and magnetic separation with calcium fluoride

Reduction roasting-magnetic separation realizes the separation of titanium and iron in high-titanium beach titanomagnetite. However, the TiO 2 grade in titanium concentrate is low, and few studies have investigated low-titanium beach titanomagnetite. The preconcentration-reduction roasting and magnetic separation process was developed to utilize the low-titanium beach titanomagnetite. The effects of graphite dosage, reduction temperature, calcium fluoride dosage, and time on the product indices were optimized. The direct reduction iron containing 94.95% iron and 0.75% TiO 2 , titanium concentrate assaying 31.10% TiO 2 were produced under optimal conditions, and metal recovery for both products exceeded 80%. Calcium fluoride increased the liquid phase and reduced the viscosity of the slag system, thereby improving the growth of iron particles. However, an excess liquid phase produced by adding more calcium fluoride inhibited the reduction of iron minerals and promoted the formation of low-titanium minerals, which affected the iron recovery and the quality of the titanium concentrate. • The process was proposed for efficient recovery of iron and titanium. • Direct reduction iron and titanium concentrate were produced. • Calcium fluoride reduced the liquidus temperature and viscosity.

Extraction of Ferronickel Concentrate by Reduction Roasting-Magnetic Separation from Low Grade Laterite Nickel Ore under the Action of Compound Additives

Extraction of Ferronickel Concentrate by Reduction Roasting-Magnetic Separation from Low Grade Laterite Nickel Ore under the Action of Compound Additives

Effect and Mechanism of CaO on Iron Recovery and Desulfurization by Reduction Roasting-Magnetic Separation of High-Sulfur Cyanide Tailings

The increasing demand for iron ore in the world causes the continuous exhaustion of mineral resources. The utilization of iron in secondary resources has become of focus. The present study was carried out to recover iron from high-sulfur cyanide tailings by coal-based reduction roasting-magnetic separation. The mechanism of CaO to increase iron recovery and reduce sulfur was investigated by observing CO and CO2 gas composition produced by the reaction, mineral composition and microstructure, distribution characteristics of sulfur, and the intercalation relationship between iron particles and gangue minerals. The results showed that the addition of CaO could increase the gasification rate of the reducing agent, increase the amount of CO2 gas produced, promote the reduction of iron minerals, and improve the metallization degree of iron. When CaO was not added, sulfur was mainly transformed into troilite, which was closely connected with iron particles and was difficult to remove by grinding and magnetic separation. With the addition of CaO, CaO preferentially formed oldhamite with active sulfur, which reduced the formation of troilite. Oldhamite was basically distributed in an independent gangue structure. There was a clear boundary between iron particles and gangue minerals. Oldhamite could be removed by grinding-magnetic separation.

Effect of additives on iron recovery and dephosphorization by reduction roasting-magnetic separation of refractory high-phosphorus iron ore

Effect of additives on iron recovery and dephosphorization by reduction roasting-magnetic separation of refractory high-phosphorus iron ore

Pelletization of hematite and synthesized magnetite concentrate from a banded hematite quartzite ore: A comparison study

A compressive pelletization study, for the utilization of an Indian Banded Hematite Quartzite ore, is presented in this communication. Iron ore concentrates have been generated utilizing the conventional beneficiation process and also by the approach of reduction roasting-magnetic separation. The Fe contents of the hematite and the synthesized magnetite concentrate were found to be 64.22 and 63.80%, respectively. The influence of different factors on the respective physical, chemical, and metallurgical properties of the fired pellets, generated through both the routes, have been compared. The pellets prepared from the synthesized magnetite attain the threshold Cold Crushing Strength (CCS) of 50 kg/pellet at a lower temperature of 1050 °C in comparison to hematite pellets (1100 °C). Also, the threshold CCS of 250 kg/pellet is attained by synthesized magnetite pellets at a lower temperature of 1250 °C compared to hematite pellets (1360 °C). The fired synthesized magnetite pellets also achieve the desired metallurgical properties i.e., Reduction Degradation Index (RDI), Reducibility Index (RI), and Swelling Index (SI) at par with the hematite pellets. Moreover, unlike the hematite pellets, the synthesized magnetite pellets do not need the addition of external carbon during the pellet making.

Comparing strategies for iron enrichment from Zn- and Pb-bearing refractory iron ore using reduction roasting-magnetic separation

Iron in refractory iron ore composed of 47.04% Fe, 0.39% Pb and 0.30% Zn was enriched through reduction roasting followed by magnetic separation in this work. The phase transformations occurring in iron ore during reduction roasting were investigated through XRD, VSM, and SEM-EDS. Results show reduction process of hematite follows Fe2O3 → Fe3O4 → FeO → Fe. The quartz in iron ore reacts with FeO to form fayalite. At elevated temperatures, fayalite decomposes into metallic iron and cristobalite solid solution. The reductively roasted product (RRP) with main phases of magnetite and metallic iron has higher magnetization intensity than that with main phases of wustite and fayalite. Iron in RRP-800 °C and RRP-1150 °C is extracted by magnetic separation, and obtained concentrates have main minerals of magnetite and metallic iron, respectively. Elevated temperature decreases zinc and lead contents in concentrate. Thus, deep reduction-magnetic separation is more suitable for enriching iron from Zn- and Pb-bearing refractory iron ore.

Efficient improvement for the direct reduction of high-iron red mud by co-reduction with high-manganese iron ore

Millions of tons of red mud produced as a by-product of the alumina industry by Bayer process not only threatens the environment but also causes waste of secondary resources. To recover iron from red mud, the technology of reduction roasting-magnetic separation to treat high-iron red mud was developed; however, it was difficult to upgrade by separating iron and alumina. In this paper, the effects of high-manganese iron ore on the direct reduction process of high-iron red mud were investigated through various tests such as reduction temperature, reduction time, C/Fe mass ratio, and addition amount of high-manganese iron ore. The results showed that the metallization rate of the direct reduction of high-iron red mud reaches 84.07% roasting at 1150 °C, 150 min and C/Fe mass ratio of 2.0. By synergistic reducing with 60% high-manganese iron ore, the metallization rate increased to 93.52%. The results of phase and microstructure evolution analysis showed that adding high-manganese iron ore, the content of ilmenite, hercynite and fayalite were reduced, and pyrophanite, galaxite and tephroite were formed, indicating that MnO, one of the reduction products of high-manganese iron ore, can react with ilmenite, hercynite and fayalite to generate pyrophanite, galaxite and tephroite in the reduction process, and further dissociated FeO, which was conducive to the reduction of high-iron red mud.

Utilization of waste coconut shells in the reduction roasting of overburden from iron ore mines

The reduction of iron ore using biomass-based reductants has opened up a new chapter because of its contribution to energy conservation and emission reduction. In this connection, the application of waste coconut shells (CS) as the reductant in the reduction roasting-magnetic separation of an iron ore overburden sample is explored. Characterization studies on the overburden having 49% Fe suggest that the sample is mostly a goethitic ore containing kaolinite as the major gangue mineral. A concentrate with 63.2% Fe at an iron recovery of 66.2% has been obtained from the low-intensity magnetic separation of the overburden roasted at a temperature of 800 °C, time of 60 min and a CS to feed ratio of 0.2. Characterization studies indicate the formation of magnetite and hematite under these optimum conditions, whereas roasting at a temperature of 900 °C and a reductant to feed ratio of 0.3 is found to form feebly magnetic phases like wustite, fayalite and complex iron aluminosilicates resulting in poor iron recovery. The thermo-gravimetric analysis studies explain the disintegration of the biomass and reduction of the iron ore thereby validating the reduction sequence as predicted using the characterization studies.

Recover Iron from Bauxite Residue (Red Mud)

Red mud is a hazardous waste generated from alumina refining industries. Unless managed properly, red mud poses significant risks to the local safety and environment. The Bayer Red Mud was considered as a low-grade iron ore with a grade of 5wt% to 20wt% iron. We adopted the reduction roasting-magnetic separation process to recover ferric from red mud by electromagnetic induction furnace. The effects of different parameters on the recovery rate of iron were studied in-depth. The optimum reduction reaction conditions were obtained that is 1wt% of carbon in red mud at 1450° roasting for 60 min and the magnetic field intensity is about 0.19T. The experimental results indicated that the grade of total iron and the iron recovery were 66.50% and 65.4%, respectively. The prove the electromagnetic induction furnace is more beneficial to iron recovery.

The Effect of Additives on Extraction of Ni, Fe and Co from Nickel Laterite Ores

As nickel sulfide deposits are exhausted, it becomes necessary to mine and process low-grade laterite ores to satisfy the need for nickel production. To achieve an efficient extraction of Ni, Fe and Co, additives such as chlorides, sulfur and sulfates, alkali oxides, fluorides, sodium carbonate and sodium hydroxide are introduced into the extraction process, and are applied in the reduction roasting-magnetic separation and chloridizing/sulfating/alkali roasting followed by a leaching process. In this paper, previously reported studies on the extraction of Ni, Fe and Co from nickel laterite ores have been reviewed with an emphasis on the additives’ effect and reaction mechanisms. Although these additives significantly improve the enrichment effect, there is a need for further research on reaction mechanisms, particularly with regard to hydrolysis of chlorides that generate HCl. The development of efficient additives that are environmentally friendly with low corrosivity and low cost should also be investigated.

Biomass briquette as an alternative reductant for low grade iron ore resources

The present study explores the application of biomass briquette, produced from the unutilized vegetative remnants, as an alternative reductant for the reduction roasting-magnetic separation of an iron ore slime sample assaying 56.2% Fe. The X-Ray Diffraction (XRD) studies indicated tridymite and quartz to be the only crystalline mineral phases present in the biomass briquettes while the Fourier Transform Infra Red (FTIR) spectra identified several organic functional groups representing the biomass. Iron ore concentrates with ∼65% Fe and ∼64% weight recovery were obtained with reduction conditions such as temperature: 650–750 °C, reductant to feed ratio: 0.15, reduction time: 30–45 min and reductant size: −3+1 mm. The analysis of the statistically designed experiments suggested that temperature is the most crucial factor followed by time, reductant to feed ratio and reductant size. Magnetite and hematite were found to be the only major phases present in the magnetic fractions produced from roasting at the optimum conditions. Many feebly magnetic phases like wustite, fayalite and clinoferrosilite appeared at higher temperature and reductant to feed ratios, which was confirmed by XRD, reflected light microscopy and quantitative mineralogical analysis.

Recovery of ferric oxide from bayer red mud by reduction roasting-magnetic separation process

A great amount of red mud generated from alumina production by Bayer process was considered as a low-grade iron ore with a grade of 5wt% to 30wt% iron. We adopted the reduction roastingmagnetic separation process to recover ferric oxide from red mud. The red mud samples were processed by reduction roasting, grinding and magnetic separating respectively. The effects of different parameters on the recovery rate of iron were studied in detail. The optimum techqical parameters were proposed with 700 °C roasting for 20 min, as 50wt% carbon and 4wt% additive were added. The experimental results indicated that the iron recovery and the grade of total iron were 91% and 60%, respectively. A novel process is applicable to recover ferric oxide from the red mud waste fines.

Biomass Reduction Roasting-Magnetic Separation of Low Grade Goethite

The average grade of iron ores in China is around 32%, about 10% lower than the world’s average level. In order to alleviate the demand of iron ore for steelmaking industries, it is urgent to develop a highly efficient, energy-saving, low-carbon and environment-friendly technology. The goethite ore from Northern Hainan Island was studied via reduction magnetization by pine, rice chaff, and corn straw biomass fuels. The magnetic properties and magnetic separation were discussed by optimizing the parameters of roasting temperature, roasting time, and the ratio of biomass fuels. The results show that we could obtain concentrated iron ore grade of pine roasting and magnetic separation grade of iron concentrate 61.64% with the recovery of 79.75% via pine fuel roasting, 61.75% with the recovery 80.16% via rice chaff, and 61.47% with the recovery of 81.28% via corn straw roasting. Thereby, we could deduce that biomass fuels for reduction roasting of low goethite ore is promising to substitute the traditional coal and coke fossil fuels.

Experimental Study on Removal of Arsenic from Sulfuric-Acid Residue of High-Arsenic

The experimental study on removal of arsenic from sulfuric-acid residue of high-arsenic was conducted in this paper. Reduction roasting–magnetic separation and sulfuric acid leaching were discussed, and the results showed that the harmful impurity arsenic can't be effectively removed by the reduction roasting-magnetic separation process from sulfuric-acid residue. The content of arsenic would be enriched with the growth of magnetic iron grade, while the effect of the arsenic removal was obvious for sulfuric acid leaching. The leach residue, in which the content of arsenic was only 0.24% with 92.29% of arsenic leaching rate was obtained from the raw ore with 2.78% of arsenic by the sulfuric acid leaching process. And the iron grade of sulfuric-acid residue reached 61.88% while content of non-ferrous metal was very Low, which can be used as a raw material of iron-smelting. This study provided a certain amount of technical support for the similar high arsenic sulfuric-acid residue recycling.

Effect of Temperature on Recovery of Iron from Waste Slag of Pyrite Processing

Recovery of iron from the waste slag is of great interest for maximum use of mineral resource, reduction of environment impact and improvement of economical benefits to the related companies. This paper is mainly focused on the effect of the temperature on recovery of iron from waste slag of pyrite processing using reduction-roasting magnetic separation method. The experimental results show that under the treatment condition in this work about 70% of the iron was recovered from the waste slag, where the iron content in the concentrate is 57%. After the further treatment with chlorinated segregation-magnetic separation, the iron content in the recovered slag can reach 83%