Reduction Roasting Process Research Articles

Production increase of high-grade crude zinc oxide pellets at Shisaka Smelting Co., Ltd.

Shisaka Smelting Co., Ltd. has recovered crude zinc oxide pellets from an electric arc furnace dust (EAF dust) by the Waelz kiln process since 1977. The EAF dust processing line consists of a reduction roasting process, a Waelz oxide washing process, and a drying/calcination process. In late years, about 90,000 tons of EAF dust is processed annually at Shisaka. The recovered zinc is sold to zinc smelters as crude zinc oxide pellets, and the amount of production of the pellets is about 40,000 tons per year. Two types of zinc oxide pellets are produced, and the product for electro-refinery requires high quality, especially in fluorine reduction. Most of fluorine are distributed to the clinker in a reduction roasting process, and others are distributed to the Waelz oxide. Conventionally, high-grade crude zinc oxide pellets were produced by washing the Waelz oxide and by volatilizing and separating fluorine under high temperature operation in a drying rotary kiln. However, formation of accretion in the kiln and damage of the shell and refractories of the kiln often occurred under the influence of high temperature operation, and stable consecutive operation of the kiln was difficult.To improve this situation, the fluorine input was reduced by compounding management of EAF dust in the reduction roasting process, and the material residence time in the drying rotary kiln was extended by reducing rotary speed. These improvements resulted in stable consecutive operation under low temperature conditions and increased production of high-grade crude zinc oxide pellets. To improve this situation, the fluorine input was reduced by compounding management of EAF dust in the reduction roasting process, and the material residence time in the drying rotary kiln was extended by reducing rotary speed. These improvements resulted in stable consecutive operation under low temperature conditions and increased production of high-grade crude zinc oxide pellets.

Precise regulation of the phase transformation for pyrolusite during the reduction roasting process

Precise regulation of the phase transformation for pyrolusite during the reduction roasting process

Efficient separation of Li and Mn from spent LiMn2O4 cathode materials by NH4HSO4 reduction roasting-selective ammonia leaching

With the imminent peak in the retirement of rechargeable lithium-ion batteries worldwide, the development of efficient methods for recycling valuable elements from LIBs has attracted considerable attention. In this work, a novel method of NH4HSO4 reduction roasting-selective ammonia leaching was proposed to thoroughly separate Li and Mn from the spent LiMn2O4 cathode materials. Using the TG-DSC-FTIR, XRD, SEM-EDS and ICP methods, the detailed mechanism of reduction roasting process was revealed, showing that the Mn4+ and Mn3+ in the spinel structure of LiMn2O4 were reduced by the NH4+ from the molten ammonium salt, and transformed into water-soluble MnSO4 and Li2Mn2(SO4)3. According to the water-leaching performance of the roasting products, the sulfation conversion rate of Mn reaches 98.1 %, while Li is almost completely transformed under the optimal roasting conditions (475 ℃, 60 min). Using the NH3·H2O-air leaching-system, complete separation of Li and Mn can be achieved. It was shown that the introduction of air into the ammonia solution at a rate of 0.2 L/min under the optimal leaching condition leads to Mn precipitation in the form of nanoscale Mn3O4 particles with a precipitation rate of over 99.99 %, while Li still remains completely leached. Based on the in situ detection of the oxidation reduction potential and pH during the selective leaching, the key mechanism of efficient Mn precipitation was revealed. that is, the increasing potential accelerates the oxidation of Mn(OH)2, and the rapid consumption of Mn(OH)2 promotes the hydrolysis of Mn2+, thereby achieving a significant improvement in the separation efficiency of Li and Mn.

Modulating red mud for the fabrication of cementitious material by analyzing the thermal evolution of hydrogarnets

This work aims to develop a modulation strategy for converting red mud (RM) into cementitious material based on elucidating the phase transformation of hydrogarnet. The results show that cementitious minerals 2CaO·SiO2 (C2S), 12CaO·7Al2O3 (C12A7), and 4CaO·Al2O3·Fe2O3 (C4AF), as well as the free iron minerals Fe and FeO, are formed by integrating calcification dealkalization and reduction roasting treatment of RM. During the reduction roasting process, CaO is preferentially combined with SiO2 and Al2O3 to form cementitious minerals, and the Fe(III) compounds in hydrogarnet and hematite can be directly reduced to free iron minerals without intermediate ferrites. By optimizing the reduction roasting parameters and eliminating the useless minerals 2CaO·Al2O3·SiO2 (C2AS), and FeO, the reduction roasting product is mainly composed of C2S, C12A7, C4AF, and Fe. Therefore, cementitious material is obtained after the magnetic separation of Fe, which possesses both early and late hydration properties. In addition, 75% Fe in RM can be recovered, and the reduced iron powder (RIP) is also useful in the cement clinker production or steel smelting process. The findings in this work lay the foundations for understanding the phase transformation of RM-derived hydrogarnet in the reduction roasting process and also provide a new reference for the modulation and utilization of RM in the cement and concrete field.

Sustainable processing of gold cyanide tailings: Reduction roasting, mechanical activation, non-cyanide leaching, and magnetic separation

Cyanide Tailings (CTs) are known as hazardous resources that accumulate hundreds of millions of tons, threatening the ecological environment. This work proposes an eco-friendly and efficient way to recover gold, iron, and silicon from CTs. By controlling the reduction atmosphere and temperature in the reduction roasting process, >99% of cyanide could be selectively removed, and 65.3% of the encapsulated gold in iron oxide and sulfide could also be released. The reduction of particle size by mechanical activation liberated 92.3% of gold encapsulated in silicate and iron oxide minerals which increased the extraction efficiency of gold in non-cyanide leaching process to 94.5%. The grade and recovery of iron concentrate obtained from the magnetic separation reached 60.9% and 74.6%, respectively, by regulating the magnetic field intensity of 70 kA/m. While the iron concentrate could be directly traded, the tailings of Si grade 28.4% (w/w) could be used in building materials. The proposed technology can realize the harmless resource utilization of the hazardous CTs with the potential for promising industrial applications.

Removal of Sodium from Vanadium Tailings by Calcification Roasting in Reducing Atmosphere.

Vanadium tailings from vanadium extraction by a sodium roasting process are solid waste and cannot be used in sintering and ironmaking due to their high sodium content. In this paper, a calcification and reduction roasting process was proposed to remove sodium from vanadium tailings. The effects of Ca(OH)2 addition, reduction temperature, and roasting time on the sodium removal behavior and compression strength of pellets were studied. The addition of Ca(OH)2 and the reduction of iron oxides promoted the sodium-containing phases to transform to be simpler, which could enhance sodium removal. The sodium removal rate was up to 93.47% and the compression strength of the reduced products was 4497 N/P, and the metallized ratio of the product was higher than 70% under the optimal conditions: roasting at 1200 °C for 2 h with the Ca(OH)2 addition of 35%. The treated product after removing sodium can be recycled in the ironmaking process in a steel company.

The study for reduction roasting of laterite residue in the presence of CaF2

Lately, an increasing number of companies invested in the hydrometallurgical process of laterite ores. In the meantime, the research on disposal of laterite residue has come under spotlight the sake of environmental protection, economic efficiency, and resource utilization. Consequently, reduction roasting process in the presence of CaF2 is proposed to treat laterite residue efficiently and recover valuable components. The thermodynamic calculation was conducted to study the mechanism of phase transformation and roasting in the presence of CaF2. It is found that CaF2 would react with iron olivine and chromite to release iron and chromium. In addition, the addition of CaF2 avails the reduction, migration, aggregation, and growth of metallic Fe and Cr. The optimal conditions for addition of CaF2 and temperature is 10% and 1200 °C, respectively. The recovery of chromium reached 95.61% at 10% CaF2 addition from 65.86% without CaF2 addition and the metallization reduction of iron increased from 77.2% to 91.87%. The function of CaF2 was further investigated by the microstructure evolution of roasting products.

A detoxification and value-added process for chromium ore processing residue (COPR) and Fe-C-bearing dust: Direct reduction-magnetic separation

Chromium ore processing residue (COPR), containing much virulent hexavalent chromium [Cr(VI)], is a by-product derived from chromate production. Fe-C-bearing dust from steel industry is very difficult to be utilized effectively because of its complex composition and unstable properties. The dust was co-processed with COPR by a direct reduction-magnetic separation process in this study. Through the strong reducing ability of solid carbon in Fe-C-bearing dust, the compounds of Cr and Fe were reduced to (Cr, Fe)7C3 alloy during the reduction roasting process and then selectively recovered by magnetic separation. In addition, the Pb and Zn compounds were reduced and volatilized into flue gas at high temperature. Under the optimal conditions, the results indicated that Cr-containing iron powder with 72.59 % Fe and 6.34 % Cr was obtained, and the recoveries of Fe and Cr were respectively 79.1 % and 76.9 %. The volatilization rates of Pb and Zn met 97.47 % and 99.95 %, respectively. The non-magnetic tailings were determined to be nontoxic and could be used as high-quality raw materials for building.

Preparation of Pd Nanoparticles Stabilized by Modified Montmorillonite for Efficient Hydrodeoxygenation of Lignin-Derived Phenolic Compounds in Water

Developing a new and efficient catalytic route for the production of alkanes by upgrading the aqueous phenolic biofuels still remains a challenge. Here, we designed and synthesized a bifunctional catalyst that uses natural montmorillonite (MMT) as support and combines metal active sites and Brӧnsted acid sites in the MMT via ion exchange and reduction roasting process. The catalytic activity of the as-synthesized Pd-MMT (H+) was evaluated by the hydrodeoxygenation (HDO) of a series of lignin-derived phenolic compounds in water. Our model reaction study reveals that the HDO of phenol undergoes an initial hydrogenation of aromatic rings to produce cyclohexanol and cyclohexanone, followed by the dehydration of cyclohexanol to provide intermediate cyclohexene and a final hydrogenation of cyclohexene to create a cyclohexane product. The combination of high metal catalytic activity and Brӧnsted acidity in Pd-MMT (H+) synergistically accelerated the HDO of phenol. Furthermore, good catalytic activity and recycling ability were also observed for other lignin-derived phenolic compounds.

Large- and Particle-Scale energy assessment of reduction roasting of nickel laterite ore for Ferronickel production via the rotary Kiln-Electric furnace process

• Mineralogical composition and moisture content govern energy consumption. • Dehydroxylation and drying use around one-third of the energy input. • Energy and exergy efficiencies amount to 66.4% and 32.3%, respectively. • Dehydroxylation, drying, and size define intraparticle temperature gradient. Ferronickel is essential in manufacturing austenitic stainless steels, nickel alloy steels, batteries, electronics, and gas turbines, among other crucial products. The Rotary Kiln-Electric Furnace process is a widely recognized pyrometallurgical route for ferronickel production. This paper focuses on the rotary kiln furnace, an intermediate stage in which partially dried minerals convert into calcine, ready for smelting in an electric arc furnace. This paper uses a unique industrial database that contains operation variables and minerals composition of a 180 t h −1 rotary kiln furnace. As a distinguishing feature, this work incorporates the effects of dehydroxylation reactions and uses intraparticle energy analysis to gain further insights into the reduction roasting process. Goethite and serpentine dehydroxylation reactions consume around 18% of the energy input of the rotary kiln furnace. Flue gases and shell losses represent around 25% and 8% of the energy input, respectively, while the vaporization of free moisture consumes nearly 15% of the energy input. The rotary kiln furnace shows energy and exergy efficiencies of 66.4% and 32.3%, respectively, leaving room for waste heat recovery. Particles with surface-to-center distances lower than 5.0 mm could behave as isothermal, while coarser particles could present significant temperature gradients. These results can assist in optimizing operating conditions and provide insights into the thermal effects of the ore mineralogical composition.

Selective separation of iron and scandium from Bayer Sc-bearing red mud

In this study, we investigated the separation of iron and scandium from Sc-bearing red mud. The red mud object of our study contained 31.11 wt% total iron (TFe), 0.0045 wt% Sc, hematite (Fe2O3) and ferrosilite (FeO·SiO2) as the main Fe-bearing minerals. The Sc-bearing red mud was treated by a novel deep reduction roasting and magnetic separation process that includes the addition of coke and CaO to extract Fe and enriching Sc from the Sc-bearing red mud. The addition of coke and CaO enhances the transformation of hematite (Fe2O3) to metallic iron (Fe0) and magnetite (Fe3O4) as well as the transformation of ferrosilite into metallic iron (Fe0). The test results show that utilizing the new process a Fe concentrate with a TFe content of 81.22 wt% and Fe recovery of 92.96% was obtained. Furthermore, magnetic separation tailings with Sc content of 0.0062 wt% and Sc recovery of 98.65% were also obtained. The test results were achieved under the following process conditions: roasting temperature of 1373 K, roasting time of 45 min, calcium oxide dosage of 20 wt%, coke dosage of 25 wt%, grinding fineness of 90% < 0.04 mm, and magnetic field intensity of 0.24 T. The major minerals in the Fe concentrate are metallic iron (Fe0) and magnetite (Fe3O4). The main minerals in the magnetic separation tailings with a low TFe content of 2.62% are CaO·SiO2, Na2O·SiO2, FeO·SiO2, Ca3Fe2Si3O12, CaAl2SiO6 and CaFe(SiO3)2.

Synergetic Utilization of Zinc-Bearing Dust by Carbothermic Reduction-Roasting Process: Phase Transformation and Morphological Evolution

Synergetic Utilization of Zinc-Bearing Dust by Carbothermic Reduction-Roasting Process: Phase Transformation and Morphological Evolution

Separation of alumina and silica from metakaolinite by reduction roasting−alkaline leaching process: Effect of CaSO4 and CaO

Limestone (CaCO3), which could promote sulfur fixation, was added to coal gangue during roasting in a circulating fluidized bed (CFB) boiler. CaO and CaSO4 were the main Ca-bearing minerals while metakaolinite was the major Al-bearing mineral in CFB slag. The effect of CaSO4 and CaO on the separation of alumina and silica from metakaolinite by reduction roasting−alkaline leaching process was studied. Results showed that metakaolinite was completely converted into hercynite and silica solid solutions (i.e., quartz and cristobalite solid solutions) by reduction roasting with hematite. More than 95% of silica in the reduced specimen was removed by alkaline leaching. The addition of CaSO4 and CaO remarkably decreased the separation efficiency of alumina and silica in metakaolinite, which could be attributed to the formation of Si-bearing minerals: (1) Fayalite and anorthite were formed during the reduction roasting process; (2) Fayalite was stable while anorthite was converted into sodalite and wollastonite during the alkaline leaching process. This study demonstrates that sulfur in coal gangue should be fixed by treating the exhaust gas instead of controlling the combustion process of CFB to achieve the comprehensive recovery of silica and alumina from the CFB slag.

Reducing effect of biomass derived char on iron ore fines; a statistical investigation and regression modelling

India is an economically developing country. Country’s development and growth is largely interlinked with iron and steel industry as well as availability of energy and its utilization. Energy sector and iron and steel industry mainly consumes convectional and fossil fuel like coal and gas. Present coal reserves of India will last for about 30-40 years at present consumption rate. Consumption of conventional fuels is not economically feasible and environment friendly. Biomass can be an alternative source of fuel for numerous engineering and scientific applications. The char derived from biomass known as biochar can be utilized in the iron and steel-making processes. It can lessen the coke consumption rate and subsequently reduce pollution as well as cost economics. Utilization of low and lean grade iron ore is need of the hour. Removal of gangue impurities from lean and low-grade iron ore is difficult through convectional beneficiation process. The reduction roasting process can be adopted to counter these challenges. The present study focuses on the reduction behavior of iron ore using three various biochar derived from three biomass, viz; wood dust, sugarcane bagasse and coconut shell. A single factorial Design of Experiment with two levels and three variables was adopted and a first-order regression equation was generated to estimate the degree of reduction. The Student’s T-test and Fisher test were performed to validate the regression equation. The obtained results showed that the biochar can be used as a substitute reductant. However, the residence time and temperature play a vital role in the reduction process. The obtained regression equation also validates the effect of residence time and temperature on the reduction process.

A novel method for carbon removal and valuable metal recovery by incorporating steam into the reduction-roasting process of spent lithium-ion batteries

Oxygen-free roasting could efficiently achieve the recovery of valuable metals from spent lithium-ion batteries (LIBs), but the roasted products have the drawbacks of a high carbon (C) content and a complex separation process. Hence, in this study, a new method incorporating steam (H2O) into the reduction-roasting recovery process of spent LIBs (steam roasting) was proposed to realize carbon removal and valuable metal recovery simultaneously. The influence of steam on the reduction-roasting process of spent LiNi0.6Co0.2Mn0.2O2 batteries (NCM) was investigated through experimental methods and thermodynamic analysis. The results indicated that the addition of steam could dramatically facilitate the decomposition and reduction process of spent NCM, and the carbon removal efficiency could reach 84%. H2O only acted on the reaction process of the anode material, and the main component C could be efficiently gasified by steam to produce hydrogen (H2) and carbon monoxide (CO), which could significantly accelerate the reduction process of CoO and NiO. The optimal conditions for valuable metal recovery and carbon removal were a H2O/C mole ratio of 5:1 and a reduction-roasting temperature of 1123 K. After steam roasting, the magnetic recovery efficiencies of Co and Ni were as high as 90% and 93%, respectively. The final recovery products were Co, Ni, and Li2CO3 with high purities. Therefore, this study is expected to provide a novel approach to achieve efficient disposal and recovery of metals from spent LIBs.

A Combined Soda Sintering and Microwave Reductive Roasting Process of Bauxite Residue for Iron Recovery

In this study an integrated process is presented as a suitable method to transform Fe3+ oxides present in bauxite residue into magnetic oxides and metallic iron through a microwave roasting reduction, avoiding the formation of hercynite (FeAl2O4). In the first step, all the alumina phases were transformed into sodium aluminates by adding sodium carbonate as a flux to BR and then leached out through alkali-leaching to recover alumina. Subsequently, the leaching residue was mixed with carbon and roasted by using a microwave furnace at the optimum conditions. The iron oxide present in the sinter was converted into metallic iron (98%). In addition, hercynite was not detected. The produced cinder was subjected to a wet high intensity magnetic separation process to separate iron from the other elements.

Co-Treatment of Spent Pot-Lining and Red Mud for Carbon Reutilization and Recovery of Iron, Aluminum and Sodium by Reductive Roasting Process

Spent pot-lining (SPL) and red mud (RM) are the two major solid wastes of the aluminum industry. In this study, an innovative method has been proposed for co-treatment of SPL and RM to reuse carbon and recover metal (iron, aluminum and sodium) by a reductive roasting-leaching-magnetic separation process (RRLMS process). Moreover, the transformation behaviors of fluoride, cyanide and sulfur present in these residues were studied. The effects of parameters such as temperature, CaO/SiO2 molar ratio, addition amount of SPL, Na2O/Al2O3 molar ratio and roasting time on the result of the process were investigated. Under optimum conditions, the recovery extents of Al2O3 and Na2O were 83.12 and 91.80 pct, respectively. The corresponding leaching extent and loss of F upon roasting process were 16.03 and 35.27 pct, respectively, and only 29.02 pct of ST in the roasted product was leached. Furthermore, reduction extent of 78.65 pct and a metallization extent of 62.83 pct for iron minerals were achieved. The SPL-RM mixture after treatment was rendered non-hazardous. Finally, wet magnetic separation at 1.2 A current (magnetic field strength of approximately 130 mT) provided 30.83 wt pct concentrate yield with 59.09 wt pct total iron concentration and iron recovery extent of 65.25 pct from the leached residue.

Reductive roasting mechanism of copper slag and nickel laterite for Fe-Ni-Cu alloy production

Direct reduction-magnetic separation process (DRMSP) is a highly effective and clean method to upgrade the complex resources, which has been widely used to recovery the value metals in copper slag (CS) and nickel laterite (NL) in recent years. Adequate growth of the alloy particles is a key parameter influencing the complete extraction of alloys from CS and NL in this process. Therefore, the liquid phase formation mechanism, growth kinetics of the alloy particles, and the correlation between the alloy particle growth and liquid phase formation were studied to reveal the synergistic effect of the co-reduction of CS and NL. The results indicated that fayalite in the copper slag reacted with forsterite in nickel laterite to form augite group minerals with low melting points, resulting in more liquid phase formation in the reductive roasting process. A comparison with the reduction kinetic parameters of the single nickel laterite showed that the growth index and activation energy decreased significantly from 2.85 and 272.98 KJ/mol to 2.08 and 171.99 KJ/mol, respectively, after the addition of 40% copper slag, which confirmed that copper slag promoted the particle growth. Moreover, the liquid phase increased the total cohesive force between the alloy particles, revealing the correlation between alloy particle growth and liquid phase.

Analysis of the effect of temperature on the reduction roasting process of Lampung manganese ore using palm kernel shell charcoal

Lampung Province has many manganese ore resources that have not been fully utilized. According to Indonesian Minister of Energy and Mineral Resources regulation no. 5 of 2017, manganese ore is prohibited from being exported before the ore is processed into a concentrate with 49% manganese content. The type of mineral contained in manganese ore used in this experiment is pyrolusite (MnO2). The method used to improve the Mn content used in this experiment is to reduce roasting. The reducing agent in this experiment is 25% palm kernel. The roasting process is carried out at 1000 °C, 1100 °C and 1200 °C. Meanwhile, the holding time varies from 30 to 150 minutes. The results obtained from baking are characterized using XRF to determine the final product content. XRD and SEM-EDS are used for the result identification phase. The highest content of manganese was 41.28% by weight obtained after baked at 1100 °C for 120 minutes with the formed phase being Mn2SiO4.

Synthesis and magnetism property of manganese ferrite MnFe2O4 by selective reduction and oxidization roasting process

A selective reduction followed by an oxidization roasting process has been reported as an effective route to synthetize spinel manganese ferrite (MnFe2O4). In the current work, during the selective reduction process, the FeyMn1−yO (0 ≤ y ≤ 1) samples that acted as intermediates for synthesizing MnFe2O4 were successfully synthesized from Fe2O3 and Mn2O3 systems. The y-value in the synthetic FeyMn1−yO sample was in the range of 0–1 at 800 °C after 30 min. Next, during the oxidization roasting process, the synthetic MnFe2O4 micro-particles with saturation magnetization of 73.7 emu/g were successfully prepared from the FeyMn1−yO samples by an oxidization roasting process for 30 min at 1000 °C in air atmosphere. The formation mechanism and interfacial reaction of manganese ferrite spinel MnFe2O4 samples were systematically investigated by SEM/EDS, XRD, XPS and VSM. Under low temperature (<950 °C), the main reactions were the oxidization of FeyMn1−yO to MnxFe3−xO4 (1 < x ≤ 3), MnxFe3−xO4 (0 < x < 1) and Fe2O3. Under high temperature (>1000 °C), the MnyFe1−yO sample was oxidized to the MnFe2O4 sample, and the normal and inverse spinel structures of MnFe2O4 samples inevitably coexisted and were co-transformed at the same time. This study reported a simple synthetic route that combined selective reduction with an oxidization roasting method to successfully synthesize MnFe2O4 micro-particles. Furthermore, this method could be extended to fabricate other spinel ferrite particles of interest.