Sintering Dust Research Articles

A Novel Technique for Preparation and Separation of Iron Carbide from Sintering Dust

A Novel Technique for Preparation and Separation of Iron Carbide from Sintering Dust

Sewage sludge enhances cold-pressed pelletization and carbothermic reduction of steel plant sintering dust

The sludge-based forming thermal reduction can be used to improve the resource utilization ability of sintering dust. This paper discussed the feasibility and mechanism of sewage sludge as a binder and reducing agent to facilitate iron recycling from sintering dust by mixing wet sludge to form and adding dry sludge to reduce. The results showed that a 1.4% ratio of sewage sludge significantly enhanced the strength of metallurgical pellets, and the compressive strength of wet and dry pellets reached 309.5 and 1233.5 N/P. Meanwhile, with the addition of dry sludge (S/Fe = 2.0), the metallization ratio can be up to 88.4%. Sewage sludge has a more efficient reduction potential than other carbon sources as reducing agents. Combined with XRD, XPS, TG-MS, TG-FTIR, and other characterization methods, the reduction phenomenon of iron was confirmed, and the migration and transformation of metals in sintering dust and the segmented volatilization rule of Pb, Zn, K, Na, and other elements were revealed. It is proven that sludge as the disposal route of metallurgical dust cold-pressed forming and reduction is a green and sustainable view and promising research direction.

Effect of Recycling Sinter Dust as Calcium Ferrite in the Sintering Process on Sinter Quality and Emissions of CO2, NO, and SO2

Effect of Recycling Sinter Dust as Calcium Ferrite in the Sintering Process on Sinter Quality and Emissions of CO2, NO, and SO2

Treatment of chromium-containing sludge using sintering and ironmaking combined technology: A risk-reducing strategy for environmental impact

The efficient, safe and eco-friendly disposal of the chromium-containing sludge (CCS) has attracted an increasing concern. In this study, Co-processing of CCS was developed via employing sintering and ironmaking combined technology for its harmless disposal and resource utilization. Crystalline phase and valence state transformation of chromium (Cr), technical feasibility assessment, leaching risk, characteristics of sintered products, and pollutant release during CCS co-processing were investigated through a series of laboratory-scale sintering pot experiments and large scale industrial trials. The results showed that the content of Cr(VI) in sintered products first increased then decreased with increasing temperature ranges of 300 °C–800 °C, and reached a maximum of 2189.64 mg/kg at 500 °C. 99.99% of Cr(VI) can be reduced to Cr(III) at above 1000 °C, which was attributed to the transformation of the Cr(VI)-containing crystalline phases (such as, MgCrO4 and CaCrO4) to the (Mg, Fe2+)(Cr, Al, Fe3+)2O4. The industrial trial results showed that adding 0.5 wt‰ CCS to sintering feed did not have adverse effects on the properties of the sintered ore and the plant's operating stability. The tumbler index of sinter was above 78% and the leaching concentrations of TCr (0.069 mg/L) was significantly lower than the Chinese National Standard of 1.0 mg/L (GB5085.3–2007). The TCr contents of sintering dust and blast furnace gas (BFG) scrubbing water were less than 0.19 wt‰ and 0.11 mg/L, respectively, which was far below the regulatory limit (1.5 mg/L, GB13456-2012). The mass balance evaluation results indicated that at least 89.9% of the Cr in the CCS migrated into the molten iron in the blast furnace (BF), which became a useful supplement to the molten iron. This study provided a new perspective strategy for the safe disposal and resource utilization of CCS in iron and steel industry.

Influence of Aging Time on Filtration Performance of P84 Filter Media with Seam.

Although the area with the seam is approximately 4% of the total area of an industrial filter bag, a more extensive investigation of the influence of this region on surface filtration is necessary since the small seam holes can be a conduit for the passage of fine particles even after a certain time of use of the filter bag. Therefore, this work aimed to assess the influence of aging time on the filtration performance of P84 filter bags (samples without and with seam) used in an industrial bag filter, regarding tensile mechanical properties, air permeability, fractional separation efficiency, and filtration cycles. The particulate matter applied (sinter dust) to evaluate the efficiency and to perform the cycles was collected in the hoppers of an industrial bag filter installed in the primary dedusting system of a sinter plant in the steel industry. The results showed that the filter bag aged for 10 months presented a fractional separation efficiency of almost 100%, even for the samples with a seam, suggesting that the seam holes were sealed by the powder in the industrial installation. As for the tensile mechanical properties, the tests showed that the aging of the filter bag caused a reduction in the tensile strength of the filter medium. With respect to air permeability and filtration cycles, the longer the aging time of the filter bag, the more similar was the filtration performance of the samples without and with seam.

Selective separation of anglesite from iron ore sintering Dust: A novel aggregate flotation method

Iron ore sintering dust, a solid waste produced during steel manufacturing, contains high levels of lead and iron compounds, particularly anglesite and hematite. Traditional sulfidation flotation methods struggle to effectively separate these fine-grained minerals. This study introduces a selective aggregate flotation method that enhances selectivity through a synergistic use of sodium lauryl sulfate (SLS) and sodium tripolyphosphate (STPP). The results from flotation experiments show a remarkable reduction in hematite recovery to 7.3% from 19.0%, while maintaining a high recovery of over 90% for anglesite, yielding a more efficient separation. Analytical tests such as grading analysis, zeta potential, FT-IR and XPS analysis observed that SLS’s ability to chemically adsorb onto the lead ions in anglesite aids in the aggregation of these particles, enhancing their recovery. In contrast, STPP adsorbs onto iron ions on the hematite surface, preventing SLS from adhering to it and thus promoting the dispersion of hematite particles. This differential chemical interaction creates significant physical differences between anglesite and hematite, enabling their effective separation during beneficiation. Overall, this innovative approach provides new ideas for an efficient strategy to recover precious metals from sintering dust.

In-depth study on the synergistic conversion mechanism of iron ore with waste biochar for co-producing directly reduced iron (DRI) and syngas

Waste biochar and waste iron ore sintering dust were synergistically resourced to produce directly reduced iron (DRI) and combustible syngas in this study. A solid product with 92.45 % metallization ratio and a combustible syngas (65.69 % CO, 8.03 % CH4) with a yield of 1170.9 ml/g were obtained at 1000 °C for 60 min with 1.2 mol(C/Fe). The CO production of biochar conversion was increased by adding iron ore sintering dust, about 769.3 mL/g at 1000 °C for 60 min, 7.17 times that of biochar pyrolysis alone (107.3 mL/g). The co-conversion was the generation, growth and aggregation of iron grains for the sintering dust. This synergistic conversion achieved the recycling of these two solid waste resources to produce high-value DRI and high-calorific-value syngas, as industrial raw materials and fuels, saving fossil resources and fuels. The biochar pyrolysis, gasification and the reconversion of pyrolysis products occurred during their co-conversion. The gas production of biochar pyrolysis and gasification were 280.7 ml/g and 933.8 ml/g, while the reduction degrees of iron ore by the gas and solid from biochar pyrolysis were 12.64 % and 79.98 %. Their well-mixed state during the co-conversion process facilitated the reconversions of pyrolysis products by improving diffusion efficiency.

Synergistic conversion of iron ore sintering dust and waste biochar to produce direct reduction iron and syngas: Gasification, reduction behavior and thermodynamic analysis

Waste biochar from biomass power generation and sintering dust from ferrous metallurgy were skillfully used to produce direct reduced iron (DRI) and syngas via a synergetic conversion in this study. The thermodynamic analysis of their related reactions, biochar conversion and reduction behavior of sintering dust were investigated. The biochar gasification and reduction of sintering dust were coupled and promoted by each other at 1000 °C for 60 min with 1.2 mol (C/Fe). For biochar conversion, adding sintering dust deepened the pyrolysis of the volatiles in the waste biochar to generate more CH4, and it provided more oxygen atoms, gasifying carbon atoms in the fixed carbon to generate more CO. The CO and CH4 yield from biochar conversion with iron oxides of sintering dust increased by 633.8% and 41.5% to its pyrolysis alone. For the reduction of sintering dust, the whole conversion process of sintering dust was the generation, aggregation and growth of the iron grains, including the generation of metallic iron grains, forming curved bars and composite flocculent metallic iron, and its larger lumps particles finally. A DRI with a 92.4% metallization ratio, meeting the requirements of the subsequent electric arc furnaces, was obtained at 1000 °C for 60 min with 1.2 mol (C/Fe). This study achieves an efficient and reciprocal conversion of these two solid waste resources. It offers an essential research reference for fuel gasification and DRI processes.

A novel approach to treating nickel-containing electroplating sludge by solidification with basic metallurgical solid waste

Nickel-containing electroplating sludge is a solid waste generated during the treatment of electroplating wastewater, often managed through solidification with materials such as cement and lime. This paper presents a novel approach for solidifying nickel-containing electroplating sludge using basic metallurgical solid waste. A mathematical model was employed to determine the kinetics of Ni2+ leaching, yielding the kinetic equation α(t) = 0.97∗(1-exp (-0.19∗t)). Rapid leaching occurred in the initial 10 min, reaching a concentration of 86.78 mg/L, followed by a slower release, peaking at 104.54 mg/L within 40 min. Through the solidification of electroplating sludge with basic waste materials, it was found that the inclusion of 2.0 % lime, 12.2 % sintering dust, and 2.5 % steel slag resulted in Ni2+ leaching concentrations of 0.28, 0.41, and 0.61 mg/L, respectively, all meeting the discharge standard of <1.00 mg/L. Phase analysis indicated that the main constituents of the solidified products were C–S–H and CaSO4, with no detectable change in the crystallinity of Ni2+ before and after solidification. Thermodynamic calculations further demonstrated that under basic solidification conditions, Ni2+ transforms from NiSO4 to Ni(OH)2. Microscopic morphology analysis revealed that the encapsulation of Ni2+ by C–S–H and CaSO4 led to the densification of the porous microstructure of the electroplating sludge, achieving effective solidification.

Efficient treatment of starch wastewater through metallic-starch complexes and magnetic flocculation

Starch wastewater poses significant environmental harm, necessitating the implementation of effective treatment methods. The current starch wastewater treatment methods have some drawbacks, such as limited application scenarios, complicated process and insufficient purification efficiency. This study focuses on the purification of starch wastewater through metallic-starch complexes (MSCs) and magnetic flocculation. Metal ions (Fe3+, Pb2+ and Al3+) were added to interact with starch and coagulate, forming MSCs, in which the O6 atom of the branched chain methanol most likely to interact with metal ions. Then, the magnetic particles, sintering dust (SD), was utilized to adsorb the MSCs and form magnetic flocs, facilitating their rapid settlement under an external magnetic field. The purification experiments were aimed at a high-concentration starch wastewater with COD concentration of 12,000 mg/L, and the results demonstrated the metal ions could effectively coordinate with starch and form MSCs, achieving a COD removal rate of over 90%. Meanwhile, to address the challenge of difficult settlement of MSCs, the addition of SD induced the magnetic flocculation with MSCs through Van der Waals force and electrostatic force, which effectively reduced settling time and decreased sedimentation layer thickness. The combined use of MSCs and magnetic flocculation achieved efficient purification of starch wastewater.

Performance of an SCR Catalyst from Sintering Dust by the Hydrothermal Method and Its Water/Sulfur Resistance

Performance of an SCR Catalyst from Sintering Dust by the Hydrothermal Method and Its Water/Sulfur Resistance

A green process for the conversion of hazardous sintering dust into K2SO4 and NH4Cl fertilizers

Sintering dust from the steelmaking industry is a hazardous waste that is rich in valuable metals. The purpose with the present study has been to design an efficient process for the preparation of K2SO4 and NH4Cl fertilizers by using sintering dust as raw material. The K, S, and Cl in the sintering dust were selectively and efficiently leached using water. The leaching of Ca impurities was then greatly reduced and the appearance of Zn and Mg was avoided. The Cl− ions in the leachate were, thereafter, adsorbed by a 201 × 7 resin to form a K2SO4 solution. Finally, the loaded Cl− on the resin was desorbed to form a NH4Cl solution, and the resin was regenerated and recycled. The purified solutions were crystallized to prepare K2SO4(s) and NH4Cl(s) products, which met the national standard of China for superior potassium sulfate and ammonium chloride, to be used for agricultural use. The recoveries of K, Cl, and S from the sintering dust were 80.78%, 92.63%, and 93.92%, respectively. Notably, the Mn content in the leaching residue increased from 9.08% to 14.19%. This could be used for the conversion of Mn impurities into recyclable manganese-rich raw materials. This green process enables an effective extraction of important impurities in hazardous sintering dust, thereby providing a new potassium source for potash fertilizer manufacturing with notable economic and environmental benefits.

Dissolution Kinetics of Chlorine from Iron Ore Sintering Dust

Chlorine is generated during iron ore sintering, mostly in the form of alkali chlorides and primarily accumulates in sintering dust, which must be removed before reusing. In this study, an in-situ monitor leaching system based was designed to detect chloride ion water leaching behaviors in real-time and improve the understanding of chlorine dissolution kinetic behaviors in water. Various parameters, including water leaching temperature, solid/liquid ratio, stirring speed, particle size and surfactant addition have been studied. Meanwhile their chlorine dissolution data exhibited a good fit to Stumm’s kinetic models. The results of kinetics analysis and transition state theory calculation on apparent activation energy demonstrated that the dissolution process was controlled by diffusion at low S/L ratio, while changed to be controlled by surface chemical reaction as the S/L ratio increased. Furthermore, increasing both temperature and stirring speed improved the chlorine removal speed. Moreover, reducing the particle size and adding 0.2% nonionic surfactant Triton X-100 reduced the surface energy and accelerated surface chemical reaction, which were also beneficial for removing chlorine from sintering dust. In addition, the SEM-EDS examination inferred that the existence of laurionite (PbOHCl) limited the chlorine dissolution rate to less than 97%, while beneficiation or hydrometallurgy treatment was needed to further remove chlorine.

Efficient Recycling of Silver and Copper from Sintering Dust by Chlorination Roasting Process

In this study, the Ag and Cu evolution in the sintering dust was extracted by chlorination roasting process, and the mechanism of the process was analyzed by atomic absorption spectroscopy, X-ray fluorescence, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectrometry. In addition, in order to better understand the chlorination roasting process, the mechanism and thermodynamics of roasting reaction were analyzed. The recovery of Ag and Cu reached 99.05% and 59.32%, respectively, under the conditions of roasting temperature of 1423 K, holding time of 60 min, and the air flow rate of 400 L/h. Thermodynamic analysis showed that MgO and SiO2 could promote the production of Cl2 and HCl and that CuO could be chlorinated by Cl2 at 1421 K, but it was not amenable for HCl. Compared with CuO, Ag was more easily chlorinated at high temperatures. Experimental results indicate that silver and copper can be efficiently extracted, indicating that the chlorination roasting is a promising pyrometallurgical treatment for the recycling of sintering dust.

The poisoning effect of sintering dust on V2O5–WO3/TiO2 catalyst for NOx removal in iron ore sintering flue gas

ABSTRACT NOx from iron ore sintering flue gas can be removed by selective catalytic reduction (SCR) over V2O5–WO3/TiO2 (VWTi) catalyst. In this work, the poisoning effects of K2SO4 and CaSO4 on the VWTi catalyst were investigated. The SCR activities and physicochemical properties of the fresh and poisoned catalysts were characterized. The results confirmed the deactivation of the poisoned catalysts, and the SCR activity decreased with increasing the concentration of the doped poisoning precursors. This reduced SCR activity could be related to the decreased reducibility of vanadium species and lower content of surface chemisorbed oxygen. Characterization of the poisoned catalysts showed migration of V 2p3/2 towards lower binding energy, reduced amount of NH3 desorption, and elimination of V=O stretching vibration bond, which could be attributed to the extension of V=O bond, consequently leading to the formation of –V–O–Ca/K bonds. A possible poisoning mechanism of the VWTi catalyst was proposed and discussed.

Effectiveness of thermal treatment on Pb recovery and Cl removal from sintering dust

Sintering dust is considered as a hazardous waste material owing to its high heavy metal content. In this study, a new technology for the treatment of sintering dust via chlorination roasting was developed. The chlorination behavior of Pb at high temperatures was studied. The volatilization behavior of Pb and Cl was found using different analytical techniques, such as scanning electron microscopy and energy dispersive X-ray spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, X-ray fluorescence, and atomic absorption spectroscopy. In addition, the thermodynamics and kinetics of the chlorination mechanism of Pb at high temperatures were studied. Thermodynamic analysis results showed that quartz and the chlorinating agent played key roles in the process of chlorination. Compared with KCl and NaCl, CaCl2 showed superiority in the chlorination. The phase transformation of sintering dust at different temperatures was analyzed. The volatilization rates of Pb and Cl reached 98.69 % and 84.55 %, respectively. The study of kinetics showed that the volatilization of PbCl2 was controlled by diffusion, and the apparent activation energy is 7.97 kJ/mol. Finally, chlorination roasting residue can be recycled for iron and steel metallurgy.

Coupling mechanism of activated carbon mixed with dust for flue gas desulfurization and denitrification

To clarify the effect of coking dust, sintering dust and fly ash on the activity of activated carbon for various industrial flue gas desulfurization and denitrification, the coupling mechanism of the mixed activated carbon and dust was investigated to provide theoretical reference for the stable operation. The results show that coking dust had 34% desulfurization efficiency and 10% denitrification efficiency; correspondingly, sintering dust and fly ash had no obvious desulfurization and denitrification activities. For the mixture of activated carbon and dust, the coking dust reduced the desulfurization and denitrification efficiencies by blocking the pores of activated carbon, and its inhibiting effect on activated carbon was larger than its own desulfurization and denitrification activity. The sintering dust also reduced the desulfurization efficiency on the activated carbon while enhancing the denitrification efficiency. Fly ash blocked the pores of activated carbon and reduced its reaction activity. The reaction activity of coking dust mainly came from the surface functional groups, similar to that of activated carbon. The reaction activity of sintering dust mainly came from the oxidative property of Fe2O3, which oxidized NO to NO2 and promoted the fast selectively catalytic reduction (SCR) of NO to form N2. Sintering dust was activated by the joint action of activated carbon, and both had a coupling function. Sintering dust enhanced the adsorption and oxidation of NO, and activated carbon further promoted the reduction of NOx by NH3; thus, the denitrification efficiency increased by 5%-7% on the activated carbon.

Concentration of Rare Earth Elements (Sc, Y, La, Ce, Nd, Sm) in Bauxite Residue (Red Mud) Obtained by Water and Alkali Leaching of Bauxite Sintering Dust

One of the potential sources of rare-earth elements (REE) is the industrial waste known as red mud (bauxite residue), in which the majority of REE from the initial bauxite are concentrated via the Bayer process. Therefore, the studies of the subject, both in Russia and outside, focus almost exclusively on red mud processing. This article looks into the possibility of REE concentration into red mud by leaching an intermediate product of the bauxite sintering process at Russian alumina refineries, namely electrostatic precipitator (ESP) dust. The experimental works were performed by X-ray diffraction (XRD)and electron probe microanalysis (EPMA) of the sinter and sinter dust. The determination of major and rare-earth elements in the sinter from the rotary kilns and in the ESP dust before and after leaching was carried out by X-ray fluorescence (XRF) and plasma mass spectrometry (ICP-MS). The study showed that it is possible to obtain red mud that contains three times more REE than traditional waste red mud after two-stage leaching ESP dust in the water at 95 °C followed by leaching in an alkaline-aluminate liquor at 240 °C. The shrinking core model was used to study the kinetics of leaching of the original ESP dust and water-treated dust in alkaline-aluminate liquor. The study showed the change in the limiting stage of the alkaline leaching process after water treatment, with the activation energy growing from 24.98 to 33.19 kJ/mol.

Flotability of laurionite and its response to sulfidization flotation

Laurionite is the main highly hazardous lead bearing waste in iron ore sintering dust due to its poor stability and high content, while its flotability and flotation separation have not been adequately investigated. In this study, the flotation behavior of laurionite and its interaction with Na2S were investigated in detail to find an economic and promising way for the separation of lead from sintering dust. The flotability and sulfidization flotation of laurionite were examined by micro-flotation experiments, zeta potential measurement, Fourier transform infrared spectroscopy (FT-IR) analysis and X-ray photoelectron spectroscopy (XPS) studies and solution chemistry calculation. The micro-flotation experiments results indicated that Na2S would improve the flotability of laurionite within a moderate dosage, otherwise decrease its float. The negativity of zeta potential observably increased when adding an appreciate amount of Na2S prior to NaBX, indicating a better adsorption of BX− on mineral surface, which would increase the flotation recovery. To figure out the mechanism behind that, the laurionite surface was analyzed by XPS, which found the formation of PbS films after adding Na2S. The FT-IR analysis showed the BX− absorbance on laurionite significantly decreased after treating with high concentration of Na2S. Moreover, the solution chemistry calculations demonstrated that the proper dosage of Na2S could enhance the flotation of laurionite by reduce free lead ion in solution and covered some part of lead mineral surface, which sharply reduced the demand of collectors in flotation. However, the excess S2− would inhibited the adsorption of BX− on laurionite surface since the formation Pb(BX)2 was weaker than PbS. These results did not only expose that the addition of appropriate amount of Na2S could enhance laurionite’s sulfidization flotation, but also provide an effective way to separate laurionite from iron ore sintering dust.

RECYRON®: Idea to Innovation to Technology in Zero-Waste Ironmaking

Waste products are actually raw materials in disguise, waiting for a smart person to identify them and put them back into use by an appropriate process. RECYRON® is a novel technology for a zero-waste ironmaking process. This process is designed to recycle all possible raw material wastes (RMWs) from an integrated steel plant to produce direct reduced iron (DRI). RECYRON® takes care all RMWs of steel plants and iron ore mines, starting from superfine ores, coke breeze, sinter dust and BF dust and sludge, mill scale, just to name a few. RECYRON® uses a simple technology like briquetting to its utmost potential to agglomerate all the wastes, and thereafter reduces it by using a rotary kiln. The reduced briquettes with high metallic iron could be used in mini-mills having electric arc furnaces (EAF), or to charge in the blast furnace to lower the coke rate as much as possible. The process is also able to generate power as the by-product. RECYRON® offers several advantages in parallel, such as reduction of landfill, complete utilization of raw materials, low CO2 footprint, and last but not the least, a highly profitable process. The financial aspects such as estimated CAPEX and OPEX along with the NPV (Net Project Value) and IRR (Internal Rate of Return) for plants are also discussed in this article.