Slag Metal Research Articles

An Experimental Study on the Melting Solidification of Municipal Solid Waste Incineration Fly Ash

Melting solidification experiments of municipal solid waste incineration (MSWI) fly ash were carried out in a high-temperature tube furnace device. An ash fusion temperature (AFT) test, atomic absorption spectroscopy (AAS), scanning electron microscope (SEM), and X-ray diffraction (XRD) were applied in order to gain insight into the ash fusibility, the transformation during the melting process, and the leaching behavior of heavy metals in slag. The results showed that oxide minerals transformed into gehlenite as temperature increased. When the temperature increased to 1300 °C, 89 °C higher than the flow temperature (FT), all of the crystals transformed into molten slag. When the heating temperatures were higher than the FT, the volatilization of the Pb, Cd, Zn, and Cu decreased, which may have been influenced by the formation of liquid slag. In addition, the formation of liquid slag at a high temperature also improved the stability of heavy metals in heated slag.

Ways of the lead-bearing slag waste utilization

The article presents the results of research on the influence of lead production slag on the environment and ecology of the city. Due to the open storage of slags, an excess of maximum permissible levels (MPL) of lead was established: near the plant, the concentration of lead in the soil exceeds 3000 mg/kg, while the MPL is 3.2 mg/kg. The data of analyzes obtained by methods of scanning electron microscopy and X-ray microanalysis, performed on a scanning electron microscope (SEM), as well as the results of X-ray fluorescence semi-quantitative analysis, performed on an X-ray fluorescence wave-dispersive spectrometer, have been presented. The results of thermal analysis of samples in air in the 20-1000 °C temperature range are presented.It was revealed that lead slag contains a fairly high amount of toxic metal compounds. It has been established that the average content of toxic metals in slags formed as a result of the activity of a lead plant is: lead - 2, 38%; zinc - 9.81%; copper - 0.97%; iron - 25.31%; silicon oxide - 24.62%; calcium oxide - 16.21%; potassium oxide - 1.42%; sulfur - 1.35% of the total sample weight.The offered technology of a selective method for the extraction of non-ferrous metals allows to enhance the ecological state of the environment and reduce their negative impact on human health by means of the disposal of the lead production slags.

Copper slag as a potential source of critical elements - A case study from Tsumeb, Namibia

SYNOPSIS At a time of resource consumption, it is important to study the chemical composition of mining and metallurgical wastes to prevent the dissipative loss of metals and metalloids from the mining value chain. In particular, the recovery of critical elements from wastes is an option to increase the resources of such materials that are economically significant and have an overall supply risk. In this paper we report on the chemical composition, in particular the critical element content, of granulated slag originating from historical smelting activities in the Tsumeb area, Namibia. Laboratory-based inductively coupled plasma-mass spectrometry (ICP-MS) and X-ray fluorescence (XRF) analyses as well as portable X-ray fluorescence (pXRF) demonstrate that the slags are on average enriched in base metals (Cu 0.7 wt%, Pb 2.7 wt%, Zn 4.7 wt%), trace metals and metalloids (Cd approx. 50 mg/kg, Mo approx. 910 mg/kg) as well as critical elements (As approx. 6300 mg/kg, Bi approx. 3 mg/kg, Co approx. 200 mg/kg, Ga approx. 100 mg/kg, In approx. 9 mg/kg, Sb approx. 470 mg/kg). While metals and metalloids such as As, Mo and Pb can be determined reliably using pXRF instruments, the technique has inherent limitations in evaluating the contents of certain critical elements (Ga, Sb). However, there are positive correlations between the As, Mo, and Pb contents determined by pXRF and the Ga and Sb contents obtained through ICP-MS and XRF. Thus, quantitative pXRF analysis for As, Mo, and Pb allows calculation of Ga and Sb abundances in the slags. This work demonstrates that pXRF analysers are a valuable tool to screen smelting slags for their chemical composition and to predict the likely contents of critical elements. Keywords: base metal slag, portable XRF, critical elements, secondary resource.

Mass Transfer in Electroslag Processes with Consumable Electrode and Liquid Metal

Experimental and numerical comparisons of mass transfer processes during the electroslag remelting with consumable electrode (ESR) and electroslag refining with liquid metal (ESR LM) showed their identical refining capacity, despite the smaller both the slag–metal contact surface (twice) and metal overheat (by 70–95 K) in the latter case. As revealed, due to effect of metal movement inside the liquid metal drop, it moves in liquid slag faster than a solid particle of the same diameter. Under comparable conditions, it is experimentally confirmed that desulphurization at the ESR takes place mainly on the contact surface between the slag and metal baths, but not in the liquid metal film at the tip of a consumable electrode.

Modeling of Two‐Phase Flow in Blast Furnace Trough

Almost 95% of the world's hot metal production is from blast furnaces, reaching a production of 1.2 billions tons in 2018 according to the World Steel Association. The trough is an important equipment within the blast furnace production process, promoting the separation between hot metal and slag after casting. However, the flow pattern inside the runner is understudied due to its complexity. Due to the turbulence in the trough during the casting, there is metal loss in the slag and also slag entrainment in the hot metal. The metal loss in the slag is the most critical situation as it directly affects the efficiency. The influence of flow rate as well as of geometrical parameters on the flow pattern inside the runner is analyzed by physical and numerical simulation. In the physical simulations, particle image velocimetry (PIV) as well as dye injection using HD cameras and residence time distribution (RTD) curves are used to characterize the flow. These techniques allow to validate the mathematical model created in CFX‐Ansys. This work stresses the changing flow features as the slag–metal ratio changes during the casting operation and the role of geometry as far as metal separation from the slag is concerned.

Multistage desulfurization mechanism to reduce sulfur content of high ferrotitanium prepared using thermite method

High ferrotitanium is used as a deoxidizer and alloying agent in steelmaking processes and is mainly produced using high-cost remelting processes. The thermite method is a simple and low-cost method for preparing low ferrotitanium. However, the high levels of S, Al, and O residues in the product severely restrict its applicability in the low-cost preparation of good-quality high ferrotitanium. In this study, a novel multistage deep reduction method for preparing high-quality high ferrotitanium is proposed, and the multistage desulfurization mechanism is systematically investigated. The results indicate that multistage desulfurization is an effective method for reducing the S content of high ferrotitanium prepared via the thermite method. During the strong desulfurization stage, Ti2S reacts with CaO at the slag–metal interface and produces CaS. The S content decreases, while the O content increases, with the increase of CaO in the CaO–Al2O3-based slag. During the deep desulfurization, Ti2S is deeply reduced by the Ca and produces CaS, thus further reducing the S content. The S content decreases with the incremental addition of Ca and can be reduced to 0.035 wt% after multistage desulfurization.

Preparation of novel chemically bonded ceramics with steel slag and potassium hydrogen oxalate

A novel chemically bonded ceramic (novel-CBC) is prepared based on the acid–base reaction of alkali metals in steel slag (SS) and oxalate anion (C2O42−) in potassium hydrogen oxalate (PO). The effects of SS/PO ratio and water–solid (W/S) ratio on the setting and compressive strength of novel-CBC were studied in this paper. Reaction products and microstructure of novel-CBC were characterized by X-ray diffractometer (XRD), field emission scanning electron microscope-energy dispersive spectroscopy (FESEM-EDS) and thermogravimetric analysis/differential scanning calorimetry (TG/DSC). An optimal formula is obtained at a SS/PO ratio of 3.0 and a W/S ratio of 0.20, which starts setting at 10 min and gives the strengths of 18.0, 25.0, 39.8 and 49.0 MPa at 1, 3, 7 and 28 days, respectively. The reactants from SS are mainly Ca-bearing phases, while only a small amount of RO phase is involved in reaction. The main reaction products of novel-CBC are calcium oxalate monohydrate (CaC2O4·H2O; whewellite) crystals and agglomerates consisting of K, Mg, Al, Si and O elements. The unreacted Ca-bearing phase particle and RO phase residue are embedded in a mixture of abundant CaC2O4·H2O crystals with smooth surfaces and a size of 0.5–1.0 µm with large amounts of the nanoscale agglomerates.

Fundamental Insight into the Dripping Criteria of Slag and Hot Metal in a Coke Bed Using Energy Minimization Model

The dripping zone of the blast furnace is important in determining the productivity and quality of hot metal. The permeability of the bed affects both of these factors. Static holdup of hot metal and slag resulting from interfacial phenomena adversely affect the permeability of the bed. To characterize the holdup in the packed bed, we assumed the packed bed as an ensemble of two-sphere contacts at various contact axis inclinations and for contact angles. We developed mathematical models to determine the shapes of stable films at these contacts taking into account interfacial and gravitational energies. The film at higher contact angles shows an asymmetric shape even in between vertical spheres, which is investigated in detail. We also show the reason for the difficulty for dripping of the liquids at smaller particle sizes.

The Design of Slag and Electroslag Remelting Production Technology of Steel Containing Zirconium

Slag–metal reaction experiments in MoSi2 resistance furnace combined with electroslag remelting (ESR) experiments in ESR furnace are used to study the effect of slag on zirconium distribution in ESR ingot by establishing a new mass transfer model of slag–metal reaction. The mass transfer model consists of Al + Al2O3, Si + SiO2, Zr + ZrO2, and Fe + FeO systems based on the penetration and film theories. Both experimental and simulated results show that the returned slag (CaF2:CaO:Al2O3:MgO:ZrO2 = 57:20:16:3:3) combined with extra 4% Al2O3 added into molten slag in the first slag-temperature-rising period can control the zirconium in ESR ingot ranging from 0.35 to 0.40% and improve the homogeneous distribution of zirconium in ESR ingot. The returned slag of Exp.A containing low silica being used in Exp.C can not only contribute to the recycling of returned slag, but also improve the homogeneous distribution of Zr along the height of ESR ingot.

Ancient Mining and Metallurgy Activities in Mazayjan District, Fars Province

Ancient Mining and Metallurgy Activities in Mazayjan District, Fars Province

Optimized Scheme for Accelerating the Slagging Reaction and Slag–Metal–Gas Emulsification in a Basic Oxygen Furnace

Basic oxygen furnace (BOF) steelmaking is widely used in the metallurgy field. The slagging reaction is a necessary process that oxidizes C, Mn, Si, P, S, and other impurities and therefore directly affects the quality of the resultant steel. Relevant research has suggested that intensifying the stirring effect can accelerate the slagging reaction and that the dynamic characteristics of the top blow are the key factor in exploring the related complex physical and chemical phenomena. To address the issue, the standard k-ω turbulence model and level-set method were adopted in the present work and a fluid dynamics model was developed for a BOF. Accordingly, the slag–metal–gas emulsion interaction and stirring effect were investigated, and the interference mechanism of a multi-nozzle supersonic coherent jet was revealed. Finally, a self-adjustment method based on fuzzy control is proposed for the oxygen lance. The results indicate that the transfer efficiency of jet kinetic energy at the gas–liquid interface is the critical factor for the slagging reaction and that multi-nozzle oxygen lances with a certain twisted angle have important advantages with respect to stirring effects and splashing inhibition. The fuzzy control method predicts that the optimal nozzle twist angle is within the range of 7.2° to 7.8°. The results presented herein can provide theoretical support and beneficial reference information for BOF steelmaking.

The leaching mechanism of heavy metals (Ni, Cd, As) in a gasification slag during acidification

The gasification slag by acidification can leach abundant heavy metals. In this paper, the fate of heavy metals (Ni, Cd, and As) in the raw slag and the acidified slag that treated by HAc and HCl was systematically investigated combined with Density Functional Theory (DFT) calculations. The results show that the content of Ni and Cd is reduced with an increasing acid concentration and meets the regulatory standards by 7 M HAc and 3 M HCl, respectively. Most of Ni combined with gehlenite is released as gehlenite dissolves during acid treatment, whereas Cd in combination with gehlenite and iron compounds is hard to release at lower HAc concentrations. Unexpectedly, the content of As tends to elevate at a higher concentration of HAc, which is due to the increase in the content of Ca by new Ca-compound formation and the higher binding capacity of Ca to As according to DFT results. Additionally, if the acid-base ratio reaches about 2.0 by acid treatment, there would be a maximum leaching rate. It is recommended that acid concentration should be controlled to avoid a secondary risk of heavy metals.

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.

Elucidating the Roles of SiO2 and MnO upon Decarburization During Submerged Arc Welding: A Thermodynamic Study into EH36 Shipbuilding Steel

By employing CaF2-SiO2 and CaF2-SiO2-MnO system fluxes, the roles of SiO2 and MnO in decarburization behaviors during submerged arc welding of EH36 shipbuilding steel have been quantified and evaluated. All possible reactions associated with C transfer and interfaces at which these reactions occur are systematically discussed. It is concluded that the addition of SiO2 and MnO exerts synergistic effects on the extent of decarburization due to increased partial pressures of O2 and SiO gases in the plasma, improved O level in the weld pool, and higher activities of the oxides, such as SiO2, MnO, and FeO, at the slag–metal interface. The investigation over the macrographic detached slag surfaces shows that the possibility of bubble nucleation is highly influenced by flux formula. The effect of heat input on decarburization is discussed, and the optimal flux compositions expected in the present study are analyzed.

USING METAL WASTE SLAGS AS THE HETEROGENEOUS CATALYSTS OF OZONE FOR TREATMENT OF PULP WASTEWATER

Catalytic ozonation is one of the promising treatment methods for removal of persistent organic compounds from water and wastewater. In this study, some metal slags such as: iron slag, lead slag, zinc slag, cadmium slag and copper slag originated from solid waste of Thai Nguyen Non-ferrous Metals Limited Company, Vietnam were used as heterogeneous catalysts for ozonation process to remove organic compounds from pulp wastewater. The effects of the initial pH (pHi) of pulp wastewater and the metal slag dosage on efficiency of decolorization and mineralization of pulp wastewater, in term of COD were investigated. The results indicated that iron slag was the most suitable catalyst for treatment of pulp wastewater by ozonation process with the highest removal efficiency of COD, namely, after 120 min of ozonation (with flowrate of O3 of 3.038 g/h) of the pulp wastewater (initial COD 1809 mg/L), COD removal efficiency, respectively, reached 91,16%; 84%; 83,83 %; 83,91%; 83,41% and 83,14% in the presence of iron, copper, zinc, lead, cadmium slag and ozone alone. Simultaneously, the color was almost completely removed (95.55 – 98.79%) by ozonation processes with using all before-mentioned metal slags as heterogeneous catalysts and ozone alone. Maximum COD and color removal efficiency obtained at pH 7 for ozonation alone and its combinations with iron slag. Moreover, an increase in the iron slag dosage from 0.125 g/L to 2.0 g/L for O3/iron slag could enhance COD and color removal of pulp wastewater. The K values (apparent first-order rate constant values) showed that the COD removal rate followed the pseudo-first-order kinetic model. This study also indicated that the main constituent FeO presence in iron slag reaction with O3 in heterogeneous catalytic ozonation system enhances removal efficiency of color and COD of pulp wastewater.

Technology for the reduction of iron oxides in the processing of metal slag scrap in the oxygen converter

The characteristic features of slag formation and oxidative metal refining in 160-tonne converters of EVRAZ ZSMK JSC using metal slag scrap in the solid metal charge are considered. Technological advantages of the process are established for the reduction of iron oxides from the slag component of the iron-containing product in the processing of waste slags.

Geopolymer Concrete by using Fly Ash, GGBS, Quarry Dust and 10mm Aggregate

Geopolymer concrete is a type of concrete which is produced by reacting with a caustic activator to aluminum and silicate bearing material. Materials such as fly ash or iron and metal slag are commonly used, which helps to create a cleaner environment. Consistently 87 to 100 million tons of flyash are created from India's coal-based thermal power stations, and force is that way into a country's success and improvement. In India, power generation spends 70% of the nation's coal generation along these lines and produces 100 million tons of debris per year. The flyash is expected to stretch by 2012 to at least 175 million tonnes per annum. Now, having seen that debris is such a useful and valuable material that it is often used for a tremendous number of uses such as construction segments, concrete, dike development, raising, dykes, agribusiness and mine filling material. It’s effectively acknowledged for scale usage as opposed to arranging at high dealing with costs. This content arrangement with geopolymer concrete to supply the geo-polymer concrete is completely supply with flyash and Ground granulated slag. Fine aggregate is replaced with powdered quarry and M.Sand. Coarse Aggregate (20 mm) is replaced with 10 mm Aggregate Sodium hydroxide (NaOH) and sodium silicate (Na2Sio3) game plans are commonly used for polymerization. The use of fly-debris and GGBS help in diminishing the contamination by dispensing with carbon-dioxide and carbon monoxide gas which is created in assembling of concrete. This paper uses fly ash, GGBS, quarry dust and 10 mm aggregate with alkaline solution to analyze geopolymer concrete.

Self-cementation solidification of heavy metals in lead-zinc smelting slag through alkali-activated materials

Lead-zinc smelting slag (LZSS) is an industrial waste which is considered as hazardous waste due to the presence of heavy metals (Pb, Zn, Cr and Cu). These heavy metals can be leached into the ecosystem to pollute the environment. Moreover, LZSS is utilized as the preparation of alkali-activated materials (AAM) because it is rich in aluminosilicates. In order to limit its leaching toxicity, LZSS is utilized to prepare AAM and achieve self-cementation solidification of its heavy metals in the current study. LZSS based alkali-activated materials (LZAC) with excellent compressive strength (96.14 MPa) were obtained through single factor and orthogonal experiments. The factors included in these experiments are temperature, Na2O equivalent, waterglass module and water-cement ratio. The results of compressive strength and leaching experiments confirmed that LZAC could be used for construction purposes. The X-ray diffraction, Fourier transform infrared spectroscopy and Field-emission scanning electron microscopy with energy dispersive spectrometry results show that heavy metals are effectively immobilized in LZAC by chemical fixation and physical encapsulation.

Mathematical model for design of optimized multi-component slag for electroslag remelting

Slag is the heart of electroslag remelting (ESR) process. A new mathematical model to design the optimized slag for ESR was developed based on slag–metal equilibrium theory, ion and molecule coexistence theory and modified Butler’s equation. It was assumed that an overall thermodynamic equilibrium did exist at electrode tip–slag interface. With this model, the equilibrium slag and its surface tension could be obtained quantitatively when the initial compositions of consumable electrode were given. An industrial experiment with four types of slags was carried out in a special steel plant in China. The variation of Al, Si and Mn corresponded well with the deviation of corresponding oxide from equilibrium, reflecting the reasonability of the model. Besides that, the effects of Al in electrode as well as CaO, CaF2 and MgO in slag on the equilibrium slag, dissolved oxygen and surface tension were discussed in detail.

Experimental Approach to Matte–Slag Reactions in the Flash Smelting Process

ABSTRACT Improving metal–slag separation in pyrometallurgical processes is increasingly important. Due to the harsh conditions, direct observations of the molten phases behavior in the settler of the Outotec Flash Smelting Furnace (FSF) are not possible and the ways to improve metal settling can only be studied by simulation and modeling. This study focuses on kinetics and mechanisms of the chemical reactions between matte droplets and slag, which were investigated in laboratory-scale heat-quench equipment at a typical smelting temperature of 1300°C as a function of time in both air and argon atmosphere. The reaction mechanism in the FSF settler was formulated and results in argon atmosphere also indicate that the oxidation of cuprous sulfide by ferric ions in the slag contributes strongly to the copper losses in the slag.