Elements In Slag Research Articles

Characterization of Taguchi optimized fiber reinforced copper slag concrete composites with strength properties

Establishing the ideal design has always been a difficulty for concrete engineers because of the inclusion of many alternative construction materials particularly when dealing with the incorporation of slag elements and fibers in concrete mix design. In this study, the Taguchi optimization method is implemented to predict the optimal mix design of fiber reinforced copper slag aggregate concrete (FRCSC) with mechanical strength properties. For this purpose, different parameters influencing mechanical strength were defined based on the available literature. The Taguchi approach was subsequently applied to develop an orthogonal array of parameters, and experimental tests were carried out in accordance with the suggested design array to acquire experimental data for each and every strength property. Three major influencing parameters like fiber length (FL), fiber percentage (FP), and copper slag content (CS) were considered in order to get optimal mix design for FRCSC. Analysis of variance was also employed to evaluate the effective factors on compressive, split-tensile, flexural, water absorption and void content properties for FRCSC. It was found that the proposed method was effective in finding the optimal mixture design from strength point of FRCSC and the experimental results indicated a significant improvement in five selected strength properties of FRCSC. From the results of Taguchi analysis, it can be concluded that, for five selected strength properties, 60% CS + 1% of fiber + 20 mm of fiber length is the optimal mix design combination for FRCSC. Finally, physical and microstructural characterization through FESEM and EDX were carried out to have a closer justification for the test results.

The development of the blast furnace metallurgy of the iron in Slovakia

Easily available sources of iron ore, the abundance of hydropower, and wood for charcoal were the prerequisites for the development of iron metallurgy in Slovakia. Since the 16th century, the bloomery process used in iron metallurgy has been gradually replaced by the blast furnace process. This new process was more economical, but it required extremely high investments. The steam engine replaced the unreliable water power in the blowing process, and coke replaced charcoal. Especially due to economic problems, the first blast furnaces in Slovakia started to be built about two hundred years later than in Western Europe. Despite the promising start, the installation of steam engines was lagging. A major drawback was the lack of road and rail networks combined with the absence of local coking coal. The introductory part of the paper compares chronologically the individual stages of the development of blast furnace production in Slovakia and abroad. Next, the paper presents comprehensive results of the analysis of samples of the slag found at 59 sites of extinct ironworks with a blast furnace, localised until now. The samples were analysed by metallographic, chemical, spectral (secondary and trace elements), and X-ray methods. In the past, these data were published with territorial restrictions and mostly in a language other than Slovak. The contents of secondary and trace elements in slag from individual sites using cluster analysis and also metallic iron content in slags categorised according to owners of the blast furnaces and the slag basicity are compared.

Long-Term Leaching Effects on CaO-Modified Iron Silicate Slag

Granulated iron silicate slag, a by-product of pyrometallurgical copper extraction, has excellent properties for construction applications. Slag modification with CaO enhances the application properties regarding pozzolanic reactivity, potentially extending slag use in the future. The slags’ short-term leaching behavior has already been investigated with promising results, while the long-term leaching effects are less studied. Therefore, this study aims to determine the long-term leaching effects on CaO-modified iron silicate slags. The CaO-modifications were conducted during full-scale slag treatment operation. The slags were characterized and leached, and the remaining slags were investigated regarding the formation of secondary phases. The long-term leaching of main and trace elements was determined over 30 days using a dynamic leaching method corresponding to an extended time period. The leaching tests showed increased leaching of the main slag elements (Si, Ca). Zn and Cu showed peak leaching after four days of leaching, and the leaching of As and Sb decreased with the increasing CaO content in the samples. After dynamic leaching, secondary phases formed on the Cu-containing inclusions on the sample surfaces. Independent of the CaO content, the leaching of Cu was increased when subjected to external acidic and oxidating conditions using static pH titration at pH 5 in dilute nitric acid.

Thermodynamic modeling of metal reduction in copper-smelting slags and experimental verification of its results

Over 110 million tons of slag were accumulated in the dumps of the Russian copper-smelting enterprises, and their number is increasing. Environmental taxes and dumps maintenance costs are burdensome, which makes it necessary to make the most complete disposal of these production wastes. At the same time, these slags contain valuable elements, in particular, iron, copper, zinc, selenium, arsenic and some others, the extraction of which can make recycling profitable. The paper presents the results of a thermodynamic calculation of the behavior of copper-smelting slag elements in the mixture with carbon during heating. Modeling was performed using the TERRA software package. The influence of the process temperature in the range of 600 – 1750 °C on reduction of iron, zinc and silicon was analyzed at the amount of carbon in the system corresponding to the stoichiometry of iron reduction reactions and exceeding the stoichiometric one. It was established that when heated above 650 °C, metallic iron appears in the system, and its full reduction is completed at 1250 °C. The appearance of metallic zinc is observed in two temperature ranges: in the first, appearance of zinc is observed with a simultaneous decrease in concentration of zinc oxide; in the second, an increase in concentration of metallic zinc with a simultaneous decrease in concentration of zinc sulfide. At temperatures above 1650 °C, silicon appears in the system. Under laboratory conditions, the processes of solid-phase reduction of iron with the capture of zinc oxide and separation of the reduction products were tested. It was established that as a result of pyrometallurgical separation by melting reduction products, iron-carbon alloys (steel and cast iron) and alloys with high silicon content can be obtained. The results of the work can be used in development of theoretical and technological foundations for the processing of copper smelting slags, which are not processed by existing technologies.

Catalytic pyrolysis of biomass impregnated with elements from steelmaking slag leaching and simultaneous fabrication of phosphorus adsorbent

Energy shortage and environmental pollution are global concerns for sustainable development, which can be improved by high value-added reuse of solid wastes. In this study, a novel strategy was proposed for reusing steelmaking slag to treat biomass and produce valuable products. The study consisted of: i) useful elements (mainly Ca and Fe) were extracted from steelmaking slag through leaching then doped onto pine as catalysts for biomass pyrolysis; and ii) the produced slag elements (SE)@char was employed as adsorbent for P removal from wastewater. Results showed that compared to raw pine, SE@pine released more CO2 and CO due to the decomposition of formed calcium citrate on particles and the reaction of carbon with CO2. In the bio-oil product from SE@pine, under the assistance of slag elements, the selectivity of total phenolic compounds dropped by half with the nitrogenous and acid groups showing the same descending trend, while the selectivity of alcohols and ketones increased. The slag elements, especially Ca and Fe, acted as catalysts for upgrading the bio-oil quality through enhancing the dehydration and dehydroxylation reactions. X-ray powder diffraction analysis indicated the presence of nano-size calcite particles on SE@char products from different pyrolysis temperatures. The SE@char from pyrolysis at 750 °C was attempted as adsorbent for phosphorus removal from aqueous solution. A phosphate adsorption capacity of 109 mg/g adsorbent was identified at the investigated conditions. The adsorption kinetics could be best described by the Elovich model, indicating the chemical reaction nature of the adsorption. This study explored the use of steelmaking slag and biomass wastes in a novel way for simultaneous production of upgraded biofuels and adsorbent for phosphorus control in wastewater.

Technological aspects of waste incinerator slag processing

Incineration is a modern global trend in the disposal of combustible solid waste. When burning garbage, solid incombustible residues are formed – slags containing aluminum, copper, zinc and lead, in quantities many times higher than the maximum permissible concentrations of these elements in soils. The material composition and morphostructural features of the material were analyzed to determine possible areas of use and ways of utilization of waste incineration plant slags. As a result of microprobe researches forms of finding of ecologically controlled elements in slag are established. Test results of slag concentration by gravitational methods and results of magnetic separation are given. Based on the studies, a basic outline of slag product processing is proposed.

Uranium removal from tin smelter slag by bisulfate fusion and acidic leaching

Slag as secondary product (waste) of tin smelter still contains not only valuable elements e.g. Ti, Nb, Ta, Zr, Hf and rare earth elements, but also radioactives such as Th and U, wich are accumulated in the slag phase during the smelting. Due to valuable element content, the slag becomes major of interest in mineral processing industries, hence the slag needs to be decontaminated before it could be processed further.Common approach to reduce U content from the slag using leaching process is considered ineffective due to association of U with refractory elements e.g. Si and Ti in the slag. To break down the refractory phases, the fusion approach by using fusing agent is required in order to release U so that they could be leached out using mild lixiviant.In this research, potassium hydrogen sulfate (KHSO4) and sulfuric acid was used as fusing agent and lixiviant, respectively. The parameters studied includes molar ratio between fusing agent and refractory elements in slag, fusion temperature, fusion time, sulfuric acid concentration in lixiviant and pulp density during leaching stage. The studies so far demonstrated that optimum condition in U removal occurred at fusion temperature 400 °C, fusion time 2 hours, molar ratio of potassium hydrogen sulfate to tin slag 5, sulfuric acid concentration 2 M and pulp density 15 ml/gr. The maximum recovery of U was 85.6%, which was significant compared to the results using direct leaching without fusion (0.1%).

Characteristics of ash and slag from four biomass-fired power plants: Ash/slag ratio, unburned carbon, leaching of major and trace elements

The utilization of biomass energy is attracting worldwide attention due to the worsening energy crisis and the concerns on carbon dioxide emission. However, the rapidly development of biomass-fired power plants generate enormous amount of slag and ash. At present, the main treatment method of biomass slag and ash is landfill, which not only requires high cost, but also causes a series of environmental issues. Aiming at this problem, the slag and fly ash from four biomass power plants were sampled and characterized. The major/trace element composition and leaching characteristics of slag and fly ash are analyzed, and the effect of volatile mineral in these solid residues on furnace efficiency is also evaluated. The results indicate that for biomass-fired grate furnaces, in the generated solid residues, the slag accounts 60 ~ 70% while the fly ash accounts for 30 ~ 40%. The volatile elements in slag are much lower than those in fly ash, and the unburned carbon content of fly ash is generally lower than that of slag. Due to the enrichment of volatile minerals in fly ash, instead of 815 °C, 550 °C is suggested to measure the unburned carbon content in fly ash. When the measuring temperature of unburned carbon decreases from 815 °C to 550 °C, the measured energy loss from the incomplete combustion of solid fuels decreases by one third, which affords a more reasonable evaluation on combustion efficiency. The contents of cadmium and lead in certain fly ash samples exceed the standard, however, all fly ash samples have a high leaching rate of potassium but low leaching rates of copper, zinc, cadmium, lead, chromium and arsenic. It indicates that the fly ash from biomass-fired grate furnace is suitable for producing potassium fertilizer by leaching instead of direct soil fertilization or landfill. The leaching rate of most minerals in slag is much lower than that in fly ash and the contents of heavy metals are far below the prescribed upper limit in standard, which indicates that the slag from biomass-fired grate boiler is more suitable for direct use in soil improvement due to the low contents of hazardous elements.

Separation of valuable elements from steel making slag by chlorination

Herein, we investigated the volatilization behavior of slag elements during chlorination of converter slag and Kambara reactor slag to develop a method for recycling steelmaking slag. Then, the effects of holding time and carbon addition (carbon reduction) (denoted as a combination of carbon reduction/chlorination) on volatilization were examined in detail. Most of the Fe in the slag was volatilized by chlorination up to 1000 °C, independently from the type of slag. Moreover, it was possible to volatilize most of the Ti and approximately 40% of the Mg by chlorination at 1000 °C for 60 min. That is, Fe and Ti were completely separated from the slag by chlorination. Fe was volatilized below 1000 °C during carbon reduction/chlorination, and remarkable volatilization (40–90%) of Ti and P was also observed until 1000 °C. Therefore, the separation of each element using the volatilization kinetics of Fe, Ti, and P was difficult during the carbon reduction/chlorination. In contrast, when carbon was added to the chlorination residue obtained at 1000 °C for 60 min and then subjected to a carbon reduction/chlorination treatment, most of the Mg, Si, Al, and Ca remained in the solid phase up to 1000 °C, and P was the only element volatilized. The volatilization temperature (>1000 °C) and the proportion of P were lower than those of the conventional carbon reduction method of slag. Therefore, it was found that the combination of chlorination and carbon reduction/chlorination methods is effective for the separation of Fe, Ti, and P from slag.

Use of Slag from the Combustion of Solid Municipal Waste as A Partial Replacement of Cement in Mortar and Concrete.

In Europe, the use of wastes in the cement and construction industry follows the assumptions of sustainability and the idea of circular economy. At present, it is observed that cement plants introduce wastes to the cement in the form of so-called mineral additives. The most often used mineral additives are: fly ash with silica fume, granulated blast furnace slag and silica fume. The use of mineral additives in the cement is related to the fact that the use of the most expensive component of cement—Portland cement clinker—is limited. The purpose of the article is a preliminary evaluation of the suitability of slag from the municipal solid waste incineration plant for its use as a replacement of cement. In this article, slag from the municipal solid waste incineration (MSWI) replaces cement in the quantity of 30%, and presents the content of oxides and elements of slag from the MSWI. The obtained results are compared to the requirements that the crushed and granulated blast furnace slag need to meet to be suitable for use as an additive of type II to the concrete. The conducted analyses confirmed that the tested slag meets the requirements for the granulated blast furnace slag as an additive to the concrete in the following parameters: CaO ≤ 18.0%, SO3 ≤ 2.5% and Cl ≤ 0.1%. At the same time, mechanical features were tested of the designed mortars which consisted of a mixture of Portland cement (CEM I) with 30% of slag admixture. The designed mortar after 28 days of maturing reached a compressive strength of 32.0 MPa, and bending strength of 4.0 MPa. When compared to the milled granulated blast furnace slag (GBFS), the obtained values are slightly lower. Furthermore, the hardened mortars were subject to a leachability test to check the impact on the environment. Test results showed that the aqueous extracts from mixtures with 30% of slag admixtures slightly exceed the limits and do not pose a sufficiant threat to the environment as to eliminate the MSWI slag from economical use.

Features of material composition of slag incineration plants

The most part of the municipal solid waste which is formed in the world is utilized by burning. The slags which are formed in the course of burning of garbage contain heavy metals from which the main ones are aluminum, copper, zinc and lead. Waste from garbage burning can be buried in special grounds or be applied as grounds at construction of waste landfill, that can significantly reduce space reserved for warehousing of waste. The analysis of material composition is carried out for definition of possible areas and ways of utilization slags of refuse incinerators. Distribution of chemical elements on fineness classes in the initial material is studied. As a result of microprobe research, the authors establish the forms of finding of ecologically controlled elements in slag. Recommendations about the choice of ways of enrichment are made.

Forms of occurrence of selected alloying elements in slag from an electric arc furnace

The chemical composition of steel slag is dependent on the type of the charge and thus the alloying elements used in the process. The conducted tests of slag from an electric arc furnace have indicated that their chemical composition contains elements classified as so-called alloying elements – with the highest content of manganese and chromium. Besides these, smaller amounts of cobalt Co, molybdenum Mo, titanium Ti and tungsten W were identified. Due to the significant concentration of Mn and Cr, it was assumed that these elements were added to the alloy on purpose to achieve certain steel properties. The presence of Co, Mo, Ti and W may be related to the type of scrap introduced into the process. To determine what components of the slags are the analysed metals related with, phase composition tests of slag were conducted based on electron scanning microscopy and X-ray diffraction method. It was established that chromium occurs in the form of impurity in the solid solution of FeO-MnO-MgO, called the “RO phase” and forming characteristic dendritic forms. Wolfram, on the other hand, creates its own cryptocrystalline phases classified as tungstates: hübnerite and ferberite. The remaining metals, that is Co, Mo, and Ti occur in a dispersed state in the amorphous substance.

Fundamentals of the refractory wear in an industrial anode furnace used in the copper-making process

This paper presents a combination of different useful techniques to identify the fundamentals of the infiltration and chemical degradation of the refractory used in the lining of an anode furnace for fire refining of blister copper. In practice, this work was carried out at the Atlantic Copper Smelter (Huelva; Spain) by a post-mortem study of the refractory used in a one-year campaign, and thermochemical calculations using the FactSage® database. The combination of both techniques created enhanced value thanks to their synergy.The infiltrations and the formation of new phases in the reaction layer were identified using microstructural analyses. The nature of these infiltrations were identified; all the refractory brick samples had been substantially infiltrated by copper and slag elements (mainly copper and iron oxides). The new phases formed were the result of the complex chemical interaction between the slag and the constituent of the refractory. Additionally, copper was incorporated to the spinel.In order to propose a model to represent this complex process, thermochemical calculations were carried out to define a baseline to explain the microstructures obtained as a consequence of the interactions between the bath and the refractory.

Charakterystyka geochemiczna wybranych pierwiastków krytycznych w żużlach po hutnictwie rud Zn-Pb

Charakterystyka geochemiczna wybranych pierwiastków krytycznych w żużlach po hutnictwie rud Zn-Pb

Dissolution of steel slags in aqueous media.

Steel slag is a major industrial waste in steel industries, and its dissolution behavior in water needs to be characterized in the larger context of its potential use as an agent for sequestering CO2. For this purpose, a small closed system batch reactor was used to conduct the dissolution of steel slags in an aqueous medium under various dissolution conditions. In this study, two different types of steel slags were procured from steel plants in India, having diverse structural features, mineralogical compositions, and particle sizes. The experiment was performed at different temperatures for 240h of dissolution at atmospheric pressure. The dissolution rates of major and minor slag elements were quantified through liquid-phase elemental analysis using an inductively coupled plasma atomic emission spectroscopy at different time intervals. Advanced analytical techniques such as field emission gun-scanning electron microscope, energy-dispersive X-ray, BET, and XRD were also used to analyze mineralogical and structural changes in the slag particles. High dissolution of slags was observed irrespective of the particle size distribution, which suggests high carbonation potential. Concentrations of toxic heavy metals in the leachate were far below maximum acceptable limits. Thus, the present study investigates the dissolution behavior of different mineral ions of steel slag in aqueous media in light of its potential application in CO2 sequestration.

Reaction, crystallization and element migration in coal slag melt during isothermal molten process

Crystallization behavior of coal slag influences the slag flow and rheology properties in the slagging gasifier. Crystallization behavior of coal slag during isothermal molten process was observed and analyzed on the in situ experiment study. Complex aluminosilicates reaction led crystal to separate out in molten slag, mainly including the hexahedral crystal and acicular crystal, which varied with slag molten temperatures. The growth of crystal size first increased and then remained stable on molten slag surface with increasing isothermal time. The distribution and migration of coal slag elements on slag surface and inside crystal were also detected by time of flight secondary ion mass spectrometry (ToF-SIMS). Al, Ca and Si homogeneously distributed on the crystal and amorphous phase, due to the high content of element in coal slag. K mainly enriched on the crystal surface and amorphous phase while Na diffused and migrated onto the crystal surface. Mg doped into the interior of crystal, and the distribution of Fe varied with crystal type.

Assessment of EAF Steel Slag Solubility by Statistical Design

Electric arc furnace (EAF) steel slag solubility was studied using experimental design and statistical analysis. The solutions between pH 4 and 10, were mixed with the EAF steel slag for 0.5 hours at 350 rpm. The effects of the operating parameters, individually and their interaction, on the dissolution of slag elements were assess using full factorial design in the statistical design of experiment. The various parameters studied were pH (4-10), size (+0.2-1.2 mm), speed (0-700 rpm) and temperature (26-50°C). The results of the experimental design indicated that the main significant parameter within the ranges studied for Cr (VI) dissolution in solution was higher speed, lower size for Ca dissolution while for Si, was the positive interaction of speed and size. Maximum Cr (VI) of 0.0104 mg/L was obtained in solution at pH 10, slag size of 0.2 mm, temperature of 50°C and rotational speed of 700 rpm. Also, complimenting the solubility studies was slag characterization using XRF, XRD and SEM/EDX analysis. From these results, it can be concluded that the operating parameters considered individually and their interaction have effect on the solubility of EAF steel slag.

Comparison of methods for quantifying active layer dynamics and bedload discharge in armoured gravel‐bed rivers

ABSTRACTSeveral methods were employed in the Ardennian rivers (Belgium) to determine the depth of the active layer mobilized during floods and to evaluate the bedload discharge associated with these events. The use of scour chains has shown that the depth of the active layer is systematically less than the b‐axis of the average particle size (D50) of the elements which compose the surface layer of the riffles. This indicates that only a partial transport exists during low magnitude floods. The bedload discharge has been evaluated by combining data obtained using the scour chains technique and the distance covered by tracers. Quantities of sediment transported during frequent floods are relatively low (0·02 t km–2) due to the armour layer which protects the subsurface material. These low values are also related to the fact that the distance calculated for mobilized bedload only applies to tracers fitted with PIT (passive integrated transponder)‐tags (diameter > 20 mm), whereas part of the bedload discharge is composed of sand and fine gravel transported over greater distances than the pebbles. The break‐up of the armour layer was observed only once, for a decennial discharge. During this event, the bedload discharge increased considerably (2 t km–2). The use of sediment traps, data from dredging and a Helley–Smith sampler confirm the low bedload transport in Ardennian rivers in comparison to the bedload transport in other geomorphological contexts. This difference is explained by the presence of an armoured layer but also by the imbricated structures of flat bed elements which increase the resistance to the flow. Finally, the use of the old iron industry wastes allowed to quantify the thickness of the bed reworked over the past centuries. In the Lembrée River, the river‐bed contains slag elements up to a depth of about 50 cm, indicating that exceptional floods may rework the bed to a considerable depth. Copyright © 2012 John Wiley & Sons, Ltd.

Use of Ferrochromium Slag as an Artificial Aggregate in Pavement Layers

Abstract This paper reports the results of experiments aiming to identify the properties of ferrochromium slag when it is used as an artificial aggregate for preparation of granular layers of flexible pavements. The experimental program consisted of three stages: (1) study of the physical and chemical properties of slag, (2) leaching of heavy elements of slag in terms of environmental impact, (3) study of the mechanical properties of specimens made with ferrochromium slag and limestone as aggregate. In the laboratory, cylindrically prepared specimens were tested in a repeated load triaxial (RLT) test apparatus. In addition, particle size analysis, abrasion, frost resistance, compaction, CA bearing ratio, and leaching tests were performed on the materials prior to RLT testing. The results indicate that the physical and mechanical properties of air-cooled ferrochromium slag are as good as those of natural aggregates. It can be used as a base or sub-base material in highway pavements and as an embankment material. Furthermore, the use of the slag as aggregate in pavement layers reduces the requirement for natural aggregates and saves the existing natural resources.

Long-term bedload mobility in gravel-bed rivers using iron slag as a tracer

Bedload dispersion is evaluated in gravel-bed rivers using slag elements from ironworks established along rivers in the Ardenne region, between the fourteenth and the nineteenth centuries. Large quantities of slag were dumped close to these rivers or even directly into the channels. For centuries, slag elements were dispersed in the bedload and transported by floods of varying importance. Consequently, slag may be considered as a reliable tracer to analyze bedload dispersion over several centuries. The size of slag elements was studied along 16 Ardenne rivers. The longitudinal size trend of the largest slag particles allows the effective competence of these rivers to be determined (between 19 and 129 mm for rivers where specific stream power for the bankfull discharge ranges between 20 and 134 W/m²). A direct relationship doesn't exist between these two parameters as the size of slag elements must be considered with regard to the D 50 of the bed. Selective transport was analyzed directly downstream of the input sites. The sorting distance varies from river to river and depends on the velocity of the coarse elements introduced into the river since the inception of the iron industry. Downstream of two metallurgic sites, the slag propagation fronts were located. As the periods of activity at these sites are known from historical studies, the virtual velocity of bedload movement in these rivers was estimated to be 2–4 km/century.