Ferrosilicon Industry Research Articles

Sustainable route for silica preparation from silica fume

ABSTRACT Silica fume (SF) is a major voluminous and bulky by-product of the ferrosilicon industry, and its disposal poses a significant environmental concern. To address this issue, a sustainable approach was employed to transform SF into silica powder using a precipitation method. The process involved calcination, acid precipitation, aging, and drying, utilising industrial by-products such as silica fume and calcium oxide. Various parameters, including hydrochloric acid concentration, water bath temperature, aging pH, aging temperature, and aging time, were systematically investigated to optimise the properties of the resulting silica product. The physical and chemical attributes of the processed silica were thoroughly examined using techniques such as X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), laser particle size analysis, and dibutyl phthalate (DBP) absorption tests. Under optimal conditions (hydrochloric acid concentration of 20%, water bath temperature of 90℃, aging pH 3-4, aging temperature of 90℃, and aging time of 8 hours), the resulting silica product achieved a purity of 98.5866%, a DBP absorption value of 2.85 mL/g, and a particle size of 6.07 µm, meeting national industry standards. This environmentally benign and cost-efficient synthesis route offers a practical solution for large-scale production.

Synthesis of sodium silicate using industrial by-products glauber's salt and microsilica: Effective reuse of the waste.

Large amounts of by-products, including glauber's salt (GS) and microsilica (MS), are accumulated from chlor-alkali industry and ferrosilicon industry development, which not only wastes precious resources, but also causes serious environmental problems. In order to recycle and reuse these industrial by-products, solid sodium silicate was synthesized using GS and MS as the main raw materials, and semi-coke (SC) as the reducing agent. The effects of melting parameters including GS/SC and MS/GS molar ratio, heating rate, temperature, reaction time, and SC particle size on the conversion efficiency and modulus of solid sodium silicate were investigated and optimized. Under optimal conditions, the maximum conversion efficiency of 94.91% was obtained with modulus of 2.5. Characterization analysis of the products indicated that the amorphous silicate sodium was successfully synthesized. Moreover, the reaction mechanism was investigated, which focused on the thermal behavior and phase transformation using thermo-gravimetric and differential scanning calorimetric (TG-DSC) and in-situ X-ray diffraction. Additionally, the causes and suppression measures of "glauber's salt water" (GSW) during the experiment were summarized. This work not only creates resource utilization of GS and MS, but also provides the foundation for the synthesis of sodium silicate with GS.

Status and Characteristics of Ferrosilicon Industry in China

Currently, Chinese ferrosilicon industry shows characteristics including highly concentrated industrial regions, graded utilization of materials, large-scale submerged arc furnace, and application of automation equipment. Chinese ferrosilicon industry is highly concentrated in five major regions, where mineral and electric power resources are fully exploited to develop the coal-electricity-metallurgy and coal-coke-gas-electricity--metallurgy-magnesium industrial chains. Production relies on both the silica resources of Helan mountain and Qilian Mountain, and the unique semi coke with particle size of 5-18mm produced from Jurassic sticky coal in Shenfu region. A series of different characterization methods are used to achieve the graded utilization of materials, and the smelting power consumption could be optimized to 7200-7300kWh per ton of FeSi75. China encourages and support large-scale ferrosilicon furnaces, the load of new-built submerged arc furnace in the country are around 33-40MW, and the largest furnace reaches 63MW. Erdos as the biggest ferrosilicon producer in the world, has a capacity of more than 1 million tons per year. The load of its largest furnace is 50MW. Erdos is committed to the development of full-process automation for ferrosilicon production, which covers raw material storage and transportation, batching, distribution, electrode operation, charge-mix surface treatment, furnace discharge, casting and product crushing. For instance, the use of a self-developed automatic rotary feeder reduced the smelting energy consumption by optimizing the structure of charge-mix layer. The application of the automatic tapping machine allows robots to replace manpower in key and hazardous positions. This paper deeply analyzes the ferrosilicon industry characteristics in China and provides reference for the development of the ferrosilicon industry

Sensitivity Analysis of Life Cycle Impacts Distribution Methods Choice Applied to Silica Fume Production

The construction sector is known as an important consumer of natural resources. The use of by-products from different production chains in the sector is encouraged, promoting a reduction in the extraction of natural resources, reducing the need for residues disposal and enhancing circularity. Silica fume is a by-product from the smelting process in the silicon and ferrosilicon industry, commonly used as concrete supplementary cementitious material, which provides chemical and physical effects on concrete microstructure. When LCA evaluation is conducted, different impact distribution models may be applied to assess the potential impact of the by-productss. Although their benefits are recognized, some studies still report them as burden free, having no allocated impacts . Thereby, the aim of this paper is to evaluate the differences in silica fume life cycle impacts by analyzing three scenarios from cradle to gate, considering the modeling procedures described by ISO 14040, the Cut-off model from Ecoinvent version 3.3 and the impact assessment method CML v.4.4, according to the CEN EN 15804 recommended categories. Results enhance the understanding regarding model selection and demonstrate that the selection of the proper distribution model is key, considering that this may lead to important differences in the results.

Evaluation of the anticorrosive performance of epoxy coatings containing new core/shell pigments

Purpose Core-shell is structured particles having several chemical compositions. The advantage of these particles arise from their specific design, to be used in decreasing costs by using inexpensive material (natural ore or waste material) as carrier for thin shell of active material. This study aims to prepare ferrites/silica core-shell pigments and compare their inhibition efficiency to original ferrites. These pigments have shells of different ferrites that comprise 10-15 per cent of the prepared pigments on silica fume. Silica fume which is the core is a byproduct in the ferro–silicon industry; this core comprises 85-90 per cent of the prepared pigments. Design/methodology/approach The prepared core-shell pigments were characterized using transmission electron microscopy analysis, energy-dispersive X-ray analysis and sequential wavelength dispersive X-ray fluorescence. These pigments were integrated in epoxy-based paint formulations, and the physical, mechanical and corrosion properties of dry films were examined. The corrosion properties were studied by using immersion test in 3.5 per cent NaCl for 28 days. Findings This study showed that these new eco-friendly and inexpensive pigments are similar to ferrites in their inhibition performance, i.e. they exhibited high corrosion prevention. Research limitations/implications Domestic waste materials were reused in paints and only simple modification was used, and then, their effectiveness showed similar performance to that of the original pigments. Originality/value Ferrite and ferrite/silica pigments are environmentally friendly pigments that can replace other hazardous pigments (e.g. chromates) with almost the same quality in their performance; also, they can be used in industries other than paints (e.g. paper, rubber and plastics composites).

Charcoal “Mines” in the Norwegian Woods

This paper presents lab-scale flash carbonization (FC) experiments under elevated pressure using Norwegian wood as a feedstock. The silicon and ferrosilicon industry of Norway has been urged to reduce fossil CO2 emissions by increasing the use of charcoal as a substitute for coal and coke in the production process. Because charcoal is not produced in Norway, large amounts of it are imported from south Asia. Norway now intends to produce charcoal locally using optimum carbonization techniques from local biomass and forestry waste. That is where the pressurized FC experiments come in. Birch, spruce and corresponding forest residues (FRs) were carbonized, enabling the analysis of the impact of pressure and FC canister insulation on their respective fixed carbon yields. FRs proved to be proper to make charcoal, because fixed carbon contents of 80% could be achieved at moderate pressures. The fixed carbon yields of spruce and birch wood reached over 90% of their theoretical values. The high charcoal yields can result in remarkable cost savings for the metallurgical industry while, at the same time, making excessive deforestation unnecessary. The use of coal will soon be abandoned in the ferrosilicon industry, and charcoal “mines” could become an obvious choice.

Investigations on the early hydration properties of synthesized β-belites blended cement pastes

Hydration of blended cement pastes with two types of freshly synthesized β-phase belites (β-C2S and β-Ca2SiO4), which leads to low-hydration cement, is analyzed by using thermal technique, namely isothermal conduction calorimetry. The reaction kinetics at early ages (up to 24 h) are studied for neat and belite blended cement pastes (10–30 % replacement of cement) at 30 °C. The first type of belite is synthesized by using lime sludge (LS), a paper and pulp industry residue and nano-silica (NS) through solid-state reaction, and the second one is prepared by using calcined lime sludge (CLS) and silica fume (SF), a ferrosilicon industry residue through hydrothermal–calcination method. To substantiate the results of heat of hydration, the supporting characterization techniques such as XRD, FTIR, SEM and BET analyses of synthesized belites are carried out. The role of β-C2S in the hydration of cement blends is compared in this study. A significant acceleration of the hydration process is observed in both types of belites blended cement pastes compared to control pastes. It is observed from the characterization studies that the mean inter-atomic distances of neighboring independent Ca atoms in the unit cell of the two types of belites (confirmed through Molecular Dynamics (MD) simulation), specific surface area, pore volumes and morphology of the structures are the cause for the accelerated hydraulic activity. The results show that there is an increase in the heat of hydration for the first type of belite, whereas for the second type, the trend is reversed.

β-Belite cements (β-dicalcium silicate) obtained from calcined lime sludge and silica fume

The utilization of lime sludge (LS), a pulp and paper industry residue, and silica fume (SF), a ferrosilicon industry by-product, as raw materials for the preparation of β-dicalcium silicate (β-C2S or β-belite) is investigated. β-phase belite is synthesized in a molar ratio of calcined LS/SF at 2.0 by hydrothermal method followed by calcination at 1000 °C for 2 h, which is lower temperature than conventional production temperature of about 1200 °C, and importantly without any chemical stabilizers. The produced belite cements containing 89.3% of β-belite, the rest being α-belite (5.93%), tobermorite (C–S–H, 1.71%), cristobolite (SiO2, 1.83%) and free lime (CaO, 1.24%). The micro analytical characteristic of the raw materials and formed belite are examined by means of TG-DTA-DTG, XRF, XRD, SEM with EDAX, FT-IR, BET techniques and isothermal conduction calorimetry. The hydration of pastes and compressive strength of mortars of the formed β-belite blended with ordinary Portland cement are studied with a partial replacement of cement by 10%, 20% and 30%. The reaction of β-belite in combination with Portland cement is comparable up to 10% replacement of cement to the pozzolanic reactions of other materials used in similar ways. However, it is observed that the premature stiffening of belite incorporated cement pastes takes place with low heat of hydration because of higher reactivity of belite cement incorporation.

Employment of new modified ferrite pigments in anticorrosive alkyd-based paints

Purpose – The purpose of this work is to prepare new core-shell pigments based on silca fume waste as core and ferrite pigments in the shell. Silica fume is a byproduct of the smelting process in the ferrosilicon industry. The reduction of high-purity quartz to silicon at temperatures up to 2,000°C produces SiO2 vapours which then oxidize and condense at low-temperature zones to tonnage amounts of tiny particles consisting of non-crystalline silica that is collected and sold rather than being land-filled because nowadays there is increasing environmental concern with regard to excessive volumes of solid waste hazards accumulation. Silica has no direct effect in protecting metals from corrosion, but on precipitating an effective anticorrosive pigment like ferrite on its surface with low concentrations, this can bring out new core-shell pigment with good anticorrosive performance and low cost. The new pigments will be constructed on a waste silica fume core comprising 80-85 per cent of its chemical structure and the ferrite shell that will be only about 20-15 per cent. These pigments are represented as efficient, economically feasible and eco-friendly. Design/methodology/approach – The different ferrites and ferrites/SiO2 pigments were characterized using different analytical and spectro-photometric techniques, such as X-ray diffraction, scanning electron microscopy/energy-dispersive X-ray and transmission electron microscopy (TEM). Evaluation of these pigments was done using international standard testing methods american standard testing methods (ASTM). After evaluation, the pigments were incorporated in solvent-based paint formulations based on medium oil-modified soya-bean-dehydrated castor oil alkyd resin. The physico-mechanical properties of dry films and their corrosion properties using accelerated laboratory test in 3.5 per cent sodium chloride for 28 days were determined. Findings – The results of this work revealed that ferrite/SiO2 core-shell pigments were close in their performance to that of the ferrite pigments in protection of steel, and at the same time, they verified good physico-mechanical properties. Practical implications – As silica fume has a large array of uses, these pigments can be applied in various industries such as painting, wooding coating, anti-corruption coating, powder coating, architectural paint and waterproof paints. Originality/value – Ferrite, ferrite/SiO2 are environmentally friendly pigments which can impart high anticorrosive behaviour to paint films with concomitant cost savings.

Arsenic stabilization in coal fly ash through the employment of waste materials

Coal fly ash can be considered either as an industrial waste material or as a valuable raw material. This is due to the fact that the main problem in recycling this ash is the possible presence of heavy toxic metals and the necessary reliable treatment to avoid their leaching into the environment. In this paper fluidized bed combustion (FBC) fly ash containing leachable arsenic (As) and vanadium (V) is stabilized with a new proposed technology, based on waste or by-product materials.In particular, silica fume, that is a by-product of the smelting process in the silicon and ferrosilicon industry [1], is the main stabilizing agent used in this work. It is employed here, for the first time, for stabilization of arsenic. Also other ash, containing calcium hydroxide, is employed in the stabilization process.The starting fly ashes and stabilized materials have been characterized. The results of leaching tests show that, despite the lower leachability of vanadium in respect to arsenic, the proposed method results effective in the entrapment of both elements. Based on the results of characterization a different stabilization mechanism is proposed for the two elements: vanadium seems to be stabilized by silica; concerning arsenic, it appears that calcium hydroxide acts as stabilizing agent for this element, probably due to formation of more stable phases.

Mechanisms and Kinetics of Liquid Silicon Oxidation During Industrial Refining

During oxidative ladle refining (OLR) of silicon, the metal surface is partly oxidized, resulting in the formation of a condensed silica fume (SiO2). This fugitive emission of silica represents a potential health hazard to the workers in the silicon and ferrosilicon industry. In the current work, industrial measurement campaigns aimed at recording the fume generation during OLR were performed at the Elkem Salten plant in Norway. The measured amounts of silica produced were 2.5–5.1 kg/h, depending on the gas flow rate in the refining process. The rate of silica production correlates with the total flow rate and amount of air in the purge gas, and increases as the flow rate increases. The results of this work suggest that fume generation during OLR primarily results from oxidation of the exposed metal surface, with oxygen transport from the surrounding atmosphere to the metal surface being the limiting factor. Other identified mechanisms of SiO2 formation were splashing of the metal and/or oxidation of SiO gas carried with the refining purge gas.

Utilization of silica fume in concrete: Review of durability properties

With increased environmental awareness and its potential hazardous effects, utilization of industrial byproducts has become an attractive alternative to disposal. Silica fume (SF), which is byproduct of the smelting process in the silicon and ferrosilicon industry. Silica fume is very effective in the design and development of high strength high performance concrete. This paper covers the physical, chemical properties of silica fume, and its reaction mechanism. It deals with the effect of silica fume on the permeability, freezing and thawing resistance, corrosion, sulfate resistance, carbonation, and alkali-aggregate resistance of concrete.

Controversial effects of fumed silica on the curing and thermomechanical properties of epoxy composites

The effect of fumed silica on the curing of a trimethylolpropane epoxy resin was investigated by thermal analy- sis methods like Differential Scanning Calorimetry (DSC), and Dynamic Mechanical Analysis (DMA). The fumed silica used here is a by-product of the silicon and ferrosilicon industry, consisting of micro and nanosized particles. Both the cur- ing reaction and the properties of the obtained composites were affected by the filler content. Different trends were observed for filler contents above and below the 30 wt%. Up to 30 wt%, the behaviour can be explained as a predominantly agglomeration effect. For 30 wt% and higher filler contents, single particles seem to play a more important role.

Microstructure and Characterizations of Portland-Bottom Ash-Silica Fume Cement Pastes

This research investigated the microstructure and characterization of Portland-bottom ash-silica fume cement pastes. Bottom ash, a by – product from coal-fired thermal power plants, was obtained from Mae Moh power plant, Lampang, Thailand. It currently exists as waste approximately 1.5 MT per year and has not been put to use. Unlike its counterpart, fly ash, which is recognized as an alternative material used to replace part of Portland cement. Silica fume, a nanomaterial from ferrosilicon industry, is nanoparticle and highly amorphous. It is highly pozzolanic reaction and could improve properties of Portland-bottom ash cement pastes. Thus, this research investigated the effect of silica fume on microstructure and characterization of Portland-bottom ash-silica fume cement pastes. The ratios of bottom ash used to replace Portland cement were 0, 10, 20 and 30 percent by weight and silica fume was added at 5 and 10 percent by weight. Compressive strength test was then carried out. SEM and TGA were used to study the microstructure of Portland-bottom ash-silica fume cement pastes. The results show that, the compressive strength of Portland-Bottom ash-silica fume cement pastes increased with added silica fume at 5 and 10 percent. SEM micrographs show C-S-H gel and silica fume around the cement particle in Portland-bottom ash-silica fume cement pastes which gives a highly dense and less porous microstructure. TGA graphs show Ca(OH)2 decreased with silica fume content.

Corrosion of Steel in Concrete: Some Fundamental Aspects of Concrete with Added Silica

Abstract Silica, which is a waste product of the ferrosilicon industry, has been used as an additive to concrete. This silica-fume material consists of minute spherical silica particles with pozzol...