The density is higher than that of blast furnace slag or many commonly used natural rocks, and this can influence marketing; for some applications, such as use in waterways, the density is an asset. Through the ispatguru.com website I share my knowledge and experience gained through my association with the steel industry for over 54 years. Slag-tap furnace definition is - a blast furnace or pulverized-fuel furnace with a tap opening in the bottom for removal of slag. Monitoring through sound and light emissions from the EAF has also been attempted as a method of foam monitoring. Superficial gas velocity is normally measured in meter per second (m/s) and is the true gas velocity multiplied by the volume fraction of the gas. Normal compositions of steelmaking slags observe an intermediate behaviour. The roof is also made of water-cooled panels and has three circular openings, equally spaced, for insertion of the cylindrical electrodes. The various formulations are reported in Table 2. Critical to maintaining the foaming slag is the monitoring of its condition. It is important to note that iron oxide is the source for the oxygen component required for the combustion of carbon, not gaseous oxygen, and thus some oxidation of the steel bath is needed for slag foaming. Ferrous and non-ferrous smelting processes produce different slags. It also uses twice the fuel. Silicon dioxide reacts with calcium oxide to form calcium silicate (called slag) which is liquid in the furnace. 9.1 Formation of Potassium Slag in Olivine Fluxed Blast Furnace Pellets ... yield the formula (Mg 1.9Fe 0.1)SiO 4. In the interface between slags and liquid metals there is generally a large gradient in interfacial tension. In the slag foaming process, carbon is injected into the slag, reacts with iron oxide in the slag to produce CO gas, which foams the slag. However, it is possible that all of the slag present is required to produce the foam and no dense layer exists. Slags with intermediate iron oxide contents and high basicities near the lime saturation zone have also intermediate FIs and the presence of solid particles of lime solution can assist to stabilize foam formation. Gas causes foam bubbles to form on top of a dense layer of slag. Blast furnace slag is recovered by melting separation from blast furnaces that produce molten pig iron. Currently, arc distortion appears to be the most widely utilized signal in AC furnace operations for monitoring foam condition, as the sensors and programs required are often integrated with the sophisticated electrode regulator. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. sion method with R2 = … If the consistency of the slag is suitable for sustaining foam, the simple injection of carbon into slag causes the slag to foam. Blast Furnace and Process Description:- Iron blast furnace is a vertical shaft, which is used to melt the iron ore and to produce hot metal by heat exchange and chemical reaction.The burden charge consisting of iron oxide, flux and coke and it provides through the throat from the top of the furnace. Thus, the scrap intercepts most of the arc radiation and little passes through to the sidewalls. Through previous calculations and trial and error procedures, it was found that a mass flow rate of graphite equal to 25 kg/min was good enough to produce stable foam. Comparison of the slag viscosity calculated from the formula in this study and the measured viscosity of practical blast furnace slag during the cooling stage (1600 K–1800 K). the ladle furnace is higher spread of incoming sulphur, as shown in Figure 4. Improved Slag Formation in the Blast Furnace by Co-injection of Basic Fluxes, Together with Pulverized Coal, through the Tuyeres Jan-Olov Wikström1, Peter Sikström1, Lena Sundqvist2 and Guangqing Zuo3 1. It also uses twice the fuel. By covering as much of the exposed arc as possible, a foaming slag intercepts this energy, prevents it from reaching the walls, and passes it to the steel bath instead. The concentration of FeO is considered to be lower than in the rest of the slag at the interface between slag and metal, where reactions which form CO occur. The specific surface of the GGBFS is about 4000 cm2/g. For basic slags, the content of FeO is generally considered at optimum level ranging from 15 % to 25 %. Blast Furnace Slag is gained as a derivative in the removal of iron from its ore. Welcome to the ECHA website. Enter your e-mail address and your password. It will take less then a minute, Technological and other processes/equipments associated with steel industry, Management in steel plant along with training and development, Raw materials and other materials used in steel plants, Marketing Concepts and Comparison with Selling Concepts, Bulk Material Storage and Storage Yard Machines, Role of Safety and its Importance in a Steel Organization, Role of Leadership in the Management of Organizations. It also reduces radiation losses, since the slag isolates the light beams. Raw Materials:. Gas injection, however, produces larger bubbles and less stable foam. The foaming of the slag is significantly affected by the gas flow into the furnace, but is also affected by the slag properties, the latter controlled by the viscosity, density and surface tension. Gas generation is indispensable in order to succeed with a foaming slag practice. Slags from these processes are usually strong and rock-like, with the potential for use as aggregates in a variety of applications. The slags that form in electric furnace melting result from complex reactions between silica (adhering sand and dirt from casting returns), oxides from scrap, other oxidation by-products from melting and reactions with refractory linings. For example, an excessive amount of slag may result in increased furnace refractory wear, more slag transfer to the pouring ladle (increased probability of This in turn protects the refractories from wear, which reduces the amount of down-time for maintenance work. The reaction is given by C (injected) + (FeO) = Fe + CO. CO for foaming is also produced by decarburization of the metal given by the reaction C (in metal) + 1/2 O2 = CO. Foamy slag formation can be divided into 3 steps. Figure 5 shows the viscosity variation in a CaO-SiO 2- Comparison of the slag viscosity calculated from the formula in this study and the measured viscosity of prac-tical blast furnace slag during the cooling stage (1 600 K–1 800 K). At the initial moment of the contact of carbon and slag the direct reduction reaction takes place, forming a gas film separating solid carbon and liquid slag phases as it … This enables bubbles to form, since less FeO content results in a lower surface tension, which gives rise to the Marangoni effect. furnace (carbon steel production)_EAFC_HES, Slaf, steelmaking, elec. The FI decreases with increasing bubble size. The slag consists of various oxides, which can be divided into three categories, namely (i) basic oxides (such as CaO, MgO and FeO), acidic oxides (such as SiO2) and amphoteric oxides (such as Al2O3). It is useful to know what is meant by slag foaming. It has also been observed in the steelmaking process that the presence of surface active components promote foaming. The slag generated from a steelmaking cycle is later processed, and the final product after processing is referred to as basic-oxygen-furnace slag (BOF slag). The gas bubble generation reaction, the reduction of FeO in slag by added carbon and carbon dissolved in metal. The thermal benefits of a good foaming slag are due to the shift in the heat transfer path to the bath and away from the sidewalls. Depending upon the particular blast furnace operation, the slag is composed primarily of sulfur and oxides of aluminum, calcium, magnesium, and silicon. google_ad_client = "ca-pub-7057920448327527"; /* 300x250, created 1/18/11 */ google_ad_slot = "4743063532"; google_ad_width = 300; google_ad_height = 250; Slag foaming has become an important and critical practice for the modern electric arc furnace (EAF) since a good foaming slag contributes considerable efficiency and other benefits to the process. in a huge container called a blast furnace. furnace comprises the following major equipment parts as seen in Fig. This website uses cookies to ensure you get the best experience on our websites. Blast furnace slag in granulated form procured from Visakhapatnam Steel Plant, Visakhapatnam, India. It can be viewed as the time for the gas to pass through the slag. The oxides are then reduced in a blast furnace that is 80–100 feet high and about 25 feet in diameter (Figure \(\PageIndex{2}\)) in which the roasted ore, coke, and limestone (impure CaCO 3) are introduced continuously into the top. Thus, the FI can be interpreted as a measure of the time it takes for the process gases to vertically pass through the foam. During the melting process the fluxes combine with non-metallic scrap components and […] The Si and Al in the scrap are oxidized first to form SiO 2 and Al 2O 3 (fluxing oxides). The inferences from the curves are given below. To obtain a suitable viscosity, it is important to have an appropriate basicity of the slag. Slags, steelmaking, elec. satyendra; May 27, 2013; 6 Comments ; alumina, Basicity, magnesia, slag, Slag basicity, Slag drainage, Slag fluidity, viscosity,; High Alumina Slag and Blast Furnace Operation. The slags that form in electric furnace melting result from complex reactions between silica (adhering sand and dirt from casting returns), oxides from scrap, other oxidation by-products from … Foaming slag in steelmaking operations results from the generation of CO bubbles, through the reduction reactions , (i) CO2 + C(s) = 2CO (the Boudouard reaction), (ii) CO + Fe2O3 = CO2 + 2FeO, (iii) CO + FeO = CO2 + Fe, and (iv) C(s) + FeO = CO + Fe. This happens because initially as the FeO content increases, the rate of fist reaction and CO generation increases and, hence, the foaming increases. When the slag in the pouring mold has cooled, there will be a lead button at the bottom of the slag. For gas hold-up, expansion decays rapidly after the gas stops. Slag Pit Furnace 'Celtic Iron Age' October 9, - 2011 Short Shaft Furnace using Bratton's Run rock ore. In order to build up foam in a slag, the viscosity needs to be high enough to constitute a hindrance for the ascent of the bubbles. 1.3 Mineral Reactions in the Pelletising Process The mineral reactions in LKAB’s blast furnace pellets during the pelletising process have been thoroughly investigated by Niiniskorppi (2004). Slag is primarily composed of CaO, SiO 2 , aluminum oxide (Al 2 O 3 ), and magnesium oxide (MgO). Smelting process optimization In the normal slag operating region, changes in the basicity would have Table 2: Formulation of hydraulically bound mixtures Formula 1 Formula 2 Formula 3 Formula 4 CBFS 80 80 80 80 Abstract: The estimated glass content of a vitrified slag is very sensitive to the method employed. Slag forms shard-like particles, that are usually larger than cement grains. Some of top companies that supply Blast Furnace Slag are AfriSam (South Africa), JFE Steel Corporation (Japan) and Tatametaliks (India). References 15 and These reactions are responsible for the CO formation. Team Members: Darrell Markewitz, Marcus Burnham, Neil Peterson, The reason to run this system was a preliminary test towards a possible public demonstration at the 'Earth Air Celtic Festival', Goderich, for early August 2012. This information has not been reviewed or verified by the Agency or any other authority. The "slag balance" now starts to shift and the slag becomes more liquid. Slag is the stony waste material separated from metals during the process of refining of ore. Its chemical formula is CaSiO3. In the slag foaming process, carbon is injected into the slag, reacts with iron oxide (FeO) in the slag to produce carbon monoxide (CO), which foams the slag. and the electric power input can be increase with foamy slag. Fig 1 shows a schematic diagram of chemical reactions for slag foaming in EAF. Table 2 Minerals of Air-cooled Blast Furnace Slag Mineral Formula Akermanite 2CaO-MgO-2SiO 2 Gehlenite 2CaO-Al 20 3-SiO 2 Wollastonite CaO-SiO 2 Dicalcium silicate 2CaO-SiO 2 Merwinite 3CaO-Mgo-2SiO 2 Anorthite CaO-Al 2O 3-2SiO 2 Monticellite CaO-MgO-SiO 2 The chemical composition of blast-furnace slag is a significant factor in the potential Initially, oxygen is injected into the molten metal (step 1). As per a study, the variations in foaming slag quality can account for + /- 0 kWh/t in demand for the electrical energy. There are basically two requirements for foaming namely (i) reactions or processes that generate small gas bubbles, and (ii) suitable slag properties to keep the bubbles as stable foam. 2a. At low iron oxide contents slag basicity influences strongly the foaming stability. 4. Sites of these reactions can be located as (i) at the slag-metal interface, (ii) at the gas-metal interface, (iii) at the carbon slag interface, and (iv) at slag-gas and carbon-gas interfaces. of the EAF slag LD slag has a series of advantages over natural rock in the field of road construction. The iron reduction in this zone is mixed controlled by mass transfer and chemical reaction mechanisms. Among its measurable benefits in concrete are better workability and finishability, higher compressive and flexural strengths, and improved resistance to aggressive chemicals. The FeO is generated in situ as the major oxidation product of the oxygen blow and is hence the major component in the slag (higher than 20 %). A change of viscosity can also be achieved through an alteration of the content of FeO. This occurs at around 20 % to 40 % FeO depending on other conditions. In the EAF steelmaking process, long arc operation occurs in conjunction with a foamy slag practice. Foaming slag can be slowly built up as the scrap melts and the furnace sidewalls and roof become progressively exposed to heat radiating from the arcs, reaching a maximum height during the refining stage of the heat. Carbon consumption takes place through the Boudouard reaction, and thus the rate of CO generation is proportional to the rate of addition of carbon to an EAF slag, once the reaction has reached steady state. blast furnace slag compositions and higher target viscosities, the resulting temperature is likely to yield a multiphase slag, where the solids contribute significantly to the increase in viscosity. However, the Marangoni flow, which helps the removal of CO bubbles from the interface, can be generated without surface active elements. Iron Ore e.g. In addition to this, the foam helps to reduce noise from the EAF, which provides a better working environment. Another advantage with foaming slag is the reduction of power and voltage fluctuations. research, method of production and optimum conditions for foamy slag in 200 tons electric arc furnace were investigated. All these reactions are CO formers giving stirring energy for mass transfer between metal slag, carbon, and gas phases and they can be considered as a necessary condition for slag foaming. Reference substance name: Calcium EC Number: 231-179-5 EC Name: Calcium CAS Number: 7440-70-2 Molecular formula: Ca IUPAC Name: calcium The quality of the slag foaming is an important factor in the EAF steelmaking process since it ensures that the heat from the liquid bath is not lost through the EAF walls. The diagram shows the reaction sites during injection of carbon during steel melting-refining processes in an EAF. Thus, the presence of solid particles contributes to an increase of the apparent viscosity. Create your account. 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