What is molten slag?
A waste product of smelting; usually a mixture of silicates.
What is slag composed of?
Slag is mainly a mixture of metal oxides and silicon dioxide. Broadly, it can be classified as ferrous (by-products of processing iron and steel), ferroalloy (by-product of ferroalloy production) or non-ferrous/base metals (by-products of recovering non-ferrous materials like copper, nickel, zinc and phosphorus).
What is the raw material of blast furnace slag?
Blast furnace slag is a mixture of various metals, metal oxides, alumina and silica produced from iron ore melting (Marwaha et al., 2018).
Is slag the same as pig iron?
Blast furnace slag is recovered by melting separation from blast furnaces that produce molten pig iron. It consists of non-ferrous components contained in the iron ore together with limestone as an auxiliary materials and ash from coke. Approximately 290 kg of slag is generated for each ton of pig iron.
Is molten slag calcium silicate?
Calcium silicate, also known as slag, is produced when molten iron is made from iron ore, silicon dioxide and calcium carbonate in a blast furnace.
Is slag a cement?
Portland blast furnace cement (simply called slag cement) refers to the hydraulic binding material ground by mixing Portland cement clinker, granular blast furnace slag, and appropriate amount of gypsum, code-named P • S. The mixed amount of granular blast furnace slag in cement is 20% ~ 70% by weight.
How hot is molten slag?
It taps out from the blast furnace as a molten liquid at a temperature of 1400°C–1500°C and occurs either as a crystalline or granulated form depending on the treatment method for the molten liquid slag.
How is slag removed from molten metal?
The slag removal process is carried out by dispersing natural granular perlite on top of the molten metal. The coagulating, encapsulating effect of the perlite allows slag to be easily removed from ladles and furnaces.
What is the chemical name for slag?
The hot air is blasted and FeO is converted in to ferrous silicate FeSiO3 (slag).
What is the chemical composition of boiler slag?
The most abundant elements in the slag were oxygen, aluminum, silica and calcium. The major chemical components included CaO, SiO2, Al2O3, Fe2O3, and MgO. The minerals found in the slag were anorthite, gehlenite, akermanite, diopside, and esseneite.
What is the difference between blast furnace slag and steel slag?
The slag produced at blast furnace during pig iron manufacturing is called blast furnace slag. The slag produced at steel melting shop is known as steel slag.
Is blast furnace slag toxic?
Blast furnace slag may contain small quantities of hazardous heavy metals, usually in the glassy silicate phase. Blast furnace slags pose little immediate hazard. A single short-term exposure to the dry powder is not likely to cause serious harm.
What are the uses of molten slag?
Slag floats on the surface of the molten metal, protecting it from oxidation by the atmosphere and keeping it clean. Slag forms a coarse aggregate used in certain concretes; it is used as a road material and ballast and as a source of available phosphate fertilizer.
What are the two types of slag?
The main types of slags that are generated from the iron and steelmaking industries are classified as follow:(i)blast-furnace slag (ironmaking slag),(ii)steel-furnace slag,(a)basic-oxygen-furnace (BOF) slag,(b)electric-arc-furnace (EAF) slag,(c)ladle slag.
Why is slag called slag?
slag - loose woman or treacherous man - the common association is with slag meaning the dross which separates during the metal ore (typically iron) smelting process. In fact the iron smelting connection is probably more of a reinforcing influence rather than an originating root of the expression.
How do you separate slag from molten iron?
A more effective method is to use a slag cleaner that is positioned above the slag and draws it off by suction. A typical slag cleaner is illustrated in Fig. 1, wherein a slag cleaner 4 with a suction head 5 is positioned slightly above the surface of the slag 3 floating on molten iron 2 in a vessel 1.
Is molten slag more dense than molten iron?
The slag floats on top of the molten iron because the iron is denser and sinks through the liquid slag.
Is slag more dense than molten iron?
So, molten metal should be at bottom and slag floats above. So, slag should have low density as compared to molten metal.
Is slag cheaper than cement?
With cement being the costliest ingredient, substituting fly ash or slag can help maintain a stronger mix at a lower cost. Fly ash and Slag will typically be 18% cheaper than Portland cement.
Is slag stronger than cement?
Concrete made with recycled steel slag is 17 percent stronger than traditional concrete. Disposing of slag is a millennia-old problem, but the "waste material" is highly sought in construction.
Can slag be recycled?
However, re-use in steel production is limited at present, but for many years steelmaking slags have been utilized and recycled in the civil engineering industry as cement, roadbed material, aggregate in concrete and in the stabilization of riverbanks (Motz and Geiseler, 2001).
Is slag toxic to humans?
The slag in this massive pile still contains high levels of lead and arsenic, both of which are harmful to human health. The children who turned the slag pile into a playground are not the only ones at risk.
Is slag safe to touch?
A single, short-term exposure to the dry powder presents little or no hazard. with large amounts of slag can cause moderate eye irritation, redness and burning. Eye exposures require immediate first aid to prevent damage to eye. Skin Contact: Slag may cause dry skin, discomfort, irritation and dermatitis.
How does slag explode?
Vapor explosions are a physical phenomenon in which explosive boiling occurs when heat contained in molten slag is rapidly converted to gas, and although steel mills make efforts to prevent such a phenomenon, one or more vapor explosion accidents cause fatalities and property damage every year [1-3].
Can you extract metal from slag?
By applying mineral processing technologies, such as crushing, grinding, magnetic separation, eddy current separation, flotation and so on, leaching or roasting, it is possible to recover metals such as Fe, Cr, Cu, Al, Pb, Zn, Co, Ni, Nb, Ta, Au, and Ag etc. from the slags.
How is slag repurposed?
Almost all of the slag from the steel industry in those countries is used for the manufacturing of high-quality products for the cement and building materials industries, aggregates for road construction and fertilizers. Only small quantities end up in waste disposal sites or are used for landfilling.
How do you dissolve slag?
Laboratory-scale batch experiments showed that iron and steel slags rapidly dissolve in acetic acid in a few minutes and the exothermic nature of the reaction was verified.
Is steel slag toxic?
Among its various applications, EAF slag is used in a loose or unencapsulated form as ground cover material for residential landscaping. However, the slag generated from the EAF process can contain toxic metals, which can be hazardous to human and environmental health.
Why is slag blue?
Interestingly, it is also the variety (oxidation state) of sulfur in the slag that causes Leland Blues to appear so boldly blue and green. It is very likely that this self-same sulfur is the source of much of the fluorescence we see in this material.
Is slag Organic?
Although variable in specific contents, steel slag is generally comprised of calcium and magnesium oxide and silicate, compounds of iron, manganese and other heavy metals [4]. Some slag contains organic pollutants such as polycyclic aromatic hydrocarbons [6, 7].
Can you burn coal slag?
#2 It burns!
In the past, coal sorting was done manually and the fragments of rock were larger in size. The old slag heaps therefore contain a lot of empty spaces and carbon-rich deposits (up to 30%). These are therefore even more prone to mass combustion.
What is steel mill slag made of?
These impurities consist of carbon as gaseous carbon monoxide, and silicon, manganese, phosphorus and some iron as liquid oxides, which combine with lime and dolime to form the steel slag.
How is coal slag made?
When coal is “fired” at over 2,500 degrees, it melts and produces a by-product called slag. The slag is cooled through a process called vitrification which causes it to solidify and form sharp, angular granules in a variety of sizes.
What is molten slag in blast furnace?
Blast furnace slag is a nonmetallic coproduct produced in the process. It consists primarily of silicates, aluminosilicates, and calcium-alumina-silicates. The molten slag, which absorbs much of the sulfur from the charge, comprises about 20 percent by mass of iron production.
Can slag replace cement?
There are also some studies on the substitutions of cement by ground granulated blast furnace slag (GGBFS) [5,17,18,19,20], even getting up to 80% of the cement removed by this type of slag. Khatib et al. [21] replaced up to 80% of cement by GGBFS making different substitutions.
How is blast furnace slag made?
Slag forms when iron ore is melted and reduced into molten pig iron in blast furnaces. The amount of slag generation is roughly 300 kg per ton of pig iron produced, and the annual production of blast furnace slag (BF slag) in Japan exceeds 24 million t (all units herein are metric).
Is slag a carcinogen?
Carcinogenicity: Slag is not listed as a carcinogen by IARC or NTP; however, slag contains trace amounts of crystalline silica and hexavalent chromium which are classified by IARC and NTP as known human carcinogens.
Why is slag toxic?
Some steel slags contain higher amounts of toxic metals, such as chromium, nickel, manganese, vanadium and molybdenum [51].
Why is slag harmful?
Steel slag has been used widely as an aggregate in road application, but it could pose a contamination risk for the environment due to considerable heavy metals (HMs).
What is molten slag?
A waste product of smelting; usually a mixture of silicates.
Why doesn't molten iron react with air?
The only reason you don't see it bursting into flames is because the surface is rapidly oxidized which inhibits further reaction. If you were to spray molten iron into the air it would burn violently. If you watch video of molten iron being poured you can see it flaring up as the molten metal hits the air and burns.
Why is slag important?
Metallurgical slags play an important role in the extraction and refining of metals. They are formed when a flux material, added to or included in the charge, reacts with unwanted minerals during extraction or smelting, or with the products of the oxidation of unwanted solute elements during refining.
How hot is molten slag?
It taps out from the blast furnace as a molten liquid at a temperature of 1400°C–1500°C and occurs either as a crystalline or granulated form depending on the treatment method for the molten liquid slag.
Is slag heavy?
Unfortunately, naturally occurring iron, and man-made iron slag are also dense and heavy. Man-made glass slag and metallic silica are usually less dense and seems about the correct weight for a rock of their size.
Is slag bad for the environment?
Slags contain traces of heavy metals, but the concentrations of heavy metals might not be enough to pose environmental risks (Gwon et al., 2018); however, it is believed that the long-term application of slag fertilizer in agriculture may accumulate heavy metals/metalloids in soil and may cause health risks.
Is slag good or bad?
But some recent research here at USGS might change slag's poor public image. It turns out that, although slag is most known for being what's left when metals have been removed, slag itself might be good at removing some negative chemicals from the environment.
What is another name for slag?
cinder. ember. ash. piece of burned coal or wood or iron slag.
How is slag removed from molten metal?
The slag removal process is carried out by dispersing natural granular perlite on top of the molten metal. The coagulating, encapsulating effect of the perlite allows slag to be easily removed from ladles and furnaces.
Is slag molten iron?
During the process of smelting iron, ferrous slag is created, but dominated by calcium and silicon compositions. Through this process, ferrous slag can be broken down into blast furnace slag (produced from iron oxides of molten iron), then steel slag (forms when steel scrap and molten iron combined).
What makes slag hard to remove?
Too high a current together with a high welding speed will also cause sidewall undercutting which makes slag removal difficult. It is crucial to remove all slag before depositing the next run. This can be done between runs by grinding, light chipping or wire brushing.
How do you remove slag from molten aluminum?
There are five aluminium slag removal methods, the main principle of five methods includes chemical slagging, density difference, flotation slagging, flux dissolution, mechanical filtration. AdTech degassing unit and filtering units mainly adopt flotation slagging and mechanical filtration principles.
Is slag the same as molten metal?
Liquid slag is lighter than liquid iron, therefore it floats on the iron. Slag is the impurity separated from iron after its purification. Slag is mostly inert minerals consisting of carbon, sand, soil, rocks, metal oxides, etc., and being lighter its easily separated just by tilting a little the liquid iron crucible.
Is molten slag calcium silicate?
Calcium silicate, also known as slag, is produced when molten iron is made from iron ore, silicon dioxide and calcium carbonate in a blast furnace.
What turns iron into steel?
To make steel, the iron needs to be separated from the oxygen and a tiny amount of carbon needs to be added. Both are accomplished by melting the iron ore at a very high temperature (1,700 degrees Celsius or over 3,000 degrees Fahrenheit) in the presence of oxygen (from the air) and a type of coal called coke.
What are the two types of slag?
The main types of slags that are generated from the iron and steelmaking industries are classified as follow:(i)blast-furnace slag (ironmaking slag),(ii)steel-furnace slag,(a)basic-oxygen-furnace (BOF) slag,(b)electric-arc-furnace (EAF) slag,(c)ladle slag.
Why is molten slag above molten iron?
The slag floats on top of the molten iron because the iron is denser and sinks through the liquid slag. The carbon dioxide gas produced is vented out from the top of the furnace.
Is slag better than limestone?
The results indicated that the durability characteristics of steel slag cement concretes were better than those of crushed limestone aggregate concrete.
What are the disadvantages of slag?
The primary disadvantage of using steel slag is that it's not suitable for all applications. For example, while the compressive strength makes it useful in roadbeds, its lack of tensile strength makes it unsuitable for use in structures that need to bear weight or withstand movement (like bridges).
Is slag cheaper than concrete?
And lastly, when you just want to cut down the material costs of concrete. With cement being the costliest ingredient, substituting fly ash or slag can help maintain a stronger mix at a lower cost. Fly ash and Slag will typically be 18% cheaper than Portland cement.
Is slag the same as fly ash?
The content of fly ash is usually controlled between 20% and 30%. Slag powder is a by-product of the ironmaking process, and the entire process is strictly controlled, so its chemical composition remains relatively stable even if the source of raw materials fluctuates.
What is molten slag in blast furnace?
Blast furnace slag is a nonmetallic coproduct produced in the process. It consists primarily of silicates, aluminosilicates, and calcium-alumina-silicates. The molten slag, which absorbs much of the sulfur from the charge, comprises about 20 percent by mass of iron production.
What does slag mean slang?
noun. plural slags. Britannica Dictionary definition of SLAG. [count] British slang, offensive. : a woman who has many sexual partners.
What is a synonym for molten slag?
ashes cinders dross refuse residue scoria.
Why is molten slag above molten iron?
The slag floats on top of the molten iron because the iron is denser and sinks through the liquid slag. The carbon dioxide gas produced is vented out from the top of the furnace.