Properties and Uses of Steelmaking Slag...

Properties and Uses of Steelmaking Slag Steelmaking slag is an integral part of the steelmaking process. It is produced during the separation of the liquid steel from impurities in steelmaking furnace and is a non-metallic by-product of steelmaking process. It occurs as a molten liquid melt and is a complex solution of silicates and oxides which solidifies upon cooling. It primarily consists of silicates, alumina silicates, calcium aluminum silicates, iron oxides and crystalline compounds. During steelmaking, slag is produced in the hot metal pretreatment processes (desulphurization, desiliconization, and dephosphorization etc.), in the primary steelmaking processes (basic oxygen furnace, electric arc furnace, and induction furnace), slag formed during the secondary refining processes (this slag is sometimes called ?secondary refining slag? or ?ladle slag?), and slag formed in tundish during continuous casting of steel (also known as tundish slag). The slag generated in the basic oxygen furnace (BOF) and electric arc furnace (EAF) is of basic nature while the slag is of acidic nature in induction furnace because of the use of silica ramming mass as the lining material. Since most of the steel produced in the world is by BOF and EAF processes, hence slag from these processes is discussed in this article. The processing of the steelmaking slag (Fig 1) is normally carried out by (i) solidifying and cooling of the hot liquid slag, (ii) crushing and magnetic separation treatment of the slag to recover the scrap, (iii) crushing and classification of the slag for grain size adjustment to manufacture the slag product, and (iv) aging treatment of the slag product for improving its quality and volumetric stability. These processes are explained below.   Fig 1 Processing of steelmaking slag As steelmaking slag is formed, it is in a molten or red-hot state at...

Energiron Direct Reduction Technology Sep08

Energiron Direct Reduction Technology...

Energiron Direct Reduction Technology Energiron direct reduction technology is a gas based direct reduction technology. Energiron process converts iron ore pellets or lumps into metallic iron. It uses the HYL direct reduction technology developed jointly by Tenova and Danieli and is a competitive and environmentally clean solution for lowering the liquid steel production cost. It uses a simple plant configuration, has flexibility for using different sources of reducing gases and has a very efficient and flexible use of iron ores. A key factor in many of the process advantages is directly related to its pressurized operation. Energiron is the name of the direct reduced iron (DRI) product produced by the Energiron direct reduction technology. The product is so named since it carries substantial energy with it which is realized during the steel making process. Energiron is a highly metallized product with the carbon (C) content which is controllable in the range of 1.5 % to 5.0 %. The higher C content of Energiron generates chemical energy in the electric arc furnace (EAF) melting process. The uniquely stable characteristic of Energiron DRI makes it a product which can be safely and easily transported without briquetting, following standard IMO (International Maritime Organization) guidelines. The process is flexible to produce three different product forms, depending on the specific requirements of each user. The three forms of Energiron DRI are cold DRI, HBI (hot briquetted iron) or hot DRI (‘Hytemp’ iron with discharge temperature greater than 700 deg C). Cold DRI discharge is normally used in an adjacent steel melt shop close to the direct reduction plant. It can also be shipped and exported. HBI is the DRI which is discharged hot, briquetted, and then cooled. It is a merchant product usually meant for overseas export. Hytemp Energiron...

Development of the Technology of Electric Arc Furnace Steelmaking May05

Development of the Technology of Electric Arc Furnace Steelmaking...

Development of the Technology of Electric Arc Furnace Steelmaking  Development of the steelmaking technology takes place for meeting of a number of requirements. These requirements can be classified into four groups as given below. The technology has to meet the process requirements needed for producing different steel grades of required qualities. The technology is to meet the economic requirements needed for controlling the cost of production so that produced steel products are competitive. The technology is to meet the emission levels set by the regulatory agencies. The technology is to meet the health and safety requirements so that operators work in the area without any dangers, stress and stains. To understand electric arc furnace (EAF), it is necessary to understand what an electric arc is. An electric arc is a form of electrical discharge between two electrodes, separated by a small gap (typically, normal air). The best known example of this is lightning. Anyone who has performed arc welding is also familiar with electric arcs. If one connects the work piece to the negative side of a DC power source and an electrode to the positive side, touch the electrode momentarily and draw it a small distant apart from the work piece, then a stable electric arc forms between the electrodes and the work piece  and the heat from this arc is sufficient to melt the electrode and weld the work pieces together. The same idea is used in a larger scale in an electric arc furnace. The history of electric arc furnace (EAF) steelmaking is not very old. It is only slightly more than a century when the first furnace was commissioned to melt steel by utilizing electric power. The initial development of the technology took place, since these units made it possible...

Understanding Electric Arc Furnace Steel Making Operations Feb18

Understanding Electric Arc Furnace Steel Making Operations...

Understanding Electric Arc Furnace Steel Making Operations  Electric arc furnace (EAF) steel making technology is more than hundred years old. Though De Laval had patented an electric furnace for the melting and refining of iron in 1892 and Heroult had demonstrated electric arc melting of ferro alloys between 1888 and 1892, the first industrial EAF  for steel making only came into operation in 1900. Development was rapid and there was a tenfold increase in production from 1910 to 1920, with over 500,000 tons being produced in 1920, though this represented still only a very small percentage of the global production of steel  of that time. Initially, EAF steelmaking was developed for producing special grades of steels using solid forms of feed such as scrap and ferro alloys. Solid material were firstly melted through direct arc melting, refined through the addition of the appropriate fluxes and tapped for further processing. Fig 1 shows a typical plan and section view of an EAF Fig 1 Typical plan and section view of an EAF  Electric arc furnaces range in capacity from a few tons to as many as 400 tons, and a steel melting shop can have a single furnace or up to three or four. In brief, these furnaces melt steel by applying an AC current to a steel scrap charge by mean of graphite electrodes. It requires a tremendous quantity of electricity. The melting process involves the use of large quantities of energy in a short time and in some instances the process has caused disturbances in power grids. These disturbances have usually been characterized as ‘flicker’ (brief irregularities in voltage a fraction of the 50 -60 Hz cycle in length), and ‘harmonics’ (irregularities that tend to occur in a pattern repetitive to the 50-60 Hz...

Submerged Arc Furnaces Jul15

Submerged Arc Furnaces...

Submerged Arc Furnaces  industrial utilization of electrical energy started with the development of the dynamo machine by Werner von Siemens. Electric arc furnaces have been used for many years both for the melting of scrap iron (open arc furnaces) and for reduction processes (submerged arc furnaces). In case of the submerged arc furnace (SAF), ore and reducing agent are fed to the furnace continuously from the top so that the electrodes are buried in the mix and the arc is submerged. The furnace is named submerged-arc furnace since the arc is submerged. The most common physical arrangement consists of a circular bath with three vertical electrodes arranged in a triangle. Six electrode furnaces with circular or rectangular baths are also used but they are less common. Submerged arc furnaces have found their application in more than 20 different main industrial areas such as ferro alloy, chemical industry, lead, zinc, copper, refractory, titanium oxide, recycling, phosphorus etc. A typical schematic diagram of a submerged arc furnace for ferro chrome production along with material balance is given at Fig.1 Fig 1 Typical schematic diagram of a submerged arc furnace for ferro chrome production along with material balance.  History  The increasing demand for ferro alloys and deoxidation agents in steel making in the beginning of the twentieth century led to the development of the first submerged arc furnace. The construction of the first SAF was started in 1905. This 1.5 MVA unit was installed in Horst Ruhr, Essen, Germany for the production of calcium carbide. It was successfully commissioned in 1906 and was based on DC (direct current) technology. Since then a large number of SAFs (both with DC and AC based furnaces) have been commissioned with diverse applications. Today, the majority of submerged arc furnaces are...