Sinter Quality and Process of Sintering Iron Ores Nov21

Sinter Quality and Process of Sintering Iron Ores...

Sinter Quality and Process of Sintering Iron Ores Sinter is normally the major component of the blast furnace (BF) charge burden. Sinter consists of many mineral phases produced during process of sintering of iron ores. The quality and properties of sinter are dependent on the mineral structure of sinter. However, since the sintering conditions are usually not uniform throughout the sinter bed, the phase composition, and therefore the sinter quality, varies in the sinter bed. The structure of sinter is not uniform. It consists of pores (of varying sizes) and a complex aggregate of mineral phases, each with different properties. It is the combination of these pores and mineral phases, and the interaction between them that determines the sinter quality, but also makes the prediction of sinter properties very difficult. Though a large number of investigations have been carried out on sinter, still the correlation between the chemical composition and mineralogy of sinter with its properties and behaviour is still not clearly understood. Schematics of sinter mix and the product sinter are at Fig 1. Fig 1 Schematics of sinter mix and product sinter  Sintering process is a generic term that is used to describe the process of agglomeration of a green mix of iron ores, fluxes and coke and plant solid wastes having a particle size of -10 mm so as to produce sinter  which can withstand operating pressure and temperature conditions existing in a BF. Solid wastes such as dusts, sludges, slags and mill scales etc. are used for their utilization in sinter mix because of the complex chemical structure and mineral components of these materials. The process of sintering is described in detail in a separate article which is available under the link http://ispatguru.com/the-sintering-process-of-iron-ore-fines-2/ During the process of sintering, as the...

Titanium in Steels

Titanium in Steels  Titanium (Ti) (atomic number 22 and atomic weight 47.90) has density of 4.52 gm/cc. Melting point of Ti is 1660 deg C and boiling point is 3287 deg C. Ti is a highly active element. It usually forms a stable oxide coating at room temperature on its surface, which limits further oxidation. The phase diagram of the Fe (iron)-Ti binary system is at Fig 1. Fig 1 Fe-Ti phase diagram Ti forms stable compounds with oxygen (O), carbon (C), nitrogen (N) and sulfur (S) at temperatures of steelmaking. It is sometimes used in steelmaking because of its property for fixing of these elements in order to reduce their harmful effects. Ti is also used for the purpose of grain refining in many steels. In many respects, functions of Ti are similar to the addition of both aluminum (Al) and niobium (Nb). Ti is more expensive than Al; hence it is rarely used as a deoxidizer.  The reactivity of Ti is similar to that of magnesium (Mg) and it can quite easily be set on fire. It burns with a bright white flame, which can be harmful to look at. Ferrotitanium powder is also flammable, with the powder having finer size and higher Ti content being more hazardous. Ti ores are mainly ilmenite (FeO.TiO2) and rutile (TiO2).  Addition agents Ti containing addition agents are Ti metal scrap, ferroalloys and master alloys. Ti metal scrap may be of commercial purity Ti. Ti metal scrap is of two types one with 6 % Al and 4 % vanadium (V) while the second with 6 % Al, 2 % tin (Sn), 4 % zirconium (Zr), and 2 % molybdenum (Mo). Sn is usually an unwanted element in steels. Since the melting point of Ti is...

Forward and Backward Integrations...

Forward and Backward Integrations Forward and backward integrations are two integration strategies which are adopted by organizations to gain competitive advantages in the market and to gain control over the value chain of the industry under which they are operating. These strategies are one of the major considerations when developing future plans for an organization. Together these two strategies are known as vertical integration.  The process of backward and forward integrations is shown in Fig 1 Fig 1 Process of backward and forward integration Vertical integration is the degree to which the organization owns its upstream suppliers and its downstream buyers for further product processing. Contrary to the horizontal integration, which is a consolidation of many organizations that handle the same part of the production process, vertical integration is typified by one organization engaged in different parts of production (e.g. production of raw materials, manufacturing, transporting, marketing, and/or downstream processing of end products. Vertical integration describes when an organization purchases or starts a company that it either buys from or sells to and integrates this new business into its own. In case of forward integration the organization integrates its businesses toward the end customer while in case of backward integration the organization integrates its activities in the direction away from the customer. Backward integration can be a part of the organizational strategy due to the competitive benefits it provides. Organizations which governs the entire value chain are, however, very rare. Some organizations choose to adopt for forward integration while other organizations opt for backward integration. Also some other organizations continue to operate disintegrated depending on the environment under which these organizations are operating and also depending upon the future strategic planning which these organizations have done for their future operations. Forward integration extends organizational...

Carbonization of Coal for Metallurgical Coke Production Nov15

Carbonization of Coal for Metallurgical Coke Production...

Carbonization of Coal for Metallurgical Coke Production Carbonization of coal is also known as coking of coal. The process consists of thermal decomposition of coals either in the absence of air or in controlled atmosphere to produce a carbonaceous residue known as coke. Carbonization of coal can be carried out at the following three temperature ranges. Low temperature carbonization is normally carried out in the temperature range of 500 deg C to 700 deg C. In this type of carbonization, the yields of liquid products are higher and there is lower gaseous product yield. The coke produced is having higher volatile matter and is free burning. Medium temperature carbonization is done at temperature range of around 800 deg C. This carbonization produces smokeless soft coke. By products produced are similar in characteristics to high temperature carbonization. Medium temperature carbonization is rarely practiced these days. High temperature carbonization is carried out at a temperature which is above 900 deg C. This carbonization gives higher yield of gaseous products and lower yield of liquid products. This carbonization produces hard coke and is normally employed for the production of metallurgical coke from coking coals. Process of carbonization of coal The coal to coke transformation takes place as the coal is heated. When the state of fusing is reached, the layer of heated coal softens and fuses. From about 375 deg C to 475 deg C, the coal decomposes to form plastic layer.  Destructive distillation reactions proceed rapidly in the plastic layer with evolution of volatile products. At about 475 deg C to 600 deg C, there is a marked evolution of tar, and aromatic hydrocarbon compounds. The gas and condensable vapour are entrapped in the plastic mass and, as they expand tend to swell it. As the...

Niobium in Steels

Niobium in Steels  Niobium (Nb) (atomic number 41 and atomic weight 92.91) has density of 8.57 gm/cc. The element is also known as Columbium (Cb). Melting point of Nb is 2467 deg C and boiling point is 4740 deg C. Cb was discovered in 1801 by Charles Hatchett, who named the element to signify the American origin. This name was used in USA while Europe used the name niobium for the same element. To end this confusion, the name niobium was chosen for element 41 at the 15th Conference of the Union of Chemistry in Amsterdam in 1949. A year later this name was officially adopted by the International Union of Pure and Applied Chemistry (IUPAC) after 100 years of controversy, despite the chronological precedence of the name Columbium. Columbium name is still used in many places in USA. The phase diagram of the Fe-Nb binary system is at Fig 1. Fig 1 Fe-Nb phase diagram  The use of Nb dates back to 1925 when it was used to replace tungsten (W) in tool steel production. By the 1930s, Nb was being used to prevent corrosion in stainless steels. The ability of Nb to maintain fine grain sizes in steels at higher temperatures has been known since 1940s and steels that take advantage of this effect have been commercially produced for many years. In recent years, however, Nb is being known more as one of the most important element for the micro alloying. Nb plays an important role in HSLA (high strength low alloy) steels. Nb also has important applications in tool steels, wear and abrasion resistant steels, steels for high temperature service, stainless steels and super alloys. Many of these uses depend on the strong affinity of Nb for carbon (C) and/or nitrogen (N). Addition agents...