Anthracite Coal

Anthracite Coal Anthracite coal derives its name from the Greek word ‘anthrakít?s’, literally meaning ‘coal-like’.  It is frequently being referred as hard coal and is one of the four types of coals. Other types of coals are lignite coal, sub- bituminous coal and bituminous coal. Since anthracite coal had been subjected to the intense pressure and heat, it is the most compressed and hardest coal available. Being a hard coal, it contains greater potential to produce heat energy than softer, geologically ‘newer’ coal. As per ISO 11760:2005, anthracite coal is defined as the coal, synonymous with high-rank coal, having a mean random vitrinite reflectance, equal to or greater than 2.0 % but less than 6.0 %, or, preferably, a mean maximum reflectance, , less than 8.0 % for geologically unaltered coal. Geology and mining of anthracite coal Anthracite coal was formed from bituminous coal when great pressures had developed in the folded rock. Transformation of the bituminous coal into anthracite is called ‘Anthracitization’. It was formed during the Carboniferous Age, when the dense green vegetation that thrived during the tropical climate of the time fossilized. It is the oldest and cleanest type of coal. It is the rarest and most mature coal. It is a hard, compact variety of coal. It has the highest ranking amongst all the four types of coals. It has undergone the most metamorphosis. It has the highest fixed carbon content and the least impurities. It has the highest energy density amongst all types of coal. The formation of anthracite coal is shown in Fig 1. Fig 1 Formation of anthracite coal Anthracite coal normally occurs in old geological formations which have spent the longest time underground. It is the rarest and most mature coal which accounts for only around 1 % of the world’s total coal reserves. The major reserves of the anthracite coal are...

Lignite Coal

Lignite Coal Lignite coal is a natural resource which is readily available. It is often referred to as brown coal. It has some special characteristics which make it different from other coals. Lignite coal is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It is considered to be the lowest rank of coal due to its relatively low heat content. It has lowest carbon (C) content amongst all types of coals. It is mined all around the world and is mainly used as a fuel for steam and electric power generation. Since it is not economical to transport lignite coal, it is not traded extensively on the world market when compared with higher grades of coal. Large reserves of lignite coal are available in limited areas of the world. Australia, USA and China have the major reserves of lignite coal. Germany has the largest number of power plants based on the lignite coal. In USA, most of the reserves are located in the North Dakota province while in India, the lignite coal reserves are in Neyveli in Tamil Nadu and in Rajasthan. Around 17 % of the world’s coal reserves are lignite coal. As the world’s oil and gas reserves decline, other sources have become attractive. That is why there is a sustained interest in the use of lignite coal. Coals are classified by rank according to their progressive alteration in the natural metamorphosis from lignite to sub bituminous coal to bituminous coal and to anthracite. Coal rank depends on the volatile matter, fixed carbon, inherent moisture, and oxygen, although no one parameter defines rank. Typically coal rank increases as the amount of fixed carbon increases and the amount of volatile matter decreases. Coal is a complex combination of organic matter and inorganic ash formed over eons from successive layers of fallen vegetation....

Production of Ferro-Silicon Jun27

Production of Ferro-Silicon...

Production of Ferro-Silicon Ferro-silicon (Fe-Si) is a ferro-alloy having iron (Fe) and silicon (Si) as its main elements. The ferro-alloy normally contains Si in the range of 15 % to 90 %. The usual Si contents in the Fe-Si available in the market are 15 %, 45 %, 65 %, 75 %, and 90 %. The remainder is Fe, with around 2 % of other elements like aluminum (Al) and calcium (Ca). Fe-Si is produced industrially by carbo-thermic reduction of silicon dioxide (SiO2) with carbon (C) in the presence of iron ore, scrap iron, mill scale, or other source of iron. The smelting of Fe-Si is a continuous process carried out in the electric submerged arc furnace (SAF) with the self-baking electrodes. Fe-Si (typical qualities 65%, 75% and 90% silicon) is mainly used during steelmaking and in foundries for the production of C steels, stainless steels as a deoxidizing agent and for the alloying of steel and cast iron. It is also used for the production of silicon steel also called electrical steel. During the production of cast iron, Fe-Si is also used for inoculation of the iron to accelerate graphitization. In arc welding Fe-Si can be found in some electrode coatings. The ideal reduction reaction during the production of Fe-Si silicon is SiO2+2C=Si+2CO. However the real reaction is quite complex due to the different temperature zones inside the SAF. The gas in the hottest zone has a high content of silicon mono oxide (SiO) which is required to be recovered in the outer charge layers if the recovery of Si is to be high. The recovery reactions occur in the outer charge layers where they heat the charge to a very high temperature. The outlet gas form the furnace contains SiO2 which can...

Production of Silico-Manganese in a Submerged Arc Furnace Jun09

Production of Silico-Manganese in a Submerged Arc Furnace...

Production of Silico-Manganese in a Submerged Arc Furnace Silico-manganese (Si-Mn) is an alloy used for adding both silicon (Si) and manganese (Mn) to liquid steel during steelmaking at low carbon (C) content. A standard Si-Mn alloy contains 65 % to 70 % Mn, 15 % to 20 % Si and 1.5 % to 2 % C. Si-Mn alloy grades are medium carbon (MC) and low carbon (LC). The steelmaking industry is the only consumer of this alloy. Use of Si-Mn during steelmaking in place of a mix of high carbon ferro-manganese (Fe-Mn) alloy and ferro-silicon (Fe-Si) alloy is driven by economic considerations. Both Mn and Si are crucial constituents in steelmaking. They are used as deoxidizers, desulphurizers and alloying elements. Si is the primary deoxidizer. Mn is a milder deoxidizer than Si but enhances the effectiveness due to the formation of stable manganese silicates and aluminates. It also serves as desulphurizer. Manganese is used as an alloying element in almost all types of steel. Of particular interest is its modifying effect on the iron-carbon (Fe-C) system by increasing the hardenability of the steel. Si-Mn is produced by carbo-thermic reduction of oxidic raw materials in a three-phase, alternating current (AC), submerged arc furnace (SAF) which is also being used for the production of Fe-Mn. Operation of the process for the Si-Mn production is often more difficult than the Fe-Mn production process since higher process temperature is needed. The common sizes of the SAF used for the production of Si-Mn are normally in the range 9 MVA to 40 MVA producing 45 tons to 220 tons of Si-Mn per day. In the carbo-thermic reduction of oxidic raw materials, heat is just as essential for reduction as C is, due to the endothermic reduction reactions and a...

Tecnored Process for Ironmaking Apr30

Tecnored Process for Ironmaking...

Tecnored Process for Ironmaking Tecnored process was developed by ‘Tecnored Desenvolvimento Tecnológico S.A.’ of Brazil and is based upon a low pressure moving bed reduction furnace which reduces cold bonded, carbon bearing, self-fluxing, and self-reducing pellets. Reduction is carried out in a short height shaft furnace of distinct design at typical reduction temperatures. The process produces hot metal (liquid iron). Tecnored technology has been conceived and developed to be a ‘coke-less’ ironmaking process, thus avoiding the investment and operation of environmentally harmful  coke ovens besides significantly reducing green-house gas emissions in the production of hot metal. Tecnored process uses a combination of hot and cold blast and requires no additional oxygen. It eliminates the need for coke plants, sinter plants, and tonnage oxygen plants. Hence, the process has much lower operating and investment costs than those of traditional ironmaking routes. Tecnored process is flexible with regard to the type of iron bearing and carbon bearing raw materials which it can process. The ability of the process to smelt either pellets or briquettes, or even mixed charges of both, provides means of using a wide range of alternative feed materials. The process has got good productivity and high energy efficiency. Tecnored process is also being claimed to be suitable for producing ferro alloys such as ferro manganese. History of development The history of the development of the Tecnored process comprises different phases with different goals, testing a wide range of raw materials and using distinct sizes and concepts of the reactor. During the period 1979 to 1985, development activities were carried out regarding the use of pyrite cinder containing self-reducing pellets as metallic burden in cupola furnaces. This concept of self-reduction was adapted to develop the new process.  In 1985 the concept of the Tecnored...