Coal and Steel
Steel is an essential material for modern life. The manufacture of steels delivers the goods and services that our societies need - healthcare, telecommunications, improved agricultural practices, better transport networks, clean water and access to reliable and affordable anergy.
Raw Material
The supply of raw materials is a key issue for the world steel industry. It projects that examine the avaibility of raw materials, such as iron ore, coking coal, freight and scrap. Iron ore and coking coal are used mainly in the blast furnace process of ironmaking. For this process, coking coal is turned into coke, an almost pure form of carbon, which is used as the main fuel and reductant in a blast furnace.
Typically, it takes 1.5 tonnes of iron ore and arround 450 kg of coke to produce a tonne of pig iron, the raw iron that comes out of blast furnace. Some of coke can be replaced by injecting pulverized coal into blast furnace.
Coking Coal Characteristic
Coking coal has its own characteristic, such as cokeability. The cokeability of coal is determined from demonstrable plasticity within a certain temperature interval, during which its structure and chemical composition change (while releasing some of the coal constituents). The end of product of these changes is a fuel with a whole new quality - coke. The cokeability is the given degree of coalification and the petrographic composition of the coal.
Degree of coalification - this quality is usually expressed as the content of volatile matter, or as the light reflecttivity of the vitrinite content ( a hard coal constituent visible under microscope). The greater the volatile matter content, the lower the degree of coalification. In this case of vitrinite light reflectivity, the lower the reflectivity, the lower the degree of coalification.
Petrographic composition is detemined by the given composition and qualities of the original plant material and by the conditions that influenced the formation of the coal stratum and the process of its coalification.
The above properties determine whether a coal is suitable for coking or for use in the energy sector.
Steel Produced (by Coking Coal)
Steel is an alloy based primarily on iron. As iron occurs only as iron oxides in the erath's crust, the ores must be converted, or "reduced", using carbon. The primary source of this carbon is coking coal.
Coking coal is converted to coke by driving off impurities to leave almost pure carbon. The physical properties of coking coal cause the coal to soften, liquefy and then resolidify into hard but porous lupms when heated in the absence of air. Coking coal must also have low sulphur and phosporous contents. Almost all metallurgical coal is used in coke ovens.
The coking process consists of heating coking coal to around 1000 - 1100 degree C in the absence of oxygen to drive off the voalite matter compounds (pyrolysis). This process results in a hard porous material - coke. Coke is produced in a coke battery which is composed of many coke ovens stacked in rows into which coal is loaded.
The coking process takes place over long periods of time between 12-36 hours in the coke ovens. Once pushed out of the vessel the hot cokes is then qunched with either water or air to cool it before storage or is transferred directly to the blast furnace for use in iron making.
During the iron-making process, a blast furnace is fed with the iron ore, coke and small quantities od fluxes (minerals, such as limestone, which are used to collect impurities). Air which is heated to about 1200 degree C is blown into furnace through nozzles in the lower section. This air causes the coke to burn, producing carbon monoxide which reacts with the iron ore, as well as heat to melt the iron. Finally, the tap hole at the bottom of the furnace is opened and molten iron and slag (impurities) are drained off.
There are 2 methods are commonly used to produce steel, Basic Oxygen Furnaces and Electric Arc Furnaces. Basic oxygen furnaces currently produce about 70% of the world's steel. A further 29% of steel is produced in Electric arc furnaces.
Basic oxygen furnaces use arround 0.6 tonnes (600 kg) of coke produce 1 tonne of steel, which means that around 770 kg of coal are used to produce 1 tonne of steel through this methods. Electric arc furnaces do not use coal as raw material, but many are reliant on the electricity generated by coal-fired power plant elsewhere in the grid. Around 150 kg of coal are used to produce 1 tonne of steel in electric arc furnaces.
Pulverised Coal Injection (PCI) technology involves injecting coal directly into blast furnace to provide the carbon for iron-making - displacing some of the coke required for the process. A wider range of coals can be used in PCI, including steam coal which has a lower content than coking coal. this method has a number advantages, including reducing overall costs and prolonging the life of existing coke batteries.
Source : www.worldcoal.org and www.worldsteel.org
Related article : Coking Coal Introduction
Coking Coal Characteristic
Coking coal has its own characteristic, such as cokeability. The cokeability of coal is determined from demonstrable plasticity within a certain temperature interval, during which its structure and chemical composition change (while releasing some of the coal constituents). The end of product of these changes is a fuel with a whole new quality - coke. The cokeability is the given degree of coalification and the petrographic composition of the coal.
Degree of coalification - this quality is usually expressed as the content of volatile matter, or as the light reflecttivity of the vitrinite content ( a hard coal constituent visible under microscope). The greater the volatile matter content, the lower the degree of coalification. In this case of vitrinite light reflectivity, the lower the reflectivity, the lower the degree of coalification.
Petrographic composition is detemined by the given composition and qualities of the original plant material and by the conditions that influenced the formation of the coal stratum and the process of its coalification.
The above properties determine whether a coal is suitable for coking or for use in the energy sector.
Steel Produced (by Coking Coal)
Steel is an alloy based primarily on iron. As iron occurs only as iron oxides in the erath's crust, the ores must be converted, or "reduced", using carbon. The primary source of this carbon is coking coal.
Coking coal is converted to coke by driving off impurities to leave almost pure carbon. The physical properties of coking coal cause the coal to soften, liquefy and then resolidify into hard but porous lupms when heated in the absence of air. Coking coal must also have low sulphur and phosporous contents. Almost all metallurgical coal is used in coke ovens.
The coking process consists of heating coking coal to around 1000 - 1100 degree C in the absence of oxygen to drive off the voalite matter compounds (pyrolysis). This process results in a hard porous material - coke. Coke is produced in a coke battery which is composed of many coke ovens stacked in rows into which coal is loaded.
The coking process takes place over long periods of time between 12-36 hours in the coke ovens. Once pushed out of the vessel the hot cokes is then qunched with either water or air to cool it before storage or is transferred directly to the blast furnace for use in iron making.
During the iron-making process, a blast furnace is fed with the iron ore, coke and small quantities od fluxes (minerals, such as limestone, which are used to collect impurities). Air which is heated to about 1200 degree C is blown into furnace through nozzles in the lower section. This air causes the coke to burn, producing carbon monoxide which reacts with the iron ore, as well as heat to melt the iron. Finally, the tap hole at the bottom of the furnace is opened and molten iron and slag (impurities) are drained off.
There are 2 methods are commonly used to produce steel, Basic Oxygen Furnaces and Electric Arc Furnaces. Basic oxygen furnaces currently produce about 70% of the world's steel. A further 29% of steel is produced in Electric arc furnaces.
Basic oxygen furnaces use arround 0.6 tonnes (600 kg) of coke produce 1 tonne of steel, which means that around 770 kg of coal are used to produce 1 tonne of steel through this methods. Electric arc furnaces do not use coal as raw material, but many are reliant on the electricity generated by coal-fired power plant elsewhere in the grid. Around 150 kg of coal are used to produce 1 tonne of steel in electric arc furnaces.
Pulverised Coal Injection (PCI) technology involves injecting coal directly into blast furnace to provide the carbon for iron-making - displacing some of the coke required for the process. A wider range of coals can be used in PCI, including steam coal which has a lower content than coking coal. this method has a number advantages, including reducing overall costs and prolonging the life of existing coke batteries.
Source : www.worldcoal.org and www.worldsteel.org
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