Composition and differences between reduced coal and coal used for combustion
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Since I have just entered this industry and didn’t study this field before, I have a rather naive question: The smelting plant where I work uses coal as fuel and reduced coal as a reducing agent. I would like to know what the specific differences are in their compositions!
Coal is not divided into reducing coal and fuel coal; it’s merely the case that different requirements are placed on its quality depending on its intended use. Such as ash content, calorific value, etc.
The answer above is correct; for use in combustion, a high heat generation capacity is definitely required, while for reduction processes, low ash content as well as specific characteristics regarding cinders are necessary
Young lignite. Characteristics of lignite include high moisture content, low density, non-cohesiveness, and varying amounts of humic acid. Its oxygen content is usually around 8+/;>/, it has strong chemical reactivity, poor thermal stability, and breaks down severely when heated. It tends to weather and fragment into small pieces in air, with a low calorific value. Lignite can be used as fuel, as well as a raw material for pressure gasification, hydrocarbon liquefaction, low-temperature carbonization, and the production of activated carbon and lignite wax. Additionally, young lignite is suitable for use as organic fertilizers such as ammonium humate.
II. Long-flame coal. Long-flame coal is the coal with the lowest degree of coalification. It is black in color, has an asphaltine luster, and either has poor cohesiveness or no cohesiveness at all. When heated, it produces a certain amount of gum, and the resulting coke is in the form of fine, long strips with very poor strength and a high rate of pulverization. It is generally used as a raw material for gasification and liquefaction, as well as for domestic fuel.
III. Non-caking coal. Non-caking coal is a type of bituminous coal that results from considerable oxidation of the original materials during the early stages of coal formation. It falls within the range of low to medium degree of coalification. Its characteristics include a high oxygen content and moderate volatiles. When heated, it hardly produces any gum and has no cohesiveness. Non-caking coal can be used as a raw material for gasification, as well as for power and domestic fuel.
IV. Weakly caking coal. Weakly caking coal is a type of bituminous coal with relatively weak cohesiveness, belonging to the range of low to medium degree of coalification. It has moderate volatiles, and during coking, it produces a small amount of gum. Some of it can form coke with moderate strength, while only a portion can form coke in fragmented form. Weakly caking coal is mostly suitable as a raw material for gasification or as a fuel for power generation; it can also be used in appropriate amounts in mixed coal coking.
V. Moderately caking coal. Moderately caking coal is a type of coal with medium degree of coalification and moderate cohesiveness, along with moderate volatiles. Some of this coal can form coke with sufficient strength when coked alone, making it suitable as a raw material for mixed coal coking. The coal with weaker cohesiveness produces coke of poor strength and a high rate of pulverization when coked alone. Moderately caking coal is suitable as a raw material for gasification or as a fuel for power generation; it can also be used in appropriate amounts in mixed coal coking.
VI. Gas coal (%&) Gas coal is a type of bituminous coal with a low degree of coalification. Its main characteristics are high volatiles and moderate cohesiveness. When heated, it produces high levels of volatiles and tar. During coking, the crush resistance and wear resistance of the resulting coke are slightly lower compared to other types of coal used for coking. The coke produced is usually in the form of fine, long strips, is fragile, and has many vertical cracks. In mixed coal coking, adding gas coal can increase the gas yield and the recovery rate of chemical products. In addition to being used in mixed coal coking, gas coal is also a raw material for oil refining, gasification, and liquefaction, as well as a fuel for power generation.
VII. Gas-fertilizer coal. Gas-fertilizer coal is a special type of fertilizer coal with very high volatiles and a thick gum layer; some call it liquid fertilizer coal. When coked alone, it produces large amounts of gases and liquid chemical products. The strength of the resulting coke is higher than that of gas coal but lower than that of fertilizer coal. Gas-fertilizer coal is most suitable for high-temperature carbonization as a raw material for urban gas. It can also be used in mixed coal coking to increase the chemical product output of coking plants.
VIII. Fertilizer coal. Fertilizer coal is a type of bituminous coal with medium degree of coalification, belonging to the category of coal with medium to high volatiles and strong cohesiveness. When heated, it produces large amounts of gum. When coked alone, it produces coke with good fluidity, but it has many horizontal cracks and honeycomb structures. The wear resistance of the coke is somewhat poor, so it is not suitable for coking alone. Fertilizer coal is generally used as a primary raw material in mixed coal coking.
IX. Semi-coking coal. Semi-coking coal is a type of coal with high volatiles and strong cohesiveness. It lies between coking coal, fertilizer coal, and gas coal in terms of coalification degree. When coked alone, it produces coke of good quality. The crush resistance of this coke is similar to that of fertilizer coal, while its wear resistance is slightly lower. When used in single-coal coking, it produces coke with good fluidity and high strength, suitable for use in medium-sized blast furnaces. In mixed coal coking, the amount of semi-coking coal used can vary widely to produce coke with high strength. It is a high-quality base coal for mixed coal coking. (Chapter 1: Basic Composition and Structure of Coal)
X. Coking coal. Coking coal is a type of bituminous coal with medium degree of coalification. When heated, it produces gum with high thermal stability. When coked alone, it produces coke with large size, few cracks, and high wear resistance, making it an excellent raw material for coking.
XI. Thin coal. Thin coal is a type of bituminous coal with a higher degree of coalification. It has moderate cohesiveness and can produce a considerable amount of gum during coking. It can also form coke with large size, few cracks, and good crush resistance when coked alone. However, the fluidity and wear resistance of its coke are relatively poor, so it is better suited for use in mixed coal coking. Adding thin coal to mixed coal coking can increase the coke yield and the size of the coke pieces.
XII. Poor-thin coal. Poor-thin coal is a type of bituminous coal with a certain degree of cohesiveness and a higher degree of coalification. Although its coking ability is slightly inferior to that of typical thin coal, adding it in appropriate proportions to mixed coal coking can still have a similar effect to thin coal. Poor-thin coal can be used as fuel for domestic and industrial purposes.
XIII. Lean coal. Lean coal is a type of bituminous coal with the highest degree of coalification. It has low volatiles. It generally has no cohesiveness or only weak cohesiveness, so it cannot form coke. When burned, it produces a short flame and is resistant to burning. Lean coal is mainly used as fuel for power generation and domestic use.
XIV. Anthracite. Anthracite is the type of coal with the highest degree of coalification. It can be divided into three subcategories: Type “!” represents the oldest anthracite, Type “#” represents typical anthracite, and Type “$” represents young anthracite. Anthracite has volatiles less than “!%” and fixed carbon greater than &!%. It has high hardness and density. Anthracite is mainly used for domestic purposes and as a raw material for producing synthetic ammonia. Some types of young anthracite can also be used for power generation. Anthracite with low ash and sulfur content, and good grindability, is suitable as fuel for blast furnace injection and sintering of iron ore. It can also be used as a raw material for producing carbon materials and activated carbon. Generally, anthracite and bituminous coal are collectively referred to as hard coal.
II. Long-flame coal. Long-flame coal is the coal with the lowest degree of coalification. It is black in color, has an asphaltine luster, and either has poor cohesiveness or no cohesiveness at all. When heated, it produces a certain amount of gum, and the resulting coke is in the form of fine, long strips with very poor strength and a high rate of pulverization. It is generally used as a raw material for gasification and liquefaction, as well as for domestic fuel.
III. Non-caking coal. Non-caking coal is a type of bituminous coal that results from considerable oxidation of the original materials during the early stages of coal formation. It falls within the range of low to medium degree of coalification. Its characteristics include a high oxygen content and moderate volatiles. When heated, it hardly produces any gum and has no cohesiveness. Non-caking coal can be used as a raw material for gasification, as well as for power and domestic fuel.
IV. Weakly caking coal. Weakly caking coal is a type of bituminous coal with relatively weak cohesiveness, belonging to the range of low to medium degree of coalification. It has moderate volatiles, and during coking, it produces a small amount of gum. Some of it can form coke with moderate strength, while only a portion can form coke in fragmented form. Weakly caking coal is mostly suitable as a raw material for gasification or as a fuel for power generation; it can also be used in appropriate amounts in mixed coal coking.
V. Moderately caking coal. Moderately caking coal is a type of coal with medium degree of coalification and moderate cohesiveness, along with moderate volatiles. Some of this coal can form coke with sufficient strength when coked alone, making it suitable as a raw material for mixed coal coking. The coal with weaker cohesiveness produces coke of poor strength and a high rate of pulverization when coked alone. Moderately caking coal is suitable as a raw material for gasification or as a fuel for power generation; it can also be used in appropriate amounts in mixed coal coking.
VI. Gas coal (%&) Gas coal is a type of bituminous coal with a low degree of coalification. Its main characteristics are high volatiles and moderate cohesiveness. When heated, it produces high levels of volatiles and tar. During coking, the crush resistance and wear resistance of the resulting coke are slightly lower compared to other types of coal used for coking. The coke produced is usually in the form of fine, long strips, is fragile, and has many vertical cracks. In mixed coal coking, adding gas coal can increase the gas yield and the recovery rate of chemical products. In addition to being used in mixed coal coking, gas coal is also a raw material for oil refining, gasification, and liquefaction, as well as a fuel for power generation.
VII. Gas-fertilizer coal. Gas-fertilizer coal is a special type of fertilizer coal with very high volatiles and a thick gum layer; some call it liquid fertilizer coal. When coked alone, it produces large amounts of gases and liquid chemical products. The strength of the resulting coke is higher than that of gas coal but lower than that of fertilizer coal. Gas-fertilizer coal is most suitable for high-temperature carbonization as a raw material for urban gas. It can also be used in mixed coal coking to increase the chemical product output of coking plants.
VIII. Fertilizer coal. Fertilizer coal is a type of bituminous coal with medium degree of coalification, belonging to the category of coal with medium to high volatiles and strong cohesiveness. When heated, it produces large amounts of gum. When coked alone, it produces coke with good fluidity, but it has many horizontal cracks and honeycomb structures. The wear resistance of the coke is somewhat poor, so it is not suitable for coking alone. Fertilizer coal is generally used as a primary raw material in mixed coal coking.
IX. Semi-coking coal. Semi-coking coal is a type of coal with high volatiles and strong cohesiveness. It lies between coking coal, fertilizer coal, and gas coal in terms of coalification degree. When coked alone, it produces coke of good quality. The crush resistance of this coke is similar to that of fertilizer coal, while its wear resistance is slightly lower. When used in single-coal coking, it produces coke with good fluidity and high strength, suitable for use in medium-sized blast furnaces. In mixed coal coking, the amount of semi-coking coal used can vary widely to produce coke with high strength. It is a high-quality base coal for mixed coal coking. (Chapter 1: Basic Composition and Structure of Coal)
X. Coking coal. Coking coal is a type of bituminous coal with medium degree of coalification. When heated, it produces gum with high thermal stability. When coked alone, it produces coke with large size, few cracks, and high wear resistance, making it an excellent raw material for coking.
XI. Thin coal. Thin coal is a type of bituminous coal with a higher degree of coalification. It has moderate cohesiveness and can produce a considerable amount of gum during coking. It can also form coke with large size, few cracks, and good crush resistance when coked alone. However, the fluidity and wear resistance of its coke are relatively poor, so it is better suited for use in mixed coal coking. Adding thin coal to mixed coal coking can increase the coke yield and the size of the coke pieces.
XII. Poor-thin coal. Poor-thin coal is a type of bituminous coal with a certain degree of cohesiveness and a higher degree of coalification. Although its coking ability is slightly inferior to that of typical thin coal, adding it in appropriate proportions to mixed coal coking can still have a similar effect to thin coal. Poor-thin coal can be used as fuel for domestic and industrial purposes.
XIII. Lean coal. Lean coal is a type of bituminous coal with the highest degree of coalification. It has low volatiles. It generally has no cohesiveness or only weak cohesiveness, so it cannot form coke. When burned, it produces a short flame and is resistant to burning. Lean coal is mainly used as fuel for power generation and domestic use.
XIV. Anthracite. Anthracite is the type of coal with the highest degree of coalification. It can be divided into three subcategories: Type “!” represents the oldest anthracite, Type “#” represents typical anthracite, and Type “$” represents young anthracite. Anthracite has volatiles less than “!%” and fixed carbon greater than &!%. It has high hardness and density. Anthracite is mainly used for domestic purposes and as a raw material for producing synthetic ammonia. Some types of young anthracite can also be used for power generation. Anthracite with low ash and sulfur content, and good grindability, is suitable as fuel for blast furnace injection and sintering of iron ore. It can also be used as a raw material for producing carbon materials and activated carbon. Generally, anthracite and bituminous coal are collectively referred to as hard coal.
The material used for reduction is generally called feed coal; reduction relies mainly on its carbon content and volatile phenols, with a low sulfur content being preferred. In reduction, C and CO are generally used as reducing agents, and redox reactions occur simultaneously ； Coal used for combustion is generally called fuel coal; it undergoes an oxidative combustion process. Of course, coal with a high calorific value and high volatile content burns more easily.
In the alumina production process using the sintering method, anthracite is added to the raw slurry to convert high-valent sulfur into low-valent sulfur for removal from the process, while bituminous coal is used as fuel for high-temperature sintering during the curing of the clinker.