【Prized Discussion】Discussion on coal quality and coal blending issues

Both types of coal have high volatilities and high X values, indicating gasier coal properties; therefore, when using them, it is appropriate to add some lean coal or poor-quality coal to prevent the coke particles from becoming too small

1. Based on the volatile matter content and the G value of cohesion, it indeed belongs to category 1/3 coking coal; due to its high volatile matter content and cohesion, an appropriate amount of lean coal, weakly cohesive coal, or poor-quality coal with lower cohesion can be added. Given that the maximum thickness y value of its gel layer is moderate, coal types with slightly poor adhesiveness should not be used in large proportions. 2. Based on the volatile matter content and the bonding index G value, it should be classified as bituminous coal; when blending coal, the proportion of coking coal and lean coal can be increased appropriately.

The volatiles content of the first type of coal is higher than that of 1/3 coking coal; if it is to be used as a coking coal substitute for 1/3 coking coal, an appropriate increase in the proportion of lean coal should be made. For the second type of coal, since its G value is relatively low, if it is to be used as a substitute for 1/3 coking coal, bituminous coal needs to be added ； If the volatiles content is high when used as coking coal, the proportion of lean coal should be increased appropriately.

The first type of coal should be 1/3 coking coal with a relatively low degree of metamorphism; if it is used to replace traditional 1/3 coking coal, an appropriate amount of lean coal should be added, in a ratio with 1/2 medium-viscosity coal. The second type of coal should be bituminous coal, as its G value is relatively low; if it is to be used as a substitute for 1/3 of the coking coal, bituminous coal or an increased proportion of coking coal needs to be added. However, since it may be combined with relatively rich coal, the particle size might be small; therefore, it is necessary to add an appropriate amount of leaner coal, in a ratio of 1/2 with medium-cohesion coal.

I agree with what was said on the 3rd floor. If it is bituminous coal, its cohesion is lower during coking, and it contracts more significantly; therefore, it is necessary to add substances with strong cohesion that can resist contraction in order to ensure the quality of the coke. The yield of coking chemical products should be increased as much as possible, while ensuring the quality of coke.

Both types of coal have a relatively high volatile matter content, but their caking index is acceptable; the specific solution is to increase the use of low-caking coal, weakly caking coal, or lean coal

Question: 1. Can coal with a volatile matter content of 36–41, a G value of 70–80, X=44, Y=13, an ash content below 10, and a sulfur content below 0.6 be used as 1/3 coking coal for coke production? If possible, what considerations should be taken into account regarding the proportions? 2. The volatile matter content is between 34 and 38, the G value is between 50 and 57, X=52, Y=10.5; the ash content is below 10, and the sulfur content is below 0.7. Can coal of this type be used as coking coal or 1/3 coking coal for coke production? If possible, what issues need to be considered regarding the proportions? Answer: The proportion of premixed compacted coke. 1. It can certainly be used as 1/3 coke; we will use this type of coal as 1/3 coke. However, when using it, care must be taken to ensure an adequate amount of coking coal is used, otherwise the coke will have many cracks and poor strength. We use low-cost, high-sulfur fertilizer coal in combination with it; coking coal and lean coal are each accounted for 25% by the four companies. 2. When it comes to 1, the G value is on the low side; we don’t have coal of that kind, and coking coal certainly won’t work. 1/3 is acceptable. This requires increasing the proportion of coking coal and fat coal relative to 1. I’d be grateful if its proportion could reach 15%.

The volatile content is high, and the y-value is low. What about the other types of coal you have and their quality? We can’t consider only these two types of coal. It cannot be used as 1/3 coking coal; it must be used as gas coal. The ratio must strictly be <15%. Relatively speaking: those with a high volatile content have a decent y value, while those with a low volatile content have a lower y value; overall, the quality is comparable.

Agree to use gas coal as mentioned above. The proportion should be less than or equal to 10%. Although this type of coal has a G value of 70–80, its colloid viscosity is lower than that of coking coal (it is generally thinner and less viscous). 10% to 15% of lean coal can be added, and the amount of high-quality coking coal should be increased for use in combination with it.

Coking coal is a type of bituminous coal with medium and low volatilities, as well as medium and high caking properties. A term used for bituminous coal with a high degree of coalification and good coking properties. Also known as primary coking coal. 　 Coking coal is divided into two categories. For the first category of coking coal, the dry ash-free basis volatile matter content Vdaf is between 10% and 28%, the caking index G is greater than 65, and the maximum thickness of the gum layer is y ≤ 25 mm. This type of coal has excellent coking properties, allowing it to be used alone to produce high-quality blast furnace coke. Another type of coking coal has a dry ash-free basis volatile matter content of Vdaf > 20%–28%, and a caking index of G > 50–65; its caking property is inferior to that of the former type. Coking coal has moderate volatiles and good caking properties; it is a typical coking coal that can form a gel with excellent thermal stability when heated. When coked separately, coke with large size, few cracks, high crush resistance can be obtained, and it also has good wear resistance. However, the resulting expansion pressure is high, making coke pushing difficult; therefore, gas coal, lean coal, etc., must be added to improve operating conditions and enhance coke quality. In coking blend coals, coking coal can serve as the framework of coke and help mitigate shrinkage stresses, thereby improving the mechanical strength of coke; it is therefore an excellent raw material for coking. 1/3 coking coal has properties that lie between those of coking coal and fat coal; it has a negative impact on the strength of coke, but a positive effect on the volume of gas produced and the yield of chemical products. It also helps to prevent problems related to difficult tapping. It is recommended that its proportion not exceed 15%, as exceeding this level results in a significant decrease in coke strength.

The first type of coal is gas-prone and can be used to replace part of the coking coal, but considering the thermal properties of coke, it is necessary to incorporate an appropriate amount of highly cohesive coking coal; if the size of the coke particles is a concern, then a suitable amount of lean coal can be added. The G value of the second type of coal is too low, so it cannot be used as 1/3 coking coal

The answers upstairs are all professional and detailed. Another question: After blending the coals, since various parameters are similar to those of 1/3 coking coal, is it possible to produce metallurgical coke that meets national standards by using 1/3 coking coal alone (given appropriate sulfur and ash levels)? Are there any factories that do this? It is said that the Baotou Iron and Steel Co.’s coking plant uses 1/3 coal for coking on its own, but in most cases in China, coal is blended with other materials.

Regarding the two types of coal on the first floor, although they are classified as 1/3 coking coal, it is recommended to use them as gas coal. Such a high volatile content indicates that these coals are relatively young and have a low degree of metamorphism; if used in coal blends, they can only serve as an additive, to be used alongside coking coal and bituminous coal, with the amount used estimated to be no more than 15%. Regarding coking with pure 1/3 coking coal on the 13th floor, whether it is feasible to use pure coal for coking depends on the quality of the 1/3 coking coal. Since the category of 1/3 coking coal covers a wide range, even though it is all classified as 1/3 coking coal, there are significant differences in quality. Additionally, 1/3 coking coal is also a valuable resource for coking; it is not recommended to use it alone for coking, and more bituminous coal should be employed.