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When carrying out coking coal blending, the main quality requirements for the blended coal include: chemical composition parameters such as ash content, sulfur content, and phosphorus content; technological property parameters such as degree of coalification and caking property; coal petrography parameters; and process condition parameters such as moisture content, fineness, and bulk density. (1) Ash content of blending coal: The ash in coal remains entirely in the coke after coking. The ash content criterion for blending coal is determined by calculating it based on the ash content criterion specified for coke; that is, Ash content of blending coal (A_coal) = Ash content of coke (A_coke) × Total coke yield (K, %). Different types of coke have varying requirements regarding ash content. Generally, an ash content of 7%–8% is considered suitable for metallurgical coke and foundry coke, while around 15% is appropriate for gasification coke. (2) Sulfur content in the blending coal: Approximately 60%~70% of the sulfur in the coal is transferred to the coke. Since the coke formation rate of the blending coal is 70%~80%, the sulfur content in the coke is about 80%~90% of that in the blending coal. Thus, the upper limit for the sulfur content in the blended coal can be calculated based on the sulfur requirements for coke. (3) Phosphorus content in the coaling coal: Since coke with a high phosphorus content increases the cold brittleness of pig iron, it is required that the phosphorus content in the coaling coal be below 0.05% during production. When Chinese metallurgical coke and foundry coke are exported, foreign buyers have very strict requirements regarding phosphorus content; there are generally no special requirements for phosphorus content in gasification coke. (4) Degree of coalification of blending coal: The most commonly used indicators to express the degree of coal transformation are volatile matter Vdaf and average maximum reflectance max, and there is a close relationship between the two. Determining the vitrinite rank control value for blending coal should be based on a comprehensive consideration of factors such as requirements, feasibility, rational use of resources, and economic efficiency. The volatiles of the blending coal have a direct impact on the final shrinkage of coke, its degree of cracking, as well as the yield and quality of chemical products. To balance coke quality as well as the yield of coke oven gas and coking chemical products, countries generally keep the volatility of the coal used in coke ovens within the range of 28% to 32%. For the conventional coking coal used to produce coke for large blast furnaces, the appropriate range for controlling the degree of coalification is max=1.2%~1.3%, which corresponds to Vdaf=26%~28%. However, it should also be considered in light of the specific circumstances, along with the appropriate range for the adhesiveness indicators. The volatiles content of the coal used for gasification coke should be greater than 30%. (5) Coaling coal’s caking property: The caking property of coaling coal is an important factor affecting coke strength. Countries use different indicators to characterize adhesiveness. Commonly used indicators include the coal expansion degree b, coal fluidity MF, vitrinite index y and X, as well as the caking index G; higher values of these indicators indicate stronger caking properties. The appropriate ranges for the cohesion indicators of most chamber-type coking coals are as follows: the maximum fluidity MF value is 70 (or 100)–103 ddpm, the O-A expansion degree is ≥50%, the maximum gel layer thickness y is 17–22 mm, and G is 58–72. Gasified coke has lower requirements for the bonding properties of coal blends. The caking index of blended coal generally cannot be calculated by simply adding the caking indices of individual coals. (6) Coal lithological components of blended coal: The proportions of the coal lithological components in blended coal should be appropriate. The active components among the microscopic components of blended coal should constitute the majority, but there should also be an appropriate amount of inert components to serve as a framework, which helps to form dense coke and also reduces shrinkage stresses and the formation of cracks. The appropriate proportion of inert components varies depending on the degree of coalification; when the average maximum reflectance max of the coal blend is <1.3, 30%~32% is a suitable value ； When max > 1.3, 25%–30% is preferable. When using coal with high volatile matter, the content of the stable components also needs to be considered. (7) Moisture content of blending coal: Regardless of the type of coke being produced, the moisture content of blending coal is generally required to be between 7% and 10%, with this level needing to remain stable in order to avoid affecting the stability of the heating regime in the coke oven. For production, high moisture content will prolong the coking time; for every 1% increase in the moisture content of the coal, the coking time increases by 20 minutes, which reduces output and increases energy consumption. Secondly, if the moisture content of the coal blend is too high, the amount of phenols produced increases. Furthermore, under normal fineness conditions, the bulk density is lowest when the moisture content of the coal mixture is 7%–8%; drying the coal can increase the bulk density, thereby improving the cohesion of the coal material. (8) Fineness of blending coal: Fineness is an indicator used to measure the degree of pulverization of coking coal, expressed as the percentage by mass of coal with particle sizes less than 3 mm in the total blending coal. Coking plants around the world determine the fineness control parameters based on the quality of the coal available to them and the technical characteristics of the coal used in the furnaces. Grinding coal to a certain fineness ensures uniform mixing. Thereby improving the uniformity of the internal structure of the coke. However, excessive pulverization reduces the cohesion and bulk density of the coal fed into the furnace, thereby lowering the quality and yield of coke. In blended coal, weakly caking coal should be finely ground, while the fineness of strongly caking coal should not be too high, as this helps to improve the quality and yield of coke. Generally, the control range for the fineness of blended coal is as follows: during conventional coking, the proportion of particles smaller than 3 mm is 72%~80%; during coking with blended coal, it is around 85%; and during rammed coking, it is over 90%. The main measures to control the fineness of blended coal include: properly selecting the coal crusher ； Before crushing, screen out coal with a particle size of less than 3 mm to avoid repeated crushing. (10) Bulk density of blended coal: This quality control parameter refers to the mass of coal per unit volume in the carbonization chamber of a coke oven, and is usually expressed in kg/m3. The high bulk density of the coal blend not only increases coke yield but also helps improve coke quality. However, as the pile density increases, the expansion pressure also rises, and excessive expansion pressure from the blending coal can cause damage to the coke oven structure. Therefore, while increasing the bulk density of the blended coal to improve coke quality, it is essential to prevent the expansion pressure from exceeding its limit value; this limit value varies depending on the test conditions, ranging between 10 and 24 kPa.