Unveiling the Intricate World of Coke: A Comparative Analysis of Different Origins

In the realm of industrial raw materials, coke stands as a crucial component, powering various sectors such as steelmaking, foundry, and chemical production. The quality and characteristics of coke can vary significantly depending on its origin, influenced by multiple factors. This in - depth analysis will explore the differences among cokes from different domestic and international sources, guiding industry players in making informed procurement and blending decisions.

The Root Causes of Coke Variations

The disparities in coke quality stem from several factors, including the type of coking coal, the age of the coal formation, coal washing levels, coal blending structures, and coking furnace technologies. The core differences are primarily reflected in five key dimensions: ash content, sulfur content, cold and hot strength, alkali metals, and pore structure.

Key Indicators of Coke Quality

Composition

• Ash Content (Ad): An important factor affecting coke quality. Lower ash content is generally preferred as it reduces slag formation during use.

• Total Sulfur (St): High sulfur can negatively impact the quality of the final products, especially in steelmaking.

• Fixed Carbon (FC): The higher the fixed - carbon content, the more energy - rich the coke.

• Volatile Matter (Vd): Influences the coking process and the properties of the resulting coke.

• Alkali Metals (K/Na): Can catalytically affect the coke's reactivity, with higher levels often being detrimental.

• Phosphorus: Although not always a primary focus, it can also impact coke performance in certain applications.

Cold Strength

• M40 (Fragmentation Resistance): A measure of the coke's ability to resist breakage. Higher values indicate better quality.

• M10 (Abrasion Resistance): Represents the coke's resistance to wear. Lower values are desirable.

Thermal Performance

• CRI (Coke Reactivity Index): Lower CRI values imply that the coke is less reactive at high temperatures, which is beneficial.

• CSR (Coke Strength after Reaction): Higher CSR values indicate better strength retention after a reaction, crucial for maintaining the integrity of the coke in high - temperature processes.

Comparative Analysis of Domestic Mainstream Coke Producing Areas

1. Shanxi Coke (Lvliang / Jiexiu / Liulin, Top - tier Metallurgical Coke in China)

• Raw Material Foundation Approximately 60% of China's high - quality coking and fat coals are concentrated here. These are Carboniferous - Permian aged coals, with moderate metamorphism and extremely strong caking properties (G = 85 - 95, Y = 18 - 30).

• Composition Characteristics Ash Content: First - grade coke ≤ 12.5%, quasi - first - grade 12.5 - 13%, with stable low - ash levels. Sulfur Content: 0.6 - 0.8%, and Liulin's low - sulfur mines can achieve 0.55 - 0.65%, among the lowest in the industry. Fixed Carbon: 86 - 88%, with few impurities. Alkali Metals: Extremely low, resulting in weak catalytic reactions.

• Quality Performance Cold Strength: M40 ≥ 82 - 86, M10 ≤ 6.0 - 7.5, featuring uniform lump size, few cracks, and little coke fines. Hot Strength: CRI 22 - 26, CSR 63 - 68, boasting the best high - temperature skeleton stability in the country.

• Advantages, Disadvantages & Applications Advantages: High cold and hot strength, low sulfur and low ash, and the most stable quality. Disadvantages: The highest price. Applications: Suitable for large blast furnaces above 1000m³, high - end foundry, and stainless - steel smelting.

2. Inner Mongolia Coke (Ordos, Wuhai)

• Raw Material Foundation Predominantly lean coal and meager - lean coal, with a scarcity of coking /fat coals, necessitating a large amount of Purchasing coal for blending. The raw coal is shallow - buried with a high content of gangue, increasing the washing cost.

• Composition Characteristics Ash Content: Generally high, ranging from 13.2 - 14.5%, and can reach 15% in small and medium - sized coking plants. Sulfur Content: 0.75 - 1.0%, with some mine areas having high - sulfur raw coal. Fixed Carbon: 84 - 86%, and the alkali metals (potassium and sodium) in the ash are higher than those in Shanxi coke.

• Quality Performance Cold Strength: M40 76 - 81, M10 7.5 - 9.0, with poor abrasion resistance and fragility during transportation. Hot Strength: CRI 27 - 32, CSR 56 - 62, prone to pulverization at high temperatures.

• Advantages, Disadvantages & Applications Advantages: Low pit - mouth cost and large supply volume. Disadvantages: High ash content, weak hot strength, and large quality fluctuations. Applications: Suitable for small and medium - sized blast furnaces, chemical gasification, and fuel for self - supplied power plants. Often mixed with Shanxi coke.

3. Shandong Coke (Rizhao, Jining, Weifang, Coastal Producing Areas)

• Raw Material Foundation Local coking coal is scarce, relying on a blend of domestic coal and imported Australian or Mongolian coal. While the blending is flexible, the coal sources are diverse.

• Composition Characteristics Ash Content: Moderate, from 12.8 - 13.8%, offsetting local high - ash coal with imported low - ash coal. Sulfur Content: Fluctuates greatly, from 0.65 - 0.95%. Sulfur is low when using pure Australian coal for blending, but increases when using more Mongolian coal. Alkali Metal Content: Moderate, with a slightly higher volatile matter than Shanxi coke.

• Quality Performance Cold Strength: M40 78 - 83, M10 7.0 - 8.5, between Shanxi and Inner Mongolia cokes. Hot Strength: CSR 59 - 65, with higher hot strength as the proportion of imported coal increases.

• Advantages, Disadvantages & Applications Advantages: Convenient port logistics and the ability to flexibly adjust imported coal for quality improvement. Disadvantages: Dependence on external coal sources, and the diverse coal sources lead to unstable indicators. Applications: Suitable for coastal steel mills in East China, foundry, and the aluminum industry.

4. Shaanxi Coke (Yulin, Hancheng)

• Raw Material Foundation Predominantly Jurassic coal, with high volatile matter, medium caking properties, and limited reserves of coking coal.

• Composition Characteristics Low - Sulfur Advantage: St 0.55 - 0.7%; Ash Content: 13 - 14%; Slightly higher volatile matter.

• Quality Performance Cold strength is acceptable, but hot strength is average, with CSR mostly between 57 - 63. The pores are relatively large, resulting in higher high - temperature reactivity.

• Applications Used in small and medium - sized blast furnaces in the northwest, calcium carbide production, and chemical gasification. Often used as a low - sulfur blending coke.

5. Xinjiang Coke (Hami, Fukang)

• Raw Material Foundation Jurassic low - metamorphic coal, with high oxygen content, more aliphatic hydrocarbons, high volatile matter, and extremely low ash and sulfur.

• Composition Characteristics Ultra - low Sulfur: St＜0.6% across the production area, Ash Content: 11.5 - 13%, and extremely low phosphorus. However, the raw coal has many oxygen - containing functional groups, resulting in well - developed pores and a loose coke structure.

• Quality Performance Cold strength is average, M40 75 - 80; hot strength is weak, with a high CRI and CSR of 55 - 61.

• Applications Suitable for small blast furnaces, ferrous alloys, and chemical gasification in the northwest, capitalizing on its low - sulfur advantage.

6. Hebei Coke (Handan, Tangshan)

• Close to Shanxi, it purchases a large amount of Shanxi clean coal for blending. The finished product indicators are similar to those of Shanxi coke, but the coking furnace scale is relatively small, and the blending cost is higher. Ash content is 12.8 - 13.3, sulfur content is 0.68 - 0.82, and CSR is 60 - 66, between Shanxi and Shandong cokes.

Comparative Analysis of Imported Coke / Coke Made from Imported Coal (Australia, Mongolia, Russia)

1. Coke Made from Australian Coking Coal

• Composition: Extremely low ash (10 - 11.8%), medium - low sulfur 0.6 - 0.75%, with few impurities.

• Performance: Extremely high cold and hot strength, CSR≥65, and extremely low alkali metals. It is the first choice for high - end coal blending.

• Shortcomings: Expensive price and long shipping cycle.

2. Coke Made from Mongolian Coal

• Composition: Low sulfur 0.6 - 0.9, but high ash 13.5 - 15, and a low Y - value of only 15 - 20, indicating weak caking.

• Performance: The coke has many cracks, is brittle, with poor M10, and a generally low CSR of less than 60.

• Positioning: A low - cost blending coal, only suitable for small - scale blending and unable to produce first - grade coke alone.

3. Coke from Russian Coking Coal

• The coking index fluctuates between 70 - 85, with medium ash and sulfur content. The coke has poor abrasion resistance, with a high M10, and is mostly used for ordinary smelting.

Summary of Core Causes of Composition Differences

Sulfur Content Differences

• Carboniferous - aged Shanxi coal＜Jurassic - aged Xinjiang / Shaanxi coal＜Inner Mongolia and local gas coal. Coal near the sea or in shallow layers contains more sulfides, resulting in higher sulfur content.

Ash Content Differences

• Coking and fat coal producing areas (Shanxi)＜Australian coal＜Shandong blended coke＜Inner Mongolia and Xinjiang lean coal. Poor mining conditions and a high gangue content lead to a significant increase in ash content.

Cold and Hot Strength Differences

• The higher the proportion of high - G and high - Y coking and fat coals, the denser the coke skeleton, resulting in higher M40 and CSR values. A high proportion of lean coal and gas coal leads to more pores and easier pulverization.

Hazards of Alkali Metals

• Inner Mongolia and Indonesian coals have high potassium and sodium content, which can catalyze the reaction between coke and CO₂, directly increasing CRI and reducing CSR, and potentially causing blast furnace collapse.

Quick Selection Tips for Procurement / Coal Blending

• For large blast furnaces aiming for smooth operation and low fuel ratio: Prioritize first - grade coke from Lvliang, Shanxi, and blend with a small amount of Australian coal.

• To control raw material costs for small and medium - sized blast furnaces: Use Inner Mongolia coke as the main component, and add 30% Shanxi coke to improve hot strength.

• For producing low - sulfur hot metal and foundry: Use low - sulfur coke from Xinjiang and Hancheng as blending coal.

• For coastal steel mills with logistics as a priority: Choose Shandong port coke and adjust the proportion of imported coal as needed.

This comprehensive analysis provides a detailed understanding of the differences in cokes from various origins, enabling industry professionals to make more informed decisions in their procurement and production processes.