High Volatility Metallurgical Coal
COKE
Coke Production
Although high-quality coke for blast furnaces is often based on medium- and low-volatility coals due to their high fixed carbon content and strength, high-volatility coal is essential for optimizing the properties of the coke mix and ensuring the formation of coke with the appropriate characteristics for the steelmaking process. Its inclusion allows steelmakers to adjust coke quality and furnace efficiency.
What is volatile matter in coal?
Volatile matter in coal refers to the organic compounds released as gases and vapors when coal is heated in the absence of air. These compounds include methane, ethane, hydrogen, and other light hydrocarbons. In the context of metallurgical coal, the percentage of volatile matter is a key factor in determining its classification and behavior during the coking process (transformation into coke).
Metallurgical coals are generally classified by their volatile matter content into: Low volatility, Medium volatility, and High volatility.
Characteristics of High Volatility Metallurgical Coal
High volatile compound content: As its name indicates, this coal has a high percentage of volatile matter.
Lower fixed carbon: Compared to low or medium volatility coals, it usually has a slightly lower percentage of fixed carbon.
Good plasticity: During heating, high volatility coals usually soften and acquire good plasticity, which is crucial for the formation of a cohesive and strong coke structure.
Swelling capacity: They have a good swelling capacity when heated, which also contributes to coke formation.
Use in the Steel Industry
High-volatility metallurgical coal is rarely used alone to produce high-quality coke for blast furnaces. Instead, it is a vital component in the coal mixture used in coke oven batteries.
Formation of the "coke mixture": To obtain coke with ideal physical and chemical properties (mechanical resistance, porosity, reactivity, low sulfur and ash content), steel mills usually mix different types of metallurgical coals.
Improved plasticity: High volatility coals add plasticity to the mixture, helping the coal particles to fuse and form a solid, homogeneous mass during coking.
Gas generation: During the process, volatile matter is released as coke gas, which can be recovered and used as an energy source within the steel plant or for other purposes.
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Favorable physical and chemical properties
The coal from the Cúcuta area stands out for its high steelmaking quality due to:
Low phosphorus content: This is its most valuable feature. By preventing brittleness in steel, it allows the production of ultra-low phosphorus coke, which is in high demand for high-strength steels.
Low sulfur and ash: Reduced sulfur levels prevent defects in the metal, while low ash content ensures greater purity and thermal efficiency.
High calorific value: Its superior energy capacity optimizes performance in industrial processes.
Volatility range: The supply of high and medium volatile coals facilitates precise blends to obtain coke with ideal porosity and strength.
Reactivity: Its reactive nature significantly improves chemical performance within the blast furnace.
Geological Formations and Maturity
The coal deposits in Norte de Santander are located in specific geological formations (such as the Los Cuervos and Carbonera Formations) that have favored the formation of high-quality bituminous coals. The thermal maturity of these coals (the degree of geological transformation) has been suitable for producing a mineral with the necessary properties for coking.
Market Positioning
The quality of coal from Cúcuta has allowed companies in the region to position themselves as leaders in the Colombian metallurgical coal and coke market, with a significant presence in international markets across Latin America, Central America, Europe, Asia, and the United States. This is a direct reflection of the unique and desirable properties of their coal.
Quality specifications for coking coal
CHEMICAL PROPERTIES
"Values according to ASTM D standards"
Humidity
7.0% MÁX
Ashes
(on a dry basis)
7.5% MAX
Fixed coal
(on a dry basis)
56.5% MAX
Volatile Matter
(on a dry basis)
36%
Total sulfur
(on a dry basis)
0.90% MAX
"Values according to ASTM D standards"
ASH ANALYSIS (X-ray fluorescence analysis)
K2O
(on a dry basis)
1.11% MAX
Na2O
(on a dry basis)
0.35% MAX
P (Phosphorus)
(on a dry basis)
0.0001% MAX
PHYSICAL PROPERTIES - GIESELER PLASTOMETER
"Values according to ASTM D standards Except for expansion (ISO)"
Softening temperature
370 MIN (°C)
Resolidification temperature
480 MIN (°C)
Maximum fluidity
30,000 MIN (ddpm*)
Dilatation
(Audibert Arnu) +d
+200 MIN.
Ash melting point
1,482 MIN (°C)
Free swelling index (FSI)
8.0 MIN
Light transmittance
(No oxidation)
90 MIN (%)
Reflactance of reactive vitrinite
0.95 MIN (%)
Stability
48 MIN
GRANULOMETRIC ANALYSIS (screening)
"Values according to ASTM D standards"
+50.8 mm
%
-50.8 mm
+25.4 mm
MAX. %
-25.4 mm
+12.7 mm
MAX. %
-12.7 mm
+0.42 mm
MIN. %
+0.42 mm
MAX. %