Generally, it is necessary to forcibly dry the moisture in raw coke before calcination, especially in the following scenarios where drying is an essential process:
I. Negative Impacts of Moisture on the Calcination Process
1. Affecting the Efficiency of Volatile Matter Discharge
When raw coke (such as petroleum coke and anthracite) contains excessive moisture, the evaporation of water consumes a large amount of heat, leading to temperature fluctuations in the calcination furnace during the initial stage. This affects the stable discharge of volatile matter (such as sulfur and hydrogen compounds). For example, petroleum coke mainly discharges moisture below 200°C. If the moisture is not fully removed, the volatile matter discharge stage (500-700°C) may be delayed due to insufficient temperature, resulting in uneven shrinkage of the raw material and an increased risk of product cracking.
2. Reducing the Physical Properties of Raw Materials
Moisture reduces the cohesiveness between raw material particles, making pre-processing operations such as crushing, screening, and grinding difficult. For instance, petroleum coke with a moisture content exceeding 10% is prone to clogging equipment during crushing and produces uneven particle sizes after grinding, affecting the quality of subsequent mixing and forming processes.
3. Increasing Energy Consumption and Costs
The evaporation of moisture requires additional heat. If not pre-dried, the calcination furnace needs to consume more fuel to maintain the temperature. Taking petroleum coke as an example, reducing the moisture content by 1% can save approximately 20 kilojoules per kilogram of heat consumption, and drying treatment can significantly reduce production costs.
II. Enhancements in Calcination Quality through Drying
1. Improving the Density and Strength of Raw Materials
After drying, the moisture content of raw materials drops below 0.3%. During calcination, the discharge of volatile matter is more thorough, and the volume shrinkage of raw materials is uniform. The true density (e.g., increasing from 1.42-1.61 g/cm³ to 2.00-2.12 g/cm³ for petroleum coke) and mechanical strength of the raw materials are significantly improved, reducing secondary shrinkage of products during the baking stage.
2. Enhancing Conductivity and Oxidation Resistance
During calcination, the molecular structure of raw materials undergoes rearrangement, and the resistivity decreases (e.g., the resistivity of petroleum coke decreases with increasing calcination temperature), improving conductivity. Meanwhile, a pyrolytic carbon film deposits on the particle surface, enhancing oxidation resistance and extending the service life of products.
3. Optimizing Process Stability
Dried raw materials with balanced moisture content can avoid severe temperature fluctuations in the calcination furnace and reduce thermal stress damage to equipment. For example, by controlling the moisture content of coal entering the coke oven below 3%, coke plants can extend the lifespan of coke ovens by more than 10 years and reduce the deformation rate of coke oven chamber walls by 90%.
III. Practical Requirements for the Drying Process
1. Temperature and Time Control
The drying temperature is typically between 110-130°C, and the time needs to be adjusted according to the particle size and initial moisture content of the raw materials. For example, petroleum coke with a particle size of less than 3 mm requires approximately 2-4 hours of drying to ensure uniform moisture evaporation.
2. Equipment Selection
Common drying equipment includes rotary kilns and drum dryers. Rotary kilns achieve efficient drying through countercurrent heating, while drum dryers reduce material adhesion and improve drying efficiency with internal guide plates and cleaning devices.
3. Environmental and Safety Measures
The drying system should be equipped with dust removal devices (such as cyclone dust collectors + wet dust collectors) to reduce exhaust dust, with a dust removal efficiency of up to 99% or more. Meanwhile, the combustion system adopts a gas-fired burner, which is easy to operate and reliable.
Post time: Apr-13-2026