Скачать или смотреть Pulverizing Coal into Fine 100μm Particles Cement Plant Boiler Combustion Babcock Wilcox Mitsubishi

https://cementl.com/ In cement plants, coal is a primary fuel for the kiln and power generation boilers. To achieve efficient combustion, the coal must be pulverized into fine particles, typically around 100 μm, so that it can ignite quickly and burn completely. Pulverization is performed by specialized mills such as vertical roller mills, bowl mills, or roll wheel pulverizers, depending on plant design, fuel properties, and capacity requirements. The title includes babcock wilcox is for volume, thank you for your understanding.

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Raw coal, often sized below 50 mm, is fed into the pulverizer at controlled rates using gravimetric feeders. The mill’s grinding mechanism crushes the coal between rollers and a rotating table, or between rollers and a grinding ring. For vertical roller mills, centrifugal force spreads the coal outward under the rollers, while in bowl mills, a rotating table carries coal under spring- or hydraulically-loaded rollers. The grinding force is adjusted based on coal hardness, moisture content, and required fineness.

Hot primary air is introduced into the mill, usually at 200–300 °C, serving two functions: drying the coal and carrying fine particles upward to the classifier. The classifier ensures that only coal particles below the target size—approximately 100 μm—are sent to the furnace, while coarse particles are returned for further grinding. This ensures uniform particle size distribution, which is critical for stable boiler operation and complete combustion.

The pulverizer capacity is determined by boiler load and coal properties. For a medium cement plant boiler producing 50–100 tons per hour of steam, mills are designed to handle similar amounts of coal per hour. Fineness of 100 μm allows rapid ignition in the furnace, minimizing flame fluctuations and reducing unburnt carbon in ash. Maintaining a narrow particle size distribution also reduces slagging and fouling in the boiler.

Wear management is a key concern in coal pulverization. Rollers, grinding rings, and table liners are exposed to abrasive coal ash. Many plants use high-chromium alloy wear parts or ceramic inserts to extend service life. Regular inspection and replacement of worn components help maintain consistent grinding pressure, particle fineness, and mill efficiency.

During operation, several parameters are continuously monitored:

Differential pressure across the mill, indicating material bed thickness and airflow.

Coal fineness from the classifier, ensuring the 100 μm target is met.

Roller or table vibration, indicating wear or imbalance.

Mill outlet temperature, usually maintained between 70–85 °C, to prevent condensation in coal transport ducts.

Safety is also critical because pulverized coal is combustible. Mills are equipped with explosion vents, CO monitoring, and inerting systems using nitrogen or CO₂. Proper air velocity and classifier settings prevent accumulation of fine coal in the mill housing, reducing the risk of fire or explosion.

In cement plant boilers, the quality of pulverized coal affects flame shape, heat transfer, and clinker chemistry. Fine particles (~100 μm) burn completely and release heat quickly, stabilizing kiln temperature and steam generation. Incomplete combustion can lead to higher fuel consumption, unstable kiln operation, and increased emissions of CO and unburnt carbon.

Operational notes highlight the importance of consistent mill feed, stable hot air supply, and proper classifier adjustment. Changes in coal moisture, hardness, or ash content must be compensated by adjusting grinding pressure, classifier speed, or airflow. Regular maintenance of mill internals and monitoring of wear parts ensure the mill continues to produce coal particles consistently at the 100 μm target.

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