Coal Powder Preparation System: Safety, Explosion Prevention & Automation
A coal powder preparation system is a complex and potentially hazardous plant segment in coal-fired power stations, cement kilns, and blast furnaces. Its design revolves around three pillars: reliable fuel supply, stringent safety and explosion prevention, and advanced automation and control.
Safety and Explosion Prevention Design is paramount because pulverized coal is highly combustible and, under certain conditions, explosive. Key design principles include:
Inerting and Purging: Systems are designed to be purged with inert gas (usually nitrogen or CO₂) during start-up and shutdown to evacuate oxygen. During operation, maintaining oxygen levels below safe thresholds in the mill and bag filter is critical.
Explosion Venting: Pressure-relief vents with rupture disks are strategically installed on the mill body, cyclone, and dust collector. These vents are sized to safely release explosive overpressure to a designated safe area, preventing catastrophic structural failure.
Explosion Suppression: In some designs, high-speed suppression systems detect a pressure rise (incipient explosion) and inject a flame-suppressing chemical (e.g., monoammonium phosphate) within milliseconds to quench the reaction.
Temperature Monitoring and Control: Multiple thermocouples monitor mill inlet/outlet temperatures, bearing temperatures, and bag filter temperatures. Strict upper limits (often 75°C at mill outlet for bituminous coal) are enforced to prevent ignition. Automatic tripping of feeders and injection of inert gas occur upon high-temperature detection.
