Abstract
A pulverized coal processing system for producing coal powder used in aluminum alloy smelting process was introduced. The explosibility of the coal used in the system was measured, and the hazards of the process were analyzed. Explosion prevention and protection methods applied in the process were described including atmospheric inerting, powder inerting and venting. Atmospheric inerting is the main method to prevent dust explosions in this process. Process monitoring and control are parts of explosion protection in combustible powder manufacture. Process parameters such as temperatures and concentrations of CO and O2 are monitored by a distributed data acquisition and control system. Spontaneous combustion of coal is the most possible ignition source, and CO monitoring is an effective method to detect spontaneous combustion. Experiences show that, auto-ignition may occur in the drying system when CO concentration is above 500 ppm. When the oxygen concentration is controlled at less than 5%, there will be no explosion hazard in the coal pulverization and drying process.