Analysis and Prevention of Self-combustion in Ash Silo Caused by Pure Lignite Burning

Abstract

In recent years， the price of domestic thermal coal has been high. For cost consideration， thermal power plants generally burn lignite now. In addition， the frequency of deep peak shaving of thermal power units has increased significantly to consume new energy power. During the unit start-up and low-load operation， because of the low furnace flame temperature, the combustion of pulverized coal is not sufficient， causing a great risk of spontaneous combustion after being transported to the ash silo through the ash handling system. The paper analyzes the spontaneous combustion of ash silo during the commissioning of start-up for an ultra-supercritical unit that adopts pure lignite. Measures such as hot water warming furnace start-up， stratified ash storage and reasonable control of ash storage level are taken， which can reduce low-load running time by 54%， prevent concentrated accumulation of unburned pulverized coal. In addition， by increasing the evenness of fluidization air and reducing heat storage of ash silo， operation stability and safety of the unit is guaranteed， which provides a reference for the prevention and control of self-combustion in ash silo of lignite-fired units.

Keywords

• pure lignite burning
• self-combustion in ash silo
• low-load operation
• deep peak shaving
• unit start-up
• coal-fired unit