Formation of Fly Ash Microspheres

In coal-fired power plants, coal is typically ground into fine powder and injected into the furnace of the power boiler for suspended combustion. Most of the combustible components of coal (carbon and organic matter) are burned, while the non-combustible clay-based components (silicon, aluminum, iron, magnesium, etc.) begin to melt at the high temperature of 1,300°C in the furnace, forming a porous symbiosis of quartz glass and mullite.

Fly ash microspheres refer to the hollow glass microspheres in fly ash with a density lower than water, which are a type of bead-shaped particles in fly ash and 得名 (named) for their ability to float on water. They are generated when clay-based materials melt into micro-droplets during the combustion of coal powder in the boiler of a thermal power plant. Under the action of turbulent hot air in the furnace, these droplets spin at high speed to form round silicon-aluminum spheres. Gases such as nitrogen, hydrogen, and carbon dioxide produced by combustion and pyrolysis reactions rapidly expand within the molten high-temperature silicon-aluminum spheres. Under the action of surface tension, hollow glass bubbles are formed, which then enter the flue and cool rapidly. After hardening, they become high-vacuum vitreous hollow microspheres, namely fly ash microspheres.

Derived from fly ash, fly ash microspheres possess many properties of fly ash, but due to their unique formation conditions, they exhibit superior performance compared to fly ash. They are lightweight, non-metallic, multi-functional new powder materials, hailed as "space-age materials."