How is fly ash produced and utilized?

1. Formation process of fly ash (combustion process): pulverized coal burns in suspension in the furnace, and most combustible substances in the coal can be burned out in the furnace, while noncombustible substances (mainly ash powder) in the pulverized coal are mixed in high-temperature flue gas. These incombustible materials are partially melted due to high temperature, and a large number of fine spherical particles are formed due to their surface tension. Under the suction of the induced draft fan at the tail of the boiler, flue gas containing a large amount of ash powder flows to the tail of the boiler. With the decrease of flue gas temperature, some molten fine particles are in a glassy state due to a certain degree of rapid cooling, which has high potential activity. Before the induced draft fan discharges the flue gas into the atmosphere, these tiny spherical particles are separated and collected by the dust collector, which is the fly ash. Usage: Fly ash is an important raw material for the production of aerated bricks by aerated brick equipment. The steam and gas evaporated from pulverized coal are partly discharged into the atmosphere and partly condensed on the surface of fly ash. In order to control the pollution of SO x, limestone slurry or limestone powder is introduced before flue gas discharge to capture SO x in flue gas, especially when coal with high sulfur content is used as fuel. 75% ~ 85% of the total coal ash becomes fly ash, and the rest is bottom ash and furnace ash. China takes coal as the main energy source, and 76% of its electricity is generated by coal, which consumes more than 400 million tons of coal annually, accounting for 1/3 of the national raw coal output. Fly ash is one of the industrial waste residues with large emissions in China. 1997, the national fly ash emission has exceeded1000000 tons, and by 2005, the annual fly ash emission has reached1000000 tons, making it the largest ash discharging country in the world. If a large amount of fly ash is not treated, it will produce dust and pollute the atmosphere. If it is discharged into the water system, it will cause river siltation, and the toxic chemicals in it will also cause harm to human body and biology, and it will also occupy a lot of land. Therefore, the treatment and utilization of fly ash has attracted extensive attention.