What Is Boiler Coking

Boiler Coking is the accumulated block formed by local fuel accumulation at burner nozzle, fuel bed or heating surface. It is common for coal fired boiler or oil boiler, under the circumstance of high temperature and less oxygen. In general, the ash particles are cooled together with the flue gas due to the heat absorption of the furnace water wall. If the liquid slag particles are solidified before approaching water wall or furnace wall, it will form a loose ash layer when attaching to the tube wall of heating surface, which can be removed by blowing ash. When the furnace temperature is high, some ash particles have reached a molten or semi-molten state. If such ash particles are not sufficiently cooled to a solidified state, it has a higher bonding ability. It easily adheres to the heating surface or furnace wall, and even reaches the molten state.

What Is Boiler Slagging

During the combustion process, the easily fusible or gasified substances in the pulverized coal particles volatilize rapidly. It congeals or sticks to the heating surface or furnace wall when the temperature drops. Or it congeals on the surface of fly ash particles and becomes a molten alkali film, and then adheres to the heating surface to form an initial slagging layer. If the coal boiler bed temperature is too high, the slag temperature will be as high as 1040°C. The slag will soften and form slagging. The slag cools rapidly to form hard lumps, arising operational problems like stoppage of the slag extractor. There is a large amount of ash in the fuel. Most of the ash will melt into a liquid state or appear in a softened state. As surrounding water walls continuously absorb heat, the temperature is getting lower and lower from the center of burning flame. As the temperature decreases, the ash will change from liquid to softened, hardened to solid. If the ash touches the heating surface when it is still in a softened state, it will harden due to sudden cooling and adhere to the heating surface, thus forming boiler coking.


Post time: Jul-19-2021