What characterizes the principle of "circulating fluidized bed" (CFB) combustion?

The principle of "circulating fluidized bed" (CFB) combustion is characterized by maintaining a suspension of solid fuel particles in a bed of air. This unique feature allows solid fuels to be efficiently combusted in a way that promotes better mixing and higher combustion efficiency. In a CFB, air is introduced at the bottom of the bed, causing the solid particles to become fluidized — resembling a boiling liquid. This process not only enhances the contact between the fuel and the air (oxygen) needed for combustion but also allows for effective combustion at lower temperatures compared to conventional combustion methods. This characteristic of keeping solid fuel suspended enables improved heat transfer and minimizes the formation of pollutants such as nitrogen oxides (NOx) and sulfur oxides (SOx), making CFB technology an environmentally friendly option for burning solid fuels.