Improving Steam System Performance with fluidised bed boilers, Steam is an indispensable means of delivering energy. Low toxicity, high efficiency, most of the heat content of steam is stored as latent heat hence large quantities of heat can be transferred efficiently at constant temperature. Steam system operation is divided into four categories- Generation, distribution, end use, recovery.
Fluidized bed boiler is the newest and cleanest way of generating steam. The traditional grate fuel firing systems have got limitations and are techno-economically unviable to meet the challenges of future. Fluidized bed combustion has emerged as a viable alternative and has significant advantages over conventional firing system and offers multiple benefits – compact boiler design, fuel flexibility, higher combustion efficiency and reduced emission of noxious pollutants such as SOx and NOx..
MECHANISM OF A FLUIDIZED BED BOILER
When an evenly distributed air or gas is passed upward through a finely divided bed of solid particles such as sand supported on a fine mesh, the particles are undisturbed at low velocity. As air velocity is gradually increased, a stage is reached when the individual particles are suspended in the air stream – the bed is called “fluidized”.
With further increase in air velocity, there is bubble formation, vigorous turbulence, rapid mixing and formation of dense defined bed surface. The bed of solid particles exhibits the properties of a boiling liquid and assumes the appearance of a fluid – “bubbling fluidized bed”.