Suspension firing pulverized coal furnaces

Fluidized bed combustion of coal is used to reduce the emission of sulfur dioxide and NO into the enviromnent. In this technology the pulverized fuel is burnt in a fluidized bed combustor after being blended with limestone or dolomite, which act as soibents for SO2. The burning temperature is significantly lower than is common in the production of fly ashes in suspension-fired furnace chambers, at around 850°C. The process may take place at atmospheric pressure (atmospheric fluidized bed combustion, AFBC) or elevated pressure (pressurized fluidized bed combustion, PFBC). 

The first suspension-fired furnace in the United States was designed like the one shown for vertical firing in Fig 17.24. Pulverized coal (about 70% through a 200-mesh screen) is transported to the burner with primary air, the amount of this air being about 20 percent of that needed for complete combustion. The... 

CycUme Furnaces In cyclone firing (Fig. 24-l4d) the coal is not pulverized but is crushed to 4-mesh (4.76-mm) size and admitted tangentially with primary air to a horizontal cylindrical chamber, called a cydone furnace, which is connected peripherally to a boiler furnace. Secondary air also is admitted, so that most all of the coal bums within the chamber. The combustion gas then flows into the boiler furnace. In the cyclone furnace, finer coal particles burn in suspension and the... 

In a pulverized boiler, the coal is ground to the consistency of talcum powder in a mill, and then entrained in an air stream that is fed through the burners to the boiler combustion chamber.6 Firing, therefore, occurs in suspension. Pulverized boilers can be wet-bottom, which means that coals with low ash fusion temperatures are used, and molten ash is drained from the bottom of the furnace, or can be dry bottom, which means that coals with high ash fusion temperatures are used, and dry ash removal techniques can occur.6... 

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