Laminar Combustion Firebox

a firebox for a furnace or steam boiler in which the fuel bed is loaded onto a grate and combustion occurs in an air stream that penetrates the bed, usually in an upward direction.

The following types of laminar combustion fireboxes are distinguished: those with a stationary grate and a stationary fuel bed, those with a mobile chain grate, and those with a stationary, for example, inclined, grate, over which the fuel is moved by gravity. In laminar combustion fireboxes equipped with a mobile bed, the fuel undergoes several successive stages, including predrying, sublimation of volatile substances, and combustion of volatile substances and coke. The appropriate regulation of operating conditions for each stage makes it possible to improve the combustion process. In the past, laminar combustion fireboxes were the principal device for combustion of large quantities of fuel. However, after the appearance of chamber furnaces, the use of laminar combustion fireboxes was confirmed to low-power boiler installations and industrial furnace applications.

Fireboxes with a fluidized bed appear to have considerable promise. In these fireboxes the temperature of the fuel bed is kept within an optimum range with the aid of heat exchangers (the heating surfaces of a boiler) located within the fuel bed. The advantages are the high intensity of the fuel combustion and the feasibility of removing oxides of sulfur and nitrogen from the fuel gases by introducing the appropriate adsorbing agents into the fluidized bed.