Design Features

The BSP Multiple Hearth Furnace (see cross section at right) is constructed of numerous circular hearths enclosed in a refractory-lined steel shell. In the center of the cylindrical shell is a vertical rotating shaft with radial arms and rabbling teeth which move the feed material in a spiral path across each hearth. The material is constantly agitated and exposed by the rabbling teeth as it travels across the hearth before it falls through drop holes from level to level.Process air can be supplied in regulated quantities by combustion air blowers through burners or ports, or by induction through air ports.

Shaft arms are cooled by forced air from a fan. The shaft has double-walled construction. Cool air flows up the center tube, through the rabble arms and back into the shaft annulator space to exit at the top of the furnace. Hot air is ducted back into the furnace for reuse as combustion air.

Furnace refractory and layers of insulation in the thick walls conserve heat and maintain low shell temperatures. Hearths can be constructed of standard firebrick shapes or special shapes which provide greater stability and lower weight.

Automatic draft and oxygen monitoring equipment are utilized to minimize power draw and fuel demand while assuring clean combustion.