Countercurrent calcining of lime in shaft furnace - contg. recuperator preheating air for combustion of the fuel

摘要

The furnace has a preheating zone (I); recuperation zone (II); calcining zone (III); and pref. two cooling zones (IVa, IVb). The air for combustion is preheated partly by flowing up zones (IVa, IVb) and partly in a recuperator, located inside the shaft in zone (II), from which the air flows into zone (IVa); both streams of air then flow up the shaft. A suction fan is pref. fitted at the top of the shaft to draw air and gases up the furnace. Zone (III) pref. includes cooled beams supporting burners fed with fuel; and the gas currents in the furnace are controlled by adjusting the suction fan. The recuperator is pref. an undulating pipe collecting heat from the gas streams. Increased thermal efficiency is achieved when roasting limestone.