Abstract: A cement clinker manufacturing apparatus which includes a suspension preheater, a precalcining furnace, a clinkering furnace such as a rotary kiln and a clinker cooler. Combustion air for use in the clinkering furnace is supplied from the clinker cooler. Combustion air for use in the calcining furnace is supplied from an indirect heat exchanger which receives hot gas from the outlet of the suspension preheater. This hot gas is placed in indirect heat exchange with ambient air to heat the ambient air. The thus heated ambient air is then supplied to the calcining furnace. The invention is particularly useful where the clinker cooler exhaust air cannot be used in the calcining furnace as preheated combustion air. A valve can be provided for regulating the volume of heated air supplied to the calcining furnace from the indirect heat exchanger.