| The essential characteristic of a grate cooler is a layer of clinker spread on a more-or-less horizontal perforated grate, through which cold air is blown. The grate is made of steel, and the cold air keeps it sufficiently cool to avoid melting or burning. The clinker progresses through the cooler by moving more-or-less horizontally along the grate, and so the direction of the cooling air is roughly at right angles to the direction of movement of the clinker, and the cooler functions as a cross-current heat exchanger. This mechanism is inherently less efficient than a counter-current heat exchanger such as a rotary or planetary cooler, but there are distinct advantages:
the hot clinker at the inlet is treated with cold air rather than partially heated air, so that a rapid quenching effect is possible, improving clinker quality by preserving reactive high-temperature silicate polymorphs.
by using air in excess of that needed for combustion, the clinker can readily be cooled below 200°C.
it is easy to tap off exhaust hot air streams in desired temperature ranges for use in other processes - e.g. calciner tertiary air or drying air for fuel or raw materials. |
