Semi Dry Process Cement,Semi dry Grinder

In the semi-dry process, dry raw meal is pelletised with 10-12% of water on an inclined rotating table (“granulating disc”) and fed to a horizontal travelling grate preheaterin front of the rotary kiln (“Lepol” system). The pelletised material is dried, pre-heated and partly calcined on the two-chamber travelling grate making use of the hot exhaust gases from the kiln. A higher degree of calcination can be achieved by burning part of the fuel in the hot chamber of the grate preheater.

The hot exhaust gases from the kiln first pass through a layer of preheated pellets in the hot chamber. After intermediate dedusting in cyclones, the gases are drawn once again through a layer of moist pellets in the drying chamber of the grate. As much of the residual dust is precipitated on the moist pellet bed, the total dust load of the exhaust gases at the preheater outlet is low.

As a drawback of the semi-dry process, kiln exhaust gases cannot be utilised in the raw meal drying and grinding system due to the low temperature level. The maintenance costs of grate preheaters are high. Modern installations rarely use the semi-dry process.