There is no doubt that refractory materials, or the lining employed inside rotary kilns, are crucial in ensuring process efficiency and prolonging the lifespan of these machines. On this page, we will cover all aspects of kiln refractories, including how it works, the different types of refractories, and so on.
Cement Kilns/Rotary Kilns Process:
As rotary kilns were introduced, cement manufacturing processes became sharply defined based on how raw materials are fed into them. In addition to grinding raw materials with water, raw materials were ground dry, forming a powder or “raw meal”, or ground with water to form a slurry.
- During the Wet Process, the liquid slurry is fed into the kiln system, followed by the evaporation of water.
- As part of the Semi-Wet Process, raw materials are prepared as a slurry, after which a considerable amount of water is removed mechanically by filtration and then fed into the kiln.
- In the Dry Process, raw meal powder is fed into the drying system.
- In the Semi-Dry Process, the dry raw meal is modified by adding a limited amount of water (10-15%), resulting in nodules, which are fed into kilns.
Types of Rotary Kilns/Cement Kilns Refractories
A castable refractory and a brick refractory are the two most popular types of kiln refractory.
Castable Refractory
Castable refractory is delivered as a powder and is combined with water on-site. Anchors must be installed before the mixture can be placed. These y-shaped anchors, which are comparable to rebar in cement, contribute to the strength of the castable lining. After the anchors have been installed, the cement-like slurry is pumped into the rotary kiln’s liner and left to set for several days.
The downside of utilizing a castable refractory in a rotary kiln is that it is easily damaged during installation. When castable refractory is built correctly, it may almost match the quality of brick. However, if fitted poorly, there might be a significant variation in quality, and the refractory’s life can be significantly shortened.
Bricks Refractory
Brick is burnt in a furnace under precisely regulated circumstances, allowing it to obtain greater characteristics than a castable refractory of comparable composition.
While brick is more expensive than castable, it does not require anchoring and has superior quality, but installation costs are higher. Refractory bricks are usually used when processing highly abrasive materials since castables are not strong enough to handle such materials.
Importance of Rotary Kilns Refractories
In rotary kilns, high temperatures cause materials to undergo chemical reactions. In most cases, carbon steel shells exposed to these high temperatures would be immediately destroyed by these temperatures. Due to this, the refractory material is used.
The only rotary kilns that use refractory are direct-fired, while indirect-fired kilns transfer heat primarily through the wall of the kiln. As another barrier, refractory reduces the efficiency of the process as heat passes through it before it meets the material. Therefore, indirect-fired kilns use heat-resistant materials instead of refractory.
Due to their lack of combustion chambers, direct-fired kilns are required for refractory. The flame is therefore continuously in direct contact with the inner parts of the kiln, necessitating the need for refractory.
Last Verdict
Thanks for taking the time to read our blog, and we hope you found it to be interesting. For more information on refractory materials, go to Ganesha’s – Manufacturers of Advances Industrial Machinery, one of the largest refractory brick manufacturers in India.
