Concrete is one of the most popular, common, and affordable building materials in the world – and it’s thanks to industrial kilns. Modern operations can create concrete in huge quantities easily, and concrete can even be recycled, due to well-understood processes for creating concrete mixes within a large kiln.
Here’s how it happens.
How An Industrial Kiln Processes Cement
1 – Preheating
Modern processes for creating concrete begin by pre-heating the raw materials, called raw meal. The meal is made primarily of clay and limestone, but one of the key elements of cement manufacture is that the limestone must be calcinated – removing CO2 within the mix.
So to begin, the meal is heated to a temperature just a bit below that of the kiln itself – around 800°C. This is typically done in a cyclone preheater, where the meal is fed into a vertical cylinder with high airflow to heat the particulate clinker evenly.
2 – Precalcination
After the raw meal is heated, it goes into a chamber called a precalcinator. This extends the heating process and begins releasing CO2. One common method is to mix the meal with pulverized coal, heating it until the coal combusts, sending that energy directly into the raw materials. This prepares the meal for its time in the kiln.
3 – Into the industrial kiln
After precalcination, the meal has already lost much of its CO2 content, so its time in the kiln can be relatively short. Its temperature is raised even higher – up to 1300-1450°C – which burns off the rest of the CO2 and completes the calcination process. This is a significant improvement over older methods of calcinating concrete, which required long stays in gigantic kilns which could be 200m in length or more.
Once the meal reaches the bottom of the kiln, chemical processes have converted it into tricalcium silicate – the main ingredient in common concrete. This is also called clinker.
4 – Cooling
Finally, the clinker falls into a chamber below the kiln to be cooled. This is generally accomplished with airpower for low energy costs. Once cool, the clinker is ready to be mixed with other additives and packaged as ready-to-mix concrete.
Kiln Technology Company is one of the country’s leading providers of industrial kilns, installation, repairs, and associated parts and supplies. Contact us for Kiln component reconditioning and kiln spares.