There are rotary kilns for sale intended to support a variety of industries – but few industries rely more heavily on kilns than cement production. Kilns are used at almost every step of the process of creating cement and can also be utilized for recycling/reusing old cement as well.
Anyone in the cement industry would be wise to partner with rotary kiln manufacturers to provide service and support, to ensure high levels of productivity for years to come. Here’s how it happens.
Use Of Rotary Industrial Kilns to Create Cement
The primary use of kilns in cement manufacturing is by creating clinker, the raw material from which concrete is made. Clinker is a fusion of limestone and clay (or other aluminosilicate materials), which must be carefully heated so that they fuse without melting, called sintering. This clinker is then ground up, and mixed with a small amount of gypsum, to create dry Portland Concrete which is ready for use.
Kilns are perfect for the creation of clinker because they can achieve the necessary heat envelope to create the clinker without fully melting it.
Step 1 – Preheating
The clinker begins as a material called meal, which is simply a mixture of the raw ingredients. This cannot be sent directly into the kiln, so first it’s pre-heated up to approximately 800°C. Typically, a multi-stage cyclone pre-heater is used, blowing hot air through the meal as it moves through two or more cyclone chambers.
When the system is designed for concrete from the start by experienced rotary kiln manufacturers, the pre-heating process can actually be powered mostly by waste heat from the kiln itself – decreasing fuel costs.
Step 2 – Precalcination
Before the heated meal can be fully treated, it also needs to be mixed with pulverized coal to increase heat transfer. This happens in a precalcination chamber. As the coal hits the already-heated meal, it ignites, transferring more heat into the mixture. This causes it to decompose, and release carbon dioxide.
Step 3 – Sintering
The meal is now ready for calcination, also called sintering. The meal enters the kiln and is heated further, causing more decomposition and more CO2 release. As it heats up, the minerals begin to fuse, ultimately creating tricalcium silicate – the main component of Portland cement.
Step 4 – Cooling
Finally, the clinker must cool down, which happens in a grate-based cooler that allows air to be directly blown onto the superheated material. Modern techniques allow this to be accomplished quickly, and with minimal heat loss. Most heat is captured and sent back into the pre-heater, as mentioned above.
The US Concrete Industry Relies on Kiln Technology Company Company
We are recognized as one of the nation’s leading providers of rotary kilns for sale, kiln servicing and repairs, and even kiln decommissioning. Whether you produce concrete or rely on kilns for other aspects of your own materials production, Kiln Technology Company can be your reliable partners in keeping your kiln turning smoothly.