A lime kiln is used for calcination of limestone (calcium carbonate) to produce quicklime also called burnt lime. And the chemical formula is CaCO₃+ heat = CaO +CO₂. Usually, the heat is around 900℃ , but a temperature around 1000℃ makes the calcination process more quickly. Of course, the temperature can not be too high for it can produce dead lime. Due to the fact that the process is conducted in high temperature, the insides of lime kilns are equipped with refractory materials, while the outer structures are built with sturdy steels.
Lime Production Plant
Lime production plant is a whole production line to make quicklime. Lime processing plant is often equipped with either rotary lime kiln or vertical lime kiln. For lime kiln is the core equipment of the plant to produce burnt lime. Of course, except lime kiln, there are also other machines in the lime calcination plant. For example, there are crusher, dust collector, packing machine, transferring systems and so on. With extended experience, Daswell machinery provides advanced lime kiln technology. And we design and manufacture lime kilns according to customers’ specific needs.
Limestone Calcination Process
To produce quicklime in lime kilns, there are mainly three processes. The first stage is preheating. The second stage is calcining. And the third stage is cooling. In the preheating stage. The feed limestone is preheated by the exhaust hot air from the lime kiln, so that partially of the limestone will be calcined. As a result, the preheating process can make sure that the limestone is fully calcined as well as save energy along the process. In the calcining process, the partially burnt limestone will be burnt thoroughly. And usually the temperature in this stage is the highest in the lime kiln. In the cooling stage, the burnt limestone will be cooled down by the air so that it can be handled by conveyors and so on. In fact, except for these three stages, there are also crushing, dust collecting, packing and so on. Firstly, the limestone is crushed in primary or even secondary crusher so that the feed limestone is of required size. Then the fed limestone will be fed into lime kiln, going through preheating, calcining and cooling stages. And then the cooled down quicklime will enter into dust collectors to reduce dust. Finally, the quicklime is directed to product silo through conveyor, waiting for being packed.
Types of Lime Kilns
Typically, there are two kinds of lime kilns. One is rotary lime kiln and the other is vertical shaft lime kiln. Rotary lime kiln is a horizontal or inclined cylinder which can rotate due to rings and wheels attached. And vertical lime kiln, as the name implies, is vertical.
Rotary Lime Kiln for Lime Calcination
Limestone rotary kiln is inclined cylinder that can rotate. At the higher end, limestone is fed in. While at the lower end, it is the furnace where a great variety of fuels can be used to burn the limestone, such as coal, gas, oil and so on. For modern lime calcination plant with rotary lime kiln, it is often equipped with vertical preheater and vertical cooler. That is the three stages of the limestone calcination are conducted separately in these three parts: the preheating process in vertical preheater, the calcination process in the rotary lime kiln, and the cooling stage in the vertical cooler. This system can improve quicklime production capacity while reduce energy consumption during the whole lime calcining process. Besides, with advanced system, the rotary lime kiln can come with shorter lengths, which can also reduce heat losses due to long lengths of the rotary lime kiln. Rotary lime kiln with preheater and cooler is advanced lime kiln technology for new lime calcination plant. And it is also good solution for existing quicklime plant upgrade.
Vertical Lime Kiln for Quicklime Plant
As for the vertical lime kiln, it consists all three stages all in one. Usually, the upper side of the vertical shaft lime kiln is the preheating chamber. The central part is calcination chamber and the lower part of the lime kiln is cooling chamber. In light of this design, feed limestone with required sizes will be fed into the lime kiln from top. And after being preheated, the partially burnt limestone will enter into the calcination chamber. In this chamber, the preheated limestone will be fully calcined. And finally in the cooling stage, the burnt limestone is cooled down by the air from outside of the lime kiln. Besides, the furnace of vertical lime kiln is at the bottom.