Rotary kiln preheater is one of main engines of active lime equipment, main foundation of which is convey limestone materials sent from the upper part into the preheater and at the same time preheat materials evenly to about 900℃ in the preheater by high temperature waste gas (1150℃) exhausted from kiln after calcination. There is 30% of CaCO3 degradation in the preheater in the process of preheating and then it will be pushed into rotary kiln to calcine by hydraulic push rod, which can not only shorten calcination time, but also produce the lime with high activity.
According to the operating principle of lime rotary kiln preheater, limestone is partially decomposed at finishing the drying and heating. When limestone particles enter into the lime rotary kiln and don’t contact with high temperature zone of the flame yet, under the effect of convective heat transfer of waste gas heat, degradation is still on. That is to say, this stage is actually refers to material decomposition stage theoretically.
The so-called firing or firing stage in the lime rotary kiln refers to limestone particles after preheating from contacting with flame radiation heat transfer to before passing through flame radiative zone in the lime rotary kiln. Under the effect of high temperature of the flame, limestone particles complete chemical reaction and finally are burned to lime. This process (stage) is often finished in 30-40 minutes.
On the rotary kiln equipped with rotary kiln preheater, firing area is often set up about 10 meters from the back of the discharge end of the Rotary lime kiln and extended 20-25 meters to lime rotary kiln (feed end). Flame length is generally distributed in this area, which is so-called firing zone.
The calcination process in the rotary kiln is composed by many stages, among which is interdependence, interplay, interaction and constantly changing. Thus, there is no district boundaries for the division of firing zone or other “zones” of the rotary kiln.
3. Rotary kiln cooler
After high heat lime particles entering into the rotary kiln cooler, heat dissipation and heat exchange transfer are carried out at penetration of secondary air and lime particles are forcibly cooled below 100℃.
The cooling of the lime clinker in the cooler is generally finished in 40 minutes, the main purpose of which is to realize the characteristics of “quench” of active lime to prevent that lime clinker continues to react under high temperature after taking out of rotary kiln and leads to crystal growth and the change of active property. “Quench” is good for high yield, transportation and storage. Through the rapid transmission of material waste heat, high-quality high temperature combustion air can be obtained.
Anyway, in the calcination system of the lime rotary kiln equipped with rotary kiln preheater and rotary kiln cooler, the relationship among preheating, calcination (firing) and cooling is always interplay, interaction and interdependence. Material is preheated in the preheater, while 25% of decomposition rate is required at the same time, which is the base to finish the calcination. Material can be calcined to high-quality lime product in the good calcination environment in the lime rotary kiln and quench cooling of material is finished in the cooler.
Great Wall Machinery accepts 200-1500t/d active lime production line contracting project, with the ability to provide research report, design, equipment, civil engineering, installation and debugging. Great wall machinery can provide standard one-stop“turnkey project” service for customers.