High Efficiency Energy Saving Cement Rotary Kiln

Technical features of ZTIC cement rotary kiln
The kiln body is made of high-quality carbon steel plates or alloy steel plates and is welded using automatic welding technology;
Wheel belts, supporting wheels and open gears are all made of alloy cast steel;
The sliding bearing adopts large clearance non-scraping bearing;
The transmission device adopts hard tooth surface reducer, elastic diaphragm coupling and DC motor;
Adopt hydraulic gear wheel;
Preheater scale sealing devices are installed at the kiln head and kiln end to ensure tight sealing of the cylinder;
Equipped with slow-turn drive.
 

Wet kiln
The early cement rotary kiln was called "wet kiln". Its basic structure is simpler than the modern improved kiln body, and the raw meal is fed in the form of slurry at normal temperature.
Wet kilns can be up to 200 meters long and 6 meters in diameter. The reason why the kiln body needs to be designed to be longer is because a large amount of water in the slurry needs to be evaporated and removed, and the heat transfer efficiency of this process is low.
The slurry used in wet kilns has a moisture content of approximately 40%, and evaporating this moisture requires a large amount of energy. Therefore, various improvements in wet processes have the core goal of reducing the moisture content of raw materials. For example, the application of a "filter press" (think of an accordion-like piece of equipment 10-20 meters long and several meters wide), this type of improved process is called a "semi-wet" process.
The reason why the wet process has been used for more than a century is that many raw materials are suitable for mixing in the form of slurry; in addition, for a long period of time, it was technically difficult to fully mix dry powder materials.
There are still many wet kilns in operation, usually with some high-tech components installed. However, new cement kilns all use the "dry" process.
 

Dry process kiln
In a modern cement plant, the uniformly mixed raw meal enters the kiln body through the preheater tower. The hot gas discharged from the kiln (usually including the cooled clinker at the end of the kiln) is used to heat the raw meal, so the raw meal has a certain temperature before entering the kiln.
The thermal efficiency of the dry process is much higher than that of the wet process for two main reasons:
First of all, the most obvious thing is that the raw material is in dry powder form and contains almost no water that needs to be evaporated;
Secondly, the heat transfer process in dry kilns is more efficient (this is relatively less intuitive).
The core equipment of this process is a heat exchanger called a "suspended preheater". It is a tower equipped with multiple sets of cyclones. The high-speed flowing hot air makes the raw meal powder suspended in the air. During this process, the temperature of the raw material continues to increase, while the temperature of the gas gradually decreases, and finally the temperature of the raw material and the gas temperature are close to the same.
The basic system of the dry process consists of a kiln body and a suspended preheater: raw materials such as limestone and shale are finely ground and mixed to form raw meal. The raw meal is input from the top of the preheater tower and passes through each group of cyclones in the tower in sequence. The hot gas discharged from the kiln and the hot air usually from the clinker cooler are sent into the cyclone, and the heat is efficiently transferred from the high-temperature gas to the raw meal.
The reason for the high efficiency of this heating process is that the specific surface area (surface area per unit volume) of the raw meal particles is large, and the temperature difference between the high-temperature gas and the low-temperature raw meal is significant. Typically, 30%-40% of the raw meal has completed the decarburization reaction before entering the kiln.
The improved version of the dry process is the "precalciner kiln", which is currently used in most new cement plants. Its principle is similar to the dry suspension preheater system, but a new burner (i.e. precalciner) is added. With the help of additional heat, 85%-95% of the raw meal can complete the decarburization reaction before entering the kiln.