As the cement becomes a building material with extremely high comprehensive utilization value, it has more and more wide applications around the world, such as metallurgy, coal mine, engineering, building materials.
At the same time, the demand of cement equipment becomes larger. Among all types of cement equipment, the kiln for cement is no doubt recognized as the core part in the cement production line.
The kiln for cement, normally called cement kiln, kiln in the cement. In the whole cement plant, after the raw meal is done from the last step, kiln for cement is used to calcine raw meal into clinker for making cement. Generally, cement kiln has a great influence on the cement quality.
For meeting different needs of cement manufacture, cement kiln with various functions are developed. Rotary kiln and shaft kiln are two main types of kiln for cement making. They are very different in shape, features, or cement manufacturing process. Next, we will introduce them one by one.
Cement rotary kiln
Rotary kiln, also called cement rotary kiln, is horizontal (slightly inclined) and do the rotary motion. The cement rotary kiln has many classifications, in general, there are dry process and wet process according to the raw meal manufacturing process, so the related rotary kiln needed in the cement production can be divided into dry process rotary kiln and wet process rotary kiln. Cement rotary kiln can also be classified by different heat exchange device in the kiln or kiln end.
| Product Specification （m） | Kiln dimensions | Motor power （kw） | Total weight （t） | ||||
|---|---|---|---|---|---|---|---|
| Diameter （m） | Length （m） | Obliquity （%） | Capacity （t/d） | Rotation speed （r/min） | |||
| Φ2.5×40 | 2.5 | 40 | 3.5 | 180 | 0.44-2.44 | 55 | 149.61 |
| Φ2.5×50 | 2.5 | 50 | 3 | 200 | 0.62-1.86 | 55 | 187.37 |
| Φ2.5×54 | 2.5 | 54 | 3.5 | 280 | 0.48-1.45 | 55 | 196.29 |
| Φ2.7×42 | 2.7 | 42 | 3.5 | 320 | 0.10-1.52 | 55 | 198.5 |
| Φ2.8×44 | 2.8 | 44 | 3.5 | 450 | 0.437-2.18 | 55 | 201.58 |
| Φ3.0×45 | 3 | 45 | 3.5 | 500 | 0.5-2.47 | 75 | 210.94 |
| Φ3.0×48 | 3 | 48 | 3.5 | 700 | 0.6-3.48 | 100 | 237 |
| Φ3.0×60 | 3 | 60 | 3.5 | 800 | 0.3-2 | 100 | 310 |
| Φ3.2×50 | 3.5 | 50 | 4 | 1000 | 0.6-3 | 125 | 278 |
| Φ3.3×52 | 3.3 | 52 | 3.5 | 1300 | 0.266-2.66 | 125 | 283 |
| Φ3.5×54 | 3.5 | 54 | 3.5 | 1500 | 0.55-3.4 | 220 | 363 |
| Φ3.6×70 | 3.6 | 70 | 3.5 | 1800 | 0.25-1.25 | 125 | 419 |
| Φ4.0×56 | 4 | 56 | 4 | 2300 | 0.41-4.07 | 315 | 456 |
| Φ4.0×60 | 4 | 60 | 3.5 | 2500 | 0.396-3.96 | 315 | 510 |
| Φ4.2×60 | 4.2 | 60 | 4 | 2750 | 0.41-4.07 | 375 | 633 |
| Φ4.3×60 | 4.3 | 60 | 3.5 | 3200 | 0.396-3.96 | 375 | 583 |
| Φ4.5×66 | 4.5 | 66 | 3.5 | 4000 | 0.41-4.1 | 560 | 710.4 |
| Φ4.7×74 | 4.7 | 74 | 4 | 4500 | 0.35-4 | 630 | 849 |
| Φ4.8×74 | 4.8 | 74 | 4 | 5000 | 0.396-3.96 | 630 | 899 |
| Φ5.0×74 | 5 | 74 | 4 | 6000 | 0.35-4 | 710 | 944 |
| Φ5.6×87 | 5.6 | 87 | 4 | 8000 | Max4.23 | 800 | 1265 |
| Φ6.0×95 | 6 | 95 | 4 | 10000 | Max5 | 950×2 | 1659 |
Wet process rotary kiln
Wet process rotary kiln is obviously applied wet process cement production. In the wet process cement production, the raw meal is made into a slurry with a water content of 32% to 40%. Since it is prepared into the fluid slurry, the raw materials are mixed well, the raw meal composition is uniform, and the quality of the fired clinker is high, which is the main benefit of the wet process production.
Dry process rotary kiln
The advantages and disadvantages of dry process rotary kiln and wet process rotary kiln are the opposite. Dry process production makes the raw meal into raw meal dry powder, and the moisture content is generally less than 1%, so it reduces the heat required to evaporate water compared with wet process production. The hollow kiln has high heat consumption due to the high exhaust gas temperature. Dry process production makes the raw meals into the dry powder, which has worse fluidity than mud. Therefore, the raw materials are not well mixed and the ingredients are not uniform.
Shaft kiln
Shaft kiln, also known as the vertical kiln, the body of shaft kiln is vertical and fixed. There are two kinds of shaft kiln: ordinary shaft kiln and machinery shaft kiln.
Ordinary shaft kiln uses hand loading and unloading, or mechanical loading and hand unloading. Mechanical shaft kiln uses mechanical loading and unloading. Mechanical shaft kiln is operated continuously, and its output, quality, and labor productivity are higher than ordinary shaft kiln. According to the technical policy requirements of building materials, small cement plants use mechanized shaft kilns to gradually replace ordinary shaft kilns.
| Size（m） | Φ3.2*11 | Φ3.3*11 | Φ3.6*11 | Φ3.8*11 | Φ4.0*11 | Φ4.2*11 | Φ5.0*11 |
|---|---|---|---|---|---|---|---|
| Capacity（t/h） | 12～14 | 14～16 | 18～20 | 23～25 | 25～28 | 28～30 | 30～35 |
| Motor Power（KW） | 22 | 22 | 37 | 37 | 37 | 45 | 55 |
| Reducer | W540 | W540 | W650 | W650 | W650 | W650 | W650 |
| Fan | ZL94WD | ZL94WD | ZL103WD | ZR7-60D | ZR7-60D | ZR-700 | ZL103WD(2) |
| Total Weight(no refractory material)(t) | 82 | 88 | 100 | 115 | 125 | 135 | 180 |
Benefits of shaft kiln
High heat efficiency
In the shaft kiln system, the material is powered from the top down, and the combustion air is powered from the bottom up. The heat carried by the high-temperature material preheats the combustion air. The process is reasonable and the heat loss is small. The discharge temperature can be controlled within the ambient temperature of +60℃, so the working principle is reasonable. The disadvantage of the traditional shaft kiln is the poor combustion conditions, because the internal calcination of the cake and the large material ball is prone to lack of oxygen and incomplete combustion. With the continuous advancement of technology, such as the further improvement of batching control technology, strengthening of the raw meal homogenization, the improvement of kiln structure, air supply method, and the small material ball can greatly reduce the water content of the material ball. The heat consumption of modern shaft kiln clinker can be controlled within (600～700)×4.18kj. In a word, shaft kiln is a device with high thermal efficiency.
The heat transfer method of cement rotary kiln is mainly radiation. The filling rate of materials in the kiln is generally only 5-17%. Most of the space is idle. Its outer surface area is large, heat dissipation is large, and heat preservation is difficult. As a thermal equipment, its thermal efficiency is not high, generally only 40%.
High resource utilization rate
The new dry-process cement production has strict requirements on raw materials. K2O, Na2, Cl- and SO3 are listed as harmful components, which makes many mineral resources unusable. But shaft kiln cement manufacturing (VSK cement plant) does not have these limitations. It will be applicable for some mineral resource that is used as waste mineral resources by new dry-process cement technologies.
