JPS59131878A - Rotary kiln for baking cement raw material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotary kiln structure in which a suspension preheater is connected to the raw material end, and in particular aims to optimize the granulation action within the kiln, thereby reducing the amount of fine clinker and lump clinker. This invention relates to a rotary kiln designed to increase the amount of rice granule clinker with appropriate precision by reducing the amount of clinker.

FIG. 1 shows an example of a firing apparatus used for preheating and firing cement raw materials. This apparatus mainly includes a suspension preheater 1 formed by vertically arranging cyclones C1 to C4 for preheating raw materials and a calcining furnace 2, a rotary kiln 3 for firing clinker, and a clinker cooler 4.

In such a clinker firing apparatus, the raw material powder A that descends sequentially through cyclones 01 to C3 is gradually preheated by the hot air that is sucked in by the exhaust gas induced draft fan 8 and ascends through the gas duct 7. It is supplied to the calcining furnace 2. In the calcining furnace 2, high-temperature air from the clinker cooler 4 is introduced through the bleed air duct 13, and fuel for calcining is supplied from the burner 6a, and the raw material powder A is calcined by receiving this heat. be done. The calcined raw material enters the lowermost cyclone C4 and is then introduced into the rotary kiln 3 via the connection housing 12.

High temperature air from a clinker cooler 4 and firing fuel from a burner 6b are introduced into the rotary kiln 3, and the clinker that has been fired at high temperature is discharged to the cooler 4. The discharged clinker is transferred through the ventilation grid 141- of the cooler 4, where it is cooled by cold air sent from the forced air blower 10, crushed by the crusher 15, and transported to the next culm by the conveyor 16, etc. be done. Further, the excess air in the clinker cooler 4 is sucked by the induced draft fan 9, and the fine clinker dust contained therein is removed by the dust collector 1.
7 and combined into finished clinker.

A rotary kiln using such a cement raw material firing method has many advantages compared to other firing methods, such as a larger throughput per kiln internal volume and a longer lifespan for the refractory lining for the kiln body.

However, on the other hand, the clinker fired in a kiln using this method has a wide range of particle sizes, and in addition to granular clinker with an appropriate particle size, it also contains larger amounts of large-diameter lump clinker and fine-grained clinker compared to other firing methods. Based on this, we will evaluate the performance of the firing process and the subsequent crushing process, and the quality of the finished product.
This has caused various problems in terms of IT.

The reason why the particle size range of clinker increases as described above in a rotary kiln connected to a suspension pre-chiller is considered to be as follows.

In other words, cement raw materials contain lime (CaCO3) as the main component.
), silicic acid content (S i 02 ), alumina content (A6
203) and iron oxide (Fe203), and the lime component is calcined prior to the clinker formation reaction to form quicklime (Ca
b).

The cement raw material, which has been preheated and partially calcined in the suspension preheater as described above and heated to 800 to 900'C, is then fed into the rotary kiln, where it is heated in a cascade motion toward the exposed end. Heats up while moving.

In this way, the angle between 120° and 13° near the middle of the kiln
A part of the raw material powder that reached the temperature range of 00°C culm melted and changed into a liquid phase and underwent granulation, and the maximum temperature reached 145°C.
The granules continue to grow in the firing zone on the first side of the kiln, which reaches a culm degree of 0°C.

Iron oxide in cement raw materials has a relatively low melting temperature.
It plays the role of a solvent during the clinker granulation and formation reaction described above.

In a rotary kiln connected to a suspension breheater, the processing capacity of the kiln is large, so the material movement speed in the axial direction of the kiln is set to be faster. is getting wider.

When the granulation effect is performed in such a wide granulation area, the melting of iron oxide as a solvent is promoted in the upstream part of the granulation area when viewed in the flow direction of the raw material, and the granulation effect is improved in this area. However, since a large amount of iron oxide is consumed in the initial granulation, the latter half (downstream part) of the granulation region is
In this case, the iron oxide content in the unreacted raw material powder is relatively insufficient,
Good granulation cannot be performed, and many large-diameter lumpy clinkers enlarged by the initial granulation and fine granular clinker left behind from the granulation are formed, resulting in fine particles with an intermediate appropriate particle size. The whipping of granular clinker will be relatively reduced. The tendency toward earthworks is particularly noticeable in rotary kilns connected to suspension breheaters with a calciner, which have a large processing capacity per kiln internal volume.

In this respect, the shape of the conventional rotary kiln in which the suspension breheater is connected to the first end of the raw material is mainly
A straight cylindrical body 20 as shown in Figure 2(a) is used, and there is a kiln 23 in which the diameter of the body 2I at the large end is larger than that of the outlet side body 22 (see Figure 2(b)). Or, conversely, a kiln 26 in which the diameter of the outlet side body 24 is larger than the diameter of the inlet side body 25 (see FIG. 2(c)), or even a second
Kilns with different diameters, such as a kiln 30, in which the diameters of the bodies on the inlet side 27 and the outlet side 28 are larger than those of the intermediate body 29, as shown in FIG. 3(d), are used or proposed. However, these shapes lack the ability to actively control the granulation action within the kiln, and it has not been possible to optimize the particle size range of the obtained clinker.

Therefore, in addition to the various functions of the conventional rotary kiln, the purpose of the present invention is to focus on the function of granulating raw materials within the kiln, which has not been considered much in the past, and to provide a special shape to the kiln body. The aim is to improve quality and performance in the cement manufacturing process by creating suitable granulation conditions in the granulation zone and forming a large amount of granular clinker with relatively uniform accuracy. Focusing on the fact that the above-mentioned drawback in terms of accuracy range in a conventional rotary kiln having a kiln at the raw material end is due to the expansion of the granulation area, the kiln is constructed so that the granulation operation is completed in a relatively narrow area in the axial direction of the kiln, This is intended to alleviate the situation in which unreacted raw material powder with a relative lack of iron oxide remains on the downstream side of the granulation region, and to limit the particle size of the clinker to an appropriate width.

FIG. 3(a) shows a side view of a rotary kiln according to an embodiment of the present invention. Raw materials are fed into the kiln from the left end of the diagram. As is clear from the figure, the kiln body Ka has an enlarged body part 31 in the middle part thereof, which has a larger diameter than the front and rear body parts, and this enlarged body part 31 expands in the direction in which the raw materials in the kiln flow. It is constructed by connecting a tapered enlarged part 32 that extends in diameter and a tapered reduced diameter part 33 that reduces its diameter in the same direction, and the arrangement position of this enlarged body part 31 in the kiln axial direction is determined by the diameter of the kiln. The temperature region is defined as a granulation region, which is a temperature region in which a granulation action is given to the raw material powder that is supplied from the end and moves downstream while being heated.

The phenomenon of granulation in the enlarged body as shown in letter L will be explained below.

When we experimentally observed the cascade motion of raw materials containing particles of various diameters in a rotating cylindrical shell on a cross section perpendicular to the cylinder axis, we found that *■ granular raw materials transfer and fall near the surface of the layer, and reach the top of the raw material layer. It sinks into the bottom and is carried near the cylinder wall as the cylinder rotates, leaving a trace that appears on the surface of the raw material layer at the highest position, but fine grained or powdered raw materials are left in the center or bottom of the layer. Therefore, the raw material that has reached the enlarged body part 31 is moved in the kiln axial direction by the reduced diameter part 33, which has a steeper slope than the enlarged diameter part 32. The flow is Iil+l-, where it undergoes a granulation action, and as the particle size gradually increases, it moves near the surface of the raw material layer, and only the phase particles with an appropriately developed particle size move to the enlarged body 3.
1, the rivulet and powdered raw materials with undeveloped particle sizes are blocked by the weir + I = weir + I = impeded from advancing downstream. The powder is mixed with the powdered raw material that continuously flows into the expanded body, and granulation is performed.

Due to such a granulation mechanism, only *■ granular raw materials whose particle size has developed beyond a certain level are transferred from the weir formed by the diameter-reduced portion 33 to the subsequent firing zone, where they become clinker and become fine granules and powder. The shaped raw material is dammed up by the reduced diameter section and remains there to continue granulation activity, so the amount of fine clinker in the firing zone decreases, and the coarse grained raw material is also reduced downstream of the expanded body section (calcination zone). Since there is no powdery raw material in the surrounding area, the clinker cannot grow further and become larger, and therefore the amount of lumpy clinker decreases, and in this way, it is possible to form a large amount of granular clinker with relatively uniform particle size. be.

Regarding the shape of the enlarged body part, if the slope of the reduced diameter part is steeper to some extent, the effect of the weir 11 will be greater. Also, compared to forming a weir by providing an annular refractory protrusion along the inner circumference of the fuselage, the weir is formed by a reduced diameter part of the enlarged body part, which is an enlarged part of the fuselage. The structure of the refractory lining is stable, and no extra pressure loss occurs in the passing gas.

The position of the enlarged body in the axial direction of the kiln is selected in accordance with the position of the granulation region, which varies depending on the type of suspension preheater and, therefore, the degree of calcination of the raw material powder supplied to the kiln. For example, a rotary kiln equipped with a suspension preheater with a calcining furnace has an enlarged body closer to the inlet side of the kiln than a suspension preheater without a calciner.

In an actual kiln, the position of the granulation area moves slightly in the direction of the kiln axis depending on various dyeing industry conditions, so when designing the kiln, it is necessary to take into account fluctuations in the operating conditions. As shown, it is desirable to provide a plurality of enlarged body portions 31, 31, . . . in the 0 direction of the kiln axis. Also, the amount of powder raw material that stays in the expanding body is il! It is also possible to increase the volume of the enlarged body part 31 by providing a parallel body part 34 as shown in FIG. The front and rear torsos connected to the enlarged torso have different diameters,
Furthermore, it is also possible to combine a weir with an annular projection with an enlarged body, and these degree of design changes are within the scope of the present invention.In the embodiments described above, the rotary kiln according to the present invention is There are no restrictions on the type of suspension preheater and calciner, or the type of clinker cooler. For example, even if a vertical packed bed type cooler is used, the clinker particle size range is narrow, so the cooling air There are no operational problems such as drifting of the flow, and as a result, it is possible to reduce fuel consumption in the firing process.

As described above, the present invention provides a rotary kiln for firing cement raw materials 1 in which a suspension preheater is connected to the raw material end side, which has a tapered enlarged diameter part and a tapered diameter part in the granulation area in the middle of the kiln body. Or, since it is a rotary kiln for firing cement raw materials, which is characterized by forming two or more enlarged barrels, fine grained or powdered raw materials are particularly produced among the raw materials supplied into the rotary kiln from the suspension preheater. Enlargement provided in the grain area) 111
＊■
Since the raw material becomes granular and is sent to the firing area, the amount of fine grain or powdered clinker in the clinker obtained is reduced, and since there is less powdered raw material in the firing area that causes granulation, no further The granulation effect of 1- did not occur, the amount of clumpy clinker was reduced, and a large amount of granular clinker with relatively uniform precision was successfully formed.

[Brief explanation of drawings]

Figure 1 is a process diagram showing an example of a firing device used to preheat and fire cement raw materials, and Figures 2 (a) to (
d) is a side view showing the schematic shape of a conventional rotary kiln, and FIGS. 3(a) and 2(b) are side views showing the schematic shape of a rotary kiln according to an embodiment of the present invention, respectively. . Ka...kiln body, 31...enlarged body 32
... Expanded diameter section, 33... Reduced diameter section 34...
Parallel torso. Applicant Kobe Steel Co., Ltd. Agent Patent Attorney Takeyu Honjo 3 Figure 1, upper t

Claims (1)

[Scope of Claims] 1. A rotary kiln for firing cement raw materials in which a suspension preheater is connected to the raw material end side, which has a tapered enlarged diameter part and a tapered diameter part in the granulation region in the middle of the kiln body. Or a rotary kiln for firing cement raw materials, characterized in that two or more enlarged barrels are formed. 2. The rotary kiln for firing cement raw materials according to claim 1, wherein the slope of the reduced diameter portion is steeper than the slope of the expanded diameter portion.