JPS6156177B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluidized fluidized kiln for firing powder raw materials such as cement or alumina, and a fluidized kiln installed below the kiln to air cool the high-temperature clinker fired in the kiln. The present invention relates to a powder raw material firing equipment that includes a cooler and a clinker discharge chute that connects the bottom of the firing furnace and the cooler.

A conventional high-temperature fluidized firing furnace has a configuration as shown in FIG. 5, for example. In FIG. 5, 21 is a high-temperature fluidized firing furnace for firing powder raw materials such as cement or alumina, 22 is a freeboard section, 23 is a dense fluidized bed section, 24 is a lean fluidized bed section,
25 is a clinker discharge chute, 26 is an arrow indicating the supply of secondary air for combustion, 27 is a burner, 28 is a raw material supply chute for supplying calcined raw materials, 29
is a fluid medium, 30 is a flow surface, and 31 is an arrow indicating an upward flow for forming a jet stream.

Then, the superficial velocity of each part is the freeboard part 2
2 is 0.8 meters per second, and dense fluidized bed part 23 is 2.4 meters per second.
meters per second in the dilute fluidized bed section 24 below.
It is 8.7 meters. In addition, in the lean fluidized bed section 24 where the flow rate is high, the clinker is literally diluted, so there is good contact between the air and the fuel, so the burner 27 is set here for combustion.

The method of charging the calcining raw material into the firing furnace 21 is that the calcining raw material collected from the pre-stage cyclone (not shown) and calcined in the calcining furnace (not shown) is fed through the raw material supply chute 28. The liquid is guided to the dense fluidized bed section 23 and placed 100 to 200 mm below the fluidized surface 30.

The reaction mechanism in the kiln 21 is that initially, crushed clinker (referred to as seed clinker) with a diameter of about 1 to 5 mm (average particle diameter 2 mm) is introduced into the kiln 21 as a fluid medium. , the temperature is raised to 1300° C. or higher, and the above-mentioned calcined raw material is introduced therein. The calcined raw material introduced in this way adheres to the liquid phase on the surface of the seed clinker,
The reaction progresses by turning itself into a liquid phase. Fluidized bed has very good heat exchange properties. It is thought that the calcined raw material at about 800°C is heated to 1300°C or higher in an extremely short period of time, and the reaction takes place.

The firing temperature is controlled at 1,300 to 1,350°C; if it is raised too high, the liquid phase ratio of the clinker in the furnace will become excessive, particles will stick to each other, and it will become impossible to flow (this is called sintering). If the temperature is lower than 1260°C, a liquid phase will not be formed on the surface of the clinker in the furnace, and the raw material will not be able to adhere to the clear in the furnace (this is referred to as poor uptake).

In this way, the calcining raw material adheres to the fluidized medium in the fluidized fluidized firing furnace 21 and grows as product clinker. Since the clinker that has reached a certain particle size is discharged from the kiln 21 through the clinker discharge chute 25, it is necessary to replenish a new medium corresponding to the clinker discharge chute 25. This replenishment medium is called nuclear clinker. That is,
During normal operation after startup, clinker grows using this nuclear clinker as a nucleus. Therefore, the relationship holds that the number of input core clinkers is equal to the number of product clinkers. In other words,
If the number of nuclear clinkers is large, the number of product clinkers will also be large, and if the amount of raw material input is constant, the product clinker will have a small diameter as a result, and conversely, if the number of nuclear clinkers is small, the product clinker will have a large diameter. In order to form a stable fluidized bed, it is necessary to input an amount of core clinker with an appropriate particle size distribution commensurate with the amount of raw material input.

As described above, it is necessary to replenish the kiln 21 with nuclear clinker commensurate with the product clinker discharged from the fluidized kiln 21 through the clinker discharge chute 25, but in the conventional fluidized kiln 21, the clinker discharge chute 25, it is not possible to classify product clinker with a particle size suitable for core clinker and return it to the firing furnace 21, so even clinker with approximately the same diameter as the core is discharged as product clinker. For this reason, as nuclear clinker, either a part of the product clinker after cooling is used, or a fine piece obtained by sieving the clinker after cooling is used.
Thermal loss was large, and the amount of nuclear clinker input had to be about 20% of the product clinker.

In order to reduce thermal loss, it is conceivable to install a sieve device directly under the clinker discharge chute 25 to return small-diameter clinker to the fluidized furnace, but since the clinker is at a high temperature, maintenance is extremely difficult. , and the equipment cost including the transportation device for returning it would be enormous, making it impractical.

In addition, in the conventional process where the fluidized fluidized furnace and the cooler are directly connected, adjusting the wind speed and layer thickness changes the heat recovery amount and temperature of the cooler, causing temperature fluctuations in the fluidized fluidized furnace and the cooler. Particle size control is difficult because it disturbs stable operation.

The present invention supplies exhaust air from a clinker cooler to a clinker discharge chute and uses it as air required in a fluidized fluidized kiln, and also forms a plurality of classification zones with different wind speeds in the chute. Of the clinker descending inside the chute, by making it function as a classifier,
The particle size suitable for nuclear clinker can be returned to the fluidized calcination furnace at high temperature, reducing thermal loss, and reducing the amount of nuclear clinker fed into the fluidized calcination furnace to approximately the same amount as the product clinker production. 5%, and even with the same air flow rate used in a fluidized fluidized furnace, the classified particle size can be adjusted over a wide range. It is an object of the present invention to provide a powder raw material firing facility that allows diameter control and stable operation of both the firing furnace and the cooler.

For this reason, the present invention provides a plurality of cooler exhaust ducts whose lower ends are connected to a clinker cooler and whose upper ends are connected in the middle of a clinker exhaust chute provided between the bottom of the fluidized fluidized kiln and the cooler. , and the connection position of each upper end of the plurality of cooler exhaust ducts to the clinker discharge chute is vertically arranged so as to form a plurality of classification zones having different wind speeds in series in the clinker discharge chute. It is characterized by being different.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention.
In the figure, 1 is a fluidized furnace for firing powder raw materials such as cement or alumina, 2 is a cooler for air-cooling the high-temperature clinker fired in the furnace 1, and 3 is the bottom of the furnace 1. A clinker discharge chute connected to the cooler 2, 4 a rotary feeder installed at a relatively lower part of the chute, and supplying an appropriate amount of clinker in the chute 3 to the cooler 2 while acting as a gas seal; 5 a rotary feeder; A powder raw material supply device attached to the kiln 1, 6 a kiln burner, 7 a kiln exhaust pipe, 8 a fan for supplying air to the cooler 2, and 9 cooled from the cooler. This is a clinker extraction device that takes out clinker. A first cooler exhaust duct 10 has a lower end connected to the cooler 2 and an upper end connected halfway to the clinker exhaust chute 3. Reference numeral 11 designates a second cooler exhaust duct, which is also connected to the cooler 2 at its lower end and to the clinker exhaust chute 3 at its upper end. Moreover, the connection position of the upper end of the first cooler exhaust duct 10 to the clinker discharge chute 3 is higher than the connection position of the upper end of the second cooler exhaust duct 11 to the clinker discharge chute 3. Further, 12 is a first air volume adjustment damper provided midway through the first cooler exhaust duct 10, and 13 is a second air volume adjustment damper provided midway through the second cooler exhaust duct. Furthermore, 14 is a first classification zone formed in the chute 3, and 15 is a second classification zone, which will be described later.

In the powder raw material firing equipment configured as shown in FIG. 1, high-temperature exhaust from a cooler 2 is used as the fluidizing air and hot firing air required in the fluidized fluidized firing furnace 1. In other words, the cooling air pressurized by the fan 8 cools the high-temperature clinker in the cooler 2 and becomes high temperature, and the exhaust air is discharged from the cooler 2.
From there, it passes through the first cooler exhaust duct 10 and the second cooler exhaust duct 11 in parallel, rises inside the clinker discharge chute 3, and is fed to the fluidized fluidized kiln furnace 1. Therefore, the high-temperature exhaust gas becomes an upward airflow in the clinker discharge chute 3, and when the clinker fired in the fluidized fluidized furnace 1 descends in the chute 3, it is classified by the upward airflow. The clinker discharge chute 3 will also serve as a classifier. Moreover, since the connection position of the upper end of the duct 10 to the chute 3 is higher than the connection position of the upper end of the duct 11 to the chute 3, the air volume in the second classification zone 15 is lower than that in the duct 11. However, the air volume in the first classification zone 14 is the sum of the air volume passing through the ducts 10 and 11. Therefore, the air volume of the updraft in the first classification zone 14 is equal to the air volume in the second classification zone 15. It is larger than the air volume of the updraft.

Therefore, for example, by adjusting the second air volume adjustment damper 13 to adjust the air volume supplied from the duct 11 to the second classification zone 15,
5 is the fluidization start speed of the target particles, and while considering the air volume supplied from the duct 11, the air volume supplied from the duct 10 to the first classification zone 14 is adjusted to the first The air velocity in the first classification zone 14 is made to be slightly lower than the terminal velocity of the target particles by adjusting the air volume damper 12 or the like.

Then, first, the particle group in the fluidized bed of the fluidized fluidized firing furnace 1 falls into the first classification zone 14, where the air from the duct 10 crosses the particle group and diffuses it, at the same time separating microparticles finer than the separation target particles. Most of it is returned to the firing furnace 1 on the airflow from below. That is, since the wind speed of the ascending air current in the first classification zone is set below the terminal velocity of the target particles, the first classification is performed here. At this time, some of the microparticles fall into the second classification zone 15 together with the target particles, but here they are further transformed into microparticles by riding on the updraft whose wind speed has reached the fluidization start speed and becoming the target particles. It is separated into two, pushed up to the first classification zone 14, and returned to the fluidized calcination furnace 1 on the air current. That is, second classification is performed by the second classification zone 15, and target particles resulting from this classification can be supplied to the cooler 2. In other words, the upper part of the classification zone in the clinker discharge chute 3 is the first classification zone 14, and the lower part is the second classification zone 15. By flowing this air, small-sized particles (2 mm or less), including those suitable for nuclear clinker, are prevented from falling and returned to the fluidized fluidized kiln 1. However, since the clinker in the fluidized bed is violently flowing as a mass, some of the small particles are not classified and fall into the second classification zone 15 along with the large particles. Therefore, the second classification zone 15
The system has a function of returning particles smaller than the target particle diameter to the first classification zone 14 by flowing an amount of air corresponding to the fluidization start speed of the target particle diameter.

In addition, the passage cross-sectional area of the chute 3 and both exhaust ducts 10 and 11 and the fan 8 are adjusted in order to satisfy the air volume required by the fluidized firing furnace 1 and the above-mentioned wind speed in each zone 14 and 15. If the capacity is designed in advance, there is no need to provide both dampers 12 and 13.

FIG. 2 shows a second embodiment of the present invention.
The first embodiment is an overflow shot 1.
6 and rotary feeder 17 with gas sealing properties
The only difference is that a is provided, and the rest is exactly the same, so a detailed explanation will be omitted.

FIG. 3 shows a third embodiment of the present invention.
The fluidized firing furnace 1 is provided with a wind box 18, and the wind box 18 and the cooler 2 are connected by a third cooler exhaust duct 19.
Further, a third air volume adjusting damper 20 is provided in the middle of the duct 19. Therefore, the classification action in the clinker discharge chute 3 is the same as in the first and second embodiments, but the amount of air supplied to the fluidized fluidized kiln 1 is increased from the clinker discharge chute 3. In addition to the airflow, the amount of air passing through the exhaust duct 19 is also added.

FIG. 4 shows a fourth embodiment of the present invention.
The third embodiment is an overflow shot 1.
6 and rotary feeder 17 with gas sealing properties
and the flow passage cross-sectional area of the portion of the clinker discharge chute 3 forming the second classification zone 15 is the same as that of the first
The only difference is that the cross-sectional area of the flow path is larger than that of the portion forming the classification zone 14.

As described above, the present invention provides a plurality of cooler exhausts whose lower ends are connected to a clinker cooler and whose upper ends are connected in the middle of a clinker exhaust chute provided between the bottom of the fluidized fluidized kiln and the cooler. Equipped with a duct,
Further, the upper end portions of the plurality of cooler exhaust ducts are connected to the clinker discharge duct at different positions in the upper and lower positions, so that a plurality of classification zones having different wind speeds are formed in series in the clinker discharge chute. Therefore, in the upper classification zone of the chute, by flowing air at the terminal velocity of the target particle size for classification, the falling clinker, including those with a particle size suitable as nuclear clinker, is transferred to the fluidized fluidized kiln. It is possible to return the core clinker to a high temperature, reducing thermal loss, and as a result of experiments, it has become possible to reduce the amount of nuclear clinker fed into the fluidized fluidized kiln to about 5% of the production amount of product clinker. Moreover, even with the same air volume used in a fluidized fluidized furnace, the chute can function as a classifier, allowing the classified particle size to be adjusted over a wide range, and keeping the air velocity and layer thickness constant in the furnace. Since particle size can be controlled without any change, stable operation of both the fluidized fluidized kiln and clinker cooler is possible. Furthermore, since the classification is carried out by the exhaust air from the cooler, heat recovery is good, and even if there is a slight change in air volume, there is little effect on the temperature of the fluidized kiln as a disturbance.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention.
The figure is an elevational view of the first embodiment, Figure 2 is an elevational view of the second embodiment, Figure 3 is an elevational view of the third embodiment, Figure 4 is an elevational view of the fourth embodiment, FIG. 5 is an elevational view of a conventional fluidized fluidized kiln. DESCRIPTION OF SYMBOLS 1... Fluidized firing furnace, 2... Cooler, 3... Clinker discharge chute, 10... First cooler exhaust duct, 11... Second cooler exhaust duct, 14... First classification zone, 15... ...Second classification zone.

Claims (1)

[Claims] 1. A fluidized fluidized firing furnace for firing powder raw materials, a cooler provided below this firing furnace to air-cool the high-temperature clinker fired in the firing furnace, and a bottom of the firing furnace connected to the cooler. In a powder raw material firing equipment equipped with a clinker discharge chute,
A plurality of cooler exhaust ducts are provided whose lower ends are connected to the cooler and whose upper ends are connected in the middle of the clinker discharge chute, and a plurality of classification zones having different wind speeds are formed in series in the clinker discharge chute. A powder raw material sintering equipment characterized in that the connection positions of the upper end portions of the plurality of cooler exhaust ducts to the clinker discharge chute are vertically different.