JPH0672035B2 - Method and apparatus for manufacturing ultra-light aggregate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method and an apparatus for producing an ultralight aggregate used for construction and civil engineering.

(Prior Art and Problems Thereof) In recent years, the number of apartments has been increasing due to deterioration of living environment and changes in housing conditions. As a structural material for such a building, a material having a low thermal conductivity, an excellent dew-proof property, and a high sound-insulating property is desired, and ultra-lightweight concrete is widely used.

Aggregate raw materials for ultra-lightweight concrete include perlite and leucite. All of them can be heated, fired and foamed to obtain an ultra-lightweight aggregate, but these materials have low compressive strength and are not very suitable as an ultra-lightweight aggregate.

Effervescent shale, clay, slate, coal ash, etc., foam when heated to high temperatures to make them lighter and become ordinary lightweight aggregates (apparent specific gravity 1.2 to 1.3), but with an apparent specific gravity of 0.8 or less. It is difficult to make a lightweight aggregate and cannot be mass produced. The reason is that if the raw materials are fired at a high foaming temperature necessary to make them ultra-lightweight aggregates, the phenomenon of fusion of particles to each other or to the furnace wall occurs during the firing, so Because it has to be fired at a low temperature.

Conventionally, in order to produce a lightweight aggregate having a specific gravity of 1 or less, a rotary kiln is prepared by adding a foaming auxiliary material such as carbon, iron oxide or silicon carbide to a raw material such as expandable shale, clay, coal ash and slate. Alternatively, it is known to produce it on a research test scale by firing and foaming in a fluidized kiln or the like. However, even in this conventional method, since the fusion of the raw material particles during the firing and the fusion of the raw material particles to the furnace wall are likely to occur, the firing temperature cannot be increased so much that the resulting lightweight aggregate The apparent specific gravity is at most 0.9 to 1.0, and it is difficult to obtain a lightweight aggregate having a lower apparent specific gravity.

(Problem of the invention) It is an object of the present invention to provide a method and an apparatus for producing an ultralight aggregate having an apparent specific gravity of 0.8 or less in an industrially advantageous manner.

(Means for Solving the Problems) The present inventors have completed the present invention as a result of intensive studies to solve the above problems.

That is, according to the present invention, when the powdery raw material is molded into a constant shape and the bulk raw material is supplied to the rotary kiln for firing and foaming, the kiln main body of the rotary kiln is preliminarily sequentially fed from the raw material supply side with a small diameter portion and a slope. Steps and large-diameter parts are configured to preheat in the small-diameter part, remove powder in the raw material and add anti-fusion agent in the small-diameter part, and then expand and foam at high temperature in the large-diameter part. There is provided a method of manufacturing an ultralight aggregate characterized by:

Further, according to the present invention, a raw material tank containing powdered shale, clay, coal ash, etc., a binder tank containing a forming aid such as a binder, and these are mixed to form a lumpy raw material of a certain shape. It consists of a hardening device and a rotary kiln for firing and foaming this lumped raw material.
The kiln main body is formed in advance with a small diameter part, an inclined stepped part, and a large diameter part in order from the raw material supply side in advance, the tip is located at the large diameter part and the combustion burner, and the small diameter part is sequentially provided from the raw material supply side. The device for removing powder in the feedstock and the anti-fusing agent charging device are arranged by adding a mechanism for opening the communication passage of the peripheral surface of the small diameter part according to the rotation of the kiln main body, and the inside of the kiln main body is always An ultra-lightweight aggregate manufacturing apparatus configured to be shielded from the outside air is provided.

The lump raw material used in the present invention is composed of an expandable inorganic lump molded product which causes foaming when heated at a high temperature. As the expandable inorganic material that is a lumpy raw material, any one that has been conventionally generally used as a raw material for producing a lightweight aggregate may be used.
Examples of such a material include shale, clay, coal ash, and slate. In order to obtain a lumpy raw material from the raw material inorganic material, a molding aid such as a binder or water may be added to the powdery raw material inorganic material, and the raw material inorganic material may be molded into a desired shape using a molding machine such as a pelletizer or an extrusion molding machine. The shape of the bulk raw material can be spherical, pellet-shaped, columnar, etc.,
Its size is usually about 2.0 to 20 mm.

In order to produce an ultralight aggregate according to the present invention, a rotary kiln configured in a small diameter portion, an inclined step portion and a large diameter portion in order from the raw material side is introduced, and the massive raw material is introduced into the preheating zone of the small diameter portion, and 600 ° C. The temperature range above which foaming does not occur, usually 600 to 90
It preheats to the temperature of 0 degreeC, and removes the inorganic powder contained in it from the obtained preheated material. When the lump raw material is introduced into the small diameter portion and heated, inorganic powder is generated due to the frictional force between the lump raw materials and the like.

According to the studies by the present inventors, it was found that this inorganic powder promotes mutual fusion of the bulk raw material foams and fusion to the furnace wall when the bulk raw material is heated to its foaming temperature. It was Therefore, in the present invention, the inorganic powder contained in the preheated material of the small diameter portion is removed before it is introduced into the large diameter portion.

The preheated material from which the inorganic powder has been removed is added with an anti-fusion agent and introduced into the foaming heating zone of the large diameter portion, where the bulk raw material is heated to the foaming temperature to form a foamed material. The heating temperature in the foaming heating zone is 1000 ° C. or higher. The upper limit of the foaming temperature is the temperature at which the foams do not fuse with each other,
The specific temperature is different depending on the type of raw material, the type of anti-fusion agent and the addition amount, and cannot be uniquely determined,
Usually, it is about 1100 to 1200 ° C.

As the anti-fusing agent, an inorganic powder having high fire resistance that does not fuse at the foaming heating temperature is used. Examples of such materials include refractory clay powder, clay chamotte powder, silica stone powder, and alumina powder. The amount added is usually
The ratio is 2 to 10 parts by weight with respect to 100 parts by weight of the raw material aggregate.

The atmosphere in the rotary kiln used in the present invention is preferably a reducing or low oxidizing atmosphere having an acidity concentration of 5 vol% or less, preferably 0 to 3 vol%, together with the preheating zone and the foaming zone. By maintaining the heating atmosphere in such a reducing or low-oxidizing atmosphere, oxidation of the raw material is prevented,
It is possible to promote foaming of the raw material aggregate.

An embodiment of the apparatus according to the present invention will be described with reference to the drawings. In the overall view of FIG. 1, reference numeral 1 is a raw material tank, which contains powdery shale, clay, coal ash, etc. as described above. Reference numeral 2 denotes a binder tank, which contains a molding aid such as a binder. These are mixed and conveyed through a screw conveyor 3, made into a water-wet powder by a kneading machine 4, formed by a granulator 5, dried by a dryer 6, and powder components are removed by a vibrating screen 7. , Sent to rotary kiln as required raw material.

The kiln main body 8 of the rotary kiln has a small diameter portion a, an inclined step portion b, and a large diameter portion c from the raw material supply side toward the fired product discharge side.
The front end of the raw material supply side is sealed with the furnace hood 9 and the fired product discharge side is sealed with the front hood 10, and is supported by the receiving and supporting rollers and rotated at a low speed. The front hood 10 is provided with a combustion burner 11 with its tip positioned in the large diameter portion c, and the fired product is taken out from the lower end of the front hood 10 and cooled by a double damper cooler 27. Also, the burning smoke is the furnace hood 9
After the dryer 6 is heated, the dust is removed by the bag filter 13 and discharged from the exhaust stack (chimney) 14.

Further, in the rotary kiln according to the present invention, the kiln main body 8 has a stepped shape of a small diameter portion a and a large diameter portion c, and a powder removing device 15 and a melting device for removing the powder in the enclosed raw material on the peripheral surface of the small diameter portion. The anti-adhesion agent charging device 16 is attached so that the powders can be removed and the anti-fusion agent can be supplied directly in the small diameter portion a.

That is, the internal structure of the kiln main body 8 to which each of the above devices is attached will be described with reference to FIG.
The purpose is to remove pulverized powder (which serves as a fusion promoter in the high temperature zone) when the bulk material is fed into the kiln and moved inside the kiln.
It is installed at a position of ~ 700 ℃. As is clear from FIGS. 3 (A) and 3 (B), this device forms a part of the peripheral surface of the kiln main body 8 on a sieving surface by a wire net 17, and the powder is passed through the wire net 17 by rotation and the kiln main body 8 is rotated. A ring-shaped cover 18 that is discharged from the inside and that is in sliding contact with the outer surface of the kiln main body 8 while covering this portion is fixed to the base as a take-out port 19. A water cooling pipe 20 is provided at the outlet 19 and the outside air is prevented from entering as much as possible through the rotary valve 21. The inner diameter of the kiln a of the wire net 17 is
40 cm (kiln a length of 1.256 m), width 30 cm, length
It is a metal wire mesh with a heat resistance of about 40 cm, and the removal powder receiving port and cover are made of a heat resistant material to prevent air intrusion (when rotating, the asbestos band of the receiving port and the cover asbestos band rub) . As the heat resistant material, inorganic fibers such as alumina fibers and asbestos fibers are used. Since the pressure inside the kiln main body 8 is positive, practically no outside air enters.

Next, as shown in FIGS. 4 (A) and 4 (B), the anti-fusion agent feeding device 16 has a semi-circular curved pipe on the outer peripheral surface of the kiln main body 8.
While 22 is fixed, one side of this curved pipe 22 is formed as an outlet 23 and one side is formed as a charging port 24, and a fusion preventing agent is charged at the upper part of the charging port by rotation of the kiln. The anti-fusing agent drops in the tube as it rotates, and the outlet of the tube is sprinkled onto the agglomerate raw material particles in the kiln at the upper part. As a result, the raw material particles are sprinkled with the anti-fusion agent and no fusion occurs. The curved pipe 22 is provided with an openable damper 25 at the inlet of the pipe to prevent air from entering the furnace from the outside, and the flexible damper is opened when the anti-fusing agent is charged and when it is sprayed in the furnace. Like In order to add the anti-fusing agent to the inlet of the tube during rotation of the kiln, a fixed-quantity feeder 26 is installed above the anti-fusing agent feeding position (see Fig. 1), and the contact rod attached to the outer wall of the kiln rotates the feeder during rotation. By contacting the limit switch 26, the fixed-quantity feeder 26 operates and feeds the anti-fusing agent into the inlet 24 of the tube. The anti-fusing agent charging device is installed at a position where the furnace temperature is 800 to 900 ° C. As described above, as the anti-fusing agent, usually, refractory clay powder, clay chamotte powder, silica stone powder, alumina powder, etc. are used.

Next, 27 shows a cooler with a double damper (see FIGS. 1 and 2). This cooler is provided at the lower end of the furnace front hood 10, and the firing products are taken out by the upper and lower dampers 28, 29 in order to prevent outside air from entering the furnace. That is, when the cooling tank 27 is filled with the baked product, the upper damper 28 is closed, the lower damper 29 is opened, and the baked product is discharged to the outside of the furnace. When the discharge is completed, the lower damper 29 is closed and the upper damper 28 is opened. The device is motorized and is operated by a timer. Further, since the fired product is in a high temperature state, a water-cooled tubular type cooling device is provided from inside or outside the cooling tank to cool the fired product.

(Effects of the Invention) As described above, in the rotary kiln of the present invention, since the kiln main body 8 is formed in the small diameter portion a and the large diameter portion c, the raw material is rapidly preheated in the small diameter portion a and the next large Diameter c
At the time of heating at a high temperature in, heat foaming can be performed. Also, do not touch the flame of the firing burner,
The fusion of particles is prevented and the powder removing device 15
Is provided so that the powder is actively excluded. The length of the kiln main body 8 is 1 for the inner diameter in front of the furnace (fired material discharge port),
It should be 10-12. Mainly in the kiln, the inner diameter of the small diameter part a
In the case of 1m, the length is 7m to 8m, and the inner diameter of the large diameter part c is
It can be 1.5 m long and 3-4 m long.

Further, in the rotary kiln of the present invention, the anti-fusing agent is directly charged in the kiln main body 8 so that it is efficient. In other words, the conventional method for introducing anti-fusion powder in the kiln is
There is known a method of charging from the bottom of the furnace with a mass of raw material, and a method of charging from the front of the furnace.However, in the case of, in the case of, the abrasion powder of the mass of raw material becomes a mixed powder and the fusion preventing effect is low, It is possible to use the anti-fusion agent. in the case of,
This method is also ineffective because it is skipped by the gas velocity of the combustion burner. According to the method of the present invention, it is possible to put in the optimum kiln temperature position. Further, by carrying out the charging into the kiln at a position where it touches the lumpy raw material, it is possible to prevent the fusion preventing agent from being spread over the gas flow rate.

Next, the apparent specific gravity of the fired product fired under various firing conditions is displayed.
Shown in 1.

Conditions (Experiment No. 1-4) Raw material: Expanded shale, Forming: Pelletizer, Particle size: 9-10m /
m, anti-fusing agent: clay chamotte 3%, firing time: 40 minutes,
Processing amount: 40 kg / h, kiln: small diameter part; inner diameter 40 cm, length 4 m,
Large diameter part; inner diameter 60 cm, length 2 m.

As shown in Table-1, in Experiment No. 2, it was possible to obtain an ultralight aggregate with an apparent dry specific gravity of 0.5.

The apparent specific gravity of the fired product obtained by firing the same molded product in a general-purpose kiln (without powder removal, fusion prevention, and oxidation prevention equipment, straight diameter kiln) was 1.2 to 1.3.

The maximum firing temperature is the maximum temperature as long as the fusion phenomenon between the grains does not occur under each condition. That is, above this temperature, fusion occurs and firing operation is not possible.

[Brief description of drawings]

The drawings show an example of the apparatus according to the present invention. Fig. 1 is an overall system diagram, Fig. 2 is a side sectional view of a rotary kiln,
3 (A) and 3 (B) are a front sectional view and a side sectional view of the powder removing device, and FIGS. 4 (A) and 4 (B) are a front sectional view and a side sectional view of the anti-fusion agent charging device. 1 ... Raw material tank, 2 ... Binder tank, 4 ... Kneader, 5 ... Granulator, 6 ... Dryer, 8 ... Kiln main unit,
a: small diameter part, b: inclined step part, c: large diameter part, 9 ...
Furnace bottom hood, 10 ... Front furnace hood, 11 ... Combustion burner,
15 …… Powder removing device, 16 …… Fusing prevention agent feeding device, 17…
… Wire mesh, 18 …… Cover, 22 …… Curved pipe.

Claims (2)

[Claims] 1. A lump-shaped raw material obtained by molding a powdery raw material into a fixed shape is supplied to a rotary kiln for firing and foaming, and the kiln main body of this rotary kiln is preliminarily sequentially from the raw material supply side to a small diameter portion and an inclined step portion, It is characterized in that it is configured in a large diameter part, preheated in a small diameter part, removes powdered material in the raw material and adds an anti-fusion agent in this small diameter part, and then expands and foams at a high temperature in the large diameter part. A method for manufacturing an ultralight aggregate. 2. A raw material tank containing powdered shale, clay, coal ash, etc., a binder tank containing a molding aid such as a binder, and a device for mixing these to solidify a lumpy raw material of a certain shape. , Consisting of a rotary kiln for firing and foaming this massive raw material, and the rotary kiln is formed in such a manner that the kiln main body is formed in advance with a small diameter portion, an inclined step portion, and a large diameter portion in order from the raw material supply side, and the tip is attached to the large diameter portion. Located in the combustion burner, and a device for removing powder in the raw material in sequence from the raw material supply side to the small diameter part, and an anti-fusion agent injection device that opens a communication passage on the peripheral surface of the small diameter part according to the rotation of the kiln. An ultra-lightweight aggregate manufacturing apparatus that is arranged with the addition of a mechanism that keeps the inside of the kiln mainly shielded from the outside air.