JPS5855363A - Manufacture of artificial lightweight aggregate - 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 method for manufacturing an artificial lightweight fine aggregate used as a concrete aggregate for construction.

Generally, artificial lightweight fine aggregates include shale, clay, slate, etc.
-X material is heated to, for example, 1120°C, and in the temperature range where it becomes semi-molten, gas is generated inside the material, and this is wrapped in the melt to form an aggregate with a porous structure. It is used for purposes such as structural lightweight concrete aggregates in civil engineering and construction, sgritton elements for high-grade interiors and exteriors, gravel and sand for filtration, and has stable specific gravity, particle size distribution, and strength, and Conc 9 with normal conductivity
-) (It is characterized by a low D of about 1/3. Also, during production, the process of pulverizing raw materials and sifting and calcining @
Conventionally, a rotary kiln is used for firing.

However, when firing in a rotary kiln, it takes a relatively long time for the raw material to become foamy and semi-molten, and during this time the gas component that contributes to foaming is consumed, resulting in a decrease in foaming properties and the raw material particles being heated up. Because it is heated in contact with the MPIIk state, raw material particles tend to fuse together to form clinker9, and troubles such as adhesion to the furnace wall and formation of rings tend to occur. There is.

Furthermore, in the case of a p-merry kiln, it is difficult to control the temperature during firing, and it is difficult to maintain the temperature conditions for stable operation, which is a fatal drawback in the production of artificial lightweight aggregates.

In order to eliminate the drawbacks caused by the above-mentioned firing in a rotary kiln, the present invention aims to overcome the drawbacks that occur when firing in a rotary kiln. It was developed with a focus on the fact that it is possible to perform firing at high temperatures (because it is less dangerous and the temperature can be easily controlled). The primary heating device preheats and dries the raw material and disperses and removes the ultrafine powder contained in the raw material, while the raw material from which the ultrafine powder is dispersed and removed is preheated and is then quantitatively fed to the secondary preheater by a quantitative feeder. After preheating, the particles are supplied to a fluidized fluidized furnace and fired while controlling the flow rate and firing temperature sound by utilizing the fluidized state of the particles in the fluidized fluidized furnace. This is done using the hot air generated by the recovery of product sensible heat.
The flow velocity control is performed to lower the flow velocity in the 7-reel board part by dividing it into an inclined part and a flowing part, and to increase the diameter of the freeboard part (as compared to the diameter of the flow plow part), thereby reducing the carryover ratio. Slope t continuous from the tip of the pipe
-7 By providing a notch that is the same as the diameter of the Lee board and making it continuous with the over pipe, deposits on the P77 Lee board are prevented and long-term stable firing is ensured.Many small holes are drilled. A small hole was placed on the furnace wall at the lower end of the slope, and air was blown out along the furnace wall to prevent accumulation on the slope and ensure long-term stable firing. One feature is that the firing temperature distribution is controlled by mixing steam into the spraying air, and the firing temperature distribution is controlled by blowing air into the raw material charging pipe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for producing artificial lightweight fine aggregate according to the present invention will be explained below with reference to the embodiments shown in the drawings.

The first m is the method t1 for producing artificial lightweight fine aggregate according to the present invention.
! The pulverized and sieved raw material is transferred from the raw material tank 1 via the conveyor 2 to primary heat @
3, p1 Here, the product is preheated and dried by hot air generated by recovering the product sensible heat from the product cooler 17, which will be described later, and the ultrafine powder (0
, 074-φ or less) are dispersed and removed.

The raw material, which has been preheated and dried and from which the ultrafine powder has been dispersed and removed, is transferred to a service hopper 5VC via a conveyor 4, and is then quantitatively transferred to a secondary preheater 7 by a quantitative supply device 6 connected to the service hopper 5. The supplied raw material is preheated in the secondary preheater 7 by the combustion exhaust gas from the carryover separator 8 and is introduced into the fluidized fluidized furnace 9 via the raw material charging pipe 15. The fluidized furnace 9 is heated by a burner 11 to a predetermined temperature (for example, 1115°C to 1125°C).
The raw material introduced into the fluidized fluidized furnace 9 is heated and foamed, and the fine powder is carried by the air flow and separated from the gas flow by the carryover separator 8, and the waste material other than the fine powder is removed from the waste gas stream. 70 - Overflows through the pipe 16, and both enter the product cooler 17 where they are cooled and taken out as a product. Note that the fluidizing air sent into the fluidized fluidized furnace 9 is passed through the freeboard portion (upper part 1l) 9 of the fluidized fluidized furnace 9 by a Roots blower 13.
Air is fed into the fluidized fluidized furnace 9 through a nozzle 12 provided at the bottom of the fluidized fluidized furnace 9 through a heat exchanger 10 provided at Wow. In addition, the exhaust gas of the circulating air of the secondary preheater 7 and the primary heat aS air from which the product sensible heat is recovered in the product cooler 17 are discharged from the exhaust blower 18 to the outside of the system.

When artificial lightweight fine aggregate is used as aggregate for concrete, its particle size distribution is a problem, especially K O, 3vm.
- It is required that the amount of passage is 20% or more and that the amount of passage is less than 0.074. Therefore, in order to satisfy this requirement, a powerful pulverizer must be used in the raw material pulverization process, and as a result, the 0.0741 sieve excess is IO
There will be about N. This can be fed into a fluidized fluidized furnace and the internal temperature is very unstable, making it easy to produce p1 clinker. Therefore, as mentioned above, - the second heating device 3
At the same time as preheating the raw material, ultrafine powder (0,074
■φ)! This is preferable in terms of separation and removal, stable operation, and improvement in product quality. Nine, preheating the raw material is shale containing a large amount of moisture (xi~20X)t@0
This is important in terms of reducing the amount of moisture in the raw materials (described later).
Quantitative supply of raw materials and Ic are important keys that constitute the present invention.

Factors that determine the specific gravity of artificial lightweight fine aggregate include, in addition to the expandability of the raw material, the thermal history of the raw material during calcination, the calcination temperature, and the zero residence time of the raw material at that temperature. It has been confirmed that the specific gravity varies depending on the particle size of the raw material. For example, if the typical particle size distribution and specific gravity of fluidized fine aggregate are shown,
This is p as shown in the table.

As can be seen from Table 1 of Crane and Table 1 of Iris, the specific gravity increases as the particle size decreases. Therefore, a lighter fine aggregate is obtained.
Although it is preferable to use #l, which has a small FI particle size, and high-temperature, long-staying buds, in the case of fluidized firing, the tendency is the opposite. Fluidized firing is a method of firing particles by flowing them in the air at a speed lower than the terminal velocity of the particles, but the ζO terminal velocity differs depending on the particle size and specific gravity. For example, Table 2 shows the relationship between particle size and terminal velocity.

Table 2 However, as a result of the test, in order to maintain a good fluidity state and burn the heavy oil smoothly in the furnace, K is 2 to B, 5 ml s.
It has been confirmed that ec@degree O flow interception (superficial velocity) is necessary, and from this and Table 2, 50X or more (t)% is greater than the terminal velocity, so there is carryover. It will not stay inside. This means that the problem that the smaller the particle size is, the more difficult it is to reduce the specific gravity unless it is fired at a high temperature and long distillation cannot be solved], making it difficult to reduce the weight of the aggregate as a whole.

As a measure against ζO, the present invention provides a fluidized furnace 9 with a freeboard section 91, an inclined section 92 and a fluidized section 9, as shown in FIG.
30 divided into three, flowing section 93]7 re-board section 91
C) Increase the diameter to lower the flow velocity of the freeboard section 91,
The fine particles carried over from the flow section 93 are made to flow in the freeboard section 91 while ensuring sufficient temperature and residence time. However, by making the diameters of the two parts 91 * e 3 different, a new problem arises: fine grains accumulate on the resulting inclined part 92 and become clinker, but this can be prevented. Butterfly as an effective means, over 70-
The end of the eve 16 is attached to the lower end of the inclined part 920, and a cutout part 94 is provided that is the same as the diameter of the freeboard part 91 (2) of the inclined part 92t that continues from the tip, and the freeboard part 91 and the inclined part 92 Flowing fine particles t
It is only necessary to make it easier to take out as an overflow. Also,
The wall surface of the fluidized bed furnace 9 in the inclined part 12 has a phenomenon in which fine particles are easily deposited because the upward flow velocity is hardly obtained due to its shadow, so the pipe 95 with many small holes is used. (M520 lower end O furnace wall with a small hole)
It is effective to blow air along the furnace wall.

On the other hand, compared to a rotary kiln, a fluidized fluidized furnace is characterized by the fact that the temperature inside the furnace is constant and controlled, but when heavy oil is burned in the burner 11 in the furnace, the oii* distribution inside the furnace depends on the combustion state. However, there is a problem in that the C) II direct distribution in the vertical direction 41 has a deviation. The firing temperature must be controlled at the highest temperature in the furnace, so if the temperature distribution is uneven, the average temperature will be low. In general, the combustion mechanism of heavy oil in a fluidized reactor is different from normal combustion1.The sprayed heavy oil first adheres to the fluidized particles O surface in the form of mKJl,
It is believed that this is where it vaporizes and burns. Therefore, the factors that affect the combustion state of heavy oil are: (1) Heavy oil O spray state (heavy oil temperature, atomizing air and steam O amount) (!) Fluid state and specific surface area of fluidized particles (1) Vaporization of heavy oil Velocity<at depends on the surface temperature of the moving particles and the temperature of the inlet air) (4) Examples include the combination of fluidizing air, heavy oil, and OS.

Now, as shown in FIG.
m (4,110Cm@, 140cmQ 200cm■) When the temperature is measured at four points, when the burning speed of heavy oil is too fast, the temperature distribution becomes ①→■0→■, and the temperature distribution is at the bottom of the fluidized fluidized furnace 9. It was confirmed that it is easy to build up clinker, and conversely, when the combustion rate of heavy oil is slow, the temperature distribution is 0 → 0 → (8) → confinement, making it difficult to build up clinker on the inclined portion 92. A state between the two O is most preferable from the point of view of temperature stability and temperature distribution width, and empirically KB→1125°C, A,
The best temperature distribution is C-41115°C, D+1070°C (2)j.

In order to achieve such temperature distribution, the above (1) to (4)
The most controlling factor is the amount of raw material charged per unit time, followed by the moisture content and particle size of the raw material. It can be said that it is a distribution.

That is, as the amount of raw material charged increases, the heavy oil O combustion rate decreases, and even if the water content of the raw material is lower and the P particle size distribution is smaller, the combustion rate increases. Therefore, in order to maintain an appropriate temperature distribution in response to these fluctuations, if steam is mixed into the air for fuel spraying, the combustion speed of heavy oil can be lowered.

In addition, if there are many fine particles that should be carried over during heating, the combustion rate becomes faster and clinker tends to form in the lower part of the fluidized bed furnace. This is because the fine particles flow down from the raw material charging pipe to the low flow rate section on the wall surface of the fluidized fluidized furnace to the lower part of the fluidized fluidized furnace.To prevent this, K connects a pipe for blowing air to the raw material charging pipe. At the same time, this air blows away the fine particles to the inside of the fluidized bed furnace where the flow rate is high.
It is best to prevent it from flowing down to the lower part of the fluidized bed furnace due to the rising air current.

As mentioned above, as can be explained in detail with reference to the example of nine seeds shown on side E, according to the method for producing artificial lightweight fine aggregate according to the present invention, the flow rate and temperature can be reliably controlled. Stable operation is possible, and the specific gravity, particle size distribution, and strength of the product are stabilized.

[Brief explanation of the drawing]

Fig. 1 is a system diagram explaining the manufacturing method according to the present invention W14, Fig. 211 is a cross-sectional view of the main part of the fluidized bed furnace used in the manufacturing method according to the present invention, and Fig. 3 is an explanatory diagram of the temperature distribution in the fluidized bed. be. In the WI plane, 3 is a primary heater, 6 is a constant supply device, 7 is a secondary preheater, 9 is a fluidized fluid furnace, 91 is a freeboard part, 92 is an inclined part, 93 is a fluidized part, 94 is a notch part, 95 is a pipe. Patent applicant: Mitsui Kinzoku Mining Co., Ltd. Representative Patent Attorney: Shibu Mitsuishi (1 other person)

Claims (1)

[Claims] (1) The pulverized and sieved raw material is preheated and dried using a primary heater, and the ultrafine powder contained in the KW material is dispersed and removed; After preheating the raw material by quantitatively supplying it to the secondary preheater (using a quantitative supply device), it is supplied to the fluidized fluidized furnace, and this is done while controlling the flow rate and firing temperature using the fluidized Sat of particles in the fluidized fluidized furnace. A method for producing artificial lightweight fine aggregate, which comprises t-calcination. (2) - Preheating and drying using a secondary heating device - A method for producing artificial lightweight fine aggregate according to claim 1 JJ, characterized in that the process is carried out using hot air generated by recovering sensible heat of the product. (8) Fluidized fluid furnace t-79 - divided into board section, inclined section and fluidized section, and make the diameter of the freeboard section 1 m larger than the diameter of the freeboard section. A method for producing artificial lightweight fine aggregate according to claim 1, characterized in that flow rate control is performed to reduce the flow rate. (4) By providing a notch in the sloping part that continues from the tip of the over-70-pipe to be the same as the O diameter of the 7-reboard part and making it continuous with the over-70-vib, the accumulation in the freeboard part can be reduced. 1. Claims [1g] The method for producing an artificial lightweight fine aggregate according to item 1. (6) A pipe with many small holes is slanted at the lower end O.
Claim 1, Claim 1, characterized in that long-term stable firing is ensured by preventing O deposition on the p-inclined portion by arranging it in the pores and blowing air along the small holes and the furnace wall. Or the method for producing an artificial lightweight fine aggregate according to item 4. (6) A method for producing artificial lightweight fine aggregate according to claim 8, item 1, characterized in that the firing temperature o*yt distribution is controlled by adding steam to the air for fuel spraying. (7) The method for producing artificial lightweight fine aggregate according to claim 1, characterized in that the temperature distribution and sound of the firing temperature are controlled by blowing air into the raw material charging pipe.