JP3430236B2 - Composition for artificial lightweight aggregate and method for producing artificial lightweight aggregate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] The present invention relates to a composition for artificial lightweight aggregate.
And a method for producing an artificial lightweight aggregate. [0002] [Prior art and its problems] Recent diversification of energy raw materials
Coal ash by-products increased due to increased coal use
are doing. The recovered coal ash has an unburned carbon content (JIS
A 6201) is less than 5% by weight for mortar and concrete
It is used as an admixture material such as 5 weight
% Is used as a raw material for cement etc.
Most of it was used for landfill. When
In recent years, it has been extremely difficult to secure landfill sites in recent years
And the promotion of coal ash utilization is
It is strongly demanded from the point of view of business and natural environment protection. On the other hand, with the recent weight reduction of building materials,
The demand for lightweight aggregates is increasing. Therefore, the use of coal ash
In order to promote this, a sintered type
Artificial lightweight aggregates have been developed and some of them have been
You. However, the above sintered type has an apparent specific gravity
It is as large as 1.3 to 1.6, and there is a limit to its lower specific gravity.
Was. On the other hand, a sintered type artificial lightweight aggregate is used.
Foam type that can produce low specific gravity
There are also artificial lightweight aggregates. This type of artificial lightweight aggregate
The firing process generally comprises the following two steps. (I) Sintering process This is the sintering process of the granulated material,
The sintering proceeds due to the softening / shrinking of the particles. (Ii) Foaming process Following the sintering process, by further raising the temperature,
Gas is generated due to the melting of the components and decomposition of the iron oxide.
At this time, the melt expands due to the generated gas.
In addition, a dense layer is formed on the surface. As a result, lightweight
Thus, an artificial lightweight aggregate with little water absorption can be obtained. However, a foam-type artificial lightweight aggregate
When coal ash is used as a raw material in the production of
Due to the unique properties of coal ash, various
Problems arise. First, coal ash is essentially softened by heating
When coal ash is granulated and fired, the granulated material is
When the softening point is reached, the shape cannot be maintained (ie
Loss of standing), easily deform and fill the voids between the granules
I will do it. Moreover, the coal ash particles themselves also self-shrink.
Rub Thus, the specific gravity of the granulated material to be used as the aggregate is
And the weight of the product cannot be reduced. Secondly, coal ash is generated during its production process.
Is heated to a high temperature in the boiler and then rapidly cooled.
Is amorphous, and the temperature difference from the softening point to the melting point
Is extremely narrow. For this reason, coal ash
As soon as the granules are fired, they reach the melting point,
The melt covers the surface of the granulated material, then vitrifies and opens
Blocks the hole. Moreover, the self-collection of coal ash particles
The space itself is reduced by the shrinkage. As a result, into the granulated material
Supply of oxygen is interrupted, and a large amount of unburned carbon remains in the granulated product.
Will stay. That is, a large amount of unburned carbon remains
Not only increases the ignition loss of the aggregate, but also
Fe that contributes to foam_TwoO_ThreeReduced by residual unburned carbon
If the granulated material does not foam at all or is insufficiently foamed
Become. In the above case, the amount of residual unburned carbon is reduced.
As a method to reduce the amount, reduce the amount of unburned carbon by providing a calcining process.
After reducing the amount, baking for the purpose of foaming is two steps
(Japanese Unexamined Patent Publication No. 4-238842)
Gazette). However, if firing is performed in two stages,
It is very disadvantageous in terms of energy cost etc.
Take full advantage of using coal ash as raw material
Can not do. [0011] SUMMARY OF THE INVENTION Accordingly, the present invention
Artificial light weight with charcoal ash as the main raw material, especially light weight
Its main purpose is to provide aggregate. [0012] Means for Solving the Problems The present inventor has proposed the above-mentioned prior art.
In view of the problems of the art, we conducted intensive research and found that coal ash
A specific material that is difficult to soften and melt is mixed with coal ash.
When manufacturing artificial lightweight aggregates using
Found that the above problem could be substantially solved and
Ming has been completed. That is, the present invention relates to the composition of the following item 1 and
It relates to the production method of item 2. 1. (A) (a) a crystalline silica ore having a crystal grain size of 5 μm or more
Containing at least 50% by weight of SiO2_TwoContent is 50
It is obtained by crushing rocks that are more than
(B) 50 to 95% by weight of the pulverized product has a particle size of 10 to 25.
5 to 95% by weight of a powder which is 0 μm powder; (B) 95 to 5 layers of coal ash having a maximum particle size of 200 μm or less
amount% A composition for an artificial lightweight aggregate, comprising: 2. (A) (a) A crystal grain size of 5 μm or more
Containing at least 50% by weight of crystalline silica mineral_Two
Rocks with a content of 50% by weight or more obtained by crushing
And (b) 50-95% by weight of the pulverized material is granulated
5 to 95% by weight of a powdery substance which is a powder having a diameter of 10 to 250 μm
as well as (B) 95 to 5 layers of coal ash having a maximum particle size of 200 μm or less
amount% Is granulated by mixing and then firing.
Manufacturing method of artificial lightweight aggregate. Hereinafter, the present invention will be described in detail. The composition of the present invention comprises (A) (a) having a crystal grain size of 5 μm.
containing at least 50% by weight of crystalline silica mineral
And SiO_TwoRocks with a content of more than 50% by weight
(B) 50 of the pulverized material.
~ 95% by weight of powder having a particle size of 10 ~ 250μm
5 to 95% by weight and (B) the maximum particle diameter is 200 μm or less
Of coal ash of 95 to 5% by weight. The crystalline silica mineral has a crystal grain size of 5 μm or less.
Any of the above can be used.
Natural minerals with characteristics include, for example, feldspar, quartz, mica, etc.
Minerals. Contains at least 50% by weight of the above crystalline silica mineral.
Having and SiO_TwoRock having a content of 50% by weight or more
The type is not particularly limited, for example, page
Rock, slate, sandstone, quartzite, granite and the like are preferred. In the present invention, the above-mentioned crushed rocks are
Powder having a particle size of 10 to 250 μm
A powdery substance occupying% by volume is used. Furthermore, the particle size of the powder
Coarse particles exceeding about 1/10 of the diameter of the grain are not present.
Preferably not present. As a result of an increase in coarse particles, powder having the above-mentioned particle size range is obtained.
If the weight of the powder is less than 50% by weight,
Granulation before firing
The strength of the product is reduced, and the particle shape cannot be maintained until firing.
As a result of increasing the fine powder content, the powder having the above-mentioned particle size range becomes 50 wt.
%, The voids inside the granulated material decrease.
In addition, it becomes easy to shrink and soften during firing, and oxygen supply to the inside
Unburned carbon remains in the fired product due to inhibition
The amount increases and the resistance to softening decreases
The independence of the fired product will be impaired. Also, the above grain
If the powder in the diameter range exceeds 95% by weight, the amount of fine powder
And the cohesion of the powder during granulation is reduced.
Therefore, the formability of the granules is poor, and the strength of the granulated material before firing is low.
Become. Adjustment of these particle sizes is in accordance with a conventional method such as a pulverization method.
Good. On the other hand, as coal ash, the maximum particle size is 20
One having a thickness of 0 μm or less is used. If it exceeds 200μm
Is not preferred because the sinterability decreases. Note that the particle size
The lower limit is not particularly limited, but is usually up to about 0.5 μm.
No. Methods for preparing this particle size include sieving and wind
Can be carried out by a standard method such as a grading method or a pulverizing method.
The pulverization method is suitable from the viewpoint of ease of application. The book
In the invention, the properties and the like of coal ash are not limited.
Coal ash can be used. The above-mentioned powdery substance and coal ash in the composition of the present invention
The mixing ratio is usually 5 to 95% by weight of powdery material, coal ash
Is 95 to 5% by weight. 5 layers of powdered material
If the amount is less than%, suppression of softening shrinkage during firing of the granulated material
Control becomes insufficient, and if it exceeds 95% by weight,
Not only lower, but also insufficient foaming
Absent. In the composition of the present invention, Fe_TwoO_ThreeIs 4 ~
More preferably, the content is 10% by weight. Fe_Two
O_ThreeIs the mixing of the powdery substance and coal ash during firing.
Contributes to the foaming of the granules obtained. That is,
At the firing temperature, some of the coal ash, which is the matrix,
Raw material components in a molten state while maintaining appropriate viscosity
Fe inside_TwoO_ThreeO dissociated from_TwoDue to gas generation
It is. The above Fe_TwoO_ThreeWhen the content is less than 4% by weight
Cannot obtain the above effects sufficiently. More than 10% by weight
Not only softens too much and unburnt carbon tends to remain.
And it is very easy to foam, making it difficult to control the specific gravity.
Is not preferred. Fe_TwoO_ThreeIs Fe contained in the rock
_TwoO_ThreeBesides, for example, blast furnace dust generated at steelworks
Can be used as a supply source. Also, when firing
Silica purity for more effective suppression of agglomeration of granules
Spraying of fine powder such as silica stone having a high content may be used together. In the production method of the present invention, the above-mentioned powdery substance and coal
The granules are obtained by mixing with ash and then calcined. Granulation method
Known granulation such as extrusion granulation, tumbling granulation, etc.
Method can be adopted, but rolling is possible especially because large-scale processing is possible.
Granulation is preferred. For example, dish-type granulator (bread-type pelletizer)
To supply powder and water to the rolling plate
Can be performed. In this case, good powder cohesion
Pulp waste liquid etc. to increase the strength of the granulated material.
Can also be used as an underlayer. In terms of particle size, JI
S A 5002 (Lightweight concrete aggregate for structure)
What is necessary is just to adjust the particle size during operation so as to match. The firing conditions for the obtained granules are as follows:
Depending on the composition of the desired aggregate, the desired physical properties of the aggregate, the intended use of the aggregate, etc.
The temperature may be set at about 1000 to 1450 ° C.
~ 30 minutes, preferably at about 1100-1300 ° C
It takes about 20 minutes and the firing atmosphere is an oxidizing atmosphere. In the firing step, firing time and holding
The state of the fired material changes with time, and this process
Process and foaming process. During the sintering process
Rix coal ash is in a semi-molten state after softening. this
In the stage, the sintering of the granules proceeds with the temperature rise,
Although the increase occurs, remarkable
Shrinkage is suppressed and porosity is not lost. As a result, coal ash
Oxidation of the unburned carbon inside proceeds sufficiently. Raise the temperature further
The process proceeds to the next foaming process.
The powder is in a semi-molten to molten state. In this process,
O generated by decomposition of iron oxide_TwoGranulated matter is generated by gas
A glassy substance of coal ash that foams, leaving bubbles inside
Covers the surface and forms a dense film. In this way, it is excellent in lightness and has a loss on ignition.
And an artificial lightweight aggregate with little water absorption can be obtained. [0027] According to the present invention, a material that is harder to soften and melt than coal ash
As a material, powder of specific rock is mixed with coal ash. This place
In this case, the powdery material becomes a skeleton of the granulated material during firing.
As a result, softening and shrinkage can be suppressed, so that oxygen is
Can react well with some carbon. This allows simultaneous
To Fe_TwoO_ThreeCan also prevent the reduction of granules
To Fe_TwoO_ThreeCan contribute to the independence of the granules during firing.
It is also possible to increase or reduce the fusion of the granules
it can. That is, coal ash is used as a binder during granulation.
Material that serves as a skeleton of the fired material during firing
Of Fe powder as an adhesive between Fe and Fe_TwoO_ThreeDeparture by
It plays a role as a foam material. [0029] As described above, the artificial lightweight aggregate of the present invention is effective against coal ash.
Is manufactured by blending specific rocks.
As a result of suppression or prevention of shrinkage, it exhibits excellent lightness
Can be In addition, there is substantial residual unburned carbon
Not greatly reduced ignition loss.
It can also demonstrate qualitative properties. Further, in the artificial lightweight aggregate of the present invention,
Is coal ash, a by-product of coal utilization, and crystalline silica
Rocks that have not been fully utilized in the past due to their high mineral content
Because stone and raw materials are used, the effective use of these materials
Can greatly contribute. In the present invention,
Coal ash of all properties, regardless of carbon content
It can also be used as a raw material. The person of the present invention having such excellent characteristics
Lightweight aggregate can be applied to various uses,
Particularly useful for applications such as lightweight PC boards used in high-rise buildings
It is. [0032] The following examples and comparative examples show the present invention.
Clarify the features. Example 1 and Comparative Example 1 Using sandstone as a mixed material for coal ash, the raw materials shown in Table 1
Granulated material (raw material mixture No. 3-6)
Carbon content about 6%), and the mixture gives sintering properties
The effects were investigated. As Comparative Example 1, no sandstone was blended.
The above effects were also examined using the raw material formulations Nos. 1 and 2. Using the raw material formulations Nos. 3 to 6 of the present invention,
The results (Example 1) are shown in Table 2, and the raw material formulations for comparison are shown.
Table 3 shows the results obtained using Nos. 1 and 2 (Comparative Example 1).
Shown. [0035] [Table 1] [0036] [Table 2] [0037] [Table 3] As can be seen from Table 3, Comparative Example 1
Firing Nos. 13 to 18 have a large loss on ignition, and the fired product is self-supporting
Some of them were inadequate. In particular, firing Nos. 13 to 16
Has a loss on ignition of JIS A 5002 (concrete aggregate for structure)
It was confirmed that the value exceeded the standard value of 1%. On the other hand, in Example 1, sandstone was blended.
For raw material formulation Nos. 3-6, 900 ° C for 20 minutes
Along with firing Nos. 1 to 4 which set the calcining stage to be held,
Firing Nos. 5 to 12 also have a small loss on ignition and are independent of the fired product.
Was also good. From this, it is fired by mixing sandstone
It can be seen that the softening / shrinkage of the object is suppressed. Example 2 and Comparative Examples 2 and 3 As Example 2, coal ash having an average particle diameter shown in Table 4 (residual
About 12% of unburned carbon) and sandstone crushed to the specified particle size
After granulating with the mixture, baking at 1250 ° C
Lumber was manufactured. Table 4 shows the results. In addition, any
Granulated material is also Fe_TwoO_ThreeWas contained at 5% by weight. As Comparative Example 2, the average particle size shown in Table 5 was
After granulating with coal ash (residual unburned carbon amount about 6%) alone, 1
It was fired at 250 ° C. to produce an aggregate. Table 5 also shows the results
Show. Further, as Comparative Example 3, the particle size was adjusted out of the particle size range of the present invention.
Granulated using an equal mixture of sandstone and coal ash
Then, it was fired at 1250 ° C. to produce an aggregate. The result
It is shown in Table 6. [0042] [Table 4] As shown in Table 4, those containing sandstone
Ignition loss gradually decreases over time of firing
You can see that. For specific gravity, 5 minutes firing
Increased due to shrinkage of calcined material due to softening of coal ash
However, due to the presence of hard-to-soften sandstone, internal voids can be secured.
As a result, sufficient unburned coal is
It can be seen that the element burns and the loss on ignition decreases.
You. In addition, there is no effect of residual unburned carbon by firing for 15 minutes.
It shows good foaming properties and its specific gravity is very small.
You can see that it is. [0044] [Table 5] As is evident from Table 5, the single use of coal ash
Water absorption decreases as the particles become finer.
However, the finer the powder, the more open the surface of the granulated material.
Water is no longer penetrated by closing the holes
Is shown. In addition, shrinkage during firing is large due to pulverization.
And reduced internal porosity and vitrified surface
Since the supply of oxygen to the inside of the granules is impeded,
Ignition loss also increased as a result of the presence of unburned carbon. one
On the other hand, if the firing time is increased to reduce the ignition loss,
The fired product will melt. Even if it does not melt,
Specific gravity increases due to residual unburned carbon inhibiting foaming
And could not be reduced in weight. [0046] [Table 6]As can be seen from Table 6, crushed sandstone grains
If the degree is too small, it is difficult to soften the crystalline material
That the coal ash firing temperature range is narrow.
Dominant, immediately after sintering, the entire grain melts,
Fusion occurred. On the other hand, if the particle size is too coarse,
It takes time from sintering to foaming, and energy costs
Not only becomes excessive, but also deteriorates moldability during granulation, etc.
It can be seen that the adverse effect of the above occurs. Embodiment 3 As shown in Table 7, coal ash and sandstone with different particle sizes were used.
After granulating the mixture with different mixing ratio (%), 1250
Fired at ℃. Table 7 shows the results. [0049] [Table 7] As is clear from Table 7, the mixing ratio of sandstone is
If the amount is too large, only the effect of suppressing softening shrinkage during firing increases.
No, because the residual unburned carbon concentration of the granulated product is diluted.
Heat loss is easily reduced. The coarser the grain size of the sandstone, the softer it is during firing.
It is easy to suppress granulation and shrinkage, and it is easy to maintain the gap between particles of the granulated material
No. As a result, oxygen is easily supplied to the inside,
It can be seen that the amount decrease is faster. That is, the book
Stable by mixing sandstone within the range of the inventive mixing ratio
It can be seen that an expanded foam state is obtained. Embodiment 4 As shown in Table 9, a mixture of the chemical components shown in Table 8 was used.
Replace the rock type of the mixed material with pulverized particles to a predetermined particle size,
Mix and fire. In this case, slate and sandstone are 125
0 ℃, silica and standard sand are fired at 1300 ℃ respectively
Was. In Table 8, for standard sand, check the crystal grain size, etc.
Due to the difficulty, only the chemical components are described. [0053] [Table 8][0054] [Table 9] As can be seen from Table 9, SiO_TwoHigh purity
High in crystalline silica minerals and not expandable
Rocks that have not been used as a material for artificial lightweight aggregate
Even if blended in large amounts, the mixed material and coal ash have a particle size within the range of the present invention.
In this case, the residual unburned carbon can be sufficiently consumed during firing.
Wear. As a result, when the ignition loss of the fired material is reduced,
Fe_TwoO_ThreeCoal ash
It acts as both a binder and a foam, helping to reduce its weight.
You can see that it is giving. Embodiment 5 By using each of the sandstones shown in Table 10,
The effect of silica mineral was investigated. Table 10 shows the results.
Show. A mixture of sandstone and coal ash in the same amount is Fe_Two
O_ThreeWas adjusted to 5% by weight, and then granulated,
20 minutes from 1000 ° C to 1000 ° C, 1250 to 1000 ° C
To 10 ° C in 10 minutes, and held at 1250 ° C for 15 minutes for baking.
Done. Table 10 shows the evaluation of the obtained fired product. [0057] [Table 10] As is apparent from Table 10, the compositions differed.
Even if sandstone is used, the specified SiO_TwoCrystalline silica by content
Use it after adjusting the mineral content to the desired particle size.
It can be seen that a good quality artificial lightweight aggregate can be obtained. Embodiment 6 Fe_TwoO_ThreeTable 11 shows the effect of the content of
Of an equal mixture of sandstone and coal ash (raw material No. 1)
And Fe_TwoO_ThreeTo adjust the ingredients
Thus, a granulated product composed of raw materials Nos. 2 to 6 was prepared. This
Each of these granules was fired under the following conditions to obtain
The fired product obtained was evaluated. Table 12 shows the results. [Firing conditions] 1250 ℃ firing: 800 → 1000 ℃ / 20min, 1000 → 1250 ℃ / 10
Min, 1250 ° C / 15 min hold 1300 ℃ firing: 800 → 1000 ℃ / 20min, 1000 → 1300 ℃ / 10
Min, 1300 ℃ / 15min 1350 ℃ firing: 800 → 1000 ℃ / 20min, 1000 → 1350 ℃ / 10
Min, 1350 ℃ / 15min [0061] [Table 11] [0062] [Table 12] Here, in raw material No. 1 as a comparative example, 1
Even at 350 ° C firing, the matrix coal ash is in the melting stage
And still in the sintering stage, with many surface porosity
Because of high water absorption. Also, because it is in the process of contracting,
Specific gravity has increased, resulting in higher crush strength
You can see that. On the other hand, the raw materials Nos.
Then, even at 1300 ° C firing, Fe_TwoO _ThreeYaki when the amount increases
Since the setting is faster, the specific gravity increases due to shrinkage,
When the amount added is too large, foaming tends to occur, so the specific gravity is small.
It becomes. On the other hand, the crushing strength moves in proportion to the value of specific gravity.
Show. Furthermore, the water absorption rate is such that sintering is easy to proceed,
It can be seen that the amount decreases in proportion to the amount added. When the firing temperature reaches 1350 ° C.,
Since the sintering phase ends sooner,
The conclusion is over and Fe_TwoO_ThreeSpecific gravity and absorption are inversely proportional to the amount
It can be seen that the water content and the crushing strength are reduced. More than
Therefore, Fe_TwoO_ThreeContributes to foaming in fired products
You can see that there is.

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Nobuyuki Inumaru 2-21 Kita-bankan-508 No. 221, Uchiage, Neyagawa-shi, Osaka (72) Inventor Mitsuhiro Ishii 22239-1, Yamadashita, Ayaue-cho, Aya-gun, Kagawa Pref. Inventor Takuo Nojiri 4-16-22 Yamanouchi, Sumiyoshi-ku, Osaka-shi, Osaka (72) Inventor Hironobu Murai 698-5, Mitsui, Tadotsu-cho, Nakatado-gun, Kagawa Prefecture (72) Inventor Yoshikatsu Nishino Osaka-Sayama, Osaka 1-27-19, Ikejirinaka (56) References JP-A-3-88749 (JP, A) JP-A-4-119952 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) ) C04B 18/08 C04B 14/04 C04B 14/02 C04B 18/10

Claims (1)

(57) [Claim 1] (A) (a) 50% by weight or more of a crystalline silica mineral having a crystal grain size of 5 μm or more and SiO 2
₍₂ ) A powder obtained by pulverizing sandstone and / or quartzite having a content of 50% by weight or more, and (b) 5
0 to 95% by weight is a powder having a particle size of 10 to 250 μm, and 5 to 95% by weight; and (B) 95 to 5% by weight of coal ash having a maximum particle size of 200 μm or less , containing Fe ₂ O ₃ . The amount is 4-10% by weight
Granulated by mixing the composition for artificial lightweight aggregates ,
Subsequently, the method is fired at 1100 to 1300 ° C., and a method for producing an artificial lightweight aggregate.