KR20190113527A - Fly ash production method and coal ash, cement composition - Google Patents

Abstract

Coal ash containing a lot of unburned carbon can be used without treatment by classification, and it provides a coal ash which can improve the uniformity at the time of mixing in soil improvement of a viscous soil, and its manufacturing method.
Coal ash production including crushing coal ash having an ignition loss of 3.5% by mass or more so that the ratio (Lg / Lp) of the light ash (Lg value) after pulverization to the light ash (Lp value) of crushed coal is 0.9 or less. Method and the like.

Description

Fly ash production method and coal ash, cement composition

The present invention relates to a method for producing coal ash, coal ash, and a cement composition.

Since viscous soils have very small particle sizes and are solidified, in the ground improvement, mixing and stirring with solidified materials are not easy. To solve this problem, a special stirring device is used, or a method such as increasing the water ratio to improve the uniformity of the solidified material or using a dispersant acting on the soil particles together with the solidified milk is employed. ought.

On the other hand, the safety of a nuclear power plant is questioned, and the operation rate of a thermal power plant is increasing, and the effective use of the coal ash discharged with the operation becomes an issue further.

Fly ash, which occupies most of the ash, is used as a mixed material of concrete, and its quality is defined in detail by JIS, and treatment such as classification is required to maintain a constant quality. It is hard to say that coarse powder etc. which were excluded by classification are effectively used, for example, being embedded.

Moreover, it is known that unburned carbon in coal ash has an adverse effect (adhesion adsorption, etc.) at the time of concrete manufacture, and various methods are proposed regarding the removal method (for example, patent documents 1-3). Reference).

Japanese Patent Application Laid-Open No. 08-026740 Japanese Unexamined Patent Application Publication No. 11-011999 Japanese Unexamined Patent Publication No. 2007-054773

However, the method proposed by patent documents 1-3 requires a new installation, a running cost becomes high, a classification efficiency becomes low, etc., becomes a problem.

In addition, if an additive such as coal ash is mixed with the solidified material and the effective use thereof can be achieved, the amount of the solidified material can be reduced, and the cost down such as the decrease in the amount of varnish can be expected.

However, if the object to be treated is soil such as viscous soil, as described above, since mixing and stirring with the solidified material are not easy, there are problems such as cost increase and low efficiency as the solidified material known in the present state. From the viewpoint of the effective use of coal ash, it is preferable that all of them can be used. In addition, if the uniformity at the time of mixing in cohesive soil improvement is improved by simple treatment without requiring treatment such as removal of unburned carbon, such a technique is not known in the present state. .

Therefore, this invention can use the coal ash which contains a lot of unburned carbon, without classifying, and can improve the uniformity at the time of mixing in soil improvement of viscous soil, its manufacturing method, and its coal ash It is an object to provide a cement composition using.

As a result of earnestly examining in order to achieve the said objective, the present inventors have found that the coal ash obtained by grind | pulverizing this in the predetermined | prescribed range is a coal ash with a large amount of ignition loss which may be inferior in the case of concrete manufacture. It discovered that the uniformity at the time of mixing in the ground improvement of a viscous soil was able to be improved, and the present invention was considered. That is, the present invention is as follows.

[1] grinding of coal ash having a loss in ignition of 3.5% by mass or more such that the ratio (Lg / Lp) of the brightness (Lg value) of the crushed coal ash to the brightness (Lp value) of the crushed coal ash is 0.9 or less; Method of manufacturing fly ash.

[2] The method for producing coal ash according to [1], wherein the ash ash is pulverized so that the ratio (Lg / Lp) of the brightness (Lg value) of the crushed ash to the coal ash (Lp value) before pulverization is 0.6 or more.

[3] The ratio of the content (Vg) of particles having a particle diameter of 45 µm or more measured by the above measuring method of coal ash after grinding to the content (Vp) of particles having a particle diameter of 45 µm or more measured by laser diffraction scattering particle size distribution measurement method of coal ash before grinding. The manufacturing method of the coal ash as described in [1] or [2] which grinds so that (Vg / Vp) may be 0.85 or less.

[4] loss of ignition loss is not less than 3.5% by mass, particle size of 45 µm or more, measured by laser diffraction scattering particle size distribution method, 20 to 45 vol%, with specific particle area of 3200 to 4200 cm ² / g And a light ash (Lg value) of pulverized coal ash having a lightness (Lg value) of 25.0 to 50.0, and a ratio (Lg / Lp) of the light ash (Lg value) of crushed ash ash after crushing to the lightness (Lp value) of coal ash before pulverization is 0.9 or less.

[5] The coal ash according to [4], wherein the loss on ignition is 8.0% by mass or less.

[6] A cement composition comprising the coal ash according to [4] or [5] and cement.

[7] The cement composition according to [6], wherein the cement is at least one cement selected from the group consisting of ordinary portland cement, crude steel portland cement, medium heat portland cement, and low heat portland cement.

[8] The cement composition according to [6] or [7], wherein the amount of the coal ash is 40% by mass or less based on the total amount of the cement composition.

According to the present invention, coal ash containing a lot of unburned carbon can be used without treatment by classification, and the coal ash and its manufacturing method which can improve the uniformity at the time of mixing in improving the soil of cohesive soil, and the coal ash thereof The used cement composition can be provided. Thereby, it is possible to use all the coal ash generated in a thermal power plant as a raw material, and the improvement of the work efficiency in soil improvement can also be anticipated.

[Method of manufacturing coal ash and coal ash]

(1) Method of manufacturing coal ash:

In the method for producing coal ash according to the embodiment of the present invention, the ratio (Lg / Lp) of the coal ash (Lg value) after the pulverization to the brightness (Lp value) of the coal ash before pulverization is reduced to the coal ash having an ignition loss of 3.5% by mass or more. Grinding to 0.9 or less.

The present invention can produce coal ash (modified coal ash) that can improve the mixing properties with viscous soils when predetermined crushing is carried out to coal ash having a large loss in ignition of 3.5% by mass or more and used for improving the soil. .

Here, the loss on ignition is proportional to the amount of unburned carbon in the coal ash, and the term `` large loss on ignition of 3.5% by mass or more '' indicates that there is much so-called unburned carbon. Then, by performing a predetermined pulverization on the coal ash having a large amount of ignition loss, exposing at least a portion of unburned carbon contained in the coal ash particles to the surface side of the particles, the cement ash is mixed with the clay particles by using the coal ash. Can improve sex. Unburned carbon exposed to the surface of coal ash particles by pulverization exhibits the same properties and conditions as unburned carbon in powder particles existing before pulverization, and the properties and states are hydrophobic. That is, due to the predetermined grinding, the unburned carbon exposed to the surface of the particles of coal ash is increased compared with before grinding, so that the hydrophobicity becomes stronger. For example, when cement and this coal ash are mixed and used as a solidifying material, the hydrophobic unburned carbon exposed to the surface of the particles does not exhibit excessive water absorption during cement kneading, and is used for improving soils with high water content. In this way, the dispersibility of clay particles and cement particles can be efficiently improved.

The ignition loss of coal ash is related to the content of unburned carbon, and when ignition loss is large, it can be estimated that there is also much content of unburned carbon contained in coal ash. Therefore, if the ignition loss of coal ash is less than 3.5 mass%, since the absolute amount of unburned carbon showing hydrophobicity becomes small, the dispersibility of clay particles cannot be improved. It is preferable that it is 3.5 mass% or more and 9.0% mass or less, and, as for the loss of ignition of coal ash, it is more preferable that they are 6.0 mass% or more and 9.0 mass% or less. Ignition loss can be measured by the method as described in the Example mentioned later.

Coal ash having a loss in ignition of 3.5% by mass or more is ash generated in a coal-fired power plant, for example, and may be produced by pulverized coal combustion. Examples of the coal ash include coal ash dropped by passing through an air filter or a coal blower from the combustion gas of the combustion boiler, coal ash collected by an electric dust collector, coal ash dropped on the furnace bottom of the combustion boiler, and the like.

For example, the crushing device is used to reduce the ignition loss of coal ash having 3.5% by mass or more so that the ratio (Lg / Lp) of the light ash (Lg value) after the crushing to the light ash (Lp value) of the crushed coal is 0.9 or less. Crush. This exposes the unburned carbon powder contained in the coal ash particles.

As a grinding | pulverization apparatus, a ball mill and a vibration mill (to give a vibration to a container, and transmit a vibration to the medium (ball or rod) in a container, etc.) can be used.

In grinding | pulverization, the brightness (Lp value) of the coal ash before grinding | pulverization is measured first, and let ratio (Lg / Lp) of this and the brightness (Lg value) of this coal ash after grinding | pulverization be 0.9 or less. The coal ash to be pulverized may crush the entire amount of coal ash to be used or a part of the coal ash may be pulverized. In addition, the pulverized coal ash may be mixed with the non-pulverized coal ash and used as the coal ash after grinding. A portion of the coal ash is pulverized, and even if the coal ash is pulverized after mixing the pulverized coal ash, the ratio of the brightness (Lp value) of the coal ash before pulverization and the brightness (Lg value) of the coal ash after pulverization including the pulverized coal ash (Lg / What is necessary is just to grind so that Lp) may be 0.9 or less.

Here, the brightness of coal ash is related to blackness, and is mainly an indicator of the amount of unburned carbon exposed to the surface. When Lg / Lp, the ratio before and after pulverization exceeds 0.9, the contained unburned carbon is sufficiently present on the surface. When it is set as the solidified material mixed with cement in such a state, the dispersibility of clay particle and cement particle cannot be improved efficiently.

It is preferable to make Lg / Lp into 0.6 or more and 0.9 or less, and it is more preferable to set it as 0.6 or more and 0.85 or less. By setting it as 0.6 or more, the grinding | pulverization of a spherical particle can be suppressed as much as possible, and a fluid fall can be suppressed.

The brightness of coal ash can be measured and calculated | required by the method as described in the Example mentioned later.

In addition, in view of the fact that many particles having a particle diameter of 45 µm or more are non-spherical and can be expected to improve fluidity by exposing spherical particles which are pulverized and micronized and contained therein, laser diffraction scattering particle size distribution measuring method of coal ash before grinding is performed. Ratio (Vg) of content (Vg) (vol%) of particle | grains 45 micrometers or more measured by the laser diffraction scattering type particle size distribution measuring method after grinding | pulverization with respect to content Vp (volume%) of particle | grains 45 micrometers or more measured in particle size (Vg) / Vp) is preferably pulverized to 0.85 or less. As for ratio (Vg / Vp), it is more preferable to grind so that it may become 0.6 or more and 0.80 or less. Coal ash may grind | pulverize the particle | grains whose particle diameter is 45 micrometers or more, mix this crushed coal ash with the coal ash which is not comminuted, and may use it as the coal ash after grinding | pulverization.

As mentioned above, the coal ash which can improve the dispersibility of a clay particle easily by predetermined grinding | pulverization is obtained. In other words, it is possible to use all of the coal ash generated from the thermal power plant as a raw material, and there is no problem such as requiring a new facility or increasing the running cost, thereby improving the work efficiency in improving the ground. have.

(2) coal ash:

In the coal ash of the embodiment of the present invention, the loss in ignition is 3.5% by mass or more, the content of particles having a particle size of 45 μm or more measured by a laser diffraction scattering particle size distribution method is 20% by volume or more and 45% by volume or less, and the specific surface area of the blain is 3200-4200 cm ² / g, the pulverized coal ash having a lightness (Lg value) of 25.0 to 50.0, and the ratio (Lg value) of the brightness (Lg value) of coal ash after pulverization to the lightness (Lp value) of coal ash before pulverization. Is 0.9 or less.

If the ignition loss of coal ash is less than 3.5 mass%, since the absolute amount of unburned carbon showing hydrophobicity becomes small, the dispersibility of clay particles cannot be improved. It is preferable that it is 3.5 mass% or more and 9.0 mass% or less, and, as for the ignition loss of coal ash, it is more preferable that they are 6.0 mass% or more and 9.0 mass% or less.

When the content of particles having a particle size of 45 μm or more measured by laser diffraction scattering particle size distribution method in coal ash is less than 20% by volume, there are few non-spherical particles, and the effect of improving the dispersibility by releasing unburned carbon particles by grinding. When the content is lowered and exceeds 45% by volume, there are many non-spherical particles, and the fluidity is lowered or the hydration activity of the coal ash itself is lowered.

It is preferable that they are 20 volume% or more and 45 volume% or less, and, as for content of particle | grains of particle size 45 micrometers or more, it is more preferable that they are 23 volume% or more and 43 volume% or less.

If the fly ash specific surface area is less than 3200 cm ² / g, the hydration activity may be lowered and a predetermined strength may not be obtained. If it exceeds 4200 cm ² / g, the fluidity decreases.

Blaine specific surface area, preferably in the 3200 ~ 4200cm ² / g, and more preferably 3300 ~ 4000cm ² / g.

In addition, if the lightness (Lg value) of the pulverized coal ash is less than 25.0, the unburned carbon is large and black light increases, and when the ground is improved, a color difference occurs with the surrounding ground, and when it exceeds 50.0, it is released. When unburned carbon is small and mixed with viscous soil, good fluidity is not obtained, and there is a possibility that it cannot be uniformly mixed.

It is preferable that it is 30.0-50.0, and, as for the lightness of coal ash, it is more preferable that it is 35.0-45.0.

When the ratio (Lg / Lp) of the light ash (Lg value) after grinding to the light ash (Lp value) before grinding is more than 0.9, the contained unburned carbon does not exist sufficiently on the surface. When the solidified material mixed with cement in a state, dispersibility of clay particles and cement particles cannot be improved efficiently.

The ratio is preferably 0.6 or more and 0.9 or less, and more preferably 0.6 or more and 0.85 or less.

The coal ash of embodiment of this invention can be manufactured by the manufacturing method of the coal ash of embodiment of this invention. In the production of coal ash according to the embodiment of the present invention, a grinding device such as a ball mill or a disk mill is used, and each time, the particle size distribution, the blain specific surface area, and the color difference are measured to confirm that the predetermined physical property values have been obtained. desirable.

Although it is preferable to use the coal ash of embodiment of this invention as a cement composition mentioned later, it can apply to the other various uses taking advantage of the characteristic.

[Cement Composition]

The cement composition of embodiment of this invention contains the coal ash of embodiment of this invention, and cement.

The kind of cement is not particularly limited and is preferably at least one selected from the group consisting of portland cement, crude steel portland cement, medium heat portland cement and low heat portland cement.

It is preferable that content of the coal ash with respect to cement composition whole quantity exceeds 5 mass% and is 40 mass% or less. It can use as a solidified material by exceeding 5 mass% and being 40 mass% or less. As for the said content, it is more preferable that they are 25 mass% or more and 35 mass% or less.

In the cement composition, in addition to coal and cement, gypsum, blast furnace slag, lime lime powder, quicklime and the like may be mixed. For these mixing, a V-type mixer, a rocking mixer, a fan mixer, a rotating revolution mixer, or the like can be used.

It is preferable to provide the cement composition of embodiment of this invention as a cement type solidifying material, and it is more preferable to provide it as a cement type solidifying material for the ground improvement of a viscous soil.

In the case of a cement-based solidified material for improving the ground of viscous soils, the water (kneaded water) used when kneading is preferably 80 to 120 parts by mass, and 85 to 110 parts by mass with respect to 100 parts by mass of the cement composition. It is more preferable to do.

Example

Next, although an Example demonstrates this invention in detail, this invention is not limited at all by these Examples.

(Production of coal ash A-F)

Each of the coal ashes A to F generated at a thermal power plant in Japan was crushed by a test ball mill (inner volume 100L). In addition, the degree of grinding | pulverization was adjusted by confirming powder physical property with the laser diffraction particle size distribution meter, a blain specific surface area measuring device, and a color chromaticity meter.

Coal ash properties and conditions (ignition loss, carbon amount, ratio of MT-45μR before and after crushing, ratio of MT-45μR before and after crushing, the ratio of Blaine specific surface area, L value and L value before and after grinding) are shown in the following table. 1 is shown.

In addition, the characteristics and state of coal ash were calculated | required as follows.

(1) loss of ignition:

It calculated | required based on JIS A6201: fly ash for concrete (975 degreeC 15 minute ignition).

(2) Carbon amount (carbon amount):

It measured and calculated | required by the carbon-sulfur analyzer (EMIA-320V) in the solid made by Horiba Corporation.

(3) MT-45 μR (content of particles with a particle diameter of 45 μm or more):

It measured and calculated | required with the laser diffraction type particle size distribution meter (Microtrack MT-3300EX by Nikkiso Corporation). Content (Vp) (volume%) of particles having a particle size of 45 μm or more measured by laser diffraction scattering particle size distribution measuring method of coal ash before pulverization and particles having a particle size of 45 μm or more measured by laser diffraction scattering particle size distribution measuring method of coal ash after grinding Laser diffraction scattering particle size distribution of coal ash after pulverization with respect to content Vp (volume%) of particle | grains of 45 micrometers or more measured by the coal diffraction scattering particle size distribution measurement method of coal ash before grinding | pulverization from content (Vg) (vol%). The ratio (Vg / Vp: MT-45 µR ratio) of the content (Vg) (volume%) of the particles having a particle size of 45 µm or more measured by the measuring method was determined.

(4) Blaine specific surface area

It calculated | required based on JIS R5201: the physical test method of cement.

(5) Color Difference (L value):

The brightness (L value) prescribed | regulated by CIE (International Illumination Commission) was measured and calculated | required using the color-color difference meter (CR-300) by Konica Minolta Japan. Ratio of the brightness (Lg value) of coal ash after grinding to the brightness (Lp value) of coal ash before grinding from the brightness (Lp value) of coal ash before grinding and the coal ash (Lg value) after grinding (Lg / Lp: L value ratio) Saved.

 (Combination test related to Examples and Comparative Examples)

30 g of coal ashes A to F after crushing, 70 g of cement (common portland cement made by Sumitomo Osaka Chemical Co., Ltd.), and 100 g of kneaded water were sufficiently homogenized using a hand mixer to prepare cement milk. This mixture is kneaded with a kaolin (manufactured by Kishida Chemical Co., Ltd.) 1L (wet density 1.846 g / cm ³ ) as a viscous soil in a rotating and revolving mixer, and then kneaded to prevent the compaction of the stabilized soil. The specimen was manufactured in accordance with "Test Method Production Method."

It shows about compounding (water content ratio 35 mass%) in following Table 2.

In addition, the coal ash E and the coal ash F are the same sample, and the grade of grinding | pulverization differs. Fly ash G and fly ash H are also the same.

After kneading, the mixing property between the solidified material and the viscous soil was evaluated by a vane shear test. In the vane shear test, the vane vane which welded the stainless steel plate (0.5 cm x 3 cm) in the straight direction was attached to the front-end | tip of the torque driver made by Tonichi Corporation, and this was press-fitted in the sample, and measured the maximum torque The vane shear resistance value was calculated | required from (refer Table 2 below). The results are shown in Table 2 below. In addition, the evaluation index (refer to the following) based on the resistance value is also written together.

G (good): vane shear resistance <10.0kN / m ²

Av (typical: average): 10.0 kN / m ² ≤ vane shear resistance ≤ 12.0 kN / m ²

P (poor) x: vane shear resistance value> 12.0 kN / m ²

From comparison of Examples 1-3 and 5 and Comparative Examples 1-3 and 5, Examples 1-3 and 5 using the pulverized coal ash had low vane shear resistance values, and kneading property was favorable. As is evident from Example 4, the kneading property of at least a good amount of water than that of Example 1 was ensured. In Comparative Examples 4 and 6, the degree of grinding was lower than that in Examples 1 and 5, and the kneading property was insufficient.

According to the present invention, with the increase in the amount of power generation in a coal-fired power plant, the coal ash whose generation amount is increasing can be used effectively, and the uniformity at the time of mixing in the ground improvement of a viscous soil can be improved.

Claims (8)

Coal ash production including crushing coal ash having an ignition loss of 3.5% by mass or more such that the ratio (Lg / Lp) of the light ash (Lg value) after the crushing to the light ash (Lp value) of the crushed coal is 0.9 or less. Way. The method of claim 1,
A method of producing coal ash, which is pulverized so that the ratio (Lg / Lp) of the brightness (Lg value) of the coal ash after grinding to the brightness (Lp value) of the coal ash before grinding is 0.6 or more. The method according to claim 1 or 2,
Ratio of content (Vg) of particle | grains of 45 micrometers or more measured by the said measuring method of the coal ash after grinding | pulverization to content (Vp) of the particle | grains of 45 micrometers or more measured by the laser diffraction scattering type particle size distribution measuring method of coal ash before grinding | pulverization (Vg / The manufacturing method of the coal ash which grinds so that Vp) may be 0.85 or less. The loss in ignition is 3.5% by mass or more, the content of particles having a particle size of 45 µm or more measured by laser diffraction scattering particle size distribution measurement is 20% by volume or more and 45% by volume or less, and the specific surface area of the blain is 3200-4200 cm ² / g, Coal ash which is crushed coal ash with (Lg value) of 25.0-50.0, and ratio (Lg / Lp) of the brightness (Lg value) of the crushed coal ash to crushed coal ash (Lp value) before crushing is 0.9 or less. The method of claim 4, wherein
Coal ash with an ignition loss of 8.0% by mass or less. The cement composition containing the coal ash of Claim 4 or 5, and a cement. The method of claim 6,
The cement composition is at least one cement selected from the group consisting of ordinary portland cement, crude steel portland cement, medium heat portland cement, and low heat portland cement. The method according to claim 6 or 7,
It is a cement composition whose content of the said ash ash exceeds 40 mass% with respect to cement composition whole quantity, and is 40 mass% or less.