JP2021094538A - Method for manufacturing modified fly ash - Google Patents

Abstract

To provide a method for manufacturing fly ash, capable of reducing the amount of unburnt carbon using a new flotation process capable of suppressing the used amount of a scavenger.SOLUTION: A method for manufacturing modified fly ash, capable of separating unburnt carbon from fly ash by an ore floatation method to reduce the content of the unburnt carbon comprises: a slurry preparation step of preparing slurry including the fly ash, water, a scavenger and a foaming agent; a froth removal step of supplying gas from below to the slurry to cause air bubbles and remove froth including the unburnt carbon and formed on the slurry; a scavenger replenishment step of adding the water and the scavenger to the slurry after removing the froth; and an additional froth removal step of supplying the gas from below to the slurry after adding the water and the scavenger to cause air bubbles and remove froth including the unburnt carbon and formed on the slurry.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing modified fly ash with a reduced amount of unburned carbon.

Fly ash is used as a cement mixture, concrete mixture, mortar mixture, etc., but it is generally considered that this fly ash is preferably one having a small amount of unburned carbon, which is the unburned residue of carbon. .. For example, if the amount of unburned carbon in fly ash is large, unburned carbon may emerge on the surface of mortar or concrete, and black parts may be generated. In addition, there is a problem that chemicals such as chemical admixtures added to mortar and concrete are adsorbed on unburned carbon.

However, in general, fly ash generated from a coal-fired power plant has a non-uniform amount of unburned carbon, and some of them are present in an amount of about 15% by mass. The current situation is that it is limited to the department.

Under such circumstances, various methods for reducing unburned carbon contained in fly ash have been proposed. For example, a combustion method, a classification method, a flotation method (hereinafter referred to as flotation), and the like have been proposed. ..

Flotation is one of the methods that can efficiently remove unburned carbon in fly ash, and in this flotation, in order to improve the separability of ash particles and unburned carbon particles in fly ash. A flotation agent is used, and a foaming agent is used to promote the formation and stabilization of air bubbles. Kerosene and heavy oil are generally used as the collecting agent, and pine oil, MIBC and the like are generally used as the foaming agent.

However, in this fly ash flotation process, the ratio of these drug costs is large, and the high drug cost is a big problem. In addition, since chemicals are contained in products and waste liquids, there is a problem that a process for removing them is required. Furthermore, if a collecting agent such as kerosene contained in a product is attempted to be removed by heating, CO ₂ is generated from the kerosene, which is not preferable from the viewpoint of environmental impact.

As a flotation method that reduces the amount of such a collecting agent used, for example, water is added to fly ash to form a slurry, a collecting agent is added to the slurry, and rotation that penetrates the cylindrical body in the axial direction. The slurry and the submerged stirring device provided with a shaft, a plurality of chambers formed by dividing the inside of the main body in the axial direction, and a stirring blade fixed to the rotating shaft and rotating inside each chamber. A collecting agent is supplied to apply a shearing force, a foaming agent is added to the slurry and the collecting agent to which the shearing force is applied, and the mixture is stirred to generate bubbles, and the unburned carbon of the fly ash is added to the bubbles. A method for removing unburned carbon in fly ash, which is characterized by adhering and flotating the foam, has been proposed (see Patent Document 1).

However, this method uses a special submerged stirrer, and it has been pointed out that there is a problem with this submerged stirrer as well as an increase in cost due to the introduction of a new device (patented). Reference 2).

Japanese Unexamined Patent Publication No. 2007-7485 Paragraphs [0006] and paragraphs [0007] of JP-A-2007-167787.

An object of the present invention is to provide a method for producing modified fly ash, which produces fly ash with a reduced amount of unburned carbon by using a novel flotation process capable of suppressing the amount of a collecting agent used.

As a result of diligent studies in view of the above problems, the present inventors can significantly reduce the amount of the collecting agent used and unburned by performing the addition of the collecting agent and the flotation separation in a plurality of times. We have found that carbon can be sufficiently removed, and have completed the present invention.

In addition, the present inventors use a normal floating beneficiation method to produce fly ash (hereinafter referred to as biomass co-firing ash) generated when biomass-based fuel, which has been increasing in amount in recent years, is burned in combination with coal. It was found that the amount of unburned carbon could not be sufficiently removed, and that the amount of unburned carbon could be sufficiently reduced even in such a biomass co-firing ash by using the method of the present invention.

That is, the present invention is as follows.
[1] A method for producing a modified fly ash in which the amount of unburned carbon is reduced by separating unburned carbon from the fly ash by a flotation method, wherein the fly ash, water, a collector and a foaming agent are produced. A slurry preparation step of preparing a slurry containing the above-mentioned slurry, and a flotation removing step of supplying gas from below to the slurry to generate bubbles and removing the flotation containing unburned carbon formed on the slurry. , A collecting agent replenishment step of adding water and a collecting agent to the slurry from which the flotation has been removed, and supplying gas from below to the slurry to which the water and the collecting agent have been added to generate bubbles. A method for producing a modified fly ash, which comprises an additional flotation removing step of removing the flotation containing unburned carbon formed on the slurry.

[2] Production of the modified fly ash according to [1], wherein the amount of the collecting agent added in the slurry preparation step is 1.0 to 30% by mass of the amount of unburned carbon in the fly ash. Method.
[3] The modification according to [1] or [2], wherein the amount of the collecting agent added in the collecting agent replenishing step is 10 to 50% by mass of the amount of the collecting agent added in the slurry preparation step. How to make quality fly ash.
[4] The modification according to any one of [1] to [3], wherein the total amount of the collecting agent added is 1.2 to 35% by mass of the amount of unburned carbon in fly ash. How to make fly ash.
[5] The method for producing a modified fly ash according to any one of [1] to [4], wherein no foaming agent is added in the step after the floss removing step is completed.
[6] The method for producing a modified fly ash according to any one of [1] to [5], wherein the fly ash contains 7.0% by mass or more of unburned carbon.
[7] The method for producing a modified fly ash according to any one of [1] to [6], wherein the fly ash is a biomass co-firing ash.

According to the method for producing modified fly ash of the present invention, the amount of unburned carbon in fly ash can be sufficiently reduced by using a small amount of a collecting agent.

It is a graph which shows the relationship between the amount of collecting agent used in Comparative Example 1 and the amount of unburned carbon (ignition loss) of modified fly ash.

The method for producing a modified fly ash of the present invention is a method for producing a modified fly ash in which unburned carbon is separated from the fly ash by a flotation method to reduce the amount of unburned carbon, and is described in the following (1). ) To (4).

(1) Slurry preparation step of preparing a slurry containing fly ash, water, a collecting agent and a foaming agent (2) Gas is supplied from below to the slurry to generate bubbles, which are formed on the slurry. Frost removal step of removing foam containing unburned carbon (3) Slurry to which water and a collector are added to the slurry from which the floss has been removed (4) Slurry to which water and a collector are added On the other hand, an additional floss removing step of supplying gas from below to generate bubbles and removing the floss containing unburned carbon formed on the slurry.

In the conventional technique, unburned carbon is removed by a slurry preparation step and a floss removing step, but in the method of the present invention, a collecting agent replenishing step and an additional floss removing step are additionally performed. .. The process in the method of the present invention may be a batch process or a continuous process.

The method of the present invention can sufficiently reduce the amount of unburned carbon in fly ash (hereinafter, may be referred to as ignition loss) even if the amount of the collecting agent added is smaller than that of the conventional method. .. Therefore, it is possible to reduce the cost of chemicals and the amount of waste liquid and chemicals mixed in the product. In addition, the amount of unburned carbon can be sufficiently reduced even with biomass co-firing ash, which is difficult to remove unburned carbon.

Hereinafter, each step in the method of the present invention will be described in detail.
(1) Slurry preparation step The slurry preparation step is a step of preparing a slurry containing fly ash, water, a collecting agent, and a foaming agent. For example, it is preferable to add a foaming agent after mixing and stirring fly ash, water, and a collecting agent to form an emulsion. The mixer used for mixing and stirring is not particularly limited as long as it has a sufficient shearing force and oil droplets can be dispersed in water and emulsified, and conventionally known mixers can be used.

The fly ash to be processed in the method of the present invention (sometimes referred to as raw material fly ash) includes general fly ash generated in coal-fired power plants and other facilities that burn coal, as well as coal and other than coal. A variety of fly ash can be used, such as the fuel (biomass-based fuel, etc.) and fly ash generated by co-firing combustible waste.

The amount of unburned carbon in the raw material fly ash is not particularly limited, but the amount of unburned carbon is preferably 7.0% by mass or more, more preferably 9.0% by mass or more, still more preferably 10.0% by mass or more. When fly ash is used, the effect of the present invention appears more prominently.
In addition, the effect of the present invention appears more prominently in the biomass co-firing ash in which coal and biomass fuel are co-firing.

According to the method of the present invention, the amount of unburned carbon is 5.0% by mass or less, preferably 3.0% by mass or less, more preferably 2.0% by mass or less, still more preferably 1.5% by mass or less, particularly. It can be preferably reduced to 1.0% by mass or less.

The amount of unburned carbon in the present invention is measured by using the method for measuring ignition loss described in JIS A 6201. In the present invention, it is treated as ignition loss = unburned carbon amount.

The mixing ratio (mass ratio) of the raw material fly ash and water is preferably about 1: 100 to 50: 100. By blending in this range, the treatment can be performed efficiently.

The collecting agent is an agent for improving the separability of ash particles and unburned carbon particles in fly ash, and in the method of the present invention, for example, kerosene, light oil, and heavy oil are conventionally floated. Known collectors used in the selection can be used.

The amount of the collector added in this step can be changed depending on the type of fly ash and the amount of unburned carbon, but as described above, a smaller amount may be added as compared with the case of conventional flotation. .. For example, the amount of unburned carbon in fly ash is preferably 1.0 to 30% by mass, more preferably 1.2 to 25% by mass, and further preferably 1.5 to 20% by mass. preferable.

In particular, when ordinary fly ash (coal-fired ash) is used, the effect can be easily obtained even in a small amount. Therefore, the amount of the collecting agent added is preferably the amount of unburned carbon in the fly ash. It may be less than 0% by mass, more preferably 4.0% by mass or less, still more preferably 3.0% by mass or less, and particularly preferably 2.0% by mass or less. On the lower limit side, the amount of unburned carbon in fly ash is preferably 1.0% by mass or more, more preferably 1.2% by mass or more, and further preferably 1.5% by mass or more.

On the other hand, when biomass co-firing ash is used as fly ash, a large amount of collecting agent tends to be required as compared with the case of coal-only burning ash, and the amount of collecting agent added is unburned in fly ash. The amount of carbon is preferably 5% by mass or more, more preferably 8% by mass or more, and further preferably 10% by mass or more. On the upper limit side, the amount of unburned carbon in fly ash is preferably 30% by mass or less, more preferably 25% by mass or less, and further preferably 20% by mass or less.
As described above, the biomass co-firing ash is the ash produced when the biomass-based fuel is fired together with coal, but the above tendency is remarkable when the co-firing rate of the biomass-based fuel exceeds 10% by mass. is there.

Foaming agents are added to promote the formation and stabilization of bubbles. As the foaming agent, known foaming agents such as pine oil, MIBC, and tarpineol, which have been conventionally used in flotation, can be used.

The amount of the foaming agent added can be changed depending on the type of fly ash and the amount of unburned carbon, but in general, it is preferable to add 0.1 mL or more with respect to 1000 mL of water used in the slurry preparation step. As a result, the stability of bubbles can be increased and the efficiency of removing unburned carbon can be improved.
In the method of the present invention, if the foaming agent is added in this step, it is not always necessary to add the foaming agent in the step after the floss removing step (for example, the collecting agent replenishment step).

(2) Floss removing step The floss removing step is a step of supplying gas from below to the slurry to generate bubbles and removing the floss containing unburned carbon formed on the slurry.

In this step, bubbles are generated by supplying gas from below, and unburned carbon is attached to the bubbles and floated on the slurry as floss to remove the unburned carbon from the slurry. The floss that floats on the slurry can be removed, for example, by spontaneously overflowing or mechanically scraping.

The processing of this step is usually performed using a known flotation machine. The flotation machine is composed of, for example, a flotation machine cell, an impeller, an air supply mechanism, and the like. While stirring the slurry supplied into the flotation machine cell with an impeller, gas is supplied from below to generate bubbles, and floss is floated on the slurry to remove unburned carbon.

Here, the total amount of slurry supplied into the flotation machine cell is not particularly limited, but generally, it is preferably supplied in the range of 50 to 95% with respect to the capacity of the flotation machine cell, and is supplied in the range of 60 to 85%. It is more preferable to do so. By supplying in this range, it is possible to prevent the slurry other than floss from overflowing and to carry out the treatment efficiently.

The type of gas used in this step is not particularly limited, but it is preferable to use air from the viewpoint of economy. Examples of the gas supply method include a method of forcibly supplying gas using a compressor and the like, and a method of naturally aspirating using the rotation of the impeller.

(3) Collection agent replenishment step The collection agent replenishment step is a step of adding (replenishing) water and a collection agent to the slurry from which floss has been removed in the floss removal step.
The conventional flotation was completed in the floss removing step, but in the method of the present invention, the collecting agent replenishing step and the additional floss removing step are performed after this. As a result, unburned carbon can be sufficiently removed while suppressing the amount of the collecting agent used.
The collection agent replenishment step and the additional floss removal step may be repeated depending on the amount of unburned carbon remaining.

As the collecting agent used in this step, conventionally known ones can be used as in the slurry preparation step, but the same type of collecting agent as that used in the slurry preparation step is preferable. Further, it is preferable to mix and stir the slurry before adding the collector. Thereby, unburned carbon can be removed more effectively.

The amount of the collecting agent added in this step is preferably 10 to 50% by mass, more preferably 15 to 45% by mass, and 20 to 40% by mass of the amount of the collecting agent added in the slurry preparation step. Is more preferable. The ratio of water and the collecting agent is not particularly limited, but it is preferably about the same as the ratio of water and the collecting agent in the slurry in the slurry preparation step (the concentration of the collecting agent is in the range of about ± 10% by mass).

Further, the water and the collecting agent are preferably supplied so that the total amount of the slurry after replenishment is in the range of 50 to 95% with respect to the capacity of the flotation machine cell, as in the floss removing step, and is 60 to 85. It is more preferable to supply in the range of%.

(4) Additional Floss Removal Step The additional floss removal step was formed on the slurry by supplying gas from below to the slurry to which water and the collector were added in the collector replenishment step to generate bubbles. This is a step of removing floss containing unburned carbon. The operation in this step is basically the same as the operation in the floss removing step.

The above (1) slurry preparation step to (4) additional floss removal step are performed, and finally the remaining slurry is recovered. The modified fly ash recovered in this way has a reduced amount of unburned carbon compared to the conventional flotation, even though it uses only a small amount of collecting agent compared to the conventional flotation. It becomes a thing.

The total amount of the collecting agent added in the method of the present invention is preferably 1.2 to 35% by mass, more preferably 1.5 to 30% by mass, based on the amount of unburned carbon in fly ash. It is more preferably 1.8 to 25% by mass.

In particular, when ordinary fly ash (coal-fired ash) is used, the effect can be easily obtained even in a small amount, so the amount of the collector added is 5.0 mass of the amount of unburned carbon in the fly ash. It may be less than%, preferably 4.0% by mass or less, and more preferably 3.0% by mass or less. On the lower limit side, the amount of unburned carbon in fly ash is preferably 1.2% by mass or more, more preferably 1.5% by mass or more, and further preferably 1.8% by mass or more.

On the other hand, when biomass co-firing ash is used as fly ash, a large amount of collecting agent tends to be required as compared with the case of coal-only burning ash, and the amount of collecting agent added is unburned in fly ash. The amount of carbon is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 18% by mass or more. On the upper limit side, the amount of unburned carbon in fly ash is preferably 35% by mass or less, more preferably 30% by mass or less, and further preferably 25% by mass or less.

(5) Dehydration / Drying Step Since the remaining slurry contains water and chemicals, it is preferable to dehydrate it. The dehydration method is not particularly limited, and industrially, it can be carried out using a known dehydrator such as a screw press or a filter press.

The cake obtained after dehydration is then dried. The drying method is not particularly limited, and a known method can be used. Industrially, a fluidized bed dryer, a rotary dryer, or the like can be used.

The modified fly ash thus obtained may be used alone or in combination with other components as a cement mixture, a mortar mixture (mortar admixture), a concrete mixture (concrete admixture), or the like. Can be done. On the other hand, the recovered unburned carbon can be used as fuel or the like.

Examples and comparative examples are shown below, but the technical scope of the present invention is not limited thereto.
In this embodiment, the amount of unburned carbon in fly ash is referred to as ignition loss. The measurement of ignition loss was performed by the measurement method of ignition loss described in JIS A 6201.

As the raw material fly ash, two types of fly ash A (biomass mixed ash) and fly ash B (coal-only ash) shown in Table 1 below were used.
Fly ash A was fly ash generated when coal and biomass fuel (wood pellets) were used as fuel, and the loss on ignition was 10.6% by mass.
Fly ash B was fly ash generated when only coal was used as fuel, and the ignition loss was 9.7% by mass.

In the treatment of this example, clean water was used as water, kerosene was used as a collecting agent, and pine oil was used as a foaming agent. The mass of the collecting agent and the foaming agent was calculated assuming that the specific gravity of kerosene was 0.8 g / ml and the specific gravity of pine oil was 0.92 g / ml.

The processing conditions in the slurry preparation step are as follows.
Mixer type: Household mixer Mixer capacity: 3000mL
Stirring blade diameter: φ80 mm
Stirring blade rotation speed: 5000 rpm
Processing time: 3 minutes

The processing conditions in the floss removing step and the additional floss removing step are as follows.
Cell capacity: 3000 mL
Impeller diameter: φ60mm
Impeller rotation speed: 1400 rpm
Processing time (per time): 5 minutes Gas supply method: Naturally aspirated type by impeller rotation

First, as Comparative Example 1 and Examples 1 to 5, an example in which fly ash A (biomass co-firing ash) is used will be shown.

[Comparative Example 1]
A slurry was prepared by mixing and stirring 500 g of fly ash A, 2500 mL of water, and a predetermined amount of a collector. At this time, the amount of the collecting agent used was 1 mL, 10 mL, 30 mL, 50 mL, and 70 mL (collecting agent / water = 0.04 to 2.8 Vol%). The total amount of slurry at this time was about 90% of the capacity of the flotation machine cell. 1 mL of foaming agent was added to the slurry (slurry preparation step). Then, a flotation process was performed to remove the generated floss and recover the remaining slurry (floss removal step). After dehydrating the remaining slurry by suction filtration, it was dried at 100 ° C. for 24 hours to sufficiently remove water to obtain modified fly ash, and ignition loss was measured.

FIG. 1 shows the relationship between the amount of the collecting agent used and the ignition loss of the modified fly ash. The addition ratios of the collecting agent (1 mL, 10 mL, 30 mL, 50 mL, 70 mL) to the amount of unburned carbon in the raw material fly ash are 1.5% by mass, 15.1% by mass, and 45.3% by mass, respectively. , 75.5% by mass and 105.7% by mass.

[Example 1]
Floth treatment was performed using 10 mL of the collecting agent and 1 mL of the foaming agent in the same procedure as in Comparative Example 1 to remove the generated floss (slurry preparation step, floss removing step). At this time, 850 mL of the slurry remaining in the flotation machine cell was removed at the same time as flossing. After adding 850 mL of a mixture of water and a collecting agent (collecting agent / water = 0.4 Vol%) to the remaining slurry (collecting agent replenishment step), a flotation treatment is performed in the same manner to generate the slurry. The floss was removed and the remaining slurry was recovered (additional floss removal step).

In this embodiment, the liquid level was adjusted to the same level as the first flotation process for the purpose of satisfying the conditions, and the second and subsequent flotation processes were performed. After dehydrating the remaining slurry by suction filtration, it was dried at 100 ° C. for 24 hours to sufficiently remove water to obtain modified fly ash, and ignition loss was measured.

The ignition loss of the modified fly ash obtained after the second flotation treatment was 1.6% by mass.
The total amount of the collecting agent used in the two flotation treatments was 13.4 mL. The ratio of the collecting agent added to the amount of unburned carbon in the raw material fly ash was 15.1% by mass (slurry preparation step) and 5.1% by mass (collecting agent replenishment step), for a total of 20. It was 2% by mass.

[Example 2]
The flotation process was repeated three times in the same procedure as in Example 1 (the collection agent replenishment step and the additional floss removal step were repeated twice). Of the slurry remaining after the second flotation, 660 mL was removed at the same time as the floss, so a mixture of water and a collector (collector / water = 0.4 Vol%) before the third flotation. ) Was added in an amount of 660 mL.

The ignition loss of the modified fly ash obtained after the third flotation treatment was 1.4% by mass.
The total amount of the collecting agent used in the three flotations was 16.0 mL. The ratio of the collecting agent added to the amount of unburned carbon in the raw material fly ash was 15.1% by mass (slurry preparation step), 5.1% by mass (first collecting agent replenishment step), and 4.0. It was mass% (second collection agent replenishment step), and the total was 24.2 mass%.

[Example 3]
In addition to the procedure shown in Example 1, a series of treatments were carried out by adding a foaming agent as well as a mixture of water and a collecting agent before the second flotation treatment. Specifically, 800 mL of a mixture of water and a collecting agent (collecting agent / water = 0.4 Vol%) and 0.3 mL of a foaming agent were added before the second flotation treatment. The additional amount of the foaming agent was calculated by the following method. That is, assuming that the concentration of the foaming agent in the slurry has not changed before and after the first flotation treatment, in order to make the concentration of the foaming agent in the second flotation treatment equivalent to that of the first treatment, water is used. The value obtained by dividing the additional amount of the mixture with the collecting agent by 2510 (2500 mL of water + 10 mL of the collecting agent) was taken as the additional amount of the foaming agent.

The ignition loss of the modified fly ash obtained after the second flotation treatment was 1.7% by mass.
The total amount of the collecting agent used in the two flotation treatments was 13.2 mL. The ratio of the collecting agent added to the amount of unburned carbon in the raw material fly ash was 15.1% by mass (slurry preparation step) and 4.8% by mass (collecting agent replenishment step), for a total of 19. It was 9% by mass.

[Example 4]
In addition to the procedure shown in Example 2, a series of treatments were carried out by adding a foaming agent as well as a mixture of water and a collecting agent before the second and third flotation treatments.
Specifically, 800 mL of a mixture of water and a collecting agent (collecting agent / water = 0.4 Vol%) and 0.3 mL of a foaming agent were added before the second flotation treatment. Further, before the third flotation treatment, 570 mL of a mixture of water and a collecting agent (collecting agent / water = 0.4 Vol%) and 0.2 mL of a foaming agent were added.

The ignition loss of the modified fly ash obtained after the third flotation treatment was 1.3% by mass.
The total amount of the collecting agent used in the three flotations was 15.5 mL. The ratio of the collecting agent added to the amount of unburned carbon in the raw material fly ash was 15.1% by mass (slurry preparation step), 4.8% by mass (first collecting agent replenishment step), and 3.4. It was mass% (second collection agent replenishment step), and the total was 23.4 mass%.

The above results are shown in Table 2.

As shown in Table 2, in Examples 1 to 4 according to the present invention, the ignition loss was reduced even though the amount of the collecting agent used was smaller than that of Comparative Example 1 (30 mL). Further, Examples 2 and 4 in which the collecting agent replenishment step and the additional floss removing step are repeated twice are stronger than those in Examples 1 and 3 in which the collecting agent replenishing step and the additional floss removing step are repeated once. The heat loss has been reduced.
The conventional method of Comparative Example 1 could not sufficiently reduce the ignition loss of the biomass co-firing ash, but in the methods of Examples 1 to 4 according to the present invention, the amount of the collecting agent used was small. Nevertheless, it could be reduced to nearly 1%.
It should be noted that a sufficient ignition loss reduction effect was obtained without adding a foaming agent in the step after the floss removal step was completed. Therefore, in the method of the present invention, it is not necessary to add an expensive foaming agent.

Next, as Comparative Example 2 and Example 5, an example in which fly ash B (coal-fired ash) is used will be shown.

[Comparative Example 2]
A slurry was prepared by mixing and stirring 500 g of fly ash B, 2500 mL of water, and a predetermined amount of a collector. At this time, the amounts of the collecting agent used were 1 mL and 10 mL (collecting agent / water = 0.04 Vol% and 0.4 Vol%). 0.3 mL of foaming agent was added to the slurry (slurry preparation step). Then, a flotation process was performed to remove the generated floss and recover the remaining slurry (floss removal step). The remaining slurry was dehydrated by suction filtration and then dried at 100 ° C. for 24 hours to sufficiently remove water to obtain a modified fly ash.

The ignition loss of the obtained modified fly ash was 2.2% by mass when 1 mL of the collecting agent was used (1.5% by mass of the collecting agent added to the amount of unburned carbon), and the collecting agent was used. When 10 mL was used (the addition ratio of the collector to the amount of unburned carbon was 15.1% by mass), it was 1.6% by mass.

[Example 5]
Floth treatment was performed using 1.0 mL of the collecting agent and 0.3 mL of the foaming agent in the same procedure as in Comparative Example 2 to remove the generated floss (slurry preparation step, floss removing step). At this time, it was found that 660 mL of the slurry remaining in the flotation machine cell was removed at the same time as flossing. After adding 660 mL of a mixture of water and a collecting agent (collecting agent / water = 0.4 Vol%) to the remaining slurry (collecting agent replenishment step), a flotation treatment was performed in the same manner to generate the slurry. The floss was removed and the remaining slurry was recovered (additional floss removal step).

After dehydrating the remaining slurry by suction filtration, it was dried at 100 ° C. for 24 hours to sufficiently remove water to obtain modified fly ash, and ignition loss was measured.

The ignition loss of the modified fly ash obtained after the second flotation treatment was 0.7% by mass.
The total amount of the collecting agent used in the two flotation treatments was 1.3 mL. The addition ratio of the collecting agent to the amount of unburned carbon in the raw material fly ash is 1.7% by mass (slurry preparation step) and 0.4% by mass (collecting agent replenishment step), for a total of 2. It was 1% by mass.

The above results are shown in Table 3.

As shown in Table 3, in Example 5 according to the present invention, the ignition loss was reduced even though the amount of the collecting agent used was smaller than that of Comparative Example 2 (10 mL). Further, in Example 5, an extremely low ignition loss of 1.0% or less was realized.

According to the method for producing modified fly ash of the present invention, modified fly ash useful as a cement mixture, mortar mixture, concrete mixture and the like can be obtained, which is industrially useful.

Claims (7)

It is a method of separating unburned carbon from fly ash by the flotation method to produce modified fly ash with a reduced amount of unburned carbon.
A slurry preparation step for preparing a slurry containing fly ash, water, a collecting agent, and a foaming agent, and
A floss removing step of supplying gas from below to the slurry to generate bubbles and removing floss containing unburned carbon formed on the slurry.
A collection agent replenishment step of adding water and a collection agent to the slurry from which the floss has been removed, and a collection agent replenishment step.
An additional floss removing step of supplying gas from below to the slurry to which the water and the collecting agent have been added to generate bubbles and removing the floss containing unburned carbon formed on the slurry.
A method for producing a modified fly ash, which comprises. The method for producing modified fly ash according to claim 1, wherein the amount of the collecting agent added in the slurry preparation step is 1.0 to 30% by mass of the amount of unburned carbon in the fly ash. The production of the modified fly ash according to claim 1 or 2, wherein the amount of the scavenger added in the scavenger replenishment step is 10 to 50% by mass of the amount of the scavenger added in the slurry preparation step. Method. The method for producing a modified fly ash according to any one of claims 1 to 3, wherein the total amount of the collecting agent added is 1.2 to 35% by mass of the amount of unburned carbon in the fly ash. .. The method for producing a modified fly ash according to any one of claims 1 to 4, wherein no foaming agent is added in the step after the floss removing step is completed. The method for producing a modified fly ash according to any one of claims 1 to 5, wherein the fly ash contains 7.0% by mass or more of unburned carbon. The method for producing a modified fly ash according to any one of claims 1 to 6, wherein the fly ash is a biomass co-firing ash.

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