JP7079179B2 - Manufacturing method of coal ash granulation - Google Patents

Description

The present invention relates to a method for producing a coal ash granule having a uniform particle size.

Coal ash generated from coal-fired power plants can be used as concrete admixtures and cement admixtures that utilize pozzolan reactivity, and can also be used as roadbed materials and aggregates by adding cement and water to form granules. Can also be used as. A bread-type pelletizer is generally known as a powder granulator, but since the bread-type pelletizer does not seal the bread, the powder and the granulated material are likely to dissipate and the mixing becomes insufficient. Therefore, in granulation using a bread-type pelletizer, the powder must be mixed in advance using a mixer, but in that case, granulation requires two steps of mixing and molding, and the apparatus mixes. Since two machines, a machine and a granulator, are required, the production efficiency of the bread-type pelletizer is low and the cost is high. Further, as will be described later, the particle size of the coal ash granules produced by using the bread-type pelletizer varies widely from 0.6 mm to 10 mm or more, and it is difficult to adjust the particle size.

Therefore, in the production of granulated products using a bread-type pelletizer, several methods for making the particle size uniform have been proposed. for example,
In the method for producing coal ash sand described in Patent Document 1, a rotary blade that collides with the falling powder is provided in a region where the powder falls on the rotary pan, and the powder scattered by the collision with the rotary blade collides. A bread-type granulator provided with a fixing plate for this purpose is used.
The method for producing a granulating raw material for sintering described in Patent Document 2 is a mixing step of adding water to a blending raw material and mixing with a drum mixer, and a granulating step of granulating the mixed raw material with a pan-type pelletizer. This is a method for producing a granulation raw material for sintering, and is a method for producing by crushing a mixed raw material containing coarse particles between the mixing step and the granulation step.

In the method for producing a granulating raw material for sintering described in Patent Document 3, the type, rotation speed, and pressing of the crushing blade are determined according to the size of the particle size of the compounded raw material that rolls in a pan-type pelletizer in a vortex shape. Pseudo-particles having the same particle size, which are desirable as a granulation raw material for sintering, are continuously re-granulated in the pan-type pelletizer while crushing according to the particle size by adjusting the force or the like. It is a manufacturing method.
In the method for producing a granulating raw material for sintering described in Patent Document 4, coarse pseudo-particles in a rolling layer of a compounding raw material staying in a bread-type pelletizer are formed on a wall surface scraper and / or a bottom surface in the bread-type pelletizer. This is a method in which a scraper with a crushing function, which consists of a scraper, scrapes off the deposits and at the same time crushes the deposits, and re-granulates the particles to an appropriate particle size.

Further, in the method for producing a granulation raw material for sintering described in Patent Document 5, coarse pseudo-particles in a rolling layer of a compounding raw material staying in a bread-type pelletizer are projected from a plurality of crushed teeth. This is a method of re-granulation to an appropriate particle size while crushing by a pair of crushing rolls rotating in opposite directions.

Japanese Unexamined Patent Publication No. 2-251408 Japanese Unexamined Patent Publication No. 2014-201763 Japanese Unexamined Patent Publication No. 2014-227568 Japanese Unexamined Patent Publication No. 2014-234545 Japanese Unexamined Patent Publication No. 2015-54980

However, all of the methods of Patent Documents 1 to 5 require a drastic modification of the bread-type pelletizer, and the modified device has low versatility.

Therefore, an object of the present invention is to provide a method for producing a coal ash granulated product having a simple granulation process and a granulation apparatus and a narrow particle size distribution.

Therefore, as a result of diligent studies on the production method, the present inventor has found that a method for producing coal ash granules under specific operating conditions using a specific granulation device can achieve the above-mentioned problems, and the present invention has been found. Was completed.
That is, the present invention is a method for producing a coal ash granulated product having the following constitution.

[1] A method for producing a coal ash granulated product using a granulator having a rotating drum having a lid that can be opened and closed, which comprises the following steps (A) to (C). Production method.
(A) With the covered surface of the rotary drum facing up, a powder containing at least coal ash and a binder is poured into the rotary drum having an inclination angle of 0 to 45 ° from the vertical, and then the lid is closed. Preliminary mixing step (B) With the lid of the rotating drum open, the rotation with the lid of the rotating drum facing up and the rotation having an inclination angle of 5 to 45 ° from the vertical. While rotating the drum at 15 to 20 rpm for 25 to 30 minutes, water is intermittently added to the rotating drum to produce granulated nuclei. (C) A state in which the lid of the rotating drum is opened. Alternatively, in the closed state, the particle size adjusting step of adjusting the particle size of the granulated product while rotating the rotating drum at 1 to 5 rpm for 5 to 10 minutes.
[2] A method for producing a coal ash granulated product using a granulator having a rotating drum having a lid that can be opened and closed, which comprises the following steps (D) to (F). Production method.
(D) With the covered surface of the rotary drum facing up, a powder containing at least coal ash and a binder is poured into the rotary drum having an inclination angle of 0 to 45 ° from the vertical, and then the lid is closed. Preliminary mixing step (E) With the lid of the rotating drum open, the rotation with the lid of the rotating drum facing up and the rotation having an inclination angle of 5 to 45 ° from the vertical. While rotating the drum at 15 to 20 rpm for 25 to 30 minutes, water is intermittently added to the rotating drum to produce granulated nuclei. Step for producing granulated nuclei (F) With the lid of the rotating drum open. , While rotating the rotating drum at 1 to 5 rpm for 5 to 10 minutes, water is intermittently added to the rotating drum to prepare granulated nuclei, and the particle size of the granulated product is adjusted.
[3] The coal ash granulated product according to the above [1] or [2], wherein the water addition is performed at a position where the powder that repeatedly rises and falls in the rotary drum starts to fall due to the rotation of the rotary drum. Production method.

In the method for producing a coal ash granulated product of the present invention, the granulation process and the granulation apparatus are simple, and the particle size distribution of the obtained granulated product is narrow. Further, the method for producing a coal ash granulated product of the present invention can be applied to the granulation of powders other than coal ash, and is highly versatile.

It is a figure which shows an example of the granulation machine which installed the rotary drum which has the openable and closed lid used in this invention in the vertical direction, (A) is a front view, (B) is a side view, (C) is a plane. It is a figure. It is a photograph showing a state in which the lid of the rotary drum is opened and granulation is performed in a state where the rotary drum is tilted. However, as the rotary drum shown in FIG. 2, a drum larger than the rotary drum shown in FIG. 1 was used. It is a figure which shows the particle size distribution of a coal ash granulation.

As described above, the method for producing a coal ash granulated product of the present invention is a method for producing a coal ash granulated product using a granulator having a rotary drum having a lid that can be opened and closed, and (A) reserve. A method for producing a coal ash granule, which includes a specific mixing step, (B) a granulation nucleus producing step, and (C) a particle size adjusting step.
Hereinafter, the present invention will be described separately for each step of the method for producing a coal ash granulated product and each raw material used for the method for producing a coal ash granulated product.

1. 1. Each step of the method for producing coal ash granulated product (A) Preliminary mixing step The step is performed in a rotating drum having an inclination angle of 0 to 45 ° from the vertical with the lidped surface of the rotating drum facing up. This is a step of adding powder containing at least coal ash and a binder, and then closing the lid and rotating the powder to premix.
As shown in FIG. 1, the granulator used in the present invention is a granulator equipped with a rotary drum 1 having a lid 2 that can be opened and closed, and the coal ash in the rotary drum 1, a binder, and the like are used. By the rotation of the rotary drum 1, the ascending motion and the falling motion are repeatedly mixed in the rotary drum 1. When the inclination angle of the rotating drum is 0 to 45 °, the powder does not scatter to the outside even when the lid is open, and the powder can be efficiently mixed.
The same can be said for the (D) preliminary mixing step as in the (A) preliminary mixing step.

(B) Granulation Nucleus Fabrication Step In this step, with the lid of the rotating drum open, the rotating drum having an inclination angle of 5 to 45 ° from the vertical is 15 with the side with the lid of the rotating drum facing up. This is a step of intermittently adding water to the rotating drum while rotating at ~ 20 rpm for 25 to 30 minutes to prepare granulated nuclei.
The tilt angle of the rotating drum is adjusted in the range of 5 to 45 ° from the vertical direction while checking the state of granulation. If the inclination angle of the rotating drum is less than 5 °, the powder may scatter, and if it exceeds 45 °, the production efficiency of the granulated nuclei may decrease.
Further, when the rotation speed of the rotating drum is 15 to 20 rpm, granulation nuclei having uniform particle sizes are easily formed, and the time (rotation time) required for producing the granulation nuclei is as short as 25 to 30 minutes.
In the present invention, the water drops the powder that repeatedly rises and falls in the rotating drum due to the rotation of the rotating drum in order to prevent the aggregation of granulation nuclei, the promotion of particle growth, and the adhesion of the powder to the drum. It is preferable to carry out at the starting position.
The same can be said for the (E) granulation nuclei preparation step as in the (B) granulation nuclei preparation step.

(C) Particle size adjusting step In this step, the particle size of the granulated product is adjusted while the rotating drum is rotated at 1 to 5 rpm for 5 to 10 minutes with the lid of the rotating drum opened or closed. This is the process of adjustment.
If the rotation speed of the rotating drum is 1 to 5 rpm and the rotation time is 5 to 10 minutes, it is difficult for the granulated nuclei to grow, so that it is easy to maintain the initial particle size and narrow particle size distribution of the granulated nuclei.
In the (F) particle size adjusting step, as compared with the (C) particle size adjusting step, water is intermittently added to the rotating drum while rotating the rotating drum with the lid of the rotating drum open. The difference is that the granulated nuclei are produced in the same way, but when it is difficult to produce the granulated nuclei, the granulated nuclei preparation process is extended, and in the (F) particle size adjustment step, the granulated nuclei are produced and the grains are produced. This is an embodiment in which the diameter is adjusted at the same time.
In addition, in order to prevent the aggregation of granulation nuclei, the promotion of particle growth, and the adhesion of powder to the drum, the water addition in the (F) particle size adjustment step also rises and falls in the rotating drum due to the rotation of the rotating drum. It is preferable to carry out the procedure at a position where the powder starts to fall.

2. 2. Raw materials used in the production method of coal ash granules The essential raw materials used in the production method of the present invention are coal ash, binder, and water.
(1) Coal ash The coal ash used in the present invention is not particularly limited, and is, for example, a dust collector from the combustion gas generated when pulverized coal is burned in a coal-fired power plant, an oil refinery factory, another chemical factory, or the like. Examples include the powder collected by the fly ash and the fly ash specified in JIS A 6201 "Fly ash for coal". The brain specific surface area of the coal ash is preferably 2500 to 7000 cm ² / g, more preferably 2600 to 6000 cm ² / g.

(2) Bonding material Examples of the bonding material used in the present invention include the following organic bonding materials and inorganic bonding materials.
(i) Organic binders Organic binders include, for example, starches, polyvinyl alcohols, cellulose derivatives, polyalkylene oxides, polycarboxylic acids, polyvinylpyrrolidone, polyvinyl acetate, polyurethanes, ethylene / vinyl acetate resins, styrene / butadiene rubbers, etc. One or more selected from natural rubber, agar, and gelatin can be mentioned.

Examples of the starches include modified starches such as pregelatinized starches, oxidized starches, and starch derivatives, and dextrins, in addition to starches.
Examples of the cellulose derivative include carboxymethyl cellulose and a salt thereof, hydroxypropylmethyl cellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, ethyl cellulose, hydroxymethyl cellulose and the like.
Examples of the polyalkylene oxide include polyethylene oxide, polypropylene oxide, and a copolymer of ethylene oxide and propylene oxide.
Examples of the polycarboxylic acids include polyacrylic acid and its salt, polyacrylic acid ester, polymethacrylic acid and its salt, polymethacrylic acid ester and the like. Polycarboxylic acids include both homopolymers and copolymers.
Among these organic binders, starches and polyvinyl alcohol are preferable because they impart appropriate plasticity to coal ash, have excellent shapeability, and are easy to granulate.

In particular, the contents of amylose and amylopectin in the starches are preferably 10% or more and less than 90%, more preferably 13% or more and less than 87%, still more preferably 15% or more and less than 85%, respectively. ..
When the content of amylose is 10% or more, the glue is easily aged (crystallized) and the hardness is increased, so that the strength of the granulated product is improved. Further, when the content of amylopectin that increases the viscosity of the glue is less than 90%, the viscosity of the glue is lowered and the kneaded product containing coal ash is easily kneaded.
Here, the starches having an amylose and amylopectin content of 10% or more and less than 90%, respectively, are, for example, corn starch, wheat starch, rice starch, bean starch, potato starch, glutinous rice starch, sweet potato starch, and tapioca starch. Such as starch, and the above-mentioned chemical starch made from these starches.
Of the organic binders, the water-soluble binder is mainly used in the form of an aqueous solution (including a paste), and the water-insoluble binder is mainly used in the form of an emulsion.

(Ii) Inorganic binder The inorganic binder is selected from, for example, cement, gypsum powder, pozzolan powder, silica powder, limestone powder, cement kiln dust, swelling material, construction-generated soil powder, incineration ash, slag powder, and clay powder. One or more of them can be mentioned.
The cement is not particularly limited, and is one selected from ordinary Portland cement, early-strength Portland cement, ultra-early-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, blast furnace cement, silica cement, eco-cement and the like. The above can be mentioned.
In addition, the gypsum powder may be one or more selected from dihydrate gypsum, flue gas desulfurization gypsum, phosphoric acid gypsum, titanium gypsum, hydrofluoric gypsum, refined gypsum, semi-hydrated gypsum, anhydrous gypsum and the like.
The slag powder is selected from blast furnace granulated slag, blast furnace slow cooling slag, converter slag, secondary refining slag, electric furnace system slag, ferronickel slag, copper slag, electric furnace oxidized slag, and coal gasification molten slag. One or more types can be mentioned. Among these, blast furnace granulated slag is preferable because it has excellent latent hydraulic limeness.
Further, the pozzolan powder may be one or more selected from volcanic ash, shirasu, volcanic rock powder, silicic acid clay powder and the like.

Cement kiln dust preferably has a K ₂ O content of 5 to 40% by mass, a Cl content of 3 to 30% by mass, and SO ₃ from the viewpoint of long-term strength development of coal ash granules. The content is 5 to 20% by mass, and chlorine bypass dust is particularly preferable.
Examples of the clay powder include one or more selected from bentonite, kaolin, talc, acidic white clay, attapargite, sepiolite, diatomaceous earth, sepiolite, zeolite and the like.
Examples of the expansion material include calcium sulfoluminate-based expansion material and lime-based expansion material, and examples of the construction-generated soil powder include soil and residual soil generated from a construction site, a construction site, and the like, and the incineration ash includes the incineration ash. Examples thereof include sewage sludge incineration ash, urban waste incineration ash, and RDF incineration ash.

Among these inorganic binders, cement is preferable, and more preferably, ordinary Portland cement, early-strength Portland cement, and ultra-early-strength cement can be used because they have excellent early strength development and can increase the production efficiency of granulated products. Portland cement and eco-cement.
The brain specific surface area of the inorganic binder is preferably 2000 to 10000 cm ² in terms of cost, availability, ease and strength of granulation of granulated product, and strength development of coal ash granulated product. / G, more preferably 2500 to 9000 cm ² / g, still more preferably 3000 to 8000 cm ² / g.
The organic binder and the inorganic binder may be used alone or in combination.

(3) Water The water is not particularly limited, and examples thereof include tap water, reclaimed water, treated sewage water, and water separated from ready-mixed concrete sludge.
Further, in the steps of producing the granulated nuclei of (B), (E) and (F), "intermittently adding water" means that the supply amount and the supply rate of water differ depending on the amount of the powder raw material. Although it cannot be determined unambiguously, it is advisable to add water intermittently (intermittently) while checking the granulation state as appropriate.

(4) Formulation of each raw material of coal ash granulation Next, the composition of each raw material of coal ash granulation will be described.
In the coal ash granules containing the organic binder, the total of the coal ash and the organic binder is 100% by mass, the coal ash is preferably 95 to 99.5% by mass, and the organic binder is 0.5 to 5%. It contains 2 to 35 parts by mass of water with respect to 100 parts by mass of the total of coal ash and organic binder.
If the blending ratio of coal ash is less than 95% by mass, the amount of coal ash processed is relatively small, and if it exceeds 99.5% by mass, the amount of organic binder is relatively small and the strength of the granulated product may decrease. be. The blending ratio of coal ash is more preferably 96 to 99% by mass.
Further, if the mixing ratio of water is less than 2 parts by mass, granulation may be difficult, and if it exceeds 35 parts by mass, problems such as adhesion of the kneaded material to the granulation apparatus or the like during granulation are likely to occur. The mixing ratio of water is more preferably 3 to 30 parts by mass, still more preferably 5 to 25 parts by mass, and particularly preferably 10 to 20 parts by mass with respect to 100 parts by mass of the total of coal ash and the organic binder.

Further, in the coal ash granulation containing the inorganic binder, coal ash is preferably used, with the total of the coal ash and the inorganic binder being 100% by mass. It contains 60 to 99.5% by mass and 0.5 to 40% by mass of an inorganic binder, and contains 2 to 35 parts by mass of water with respect to 100 parts by mass of coal ash and the inorganic binder in total.
When the blending ratio of coal ash is less than 60% by mass, the amount of coal ash processed is relatively small, and when it exceeds 99.5% by mass, the amount of inorganic binder is relatively small and the strength of the granulated product decreases. There is. The blending ratio of coal ash is more preferably 70 to 96% by mass, still more preferably 78 to 94% by mass.
Further, if the mixing ratio of water is less than 2 parts by mass, granulation may be difficult, and if it exceeds 35 parts by mass, problems such as adhesion of the kneaded material to the granulation apparatus or the like during granulation are likely to occur. The mixing ratio of water is more preferably 3 to 30 parts by mass, still more preferably 5 to 25 parts by mass, and particularly preferably 10 to 20 parts by mass with respect to 100 parts by mass of the total amount of powder.

The coal ash granules produced using the present invention do not adhere to each other even if they are piled up immediately after production. The obtained coal ash granules are preferably cured in order to promote the development of strength by the binder, but there is no limitation on such a curing method, and aerial curing such as standing in a place where rain or the like can be prevented. Is enough.
The coal ash granules of the present invention can be made into a powder capable of exhibiting the pozzolan reactivity originally possessed by the coal ash (powder) by crushing the coal ash granules when the mixing amount of the binder is small. It can be easily returned. Further, by increasing the mixing amount of the binder, the crushing strength of the coal ash granulated product can be increased, and after the predetermined curing, it can be used as a roadbed material or an aggregate. Further, when the coal ash granulated product of the present invention is calcined at a temperature of about 1000 ° C., a coal ash granulated product having higher crushing strength can be obtained.

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples.
1. 1. Materials used (1) Coal ash The coal ash used is fly ash type IV specified in JIS A 6201, with a brain specific surface area of 3300 cm ² / g and ignition loss of 3.18%.
(2) Binder The binder used is pregelatinized starch (manufactured by Japan Corn Starch).
(3) Tap water

2. 2. Manufacture of coal ash granules (A) Preliminary mixing process Combined in the rotating drum of the mixer shown in Fig. 1 (tilt angle is 18 °, lid diameter / rotating drum inner diameter ratio is 0.45). After putting the coal ash and the binder so that the mass ratio of the material / (coal ash + binder) is 0.02, cover it, and then rotate the rotating drum at 20 rpm for 20 minutes to combine it with the coal ash. The materials were mixed in advance.
(B) Granulation nuclei production step Next, open the lid and rotate the rotating drum at 20 rpm for 20 minutes so that the mass ratio of water / (coal ash + binder) is 0.27. Water was added intermittently using a sprayer toward the drop start position of the powder inside.
(C) Particle Size Adjusting Step The water addition was stopped, the lid was closed, and the rotary drum was rotated at 5 rpm for 10 minutes to adjust the particle size of the granulated product to obtain a coal ash granulated product (Example).
For comparison, the coal ash, pregelatinized starch, and water were put into a Hobart mixer (A-200 manufactured by Hobart Japan) at the same mass ratio as described above, and at a low speed (the rotation speed of the agitator was 107 rpm). The kneaded product was kneaded for 1 minute to prepare a kneaded product. Next, the kneaded product was put into a pan-type pelletizer (pan: inner diameter 60 cm x depth 15 cm, angle 48 °, rotation counterclockwise, rotation speed 22 rpm) and granulated to produce coal ash granules (comparison). Example 1) was manufactured.
Further, as a comparison, a coal ash granulated product (Comparative Example 2) was produced in the same manner as in Examples except that the particle size adjusting step (C) was omitted.

3. 3. Particle size measurement of coal ash granules Next, the obtained coal ash granules (Example 1, Comparative Example 1, and Comparative Example 2) had a mesh size of 10 mm, 5 mm, 2.5 mm, and 1.2 mm. The particle size distribution was measured by classifying with a sieve of 600 μm and 300 μm.
These results are shown in FIG.

As shown in FIG. 3, according to the production method of the present invention, mixing and granulation can be continuously performed simultaneously in the same apparatus, and small diameter (1.2 to 2.5 mm) coal ash granulation with a narrow particle size distribution is performed. You get things.

1 rotary drum 2 lid 3 motor

Claims (3)

A method for producing coal ash granules using a granulator having a rotary drum having a lid that can be opened and closed, the method for producing coal ash granules, which comprises the following steps (A) to (C).
(A) With the covered surface of the rotary drum facing up, a powder containing at least coal ash and a binder is poured into the rotary drum having an inclination angle of 0 to 45 ° from the vertical, and then the lid is closed. Preliminary mixing step (B) With the lid of the rotating drum open, the rotation with the lid of the rotating drum facing up and the rotation having an inclination angle of 5 to 45 ° from the vertical. While rotating the drum at 15 to 20 rpm for 25 to 30 minutes, water is intermittently added to the rotating drum to produce granulated nuclei. (C) A state in which the lid of the rotating drum is opened. Alternatively, in the closed state, the particle size adjusting step of adjusting the particle size of the granulated product while rotating the rotating drum at 1 to 5 rpm for 5 to 10 minutes. A method for producing coal ash granules using a granulator having a rotary drum having a lid that can be opened and closed, the method for producing coal ash granules, which comprises the following steps (D) to (F).
(D) With the covered surface of the rotary drum facing up, a powder containing at least coal ash and a binder is poured into the rotary drum having an inclination angle of 0 to 45 ° from the vertical, and then the lid is closed. Preliminary mixing step (E) With the lid of the rotating drum open, the rotation with the lid of the rotating drum facing up and the rotation having an inclination angle of 5 to 45 ° from the vertical. While rotating the drum at 15 to 20 rpm for 25 to 30 minutes, water is intermittently added to the rotating drum to produce granulated nuclei. Step for producing granulated nuclei (F) With the lid of the rotating drum open. , While rotating the rotating drum at 1 to 5 rpm for 5 to 10 minutes, water is intermittently added to the rotating drum to prepare granulated nuclei, and the particle size of the granulated product is adjusted. The method for producing coal ash granules according to claim 1 or 2, wherein the water addition is performed at a position where the powder that repeatedly rises and falls in the rotary drum starts to fall due to the rotation of the rotary drum.

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