JP2015105223A - Porous granulated calcination product and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alumina porous granulated calcination product that has a large specific surface area as well as homogeneous network-like pores to the interior.SOLUTION: The porous granulated calcination product is produced by firmly connecting innumerable alumina particles while leaving mainly communicated pores in a network-like state over the whole cross-section of granulated product particle; the pore is controlled in the inner diameter by the droplet size of pore-forming agent; and a pore-forming agent (emulsion) is sprayed on the raw material and a coating layer of pore-forming agent is formed over the surface of raw material particles to control the inner diameter of pore.

Description

  The present invention relates to a porous granulated fired product and a method for producing the same. Here, the porous granulated fired product of alumina will be mainly described as an example, but the production method of the present invention can be applied to other porous granulated fired products of ceramic.

  Here, “sintering” means that a granulated product made of fine alumina powder is solidified by high-temperature treatment at a temperature (for example, 700 ° C.) or higher at which a γ-form is obtained. However, complete sintering in which the pores are completely blocked is not included.

  In the following description, “%” and “part” indicating a blending unit mean “% by mass” and “part by mass”, respectively, unless otherwise specified.

  Each characteristic value is defined as follows.

    “Average particle diameter” means a median diameter and is a value measured by a laser diffraction method (average particle diameter less than 50 μm or a value obtained by JIS standard mesh sieve (average particle diameter of 50 μm or more)).

    “Specific surface area”: JIS Z 8830 “Method for measuring specific surface area of powder by gas adsorption” (value measured according to BET method j).

    “Sphericality”: An arithmetic average value (n = 10) measured by a binarization measurement method by an image analysis method using a scanning electron microscope (SEM).

    “Pore diameter”: a mean value of arithmetic calculation (n = 10) determined by a binary valence measurement method among image analysis methods using a scanning electron microscope (SEM).

    “Compressive strength” ·· Measured according to JISR1608 “Testing method for compressive strength of fine ceramics”.

  Alumina is widely used based on its high heat resistance and low reactivity. In particular, α-alumina porous granulated calcined products are used as materials for functional products in various applications, catalyst carriers, microorganism fixed beds, culture beds, and filtration media.

  And these porous granulated calcined products are required to be able to control pore distribution easily and inexpensively and to be used as a high-strength catalyst carrier, and to further contain a low soda content ( Patent Document 1).

  In order to meet these requirements, Patent Document 1 proposes a method of manufacturing an α-alumina molded body (α-alumina fired product) having the following configuration.

  “At least partially rehydratable alumina powder obtained by calcining gibbsite crystal aluminum hydroxide with controlled particle size and bulk density is mixed with water, and this mixture is molded to form a molded body The molded body is rehydrated while being held in a humid atmosphere or steam at 110 to 200 ° C., and then the rehydrated molded body is fired at 1200 ° C. or higher. . "

  In Patent Document 1, paragraphs 0051 and 0052, the calcined rehydratable alumina powder raw material is formed into a spherical granulated product having a diameter of 2 to 4 mm while spraying water using a dish granulator. And firing the granulated product.

  Further, although not related to the porous granulated fired product of α-alumina, Patent Document 2 proposes a method for producing a transition alumina molded body (active alumina molded body) (precursor of porous fired product) having the following configuration. ing.

  “In a method for producing a transition alumina molded product obtained by wet-molding a transition alumina powder having at least partially rehydratability, rehydrating, and then firing the rehydrated molded product, A process for producing a transition alumina molded article characterized by having a powder or latex mainly composed of polymethacrylate having a center particle diameter of 0.01 to 100 μm during wet molding. ”

  In paragraph 0032 of Patent Document 2, mixed powder obtained by adding polymethyl methacrylate, which is a pore-forming agent, to calcined rehydratable alumina is mixed using a rolling granulator equipped with a rotating dish. In addition, it is described that a spherical granulated product (wet molding) having a diameter of 2 to 4 mm is formed while spraying water, and the granulated product is fired after rehydration treatment.

JP 2003-48768 A JP-A-8-245281

  However, any of the methods for producing the above-mentioned porous granulated calcined product or precursor thereof requires the rolling granulated product to be rehydrated by introducing it into an autoclave, etc. Was bulky. Further, it is difficult to prepare a granulated fired product in which pores are formed up to the inside, that is, pores communicating in a mesh shape are formed on the entire particle cross section.

  An object of the present invention is to provide a porous granulated fired product of alumina that can solve the above problems (problems and demands) and a method for producing the same.

  As a result of diligent development to solve the above-mentioned problems, the present inventors have conceived a porous granulated fired product (1) having the following constitution and a production method (2) thereof.

  (1) An innumerable alumina particle is a granulated fired product obtained by consolidating the pores that remain mainly in the entire cross-section of the granulated particles, and the pores have an inner diameter of pores. It is controlled by the droplet diameter of the forming agent.

  The pores that communicate with each other are formed in a mesh shape on the entire cross section of the granulated particles, so that it is easy to obtain a large specific surface area, and the mesh pore size is uniform, so the strength and quality of the granulated fired product Is easy to stabilize.

  (2) The method for producing a porous granulated fired product having the above-described configuration has the following configuration.

A raw material comprising alumina fine powder, including a granulation step of wet granulation while spraying a liquid agent using a rolling granulator equipped with a rotating dish, and a firing step of firing the granulated product,
The granulation step is
1) A pore-forming agent is primarily introduced into the raw material charged from the upper part side facing the discharge part located obliquely below the rotating dish and primaryly circulated along the outer peripheral part of the rotating dish. Spraying process,
2) a step of secondary spraying the binder on the raw material after the primary spraying that undergoes secondary rolling circulation inside the primary rolling circulation; and
3) A step of granulating the raw material after the secondary spraying into a granulated product of a required diameter by further granulation by rolling.
Each sub-process of
The primary / secondary spraying is performed at the reversing side portions where the primary / secondary rolling circulation circulates, respectively.

  In the above production method, it is not necessary to put the granulated product after wet granulation into an autoclave or the like for rehydration as in the prior art, and the production man-hours and heat energy cost can be reduced. In addition, by spraying each spray solution at a different position on the rotating dish, the amount of spray of these drugs per unit time can be adjusted, and a porous granulated calcined product having a homogeneous specific surface area, pore diameter and particle size can be easily obtained. Can be obtained.

  In addition, if each spray position is not the reversal side part of rolling circulation, the overlap of each primary and secondary rolling circulation is large, and spraying at another position is difficult.

It is a model sectional view in the granulated particle of the porous granulated fired product of the present invention. It is a side view of the rotating plate of the rolling granulator used for this invention. It is an operation explanatory top view of a rotating plate similarly. It is model explanatory drawing of the granulation process in the manufacturing method of this invention. It is model explanatory drawing of a baking process similarly. (A) and (B) are an SEM photograph (× 50 times) and an enlarged SEM photograph (× 1000 times) of each granulated product in Example 1 and Comparative Example 1. FIG.

  Hereinafter, the porous granulated fired product of the present invention and the production method thereof will be described with reference to the drawings.

  The porous fired granulated particles 11 are formed by solidifying pores (hereinafter simply referred to as “pores”) 13 in which innumerable alumina particles are mainly communicated with each other (see FIG. 1). ). The pore 13 has an inner diameter controlled by the droplet diameter of the pore-forming agent.

  Here, the practical characteristics of the fired product will be described below. Select from these ranges as appropriate.

1) Average particle diameter (median): 0.1 to 5 mm (preferably 0.5 to 5 mm),
2) Specific surface area (BET): 0.1 to 10 m ² / g (preferably 0.5 to ⁵ m ² / g),
3) Sphericity: 1.0-1.5,
4) Pore diameter: 0.5-50 μm.

  Next, the manufacturing method of the porous granulated fired material of this invention is demonstrated based on FIGS.

  It is premised on including a granulation step of granulating while using an alumina fine powder as a raw material while coating a drug using a rolling granulator equipped with a rotating dish, and a firing step of firing the granulated product.

The characteristics of the fine alumina powder used as the raw material differ depending on the required characteristics of the granulated fired product. For example, when used for a catalyst carrier or the like, the porous granulated calcined product is required to have a characteristic that the soda content is low and the pore distribution is dense. For this reason, calcined alumina fine powder, which is a relatively inexpensive alumina fine powder, that is commercially available as low soda alumina fine powder (α alumina) having a low content of soda components can be suitably used. Specifically, it is desirable to use a soda (Na ₂ O standard) content of 0.3% or less, further 0.1% or less, and an average particle size of 0.1 to 100 μm, more preferably 1 to 5 μm. The alumina fine powder as a raw material may be β alumina or γ alumina (including ρ, χ, η, and δ).

  As the drug, 1) a pore-forming agent (primary spray solution) and 2) a binder (secondary spray solution) are used. Specifically, it is as follows.

1) Pore forming agent (primary spray):
As the pore forming agent, water-insoluble polymers (synthetic resin, natural rubber or synthetic rubber) dispersed in water can be used. The reason why water is used as a dispersion medium is that the drying speed can be easily controlled. The pore-forming agent is preferably one that does not have wettability with respect to the particle surface of the raw material after primary spraying (contact angle is obtuse). This is because the pore-forming agent droplets do not spread on the particle surface and the droplet diameter can be easily controlled.

  The synthetic resin may be thermoplastic or thermosetting. Specifically, polyvinyl acetates (PVAC) (including copolymers), acrylic resins (polyacrylic acid ester, polymethacrylic acid ester), novolac-type phenolic resin, which can be smoothly eliminated during firing, Polyolefin, copolymerized nylon, copolymerized polyester and the like can be suitably used. As the synthetic rubber, polyisoprene can be preferably used. Among these, PVACs are desirable because they are easy to prepare a spray solution (emulsion) having good fluidity.

  The primary spray liquid is usually an emulsion, but may be a latex or a suspension. In the case of an emulsion, the concentration of the primary spray liquid is 1 to 50%, preferably 5 to 15%. When the concentration is too high, it becomes difficult to obtain a granulated product composed of particles having a high sphericity. If the concentration is too low, it becomes difficult to obtain an appropriate pore size in the granulated particles.

2) Binder (secondary spray):
The binder may be inorganic or organic. An organic system which is thermally decomposed and volatilized by firing and does not substantially remain in the alumina fine particles is desirable. In the case of an inorganic system, if it remains, it may become a catalyst poison, which may hinder the function of the alumina crystal. Among organic systems, a water-soluble organic polymer excellent in spray handling is desirable. As the water-soluble organic polymer, polyvinyl alcohol (PVAL), polyvinyl acetal / polyvinylpyrrolidone, acrylic monomer, cellulose derivative (CMC / HPC / HPMC, etc.), starch and the like can be suitably used.

  The secondary spray liquid is usually an aqueous solution, but a polar solvent may be appropriately added to adjust the volatility. The concentration of the tertiary spray solution is 1 to 30%, preferably 5 to 15%. When the concentration is high, it becomes difficult to obtain a granulated body with high sphericity.

  In the case of an organic system, it is possible to use the same or the same kind of resin as the pore forming agent and spray it at a different position to form a binder spray.

3) Lubricant Any lubricant can be used as long as it increases the fluidity of the granulated product. An organic lubricant that adheres to the granulated material and is pyrolyzed and volatilized by firing and does not require a separation operation is desirable. As the organic lubricant, synthetic resin fine powder, fatty acid esters, metal soaps, hydrocarbons (such as paraffin wax), and the like can be used. Of these, a synthetic resin fine powder having a low water absorption rate (for example, ASTM D570: 0.5% or less) is desirable. This is because the handleability is good and the fluidity increasing action is stable. Specific examples include fine powders such as PMMA, polyethylene, and polyester (PET). The average particle size of these lubricants is 1 to 50 μm.

  The present invention provides a granulation step of wet granulating a raw material made of fine alumina powder using a tumbling granulator equipped with a pan-type rotating dish while spraying with a liquid agent, and a firing step of firing the granulated product Assuming that

  This granulation step includes the following sub-steps of 1) primary spraying step, 2) secondary spraying step, and 3) granulating step.

  More specifically, it is performed as follows. In the following description, the unit of spray amount: part / min is based on 100 parts of the alumina raw material.

  Prior to the spraying process, a primary spray solution and a secondary spray solution are prepared. Moreover, in order to spray those spray liquids, two two-fluid atomizers (sprayer) which mix and spray each spray liquid and air are attached to a rolling granulator (not shown). And in this embodiment, the nozzle of each sprayer is distribute | arranged along the inclination diameter (inclination angle 30-45 degrees) D which extends diagonally upwards from the discharge | emission site | part (discharge chute 19) of the rotating tray 17. FIG. Here, the spray nozzles are arranged along the inclined diameter D because the sprayer nozzles are easily separated from each other (lateral (horizontal) direction and vertical direction), and the spray liquids during spraying are unlikely to overlap each other. It is.

  In the illustrated example, spray nozzles are arranged along the inclined diameter in the 45 ° direction from the raw material charging site side to the primary spray site A zone and the secondary spray site B zone so as to enable spraying with substantially the same width. The spray width at this time is 50 to 75 mm, respectively, when the inner diameter of the rotating dish is 300 mm.

Then, the rotating dish is adjusted to the average particle diameter of the raw material at the rotation speed: 15 to 60 min ⁻¹ , desirably 25 to 45 min ⁻¹ , and the inclination angle 20 to 70 °, desirably 40 to 70 °. Rotate in correspondence. These conditions are appropriately adjusted while monitoring the granulation state in the rotating dish. Outside these rotational speed and tilt angle ranges, it is difficult to roll and circulate while classifying the raw material, the raw material after primary spraying, and the raw material after secondary spraying.

  In addition, since the angle of repose becomes large when the particles are wet (in a wet state), it is necessary to set the inclination angle relatively large.

1) Primary spraying process:
The raw material (low soda alumina fine powder) which is fine alumina powder is charged into the raw material charging portion (the upper part of the A band) of the rotating dish 17 during operation.

  The input material circulates in a primary rolling manner along the outer peripheral portion (inside the rim portion 17a) of the rotating dish 17. In other words, after being lifted by the centrifugal force along the outer periphery of the rotating dish, through the lower end outer peripheral part of the rotating dish and beyond the upper end of the rotating dish to the position above the A band, the gravity is reversed by surpassing the centrifugal force. Then, draw a large arc and perform primary rolling circulation through the A band.

  A pore-forming agent (primary spray solution) is primarily sprayed to the input raw material in the A zone (a part on the reversal side of the primary rolling circulation, preferably a part immediately after the reversal) (see FIG. 4 (1)).

  In the part immediately after reversal, the raw material that circulates and circulates almost no downward, and can be sprayed while the aggregate density of the powder is high, and the spray efficiency is good (the same applies to the secondary spray).

  This pore-forming agent aggregates the particles of the raw material after the primary spraying and performs primary granulation, and at the same time, controls the gap between the particles by the droplet size of the pore-forming agent, and has the pore size formed in the firing step. Responsible for regulation (Fig. 4 (2)).

  The spraying conditions for the secondary spraying are appropriately selected in the range of droplet diameter: 10 to 1000 μm, desirably 10 to 30 μm, unit time spraying amount: 0.01 to 4.5 parts / min, desirably 1 to 3 parts / min. The total spray amount is 1 to 30 parts, preferably 1 to 25 parts, per 100 parts of the alumina raw material powder.

  When the unit time spray amount or the total spray amount of the pore forming agent is small, it is difficult to obtain a sufficient pore density or continuous pores in the granulated fired product. On the other hand, when the spray amount per unit time or the total spray amount is large, the degree of variation in pore diameter and the pore density increase, and the granulated shape tends to be irregular or irregular.

2) Secondary spraying process:
The primary sprayed raw material (fine powder) composed of particles coated with the primary spray liquid is circulated in a secondary rolling manner inside the primary rolling circulation. That is, since the raw material after the primary spray increases in weight due to the pore forming agent coating and further the primary granulation, the position superior to the centrifugal force of gravity is in front of the input raw material and does not reach the position above the A band. Invert, draw a middle arc, and perform secondary rolling circulation through the B band.

  In addition, the particle group which was not coat | covered with the primary spray liquid is primary-rolled and circulated, reaches A zone | band, and primary spray is repeated.

  Then, the binder (secondary spray liquid) is secondarily sprayed on the raw material after the primary spraying in the B band (reverse side portion of the secondary rolling circulation).

  The spraying conditions at this time are appropriately selected within the range of droplet diameter: 10 to 1000 μm, desirably 10 to 30 μm, unit time spraying amount: 0.01 to 4.5 parts / min, desirably 1 to 3 parts / min. The total spray amount is 1 to 30 parts, preferably 1 to 25 parts, per 100 parts of the alumina raw material powder.

  If the unit time spray amount or the total spray amount of the pore forming agent is small, it is difficult to obtain a sufficient pore density or continuous pores in the granulated fired product. On the other hand, when the spray amount per unit time or the total spray amount is large, the degree of variation in pore diameter and the pore density increase, and the granulated shape tends to be irregular or irregular.

3) Granulation process:
The raw material after secondary spraying, in which the particles of the primary granulated material are coated with the secondary spray liquid, while rolling with a small diameter passing through the inner side of the B zone, which substantially overlaps with the secondary rolling circulation, Secondary spraying is also repeated, and the growth of granulation proceeds and the secondary granulated product (product granulated product) having a required diameter is sized. Thereafter, the product granulated material is discharged from the discharge chute 19.

  In addition, it is desirable to add the lubricant when the raw materials are added. This is because the raw material is prevented from adhering to the rotating dish rim after spraying, and the raw material is crushed more smoothly. The addition amount of the lubricant at this time is 1 to 50 parts, preferably 10 to 40 parts with respect to 100 parts of the raw material powder to be additionally charged.

  Next, the product granulated product prepared above is fired using an electric furnace or the like. A model cross-sectional view of the firing process is shown in FIG.

  The firing conditions at this time are described below.

  Temperature increase rate: 100 to 700 ° C./h, desirably 200 to 400 ° C./h. If the heating rate is too high, cracks are likely to occur in the fired product. Conversely, if it is too slow, productivity will decrease.

  When the granulated product is γ-alumina, the ultimate temperature and the holding time are 500 to 1100 ° C. × 1 to 24 hours, preferably 600 to 1100 ° C. × 1 to 20 hours. When the granulated product is α-alumina, the temperature is 1500 to 2000 ° C. × 0.1 to 3 hours, preferably 1650 to 1850 ° C. × 0.5 to 1 hour.

  In this firing step, as shown in FIGS. 5A, B, C, and D, as the firing proceeds, the granulated particles shrink, the pore diameter also shrinks, and the compressive strength gradually increases. In this way, as shown in FIG. 1, pores communicating mainly are formed in a mesh shape over the entire cross section of the granulated particles of the granulated fired product.

  As described above, the case where the raw material is an alumina fine powder has been described as an example, but the present invention relates to a ceramic fine powder fired product (1) having the following configuration in which the alumina fine powder is replaced with a ceramic fine powder, and a manufacturing method (2) thereof. It also extends.

  (1) A porous granulated fired product in which countless ceramic particles remain in a net-like manner in which the pores that mainly communicate with each other remain in the entire cross section of the granulated particles, and the ceramic particles are A network-like pore is formed in the whole particle, which is solidified with the pores remaining.

(2) A method for producing the porous granulated fired product,
Including a granulation step of wet granulating a raw material made of ceramic fine powder while spraying with a liquid agent using a rolling granulator equipped with a rotating dish, and a firing step of firing the granulated product,
The granulation step includes
1) The pore forming agent is primary sprayed on the charged raw material that is charged from the upper part side facing the discharge part located at the obliquely lower part of the rotating dish and performs primary rolling circulation along the outer peripheral part of the rotating dish. The process of
2) a step of secondary spraying the binder on the raw material after the primary spraying that undergoes secondary rolling circulation inside the primary rolling circulation; and
3) The step of granulating the raw material after secondary spraying into a granulated product of the required diameter by further granulating growth by rolling.
Each sub-process of
The primary / secondary spraying is performed at the reversing side portions where the primary / secondary rolling circulation is performed, respectively.

Examples of the ceramic as the raw material (fine powder) include magnesium oxide (MgO), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), calcium oxide (CaO), and beryllium oxide (BeO).

  Examples carried out together with comparative examples to confirm the effects of the present invention will be described below. The rolling granulator used in both the examples and comparative examples was equipped with a rotating dish having an inner diameter of 300 mm. And the A belt | band | zone and B belt | band | zone in a rotating plate are as showing in above-mentioned FIG.

  In addition, the raw materials used, the chemicals, and the specifications are as follows.

1) Raw materials-Calcined alumina fine powder (low soda alumina) ... average particle diameter: 2.5 µm, Na ₂ O: 0.08%, specific surface area: 1.4 g / m ²
2) Drugs ・ Porosity forming agent (primary spray solution): 10% emulsion of PVAC (average particle size: 10 μm), PVAC particle size: 1 μm
・ Binder (secondary spray): 10% aqueous solution of PVAL,
・ Lubricant: PMMA fine powder (average particle size 5 μm).

<Example 1>
After introducing 100 g of low soda alumina from a raw material charging site into a rotating dish that is adjusted to an inclination angle of 55 ° and rotates at a rotational speed of 25 min ⁻¹ , the rotational speed and the rotational speed are set so that proper rolling circulation occurs in the raw material powder. Operate while adjusting the tilt angle. At that time, the range of the rotation speed and the inclination angle was set to the former: 25 to 35 mm ⁻¹ and the latter: 55 to 62 °.

  1) A pore-forming agent (primary spray solution) was sprayed in the A zone on the input raw material that undergoes primary rolling circulation. At this time, spraying was carried out while adjusting the spray pressure and the spray amount per unit time so that the droplet diameter was 10 μm. The total spray amount at this time was set to 20 parts with respect to 100 parts of the raw material. And since the unit time spray amount of the secondary spray liquid was set to 2.5 parts / min, the total spray time is 8 minutes.

  2) The binder (secondary spray solution) was sprayed in the B zone on the secondary sprayed raw material that circulates in a secondary rolling manner. The total spray amount of the binder at this time was set to 10 parts (in terms of solid content) with respect to 100 parts of the raw material powder including the next sizing step. The unit spray amount of the secondary spray solution was set to 1.25 parts / min so as to correspond to the total spray time of the primary spray solution of 8 minutes. This is to enable continuous granulation by simultaneous spraying.

  3) The material after secondary spraying is sized until the growth of granulation reaches the required granulated particle size by repeating the rolling circulation through the inner side of the B band.

  Then, immediately before the end of granulation, which is the final stage of the granulation, in this example, 10 parts before 10 minutes before adding 5 parts of lubricant to the raw material, the unit time input is 2.5 parts / min. In this way, it was dividedly charged from the raw material charging site.

  During the rolling granulation operation, the temperature of the spray liquid and the spray amount per unit time were adjusted so that the temperature in the rotating dish was 28 ° C. or lower and 18 ° C. or higher. This is because if the temperature is too high or too low, the volatilization rate of the spray liquid is too fast or too slow, and granulation is not performed smoothly. In addition, in order to reduce the temperature in a rotating tray by evaporative heat, the electric heater was arrange | positioned by the non-contact type in the back side position of the rotating tray.

  Next, the wet granulated material thus prepared was heated to an ultimate temperature of 900 ° C. at a temperature rising rate of 300 ° C./h and held for 3 hours, and further heated to an ultimate temperature of 1680 ° C. at the same temperature rising rate for 0.5 h. The fired product (partially fired product) in which the pores remained was retained.

<Comparative Example 1>
In Example 1, except that the water-soluble polymer liquid (PVAL dispersion liquid) was used instead of the water-insoluble polymer dispersion liquid (PVAC dispersion liquid), the same feed amount, spray amount, and operating conditions were used. The wet granulated product obtained by dynamic granulation was fired under the same conditions.

  FIG. 6 shows SEM photographs (50 times and 1000 times) of Example 1 and Comparative Example 1 thus prepared. It can be seen from the SEM photograph that the product of the present invention has a spherical shape with high sphericity.

  The specific surface area, soda component, and compressive strength (particle strength) were also measured and are shown in Table 1.

  From the results of Example 1 and Comparative Example 1, the following was found.

  (1) The particle strength of the example was substantially the same as that of the fired product (comparative example 2) according to the conventional method using the same low soda alumina as that of example 1.

  (2) The specific surface area of Example 1 is slightly larger than the fired product obtained by the conventional method using the same low soda alumina as that of Example 1 (Comparative Example 2). It is assumed that the pores are homogeneous.

  (3) The soda component of Example 1 is about 1/4 of the raw material and less than Comparative Example 1.

  And the scanning electron microscope (SEM) photograph of the granulated material of each Example and a comparative example was image | photographed with low magnification (* 50 time) and high magnification (* 1000 time). Those SEM photographs are shown in FIGS. 6 (A) and 6 (B). From the SEM photograph of FIG. 6, it can be seen that Example 1 of the present invention is not much different from the sphericity in Comparative Example 1, but has a high porosity and a more uniform pore density.

11 Porous granulated fired particles 13 Porosity

Claims (10)

Innumerable alumina particles are porous granulated fired products formed by solidifying the pores that mainly communicate with each other in the entire cross-section of the granulated particles, and the pores have pore diameters that form pores. Controlled by the droplet size of the agent,
A porous granulated fired product characterized by the above. The porous granulated fired product according to claim 1, wherein the content of the soda component (Na ₂ O equivalent; the same shall apply hereinafter) is less than 0.03%.   The porous granulated fired product according to claim 1 or 2, wherein a pore diameter (arithmetic average value) of the granulated particles is adjusted to 0.5 to 50 µm. The average particle diameter (median diameter) of the granulated particles is 0.1 to 5 mm, and the specific surface area (BET method) is 0.1 to 10 m ² / g. Porous granulated fired product. A method for producing a porous granulated product according to any one of claims 1 to 4,
A raw material comprising alumina fine powder, including a granulation step of wet granulation while spraying a binder using a rolling granulator equipped with a rotating dish, and a firing step of firing the granulated product,
The granulation step includes
1) Porosity is formed in the raw material charged from the upper part facing the discharge part (discharge chute) located diagonally below the rotating dish and performing primary rolling circulation along the outer peripheral part of the rotating dish. A step of first spraying the agent,
2) a step of secondary spraying the binder on the raw material after the primary spraying that undergoes secondary rolling circulation inside the primary rolling circulation;
3) The step of granulating and growing the raw material after the secondary spray into a granulated product of a required diameter by further rolling circulation.
Each sub-process of
The primary and secondary sprays are respectively performed on the reversing side portions where the primary and secondary rolling circulation is performed.
A method for producing a porous granulated fired product. The alumina fine powder, Na 2 _O content: The process according to claim 5 porous granulated burned material of wherein from 0.3% or less of the alumina fine powder The method for producing a porous granulated calcined product according to claim 6, wherein the alumina fine powder is a calcined alumina fine powder having a Na ₂ O content of 0.1% or less and a median particle size of 0.1 to 100 µm. .   The method for producing a porous granulated baked product according to any one of claims 5 to 7, wherein a lubricant is added simultaneously when the raw materials are batch-wise or continuously charged into the charging portion of the rotating dish. .   An infinite number of ceramic particles are porous granulated fired products formed by solidifying pores that communicate mainly with the entire cross section of the granulated particles. A porous granulated fired product characterized in that it is controlled by the droplet diameter. A method for producing a porous granulated fired product according to claim 9,
Using a rolling granulator equipped with a rotating dish with a raw material made of ceramic fine powder, including a granulation step of wet granulation while spraying a binder, and a firing step of firing the granulated product,
The granulation step includes
1) The pore forming agent is primary sprayed on the charged raw material that is charged from the upper part side facing the discharge part located at the obliquely lower part of the rotating dish and performs primary rolling circulation along the outer peripheral part of the rotating dish. The process of
2) a step of secondary spraying the binder on the raw material after the primary spraying that undergoes secondary rolling circulation inside the primary rolling circulation;
3) The step of granulating and growing the raw material after the secondary spray into a granulated product of a required diameter by further rolling circulation.
Each sub-process of
The primary and secondary sprays are respectively performed on the reversing side portions where the primary and secondary rolling circulation is performed.
A method for producing a porous granulated fired product.