JPH1081576A - Production of inorganic porous material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an inorganic porous material having a high porosity and excellent in strength by forming granules using a raw material which is discharged from a foundry as sludge waste and has a specific ignition loss, heating the obtained granules at a specified temperature and baking them. SOLUTION: Sludge material is obtained by filtering sludge waste discharged from a foundry and containing also domestic wastewater and appropriately drying the residue. The obtained sludge material containing silica and alumina as main components and having an ignition loss of >=20% by weight is used as a raw material. The material is mixed with water in such a manner so that the water content becomes preferably 10-30%. Subsequently, granules or blocks are produced from the mixture, and the granules or blocks are heated up to >=80 deg.C and baked.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an inorganic porous body having pores.

[0002]

2. Description of the Related Art Focusing on the fact that dust discharged from a foundry as waste contains a large amount of carbon that can function as a pore-forming material, an inorganic porous material is produced using the dust. The following technology has been proposed in recent years (Niigata Industrial Technology Center: 1992, No. 21 Research Report).

According to this technique, dust extruded as waste from a foundry is used as a raw material, the raw material is wet-kneaded, and then a continuous extruded body is formed by extrusion. Thereafter, the continuous extruded body is cut into a predetermined length by a cutter, thereby forming a columnar granular body having a diameter of about 1 mm. The granular material is dried and fired in a high temperature region to obtain an inorganic porous material. This technology has recently been regarded as promising because it can effectively use the dust that has been discarded.

[0004]

According to the inorganic porous material according to the above-mentioned technology, high strength tends to be obtained if the porosity is low, and low strength tends to be obtained if the porosity is high. That is,
High strength and high porosity tend to conflict. Further, according to the above-described conventional technique, after forming a continuous extruded body by extrusion molding as described above, the continuous extruded body is cut into a predetermined length by a cutter to form a columnar granular body, and the granular body is formed. Is dried and fired. Therefore, at the time of cutting, "cut sagging" is likely to occur on the cut surface of the granular material. This may protrude locally and become an edge portion. Even if such an inorganic porous body is fired, it is considered that the edge portion is easily damaged and the strength characteristics are not always sufficient.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a method for producing an inorganic porous body which is advantageous for securing strength while maintaining a high porosity. And

[0006]

[Means for Solving the Problems]

(1) Sludge waste from a foundry contains a large proportion of fine colloid particles, and thus contains many fine particles having a small particle diameter. Further, the sludge waste contains more organic substances that are burned off by burning and form pores, compared to ordinary dust waste. The present inventor has paid attention to this point, and has noticed that if a sludge material formed from sludge waste is used as a raw material, strength can be increased while maintaining a high porosity of a fired inorganic porous body. The present inventor has developed a method for producing an inorganic porous body according to No. 1.

Further, the inventor of the present invention has proposed that, even if dust waste discharged from a foundry is used as a raw material in the same manner as in the prior art, the continuous extruded body is not cut by a cutter to obtain granules, By adopting a method of granulating the granular material by using the friction between the blade and the stirring blade, attention is paid to the fact that the edge-shaped protrusions can be reduced and the strength can be increased while securing the porosity of the inorganic porous material. The present inventors have developed a method for producing an inorganic porous material according to claim 2.

(2) That is, in the method for producing an inorganic porous material according to the first aspect, a sludge material containing silica and alumina discharged from a foundry as sludge waste is used as a main component, and ignition loss is reduced by weight. A step of obtaining granules or aggregates from a mixture of water and raw materials using a raw material having a ratio of 20% or more, and heating the granules or aggregates to 800 ° C. or higher,
And baking to obtain an inorganic porous body.

The method for producing an inorganic porous material according to claim 2 is characterized in that silica discharged from a foundry as dust waste,
Using a raw material whose main component is dust containing alumina and whose ignition loss is 10% or more by weight, a mixture of water and the raw material is stirred using a stirring blade to form a non-cylindrical granular material. The method is characterized in that a granulating step of granulating and a firing step of heating the granular body to 800 ° C. or higher and firing to obtain an inorganic porous body are sequentially performed.

According to a third aspect of the present invention, in the method for producing an inorganic porous material according to the first or second aspect, the raw material contains a carbon-based powder, and the average particle diameter of the carbon-based powder is the same as that of the first aspect. The average particle size of the constituent particles or the average particle size of the particles forming the dust of claim 3 is larger than the average particle size. Ignition loss refers to weight loss that is burned off by high heat during firing, and mainly means the amount of organic substances that are burned off by high heat during firing. Ignition loss does not cover water. (3) According to the method of the first aspect, as described above, the sludge waste from the foundry has a large proportion containing fine colloid particles, and therefore contains many fine particles having a small particle diameter. The smaller the particle size, the higher the bonding strength during firing,
If a raw material containing sludge discharged as sludge waste as a main component is used, the strength of the inorganic porous body is ensured.

Further, the sludge waste contains more organic substances which are burned out by burning and form pores, as compared with ordinary dust waste, so that the ignition loss is set to 20% or more by weight.
The porosity of the inorganic porous body is ensured. According to the manufacturing method of the first aspect, when forming the granular material, the mixture of water and the raw material is stirred by the stirring blade, thereby utilizing the friction between the stirring blade and the raw material. It may be formed, or a continuous extruded body formed from the mixture may be cut into a predetermined length by a cutter to form a granular body. In the former case, the occurrence of edge portions due to "cutting sag" is small, and therefore, it is more advantageous to secure strength while securing porosity of the inorganic porous body.

The inorganic porous material produced by the production method according to the first aspect is characterized in that a weight ratio of silica is 50% or more and alumina is 20% or more.
% And a porosity of 40% or more.
Therefore, it is advantageous to secure strength while maintaining a high porosity. Such an inorganic porous body has a high porosity and water retention. Furthermore, strength is secured and breakage resistance is high. This is probably because the alumina component is large. In this specification,% is based on weight ratio unless otherwise specified.

According to the second aspect of the present invention, a method is employed in which the granular material is granulated by utilizing the friction between the raw material and the stirring blade, and the edge-shaped protruding portion of the granular material is reduced. According to the method of the third aspect, the raw material includes a carbon-based powder, and the carbon-based powder has a pore-forming function during firing. Since the average particle diameter of the carbon-based powder is larger than the average particle diameter of the particles constituting the sludge material or the average particle diameter of the particles constituting the dust, the porosity and the bubble size of the inorganic porous body are secured. .

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) In Embodiment 1, sludge discharged from a foundry for producing cast iron as sludge waste is used as a raw material. The sludge material used in the first embodiment is a cake-shaped dry sludge material obtained by filtering sludge waste collected in a drainage storage of a foundry by a filter press and drying it appropriately by sunlight or heat treatment.

The sludge waste constituting the sludge material includes mud of water containing dust discharged from a production line of a foundry, mud of domestic wastewater (including wastewater from toilets and canteens) of a foundry. It contains a large amount of organic substances that are mixed and therefore burnt off at the firing temperature. Therefore, the ignition loss is large. FIG. 1 shows an example of the particle size distribution of the particles constituting the sludge material used in the first embodiment. The horizontal axis in FIG. 1 shows the particle diameter of the particles constituting the sludge material, and the vertical axis shows the relative particle amount (wt%). FIG.
As can be understood from FIG. 5, the particle diameter of the particles constituting the sludge material is 3.365 μm in median diameter and 3.1 in mode diameter.
It was 76 μm. Thus, the particles constituting the sludge material tend to be minute. The median diameter means the diameter of the median. The mode diameter means the maximum value diameter.

This sludge material contains 50% or more of silica and 20% or more of alumina. In particular, this sludge material has 20 alumina.
% Or more, which was advantageous for producing a high-strength inorganic porous body having a high alumina content. After drying the above-mentioned cake-like sludge material, it was crushed finely. Furthermore,
The kneader 1 schematically shows the crushed sludge material in FIG.
0, and water was appropriately mixed so as to be 10 to 30% of water, and kneaded with a kneader 10 to obtain a mixture. Where water 10
~ 30% means that the mixture of sludge and water as raw materials is 10%.
When it is 0%, it is a ratio containing 10 to 30% of water. If the method of adding water to the dried sludge material is employed in this manner, the water content of the mixture can be appropriately adjusted, and the granulation property can be appropriately secured. In this sense, it is preferable to use a dry sludge material as the sludge material.

A kneader 10 shown in FIG. 3 has a bottomed container 11 which accommodates raw materials and rotates in the direction of arrow X1.
The rotating shaft 12 is provided so as to be rotatable in the direction of the arrow X2, a motor 13 for rotating the rotating shaft 12, and a number of stirring blades 14 provided in the rotating shaft 13 in the container 11. . The container 11 is inclined with respect to the horizontal line.

FIG. 3B is a schematic view of the stirring blade 14. As shown in FIG. 3 (B), the stirring blade 14 is a plate-like blade portion 1.
4i. Due to the rotation of the plate-like blades 14i, the raw material rolls under the plate-like blades 14i, and is gradually granulated to grow into granular granular materials W. The plate-like blade portion 14i is the container 11
It is considered that the particles hardened to some extent become growth nuclei and are pressed against the raw material deposited on the bottom surface of the container 11 and the granulation of the granular material W proceeds. In the first embodiment, granulation is performed so that the diameter becomes, for example, 1 to 20 mm, and a granular material W in a raw state is formed. It is also possible to set the size of the granular material W to 20 mm or more, or 30 mm or more.

Generally, in order to reduce the particle size during granulation, the granulation time may be shortened. To increase the particle size, the granulation time may be extended. The granular material W formed as described above is heated and held at 140 ° C. for 60 minutes to perform a drying treatment, thereby removing moisture from the granular material W. Further, the dried granular material W is fired in the air at 1000 ° C. for 30 minutes or more, thereby forming an inorganic porous material. As schematically shown in FIG. 4, the inorganic porous body Wa has an elliptical granular shape.

If the firing temperature is too high, an excessive liquid phase is generated, which is advantageous for improving the strength, but is not preferable because the porosity tends to decrease. The ignition loss of the raw material according to Embodiment 1 exceeds 20%. Ignition loss means a ratio of weight loss by high-temperature heating at the time of baking, based on a state after removing water by drying. In the present embodiment, the ignition loss is determined by drying the sample at 140 ° C. for 60 minutes to remove water, weighing the sample (W1), and further weighing the sample after calcination (W2), The weight of the difference is defined as ΔW, and the ignition loss = {(ΔW / W1) × 100}.
%.

[0021] The sludge material contains a large amount of organic components which are burned off by heating during firing, and thus have a large ignition loss. In sludge, the value of ignition loss is likely to differ depending on the sampling location. Therefore, it is possible to employ a raw material having a loss on ignition of 20% or more, a raw material of 25% or more, a raw material of 30% or more, and a raw material of 35% or more. When the porosity of the inorganic porous body after the above-mentioned firing was measured, a porosity of 50% or more, 60% or more, and 65% or more was obtained. Because the ignition loss of raw materials is large,
It is considered that the amount of pores increased. In particular, the sludge waste constituting the sludge material contains domestic wastewater, which tends to increase the amount of organic substances that are burned off by high-temperature heating, so that the porosity is easily secured.

The porosity is based on the volume ratio, that is, {(volume of pores of inorganic porous particles / apparent volume of inorganic porous particles) × 100}%. An example of the composition of the sludge material used in the first embodiment before and after firing is shown in Table 1 together with the ignition loss and the porosity of the inorganic porous body formed from the sludge material.

[0023]

[Table 1] The composition analysis shown in Table 1 was performed by X-ray fluorescence analysis, and the composition ratio did not include the amount corresponding to the loss on ignition before and after firing. The same applies to the tables described later.

Further, Table 2 shows the composition of sludge collected at the same place on different collection dates, before and after firing, together with the loss on ignition and the porosity of the inorganic porous material formed from the sludge. As can be understood from Table 2, this sludge material contains 20% or more of alumina, which is advantageous for securing the strength of the inorganic porous body after firing. Further, the loss on ignition of the sludge material is as high as 22% or more, which is advantageous for securing the porosity of the inorganic porous body after firing. Incidentally, as can be understood from Table 2, the porosity is 48% or more.

[0025]

[Table 2] According to the first embodiment, the firing temperature is appropriately selected depending on the type of the raw material. However, in order to increase the porosity of the inorganic porous body, it is preferable to suppress the generation of a liquid phase. To increase it, one can expect the formation of a liquid phase. However, in order to increase the porosity, a baking temperature at which a liquid phase does not occur, or a baking temperature at which a liquid phase occurs even if it is very small is preferable. In consideration of such circumstances, the upper limit of the sintering temperature is 1000 ° C., 1050 ° C., 11
00 ° C, 1200 ° C, lower limit 800 ° C, 850
° C, 900 ° C, and 950 ° C. The same can be said for the firing temperature according to other embodiments.

In the first embodiment, the granular material is formed. However, the present invention is not limited to this. (Embodiment 2) Embodiment 2 has basically the same configuration as Embodiment 1. However, the first embodiment uses a sludge material not containing coal powder as a raw material, but the second embodiment differs in that a sludge material containing coal powder as a carbon-based powder is used as a raw material.

According to the second embodiment, in addition to the sludge which tends to contain organic components, the coal powder which is burned off during firing is mixed, so that the ignition loss of the raw material is more likely to further increase. Accordingly, the ignition loss of the raw material may exceed 24% or 30%. Depending on the type of sludge and coal powder, it often exceeds 35%. When a raw material having a large ignition loss is used in this manner, a large porosity of the inorganic porous body is secured, and depending on the type of the raw material, the porosity is 40%, 45%, or 5%.
Exceeding 0%, 60% and 65% can also be expected.

In the second embodiment, the average particle size of the coal powder is larger than the average particle size of the sludge material in order to secure the porosity of the inorganic porous body. (Embodiment 3) Embodiment 3 is basically the same as Embodiment 1 described above. However, the difference is that dust discharged as dust waste from a dust collector of a foundry for producing cast iron is used as a raw material.

FIG. 2 shows an example of the particle size distribution of the dust particles used in the present embodiment. The horizontal axis in FIG. 2 indicates the particle size of the dust particles, and the vertical axis indicates the relative particle amount (wt%). As can be understood from FIG. 2, the median diameter of the particle size of the dust particles is 7.
The diameter was 652 μm and the mode diameter was 13.711 μm. As can be understood from a comparison between FIG. 1 for sludge and FIG. 2 for dust, the particle size of the dust particles is larger than that of the sludge material. There were many.

This dust contains 50% or more of silica and 10% or more of alumina. An example of the composition of the dust before firing used in Embodiment 3 is shown in Table 3 together with the ignition loss and the porosity of the inorganic porous body formed by the dust. As can be understood from Table 3, in the dust of this embodiment, the amount of alumina and the ignition loss are smaller than those of the sludge. It is considered that the ignition loss is smaller than that of the sludge material because it is dust of the molding sand constituting the mold into which the high-temperature molten metal is cast.

[0031]

[Table 3]

[0032]

Example 1 and Example 2 In Example 1, an inorganic porous body is formed based on the procedure of Embodiment 1 described above, using a sludge material not containing coal powder as a raw material. The particle size distribution of the sludge particles used in Example 1 is shown in FIG.
Is the same as The composition of the sludge material as the raw material, the ignition loss, and the like are the same as in Table 1. The firing temperature is 1000 ° C. and the firing time is 120 minutes. The porosity of the inorganic porous body is 51%.

In the second embodiment, a sludge material containing coal powder is used as a raw material to form an inorganic porous body based on the second embodiment. The ratio of the raw materials is the ratio of the coal powder 1 to the sludge material 10 by weight, and the mixture is adjusted so that the water content is 20%. The particle size of the coal powder is indicated by a characteristic line K3 in FIG. As can be understood from the characteristic line K3, 0.
Coal powder having a size of about 4 to 100 μm is employed. The most frequent range of this coal powder is about 15 to 30 μm.

The particle size distribution of the sludge particles according to the second embodiment is basically the same as that of the first embodiment. The composition of the sludge material as the raw material, the ignition loss, and the like are the same as in Example 1. The firing temperature is 1000 ° C. and the firing time is 120 minutes. The porosity of the inorganic porous body is larger than that of Example 1 and is 67%. The pores of the fired inorganic porous materials according to Example 1 and Example 2 formed as described above were measured. The measurement is performed by using a mercury intrusion type porosimeter (Shimadzu-Micromeritics), applying pressure while immersing the test piece in mercury, and measuring the amount and pressure of mercury entering the test piece. The distribution was determined. Fig. 5 (A) shows the measurement results.
It is shown in (B).

The horizontal axis of FIG. 5A shows the pore diameter of the inorganic porous material, and the vertical axis of FIG. 5A shows the pore volume. FIG.
The characteristic line H1 of (A) indicates the pore volume accumulated in the inorganic porous body according to Example 1 using a sludge material not containing coal powder as a raw material in order from the side having the smaller pore diameter. FIG.
The characteristic line H2 of (A) shows the pore volume accumulated in the inorganic porous body according to Example 2 using a sludge material containing coal powder as a raw material in ascending order of the pore diameter.

The horizontal axis of FIG. 5B shows the pore diameter of the inorganic porous material and the particle size of the coal powder, and the left side of the vertical axis shows the value obtained by differentiating the characteristic line of FIG. A) shows the slope of the characteristic line, and the right side of the vertical axis shows the coal powder particle size ratio. FIG. 5 (B)
The characteristic line K1 indicates the particle size distribution of the pores of the inorganic porous body according to Example 1 using a sludge material not containing coal powder as a raw material.
As shown by the characteristic line K1, according to the inorganic porous material of Example 1, pores of each size of about 0.04 to 13 μm are generated, and the most frequent range of pore diameters is 3 to 4 μm.

Further, the characteristic line K2 in FIG. 5B shows the particle size distribution of the pores of the inorganic porous material of Example 2 using the sludge containing coal powder as a raw material. As shown by the characteristic line K2, in Example 2, the diameter of the pores is 3 to 4 μm in the most frequent range. Example 1
The reason why the pore diameter of Example 2 and the pore diameter of Example 2 become the same level is considered to be the effect of shrinkage of the inorganic porous material due to firing. Moreover, the characteristic line K2 has a higher peak value than the characteristic line K1.

The characteristic line K3 indicated by the dotted line in FIG.
Shows the particle size distribution of the coal powder mixed with the raw material in Example 2. As can be understood from the comparison between the characteristic lines K2 and K3, it is understood that the pore diameter of the inorganic porous body formed from the raw material containing the coal powder is much smaller than the particle diameter of the coal powder. This is considered to be due to the effect of shrinkage of the inorganic porous material due to firing. Example 3 and Example 4 In Example 3, an inorganic porous body was formed based on Embodiment 1 using a sludge material not containing activated carbon as a raw material. Example 3
The particle size distribution of the particles of the sludge material according to the above is basically the same as in FIG. The composition of the sludge material as the raw material, the ignition loss, and the like are the same as in Table 1. The firing temperature is 1000 ° C. and the firing time is 1
20 minutes. The porosity of the inorganic porous body is 51%.

In the fourth embodiment, activated carbon is employed in place of coal powder, and a sludge material containing activated carbon is used as a raw material to form an inorganic porous body based on the second embodiment. The ratio of the raw materials is the ratio of activated carbon 1 to sludge 10 by weight, and the water content is 20%.
Adjust the mixture so that The particle size of the activated carbon is shown by a characteristic line P3 in FIG. As shown by the characteristic line P3, activated carbon having a size of about 0.4 to 100 μm is employed.

The particle size distribution of the sludge particles according to Example 4 is the same as in FIG. The composition of the sludge material as the raw material, the ignition loss, and the like are the same as in Table 1. The firing temperature is 1000 ° C. and the firing time is 120 minutes. The porosity of the inorganic porous material is 69
%. The pores of the fired inorganic porous materials according to Examples 3 and 4 were measured in the same manner as described above. Fig. 6 shows the test results.
(A) and (B) show. The vertical axis and the horizontal axis of FIG.
The vertical axis and the horizontal axis of FIG. The vertical and horizontal axes in FIG. 6B correspond to the vertical and horizontal axes in FIG. 5B, respectively.

The characteristic line M1 in FIG. 6 (A) shows the pore volume accumulated from the smaller pore diameter side in the inorganic porous material according to Example 3 using a sludge material not containing activated carbon as a raw material. A characteristic line M2 in FIG. 6 (A) shows the pore volume accumulated from the smaller pore diameter side in the inorganic porous material according to Example 4 using a sludge material containing activated carbon as a raw material. FIG.
The characteristic line P1 in (B) shows the particle size distribution of the pores of the fired inorganic porous material using a sludge material not containing activated carbon as a raw material,
This is substantially the same as the characteristic line K1 in FIG. As shown by the characteristic line P1, according to the fired inorganic porous body formed of a raw material containing no activated carbon, there are many pores of about 1 to 5 μm, and the most frequent range of the diameter of the pores is 3 to 4 μm. is there.

The characteristic line P2 in FIG. 6 (B) shows the particle size distribution of the pores of the inorganic porous material after firing using sludge containing activated carbon as a raw material. As shown by the characteristic line P2, according to the inorganic porous body of Example 4 formed of a raw material containing activated carbon, the content of the inorganic porous material was set to 0.1.
There are many pores of about 5 to 2.5 μm, and the most frequent pore diameter range is 1 to 2 μm. On the other hand, a dotted characteristic line P3 in FIG. 6B shows the particle size distribution of the activated carbon used in Example 4.
As shown by the characteristic line P3, the most frequent range of the particle size of the activated carbon is 3 to 10 μm. As can be understood from the comparison between the characteristic lines P2 and P3, it is understood that the average diameter of the pores of the inorganic porous material is smaller than the average particle size of the activated carbon. This is considered to be due to the effect of shrinkage of the inorganic porous material due to firing. Example 5 According to Example 5, an inorganic porous body is formed based on Embodiment 3 by using dust containing no coal powder or activated carbon as a raw material. The particle size distribution of the dust particles according to Example 5 is the same as that in FIG. The composition of the dust as a raw material, the ignition loss, and the like are shown in Table 3 as NO. Substantially the same as 2A. The firing temperature is 10
00 ° C., baking time is 120 minutes. The porosity of the inorganic porous body is 42%.

Then, the pores of the fired inorganic porous material were measured in the same manner as described above. The test results are shown in FIGS. The vertical and horizontal axes in FIG. 7A correspond to the vertical and horizontal axes in FIG. 5A, respectively. The vertical axis and the horizontal axis of FIG.
The ordinate and the abscissa of (B) correspond respectively. The characteristic line S1 in FIG. 7A indicates that in the inorganic porous material according to Example 5,
The pore volume accumulated from the side with the smallest pore diameter is shown.
The characteristic line T1 in FIG. 7B is obtained by differentiating the characteristic line S1 and shows the particle size distribution of the pores of the inorganic porous body after firing.
As shown by the characteristic line T1, the pore diameter of the inorganic porous material is 0.1 mm.
It ranges from about 01 to 200 μm, but the most frequent area is 1
0 to 25 μm.

As can be understood from a comparison between FIG. 1 for sludge and FIG. 2 for dust, the average particle size of the dust particles is considerably larger than the average particle size of the sludge particles. It is considered that the pore diameter became larger. Strength test The strength of the inorganic porous body after firing was also tested. In this strength test, an inorganic porous body (target diameter: 2 mm) is placed on the upper surface of a vertically movable horizontal table, and the horizontal table is raised at a low speed, so that the inorganic porous body is placed on the pressure cage above the horizontal table. The body was pressed and the strength was evaluated by the load when the inorganic porous body was crushed.

In this strength test, the sample A (corresponding to Example 1) was made of an inorganic porous material made of a sludge material not containing coal powder, and an inorganic porous material made of dust containing no coal powder was used as a sample. Sample B (corresponding to Example 5) was used, and an inorganic porous body using sludge mixed with coal powder as a raw material was used as Sample C (corresponding to Example 2). Further, as a comparative example, diatomaceous earth was granulated in the same procedure as in Example 1 and fired (firing temperature: 1000).
C., firing time: 120 minutes) to form an inorganic porous body,
This was designated as Sample D. Sample D was also subjected to the same strength test.

Further, regarding the samples A to D described above, the case where the inorganic porous body was in a dry state and the case where the inorganic porous body was
A strength test was performed separately for the case where the sample was moistened in water for 4 hours. The latter considers that a water-retaining state will be attained if used as a soil conditioner. The test results are shown in FIG. In FIG. 8, black marks such as ● and Δ indicate a wet state. A white mark such as 、 or □ indicates a dry state. The number N of samples was 12 each.

As can be understood from FIG. 8, the average strength of sample A, the average strength of sample B, and the average strength of sample C according to the present invention are high. On the other hand, the average strength of the sample D according to the comparative example is lower than that of the samples A, B, and C according to the present invention. This is considered to be because diatomaceous earth in Sample D according to Comparative Example had a low alumina content. Further, among the products of the present invention, when comparing Samples A and C using sludge as a raw material and Sample B using dust as a raw material, Sample A and Sample C have higher average strength than Sample B. With. The reason is that, as can be understood from the comparison between Table 1 and Table 2, the sludge material has a higher alumina content than the dust,
It is considered that the particles constituting the sludge material as the raw material are finer.

The target diameter size of the inorganic porous material is 4 mm,
The strength test was similarly performed for the cases of 6 mm and 10 mm. The same test was performed when the target diameter size was set to 20 mm or more. In these cases as well, similarly, a sample obtained by using a sludge material having a high alumina content and a small particle diameter as a raw material had a higher average strength than a sample obtained using dust as a raw material.

(Supplementary Note) The following technical idea can be understood from the above-described embodiment. The inorganic porous body produced in claim 1 is in the form of granules having pores, contains 50% or more of silica by weight, 20% or more of alumina, and has a porosity of 40% or more by volume. And The method according to claim 1, wherein the sludge material contains 50 to 70% of silica and 18% to 30% of alumina by weight. In this case, the alumina content is high, which is advantageous for obtaining a high-strength inorganic porous body.

[0050]

According to the manufacturing method of the first aspect, as described above, the sludge material, which tends to increase the amount of organic substances which are easily burned off by heat during firing, is used as the main component of the raw material. In addition, the ignition loss of the raw material can be made 20% or more by weight ratio, and the porosity of the inorganic porous body after firing is secured. This is because the portion corresponding to the loss on ignition is burned out and becomes substantially pores. Therefore, when used as a soil improvement material buried in the soil, water retention is likely to be improved.

Further, according to the manufacturing method of the first aspect, a sludge material containing silica and alumina discharged from a foundry as sludge waste is used as a raw material. Silica and alumina contained in sludge are often in the form of fine particles.
The firing property is improved. Therefore, it is advantageous to improve the firing strength while maintaining the porosity of the inorganic porous body high.
Therefore, the breakage resistance of the inorganic porous body is improved, and the life can be extended. Therefore, when used as a soil improving material buried in the soil, the strength characteristics are further improved. In the case of a block, if it is used as a block, the durability of the block can be ensured.

According to the manufacturing method of the present invention, since the dust discharged from the foundry as dust waste and having a loss on ignition of 10% or more by weight is used, the strength of the inorganic porous body is reduced. This is advantageous for improving the porosity while maintaining the porosity. This is because the portion corresponding to the loss on ignition becomes substantially a pore. Furthermore, according to the manufacturing method of the second aspect, unlike a conventional technique in which a continuous extruded body is cut into a columnar shape having a predetermined length by a cutter to obtain a granular body, a non-cylindrical granular body is granulated. , The occurrence of an edge portion caused by “cutting sag” can be suppressed. Therefore, it is advantageous to secure the strength while securing the porosity of the inorganic porous body.

According to the manufacturing method of the third aspect, the carbon-based powder (coal powder, activated carbon, graphite powder, etc.) is burned off during firing and functions as a pore-forming material. The rate is easily secured. Further, the average particle size of the carbon-based powder mixed with the raw material is larger than the average particle size of the particles constituting the sludge material or the average particle size of the particles constituting the dust. Therefore, it is more advantageous for improving the porosity of the inorganic porous body after firing.

[Brief description of the drawings]

FIG. 1 is a graph showing a particle size distribution of sludge material particles.

FIG. 2 is a graph showing a particle size distribution of dust particles.

FIG. 3 is a configuration diagram showing a kneader for granulating.

FIG. 4 is a perspective view showing a typical form of an inorganic porous body.

FIG. 5 is a graph showing pore distribution and the like according to Example 1 and Example 2.

FIG. 6 is a graph showing pore distribution and the like according to Example 3 and Example 4.

FIG. 7 is a graph showing pore distribution and the like according to Example 5.

FIG. 8 is a graph showing the results of a strength test of an inorganic porous body.

[Description of References] In the drawing, 10 is a kneader, 12 is a rotating shaft, 14 is a stirring blade,
14i denotes a plate-like blade portion.

Claims (3)

[Claims] A sludge material containing silica and alumina discharged from a foundry as sludge waste is used as a main component, and a raw material having a loss on ignition of 20% or more by weight is used, and water and the raw material are mixed. A step of obtaining a granular body or an agglomerate from the mixture obtained above, and a step of heating the granular body or the agglomerate to 800 ° C. or higher and firing to obtain an inorganic porous body. A method for producing a porous body. 2. A raw material whose main component is dust containing silica and alumina discharged as dust waste from a foundry and whose ignition loss is 10% or more by weight, and water and the raw material are mixed. A granulating step of agitating the mixture using a stirring blade to granulate the non-cylindrical granules; and a baking step of heating the granules to 800 ° C. or higher and calcining to obtain an inorganic porous body. A method for producing an inorganic porous body, which is performed in order. 3. The method according to claim 1, wherein the raw material contains carbon-based powder, and the average particle size of the carbon-based powder is the average particle size of the particles constituting the sludge material according to claim 1. Item 2. A method for producing an inorganic porous material, wherein the average particle size of the particles constituting the dust according to Item 2 is larger than the average particle size.