JPH08239254A - Artificial aggregate and manufacturing method thereof - Google Patents

Abstract

(57) [Abstract] [Purpose] The present invention can be applied to almost all compositions of sewage sludge or coal ash (fly ash), and can be used for mortar, concrete, asphalt aggregates, backfill materials, roadbed materials, and laying materials. Furthermore, the present invention provides an artificial aggregate that can be effectively used in large quantities as a carrier for plant cultivation or water filtration, and a method for producing the same. [Structure] The sewage sludge, quick limes, and coal ash are the main components, and they are fired.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an artificial aggregate that effectively utilizes waste such as sewage sludge and coal ash (fly ash), and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, coal ash (fly ash) and various sludges have been used as raw materials, and artificial aggregates produced by sintering or agglomerating these have been produced, mainly for concrete aggregates, plant cultivation or water filtration. It is used as a carrier.

However, since the chemical composition or the mineral composition of coal ash and sludge is variously changed, the fluctuation of the specific gravity of the obtained artificial aggregate is large due to the variation between lots in the raw material or when the raw material species is changed. Therefore, there has been a problem that the required physical properties such as strength and water absorption cannot be adjusted. Therefore, as a civil engineering / construction concrete requiring reliability, there is a drawback that only a specific raw material type, for example, coal ash (fly ash) with a fixed coal type used, can be used as a raw material. In other words, coal ash using overseas coal that includes import destinations of several countries or more, or various sewage sludges cannot be used as raw materials for high-quality artificial aggregates as they are.

Further, recycled resources such as sewage sludge often generate offensive odors such as ammonia, and if they are left as they are, the bad odors are radiated to the surroundings and the working environment is extremely bad.

[0005]

The present invention can be applied to almost all compositions of sewage sludge or coal ash (fly ash), and is suitable for mortar, concrete, aggregate for asphalt, backfill material, roadbed material, and laying material. Furthermore, it is an object of the present invention to provide an artificial aggregate that can be effectively used in large quantities as a carrier for plant cultivation or water filtration, and a method for producing the same.

[0006]

To achieve the above object, according to the artificial aggregate of the present invention, sewage sludge, quicklimes and coal ash are fired as main components (claim 1). ), Sewage sludge and quicklime are mixed to obtain dehydrated powder and coal ash as main components (claim 2), and the ash content of the dehydrated powder is 80% by weight or more. (Claim 3).

Further, according to the method for manufacturing an artificial aggregate of the present invention, sewage sludge and quicklime are mixed to obtain dehydrated powder, and the coal ash is contained in the dehydrated powder in a weight ratio of 80% or more. After that, the mixture is baked at a temperature of 1000 ° C. to 1450 ° C. (claim 4). The present invention will be described in detail below.

The sludge treated in the present invention is mainly sludge generated in a sewage treatment plant, but in addition to this, sludge generated by human waste, domestic wastewater, industrial wastewater treatment and the like is included. These sludges generally have a water content of 60 to 120 at the treatment plant.
The sewage sludge is used in the present invention because it has been dehydrated up to about 100%.

[0009] Quicklimes are not limited to calcined limestone products as long as they contain CaO as a main component, and calcined shell products, slag, calcined dolomite, etc. can be used, and sludge having a water content of about 100% can be used by a hydration reaction. A water content of about 10% or less, which can obtain a heat of reaction capable of drying, is preferable, and the content of CaO is 50% or more, preferably 70% or more.

The amount of quicklime mixed with the sewage sludge depends on the water content of the sewage sludge, but is generally 50 to 150 parts by weight, preferably 80 to 13 parts by weight per 100 parts by weight of the sewage sludge.
About 0 parts by weight is used. If the amount of quicklime added is less than this range, the sludge will not be sufficiently dried and will have a bad odor, and the deodorizing effect will be weakened even if coal ash described later is added. Further, if the amount of quick lime added is too large, the cost becomes high, which is not preferable.

Next, coal ash includes fly ash, which is usually called raw powder, generated from thermal power plants and private power plants, as well as coal ash in a broad sense such as bottom ash, clinker ash and fluidized bed ash. The particle size of coal ash having a BET specific surface area of 1.0 m ² / g or more, preferably 2.0 m ² / g or more is preferably used because it is excellent in the aggregate raw material and the deodorizing effect. Further, the coal ash may contain a large amount of unburned carbon, and the deodorizing effect can be suitably obtained by the ammonia adsorption action of the unburned carbon. 80% by weight or more, preferably 100% by weight of dehydrated powder (hereinafter referred to as "campun") obtained by mixing such coal ash with the sludge and limes.
By adding and mixing in an amount of not less than wt%, the ammonia odor can be removed, and a mixture as an artificial aggregate raw material having extremely excellent fluidity and good handling properties can be obtained.

The above mixture is fired to obtain the artificial aggregate of the present invention. The mixture is granulated or shaped by adding an appropriate amount of a granulation aid and water to produce pellets for firing of about 5 to 15 mm. It is desirable to do. For granulation, various granulation methods such as pressure molding, extrusion molding, and rolling granulation can be applied, and in particular, a pan pelletizer is preferably used because of ease of molding.
Bentonite can be preferably used as a granulation aid, and this is granulated by adding 10 parts by weight or less and 20 parts by weight or less of water to 100 parts by weight of incinerated ash and the mixed material.

Next, the granulated pellets are fired. Firing
It is carried out in a temperature range of 1000 to 1450 ° C. by using various firing furnaces such as a rotary kiln, a kiln and a moving grate furnace. If the firing temperature is lower than 1000 ° C., it is not preferable in terms of water absorption and strength, and if the firing temperature is higher than 1450 ° C., the fusion between the aggregates becomes severe, which is not economical.

[0014]

The specific gravity of the artificial aggregate mainly composed of SiO ₂ , Al ₂ O ₃ largely depends on the firing temperature and the content of the flux (alkali and alkaline earth metal elements) in the raw material. What has been known since Riley (1951) is CaO + MgO + FeO + Fe ₂ O ₃ + Na ₂ O + K.
_{When the} content of ₂ O is in the range of 12 to 20% of the whole, the weight is reduced by foaming, and when the content is larger than that, the weight is melted. Therefore, it is possible to adjust the specific gravity, which could not be controlled only by the chemical composition of the raw material, by using some kind of additive material.

On the contrary, if the amount of the flux is too large, not only a high quality artificial aggregate cannot be obtained by melting and adhering at a low temperature but also the kiln and other firing devices are often damaged. This is common in sewage sludge incinerators. That is, if the amount of the added flux is too large or too small, the specific gravity adjustment will not be successful. Originally, elemental calcium oxide has a high melting point so that it becomes a refractory, but even a slight amount of SiO ₂ + A
The presence of oxides such as l ₂ O ₃ + Fe ₂ O ₃ has the drawback of forming a flux with them and corroding the refractory. Table 1 gives examples of the composition of sewage sludge and coal ash. It is confirmed that some of the sewage sludge and coal ash are melted and cannot retain their original shape when heated to 1200 ° C or higher as they are in view of the conditions of Riley. To be

[0016]

[Table 1]

Reagents, limestone powder, quick lime, slaked lime, and the like can be used if the chemical composition permits the composition adjustment, but it is not preferable in terms of cost to use these virgin raw materials for waste treatment. Therefore, the present inventors evaluated various recycled resources and found that the specific gravity can be effectively adjusted by using a campun obtained by adding quicklime to sewage sludge. That is, quick lime is hydrated to form fine particle calcium hydroxide (specific surface area of 10 m ² / g or more). This is mainly the flux component. On the other hand, sewage sludge is dehydrated and dried, and mainly contains organic matter and S
It contains inorganic substances of iO ₂ + Al ₂ O ₃ + Fe ₂ O ₃ + CaO ≧ 70% and odorous substances such as ammonia and isovaleric acid.

Originally, the sewage sludge itself can be made into a high-quality artificial aggregate by mainly using the inorganic components as the foaming source. However, since it produces a malodorous substance mainly composed of ammonia, the working environment is poor and all the processes are closed, which causes a cost increase. It is a feature of the present invention that the disadvantage can be reduced to at least 1/10 of the initial Annimore concentration at the time of use. It is also worth noting that the spoilage bacteria are killed by making them campund. It has been considered to be disadvantageous for effective use of sewage sludge, and it can be removed by compensating easily perishable with a high water content, easy to store and store, and transport and transfer should be much better than slurry. You can Further, the malodor is also removed by the activated carbon adsorption action of the unburned carbon present in the coal ash described later. Therefore, the coal ash of the present invention is used for 8
Addition of 0% by weight or more, preferably 100% or more makes almost no odor. When it is desired to reduce the amount of fly ash added, a small amount of deodorant such as activated carbon, acid clay, or vanadium sulfate may be added.

On the other hand, as for coal ash, a lot of coal-fired power plants have been operating in recent years, and mainly fly ash has been produced.
Most of the materials that are effectively used as cement admixtures are not used and are directly landfilled. The main reason for this is that the quality of fly ash and other coal ash varies greatly including the chemical composition, making it difficult to use as an industrial raw material. Table 1 gives some examples of such variations. Taking artificial aggregates as an example, one kind of coal ash has a specific gravity of 1 or less at 1200 ° C, while another kind of coal ash melts at 1200 ° C and adheres to the side wall. The problem was that the specific gravity could not be adjusted at all. On the other hand, in the present invention, SiO
₂ + Al ₂ O ₃ is a large amount, and to the coal ash lacking in flux, 10 to 30% by weight of Kampung mainly composed of Ca (OH) ₂ is added to the foam to reduce the foaming weight.
When added in an amount of not less than wt%, the weight of the aggregate is increased, so that it is possible to adjust the specific gravity of the aggregate, and it is possible to obtain a product having a quality as required. In the actual process, it is desirable to incorporate a fluorescent X-ray device or the like for automatic chemical analysis, calculate the amount of addition of Campun, automatically open and close the feeder, and feed a fixed amount.

The mixture is granulated, or if it can be formed naturally or a moving grate can be used, the mixture as it is is put into a firing furnace without being granulated.
The organic material burns in the charged raw material up to around 900 ° C., and water scatters. However, at this time, the particle binding force becomes the minimum, so it is usual to add some kind of holding material (bentonite, etc.). Next, sintering progresses due to the flux melted at around 1200 ° C. If there is a large amount of flux, the sintering continues, and within a certain range (12 to 20%), foaming occurs and the weight is reduced. SiC, Si ₃ N ₄ , F
It is also possible to add a foaming accelerator such as e ₂ O ₃ .

[0021] Whether or not foaming is performed, the fired product is cooled to become a product before the aggregates are fused. In the present invention, sintering proceeds at a temperature of 1000 ° C. or higher. still,
The artificial aggregate of the present invention can be applied regardless of the particle size of the aggregate, and it can be applied to coarse aggregate (diameter 5 to 15 mm) and fine aggregate (diameter 0.6 to 5 mm) which are usually required for concrete kneading. It corresponds to both.

Since the specific gravity of the obtained artificial aggregate can be adjusted, not only is it easy to mix and mix concrete,
From the specific gravity of 1 or less and floating in water, the specific gravity of 2.5 or more and the original gravity of fly ash or more can be obtained, and it can be used for various concrete products. Further, it is possible to stop the sintering in the middle to obtain a product having a large number of pores and a high water absorption rate, and by utilizing its water retention ability, it can be used for planting hydroculture and the like, and can also be used as a filter bacteria carrier.

[0023]

Example 1 Sludge shown in Table 1 and quicklime were mixed with a hover mixer at a weight ratio of 1: 1 to obtain a campun having a water content of 3%. Similarly, sludge is used to obtain a water content of 2.5.
You got a% Kampung. Fly ash A of Table 1 was added to these two types of companions together with 2% by weight of bentonite at various ratios, and granulated to a size of φ10 mm, and each temperature was maintained for 10 minutes in an electric furnace (heating rate 20 ° C./minute). ) And obtained the artificial aggregate. Table 2 shows the specific gravity and water absorption of the obtained aggregate. It can be seen that, while the campun itself without addition of fly ash does not have shape retention, when 100% or more is added, not only shape retention but also foam weight reduction and low water absorption are obtained.

[0024]

[Table 2]

[0025]

Example 2 Using the campun used in Example 1, fly ashes A to F in Table 1 together with 2% by weight of bentonite,
Further, fluidized bed ash G was added at various ratios, granulated to a diameter of 10 mm, and then fired at each temperature. After measuring the specific gravity and water absorption of the obtained aggregate, the crush strength was measured according to the JIS Z8841 granulated product strength test method. The results are shown in Table 3. still,
As shown in FIG. 1, commercially available fly ash calcined aggregate has a specific gravity of 1.39 to 2.05, a water absorption rate of 10.7 to 43.5%, and a crush strength of 28 to 1
It is about 20 Kgf, and the specific gravity of the aggregate that burns only sewage sludge is 1.32 to 2.30, the water absorption rate is 8.8 to 37.2%, and the crushing strength is 25 to
It is about 108 Kgf, and in all cases, the artificial aggregate of the present invention exhibits superior physical properties.

[0026]

[Table 3]

[0027]

Example 3 A mixture of 2% by weight of bentonite and 500% by weight of fly ash A was added to the campun used in Example 1 and the mixture was granulated into φ10.0 ± 2.5% mm.
Using a rotary kiln with a diameter of 650 mm and a length of 10 m, a Kg of 1260 ° C with a focal temperature of 10 minutes and a specific gravity of 1.25
± 0.25 coarse aggregate A was obtained. Also, in the same manner, add 5% bentonite and 5% fly ash D to the camp.
Granulate the mixture added with 00 wt% to φ10.0 ± 2.5 mm, 1
Firing was performed at 310 ° C. for a residence time of 10 minutes to obtain a coarse aggregate B having a specific gravity of 1.25 ± 0.3. For comparison, river gravel was used as coarse aggregate C (specific gravity
2.52), commercially available fly ash aggregate is coarse aggregate D (specific gravity 1.
66) Prepared separately. Further, by the same operation as described above, a fine aggregate A having φ2.0 ± 0.5 mm and a specific gravity of φ1.60 ± 03 was obtained from a mixture of Campun and fly ash A 500% by weight. In addition, river sand with a specific gravity of 2.16 was used as fine aggregate B.

Using the above coarse aggregates and fine aggregates, concrete products were obtained in the mixing ratios shown in Table 4 below, and the obtained concrete products had a diameter of 100 mm and a high height according to JIS A 5002 (compressive strength test method). A 180-day specimen was subjected to a 28-day compressive strength test. Table 4 shows the results
Also described in. It should be noted that, when manufacturing a concrete product, the original mixing ratio should be determined by the addition of an optimum mixing ratio and an AE agent.
%, Slump 8 cm, and fine aggregate ratio 40%. In each case, concrete with high physical properties was obtained in which the strength was not reduced even if the specific gravity was lightened.

[0029]

[Table 4]

[0030]

Example 4 The moisture content of the campun used in Example 1 was 3
% Of this compound was placed in a 100 ml plastic tank, and the concentration of ammonia generated after standing for 24 hours was measured and found to be 0.8% (8000 ppm). 20ppm, 200 with the addition of 500% by weight of fly ash A.
With the addition of 0% by weight, generation of less than 1 ppm was suppressed.

[0031]

[Example 5] As in Example 3, 100% by weight of fly ash A together with 2% by weight of bentonite was added to a camp, and baked at 1180 ° C to obtain a specific gravity of 1.95 and a water absorption rate of 27% of φ10.0 ± 2.5 mm. I got the aggregate. This aggregate was filled in an experimental septic tank (500 × 500 × 1000) so that the porosity was 35%, and soaked in tap water (reservoir) for 1 month to attach filter bacteria. For comparison, a septic tank filled with commercially available boulders of the same particle size was also prepared.

After 1 month, 35 mg of BOD was added to each tank.
Flow rate of 20 ° C sewage effluent containing 20 mL / l and SS42 mg / l.
85 to 8.5 l / min (0.5 to 5.0 hours converted to residence time)
The liquid was sent within the range of, and aeration with compressed air was also performed. On the third day after the start of the liquid feeding, the liquid feeding was stopped, and clear water was fed from the reverse direction at a rate of 20 l / min to perform back washing, and the results shown in Table 5 were obtained.

[0033]

[Table 5]

As is clear from the above results, it is confirmed that the aggregate of the present invention has a much better sludge removal rate than the conventional cobblestone. In addition, when this filter material was taken out and the substance in the water in the voids was observed with a microscope, a large number of aerobic bacteria and protozoa such as Zoclaea and Spherotilus could be observed.

[0035]

[Effects of the Invention] Industrial wastes such as sewage sludge and coal ash, which have been increasing in recent years, can be effectively used in large quantities as various concrete products by firing into aggregates whose density can be adjusted. It can also be used for environmental purification such as plant cultivation, and has various uses.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between specific gravity of artificial aggregate and crush strength.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Kato 2-4-2 Daisaku Sakura, Chiba Prefecture Chichibu Onoda Central Research Institute

Claims (4)

[Claims] 1. An artificial aggregate obtained by firing sewage sludge, quicklimes, and coal ash as main components. 2. An artificial aggregate obtained by firing dehydrated powder obtained by mixing sewage sludge and quicklimes and coal ash as main components. 3. The artificial aggregate according to claim 2, wherein the amount of coal ash is 80% by weight or more based on the dehydrated powder. 4. Sewage sludge and quicklimes are mixed to obtain dehydrated powder, and coal ash is added to the dehydrated powder so that the weight ratio is 80% or more, and then the mixture is heated to 1000 ° C. to 1450 ° C.
A method for producing an artificial aggregate, which comprises firing at the temperature of.