JP6289407B2 - Ash granulated solidified body - Google Patents

Description

  The present invention relates to an ash granulated solidified body obtained using paper sludge incinerated ash.

  In recent years, there has been a strong demand for the reduction of industrial waste or the establishment of a reuse method from the viewpoints of the preservation of the global environment and the establishment of a recycling society. In the paper manufacturing industry, establishment of a method for reusing paper sludge incinerated ash generated when incinerated paper sludge generated from a pulp manufacturing process, a paper manufacturing process, a used paper processing process, and the like is one of the problems.

  In general, paper sludge incineration ash is the soil environment standard (Ministry of the Environment Notification No. 18 No. 48, revised Ministry of the Environment Notification No. 48), the amount of elution of harmful components often exceeds the standard value. Among these harmful components, organic harmful components are decomposed at the time of incineration, so there are few problems with paper sludge incineration ash, but the elution amount of inorganic harmful components such as fluorine, boron, hexavalent chromium and lead is Often the standard is exceeded. In particular, the elution amount of fluorine and hexavalent chromium often exceeds the standard. Paper sludge incineration ash whose toxic substance elution amount exceeds the soil environmental standard value cannot be directly landfilled. It is obliged to have to be landfilled at a prevented disposal site. Alternatively, when landfilling is performed, an intermediate treatment is required to suppress the elution of harmful substances. There are chemical (chelate) treatment and melt solidification treatment as intermediate treatment, but expensive chelating agents require several percent of the ash to be treated, and melt solidification treatment requires equipment costs and a lot of energy. The intermediate processing method increases the incineration ash processing cost. In addition, securing a landfill site itself has become increasingly difficult in recent years.

  Therefore, it is very beneficial to promote the reuse of paper sludge incineration ash in addition to the effects of preserving the global environment and building a recycling society, as well as the effect of reducing processing costs. In order to effectively use paper sludge incineration ash for soil improvement materials and roadbed materials, methods for producing solidified bodies are known (for example, see Patent Documents 1 to 3).

Japanese Patent Laid-Open No. 2003-292956 JP 2005-313032 A JP 2011-212563 A

  The problem of the present invention is that when used as a soil material such as a backfill material, embankment material, retaining wall lining material, geological improvement material, roadbed material, frost heave suppression material, etc., it is excellent in strength after compaction and harmful components It is to provide an ash granulated solidified body that is sufficiently suppressed in elution and is lightweight. Here, “light weight” means that the apparent density representing the weight per unit volume of the ash granulated solidified body is small. If it is a lightweight ash granulation solidified body, it can be used as a roadbed material for a soft ground with a high water content, and it is excellent in drainage even against rainfall.

  The above-mentioned problems of the present invention include paper sludge incineration ash having a CaO content of 21% by mass or more, coal ash, ferrous sulfate as a reducing agent, and a flocculant obtained by a measurement method defined in JIS M 8221: 1997. And at least one selected from polyferric sulfate and aluminum sulfate, and water, and has at least one peak in the particle size distribution curve and the full width at half maximum of 2.0 mm or more. It is solved by an ash granulated solidified body having an average particle diameter of 1.8 mm or more and 6.0 mm or less.

  According to the present invention, when used as a soil material, it is possible to provide an ash granulated solidified body which is excellent in strength after compaction, elution of harmful components is sufficiently suppressed, and is lightweight.

  Hereinafter, the present invention will be described in detail.

  Paper sludge is waste generated from a pulp manufacturing process, a paper manufacturing process, a used paper processing process, and the like, and is usually also referred to as a papermaking sludge. Paper sludge contains various raw materials generally used in the papermaking field, and is used as pigments and fillers, inorganic substances such as silica, calcium carbonate, talc, kaolin and cinnabar, organic materials such as pulp and papermaking chemicals. Contains materials and ink components contained in waste paper.

  Paper sludge incineration ash is ash obtained by incinerating the paper sludge with a combustion device. A combustion apparatus is not specifically limited, A conventionally well-known apparatus can be used. Examples of the combustion apparatus include a rotary kiln, a cyclone type, and a fluidized bed type incinerator. The combustion temperature is not particularly limited, but is preferably 500 ° C. or higher. The time for incineration can be selected as appropriate.

  The paper sludge incineration ash can be pretreated before kneading. The pretreatment can include, for example, pulverization, crushing, crushing, classification, recombustion, re-drying, magnetic separation, and the like, and can be performed using any suitable apparatus known to those skilled in the art. Of course, it can also be used for kneading as it is. From the viewpoint of energy consumption and cost, it is preferable not to perform these pretreatments.

  When incinerating paper sludge, the paper sludge may be mixed with other materials. Other materials include, for example, waste tires, RDF (garbage solid fuel), RPF (industrial waste plastic / waste paper solid fuel), wood chips, sawdust, cotton, rayon, hemp, newspaper, magazine, water sludge, wastewater sludge, Other general combustible materials can be mentioned. As long as it is used for auxiliary combustion, fossil fuels such as heavy oil and coal may be mixed with paper sludge. However, other materials and fossil fuels used for mixed firing are in a level that does not impair the porosity that is the property of paper sludge incineration ash.

  The paper sludge incineration ash of the present invention has a CaO content of 21% by mass or more determined by a measurement method defined in JIS M 8221. Paper sludge incineration ash is derived from calcium compounds in various raw materials used in the papermaking field and contains quicklime (CaO). In the paper sludge incineration ash, the CaO content varies depending on the content of the paper sludge. The present invention is to use paper sludge incinerated ash that finally has a CaO content of 21% by mass or more.

Coal ash is usually called fly ash and contains a large amount of calcium aluminate (CaO.Al ₂ O ₃ ) and silica (SiO ₂ ).

  The ash granulated solidified product of the present invention is a paper sludge incinerated ash having a CaO content of 21% by mass or more determined by a measurement method defined in JIS M 8221: 1997, coal ash, ferrous sulfate as a reducing agent, It is obtained by kneading at least one selected from polyferric sulfate and aluminum sulfate as a flocculant and water. Paper sludge incineration ash, coal ash, ferrous sulfate as reducing agent, at least one selected from polyferric sulfate and aluminum sulfate as flocculant, and water may be supplied and kneaded at once. . Moreover, you may knead | mix, supplying 1 type or multiple types sequentially.

  The effect of the present invention that the elution of harmful components can be sufficiently suppressed and the weight is reduced is that paper sludge incineration ash having a CaO content of 21% by mass or more, coal ash, ferrous sulfate as a reducing agent, and poly as an aggregating agent. It can be obtained by a synergistic effect of a system of kneading at least one selected from ferric sulfate and aluminum sulfate and water. That is, it is considered as follows.

And quicklime paper sludge in ash, coal ash, and the sulfates and water react chemically and produce a acicular crystals ettringite _{(3CaO · Al 2 O 3 ·} 3CaSO 4 · 32H 2 O). When ettringite incorporates harmful components such as fluorine and hexavalent chromium into the crystal structure, elution of harmful components from the resulting ash granulated solidified product is suppressed. Further, the ettringite becomes needle-like crystals, the voids inside the ash granulated solidified body increase, and as a result, the ash granulated solidified body becomes light.
Furthermore, ettringite can be produced effectively because coal ash contains a large amount of calcium aluminate. In addition, since the coal ash contains a large amount of silica (SiO ₂ ), calcium silicate crystals (tobermorite, 5CaO · 6SiO ₂ · 5H ₂ O) are efficiently produced by the reaction between quick lime and silica in the paper sludge incineration ash. Can be generated. The calcium silicate crystal can generate caspodyne (3CaO.2SiO ₂ .CaF ₂ ) by reaction with fluorine, and suppress elution of fluorine.
Ferrous sulfate is a reducing agent, and can reduce hexavalent chromium that ettringite cannot take up to trivalent chromium. Trivalent chromium is harmless. Kneading paper sludge incineration ash having a CaO content of 21% by mass or more, coal ash, at least one selected from ferrous sulfate as a reducing agent, polyferric sulfate and aluminum sulfate as a flocculant, and water In the system, it is difficult to obtain such a reducing action with other reducing agents such as ferrous chloride.
At least one selected from polyferric sulfate and aluminum sulfate is a flocculant and can be separated as a solid by aggregating trivalent chromium produced by ferrous sulfate. Thereby, it can suppress oxidizing and returning to hexavalent chromium again. Kneading paper sludge incineration ash having a CaO content of 21% by mass or more, coal ash, at least one selected from ferrous sulfate as a reducing agent, polyferric sulfate and aluminum sulfate as a flocculant, and water In the system, it is difficult to obtain such an aggregating action with other aggregating agents. Further, at least one selected from polyferric sulfate and aluminum sulfate does not hinder the production of ettringite.

  Water is required for reaction with quicklime and the production of ettringite. The size and shape of the ash granulated solidified body can be controlled by the amount of water added and the kneading time.

  The ash granulated solidified product of the present invention has at least one peak in the particle size distribution curve, the half width of the maximum peak is 2.0 mm or more and 6.0 mm or less, and the average particle diameter is 1.8 mm or more and 6.0 mm. It is as follows. In the present invention, the average particle size is the average particle size of ash granulated solidified single particles. When the ash granulation solidified body forms secondary aggregates and multi-aggregates, it is the average particle diameter of single particles constituting the aggregates. The full width at half maximum of the maximum peak and the average particle diameter in the particle size distribution curve of the ash granulated solidified product are obtained by photographing the ash granulated solidified product using an optical microscope and regarding the photographed single particle as a spherical shape with an approximate area. The diameter is calculated and measured by measuring 200 ash granulated solidified bodies existing in the photographed image. A particle size distribution curve in which the vertical axis represents frequency (%) and the horizontal axis represents particle diameter (mm) can be obtained from the measured particle diameter data using particle image analysis software or the like. From the obtained particle size distribution curve, the full width at half maximum can be determined as the width at the half height of the peak height of the maximum peak. The maximum peak means the highest peak in the particle size distribution curve. If the half width of the maximum peak is small, the particle size distribution curve will have a distinct maximum peak.

If the full width at half maximum is more than 6.0 mm, the ash granulated solidified product will not be lightweight. If the half width is less than 2.0 mm, the strength after compaction cannot be obtained. This reason is considered to be due to the formation of appropriate voids between the ash granulated solidified bodies.
When the average particle diameter is less than 1.8 mm, the ash granulated solidified product is not light. When the average particle diameter is more than 6.0 mm, the ash granulated solidified body cannot obtain the strength after compaction.

  The ash granulated solidified product corresponding to the particle size distribution curve and the average particle size of the present invention can be obtained by adjusting the amount of water added and the kneading time. Moreover, it can obtain by performing a classification work as needed.

  The kneading is a conventionally known apparatus and is not particularly limited. For example, an apparatus equipped with a kneading roll and a kneading blade is preferable, and a rolling kneader is more preferable. Examples of such an apparatus include Peregia manufactured by Kitagawa Iron Works, Eirich Intensive Mixer manufactured by Nihon Eirich Co., Ltd., and Elba EMS type mixer manufactured by Kurihara Co., Ltd.

  The ash granulated solidified body is preferably cured after kneading. Curing improves the strength of the ash granulated solidified body, and when used as a soil material, the strength after compaction is excellent. Curing methods can be broadly divided into natural curing and forced curing. Curing can be either natural curing or forced curing. Natural curing is a method of standing for a long time without particularly changing hands, and it is preferable to leave it for 5 days or more. Forced curing is a method of curing in a short time in a high temperature state. Curing is preferably carried out at less than 40 ° C. This is because when used as a soil material, the strength after compaction is superior, and the elution of harmful components is more sufficiently suppressed.

  The ash granulated solidified body is suitable for a soil material. For example, it is suitable for a soil material used for a backfill material, a banking material, a retaining material for a retaining wall, a geological improvement material, a roadbed material, a frost heave suppression material and the like. The ash granulated solidified body may be used alone for each application. Further, it may be used by mixing with other soil materials.

  The ash granulated solidified body can appropriately contain conventionally known additives such as a curing accelerator, a dispersant, and an enhancer as long as the desired effects of the present invention are not impaired.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Moreover, the mass% and mass part shown in an Example show the value of dry solid content or a substantial component.

(Evaluation of strength after compaction)
The original ground where excavation work will be performed was excavated. The excavation part surface was leveled using mountain sand. Finally, a rectangular parallelepiped space having a size of 2 m × 2 m and a depth of 0.2 m from the surface of the original ground was produced. In this space, the ash granulated solidified body of each Example and each Comparative Example was laid uniformly, and the surface was subjected to a rolling process by a rolling roller to perform a backfilling operation. Three days after the backfilling operation, the cone index was measured. Here, the “cone index” is a kind of penetration resistance to the compacted ground, and was measured based on JIS A 1228: 2009 “Cone index test method for compacted soil”. The cone index was measured at five arbitrary locations, and the average value was divided into the following three stages. In the present invention, the ash granulated solidified body is excellent in strength after compaction when used as a soil material as long as the evaluation is 2 or more.
3: 1200 kN / m ² or more.
2: 900 kN / m ² or more and less than 1200 kN / m ² .
1: Less than 900 kN / m ² .

(Evaluation of suppression of elution of harmful components)
Evaluation of suppression of harmful component elution was judged from the amount of harmful component eluted from the ash granulated solidified product.
The amount of elution of harmful components from the ash granulated solidified body was measured according to Notification No. 18 of 2003 Ministry of the Environment. The ash granulated solidified body was crushed with a mortar, and passed through a non-metallic sieve having a mesh opening of 2 mm. 50 g of the obtained ash granulated solidified product and 500 mL of water (pure water, pH 5.8 to 6.3) were mixed and continuously shaken with a shaker at room temperature and normal pressure for 6 hours (shaking width 4 to 5 cm). , Vibration frequency 200 times / min). The resulting suspension was allowed to stand for 30 minutes, then centrifuged at about 3000 rpm for 20 minutes, the supernatant was filtered through a membrane filter with a pore size of 0.45 μm, and the filtrate was collected. Was accurately measured and used as a test solution. The elution standard is 0.8 mg / L or less of fluorine, 1 mg / L or less of boron, 0.05 mg / L or less of hexavalent chromium, and 0.01 mg / L or less of lead. The elution amounts of boron and lead from the ash granulated solidified bodies of each Example and each Comparative Example were both below the elution amount standard value. The elution amounts of fluorine and hexavalent chromium were divided into the following three stages. In the present invention, if the ash granulated solidified body is evaluated as ○, the elution of harmful components is sufficiently suppressed.
○: Elution amount standard value or less for both fluorine and hexavalent chromium.
Δ: Either fluorine or hexavalent chromium exceeds the elution amount reference value.
X: Both elution amount standard values exceed fluorine and hexavalent chromium.

(Evaluation of light weight)
The evaluation regarding the light weight of the ash granulated solidified body was judged by measuring the apparent density per unit volume.
1000 mL of the ash granulated solidified body was measured using a beaker, and the apparent density per unit volume was measured from the mass at that time. The measurement was divided into the following three stages. In the present invention, the ash granulated solidified body is light if it has an evaluation of 2 or more.
3: Less than 1.15 g / cm ³ 2: 1.15 g / cm ³ or more and less than 1.30 g / cm ³ 1: 1.30 g / cm ³ or more

(Preparation of paper sludge incineration ash)
Paper sludge, waste tires, and wood chips discharged from the paper mill were appropriately adjusted in amounts and incinerated at about 900 ° C. using an incinerator to obtain paper sludge incineration ash A and B. The chemical composition of each of the paper sludge incineration ash A and B is shown in Table 1.

(Preparation of ash granulated solidified product)
The ash granulated solidified body of each Example and each Comparative Example was prepared by the following procedure.
Paper sludge incineration ash and coal ash are mixed in a kneader (made by Kitagawa Iron Works Co., Ltd., trade name Pelegaia) so that the total mass of paper sludge incineration ash and coal ash is 25% by mass% as shown in Table 2. I put it in. Furthermore, with respect to 100 mass parts of total mass of paper sludge incineration ash and coal ash, the reducing agent and the coagulant | flocculant of a 15 mass% density | concentration respectively were thrown into the mass part of Table 2, respectively. Further, 5 L of water was added, and kneading was performed with a kneader. The ash of each example and each comparative example was adjusted by adjusting the amount of water added and the kneading time so that the half width of the maximum peak and the average particle size in the particle size distribution curve were as shown in Table 2. A granulated solidified body was obtained. The ash granulated solidified body of each Example and each Comparative Example was used after natural curing for 7 days after the kneading step.

The reducing agents and flocculants in Table 2 are as follows.
Ferrous sulfate: Showa Chemical Co., Ltd., ferrous sulfate heptahydrate commercial product Sodium sulfite: Daito Chemical Co., Ltd., commercial product Aluminum sulfate: Asada Chemical Industry Co., Ltd., commercial product Polyferric sulfate: Taiki Pharmaceutical Co., Ltd., commercial product Polyaluminum chloride: Daimei Chemical Co., Ltd., commercial product

  Each evaluation result is shown in Table 2 for each example and each comparative example.

  From Table 2, in each example that is an ash granulated solidified product corresponding to the present invention, when used as a soil material, it is excellent in strength after compaction, elution of harmful components is sufficiently suppressed, and is lightweight. I understand that. On the other hand, it turns out that the effect of this invention cannot be acquired in each comparative example which is an ash granulation solidification body which does not correspond to this invention.

Claims (1)

  Paper sludge incineration ash having a CaO content of 21% by mass or more, coal ash, ferrous sulfate as a reducing agent, polyferric sulfate and sulfuric acid as a flocculant obtained by a measuring method defined in JIS M 8221: 1997 It is obtained by kneading at least one selected from aluminum and water, and has at least one peak in the particle size distribution curve, and the half-value width of the maximum peak is 2.0 mm or more and 6.0 mm or less, and the average particle diameter Ash granulated solidified body having a diameter of 1.8 mm or more and 6.0 mm or less.