JP6722969B2 - Silicate fertilizer and method for producing the same - Google Patents

Description

The present invention relates to a siliceous fertilizer having high water solubility of silicic acid and a method for producing the same.

The siliceous fertilizer includes silicic acid (calcium silicate) and potassium silicate (potassium silicate) fertilizers, which have been conventionally used for rice cultivation and the like. Of these fertilizers, Caikal mainly contains SiO ₂ , CaO, and Al ₂ O ₃ , and is effective in replenishing soil with silicic acid and correcting acidic soil.
However, the elution amount of silicic acid from silica gel exceeds 30% in hydrochloric acid aqueous solution, but it is as small as 5% at a pH of soil of about 5 to 7, so when about 200 kg of silica gel is applied per 1000 m ^{2 of} paddy field. However, it is a heavy burden for farmers due to the labor and cost. In addition, since Caikal does not contain any of the three elements of fertilizer, nitrogen, phosphorus, and potassium, it is usually necessary to mix a large amount of Caikal with other fertilizers containing the three elements of fertilizer. For example, even when mixed with fertilizer, which has a relatively large amount of silicic acid elution, even in the neutral range, the amount of silica added is as large as 200 kg for 40 kg of fertilizer.
The amount of silicic acid eluted is different from the amount of soluble silicic acid (the amount of silicic acid dissolved in a 0.5 mol hydrochloric acid aqueous solution).

Therefore, some siliceous fertilizers having improved low water solubility of silicic acid, which is a defect of silica, have been proposed.
For example, the siliceous fertilizer described in Patent Document 1 is produced by adding an organic binder (sucrose or molasses) having a specific dissolution rate to water to a powder of a siliceous composition having a specific particle size. It is a silicic acid fertilizer made by granulating. Then, the elution amount of the silicic acid content of the fertilizer within 16 months measured by the ion exchange method is 16% by mass or more.
Further, the siliceous fertilizer described in Patent Document 2 is a fertilizer in which the organic binder is starch that has been gelatinized.
Further, any of the above siliceous fertilizers is an amorphous substance containing 1 to 20% by mass of MgO, 30 to 50% by mass of SiO ₂ , and also CaO and P ₂ O ₅ .
Furthermore, the siliceous fertilizer described in Patent Document 3 has SiO ₂ , MgO, CaO, and P ₂ O ₅ as main components, contains 12% by mass or more and less than 30% by mass of SiO _2, and is measured by an ion exchange method. The fertilizer has a silicic acid content elution amount of 10 mass% or more within 10 days. However, in the production of the siliceous fertilizer, serpentine, which is a natural phosphate rock, must be used, and since the molten slag is formed by a batch method, energy consumption and productivity are not economical.

By the way, the above-mentioned phosphate fertilizer such as fertilizer is produced by using phosphate rock which is a natural resource as a part of the raw material. However, in Japan, phosphorus is not produced as a natural resource, so almost all of it has to rely on imports, but in recent years, natural phosphorus is being depleted worldwide, and the price of phosphorus has risen sharply and It is difficult to secure. Therefore, in the field of manufacturing phosphate fertilizers, as an alternative to natural phosphorus resources, sewage sludge incinerator ash having a phosphorus content of 20 to 30 mass%, which is almost the same as that of phosphate rock, is considered. In Japan, a large amount of sewage sludge and its incinerated ash are generated at 2.2 million tons and 300,000 tons per year, respectively, so the treatment of sewage sludge is a social requirement. In addition, since the sewage sludge incineration ash contains phosphoric acid and silicic acid, it is suitable as a raw material for the siliceous fertilizer of the present invention.
Further, effective utilization of hydroxyapatite and magnesium ammonium phosphate recovered by HAP method or MAP method from wastewater containing phosphorus such as sewage, night soil, and livestock wastewater is also desired.

JP, 2002-068871, A JP, 2002-068870, A JP 2002-047081 A

Therefore, an object of the present invention is to provide a silicic acid fertilizer produced by using sludge or incinerated ash thereof as a part of a raw material and having high water solubility of silicic acid.

The inventors of the present invention investigated a siliceous fertilizer capable of achieving the above-mentioned object, and found that the following siliceous fertilizer had high water solubility of silicic acid, and completed the present invention. That is, the present invention is a siliceous fertilizer and the like having the following constitution.

[1] Composition formula 2CaO·xSiO ₂ ·yP ₂ O ₅ (where x>0, y≧0, 0.85<x+y≦1.00 and 0.65<[x/(x+y)]≦1.00 ) Is a siliceous fertilizer containing a mineral represented by (4) and having a CaO content of 50 to 60% by mass, wherein the water-weakly acidic cation exchange resin method has a water-soluble silicic acid content of 6% or more. , Siliceous fertilizer.
[2] The mass ratio of components other than (A) SiO ₂ , (B) CaO, and (C) CaO and SiO ₂ in the siliceous fertilizer is as shown in the triangular diagram of FIG.
Point (a) [(A)/(B)/(C)=43/50/7],
Point (a) [(A)/(B)/(C)=33/60/7],
Point (C) [(A)/(B)/(C)=10/60/30], and
Point (D) [(A)/(B)/(C)=10/50/40]
The siliceous fertilizer according to the above [1], which is in a range surrounded by.
[3] The method for producing a siliceous fertilizer according to the above [1] or [2],
A mixing step for obtaining a mixed raw material by at least mixing one or more kinds selected from sludge, dehydrated sludge, dried sludge, sludge charcoal, sludge incineration ash, and sludge molten slag to obtain a mixed raw material;
A method for producing a silicic acid fertilizer, comprising a step of calcining the mixed raw material at 1,300 to 1,400° C. using a calcining furnace to obtain a silicic acid fertilizer as a calcined product.
[4] In the mixing step, further, at least one selected from hydroxyapatite and magnesium ammonium phosphate recovered from the phosphorus-containing wastewater by the HAP method or the MAP method, and a phosphate fertilizer is mixed, The method for producing a siliceous fertilizer according to the above [3].
[5] The method for producing a siliceous fertilizer according to the above [3] or [4], wherein the firing furnace is a rotary kiln.

The silicic acid fertilizer of the present invention contains silicic acid having high water solubility. Further, the method for producing a siliceous fertilizer of the present invention, (i) sludge and its derived products of sludge such as incinerated ash can be effectively used, and (ii) less energy consumption during firing as compared with the production of molten fertilizer Therefore, it contributes to energy saving. (iii) When a rotary kiln is used in the firing furnace, continuous production is possible and production efficiency is high.

2 is an X-ray diffraction chart of the siliceous fertilizer of the present invention (Examples 3, 8 and 11). _(A) SiO 2, a triangular diagram showing the (B) CaO, and (C) CaO and the mass ratio of the components except the SiO _2.

Hereinafter, the present invention will be described in detail by dividing it into a silicic acid fertilizer and a method for producing the same.
1. Silicate fertilizer The siliceous fertilizer of the present invention has a composition formula 2CaO.xSiO ₂ .yP ₂ O ₅ (where x>0, y≧0, 0.85<x+y≦1.00 and 0.65<[ x/(x+y)]≦1.00), which is a silicic acid fertilizer having a CaO content of 50 to 60% by mass, the water-weakly acidic cation exchange resin method being used. Water-soluble silicic acid is 6% or more. The minerals represented by the above composition formula are Nagelschmittite (7CaO·2SiO ₂ ·P ₂ O ₅ ), 14.92CaO·5.65SiO ₂ ·1.175P ₂ O ₅ , 15CaO·6SiO ₂ ·P ₂ O. ₅ , dicalcium silicate (2CaO.SiO ₂ ), etc., and these have high water solubility of silicic acid.
The content of CaO in the siliceous fertilizer is 50 to 60% by mass. When the content is 50 to 60% by mass, as shown in Table 2 below, the water-soluble silicic acid content by the water-weakly acidic cation exchange resin method is 6% or more. Here, the water-soluble rate of silicic acid is the mass ratio (%) of water-soluble silicic acid by the water-weakly acidic cation exchange resin method to the total silicic acid in silicic acid fertilizer. Further, water-soluble silicic acid prepared by the water-weakly acidic cation exchange resin method is a method for evaluating the solubility of the silicic acid component in the vicinity of neutrality (pH=7). Measure according to the method described.

Reference A: Naoto Kato "Ministry of Agriculture, Forestry and Fisheries/Agricultural Environmental Technology Research Institute Report" 16: 9-75 (1998)
Reference B: Kato and Owa Co., Soil Sci. Plant Nutr. , Vol. 43, No. 2, pp. 351-359 (1997).

Here, in the measurement of water-soluble silicic acid, the ion exchange resin is used because the increase in pH caused by the dissolution of alkaline substances such as alkaline earth metals from the siliceous fertilizer in the solution This is because the exchange ability is used to prevent this. Since the paddy soil is almost neutral and has a high pH buffering capacity, the ion-exchange method can be used to evaluate the water solubility of silicic acid in an environment closer to the actual paddy field. The oxides in the raw materials and the siliceous fertilizer can be quantified by the fundamental parameter method using a fluorescent X-ray device.

In addition, the siliceous fertilizer of the present invention preferably has a mass ratio of (A) SiO ₂ , (B) CaO, and (C) components other than CaO and SiO ₂ in the siliceous fertilizer, In the triangular diagram shown in FIG.
Point (a) [(A)/(B)/(C)=43/50/7],
Point (a) [(A)/(B)/(C)=33/60/7],
Point (C) [(A)/(B)/(C)=10/60/30], and
Point (D) [(A)/(B)/(C)=10/50/40]
It is a silicic acid fertilizer within the range surrounded by. If the mass ratio of (A) SiO ₂ , (B) CaO, and the components other than (C) CaO and SiO ₂ is within the range of the triangular diagram shown in FIG. improves. The total of the components (A), (B), and (C) is 100. Further, the “within the enclosed range” includes the boundary line.

2. Method for producing silicic acid fertilizer
The method for producing a siliceous fertilizer of the present invention comprises at least one selected from sludge, dehydrated sludge, dried sludge, sludge charcoal, sludge incineration ash, and sludge molten slag, and a calcium source, to prepare a mixed raw material. It is a manufacturing method including, as an essential step, a mixing step of obtaining and a firing step of firing the mixed raw material at 1300 to 1400° C. in a firing furnace to obtain a siliceous fertilizer as a fired product. Hereinafter, the mixing step and the firing step will be described separately.

(1) Mixing step This step is a step of mixing the raw materials to obtain a mixed raw material (raw material for firing) so that the content of CaO in the fired product is 50 to 60% by mass. The raw material is pulverized by a ball mill, a roller mill, a rod mill, or the like, if necessary, in order to make the particle size easy to mix.
In addition, as a method for mixing the raw materials, for example, after burning a part of each raw material in an electric furnace or the like, the amount of oxide in the baked ash is quantified, and the respective raw materials are mixed based on the quantitative value and a predetermined composition. There is a method. The quantification of the oxide can be performed by a fundamental parameter method using a fluorescent X-ray apparatus. The chemical composition of the raw material before firing is almost the same as the chemical composition of the fired material except for the volatile components due to firing, and therefore, in order to obtain a fired material having a CaO content of 50 to 60 mass%, It is sufficient to use a raw material for firing in which the content of CaO satisfies the above range. However, for accuracy, a part of the raw material is fired in an electric furnace or the like, and the correlation between the content of CaO in the raw material and the content of CaO in the fired product is grasped in advance. Based on the correlation, it is preferable to correct the mixing ratio of the raw materials so that the target content of CaO in the fired product is adjusted.

Among the raw materials to be mixed in the mixing step, the sludge is an organic substance obtained by separating by sedimentation or filtration in the process of sewage treatment in a sewage terminal treatment plant or human waste treatment in a human waste treatment plant, and these wastewater treatment processes. It is a mud-like substance containing inorganic substances. The dehydrated sludge is obtained by dehydrating the mud matter by centrifugation or the like.
The sludge dried product is obtained by drying the sewage sludge in the sun or drying it with a drier to have a water content of about 50% by mass or less.
Further, the sludge charcoal-based material is obtained by heating the sludge to convert a part or all of the organic matter contained in the sludge into carbonized material. The heating temperature is preferably 300 to 800°C, more preferably 500 to 700°C. If the heating temperature is lower than 300°C, it takes time to carbonize, and if it exceeds 800°C, the carbide may burn. In order to suppress the combustion, heating is preferably performed in anoxic or hypoxic state. Since the carbide also serves as a part of fuel in the production of the siliceous fertilizer of the present invention, the energy required for production can be saved accordingly.
The sludge incineration ash is a residue obtained by incinerating sludge. The sludge melting slag is obtained by melting the sludge incineration ash at 1350°C or higher.
Even if the sludge or the like has a different form or moisture content, the chemical components and the composition thereof after incineration or firing are the same or substantially the same, so any one may be used as a part of the raw material for firing. .. The chemical composition of sewage sludge incineration ash is shown in Table 1 below.

Further, the calcium source is a raw material used for preparing so that the content of CaO in the siliceous fertilizer is in the range of 50 to 60% by mass, and further, the component (A) and the component (B). It is used for adjusting the mass ratio (chemical composition ratio) of the component and the component (C) to be within the above range. The calcium source is at least one selected from calcium carbonate, calcium oxide, calcium hydroxide, calcium phosphate, calcium chloride, calcium sulfate, limestone, quick lime, slaked lime, cement, steel slag, waste concrete, and fresh consludge. ..

Furthermore, as a raw material for adjusting the chemical composition ratio, a silicic acid source and a phosphoric acid source can be used in addition.
The silicic acid source may be at least one selected from coal ash, silica stone, silica sand, foundry sand, shale, clay, zeolite, diatomaceous earth, clay, volcanic ash, steel slag, waste concrete, and raw consludge. From the viewpoint of easy adjustment of the chemical composition ratio, a silicic acid source having a SiO ₂ content of 50 mass% or more is preferable. Among the above-mentioned silicic acid sources, iron and steel slag, waste concrete, fresh conslud and the like also function as a calcium source.
In addition, the phosphoric acid source is selected from hydroxyapatite and magnesium ammonium phosphate recovered from phosphorus-containing wastewater such as sewage, human waste, and barn wastewater by the HAP method or MAP method, and a phosphate fertilizer. One or more may be mentioned.

(2) Firing step This step is a step of firing the mixed raw material using a firing furnace. The mixed raw material is fired as a powder, fired in a slurry by adding water to the powder, or fired in a dehydrated cake state, or to further increase firing efficiency, The powder, a cement solidified product of the powder, or the like is granulated or molded by a granulating machine such as a pan pelletizer or a molding machine such as a briquette machine or a roll press, and then fired.
In the firing step, the firing temperature is preferably 1300 to 1400°C. If the temperature is lower than 1300, firing is insufficient and the water solubility of silicic acid is low, and if it exceeds 1400°C, the fired product may melt and become a melt. The firing furnace is preferably a rotary kiln because continuous production is possible. The firing time is preferably 10 to 60 minutes, more preferably 20 to 40 minutes. If the time is less than 10 minutes, the firing will be insufficient, and if it exceeds 60 minutes, the production efficiency will decrease.

(3) Grinding and granulating step This step is a step of adjusting the particle size of the fired product, in order to suppress the generation of dust, facilitate the handling of fertilizer, and sufficiently exert the fertilizer effect. , Is an optional step that is selected when it is necessary to adjust the particle size of the fertilizer. The particle size is preferably 0.1 to 10 mm, more preferably 0.5 to 5 mm.
As the crushing means, for example, a jaw crusher, a roller mill, a ball mill, a rod mill or the like can be used. Further, as the granulating means, for example, a pan type mixer, a pan pelletizer, a briquette machine, a roll press, an extrusion molding machine and the like can be used.
Further, in the step, it is possible to appropriately add a component of silicic acid or phosphoric acid or newly add other fertilizer components such as nitrogen, potassium, and magnesia depending on the use of the fertilizer.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.
1. Manufacture of Silica Fertilizer Using sewage sludge incineration ash, hydroxyapatite, phosphate fertilizer, calcium carbonate powder (manufactured by Ube Materials Co., Ltd.), and silica sand powder having the chemical composition shown in Table 1, and the examples shown in Table 2 1 to 14 and Comparative Examples 1 to 6 were mixed to prepare mixed raw materials. Next, the mixed raw material was molded by a uniaxial pressure molding machine to prepare a cylindrical raw material having a diameter of 40 mm and a height of 10 mm. Further, after the cylindrical raw material was placed in an electric furnace, the temperature was raised to a temperature shown in Table 2 at a heating rate of 20° C./minute, and the material was fired at the temperature for 10 minutes to obtain a fired product. Obtained. Further, the calcined product was pulverized using an iron mortar until it passed through a sieve having openings of 600 μm to produce powdery siliceous fertilizers (Examples 1 to 14 and Comparative Examples 1 to 6). Table 3 shows the major minerals (marked with ◯) identified in the siliceous fertilizer, and FIG. 1 shows the X-ray diffraction charts of Examples 3, 8 and 11. The chemical composition of the siliceous fertilizer after firing was almost the same as the chemical composition of the mixed raw material before firing, except for the volatile components due to firing.

2. Measurement of Water-Soluble Silicic Acid and Soluble Phosphoric Acid Water-soluble silicic acid was measured by the following procedure using the water-weakly acidic cation exchange resin method, and the water solubility of silicic acid was calculated.
That is, a beaker made of resin containing 2 g of an ion exchange resin (trade name: Amberlite IRC-50 [registered trademark], manufactured by Organo) that has been previously subjected to reverse regeneration treatment using an aqueous sodium hydroxide solution and dilute hydrochloric acid, and 1 liter of pure water. 0.2 g of the siliceous fertilizers of the above-mentioned Examples and Comparative Examples were added therein, and the mixture was gently stirred with a magnetic stirrer for 10 minutes, and then allowed to stand for 10 days. After the lapse of 10 days, the mixture was gently stirred with a magnetic stirrer for 10 minutes again, and allowed to stand for 30 minutes, 2 ml of the supernatant was collected in a measuring flask, and 1 ml of hydrochloric acid (1+1) was added to 20 ml. Diluted. The concentration of Si in the solution was quantified by ICP emission spectrometry and converted into the concentration of SiO ₂ . Further, the solubilized phosphoric acid was measured by the ammonium vanadomolybdate method defined in the Fertilizer Analysis Method (Ministry of Agriculture, Forestry and Fisheries Research Institute for Agricultural Environmental Technology), and the solubilized rate of phosphoric acid was calculated. The results are shown in Table 2.
As shown in Table 2, the silicic acid fertilizers of the present invention (Examples 1 to 14) had a high water-soluble silicic acid content of 6.6% or more and a water-solubility rate of 31% or more. On the other hand, the water-soluble silicic acid of the siliceous fertilizers of Comparative Examples 1 to 6 was 4.0% or less, and the water solubility was 20% or less, which were low at all. In addition, the dissolution rate of Examples was as high as 82% or more except for Example 14.

From the above results, the siliceous fertilizer of the present invention has high water solubility of silicic acid and high solubility of phosphoric acid, and can contribute to resource saving of phosphorus by recycling sewage sludge and the like. Further, the method for producing siliceous fertilizer of the present invention consumes less energy in firing as compared with the production of molten fertilizer, so that it can contribute to energy saving, and when a rotary kiln is used, continuous production is possible. Higher production efficiency.

Claims (4)

Composition formula 2CaO·xSiO ₂ ·yP ₂ O ₅ (where x>0, y≧0, 0.85<x+y≦1.00 and 0.65<[x/(x+y)]≦1.00) Which is a silicic acid fertilizer containing 50 to 60% by mass of CaO and containing 6% or more of water-soluble silicic acid by a water-weakly acidic cation exchange resin method. a quality fertilizer
The mass ratio of (A) SiO ₂ , (B) CaO, and the components other than (C) CaO and SiO ₂ in the siliceous fertilizer is as shown in the triangular diagram of FIG.
Point (a) [(A)/(B)/(C)=24/50/26],
Point (a) [(A)/(B)/(C)=21/60/19],
Point (C) [(A)/(B)/(C)=10/60/30], and
Point (D) [(A)/(B)/(C)=10/50/40]
Silica fertilizer in the area surrounded by. The method for producing a siliceous fertilizer according to claim 1 ,
A mixing step for obtaining a mixed raw material by at least mixing one or more kinds selected from sludge, dehydrated sludge, dried sludge, sludge charcoal, sludge incineration ash, and sludge molten slag to obtain a mixed raw material;
A method for producing a silicic acid fertilizer, comprising a step of calcining the mixed raw material at 1,300 to 1,400° C. using a calcining furnace to obtain a silicic acid fertilizer as a calcined product. In the mixing step, further, mixed hydroxyapatite and magnesium ammonium phosphate was recovered using HAP method or MAP method from wastewater containing phosphorus and one or more selected from phosphate fertilizer, claim 2 The method for producing a siliceous fertilizer according to 1. The sintering furnace is a rotary kiln, the manufacturing method of silicate fertilizer according to claim 2 or 3.

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