JP2018043888A - Silicic fertilizer and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicic acid fertilizer having a low content of gerenite and a high content of water-soluble silicic acid and a high water content of silicic acid, and a method for producing the same. The silicic acid fertilizer of the present invention is a fertilizer containing SiO2, Al2O3, and P2O5 that satisfy the following formula (A). 4.0 ≦ (SiO2-Al2O3) /P2O5 ≦ 25.0 (A) However, the chemical formula in the formula (A) represents the number of moles of the chemical substance in the siliceous fertilizer. Further, the method for producing a silicic acid fertilizer of the present invention is a method for producing the silicic acid fertilizer, wherein a mixed raw material containing at least a silicic acid source, a phosphoric acid source, and a calcium source is mixed at 1.25 to 1400 ° C. This is a method of firing and manufacturing. [Selection diagram] Fig. 1

Description

The present invention relates to a siliceous fertilizer having a low content of gehlenite (2CaO.Al ₂ O ₃ .SiO ₂ ), a high content of water-soluble silicic acid and a high water content of silicic acid, and a method for producing the same.

Conventionally, siliceous fertilizers include calcium (calcium silicate) and potassium silicate (potassium silicate) fertilizers, which have been used for rice cultivation. Of these fertilizers, calcium mainly contains SiO ₂ , CaO, and Al ₂ O ₃ , and has effects such as replenishment of silicic acid to the soil and correction of acidic soil.
However, although the silicic acid elution amount from the calcium exceeds 30% in the hydrochloric acid aqueous solution, the soil pH is about 5% when it is about 5-7, so when applying about 200 kg of calcium per 1000 m ^{2 of} paddy field There is a big burden on farmers in terms of labor and cost. Further, since calcium does not contain any of the three elements of fertilizer, nitrogen, phosphorus, and potassium, it is usually necessary to mix a large amount of calcium with other fertilizers that include the three elements of fertilizer. For example, even in the case where silica is mixed with molten fertilizer having a relatively large amount of silicic acid in the neutral range, the mixing amount of calcium is as large as 200 kg with respect to 40 kg of molten manure.
The silicic acid elution amount is different from soluble silicic acid (amount of silicic acid eluted in a 0.5 molar hydrochloric acid aqueous solution).

Therefore, several siliceous fertilizers that improve the low water solubility of silicic acid, which is a drawback of calcium, have been proposed.
For example, the siliceous fertilizer described in Patent Document 1 is prepared by adding an organic binder (sucrose or molasses) having a specific water dissolution rate to a powder of a siliceous composition having a specific particle size. Granulated silicic fertilizer. And the silicic acid elution amount of this fertilizer within one month measured using the ion exchange method is 16 mass% or more.
Moreover, the siliceous fertilizer described in Patent Document 2 is a fertilizer made of starch in which the organic binder is gelatinized.
Any of the above siliceous fertilizers is an amorphous substance containing 1 to 20% by mass of MgO and 30 to 50% by mass of SiO ₂ as well as CaO and P ₂ O ₅ .
Furthermore, the siliceous fertilizer described in Patent Document 3 is composed mainly of SiO ₂ , MgO, CaO, and P ₂ O ₅ , and contains SiO ₂ in an amount of 12% by mass or more and less than 30% by mass. The silicic acid elution amount within 10 days measured by using is 10% by mass or more. However, in the production of the siliceous fertilizer, serpentinite, which is a natural phosphate ore, must be used, and since it is a molten slag by a batch method, it is economical in terms of production cost, energy consumption and productivity. is not.
Moreover, the siliceous fertilizer described in Patent Document 4 contains fertilizer slag containing a specific amount of CaO, SiO ₂ , MgO, and Al ₂ O ₃ and a ratio of CaO / SiO _{2 in} a specific range as a raw material. However, in Patent Document 4, there is no specific description of a method for producing siliceous fertilizer using the slag. Whether the slag is siliceous fertilizer or the raw material of siliceous fertilizer. It is unknown whether there is.

By the way, the phosphate fertilizer such as the above-mentioned fertilizer is manufactured using a phosphorous ore which is a natural resource as a part of the raw material. However, in Japan, since phosphorus is not produced as a natural resource, almost all of it must be relied on for imports. However, in recent years, natural phosphorus has been depleted worldwide, and the price of phosphorus has soared. It has become difficult to secure. Therefore, in the fertilizer manufacturing field, sewage sludge incineration ash having a phosphorus content of 20 to 30% by mass, which is almost the same as that of phosphorus ore, is considered as an alternative to natural phosphorus resources. In Japan, sewage sludge and its incinerated ash are generated in large quantities of 2.2 million tons and 300,000 tons annually, respectively, so the treatment of sewage sludge was also a social request. And since sewage sludge incineration ash contains both phosphoric acid and silicic acid, it is suitable also as a raw material of siliceous fertilizer.
However, when sewage sludge incineration ash is used as a phosphorus source for siliceous fertilizer, Al ₂ O ₃ contained in a large amount in the sewage sludge incineration ash reacts with SiO _{2 in the} process of fertilizer production (firing or melting) and gelenite. Since silicic acid in gelenite is poorly soluble, there is a problem that the content of water-soluble silicic acid in fertilizer decreases.
In addition, as a phosphorus source other than sewage sludge incineration ash, phosphorus was recovered from wastewater containing phosphorus such as sewage, human waste, and livestock wastewater using the HAP (hydroxyapatite) method, the MAP (magnesium ammonium phosphate) method, etc. The effective use of later hydroxyapatite and magnesium ammonium phosphate is also desired.

JP 2002-066871 A JP 2002-068870 A JP 2002-047081 A JP 2007-284289 A

  Accordingly, an object of the present invention is to provide a siliceous fertilizer having a low gehlenite content, a high content of water-soluble silicic acid and a high water content of silicic acid, and a method for producing the same.

  The present inventors have studied silicic acid fertilizers that can achieve the above object, and the following silicic acid fertilizers have low gehlenite content, high water soluble silicic acid content and high silicic acid water content. As a result, the present invention has been completed. That is, this invention is a siliceous fertilizer etc. which have the following structure.

[1] A siliceous fertilizer containing SiO ₂ , Al ₂ O ₃ , and P ₂ O ₅ satisfying the following formula (A).
4.0 ≦ (SiO ₂ —Al ₂ O ₃ ) / P ₂ O ₅ ≦ 25.0 (A)
However, the chemical formula in the formula (A) represents the number of moles of the chemical substance in the siliceous fertilizer.
[2] The siliceous fertilizer according to [1], wherein the content of water-soluble silicic acid is 15% or more.
[3] A method for producing the siliceous fertilizer according to [1] or [2],
A method for producing a siliceous fertilizer, wherein a mixed raw material containing at least a silicic acid source, a phosphoric acid source, and a calcium source is fired at 1250 to 1400 ° C.
[4] The method for producing a siliceous fertilizer according to [3], wherein the silicic acid source is calcium silicate.
[5] The method for producing siliceous fertilizer according to [3] or [4], wherein the apparatus used for the firing is a rotary kiln.

The siliceous fertilizer of the present invention has a high content of water-soluble silicic acid.
Moreover, the method for producing siliceous fertilizer of the present invention has the following effects (i) to (iii).
(i) Calcium silicate can be effectively used as a silicate source for siliceous fertilizers.
(ii) Less energy consumption during production compared to molten fertilizer production.
(iii) When a rotary kiln is used as the firing device, continuous production of siliceous fertilizer becomes possible and manufacturing efficiency is improved.

The X-ray diffraction diagram of the baked product of Example 7 and Comparative Example 1 is shown.

Hereinafter, the present invention will be described in detail by dividing it into siliceous fertilizer and its production method.
1. Silicate fertilizer The siliceous fertilizer of the present invention is a siliceous fertilizer containing SiO ₂ , Al ₂ O ₃ , and P ₂ O ₅ that satisfies the formula (A). And the content rate of the water-soluble silicic acid of the siliceous fertilizer of this invention becomes like this. Preferably it is 15% or more. As shown in Table 1 below, the siliceous fertilizer satisfying the formula (A) has a water-soluble silicic acid content of 16.81% or more measured using a water-weakly acidic cation exchange resin method. And high. The molar ratio of the formula (A) is preferably 5.0 or more and 10.0 or less.
Here, the water-weakly acidic cation exchange resin method is a method for evaluating the solubility of a silicic acid component in a fertilizer around neutrality (pH = 7). It can be measured according to the method described.
Reference A: Naoto Kato, “Report from the Ministry of Agriculture, Forestry and Fisheries, Research Institute for Agricultural Environment Technology”, Vol.
Reference B: Kato and Owa, Soil Sci. Plant Nutr. , 43, 2, 351-359 (1997)

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

2. Production method of siliceous fertilizer The production method of siliceous fertilizer of the present invention is a method of producing a mixed raw material containing at least a silicic acid source, a phosphoric acid source, and a calcium source at 1250 to 1400 ° C. A mixing step of mixing a silicic acid source, a phosphoric acid source, a calcium source and the like to obtain a mixed raw material, and a firing step of firing the mixed raw material to obtain a silicic fertilizer that is a calcined product. Included as a process.
Hereinafter, the manufacturing method of the siliceous fertilizer of this invention is divided into a mixing process and a baking process, and is demonstrated.

(1) Mixing step The silicic acid source is not particularly limited. Amorphous calcium silicate hydrate after recovering phosphorus, amorphous calcium silicate hydration after recovering phosphorus from the viewpoint of effective utilization of raw conslag etc. and phosphorus recovery material after recovering phosphorus 1 or more selected from a composite of a product and calcium hydroxide (hereinafter referred to as “phosphorus recovery material after recovering phosphorus”). The amorphous calcium silicate hydrate and the composite of amorphous calcium silicate hydrate and calcium hydroxide are prepared by mixing, for example, an aqueous sodium silicate solution and lime such as slaked lime or quick lime without heating. Since it is manufactured, it contains 30% by mass of silicic acid. Further, since the adjustment of the chemical composition ratio is easy, the content of SiO ₂ is preferably silicic acid source of at least 50 mass%. In addition, among the silicic acid sources, steel slag, waste concrete, raw consludge, phosphorus recovery material after recovering phosphorus, and the like also function as a calcium source.

The phosphoric acid source is not particularly limited, but is selected from sludge, dewatered sludge, sludge dry matter, sludge carbide, sludge incineration ash, sludge molten slag, phosphorus recovery material after recovering the phosphorus, and molten manure. 1 type or more to be mentioned.
The sludge is a sludge containing organic substances and inorganic substances obtained by separation or precipitation in the process of sewage treatment at the end treatment plant of sewage, urine treatment at the sewage treatment plant, and these wastewater treatments. The dewatered sludge is obtained by dewatering the mud by centrifugation or the like.
The dried sludge is obtained by drying the sewage sludge by sun drying or drying to make the water content approximately 50% by mass or less.
Moreover, the said sludge carbide heats sludge and makes a part or all of the organic substance contained in sludge carbide. The heating temperature is preferably 300 to 800 ° C, more preferably 500 to 700 ° C. If the heating temperature is less than 300 ° C, it takes time for carbonization, and if it exceeds 800 ° C, the carbide may burn. In order to suppress the combustion, it is preferably heated in an oxygen-free or low-oxygen state. Since the carbide also becomes part of the fuel in the production of the siliceous fertilizer of the present invention, the energy required for the production can be saved correspondingly.
The sludge incineration ash is a residue (such as sewage sludge incineration ash) 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 and the like have different forms and moisture contents, the chemical components after firing and the compositions thereof are the same or substantially the same, and therefore any of them may be used as a part of the raw material for firing.

  Further, the calcium source is one or more selected from calcium carbonate, calcium oxide, calcium hydroxide, calcium phosphate, calcium chloride, calcium sulfate, limestone, quicklime, slaked lime, cement, steel slag, gypsum, livestock feces incineration ash, and the like. Is mentioned.

In the mixing step, raw materials such as a silicate source, a phosphoric acid source, and a calcium source are mixed so that SiO ₂ , Al ₂ O ₃ , and P ₂ O ₅ in the mixed raw material satisfy the formula (A). . Moreover, in order to make the particle size easy to mix, the raw material may be pulverized by a ball mill, a roller mill, a rod mill or the like, if necessary.
As a raw material mixing method, for example, after firing a part of each raw material in an electric furnace or the like, the oxide in the fired ash is quantified, and the raw materials are mixed based on the quantitative value and a predetermined composition. Can be mentioned. The oxide can be quantified by a fundamental parameter method using a fluorescent X-ray apparatus. As shown in Table 1, the chemical composition of the mixed raw material before firing (representing SiO ₂ and CaO as a representative example) is substantially the same as the chemical composition of the fired product after firing, except for the volatile components produced by firing. Therefore, in order to obtain a siliceous fertilizer (fired product) that satisfies the above formula (A), it is usually sufficient to fire using a mixed raw material that satisfies the above formula (A). However, for the sake of accuracy, a part of the mixed raw material is fired in an electric furnace or the like, and the content of SiO ₂ , Al ₂ O ₃ and P ₂ O _{5 in} the mixed raw material, The correlation with the content of SiO ₂ , Al ₂ O ₃ , and P ₂ O ₅ is grasped in advance, and based on the correlation, the mixing ratio of the raw materials is determined based on the SiO ₂ , Al in the desired fired product. It is preferable to correct the content to ₂ O ₃ and P ₂ O ₅ .

(2) Firing step The firing step is a step of firing the mixed raw material at 1250 to 1400 ° C to obtain a silicic fertilizer that is a fired product. In order to increase the firing efficiency, the mixed raw material is fired in the form of powder, or is fired in a slurry state by adding water to the powder, or fired in the state of a dehydrated cake. The powder or a cement kneaded product of the powder is granulated and molded by a granulator such as a pan pelletizer, a briquette machine, or a roll press, and then fired. Further, if the firing temperature is less than 1250 ° C., the 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 temperature is preferably 1290 to 1350 ° C. Moreover, since the apparatus used for the said baking can perform the continuous production of siliceous fertilizer, Preferably a rotary kiln is mentioned. The firing time is preferably 10 to 60 minutes. When the firing time is less than 10 minutes, the firing is insufficient, and when it exceeds 60 minutes, the production efficiency is lowered. The firing time is more preferably 20 to 40 minutes.

(3) Grinding and granulating step This step is a step of adjusting the particle size of the fired product, to suppress the generation of dust, to facilitate the handling of fertilizers, and to fully demonstrate the fertilizer effect. This is an optional step selected when adjustment of the fertilizer particle size is required. The particle size is preferably 0.1 to 10 mm, more preferably 0.5 to 5 mm.
As the pulverizing means, a jaw crusher, a roller mill, a ball mill, a rod mill or the like can be used. As the granulating means, a bread mixer, a pan pelletizer, a briquette machine, a roll press, an extrusion molding machine or the like can be used.
Moreover, in this process, depending on the use of the fertilizer, components of silicic acid and phosphoric acid can be added as appropriate, and other fertilizer components such as nitrogen, potassium and bitter earth can be newly added.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.
1. Manufacture of siliceous fertilizer Examples 1 to 1 shown in Table 1 using sewage sludge incinerated ash, calcium silicate powder (calcium for fertilizer, Kumiai Silicic Acid Mime Lime: manufactured by Kashimura Lime Industry Co., Ltd.), and calcium carbonate powder 7 and Comparative Examples 1 to 18 were mixed according to the blending to prepare a mixed raw material. Next, the mixed raw material was used to form a cylindrical raw material having a diameter of 40 mm and a height of 10 mm using a uniaxial pressure molding machine. Further, after the cylindrical raw material is placed in an electric furnace, the temperature is raised to a temperature shown in Table 1 at a rate of temperature increase of 20 ° C./minute, and the fired product is fired for 10 minutes at the temperature. Obtained. Further, the fired product was pulverized using an iron mortar until it passed through a sieve having an opening of 600 μm, and powdered fired products having the chemical composition shown in Table 1 (Examples 1 to 7 and Comparative Example 1). To 18). In addition, as shown in Table 1, the chemical composition of the fired product was almost the same as the chemical composition of the mixed raw material before firing (typically, SiO ₂ and CaO are shown) except for the volatile components by firing. .

2. Water-soluble silicic acid Water-soluble silicic acid was measured by the following procedure using the water-weakly acidic cation exchange resin method, water-soluble silicic acid was measured, and the water solubility of silicic acid was calculated.
Specifically, a resin containing 2 g of ion exchange resin (trade name: Amberlite IRC-50 [registered trademark], manufactured by Organo Corporation) and 1 liter of pure water, which was reversely regenerated using an aqueous sodium hydroxide solution and dilute hydrochloric acid in advance. In the beaker made, 0.2 g of the siliceous fertilizer of each of the above examples and comparative examples was added, and the mixture was gently stirred for 10 minutes with a magnetic stirrer and allowed to stand for 10 days. After 10 days have passed, the mixture was gently stirred again with a magnetic stirrer for 10 minutes, then left to stand for 30 minutes, 2 ml of the supernatant was taken up into a volumetric flask, 1 ml of hydrochloric acid (1 + 1) was added, and then 20 ml. Diluted. Next, the concentration of Si in the aqueous solution was quantified using ICP emission analysis, converted to the concentration of SiO ₂ , water-soluble silicic acid was measured, and the water solubility of silicic acid was calculated. The results are shown in Table 1.

As shown in Table 1, the water-soluble silicic acid of the fired products (silicic acid fertilizer) of Examples 1 to 7 was 16.81 to 20.06%, and the water solubility of silicic acid was 79 to 87%. it was high. On the other hand, the water-soluble silicic acid of the fired products of Comparative Examples 1 to 18 was 3.22 to 12.27%, and the water content of silicic acid was 9 to 69%, both low. In addition, the water-soluble rate of the said silicic acid is the mass ratio (%) of the water-soluble silicic acid by the water-weakly acidic cation exchange resin method with respect to the total silicic acid in silicic acid fertilizer.
FIG. 1 shows an X-ray diffraction diagram of the fired product of Example 7 having the lowest water-soluble silicic acid among Examples and Comparative Example 1 having the highest water-soluble silicic acid among Comparative Examples. As shown in FIG. 1, the X-ray diffraction intensity of gehlenite in the fired product of Example 7 is lower than the X-ray diffraction intensity of gehlenite in the fired product of Comparative Example 1, so that in the fired product of the example It can be seen that the gehlenite content is lower than the gehlenite content in the fired product of the comparative example.

  From the above results, the siliceous fertilizer of the present invention has a low gehlenite content, a large amount of water-soluble silicic acid, and a high water-solubility of silicic acid. Moreover, the manufacturing method of the siliceous fertilizer of this invention has little energy consumption in baking compared with manufacture of molten fertilizer, and when a rotary kiln is used, continuous production is possible and production efficiency is high.

Claims (5)

A siliceous fertilizer containing SiO ₂ , Al ₂ O ₃ , and P ₂ O ₅ that satisfies the following formula (A).
4.0 ≦ (SiO ₂ —Al ₂ O ₃ ) / P ₂ O ₅ ≦ 25.0 (A)
However, the chemical formula in the formula (A) represents the number of moles of the chemical substance in the siliceous fertilizer.   The siliceous fertilizer according to claim 1, wherein the content of water-soluble silicic acid is 15% or more. A method for producing the siliceous fertilizer according to claim 1 or 2,
A method for producing a siliceous fertilizer, wherein a mixed raw material containing at least a silicic acid source, a phosphoric acid source, and a calcium source is fired at 1250 to 1400 ° C.   The method for producing siliceous fertilizer according to claim 3, wherein the silicic acid source is calcium silicate.   The manufacturing method of the siliceous fertilizer of Claim 3 or 4 whose apparatus used for the said baking is a rotary kiln.

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