Fertilizer manufacturing method

Abstract

To provide a method for producing a fertilizer, which is simple and low cost and can rapidly produce a fertilizer that can be easily spread. [Solution] The method for producing a fertilizer according to the present invention includes a moisture content adjusting step of adjusting the moisture content to more than 8% and less than 65% by mixing the organic sludge generated in the process of sewage or wastewater treatment and the biomass combustion ash, which is the combustion ash of biomass, in a mixing ratio of more than 1 and less than 9, assuming that the total weight of the organic sludge is 10. It is more preferable to adjust the moisture content to 22 to 43% by mixing the organic sludge in a mixing ratio of 3 to 6 by weight.

Description

[Technical field]

[0001] The present invention relates to a process for producing fertilizer from organic sludge generated during sewage or wastewater treatment. [Background technology]

[0002] It has been known that organic sludge generated during sewage or wastewater treatment is rich in fertilizer components such as nitrogen, phosphorus, and potassium. For this reason, in order to reuse organic sludge, treatment such as artificial fermentation and composting is carried out. For example, JP 2013-72051 A discloses a method of composting organic sludge by fermenting it with hyperthermophilic bacteria (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-72051 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional composting treatment of organic sludge, including the invention described in Patent Document 1, fermentation takes a long time. This requires facilities to store the organic sludge during fermentation, and the management is time-consuming, resulting in problems such as increased facility and management costs. On the other hand, organic sludge that has not been composted has an extremely high moisture content and is difficult to handle, so there is a problem that it cannot be spread as fertilizer as it is.

[0005] The present invention has been made to solve such problems, and has an object to provide a method for producing a fertilizer that is simple, low-cost, and capable of quickly producing a fertilizer that is easy to spread. [Means for solving the problem]

[0006] As a result of intensive research into achieving the above-mentioned object, the inventors have found that the above-mentioned object can be achieved by mixing organic sludge generated during sewage or wastewater treatment processes with biomass combustion ash, which is ash from biomass combustion, in a predetermined mixing ratio and adjusting the mixture to a predetermined moisture content, which has led to the completion of the following inventions.

[0007] In order to solve the problem of quickly producing a fertilizer that is easy to spread while being simple and low-cost, the production method of the present invention has a moisture content adjustment step of adjusting the moisture content to more than 8% and less than 65% by mixing organic sludge generated in the process of sewage treatment or wastewater treatment and biomass combustion ash, which is biomass combustion ash, in a blending ratio of more than 1 and less than 9 by weight, where the total weight of the organic sludge generated in the process of sewage treatment or wastewater treatment and biomass combustion ash is 10.

[0008] In addition, as one aspect of the present invention, in order to solve the problem of further improving ease of handling as a fertilizer, in the moisture content adjustment step, the moisture content may be adjusted to 22 to 43% by mixing the organic sludge in a weight ratio of 3 to 6, where the total weight of the organic sludge and the biomass combustion ash is 10.

[0009] Furthermore, as one aspect of the present invention, in order to solve the problem of improving the effect of reducing the moisture content by biomass combustion ash, the biomass combustion ash may be fly ash having an average particle size of 44 μm or less as measured by a laser diffraction / scattering method.

[0010] In addition, as one aspect of the present invention, in order to solve the problem of promoting the effect of reducing the moisture content, the biomass combustion ash may be replaced with calcium oxide within a range of less than 80 wt %.

[0011] Furthermore, as one embodiment of the present invention, in order to solve the problem of suppressing the generation of ammonia and leaving more nitrogen components in the fertilizer, a pH adjustment step may be included in which 12 to 29 wt % of sulfuric acid is added to the biomass combustion ash to adjust the hydrogen ion exponent (pH).

[0012] In addition, as one aspect of the present invention, in order to solve the problem of suppressing the generation of ammonia and allowing a larger amount of nitrogen components to remain in the fertilizer, an ammonia generation suppression step may be provided in which magnesium chloride and phosphoric acid are added to the organic sludge to suppress the generation of ammonia. Effect of the Invention

[0013] According to the present invention, a fertilizer that is easy to spread can be quickly produced in a simple and low-cost manner. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram showing an embodiment of a method for producing a fertilizer according to the present invention. [Diagram 2] 1 is a flowchart showing a method for producing a fertilizer according to the present embodiment. [Diagram 3] 1 is a table showing the experimental results of Example 1. [Figure 4] 1 is a table showing the experimental results of Example 2. [Diagram 5] 13 is a table showing the experimental results of Example 3. [Figure 6] 13 is a table showing the experimental results of Example 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] An embodiment of a fertilizer manufacturing method according to the present invention will be described below with reference to the drawings. The fertilizer manufacturing method of this embodiment is for manufacturing fertilizer from organic sludge generated in the process of sewage treatment or wastewater treatment, and includes a moisture content adjustment step (step S3), an ammonia generation suppression step (step S1) and a pH adjustment step (step S2) as pretreatment, as shown in Figures 1 and 2. Each step will be described in detail below.

[0016] The moisture content adjusting step is a step of adjusting the moisture content of the fertilizer. In this embodiment, as shown in FIG. 1, the moisture content adjusting step adjusts the fertilizer to a predetermined moisture content by mixing organic sludge generated in the process of sewage treatment or wastewater treatment and biomass combustion ash, which is the combustion ash of biomass, in a predetermined mixing ratio.

[0017] Organic sludge is organic muddy material that is removed by settling or filtration during each process of sewage or wastewater treatment. Biomass combustion ash is ash obtained by burning biomass, which is an organic resource derived from living organisms. In this embodiment, fly ash obtained by burning plant-derived raw materials such as wood chips and palm kernel shells (PKS) in a biomass power plant is used as the biomass combustion ash.

[0018] In this embodiment, based on the results of Example 1 described later, when the total weight of the organic sludge and biomass combustion ash is taken as 10, the weight ratio of the organic sludge is mixed at a blending ratio of more than 1 and less than 9. As a result, the biomass combustion ash absorbs the moisture in the organic sludge, so that a fertilizer with an adjusted moisture content of more than 8% and less than 65% is produced simply and at low cost.

[0019] If the moisture content is more than 8% and less than 65%, the organic sludge and biomass combustion ash can be mixed evenly, improving the quality of the fertilizer. In addition, excessive drying will cause the fertilizer to turn into powder, but if the moisture content is over 8%, this will not happen, making it less likely to fly up into the air and suitable for large-scale spreading. Furthermore, if the moisture content is less than 65%, the moisture will be removed appropriately, making it easier to handle, and easier to transport and spread.

[0020] Furthermore, in this embodiment, in the moisture content adjusting step, it is more preferable to mix the organic sludge with the biomass combustion ash in a weight ratio of 3 to 6, assuming that the total weight of the organic sludge and biomass combustion ash is 10. This adjusts the moisture content to 22 to 43%, further improving ease of handling as a fertilizer.

[0021] Furthermore, in this embodiment, based on the results of Example 2 described later, it is more preferable that the biomass combustion ash is fly ash having an average particle size of 44 μm or less as measured by a laser diffraction / scattering method. This increases the specific surface area of ​​the biomass combustion ash, which absorbs more water in the organic sludge, improving the effect of reducing the moisture content.

[0022] In addition, in this embodiment, based on the results of Example 3 described later, it is more preferable that the biomass combustion ash is replaced by calcium oxide (CaO) such as quicklime within the range of less than 80 wt%. This allows the calcium oxide to react vigorously with the moisture in the sludge, absorb it, generate heat, and promote drying, thereby improving the effect of reducing the moisture content.

[0023] The biomass combustion ash contains at least silicon dioxide (SiO2), calcium oxide (CaO), and aluminum oxide (Al2O3). The organic sludge and the biomass combustion ash are mixed by a stirrer (not shown).

[0024] According to the moisture content adjustment process described above, it is only necessary to mix organic sludge and biomass combustion ash in a specified ratio and adjust the moisture content to a specified level, making it possible to quickly produce a fertilizer that is simple, low-cost, and easy to spread.

[0025] However, since biomass combustion ash is alkaline, when it is mixed with neutral organic sludge, the hydrogen ion exponent (pH) increases, and ammonia (NH3) is easily generated. This reduces the nitrogen component, which is one of the three elements of fertilizer, and generates a foul odor. For this reason, in this embodiment, as shown in FIG. 1, a pH adjustment process and an ammonia generation suppression process are provided as optional processes for suppressing the generation of ammonia.

[0026] The pH adjustment step is a step of adjusting the hydrogen ion exponent of the biomass combustion ash. Specifically, as shown in FIG. 1, the pH adjustment step adds sulfuric acid, which exhibits strong acidity, to the biomass combustion ash before it is mixed with the organic sludge, to adjust the hydrogen ion exponent. In this embodiment, based on the results of Example 4 described later, 12 to 29 wt % of sulfuric acid is added to the biomass combustion ash. As a result, the hydrogen ion exponent of the biomass combustion ash becomes 8.5 or less, which is in the neutral range, so that even if it is mixed with the organic sludge, the generation of ammonia is suppressed and more nitrogen components remain in the fertilizer.

[0027] The ammonia generation suppression step is a step of suppressing the generation of ammonia from organic sludge. In this embodiment, in the ammonia generation suppression step, magnesium chloride and phosphoric acid are added to the organic sludge before it is mixed with the biomass combustion ash. As a result, the ammonium ions in the organic sludge react with the magnesium ions and phosphate ions and are fixed as magnesium ammonium phosphate (MAP). In this way, if the organic sludge has ammonium ions fixed therein, the generation of ammonia is suppressed and more nitrogen components remain in the fertilizer even when the organic sludge is mixed with biomass combustion ash whose hydrogen ion exponent is not adjusted.

[0028] Furthermore, if the hydrogen ion exponent of the biomass combustion ash is adjusted to neutral (pH 7) or less in the pH adjustment process, the generation of ammonia can be completely suppressed. However, since the raw material cost of sulfuric acid is expensive, the cost required to retain more nitrogen components in the fertilizer can be reduced by reducing the amount of sulfuric acid added and using it in combination with the ammonia generation suppression process.

[0029] According to the method for producing a fertilizer of the present embodiment as described above, the following effects are obtained. 1. It is possible to quickly produce fertilizer that is simple, low-cost, and easy to spread. 2. By adjusting the mixture ratio and moisture content to the optimum, it is possible to further improve the ease of handling as a fertilizer. 3. By using fly ash as biomass combustion ash, the effect of reducing the moisture content of the biomass combustion ash can be improved. 4. By replacing part of the biomass combustion ash with calcium oxide, the moisture content can be reduced. 5. By adjusting the pH of biomass combustion ash to below the neutral range, it is possible to suppress the generation of ammonia and retain more nitrogen components in the fertilizer. 6. By fixing the ammonium ions in the organic sludge, the generation of ammonia can be suppressed and more nitrogen components can be retained in the fertilizer.

[0030] Next, specific examples of the method for producing a fertilizer according to the present invention will be described. Note that the technical scope of the present invention is not limited to the examples shown below. EXAMPLES

[0031] In this Example 1, an experiment was conducted to determine the suitable blending ratio of organic sludge and biomass combustion ash. Specifically, dewatered sludge from an organic sludge treatment facility was used as the organic sludge. Also, wood chips and palm kernel shell (PKS) fly ash burned in a stoker boiler at a biomass power plant were used as the biomass combustion ash.

[0032] The organic sludge and biomass combustion ash were mixed at weight ratios of 1:9 to 9:1, and after mixing for 2.5 minutes, the moisture content was measured. The results are shown in Figure 3. As shown in Figure 3, when the weight ratio of organic sludge to biomass combustion ash was 1:9, the moisture content was too low at 8%, making it difficult to mix uniformly. Also, when the weight ratio of organic sludge to biomass combustion ash was 9:1, the moisture content was too high at 65%, making it difficult to mix uniformly.

[0033] On the other hand, when organic sludge and biomass combustion ash are mixed at a weight ratio of 2:8 to 8:2, the moisture content is appropriately adjusted to 18 to 62%, as shown in Figure 3, and it has been confirmed that the fertilizer is easy to handle. Also, when organic sludge and biomass combustion ash are mixed at a weight ratio of 3:7 to 6:4, the moisture content is adjusted to 22 to 43%, and it has been confirmed that the fertilizer is even easier to handle.

[0034] According to the results of this Example 1 as described above, when the total weight of the organic sludge and biomass combustion ash is 10, it is shown that it is preferable to adjust the moisture content to more than 8% and less than 65% by mixing the organic sludge at a weight ratio of more than 1 and less than 9. In this case, the weight ratio of the biomass combustion ash is also more than 1 and less than 9. It is also shown that it is more preferable to adjust the moisture content to 22 to 43% by mixing the organic sludge at a weight ratio of 3 to 6. EXAMPLES

[0035] In this Example 2, an experiment was conducted to identify an average particle size suitable for biomass combustion ash. Specifically, as shown in Fig. 4, fly ash collected at three different biomass power plants A to C was used as the biomass combustion ash. The fuel used at biomass power plant A was palm kernel shell (PKS), the fuel used at biomass power plant B was palm kernel shell (PKS) and wood pellets, and the fuel used at biomass power plant C was palm kernel shell (PKS), bark, thinning material, etc.

[0036] After each of the above-mentioned biomass combustion ashes was dispersed in methanol by stirring, the average particle size was measured by the laser diffraction / scattering method using a laser diffraction / scattering type particle size distribution measuring device (HORIBA, LTD.: LA-950). The results are shown in Figure 4. As shown in Figure 4, the average particle size of all the fly ashes was 44 μm or less.

[0037] The results of Example 2 as described above show that the fly ash that has a large specific surface area and can absorb more water in the organic sludge to improve the effect of reducing the moisture content is preferably one having an average particle size of 44 μm or less as measured by the laser diffraction / scattering method. EXAMPLES

[0038] In this Example 3, an experiment was conducted to identify a suitable ratio when replacing biomass combustion ash with calcium oxide. Specifically, a reference sample was prepared by mixing the organic sludge and biomass combustion ash used in the above Example 1 at a weight ratio of 5:5. In addition, the reference samples were prepared by replacing the biomass combustion ash with calcium oxide (quicklime) at weight ratios of 4:1 to 0:5.

[0039] Then, using the test methods stipulated in the Fertilizer Testing Methods, each sample was analyzed for moisture, nitrogen, phosphate, potassium, carbon-nitrogen ratio (C / N ratio), copper, zinc, and lime content (%). The results are shown in Figure 5. As shown in Figure 5, whether looking at the results on a spot basis or on a dry basis, there was no significant change in the nitrogen content, which is the three essential elements of fertilizer, regardless of the calcium oxide substitution ratio.

[0040] In addition, it was confirmed that the other two elements, phosphorus (P2O5) and potassium (K2O), were contained to a certain extent when the calcium oxide substitution ratio was up to 2:3 (60wt%), and had desirable components as a fertilizer. On the other hand, it was confirmed that when the calcium oxide substitution ratio was 1:4 (80wt%), phosphorus and potassium were significantly reduced.

[0041] According to the results of Example 3 described above, it was shown that by replacing biomass combustion ash with calcium oxide (CaO) such as quicklime within the range of less than 80 wt%, it is possible to improve the effect of reducing the moisture content while maintaining the three essential elements of fertilizer. EXAMPLES

[0042] In this Example 4, an experiment was conducted to determine the amount of sulfuric acid added when adjusting the hydrogen ion exponent of biomass combustion ash. Specifically, sulfuric acid was added at various addition rates to the biomass combustion ash used in the above-mentioned Example 1. The resulting product was then added to 10 times the amount of water, and the hydrogen ion exponent of the liquid after mixing with a stirrer for 5 minutes was measured. The results are shown in Figure 6.

[0043] As shown in Figure 6, when the addition rate of sulfuric acid to biomass combustion ash is 11 wt% or less, the hydrogen ion exponent exceeds 9, confirming that the biomass combustion ash still exhibits alkaline properties. On the other hand, when the addition rate of sulfuric acid to biomass combustion ash is 12 wt% or more, the hydrogen ion exponent becomes 8.5 or less, confirming that the biomass combustion ash has been neutralized to the neutral range.

[0044] However, as mentioned above, adding too much sulfuric acid increases the raw material cost. In this regard, when the sulfuric acid is added to the biomass combustion ash at a rate of 29 wt%, the hydrogen ion exponent is 7.0, which is almost neutral. Therefore, it can be said that the effect of suppressing ammonia generation remains almost the same even if sulfuric acid is added at a rate of more than 29 wt%.

[0045] The results of Example 4 described above show that when adjusting the hydrogen ion exponent of biomass combustion ash, the pH can be reduced to the desired neutral range by adding 12 to 29 wt % sulfuric acid.

[0046] The method for producing a fertilizer according to the present invention is not limited to the above-described embodiment, and can be modified as appropriate.

[0047] For example, in the above-described embodiment, an ammonia generation suppression step (step S1) and a pH adjustment step (step S2) are performed as pre-treatments for suppressing the generation of ammonia. However, if a predetermined nitrogen component is contained in the fertilizer produced only by the moisture content adjustment step (step S3), it is not necessary to perform the ammonia generation suppression step (step S1) or the pH adjustment step (step S2).

Claims

1. an ammonia generation suppression step of adding magnesium chloride and phosphoric acid to organic sludge generated during sewage treatment or wastewater treatment to suppress the generation of ammonia; A pH adjustment process of adding 12 to 29 wt % sulfuric acid to biomass combustion ash, which is biomass combustion ash, to adjust the hydrogen ion exponent (pH); A moisture content adjustment step of adjusting the moisture content to more than 8% and less than 65% by mixing the organic sludge at a weight ratio of more than 1 and less than 9, where the total weight of the organic sludge and the biomass combustion ash is 10; The method for producing a fertilizer comprising the steps of:

2. 2. The method for producing a fertilizer according to claim 1, wherein in the moisture content adjusting step, the moisture content is adjusted to 22 to 43% by mixing the organic sludge in a blending ratio of 3 to 6 by weight, where the total weight of the organic sludge and the biomass combustion ash is 10.

3. 2. The method for producing a fertilizer according to claim 1, wherein the biomass combustion ash is fly ash having an average particle size of 44 μm or less as measured by a laser diffraction / scattering method.

4. 2. The method for producing a fertilizer according to claim 1, wherein the biomass combustion ash is replaced by calcium oxide in a range of less than 80 wt %.

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