Method for producing fertilizer

Abstract

The present invention addresses the problem of providing a method for producing a fertilizer that can easily and quickly produce a fertilizer that is easy to spread at low cost. The method for producing a fertilizer according to the present invention comprises a water content adjustment step for adjusting the water content by mixing the organic sludge at a weight ratio of more than 1 and less than 9 when the total weight of the organic sludge generated during sewage treatment or drainage treatment and the biomass combustion ash, which is the biomass combustion ash, is 10. Therefore, the moisture content is adjusted to be more than 8% and less than 65%. Furthermore, preferably, the organic sludge is mixed according to the weight ratio of 3-6, so that the water content is adjusted to 22%-43%.

Description

Technical Field

[0001] The present invention relates to a method for producing fertilizer from organic sludge generated in the process of sewage treatment or drainage treatment. Background Art

[0002] In the past, it is known that organic sludge generated in the process of sewage treatment or drainage treatment contains rich fertilizer components such as nitrogen, phosphorus, and potassium. Therefore, for the purpose of reusing organic sludge, artificial fermentation and composting are carried out. For example, in Japanese Patent Publication No. 2013-72051, a method for composting organic sludge by fermenting it with hyperthermophilic bacteria is disclosed (Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-72051 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, including the invention described in Patent Document 1, in the conventional composting treatment of organic sludge, fermentation requires a long time. Therefore, there is a problem that not only is equipment for storing the organic sludge during fermentation necessary, but management is time-consuming, and equipment and management costs increase. On the other hand, there is a problem that the organic sludge that has not been composted has an extremely high water content and is difficult to handle, and therefore cannot be directly spread as a fertilizer.

[0008] The present invention has been made to solve such a problem, and an object of the present invention is to provide a method for producing a fertilizer that can produce a fertilizer that is easy to spread simply and at low cost, and quickly.

[0009] Means for solving problems

[0010] The inventors of the present invention have conducted intensive research to achieve the above-mentioned purpose, and as a result, have found that the above-mentioned purpose can be achieved by mixing organic sludge generated in the process of sewage treatment or drainage treatment and biomass combustion ash which is biomass combustion ash in a specified ratio and adjusting the moisture content to a specified ratio, thereby completing the various inventions shown below.

[0011] In order to simply, at low cost, and quickly manufacture fertilizer that is easy to spread, the method for manufacturing fertilizer of the present invention has a moisture content adjustment step. When the weight of organic sludge generated in the process of sewage treatment or drainage treatment and biomass combustion ash as biomass combustion ash is set to 10 as a whole, the weight ratio of the organic sludge is greater than 1 and less than 9, thereby adjusting the moisture content to greater than 8% and less than 65%.

[0012] In addition, as one embodiment of the present invention, in order to solve the problem of further improving the operability as a fertilizer, in the moisture content adjustment process, the moisture content can be adjusted to 22% to 43% by mixing the organic sludge in a weight ratio of 3 to 6, while the total weight of the organic sludge and the biomass combustion ash is set to 10.

[0013] Furthermore, as one embodiment of the present invention, in order to solve the problem of improving the effect of reducing the moisture content of 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.

[0014] Furthermore, 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 in a range of less than 80 wt%.

[0015] Furthermore, as one embodiment of the present invention, in order to solve the problem of suppressing the generation of ammonia and allowing more nitrogen components in the fertilizer to remain, a pH adjustment step may be provided, in which 12 to 29 wt % of sulfuric acid is added to the biomass combustion ash to adjust the hydrogen ion index (pH).

[0016] Furthermore, as one aspect of the present invention, in order to solve the problem of suppressing the generation of ammonia and allowing more nitrogen components in the fertilizer to remain, the present invention may include an ammonia generation suppression step of adding magnesium chloride and phosphoric acid to the organic sludge to suppress the generation of ammonia.

[0017] Effects of the Invention

[0018] According to the present invention, a fertilizer that is easy to spread can be produced simply, at low cost, and quickly. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a diagram showing one embodiment of the method for producing the fertilizer of the present invention.

[0020] Figure 2 1 is a flowchart showing the method for producing the fertilizer according to the present embodiment.

[0021] Figure 3 This is a table showing the experimental results of Example 1.

[0022] Figure 4 This is a table showing the experimental results of Example 2.

[0023] Figure 5 This is a table showing the experimental results of Example 3.

[0024] Figure 6 This is a table showing the experimental results of Example 4. DETAILED DESCRIPTION

[0025] Hereinafter, an embodiment of the method for producing fertilizer of the present invention will be described using the accompanying drawings. The method for producing fertilizer of this embodiment is used to produce fertilizer from organic sludge generated in the process of sewage treatment or drainage treatment, such as Figure 1 and Figure 2 As shown, the method includes a water content adjustment step (step S3), an ammonia generation suppression step (step S1) as a pretreatment, and a pH adjustment step (step S2). Each step will be described in detail below.

[0026] The moisture content adjustment process is a process for adjusting the moisture content of the fertilizer. Figure 1 As shown, in the moisture content adjustment step, organic sludge generated in the process of sewage treatment or drainage treatment and biomass combustion ash, which is biomass combustion ash, are mixed at a predetermined ratio to adjust the fertilizer to a predetermined moisture content.

[0027] Organic sludge is an organic substance in a muddy substance removed by sedimentation or filtration in each process of sewage treatment or drainage treatment. In addition, biomass combustion ash is ash obtained by burning biomass, which is an organic resource derived from living organisms. In this embodiment, in a biomass power plant, fly ash obtained by burning raw materials derived from plants such as wood chips or palm coconut shells (PKS: Pl am Kernel Shell ll) is used as biomass combustion ash.

[0028] In this embodiment, based on the results of Example 1 described later, when the total weight of organic sludge and biomass combustion ash is set to 10, the organic sludge is mixed at a weight ratio greater than 1 and less than 9. Thus, since the biomass combustion ash absorbs the moisture in the organic sludge, it is possible to simply and inexpensively manufacture a fertilizer whose moisture content is adjusted to greater than 8% and less than 65%.

[0029] If the moisture content is greater than 8% and less than 65%, the organic sludge and the biomass combustion ash can be easily mixed evenly, so the quality as a fertilizer is improved. In addition, if it is too dry, the fertilizer will be powdered, but if the moisture content is greater than 8%, since this does not happen, it is difficult to fly in the air and remains in a state suitable for large-scale spreading. Furthermore, if the moisture content is less than 65%, the water is appropriately lost and it is easy to handle, so it becomes a state that is easy to carry and spread.

[0030] In addition, in the present embodiment, it is more preferred that in the moisture content adjustment step, the organic sludge is mixed with the biomass combustion ash at a weight ratio of 3 to 6 when the total weight of the organic sludge and the biomass combustion ash is set to 10. Thus, since the moisture content is adjusted to 22% to 43%, the ease of handling as a fertilizer is further improved.

[0031] Moreover, in this embodiment, based on the results of Example 2 described later, it is more preferred 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. As a result, the specific surface area of ​​the biomass combustion ash increases, and more water in the organic sludge is absorbed, thereby improving the effect of reducing the water content.

[0032] In addition, in this embodiment, based on the results of Example 3 described later, it is more preferred that the biomass combustion ash is replaced by calcium oxide (CaO) such as quicklime within a range of less than 80wt%. As a result, calcium oxide reacts violently with the water in the sludge to absorb and generate heat, promoting drying, thereby improving the effect of reducing the water content.

[0033] In addition, the biomass combustion ash contains at least silicon dioxide (SiO2), calcium oxide (CaO) and aluminum oxide (Al2O3). In addition, the organic sludge and the biomass combustion ash are mixed by a stirring device (not shown) or the like.

[0034] According to the above-mentioned moisture content adjustment process, since the organic sludge and the biomass combustion ash are mixed at a predetermined ratio and adjusted to a predetermined moisture content, it is possible to simply and at low cost and quickly produce a fertilizer that is easy to spread.

[0035] However, since biomass combustion ash is alkaline, if it is mixed with neutral organic sludge, the hydrogen ion index (pH) increases, and ammonia (NH3) is easily generated. In this way, the nitrogen content, one of the three elements of fertilizer, is reduced, and a bad smell is generated. Therefore, in this embodiment, Figure 1 As shown, as optional treatments for suppressing ammonia generation, there are a pH adjustment step and an ammonia generation suppression step.

[0036] The pH adjustment process is a process for adjusting the hydrogen ion index of biomass combustion ash. Specifically, Figure 1As shown, the pH adjustment step adds sulfuric acid showing strong acidity to the biomass combustion ash before mixing with the organic sludge to adjust the hydrogen ion index. 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, since the hydrogen ion index of the biomass combustion ash becomes 8.5 or less, which is a neutral region, the generation of ammonia is suppressed even when mixed with the organic sludge, thereby leaving more nitrogen components in the fertilizer.

[0037] The ammonia generation suppression step is a step of suppressing the generation of ammonia from the organic sludge. In the present embodiment, in the ammonia generation suppression step, magnesium chloride and phosphoric acid are added to the organic sludge before being mixed with the biomass combustion ash. As a result, the ammonium ions in the organic sludge react with the magnesium ions and the phosphate ions, and are fixed as magnesium ammonium phosphate (MAP). In this way, if the organic sludge is fixed with ammonium ions, the generation of ammonia can be suppressed even if it is mixed with the biomass combustion ash whose hydrogen ion index is not adjusted, thereby leaving more nitrogen components in the fertilizer.

[0038] In addition, if the hydrogen ion index of the biomass combustion ash is adjusted to neutral (pH 7) or below by the pH adjustment process, the generation of ammonia can be completely suppressed. However, since the raw material cost of sulfuric acid is high, the cost of leaving more nitrogen components in the fertilizer can be reduced by suppressing the amount of sulfuric acid added and using the ammonia generation suppression process.

[0039] According to the method for producing fertilizer according to the above embodiment, the following effects can be achieved.

[0040] 1. It is possible to produce fertilizer that is easy to spread simply, at low cost, and quickly.

[0041] 2. By adjusting to the most appropriate ratio and moisture content, the ease of handling as a fertilizer can be further improved.

[0042] 3. By using fly ash as biomass combustion ash, the effect of reducing the moisture content of biomass combustion ash can be enhanced.

[0043] 4. By replacing part of the biomass combustion ash with calcium oxide, the effect of reducing the moisture content can be promoted.

[0044] 5. By adjusting the hydrogen ion index of biomass combustion ash to below the neutral region, the generation of ammonia can be suppressed, allowing more nitrogen components in the fertilizer to remain.

[0045] 6. By fixing the ammonium ions in the organic sludge, the production of ammonia can be inhibited, so that more nitrogen components in the fertilizer remain.

[0046] Next, specific examples of the method for producing the fertilizer of the present invention will be described. In addition, the technical scope of the present invention is not limited to the examples shown below.

[0047] [Example 1]

[0048] In this Example 1, an experiment was conducted to determine the appropriate ratio of organic sludge and biomass combustion ash. Specifically, dehydrated sludge in an organic sludge treatment facility was used as the organic sludge. In addition, wood chips burned in a coal-fired boiler of a biomass power plant and fly ash of palm coconut shell (PKS) were used as the biomass combustion ash.

[0049] The organic sludge and biomass combustion ash were mixed at weight ratios of 1:9 to 9:1, and the water content was measured after mixing for 2.5 minutes. The results are shown in Figure 3 .like Figure 3 As shown, when the weight ratio of organic sludge to biomass combustion ash is 1:9, it is difficult to mix them evenly because the water content is too low, 8%. In addition, when the weight ratio of organic sludge to biomass combustion ash is 9:1, it is difficult to mix them evenly because the water content is too high, 65%.

[0050] On the other hand, when the organic sludge and the biomass combustion ash are mixed in a weight ratio of 2:8 to 8:2, as Figure 3 As shown, it was confirmed that the moisture content was appropriately adjusted to 18% to 62%, which is a shape that is easy to handle as fertilizer. In addition, when organic sludge and biomass combustion ash are mixed in a weight ratio of 3:7 to 6:4, it was confirmed that the moisture content was adjusted to 22% to 43%, and the ease of handling as fertilizer was further improved.

[0051] According to the results of Example 1 above, it is known that, preferably, when the weight of the organic sludge and the biomass combustion ash is set to 10 as a whole, the water content is adjusted to be greater than 8% and less than 65% by mixing the organic sludge at a weight ratio greater than 1 and less than 9. At this time, the weight ratio of the biomass combustion ash is also greater than 1 and less than 9. In addition, it is known that, more preferably, the water content is adjusted to 22% to 43% by mixing the organic sludge at a weight ratio of 3 to 6.

[0052] [Example 2]

[0053] In this Example 2, an experiment was conducted to determine the average particle size suitable for biomass combustion ash. Specifically, Figure 4As shown, fly ash collected from three different biomass power plants A to C is used as biomass combustion ash. In addition, the fuel of biomass power plant A is palm coconut shell (PKS), the fuel of biomass power plant B is palm coconut shell (PKS) and wood pellets, and the fuel of biomass power plant C is palm coconut shell (PKS), bark and thinning wood.

[0054] After each of the above biomass combustion ashes was dispersed by stirring in methanol, the average particle size was measured by laser diffraction / scattering method using a laser diffraction / scattering particle size distribution measuring device (Horiba Ltd.: LA-950). The results are shown in Figure 4 .like Figure 4 As shown, the average particle size of any fly ash was 44 μm or less.

[0055] From the results of Example 2 above, it is understood that the fly ash having a large specific surface area and increasing the effect of reducing the moisture content by absorbing more water in the organic sludge preferably has an average particle size of 44 μm or less as measured by the laser diffraction / scattering method.

[0056] [Example 3]

[0057] In this Example 3, an experiment was conducted to determine the appropriate ratio when replacing biomass combustion ash with calcium oxide. Specifically, the organic sludge and biomass combustion ash used in the above Example 1 were mixed at a weight ratio of 5:5 to prepare a reference sample. In addition, in the reference sample, samples were prepared in which the biomass combustion ash was replaced with calcium oxide (quicklime) at a weight ratio of 4:1 to 0:5.

[0058] Then, the contents (%) of water, nitrogen, phosphoric acid, potassium, carbon-nitrogen ratio (C / N ratio), copper, zinc, and lime were analyzed for each sample using the test method specified in the test method for fertilizers, etc. The results are shown in Figure 5 .like Figure 5 As shown, the results of observing the actual products and the dried products showed that no significant change was observed in the content of nitrogen, one of the three elements of fertilizer, regardless of the replacement ratio of calcium oxide.

[0059] In addition, it was confirmed that until the replacement ratio of calcium oxide reached 2:3 (60 wt%), phosphorus (P2O5) and potassium (K2O) as the other two elements were contained to some extent, and it had a composition preferred as a fertilizer. On the other hand, it was confirmed that when the replacement ratio of calcium oxide was 1:4 (80 wt%), phosphorus and potassium were significantly reduced.

[0060] According to the results of Example 3 above, by replacing the biomass combustion ash with calcium oxide (CaO) such as quicklime within a range of less than 80 wt%, the three elements of fertilizer can be maintained and the effect of reducing the moisture content can be improved.

[0061] [Example 4]

[0062] In this Example 4, an experiment was conducted to determine the amount of sulfuric acid added when adjusting the hydrogen ion index of biomass combustion ash. Specifically, sulfuric acid was added to the biomass combustion ash used in the above Example 1 at various addition rates. Then, the obtained product was put into 10 times water, and the hydrogen ion index of the liquid after mixing with a stirrer for 5 minutes was measured. The results are shown in Figure 6 .

[0063] like Figure 6 As shown, it was confirmed that when the addition rate of sulfuric acid to biomass combustion ash was 11wt% or less, the hydrogen ion index was greater than 9, and the biomass combustion ash still showed alkalinity. On the other hand, it was confirmed that when the addition rate of sulfuric acid to biomass combustion ash was 12wt% or more, the hydrogen ion index was 8.5 or less, and the biomass combustion ash was neutralized to the neutral region.

[0064] However, as mentioned above, if sulfuric acid is excessively added, the raw material cost increases. In this regard, when the addition rate of sulfuric acid to biomass combustion ash is 29wt%, the hydrogen ion index is approximately neutral at 7.0. Therefore, it can be said that even if sulfuric acid is added in an amount greater than 29wt%, the effect of suppressing ammonia production is almost unchanged.

[0065] From the results of Example 4 above, it can be seen that when adjusting the hydrogen ion index of biomass combustion ash, the pH can be lowered to a desired neutral region by adding 12 to 29 wt % of sulfuric acid.

[0066] In addition, the method for producing the fertilizer of the present invention is not limited to the above-mentioned embodiment, and can be modified appropriately.

[0067] For example, in the above-mentioned embodiment, as pretreatment for suppressing ammonia production, the ammonia production suppression step (step S1) and the pH adjustment step (step S2) are performed. However, when the fertilizer manufactured only by the moisture content adjustment step (step S3) contains a predetermined nitrogen component, the ammonia production suppression step (step S1) or the pH adjustment step (step S2) may not be performed.

Claims

1. A method for producing a fertilizer, comprising a moisture content adjusting step, wherein the weight ratio of organic sludge generated in a sewage treatment or drainage treatment process and biomass combustion ash as biomass combustion ash is set to 10 as a whole, and the moisture content is adjusted to be greater than 8% and less than 65% by mixing the organic sludge at a weight ratio greater than 1 and less than 9.

2. The method for producing a fertilizer according to claim 1, wherein in the moisture content adjustment step, when the total weight of the organic sludge and the biomass combustion ash is set to 10, the weight ratio of the organic sludge is mixed at 3 to 6, thereby adjusting the moisture content to 22% to 43%. 3 . 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. The method for producing fertilizer according to claim 1, wherein the biomass combustion ash is replaced by calcium oxide in a range of less than 80 wt%. 5 . The method for producing a fertilizer according to claim 1 , further comprising a pH adjustment step of adding 12 to 29 wt % of sulfuric acid to the biomass combustion ash to adjust a hydrogen ion index.

6. The method for producing a fertilizer according to claim 1, further comprising an ammonia production suppressing step of adding magnesium chloride and phosphoric acid to the organic sludge to suppress the production of ammonia.

Images