Fertilizer manufacturing method

Abstract

To provide a method for producing fertilizer that enables effective use of by-products after methane fermentation treatment, which is mainly from livestock excrement discharged from livestock farms, dairy farms, etc., and livestock feed residue, and is capable of reducing the emission of industrial waste.SOLUTION: A method for producing fertilizer includes: a pulverization / slurrification step in which raw materials containing at least one of livestock excrement, food waste, and agricultural waste, which are organic substances, are finely pulverized and processed into a slurry that contains no solids at all; a fermentation step in which the raw materials pulverized and processed into slurry in the pulverization / slurrification step are fed into a fermentation tank and fermented; a dewatering step in which the raw materials fermented in the fermentation step are centrifugally dewatered to remove sludge; a drying step in which the raw materials obtained by dewatering and sludge removal in the dewatering step are dried to produce fertilizer; and a granulation step in which the fertilizer dried in the drying step is granulated.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing fertilizer.

Background Art

[0002] In recent years, the types and amounts of livestock excrement discharged from livestock and dairy farming enterprises and food waste discharged from food industry enterprises have been increasing. In particular, in the livestock and dairy farming industry, the treatment of excrement from livestock has fallen behind, leading to problems such as excessive nitrite nitrogen and bad odors due to discharging it into the local area, which has become a social problem.

[0003] In addition, the raw materials for organic and inorganic fertilizers were originally kneaded with unfermented cow dung and fermented into compost in a compost shed. However, the smell is strong, and the demand has decreased among current Japanese farmers even as compost. The dairy and livestock industries have been troubled by its treatment.

[0004] Regarding these, conventionally, for example, as shown in Patent Document 1, there is known a system in which organic substances containing a large amount of solids such as food residues, livestock manure, and woody raw materials are subjected to methane fermentation by anaerobic microorganisms to generate methane gas. After slurrying raw materials such as food waste, methane fermentation is carried out.

[0005] However, in conventional methane fermentation, the liquid fertilizer and solid residues discharged in large quantities cannot be effectively utilized, and they had to be treated as industrial waste.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention has been made in view of the above points, and its object is to effectively utilize the by-products after methane fermentation treatment mainly using livestock excrement discharged from livestock farms, dairy farms, etc., and the residues of other livestock feed, reduce the discharge of industrial waste, and provide a method for manufacturing a fertilizer capable of manufacturing high-quality inorganic fertilizer.

Means for Solving the Problems

[0008] In order to solve the above problems, the method for manufacturing a fertilizer according to the present invention includes a pulverization and slurrying step (A) of finely pulverizing a raw material containing at least any one of livestock excrement, food waste, and agricultural waste, which are organic substances, and processing it into a slurry state containing no solid content, a fermentation step (B) of charging the raw material pulverized and processed into a slurry state in the pulverization and slurrying step (A) into a fermentation tank and fermenting it, a dehydration step (C) of dehydrating the raw material fermented in the fermentation step (B) by centrifugation to extract sludge, a drying step (D) of drying the raw material dehydrated and having sludge extracted in the dehydration step (C) to manufacture a fertilizer, and a granulation step (F) of granulating the fertilizer dried in the drying step (D).

[0009] According to the method for manufacturing a fertilizer of the present invention, by finely pulverizing and processing the organic-based inorganic substances of the raw materials into a slurry state in the pulverization and slurrying step, the conversion efficiency of the organic substances can be maximally extracted, so the fermentation rate in the fermentation step can be increased, and a fertilizer can be manufactured from the remaining raw materials with the maximum amount of organic substances extracted. In addition, since the raw material processed into a slurry state and containing no solid content is fermented, the dissolution rate of the manufactured fertilizer is very fast, and it becomes a fertilizer with quick-acting properties.

[0010] In the conventional fertilizer manufacturing method, all residues were made into compost or treated as industrial waste. However, according to the fertilizer manufacturing method of the present invention, all of them become organic-inorganic fertilizers and the discharge of residues can be eliminated. Therefore, according to the fertilizer manufacturing method of the present invention, it is possible to effectively utilize the by-products after treatment in a biomass methane gas plant using livestock excrement discharged from livestock farms, dairy farms, etc., and the residues of other livestock feeds as raw materials, and it is possible to eliminate the discharge of industrial waste from those industries.

[0011] Also, in the fertilizer manufacturing method of the present invention, in the dehydration step (C), it is desirable that the water content of the raw material after dehydration is about 80%.

[0012] Also, in the fertilizer manufacturing method of the present invention, in the drying step (D), it is desirable that the water content of the fertilizer after drying is 55% - 60%.

[0013] When the water content of the fertilizer after drying is 55% - 60%, the water content during granulation is set to 55% - 60%. If the water content of the fertilizer before granulation is too low (overdried), granulation becomes difficult and the risk of crushing increases. By increasing the water content to a certain extent, the ease of granulation can be ensured. Also, when the water content of the finally manufactured fertilizer is 55% - 60%, the fertilizer will not be scattered by the wind when spread on a field or the like.

[0014] Also, in the fertilizer manufacturing method of the present invention, in the pulverization / slurry formation step (A), it is desirable to process the raw material into a complete slurry state containing no solid content by passing it through an ultrafiltration membrane.

[0015] By processing the raw material into a complete slurry state containing no solid content in the pulverization / slurry formation step, in the subsequent fermentation step, the organic matter can be completely fermented so that the residue does not contain organic matter. As a result, the manufactured fertilizer becomes a fertilizer that exhibits excellent effects as an inorganic fertilizer.

[0016] In addition, in the fertilizer production method of the present invention, at least a part of the supernatant from which sludge has been separated in the dehydration step (C) may be returned to the fermentation step (B) for re-fermentation treatment.

[0017] In addition, in the fertilizer production method of the present invention, when drying the raw material in the drying step, a deodorization treatment for deodorizing the odor from the raw material may be further performed, and the deodorization treatment may be a catalytic oxidation deodorization treatment.

[0018] When drying the raw material in the drying step, since the residue of the raw material contains a large amount of NH3, a lot of odor is generated. Therefore, by performing a deodorization treatment for deodorizing the odor from the raw material in the drying step, the odor generated along with the drying step can be effectively deodorized.

[0019] In addition, in the fertilizer production method of the present invention, a bag-packing and packing step of bag-packing and packing the fertilizer granulated in the granulation step may be further performed. The reference numerals in the above parentheses are shown for reference as the drawing reference numerals of the corresponding components in the embodiments described later.

Advantages of the Invention

[0020] According to the fertilizer production method of the present invention, it is possible to make effective use of the by-products after the methane fermentation treatment using the livestock excrement discharged from livestock farms, dairy farms, etc., and the residues of other livestock feeds as the main raw materials, and to greatly suppress the discharge of industrial waste. In addition, the dissolution rate of the produced fertilizer is very fast, and it becomes a high-quality inorganic fertilizer with quick-acting properties.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0022] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram for explaining a fertilizer production method according to an embodiment of the present invention. As shown in the figure, the fertilizer production method according to an embodiment of the present invention includes a pulverization and slurrying step (A) of finely pulverizing a raw material containing at least any one of livestock excrement, food waste, and agricultural waste, which are organic substances, and processing them into a slurry state; a fermentation step (B) of fermenting the raw material pulverized and processed into a slurry state in the pulverization and slurrying step (A); a dehydration step (C) of dehydrating the raw material fermented in the fermentation step (B) by centrifugation to extract sludge; a drying step (D) of drying the raw material from which sludge has been extracted by dehydration in the dehydration step (C) to produce fertilizer; a deodorization step (E) of deodorizing the odor from the raw material when drying the raw material in the drying step (D); a granulation step (F) of granulating the fertilizer dried in the drying step (D); a bagging and packing step (G) of bagging and packing the fertilizer granulated in the granulation step (F); and a product unloading step (H) of unloading the packed fertilizer product. Hereinafter, the contents of each step (process) will be described in order.

[0023] [Pulverization and slurrying step (A)] As means for performing the pulverization and slurrying treatment in the pulverization and slurrying step (A), a grinder (pulverization device) 4 in which the organic waste 2 as a raw material is finely pulverized is provided. The grinder 4 is, for example, a wet bead mill. The wet bead mill here has conventionally been used, for example, when finely pulverizing metals such as rare metals and paints. A slurry-like raw material in which the material to be pulverized is mixed with a liquid is supplied in predetermined amounts and finely pulverized by the beads filled inside.

[0024] And in this crushing and slurrying step (A), the slurry-like organic waste 2 mixed with a liquid is supplied to the grinder 4 in predetermined amounts, and the organic waste 2 is finely crushed in a so-called batch manner to become crushed organic matter. Depending on the type and state of the organic waste 2, a pretreatment crushing means may be separately provided in front of the grinder 4 so that it can be finely crushed by the grinder 4 more easily. That is, the organic waste 2 may be crushed in advance by the pretreatment crushing means, then mixed with a liquid to form a slurry, and this slurry-like organic waste 2 may be finely crushed by the grinder 4.

[0025] Incidentally, the organic waste 2, which is the raw material input into the grinder 4 in this crushing and slurrying process, may be livestock manure, okara, shochu lees, etc. Also, in this crushing and slurrying process, it is necessary that the raw material be ultra-finely crushed by the grinder 4 and that the particle sizes of the ultra-finely crushed substances be relatively uniform.

[0026] [Fermentation step (B)] As a means for performing the fermentation treatment in the fermentation step (B), a methane fermentation tank 6 is provided. In the methane fermentation tank 6, anaerobic microorganisms are filled, and the crushed organic matter, which is the organic matter finely crushed by the grinder 4, is decomposed by the anaerobic microorganisms and undergoes methane fermentation.

[0027] The methane fermentation tank 6 is a closed reaction tank, filled with methane bacteria, which are anaerobic microorganisms not shown in the figure, inside, and maintained under anaerobic conditions. Also, a stirrer is installed in the methane fermentation tank 6 to mix the crushed organic matter so that the methane bacteria act uniformly on it.

[0028] And in the methane fermentation tank 6, the crushed organic matter is decomposed by anaerobic microorganisms and methane fermentation is carried out. As the methane fermentation progresses, methane gas and a digestive fluid in which methane is decomposed and fertilizer components such as nitrogen and phosphorus remain are generated.

[0029] Although not shown, a UF membrane separation device is connected to the methane fermentation tank 6 via a piping member, and the upper layer of the digested liquid in the methane fermentation tank 6 is supplied to the UF membrane separation device.

[0030] The UF membrane separation device separates the digested liquid into a concentrated liquid containing TS such as particulate crushed organic matter that does not pass through the pores and a permeate that passes through the pores by, for example, a UF membrane (ultrafiltration membrane) having pores with a pore size of about 0.03 μm.

[0031] Although not shown, the UF membrane separation device may be connected to the methane fermentation tank via a piping member as a return means for the return path. With this configuration, the concentrated liquid is returned from the UF membrane separation device to the methane fermentation tank 6.

[0032] When the concentrated liquid is returned from the UF membrane separation device to the methane fermentation tank 6, a water flow is generated in the methane fermentation tank 6, and the contents of the methane fermentation tank 6 are agitated by this water flow. Further, since the concentrated liquid is returned to the methane fermentation tank 6, the methane fermentation in the methane fermentation tank 6, the concentration separation of the digested liquid in the UF membrane separation device, the return of the concentrated liquid from the UF membrane separation device to the methane fermentation tank 6, and the agitation of the contents in the methane fermentation tank 6 by the return are substantially repeated.

[0033] Although not shown, an aerobic aeration device for treating the drainage from the methane fermentation tank 6 is provided.

[0034] In addition, as the product generated in this fermentation step (B), it is also possible to use the solid residue generated as a by-product in biomass methane gas power generation.

[0035] [Dehydration step (C)] As a means for performing dehydration treatment in the dehydration process (C), a dehydrated sludge extraction centrifuge (centrifuge) 8 for extracting and dehydrating solids (inorganic substances) is provided. The dehydration treatment in the dehydrated sludge extraction centrifuge 8 is performed without adding a flocculant. That is, the residue of the raw material is ultra-finely pulverized by the grinder 4 in the previous pulverization / slurrying process (A), and the particle sizes of the ultra-finely pulverized substances are uniform, so that appropriate dehydration treatment can be performed without adding a flocculant. By this dehydration treatment, the water content after treatment becomes about 80%.

[0036] Also, in this dehydration process (C), at least a part of the supernatant from which the sludge has been separated may be returned to the fermentation process (B) for re-fermentation treatment.

[0037] [Drying Process (D)] As a means for performing drying treatment in the drying process (D), a drying device 10 is provided. Specifically, the drying device 10 may be, for example, a rotary dryer. In the drying treatment, the inorganic residue taken out from the dehydrated sludge extraction centrifuge 8 in the previous dehydration treatment is put into the drying device 10. As the extracted sludge solid content, a residue with a water content of about 80 - 90% is put into the drying device 10. It is dried in the drying device 10 until the water content becomes 50 - 60%. By drying in the drying device 10, a powdery fertilizer is produced.

[0038] In this drying process (D), the fertilizer being dried is sterilized by setting the temperature inside the drying device 10 to about 170°C. By sterilizing the fertilizer to be produced at a temperature of about 170°C, it becomes a harmless and safe fertilizer that does not harm plant growth and does not harm the people engaged in farming operations.

[0039] Note that in this drying process (D), it is also possible to dry the residue using the exhaust heat generated in other plants. By using the exhaust heat generated in other plants, effective utilization of the exhaust heat becomes possible, contributing to the improvement of energy efficiency and the effective utilization of resources.

[0040] [Deodorization Process (E)] When drying with the drying device 10, a large amount of NH3 is contained in the residue, so a lot of odor is generated. Therefore, as a measure against odor, catalytic combustion deodorization is performed by the catalytic combustion oxidation deodorization device 12. The exhaust gas from the catalytic combustion oxidation deodorization device 12 is discharged through the exhaust pipe 14.

[0041] [Granulation step (F)] As a means for performing the granulation treatment in the granulation step (F), a granulation device 16 is provided. Specifically, the granulation device 16 may be, for example, a continuous granulator. The powdery fertilizer generated in the previous drying step (D) is put into the granulation device 16, and granulation is performed into a spherical shape with a diameter of approximately 5 mm or a cylindrical shape with a diameter of 5 mm. Here, the powdery fertilizer that has exited the drying device 10 in the previous drying treatment is put into the granulation device 16 in a state where the water content is about 50%. By setting the water content in this way, granulation by the granulation device 16 becomes easy, and the fertilizer components can be made to last longer.

[0042] [Bagging and packing step (G)] As a means for performing the bagging and packing treatment in the bagging and packing step (G), a bagging and packing device (packing device) 18 is provided. The fertilizer processed into granules by the granulation device 16 is bagged and packed by the bagging and packing device 18.

[0043] [Product discharging step (H)] The fertilizer bagged and packed by the bagging and packing device 18 is discharged by the conveyor 22 through the product hopper 20 in the product discharging step (H).

[0044] The manufacturing method of the fertilizer according to one embodiment of the present invention has been described above. Most of the components of the fertilizer manufactured by the manufacturing method according to the present invention are inorganic substances, and the organic substances are dead bodies of methanogens, refractory lignin, etc. The rest are inorganic nitrogen, phosphorus, potassium, calcium, and ash.

[0045] And according to this fertilizer manufacturing method, by pulverizing and slurrying the raw material organic and inorganic substances through fine pulverization and processing them into a slurry state, the conversion efficiency of the organic substances can be maximized. Therefore, the fermentation rate in the fermentation process can be increased, and fertilizers can be manufactured using the remaining raw materials from which the organic substances have been maximally extracted. Also, since the raw materials processed into a slurry state and containing no solid content are fermented, the dissolution rate of the manufactured fertilizer is extremely fast, resulting in a fertilizer with quick-acting properties.

[0046] In the conventional fertilizer manufacturing methods, all the residues were made into compost or treated as industrial waste. However, according to the fertilizer manufacturing method of the present invention, all of them become organic-inorganic fertilizers and the discharge of residues can be eliminated. Therefore, according to the fertilizer manufacturing method of the present invention, it is possible to make effective use of the by-products after treatment in a biomass methane gas plant using livestock excrement discharged from livestock farms, dairy farms, etc., and the residues of other livestock feeds as raw materials, and the discharge of industrial waste from those industries can be eliminated.

[0047] Also, in this fertilizer manufacturing method, the water content of the fertilizer after drying in the drying step (D) is set to 55% - 60%, so the water content during granulation is also 55% - 60%. If the water content of the fertilizer before granulation is too low (over-dried), granulation becomes difficult and the risk of crushing increases. By increasing the water content to a certain extent, the ease of granulation can be ensured. Also, since the water content of the finally manufactured granular fertilizer is 55% - 60%, when the fertilizer is scattered on a field, etc., it will not easily be scattered by the wind.

[0048] Also, in this fertilizer manufacturing method, through the pulverization and slurrying treatment, the raw materials are processed into a complete slurry state containing no solid content. In the subsequent fermentation process, the organic substances can be completely fermented so that no organic substances are contained in the residues. As a result, the manufactured fertilizer becomes a fertilizer that exhibits excellent effects as an inorganic fertilizer.

[0049] Figure 2 is a table showing an example of the component ratios of raw materials or fertilizers in each of the above steps. The components and their ratios of raw materials or fertilizers in each step are, as an example, as shown in the table of this figure. Note that in the table of this figure, the dehydration step (C) shows the value after input (after the end of the step), and all other steps show the values before input (before the start of the step).

[0050] As described above, the embodiments of the present invention have been explained. However, the present invention is not limited to the above embodiments, and various modifications are possible within the scope of the claims and the technical idea described in the specification and the drawings.

Explanation of Signs

[0051] A Crushing and slurrying step B Fermentation step C Dehydration step D Drying step E Deodorization step F Granulation step G Bagging and packing step H Product unloading step 2 Organic waste (raw material) 4 Grinder (crushing device) 6 Methane fermentation tank 8 Dewatered sludge extraction centrifuge 10 Drying device 12 Catalytic combustion oxidation deodorization device 14 Exhaust stack 16 Granulation device 18 Bagging and packing device 20 Product hopper 22 Conveyor

Claims

1. A pulverization / slurrying step of processing a raw material containing at least any one of livestock excrement, food waste, and agricultural waste, which are organic substances, into a slurry state by mixing with a liquid and finely pulverizing; A fermentation step of generating a digestion liquid by charging the raw material processed into a slurry state in the pulverization / slurrying step into a fermentation tank and fermenting it; A dehydration / drying step of manufacturing a fertilizer by dehydrating the digestion liquid generated in the fermentation step by centrifugation without adding a flocculant and further drying it; A granulation step of granulating the fertilizer manufactured in the dehydration / drying step; comprising; returning at least a part of the supernatant separated by the centrifugation in the dehydration / drying step to the fermentation tank for re-fermentation treatment A method for manufacturing a fertilizer, characterized in that.

2. The method for manufacturing a fertilizer according to claim 1, characterized in that in the dehydration / drying step, the water content of the digestion liquid dehydrated by the centrifugation is about 80%.

3. The method for manufacturing a fertilizer according to claim 1 or 2, characterized in that the water content of the fertilizer manufactured in the dehydration / drying step is 55% - 60%.

4. The method for manufacturing a fertilizer according to any one of claims 1 to 3, characterized in that by passing the upper layer of the digestion liquid in the fermentation tank through an ultrafiltration membrane, a concentrated liquid containing particulate organic substances that do not pass through the pores of the ultrafiltration membrane is obtained, and the concentrated liquid is returned to the fermentation tank.

5. In the dehydration / drying step, when drying the residue obtained by dehydrating the digestion liquid, a deodorization treatment for deodorizing the odor from the residue is further performed, The method for manufacturing a fertilizer according to any one of claims 1 to 4, characterized in that the deodorization treatment is a catalytic oxidation deodorization treatment.

6. The method for manufacturing a fertilizer according to any one of claims 1 to 5, characterized in that it has a bagging and packing step of bagging and packing the fertilizer granulated in the granulation step.

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