Fermented and dried product manufacturing method

Abstract

To more stably produce a fermented and dried product by using a methane fermentation residue as a main raw material.SOLUTION: An aerobic fermentation treatment with:, as a main raw material, a methane fermentation residue obtained with much of easily decomposable organic matter being consumed with methane fermentation, generated at a sewage treatment step; and, as an auxiliary raw material, 20 pts.mass to 30 pts.mass of meat-and-bone meal and / or waste white clay based on 100 pts.mass of the methane fermentation residue and 10 pts.mass to 30 pts.mass of fermented chicken droppings based on 100 pts.mass of the methane fermentation residue is carried out in a vertical closed fermenter for 10 to 20 days to thereby produce a fermented and dried product having a water content of 20% to 30%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a fermented and dried product and the fermented and dried product. [Background technology]

[0002] Patent Document 1 discloses an apparatus for composting organic waste such as sludge by fermenting and drying it in a sealed container. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-172272 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, the introduction of a methane fermentation process for recovering methane gas using excess sludge generated during sewage treatment at sewage treatment plants, etc., has been progressing. However, the method described in Patent Document 1 may require a long time for fermentation treatment when using sludge with a low organic matter content, such as methane fermentation residue after methane fermentation treatment.

[0005] The present disclosure has been made in view of the above, and aims to provide a technology for more stably producing a fermented and dried product using methane fermentation residue as a main raw material. [Means for solving the problem]

[0006] To achieve the above object, a fermented and dried product production method according to one embodiment of the present disclosure uses, as a main raw material, methane fermentation residue (digested sludge) generated in a sewage treatment process, in which most of the easily decomposable organic matter has been consumed by methane fermentation, and uses, as secondary raw materials, 20 to 30 parts by mass of meat and bone meal and / or waste clay per 100 parts by mass of the methane fermentation residue, and 10 to 30 parts by mass of fermented chicken manure per 100 parts by mass of the methane fermentation residue, by aerobic fermentation treatment in a vertical sealed fermenter for 10 to 20 days, thereby producing a fermented and dried product with a moisture content of 20% to 30%.

[0007] In the above-mentioned method for producing a fermented and dried product, 100 parts by mass of methane fermentation residue is mixed with 20 to 30 parts by mass of meat and bone meal and / or waste clay and 10 to 30 parts by mass of fermented chicken manure as auxiliary raw materials, and aerobic fermentation treatment is carried out in a vertical sealed fermenter for 10 to 20 days to produce a fermented and dried product with a moisture content of 20% to 30%. By using the above-mentioned auxiliary raw materials, a fermented and dried product can be stably produced even when a raw material with a low content of organic matter that contributes to fermentation drying, such as methane fermentation residue, is used.

[0008] In the aerobic fermentation treatment, the amount of air sent to the vertical sealed fermenter is 0.1 Nm 3 / min / m 3 ~0.25Nm 3 / min / m 3 The above-mentioned embodiment may be adopted.

[0009] By setting the amount of air sent to the vertical sealed fermenter within the above range, the inside of the vertical sealed fermenter becomes suitable for fermenting and drying the raw materials, allowing for more stable production of fermented and dried products.

[0010] A fermented and dried product according to one embodiment of the present disclosure is produced using, as a main raw material, methane fermentation residue (digested sludge) generated in a sewage treatment process, in which most of the easily decomposable organic matter has been consumed by methane fermentation, and using, as secondary raw materials, 20 to 30 parts by mass of meat and bone meal and / or waste clay per 100 parts by mass of the methane fermentation residue, and 10 to 30 parts by mass of fermented chicken manure per 100 parts by mass of the methane fermentation residue, and has a moisture content of 20% to 30%, an available calorie of 1,500 kcal / kg-as-is or more, a fuel ratio of 0.1 to 0.3, an arsenic content of 0.005 wt% or less, a cadmium content of 0.0005 wt% or less, a mercury content of 0.0002 wt% or less, a nickel content of 0.03 wt% or less, a chromium content of 0.05 wt% or less, and a lead content of 0.01 wt% or less.

[0011] The fermented and dried product described above uses methane fermentation residue as the main raw material, but has a moisture content, available calorific value, and fuel ratio within the above ranges, and also contains arsenic, cadmium, mercury, nickel, chromium, and lead at or below the above values, making it suitable for use as an energy source, for example. [Effects of the Invention]

[0012] According to the present disclosure, a technique is provided for more stably producing a fermented and dried product using methane fermentation residue as a main raw material. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of a fermentation drying system according to one embodiment. [Figure 2] FIG. 2 is a schematic diagram of the fermenter. [Figure 3] FIG. 3 is a diagram illustrating gas flow into and out of the fermenter. [Figure 4] FIG. 4 is a diagram illustrating the material balance into the fermenter in Example 1. [Figure 5] FIG. 5 is a diagram showing the change in the amount of air sent during the test period in Example 1. [Figure 6]FIG. 6 is a diagram illustrating the material balance into the fermenter in Example 2. [Figure 7] FIG. 7 is a diagram showing the change in the amount of air sent during the test period in Example 2. [Figure 8] FIG. 8 is a diagram illustrating the mass balance into the fermenter in Example 3. [Figure 9] FIG. 9 is a graph showing the change in the amount of air sent during the test period in Example 3. [Figure 10] FIG. 10 shows the analysis results (harmful substances) of the fermented and dried product obtained in Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicated explanations will be omitted.

[0015] [Fermentation and drying system] Fig. 1 is a schematic diagram of a fermentation drying system (fermentation drying apparatus) according to one embodiment of the present disclosure. The fermentation drying system 1 is a system that receives fermentation raw materials and produces a fermented and dried product or compost through a fermentation and drying process using aerobic fermentation heat. The target of the fermentation and drying process performed by the fermentation and drying system 1 is methane fermentation residue, i.e., digested sludge, generated at sewage treatment plants.

[0016] Medium-sized sewage treatment plants serving populations of 10,000 to 100,000, and large-scale sewage treatment plants serving populations of 100,000 or more, are increasingly introducing a methane fermentation process (digestion process) in which methane gas is recovered by anaerobic fermentation from excess sludge generated in the activated sludge method sewage treatment process. The digested sludge used in the fermentation drying system 1 is the residue generated in this methane fermentation process. In the following embodiments, the target of the fermentation drying process by the fermentation drying system 1 may be described as methane fermentation residue or digested sludge.

[0017] As shown in Fig. 1, the fermentation drying system 1 includes a fermentation drying facility 2 and an facility control unit 3. The fermentation drying facility 2 includes a fermenter 21, a raw material supply unit 22, a dried material discharge unit 23, an air blower 24, an air heater 25, a dust removal tower 26, an exhaust fan 27, and a cleaning and deodorization tower 28. The fermentation drying system 1 produces a fermented and dried product (dried sludge) or compost obtained by fermenting and drying methane fermentation residue (digested sludge). In addition, exhaust gas generated during the fermentation of the digested sludge is subjected to a predetermined treatment.

[0018] The fermenter 21 has the function of inputting fermentation raw materials and carrying out fermentation treatment. In the fermenter 21, aerobic treatment is carried out using aerobic microorganisms. In addition to the main raw material, auxiliary raw materials that contribute to fermentation, etc. are input into the fermenter 21 via line L1. In the following description, the "fermentation raw materials" refers to the entire raw material including the main raw material and auxiliary raw materials.

[0019] The amount of raw material supplied to the fermenter 21, the blending ratio, and the like are adjusted, for example, by a raw material supply unit 22. A fermented and dried product is discharged from the fermenter 21 via a line L2. The amount of the fermented and dried product discharged is adjusted, for example, by a dried product discharge unit 23. Air is supplied to the fermenter 21 via a line L3. Gas and water vapor (hereinafter referred to as exhaust) generated during fermentation in the fermenter 21 are discharged via a line L4.

[0020] The raw material supply unit 22 has a function of adjusting the supply amount, blending ratio, etc. of the fermentation raw materials supplied to the fermenter 21. Details of the fermentation raw materials will be described later, but in addition to the main raw material to be fermented and dried, multiple types of raw materials such as auxiliary raw materials can be supplied to the fermenter 21. The supply amount, blending ratio, etc. of the fermentation raw materials can affect the state of fermentation and drying in the fermenter 21. Therefore, by adjusting the supply amount, blending ratio, etc. of the fermentation raw materials in the raw material supply unit 22, the fermentation and drying in the fermenter 21 can be controlled.

[0021] The dried material discharge unit 23 has a function of adjusting the discharge amount of the fermented and dried material. In Fig. 1, the dried material discharge unit 23 is shown schematically as being provided on line L2, but in general, the dried material discharge unit 23 opens and closes the discharge port of the fermenter 21 (described later) while an operator of the fermentation and drying system 1 checks the discharge amount and the quality of the fermented and dried material on-site. Alternatively, the discharge port may be opened and closed by a mechanism that controls the opening and closing of the discharge port of the fermenter 21 (described later) based on a change in the weight of the fermenter.

[0022] The air blower 24 has a function of supplying gas to the line L3. A motor M1 is connected to the air blower 24, and the air blower 24 is driven by the motor M1 to introduce air from outside into the line L3.

[0023] The air heater 25 has a function of heating the gas introduced into line L3. The temperature of the air introduced into the fermenter 21 is, for example, about 50°C to 80°C. The air heater 25 has a function of heating the gas flowing through line L3 so that the gas falls within a predetermined temperature range. Upstream of the air heater 25, a heat exchange means (not shown) may be provided that uses, for example, the heat of the exhaust air through line L4 to heat the outside air introduced into the vessel from the air supply fan. The form of the heat exchange means is not particularly limited, and the exhaust gas from line L4 is cooled by heat exchange. Meanwhile, the heated air is introduced into the fermenter 21 via line L3.

[0024] The dust removal tower 26, exhaust fan 27, and cleaning deodorization tower 28 are provided on line L4 that discharges exhaust gas from the fermenter 21. The dust removal tower 26 and cleaning deodorization tower 28 function as wet deodorization devices that perform deodorization treatment on the exhaust gas.

[0025] The dust removal tower 26 receives the exhaust gas flowing through line L4 and has the function of removing dust contained in the exhaust gas. Equipment such as a scrubber is used as the dust removal tower. The gas from which the dust has been removed is sent to the cleaning and deodorizing tower 28 via an exhaust fan 27.

[0026] The exhaust fan 27 has the function of moving the exhaust gas in the line L4. A motor M2 is connected to the exhaust fan 27, and the exhaust gas is moved downstream by driving the exhaust fan 27 through the operation of the motor M2. The fan can be one whose fan rotation speed can be controlled by the inverter frequency.

[0027] The cleaning deodorization tower 28 functions to remove trace odorous components, such as ammonia and hydrogen sulfide, contained in the exhaust gas from the fermenter. As an example, the cleaning deodorization tower is a wet cleaning tower, and can be an acid cleaning deodorization tower using dilute sulfuric acid. The cleaning deodorization tower 28 is not limited to an acid cleaning deodorization tower, and various configurations can be used as long as they perform oxidizing agent cleaning deodorization, such as alkali cleaning deodorization or alkali / hypochlorous acid water cleaning deodorization, and remove odorous components. The cleaning deodorization tower can be selected appropriately depending on the gas to be treated. For example, an acid cleaning tower is used when ammonia is to be deodorized. Furthermore, multiple cleaning deodorization towers can be connected in series depending on the type and number of gases contained in the exhaust gas and the allowable component concentrations after treatment. If there is a possibility of hydrogen sulfide generation, an alkali / hypochlorous acid water cleaning deodorization tower combining sodium hydroxide and sodium hypochlorite may be further installed.

[0028] The wet deodorizing device is not limited to the above configuration. For example, it may include an adsorption tower filled with activated carbon, which removes trace odor components that cannot be sufficiently removed by the action of the liquid through the adsorption action of the activated carbon. The adsorption tower may be installed at the final stage of the multiple treatment devices.

[0029] The fermentation drying equipment 2 may be provided with a plurality of sensors at various locations. FIG. 1 illustrates a plurality of sensors 29a to 29g that may be provided in the fermentation drying system 1. For example, sensor 29a is a weighing scale that measures the weight of the fermenter 21. Sensor 29b is a pressure gauge that measures the pressure (atmospheric pressure) inside the fermenter 21 (more precisely, inside a container described below). Sensor 29c is a thermometer that measures the temperature inside the fermenter 21. Sensor 29d is a flow meter that measures the amount of gas supplied to line L3. A thermometer that measures the temperature of the gas, a pressure gauge that measures the pressure of the gas, or the like may be provided in the same location as sensor 29d. Sensor 29e is a thermometer that measures the temperature of the gas heated by the air supply heater 25. Sensor 29f is a thermometer that measures the temperature of the exhaust gas from the fermenter 21, and sensor 29g is an oxygen concentration meter that measures the oxygen concentration of the exhaust gas. In this way, the fermentation drying equipment 2 may be provided with various sensors for checking its operation.

[0030] The equipment control unit 3 has the function of controlling each unit of the fermentation drying equipment 2. The equipment control unit 3 receives output signals from a plurality of sensors and the like provided at various locations in the fermentation drying system 1 and from each of the above units. Based on these output signals, the equipment control unit 3 can change the control content of the equipment.

[0031] [Fermentation tank] Next, the fermenter 21 will be described. FIG. 2 is a schematic diagram of the fermenter 21. The fermenter 21 is a sealed, vertical fermenter. The fermenter 21 has a container 41 that extends vertically (direction A in the figure) relative to the installation surface. An inlet 42 is provided above the container 41, through which the main raw material, auxiliary raw materials, etc. are introduced. Upstream of the inlet 42, the raw material supply unit 22 is connected via a line L1. Furthermore, an outlet 43 is provided below the container 41, through which the fermented and dried material after processing in the container 41 is discharged. The outlet 43 is connected to the dried material discharge unit 23 via a line L2.

[0032] Both the inlet 42 and the outlet 43 are provided with lids or other openable or detachable cover-like members (not shown) to form a sealed structure for the fermenter 21. By attaching these cover-like members to the inlet 42 and the outlet 43, the container 41 of the fermenter 21 can be sealed. In this way, the fermenter 21 enables aerobic fermentation in a sealed system. From the viewpoint of further improving the efficiency of drying the contents using the heat of aerobic fermentation, the fermenter 21 may have a thermally insulated structure, for example, by arranging a thermal insulating material on the outer peripheral surface of the container 41.

[0033] The fermenter 21 is equipped with agitation equipment 44 for mixing the raw materials in the fermenter. As an example, the agitation equipment 44 includes an agitation blade 44a provided within the vessel 41, a rotating shaft 44b connected to the agitation blade 44a, and a rotation drive device (not shown) provided outside the vessel 41. The agitation blade 44a is connected to the rotation drive device provided outside the vessel 41 via the rotating shaft 44b and rotates in a fixed direction using a hydraulic cylinder as a drive source. The agitation blades 44a may be provided in multiple stages spaced apart at predetermined intervals from the bottom to the top of the rotating shaft 44b. By further providing the agitation equipment 44, the raw materials can be appropriately mixed while preventing excessive compaction of the contents, thereby improving the efficiency of aerobic fermentation.

[0034] The fermenter 21 also includes an air supply means 45 for supplying an oxygen-containing gas, such as air, into the fermenter 21, and an exhaust means 46 capable of exhausting the gas inside the vessel 41 to the outside of the vessel 41. The oxygen-containing gas F can be, for example, air. As an example, the oxygen-containing gas F may be supplied to the lower part of the fermenter 21 from the air supply means 45 provided outside the vessel 41, via a hollow rotating shaft 44b and through a vent hole in the agitator blade 44a. The air supply means 45 is connected to line L3, and the gas flowing through line L3 is supplied as the oxygen-containing gas. In the example shown in FIG. 2, the agitator blade 44a provided at the bottom is provided with a plurality of gas circulation holes through which the oxygen-containing gas F can circulate. In this case, the oxygen-containing gas F can be evenly supplied to the vessel 41 while the contents are being agitated by the agitator blade 44a. The oxygen-containing gas F present in the vessel 41 and the gas produced by aerobic fermentation are exhausted as exhaust gas to a line L4 (see FIG. 1) via an exhaust means 46 provided above the vessel 41.

[0035] In order to increase the contact efficiency between the oxygen-containing gas and the contents and increase the aerobic fermentation efficiency of the fermentation target within the container 41, the oxygen-containing gas F can be supplied from the vertically lower side of the container 41, and the exhaust gas containing the oxygen-containing gas F can be exhausted from the vertically upper side of the container 41.

[0036] The fermentation raw materials are continuously or intermittently fed into container 41 of fermenter 21 through inlet 42. After aerobic fermentation in fermenter 21, the fermentation raw materials are continuously or intermittently discharged as fermented dry matter through outlet 43. The amount of fermented dry matter discharged is determined based on the following: "the amount of fermentation raw materials and auxiliary raw materials fed in on the previous day" - "the amount of weight loss in the fermenter per day (calculated based on the results of weighing using the weighing scale shown by sensor 29a in Figure 1)."

[0037] In the fermenter 21 described above, the fermentation raw material is introduced into the vessel 41 through the inlet 42, and after the processed material is fermented within the vessel, the fermented and dried product is removed through the outlet 43 at the bottom of the vessel 41. In the fermenter 21, a predetermined amount of outside air is introduced through the vent holes in the lowest agitator blade 44a by the air supply means 45, and the air is exhausted through the exhaust means 46. In this state, each agitator blade 44a is rotated at a low speed to aerate and agitate the fermentation raw material, efficiently bringing the aerobic bacteria, organic components, and oxygen into contact with each other within the vessel, thereby carrying out fermentation. At the same time, the contents are dried by the fermentation heat. The air exhausted through the exhaust means 46 contains gases such as carbon dioxide and ammonia, as well as water vapor, generated during the fermentation process, compared to the gas introduced into the vessel through the vent holes and flowing upward while passing through the processed material.

[0038] [Fermentation ingredients] The raw materials used to produce the fermented and dried product or compost in the fermenter 21 include a main raw material, which is the component to be fermented and dried or composted, and auxiliary raw materials, etc., that assist the fermentation and drying or composting of the main raw material. Details of each raw material and their mixing ratios are explained below.

[0039] (Main raw material) As described above, the main raw material is methane fermentation residue (digested sludge) generated in the methane fermentation process (digestion process), in which methane gas is recovered from excess sludge generated in a sewage treatment process by anaerobic fermentation. Methane fermentation residue (digested sludge) is a sludge-like or paste-like substance containing organic matter, inorganic matter, and water. The methane fermentation residue (digested sludge) may be used as is, or may be used after adjusting the moisture content.

[0040] The moisture content of the main raw material is not particularly limited, but is, for example, about 50% to 90%, and preferably 50% to 85%.

[0041] In addition, in the methane fermentation residue (digested sludge), organic matter that can be rapidly decomposed by fermentation bacteria (easily decomposable organic matter) is consumed during the methane fermentation process, and as a result, the content of easily decomposable organic matter in the methane fermentation residue (digested sludge) is significantly reduced.

[0042] Table 1 shows data showing the componential characteristics of methane fermentation residue. Table 1 shows the analytical values ​​for proximate analysis (JIS M8812), elemental analysis (JIS M8819), and readily decomposable organic matter (concentration of acid detergent fiber (ADF) soluble organic matter calculated from ADF analysis values) for undigested sludge (raw sludge) generated at City A's sewage treatment plant, which does not have a digestion process, and digested sludge (methane fermentation residue) generated at City B's sewage treatment plant, which does have a digestion process. Table 1 also shows the results of an analysis performed using the following procedure, applying JIS M8812.

[0043] First, a dried sample of the raw sludge was divided into smaller pieces to prepare a dried sample. The dried sample was then placed in a thermostatic chamber at 107°C, and the loss on drying was determined as the total moisture (wt%-AR). Next, the dried sample was placed in a humidity-controlled container in an air atmosphere at 30°C and 75% relative humidity for 3 to 6 hours, or left in a test room to prepare an adjusted sample. The loss on drying of this adjusted sample in a thermostatic chamber at 107°C was determined as the inherent moisture (wt%-AD). Alternatively, the adjusted sample was placed in a thermogravimetric analyzer (TGA), and the inherent moisture (wt%-AD) was determined from the change in weight around 107°C.

[0044] Next, the above prepared sample was completely combusted in air at 815°C, and the residual fraction was taken as the ash content (wt%-AD). Alternatively, the prepared sample was measured using a thermogravimetric analyzer (TGA) to determine the ash content (wt%-AD) from the weight change around 815°C.

[0045] Next, the prepared sample was placed in a crucible with a lid, and heated at 900°C for 7 minutes in an air-tight container. The weight loss was calculated by subtracting the inherent moisture content from the weight loss, and the volatile content (wt%-AD) was calculated. The fixed carbon (wt%-AD) was calculated by subtracting the inherent moisture, ash, and volatile content from the weight of the prepared sample.

[0046] Furthermore, the prepared sample was placed in a bomb calorimeter to measure the calorific value, which was then used as the GCV (kcal / kg-AD).

[0047] As shown in Table 1, the easily degradable organic matter content in undigested sludge was 5.2%, while that in digested sludge was reduced to 1.5%. Easily degradable organic matter is primarily the organic matter that is subject to primary fermentation (rapid fermentation) during the fermentation and drying process. Converting the easily degradable organic matter concentration and ash concentration to a dry basis and calculating the easily degradable organic matter concentration / ash concentration yields 1.94 (= (5.2 ÷ (1 - 0.78)) ÷ (10.97 ÷ (1 - 0.0991)) for undigested sludge and 0.29 (= (1.5 ÷ (1 - 0.815)) ÷ (24.85 ÷ (1 - 0.1152)) for digested sludge. Assuming the ash concentration remains constant before and after methane fermentation, this means that approximately 85% of the easily degradable organic matter (= (1.94 - 0.29) ÷ 1.94 × 100) was consumed in methane fermentation.

[0048] [Table 1]

[0049] (auxiliary raw materials) The fermentation raw material may contain an auxiliary raw material. The auxiliary raw material is a material that, when contained together with the main raw material, promotes stable aerobic fermentation of the main raw material when the fermentation raw material is subjected to fermentation.

[0050] When the main raw material is the methane fermentation residue (digested sludge) described above, at least the following two types of secondary raw materials are used. (1) Meat and bone meal and / or waste clay (2) Fermented chicken manure

[0051] These secondary raw materials are used to reduce the moisture content of the main raw material, to increase the breathability of the fermentation raw material containing the main raw material and secondary raw materials, to supply easily decomposable organic matter that serves as a nutrient source for the microorganisms that contribute to aerobic fermentation, and to supply aerobic microorganisms that allow aerobic fermentation to proceed efficiently.

[0052] Of the two types mentioned above, meat and bone meal and / or waste clay serve as nutrients containing a large amount of organic matter (easily decomposable organic matter) that is the primary fermentation target of aerobic fermentation bacteria in the fermentation and drying process. Because methane fermentation residue (digested sludge) has a low content of easily decomposable organic matter, it may be necessary to use an appropriate amount of nutrients. Because meat and bone meal and / or waste clay contain more easily decomposable organic matter than methane fermentation residue (digested sludge), they are suitable as nutrients. By using an appropriate amount of nutrients, it becomes possible to stably and quickly ferment, dry, and compost the methane fermentation residue (digested sludge) down to a moisture content of approximately 20% to 30%.

[0053] In addition, fermented chicken manure serves as a bacterial material containing bacteria effective for aerobic fermentation. Because methane fermentation residue (digested sludge) contains a low content of aerobic fermentation bacteria and contains almost no easily decomposable organic matter, it is effective to continuously use fermented chicken manure as a bacterial material in the fermentation and drying process. By incorporating an appropriate amount of fermented chicken manure and maintaining a stable ecosystem of high-quality aerobic fermentation bacteria in the fermentation tank, it becomes possible to stably and quickly ferment, dry, and compost the methane fermentation residue (digested sludge) down to a moisture content of approximately 20% to 30%.

[0054] Meat and bone meal is made by heat treating the scraps of meat and bones that remain after removing the meat from the meat production process, removing fats and oils, drying, and crushing them into powder.

[0055] Waste clay is the residue that remains after oil-containing clay (diatomaceous earth) that is generated during the edible oil manufacturing process is compressed and removed using a filter press or similar.

[0056] Fermented chicken manure is a fermentation product obtained by subjecting chicken manure to primary fermentation treatment, and is distributed as compost.

[0057] The results of industrial analysis (JIS M8812) of representative meat and bone meal, waste clay, and fermented chicken manure are shown in Table 2. Table 2 shows the results of analysis conducted according to the following procedure, applying JIS M8812.

[0058] First, a dry sample of the auxiliary raw material was reduced to prepare a dry sample, and the drying loss of the dry sample in a thermostatic chamber at 107°C was taken as the total moisture content (wt%-AR). Next, the dry sample was placed in a humidity-controlled container in an air atmosphere at 30°C and 75% relative humidity for 3 to 6 hours, or left in a test room to prepare an adjusted sample. The drying loss of this adjusted sample in a thermostatic chamber at 107°C was taken as the inherent moisture content (wt%-AD). Alternatively, the adjusted sample was placed in a thermogravimetric analyzer (TGA), and the inherent moisture content (wt%-AD) was determined from the change in weight around 107°C.

[0059] Next, the above prepared sample was completely combusted in air at 815°C, and the residual fraction was taken as the ash content (wt%-AD). Alternatively, the prepared sample was measured using a thermogravimetric analyzer (TGA) to determine the ash content (wt%-AD) from the weight change around 815°C.

[0060] Next, the prepared sample was placed in a crucible with a lid, and heated at 900°C for 7 minutes in an air-tight container. The weight loss was calculated by subtracting the inherent moisture content from the weight loss, and the volatile content (wt%-AD) was calculated. The fixed carbon (wt%-AD) was calculated by subtracting the inherent moisture, ash, and volatile content from the weight of the prepared sample.

[0061] Furthermore, the prepared sample was placed in a bomb calorimeter to measure the calorific value, which was then used as the GCV (kcal / kg-AD).

[0062] The analytical values ​​shown are for easily decomposable organic matter (concentration of acid detergent fiber (ADF) soluble organic matter calculated from the ADF analytical value). For waste clay, the oil concentration analytical value (based on the Fertilizer Test Method) was minus 20%.

[0063] [Table 2]

[0064] The form of the secondary ingredients is not particularly limited, and may be, for example, solid, granular, powdery, paste-like, etc. Of the secondary ingredients, meat and bone meal and / or waste clay may be contained in an amount of 20 to 30 parts by mass, preferably 24 to 29 parts by mass, per 100 parts by mass of the main ingredient. Furthermore, fermented chicken manure may be contained in an amount of 10 to 30 parts by mass, preferably 16 to 21 parts by mass, per 100 parts by mass of the main ingredient. In this case, the weight of the main ingredient used as a reference is the weight in its as-is (water-containing) state.

[0065] (Other auxiliary materials; ventilation aids) In addition, a ventilation aid may be included as a secondary raw material other than the two above-mentioned secondary raw materials to reduce moisture content and improve breathability. Examples of ventilation aids that can be used include organic ventilation aids such as rice straw, rice husks, sawdust, bark, plants, or dried or crushed materials thereof, and inorganic ventilation aids such as perlite, zeolite, diatomaceous earth, and coal ash. The inclusion of a ventilation aid can ensure breathability while preventing excessive compaction, which is expected to promote stable and effective aerobic fermentation of the main raw material. However, when using a vertical sealed fermenter, the use of a ventilation aid as a secondary raw material is not required.

[0066] The form of the ventilation aid is not particularly limited, and may be, for example, solid, granular, powdery, pasty, fluid, liquid, etc. The content of the ventilation aid can be adjusted appropriately depending on the physical properties and purpose of the auxiliary raw materials used, and may be 5 to 80 parts by mass, or 5 to 50 parts by mass, per 100 parts by mass of the main raw material. In this case, the weight of the main raw material used as a reference is the weight in a water-containing state.

[0067] [Mixing of fermentation ingredients and moisture content] The fermentation raw material can be, for example, a mixture of a main raw material and an auxiliary raw material. As an example, the main raw material and the auxiliary raw material may be premixed (premixed) to prepare a mixture of fermentation raw materials before being supplied to a fermentation device such as the fermenter 21. Alternatively, only the auxiliary raw materials may be premixed at a predetermined blending ratio and then charged into the fermenter 21, and the main raw material may then be charged into the fermenter 21 and mixed to prepare the mixture. Furthermore, the auxiliary raw material and the main raw material may be charged separately into the fermenter 21, and the raw materials may be mixed in the fermenter 21 to prepare the mixture. In this way, the method of mixing the fermentation raw materials is not particularly limited.

[0068] To ensure a sufficient amount of moisture for stable aerobic fermentation from the initial stage of fermentation, the moisture content of the fermentation raw material can be set to 45% or more and 75% or less. Furthermore, a moisture content of 55% or more and 65% or less allows aerobic fermentation to proceed more stably. The moisture content of the fermentation raw material can be appropriately adjusted, for example, by selecting the blending ratio of the raw materials to achieve the desired moisture content, or by adding water to the raw materials or fermentation raw material.

[0069] As described above, by supplying the fermentation raw materials to the container 41 of the fermenter 21 so that the fermentation raw materials are mixed in the fermenter 21, the raw materials can be subjected to aerobic fermentation treatment.

[0070] [Manufacturing method of fermented products] As a method for producing a fermented product, an example of the operating procedure of the fermenter 21 will be described. First, raw materials such as the main raw material and auxiliary raw materials are charged into the fermenter 21 through the charging port 42, leaving a space of 10 to 30% of the internal volume of the vessel 41. By charging the raw materials while leaving a space of this size, the raw materials can be stirred and aerated sufficiently and uniformly. Therefore, fermentation and drying can be carried out efficiently within the vessel 41. The charging of the raw materials may be continuous or intermittent, and may be carried out once a day at a predetermined time, for example. In other words, the raw materials can be charged multiple times at predetermined intervals (at regular intervals). When the raw materials are charged intermittently, the efficiency of the raw material charging process can also be improved.

[0071] Furthermore, the raw material continues to be fermented and dried in the fermenter 21 for a predetermined residence time (approximately 10 to 20 days), and a predetermined amount of the fermented and dried product is removed periodically (for example, every day) from the discharge outlet 43. The residence time of the raw material may preferably be 12 to 18 days. Both the removal of the fermented and dried product and the addition of the raw material may be performed once a day at a predetermined time.

[0072] The raw material is added after the fermented and dried product is removed from the discharge port 43. In this way, the fermentation process is carried out continuously by repeatedly adding a portion of the raw material and removing a portion of the fermented product in a fixed time cycle. The fermented and dried product obtained by the above procedure is a powdery or granular solid, and is partially in the form of a lump.

[0073] The equipment control unit 3 controls the fermentation tank 21 and each device in its periphery, thereby maintaining a high level of fermentation rate in the fermentation tank 21. As an example, the equipment control unit 3 can adjust the air flow rate sent by the air sending means 45 to the container 41 of the fermentation tank 21, and adjust the exhaust volume by the motor M2 of the exhaust fan 27 used to exhaust gas from the fermentation tank 21. The adjustment of the air flow rate and the exhaust volume will be described later.

[0074] As the fermentation of the fermentation raw material progresses, the moisture content of the fermentation raw material gradually decreases. As a result, the moisture content of the fermented and dried product is 20% to 30%, preferably about 22% to 28%. The fermented and dried product is in the form of a homogeneous powder. A moisture content of 20% or more can prevent dust from being generated from the fermented and dried product during handling.

[0075] [Facility Control Unit] The equipment control unit 3 acquires information related to the operating state of the fermentation drying equipment 2, such as sensor signals, and calculates the air supply flow rate based on this information.The equipment control unit 3 has the function of controlling each part of the fermentation drying equipment 2 based on the result of the calculation.

[0076] The information related to the operating state may include, in addition to signals from sensors 29a-29g installed at various locations in the fermentation and drying equipment 2, information related to the operating status and inverter frequency of the motor M1 of the air blower 24, the inverter frequency and operating status of the motor M2 of the exhaust fan 27, and other information related to the operating status of each part of the fermenter 21. Based on this information, the equipment control unit 3 calculates a set value for the air flow rate to the fermenter 21, which is used to control the operation of the fermentation and drying equipment 2. This will be described in detail later. Based on the calculated set value, the equipment control unit 3 calculates a command signal for the air blower 24 that supplies air to the fermenter 21 and outputs an operation signal to the air blower 24. Based on pressure information about the fermenter, the equipment control unit 3 sets the motor frequency of the exhaust fan 27 that exhausts air from the fermenter 21 so that the pressure inside the fermenter reaches a predetermined (target) pressure, and outputs an operation signal for the exhaust fan 27 based on this command. Here, standard PID control can be used to set the motor frequency of the exhaust fan based on the fermenter pressure.

[0077] The hardware of the equipment control unit 3 may be configured, for example, by one or more control computers. For example, the equipment control unit 3 may have circuits including one or more processors, memory, storage, input / output ports, timers, etc. With the above configuration, the equipment control unit 3 controls each unit included in the fermentation drying system 1. Note that the hardware configuration of the equipment control unit 3 is an example and is not limited to the above.

[0078] [Calculation of fermentation heat and control of air supply volume] The control unit 9 calculates a fermentation index to grasp the fermentation status in the fermenter 21. Specifically, the fermentation index is the "amount of heat of fermentation" per predetermined time calculated based on the ventilation volume (intake air volume, exhaust volume), intake air temperature, exhaust air temperature, intake air humidity, and exhaust air humidity. That is, the control unit 9 has a function to calculate the amount of heat of fermentation. The control unit 9 may also have a function to output the calculated amount of heat of fermentation. The control unit 9 may also have a function to control the amount of air sent based on the output amount of heat of fermentation.

[0079] The amount of heat of fermentation is calculated from the difference between the amount of heat of the exhaust gas discharged from the fermenter 21 and the amount of heat of the air sent to the fermenter 21. That is, the amount of heat of fermentation satisfies the relationship shown in the following formula (1). Fermentation heat (kJ / min) = Exhaust heat (kJ / min) - Air supply heat (kJ / min) ... (1)

[0080] FIG. 3 shows the balance of supply and exhaust in the container 41 of the fermenter 21. As described above, the fermentation process is carried out in the fermenter 21 (container 41) while supplying and exhausting air. At this time, the dry gas volume V0 (Nm 3 / min), amount of water vapor S0 (kg / min), and air supply temperature T0 (°C). In addition, as fermentation progresses in the fermentation raw material that has received the air supply, gas is discharged from the fermentation raw material (fermented dried material) into the container 41. If the exhaust gas discharged from the fermentation raw material is designated as exhaust gas 1, then the amount of dry gas V1 (Nm 3 / min), the amount of water vapor S1 (kg / min), and the exhaust temperature T1 (°C). Furthermore, gas is exhausted from the container 41 to the outside via the exhaust line L4. If the exhaust gas discharged from the container 41 is called exhaust gas 2, then the dry gas amount V2 (Nm 3 / min), the amount of water vapor S2 (kg / min), and the exhaust temperature T2 (°C).

[0081] As described above, the amount of fermentation heat can be calculated based on the above formula (1). As shown in formula (1), the amount of fermentation heat is found from the difference between the amount of exhaust heat and the amount of supplied air heat, but more accurately, the amount of exhaust heat used to calculate the amount of fermentation heat refers to the amount of heat of exhaust 1 shown in Figure 3, and the amount of supplied air refers to the amount of heat of supplied air 1 shown in Figure 3.

[0082] Here, the calorific value of the supplied air 1 is calculated, for example, by the following method: 1) Calculate the molar ratio (-) of dry gas to water vapor in the supplied gas from the atmospheric relative humidity (if no actual measurement is available, this may be fixed at 75%), the outside air temperature, and the saturated water vapor pressure at that time (according to the Japan Society of Mechanical Engineers steam table, etc.). 2) The amount of wet gas (Nm m) is calculated from the actual measurements of the flow meter, thermometer, and pressure meter provided at the position indicated by the sensor 29d on the gas supply line L3 in FIG. 3 / min) is calculated. 3) The amount of wet gas is the amount of dry gas V0 (Nm 3 / min) and water vapor content (Nm 3 / min), so the molar ratio of dry gas and water vapor in the above 1. air supply gas (-) and the amount of wet gas in 2. (Nm 3 / min), the dry gas volume V0 (Nm 3 / min) and the amount of water vapor S0 (kg / min). 4) The dry gas volume V0 (Nm m) in 3 above is calculated using the enthalpy of air and water vapor (according to the steam table of the Japan Society of Mechanical Engineers, etc.) measured by a thermometer that measures the temperature of the gas heated by the air supply heater 25, which is provided at the position indicated by the sensor 29e on the air supply line L3 in FIG. 3 Calculate the amount of heat of the air supplied from the amount of water vapor S0 (kg / min) and the amount of water vapor S0 (kg / min).

[0083] Next, the heat content of the exhaust gas 1 is calculated, for example, in the following way: 5) The relative humidity of exhaust gas 1 is assumed to be 100%. (This is a reasonable assumption given the structure of the sealed vertical fermenter.) (Assumption A) 6) Exhaust gas 1 is discharged from the fermentation raw material filling section in the container 41 (Fig. 2) into the space above the container 41. Therefore, the dry gas volume V1 (Nm m) of exhaust gas 1 required to calculate the exhaust heat is 3It is difficult to directly measure (accurately grasp) the amount of water vapor S1 (kg / min) and T2. 7) Therefore, we assume that exhaust 1 and exhaust 2 are exactly the same, and V1 = V2, S1 = S2, and T1 = T2. (Assumption B) 8) Furthermore, we assume that the amount of dry gas does not change as the aeration gas passes through the fermenter (a reasonable assumption based on the reaction equation for aerobic fermentation), and set V1 = V2 = V0 (Assumption C). 9) Based on the actual measurements of the pressure gauge (atmospheric pressure) inside the container 41, shown as sensor 29b in FIG. 1, and the thermometer (sensor 29f) that measures the temperature of the exhaust gas from the container 41, and the above-mentioned assumption A, the saturated water vapor pressure of the exhaust 2 and the partial pressure of the dry gas are set, and S2 is calculated from V2 (= V1 = V0). 10) Using the enthalpy of air and water vapor in the temperature measured by the thermometer that measures the temperature of the exhaust gas from the container 41 shown as the sensor 29f in FIG. 1, the above-mentioned dry gas amount V2 (= V0) (Nm 3 Calculate the exhaust heat quantity from the amount of steam S2 (kg / min) and the amount of water vapor S2 (kg / min). 11) It is also possible to measure V2 instead of step 8 above. Install a flow meter, thermometer, and pressure gauge in the exhaust line L4. Assuming the relative humidity at the measurement point is 100%, the dry gas flow rate V2 (Nm3 / min) can be calculated from the wet gas flow rate (actual flow meter measurement value) and saturated water vapor pressure.

[0084] From the above, the formula (1) can also be expressed as the following formula (3). Fermentation heat amount = Exhaust heat amount (V1, S1, T1) - Supply air heat amount (V0, S0, T0) (...(1)) = Exhaust heat (V2, S2, T2) - Intake heat (V0, S0, T0) = Exhaust heat (V0, S2, T2) - Supply heat (V0, S0, T0) ... (3)

[0085] Although V1, S1, and T1 included in the above formula (1) are measured values ​​or are difficult to calculate from measured values, V0, S0, S2, T0, and T2 included in the formula (3) can be measured values ​​or calculated values ​​from measured values. Therefore, the fermentation heat can be calculated using the above formula (3).

[0086] The control unit 9 may be configured to calculate and adjust the amount of air sent so that the fermentation heat amount, or the amount of change in fermentation heat amount, or the amount of fermentation heat amount and exhaust temperature, or the amount of change in fermentation heat amount and exhaust temperature, become appropriate values ​​based on the fermentation heat amount obtained by the calculation results using the above method.

[0087] In order to adjust the air supply flow rate in the fermenter 21, it is necessary to adjust the amount of gas supplied to the air supply means 45; specifically, it is necessary to adjust the inverter frequency of the motor M1 that drives the air blower 24. Therefore, once the air supply rate is determined by the above calculation, the inverter frequency of the motor M1 that drives the air blower 24 is calculated based on the result of the calculation in order to change the air supply rate. The inverter frequency can be calculated by the equipment control signal output unit 33 of the equipment control unit 3. The devices and parameters to be adjusted can vary depending on the configuration of the air supply means 45 and the various units upstream thereof that supply air. For example, in addition to parameters that control the rotation speed of the air blower 24, such as the inverter frequency of the motor M1 that drives the air blower 24, adjustment of the opening of the air blower discharge valve can be used.

[0088] [Use of fermented and dried products] The fermented and dried product has a moisture content of 20% to 30%, preferably about 22% to 25%. The fermented and dried product is in the form of a homogeneous powder. A moisture content of 20% or more prevents dust generation from the fermented and dried product during handling. The fermented and dried product has an available calorific value of 1,500 kcal / kg-solid or more, and a fuel ratio similar to that of biomass fuel, specifically in the range of 0.1 to 0.3. Furthermore, the fermented and dried product has an arsenic content of 0.005 wt% or less, a cadmium content of 0.0005 wt% or less, a mercury content of 0.0002 wt% or less, a nickel content of 0.03 wt% or less, a chromium content of 0.05 wt% or less, and a lead content of 0.01 wt% or less.

[0089] The fermented and dried product can be used, for example, as an alternative fuel to fossil fuels, as a thermal energy source in thermal power plants, cement kilns, general boilers, general combustion furnaces, etc. The fermented and dried product may also be used in agriculture, for example, as sewage sludge fermented compost (classified as "sludge fertilizer" under the Fertilizer Control Act). In other words, the fermented and dried product obtained by the above method can be used for known applications of fermented and dried products obtained from sewage sludge. However, the fermented and dried product is particularly suitable for use as a thermal energy source.

[0090] [Example] For the purpose of confirming the fermentation and drying method of the fermentation raw material in the fermentation and drying system 1 described above and the results thereof, evaluations were carried out in Examples 1 to 3 and Comparative Example 1 as follows.

[0091] [Assumptions for each evaluation] Vertical sealed fermentation tank with a capacity of 39m 3 A fermentation tank (manufactured by Chubu Ecotec, model number: C-40ET) was prepared. The designed sewage sludge treatment capacity of this fermentation tank is 2 tons per day in terms of sewage sludge (undigested sludge). In addition, the wet deodorization equipment was designed to treat 25 m3 per minute. 3 The equipment was connected to a combined dust removal tower and ammonia absorption tower with a processing capacity of 1000 m / s. Furthermore, a roots blower with an inverter-controlled rotation speed was used to adjust the air flow rate to the fermentation tank.

[0092] The main raw material for fermentation fed into the fermenter was the methane fermentation residue (digested sludge) shown in Table 1 above. The secondary raw materials used were meat and bone meal (Examples 1 and 2), waste white clay (Example 3), and fermented chicken manure (Examples 1 to 3). Furthermore, in Example 1, coal ash was also used as an aeration aid. The proximate analysis values ​​of the methane fermentation residue (digested sludge) are shown in Table 1. The proximate analysis values ​​of the meat and bone meal, waste white clay, and fermented chicken manure are shown in Table 2.

[0093] In each example and comparative example, the fermentation raw materials were added at a fixed time once a day. More specifically, a premix of the auxiliary raw materials at a predetermined blending ratio and the methane fermentation residue (digestion residue sludge) were separately added to the fermentation tank in order to maintain the blending ratio in the fermentation tank at a predetermined value.

[0094] The fermented and dried product was discharged from the fermentation tank at a fixed time once a day. The amount of fermented and dried product discharged was measured using a load cell attached to the fermentation tank. The discharge amount was adjusted by the weight balance around the fermentation tank (raw material input (kg / day) = product discharge (kg / day) + fermentation weight loss (kg / day)).

[0095] The exhaust temperature and heat of fermentation in the fermenter were monitored, and the fermentation status was quantified based on the results. The air supply volume was configured to follow changes in the fermentation status. Specifically, a method was used to control the air supply volume based on the amount of heat of fermentation described above.

[0096] [Example 1] In Example 1, meat and bone meal and fermented chicken manure were used as secondary raw materials, and coal ash was used as an aeration aid. The fermentation tank was operated from January 23 to 31, 2021, under the conditions shown in Table 3 for the amounts of the main raw materials and secondary raw materials added.

[0097] [Table 3]

[0098] As shown in Table 3 above, the input amount of methane fermentation residue (digested sludge) was adjusted to approximately 1.3 to 1.4 t / day. The average during the test period was 1,358 kg / day. In addition, meat and bone meal, coal ash, and fermented chicken manure were used as secondary raw materials. The average amounts of meat and bone meal and fermented chicken manure used during the test period were 29% and 19%, respectively, of the methane fermentation residue (digested sludge). This amounts to 29 parts by mass and 19 parts by mass per 100 parts by mass of methane fermentation residue (digested sludge).

[0099] Furthermore, no main or auxiliary ingredients were added on January 24th or 31st, but two days' worth of main and auxiliary ingredients were added the day before.

[0100] Table 3 also shows the discharge amount and moisture content of the fermented and dried product. The discharge amount was adjusted daily based on the fermenter weight balance. The average amount during the test period was 822 kg / day. The weighted average moisture content was 23.5%. The discharged fermented and dried product was in a homogeneous powder form with good fluidity.

[0101] The weight of the fermentation tank was continuously monitored during the test period. The weight at 6 AM during the test period is shown in Table 3. The weight value was adjusted for the input weight and discharge flow rate, and the weight loss per day (6 AM to 6 AM the next day) (the sum of the amount of water evaporation and the amount of organic matter decomposition) was calculated, and the results are also shown in Table 3.

[0102] As a result, the average weight loss per day during the test period was 1,156 kg / day. The average weight of the fermentation tank during the test period (average of weight measurements at 6 AM) was 25,317 kg.

[0103] The temperature profile of the fermenter during the test period was good.

[0104] The material balance around the fermenter according to Example 1 above is shown in Figure 4. The values ​​shown in Figure 4 are a summary of the average values ​​in Table 3. From the material balance (weight balance) shown in Figure 4, which was created based on these results, it was considered that the amount of fermented and dried material discharged from the fermenter was appropriately managed. From another perspective, the results shown in Figure 4 are considered to be highly reliable as a steady-state balance. From the weight balance in Figure 4, the average treatment time was calculated to be 17.4 days.

[0105] Figure 5 shows the change in the amount of air sent during the test period in Example 1. The amount of air sent was 4 to 7 Nm depending on the fermentation situation. 3 The capacity of the fermenter is 39 m 3 Therefore, the air flow rate is 0.10 to 0.18 Nm 3 / min / m 3 This becomes:

[0106] As described above, the results of Example 1 confirmed that a high-quality fermented dried product (fermented dried sludge) can be stably produced from methane fermentation residue (digested sludge) using a vertical sealed fermenter.

[0107] [Example 2] Example 2 is an example in which meat and bone meal and fermented chicken manure were used as secondary raw materials. The fermentation tank was operated from March 20 to 28, 2021, under the conditions shown in Table 4 for the amounts of main raw materials and secondary raw materials added.

[0108] [Table 4]

[0109] As shown in Table 4 above, the amount of methane fermentation residue (digested sludge) input was adjusted to approximately 1.5 to 2.0 t / day. The average during the test period was 1,662 kg / day. In addition, meat and bone meal and fermented chicken manure were used as secondary raw materials. The average amounts of meat and bone meal and fermented chicken manure used during the test period were 24% and 21% of the methane fermentation residue (digested sludge), respectively. This amounts to 24 parts by mass and 21 parts by mass per 100 parts by mass of methane fermentation residue (digested sludge).

[0110] Furthermore, no main or auxiliary ingredients were added on March 28th, but two days' worth of main and auxiliary ingredients were added the day before.

[0111] Table 4 also shows the discharged amount of fermented and dried material and its moisture content. The discharged amount was adjusted daily based on the fermenter weight balance. The average amount during the test period was 1,025 kg / day. The weighted average moisture content was 21.7%. The discharged fermented and dried material was in a homogeneous powder form with good fluidity.

[0112] The weight of the fermentation tank was continuously monitored during the test period. The weight at 6 AM during the test period is shown in Table 4. The weight value was adjusted for the input weight and discharge flow rate, and the weight loss per day (6 AM to 6 AM the next day) (the sum of the amount of water evaporation and the amount of organic matter decomposition) was calculated, and the results are also shown in Table 4.

[0113] As a result, the average weight loss per day during the test period was 1,387 kg / day. The average weight of the fermentation tank during the test period (average of weight measurements at 6 AM) was 26,531 kg.

[0114] The temperature profile of the fermenter during the test period was good.

[0115] The material balance around the fermenter according to Example 2 is shown in Figure 6. The values ​​shown in Figure 6 are a summary of the average values ​​in Table 4. From the material balance (weight balance) shown in Figure 6, which was created based on these results, it was considered that the amount of fermented and dried material discharged from the fermenter was appropriately managed. From another perspective, the results shown in Figure 6 are considered to be highly reliable as a steady-state balance. From the weight balance in Figure 6, the average treatment time was calculated to be 15.4 days.

[0116] Figure 7 shows the change in the amount of air sent during the test period in Example 2. The amount of air sent was 4 to 7 Nm depending on the fermentation situation. 3 The capacity of the fermenter is 39 m 3 Therefore, the air flow rate is 0.10 to 0.18 Nm 3 / min / m 3 This becomes:

[0117] As described above, the results of Example 2 confirmed that a high-quality fermented and dried product (fermented and dried sludge) can be stably produced from methane fermentation residue (digested sludge) using a vertical sealed fermenter.

[0118] [Example 3] Example 3 is an example in which waste clay and fermented chicken manure were used as auxiliary raw materials. From February 20 to March 7, 2021, the fermentation tank was operated under the conditions shown in Table 5 for the amounts of main raw materials and auxiliary raw materials added.

[0119] [Table 5]

[0120] As shown in Table 5 above, the input amount of methane fermentation residue (digested sludge) was adjusted to approximately 2.0 t / day. The average during the test period was 1,923 kg / day. In addition, waste clay and fermented chicken manure were used as secondary raw materials. The average amounts of meat and bone meal and fermented chicken manure used during the test period were 25% and 16%, respectively, relative to the methane fermentation residue (digested sludge). This amounts to 25 parts by mass and 16 parts by mass per 100 parts by mass of methane fermentation residue (digested sludge).

[0121] Furthermore, no main or auxiliary ingredients were added on February 21st, 23rd, 27th, and March 7th, and two days' worth of main and auxiliary ingredients were added the day before.

[0122] Table 5 also shows the discharge amount and moisture content of the fermented and dried product. The discharge amount was adjusted daily based on the fermenter weight balance. The average amount during the test period was 1,150 kg / day. The weighted average moisture content was 21.7%. The discharged fermented and dried product was in a homogeneous powder form with good fluidity.

[0123] The weight of the fermentation tank was continuously monitored during the test period. The weight at 6 AM during the test period is shown in Table 5. The weight value was adjusted for the input weight and discharge flow rate, and the weight loss per day (6 AM to 6 AM the next day) (the sum of the amount of water evaporation and the amount of organic matter decomposition) was calculated, and the results are also shown in Table 5.

[0124] As a result, the average weight loss per day during the test period was 1,548 kg / day. The average weight of the fermentation tank during the test period (average of weight measurements at 6 AM) was 25,464 kg.

[0125] The temperature profile of the fermenter during the test period was good.

[0126] The material balance around the fermenter according to Example 3 is shown in Figure 8. The values ​​shown in Figure 8 are a summary of the average values ​​in Table 5. From the material balance (weight balance) shown in Figure 8, which was created based on these results, it was considered that the amount of fermented and dried material discharged from the fermenter was appropriately managed. From another perspective, the results shown in Figure 8 are considered to be highly reliable as a steady-state balance. From the weight balance in Figure 8, the average treatment time was calculated to be 13.1 days.

[0127] Figure 9 shows the change in the amount of air sent during the test period in Example 3. The amount of air sent was 4 to 7 Nm depending on the fermentation situation. 3 The capacity of the fermenter is 39 m 3 Therefore, the air flow rate is 0.10 to 0.18 Nm 3 / min / m 3 This becomes:

[0128] As described above, the results of Example 3 confirmed that a high-quality fermented and dried product (fermented and dried sludge) can be stably produced from methane fermentation residue (digested sludge) using a vertical sealed fermenter. It was also confirmed that a fermented and dried product can be stably produced even when the nutrient material is changed from meat and bone meal to waste clay.

[0129] [Evaluation of fermented dried product] (Evaluation of fuel quality) The results of proximate analysis (JIS M8812) of the fermented and dried products (fermented and dried sludge) in Examples 2 and 3 are shown in Table 6. Table 6 shows the results of analysis conducted according to the following procedure, applying JIS M8812.

[0130] First, a dried sludge sample was divided into smaller pieces to prepare a dried sample. The dried sample was then placed in a thermostatic chamber at 107°C, and the loss on drying was determined as the total moisture content (wt%-AR). The dried sample was then placed in a humidity-controlled container in an air atmosphere at 30°C and 75% relative humidity for 3 to 6 hours, or left in a test room to prepare an adjusted sample. The loss on drying of this adjusted sample in a thermostatic chamber at 107°C was determined as the inherent moisture content (wt%-AD). Alternatively, the adjusted sample was placed in a thermogravimetric analyzer (TGA), and the inherent moisture content (wt%-AD) was determined from the change in weight around 107°C.

[0131] Next, the above prepared sample was completely combusted in air at 815°C, and the residual fraction was taken as the ash content (wt%-AD). Alternatively, the prepared sample was measured using a thermogravimetric analyzer (TGA) to determine the ash content (wt%-AD) from the weight change around 815°C.

[0132] Next, the prepared sample was placed in a crucible with a lid, and heated at 900°C for 7 minutes in an air-tight container. The weight loss was calculated by subtracting the inherent moisture content from the weight loss, and the volatile content (wt%-AD) was calculated. The fixed carbon (wt%-AD) was calculated by subtracting the inherent moisture, ash, and volatile content from the weight of the prepared sample.

[0133] Furthermore, the prepared sample was placed in a bomb calorimeter to measure the calorific value, which was then used as the GCV (kcal / kg-AD). The fuel ratio (-) is an index of the flammability of the fuel, and is expressed as fixed carbon (kcal / kg-AD) / volatile matter (kcal / kg-AD).

[0134] Table 6 also shows the measurement results for wood pellets in addition to the fermented and dried products obtained in Examples 2 and 3. The measurement results for wood pellets are partially quoted from Table 1 in the Forest Products Research Station Report, Vol. 20, No. 2, 2006, "Fuel Properties of Pellet Fuel Made from Hokkaido Wood Biomass."

[0135] [Table 6]

[0136] In Table 6, the calorific values ​​of GCV-AD on an air-dry basis were 2,390 kcal / kg and 2,320 kcal / kg, respectively. Also, from the results shown in Tables 4 and 5 above, assuming the total moisture content on a bulk basis to be 21.7% and the heat of evaporation of water to be 600 kcal / kg, the available calorific value on a bulk basis can be calculated as follows: (1) Example 2 Available calorific value on a solid basis (moisture content 21.7%) =2,390÷(1-0.107)×(1-0.217)-600×0.217 =1,970kcal / kg-physical (2) Example 3 Available calorific value on a solid basis (moisture content 21.7%) =2,320÷(1-0.089)×(1-0.217)-600×0.217 =1,870kcal / kg-physical

[0137] According to the above results, the effective calorific value on a bulk basis is approximately 1,900 kcal / kg-bulk, which is significantly larger than 1,500 kcal / kg-bulk and is therefore considered to function effectively as fuel.

[0138] Furthermore, the GCV-DAF calorific values ​​on a DAF (dry ash free) basis, which is an index of combustibility, were 5,040 kcal / kg-DAF and 5,510 kcal / kg-DAF, respectively. The fuel ratios were 0.16 and 0.19, respectively. These results are close to those of wood pellets (white pellets), which are a typical biomass fuel (fossil fuel alternative) in circulation, as shown in Table 6. In other words, it was confirmed that the fuel ratio was approximately 0.1 to 0.3.

[0139] From the above results, it is believed that the fermented and dried product (fermented and dried sludge) produced by the method shown in the above embodiment can be used as an alternative fuel to fossil fuels.

[0140] (Evaluation of compost quality) The fermented and dried product (fermented and dried sludge) obtained in Example 3 was subjected to heavy metal analysis based on the Fertilizer and Other Materials Testing Methods (2020). The results are shown in Table 7. Table 7 shows the standard values ​​for "sludge fermentation fertilizer (sludge generated from sewage treatment plants that has been thickened, digested, dehydrated, or dried, and then composted)" under the Fertilizer Control Act. As shown in Table 7, it was confirmed that the content of all heavy metals was below the standard values ​​specified in the Fertilizer Control Act. Thus, it was confirmed that the fermented and dried product had an arsenic content of 0.005 wt% or less, a cadmium content of 0.0005 wt% or less, a mercury content of 0.0002 wt% or less, a nickel content of 0.03 wt% or less, a chromium content of 0.05 wt% or less, and a lead content of 0.01 wt% or less.

[0141] [Table 7]

[0142] Figure 10 also shows the results of the elution test for 25 hazardous substances. Figure 10 also shows the standard values ​​for all items in Appendix 1 of the Prime Minister's Office Ordinance Prescribing the Judgment Criteria for Industrial Waste (Prime Minister's Office Ordinance No. 5 of 1973). As shown in Figure 10, it was confirmed that the values ​​for all 25 hazardous substances were below the standard values.

[0143] From the results shown in Table 7 and Figure 10, it is considered that the fermented and dried material (fermented and dried sludge) produced by the method shown in the above embodiment can be used as compost from the standpoint of the amount of residual harmful substances.

[0144] [Effect] In the above-mentioned method for producing a fermented and dried product, 100 parts by mass of methane fermentation residue (digested sludge) in which most of the easily decomposable organic matter has been consumed by methane fermentation is mixed with 20 to 30 parts by mass of meat and bone meal and / or waste clay and 10 to 30 parts by mass of fermented chicken manure as auxiliary raw materials, and aerobic fermentation treatment is carried out in a vertical sealed fermenter for 10 to 20 days to produce a fermented and dried product with a moisture content of 20% to 30%. By using the above-mentioned auxiliary raw materials, a fermented and dried product can be stably produced even when a raw material with a low content of organic matter that contributes to fermentation and drying, such as methane fermentation residue, is used.

[0145] In aerobic fermentation treatment, the amount of air sent to the vertical sealed fermentation tank is 0.1 Nm 3 / min / m 3 ~0.25Nm 3 / min / m 3 By setting the amount of air sent to the vertical sealed fermenter within the above range, the inside of the vertical sealed fermenter becomes suitable for fermenting and drying the raw material, and therefore, a fermented and dried product can be produced more stably.

[0146] Furthermore, by using the above-mentioned method for producing a fermented and dried product, a fermented and dried product can be obtained that is produced using, as a main raw material, methane fermentation residue (digested sludge) generated in a sewage treatment process in which most of the easily decomposable organic matter has been consumed by methane fermentation, and using, as secondary raw materials, 20 to 30 parts by mass of meat and bone meal and / or waste clay per 100 parts by mass of the methane fermentation residue, and 10 to 30 parts by mass of fermented chicken manure per 100 parts by mass of the methane fermentation residue, and that has a moisture content of 20 to 30%. This fermented and dried product has an effective calorific value of 1,500 kcal / kg-weight or more, a fuel ratio of 0.1 to 0.3, an arsenic content of 0.005 wt% or less, a cadmium content of 0.0005 wt% or less, a mercury content of 0.0002 wt% or less, a nickel content of 0.03 wt% or less, a chromium content of 0.05 wt% or less, and a lead content of 0.01 wt% or less. While this fermented and dried product uses methane fermentation residue as the main raw material, its moisture content, effective calorific value, and fuel ratio are within the above ranges, and the contents of arsenic, cadmium, mercury, nickel, chromium, and lead are below the above values. Therefore, it is suitable for use as an energy source, for example, as a heat source.

[0147] [Variations] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments and can be modified in various ways.

[0148] For example, the configurations of the fermentation drying system 1, the fermentation drying equipment 2, the equipment control unit 3, etc. described above are merely examples and can be changed as appropriate. Furthermore, the control content of the equipment control unit 3 may be changed as appropriate depending on the device configuration.

[0149] Furthermore, the equipment control unit 3 may perform a control that combines the above-described adjustment of the air flow rate with operation control of the fermenter using other sensor information and the like. [Explanation of symbols]

[0150] 1...fermentation drying system, 2...fermentation drying equipment, 3...equipment control unit, 21...fermenter, 24...air blower, 29a to 29g...sensors, 41...container, 45...air supply means, 46...exhaust means.

Claims

1. A method for producing a fermented and dried product, which uses a methane fermentation residue, obtained by consuming most of the easily decomposable organic matter generated in a sewage treatment process, as a main raw material, and 20 to 30 parts by mass of meat and bone meal and / or waste white clay per 100 parts by mass of the methane fermentation residue and 10 to 30 parts by mass of fermented chicken manure per 100 parts by mass of the methane fermentation residue as secondary raw materials, by aerobic fermentation treatment in a vertical sealed fermenter for 10 to 20 days to produce a fermented and dried product with a moisture content of 20% to 30%.

2. In the aerobic fermentation treatment, the amount of air sent to the vertical sealed fermenter is 0.1 Nm ３ / min / m ３ ~0.25 Nm ３ / min / m ３ The method for producing a fermented and dried product according to claim 1 .

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