Stirring device and stirring method

Abstract

To provide a stirrer and a stirring method capable of adequately stirring and mixing a stirring object having a high viscosity or a stirring object in which solids floating on a liquid surface are contained.SOLUTION: A stirrer 1 includes a stirring tank 11 which is laterally mounted with a lateral surface and has an approximately columnar whole shape, a rotation shaft 12 which is elongated in a center axis direction of a longitudinal direction in an internal part of the stirring tank 11 and rotatably pivotally-supported, and at least one stirring member 13 which is supported by the rotation shaft 12 and is rotated around a shaft core of the rotation shaft 12. Therein, the stirring member 13 has a support 13a whose one side end is connected to the rotation shaft 12 and the other end is elongated to a direction separated from the rotation shaft 12, and a stirring paddle 13b which is provided on the other side end of the support 13a and can scrape up a stirring object of solid, and the stirring paddle 13b has a stirring face which gets to parallel to an elongated direction of the rotation shaft 12, and an area of the stirring face falls in the range of 4 to 45% with respect to the maximum cross-section area of a cross-section which passes through a center shaft in the longitudinal direction of the stirring tank 11.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a stirring device and a stirring method, and more particularly, for example, to a stirring device and a stirring method that can be used for stirring and mixing raw materials for methane fermentation and water in the process of wet methane fermentation.

Background Art

[0002] Conventionally, in methane fermentation in which organic substances contained in livestock manure, sludge, food residues, etc. are decomposed into methane gas and carbon dioxide gas, it is carried out by utilizing the metabolic action of methane fermentation microorganisms (for example, acid-producing bacteria, acetic acid-producing bacteria, and methane-producing bacteria, etc.) under anaerobic conditions without oxygen. Methane fermentation is classified into wet methane fermentation and dry methane fermentation according to the solid concentration of the raw material to be fermented. Generally, wet methane fermentation targets raw materials with a solid content concentration in the range of 4% to 12% by mass based on the total mass, and dry methane fermentation targets raw materials with a solid content concentration in the range of 20% to 40% by mass based on the total mass. However, in dry methane fermentation, due to the high solid content concentration, there are many equipment troubles such as failures of the stirring device. Therefore, the popularity rate of wet methane fermentation is higher than that of dry methane fermentation.

[0003] The process of wet methane fermentation generally consists of pretreatment in a raw material receiving tank, fermentation treatment in a fermentation tank, desulfurization treatment, and gas storage. Here, the raw materials for methane fermentation often have a relatively high water content, for example, around 80% by mass based on the total mass. Therefore, in wet methane fermentation, it is essential to adjust the water content (pretreatment) of solid substances such as livestock manure, sludge, and food residues by adding water or the like in the pretreatment. Examples of the mixing method of the raw material and water in the pretreatment include a method using a vertical shaft stirrer (Patent Document 1) or an in-water mixer.

[0004] The vertical-axis stirrer described in Patent Document 1 has a rotatable shaft arranged at the center of a vertical cylindrical stirring tank from outside the tank. At the lower part of the rotating shaft, a flat-bottom paddle is attached with a slight gap from the bottom wall surface of the stirring tank, and a lattice blade composed of vertical and horizontal members is attached above the bottom paddle. However, in such a vertical-axis stirrer, even though it can mix the solids settled in the liquid with the liquid, it is difficult to sink the solids floating on the liquid surface into the liquid and stir and mix them. Therefore, it is difficult to achieve sufficient stirring with the vertical-axis stirrer described in Patent Document 1.

[0005] Examples of underwater mixers include those equipped with a motor that can be rotated at a constant speed, a stirring blade attached to the rotating shaft of the motor, and a guide ring provided so as to surround the outer periphery of the stirring blade. However, in such an underwater mixer, as in the case of the vertical-axis stirrer, although it can mix the solids settled in the water with the water, it is difficult to sink the solids floating on the water surface into the water and stir and mix them. In addition, the stirring blade may wear due to contact with the solid matter in the raw material, resulting in a decrease in stirring performance. Furthermore, when stirring a raw material with a viscosity in a high-viscosity range of, for example, tens of thousands of cP or more, it remains around the underwater mixer where the stirrable area is installed, and it is difficult to achieve sufficient stirring.

[0006] As a method for solving these problems, for example, a method using a horizontal shaft stirrer (Patent Document 2) can be mentioned. The horizontal shaft stirrer described in Patent Document 2 includes a cylindrical stirring tank having a material inlet and a sludge slurry outlet, a number of protrusions forming a concavo-convex surface provided on the inner wall surface of the stirring tank, and a plurality of stirring blade members rotatably attached inside the stirring tank. Further, the stirring blade member includes a support column implanted on the rotating shaft and a stirring blade provided at the tip of the support column. The tip of the stirring blade is configured as a sludge scraping surface that slidably contacts the tip of the protrusion, and the side surface of the stirring blade is configured as a sludge stirring surface. However, since the stirring surface of the stirring blade is provided inclined with respect to the center line of the rotating shaft, even when the stirring blade tries to catch the solid floating on the liquid surface and sink it into the liquid, the solid detaches from the stirring blade, and there are cases where the solid cannot be sufficiently sunk into the liquid and stirring and mixing cannot be performed.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] The present invention has been made in view of the above problems, and an object thereof is to provide a stirring device and a stirring method capable of sufficiently stirring and mixing a stirring object containing a high-viscosity stirring object or a solid floating on the liquid surface.

Means for Solving the Problems

[0009] The above-described conventional problems are solved by the invention described below. That is, in order to solve the above problems, the stirring device according to the present invention includes a stirring tank that is placed horizontally on its side and into which solid and liquid objects to be stirred are introduced, and the overall shape of the stirring tank is substantially cylindrical; a rotating shaft that extends in the central axis direction in the longitudinal direction inside the stirring tank and is rotatably supported; and at least one stirring member that is supported by the rotating shaft and rotates around the axis of the rotating shaft. The stirring member has a support column with one end connected to the rotating shaft and the other end extending in a direction away from the rotating shaft, and a stirring paddle provided at the other end of the support column and capable of scraping up the solid object to be stirred. The stirring paddle has a stirring surface parallel to the extending direction of the rotating shaft, and the area of the stirring surface ranges from 4% to 45% of the maximum cross-sectional area of the cross-section passing through the central axis in the longitudinal direction in the stirring tank.

[0010] According to the above configuration, as a device for stirring solid and liquid objects to be stirred, a stirring member that is rotatable around the axis of the rotating shaft is provided. Further, the stirring member has a support column with one end connected to the rotating shaft and the other end extending in a direction away from the rotating shaft, and a stirring paddle provided at the other end of the support column, and the stirring paddle can scrape up the solid object to be stirred. Furthermore, since the stirring paddle has a stirring surface parallel to the extending direction of the rotating shaft, for example, even when the solid object to be stirred floats on the liquid surface, the stirring paddle can catch the solid object to be stirred and sink it into the liquid for stirring and mixing. Also, by setting the area of the stirring surface of the stirring paddle in the range of 4% to 45% of the maximum cross-sectional area of the cross-section passing through the central axis in the longitudinal direction in the stirring tank, while suppressing the excessive stirring power for rotating the stirring member, even when the viscosity of the object to be stirred is high, it is possible to prevent the stirring from staying locally in the stirring tank and enable stirring over a wider range. As a result, the stirring efficiency can be improved.

[0011] In the above configuration, it is preferable that the maximum distance from the rotating shaft to the foremost end of the stirring paddle in the stirring member is in the range of 90% to 99.5% of the minimum distance from the rotating shaft to the inner wall surface of the stirring tank.

[0012] By setting the gap between the tip of the stirring paddle of the stirring member and the inner wall surface of the stirring tank within the above numerical range, it is possible to reduce the clamping of the solid object to be stirred between the stirring paddle and the inner wall surface of the stirring tank, and reduce or suppress the wear of the inner wall surface of the stirring paddle and the stirring tank. In addition, it is possible to prevent the stirring from staying locally in the stirring tank, enable stirring over a wider range, and improve the stirring efficiency.

[0013] In addition, in the above configuration, a plurality of the stirring members are provided at arbitrary positions on the rotating shaft in a mutually separated state, and the lengths of the columns of each stirring member and the directions extending from the rotating shaft are the same as or different from each other, and the areas and shapes of the stirring surfaces of the stirring paddles of each stirring member are preferably the same as or different from each other.

[0014] In addition, in the above configuration, a plurality of the stirring members are provided at the same position on the rotating shaft such that the respective columns extend in different directions, and the lengths of the columns of each stirring member are the same as or different from each other, and the areas and shapes of the stirring surfaces of the stirring paddles of each stirring member are preferably the same as or different from each other.

[0015] In the above configuration, it is preferable that the shape of the stirring surface of the stirring paddle is flat or annular frame-shaped.

[0016] By making the shape of the stirring surface of the stirring paddle flat, for example, when rotating the stirring member to stir, it is possible to surely capture the solid object to be stirred floating on the liquid surface by the stirring paddle, and improve the stirring efficiency. In addition, by making the shape of the stirring surface of the stirring paddle annular frame-shaped, it is possible to stir while suppressing an excessive stirring power even when the object to be stirred has a high viscosity.

[0017] Furthermore, in the above configuration, it is preferable that the inner wall surface of the stirring tank is a smooth surface.

[0018] For example, as in the aforementioned Patent Document 2, when the tip of the stirring blade is provided as a sludge scraping surface that slidably contacts the tip of the protrusion on the inner wall of the stirring tank, a solid stirring object accumulates on the protrusion, making it difficult to uniformly mix the solid stirring object with the liquid stirring object. Further, when the solid stirring object is a hard sludge mass with high mechanical strength, intense wear occurs at the tip of the stirring blade at the protrusion portion of the inner wall of the stirring tank, leading to a decrease in stirring performance. However, by making the inner wall surface of the stirring tank a smooth surface as in the above configuration, it is possible to prevent the solid stirring object from accumulating on the inner wall surface, and to better stir and mix the solid stirring object and the liquid stirring object. Further, even if the solid stirring object is hard and has high mechanical strength, wear at the tip of the stirring paddle can be suppressed or reduced, preventing a decrease in stirring performance.

[0019] In addition, in order to solve the above problems, the stirring method according to the present invention is a stirring method using the above stirring device, wherein the liquid level height of the liquid stirring object in a state where the solid and liquid stirring objects are charged into the stirring tank is in the range of 30% to 90% with respect to the height from the bottom surface to the top surface inside the stirring tank, and at least a part of the stirring paddle in the at least one stirring member protrudes from the liquid level of the liquid stirring object, and the stirring member is rotated around the axis of the rotating shaft to stir and mix the solid stirring object and the liquid stirring object.

[0020] In the above configuration, the liquid level height of the liquid stirring object with the solid and liquid stirring objects put into the stirring tank is set in the range of 30% to 90% with respect to the height from the bottom surface to the top surface inside the stirring tank. Also, for at least one of the stirring members, at least a part of the stirring paddle is rotated around the axis of the rotating shaft so as to protrude from the liquid level of the liquid stirring object. Further, the stirring surface of the stirring paddle is parallel to the extending direction of the rotating shaft. Thereby, in the above configuration, for example, even when the solid stirring object floats on the liquid level, when the stirring paddle protrudes from the liquid level, after scraping up the solid stirring object, it can be dropped onto the liquid level. Also, when the stirring paddle sinks into the liquid, the solid stirring object can be hooked and submerged in the liquid for stirring.

[0021] Also, in the above configuration, since the area of the stirring surface of the stirring paddle is set in the range of 4% to 45% with respect to the maximum cross-sectional area of the cross-section passing through the central axis in the longitudinal direction in the stirring tank, while suppressing the stirring power for rotating the stirring member from becoming excessive, even when the viscosity of the stirring object is high, it is possible to prevent the stirring from staying locally in the stirring tank and perform mixing.

[0022] In the above configuration, the rotation speed of the stirring member is -1 ~30 min -1 and preferably in this range.

[0023] By setting the rotation speed of the stirring member to 1 min -1 or more, even when the viscosity of the stirring object is high (for example, when the viscosity is tens of thousands of cP or more), good stirring by the stirring member can be maintained. On the other hand, by setting the rotation speed of the stirring member to 30 min -1 or less, it is possible to suppress the stirring power for rotating the stirring member from becoming excessive. Also, it is possible to reduce or prevent wear of the stirring paddle etc. due to contact with the solid stirring object.

Advantages of the Invention

[0024] According to the means described above, the present invention has the following effects. That is, according to the present invention, for example, even when the solid object to be stirred floats on the liquid surface, the stirring paddle of the stirring member can catch the solid object to be stirred and sink it into the liquid for stirring and mixing. Further, even when the viscosity of the object to be stirred is high, it is possible to prevent the stirring from being limited to local stirring in the stirring tank, enable stirring over a wider range, and improve the stirring efficiency.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0026] (Embodiment 1) [Stirring Device] The stirring device according to Embodiment 1 will be described below with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional side view showing the stirring device according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view taken along the line A-A' of FIG. 1. In addition, parts unnecessary for the description are omitted, and there are parts illustrated with magnification, reduction, etc. to facilitate the description.

[0027] As shown in Fig. 1, the stirring device 1 of the present embodiment is a so-called horizontally placed stirring device, and includes at least a stirring tank 11, a rotating shaft 12, a stirring member 13, a solid inlet 16, a liquid inlet 17, and a discharge port 18. The stirring device 1 of the present embodiment can be suitably used, for example, in wet methane fermentation for pretreatment such as stirring and mixing a solid stirring object such as livestock manure, sludge, food residues, etc. and a liquid stirring object such as water.

[0028] As shown in Figs. 1 and 2, the stirring tank 11 has an overall cylindrical shape and is placed horizontally on its side. The inner wall surface of the stirring tank 11 is preferably a smooth surface. Thereby, it is possible to prevent the solid stirring object from depositing as in the case where protrusions or the like are provided on the inner wall surface, and to make the stirring and mixing of the solid stirring object and the liquid stirring object better. In addition, it is possible to reduce the solid stirring object from being sandwiched between the inner wall surface of the stirring tank 11 and the stirring member 13. As a result, even when the solid stirring object is hard and has a large mechanical strength, it is possible to suppress or reduce the wear of the inner wall surface of the stirring tank 11 and the tip of the stirring member 13.

[0029] The rotating shaft 12 extends in the central axis direction in the longitudinal direction inside the stirring tank 11. The rotating shaft 12 penetrates the stirring tank 11 and is horizontally supported between a pair of bearings 14a and 14b provided outside the stirring tank. Further, a motor 15 is connected to one end of the rotating shaft 12. And the rotating shaft 12 can be rotated at an arbitrary rotational speed by the drive of the motor 15. Thereby, the stirring member 13 can be swiveled in the direction indicated by the arrow in Fig. 2. Incidentally, the rotating shaft 12 may be provided at a position deviated from the central axis in the longitudinal direction inside the stirring tank 11 as long as the stirring member 13 does not contact the inner wall surface.

[0030] The cross-sectional shape in the direction perpendicular to the extending direction (axial direction) of the rotating shaft 12 is substantially circular. The diameter of the cross-sectional shape in that case is not particularly limited and can be set as appropriate according to need.

[0031] The stirring member 13 has a function of stirring a solid object to be stirred and a liquid object to be stirred, and four stirring members 13 are provided on the rotating shaft 12. Each stirring member 13 is composed of a support column 13a and one stirring paddle 13b.

[0032] The support column 13a is rod-shaped. One end thereof is connected to the rotating shaft 12, and the other end extends in a direction away from the rotating shaft 12. Further, a stirring paddle 13b is provided at the other end. Thereby, each stirring member 13 can rotate around the axis of the rotating shaft 12 along with the rotation of the rotating shaft 12. Also, each support column 13a is connected to the rotating shaft 12 at positions spaced apart from each other at equal intervals and perpendicular to the rotating shaft 12. Furthermore, the direction in which each support column 13a extends away from the rotating shaft 12 is different by 180° from each other when viewed from the axial direction of the rotating shaft 12. The cross-sectional shape of the support column 13a (the cross-sectional shape in the direction perpendicular to the axial direction of the support column 13a) is substantially circular. However, the present invention is not limited to this cross-sectional shape. The cross-sectional shape of the support column 13a may be, for example, rectangular.

[0033] The stirring paddle 13b is a flat plate having an overall rectangular shape and is connected to the support column 13a at the central portion of the stirring paddle 13b. Since the stirring paddle 13b is a flat plate having a rectangular shape, the stirring surface of the stirring paddle 13b is also rectangular. Also, the stirring paddle 13b is provided at the other end of the support column 13a such that its stirring surface is parallel to the axial direction (extending direction) of the rotating shaft 12 (see FIG. 2). By making the stirring surface parallel to the axial direction of the rotating shaft 12, for example, even if the solid object to be stirred floats on the liquid surface, the stirring paddle 13b can surely capture the solid object to be stirred and sink it into the liquid to enable effective stirring and mixing.

[0034] The area of the stirring surface is preferably 4% to 45% of the maximum cross-sectional area of the cross-section passing through the longitudinal central axis in the stirring tank 11, more preferably 6% to 30%, and particularly preferably 12% to 15%. By setting the area of the stirring surface to 4% or more, it is possible to prevent the stirring from staying locally in the stirring tank 11 and maintain good stirring. On the other hand, by setting the area of the stirring surface to 45% or less, it is possible to suppress an excessive stirring power for rotating the stirring member 13. That is, by setting the area of the stirring surface within the above numerical range, the stirring efficiency can be improved.

[0035] The thickness of the stirring paddle 13b is not particularly limited as long as the mechanical strength is maintained to the extent that the stirring paddle 13b can be prevented from deforming during stirring, depending on the material of the stirring paddle 13b. Usually, it is in the range of 3 mm to 20 mm, preferably 6 mm to 16 mm, and more preferably 9 mm to 12 mm.

[0036] The maximum distance from the rotating shaft 12 to the foremost end of the stirring paddle 13b is preferably 90% to 99.5% of the minimum distance from the rotating shaft 12 to the inner wall surface of the stirring tank 11, more preferably 92.5% to 98%, and particularly preferably 95% to 96%. By setting the maximum distance from the rotating shaft 12 to the foremost end of the stirring paddle 13b to 99.5% or less of the minimum distance from the rotating shaft 12 to the inner wall surface of the stirring tank 11, it is possible to reduce the entrapment of the solid object to be stirred between the stirring paddle 13b and the inner wall surface of the stirring tank 11. As a result, for example, even if the solid object to be stirred has a large mechanical strength and is hard, it is possible to stir while suppressing the wear of the stirring paddle 13b and the inner wall surface of the stirring tank 11. On the other hand, by setting the maximum distance from the rotating shaft 12 to the foremost end of the stirring paddle 13b to 90% or more of the minimum distance from the rotating shaft 12 to the inner wall surface of the stirring tank 11, it is possible to prevent the stirring from staying locally in the stirring tank 11 and enable stirring over a wider range. As a result, the stirring efficiency can be improved.

[0037] The solid inlet 16 is for introducing the solid object to be stirred into the inside of the stirring tank 11, and is provided at an arbitrary position on the top surface of the stirring tank 11.

[0038] The liquid inlet 17 is for introducing the liquid object to be stirred into the inside of the stirring tank 11, and is provided at an arbitrary position on the top surface of the stirring tank 11.

[0039] The discharge port 18 is for taking out the stirred mixture in which the solid object to be stirred and the liquid object to be stirred are mixed by stirring, and is provided at an arbitrary position on the bottom surface of the stirring tank 11.

[0040] In addition, in this embodiment, the case where four stirring members 13 are provided is described as an example, but the present invention is not limited to this aspect. For example, the number of stirring members 13 may be one or more as required.

[0041] Also, in this embodiment, the aspect in which the inlets for introducing the solid object to be stirred and the liquid object to be stirred are separated is described as an example, but the present invention is not limited to this. For example, an aspect in which one inlet is provided at an arbitrary position on the top surface so that the solid object to be stirred and the liquid object to be stirred can be introduced simultaneously may also be possible.

[0042] [Stirring Method] Next, a method for stirring an object to be stirred using the stirring device 1 according to this embodiment will be described below with reference to FIG. 2.

[0043] First, the drive of the motor 15 rotates the rotating shaft 12, thereby rotating the stirring member 13 around the axis of the rotating shaft 12. Next, the liquid object to be stirred is introduced into the inside of the stirring tank 11 from the liquid inlet 17. Further, the solid object to be stirred is also introduced from the solid inlet 16, and the liquid and solid objects to be stirred are stirred. Note that the introduction of the solid object to be stirred may be performed at once or sequentially multiple times.

[0044] After charging the liquid and solid objects to be stirred, the liquid level height of the liquid object to be stirred in the stirring tank 11 (i.e., the height from the bottom inside the stirring tank 11 to the liquid level of the liquid object to be stirred) is in the range of 30% to 90% when the inner diameter of the stirring tank 11 is taken as 100%, preferably in the range of 45% to 80%, and more preferably in the range of 60% to 75%. By setting the liquid level height of the liquid object to be stirred within the above numerical range, when the stirring paddle 13b of the stirring member rotating around the axis of the rotating shaft 12 reaches the top, at least a part of the stirring paddle 13b can be exposed from the liquid level of the liquid object to be stirred. Thereby, for example, when the stirring paddle 13b is exposed from the liquid level, the solid floating on the liquid level can be scraped up by the stirring paddle 13b and then dropped. Also, when the stirring paddle 13b sinks into the liquid, the solid floating on the liquid level can be hooked and sunk by the stirring paddle 13b. As a result, it becomes possible to effectively stir the solid object floating on the liquid level.

[0045] Note that the inner diameter of the stirring tank 11 means the dimension of only the stirring tank 11 and does not include the dimensions of the solid charging port 16, the liquid charging port 17, and the discharge port 18.

[0046] Also, the rotation speed of the stirring member 13 is preferably 1 min -1 ~30 min -1 and more preferably 1 min -1 ~20 min -1 and particularly preferably 1 min -1 ~10 min -1 By setting the rotation speed of the stirring member 13 to 1 min -1 or more, good stirring by the stirring member 13 can be maintained even when the viscosity of the object to be stirred is high (for example, when the viscosity is tens of thousands of cP or more). On the other hand, by setting the rotation speed of the stirring member 13 to 30 min -1 or less, it is possible to suppress an excessive load on the motor 15 that rotates the stirring member 13. Also, wear of the stirring paddle 13b and the like due to contact with the solid object to be stirred can be reduced or prevented.

[0047] The stirring surface of the stirring paddle 13b is parallel to the extending direction of the rotation axis. Therefore, the stirring member 13 performs stirring so that the stirring surface is perpendicular to the liquid surface of the object to be stirred. As a result, when the stirring paddle 13 emerges from the liquid surface, compared with the case where the stirring surface is not parallel to the extending direction of the rotation axis, the floating solid object to be stirred can be surely scraped up, and when the stirring paddle 13 sinks into the liquid, the solid object to be stirred can be hooked and sunk into the liquid. As a result, the stirring efficiency can be further improved.

[0048] Further, by extending the four stirring members 13 so that they are alternately different by 180° when viewed from the axial direction of the rotation axis 12, every time the rotation axis 12 rotates by 180°, the solid object to be stirred floating on the liquid surface can be stirred by the stirring paddle 13b. Thereby, the stirring efficiency can be improved.

[0049] The stirring time (the stirring time after the liquid and the solid objects to be stirred are charged) is not particularly limited and can be appropriately set according to the types of the liquid and the solid objects to be stirred and the like.

[0050] In addition, in the present embodiment, the case where the liquid object to be stirred and the solid object to be stirred are sequentially charged into the stirring tank 11 with the stirring member 13 rotated has been described. However, the present invention is not limited to this. For example, after the liquid object to be stirred and the solid object to be stirred are charged in advance, the stirring member 13 may be rotated to perform stirring.

[0051] (Embodiment 2) The second embodiment according to the present invention will be described below with reference to FIG. 3. FIG. 3 is a cross-sectional side view showing the stirring device according to the second embodiment. In addition, components having the same functions as those of the stirring device 1 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

[0052] [Stirring device] The stirring device 2 according to the second embodiment is different from the stirring device 1 of the first embodiment in that, in addition to the stirring member 13, it further includes four other stirring members 19.

[0053] The stirring member 19 is composed of a support column 19a and a stirring paddle 19b. The support column 19a is rod-shaped, and one end thereof is connected at a position where the stirring member 13 is connected to the rotating shaft 12. Also, the other end extends in a direction opposite to the direction in which the support column 13a moves away from the rotating shaft 12, that is, in a direction 180° different when viewed from the axial direction of the rotating shaft 12.

[0054] The cross-sectional shape of the support column 19a (the cross-sectional shape in a direction perpendicular to the extending direction of the support column 19a) is substantially circular. However, the present invention is not limited to this cross-sectional shape. For example, it may be rectangular or the like.

[0055] The overall shape of the stirring paddle 19b is rectangular, and it is connected to the support column 19a at the central portion of the stirring paddle 19b. Note that since the stirring paddle 19b is a flat plate with an overall rectangular shape, the stirring surface of the stirring paddle 19b is also rectangular. Also, the stirring paddle 19b is provided at the other end of the support column 19a such that its stirring surface is parallel to the axial direction (extending direction) of the rotating shaft 12. By making the stirring surface parallel to the axial direction of the rotating shaft 12, for example, even if the solid object to be stirred floats on the liquid surface, the stirring paddle 19b can surely capture the solid object to be stirred and sink it into the liquid for effective stirring and mixing.

[0056] The length of the support column 19a of the stirring member 19 is configured to be shorter than that of the support column 13a of the stirring member 13. Also, the area of the stirring paddle 19b of the stirring member 19 is configured to be smaller than that of the stirring paddle 13b of the stirring member 13. Thereby, it is possible to avoid the stirring paddle 19b of the stirring member 19 from contacting the stirring paddle 13b of the stirring member 13. In the present embodiment, by adopting such a configuration, in the stirring member 13 with a relatively long support column 13a, the object to be stirred is stirred in a range farther from the rotating shaft 12, while in the stirring member 19 with a relatively short support column 19a, the object to be stirred near the rotating shaft 12 can be stirred. Thereby, more efficient and uniform stirring throughout the stirring tank 11 becomes possible.

[0057] The area of the stirring surface is preferably 4% to 45% of the maximum cross-sectional area of the cross-section passing through the central axis in the longitudinal direction in the stirring tank 11, more preferably 6% to 30%, and even more preferably 12% to 15%, similar to the case of Embodiment 1. By setting the area of the stirring surface to 4% or more, it is possible to prevent the stirring from being locally stopped in the stirring tank 11 and enable stirring over a wider range. On the other hand, by setting the area of the stirring surface to 45% or less, it is possible to suppress an excessive stirring power for rotating the stirring member 13 and the stirring member 19. That is, by setting the area of the stirring surface within the above numerical range, it is possible to improve the stirring efficiency. Note that the area of the stirring surface in the present embodiment means the sum of the area of the stirring surface of the stirring paddle 13b and the area of the stirring surface of the stirring paddle 19b.

[0058] The gap between the tip end portion of the stirring paddle 19b and the inner wall surface of the stirring tank 11, that is, the maximum distance from the rotating shaft 12 to the tip end portion of the stirring paddle 19b, is not particularly limited as long as the stirring paddle 19b does not contact the stirring paddle 13b of the stirring member 13.

[0059] Note that in the present embodiment, the case where four stirring members 13 and four stirring members 19 are provided respectively has been described as an example, but the present invention is not limited to this aspect. The stirring members 13 and the stirring members 19 may be, for example, one or a plurality as required.

[0060] [Stirring method] The stirring method of the object to be stirred using the stirring device 2 according to the present embodiment can be performed in the same manner as the stirring method of the object to be stirred according to the above Embodiment 1. Therefore, the detailed description thereof will be omitted.

[0061] (Other matters) In the first and second embodiments described above, the present invention was described by taking typical examples of the position where the stirring member is provided on the rotating shaft, the length of the support column, the extending direction of the support column, the area of the stirring surface of the stirring paddle, and the shape of the stirring surface. However, the present invention is not limited to these embodiments. For example, when a plurality of stirring members are provided at arbitrary positions on the rotating shaft in a mutually separated state, the lengths of the support columns of each stirring member and the direction extending from the rotating shaft may be the same or different from each other. Further, the area of the stirring surface of the stirring paddle of each stirring member and the shape of the stirring paddle (stirring surface) may also be the same or different from each other.

[0062] Also, for example, when a plurality of stirring members are provided at the same position on the rotating shaft such that the respective support columns extend in different directions, the lengths of the support columns of each stirring member may be the same or different from each other. Further, the area of the stirring surface of the stirring paddle of each stirring member and the shape of the stirring paddle (stirring surface) may also be the same or different from each other.

[0063] In addition, when the support columns of each stirring member are extended from the rotating shaft in different directions, the angle formed by each support column when viewed from the axial direction of the rotating shaft is preferably in the range of 30° to 180°. By setting the angle to 30° or more, it is possible to reduce the local stirring by each stirring member in the stirring tank. As a result, the stirring efficiency can be improved.

[0064] Regarding the shape of the stirring paddle, in the first and second embodiments, the case where it is a rectangular flat plate was described as an example. However, the present invention is not limited to this aspect. For example, it may be a flat plate-shaped stirring paddle shown in FIGS. 4(a) to 4(f), or an annular frame-shaped stirring paddle shown in FIG. 4(g). FIGS. 4(a) to 4(g) are partial enlarged plan views showing modified examples of the stirring member.

[0065] The stirring member 21 shown in Fig. 4(a) includes a support column 21a and a plate-shaped stirring paddle 21b with a substantially rectangular planar shape. The stirring paddle 21b is connected to the support column 21a at its central portion. Further, R processing is performed on all the corners of the stirring paddle 21b, whereby wear due to contact with a solid object to be stirred can be reduced or prevented.

[0066] The stirring member 22 shown in Fig. 4(b) includes a support column 22a and a plate-shaped stirring paddle 22b with a substantially rectangular planar shape with some corners cut out. The stirring paddle 22b is connected to the support column 22a at its central portion. The cutout has a structure in which a cutout portion 22c is provided at the corner of the end opposite to the end to which the support column 22a is connected. By providing the cutout portion 22c at the said corner, wear due to contact with a solid object to be stirred can be reduced or prevented. Further, reduction of the stirring power for rotating the stirring member 22 can also be achieved.

[0067] The stirring member 23 shown in Fig. 4(c) includes a support column 23a and a plate-shaped stirring paddle 23b with a substantially circular planar shape. Further, the stirring member 24 shown in Fig. 4(d) includes a support column 24a and a plate-shaped stirring paddle 24b with a substantially elliptical planar shape. Even if the planar shapes of these stirring paddles 23b and 24b are substantially circular or substantially elliptical, wear due to contact with a solid object to be stirred can be reduced or prevented. Further, reduction of the stirring power for rotating the stirring members 23 and 24 can also be achieved.

[0068] The stirring member 25 shown in Fig. 4(e) includes a support column 25a, a first stirring paddle 25b and a second stirring paddle 25c which are plate-shaped and have a rectangular planar shape. The first stirring paddle 25b is longer than the second stirring paddle 25c. The first stirring paddle 25b and the second stirring paddle 25c are each connected to the support column 25a at the central part. Also, the first stirring paddle 25b and the second stirring paddle 25c are separated from each other at an arbitrary distance. With such a structure of the stirring member 25, even when the viscosity of the liquid stirring object is high, it is possible to suppress the excessive stirring power for rotating the stirring member 25. Also, it is possible to easily catch the solid stirring object floating on the liquid surface, and the stirring efficiency can be improved.

[0069] The stirring member 26 shown in Fig. 4(f) includes a support column 26a and two plate-shaped stirring paddles 26b which have a rectangular planar shape. Both of the two stirring paddles 26b are connected to the support column 26a at the central part. Also, the two stirring paddles 26b are separated from each other at an arbitrary distance. Even with such a structure of the stirring member 26, similar to the case of the stirring member 25, it is possible to suppress the excessive stirring power for rotating the stirring member 26, and also, by easily catching the solid stirring object floating on the liquid surface, the stirring efficiency can be improved.

[0070] The stirring member 27 shown in Fig. 4(g) includes a support column 27a and a stirring paddle 27b in the shape of an annular frame with a rectangular planar shape. The stirring paddle 27b is connected to the support column 27a at the central part. By providing an opening 27c at the center of the stirring paddle 27b, the resistance received by the stirring paddle 27b during stirring can be reduced. Thereby, even when the viscosity of the liquid stirring object is high, it is possible to suppress the excessive stirring power for rotating the stirring member 27. Also, it is possible to easily catch the solid stirring object floating on the liquid surface, and the stirring efficiency can be improved.

[0071] Note that the area and thickness of the stirring surfaces of the stirring paddles 21 to 27 are as detailed in Embodiment 1.

[0072] In the first and second embodiments, the stirring tank is described by taking a cylindrical one as an example. However, the stirring tank of the present invention is not particularly limited as long as it is columnar. For example, the present invention may include a stirring tank 31 as shown in FIG. 5. FIG. 5 is a cross-sectional view showing a stirring device according to another embodiment. The stirring tank 31 has a cross-section perpendicular to the central axis direction in the longitudinal direction that is semi-circular below the rotation axis 12 and rectangular above the rotation axis 12.

[0073] The present invention may also include a stirring tank 32 and a solid inlet 33 as shown in FIG. 6. FIG. 6 is a cross-sectional view showing a stirring device according to another embodiment. The stirring tank 32 has a cross-section perpendicular to the central axis direction in the longitudinal direction that is substantially arc-shaped except for the top surface portion. The solid inlet 33 is for introducing a solid object to be stirred into the stirring tank 32 and is provided on the top surface portion of the stirring tank 32.

[0074] In addition, when stirring a solid and a liquid object to be stirred using the stirring tank 31 or the stirring tank 32, the liquid level height of the liquid object to be stirred in the stirring tank 31 or the stirring tank 32 (the liquid level height in the state where the solid and liquid objects to be stirred are introduced into the stirring tank 31 or the stirring tank 32) is, as in the case of the first embodiment, in the range of 30% to 90%, preferably 45% to 80%, more preferably 60% to 75% with respect to the height from the bottom surface to the top surface inside the stirring tank 31 or the stirring tank 32. Here, the height from the bottom surface to the top surface in the case of the stirring tank 32 means the height to the inner wall surface of the stirring tank 32 excluding the solid inlet 33.

[0075] In addition, the present invention is also applicable to a stirring tank in the shape of a prism. When the stirring tank is in the shape of a prism, specifically, a quadrangular prism shape, a pentagonal prism shape, a hexagonal prism shape, etc. can be mentioned. However, when the stirring tank is in the shape of a triangular prism, since the solid object to be stirred may get stuck at the corner formed by the bottom surface portion and the side surface portion of the stirring tank, it is not preferable.

Examples

[0076] (Example 1) In this embodiment, the stirring device 1 shown in FIGS. 1 and 2 was used to stir coffee grounds, tea grounds, and water as the objects to be stirred. The specifications of the stirring device 1 were as follows. Diameter of the stirring tank 11: 600 mm Capacity of the stirring tank 11: 200 L Size of the stirring paddle 13: 65 mm in length, 300 mm in width, and 9 mm in thickness Total area of the stirring surface of the stirring paddle 13b: 78000 mm 2 Ratio of the area of the stirring surface of the stirring paddle 13b to the maximum cross-sectional area of the cross-section passing through the central axis in the longitudinal direction in the stirring tank 11: 15% Ratio of the maximum distance from the rotating shaft 12 to the foremost end of the stirring paddle 13b to the minimum distance from the rotating shaft 12 to the inner wall surface of the stirring tank 11: 95% Gap between the stirring paddle 13b and the inner wall surface of the stirring tank 11: 15 mm

[0077] First, the motor 15 of the stirring device 1 was driven to rotate the rotating shaft 12, thereby rotating the stirring member 13 around the axis of the rotating shaft 12. Subsequently, water was introduced into the stirring tank 11 through the liquid inlet 17. After the water was introduced, coffee grounds (moisture content 66% by mass, solid content 34% by mass) and tea grounds (moisture content 76% by mass, solid content 24% by mass) were introduced into the stirring tank 11 at once through the solid inlet 16.

[0078] Note that the rotation speed of the stirring member 13 was set to be 5 min -1 after the coffee grounds, tea grounds, and water were introduced. Also, the input amount of coffee grounds was 29.4 kg, the input amount of tea grounds was 41.7 kg, and the input amount of water was 128.9 kg. The liquid level height of the object to be stirred after the coffee grounds, tea grounds, and water were introduced was 72% with respect to the diameter of the stirring tank 11 (the height from the bottom surface to the top surface inside the stirring tank 11). Also, the mass ratio of the solid object to be stirred composed of the solid components of the coffee grounds and tea grounds was 10% by mass with respect to the total mass of the object to be stirred.

[0079] Coffee grounds and tea grounds were added, and after 30 minutes of stirring, the degree of stirring of the coffee grounds, tea grounds, and water was visually confirmed. As a result, the stirring state after 30 minutes was good, and the coffee grounds, tea grounds, and water were uniformly mixed.

[0080] Also, the viscosity of the object to be stirred after 30 minutes was measured. The viscosity of the object to be stirred was measured using a Brookfield Digital Viscometer LVDV-I+ (model number, manufactured by Eiko Seiki Co., Ltd.). As a result, the viscosity of the object to be stirred was 105,000 cP. Thereby, it was confirmed that even when the object to be stirred was in a high-viscosity state, the stirring by the stirring device 1 could be performed well.

[0081] (Example 2) In this example, the input amount of coffee grounds (moisture content 66% by mass, solid content rate 34% by mass) was 38.2 kg, the input amount of tea grounds (moisture content 76% by mass, solid content rate 24% by mass) was 54.2 kg, and the input amount of water was 107.6 kg. The mass ratio of the solid object to be stirred composed of the solid content of the coffee grounds and tea grounds was changed to 13% by mass based on the total mass of the object to be stirred. Otherwise, in the same manner as in Example 1, the coffee grounds, tea grounds, and water were stirred.

[0082] As a result, after adding the coffee grounds and tea grounds and 30 minutes of stirring, the stirring state of the coffee grounds, tea grounds, and water was good, and it was visually confirmed that these objects to be stirred were uniformly mixed. Also, the viscosity of the object to be stirred after 30 minutes was 235,000 cP, and it was confirmed that even when the object to be stirred was in an extremely high-viscosity state, the stirring by the stirring device 1 could be performed well.

[0083] (Example 3) In this example, the input amount of coffee grounds (moisture content 66% by mass, solid content rate 34% by mass) was 88.2 kg, the input amount of water was 111.8 kg, and the mass ratio of the solid object to be stirred composed of the solid content of the coffee grounds was changed to 15% by mass based on the total mass of the object to be stirred. Otherwise, in the same manner as in Example 1, the coffee grounds and water were stirred.

[0084] As a result, after the coffee grounds were put in and stirring had elapsed for 30 minutes, the stirring state of the coffee grounds and water was good, and it was visually confirmed that these objects to be stirred were uniformly mixed. Further, the viscosity of the object to be stirred after 30 minutes had elapsed was 1,776 cP, and it was confirmed that stirring with the stirring device 1 could be performed well.

[0085] (Example 4) In this example, the input amount of coffee grounds (moisture content 66% by mass, solid content rate 34% by mass) was 117.6 kg, and the input amount of water was 82.4 kg. The mass ratio of the solid object to be stirred composed of the solid content of the coffee grounds was changed to 20% by mass with respect to the total mass of the object to be stirred. Other than that, stirring of the coffee grounds and water was performed in the same manner as in Example 1.

[0086] As a result, after the coffee grounds were put in and stirring had elapsed for 30 minutes, the stirring state of the coffee grounds and water was good, and it was visually confirmed that these objects to be stirred were uniformly mixed. Further, the viscosity of the object to be stirred after 30 minutes had elapsed was 82,000 c P, and it was confirmed that stirring with the stirring device 1 could be performed well even when the object to be stirred was in a high-viscosity state.

[0087] [Table 1]

[0088] [Table 2] [Explanation of Signs]

[0089] 1, 2 Stirring device 11, 31, 32 Stirring tank 12 Rotating shaft 13, 19, 21 - 27 Stirring member 13a, 19a, 21a - 27a Support column 13b, 19b, 21b - 24b, 26b, 27b Stirring paddle 25b First stirring paddle 25c Second stirring paddle 15 Motor 16 Solid inlet 17 Liquid inlet 18 Outlet 22c Notch 27c Opening 33 Solid inlet

Claims

**Claim 1**: A stirring device used for mixing solids and liquids in the pretreatment of a fermentation process carried out in a wet methane fermentation process, comprising: A stirring tank having a substantially cylindrical overall shape, which is placed horizontally on its side and into which the objects to be stirred, i.e., the solids and the liquids, are introduced; A rotating shaft extending in the longitudinal central axis direction inside the stirring tank and rotatably supported; At least one stirring member supported by the rotating shaft and rotating around the axis of the rotating shaft; The stirring member has a support column with one end connected to the rotating shaft and the other end extending in a direction away from the rotating shaft, and a stirring paddle provided at the other end of the support column and capable of scraping up the solid object to be stirred; The stirring paddle has a stirring surface parallel to the extending direction of the rotating shaft, and the perpendicular line of the stirring surface is perpendicular to the support column of the stirring member; A stirring device in which the area of the stirring surface is in the range of 4% to 45% of the maximum cross-sectional area of the cross-section passing through the longitudinal central axis in the stirring tank. **Claim 2** The stirring device according to claim 1, wherein the maximum distance from the rotating shaft to the foremost end of the stirring paddle in the stirring member is in the range of 90% to 99.5% of the minimum distance from the rotating shaft to the inner wall surface of the stirring tank. **Claim 3** A plurality of the stirring members are provided at arbitrary positions on the rotating shaft in a mutually separated state; The lengths of the support columns of each stirring member and the directions in which they extend from the rotating shaft are the same or different from each other; The stirring device according to claim 1 or 2, wherein the areas and shapes of the stirring surfaces of the stirring paddles of each stirring member are the same or different from each other. **Claim 4** A plurality of the stirring members are provided at the same position on the rotating shaft such that the respective support columns extend in different directions; The lengths of the support columns of each stirring member are the same or different from each other; The stirring device according to any one of claims 1 to 3, wherein the areas and shapes of the stirring surfaces of the stirring paddles of each stirring member are the same or different from each other. **Claim 5** The stirring device according to any one of claims 1 to 4, wherein the shape of the stirring surface of the stirring paddle is a flat plate shape or an annular frame shape. **Claim 6** The stirring device according to any one of claims 1 to 5, wherein the inner wall surface of the stirring tank is a smooth surface. **Claim 7** A stirring method using the stirring device according to any one of claims 1 to 6, comprising: With the solid and liquid substances to be stirred placed in the stirring tank, the liquid level height of the liquid substance to be stirred is set within the range of 30% to 90% of the height from the bottom surface to the top surface inside the stirring tank. At least a part of the stirring paddles of the at least one stirring member is made to protrude from the liquid level of the liquid substance to be stirred, and the stirring member is rotated around the axis of the rotating shaft. A stirring method for stirring and mixing the solid substance to be stirred and the liquid substance to be stirred.

8. The rotational speed of the stirring member is 1 min －１ to 30 min －１ The stirring method according to claim 7, wherein the range is as follows.

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