Pellet production device and production method of pellet

Abstract

To provide a device for producing a pellet, the pellet comprising required mechanical durability and capable of being used as fuel.SOLUTION: There is provided a pellet production device which uses a raw material including coffee extraction residue, the production device comprises: multiple rollers which revolve around a drive main shaft, rotate around a roller shaft, are arranged in a circular state around the drive main shaft and have a prescribed width; a pellet production die which has a raw material pushing surface contacting the rollers; and a motor driving the rollers. The pellet production die comprises multiple open holes which penetrate in a direction orthogonal to the raw material pushing surface, and have a prescribed cross section S and a prescribed depth L. The rollers roll on the raw material pushing surface on the pellet production die at a prescribed rotation speed, press the raw material accumulated on the raw material pushing surface toward the raw material pushing surface and pushing the raw material into the open holes for molding a pellet. The open holes have a prescribed cross section of 7 mm2 or more and 50 mm2 or less, and have a prescribed depth of 30 mm or more and 100 mm or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention mainly relates to a pellet manufacturing apparatus and a method for manufacturing pellets, which use coffee extraction residues (coffee grounds) with a high moisture content after extraction as raw materials.

Background Art

[0002] In recent years, the consumption of coffee beverages has increased significantly as a favorite beverage, and accordingly, the consumption of coffee beans has also increased. Therefore, a large amount of coffee extraction residues (coffee extraction sludge obtained by extracting roasted and ground coffee beans with hot water for drinking coffee) is generated.

[0003] However, only a small part is effectively utilized, and most of them are currently discarded as general waste or industrial waste and incinerated.

[0004] Therefore, paying attention to such coffee extraction residues, a method for manufacturing fuel pellets using coffee extraction residues has been proposed (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Even the inventors of the present application considered manufacturing fuel pellets using coffee extraction residues and conducted intensive research in consideration of environmental concerns. Initially, an attempt was made to pelletize coffee extraction residues using a conventional pellet manufacturing apparatus, but unlike conventional biomass materials such as wood materials, pellets with sufficient durability values were not completed.

[0007] Therefore, after years of research, when attempting to produce pellets using coffee extraction residue, it was found that the cross-sectional area and depth of the holes in the die of the pellet manufacturing apparatus significantly affect the durability value. Furthermore, it was found that the durability of the pellets can be improved by controlling the rotational speed of the roller pressing the die and the temperature of the die, leading to the present invention.

[0008] On the other hand, from another perspective, when grinding coffee beans, the difference in the size of the ground powder has a significant impact on the taste and aroma of the coffee. Therefore, not all the powder will be exactly the same size, and there will be a mixture of small, medium-sized, and large-sized powders of various sizes.

[0009] When there are various sizes mixed, such as in the grinding particle size of coffee, by using the Rosin-Rammler distribution for analysis, the grinding condition of the coffee can be known in more detail and accurately. The Rosin-Rammler distribution is suitable for representing the distribution of sizes (how many of each size are included) when various sizes are mixed.

[0010]

Number

[0011] In the Rosin-Rammler distribution, the particle size characteristic number De refers to the particle size of the ground coffee particles such that 36.8% of the particles are larger than that size. It corresponds to the position one standard deviation minus the mean in a normal distribution and is an index commonly used statistically to represent the data distribution. The particle size characteristic number De indicates that 36.8% of the particles in the ground coffee are larger than that specific size. This allows us to determine how many particles are larger than that size and evaluate the grinding condition based on that size. Note that with a general sieve shaker and sieve, the particle size characteristic number De and the uniformity number n can be calculated.

[0012] When using pellets as fuel, the finer the particle size of the coffee extraction residue, the higher the durability. However, if the particle size is too fine, it is likely to form a bridge during transportation and is not desirable because dust is likely to fly. Since the particle size of the coffee extraction residue greatly affects the durability of the pellets, research has been repeatedly conducted on the particle size characteristic number De, which serves as a measure of particle size in the aforementioned Rosin-Rammler distribution, and the present invention has been completed.

[0013] The present invention provides an apparatus and a method for manufacturing pellets that can obtain the required durability and can be used as fuel.

Means for Solving the Problems

[0014] A pellet manufacturing apparatus according to one aspect of the present invention is a pellet manufacturing apparatus that manufactures pellets using a raw material containing coffee extraction residue, and includes a plurality of rollers having a predetermined width, arranged in a circular shape around the drive main shaft, rotating around the roller shaft while revolving around the drive main shaft, a die for pellet manufacturing having a raw material pressing surface that abuts against the rollers, and a motor that drives the rollers. The die for pellet manufacturing has a plurality of through holes with a predetermined cross-sectional area S and a predetermined depth L that penetrate in a direction perpendicular to the raw material pressing surface. The rollers roll on the raw material pressing surface of the die for pellet manufacturing at a predetermined rotational speed, and push the raw material accumulated on the raw material pressing surface into the through holes while pressing the rollers against the raw material pressing surface to form pellets. The through holes have a predetermined cross-sectional area of 7 mm 2 or more and 50 mm 2 or less, and the predetermined depth is 30 mm or more and 100 mm or less.

[0015] By using the manufacturing apparatus having this configuration, it is possible to manufacture pellets having a sufficient durability value even in the case of pellets using coffee extraction residue.

[0016] Further, this manufacturing apparatus is characterized in that the area S0 of the surface on which the roller rotates and passes at the raw material pressing surface, the cross-sectional area S of the through-hole, and the number k satisfy the following formula. (Formula) 0.15 < kS / S0 < 0.5

[0017] According to this configuration, by setting the cross-sectional area and the number of the through-holes within this range, that is, by setting the total area of the openings of the through-holes with respect to the roller passing area on the die, that is, the aperture ratio within this range, it becomes possible to manufacture pellets with higher durability. If the aperture ratio is too large, the range where the roller presses the raw material expands, so the force is dispersed and the durability of the formed pellets decreases. In addition, if the aperture ratio is too small, the pressing force increases, but the production quantity decreases.

[0018] Further, this manufacturing apparatus is characterized in that the cross-section of the through-hole is a circular cross-section, and the diameter of the circular cross-section is 3 mm or more and 8 mm or less. According to this configuration, cylindrical pellets with sufficient durability can be manufactured. Also, unlike angular pellets, since there are no corners, concentration of load hardly occurs and the durability against external force is also improved.

[0019] Further, it is desirable that the through-hole of this manufacturing apparatus has a countersink formed on the side of the raw material pressing surface that serves as the inlet portion of the raw material. According to this configuration, the countersink makes it easier for the raw material to be introduced into the through-hole, improving productivity. Also, since the countersink increases the opening area, the efficiency of pressing by the roller also increases.

[0020] Further, it is desirable that the through-hole of this manufacturing apparatus has a countersink formed on the side of the surface opposite to the raw material pressing surface that serves as the outlet portion of the raw material. According to this configuration, when the pellets formed from below the die are extruded, the separation from the die improves, and productivity is improved.

[0021] In addition, this manufacturing apparatus is characterized in that the rotational speed of the roller is 70 rpm or more and 120 rpm or less. According to this configuration, by pressing the die with the roller at a rotational speed within this range, it becomes possible to manufacture pellets with even higher durability. The higher the rotational speed of the roller, the more times the raw material is pressed and pushed into the through hole per unit time, so the durability of the pellet improves. However, if the speed is too high, the raw material cannot be firmly pressed, or the load on the motor increases.

[0022] In addition, this manufacturing apparatus further includes a cooling means using a liquid for cooling the die for pellet manufacturing. According to this configuration, by manufacturing the pellet while cooling the die for pellet manufacturing by the cooling means, it is possible to cool the die for pellet manufacturing whose temperature rises due to friction or the like and maintain it at a predetermined temperature. Thereby, it is possible to manufacture pellets with high durability.

[0023] Here, the cooling means using a liquid includes, for example, water cooling and oil cooling, and it is desirable to use water cooling means from the viewpoints of safety and cost. In addition to the above, there is also air cooling for the cooling means, but since the temperature of the die rises significantly during pellet manufacturing, it is desirable to cool the die by the cooling means using a liquid.

[0024] Moreover, as the water cooling means, for example, a water cooling jacket provided so as to cover the outer periphery, inner periphery, or lower surface of the die for pellet manufacturing and through which a liquid can pass, a configuration in which a pipe through which a liquid can pass is attached by winding around the die for pellet manufacturing, or a method of providing a passage through which a liquid can pass inside the die for pellet manufacturing can be considered.

[0025] In addition, this manufacturing apparatus further includes a guide plate that horizontally rotates around a driving main shaft and moves the raw material on the raw material pressing surface of the die for pellet manufacturing toward the driving main shaft side.

[0026] According to this configuration, when the raw material on the die is carried outward by the rotation of the roller or the like, the guide plate can guide the raw material toward the center side and guide it to the through hole for forming pellets, thereby improving productivity.

[0027] Further, this manufacturing apparatus is characterized in that the guide plate is inclined toward the traveling direction rather than the direction orthogonal to the traveling direction of the rotation.

[0028] According to this configuration, by making the guide plate have the above-described inclined shape, the raw material can be further guided toward the center side, thereby improving productivity.

[0029] Further, this manufacturing apparatus is characterized in that the guide plate is curved toward the traveling direction rather than the direction orthogonal to the traveling direction of the rotation.

[0030] According to this configuration, by making the guide plate have the above-described curved shape, the raw material can be surely guided toward the center side, and the productivity can be further improved.

[0031] According to this configuration, when the raw material on the die is carried outward by the rotation of the roller or the like, the guide plate can guide the raw material toward the center side and guide it to the through hole for forming pellets, thereby improving productivity.

[0032] Further, this manufacturing apparatus is characterized in that the lower end portion of the guide plate is close to the raw material pressing surface and has a notch in a portion passing through the region of the raw material pressing surface where the through hole is located. According to this configuration, due to the notch of the guide plate, the guide plate can guide the raw material to the region where the through hole is arranged.

[0033] In addition, this manufacturing apparatus includes a peripheral wall that surrounds the die for pellet manufacturing and the roller. According to this configuration, it is possible to prevent the raw material from scattering to the outside. Note that the peripheral wall that surrounds the die for pellet manufacturing and the roller includes a peripheral wall that surrounds a part of the die for pellet manufacturing and a part of the roller. Further, in order to prevent the raw material from scattering to the outside, it is sufficient that at least the upper and lower portions near the die surface of the die for pellet manufacturing are surrounded.

[0034] A method for manufacturing pellets according to one aspect of the present invention is a method for manufacturing pellets in which pellets are manufactured using a raw material containing coffee extraction residue by the pellet manufacturing apparatus according to any one of claims 1 to 11. The roller is rolled on the raw material pressing surface of the die for pellet manufacturing, and the roller presses the raw material accumulated on the raw material pressing surface against the raw material pressing surface while pushing the raw material into a plurality of through holes of the die for pellet manufacturing to form pellets. The raw material is characterized in that the particle size characteristic number De in the Rosin-Rammler distribution is 0.4 or more and less than 1.51.

[0035] Thereby, by setting the particle size of the raw material to a particle size characteristic number De in the Rosin-Rammler distribution of 0.4 or more and less than 1.51, it is possible to manufacture pellets having sufficient durability and usable as fuel. The reason for setting the above range is that the finer the particle size, the higher the durability, but on the other hand, if it is too fine, there is a high possibility that the through holes of the die will be clogged and the pellets cannot be extruded.

[0036] Further, in this method for manufacturing pellets, it is more preferable that the raw material has a particle size characteristic number De in the Rosin-Rammler distribution of 0.4 or more and 1.2 or less, and it is even more desirable that the particle size characteristic number De in the Rosin-Rammler distribution is 0.4 or more and less than 0.7. By doing so, the durability of the pellets can be further improved.

[0037] In addition, the method for manufacturing the pellet is characterized in that the water content of the raw material is 5% or more and less than 20%. Here, the water content is the target value after raw material adjustment. Thereby, sufficient durability of the manufactured pellet is ensured. The reason for setting the water content within the above range is that if it is less than 5%, the extruded raw material may not solidify or there is a risk of clogging the through-holes of the die, and if it is 20% or more, the extruded raw material may not solidify.

[0038] In addition, it is more desirable that the water content of the raw material is 5% or more and 14% or less in the method for manufacturing the pellet. This is because pellets with high durability can be manufactured by setting the water content within the above range.

[0039] In addition, the method for manufacturing the pellet is characterized in that the water content of the pellet is 4% or more and 12% or less. Thereby, sufficient durability of the manufactured pellet can be ensured, and since the risk of mold generation increases when the water content of the pellet exceeds 12%, this range is suitable. Also, it is more desirable that the water content of the pellet is 10% or less.

[0040] In addition, the method for manufacturing the pellet is characterized by including a step of fermenting the coffee extraction residue. According to this configuration, it is possible to increase the strength of the pellet to be formed by passing through the step of fermenting the coffee extraction residue. The method of fermentation is that the extracted coffee extraction residue is left for one day or several days to ferment. And after being fermented to a certain extent, the coffee extraction residue is dried to be used as a raw material. Note that water may be added to the dried coffee extraction residue for fermentation.

[0041] In addition, the method for manufacturing the pellet is characterized in that the raw material is coffee extraction residue or a mixture of coffee extraction residue and a woody material. From this configuration, the coffee extraction residue can be effectively utilized without being discarded, and pellets with sufficient durability can be manufactured.

[0042] Further, the method for manufacturing the pellets is characterized in that the die for manufacturing the pellets has a cooling means for cooling the die, and the pellets are manufactured while maintaining the die for manufacturing the pellets at a temperature of 80°C or lower by the cooling means.

[0043] As a result of the inventors' experimental research on pellet production, it was found that when the die temperature exceeds 80°C, there is no problem in the case of wood pellets, but when coffee extraction residue is used as the raw material, the oil content in the coffee becomes an inhibitory factor for binding and sufficient binding cannot be obtained, and there is also a risk that the raw material will clog the through-holes of the die. By manufacturing while maintaining the die at a temperature of 80°C or lower as in the above configuration, such risks can be suppressed.

[0044] Further, the method for manufacturing the pellets is characterized in that the die for manufacturing the pellets has a cooling means for cooling the die, and the pellets are manufactured while maintaining the die for manufacturing the pellets at a temperature of 60°C or lower by the cooling means.

[0045] Furthermore, by suppressing the temperature rise of the die by the cooling means and setting the temperature of the die to 60°C or lower, it is possible to manufacture pellets with even higher durability while suppressing the above risks. That is, by setting the temperature to 60°C or lower, the produced pellets will have high durability while suppressing the floating and clogging of the coffee oil content.

Effects of the Invention

[0046] The pellet manufacturing apparatus and method of the present invention can manufacture pellets with sufficient durability.

Brief Description of the Drawings

[0047]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0048] <1. Structure of Pellet Production Apparatus> Hereinafter, a pellet production apparatus according to an embodiment of the present invention will be described. FIG. 1 is a perspective view showing a pellet production apparatus according to an embodiment of the present invention (excluding the raw material hopper). FIG. 2 is a schematic view showing the configuration of the pellet production apparatus of the present embodiment. FIG. 3 is a figure showing a die for pellet production of the pellet production apparatus, (a) is a plan view, and (b) is a side view. FIG. 4 is a partially enlarged view of the pellet production apparatus, (a) is a partially enlarged view of the die for pellet production, and (b) is a partially enlarged view of the roller and the die for pellet production. FIG. 5 is a figure showing the relationship between a guide provided in the die for pellet production of the pellet production apparatus and the pellet forming holes. FIG. 6 is a cross-sectional view showing the water cooling means of the pellet production apparatus.

[0049] As shown in FIGS. 1 and 2, the pellet manufacturing apparatus 10 mainly includes a driving main shaft 1 that is rotationally driven, two rollers 2 that revolve around the driving main shaft 1 as a vertical axis while rotating about a roller shaft 2a, and a pellet manufacturing die 3 disposed below the rollers.

[0050] The driving main shaft 1 is rotationally driven by a motor (not shown). While the rollers 2 connected to both sides of the roller shaft 2a connected to the driving main shaft 1 rotate, they roll on the raw material pressing surface 3a of the pellet manufacturing die 3. Then, the raw material of the pellet is input from a raw material hopper 8 for inputting the raw material disposed above the driving main shaft onto the raw material pressing surface 3a. Due to the rotation of the rollers 2, the raw material accumulated on the raw material pressing surface 3a is pressed against the raw material pressing surface 3a and pushed into a plurality of pellet forming holes 3aa penetrating in the thickness direction of the pellet manufacturing die 3.

[0051] Then, the raw material that has passed through the pellet forming holes 3aa is extruded as an elongated cylindrical pellet from the lower surface of the pellet manufacturing die 3, and then cut to a predetermined length by a rotary cutter 7 attached to the lower surface of the pellet manufacturing die 3, and sequentially accommodated in a pellet accommodating portion 9B via a shooter 9A. Note that, instead of providing a cutter, a configuration can be adopted in which the extruded pellet breaks and falls due to its own weight. However, since pellets of a predetermined length can be formed by disposing a cutter, it is desirable to provide a cutter.

[0052] Further, the pellet manufacturing apparatus 10 is provided with a cover 4 having a peripheral wall of a predetermined height so as to surround the periphery of the rollers 2 and the pellet manufacturing die 3. This cover 4 prevents the scattering of the raw material.

[0053] As shown in FIGS. 3 and 4, the width of the rollers 2 is made larger than the width of an annular region S centered on the driving main shaft 1 where the pellet forming holes 3aa are formed. In particular, the outer portion is made wider than the conventional rollers so that the raw material is smoothly pushed onto the pellet forming holes 3aa.

[0054] Further, the roller 2 has a gear-like shape in which concave portions and convex portions are continuous, and is configured to scrape out the raw material in the concave portions and press the raw material in the convex portions. Also, since the concave portions and the convex portions are continuous, the roller 2 is configured to rotate smoothly without slipping on the raw material pressing surface 3a of the die 3 for pellet production.

[0055] The rotation speed of the roller 2 is such that the greater the number of revolutions, the greater the number of times the raw material is pushed in per unit time, so the durability of the formed pellets increases. In this embodiment, the rotation speed is set to 100 rpm. At this time, the motor is at 70 Hz. Note that the greater the rotation speed of the roller 2, the higher the durability of the formed pellets. However, increasing the rotation speed increases the load on the motor. Therefore, the rotation speed is preferably 70 rpm or more and 115 rpm or less. Within this range, pellets with sufficient durability can be produced, and the load on the motor can also be suppressed.

[0056] As shown in FIGS. 3 and 4, the die 3 for pellet production is configured in a substantially cylindrical shape with a circular plane. A plurality of pellet forming holes 3aa are arranged in an annular shape at the position where the roller 2 passes through. These pellet forming holes 3aa are through-holes with a circular cross-section, penetrate the die 3 for pellet production in the thickness direction, and are countersunk on the upper raw material pressing surface 3a side and the lower raw material discharging surface 3b side. This smoothly introduces the raw material into the pellet forming holes 3aa and smoothly separates it from the raw material discharging surface 3b.

[0057] Also, the pellet forming holes 3aa of this embodiment have a circular cross-section with a diameter of 5 mm, and the cross-sectional area is about 19.6 mm 2 2, and the depth including the countersink is 80 mm. Also, the number of pellet forming holes 3aa of this embodiment is 384, which are arranged in an annular region on the raw material pressing surface 3a of the die 3 for pellet production through which the roller 2 passes.

[0058] Note that the dimensions of the pellet forming holes 3aa are just an example. The diameter of the cross-section may be 4 mm, 6 mm, 7 mm, etc., and the depth may be 40 mm, 60 mm, 100 mm, etc. Also, the shape of the cross-section may be a rectangle, an ellipse, or other shapes other than circular.

[0059] Also, as shown in FIG. 5, on the raw material pushing surface 3a, there is provided a plate-shaped guide 5 that guides the raw material located on the outside toward the center side, that is, toward the side where the annular region (pellet forming holes 3aa) is located. The guide plate 5 is in the shape of a curved and elongated long plate, is attached to the driving main shaft 1, extends toward the outer periphery of the die 3 for pellet production, and is curved so as to move away in the direction of rotation progress with respect to the radial direction.

[0060] Also, the curved shape of this guide plate 5 is configured to curve and extend from the end on the driving main shaft side toward the outer periphery of the die 3 for pellet production, and extend a predetermined dimension in the direction of rotation progress along the outer periphery of the die 3 for pellet production (the tip side of the guide plate 5). And the guide plate 5 is erected so that the lower end of the long plate shape is close to the raw material pushing surface 3a, and a notch 5a is formed in the portion passing through the region with the pellet forming holes 3aa on the raw material pushing surface 3a.

[0061] By rotating this guide plate 5 together with the rotation of the roller 2, the raw material is guided so as to be brought closer to the region where the pellet forming holes 3aa are located. Without this guide plate 5, the raw material would be carried to the outside by centrifugal force. With the shape of this guide plate 5, the raw material can be surely carried to the region of the pellet forming holes 3aa, thereby improving the productivity of the pellets.

[0062] That is, (i) when the roller 2 passes over the region of the pellet forming holes 3aa, the raw material above the pellet forming holes 3aa becomes uneven, and (ii) the pushing force downward is different between the center side (inside) and the outer peripheral side (outside) of the roller 2. Therefore, it is difficult to use all the pellet forming holes 3aa completely evenly, but the productivity can be increased by using all the pellet forming holes 3aa as evenly as possible.

[0063] Note that although the guide 5 causes some difference in the production amount between the center side and the outer peripheral side, since all the pellet forming holes 3aa including the outer side can be used by the guide 5, it becomes possible to significantly improve the production amount.

[0064] In addition, since the outer peripheral side portion of the roller 2 moves a long distance when it makes one rotation, the force for pushing the raw material at the outer peripheral side portion is uniformly dispersed over a wide range. On the other hand, since the central side portion of the roller 2 moves only a short distance when it makes one rotation, the force for pushing the raw material at the central side portion is likely to concentrate in a narrow range. Since the force is more concentrated here, a difference in the pushing force occurs between the outer peripheral side portion of the roller 2 and the central side portion of the roller 2, but the influence can also be reduced.

[0065] Also, as shown in FIGS. 1, 2, and 6, a water-cooled jacket 6 for suppressing the temperature rise of the die is provided around the die 3 for pellet production. This water-cooled jacket 6 is composed of a jacket body 6A having a hollow annular shape with a space through which a liquid passes inside, and a water supply pipe 6B for supplying water to this extends downward, and a drain pipe 6C (not shown) for discharging water extends upward and is connected. Further, the water supply pipe 6B and the drain pipe 6C are connected to a radiator and a circulation pump (not shown), and the water supplied to the jacket body 6A is circulated.

[0066] This water-cooled jacket 6 adjusts the flow of cooling water so that the temperature of the die and the raw material does not rise during pellet forming and does not exceed a certain temperature. In the present embodiment, it is adjusted to keep the die temperature at 60°C or lower.

[0067] The reason for keeping the die temperature at 60°C or lower is that when the roller 2 rotates, the die temperature rises due to friction or the like when forming pellets with the die 3 for pellet production. If pellets are formed with the die temperature being high, the raw material becomes hot and the durability value of the formed pellets decreases. Therefore, by keeping the die temperature at 60°C or lower by the water-cooled jacket 6, the durability value of the formed pellets can be increased.

[0068] <2. Method for manufacturing pellets> When the drive main shaft 1 of the pellet manufacturing apparatus 10 configured in this way rotates, the roller 2 fixed to the drive main shaft 1 revolves around the drive main shaft 1 while rotating around the roller shaft, and rolls on the raw material pressing surface 3a of the die 3 for pellet manufacturing. Then, when the raw material is supplied through the raw material hopper 8, the raw material is put onto the raw material pressing surface 3a of the die 3 for pellet manufacturing from the raw material hopper 8.

[0069] At this time, the guide plate 5 attached to the drive main shaft 1 rotates together with the roller 2, so that the raw material is guided to approach the region where the pellet forming holes 3aa are located, and the raw material is guided to the region of the pellet forming holes 3aa.

[0070] Then, the rotating roller 2 scrapes up the accumulated raw material with the groove 2b formed on the outer peripheral surface, and pushes it into the pellet forming holes 3aa while pressing against the raw material pressing surface 3a. The raw material pushed into the pellet forming holes 3aa is formed into an elongated cylindrical rib shape in the pellet forming holes 3aa, and is pushed out from the raw material pressing surface b side.

[0071] Then, the pellet material connected in a rib shape is cut to an appropriate length by the rotary cutter 7 attached to the raw material pressing surface 3b side, passes through the shooter 9A, and is stored in the pellet storage part 9B.

[0072] Regarding the raw material, the recovered coffee extraction residue is fermented over one day to several days, then dried, and used as the raw material for pellet manufacturing. Note that it may be fermented after adding water to the dried coffee extraction residue. Also, the raw material may be only the coffee extraction residue, or it is also possible to use a raw material in which a binder such as wood chips or corn starch is mixed with the coffee extraction residue as the main raw material. The reason for fermenting the coffee extraction residue is that the strength of the formed pellets is improved compared to the raw material dried without going through the fermentation process.

[0073] <3. Conditions of the pellet manufacturing apparatus> In the pellet manufacturing apparatus 10 configured as described above, the durability of the pellets formed using coffee extraction residue as a raw material is important. This is because if the durability is low and the pellets are brittle, there is a risk that the pellets will break into pieces during transportation or handling and become unusable. Also, the durability of the pellets was measured by the method described later.

[0074] And in order to manufacture pellets with sufficient durability using coffee extraction residue, conditions such as the pellet forming holes 3aa of the manufacturing apparatus are important. Particularly important are the cross-sectional area and depth of the pellet forming holes 3aa.

[0075] As described above, the pellet forming holes 3aa of the present embodiment have a circular cross-section with a diameter of 5 mm, and a cross-sectional area of approximately 19.6 mm 2 and a depth of 80 mm including the countersink.

[0076] And when the diameter of the cross-section is less than 3 mm, in addition to the fact that the coffee extraction residue, which is the raw material, is difficult to enter, the compression due to the hole diameter is too strong and the pellets are difficult to come out of the clogged holes. Also, when the diameter of the cross-section is 8 mm or more, the compression is weak and the pellets become brittle. Also, when the depth of the hole is less than 30 mm, the distance that the coffee extraction residue, which is the raw material, passes through the hole is short, so the formed pellets become brittle. When it exceeds 100 mm, the compression of the hole is strong and the formed pellets are difficult to come out of the clogged holes. Therefore, the diameter of the cross-section is preferably 3 mm or more and 8 mm or less, and more preferably 4 mm or more and 7 mm or less.

[0077] Also, the number of pellet forming holes 3aa in the present embodiment is 384 arranged in the annular region through which the roller 2 passes. When the cross-sectional area S of the pellet forming holes 3aa, the number k, and the area S0 through which the roller 2 rotates and passes through the raw material pressing surface 3a are considered, the pellet forming holes 3aa are arranged so that 0.15 < kS / S0 < 0.5.

[0078] If this value is 0.5 or more, the force applied by the roller 2 will be dispersed, and the durability of the pellets will decrease. Also, if it is 0.15 or less, the number of formed pellets will be small, and productivity will decrease. In this embodiment, kS / S0 ≒ 19.7. In this case, the durability value of the pellets is 92.8%. Note that this numerical value is the numerical value of the mechanical durability of the pellets measured by the test described later.

[0079] Also, as shown in the following table, when the hole diameter of the pellet forming hole 3aa is changed to 7 mm, kS / S0 ≒ 38.6, and the durability of the pellets at that time is 74.8. Although 74.8 is a durability that can somehow be used, as described above, it is desirably 80% or more, more desirably 90% or more.

[0080]

Table 1

[0081] Also, the depth of the pellet forming hole 3aa, that is, the die 3 for pellet production, the durability of the formed pellets increases with increasing thickness, but it is not the case that the thicker the better. If it is too thick, the force to push down will be correspondingly required, and the compression will also become stronger, so there is a risk that the raw material will not clog the hole.

[0082] Note that the durability value of the formed pellets requires at least 70% or more in the durability test described later, desirably 80% or more, more desirably 90% or more. Also, in addition to the conditions of the manufacturing apparatus described above, the durability of the pellets is improved by, in addition to the rotation speed of the roller, the particle size, moisture content, temperature, etc. of the raw material. Hereinafter, the durability test and other preferable conditions will be described.

[0083] <4. Regarding the durability test> Subsequently, the relationship between the particle size (particle size characteristic number De) and the mechanical durability of the pellets was investigated. Here, the mechanical durability of the pellets indicates the resistance to breakage of the pellets and is defined by the mass ratio DU (%) of the portion that did not break after applying a certain amount of mechanical impact.

[0084] (Test method for mechanical durability) This test method is used to determine the pulverization resistance performance of wood pellets against mechanical impact force, and it is standardized in accordance with European Standard EN15210-1 for wood pellets. As a sieve, a metal sieve with a circular hole diameter (nominal mesh size) of 3.15 mm specified in JIS Z8801-2 was used, and as a scale, one that can measure up to 1 kg and can measure up to the 0.1 g digit was used.

[0085] (Measuring instruments) The structure and specifications of the durability tester are as shown in Figure 7. As shown in Figure 7(a), the rotating box 11 is made of smooth steel, aluminum or acrylic resin, and the protruding parts such as rivets and nails are made as small as possible and rounded at the corners, or have a structure without gaps so that fine powder does not leak. The dimensions are 300 (length) × 300 (width) × 125 (thickness) mm, and inside, buffer wings 11a (230 × 50 mm) are firmly attached in the diagonal direction, and a sample loading door 11b is provided at one location on the side.

[0086] In order to rotate the rotating box 11 at a speed of 50 rpm, as shown in Figure 7(b), a rotating shaft 13 is attached perpendicular to the wall at the center position of the 300 (length) × 300 (width) mm wall (side surface) with the measuring instrument 12 sandwiched. The durability tester is of a twin type with two rotating boxes 11, and two measurements can be made at a time.

[0087]

Table 2

[0088] From Table 2, it was found that the finer the particle size, the higher the mechanical durability. Note that although the mechanical durability increases as the particle size becomes finer, if it is too fine, it is likely to bridge during transportation, and dust is likely to fly. Also, to make the particle size finer, the production capacity of the crusher decreases and the price becomes higher. For these reasons, the particle size characteristic number De, which is a measure of the particle size in the Rosin-Rammler distribution, is desirably 0.60 - 0.65 (mm). Note that a coffee bean grinder was used as the crusher. Next, the relationship between the moisture content and the mechanical durability was investigated.

[0089]

Table 3

[0090] In Table 3, the test results for the cases of the moisture content target value (moisture target value) of the bio-based raw material being 11% and 15% showed that the durability was higher when the target value was 15% which was higher.

[0091] Also, the test results for the cases of the target values being 15%, 17%, and 19% showed that when comparing the case of 15% with the other cases, the durability increased for the cases of 17% and 19% where the target value was higher, but there was no difference between 17% and 19%.

[0092] Therefore, a target value of about 17% is considered good in terms of durability. However, if the compressing force becomes large, it may also affect the appropriate moisture content.

[0093] Also, considering only the durability, the above results are obtained. On the other hand, if there is a lot of moisture, the risk of mold growth increases. Considering the risk of mold, conversely, a lower moisture content is better. As a conclusion, considering these conditions, it was found that it is necessary to manufacture under the condition of a moisture content of 13% or less. Therefore, the moisture content of the bio-based raw material is desirably in the range of 9 - 13%.

[0094] On the one hand, it is desirable that the water content of the pellets is 10% or less. This is because if it is too low, they tend to become brittle. Also, if it exceeds 12%, the risk of mold growth increases, so it is desirable to set it at 10% or less to ensure a safety factor. To make it 10% or less, it is desirable that the water content of the raw material before molding is 13% or less.

[0095] Subsequently, the results of tests on the relationship between the addition of additives (binders), the filling amount (input amount) of bio-based raw materials, the rotation speed of the rollers, the presence or absence of cooling water, and mechanical durability are shown in Tables 4 to 7.

[0096] [Table 4]

[0097] Even when the proportion of the additive was increased, there was little effect on durability. Although adding itself is considered to have an impact, increasing the proportion did not have a significant effect. Coffee is different from the case of molding conventional wood pellets in that the particle shape is different due to being a powder, there are no binding components such as lignin, and heat is not applied during molding. It is considered that one of these differences is the factor.

[0098] As for the type of additive, starch-based corn starch had somewhat of an impact, and cellulose-based CMC and methocel had a greater impact than corn starch.

[0099] The difference in the presence or absence of the additive tends to become smaller as the mechanical durability increases. When the durability exceeds 80%, data showing that the durability increases by about 3% at most, and about 1 - 2% around 90% were obtained by adding the additive, but there are demerits such as an increase in cost and an increase in the risk of mold generation.

[0100] Therefore, although there is a merit that the durability increases when there is an additive, considering the demerits, it is considered that the additive may not be necessary.

[0101] Considering cost, mold risk, and the fact that it can be used for combustion without additives, there are no problems without additives. However, depending on the application, if it is necessary to improve durability, it is desirable to have additives.

[0102]

Table 5

[0103] A lower input amount (filling amount in kg / h) improves durability. This is thought to be because the raw material is held in the die for a longer time. As a result, durability increases as the production volume decreases, but it reaches a saturation point at some point, and it is necessary to consider productivity. Therefore, it is desirable to ensure a minimum filling amount of about 100 kg / h of the bio raw material.

[0104]

Table 6

[0105] Also, the higher the roller rotation speed (number of rotations), the higher the durability. This is because, even if the amount of biofuel pushed in per unit time is the same, the number of pushes increases. 60 Hz is the normal rotation speed, and considering the load on the motor, it is considered that the load becomes too large when exceeding 80 Hz. Therefore, operation at about 70 Hz is practical, and the rotation speed at this time is 100 rpm.

[0106] (Presence or absence of cooling water) Also, the effect of cooling by the water-cooled jacket 6 provided in the pellet manufacturing apparatus 10 was verified. This test measured the mechanical durability when the temperature of the pellet and the die was high and when it was not (pellet temperature 90°C or lower, die temperature 60°C or higher). Note that the method of raising these temperatures was to overfeed the bran, forcibly raise the temperature by friction, and measure the temperature of the pellet using a thermometer that can measure the surface temperature. The results are as shown in Table 7.

[0107]

Table 7

[0108] From these results, it was found that, in the case of pellets using coffee extraction residue, unlike wood pellets, the durability decreases as the temperature increases. In the case of wood pellets, lignin, which has the property of a thermoplastic resin, is included, and it becomes soft when heated and hard when cooled. In short, in the case of wood pellets, they solidify when molded at a high temperature, but since coffee does not contain lignin, it is considered that the binding relies on the forces of hydrogen bonds and intermolecular bonds. Since the oil content in coffee floats on the surface of the biomass raw material as the temperature increases, the oil content contained in coffee becomes an inhibitory factor for binding, and it is considered that the durability decreases by increasing the temperature.

[0109] Therefore, it was found that in order to form pellets using coffee extraction residue, it is important to form the die at a low temperature (60°C or lower). Therefore, it is desirable to use the water-cooled jacket 6 provided in the pellet manufacturing apparatus 10 to set the die temperature to 60°C or lower.

[0110] <5. Other Embodiments> As described above, the embodiments of the present invention have been described with reference to the drawings, but various additions, changes, or deletions are possible without departing from the spirit of the present invention.

[0111] ·In the above embodiment, coffee extraction residue is used as the raw material, but it is also possible to use a mixture of such coffee extraction residue and other biomass materials.

[0112] ·The groove shape of the roller can be not only a straight groove parallel to the axis, but also an inclined groove inclined with respect to the axis, a V-shaped groove, or a dimple-shaped groove.

[0113] · In addition to the above-described curved shape, the shape of the guide plate can also be configured to be inclined in the advancing direction rather than in the direction orthogonal to the advancing direction of rotation (see Fig. 8). Although the effect may be lower than that of the curved shape, a certain effect can be expected for drawing in the raw material.

[0114] · Further, in the above embodiment, the water-cooling jacket 6 is configured to cover the outer peripheral side of the die 3 for pellet production. However, the present invention is not limited to this. For example, a configuration in which a water-cooling jacket is attached to the inner peripheral side, a configuration in which water-cooling jackets are attached to both the outer and inner peripheries, a configuration in which a water-cooling jacket is attached to the lower surface of the die for pellet production, etc. can also be adopted. By doing so, for example, when the diameter of the die for pellet production is large, when it is difficult to cool the central side only with the water-cooling jacket on the outer peripheral side or there is a possibility of temperature unevenness, this can be eliminated.

Explanation of Reference Numerals

[0115] 1 Driving main shaft 2 Roller 2a Roller shaft 2b Groove 3 Die for pellet production 3a Raw material pressing surface 3aa Pellet forming hole 3b Raw material extrusion surface 4 Cover 5 Guide plate 5a Notch 6 Water-cooling jacket 6A Jacket body 6B Water supply pipe 6C Drain pipe 7 Rotary cutter 8 Raw material hopper 9A Shooter 9B Pellet storage section

Claims

1. A pellet manufacturing apparatus for manufacturing pellets using a raw material containing coffee extraction residue, a plurality of rollers having a predetermined width, arranged in a circular shape around the drive main shaft, rotating around the roller shaft while revolving around the drive main shaft, a die for pellet manufacturing having a raw material pressing surface that contacts the rollers, a motor for driving the rollers, and the die for pellet manufacturing has a plurality of through holes having a predetermined cross-sectional area S and a predetermined depth L that penetrate in a direction perpendicular to the raw material pressing surface, the rollers roll on the raw material pressing surface of the die for pellet manufacturing at a predetermined rotational speed, and push the raw material accumulated on the raw material pressing surface into the through holes while pressing the rollers against the raw material pressing surface to form pellets, the through holes are The predetermined cross-sectional area is 7 mm 2 or more and 50 mm 2 or less, and characterized in that the predetermined depth is 30 mm or more and 100 mm or less, a pellet manufacturing apparatus.

2. The area S through which the roller rotates and passes on the raw material pressing surface 0 wherein the cross-sectional area S and the number k of the through holes satisfy the following formula The pellet manufacturing apparatus according to Claim 1. (Formula 1) 0.15 < kS / S 0 < 0.5

3. The cross-section of the through hole is a circular cross-section, and the diameter R of the circular cross-section is 3 mm or more and 8 mm or less, the pellet manufacturing apparatus according to Claim 1.

4. The rotational speed of the rollers is 70 rpm or more and 120 rpm or less, the pellet manufacturing apparatus according to Claim 1.

5. further comprising a cooling means using a liquid for cooling the die for pellet manufacturing, the pellet manufacturing apparatus according to Claim 1.

6. further comprising a guide plate that rotates horizontally around the drive main shaft and moves the raw material on the raw material pressing surface of the die for pellet manufacturing toward the drive main shaft side, the pellet manufacturing apparatus according to Claim 1.

7. the guide plate is inclined in the direction of rotation progress rather than in a direction perpendicular to the direction of rotation progress, the pellet manufacturing apparatus according to Claim 6.

8. the guide plate is curved in the direction of rotation progress rather than in a direction perpendicular to the direction of rotation progress, the pellet manufacturing apparatus according to Claim 6.

9. the guide plate has its lower end close to the raw material pressing surface, and has a notch in a portion passing through the region of the raw material pressing surface where the through holes are located, the pellet manufacturing apparatus according to Claim 6.

10. A method for manufacturing pellets, which manufactures pellets using a raw material containing coffee extraction residue by the pellet manufacturing apparatus according to any one of Claims 1 to 9. Roll the roller on the raw material pressing surface of the die for pellet production, and while pressing the raw material accumulated on the raw material pressing surface against the raw material pressing surface by the roller, push it into a plurality of through holes of the die for pellet production to form pellets. The method for producing pellets is characterized in that the raw material has a particle size characteristic number De in the Rosin-Rammler distribution of 0.4 or more and less than 1.

51.

11. The method for producing pellets according to claim 10, wherein the raw material has a particle size characteristic number De in the Rosin-Rammler distribution of 0.4 or more and 1.2 or less.

12. The method for producing pellets according to claim 10, wherein the raw material has a particle size characteristic number De in the Rosin-Rammler distribution of 0.4 or more and less than 0.

7.

13. The raw material has a moisture content of 5% or more and less than 20%. The method for producing pellets according to claim 10.

14. The raw material has a moisture content of 5% or more and 14% or less. The method for producing pellets according to claim 10.

15. The pellets have a moisture content of 4% or more and 12% or less. The method for producing pellets according to claim 10.

16. The pellets have a moisture content of 4% or more and 10% or less. The method for producing pellets according to claim 10.

17. The method for producing pellets according to claim 10 is characterized by comprising a step of fermenting the coffee extraction residue. The method for producing pellets according to claim 10.

18. The raw material is coffee extraction residue, or a mixture of coffee extraction residue and a wood material. The method for producing pellets according to claim 10.

19. The die for the pellet production device has a cooling means for cooling the die. Pellets are produced while maintaining the die for the pellet production device at a temperature of 80°C or lower by the cooling means. The method for producing pellets according to claim 10.

20. The die for the pellet production device has a cooling means for cooling the die. Pellets are produced while maintaining the die for the pellet production device at a temperature of 60°C or lower by the cooling means. The method for producing pellets according to claim 10.

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