Method for controlling amount of water to be added of woody pellet re-granulating facility

Abstract

To provide a method for controlling an amount of water to be added of a woody pellet re-granulating facility which dispenses with operation of flow rate regulating valves by an operator in a process from start of a re-granulating facility to rating operation, and can automate control of an amount of water to be added, when a water supply device for adding water to woody biomass is introduced.SOLUTION: A water supply device 10 is configured so that a plurality of branch passages 110, 120 and 130 in which at least opening / closing valves 111, 121 and 131 and flow rate regulating valves 112, 122 and 132 are connected in series are connected in parallel, when an amount of water to be added from start of a re-granulating device to rating operation is regulated by the opening / closing valves and the flow rate regulating valves of the water supply device, previously sets flow rates of the water flowing in each of the branched passages 110, 120 and 130 to different predetermined values, by the flow rate regulating valves 112, 122 and 132 on the branch passages, changes the branched passage to supply water to a mixer by opening / closing control of the opening / closing valves 111, 121 and 131, and thereby gradually increases the amount of the water to be added to be supplied to the mixer.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for controlling the amount of water added to wood pellet re-granulation equipment, which controls the amount of water added to wood biomass in a re-granulation equipment for re-granulating wood pellets using wood biomass such as wood chips. [Background technology]

[0002] Pellets made from woody biomass (woody biomass pellets) are often brittle, so a lot of wood chips are generated when the pellets collide with each other during transportation, etc. Therefore, re-granulation facilities have been introduced to reuse the generated wood chips (woody biomass).

[0003] This re-granulation equipment is equipped with a re-granulation device that is substantially similar to the granulation devices shown in Patent Document 1 (Figure 8) and Patent Document 2. This re-granulation device is equipped with a material inlet into which collected wood chips are introduced together with water, a pushing device that pushes the introduced material into the inside of a ring die having many holes formed in its peripheral wall, and a press roll that presses the material pushed into the inside of the ring die against the peripheral wall of the ring die from the inside. The material pushed out of the molding holes of the ring die by the press roll is then cut to a fixed size with a cutter to re-granulate wood pellets. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-147961 A [Patent Document 2] JP 2015-173994 A Summary of the Invention [Problem to be solved by the invention]

[0005] In such a ring die type re-granulation device, the temperature of the press roll and ring die gradually increases each time the device is started up until it reaches rated operation, and the amount of wood chips supplied also increases. Therefore, in order to maintain the quality of the molded pellets, it is necessary to appropriately adjust the amount of water mixed with the wood chips. Therefore, a water supply device has been introduced that can gradually increase the amount of water mixed with the wood chips from start-up until rated operation.

[0006] Figure 5 shows an example of this, in which the water supply device 10 is configured by connecting three branch paths 110, 120, 130 in parallel, each of which has at least an on-off valve (SV1: 111, SV2: 121, SV3: 131) and a flow control valve (needle valve: 112, 122, 132) connected in series.

[0007] Each branch path has an on-off valve (SV1: 111, SV2: 121, SV3: 131) at its most upstream side, and a flow control valve (needle valve: 112, 122, 132) at its downstream side. In addition, check valves 114, 124, 134 are provided downstream of the flow control valves (needle valves) via flow meters (area type flow meters: 113, 123, 133). Therefore, whether each branch path 110, 120, 130 is used as a water supply path is determined by the on-off valves 111, 121, 131, and the amount of water supplied to each path can be adjusted by the flow control valves 112, 122, 132.

[0008] Using such a water supply device, it is also possible to control the amount of water added as follows: Since the moisture content varies depending on the selected woody biomass (tree species), first, one of the branch paths that can add the amount of water appropriate for the selected woody biomass (tree species) is selected by operating the on-off valves 111, 121, and 131.

[0009] The re-granulation equipment is then started and the wood biomass is introduced into the re-granulation equipment. As the re-granulation equipment transitions to rated operation, the temperatures of the press rolls and ring die gradually rise, and the amount of wood biomass (wood chips) fed into the re-granulation equipment also gradually increases. Therefore, in order to maintain the quality of the pellets formed, it is necessary to gradually increase the amount of water mixed with the wood chips according to the temperature range of the press rolls and ring die, or the rotation speed of the constant-volume feeder that supplies the wood chips.

[0010] Therefore, after selecting the branch path to be used, in order to adjust the amount of water to be mixed with the woody biomass introduced into the re-granulation device, as shown in Figure 5(b), it is possible to manually control the opening of flow control valves 112, 122, and 132 according to the temperature range of the press roll or ring die, or the rotation speed (frequency of the constant volume feeder) of the constant volume feeder that supplies the wood chips, and adjust the amount of water to the optimal value (value shown in the table) determined in advance during trial operation while watching the flow meter.

[0011] However, when manually adjusting the opening of the flow rate control valves 112, 122, and 132 to obtain the flow rate previously set in the trial run, an operator must be constantly present to control the flow rate control valves 112, 122, and 132 until the re-granulation apparatus reaches rated operation, which requires a lot of effort and is extremely time-consuming.

[0012] Furthermore, since the flow control valve was manually controlled while monitoring the temperature of the press roll and ring die, or the rotation speed (frequency) of the constant volume feeder, and also while monitoring the flow meter, there was variation in the control of the amount of water added (control of the flow control valve) depending on the operator, leading to inconveniences such as clogging of the regranulation equipment.

[0013] The present invention was made in consideration of the above circumstances, and its main objective is to provide a method for controlling the amount of water added to wood pellet re-granulation equipment, which eliminates the need for operators to operate the flow control valve during the process from starting up the re-granulation equipment to rated operation, even when a water supply device is installed, and which enables the control of the amount of water added to be automated without relying on the operator's judgment. [Means for solving the problem]

[0014] In order to achieve the above object, the water addition amount control method of the present invention for wood pellet re-granulation equipment comprises a mixer that mixes wood biomass with water to be fed into a re-granulation device that re-granulates wood pellets, and a water supply device that can adjust the amount of water supplied to the mixer, The water supply device is configured by connecting in parallel a plurality of branch paths, each of which has at least an on-off valve and a flow rate adjusting valve connected in series; A water addition amount control method for adjusting the amount of water to be supplied to the mixer from the start of the regranulation apparatus until rated operation by the on-off valve and the flow rate control valve of the water supply apparatus, The flow rate of each branch path is preset to a different predetermined value by the flow rate adjusting valve on the branch path, By controlling the opening and closing of the on-off valve to change the branch path for supplying water to the mixer, the amount of water to be supplied to the mixer is increased in stages. It is characterized by the following.

[0015] According to this water addition control direction, the flow control valves are used to adjust the initial flow rate through each branch path, and the flow rate over time is adjusted by changing the branch path used for water supply. In other words, instead of using an on-off valve to select a water addition path depending on the wood species and a flow control valve to adjust the flow rate over time, the flow control valves are used to set the initial flow rate of each branch path, and the on-off valves are used to change the branch path with different water supply rates over time. This makes it possible to change the amount of water supplied to the mixer over time (in stages) simply by controlling the on-off valves of each branch path, making it possible to automate the amount of water added until the regranulation device reaches its rated operation.

[0016] Here, the re-granulation device presses a press roll against the inner surface of a ring die having a number of molding holes formed in the peripheral wall, thereby extruding the woody biomass mixed with water from the molding holes, and it is preferable to change the branch path that supplies water to the mixer by controlling the opening and closing valves of each branch path based on the temperature of the ring die or the temperature of the press roll.

[0017] In such a re-granulation device, heat is generated during the process of pressing the woody biomass against the inner surface of the ring die with a press roll and extruding it through the molding holes formed in the peripheral wall of the ring die, and the temperature of the ring die or the press roll gradually increases.By changing the branch path that supplies water to the mixer based on this temperature, it is possible to appropriately change the amount of water added.

[0018] In an embodiment in which the branch paths that supply water to the mixer are changed by controlling the on-off valves of the branch paths, the branch paths may be sequentially switched to gradually increase the amount of water added. That is, as the temperature of the ring die or the temperature of the press roll increases, the on-off valve may open any of the branch paths that allows the required amount of water to be added and close the remaining branch paths.

[0019] In addition, as an embodiment in which the branch paths that supply water to the mixer are changed by controlling the on-off valves of the branch paths, it is also possible to adjust the amount of water to be added by combining the branch paths that supply water. That is, as the temperature of the ring die or the temperature of the press roll increases, the on-off valves may open one or more branch paths that allow the required amount of water to be added and close the remaining branch paths.

[0020] In order to maintain the quality of the pellets, it is preferable to change the amount of water added minutely from the time the re-granulator is started until it reaches rated operation, and it is preferable to change it at least twice. [Effects of the Invention]

[0021] As described above, according to the present invention, the flow rate through each branch path of the water supply device is preset to different predetermined values ​​using the flow control valves on those branch paths, and the branch path that supplies water to the mixer is changed by controlling the opening and closing of the opening and closing valves, thereby gradually increasing the amount of water added to the mixer.This eliminates the need for operators to operate the flow control valves during the process from starting up the re-granulation device to rated operation, and makes it possible to provide a method for controlling the amount of water added to a wood pellet re-granulation facility that can automate the control of the amount of water added without relying on the operator's judgment. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic diagram showing the overall configuration of a wood pellet re-granulation facility according to the present invention. [Figure 2] 1 shows an example of a re-granulation device used in the wood pellet re-granulation equipment of the present invention, where (a) is a side view thereof, and (b) is a perspective view of the vicinity of the ring die of the re-granulation device as seen from the front. [Figure 3] 1A and 1B are diagrams illustrating a water supply device according to the present invention, in which FIG. 1A is a schematic diagram of a water supply path, and FIG. 1B is a table illustrating water supply control. [Figure 4] 4 is a flowchart showing an example of a control operation of the water supply apparatus according to the present invention. [Figure 5] 10A and 10B are diagrams illustrating another method of water supply control, in which FIG. 10A is a schematic diagram of a water supply path, and FIG. 10B is a table illustrating water supply control. BEST MODE FOR CARRYING OUT THE INVENTION

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0024] An overview of wood biomass pellet re-granulation equipment 1 is shown in Figure 1. In this embodiment, an example will be described in which sawdust is used as a representative example of wood biomass.

[0025] In this re-granulation equipment 1, wood chips collected by a dust collector (not shown) are stored in a dust collection hopper 2, and a slide gate 3 is opened from the bottom of the dust collection hopper 2 to dispense the chips into a screw conveyor 4, which acts as a constant volume feeder. A specified amount of wood chips is then sent from the screw conveyor 4 to a mixer 5.

[0026] In the mixer 5, a fixed amount of sawdust introduced from the screw conveyor 4 is conveyed by the conveyor, while a required amount of water supplied from the water supply device 10 is sprayed from above to mix with the sawdust. The mixed wood chips and water are then fed into the re-granulating device 20 through the feeding port 21.

[0027] The re-granulating device 20 is of a ring die type as shown in FIG. The re-granulation device 20 includes an inlet 21 for introducing the material, a ring die 22 consisting of a ring-shaped annular wall body with numerous forming holes 22a formed on the peripheral wall, each approximately the size of the diameter of the pellets 26, a pushing device 23 forcibly pushing the introduced material (saw chips and water) into the ring die 22, and a press roll 24 disposed eccentrically relative to the ring die 22 inside the ring die 22. The ring die 22 is rotated by a motor 28. The press roll 24 is a planetary type that rotates while its outer surface is pressed against the inner surface of the ring die 22, extruding the material from the inside to the outside through the forming holes 22a. A cutter 25 is disposed on the outer periphery of the ring die 22 to cut the extruded material to a certain size, and a discharge port 27 for discharging the pellets 26 is provided at the bottom of the re-granulation device 20.

[0028] The material supplied to the re-granulation device 20 is formed by mixing sawdust and water in the mixer 5 to form a mass that is easy to pelletize. If the amount of water added to the sawdust is not properly controlled, pellets of the required quality cannot be formed. For example, if the amount of water added is too much, the material becomes watery, making it difficult to ensure the hardness of the pellets. On the other hand, if the amount of water added is too little, the sawdust will not clump together and will be more likely to clog the molding holes 22a.

[0029] In particular, during the transitional stage from when the regranulator 20 starts up until it reaches rated operation, the temperatures of the ring die 22 and press roll 24 gradually rise, making it easier for water to evaporate. In addition, the frequency (number of rotations) of the constant-rate feeder (screw conveyor 4) gradually increases, increasing the amount of wood chips supplied to the regranulator 20, so the amount of water added must also increase accordingly. For this reason, it is necessary to gradually change the amount of water added according to the temperature range of the ring die 22 and press roll 24 or the frequency range of the constant-rate feeder (screw conveyor 4).

[0030] Therefore, a water supply device 10 is provided to control the amount of water added to the mixer 5. As shown in Figure 3(a), this water supply device 10 is configured by connecting multiple branch paths 110, 12, 130 in parallel (three in this example), each of which has on-off valves 111, 121, 131 and flow control valves 112, 122, 132, each of which is a needle valve whose opening can be adjusted, connected in series. Each of the branch paths 110, 120, 130 is provided with an on-off valve (SV1: 111, SV2: 121, SV3: 131) at its most upstream side, and a flow control valve (needle valve: 112, 122, 132) at its downstream side. Also, check valves 114, 124, 134 are provided downstream of the flow control valves (needle valves) via flow meters (area type flow meters) 113, 123, 133.

[0031] In each of the branch paths 110, 120, 130, the needle valves 112, 122, 132 are used to set the initial flow rate of the branch paths 110, 120, 130 when the on-off valves 111, 121, 131 are open. This initial flow rate is set in advance before the re-granulation device 20 is started, and is not changed after the re-granulation device 20 is started.

[0032] The initial flow rates of the branch paths 110, 120, and 130 are set differently by the needle valves 112, 122, and 132. Because the amount of water required to be added in the mixer must be increased in stages, the initial flow rates of the branch paths are determined in advance during trial operation so that the amount of water required at each stage is achieved.

[0033] For example, during a trial run of the regranulation apparatus 20, if the relationship between the temperature of the ring die 22 or the temperature of the press roll 24, the frequency of the constant volume feeder (screw conveyor 4), and the amount of water added from the time the regranulation apparatus 20 is started until it reaches rated operation is as shown on the left side of Figure 3(b), it will be found that pellets of the required quality will be produced from the time the regranulation apparatus 20 is started until it reaches rated operation. In such a case, the initial flow rates of the flow control valves 112, 122, and 132 of the branch paths 110, 120, and 130 are set in advance as shown on the right side of Fig. 3(b) (open / close valve SV1 is set to a flow rate of 0.4 L / min, open / close valve SV2 is set to a flow rate of 0.6 L / min, and open / close valve SV3 is set to a flow rate of 0.8 L / min). Then, the conditions for opening the open / close valves (SV1, SV2, and SV3) are set as follows (see the right side of Fig. 3(b)). (1) Conditions for opening SV1 When the temperature of the regranulator (the temperature of the ring die 22 or the temperature of the press roll 24) is less than 30°C and the frequency of the constant volume feeder (screw conveyor 4) is 7Hz (2) Conditions for opening SV2: When the temperature of the regranulator (the temperature of the ring die 22 or the temperature of the press roll 24) is 30°C or higher and lower than 50°C (30°C to 50°C), and the frequency of the constant volume feeder (screw conveyor 4) is operating at 10Hz to 15Hz. (3) Conditions for opening SV3: When the temperature of the regranulator (the temperature of the ring die 22 or the temperature of the press roll 24) is 50°C or higher and the constant feeder (screw conveyor 4) is operating at a frequency of 20Hz (rated).

[0034] Then, based on these conditions, the control unit 11, which controls the operation of each on-off valve, controls the on-off valves (SV1, SV2, SV3) as follows based on a signal from a temperature sensor 12 that detects the regranulation device temperature (the temperature of the ring die or the temperature of the press roll) and a signal from a frequency sensor 13 that detects the frequency of the constant volume feeder (screw conveyor 4).

[0035] When the regranulator temperature (the temperature of the ring die or the temperature of the press roll) is below 30°C, only the first on-off valve SV1 is opened, and the second on-off valve SV2 and the third on-off valve SV3 are closed. When the temperature of the regranulator is 30°C or higher and lower than 50°C, only the second on-off valve SV2 is opened, and the first on-off valve SV1 and the third on-off valve SV3 are closed. When the temperature of the regranulator is 50°C or higher, only the third on-off valve is opened, and the first on-off valve SV1 and the second on-off valve SV2 are closed.

[0036] This flow rate adjustment, which gradually increases the amount of water added, can be switched simply by controlling the opening and closing of the on-off valves 111, 121, and 131 of each branch path depending on the temperature of the regranulation device (the temperature of the ring die or the temperature of the press roll), eliminating the need for manual adjustment of the flow rate control valves (needle valves) 112, 122, and 132 over time and enabling automatic control.

[0037] 4 shows a flowchart of an example of an operation process in which the on-off valves (first on-off valve 111, second on-off valve 121, and third on-off valve 131) are automatically controlled by the control unit 11 in accordance with the temperature of the regranulation apparatus. The automatic control of the amount of water to be added will be described below based on this flowchart.

[0038] First, immediately after starting the regranulation equipment 1 (regranulation device 20), the constant volume feeder (screw conveyor 4) is started at a rotation speed of 7 Hz (step S50). At this stage, the amount of wood chips sent to the mixer 5 is small, so only the first on-off valve SV1 is opened, and the second on-off valve SV2 and the third on-off valve SV3 are closed, limiting the water supply rate to 0.4 L / min (step S52).

[0039] After starting the regranulator 20, if the temperature of the ring die 22 or the press roll 24 exceeds 30°C and the constant volume feeder (screw conveyor 4) continues to operate at 7 Hz for 6 minutes or more (step S54), the rotation speed of the constant volume feeder is increased to 10 Hz to increase the amount of wood chips supplied to the mixer (step S56). At the same time, the on-off valves are controlled to open only the second on-off valve SV2 and close the first on-off valve SV1 and the third on-off valve SV3, switching the water supply route to the second branch route 120 and increasing the water supply rate to 0.6 L / min (step S58).

[0040] Thereafter, after six minutes or more have passed with the rotation speed of the constant volume feeder (screw conveyor 4) at 10 Hz (step S60), the rotation speed of the constant volume feeder is increased to 15 Hz in order to increase the amount of wood chips supplied to the mixer 5 (step S62). As a result, the temperature of ring die 22 or press roll 24 rises, and if this temperature reaches 50°C or higher and the constant volume feeder has been operating at 15 Hz for six minutes or more (step S64), the rotation speed of the constant volume feeder is increased to 20 Hz to increase the amount of wood chips supplied to mixer 5 (step S66).At the same time, the on-off valves are controlled to open only third on-off valve SV3 and close first on-off valve SV1 and second on-off valve SV2, switching the water supply route to third branch route 130, increasing the water supply rate to 0.8 L / min, and switching to rated operation (step S68).

[0041] In this way, the temperature of the ring die 22 or the temperature of the press roll 24 is monitored, and the amount of wood chips supplied to the mixer 5 and the amount of water supplied to the mixer 5 are gradually increased in accordance with the rise in temperature, until the operation reaches rated capacity.

[0042] Therefore, with the above configuration, the transient state from when the regranulation device is started until it transitions to rated operation is divided into multiple stages, and water is supplied to each stage through separate branch paths. The amount of water supplied at each stage (initial flow rate of each branch path) is set in advance during trial operation using a flow control valve, and the amount of water added required in the transient state is determined by switching the branch paths by controlling the opening and closing of the on-off valve according to the regranulation device temperature (temperature of the ring die or the press roll). This eliminates the need for operators to manually control the flow control valves 112, 122, 132 each time the regranulation equipment 1 is started, and also makes it possible to automate the adjustment of the amount of water added by simply controlling the opening and closing of the on-off valve in relation to the regranulation device temperature.

[0043] Furthermore, since there is no need to manually adjust the amount of water added each time the re-granulation device 20 is started, there is no variation in the water addition control by the operator, and it is possible to reduce the frequency with which the re-granulation device 20 trips due to clogging of the forming holes 22a of the ring die 22.

[0044] In the above example, three branch paths 110, 120, and 130 are provided and the water supply amount is divided into three stages (the water supply path is switched twice), but it is also possible to provide four or more branch paths and divide the water supply amount into four or more stages (the water supply amount is switched three or more times) to allow for more detailed control.

[0045] In the above example, the flow rate supplied to the mixer 5 at each stage is ensured by switching to one of the branch paths, i.e., the on-off valve of one of the branch paths that can provide the required amount of water is opened and the on-off valve of the remaining branch path is closed as the temperature of the ring die or the temperature of the press roll increases. However, the flow rate supplied to the mixer 5 may also be adjusted by combining the branch paths that supply water. That is, it is also possible to perform control such that one or more branch paths that can provide the required amount of water are opened and the remaining branch paths are closed as the temperature of the ring die 22 or the temperature of the press roll 24 increases. [Explanation of symbols]

[0046] 1 Regranulation equipment 5 Mixer 10 Water supply device 20 Regranulation equipment 22 Ring die 22a Molding hole 24 press rolls 26 pellets 110,120,130 Branching Routes 111,121,131 On-off valve 112,122,132 Flow control valve

Claims

1. The system comprises a mixer that mixes wood biomass with water to be fed into a re-granulation device that re-granulates wood pellets, and a water supply device that can adjust the amount of water supplied to the mixer. The water supply device is configured by connecting in parallel a plurality of branch paths, each of which has at least an on-off valve and a flow rate adjusting valve connected in series; A water addition amount control method for a wood pellet re-granulation facility, in which the amount of water supplied to the mixer from the start of the re-granulation device until rated operation is adjusted by the on-off valve and the flow rate control valve of the water supply device, The flow rate of each branch path is preset to a different predetermined value by the flow rate adjusting valve on the branch path, By controlling the opening and closing of the on-off valve to change the branch path for supplying water to the mixer, the amount of water to be supplied to the mixer is increased in stages. A method for controlling the amount of water added to a wood pellet re-granulation facility.

2. The re-granulation device presses a press roll against the inner peripheral surface of a ring die having a number of molding holes formed in the peripheral wall, thereby extruding the woody biomass mixed with water through the molding holes, changing the branch path for supplying water to the mixer by controlling the on-off valve of each branch path based on the temperature of the ring die or the temperature of the press roll; 2. The method for controlling the amount of water added to a wood pellet re-granulation facility according to claim 1.

3. 3. The water addition control method for wood pellet re-granulation equipment according to claim 2, wherein, as the temperature of the ring die or the temperature of the press roll increases, the on-off valve opens one of the branch paths that can obtain the required amount of water addition and closes the remaining branch paths.

4. 3. The method for controlling the amount of water added to a wood pellet re-granulation facility according to claim 2, wherein, as the temperature of the ring die or the temperature of the press roll increases, the on-off valve opens one or more branch paths that allow the required amount of water to be added and closes the remaining branch paths.

5. A method for controlling the amount of water added to a wood pellet re-granulation facility as described in any one of claims 1 to 4, characterized in that the branch path is changed two or more times from the time the re-granulation device is started up to the time it reaches rated operation.

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