Cooling structure, screw feeder, and cooling method

Abstract

To provide: a cooling structure capable of efficiently cooling the tip of a screw feeder with a cooling medium; a screw feeder; and a cooling method.SOLUTION: There is provided a cooling structure 20 of a screw feeder feeding biomass fuel into a gasification furnace, comprising an outer jacket 21 demarcating a space therein with a closed tip 21c positioned inside the furnace, and an inner jacket 22 disposed in the space of the outer jacket 21 to demarcate a forward path 23 of a cooling medium W therein and a return path 24 of the cooling medium W between itself and the outer jacket 21, with an ejection port 22a being formed on a position opposing the closed tip 21c of the outer jacket 21 so that the cooling medium W flowing through the forward path 23 is ejected therefrom.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a cooling structure, a screw feeder, and a cooling method. [Background technology]

[0002] For example, in a gasification furnace that uses biomass fuel, a screw feeder is sometimes used to supply fuel into the furnace (see Patent Document 1).

[0003] Since the screw feeder is connected to the gasification furnace and its tip faces the high-temperature inside of the furnace, the screw feeder may become hot due to heat conduction or radiation from inside the furnace. Therefore, a cooling structure may be provided to cool the entire screw feeder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-190888 A Summary of the Invention [Problem to be solved by the invention]

[0005] The tip end of the screw feeder is more likely to become hotter than other parts (for example, the base end of the screw feeder). For example, when the temperature inside the furnace is about 1000°C, the tip end of the screw feeder can reach several hundred°C, which causes thermal stress due to the temperature gradient and may lead to damage to the screw feeder depending on the situation.

[0006] In addition, the gasification gas flowing through the furnace contains water vapor, and if the screw feeder is cooled excessively, the water vapor that flows from the furnace into the screw feeder may condense. In this case, the condensed water will make the biomass fuel wet, reducing its fluidity and causing the screw feeder to become clogged. On the other hand, if the screw feeder is not cooled sufficiently, the temperature of the screw feeder may exceed the softening temperature of the lignin contained in the biomass fuel (e.g., wood-based fuel), causing the lignin to soften. In this case, the softened lignin may cause the biomass fuel to adhere to the screw feeder, reducing the fluidity of the biomass fuel and causing the screw feeder to become clogged.

[0007] The present disclosure has been made in consideration of the above circumstances, and has as its first object to provide a cooling structure, a screw feeder, and a cooling method capable of cooling the tip of a screw feeder with a cooling medium. A second object of the present invention is to provide a cooling structure, a screw feeder, and a cooling method that can maintain the screw feeder at an appropriate temperature. [Means for solving the problem]

[0008] In order to solve the above problems, the cooling structure, screw feeder, and cooling method disclosed herein employ the following measures. In other words, a cooling structure according to one aspect of the present disclosure is a cooling structure for a screw feeder that supplies biomass fuel into a gasification furnace, and includes an outer jacket that defines a space inside and has a blocked tip located inside the furnace, and an inner jacket that is provided in the space of the outer jacket, defines a forward path for a cooling medium inside and also defines a return path for the cooling medium between the outer jacket and an inner jacket with an outlet through which the cooling medium circulating along the forward path is sprayed formed in a position opposite the blocked tip of the outer jacket.

[0009] Moreover, a screw feeder according to one aspect of the present disclosure includes the above-described cooling structure and a screw, and the outer jacket of the cooling structure is a casing that houses the screw.

[0010] Moreover, a cooling method according to one aspect of the present disclosure is a cooling method using the above-described cooling structure, in which a cooling medium is ejected from the ejection port and caused to collide with the closed tip portion of the outer jacket. Effect of the Invention

[0011] According to the present disclosure, firstly, the tip of the screw feeder can be efficiently cooled by a cooling medium, and secondly, the screw feeder can be maintained at an appropriate temperature. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic configuration diagram of a screw feeder and a gasification furnace to which the screw feeder is connected according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a longitudinal cross-sectional view of a screw according to an embodiment of the present disclosure. [Diagram 3] FIG. 2 is a longitudinal cross-sectional view of a cooling structure according to an embodiment of the present disclosure. [Figure 4] 4 is a vertical cross-sectional view taken along line V shown in FIG. [Diagram 5] 4 is a graph showing the relationship between the flow velocity of the cooling medium flowing through the outward path and the pressure loss. FIG. [Figure 6] FIG. 4 is a vertical cross-sectional view showing a divided structure of an outer jacket. [Figure 7] FIG. 11 is a graph showing the relationship between the ratio of a position from a tip to an inner diameter of an outer jacket and thermal stress. [Figure 8] FIG. 4 is a vertical cross-sectional view of a cooling structure according to a first modified example. [Figure 9] 9 is a vertical cross-sectional view taken along line IX shown in FIG. 8. [Figure 10] FIG. 4 is a vertical cross-sectional view of a cooling structure according to a first modified example. [Figure 11] 11 is a vertical cross-sectional view taken along line XI shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a cooling structure, a screw feeder, and a cooling method according to an embodiment of the present disclosure will be described with reference to the drawings.

[0014] [Overview of the screw feeder] As shown in FIG. 1, the screw feeder 1 is a device for supplying fuel into the inside of a gasification furnace 50 .

[0015] The gasification furnace 50 is a facility that generates synthesis gas G from fuel in a furnace under a high-temperature environment of, for example, about 500° C. to 1250° C. The generated synthesis gas G is, for example, refined in a gas refining facility (not shown) and then supplied to a liquefaction facility (not shown) where it is synthesized as biojet fuel. As the fuel, biomass fuels that contain tar components such as lignin (for example, wood-based biomass fuels and grass-based biomass fuels) are used.

[0016] As shown in FIGS. 1 and 2, the screw feeder 1 includes a screw 11 and a cooling structure 20 serving as a casing for accommodating the screw 11.

[0017] The screw 11 is a part that moves the fuel supplied from the fuel supply pipe 32 inside the casing. The screw 11 has a rotating shaft 11a and a blade 11b attached so as to wind around the rotating shaft 11a, and extends along the direction of the rotation axis X.

[0018] The rotating shaft 11a is supported by a bearing 12 and configured to rotate about a rotation axis X by a motor 31 provided outside the casing. When the rotary shaft 11 a rotates, the blades 11 b also rotate, so that the fuel supplied from the fuel supply pipe 32 moves inside the casing and is supplied into the gasification furnace 50 .

[0019] As described above, the cooling structure 20 is a part that functions as a casing that houses the screw 11. Furthermore, inside the cooling structure 20, flow paths (outgoing path 23 and returning path 24) through which the cooling medium W flows are defined, and the temperature of the screw feeder 1 is appropriately maintained by the temperature-adjusted cooling medium W flowing through the flow paths. Examples of the cooling medium W include water / hot water.

[0020] As shown in FIG. 1, the cooling structure 20 is connected to a supply line L1 and a discharge line L2 through which a cooling medium W flows. The cooling structure 20 constitutes one circulation path together with the supply line L1 and the discharge line L2.

[0021] The circulation path is a closed path that starts at the circulation pump 34 (flow rate adjustment section), passes through a supply line L1 equipped with a temperature adjustment section 35, the cooling structure 20, and a discharge line L2, and returns to the circulation pump 34.

[0022] The temperature adjustment unit 35 is a device that adjusts (heats / cools) the temperature of the cooling medium W that is supplied to the cooling structure 20 through the supply line L1. The temperature adjustment unit 35 has, for example, a heat exchanger 35a and a heater / cooler 35b, and is configured so that heat exchange between the heat / cold generated in the heater / cooler 35b and the cooling medium W is performed in the heat exchanger 35a. The temperature adjustment unit 35 may have any configuration as long as it can adjust the temperature of the cooling medium W, and is not limited to the above configuration.

[0023] 2, the tip end portion of the screw feeder 1 is inserted into the furnace wall of the gasification furnace 50. Specifically, the tip end portion is inserted into the furnace wall having a refractory material 51 and a gasification furnace outer wall 52 attached to the outer surface of the refractory material 51. The screw feeder 1 inserted through the furnace wall is attached to the furnace wall via a mounting seat 53 and a heat insulating material 54.

[0024] The tip of the screw feeder 1 attached to the furnace wall faces the inside of the furnace. Here, the tip of the screw feeder 1 is the tip of a cooling structure 20 serving as a casing, specifically, a closed portion 21c of an outer jacket 21 described later.

[0025] [Cooling structure] As shown in FIGS. 3 and 4, the cooling structure 20 of the screw feeder 1 includes an outer jacket 21 and an inner jacket 22. For ease of explanation, the screw 11, the mounting seat 53, the heat insulating material 54, and the furnace wall (the refractory material 51 and the gasification furnace outer wall 52) are omitted in Figs. 3 and 4.

[0026] The outer jacket 21 is a double pipe with a bottom and a closed tip, having a cylindrical outer pipe 21a and an inner pipe 21b with the rotation axis X as the central axis, and a closed portion 21c connecting the tip of the outer pipe 21a and the tip of the inner pipe 21b. The outer jacket 21 is made of a metal such as stainless steel or carbon steel.

[0027] The screw 11 is housed in a space defined by the inner circumferential surface of the outer jacket 21 (in other words, the inner circumferential surface of the inner tube 21b) (see FIG. 2). A heat insulating material 54 is provided on the outer peripheral surface of the outer jacket 21 (in other words, the outer peripheral surface of the outer pipe 21a) (see FIG. 2).

[0028] An inner jacket 22 is provided in a space defined by the inner peripheral surface of the outer pipe 21a, the outer peripheral surface of the inner pipe 21b, and the inner surface of the closing portion 21c.

[0029] The inner jacket 22 is, for example, a tube extending in a direction parallel to the rotation axis X (central axis) of the inner jacket 22. At the tip of the tubular inner jacket 22, an ejection port 22a is formed. The ejection port 22a faces the inner surface of the closing portion 21c of the outer jacket 21 at a position spaced a predetermined distance (for example, equal to or greater than the hole diameter of the ejection port 22a) from the closing portion 21c. The inner jacket 22 is made of a metal such as stainless steel or carbon steel.

[0030] As shown in Fig. 4, a plurality of inner jackets 22 are provided at equal angular intervals around the rotation axis X (central axis). In the case of Fig. 4, twelve tubular inner jackets 22 are provided. In addition, the inner jacket 22 is not limited to the above configuration as long as it is configured to define an outward path 23 through which the cooling medium W flows inside and to define a return path 24 through which the cooling medium W flows between the inner jacket 22 and the outer jacket 21.

[0031] As shown in Figs. 3 and 4, the inside (interior) of the tubular inner jacket 22 serves as an outward passage 23 through which the cooling medium W flows toward the tip side (the gasification furnace 50 side). In addition, the space defined by the outer jacket 21 and the inner jacket 22, specifically, the space defined by the inner surface of the outer tube 21a, the outer surface of the inner tube 21b, the inner surface of the blocking portion 21c, and the outer surface of the inner jacket 22, is used as a return path 24 through which the cooling medium W flows toward the base end side (motor 31 side). At this time, the outward passage 23 communicates with the return passage 24 via an ejection port 22 a formed at the tip of the inner jacket 22 .

[0032] A supply line L1 for the cooling medium W is connected to an upstream portion (not shown) of the outward path 23. This allows the cooling medium W to be supplied to the outward path 23 from the supply line L1. Further, a discharge line L2 for the cooling medium W is connected to a downstream portion (not shown) of the return path 24. This allows the cooling medium W to be discharged from the return path 24 to the discharge line L2.

[0033] [About the flow of cooling medium] The cooling medium W flows as follows. As shown in FIGS. 1 and 3, the cooling medium W whose pressure has been increased by the circulation pump 34 flows into the outward path 23 of the cooling structure 20 through the supply line L1. At this time, the temperature of the cooling medium W is adjusted to an appropriate temperature by the temperature adjustment unit 35. A specific method of managing the temperature will be described later.

[0034] The cooling medium W that has flowed into the outward path 23 from the supply line L1 flows toward the tip side (the right side in FIG. 3) and is ejected from an ejection port 22a formed at the tip of the inner jacket 22.

[0035] The cooling medium W ejected from the ejection port 22a collides with the inner surface of the closed portion 21c of the outer jacket 21. At this time, the closed portion 21c located at the tip of the cooling structure 20 faces the inside of the furnace through which the synthesis gas G flows, and becomes the part with the highest temperature in the casing (cooling structure 20). By causing a jet of the cooling medium W to impinge on the blocked portion 21c, the blocked portion 21c and its vicinity can be cooled (impingement jet cooling). It should be noted that the collision of the jet is not essential, and it is sufficient that the blocked portion 21c and its vicinity are cooled by the cooling medium W. However, by using the collision jet cooling, the blocked portion 21c and its vicinity can be efficiently cooled.

[0036] The cooling medium W that collides with the blocking portion 21c changes direction so as to turn back along the inner surface of the blocking portion 21c and flows into the return path 24.

[0037] The cooling medium W that has flowed into the return line flows toward the base end side (the left side in FIG. 3), is discharged from the return line to the discharge line L2, and returns to the circulation pump . At this time, while the cooling medium W flows through the return line 24, the main portion of the outer jacket 21 is kept at a predetermined temperature by the cooling medium W. A specific method of controlling the temperature will be described later.

[0038] Here, the "main part of the outer jacket 21" refers to, for example, the base end part of the outer jacket 21 excluding the tip end part of the outer jacket 21 including the closed part 21c facing the inside of the furnace. However, the "main part of the outer jacket 21" does not include the outer circumferential surface of the outer jacket 21. As a specific example, when the inner diameter of the outer jacket 21 is d, the main portion of the outer jacket 21 is a portion of the outer jacket 21 that is 0.05d to 0.1d or more away from the tip of the outer jacket 21. In other words, the portion of the outer jacket 21 within 0.05d to 0.1d from the tip of the outer jacket 21 is the tip side portion of the outer jacket 21.

[0039] The length of the main portion of the outer jacket 21 that is the subject of temperature control is sufficiently larger (for example, four or more times larger) than the length of the tip side portion of the outer jacket 21 that is not the subject of temperature control. Here, the "length dimension" refers to the dimension along the rotation axis X (central axis).

[0040] [Temperature control] The temperature of the cooling medium W flowing into the outward path 23 of the cooling structure 20 is adjusted by a temperature adjustment unit 35. Specifically, the temperature of the cooling medium W is adjusted so that the metal temperature of the main portion of the outer jacket 21 maintained by the cooling medium W is 80°C or higher and 100°C or lower.

[0041] As shown in Fig. 1, the cooling structure 20 is provided with a temperature sensor 33 so as to be able to acquire the temperature of a desired location. Although one temperature sensor 33 is shown in Fig. 1 for the sake of convenience, the number of temperature sensors 33 may be multiple. The temperature sensor 33 is configured to be able to communicate with the control unit 36. The communication means may be wired or wireless.

[0042] The control unit 36 ​​calculates the metal temperature of the main portion of the outer jacket 21 based on information from the temperature sensor 33. The control unit 36 ​​then controls the temperature of the cooling medium W by heating / cooling the cooling medium W using the temperature adjustment unit 35 so that the metal temperature of the main portion of the outer jacket 21 is 80° C. or higher and 100° C. or lower.

[0043] The reason for setting the metal temperature at 80° C. or higher is as follows. The water vapor concentration in the synthesis gas G in the gasification furnace 50 is 40 vol% to 80 vol%. The pressure in the furnace is approximately atmospheric pressure. Therefore, the condensation temperature for the partial pressure of water vapor is approximately 77°C to 94°C. Therefore, taking these average temperatures into consideration, it is preferable to maintain the metal temperature of the main portion of the outer jacket 21 that comes into contact with the synthesis gas G containing water vapor at 80° C. or higher.

[0044] The reason for keeping the metal temperature at 100° C. or less is as follows. Lignin contained in biomass fuels can soften at about 130°C, and in the presence of moisture, the softening temperature drops further. For example, the moisture content of wood-based biomass fuels is about 10 wt%. From this, it is expected that the softening temperature of lignin exceeds at least 100°C. Therefore, it is preferable to keep the metal temperature of the main part of the outer jacket 21 that comes into contact with the biomass fuel at 100° C. or lower.

[0045] Furthermore, even if the metal temperature of the tip part of the outer jacket 21 (not the main part) exceeds 100°C, softening the lignin and causing biomass fuel to adhere to it, the area of ​​adhesion is limited to the tip part of the outer jacket 21 close to the inside of the furnace, so the adhered biomass fuel is easily pushed into the furnace by the screw 11. Therefore, the portion that needs to be kept at a metal temperature of 100° C. or less may be only the main portion of the outer jacket 21. Of course, there is no problem in keeping the metal temperature of the tip portion at 100° C. or less.

[0046] [Flow rate management] The flow rate of the cooling medium W flowing inside (inside) the inner jacket 22, i.e., through the outward path 23, is adjusted, for example, by changing the rotation speed of the circulation pump 34. Note that the flow rate may also be adjusted by a control valve provided downstream of the circulation pump 34. Specifically, the flow velocity is adjusted to be between 1 m / s and 4 m / s.

[0047] The cooling structure 20 is provided with a sensor (not shown) for measuring the flow velocity of the cooling medium W flowing through the outgoing path 23. The sensor may be, for example, a flow velocity meter that directly measures the flow velocity, or a flow meter that measures the flow rate of the cooling medium W. When the sensor is a flow meter, the flow velocity can be measured indirectly using the known flow path area of ​​the outgoing path 23 and the measured flow rate of the cooling medium W. The sensor is configured to be able to communicate with the control unit 36. The communication means may be wired or wireless.

[0048] The control unit 36 ​​calculates the flow rate of the cooling medium W flowing through the outward path 23 based on information from the sensor. The control unit 36 ​​then manages the flow rate of the cooling medium W by the circulation pump 34.

[0049] The reasons for setting the flow velocity at 1 m / s or more are as follows: For example, when the inner diameter of the inner jacket 22 is 0.002 m to 0.005 m, a flow velocity of 1 m / s allows the cooling medium to flow evenly through each inner jacket 22. If the flow velocity is less than 1 m / s, the pressure loss becomes too small, and the cooling medium may not flow evenly through each inner jacket 22. Therefore, it is preferable to set the flow velocity of the cooling medium W to 1 m / s or more so that an appropriate pressure loss occurs.

[0050] The reasons for setting the flow velocity at 4 m / s or less are as follows: For example, when the inner diameter of the inner jacket 22 is 0.002 m to 0.005 m, the inventors have found that the pressure loss increases sharply when the flow velocity exceeds 4 m / s, as shown in Fig. 5. Therefore, it is preferable to set the flow velocity of the cooling medium W to 4 m / s or less.

[0051] [About the outer jacket welds] As shown in Figs. 3 and 6, the outer jacket 21 may have a divided structure. Specifically, the outer jacket 21 may be divided into the tip side portion 21t and the main body portion 21m, and these may be joined by butt welding to form the welded portion 21w. This allows adjustment while visually checking the positions of the inner jacket 22 and the main body portion 21m, so that the cooling structure 20 can be easily manufactured with high accuracy. Furthermore, the main body 21m may be divided into the outer tube 21a and the inner tube 21b. This allows the positions of the outer tube 21a and the inner tube 21b to be adjusted, so that the return path 24 can be easily formed with high accuracy.

[0052] The tip side portion 21t is a portion on the tip side of the outer jacket 21 including the closed portion 21c facing the inside of the furnace. The main body portion 21m is a portion on the base end side of the outer jacket 21 excluding the tip side portion 21t. The length L of the tip side portion 21t is the distance from the tip of the outer jacket 21 to the welded portion 21w, and is set to, for example, 30% or more of the inner diameter d of the outer jacket 21. In other words, L≧0.3×d.

[0053] The reason for L≧0.3×d is as follows. The safety factor α when repeated loads are applied is usually set to be 5 or more, so if the allowable tensile stress (tensile strength) of the outer jacket 21 is σ, it is preferable to keep the thermal stress acting on the welded portion 21w in the range of σ / 5 or less.

[0054] Here, as shown in Figure 7, if the value (expressed as a percentage) obtained by dividing the position from the tip of the outer jacket 21 by the inner diameter d of the outer jacket 21 is taken on the horizontal axis and thermal stress is taken on the vertical axis, the inventors have found that at a position of 30% on the horizontal axis, the thermal stress falls within a range of σ / 5 or less. Therefore, in order to separate the position of the welded portion 21w from the tip by 0.3×d or more, it is preferable to satisfy L≧0.3×d.

[0055] According to this embodiment, the following effects are obtained. The cooling medium W can be ejected from the ejection port 22 a of the inner jacket 22 toward the closed portion 21 c of the outer jacket 21 . This allows the tip of the outer jacket 21, which is susceptible to the temperature inside the furnace, to be intensively cooled by the cooling medium W. In particular, the tip of the outer jacket 21 can be more efficiently cooled by causing the jet of the cooling medium W to collide with the closed portion 21c of the outer jacket 21. By cooling the tip of the outer jacket 21 in this manner, the temperature difference (temperature gradient) occurring in the portion on the tip side can be reduced, and as a result, thermal stress can be reduced.

[0056] Moreover, the outer jacket 21 can be kept at an appropriate temperature by the cooling medium W guided from the outward path 23 to the return path 24 via the ejection port 22a. This makes it possible, for example, to suppress condensation of water vapor contained in the synthesis gas G and to suppress softening of lignin contained in the biomass fuel.

[0057] In addition, when the flow rate of the cooling medium W is adjusted by controlling the circulation pump 34 so that the flow velocity of the cooling medium W in the outward path 23 is 1 m / s or more and 4 m / s or less, a sufficient amount of the cooling medium W can be evenly sprayed from each nozzle 22a while reducing the pressure loss in the outward path 23 as much as possible.

[0058] In addition, when the temperature of the cooling medium W is adjusted by controlling the temperature adjustment unit 35 based on information obtained from the temperature sensor 33, the temperature of the cooling medium W can be adjusted to maintain the temperature of the outer jacket 21 at any desired temperature.

[0059] Furthermore, when the temperature of the cooling medium W is adjusted by controlling the temperature adjustment unit 35 so that the temperature of the outer jacket 21 is kept at a temperature between 80°C and 100°C, the condensation of water vapor contained in the synthesis gas G flowing in from inside the furnace can be suppressed, and the softening of lignin contained in the biomass fuel (e.g., wood-based fuel) can be suppressed. By suppressing the condensation of water vapor, it is possible to reduce the possibility that the biomass fuel becomes wet and causes clogging of the screw feeder 1. Also, by suppressing the softening of lignin, it is possible to reduce the possibility that the biomass fuel adheres to the lignin and causes clogging of the screw feeder 1.

[0060] Furthermore, since the space in which the inner jacket 22 is provided is defined between the outer pipe 21a and the inner pipe 21b, the inner jacket 22 can be provided inside the double pipe structure.

[0061] In addition, the outer jacket 21 has a tip side portion 21t including the blocking portion 21c, and a main body portion 21m other than the tip side portion 21t, which are divided along the direction of the rotation axis X. Therefore, the positions of the inner jacket 22 and the main body portion 21m can be adjusted while being visually confirmed, and therefore the cooling structure 20 with high precision can be easily manufactured.

[0062] Furthermore, when the tip side portion 21t and the main body portion 21m are joined by a welded portion 21w, and the welded portion 21w is formed at a distance from the tip that is 30% or more of the inner diameter of the inner tube 21b, the welded portion 21w can be formed while avoiding the tip side region (region within a distance of less than 30%) where a large temperature difference (temperature gradient) occurs. This allows the welded portion 21w to be formed while avoiding an area where a large thermal stress occurs, thereby reducing the possibility that the welded portion 21w will be damaged by thermal stress.

[0063] [Variation 1] As shown in FIGS. 8 and 9, the inner jacket 22, like the outer jacket 21, may have a double pipe structure with a closed end. At this time, by providing an ejection port 22a in the closed portion 22d connecting the outer pipe 22b and the inner pipe 22c, the cooling medium W can be ejected from the outward passage 23 toward the closed portion 21c of the outer jacket 21. As shown in Fig. 9, a plurality of ejection ports 22a are provided at equal angular intervals around the central axis. In the case of Fig. 9, twelve ejection ports 22a are provided.

[0064] [Variation 2] As shown in Figures 10 and 11, the inner jacket 22 may have a hollow fin-like structure.

[0065] As shown in Fig. 11, the inner jackets 22 are formed at equal angular intervals around the central axis. In the case of Fig. 11, twelve fin-shaped inner jackets 22 are provided.

[0066] As shown in Figs. 10 and 11, the fin-shaped inner jacket 22 protrudes from the outer tube 21a of the outer jacket 21 toward the inner tube 21b so as to taper, and an outward path 23 is defined on the inside. The fin-shaped inner jacket 22 has an ejection port 22a formed at its tip.

[0067] The cooling structure, the screw feeder, and the cooling method according to the present embodiment described above can be understood, for example, as follows. That is, the cooling structure according to the first aspect of the present disclosure is a cooling structure (20) for a screw feeder (1) that supplies biomass fuel into a gasification furnace (50), and includes an outer jacket (21) that defines a space inside and has a blocked tip (21c) located inside the furnace, and an inner jacket (22) that is provided in the space of the outer jacket (21), defines a forward path (23) of a cooling medium (W) inside and defines a return path (24) of the cooling medium (W) between the outer jacket (21) and has an outlet (22a) from which the cooling medium (W) circulating through the forward path (23) is ejected, formed in a position opposite the blocked tip (21c) of the outer jacket (21).

[0068] According to the cooling structure (20) of this embodiment, the cooling structure (20) includes an outer jacket (21) that defines a space inside and has a closed end (21c) located inside the furnace, and an inner jacket (22) that is provided in the space of the outer jacket (21), defines a forward path (23) of the cooling medium (W) inside and defines a return path (24) of the cooling medium (W) between the outer jacket (21) and has an outlet (22a) from which the cooling medium (W) flowing through the forward path (23) is ejected at a position facing the closed end (21c) of the outer jacket (21), so that the cooling medium (W) can be ejected from the outlet (22a) of the inner jacket (22) toward the closed end (21c) of the outer jacket (21). This allows the cooling medium (W) to be intensively cooled at the end (21c) of the outer jacket (21), which is easily affected by the temperature inside the furnace, with the cooling medium (W). In particular, by colliding the jet of the cooling medium W with the tip portion 21c of the outer jacket 21, the tip portion 21c of the outer jacket 21 can be cooled more efficiently. By cooling the tip portion 21c of the outer jacket 21 in this manner, the temperature difference (temperature gradient) occurring in the tip portion can be reduced, and as a result, the thermal stress can be reduced. In addition, the outer jacket (21) can be kept at an appropriate temperature by the cooling medium (W) guided from the outward path (23) to the return path (24) through the outlet (22a). This makes it possible to suppress, for example, condensation of water vapor contained in the gasification gas (G) and softening of lignin contained in the biomass fuel.

[0069] The cooling structure according to the second aspect of the present disclosure, in the first aspect, includes a flow rate adjustment unit (34) that adjusts the flow rate of the cooling medium (W) supplied to the outward path (23), and a control unit (36), and the control unit (36) controls the flow rate adjustment unit (34) to adjust the flow rate of the cooling medium (W) so that the flow velocity of the cooling medium (W) in the outward path (23) is 1 m / s or more and 4 m / s or less.

[0070] The cooling structure (20) of this embodiment includes a flow rate adjustment unit (34) that adjusts the flow rate of the cooling medium (W) supplied to the outward path (23), and a control unit (36). The control unit (36) adjusts the flow rate of the cooling medium (W) by controlling the flow rate adjustment unit so that the flow velocity of the cooling medium (W) in the outward path (23) is 1 m / s or more and 4 m / s or less. Therefore, a sufficient amount of cooling medium (W) can be evenly sprayed from each nozzle (22a) while reducing pressure loss in the outward path (23) as much as possible.

[0071] The cooling structure according to a third aspect of the present disclosure, in the first or second aspect, includes a temperature adjustment unit (35) that adjusts the temperature of the cooling medium (W) supplied to the outward path (23), a temperature sensor (33) that measures the temperature of the outer jacket (21), and a control unit (36), and the control unit (36) controls the temperature adjustment unit (35) based on information obtained from the temperature sensor (33) to adjust the temperature of the cooling medium (W).

[0072] The cooling structure (20) of this embodiment includes a temperature adjustment unit (35) that adjusts the temperature of the cooling medium (W) supplied to the outward path (23), a temperature sensor (33) that measures the temperature of the outer jacket (21), and a control unit (36). The control unit (36) controls the temperature adjustment unit (35) based on information obtained from the temperature sensor (33) to adjust the temperature of the cooling medium (W). Therefore, by adjusting the temperature of the cooling medium (W), the temperature of the outer jacket (21) can be maintained at any desired temperature.

[0073] In the cooling structure according to a fourth aspect of the present disclosure, in the third aspect, the control unit (36) controls the temperature adjustment unit (35) to adjust the temperature of the cooling medium (W) so that the temperature of the outer jacket (21) is maintained at a temperature not lower than 80°C and not higher than 100°C.

[0074] According to the cooling structure (20) of this embodiment, the control unit (36) controls the temperature adjustment unit (35) to adjust the temperature of the cooling medium (W) so that the temperature of the outer jacket (21) is kept at 80°C or higher and 100°C or lower, thereby suppressing the condensation of water vapor contained in the gasification gas (G) flowing in from the furnace and suppressing the softening of lignin contained in the biomass fuel (e.g., wood-based fuel). By suppressing the condensation of water vapor, the possibility of the biomass fuel becoming wet and clogging the screw feeder (1) can be reduced. In addition, by suppressing the softening of lignin, the possibility of the biomass fuel adhering to the lignin and clogging the screw feeder (1) can be reduced.

[0075] A cooling structure according to a fifth aspect of the present disclosure is, in any one of the first to fourth aspects, such that the outer jacket (21) has a double-pipe structure having an outer pipe (21a) and an inner pipe (21b) extending along the direction of the axis (X), and the space in which the inner jacket (22) is provided is defined between the outer pipe (21a) and the inner pipe (21b).

[0076] According to the cooling structure (20) of this embodiment, the outer jacket (21) has a double-pipe structure having an outer pipe (21a) and an inner pipe (21b) extending along the direction of the axis (X). The space in which the outer jacket (21) is provided is defined between the outer pipe (21a) and the inner pipe (21b). Therefore, an inner jacket (22) can be provided inside the double-pipe structure.

[0077] A cooling structure according to a sixth aspect of the present disclosure is the fifth aspect, in which the outer jacket (21) is divided along the direction of the axis (X) to have a tip side portion (21t) including the tip portion (21c) and a main body portion (21m) other than the tip side portion (21t).

[0078] According to the cooling structure (20) of the present embodiment, the outer jacket (21) has a tip side portion (21t) including the tip portion (21c) and a main body portion (21m) other than the tip side portion (21t), which are divided along the direction of the axis (X). Therefore, the positions of the inner jacket (22) and the main body portion (21m) can be adjusted while being visually confirmed, and therefore, a highly accurate cooling structure 20 can be easily manufactured.

[0079] A cooling structure according to a seventh aspect of the present disclosure is the sixth aspect, in which the tip side portion (21t) and the main body portion (21m) are joined by a welded portion (21w), and the welded portion (21w) is formed at a distance from the tip portion (21c) that is 30% or more of the inner diameter of the inner pipe (21b).

[0080] According to the cooling structure (20) of this embodiment, the tip side portion (21t) and the main body portion (21m) are joined by the welded portion (21w), and the welded portion (21w) is formed at a distance of 30% or more of the inner diameter of the inner pipe (21b) from the tip portion (21c), so that the welded portion (21w) can be formed while avoiding the area (area within a distance of less than 30%) on the tip portion (21c) side where a large temperature difference (temperature gradient) occurs. This allows the welded portion (21w) to be formed while avoiding the area where a large thermal stress occurs. Therefore, the possibility that the welded portion (21w) will be damaged by thermal stress can be reduced.

[0081] A screw feeder (1) according to an eighth aspect of the present disclosure comprises a cooling structure (20) according to any one of the first to seventh aspects and a screw (11), and the outer jacket (21) of the cooling structure (20) is a casing that houses the screw (11).

[0082] A cooling method according to a ninth aspect of the present disclosure is a cooling method using the cooling structure (20) described in any of the first to seventh aspects, in which a cooling medium (W) is ejected from the ejection port (22a) and caused to collide with the blocked tip portion (21c) of the outer jacket (21). [Explanation of symbols]

[0083] 1. Screw feeder 11 Screw 11a Rotation axis 11b Feather 12 Bearings 20 Cooling structure (casing) 21 Outer jacket 21a outer tube 21b Inner tube 21c Occlusion (tip) 21m Main unit 21t Tip side 21w welding part 22 Inner jacket 22a spout 22b Outer tube 22c inner tube 22d Occlusion 23 Outbound 24 Return 31 Motor 32 Fuel supply pipe 33 Temperature Sensor 34 Circulation pump (flow rate control section) 35 Temperature control section 35a heat exchanger 35b Heating / cooling device 36 Control Unit 50 Gasifier 51 Fireproof materials 52 Gasifier outer wall 53 Mounting seat 54 Heat insulation material G Synthetic gas L1 Supply Line L2 Discharge line W Cooling medium X rotation axis

Claims

1. A cooling structure of a screw feeder for supplying biomass fuel into a gasification furnace, an outer jacket that defines a space inside and has a closed tip portion located inside the furnace, an inner jacket provided in the space of the outer jacket, defining a forward path of a cooling medium inside and a return path of the cooling medium between the inner jacket and the outer jacket, and having an ejection port through which the cooling medium flowing through the forward path is ejected formed at a position facing the closed tip portion of the outer jacket, and a cooling structure including the same.

2. a flow rate adjustment unit for adjusting the flow rate of the cooling medium supplied to the forward path, a control unit, and including the same, The control unit controls the flow rate adjustment unit so that the flow velocity of the cooling medium in the forward path is 1 m / s or more and 4 m / s or less to adjust the flow rate of the cooling medium. The cooling structure according to Claim 1.

3. a temperature adjustment unit for adjusting the temperature of the cooling medium supplied to the forward path, a temperature sensor for measuring the temperature of the outer jacket, a control unit, and including the same, The control unit controls the temperature adjustment unit based on the information obtained from the temperature sensor to adjust the temperature of the cooling medium. The cooling structure according to Claim 1.

4. The biomass fuel contains lignin, and the control unit controls the temperature adjustment unit so that the temperature of the outer jacket is maintained at a temperature of 80°C or more and 100°C or less to adjust the temperature of the cooling medium. The cooling structure according to Claim 3.

5. The outer jacket has a double-tube structure having an outer tube and an inner tube extending along the axial direction, and the space where the inner jacket is provided is defined between the outer tube and the inner tube. The cooling structure according to Claim 1.

6. The cooling structure according to claim 5, wherein the outer jacket has a tip side portion including the tip portion and a main body portion other than the tip side portion, which are divided along the direction of the axis.

7. The tip side portion and the main body portion are joined by a welded portion, The cooling structure according to claim 6, wherein the welded portion is formed at a distance of 30% or more of the inner diameter of the inner tube from the tip portion.

8. The cooling structure according to claim 1, a screw, and a screw feeder, wherein the outer jacket of the cooling structure is a casing for housing the screw.

9. A cooling method using the cooling structure according to claim 1, the cooling method comprising ejecting a cooling medium from the ejection port to cause the cooling medium to collide with the closed tip portion of the outer jacket.

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