Mechanical grate furnace

Abstract

The mechanical grate furnace includes: a furnace main body that defines a treatment space for conveying the object to be incinerated in the conveying direction and includes a combustion section for combustion; a furnace that extends upward from the furnace main body and discharges the exhaust gas generated in the treatment space; and a first gas nozzle that injects a part of the exhaust gas into the treatment space. The central axis of the furnace is arranged to be offset from the combustion section in the conveying direction to a different position, and the first gas nozzle injects the exhaust gas upward from the side opposite to the offset direction of the furnace in the conveying direction above the flame formed in the treatment space.

Description

Technical Field

[0001] The present disclosure relates to a mechanical grate furnace.

[0002] This application claims priority from Japanese Patent Application No. 2019-216540 filed on November 29, 2019, the content of which is incorporated herein by reference. Background Art

[0003] As a device for incinerating waste (the object to be incinerated), a mechanical grate furnace has been widely used so far. For example, as described in Patent Document 1, a mechanical grate furnace includes: a main combustion chamber having a drying section, a combustion section, and a post-combustion section arranged in order from the upstream side to the downstream side in the conveying direction; a feeder for feeding the object to be incinerated from the drying section side into the main combustion chamber; and a furnace for discharging the exhaust gas generated in the main combustion chamber.

[0004] In the main combustion chamber, a flame is formed along with the combustion of the object to be incinerated. The exhaust gas generated by this flame is discharged to the outside through a furnace located above the combustion section.

[0005] Prior Art Documents

[0006] Patent Document 1: Japanese Patent No. 6030913 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] However, as in the device described in the above Patent Document 1, when the position where the flame is formed is the same as the horizontal position of the furnace, in the regions outside the flame (i.e., the region on the drying section side and the region on the post-combustion section side), the heat of the flame does not reach sufficiently, so it is difficult to promote drying and post-combustion. As a result, it may lead to a reduction in the efficiency of the device due to an increase in NOx or an increase in unburned gas.

[0009] The present disclosure is made to solve the above problems, and an object thereof is to provide a mechanical grate furnace that can be operated with higher efficiency by optimizing the position where the flame is formed.

[0010] Technical Means for Solving the Problems

[0011] In order to solve the above problems, the mechanical grate furnace according to the present disclosure is configured to include: a furnace main body that defines a treatment space having a drying section, a combustion section, and a post-combustion section arranged in the conveying direction, and that dries, burns, and post-burns the objects to be incinerated by conveying them in the conveying direction; a feeder that supplies the objects to be incinerated to the furnace main body from the drying section side; a furnace that extends upward from the furnace main body and discharges the exhaust gas generated in the treatment space; and a gas circulation unit that has a first gas nozzle which extracts a part of the exhaust gas and injects it into the treatment space. The central axis of the furnace is arranged to be offset in the conveying direction from a position different from the combustion section, and the first gas nozzle injects the exhaust gas from a side opposite to the offset direction of the furnace in the conveying direction, so that the flame formed in the treatment space grows in the conveying direction away from the furnace.

[0012] Advantages of the Invention

[0013] The mechanical grate furnace according to the present disclosure can be operated with higher efficiency by optimizing the position where the flame is formed. Brief Description of the Drawings

[0014] Figure 1 It is an overall view showing the structure of the incineration system according to the first embodiment of the present disclosure.

[0015] Figure 2 It is a cross-sectional view showing the structure of the mechanical grate furnace according to the first embodiment of the present disclosure.

[0016] Figure 3 It is a top view showing the structure of the mechanical grate furnace according to the first embodiment of the present disclosure.

[0017] Figure 4 It is a cross-sectional view showing the structure of the mechanical grate furnace according to the second embodiment of the present disclosure.

[0018] Figure 5 It is a top view showing the structure of the mechanical grate furnace according to the second embodiment of the present disclosure.

[0019] Figure 6 It is a cross-sectional view showing the structure of the mechanical grate furnace according to the third embodiment of the present disclosure.

[0020] Figure 7 It is a cross-sectional view showing the structure of the mechanical grate furnace according to the fourth embodiment of the present disclosure.

[0021] Figure 8 It is a cross-sectional view showing the structure of the mechanical grate furnace according to the fifth embodiment of the present disclosure. Detailed Description of the Embodiments

[0022] <First Embodiment>

[0023] (Structure of Incineration System)

[0024] Hereinafter, with reference to Figures 1 to 3 the structure of the incineration system 100 and the mechanical grate furnace 1 according to the first embodiment of the present disclosure will be described. The incineration system 100 is a device for incinerating waste as an object to be incinerated. As Figure 1 shown, the incineration system 100 includes: a mechanical grate furnace 1, a heat recovery boiler 8, a cooling tower 9, a dust collection device 11, and a chimney 12.

[0025] The mechanical grate furnace 1 conveys the object to be incinerated and burns it. Along with the combustion, exhaust gas is generated from the mechanical grate furnace 1. This exhaust gas is conveyed to the heat recovery boiler 8 provided on the downstream side of the mechanical grate furnace 1. The heat recovery boiler 8 heats water by exchanging heat between the exhaust gas and water to generate steam. This steam is utilized in an external device (not shown). The exhaust gas that has passed through the heat recovery boiler 8 is cooled by the cooling tower 9 and then conveyed to the dust collection device 11. After the soot and dust are removed by the dust collection device 11, the exhaust gas is discharged into the atmosphere through the chimney 12.

[0026] (Structure of Mechanical Grate Furnace)

[0027] Next, the structure of the mechanical grate furnace 1 will be described. As Figure 1 shown, the mechanical grate furnace 1 has: a furnace main body 10; a firebox 7 extending upward from the furnace main body 10; a hopper 3 for temporarily storing the object to be incinerated; a feeder 31 for feeding the object to be incinerated into the furnace main body 10; a grate 6 provided at the bottom of the furnace main body 10; a wind box 2 provided below the grate 6; a blower B1; a primary air pipeline L1; a secondary air pipeline L2; and a gas circulation unit 4 for extracting a part of the exhaust gas and circulating it in the furnace main body 10.

[0028] A treatment space V for burning the object to be incinerated is formed inside the furnace main body 10. In this treatment space V, the object to be incinerated is conveyed in the conveying direction Da (refer to Figure 2 ) by the grate 6. In the present embodiment, the conveying direction Da is set to the horizontal direction. On the other hand, as the conveying direction Da, a direction inclined with respect to the horizontal plane can also be adopted. The firebox 7 extends upward from the upper part of the furnace main body 10. Through the firebox 7, the exhaust gas in the treatment space V is conveyed to the heat recovery boiler 8. The primary air pipeline L1 connects the blower B1 and the wind box 2. By driving the blower B1, air is supplied to the wind box 2 through the primary air pipeline L1. The wind box 2 supplies air into the treatment space V. The secondary air pipeline L2 connects the blower B1 and the inside of the firebox 7. Combustion air is supplied into the firebox 7 through the secondary air pipeline L2.

[0029] (Structure of the gas circulation section)

[0030] The gas circulation section 4 regulates the position, shape, and temperature of the flame F formed in the treatment space V by supplying the exhaust gas extracted from the flow path of the exhaust gas connecting the dust collector 11 and the chimney 12 into the treatment space V. The gas circulation section 4 includes an exhaust gas circulation pipeline L3, blowers B2 and B3, a first gas nozzle 41, and a second gas nozzle 42. The exhaust gas circulation pipeline L3 connects an intermediate position of the flow path of the exhaust gas connecting the dust collector 11 and the chimney 12 to the treatment space V. The blowers B2 and B3 press the exhaust gas in the exhaust gas circulation pipeline L3 toward the treatment space V side. The first gas nozzle 41 and the second gas nozzle 42 jet the exhaust gas into the flame F in the treatment space V.

[0031] Refer to Figure 2 , and the structure of the furnace main body 10 and the arrangement of the first gas nozzle 41 and the second gas nozzle 42 will be described in detail. As shown in this figure, the treatment space V in the furnace main body 10 is divided by an upstream surface 10A on the upstream side in the conveying direction Da, an upper surface 10B located above the air box 2 across the treatment space V, a downstream surface 10C on the downstream side in the conveying direction Da, and a plurality of air boxes 2.

[0032] The air box 2 forms the bottom surface of the treatment space V. A plurality of air boxes 2 (five as an example) are arranged in the conveying direction Da. Among these air boxes 2, two air boxes 2 counted from the upstream side in the conveying direction Da (i.e., the hopper 3 side) form a drying section 21. One air box 2 located on the downstream side of the drying section 21 forms a combustion section 22, and two air boxes 2 on the further downstream side form a post-combustion section 23. The drying section 21 dries the incinerated material supplied from the hopper 3 before burning. In the combustion section 22 and the post-combustion section 23, the dried incinerated material is burned. The burned incinerated material is discharged to the outside through a discharge chute 13 provided on the downstream side. The flame F generated by the combustion is mainly formed above the combustion section 22.

[0033] The furnace 7 is arranged at a position deviated toward the downstream side (post-combustion section 23 side) in the conveying direction Da with respect to the central portion of the furnace main body 10. More specifically, the center line O (central axis) of the furnace 7 is arranged at a position different from (not overlapping with) the above combustion section 22 in the conveying direction Da. More specifically, when the dimension of the treatment space V in the conveying direction Da is set to 100%, the center line O is arranged at a position within 25% from the downstream surface 10C. In the following description, the direction of the center line O on which the furnace 7 is arranged with respect to the central portion of the furnace main body 10 may sometimes be simply referred to as the "deviation direction".

[0034] The first gas nozzle 41 is provided on the upstream surface 10A. The first gas nozzle 41 ejects exhaust gas from the upstream surface 10A on the side opposite to the offset direction of the furnace 7 toward the downstream side in the conveying direction Da. More specifically, the flow direction of the gas ejected from the first gas nozzle 41 is adjusted so as to pass above the flame F formed in the processing space V. In addition, as Figure 3 shown, a plurality of first gas nozzles 41 are arranged at intervals in the horizontal direction (width direction Db) orthogonal to the conveying direction Da.

[0035] Again, as Figure 2 shown, the second gas nozzle 42 is provided on the upper surface 10B. The second gas nozzle 42 ejects exhaust gas downward from the upper surface 10B. The second gas nozzle 42 is provided above the combustion section 22 or at a position slightly biased toward the post-combustion section 23 side in the conveying direction Da. And, as Figure 3 shown, a plurality of second gas nozzles 42 are arranged at intervals in the width direction Db. In addition, as shown in this figure, the positions of the first gas nozzle 41 and the second gas nozzle 42 in the width direction Db are different from each other. That is, when viewed from the conveying direction Da, the first gas nozzle 41 and the second gas nozzle 42 do not overlap. Further in other words, in the width direction Db, the first gas nozzle 41 and the second gas nozzle 42 are alternately arranged.

[0036] (Function and effect)

[0037] When the mechanical grate furnace 1 is operated, first, the object to be incinerated is supplied into the processing space V from the hopper 3, and under the state of blowing air from the air box 2, after the object to be incinerated is dried, ignition is carried out. In this state, the object to be incinerated is conveyed toward the downstream side in the conveying direction Da by driving the grate 6. Along with the conveyance, the object to be incinerated passes through drying based on the drying section 21, combustion based on the combustion section 22 and the post-combustion section 23, and is discharged to the outside through the discharge chute 13. Here, the flame F generated along with the combustion of the object to be incinerated is formed above the combustion section 22. In the drying section 21, the radiant heat of the flame F is used to perform a drying process on the object to be incinerated.

[0038] Here, in the present embodiment, a part of the exhaust gas is supplied to the upper part of the flame F through the first gas nozzle 41. The first gas nozzle ejects exhaust gas into the processing space V from the drying section 21 side. Through the flow A1 of this exhaust gas (refer to Figure 2), a secondary flow A2 is formed within the processing space V, flowing from the combustion zone 22 toward the drying zone 21. Consequently, the flame F formed primarily in the combustion zone 22 is drawn by this secondary flow A2 and grows toward the drying zone 21, moving away from the combustion zone 22. In other words, the flame F grows in the conveying direction Da, away from the furnace 7. The heat from this flame F promotes the drying of the incinerated material in the drying zone 21. Consequently, NOx and unburned gases can be reduced.

[0039] Moreover, according to the above-mentioned structure, the flame F is disturbed by ejecting exhaust gas from the top of the processing space V through the second gas nozzle 42. By generating this disturbance, the combustible gas reacts with oxygen, and the oxygen-deficient area in the flame F expands. In other words, the fuel-rich area expands. As a result, the amount of NOx generated can be further reduced. In addition, the second gas nozzle 42 is arranged at a position different from the first gas nozzle 41 in the horizontal direction (width direction Db). As a result, the flow A1 of the exhaust gas ejected from the first gas nozzle 41 and the flow A3 of the exhaust gas ejected from the second gas nozzle 42 are not likely to interfere with each other. On the other hand, when these two flows A1 and A3 interfere with each other, it is difficult for any flow to reach the flame F. According to the above-mentioned structure, such a possibility can be reduced.

[0040] <Second embodiment>

[0041] Next, refer to Figure 4 and Figure 5 The second embodiment of the present disclosure will be described. In addition, the same reference numerals are given to the same structures as those in the first embodiment, and detailed descriptions thereof will be omitted. Figure 4 As shown, the furnace body 10 according to this embodiment further includes a temperature detection unit 20 for detecting the temperature distribution in the processing space V, a plurality of second gas nozzles 42A and 42B, and a flow rate control unit 50 on the upper surface 10B of the furnace body 10 .

[0042] Specifically, a thermal imager is preferably used as the temperature detection unit 20. Figure 5 As shown in FIG. 1 , it is preferable that a plurality of temperature detection units 20 (two as an example) are provided at intervals in the width direction Db.

[0043] The second gas nozzles 42A and 42B are arranged at intervals in the conveying direction Da on the upper surface 10B. Additionally, a structure with three or more second gas nozzles can also be adopted. The flow control unit 50 changes the flow rate distribution of the exhaust gas ejected from the second gas nozzles 42A and 42B respectively based on the temperature distribution detected by the temperature detection unit 20. More specifically, a structure is adopted in which the flow rate distribution is changed as described above by adjusting the opening degrees of the regulating valves (not shown) of the respective second gas nozzles among the two second gas nozzles 42A and 42B.

[0044] According to the above structure, for example, when the temperature on the post-combustion section 23 side in the processing space V becomes relatively high, the flame F can be moved toward the drying section 21 side by relatively increasing the flow rate of the exhaust gas from the second gas nozzle 42B on the post-combustion section 23 side. Conversely, when the temperature on the drying section 21 side in the processing space V becomes relatively high (more specifically, when the temperature of the drying section 21 becomes higher than the allowable value or higher than the thermal NOx generation temperature), the flame F can be moved toward the post-combustion section 23 side by relatively increasing the flow rate of the exhaust gas from the second gas nozzle 42A on the drying section 21 side. Thereby, the temperature distribution in the processing space V is optimized, and the generation amounts of NOx and unburned gas can be suppressed. Additionally, thereby, the lifespan of the equipment can also be extended.

[0045] <Third Embodiment>

[0046] Next, refer to Figure 6 The third embodiment of the present disclosure will be described. Additionally, the same reference numerals are assigned to the same structures as those in the above-described embodiments, and detailed descriptions thereof are omitted. As shown in this figure, in the present embodiment, in addition to the structure of the above-described first embodiment, the gas circulation unit 4 further has a third gas nozzle 43 that ejects a part of the exhaust gas from the downstream surface 10C. The third gas nozzle 43 is provided at a position lower than the first gas nozzle 41. The third gas nozzle 43 ejects the exhaust gas into the processing space V from the side opposite to the first gas nozzle 41. That is, the flow A4 of the gas ejected from the third gas nozzle 43 collides with the flame F in the processing space V from the downstream side in the conveying direction Da.

[0047] According to the above structure, in addition to the secondary flow A2 generated by the exhaust gas ejected from the first gas nozzle 41, the flame F can be further moved toward the first gas nozzle 41 side (drying section 21 side) by the fluid force of the flow A4 ejected from the third gas nozzle 43. Thereby, the formation position of the flame F in the processing space V is optimized, and the drying process in the drying section 21 is promoted. As a result, the generation amounts of NOx and unburned gas can be further reduced.

[0048] <Fourth Embodiment>

[0049] Next, with reference to Figure 7 a fourth embodiment of the present disclosure will be described. In addition, the same reference numerals are given to the same structures as those in the above-described embodiments, and detailed descriptions thereof are omitted. As shown in this figure, in the present embodiment, on the upper surface 10B of the furnace main body 10, in addition to the temperature detection unit 20 described in the second embodiment, a second gas nozzle 42C, a moving unit 70 that supports the second gas nozzle 42C so as to be movable in the conveying direction Da, and a moving control unit 60 that operates the moving unit 70 based on the detection result of the temperature detection unit 20 are provided.

[0050] According to the above structure, the position of the second gas nozzle 42C in the conveying direction Da can be adjusted by the moving unit 70. The position of the second gas nozzle 42C is adjusted (changed) based on the temperature distribution in the processing space V. Therefore, for example, when the temperature on the post-combustion section 23 side in the processing space V becomes relatively high, the flame F can be moved toward the drying section 21 side by moving the second gas nozzle 42C toward the post-combustion section 23 side. On the contrary, when the temperature on the drying section 21 side in the processing space V becomes relatively high (more specifically, when the temperature of the drying section 21 becomes higher than the allowable value or higher than the generation temperature of thermal NOx), the flame F can be moved toward the post-combustion section 23 side by moving the second gas nozzle 42C toward the drying section 21 side. Thereby, the temperature distribution in the processing space V is optimized, and the generation amounts of NOx and unburned gas can be suppressed. In addition, thereby, the life of the equipment can also be extended.

[0051] In addition, instead of the structure described in the above fourth embodiment, the moving unit 70 may support the second gas nozzle 42C so as to be able to change the ejection exhaust direction of the second gas nozzle 42C along the conveying direction Da. The moving control unit 60 changes the angle of the second gas nozzle 42C with respect to the upper surface 10B of the furnace main body 10 based on the temperature distribution in the processing space V, and changes the ejection direction of the exhaust gas from the second gas nozzle 42C along the conveying direction Da. And, in the same manner as in the above fourth embodiment, when the temperature on the post-combustion section 23 side in the processing space V becomes relatively high, the ejection direction of the exhaust gas from the second gas nozzle 42C can be changed toward the post-combustion section 23, so that the flame F is moved toward the drying section 21 side. In addition, when the temperature on the drying section 21 side in the processing space V becomes relatively high, the ejection direction of the exhaust gas from the second gas nozzle 42C can be changed toward the drying section 21, so that the flame F is moved toward the post-combustion section 23 side. [[ID=IO]]

[0052] In addition, in the structure described in the fourth embodiment above, it is also possible to combine the structure including the temperature detection unit 20, the plurality of second gas nozzles 42A and 42B, and the flow control unit 50 described in the second embodiment.

[0053] <Fifth Embodiment>

[0054] Next, Figure 8 a description will be given of the fifth embodiment of the present disclosure. In addition, the same reference numerals are assigned to the same structures as those in the above-described embodiments, and detailed descriptions thereof are omitted. As shown in this figure, in the present embodiment, different from the above-described embodiments, the center line O (central axis) of the furnace 7B is disposed so as to be biased toward the drying section 21 side in the conveying direction Da. More specifically, the center line O (central axis) of the furnace 7 is disposed at a position different from (a non-overlapping position with) the above-described combustion section 22 in the conveying direction Da. More specifically, when the dimension in the conveying direction Da of the processing space V is set to 100%, the center line O is disposed at a position within 30% from the upstream surface 10A'.

[0055] Moreover, the first gas nozzle 41' is provided on the surface (downstream surface 10C') on the post-combustion section 23 side of the furnace body 10', and exhaust gas is jetted from the post-combustion section 23 side toward the drying section 21 side. In addition, a third gas nozzle 43' is provided on the surface (upstream surface 10A') on the drying section 21 side of the furnace body 10'. The third gas nozzle 43' is provided at a position lower than the first gas nozzle 41'. The third gas nozzle 43' jets exhaust gas into the processing space V from the side opposite to the first gas nozzle 41'. That is, the flow A4' of the gas jetted from the third gas nozzle 43' collides with the flame F in the processing space V from the upstream side in the conveying direction Da.

[0056] According to the above structure, the center line O of the furnace 7B is disposed to be biased toward the drying section 21 side. Moreover, the first gas nozzle 41' injects exhaust gas into the treatment space V from the post-combustion section 23 side. Through the flow A1' of this exhaust gas, a secondary flow A2' from the combustion section 22 side toward the post-combustion section 23 side is formed in the treatment space V. Therefore, the flame F mainly formed in the combustion section 22 is attracted by this secondary flow A2', and grows toward the post-combustion section 23 side in a manner of leaving the combustion section 22. That is, the flame F grows in the conveying direction Da in a direction away from the furnace 7B. By the heat of this flame F, the post-combustion of the incinerated material in the post-combustion section 23 is promoted. As a result, reduction of NOx and reduction of unburned gas can be achieved. In addition, in addition to the secondary flow A2' based on the exhaust gas injected from the first gas nozzle 41', the flame F can be further moved toward the first gas nozzle 41' side (post-combustion section 23 side) by the fluid force of the flow A4' of the exhaust gas injected from the third gas nozzle 43'. Thereby, the formation position of the flame F in the treatment space V is optimized, and the post-combustion in the post-combustion section 23 is promoted. As a result, the generation amount of NOx and unburned gas can be further reduced. In addition, in terms of causing the flame F to leave the combustion section 22, the third gas nozzle 43' is not essential, and even in a structure having only the first gas nozzle 41', the position of the flame F can be optimized as described above.

[0057] (Other embodiments)

[0058] As described above, the embodiments of the present disclosure have been described in detail with reference to the drawings, but the specific structure is not limited to this embodiment, and also includes design changes and the like within the scope not departing from the gist of the present disclosure. For example, with respect to the structure described in the fifth embodiment above, it is also possible to add the structure related to the second gas nozzle 42 described in the first embodiment, the second embodiment, and the fourth embodiment (or a structure that changes the flow rate distribution of the second gas nozzles 42A and 42B and a structure that moves the second gas nozzle 42C in the conveying direction Da).

[0059] <Supplementary note>

[0060] The mechanical grate furnace 1 described in each embodiment can be understood as follows, for example.

[0061] (1) The mechanical grate furnace 1 according to the first mode includes: a furnace main body 10 that delimits a treatment space V that conveys an object to be incinerated in a conveying direction Da and burns it; a furnace 7 that extends upward from the furnace main body 10 and discharges exhaust gas generated in the treatment space V; and a first gas nozzle 41 that injects a part of the exhaust gas into the treatment space V. The center line O of the furnace 7 is arranged to deviate from a position different from the combustion section 22 in the conveying direction Da, and the first gas nozzle 41 injects the exhaust gas above a flame F formed in the treatment space V from a side opposite to the deviation direction of the furnace 7 in the conveying direction Da.

[0062] According to the above structure, the central axis (center line O) of the furnace 7 is arranged to deviate from a position different from the combustion section 22. Moreover, the first gas nozzle 41 injects the exhaust gas into the treatment space V from a side opposite to the deviation direction of the furnace 7. Through the flow of the exhaust gas, a secondary flow is formed in the treatment space V toward a side opposite to the deviation direction of the furnace 7. Therefore, the flame F mainly formed in the combustion section 22 is attracted by this secondary flow and grows in a direction away from the combustion section 22. That is, the flame F grows in the conveying direction Da in a direction away from the furnace 7. Through the heat of the flame F, the drying of the object to be incinerated in the drying section 21 or the post-combustion in the post-combustion section 23 is promoted. As a result, the reduction of NOx and the reduction of unburned gas can be achieved.

[0063] (2) In the mechanical grate furnace Ⅰ according to the second mode, the central axis (center line O) of the furnace 7 is arranged to deviate toward the post-combustion section 23 side in the conveying direction Da, and the first gas nozzle 41 is provided on the drying section 21 side of the furnace main body 10 and injects the exhaust gas from the drying section 21 side toward the post-combustion section 23 side.

[0064] According to the above structure, the central axis (center line O) of the furnace 7 is arranged to deviate toward the post-combustion section 23 side. Moreover, the first gas nozzle 41 injects the exhaust gas into the treatment space V from the drying section 21 side. Through the flow of the exhaust gas, a secondary flow is formed in the treatment space V from the combustion section 22 side toward the drying section 21 side. Therefore, the flame F mainly formed in the combustion section 22 is attracted by this secondary flow and grows toward the drying section 21 side in a manner of leaving the combustion section 2%. That is, the flame F grows in the conveying direction Da in a direction away from the furnace 7. Through the heat of the flame F, the drying of the object to be incinerated at the drying section 21 is promoted. As a result, the reduction of NOx and the reduction of unburned gas can be achieved.

[0065] (3) In the mechanical grate furnace 1 involved in the third embodiment, the center axis (center line O) of the above-mentioned furnace 7B is arranged to be biased toward the above-mentioned drying section 21 side in the above-mentioned conveying direction Da, and the above-mentioned first gas nozzle 41′ is provided on the above-mentioned after-combustion section 23 side of the above-mentioned furnace body 10′, and the above-mentioned exhaust gas is ejected from the after-combustion section 23 side toward the above-mentioned drying section 21 side.

[0066] According to the above structure, the central axis (center line O) of the furnace 7B is set to be biased toward the drying section 21 side. Moreover, the first gas nozzle 41' ejects exhaust gas from the post-combustion section 23 side into the processing space V. Through the flow of the exhaust gas, a secondary flow is formed in the processing space V from the combustion section 22 side toward the post-combustion section 23 side. Therefore, the flame F mainly formed in the combustion section 22 is attracted by the secondary flow and grows toward the post-combustion section 23 side in a manner away from the combustion section 22. That is, the flame F grows in the direction away from the furnace 7B in the conveying direction Da. The heat of the flame F promotes the post-combustion of the incineration material in the post-combustion section 23. As a result, it is possible to achieve a reduction in NOx and a reduction in unburned gas.

[0067] (4) In the mechanical grate furnace 1 involved in the fourth embodiment, the above-mentioned gas circulation part 4 also has a second gas nozzle 42, which extracts a part of the above-mentioned exhaust gas and injects it into the above-mentioned processing space V from above. In the horizontal direction orthogonal to the above-mentioned conveying direction Da, the second gas nozzle 42 is arranged at a position different from the above-mentioned first gas nozzle 41.

[0068] According to the above structure, exhaust gas is ejected from the top of the processing space V through the second gas nozzle 42, thereby generating turbulence in the flame F. By generating this turbulence, the oxygen-deficient area in the flame F expands. In other words, the fuel-rich area expands. As a result, the amount of NOx generated can be further reduced. In addition, the second gas nozzle 42 is arranged at a different position from the first gas nozzle 41 in the horizontal direction. As a result, the flow of the exhaust gas ejected from the first gas nozzle 41 and the flow of the exhaust gas ejected from the second gas nozzle 42 are unlikely to interfere with each other. On the other hand, if these two flows interfere with each other, it will be difficult for any flow to reach the flame F. According to the above structure, such a possibility can be reduced.

[0069] (5) The mechanical grate furnace 1 involved in the fifth embodiment further comprises: a plurality of the above-mentioned second gas nozzles 42A, 42B, which are arranged at intervals in the above-mentioned conveying direction Da; a temperature detection unit 20, which detects the temperature distribution in the above-mentioned processing space V; and a flow control unit 50, which changes the flow distribution of the above-mentioned exhaust gas respectively injected from the above-mentioned plurality of the above-mentioned second gas nozzles 42A, 42B based on the above-mentioned temperature distribution.

[0070] According to the above structure, a plurality of second gas nozzles 42A and 42B are arranged at intervals in the conveying direction Da, and the distribution of the flow rate of the exhaust gas ejected from these second gas nozzles 42A and 42B is adjusted (changed) based on the temperature distribution in the processing space V. Therefore, for example, when the temperature on the post-combustion section 23 side in the processing space V becomes relatively high, the flame F can be moved toward the drying section side by relatively increasing the flow rate of the exhaust gas from the second gas nozzle 42B on the post-combustion section 23 side. Thus, the temperature distribution in the processing space V is optimized, and the generation amounts of NOx and unburned gas can be suppressed.

[0071] (6) The mechanical grate furnace 1 according to the sixth aspect further includes: a moving unit 70 that moves the second gas nozzle 42C in the conveying direction Da; a temperature detection unit 20 that detects the temperature distribution in the processing space V; and a movement control unit 60 that operates the moving unit 70 based on the temperature distribution, so that the position of the second gas nozzle 42C or the direction of ejecting the exhaust gas from the second gas nozzle 42C changes along the conveying direction Da.

[0072] According to the above structure, the position of the second gas nozzle 42C in the conveying direction Da can be adjusted by the moving unit 70, or the direction of ejecting the exhaust gas from the second gas nozzle 42C can be changed along the conveying direction Da. The movement control unit 60 adjusts (changes) the position of the second gas nozzle 42C or the angle of the second gas nozzle 42C with respect to the upper surface 10B of the furnace main body 10 based on the temperature distribution in the processing space V. Therefore, when the temperature on the post-combustion section 23 side in the processing space V becomes relatively high, the flame F can be moved toward the drying section 21 side by moving the second gas nozzle 42C toward the post-combustion section 23 side or changing the ejection direction of the exhaust gas from the second gas nozzle 42C toward the post-combustion section 23. In addition, when the temperature on the drying section 21 side in the processing space V becomes relatively high, the flame F can be moved toward the post-combustion section 23 side by moving the second gas nozzle 42C toward the drying section 21 side or changing the ejection direction of the exhaust gas from the second gas nozzle 42C toward the drying section 21. Thus, the temperature distribution in the processing space V is optimized, and the generation amounts of NOx and unburned gas can be suppressed.

[0073] (7) In the mechanical grate furnace 1 according to the seventh aspect, the gas circulation unit 4 further has a third gas nozzle 43, and the third gas nozzle 43 ejects the exhaust gas into the processing space V at a position below the first gas nozzle 41 and from the side opposite to the first gas nozzle 41.

[0074] According to the above structure, in addition to the secondary flow based on the exhaust gas ejected from the first gas nozzle 41, the fluid force of the exhaust gas ejected from the third gas nozzle 43 can further move the flame F toward the first gas nozzle 41 side. As a result, the formation position of the flame F in the processing space V is optimized, and the generation amounts of NOx and unburned gas can be further reduced.

[0075] Industrial applicability

[0076] The present invention relates to a mechanical grate furnace as a device for incinerating waste. According to the present invention, by optimizing the position where the flame is formed inside the furnace body, more efficient operation can be achieved.

[0077] Explanation of reference numerals

[0078] 100 Incineration system

[0079] 1 Mechanical grate furnace

[0080] 2 Air box

[0081] 3 Hopper

[0082] 4 Gas circulation section

[0083] 6 Grate

[0084] 7, 7B Firebox

[0085] 8 Waste heat recovery boiler

[0086] 9 Cooling tower

[0087] 10 Furnace body

[0088] 10A Upstream surface

[0089] 10B Upper surface

[0090] 10C Downstream surface

[0091] 11 Dust collecting device

[0092] 12 Chimney

[0093] 13 Discharge trough

[0094] 20 Temperature detection section

[0095] 21 Drying section

[0096] 22 Combustion section

[0097] 23 Afterburning section

[0098] 31 Feeder

[0099] 41 First gas nozzle

[0100] 42, 42A, 42B, 42C Second gas nozzle

[0101] 43 Third gas nozzle

[0102] 50 Flow control section

[0103] 60 Movement control section

[0104] 70 Moving section

[0105] B1, B2, B3 Blower

[0106] F Flame

[0107] L1 Primary air pipeline

[0108] L2 Secondary air pipeline

[0109] L3 Exhaust gas circulation pipeline

[0110] O Center line (central axis)

[0111] V Processing space.

Claims

1. A mechanical grate furnace, comprising: A furnace body that defines a processing space for conveying an object to be incinerated in a conveying direction and includes a drying section for drying the object to be incinerated, a combustion section for combustion, and a post-combustion section; A firebox that extends upward from the furnace body and discharges the exhaust gas generated in the processing space; and A first gas nozzle that injects a part of the exhaust gas into the processing space, The central axis of the firebox is arranged to be biased toward the downstream side in the conveying direction relative to the combustion section, The first gas nozzle is provided on the upstream surface of the furnace body on the upstream side of the combustion section in the conveying direction, faces the downstream side in the conveying direction, and injects the exhaust gas above the flame formed in the processing space, thereby causing the flame to grow upstream of the combustion section.

2. The mechanical grate furnace according to claim 1, wherein, The mechanical grate furnace further includes a second gas nozzle that extracts a part of the exhaust gas and injects it into the processing space from above, In the horizontal direction orthogonal to the conveying direction, the second gas nozzle is provided at a position different from that of the first gas nozzle.

3. The mechanical grate furnace according to claim 2, wherein, The mechanical grate furnace further includes: A plurality of the second gas nozzles arranged at intervals in the conveying direction; A temperature detection unit that detects the temperature distribution in the processing space; And A flow control unit that changes the flow rate distribution of the exhaust gas injected from the plurality of second gas nozzles respectively based on the temperature distribution.

4. The mechanical grate furnace according to claim 2, wherein, The mechanical grate furnace further includes: A moving unit that moves the second gas nozzle in the conveying direction; A temperature detection unit that detects the temperature distribution in the processing space; and A movement control unit that operates the moving unit based on the temperature distribution, so that the position of the second gas nozzle or the direction of injecting the exhaust gas from the second gas nozzle changes along the conveying direction.

5. The mechanical grate furnace according to any one of claims 1 to 4, wherein, The mechanical grate furnace further includes a third gas nozzle that injects the exhaust gas into the processing space below the first gas nozzle and from the side opposite to the first gas nozzle.

6. A mechanical grate furnace, comprising: A furnace body that defines a processing space for conveying an object to be incinerated in a conveying direction and includes a drying section for drying the object to be incinerated, a combustion section for combustion, and a post-combustion section; A firebox that extends upward from the furnace body and discharges the exhaust gas generated in the processing space; and A first gas nozzle that injects a part of the exhaust gas into the processing space, The central axis of the firebox is arranged to be biased toward the upstream side in the conveying direction relative to the combustion section, The first gas nozzle is provided on the downstream surface of the furnace body on the downstream side of the combustion section in the conveying direction, faces the upstream side in the conveying direction, and injects the exhaust gas above the flame formed in the processing space, thereby causing the flame to grow downstream of the combustion section.

7. The mechanical grate furnace according to claim 6, wherein, the mechanical grate furnace further includes a second gas nozzle that extracts a part of the exhaust gas and injects it into the treatment space from above, in a horizontal direction orthogonal to the conveying direction, the second gas nozzle is disposed at a position different from that of the first gas nozzle.

8. The mechanical grate furnace according to claim 7, wherein, the mechanical grate furnace further includes: a plurality of the second gas nozzles arranged at intervals in the conveying direction; a temperature detection unit that detects the temperature distribution in the treatment space; and a flow rate control unit that changes the flow rate distribution of the exhaust gas ejected from the plurality of second gas nozzles based on the temperature distribution.

9. The mechanical grate furnace according to claim 7, wherein, the mechanical grate furnace further includes: a moving unit that moves the second gas nozzle in the conveying direction; a temperature detection unit that detects the temperature distribution in the treatment space; and a movement control unit that operates the moving unit based on the temperature distribution, so that the position of the second gas nozzle or the direction of ejecting the exhaust gas from the second gas nozzle changes along the conveying direction.

10. The mechanical grate furnace according to any one of claims 6 to 9, wherein, the mechanical grate furnace further includes a third gas nozzle that injects the exhaust gas into the treatment space at a position below the first gas nozzle and from a side opposite to the first gas nozzle.

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