Technical Field
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The present invention relates to a pallet monitoring system and a pallet monitoring method for monitoring pallets of a sintering machine used in the production of sintered ore.
Background Art
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In an endless pallet chain moving sintering machine for producing sintered ore for ironmaking, the floor surface of a pallet is formed by a large number of grate bars on which the sintering raw material is placed. In the endless pallet chain moving sintering machine, air within the sintering raw material is drawn downward through gaps formed between adjacent grate bars, thereby moving a combustion-melting zone in the sintering raw material downward, and thus producing sintered ore. The grate bars are supported by adjacent pallet frames and are configured so as not to detach from the pallet even when the pallet is inverted.
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In such a pallet of the endless pallet chain moving sintering machine, when the pallet width reaches as much as 5 m, one hundred or more grate bars are installed in the width direction of the pallet. The grate bars detach from the pallet frames due to impact when the sintering raw material is charged onto the pallet, or due to impacts caused by inversion at the charging section and the discharging section.
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When a grate bar detaches, the sintering raw material charged into that portion falls into a wind box below, making a hole. When such a state occurs, air leakage through the hole becomes significant, and suction air does not flow around the hole, resulting in the remaining of unsintered raw material. This leads to a significant reduction in the yield of sintered ore. When a detached grate bar is discharged together with the sintered ore, the grate bar may become caught in a chute used for transporting the sintered ore, causing clogging, or may damage a transportation conveyor. Thus, detachment of grate bars from the pallet has a significantly adverse impact on the operation of the sintering machine.
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As a technique for detecting detachment of grate bars, Patent Literature 1 discloses a grate bar detachment detection device for a sintering machine, in which a distance meter is used to measure the distance to a grate bar, and when the distance becomes infinite or increases significantly beyond a set distance, it is determined that the grate bar has detached.
Citation List
Patent Literature
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PTL 1:
Japanese Unexamined Patent Application Publication No. 4-276030 Summary of Invention
Technical Problem
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In Patent Literature 1, the distance from a fixed point is measured with a distance meter to detect the detachment of grate bars at an early stage. However, since this device is configured to detect detachment only after a grate bar has already come off, the problem remains that detachment of the grate bars cannot be suppressed. The present invention has been made in view of such prior art, and an object thereof is to provide a pallet monitoring system and a pallet monitoring method capable of identifying a grate bar that is likely to detach before the grate bar actually detaches.
Solution to Problem
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The following is a solution to solve the above problem.
- [1] A pallet monitoring system for monitoring a pallet of a sintering machine, the pallet having a floor surface formed by multiple grate bars, the system including: an imaging unit that captures an image of the multiple grate bars and generate image data; a calculation unit that calculates an inclination angle of each of the multiple grate bars based on the image data; and a determination unit that determines whether the inclination angle is greater than or equal to a predetermined threshold.
- [2] The pallet monitoring system according to [1], including a distance measuring unit that detects identification information that identifies the pallet.
- [3] The pallet monitoring system according to [1] or [2], wherein the imaging unit captures an image of the plurality of grate bars when the pallet passes through a predetermined position.
- [4] The pallet monitoring system according to any one of [1] to [3], wherein the calculation unit calculates an average value of inclination angles of a predetermined number of two or more grate bars, and the determination unit determines whether the average value is greater than or equal to a predetermined threshold.
- [5] The pallet monitoring system according to any one of [1] to [4], wherein the imaging unit is a digital camera having a lens and an image sensor, and the lens is coated with a surfactant.
- [6] A pallet monitoring method for monitoring a pallet of a sintering machine, the pallet having a floor surface formed by multiple grate bars, the method including: an imaging step of capturing an image of the multiple grate bars and generating image data; a calculation step of calculating an inclination angle of each of the multiple grate bars based on the image data; and a determination step of determining whether the inclination angle is greater than or equal to a predetermined threshold.
- [7] The pallet monitoring method according to [6], wherein the threshold is determined based on a correlation between the inclination angle of each grate bar and a number of days until each grate bar detaches.
Advantageous Effects of Invention
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In the pallet monitoring system and the pallet monitoring method according to the present invention, a grate bar that is likely to detach from the pallet is identified by determining whether the inclination of the grate bar is greater than or equal to a predetermined threshold. This allows detachment countermeasures to be taken only for grate bars that are likely to detach before they actually fall off, thereby enabling suppression of grate bar detachment while restraining an increase in maintenance costs.
Brief Description of Drawings
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- [Fig. 1] Fig. 1 is a schematic diagram illustrating an example of a sintered ore production facility.
- [Fig. 2] Fig. 2 is a schematic view of the upper surface of a pallet.
- [Fig. 3] Fig. 3 is a schematic diagram illustrating a configuration example of an image processing device.
- [Fig. 4] Fig. 4 includes schematic diagrams, one illustrating the pallet and the other illustrating grate bars.
- [Fig. 5] Fig. 5 is a graph representing the correlation between the inclination angles of grate bars and the number of days until the grate bars detach.
- [Fig. 6] Fig. 6 is a diagram illustrating the flow of a pallet monitoring method according to the present embodiment.
- [Fig. 7] Fig. 7 is a diagram illustrating an example of a pallet management table.
Description of Embodiments
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Hereinafter, a pallet monitoring system and a pallet monitoring method according to the present invention will be described using embodiments applied to a sintering machine for producing sintered ore. It is noted that the invention is not limited in any way by these embodiments.
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Fig. 1 is a schematic diagram illustrating an example of a sintered ore production facility 100. The sintered ore production facility 100 includes a pallet monitoring system 40 according to the present embodiment, and a sintering machine 10 having pallets 24 to be monitored by the pallet monitoring system 40. The sintering machine 10 is, for example, a Dwight-Lloyd sintering machine. In the sintering machine 10, the sintering raw material containing iron ore and carbonaceous material is cut from a surge hopper 12 provided in a charging section 34 of the sintering machine 10 by a roll feeder 14, and charged onto the endlessly moving pallets 24, thereby forming a charged layer of the sintering raw material. The thickness of the charged layer is controlled by adjusting the openings of multiple divided gates 16 provided in the width direction of the pallets 24.
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The carbonaceous material on the upper surface of the charged layer is ignited by an ignition furnace 18 provided downstream of the charging section 34. Furthermore, air is introduced into the charged layer by drawing air downward from a blower 22 through wind boxes 20 provided below the pallets 24, causing the carbonaceous material contained in the sintering raw material to combust. Due to the suction of the blower 22, air within the charged layer passes through gaps between grate bars 26 that form the floor surface of the pallets 24 and flows into the wind boxes 20. Consequently, the combustion position of the carbonaceous material in the charged layer gradually moves downward. The sintering raw material, sintered by the combustion heat due to the combustion of the carbonaceous material, forms a sintered cake, which is a sintered ore agglomerates, and this sintered cake is discharged from a discharging section 36. At the discharging section 36, the sintered cake that has fallen from the pallets 24 is crushed, cooled with a cooler, and granulated. In this manner, sintered ore is produced from the sintering raw material using the sintering machine 10.
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The sintering machine 10 is provided with 174 pallets 24. Fig. 2 is a schematic view of the upper surface of each pallet 24. In Fig. 2, each pallet 24 is provided with side walls 28, grate bars 26, and end grates 30. The side walls 28 are provided on both sides of each pallet 24 to prevent the charged sintering raw material from falling off. Each of three columns, i.e., column A, column B, and column C, is provided with 150 grate bars 26, and the floor surface of each pallet 24 is formed by a total of 450 grate bars 26. The grate bars 26 are supported with their upper and lower ends engaged with a pallet frame (not illustrated).
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The end grates 30, which are fixed to the side walls 28, are provided between the grate bars 26 and the side walls 28. The grate bars 26 are movably installed with respect to the pallet frame in a direction perpendicular to the traveling direction of each pallet 24. Therefore, the grate bars 26 may incline due to impact when the sintering raw material is charged onto each pallet 24, or due to impacts caused by inversion of each pallet 24 at the charging section 34 and the discharging section 36. On the other hand, since the end grates 30 are attached to the side walls 28, the end grates 30 do not incline even when the grate bars 26 incline due to such impacts.
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Now, referring again to Fig. 1, the pallet monitoring system 40 according to the present embodiment has an imaging unit 42, a distance measuring unit 44, and an image processing device 46. The imaging unit 42 is provided upstream of the charging section 34 in the moving direction of the pallets 24, and captures an image of each pallet 24 from an oblique upper position before the sintering raw material is charged. The imaging unit 42 captures an image of each pallet 24 and generates image data of each pallet 24 including a large number of grate bars 26 that constitute the floor surface, and the end grates 30. The imaging unit 42 transmits the generated image data to the image processing device 46. The imaging unit 42 is, for example, a digital camera having a lens and an image sensor. The image sensor is a CCD sensor or a CMOS sensor.
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The imaging unit 42 detects when each pallet 24 has passed through a predetermined position and captures an image of each pallet 24. By detecting passage through the predetermined position and capturing images in this manner, even when the pallet speed of the pallets 24 varies, an image of the grate bars 26 and the end grates 30 of each pallet 24 can be captured in the same way.
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Passage of each pallet 24 through the predetermined position is detected by separately installing a camera (not illustrated) that continuously captures images of the pallets 24 and monitoring the luminance values of the image data generated by the camera. At the connecting portions between successive pallets 24, the luminance value of the image data decreases significantly, and thus passage of each pallet 24 through the predetermined position can be detected by detecting this decrease in luminance.
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A large amount of dust is generated when charging the sintering raw material or when discharging a sintered cake. Accordingly, it is preferable that a surfactant be applied to the surface of the lens of the imaging unit 42. By applying a surfactant to the lens surface, electrostatic charging of the surface is suppressed, thereby suppressing adhesion of dust to the lens. As a result, whereas it was necessary to clean the lens once a month to remove adhered dust prior to applying the surfactant, after applying the surfactant, no dust adhered to the lens even after one year. The surfactant applied to the lens surface may be a nonionic surfactant, an anionic surfactant, a cationic surfactant, or an amphoteric surfactant.
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Identification information for identifying each of the 174 pallets 24 is engraved on the outer surface of the side walls 28 of each pallet 24, and a step is formed along an outer edge of the engraved portion. The distance measuring unit 44 measures the distance from the distance measuring unit 44 to the region including the identification information and generates distance information. By binarizing the distance information of the region to generate image data, the distance measuring unit 44 detects the identification information for identifying each pallet 24. The distance measuring unit 44 is, for example, a two-dimensional laser displacement meter, and the identification information is information composed of characters, numerals, and/or symbols.
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Model image data in which the identification information has been identified may be stored in advance in the distance measuring unit 44, and instead of generating binarized image data, the distance measuring unit 44 may perform geometric pattern matching to determine the similarity between the generated image data and the model image data. In this way, the distance measuring unit 44 may detect the identification information by identifying the model image having a high degree of similarity to the generated image data. The distance measuring unit 44 transmits the identified identification information to the image processing device 46.
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The image processing device 46 calculates the inclination angle of each of the grate bars 26 based on the image data transmitted from the imaging unit 42 and determines whether the inclination angle is greater than or equal to a predetermined threshold. The grate bars 26 forming the floor surface of each pallet 24 are installed so that their longitudinal directions extend along the side walls 28. The grate bars 26 incline due to impact when the sintering raw material is charged onto each pallet 24, or due to impacts caused by inversion at the charging section 34 and the discharging section 36, and their inclination angles gradually increase. When the inclination angles of the grate bars 26 become greater than or equal to a predetermined inclination angle, the grate bars 26 disengage from the pallet frame and detaches from the corresponding pallet 24. Accordingly, by calculating the inclination angle of the each of grate bars 26 with the image processing device 46 and determining whether the inclination angle is greater than or equal to the predetermined threshold, it is possible to identify the grate bars 26 that are likely to detach from the corresponding pallet 24 before they actually detach.
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Next, the image processing device 46 will be described. Fig. 3 is a schematic diagram illustrating a configuration example of the image processing device 46. The image processing device 46 is a general-purpose computer, such as a workstation or a personal computer, for example. The image processing device 46 includes a control unit 48, an input unit 50, an output unit 52, and a storage unit 54.
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The control unit 48 is, for example, a CPU or the like, and by executing various programs stored in the storage unit 54, the control unit 48 functions as a calculation unit 56 and a determination unit 58. The input unit 50 is, for example, a keyboard, a touchscreen provided integrally with a display, or the like. The output unit 52 is, for example, an LCD or CRT display. The storage unit 54 is, for example, an information storage medium such as a rewritable flash memory, a built-in hard disk or a hard disk connected via a data communication terminal, a memory card, or the like, as well as a reading/writing device therefor. The storage unit 54 stores programs and data used to calculate the inclination angles of the grate bars 26. The storage unit 54 also stores template image data generated in advance for generating a pallet management table, which will be described later.
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Next, the processing executed by the calculation unit 56 and the determination unit 58 will be described. Upon receiving image data generated by the imaging unit 42, the calculation unit 56 uses the received image data to calculate the inclination angle of each of the grate bars 26.
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Fig. 4 includes schematic diagrams, one illustrating the pallet 24 and the other illustrating the grate bars 26. Fig. 4(a) is a top view of the pallet 24, and Fig. 4(b) is an enlarged view of the Y portion of Fig. 4(a). As illustrated in Fig. 4(b), the calculation unit 56, for example, identifies five points corresponding to five different predetermined positions along the longitudinal direction of each grate bar 26, each point being at the midpoint between the positions of the two side surfaces of each grate bar 26, and calculates the inclination angle of an approximate straight line 32 passing through these five points. The inclination angle of each grate bar 26 is measured with reference to the longitudinal direction of the end grate 30 as 0°. After calculating the inclination angles of all the grate bars 26, the calculation unit 56 transmits the calculated inclination angles to the determination unit 58.
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Upon obtaining the inclination angles from the calculation unit 56, the determination unit 58 determines whether the inclination angles are greater than or equal to 6°, which is a threshold. The determination unit 58 reads the threshold from the storage unit 54 and compares the threshold with each of the inclination angles to determine whether each of the inclination angles is greater than or equal to 6°. In the present embodiment, 6° is an example of a predetermined threshold of the inclination angle, and the threshold is stored in the storage unit 54.
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Fig. 5 is a graph representing the correlation between the inclination angles of the grate bars 26 and the number of days until the grate bars 26 detach. In Fig. 5, the horizontal axis corresponds to the inclination angles (°) of the grate bars 26, while the vertical axis corresponds to the number of days (days) until the grate bars 26 detach. As illustrated in Fig. 5, when the inclination angles of the grate bars 26 are less than or equal to 6°, the grate bars 26 do not detach for at least 30 days. In the sintering machine 10 according to the present embodiment, the pallets 24 are maintained and the grate bars 26 are reinstalled every month. Therefore, by determining whether the inclination angles of the grate bars 26 are greater than or equal to 6° and identifying any grate bar with an inclination angle of 6° or more, it is possible to identify the grate bars 26 that are likely to detach from the corresponding pallet 24 before periodic maintenance is performed.
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As such, the threshold of the inclination angle is preferably determined based on the correlation between the inclination angles of the grate bars 26 and the number of days until the grate bars 26 detach. Then, the threshold of the inclination angle is set so that the number of days until a grate bar 26 detaches exceeds the period between periodic maintenance. This allows the grate bars 26 that are likely to detach from the corresponding pallet 24 to be identified before periodic maintenance is performed.
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Upon obtaining the identification information of each pallet 24 from the distance measuring unit 44, the determination unit 58 identifies the position of any grate bar with an inclination angle of 6° or more in association with the identification information of each pallet 24. The determination unit 58 identifies the position of a grate bar whose inclination angle has reached or exceeded the threshold, for example, by using columns A to C and numbers 1 to 150 assigned to these columns, with 1 corresponding to the left end of each column. The determination unit 58 causes the output unit 52 to display the position of a grate bar whose identified inclination angle has reached or exceeded the threshold, along with the inclination angle of the grate bar. This allows the operator of the sintering machine 10 to identify the grate bar that is likely to detach from the corresponding pallet 24. As a result, the operator can take detachment countermeasures only to grate bars that are likely to detach before periodic maintenance, thereby enabling suppression of grate bar detachment while restraining an increase in maintenance costs.
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Fig. 6 is a diagram illustrating the flow of a pallet monitoring method according to the present embodiment. Using Fig. 6, the flow of the pallet monitoring method according to the present embodiment will be described. The flow of the pallet monitoring method illustrated in Fig. 6 begins when, for example, the image processing device 46 is activated, and the input unit 50 receives an instruction from the operator to start pallet monitoring.
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The imaging unit 42 captures an image of the pallet 24 and generates image data (step S101). The imaging unit 42 transmits the generated image data to the image processing device 46. This step corresponds to an imaging step.
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The distance measuring unit 44 obtains identification information of the pallet 24 (step S102). The distance measuring unit 44 transmits the obtained identification information to the image processing device 46. This step corresponds to an identification information detection step. The identification information detection step (step S102) executed by the distance measuring unit 44 is not limited to this position. The identification information detection step (step S102) may be executed prior to the imaging step (step S101) executed by the imaging unit 42 as long as it is before a later-described determination step (step S104) executed by the determination unit 58. Similarly, the identification information detection step (step S102) may be executed after a calculation step (step S103) executed by the calculation unit 56.
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Upon receiving the image data from the imaging unit 42, the calculation unit 56 uses the image data to calculate the inclination angles of all of the grate bars 26 of the pallet 24 (step S103). The calculation unit 56 outputs the calculated inclination angles of the grate bars 26 to the determination unit. This step corresponds to the calculation step.
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Upon obtaining the inclination angles of the grate bars 26 from the calculation unit 56, the determination unit 58 determines whether the inclination angles are greater than or equal to the threshold (step S104). This step corresponds to the determination step. Upon receiving the identification information of the pallet 24 whose image has been captured by the imaging unit 42 from the distance measuring unit 44, the determination unit 58 identifies the position of a grate bar whose inclination angle has reached or exceeded the threshold in association with the identification information, and causes the output unit 52 to display the position.
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The determination unit 58 determines whether an instruction from the operator to end pallet monitoring has been received (step S105). When the input unit 50 has not received an instruction to end pallet monitoring from the operator, the determination unit 58 determines that it has not received an instruction to end pallet monitoring (step S105: No), and returns the process to step S101. Then, the process from step S101 to step S104 is repeatedly executed for the next pallet 24. By repeatedly executing the process from step S101 to step S104 in this way, the 174 pallets 24 provided in the sintering machine 10 are sequentially monitored, thereby enabling the identification of grate bars that are likely to detach from these pallets 24.
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On the other hand, when the input unit 50 has received an instruction to end pallet monitoring from the operator, the determination unit 58 determines that it has received an instruction to end pallet monitoring (step S105: Yes), and ends the flow of the pallet monitoring method illustrated in Fig. 6.
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In this way, with the pallet monitoring method according to the present embodiment, each pallet 24 in the sintering machine 10 is monitored, thereby enabling the identification of grate bars that are likely to detach from each pallet 24. This allows detachment countermeasures to be taken only for grate bars that are likely to detach before they actually fall off, thereby enabling suppression of grate bar detachment while restraining an increase in maintenance costs.
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The embodiment of the present invention is not limited to the above embodiment and may be modified in various ways. Although it has been described in the above embodiment using an example in which the determination unit 58 determines, for each grate bar 26, whether its inclination angle is greater than or equal to the threshold, the embodiment is not limited thereto. The determination unit 58 may, for example, determine whether an average value of inclination angles of ten grate bars is greater than or equal to the threshold. The ten grate bars are merely an example of a predetermined number of two or more grate bars for which an average value of inclination angles is calculated.
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In this case, upon calculating the inclination angles of 450 grate bars 26, the calculation unit 56 calculates an average value of inclination angles for each group of ten grate bars 26, thereby obtaining 45 average values of inclination angles of the grate bars 26 per pallet. The calculation unit 56 outputs the 45 average values of inclination angles of the grate bars 26 to the determination unit 58.
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The grate bars 26 are installed adjacent to one another. Accordingly, when one grate bar is inclined, an adjacent grate bar is also inclined due to the effect of the inclination of the one grate bar. Thus, since the inclination of one grate bar affects surrounding grate bars, it does not occur that only a specific grate bar has a significantly larger inclination angle. Therefore, even when the inclination angles of the grate bars 26 are monitored as an average value of inclination angles of ten grate bars 26, each pallet 24 can be monitored with accuracy similar to the case where the inclination angle of a single grate bar 26 is monitored.
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Upon obtaining the average value of inclination angles from the calculation unit 56, the determination unit 58 determines whether the average value of inclination angles is greater than or equal to the threshold. The determination unit 58 reads the threshold from the storage unit 54 and compares the threshold with each average value of inclination angles, thereby determining whether each average value of inclination angles is greater than or equal to the threshold.
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Fig. 7 is a table illustrating an example of a pallet management table 60. The determination unit 58 determines whether the average values of inclination angles of all the grate bars 26 in columns A to C of the pallet 24 are greater than or equal to 6°. Then, the determination unit 58 reads template image data from the storage unit 54, and generates image data of the pallet management table 60 using the average values of inclination angles, the determination results, pallet identification information, and the image data. The template image data used for generating the pallet management table 60 is generated in advance and stored in the storage unit 54.
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The pallet management table 60 includes the pallet identification information and, for each of columns A to C, the average values of inclination angles corresponding to the positions of the grate bars 26. It is preferable that an average value of inclination angles that is greater than or equal to 6°, which is the threshold of the inclination angle, be displayed in a manner different from other average values. In the example illustrated in Fig. 7, display regions of average values of inclination angles that are greater than or equal to 6° are displayed in a different color. The determination unit 58 causes the output unit 52 to display the generated pallet management table 60.
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As described above, in the pallet monitoring system 40 according to the present embodiment, the inclination angles of the grate bars 26 may be monitored based on an average value of inclination angles of a predetermined number of two or more grate bars 26. This allows the number of monitoring data items to be reduced, enabling efficient monitoring of each pallet 24 in the sintering machine 10, as well as the identification of grate bars that are likely to detach from each pallet 24.
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Although it has been described in the above embodiment using an example in which an average value of inclination angles is calculated for every ten grate bars 26, the embodiment is not limited thereto. The calculation unit 56 may calculate a maximum value of inclination angles for every ten grate bars 26. In this case, the calculation unit 56 outputs the 45 maximum values of inclination angles of the grate bars 26 to the determination unit 58, and the determination unit 58 determines whether each maximum value of inclination angles is greater than or equal to the threshold. By making such a determination, even when the inclination angle of a specific grate bar 26 suddenly becomes large, it is possible both to identify grate bars that are likely to detach from each pallet 24 and to efficiently monitor each pallet 24.
Reference Signs List
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- 10
- sintering machine
- 12
- surge hopper
- 14
- roll feeder
- 16
- divided gates
- 18
- ignition furnace
- 20
- wind boxes
- 22
- blower
- 24
- pallets
- 26
- grate bars
- 28
- side walls
- 30
- end grates
- 32
- approximate straight lines
- 34
- charging section
- 36
- discharging section
- 40
- pallet monitoring system
- 42
- imaging unit
- 44
- distance measuring unit
- 46
- image processing device
- 48
- control unit
- 50
- input unit
- 52
- output unit
- 54
- storage unit
- 56
- calculation unit
- 58
- determination unit
- 60
- pallet management table
- 100
- sintered ore production facility