Method and apparatus for measuring moisture content, method for adjusting the humidity of coal, and method for producing coke.

Abstract

To provide a technique of precisely and stably measuring moisture when measuring moisture in a coal carried on a conveyor by using a microwave.SOLUTION: A moisture measuring method for measuring moisture in coal carried on a conveyor includes: a coal pressure reduction step of reducing the pressure of a coal carried on a conveyor and levelling out a surface of the coal and compressing the coal; a layer thickness measuring step of measuring a layer thickness of the coal after the pressure of the coal is reduced in the coal pressure reduction step; a microwave sending step for sending a microwave as a transmission wave to the coal after the pressure of the coal is reduced in the coal pressure reduction step; a microwave receiving step of receiving the microwave which was sent in the microwave sending step and passed through the coal as a reception wave; a microwave change amount calculation step of comparing the transmission wave and the reception wave and calculating a change amount; and a water content calculation step of calculating a water content of the coal on the basis of the change amount calculated by the microwave change amount calculation step and the layer thickness of the coal measured in the layer thickness measuring step.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This invention relates to a method and apparatus for measuring moisture content, a method for adjusting the humidity of coal, and a method for producing coke. [Background technology]

[0002] In steel mills, coal, the raw material for coke, is transported by conveyor belts, dried in humidity control units, and then fed into coke ovens. Generally, the lower the moisture content of the raw coal, the better the quality of the coke. However, if the moisture content is too low, it can lead to problems such as increased dust generation during transport, increased risk of ignition, and clogging of the coke oven. Therefore, it is necessary to control the moisture content within a specified range.

[0003] Therefore, there are techniques that use microwaves to measure the moisture content of coal. For example, Patent Documents 1 to 3 propose a technique in which microwaves are irradiated onto coal on a conveyor belt, and the moisture content of the coal is measured from the change in the microwave propagation characteristics in the coal.

[0004] Specifically, Patent Document 1 proposes a technique for measuring moisture content using microwaves after leveling the surface of coal on a belt conveyor belt using a leveling plate (scraper) to physically uniformize the bulk density. Patent Document 2 proposes a moisture measuring device that includes a distance meter for measuring the layer thickness and a weighing machine for measuring the weight, and performs corrections on the data measured by a microwave moisture meter based on the layer thickness and the bulk density obtained from the layer thickness and weight. Patent Document 3 proposes a method for measuring moisture content without being affected by fluctuations in bulk density by embedding a microwave moisture meter in the coal seam.

[0005] Furthermore, Patent Document 4 proposes a technique for measuring both the density and water content of an object by measuring the attenuation and phase difference between microwaves that have not passed through the object and microwaves that have passed through the object. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 7-55726 [Patent Document 2] Japanese Patent Application Publication No. 6-129980 [Patent Document 3] Japanese Patent Publication No. 2014-112053 [Patent Document 4] Japanese Patent Publication No. 2019-70535 [Overview of the project] [Problems that the invention aims to solve]

[0007] Microwave-based moisture measurement technology requires information on bulk density. Normally, bulk density is measured by utilizing the property that gamma rays, a type of radiation, are attenuated as they pass through a substance. However, gamma rays are strictly regulated, and methods of measuring bulk density using gamma rays incur significant management costs.

[0008] On the other hand, the technologies described in Patent Documents 1 to 4 do not use gamma ray measurement of bulk density, so the above-mentioned inconveniences do not occur, but they have the following problems. Specifically, in the technology of Patent Document 1, the surface of the coal on the belt conveyor is leveled with a leveling plate (scraper) without measuring bulk density, and the bulk density is made physically uniform. However, in this case, the layer thickness fluctuates greatly due to fluctuations in the amount of material being measured being transported, and if the surface of the material being measured is below the range of motion of the leveling plate (scraper), correction becomes impossible. In addition, there is a problem that the material being measured is bounced off by the leveling plate (scraper), causing it to fall off the belt conveyor. The technology disclosed in Patent Document 3 also has a similar problem in that the material being measured is bounced off by a box equipped with a microwave moisture meter and falls off the belt conveyor. In the technology described in Patent Document 2, although the layer thickness and bulk density are measured and used to correct the moisture meter, if the shape of the coal seam surface in the area irradiated with microwaves is not flat, errors will occur in the measured layer thickness and bulk density themselves. Furthermore, in techniques such as Patent Document 4, which measure the density of an object from attenuation and phase, it is difficult to measure bulk density with high accuracy.

[0009] This invention provides a technology that enables highly accurate and stable moisture measurement when measuring the moisture content of coal being transported on a conveyor belt using microwaves. [Means for solving the problem]

[0010] To solve the above problems, the present invention provides the following means [1] to

[13] .

[0011] [1] A method for measuring the moisture content of coal being transported on a conveyor belt, A coal compaction step is performed to compact the coal on the conveyor, level the surface of the coal, and compress the coal. A layer thickness measurement step for measuring the layer thickness of the coal after it has been compacted by the coal compaction step, A microwave transmission step in which microwaves are transmitted as a transmission wave toward the coal that has been compacted by the coal compaction step, A microwave receiving step of receiving, as a received wave, the microwave that has been transmitted in the microwave transmission step and has passed through the coal; A microwave change amount calculation step of calculating a change amount by comparing the transmitted wave and the received wave; A moisture content calculation step of calculating the moisture content of the coal based on the change amount calculated in the microwave change amount calculation step and the layer thickness of the coal measured in the layer thickness measurement step; A moisture measurement method comprising the above.

[0012] [2] The coal compressing step is the moisture measurement method according to [1], wherein a rotating shaft is installed parallel to the width direction of the conveyor, and the coal is compressed by a roller movable in the height direction of the conveyor.

[0013] [3] The coal compressing step has a bottom surface whose surface contacting the coal on the conveyor is a plane kept parallel to the conveyor, and an inclined surface that warps upward from the bottom surface on the upstream side in the traveling direction of the conveyor, and the coal is compressed by a weight movable in the height direction of the conveyor. The moisture measurement method according to [1].

[0014] <000008�>[4] The change amount calculated in the microwave change amount calculation step includes one or both of a phase difference and an attenuation rate. The moisture measurement method according to [1].

[0015] [5] The moisture measurement method according to any one of [1] to [4], wherein a plurality of frequencies are used as the microwave.

[0016] [6] The coal compressing step is performed on the uphill portion of the conveyor. The moisture measurement method according to any one of [1] to [4].

[0017] [7] A moisture measurement device for measuring the moisture content of coal conveyed on a conveyor, A coal compressing mechanism that compresses the coal on the conveyor to level the surface of the coal and compress the coal; A layer thickness measurement unit that measures the layer thickness of the coal after being compressed by the coal compressing mechanism; A microwave transmitting unit that transmits microwaves as a transmitted wave toward the coal that has been compacted by the coal compaction mechanism, A microwave receiving unit that receives the microwaves transmitted from the microwave transmitting unit and transmitted through the coal as received waves, A microwave change amount calculation unit that calculates the amount of change by comparing the transmitted wave and the received wave, A moisture content calculation unit calculates the moisture content of the coal based on the amount of change calculated by the microwave change amount calculation unit and the layer thickness of the coal measured by the layer thickness measurement unit. A moisture measuring device equipped with the following features.

[0018] [8] The layer thickness measuring section is A distance meter for measuring the distance to the surface of the coal after it has been compacted by the coal compaction mechanism, A layer thickness calculation unit calculates the layer thickness of the coal after compaction based on the distance value measured by the distance meter, A moisture measuring device according to [7], having the following:

[0019] [9] The moisture measuring device according to [7], wherein the coal compaction mechanism is a roller whose rotating shaft is installed parallel to the width direction of the conveyor and which is movable in the height direction of the conveyor.

[0020]

[10] The moisture measuring device according to [7], wherein the coal compaction mechanism has a bottom surface which is a flat surface whose surface in contact with the coal on the conveyor is kept parallel to the conveyor, and an inclined surface which curves upward from the bottom surface on the upstream side in the direction of travel of the conveyor, and is a weight that is movable in the height direction of the conveyor.

[0021]

[11] A moisture measuring device according to any one of [7] to

[10] , wherein the coal compaction mechanism is installed on the upward slope of the conveyor.

[0022]

[12] A method for controlling the humidity of coal, comprising measuring the moisture content of coal by the moisture measurement method described in [1] above, and controlling the humidity of the coal by drying or adding water based on the measured moisture content so that the moisture content of the coal falls within a set range.

[0023]

[13] A method for producing coke, comprising charging coal that has been dehumidified by the coal dehumidification method described in

[12] above into a coke oven to produce coke. [Effects of the Invention]

[0024] According to the present invention, by compacting the coal on the conveyor to level the surface of the coal and compress it, fluctuations in the bulk density of the coal are reduced, and at the same time, fluctuations in the layer thickness within the range through which microwaves penetrate the coal are also reduced. Layer thickness measurement and calculation of changes in transmitted and received microwave waves are performed, and the moisture content of the coal is calculated based on these, enabling highly accurate and stable moisture measurement. In addition, because the coal is pressed down from above to compact it, the coal on the conveyor does not bounce off the conveyor. [Brief explanation of the drawing]

[0025] [Figure 1] This is a schematic side view showing a moisture measuring device according to the first embodiment of the present invention. [Figure 2] Figure 1 is a cross-sectional view of the coal compaction mechanism included in the moisture measurement device, seen from the downstream side in the conveying direction of the belt conveyor. [Figure 3] Figure 1 is a flowchart showing the method for measuring moisture content using the moisture measuring device. [Figure 4] This is a schematic side view showing a moisture measuring device according to a second embodiment of the present invention. [Figure 5] Figure 4 is a cross-sectional view of the coal compaction mechanism included in the moisture measurement device, seen from the downstream side in the conveying direction of the belt conveyor. [Figure 6] This is a schematic side view showing a coal compaction mechanism included in a moisture measuring device according to a third embodiment of the present invention. [Figure 7] Figure 6 is a cross-sectional view of the coal compaction mechanism, seen from the downstream side in the conveying direction of the belt conveyor. [Figure 8]This is a schematic side view showing the coal compaction mechanism included in the moisture measurement device according to the third embodiment installed on a belt conveyor with an upward slope having an angle θ from the horizontal. [Modes for carrying out the invention]

[0026] Embodiments of the present invention will be described below with reference to the attached drawings.

[0027] <First Embodiment> Figure 1 is a schematic side view showing a moisture measuring device according to the first embodiment of the present invention, and Figure 2 is a cross-sectional view of the coal compaction mechanism included in the moisture measuring device of Figure 1, viewed from the downstream side in the conveying direction of the belt conveyor.

[0028] The moisture content measuring device 1 measures the moisture content of coal C being transported on the belt conveyor B shown in Figure 1 in the direction of arrow V in the figure. The coal C is transported by the belt conveyor B to the humidity control facility, where it is dried (or hydrated) based on the moisture content measured by the moisture content measuring device 1 so that the moisture content falls within the set range. After that, the coal with the adjusted moisture content is charged into a coke oven to produce coke. Although Figure 1 shows an example where the moisture content measuring device 1 is installed before the humidity control facility, the moisture content measuring device 1 may also be installed after the humidity control facility, or it may be installed both before and after the humidity control facility. Even if the moisture content measuring device 1 is installed only after the humidity control facility, if the moisture content measured by the moisture content measuring device 1 deviates from the set range, the drying (or hydration) intensity is adjusted in a direction that brings the moisture content within the set range.

[0029] The moisture content measuring device 1 comprises a coal compaction mechanism 2, a layer thickness measuring unit 3, a microwave transmitting unit 41, a microwave receiving unit 42, a microwave change amount calculation unit 43, and a moisture content calculation unit 5.

[0030] The coal compaction mechanism 2 consists of a roller 21 for pre-compacting the coal C on the belt conveyor B and an arm 22 that holds it. As shown in Figure 2, the rotation axis 21a of the roller 21 is positioned parallel to the width direction of the belt conveyor B. The rotation axis 21a of the roller 21 is held by the arm 22. The arm 22 extends diagonally upward from the rotation axis 21a, and its upper end is rotatably held by the shaft S, and is configured to swing relative to the shaft S as shown in Figure 1. As the arm 22 swings, the roller 21 can move up and down. The roller 21 compacts the coal C being transported on the belt conveyor B from above, leveling the surface of the coal C and compressing it. The roller 21 also moves up and down in accordance with the fluctuations in the surface height of the coal C. Since this compaction by the roller 21 is performed by the weight of the roller 21 itself, a roller 21 with sufficient weight to compress the coal C is used. Furthermore, in order to suppress the bouncing of the roller 21 and improve its ability to follow fluctuations in the surface height of the coal C, an additional load may be applied to the arm 22 in a downward direction using a spring or the like.

[0031] The layer thickness measuring unit 3 includes a distance meter 31 and a layer thickness calculation unit 32. The distance meter 31 is installed on the belt conveyor B downstream of the coal compaction mechanism 2 and measures the height of the surface of the compacted coal C, i.e., the layer thickness of the coal C. The distance meter 31 is, for example, an ultrasonic distance meter that transmits ultrasonic waves U toward the surface of the coal C, receives the reflected waves, measures the time from transmission to reception of the ultrasonic waves U, and converts the distance between the distance meter 31 and the surface of the coal C based on the speed of sound. The layer thickness calculation unit 32 is a calculation device that calculates the layer thickness of the coal C on the belt conveyor B based on the measurement value of the distance meter 31. The layer thickness calculation unit 32 has the value of the distance meter 31 when there is no coal C on the belt conveyor B, i.e., the distance to the surface of the belt conveyor B, stored in advance, and calculates the layer thickness of the coal C by taking the difference between this value and the measurement value of the distance meter 31.

[0032] By using an ultrasonic rangefinder 31, the advantage is that measurements can be taken without being affected even when dust is present. Note that the rangefinder 31 is not limited to an ultrasonic type; depending on the measurement environment, a laser type, TOF (Time of Flight) type, or stereo camera may also be used.

[0033] The layer thickness measuring unit 3 may measure the layer thickness of the coal C by measuring the height of the roll 21 of the coal compaction mechanism 2. For example, a method may be adopted in which the height of the roll 21 is measured using a contact-type or non-contact sensor, or a method may be adopted in which the rotation angle of the arm 22 is measured using a potentiometer attached to the shaft S and converted into layer thickness in the layer thickness calculation unit.

[0034] The microwave transmitting unit 41 transmits microwaves as a transmitted wave toward the compacted coal seam. Specifically, it transmits microwaves of a predetermined energy and phase. The microwave receiving unit 42 receives the microwaves transmitted from the microwave transmitting unit 41 and transmitted through the coal C as a received wave. The microwave transmitting unit 41 and the microwave receiving unit 42 each consist of, for example, a horn antenna and are positioned opposite each other on the belt conveyor B after the compaction of the coal C has been performed, with the coal C in between them.

[0035] The microwave change amount calculation unit 43 is connected to the microwave transmitter 41 and the microwave receiver 42 via cables, respectively, and calculates the change amount by comparing the transmitted wave sent from the microwave transmitter 41 with the received wave received by the microwave receiver 42. The change amount may include either or both of the phase difference and the attenuation rate (energy ratio). In addition to calculating the microwave change amount, the microwave change amount calculation unit 43 also controls the operation of the microwave transmitter 41 and the microwave receiver 42.

[0036] Note that conditions such as the wavelength of the microwave used and the distance between the microwave transmitting unit 41 and the microwave receiving unit 42 can be appropriately set according to the brand and type of coal C. Further, the transmitted wave and the received wave of the microwave may be compared using microwaves of a plurality of frequencies (wavelengths) to obtain the change amount (i.e., frequency characteristics) for each frequency.

[0037] The moisture content calculation unit 5 calculates the moisture content of coal C using the change amounts of the transmitted wave and the received wave of the microwave W calculated by the microwave change amount calculation unit 43 and the layer thickness of coal C calculated by the layer thickness calculation unit. Specifically, when the phase difference is Φ (deg), the attenuation rate is A (dB), and the layer thickness is D (mm), the moisture content calculation unit 5 calculates the moisture content M (%) of coal C according to the following formula (1). M=(K Φ ×Φ / D)+(K A ×A / D)+K C ···(1) Here, K Φ 、K A 、K C are coefficients preset according to the brand and type of coal C, the distance between the microwave transmitting unit 41 and the microwave receiving unit 42, the material and thickness of the belt conveyor B, etc.

[0038] Also, the coefficients K Φ 、K A 、K C may be coefficients determined in advance using a large number of prepared coal C samples. Specifically, the coefficients K Φ 、K A 、K C can be determined in advance as follows. That is, for a plurality of prepared samples (at least 3 or more samples of coal C), the moisture content M is calculated based on the JIS standard (analytical moisture) JIS M 8811:2000 Coal and Coke - Method for Measuring Total Moisture in a Lot. In addition, for these samples, the phase difference Φ, the attenuation rate A, and the layer thickness D are also measured. Then, based on the moisture content M, the phase difference Φ, the attenuation rate A, and the layer thickness D of these samples, the coefficients K Φ 、K A 、KC To decide.

[0039] Next, we will explain the method for measuring moisture content using the moisture measuring device 1 configured in this way. Figure 3 is a flowchart showing the moisture measurement method using the moisture measuring device shown in Figure 1. First, the coal C on conveyor B is pressed down from above to level the surface of the coal C and compress it (coal compaction process; step ST1). In this embodiment, this coal compaction process is performed by the roller 21 of the coal compaction mechanism 2.

[0040] Next, the thickness of the coal layer C on the conveyor B after it has been compacted is measured (layer thickness measurement step; step ST2). The thickness of the coal layer C can be measured, for example, by measuring the height of the surface of the coal C with a distance meter 31 and calculating it with a layer thickness calculation unit 32. As described above, an ultrasonic distance meter can be suitably used as the distance meter 31.

[0041] Next, microwaves are transmitted as a transmitted wave towards the coal C that has been compacted in step ST1 on the conveyor B (microwave transmission step; step ST3). Microwave transmission is performed by a microwave transmitting unit 41, which consists of, for example, a horn antenna. The microwave transmitting unit 41 transmits microwaves W of predetermined energy and phase.

[0042] Then, the transmitted microwaves, after passing through the coal seam, are received as received waves (microwave reception process; step ST4). Microwave reception is performed by a microwave receiving unit 42, which consists of, for example, a horn antenna.

[0043] Next, the transmitted wave and the received wave are compared to calculate the amount of change (microwave change amount calculation step; step ST5). This step is performed by the microwave change amount calculation unit 43. The amount of change may include either or both of the phase difference and the attenuation rate (energy ratio).

[0044] Next, the moisture content of coal C is calculated based on the microwave change calculated in step ST5 and the layer thickness of coal C measured in step ST2 (moisture content calculation step; step ST6). This step is performed by the moisture content calculation unit 5. The moisture content is calculated at this time based on equation (1) described above.

[0045] Thus, in this embodiment, by performing the above steps ST1 to ST6 when measuring the moisture content of coal C on conveyor B, the following effects can be obtained.

[0046] Coal C is typically transported on conveyor belt B either after being cut from a hopper or transferred from another conveyor belt. In other words, since coal C is simply dropped onto the conveyor belt, there are many voids between the coal grains, resulting in a low bulk density and a large variation in bulk density.

[0047] In contrast, in this embodiment, the coal C on the conveyor B is compressed by the coal compaction mechanism 2, so the coal C is compressed, the voids between the coal C particles decrease, and the bulk density increases. If the particle size distribution is constant, the fluctuation in bulk density after compaction is small, and the bulk density becomes almost constant. The phase difference and attenuation rate calculated by the microwave change amount calculation unit 43 and included in equation (1) are quantities that depend on the bulk density of the coal C and the thickness of the coal C layer. Therefore, since the bulk density becomes almost constant due to compaction, and the thickness of the layer in the range through which microwaves are transmitted is known, the measurement accuracy of the moisture content calculated by equation (1) is improved. In addition, because the coal C is compacted and the surface of the coal C is leveled, the variation in the thickness of the layer in the range through which microwaves W are transmitted (the range between the microwave transmitting unit 41 and the microwave receiving unit 42) is reduced, and the measurement accuracy of the moisture content can be further improved.

[0048] Furthermore, by compressing the coal C on conveyor B, it is possible to suppress the coal C from being thrown off conveyor B and out of the conveyor.

[0049] Furthermore, since coal C can be compacted to make its bulk density nearly constant, as described in Patent Document 1, it is not necessary to include bulk density as a variable in the formula for calculating the moisture content of coal C, and gamma ray measurement of bulk density is unnecessary.

[0050] <Second Embodiment> Figure 4 is a schematic side view showing a moisture measuring device according to a second embodiment of the present invention, and Figure 5 is a cross-sectional view of the coal compaction mechanism included in the moisture measuring device of Figure 4, viewed from the downstream side in the conveying direction of the belt conveyor. The second embodiment is the same as the first embodiment except that a coal compaction mechanism 2' is provided instead of the coal compaction mechanism 2 of the first embodiment, so other components are denoted by the same reference numerals as in the first embodiment and their descriptions are omitted.

[0051] In the second embodiment, the coal compaction mechanism 2' consists of a weight 23 for pre-compacting the coal C on the belt conveyor B, and a pair of first arms 24a (only one shown) and a pair of second arms 24b (only one shown) for holding the weight.

[0052] The weight 23 has a bottom surface that is a flat surface parallel to the belt conveyor B and contacts the coal C on the belt conveyor B, and a chamfered portion 23a that is an inclined surface that curves upward from the bottom surface on the upstream side in the direction of travel of the belt conveyor B (direction of arrow V in the figure). The chamfered portion 23a guides the transported coal C to the lower part of the weight 23.

[0053] A pair of first arms 24a are rotatably connected to the weight 23 at their lower ends via a shaft 25a, and a pair of second arms 24b are rotatably connected to the weight 23 at their lower ends via a shaft 25b. The first arms 24a and the second arms 24b extend diagonally upward parallel to each other from their lower ends connected by shafts 25a and 25b. The upper ends of the pair of first arms 24a are held by a shaft S1, and the upper ends of the pair of second arms 24b are held by a shaft S2. The first arms 24a and the second arms 24b are configured to swing relative to shafts S1 and S2, and the swinging of the first arms 24a and the second arms 24b allows the weight 23 to move up and down while keeping its bottom surface parallel to the belt conveyor B. The weight 23 presses down on the coal C being transported on the belt conveyor B, compressing it and leveling the surface of the coal C, while moving up and down in accordance with fluctuations in the surface height of the coal C. Since this compression by the weight 23 is performed by the weight 23 itself, the weight 23 should be heavy enough to compress the coal C. Furthermore, in order to suppress the bouncing of the weight 23 and improve its ability to follow fluctuations in the surface height of the coal C, additional loads may be applied to the first arm 24a and the second arm 24b in a downward direction using springs or the like.

[0054] In this embodiment as well, the coal C can be compacted in the same way as steps ST1 to ST6 of the first embodiment, except that the compaction is performed by the weight 23 of the coal compaction mechanism 2', and the same effects as in the first embodiment can be obtained.

[0055] <Third Embodiment> Figure 6 is a schematic side view showing a coal compaction mechanism included in a moisture measuring device according to the third embodiment of the present invention, and Figure 7 is a cross-sectional view of the coal compaction mechanism of Figure 6 viewed from the downstream side in the conveying direction of the belt conveyor. The third embodiment is the same as the second embodiment except that a coal compaction mechanism 2'' is provided in which the weight 23 of the coal compaction mechanism 2' of the second embodiment is replaced with a curved plate 23'. Therefore, other components are denoted by the same reference numerals as in the second embodiment and their descriptions are omitted.

[0056] The curved plate 23', like the weight 23 in the second embodiment, has the weight necessary to compact the coal C on the belt conveyor B. The surface that contacts the coal C on the belt conveyor B has a bottom surface that is kept parallel to the belt conveyor B and an inclined surface 23'a that curves upward from the bottom surface on the upstream side in the direction of travel of the belt conveyor B (direction of arrow V in the figure). Thus, the curved plate 23' functions as a weight for compacting the coal, and because its surface that contacts the coal C on the belt conveyor B has a shape consisting of a bottom surface kept parallel to the belt conveyor B and an inclined surface 23'a that curves upward from the bottom surface on the upstream side in the direction of travel of the belt conveyor B, it has the same function as the weight 23 in the second embodiment. Therefore, the same effects as in the second embodiment can be obtained.

[0057] In this embodiment, the coal compaction mechanism 2″ may be installed on the upward-sloping section of the belt conveyor B. Figure 8 is a schematic side view showing the coal compaction mechanism 2″ included in the moisture measuring device according to the third embodiment installed on a belt conveyor B with an upward slope having an angle θ from the horizontal. When the coal compaction mechanism 2″ is installed on a belt conveyor B with an upward slope, a force F acting in the opposite direction to the direction of travel V of the belt conveyor B acts as a component of gravity acting on the warped plate 23′. As a result, a force acts to push the coal C that hits the inclined surface 23′a back in the upstream direction (opposite direction to V), and the effect of leveling the surface irregularities of the coal C is greatly increased. That is, in addition to the effect that the bulk density is stabilized to be almost constant as the coal C is compacted by the warped plate 23′, the short-period fluctuations in the thickness of the coal C layer are reduced. This also provides the effect of suppression. By suppressing short-period fluctuations in layer thickness, the variability in the measurement of the amount of change (phase difference, attenuation) during microwave transmission is also suppressed, and as a result, the accuracy of measuring the moisture content of coal C is improved. The upward slope angle θ of the belt conveyor B is preferably 10 to 15°. If θ is less than 10°, the effect of suppressing layer thickness fluctuations becomes small. Slopes greater than 15° are generally difficult to apply because they exceed the limit slope for transporting coal with a flat belt type conveyor.

[0058] Furthermore, the coal compaction mechanism 2 of the first embodiment and the coal compaction mechanism 2' of the second embodiment may also be installed on the upward sloping section of the belt conveyor B, and the same effects as in this embodiment can be obtained. Also, in the first and second embodiments, as in this embodiment, the angle θ of the upward slope of the belt conveyor B is preferably 10 to 15°.

[0059] Although embodiments of the present invention have been described above, these should be considered merely illustrative and not restrictive. The above embodiments may be omitted, substituted, or modified in various ways without departing from the spirit of the present invention.

[0060] For example, in the above embodiments, the coal compaction process was shown to be performed using a roller 21 (first embodiment), a weight 23 (second embodiment), and a curved plate 23' (third embodiment). However, the method is not limited to these, as long as it is possible to press down on the coal from above, compress it, and level the surface of the coal. [Explanation of Symbols]

[0061] 1. Moisture measuring device 2, 2', 2" Coal Suppression Mechanism 3 Layer thickness measurement section 5 Moisture content calculation section 21 Rollers 21a Rotation axis 22, 24a, 24b arms 23 weights 23′ Curved plate 25a, 25b axis 31 Distance meter 32 Layer thickness calculation section 41 Microwave Transmitter 42 Microwave Receiver 43. Microwave change amount calculation unit B Belt conveyor C Coal S, S1, S2 shafts

Claims

1. A method for measuring the moisture content of coal being transported on a conveyor belt, A coal compaction step is performed to compact the coal on the conveyor, level the surface of the coal, and compress the coal. A layer thickness measurement step for measuring the layer thickness of the coal after it has been compacted by the coal compaction step, A microwave transmission step in which microwaves are transmitted as a transmission wave toward the coal that has been compacted by the coal compaction step, A microwave receiving step, which receives the microwaves transmitted in the microwave transmission step and after passing through the coal as a received wave, A microwave change amount calculation step that calculates the amount of change by comparing the transmitted wave and the received wave, A moisture content calculation step calculates the moisture content of the coal based on the amount of change calculated in the microwave change calculation step and the layer thickness of the coal measured in the layer thickness measurement step. Equipped with, The coal compaction step is performed by using a weight that is swingable while keeping the bottom surface parallel to the conveyor, having a bottom surface that is a flat plane parallel to the conveyor and a sloping surface that curves upward from the bottom surface on the upstream side in the direction of travel of the conveyor, and swinging the weight to press down on the coal on the conveyor, in which case a force acting on the coal on the conveyor in the opposite direction to the direction of travel of the conveyor increases the compressive force on the coal, thereby increasing the effect of stabilizing the bulk density of the coal to a constant level, and also increasing the effect of leveling the surface irregularities of the coal, thereby increasing the effect of suppressing short-period fluctuations in the thickness of the coal layer.

2. The moisture measurement method according to claim 1, wherein the amount of change calculated in the microwave change amount calculation step includes either or both of the phase difference and the attenuation rate.

3. The moisture measurement method according to claim 1 or claim 2, wherein multiple frequencies are used as the microwaves.

4. A moisture measuring device for measuring the moisture content of coal being transported on a conveyor belt, A coal compaction mechanism that compacts the coal on the conveyor to level the surface of the coal and compress the coal, A layer thickness measuring unit for measuring the layer thickness of the coal after it has been compacted by the coal compaction mechanism, A microwave transmitting unit that transmits microwaves as a transmitted wave toward the coal that has been compacted by the coal compaction mechanism, A microwave receiving unit that receives the microwaves transmitted from the microwave transmitting unit and transmitted through the coal as received waves, A microwave change amount calculation unit that calculates the amount of change by comparing the transmitted wave and the received wave, A moisture content calculation unit calculates the moisture content of the coal based on the amount of change calculated by the microwave change amount calculation unit and the layer thickness of the coal measured by the layer thickness measurement unit. Equipped with, The coal compaction mechanism is installed on the upward sloping section of the conveyor and has a bottom surface that is a flat surface parallel to the conveyor and contacts the coal on the conveyor, and an inclined surface that curves upward from the bottom surface on the upstream side in the direction of travel of the conveyor, and is equipped with a weight that is swingable while keeping the bottom surface parallel to the conveyor, and the weight is swung on the inclined section to press down on the coal on the conveyor with the weight to compact the coal, and in this case a force acting on the coal on the conveyor in the opposite direction to the direction of travel of the conveyor increases the compressive force on the coal, thereby increasing the effect of stabilizing the bulk density of the coal to a constant level, and also increases the effect of leveling the surface irregularities of the coal, thereby increasing the effect of suppressing short-period fluctuations in the thickness of the coal layer, the moisture content measuring device.

5. The aforementioned layer thickness measuring section is A distance meter for measuring the distance to the surface of the coal after it has been compacted by the coal compaction mechanism, A layer thickness calculation unit calculates the layer thickness of the coal after it has been compacted based on the distance value measured by the distance meter, A moisture measuring device according to claim 4, having the following features.

6. A method for controlling the humidity of coal, comprising measuring the moisture content of coal by the moisture measurement method described in claim 1, and controlling the humidity of the coal by drying or adding water based on the measured moisture content so that the moisture content of the coal falls within a set range.

7. A method for producing coke, comprising charging coal that has been dehumidified by the coal dehumidification method described in claim 6 into a coke oven to produce coke.

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