Drying equipment

Abstract

To provide a dryer comprising a heating member that comes into contact with a drying object to dry the same, capable of uniformly drying the entire drying object while suppressing the influence of aggregate and spherical lumps.SOLUTION: A dryer comprises a heating member 130 that comes into contact with a drying object P to heat the drying object P, a radiating unit 40 for radiating electromagnetic waves toward the drying object P, an acquiring unit 128 that acquires information relating to the temperature or the moisture of the drying object P, and a radiation control unit 50 that controls the electromagnetic wave radiation by the radiating unit 40 according to the information acquired by the acquiring unit 128..SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a drying device equipped with a heating element that comes into contact with an object to be dried and dries the object. [Background technology]

[0002] In drying devices that employ a so-called conductive heat transfer method, in which the material is dried by contacting it, when drying a high-moisture material or when performing heat treatment, aggregates or granular lumps called lumps may form.

[0003] When agglomerates or lumps form, conduction heat transfer alone heats only the surface of the agglomerates, making it difficult for heat to reach the interior. This results in over-drying of the surface, increasing the resistance to internal water vapor movement and reducing the drying rate. Furthermore, drying progresses if the agglomerates or lumps break down into powder, but if they remain as agglomerates or lumps, the drying time tends to be longer. Furthermore, when attempting to stir, the agglomerates or lumps may rotate together with the stirring element rotating in the container containing the material to be dried, or the agglomerates or lumps may become caught between the stirring element and the inner wall of the container, increasing the stirring power and causing overload, making stirring impossible. Hereinafter, the term "agglomerates" may sometimes be used to refer to agglomerates.

[0004] Incidentally, in the field of drying food waste, a technique has been proposed in which food waste is dried by internal heating using microwave irradiation (see, for example, Patent Document 1).

[0005] The drying device described in Patent Document 1 constantly irradiates microwaves and controls the rotation and stopping of the rotary blades based on the humidity inside the container that holds the food waste.The container is also rotated to ensure uniform heating of the food waste. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-103449 Summary of the Invention [Problem to be solved by the invention]

[0007] However, this method is not sufficient as a means for efficiently eliminating agglomerates when they occur, and there is a limit to how uniformly the entire object to be dried can be dried, so there is room for improvement.

[0008] In view of the above circumstances, an object of the present invention is to provide a drying apparatus that can uniformly dry the entire object to be dried while suppressing the influence of aggregates and lumps. [Means for solving the problem]

[0009] The drying device of the present invention that solves the above object is a heating element that comes into contact with the material to be dried and heats the material; an irradiation unit that irradiates electromagnetic waves toward the material to be dried; an acquisition unit that acquires information about the temperature or moisture content of the material to be dried; an irradiation control unit that controls irradiation of electromagnetic waves by the irradiation unit based on the information acquired by the acquisition unit, the irradiation control unit performs a first control of reducing the output of the electromagnetic waves irradiated by the irradiating unit or shortening the irradiation time of the electromagnetic waves irradiated by the irradiating unit when the temperature of the object to be dried exceeds a target temperature based on the information on temperature acquired by the acquiring unit, and performs a second control of stopping the irradiation of the electromagnetic waves when the temperature of the object to be dried reaches a threshold temperature higher than the target temperature; The heating member heats the material to be dried while the first control is being performed. Also, a stirring mechanism that stirs the material to be dried by being driven; a stirring control unit that monitors the driving state of the stirring mechanism, and stops driving the stirring mechanism or reduces the driving speed of the stirring mechanism when the driving state is in an abnormal state before the stirring mechanism becomes inoperable, The irradiation unit may be characterized in that it constantly or intermittently irradiates the material to be dried with electromagnetic waves even when the driving of the stirring mechanism is stopped or the driving speed of the stirring mechanism is reduced. or, a stirring mechanism that stirs the material to be dried by being driven; a vibration detection unit that detects vibrations in the drying device; a stirring control unit that stops driving the stirring mechanism or reduces the driving speed of the stirring mechanism in response to a result of vibration detection by the vibration detection unit, The irradiation unit may be characterized in that it constantly or intermittently irradiates the material to be dried with electromagnetic waves even when the driving of the stirring mechanism is stopped or the driving speed of the stirring mechanism is reduced. In addition, a heating element that comes into contact with the material to be dried and heats the material; an irradiation unit that irradiates electromagnetic waves toward the material to be dried; an acquisition unit that acquires information about the temperature or moisture content of the material to be dried; an irradiation control unit that controls the irradiation of electromagnetic waves by the irradiation unit based on the information acquired by the acquisition unit. It may also be a drying device.

[0010] According to the drying device of the present invention, heating is performed from the surface side by the heating element, and heating is performed from the surface side and the interior side by the irradiation unit. Heating by the irradiation unit also effectively acts on the interior side of the material to be dried, where the drying rate has been reduced due to heating from the surface side by the heating element. As a result, the entire material to be dried can be dried uniformly. Furthermore, by controlling the irradiation of electromagnetic waves by the irradiation unit based on the information acquired by the acquisition unit, even if aggregates or lumps occur, they can be broken down in a short time, thereby suppressing their effects.

[0011] Furthermore, it is expected that the irradiation of electromagnetic waves by the irradiation unit will break hydrogen bonds, which are thought to be the cause of agglomeration, and that liquid molecules such as water contained in the material to be dried will be vibrated or evaporated by the electromagnetic waves, thereby suppressing agglomeration of the material to be dried and contributing to the suppression of the growth of agglomerates.

[0012] This drying device may have a heating element provided on the outside of the inner wall of the storage section that stores the material to be dried, or may have a heating element provided inside the storage section that stores the material to be dried.

[0013] The electromagnetic waves irradiated by the irradiating unit may have a frequency of 300 MHz or more and several tens of GHz or less, for example, ultrashort waves. That is, microwaves may also be used. Of course, if the cause of the formation of aggregates or lumps is mainly moisture, a general-purpose 2.45 GHz microwave may be used to evaporate the moisture.

[0014] The irradiation unit may be one that irradiates electromagnetic waves intermittently, or one that irradiates electromagnetic waves continuously with reduced output. Alternatively, a low-output irradiation unit may be provided in addition to a normal-output irradiation unit.

[0015] The acquisition unit may be a thermometer or a moisture meter. The thermometer may measure the temperature (item temperature) of the material to be dried during drying. It is preferable to use an optical fiber thermometer as this thermometer, taking into consideration discharge that may occur when electromagnetic waves are irradiated. The moisture meter may measure the moisture content of the material to be dried during drying, or may measure the moisture content of the material after drying. The acquisition unit may acquire information regarding the temperature of a surface of the material to be dried that is irradiated with electromagnetic waves from the irradiation unit. Specifically, the acquisition unit may acquire information regarding the temperatures of multiple locations on the surface of the material to be dried that is irradiated with electromagnetic waves from the irradiation unit, of the material to be dried stored in the storage unit.

[0016] If the temperature of the material to be dried is equal to or lower than the target temperature based on the temperature information acquired by the acquisition unit, the irradiation control unit increases the output of the electromagnetic waves irradiated by the irradiating unit or lengthens the irradiation time. Conversely, if the temperature of the material to be dried exceeds the target temperature, the irradiation control unit decreases the output of the electromagnetic waves irradiated by the irradiating unit or shortens the irradiation time. In addition, a threshold temperature higher than the target temperature is set, and when the temperature of the material to be dried reaches the threshold temperature, the irradiation of the electromagnetic waves from the irradiating unit is suspended until the temperature drops below the threshold temperature. In this way, the irradiation control unit controls the output (intensity) and irradiation time of the electromagnetic waves in the irradiating unit.

[0017] In addition, in the drying device, a stirring mechanism that stirs the material to be dried by being driven; An embodiment may also be characterized by including a stirring control unit that monitors the driving state of the stirring mechanism and stops driving the stirring mechanism or reduces the driving speed of the stirring mechanism if the driving state is in an abnormal state before becoming inoperable.

[0018] The drive of the stirring mechanism becomes more easily hindered as the agglomerates grow larger, and when the agglomerates grow to a certain size and their surfaces dry to a certain degree, the stirring mechanism becomes more likely to become inoperable. The stirring control unit stops the drive of the stirring mechanism or reduces the drive speed of the stirring mechanism when an abnormal state occurs before the mechanism becomes inoperable. Large agglomerates can cause a decrease in the drying speed, but in this embodiment, electromagnetic waves act on small agglomerates before they grow to a certain size, causing the agglomerates to break down, and eventually the abnormal state is resolved and the stirring mechanism resumes driving at the specified speed.

[0019] The stirring mechanism may include a stirring member and a drive unit that drives the stirring member. For example, the drive unit may include an electric motor, and the stirring member may be rotated by rotation of the electric motor.

[0020] The stirring control unit may determine whether the drive state is the abnormal state based on whether the value of the current flowing through the drive unit is equal to or greater than an abnormal value. That is, the stirring control unit may stop driving the drive unit or reduce the drive speed of the drive unit when the current flowing through the drive unit is equal to or greater than the abnormal value before the drive unit became inoperable. For example, the stirring control unit controls the drive unit to stop driving for a predetermined time when the current flowing through the drive unit is equal to or greater than the abnormal value, resume driving the drive unit after the predetermined time has elapsed, and stop driving the drive unit for a predetermined time when the current flowing through the drive unit again exceeds the abnormal value. Alternatively, the stirring control unit controls the drive speed of the drive unit to be reduced from a predetermined speed for a predetermined time when the current flowing through the drive unit is equal to or greater than the abnormal value, and returns the drive speed to the predetermined speed after the predetermined time has elapsed, and when the current flowing through the drive unit again exceeds the abnormal value, reduces the drive speed of the drive unit for a predetermined time.

[0021] The irradiation unit may be configured to continuously or intermittently irradiate the material to be dried with electromagnetic waves even when the driving of the stirring mechanism is stopped or the driving speed of the stirring mechanism is reduced.

[0022] In addition, in the drying device, a vibration detection unit that detects vibrations in the drying device; The stirring control unit may be configured to stop driving the stirring mechanism or reduce the driving speed of the stirring mechanism also in response to a result of vibration detection by the vibration detection unit.

[0023] When detecting the amplitude of the vibration, for example, it is believed that the amplitude increases as the aggregates grow larger and as their surfaces become harder. Alternatively, the vibration tends to increase as the aggregates grow larger. The stirring control unit stops driving the stirring mechanism or reduces the driving speed of the stirring mechanism depending on the vibration detection result. If the detection result indicates that vibrations of a predetermined amplitude have been detected continuously for a predetermined period of time or that vibrations of an amplitude greater than or equal to a predetermined value have been detected, the electromagnetic waves will effectively act on small aggregates before they grow to a certain size. As described above, the action of the electromagnetic waves causes internal heating and makes the aggregates more susceptible to breakdown. Therefore, the breakdown of the aggregates progresses, the vibration eventually subsides, and the stirring mechanism resumes driving at the predetermined speed.

[0024] The stirring mechanism may be configured to stir the material to be dried by rotating a stirring member around a rotation axis, and the vibration detection unit may be configured to detect vibrations of the rotation axis.

[0025] Alternatively, the drying device may include a storage unit that stores the material to be dried, and the vibration detection unit may detect vibrations of the storage unit. In this case, the heating member may dry the material to be dried stored in the storage unit, the irradiation unit may irradiate electromagnetic waves toward the material to be dried stored in the storage unit, and the stirring mechanism may stir the material to be dried stored in the storage unit.

[0026] The stirring control unit may be configured to stop driving the stirring mechanism or reduce the driving speed of the stirring mechanism when vibration of a predetermined amplitude is detected by the vibration detection unit, and the irradiation unit may be configured to continuously or intermittently irradiate electromagnetic waves toward the material to be dried even when driving of the stirring mechanism is stopped or the driving speed of the stirring mechanism is reduced. [Effects of the Invention]

[0027] According to the drying device of the present invention, the entire object to be dried can be dried uniformly while suppressing the influence of aggregates and lumps. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a system diagram of a drying system incorporating a drying device according to one embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing the inside of a container of the drying device shown in FIG. 1 in a see-through state. [Figure 3] 10 is a graph schematically showing the relationship between the temperature of the material to be dried measured by an optical fiber thermometer and the output of the electromagnetic wave in the electromagnetic wave generator. [Figure 4] FIG. 2 is a diagram showing a modified example of the drying device shown in FIG. [Figure 5] 10 is a graph schematically showing the relationship between the current value of the stirring motor and the driving / stopping of the stirring motor. [Figure 6] 10 is a graph showing the results of a comparative experiment. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, a drying device according to one embodiment of the present invention will be described in detail with reference to the drawings.

[0030] FIG. 1 is a system diagram of a drying system incorporating a drying device according to one embodiment of the present invention.

[0031] The drying system D1 shown in FIG. 1 includes a drying device 1 corresponding to one embodiment of the present invention and a condenser 2.

[0032] The drying apparatus 1 shown in FIG. 1 includes a container 10, a heating medium supply device 20, a dust collector (bag filter) 30, an electromagnetic wave generator 40, a control unit 50, and a vacuum pump 60. The drying apparatus 1 dries an object to be dried within the container 10. FIG. 1 shows a schematic vertical cross section of the container 10 so that the interior of the container 10 can be seen. The container 10 is supported by supports 10S and includes a main body 100 and a top plate 110 that covers the upper end of the main body 100. The drying apparatus 1 also includes a spiral ribbon 122 that is a rotationally driven stirring member and a jacket 130 that covers the interior space of the main body 100. The main body 100 is composed of a cylindrical upper portion 101 and an inverted cone-shaped portion 102 whose diameter gradually decreases with increasing distance from the upper portion 101. A discharge port 1001 is provided at the lower end of the main body 100, i.e., the lower end of the inverted cone-shaped portion 102, and the discharge port 1001 is closed by an openable discharge lid 140. In Fig. 1, the open state of the discharge lid 140 is shown by a two-dot chain line.

[0033] An input section 111 is provided on the top plate 110, and the lower end opening of the input section 111 serves as an input port 111a. In FIG. 1, a supply pipe 111P for supplying the material to be dried is connected to the input section 111. The material to be dried in this embodiment is a wet powder or granular material (for example, zeolite or calcium carbonate). The material to be dried P is stored in the main body 100 shown in FIG. 1.

[0034] The top plate 110 is also provided with an exhaust port 112. A dust collector (bag filter) 30 is attached to this exhaust port 112, and an exhaust path 112P is connected to it via the dust collector 30. A condenser 2 is provided downstream of this exhaust path 112P. The steam evaporated from the material to be dried in the main body 100 is subjected to removal of fine powder and the like by the dust collector 30, and then sent to the condenser 2 through the exhaust path 112P. Cooling water is supplied to the condenser 2, and the steam sent through the exhaust path 112P undergoes heat exchange, with most of it becoming condensed liquid, and the remainder is drawn by the vacuum pump 60, flows out of the condenser 2, and is exhausted.

[0035] The top plate 110 is also provided with a glass window 114. This glass window 114 is fitted with quartz glass that does not absorb microwaves.

[0036] The electromagnetic wave generator 40 generates so-called microwaves, and more specifically, generates 915 MHz microwaves or 2.45 GHz microwaves. In the electromagnetic wave generator 40, the output of the generated electromagnetic waves is adjusted by the control unit 50. The electromagnetic wave generator 40 is also started and stopped by the control unit 50. The electromagnetic waves generated by the electromagnetic wave generator 40 are irradiated from the glass window 114 toward the inside of the main body 100. The electromagnetic wave generator 40 corresponds to an example of an irradiation unit.

[0037] The spiral ribbon 122 is supported by a plurality of rod-shaped support members protruding radially from the drive shaft 121, and has a spiral shape that tapers downward and runs along the vicinity of the inner circumferential wall of the main body 100. An agitation motor 123 and a reducer 124 are disposed on the top plate 110. The output shaft of the reducer 124 is connected to a sealed drive shaft 121 that passes upward through the top plate 110, and when the agitation motor 123 is driven to rotate, the drive shaft 121 rotates around its axis within the main body 100. The spiral ribbon 122 is driven to rotate by the rotation of the drive shaft 121 around its axis. The rotation of the spiral ribbon 122 agitates the material P to be dried stored in the main body 100. The spiral ribbon 122, the drive shaft 121, the agitation motor 123, and the reducer 124 correspond to an example of an agitation mechanism.

[0038] Due to the agitation of the spiral ribbon 122, the material P to be dried rises along the inner peripheral wall 1021 of the inverted cone-shaped portion 102. A pair of vortex breakers 125 is provided inside the cylindrical upper portion 101. The pair of vortex breakers 125 are arc-shaped plates (see also Figure 2) located at positions opposite each other at 180 degrees. That is, the pair of vortex breakers 125 have curved surfaces. The material P to be dried, which has risen vigorously along the inner peripheral wall, collides with the pair of vortex breakers 125, is bounced off, and is guided by the curved surfaces to the center of the main body 100 and then falls. In Figure 1, the movement of the material P to be dried inside the main body 100 due to the agitation of the spiral ribbon 122 and the action of the vortex breakers 125 is indicated by dotted arrows.

[0039] A heat medium supply channel 131 and a heat medium recovery channel 132 are connected to a jacket 130 that covers the internal space of the main body 100. That is, the tip of the heat medium supply channel 131 extending from the heating medium supply device 20 is connected to the bottom of the jacket 130. Meanwhile, the rear end of the heat medium recovery channel 132, whose tip is connected to the heating medium supply device 20, is connected to the top of the jacket 130. The heating medium supply device 20 maintains the heat medium at a set temperature. The heat medium is supplied to the jacket 130 through the heat medium supply channel 131, then recovered from the jacket 130 through the heat medium recovery channel 132 and returned to the heating medium supply device 20, repeating this cycle. By circulating the heat medium through the jacket 130, the main body 100 is heated from the outside, thereby heating the material to be dried. Furthermore, by circulating the heat medium through the jacket 130 while driving the vacuum pump 60, vacuum conduction heat transfer drying can be performed. The jacket 130 corresponds to an example of a heating element.

[0040] In the drying device 1 shown in FIG. 1, various measures are taken in relation to the electromagnetic wave heating, as will be explained below.

[0041] 1, the seal portion 1101 of the drive shaft 121 on the top plate 110 is shown in gray as a schematic diagram. This seal portion 1101 is provided with a choke structure that attenuates electromagnetic waves.

[0042] Electromagnetic wave leakage detectors 126 are installed around opening and closing points and sealed points. That is, a leakage detector 126 is installed around the top plate 110, around the discharge lid 140, and around the seal portion 1101 of the drive shaft 121. Each leakage detector 126 is connected to the control unit 50, and when the leakage detector 126 detects that the amount of electromagnetic wave leakage exceeds a reference value, the control unit 50 stops the electromagnetic wave generator 40.

[0043] A shielding member 31 that blocks electromagnetic waves is installed in the exhaust duct on the primary side of the dust collector 30. In FIG. 1, (a) of the drawing pulled out from the primary side shows the shielding member 31 as seen from directly above. The shielding member 31 is a stainless steel plate member with multiple through holes. The shielding member 31 may also be honeycomb-shaped.

[0044] As will be described in detail later, the control unit 50 monitors the value of the current flowing through the stirring motor 123. Furthermore, a vibration sensor 129 is provided on the upper end of the drive shaft 121 that protrudes upward from the top plate 110, and the control unit 50 also monitors vibrations occurring in the drive shaft 121.

[0045] Countermeasures against discharge due to electromagnetic waves are also taken. Due to the movement of the material P to be dried, as indicated by the dotted arrow in Figure 1, the material P covers the spiral ribbon 122 while it is being irradiated with electromagnetic waves, and the spiral ribbon 122 is almost never exposed. Therefore, there is little risk of discharge, and a metal spiral ribbon 122 can be used. However, as a countermeasure against discharge, a resin spiral ribbon can also be used. On the other hand, the pair of eddy current breakers 125 are exposed, and there is a risk that they could become a starting point for discharge when irradiated with electromagnetic waves, so they are made entirely of resin. Examples of resins that can be used here include engineering plastics and fiber-reinforced plastics (FRP).

[0046] Furthermore, the top panel 110 is provided with a UV sensor 127 as a light detection means for detecting flashes of light caused by discharge inside the main body 100. This UV sensor 127 is connected to the control unit 50. The inside of the main body 100 is constantly monitored by the UV sensor 127, and when a flash of light is detected, the control unit 50 stops the electromagnetic wave generating device 40.

[0047] In addition, to prevent abnormal heating due to electromagnetic wave heating, the temperature (item temperature) of the materials to be dried stored in the main body 100 is monitored. Using a temperature sensor such as a thermocouple protected by a normal metal sheath can cause problems such as the possibility of electric discharge or the inability to accurately measure the temperature due to the influence of electromagnetic waves. Therefore, an optical fiber thermometer 128 is used, and the optical fiber thermometer 128 is installed so as to penetrate the peripheral wall of the inverted cone-shaped portion 102. This optical fiber thermometer 128 is also connected to the control unit 50. The temperature of the materials to be dried stored in the main body 100 is measured by the optical fiber thermometer 128 constantly or at predetermined time intervals, and the control unit 50 controls the electromagnetic wave generator 40 based on the measurement results. This control will be described in detail later, but first, the installation structure of the optical fiber thermometer 128 will be described.

[0048] FIG. 2 is a perspective view showing the inside of the container of the drying device shown in FIG.

[0049] In the drying apparatus 1 shown in FIG. 2, the agitator motor 123, dust collector 30, and other components mounted on the top plate 110 are omitted. The top plate 110 shown in FIG. 2 includes an inlet 111a, an outlet 112, a glass window 114 through which electromagnetic waves are emitted, and an insertion hole 127a for a UV sensor 127. These components are arranged in a substantially straight line for convenience, but may be arranged in any other suitable manner as needed. Also shown inside the main body 100 are a pair of vortex breakers 125 attached to the top plate 110. As can be seen from FIG. 2, the vortex breakers 125 are arc-shaped plates. Also shown inside the main body 100 is a spiral ribbon 122 supported by multiple support members 1211 projecting radially from the drive shaft 121 and revolving around the inner circumferential wall of the main body 100. A counterbalancer 1212 is provided above the drive shaft 121 to balance the spiral ribbon 122.

[0050] 2 also shows an optical fiber thermometer 128. The tip of the optical fiber thermometer 128 extends to a position where it intersects with the rotational path of the spiral ribbon 122. This makes it possible to more accurately measure the temperature of the material being stirred up by the spiral ribbon 122. The spiral ribbon 122 has a notch 1221 at a position where it intersects with the tip of the optical fiber thermometer 128, so that the spiral ribbon 122 does not actually interfere with the tip of the optical fiber thermometer 128.

[0051] FIG. 3 is a graph showing a schematic relationship between the temperature of the material to be dried measured by the optical fiber thermometer and the output of the electromagnetic wave from the electromagnetic wave generator.

[0052] The graph in Figure 3 shows the passage of time from left to right. The dotted line in the graph shows the temperature (item temperature) of the material to be dried measured by the optical fiber thermometer 128. In the explanation using Figure 3, the temperature measured by the optical fiber thermometer 128 is referred to as the temperature of the material to be dried.

[0053] The drying apparatus 1 shown in Fig. 1 performs heating by conductive heat transfer, in which a heat medium is supplied to the jacket 130 to heat the material to be dried from the surface, and electromagnetic wave heating, in which electromagnetic waves are irradiated from the glass window 114 to heat the material to be dried from the inside as well. The graph in Fig. 3, shown by the thick solid line, indicates the magnitude of the electromagnetic wave output from the electromagnetic wave generator 40. In this embodiment, the electromagnetic wave output is set at a normal output value and a reduced output value that is smaller than the normal output value.

[0054] Explaining the time progression from left to right in Figure 3, when heating by both conductive heat transfer and electromagnetic wave heating at normal output is initiated, the temperature of the material to be dried rises and eventually reaches the target temperature indicated by the dashed-dotted line. When the temperature of the material to be dried exceeds the target temperature, the control unit 50 shown in Figure 1 switches the electromagnetic wave output from normal output to reduced output, weakening the electromagnetic wave heating. Note that heating by conductive heat transfer continues. As a result, the temperature rise of the material to be dried slows down, but the temperature continues to rise until the temperature of the material to be dried reaches the threshold temperature indicated by the dashed-dotted line. When the threshold temperature is reached, the control unit 50 stops the electromagnetic wave generator 40 and suspends electromagnetic wave heating for a predetermined time. If the temperature of the material to be dried after the predetermined time has elapsed is below the target temperature, the control unit 50 shown in Figure 1 resumes electromagnetic wave heating at normal output and heats the material together with heating by conductive heat transfer.

[0055] When the temperature of the material to be dried exceeds the target temperature again, the control unit 50 reduces the output of the electromagnetic waves to a reduced output value, and when the temperature of the material to be dried again reaches the threshold temperature, the control unit 50 suspends electromagnetic wave heating for a predetermined time. If the temperature of the material to be dried exceeds the target temperature after the predetermined time has elapsed, the control unit 50 resumes electromagnetic wave heating at the reduced output value, and heats the material to be dried in addition to heating by conductive heat transfer. The control unit 50 corresponds to an example of an irradiation control unit.

[0056] When heating by conduction, the surface of the material to be dried is heated, and moisture evaporates primarily from the surface. If only the surface becomes over-dried, the resistance to moisture movement increases inside the material, slowing down the drying rate. On the other hand, with electromagnetic wave heating, the material to be dried is also heated from the inside, making it possible to compensate for the unevenness of heating caused by conduction. Furthermore, the temperature of the material to be dried is measured and the output value of the electromagnetic waves is controlled based on the measurement results, preventing the material from being overheated or drying more than necessary.

[0057] In this embodiment, when the temperature of the material to be dried exceeds the target temperature, the control unit 50 reduces the output of the electromagnetic wave generator 40. However, it may also be configured to suspend electromagnetic wave heating for a certain period of time, as is the case when the threshold temperature is reached. Furthermore, when the temperature of the material to be dried exceeds the target temperature, the temperature of the heat medium supplied to the jacket 130 may be reduced, thereby weakening heating by conductive heat transfer, as well as electromagnetic wave heating. Alternatively, two devices may be provided, one generating electromagnetic waves at a normal output level and the other generating electromagnetic waves at a reduced output level, and the control unit 50 may switch between these two devices based on the target temperature and the threshold temperature to irradiate electromagnetic waves. Furthermore, it is also possible to set the electromagnetic wave output level to three or more levels and set two or more threshold temperatures, and perform combined control.

[0058] Figure 4 is a diagram showing a modified example of the drying apparatus shown in Figure 1. In the explanation using Figure 4, components with the same names as those explained so far are denoted by the same reference numerals. Also, in Figure 4, the input unit 111, stirring motor 123, reducer 124, leak detector 126, and dust collector 30, which are provided on top of top plate 110, are omitted.

[0059] In the drying apparatus 1 shown in FIG. 4(a), a moisture meter 150 is provided on the top plate 110 instead of the optical fiber thermometer 128. The top surface of the material P stored in the main body 100 is represented schematically by a dotted line, and the moisture meter 150 irradiates the top surface with infrared light and calculates the moisture (% WB) from the reflected light. The control unit 50 uses correlation data between the temperature and moisture of the material P obtained in a prior test to determine the material temperature from the calculated moisture, and changes the output of the electromagnetic waves based on the target temperature and threshold temperature. The opening in the top plate 110 where the moisture meter 150 is attached is provided with a glass window that transmits the infrared light to isolate it from the inside of the main body 100. If necessary, a mechanism for brushing off the material adhering to the glass window and a mechanism for preventing condensation on the glass window may be provided. In addition, if the moisture meter 150 is affected by electromagnetic waves, a shutter that blocks electromagnetic waves is provided at the infrared radiation port (or reflected light receiving port), and when measuring moisture, the electromagnetic wave heating is stopped and the shutter is opened to perform the moisture measurement. Instead of a shutter, a glass window that is structured to transmit infrared light but attenuate microwaves may be used.

[0060] It is also possible to periodically discharge a small amount of the material to be dried from the outlet 1001 and measure the moisture content outside the drying device 1.

[0061] In the drying apparatus 1 shown in FIG. 4(b), a thermographic camera 151 is provided on the top plate 110 instead of the optical fiber thermometer 128. In FIG. 4(b), the imaging area of ​​the thermographic camera 151 is indicated by a two-dot chain line, and is shown as being capable of detecting the entire upper surface (see dotted line) of the material to be dried P stored in the main body 100. If it is difficult to detect the entire upper surface with one thermographic camera, multiple cameras are installed. The thermographic camera 151 measures the radiant energy from the upper surface of the material to be dried P stored in the main body 100 and converts it into temperature to obtain the temperature of the material to be dried. The output of the electromagnetic waves can also be changed based on the temperature of the material to be dried obtained by the thermographic camera 151, using the target temperature and threshold temperature described above as references.

[0062] The upper surface of the material to be dried P faces the glass window 114 and is the irradiation surface onto which the electromagnetic waves are irradiated from the glass window 114. By measuring the temperature of the surface of the material to be dried P irradiated with the electromagnetic waves at a plurality of points, it becomes possible to identify the points where the electromagnetic waves are partially absorbed and have a high temperature. The direction of irradiation of the electromagnetic waves can be adjusted, or the installation angle and height of the pair of vortex current breakers 125 can be adjusted to change the degree to which the material to be dried P is repelled or scattered toward the center of the main body 100, thereby making the electromagnetic waves work more efficiently. Alternatively, the direction of irradiation of the electromagnetic waves can be changed by providing irradiation positions (glass windows 114) at a plurality of points and selecting one or more irradiation positions from the plurality of irradiation positions to irradiate the electromagnetic waves. As with the moisture meter 150 described above, the opening in the top plate 110 where the thermographic camera 151 is attached is provided with a glass window that transmits infrared light to isolate it from the inside of the main body 100, and may be equipped with a mechanism for brushing off materials to be dried that adhere to the glass window and a mechanism for preventing condensation on the glass window as needed. Also, if the thermographic camera 151 is affected by electromagnetic waves, a shutter that blocks electromagnetic waves is provided, and when measuring temperature, the electromagnetic wave heating is stopped and the shutter is opened to measure the temperature. Instead of a shutter, a glass window that transmits infrared light but attenuates microwaves may be used.

[0063] The optical fiber thermometer 128 shown in FIG. 1, the moisture meter 150 shown in FIG. 4(a), and the thermography camera 151 shown in FIG. 4(b) correspond to examples of the acquisition unit.

[0064] FIG. 5 is a graph showing a schematic relationship between the current value of the stirring motor and the driving / stopping of the stirring motor.

[0065] In the graph of FIG. 5, time elapses from left to right. The dotted line represents the current value flowing through the agitator motor 123 acquired by the control unit 50 shown in FIG. 1. In the drying device 1 shown in FIG. 1, the aggregates are broken down by the action described in the above embodiment, combined with the use of electromagnetic wave heating. However, some aggregates and lumps may still occur and grow. If aggregates become caught between the spiral ribbon 122 and the inner peripheral wall of the main body 100, the agitation power increases, resulting in an overload, preventing the agitator motor 123 from rotating. In the graph shown in FIG. 5, the dashed-dotted line represents the current value (overload value) in the event of an overload, and the dashed-dotted line represents an abnormal value that is lower than the overload value but higher than the current value during normal rotation. The abnormal value is a preset value set in the control unit 50. The thick solid line represents the drive and stop of the agitator motor 123.

[0066] Once the agitation motor 123 starts rotating and settles down to the normal rotation speed, the current value also becomes constant. This current value is referred to as the normal value. In the example of Figure 5, it is assumed that heating is always performed by both conductive heat transfer and electromagnetic wave heating at the normal output value.

[0067] At this point, aggregates may begin to form. The aggregates are initially small, but as the agitation operation continues, they may gradually grow larger even if electromagnetic wave heating is being performed. The rotation of the spiral ribbon 122 becomes more easily hindered as the aggregates grow larger. When the rotation of the spiral ribbon 122 begins to be hindered by the aggregates, the current value flowing through the agitation motor 123 begins to increase. Eventually, this current value exceeds the abnormal value indicated by the dashed dotted line. When the acquired current value exceeds the abnormal value, the control unit 50 stops the agitation motor 123 for a predetermined time (e.g., 10 to 20 minutes). As a result, agitation of the material to be dried is not performed for the predetermined time, but electromagnetic waves are irradiated on small aggregates before they grow to a certain size. After a predetermined time has elapsed, the control unit 50 resumes driving the stirring motor 123 and acquires the current value.If the aggregates have been disintegrated and the spiral ribbon 122 is able to rotate normally, the current value will not rise above an abnormal value, and the control unit 50 will continue driving the stirring motor 123.

[0068] If the current value flowing through the agitation motor 123 again exceeds the abnormal value, the control unit 50 stops the agitation motor 123 for a predetermined time, and then resumes driving the agitation and acquiring the current value, thereby performing the same operation as described above.

[0069] Next, taking the state between t1 and t2 in Figure 5 as an example, if the aggregates are not sufficiently broken down for some reason, the current value may reach an abnormal value shortly after agitation is restarted (t1). In this case, the control unit 50 immediately stops driving the agitation motor 123 (t2), waits for a predetermined time to elapse, and then performs the same operation as described above, repeatedly stopping and restarting the agitation until the current value no longer reaches an abnormal value. Of course, the number of times the agitation is stopped and restarted is set in the control unit 50, and if this set number of times is exceeded, the entire drying operation may be stopped.

[0070] In this example, the abnormal value described above is used as an abnormal state before the motor becomes inoperable, and agitator motor 123 is stopped before the current value flowing through motor 123 reaches an overload value, thereby preventing damage to motor 123. Furthermore, because there is no need to worry about overload driving, a motor with low torque can be used, which also reduces costs.

[0071] Since electromagnetic wave heating is expected to break mainly hydrogen bonds that cause agglomeration, when the current value exceeds an abnormal value, the control unit 50 may change the output value of the electromagnetic waves to a value higher than the normal output value. Also, here, when the current value exceeds an abnormal value, the stirring motor 123 is completely stopped, but it may also be configured to continue rotating at a low speed at which growth of agglomerates is less likely to occur and the current value can be kept low.

[0072] Furthermore, when the rotation of the spiral ribbon 122 is hindered by the aggregates, abnormal vibrations occur in the drive shaft 121. The control unit 50 monitors this abnormal vibration using a vibration sensor 129 (corresponding to an example of a vibration detection unit) provided at the upper end of the drive shaft 121. The control unit 50 stops the agitation motor 123 for a certain period of time when vibrations of a predetermined amplitude or greater are detected. Even when vibrations are detected, electromagnetic wave heating continues, and the electromagnetic wave heating progresses the disintegration of the aggregates, thereby eliminating the abnormal vibrations occurring in the drive shaft 121. The control unit 50 may also stop the agitation motor 123 for a certain period of time when vibrations of a predetermined amplitude or greater are detected continuously for a certain period of time. Alternatively, the control unit 50 may also stop the agitation motor 123 for a certain period of time when vibrations of a predetermined amplitude or greater are detected continuously for a certain period of time.

[0073] 1, vibration sensor 129 is provided on drive shaft 121, but it may also be provided on top plate 110 or inverted cone-shaped portion 102. When vibration is detected, stirring motor 123 is stopped completely, but it may also be configured to continue rotating at a low speed at which growth of aggregates is unlikely to occur and vibration is suppressed.

[0074] As described above, the control unit 50 also corresponds to an example of a stirring control unit.

[0075] Next, a drying experiment was conducted using a drying apparatus having the same configuration as the drying apparatus 1 shown in Fig. 1. First, the results of an experiment comparing a case in which the electromagnetic wave generator 40 was not started and a heat medium was supplied to the jacket 130 to heat the material to be dried from the surface by conductive heat transfer alone, and a case in which both conductive heat transfer and electromagnetic wave heating were performed in which electromagnetic waves were irradiated from the glass window 114 to heat the material to be dried from the inside as well, will be described.

[0076] In this experiment, zeolite was used as the material to be dried. The moisture content of the zeolite before drying was 24% WB. The vacuum pump 60 was set to a pressure of 7 kPa inside the container 10, and vacuum conduction heat transfer drying was performed by circulating and supplying a heat medium at 60°C to the jacket 130. In addition, for electromagnetic wave heating, microwaves of 2.45 GHz were used as the electromagnetic waves, and the normal output value was set to 1.5 kW.

[0077] FIG. 6 is a graph showing the results of the comparative experiment.

[0078] In the graph shown in Fig. 6, the horizontal axis represents the drying time (minutes). The vertical axis represents the moisture content (% WB) of the material to be dried and the temperature (product temperature) (°C) of the material to be dried. The moisture content is measured using the moisture meter shown in Fig. 4(a), and the product temperature is measured using the optical fiber thermometer 128 shown in Fig. 1.

[0079] The circular plots represent the results when only vacuum conduction heating was performed, the square plots represent the results when both vacuum conduction heating and microwave heating were performed, the open plots represent product temperature, and the solid plots represent moisture content.

[0080] When drying using only vacuum conduction heat transfer, the moisture content decreased at a constant rate up to 150 minutes, with the section from 0 to 150 minutes being the constant rate drying section. After that, the drying speed decreased, and the moisture content decreased to 5% WB by 240 minutes of drying operation.

[0081] On the other hand, when both vacuum conduction heating and microwave heating were used, the drying speed in the constant rate drying section was fast, with the moisture content dropping to below 10% WB in 80 minutes and reaching 5% WB in about 100 minutes. When irradiated with microwaves, the product temperature rose quickly at low moisture content, and there was almost no drop in the drying speed in the falling rate drying section, making it possible to dry to a low moisture content in a short time. In this experiment, the microwave output was also changed based on the target temperature and threshold temperature described using Figure 3, and the zeolite moisture content after drying was dried to 5% WB.

[0082] Next, we will explain the case of drying calcium carbonate. When drying was performed using only vacuum conduction heat transfer heating, agglomerates of several centimeters in size had formed 60 minutes after the start of operation. When heating only using vacuum conduction heat transfer, only the surface of the agglomerates was dried, and once agglomerates began to form, the drying rate tended to drop sharply.

[0083] When drying was performed using both vacuum conduction heat transfer and microwave heating, aggregates formed during the drying process. However, when microwave heating was used in combination, the collapse of the aggregates was confirmed. We believe that the microwaves heated the aggregates from the inside, causing the moisture content inside to decrease at an early stage. Furthermore, since the agitation motor 123 was stopped in response to the increase in the current flowing through the agitation motor 123 and the detection of vibrations by the vibration sensor 129, as described with reference to Figure 5, the effect of internal heating by microwaves was readily apparent before the aggregates had grown large. This, combined with the heating by vacuum conduction heat transfer, promoted evaporation from both the surface and the inside of the aggregates, resulting in their collapse. We believe that this resulted in stable drying even to low moisture contents.

[0084] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims. For example, the present invention is not limited to a drying device that heats the main body 100 from the outside, but may be a drying device equipped with a heating element inside the main body 100, such as a so-called paddle dryer that dries by passing a heating medium through a rotating shaft and a paddle attached to the rotating shaft. Heating by conductive heat transfer may also be performed intermittently. The material to be dried may be a liquid material containing solids. Furthermore, in response to an increase in the current value flowing through the agitation motor 123 described with reference to FIG. 5 or detection of vibration by the vibration sensor 129, the agitation motor 123 may not be stopped (while the agitation motor 123 is constantly driven), but the microwave output may be changed based on the target temperature and threshold temperature described with reference to FIG. 3.

[0085] Note that even if a constituent element is included only in the description of the embodiment or the description of the modified example described above, that constituent element may be applied to other embodiments or modified examples. [Explanation of symbols]

[0086] D1 Drying System 1 Drying device 10 containers 100 Main body 110 Top Plate 1101 Seal part 114 Glass Window 121 Drive shaft 122 Spiral Ribbon 123 Stirring motor 125 Vortex Breaker 126 Leak Detector 127 UV sensor 128 Optical Fiber Thermometer 129 Vibration Sensor 130 Jacket 150 Moisture meter 151 Thermography Camera 20 Heating medium supply device 30 Dust collector 31 Shielding member 40 Electromagnetic Wave Generator 50 control section 60 Vacuum Pump 2 capacitors

Claims

1. a heating element that comes into contact with the material to be dried and heats the material; an irradiation unit that irradiates electromagnetic waves toward the material to be dried; an acquisition unit that acquires information about the temperature or moisture content of the material to be dried; an irradiation control unit that controls irradiation of electromagnetic waves by the irradiation unit based on the information acquired by the acquisition unit, the irradiation control unit performs a first control of reducing the output of the electromagnetic waves irradiated by the irradiating unit or shortening the irradiation time of the electromagnetic waves irradiated by the irradiating unit when the temperature of the object to be dried exceeds a target temperature, based on the information on temperature acquired by the acquiring unit, and performs a second control of stopping the irradiation of the electromagnetic waves when the temperature of the object to be dried reaches a threshold temperature higher than the target temperature; A drying device characterized in that the heating member heats the material to be dried while the first control is being performed.

2. a stirring mechanism that stirs the material to be dried by being driven; a stirring control unit that monitors the driving state of the stirring mechanism, and stops driving the stirring mechanism or reduces the driving speed of the stirring mechanism when the driving state is in an abnormal state before the stirring mechanism becomes inoperable, 2. The drying device according to claim 1, wherein the irradiation unit irradiates the material to be dried with electromagnetic waves constantly or intermittently even when the driving of the stirring mechanism is stopped or the driving speed of the stirring mechanism is reduced.

3. A stirring mechanism that stirs the material to be dried by being driven; a vibration detection unit that detects vibrations in the drying device; a stirring control unit that stops driving the stirring mechanism or reduces the driving speed of the stirring mechanism in response to a result of vibration detection by the vibration detection unit, 2. The drying device according to claim 1, wherein the irradiation unit irradiates the material to be dried with electromagnetic waves constantly or intermittently even when the driving of the stirring mechanism is stopped or the driving speed of the stirring mechanism is reduced.

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