JP7597622B2 - Layer level detection device and industrial furnace - Google Patents

Description

The present invention relates to a bed height detection device and an industrial furnace, and in particular to a bed height detection device that uses microwaves to detect the bed height level in an industrial furnace, and an industrial furnace equipped with this bed height detection device.

One type of furnace used for industrial purposes (industrial furnace) is a waste melting furnace, which gasifies and melts waste, such as general waste and industrial waste, to treat the waste. Waste melting furnaces are equipped with a bed height detection device to monitor the amount of waste inside the furnace, and are operated according to the bed height detected by this device.

Microwave level detectors are non-contact level detectors that are widely used across all technical fields. However, if they are installed as is in a waste melting furnace, they are susceptible to damage from the heat of the high-temperature gas rising inside the furnace, so protective measures are necessary to reduce the effects of heat. In addition, measures are also necessary to reduce the effects on detection accuracy caused by the adhesion of dust, oil, moisture, etc. (hereinafter referred to as "dust, etc.") that accompanies the high-temperature gas.

As a protective measure to suppress the effects of such high-temperature gases and dust, Patent Document 1 discloses a bed height detection device configured to place a heat-resistant ceramic fiber filter to separate the transmitter and receiver of a microwave level detector from the furnace space, and to supply pulse gas to this ceramic fiber filter. According to Patent Document 1, this configuration makes it possible to automatically brush off dust and other particles adhering to the surface due to the internal pressure difference between the inner and outer surfaces and the deformability of the ceramic fiber filter caused by the pulse pressure, and as a result, it is possible to suppress the impact of dust and other particles adhering to the detection accuracy.

It is true that the bed height detection device of Patent Document 1 can suppress the adhesion of dust and the like compared to previous methods. However, in a method like Patent Document 1 in which dust and the like is brushed off by the internal pressure difference between the inner and outer surfaces or the deformability of the ceramic fiber filter due to pulse pressure, if there is a lot of dust, it can be difficult to brush off the dust and the like that has adhered to the inner surface of the ceramic fiber filter, and the adhesion of dust and the like still has an effect on detection accuracy.

JP 2011-21910 A

The problem that this invention aims to solve is to provide a bed height detection device and industrial furnace that can reduce the effect on detection accuracy caused by the adhesion of dust, etc.

According to one aspect of the present invention, there is provided a high level sensing apparatus comprising:
A bed level detection device that detects the bed level in an industrial furnace using microwaves,
a microwave level detector having a transmitter for transmitting microwaves into a furnace and a receiver for receiving reflected microwaves;
a filter structure that separates the transmitting unit and the receiving unit from a furnace interior space;
a gas supply device for supplying a gas to the filter structure,
The filter structure includes a disk-shaped first filter material and an annular plate-shaped second filter material arranged on the furnace inner side of the first filter material with a predetermined gap therebetween,
A bed height level detection device configured so that gas supplied from the gas supply device enters the gap from the outer peripheral edge of the first filter material and flows toward the inner hole side of the second filter material.

According to another aspect of the present invention, there is provided an industrial furnace equipped with the bed level detection device described above.

According to the present invention, the gas supplied from the gas supply device is configured to enter the gap between the outer periphery of the first filter material and the second filter material and flow toward the inner hole side of the second filter material, so that the gas supplied from the gas supply device is actively guided to the center of the furnace inside of the filter structure. This makes it possible to suppress adhesion of dust, etc. to the furnace inside surface of the filter structure, and to automatically brush off dust, etc. that has adhered to the furnace inside surface of the filter structure.

1 is a schematic cross-sectional view of a main portion of an industrial furnace equipped with a bed height detection device according to one embodiment of the present invention. 2 is a cross-sectional view showing a specific example of the configuration of the filter storage section 25 and its vicinity in the bed height level detection device of FIG. 1 . 2 is a plan view of a filter structure in the bed height detection device of FIG. 1; AA cross-sectional view of FIG. 3. BB cross-sectional view of FIG. 3. 5 is a cross-sectional view taken along the line CC of FIG. 4 . 5 is a cross-sectional view taken along the line D-D of FIG. 4 .

FIG. 1 shows a schematic cross-sectional view of a main portion of an industrial furnace equipped with a bed level detection device according to an embodiment of the present invention.
In this embodiment, a bed height level detector 2 is disposed at the top of a waste melting furnace 1, which is an industrial furnace. The bed height level detector 2 includes a microwave level detector 21 detachably connected to a nozzle 12 formed at the top of a furnace body 11 of the waste melting furnace 1 via a gate valve 3 or the like, and a first cylindrical body 22A having an inlet through which purge gas and pulse gas are introduced. The microwave level detector 21 and the first cylindrical body 22A are detachably connected by a flange 23A. Specifically, the microwave level detector 21 is detachably provided on the upper side of the first cylindrical body 22A.

The gate valve 3 is opened and closed by a handle 31, for example, when performing maintenance work on the microwave level detector 21, and the valve is normally left open. In addition, in FIG. 1, a flange and bolts and nuts are used as a structure for making the microwave level detector 21 and the gate valve 3 detachable, but this is not limited to this.

The microwave level detector 21 has a transmitter that transmits microwaves into the furnace, a receiver that receives microwaves reflected from the top surface of the waste mass inside the furnace (i.e., the bed height level), and a calculation unit (e.g., a calculation circuit, etc.) that calculates the bed height level from the transmitted and received microwaves, for example, based on the amount of attenuation. However, the calculation unit can also be omitted from the microwave level detector 21, for example, by configuring the control unit that controls the overall operation of the waste melting furnace 1 to determine the bed height level.

The microwave level detector 21 may be equipped with a cone-shaped antenna, the diameter of which increases toward the tip, as a transmitter and receiver for transmitting and receiving microwaves. A seal member may also be provided to eliminate the gap between the tip of the microwave level detector 21 and the flange 23A.

A filter structure 24 is provided on the underside of the first cylindrical body 22A to separate the internal space of the cylindrical body 22A from the furnace space. In other words, the microwave level detector 21 is separated from the furnace space by the filter structure 24. The detailed configuration of the filter structure 24 will be described later, but it is a cartridge type that can be detached and replaced on the underside of the first cylindrical body 22A. In other words, a filter storage section 25 that stores the cartridge type filter structure 24 in a detachable and replaceable manner is provided on the underside of the first cylindrical body 22A.

The second cylindrical body 22B is connected to the underside of the filter storage section 25. The third cylindrical body 22C is connected to the underside of the second cylindrical body 22B via a flange 23B. A cylindrical rat-bar section 26 is provided inside the third cylindrical body 22C. The gate valve 3 is connected to the underside of the third cylindrical body 22C via a flange 23C.

Figure 2 shows a cross section of a specific example configuration near the filter storage section 25. In this example configuration, the filter storage section 25 is connected to the underside of the first cylindrical body 22A by seal welding, and the second cylindrical body 22B is connected to the underside of the filter storage section 25 by seal welding. The third cylindrical body 22C is connected to the underside of the second cylindrical body 22B via a flange 23B. In this example configuration, the second cylindrical body 22B is extended into the inside of the third cylindrical body 22C to form a rat-barring section 26.

Next, a specific configuration of the filter structure 24 will be described.
3 is a plan view of the filter structure 24, FIG. 4 is a cross-sectional view taken along line AA in FIG. 3, FIG. 5 is a cross-sectional view taken along line BB in FIG. 3, FIG. 6 is a cross-sectional view taken along line CC in FIG. 4, and FIG.

The filter structure 24 is an integrated unit of a first filter material 241 and a second filter material 242 arranged in a filter material mounting cassette 243, and is of a cartridge type that is detachable and replaceable with respect to the filter storage unit 25 shown in Fig. 2. Specifically, when mounting the filter structure 24 to the filter storage unit 25, the filter material mounting cassette 243 is inserted into the filter storage unit 25, and the flange portion 243a is fixed to the flange portion 25a of the filter storage unit 25 with bolts 243b. When removing the filter structure 24 from the filter storage unit 25, the fixation by the bolts 243b is released, and the filter material mounting cassette 243 is pulled out from the filter storage unit 25.
The filter material mounting cassette 243 and the filter storage unit 25 are both made of metal, specifically stainless steel, and the contact surfaces between the filter material mounting cassette 243 and the filter storage unit 25 are metal-to-metal.

The first filter material 241 is a disk-shaped material with an outer diameter of 100 mm. The second filter material 242 is an annular plate-shaped material with an outer diameter of 100 mm and an inner diameter of 40 mm, and is disposed below the first filter material 241 (inside the furnace) with a predetermined gap S. Specifically, as shown in FIG. 4, the second filter material 242 is disposed in the filter material mounting portion 243c of the filter material mounting cassette 243 via a packing 243d made of PTFE (polytetrafluoroethylene). Next, the first filter material 241 is disposed so as to be aligned with the second filter material 242 by sandwiching the tip of the PTFE support member 243e. At this time, the dimensional relationship between the first filter material 241 and the support member 243e is adjusted so that the upper surface of the first filter material 241 and the upper surface of the support member 243e are flush with each other. Then, a fixing member 243f made of PTFE is installed so as to straddle the upper surface of the first filter material 241 and the upper surface of the support member 243e, and is fixed to the filter material installation section 243c by a bolt 243g. As a result, the first filter material 241 and the second filter material 242 are integrally installed in the filter material installation section 243c with a gap S of the thickness of the tip of the support member 243e, specifically about 2 mm. Here, as shown in FIG. 3, the fixing member 243f is installed at multiple locations (four locations in this embodiment) at equal intervals along the circumferential direction of the first filter material 241. The support member 243e is also installed at multiple locations (four locations in this embodiment) corresponding to the fixing member 243f. In this embodiment, the material of the packing 243d, the support member 243e, and the fixing member 243f is PTFE, but is not limited to this, and may be other materials that have heat resistance and do not damage the first filter material 241 and the second filter material 242.
The filter material installation portion 243c has an opening, and the lower diameter of the opening is 85 mm. That is, in this embodiment, the effective outer diameter of the double filter made up of the first filter material 241 and the second filter material 242 is 85 mm.

Both the first filter material 241 and the second filter material 242 are made of quartz glass. Quartz glass has high microwave transmittance and excellent heat resistance, making it an optimal material for the filter material in a bed height detection device that uses microwaves to detect the bed height level in an industrial furnace. In addition, since quartz glass has a smooth surface, using quartz glass as the filter material makes it difficult for dust and the like to adhere to the filter material and makes it easier to brush off any adhered dust and the like.
In addition to quartz glass, other materials with high microwave transmittance include PTFE, polystyrene, borosilicate glass, alumina, etc., which can also be used as the filter material. However, when microwave transmittance, heat resistance, and surface smoothness are all considered, quartz glass is the most suitable filter material. Note that the present invention is premised on the assumption that both the first filter material 241 and the second filter material 242 are made of non-breathable materials (substances).

Referring again to FIG. 1, the bed height detection device 2 includes gas supply devices 27A and 27B that respectively supply purge gas and pulse gas to the internal space of the first cylindrical body 22A, which is separated from the furnace space by the filter structure 24. The purge gas supply device 27A continuously supplies purge gas through a gas supply pipe 272 connected to a supply source 271 of an inert gas, such as nitrogen gas. On the other hand, the pulse gas supply device 27B is configured such that a pulse gas valve 273 for generating pulse gas and a blaster tank 274 are connected to the gas supply pipe 272 connected to a supply source 271 of an inert gas, such as nitrogen gas.

The purge gas supply device 27A continuously supplies inert gas so that the space above the filter structure 24 is purged at a pressure higher than the furnace pressure. On the other hand, the operation of the pulse gas supply device 27B is controlled to generate pulse gas intermittently. For example, the pressure and/or flow rate of the gas can be changed by opening and closing the valve body of the pulse gas valve 273 to generate pulse gas. In this case, the type and shape of the valve itself are not limited, and a general valve that can automatically control the opening and closing operation can be used. Furthermore, the opening and closing operation is automatically or manually controlled, for example, by a control panel installed at the site. It is not limited to this, and can also be performed by a control unit that controls the overall operation of the waste melting furnace 1. The control unit can be configured, for example, by a computer having a CPU, and information such as the timing of generating the pulse gas can be stored in a memory or the like.

The timing of generating the pulse gas may be, for example, periodically at a predetermined cycle (e.g., every hour), or may be when the disturbance (noise, etc.) in the detection signal exceeds a predetermined threshold. Furthermore, a combination of both of these controls may be used.

In the layer height detection device 2 of the present embodiment having the above-mentioned configuration, microwaves are transmitted and received to detect the layer height level of the waste material, and an inert gas (N ₂ ) is supplied to purge at least the space above the filter structure 24 so that the pressure therein is higher than the furnace pressure. The purged gas (N ₂ ) is supplied to the filter structure 24. The gas (N ₂ ) supplied to the filter structure 24 flows toward the outer periphery of the first filter material 241 as conceptually shown in FIG. 6, and then, as conceptually shown in FIG. 7, enters the gap S between the first filter material 241 and the second filter material 242 from the outer periphery of the first filter material, and flows toward the inner hole 242a of the second filter material 242. That is, the gas (N ₂ ) supplied to the filter structure 24 enters the gap S from the outer periphery of the first filter material 241, and flows toward the inner hole 242a of the second filter material 242, as conceptually shown in FIG. 5. In this way, the gas (N ₂ ) supplied to the filter structure 24 is actively guided to the furnace inner central portion of the filter structure 24. This makes it possible to suppress adhesion of dust, etc. to the furnace inner surface of the filter structure 24, particularly to the furnace inner surface central portion of the first filter material 241 exposed to the furnace inner side from the inner hole 242a of the second filter material 242, and also makes it possible to automatically brush off dust, etc., attached to the furnace inner surface of the filter structure, particularly to the furnace inner surface central portion of the first filter material 241 described above. As a result, the effect of adhesion of dust, etc. on detection accuracy can be suppressed. Therefore, it becomes possible to perform stable detection of the layer height level over a long period of time.
In addition, by supplying an inert gas ( _N2 ) to purge the space above the filter structure 24 so that the pressure therein is higher than the pressure inside the furnace, the microwave level detector 21 can be air-cooled, thereby suppressing the effects of heat from the waste melting furnace 1.
As will be described in more detail later, in this embodiment, the central part of the furnace inner surface of the first filter material 241 described above is the part through which the stronger central beam of microwaves emitted from the microwave level detector 21 passes, and according to this embodiment, as described above, the adhesion of dust and the like can be particularly suppressed in the part through which the stronger microwave beam passes, thereby further suppressing the impact on detection accuracy caused by the adhesion of dust and the like.

Next, the preferable dimensional relationships between the components of the bed height detection device 2 will be described.
In this embodiment, when the microwave level detector 21 emits microwaves with an initial diameter of 70 mm and a spread angle of 2 degrees on each side, the microwaves have a stronger beam in the center and a weaker beam on the outside. In the following description, the stronger beam and the weaker beam are collectively referred to as the microwave beam. In addition, in FIG. 1, the irradiation range of the microwave beam is conceptually shown by the dashed line.

In this embodiment, the inner diameters of the first cylindrical body 22A and the second cylindrical body 22B located above and below the filter structure 24 are set to the minimum necessary size so that the gap with the irradiation range of the microwave beam is, for example, about 10 mm. Specifically, the inner diameter of the first cylindrical body 22A is about 90 mm, and the inner diameter of the second cylindrical body 22B is about 115 mm. In this way, by setting the inner diameters of the first cylindrical body 22A and the second cylindrical body 22B located above and below the filter structure 24 to the minimum necessary size, the flow rate of the gas passing through the filter structure 24 can be increased. This increases the effect of suppressing adhesion of dust, etc. to the furnace inner surface of the filter structure 24 and the effect of brushing off dust, etc. attached to the furnace inner surface of the filter structure 24. Furthermore, by making the inner diameters of the first cylindrical body 22A and the second cylindrical body 22B located above and below the filter structure 24 to the minimum necessary size, the area of metal-to-metal contact between the filter structure 24 and the filter storage section 25 is reduced, thereby reducing the amount of gas leakage.
The length of the first cylindrical body 22A on the upper side of the filter structure 24 is made as short as possible within a range in which the gas supply devices 27A and 27B can be installed, in order to reduce the effective outer diameter of the double filter (first filter material 241 and second filter material 242) in the filter structure 24 and thereby reduce the size of the filter structure 24. Specifically, the length of the first cylindrical body 22A is set to about 90 mm.
On the other hand, the length of the second cylindrical body 22B located below the filter structure 24 must be a length that does not interfere with the microwave beam, and in this embodiment, the length of the second cylindrical body 22B is approximately 90 mm.

As described above, the effective outer diameter of the double filter (first filter material 241 and second filter material 242) in the filter structure 24 is 85 mm, which is set based on the diameter (about 80 mm) of the irradiation range of the microwave beam at the position of the double filter. In other words, the effective outer diameter of the double filter is set with a slight margin in the irradiation range of the microwave beam.
In addition, the measurement limit diameter of the microwave level detector 21 at the position of the double filter is about 40 mm, and accordingly, the diameter of the inner hole 242a of the second filter material 242 is set to 40 mm. That is, in this embodiment, the inner diameter of the second filter material 242 (the diameter of the inner hole 242a) is set to match the measurement limit diameter of the microwave level detector 21.

The length of the third cylindrical body 22C is preferably 300 mm or more, and is about 500 mm in this embodiment. By making the length of the third cylindrical body 22C 300 mm or more, it is possible to suppress the flying of dust and the like from inside the furnace to the filter structure 24.
In this embodiment, a cylindrical anti-pole portion 26 is provided inside the third cylindrical body 22C. In this embodiment, the anti-pole portion 26 is an extension of the second cylindrical body 22B into the inside of the third cylindrical body 22C as shown in Fig. 2, and the outer diameter of this anti-pole portion 26 is larger than the outer diameters of the first filter material 241 and the second filter material 242. In addition, the protruding length of the anti-pole portion 26 is 75 mm, and it is preferable that the gap between the lower end of this anti-pole portion 26 and the irradiation range of the microwave beam is about 10 mm or more.
In this way, by providing a mouse-return section 26 inside the third cylindrical body 22C, dust and other particles rising from inside the furnace along the inner wall surface of the third cylindrical body 22C can be prevented from invading the filter structure 24.

As described above, according to this embodiment, it is possible to suppress adhesion of dust and the like to the furnace inner surface of the filter structure 24, and it is possible to automatically brush off dust and the like that has adhered to the furnace inner surface of the filter structure 24. In addition, it is possible to suppress the influence of heat from the waste melting furnace 1.

In this embodiment, the purge gas supply device 27A and the pulse gas supply device 27B are provided as gas supply devices that supply gas to the filter structure 24, but the pulse gas supply device 27B is not necessarily required and can be omitted. Also, instead of providing the pulse gas supply device 27B in the first cylindrical body 22A, it is also possible to provide it in the second cylindrical body 22B and eject the pulse gas toward the furnace inner surface of the filter structure 24.
In this embodiment, the first cylindrical body 22A is provided with the purge gas supply device 27A and the pulse gas supply device 27B, but the purge gas supply device 27A and the pulse gas supply device 27B may be provided on the flange 23A connecting the microwave level detector 21 and the first cylindrical body 22A. In this case, the first cylindrical body 22A may be omitted, and the filter structure 24 may be provided on the lower side of the microwave level detector 21.

In addition, in this embodiment, a configuration in which the microwave level detector 21 does not have an antenna is shown as an example, but the present invention is not limited to this configuration, and the microwave level detector 21 may be provided with an antenna that is, for example, cone-shaped, bowl-shaped, cylindrical, rectangular, or the like. In this case, the shape of the cylindrical body that houses the antenna (i.e., the antenna housing) can also be a shape that matches the shape of the antenna.

The location of the bed height detector 2 is not limited to the top of the furnace as shown in FIG. 1, but may be on the side of the furnace, etc. In this case, for example, two antennas, one for transmitting and one for receiving microwaves, may be placed in opposing positions on the side of the furnace. Furthermore, it is not necessary to calculate the bed height level by calculation, etc., and it is sufficient to simply detect, for example, whether the waste has piled up to a predetermined height.

Furthermore, it goes without saying that the bed height detection device 2 is not limited to being installed in a waste melting furnace 1, but can be installed in various known industrial furnaces to detect the bed height level of materials fed into the furnace, etc.
It will be apparent to those of ordinary skill in the art that various other substitutions, modifications, variations, and the like are possible.

REFERENCE SIGNS LIST 1 waste melting furnace 11 furnace body 12 nozzle 2 bed height level detection device 21 microwave level detector 22A first cylindrical body 22B second cylindrical body 22C third cylindrical body 23A, 23B, 23C flange 24 filter structure 241 first filter material 242 second filter material 242a inner hole 243 filter material mounting cassette 243a flange portion 243b bolt 243c filter material installation portion 243d packing 243e support member 243f fixing member 243g bolt 25 filter storage portion 26 rat-proof portion 27A, 27B gas supply device 271 inert gas supply source 272 gas supply pipe 273 pulse gas valve 274 blaster tank 3 gate valve 31 handle

Claims (5)

A bed level detection device that detects the bed level in an industrial furnace using microwaves,
a microwave level detector having a transmitter for transmitting microwaves into a furnace and a receiver for receiving reflected microwaves;
a filter structure that separates the transmitting unit and the receiving unit from a furnace interior space;
a gas supply device for supplying a gas to the filter structure,
The filter structure includes a disk-shaped first filter material and an annular plate-shaped second filter material arranged on the furnace inner side of the first filter material with a predetermined gap therebetween,
A bed height level detection device configured so that gas supplied from the gas supply device enters the gap from the outer peripheral edge of the first filter material and flows toward the inner hole side of the second filter material. The layer height detection device of claim 1, wherein the first filter material and the second filter material are made of quartz glass. The layer height detection device according to claim 1 or 2, wherein the filter structure is a removable and replaceable cartridge type. The bed height detection device according to any one of claims 1 to 3, comprising a cylindrical rod-shaped section having an inner diameter larger than the outer diameters of the first filter material and the second filter material, inside a cylindrical body that connects the filter structure to the inside of the furnace. An industrial furnace equipped with a bed height detection device according to any one of claims 1 to 4.

Images