JP2017161410A - Microwave level meter with horn antenna and prevention method of adhesion of volatile matter to horn antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave level meter with a horn antenna which can surely prevent the adhesion of a volatile matter to the inside of the horn antenna without complicating a device constitution, and a prevention method of the adhesion of the volatile matter to the horn antenna.SOLUTION: A microwave level meter 1 with a horn antenna comprises: a horn antenna 12 having an antenna part 10 which is arranged on a roof plate 3 of a storage tank 2 for storing a stored product 4 containing a volatile matter, emitting a microwave to a measurement face 4a of the stored product 4, and receiving the microwave which is reflected from the measurement face 4a, and a hollow truncated-cone shaped antenna horn part 11 for radiating the microwave which is emitted from the antenna part 10 to a single direction; a plurality of gas purge holes 16 which are formed at a plurality of points in the vicinity of an outlet of the antenna horn part 11; and a plurality of purge gas flow-in members 17 which are attached into the plurality of gas purge holes 16, make purge gases flow into the antenna horn part 11 from the gas purge holes 16, also make them collide with the holes, and store them in the holes.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a microwave level meter with a horn antenna attached to a storage tank of a storage containing volatile matter, and a method for preventing the attachment of volatile matter to the horn antenna.

  In general, a storage product such as coal tar obtained when carbonizing coal in a coke oven is stored in a storage tank. In this storage tank, a microwave level meter such as a microwave level meter with a horn antenna is generally installed in the storage tank in order to measure the level (storage amount) of the stored product. is there. Unlike ultrasonic level meters, microwave level meters do not use gas as a propagation medium and can be measured with little influence from the temperature, pressure, flow rate, etc. of the gas on the measurement path. Commonly used to measure the level of objects.

Conventionally, as an in-furnace level meter for measuring raw material levels such as slag level, molten steel level, raw material level, etc. in a converter, blast furnace, smelting reduction furnace, etc. using microwaves, for example, in Patent Document 1 What is shown is known.
The in-furnace level meter shown in Patent Document 1 outputs a microwave signal to a transmitting antenna and a receiving antenna inserted into the furnace, and the transmitting antenna, is reflected by a slag surface in the furnace, and is received by the receiving antenna. And a microwave radar that calculates the distance between the antenna and the slag surface from the microwave signal and outputs it as a radar measurement signal.

The transmitting and receiving antennas are composed of a metal inner tube having an enlarged diameter portion whose entire inside functions as a waveguide and the inner side functions as a horn antenna, and a metal outer tube surrounding the inner tube. The water-cooled horn antenna is provided with a gas purge port through which a purge gas flows into the proximal end side of the inner tube.
Conventionally, for example, a device disclosed in Patent Document 2 is known as a coal level measurement device for a coke oven that can accurately detect the actual level of coal charged into the coke oven.

  In the coke oven coal level measuring apparatus shown in Patent Document 2, the microwave level is placed on the upper part of a coal hopper of a coal car running on the coke oven via a protective plate made of glass, ceramic, heat-resistant resin, or the like. Install the total. The microwave level meter is equipped with a parabolic antenna for converging the injection angle. A beam with a small injection angle is injected into the furnace from the coal inlet through the inside of the coal feeding hopper, and the reflected wave from the coal surface. Is used to measure the coal level, and a wiper is installed on the lower surface of the protective plate to prevent the adhesion of coal dust.

Japanese Patent No. 2570886 JP-A-2005-306976

  By the way, when a microwave level meter with a horn antenna is installed in a storage tank to measure the storage level of stored items, a microwave level meter with a horn antenna is usually installed on the roof plate of the storage tank, and the horn antenna is installed on the roof. It is done inside the storage tank below the plate. However, if such a microwave level meter with a horn antenna is continuously used for a long time, volatile substances may stick to the inside of the horn antenna, and it may be impossible to measure the level of stored material. For example, when the stored material is coal tar, naphthalene or tar crystal is fixed inside the horn antenna.

In this case, it is necessary to periodically clean the horn antenna. However, as the number of storage tanks increases, the load on the cleaning worker increases and the cleaning cost increases significantly.
Here, when the in-furnace level meter shown in Patent Document 1 is used as a microwave level meter with a horn antenna, a purge gas is caused to flow from a gas purge port provided on the proximal end side of the inner tube, so that the horn It is also conceivable to remove volatile substances stuck inside the antenna.

However, the volatile matter fixed inside the horn antenna cannot be reliably removed simply by flowing the purge gas from the gas purge port provided on the proximal end side of the inner tube.
Moreover, when considering using the microwave level meter shown in patent document 2 as a microwave level meter with a horn antenna, it cannot be attached appropriately when there is no charcoal vehicle. Further, even if the microwave level meter is attached to the storage tank, a protection plate and a wiper are required, and the device configuration becomes complicated.

  Therefore, the present invention has been made to solve these conventional problems, and the object thereof is to reliably prevent volatiles from adhering to the inside of the horn antenna without complicating the device configuration. Another object of the present invention is to provide a microwave level meter with a horn antenna and a method for preventing the attachment of volatile matter to the horn antenna.

  In order to solve the above problems, a microwave level meter with a horn antenna according to one aspect of the present invention is a microwave level meter with a hornantenna installed on a roof plate of a storage tank that stores a storage containing volatiles. A horn antenna located in the storage tank when installed on the roof plate, which emits microwaves to the measurement surface of the stored item and receives microwaves reflected from the measurement surface A horn antenna having an antenna section and a hollow frustoconical antenna horn section that radiates microwaves emitted from the antenna section in a single direction; and provided at a plurality of locations near the outlet of the antenna horn section. A plurality of gas purge holes and purge gas attached to each of the plurality of gas purge holes flows into the antenna horn portion from each gas purge hole. Allowed to collide, and summarized in that and a plurality of purge gas inlet member to stay.

  In addition, the method for preventing volatile matter from adhering to the horn antenna according to another aspect of the present invention is a horn of a microwave level meter with a horn antenna installed on a roof plate of a storage tank for storing a stored matter containing volatile matter. A method for preventing the attachment of volatile matter to an antenna, wherein the honantena is located in the storage tank when installed on the roof plate, and emits a microwave to the measurement surface of the storage material and the measurement surface An antenna unit that receives the microwave reflected from the antenna unit, and a hollow frustoconical antenna horn unit that radiates the microwave emitted from the antenna unit in a single direction, and an outlet of the antenna horn unit The gist is to cause the purge gas to flow into the antenna horn portion from a plurality of gas purge holes provided at a plurality of locations in the vicinity so as to collide and stay.

  According to the microwave level meter with a horn antenna and the method for preventing the attachment of volatile matter to the horn antenna according to the present invention, it is possible to reliably prevent the attachment of volatile matter to the inside of the horn antenna without complicating the device configuration. It is possible to provide a microwave level meter with a horn antenna and a method for preventing volatiles from adhering to the horn antenna.

It is a schematic diagram of the state which installed the microwave level meter with a horn antenna which concerns on one Embodiment of this invention in the roof plate of the storage tank which stores the stored matter containing a volatile matter. It is a schematic diagram for demonstrating the measurement principle at the time of installing the microwave level meter with a horn antenna in the roof plate of a storage tank. It is a schematic diagram for demonstrating the problem at the time of installing the microwave level meter with a horn antenna in the roof plate of a storage tank. It is a figure for demonstrating the structure of the microwave level meter with a horn antenna which concerns on one Embodiment of this invention shown in FIG. FIG. 5 is a partial cross-sectional view for explaining a structure around a gas purge hole in the microwave level meter with a horn antenna shown in FIG. 4. In the microwave level meter with a horn antenna concerning a comparative example, it is a mimetic diagram in the state where the gas for purge was made to flow.

A microwave level meter with a horn antenna according to an embodiment of the present invention will be described below with reference to FIGS.
FIG. 1 shows a state in which a microwave level meter 1 with a horn antenna according to an embodiment of the present invention is installed on a roof plate 3 of a storage tank 2 for storing a storage item 4, for example, coal tar. The microwave level meter 1 with a horn antenna includes a horn antenna 12, a waveguide section 13, and a signal processing section 14 that performs signal processing on the microwave.

  Here, the horn antenna 12 is located in the storage tank 2 when the microwave level meter 1 with a horn antenna is installed on the roof plate 3 as shown in FIG. As shown in FIGS. 1, 2 and 4, the horn antenna 12 emits microwaves to the measurement surface 4a of the storage 4 and receives the microwaves reflected from the measurement surface 4a. And a hollow frustoconical antenna horn unit 11 that radiates microwaves emitted from the antenna unit 10 in a single direction.

As shown in FIG. 4, the horn antenna 12 is attached to the attachment plate 15 with a plurality of attachment screws with the antenna portion 10 as the base end side. The attachment plate 15 is attached to the roof plate 3 of the storage tank 2 although not shown.
The waveguide unit 13 connects the antenna unit 10 and the signal processing unit 14 and is transmitted by the signal processing unit 14 via the waveguide unit 13, the antenna unit 10, and the antenna horn unit 11. Microwaves made of electromagnetic waves are reflected from the measurement surface 4 a of the stored item 4 and received by the signal processing unit 14 via the antenna horn unit 11, the antenna unit 10, and the waveguide unit 13.

The signal processing unit 14 transmits the microwave to the waveguide unit 13 and performs signal processing on the received microwave, measures the time from when the microwave is emitted until it returns, The distance to the measurement surface 4a is calculated.
The measurement principle of the microwave level meter 1 with a horn antenna is shown in FIG. 2, and a microwave comprising electromagnetic waves is applied to the measurement surface of the storage 4 via the antenna unit 10 and the antenna horn unit 11 of the horn antenna 12. 4a, that is, fire in the direction of arrow A (downward). Then, the microwave is reflected in the direction of arrow B (upward) from the measurement surface 4 a of the stored item 4 and is received by the signal processing unit 14 through the antenna horn unit 11, the antenna unit 10, and the waveguide unit 13. . And the signal processing part 14 measures the time from returning a microwave to returning, and calculates the distance to the measurement surface 4a of the stored article 4.

Here, the antenna horn unit 11 has a function of radiating microwaves emitted from the antenna unit 10 in a single direction without diffusing, and as shown in FIG. The longer the length L from the end portion to the front end portion, the better the directivity of the microwave and the more accurate level measurement of the stored item 4 becomes possible.
The reason why the microwave level meter 1 with the horn antenna is used for level measurement in the storage tank 2 of the stored item 4 is as follows.

  In the measurement of the liquid level in the tank, there are a case where an ultrasonic level meter is used and a case where a microwave level meter is used. Here, the ultrasonic level meter uses gas as the propagation medium, whereas the microwave level meter does not use gas as the propagation medium because the microwave propagates even in vacuum. The microwave level meter can perform measurement with almost no influence on the temperature, pressure, flow velocity, etc. of the gas on the measurement path. Since coal tar obtained when carbonizing coal in a coke oven becomes solid at room temperature, it is always heated and kept warm, so the inside of the storage tank that stores coal tar is filled with naphthalene and tar vapor. Therefore, a microwave level meter that does not use gas as a propagation medium is suitable. For this reason, the microwave level meter 1 with a horn antenna is used for level measurement in the storage tank 2 of the stored item 4.

  Here, when the microwave level meter 1 with the horn antenna is installed on the roof plate 3 of the storage tank 2 so that the horn antenna 12 is located in the storage tank 2 and used continuously for several months, FIG. As shown, a volatile substance (for example, a crystalline substance such as naphthalene or tar) C is fixed inside the horn antenna 12, that is, inside the antenna horn unit 11. This makes it impossible to measure the level of the stored item 4 being stored.

  In order to solve this problem, in the microwave level meter 1 with a horn antenna according to this embodiment, as shown in FIGS. 4 and 5, the center line of the antenna horn unit 11 in the vicinity of the outlet of the antenna horn unit 11 is used. Two gas purge holes 16 are provided at two locations on the diagonal line passing through CL. Two purge gas inflow members 17 are attached to each of the two gas purge holes 16 to cause the purge gas to flow into the antenna horn part 11 from the respective gas purge holes 16 to collide and stay.

  Here, the vicinity of the outlet of the antenna horn part 11 provided with the two gas purge holes 16 means a range of 18 mm or more and 72 mm or less from the tip part (where the opening part is provided) of the antenna horn part 11. If it is less than 18 mm from the tip of the antenna horn part 11, there is a disadvantage that a purging gas retention part is generated below the tip of the antenna horn, and volatiles enter and adhere to the inside of the antenna horn. If it is larger than 72 mm from the tip of 11, the retention effect at the tip of the antenna horn is weakened, and there is a disadvantage that volatile matter adheres at the tip of the antenna horn.

The diameter of each gas purge hole 16 is preferably 2 mm or more and 6 mm or less.
Each purge gas inflow member 17 is attached so that one end communicates with the gas purge hole 16 of the antenna horn part 11 through a metal block 19, and the other end is attached to the attachment plate 15 through a joint 20. A pipe 18 connected to the first mounting member 21 and an inlet forming member 22 connected to a second mounting member 23 mounted on the mounting plate 15 so as to face the first mounting member 21. . One end of the pipe 18 is fixed to a metal block 19 as shown in FIG. As shown in FIG. 5, the metal block 19 is formed with a through hole 19 a that allows the flow path in the pipe 18 to communicate with the gas purge hole 16 of the antenna horn unit 11. The inlet forming member 22 is configured by a joint, and the inlet is formed in the inlet forming member 22.

  When the volatile matter is prevented from adhering to the horn antenna 12, the purge gas flows from the inlet formed in the inlet forming member 22 in the direction indicated by the arrow D (downward). The purge gas that has flowed into the inlet reaches the gas purge hole 16 through the inlet forming member 22, the second mounting member 23, the first mounting member 21, the pipe 18, and the through hole 19 a of the metal block 19. The purge gas flows from the gas purge hole 16 into the antenna horn portion 11 in the direction indicated by the arrow E1 in FIG. 4, and enters the antenna horn portion 11 from the gas purge hole 16 provided on the diagonal line in FIG. The purge gas that has flowed in the direction indicated by the arrow E2 collides with the vicinity of the center line CL of the antenna horn unit 11 and stays in the vicinity thereof.

  Thereby, it can prevent reliably that volatile matter (for example, crystal | crystallization things, such as naphthalene and tar) C adheres to the inner side of the antenna horn part 11 without complicating an apparatus structure. For this reason, while the instrument defect of the microwave level meter 1 with a horn antenna caused by the attachment of the volatile matter is eliminated, the cleaning work when the volatile matter adheres becomes unnecessary, and the instrument maintenance load is greatly reduced. Can do.

Here, nitrogen gas that does not react with the stored material 4 in the storage tank 2 is used as the purge gas, and the purge gas is always purged at a flow rate of 10 m ³ / h.
As another method for preventing the attachment of volatile matter to the horn antenna 12, nitrogen gas is allowed to flow into the antenna horn unit 11 and the temperature is higher than the melting point of the volatile matter (for example, 80 ° C. in the case of naphthalene). It is also conceivable to heat up to. However, in this method, the installation cost and the maintenance cost of the heating device for heating the nitrogen gas are enormous, and it is difficult to secure the installation location.

As mentioned above, although embodiment of this invention has been described, this invention is not limited to this, A various change and improvement can be performed.
For example, two gas purge holes 16 are provided in two locations on the diagonal line passing through the center line CL of the antenna horn unit 11 in the vicinity of the outlet of the antenna horn unit 11. It may be provided. In this case, a plurality of purge gas inflow members 17 are provided in each of the plurality of gas purge holes 16 to allow the purge gas to flow into the antenna horn unit 11 from the respective gas purge holes 16 to collide and stay.

  In addition, although the two gas purge holes 26 are provided at two locations on the diagonal line passing through the center line CL of the antenna horn unit 11 in the vicinity of the outlet of the antenna horn unit 11, the gas purge holes 26 are not necessarily on the diagonal line. For example, the two gas purge holes 26 may be provided at two positions shifted by 90 degrees in the circumferential direction in the vicinity of the outlet of the antenna horn unit 11 or at positions slightly shifted from two positions shifted by 180 degrees in the circumferential direction. In order to cause the purge gas that has flowed into the antenna horn part 11 from each gas purge hole 16 to collide in the vicinity of the center line CL of the antenna horn part 11, the displacement of the installation positions of the two gas purge holes 16 is as much as 180 degrees. It is preferable to be close.

Further, the purge gas may be other than nitrogen gas as long as it does not react with the stored matter 4 or volatile matter in the storage tank 2.
Further, the stored item 4 stored in the storage tank 2 may be a stored item other than coal tar.

In order to verify the effect of the present invention, the microwave level meter 1 with a horn antenna shown in FIG. 4 was installed on the roof plate 3 of the storage tank 2 storing coal tar, and nitrogen gas was formed at each inlet forming member 22. The gas was introduced from the inlet, and the gas purge holes 16 were introduced into the antenna horn unit 11.
Here, the horn length of the antenna horn part 11 (see reference symbol L in FIG. 2) is 205 mm, the diameter of the opening at the tip of the antenna horn part 11 is φ145 mm, and the antenna horn part 11 is 45 mm from the opening at the tip. Two gas purge holes 16 were provided at two locations on the diagonal line passing through the center line CL at the position. Each gas purge hole 16 has a diameter of 4 mm. Further, a stainless steel pipe 18 having a diameter of 6 mm constituting the purge gas inflow member 17 was attached so as to communicate with each gas purge hole 16 through a metal block 19. While fixing the edge part of the piping 18 to the metal block 19, the metal block 19 is fixed to the antenna horn part 11 by welding. The nitrogen gas flow rate in purging the nitrogen gas flowing into the antenna horn unit 11 from each gas purge hole 16 was 10 m ³ / h.

As a result, it was possible to prevent the crystalline substance such as naphthalene and tar from adhering to the inside of the antenna horn part 11 for a long period of time.
On the other hand, the microwave level meter 1 with a horn antenna shown in FIG. 6 was installed in the roof plate 3 of the storage tank 2 which stored coal tar as a comparative example. The microwave level meter 1 with a horn antenna shown in FIG. 6 is provided with two gas purge holes in the vicinity of the antenna portion 10 of the antenna horn portion 11 of the horn antenna 12. Nitrogen gas was allowed to flow vertically downward as indicated by arrow F from each gas purge hole toward the coal tar measurement surface. The flow rate of nitrogen gas in the purge of nitrogen gas was changed to 3 m ³ / h, 5 m ³ / h, 7 m ³ / h, and 10 m ³ / h.

  As a result, crystal matter such as naphthalene and tar adhered to the inside of the antenna horn portion 11 regardless of the flow rate of the nitrogen gas. The reason is that the shape of the antenna horn part 11 has a truncated cone shape that expands downward, and the flow rate of nitrogen gas decreases at the opening of the antenna horn part 11 and the purge effect is not sufficiently exhibited. Possible cause.

DESCRIPTION OF SYMBOLS 1 Microwave level meter with a horn antenna 2 Storage tank 3 Roof plate 4 Stored thing 10 Antenna part 11 Antenna horn part 12 Horn antenna 16 Gas purge hole 17 Gas inflow member for purge

Claims (4)

A microwave level meter with a horn antenna installed on a roof plate of a storage tank for storing a storage containing volatile matter,
A horn antenna located in the storage tank when installed on the roof plate, an antenna unit that emits microwaves to the measurement surface of the stored item and receives microwaves reflected from the measurement surface; A horn antenna having a hollow frustoconical antenna horn section that radiates microwaves emitted from the antenna section in a single direction;
A plurality of gas purge holes provided at a plurality of locations near the outlet of the antenna horn unit;
A horn comprising a plurality of purge gas inflow members attached to each of the plurality of gas purge holes, for causing a purge gas to flow into the antenna horn portion from each gas purge hole to collide and stay therewith. Microwave level meter with antenna.   Two gas purge holes are provided at two locations on the diagonal line passing through the center line of the antenna horn portion in the vicinity of the outlet of the antenna horn portion, and the purge gas inflow member is attached to each of the two gas purge holes. The microwave level meter with a horn antenna according to claim 1.   The microwave level meter with a horn antenna according to claim 1 or 2, wherein the purge gas is nitrogen gas. A method for preventing adhesion of volatile matter to a horn antenna of a microwave level meter with a horn antenna installed on a roof plate of a storage tank for storing a stored matter containing volatile matter,
The Hornantenna is located in the storage tank when installed on the roof plate, and emits a microwave to the measurement surface of the stored item and receives the microwave reflected from the measurement surface; A hollow frustoconical antenna horn that radiates microwaves emitted from the antenna in a single direction;
To a horn antenna of a microwave level meter with a horn antenna, wherein a purge gas is caused to flow into the antenna horn part from a plurality of gas purge holes provided at a plurality of locations near the outlet of the antenna horn part, and collides and stays therein. How to prevent adhesion of volatiles.

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