JP7013924B2 - Oxygen concentration measuring device and oxygen concentration measuring method - Google Patents

Description

The present invention relates to an oxygen concentration measuring device and an oxygen concentration measuring method.

As a method for treating organic water-containing waste such as sewage sludge, it is used as fertilizer by composting and put into cement manufacturing equipment. However, if organic water-containing waste having a high water content is directly put into the cement manufacturing equipment, there is a concern that the fuel efficiency of the cement manufacturing equipment may deteriorate. For this reason, organic hydrous waste is dried to granulate organic powder and put into the cement manufacturing equipment, but the dust concentration and oxygen concentration in the drying equipment reach a certain concentration, and it becomes an ignition source. When a fire is generated, it can cause a dust explosion. Therefore, as a measure to prevent a dust explosion, it is conceivable to perform gas analysis of the oxygen concentration in the drying equipment during operation to keep the oxygen concentration below a certain level.

As a method for measuring the oxygen concentration in the gas, for example, there is an oxygen gas concentration analyzer by laser light as in Patent Document 1. The analyzer described in Patent Document 1 utilizes a phenomenon in which oxygen molecules in a gas absorb light of a specific wavelength in laser light, and by detecting the absorbance of the wavelength of the light absorbed by the oxygen molecules. It analyzes the oxygen concentration. In the analyzer described in Patent Document 1, since the inside of the drying device is in an environment where a large amount of water vapor and dust are present, the purpose is to protect the analyzer itself from the intrusion of water vapor and dust and to prevent the laser light from being attenuated by the dust. As a result, the light emitting part and the light receiving part are purged.

Japanese Unexamined Patent Publication No. 2014-102140

In the analyzer described in Patent Document 1, for example, when the pressure in the drying device fluctuates, it is necessary to increase the flow rate of the gas to be purged in order to suppress the invasion of dust into the optical path. Therefore, the analyzer described in Patent Document 1 has a problem that the operating cost is high.

A main object of the present invention is to provide an oxygen concentration measuring device and an oxygen concentration measuring method having a low operating cost.

The oxygen concentration measuring device according to the present invention includes an emitting unit, a light receiving unit, a calculation unit, and a blow device. The emitting unit emits laser light. The light receiving unit faces the emitting unit via the measuring unit. The light receiving unit receives the laser light emitted from the emitting unit and transmitted through the measuring unit, and detects the absorbance of the wavelength of the light absorbed by the oxygen molecules. The calculation unit calculates the oxygen concentration in the measurement unit from the absorbance detected by the light receiving unit. The blow device blows the purge gas on the optical path of the laser beam. The blow device is configured so that the purge gas can be blown toward the measuring unit side and the purge gas can be blown toward at least one side of the emitting unit and the light receiving unit. The calculation unit estimates the oxygen concentration in the measurement unit, and when the difference between the estimated value and the calculated oxygen concentration exceeds a predetermined concentration difference, the purge gas is directed to the measurement unit side to the blow device. After that, if the difference between the estimated oxygen concentration in the measuring unit and the calculated oxygen concentration is not less than or equal to the predetermined concentration difference within a predetermined time, the blow device is used. Blow the purge gas toward at least one side of the emitting part and the light receiving part. Therefore, the amount of purge gas to be blown can be reduced. Therefore, the operating cost can be reduced.

In the oxygen concentration measuring device according to the present invention, the calculation unit sends a purge gas to the blow device when the difference between the estimated oxygen concentration in the measuring unit and the calculated oxygen concentration is equal to or less than a predetermined concentration difference. It is preferable that the blow is stopped.

In the oxygen concentration measuring device according to the present invention, the calculation unit may estimate the oxygen concentration in the measuring unit from the amount of air discharged from the measuring unit, the amount of water vapor in the measuring unit, and the oxygen concentration in the air.

In the oxygen concentration measuring apparatus according to the present invention, it is preferable to use nitrogen gas as the purge gas.

The oxygen concentration measuring device according to the present invention preferably further includes a nitrogen separation membrane that separates the nitrogen gas used for the purge gas from the air.

The oxygen concentration measuring device according to the present invention is preferably configured to adjust the flow rate of the air supplied to the nitrogen separation membrane according to the flow rate of the gas discharged from the nitrogen separation membrane.

In the oxygen concentration measuring method according to the present invention, the oxygen concentration measuring method is opposed to the emitting unit that emits the laser beam and the emitting unit via the measuring unit, receives the laser light emitted from the emitting unit and transmitted through the measuring unit, and receives oxygen molecules. A light receiving unit that detects the absorbance of the wavelength of the light absorbed by the light receiving unit, a calculation unit that calculates the oxygen concentration in the measuring unit from the absorbance detected by the light receiving unit, and a blow device that blows purge gas onto the optical path of the laser light. It is an oxygen concentration measuring method using an oxygen concentration measuring device provided, and the calculation unit estimates the oxygen concentration in the measuring unit, and the difference between the estimated value and the calculated oxygen concentration is a predetermined concentration difference. When the amount exceeds, the blow device is made to blow the purge gas toward the measuring unit side, and then, within a predetermined time, the difference between the estimated value of the oxygen concentration in the measuring unit and the calculated oxygen concentration is increased. When the concentration difference is not less than the predetermined concentration difference, the blow device is made to blow the purge gas toward at least one side of the emitting part and the light receiving part.

In the oxygen concentration measuring method according to the present invention, the calculation unit sends a purge gas to the blow device when the difference between the estimated oxygen concentration in the measuring unit and the calculated oxygen concentration is equal to or less than a predetermined concentration difference. It is preferable to stop the blow of.

According to the present invention, it is possible to provide an oxygen concentration measuring device and an oxygen concentration measuring method having a low operating cost.

It is a schematic diagram of the oxygen concentration measuring apparatus which concerns on 1st Embodiment. It is a flowchart which shows the control of the discontinuous blow which concerns on 1st Embodiment. It is a schematic diagram of the oxygen concentration measuring apparatus which concerns on 2nd Embodiment. It is a flowchart which shows the control of the discontinuous blow which concerns on 2nd Embodiment.

Hereinafter, an example of a preferred embodiment of the present invention will be described. However, the following embodiments are merely examples. The present invention is not limited to the following embodiments.

Further, in the drawings referred to in the embodiments and the like, the members having substantially the same function are referred to by the same reference numerals. Further, the drawings referred to in the embodiments and the like are schematically described. The ratio of the dimensions of the object drawn in the drawing may differ from the ratio of the dimensions of the actual object. The dimensional ratios of objects may differ between the drawings. The specific dimensional ratio of the object should be determined in consideration of the following explanation.

(First Embodiment)
FIG. 1 is a schematic diagram of the oxygen concentration measuring device 1 according to the first embodiment. The oxygen concentration measuring device 1 shown in FIG. 1 is a device that measures the oxygen concentration in the measuring unit 10. The oxygen concentration measuring device 1 is suitably used for measuring the oxygen concentration in a system such as a facility for drying combustibles such as a sewage sludge drying facility, but is also suitably used for measuring the oxygen concentration of other devices. ..

The oxygen concentration measuring device 1 includes an emitting unit 21 and a light receiving unit 31. The emitting unit 21 emits laser light L including light having a wavelength absorbed by oxygen molecules. Specifically, the emitting unit 21 includes a laser light emitting element 22 that emits the laser light L. A first pipe 23 provided with a path 23a through which the laser beam L passes is connected to the laser beam emitting element 22. A second pipe 24 provided with a path 24a through which the laser light L passes is connected to the end of the first pipe 23 on the opposite side of the laser light emitting element 22. The tip of the second pipe 24 reaches the inside of the measuring unit 10. A partition plate 25 is provided between the first pipe 23 and the second pipe 24. The partition plate 25 separates the path 23a and the path 24a. As a result, dust and the like of the measuring unit 10 are restricted from entering the path 23a. The partition plate 25 is not particularly limited as long as it transmits the laser beam L. The partition plate 25 can be made of, for example, a tempered glass plate.

The light receiving unit 31 faces the emitting unit 21 via the measuring unit 10. Specifically, the light receiving unit 31 includes a light receiving element 32. The light receiving element 32 receives the laser light L emitted from the laser light emitting element 22 and transmitted through the measuring unit 10. The light receiving element 32 is an element that detects the absorbance of the wavelength of light absorbed by oxygen molecules. A third pipe 33 provided with a path 33a through which the laser beam is transmitted is connected to the light receiving element 32. A fourth pipe 34 provided with a path 34a through which the laser beam L is transmitted is connected to an end portion of the third pipe 33 on the opposite side of the light receiving portion 31. The tip of the fourth pipe 34 reaches the inside of the measuring unit 10. A partition plate 35 is provided between the third pipe 33 and the fourth pipe 34. The partition plate 35 separates the path 33a and the path 34a. As a result, dust and the like of the measuring unit 10 are restricted from entering the path 33a. The partition plate 35 is not particularly limited as long as it transmits the laser beam L. The partition plate 35 can be made of, for example, a tempered glass plate.

The oxygen concentration measuring device 1 includes a calculation unit (not shown). The calculation unit calculates the oxygen concentration in the measurement unit 10 from the absorbance detected by the light receiving unit 31. In this way, the oxygen concentration measuring device 1 measures the oxygen concentration by the absorbance of the light having the wavelength absorbed by the oxygen molecule, but if dust or the like is present on the path of the laser light L, the laser light may be absorbed by the dust. , The measurement accuracy of oxygen concentration is lowered because it is scattered. Therefore, in the oxygen concentration measuring device 1, dust on the path of the laser beam L is removed by blowing the purge gas.

In the present embodiment, nitrogen gas is used as the purge gas in order to suppress the deterioration of the measurement accuracy of the oxygen concentration due to the purge gas. However, in the present invention, the purge gas is not limited to nitrogen gas. In the present invention, the purge gas may be a gas containing oxygen gas or a purge gas containing no oxygen. As the purge gas, for example, an inert gas such as argon may be used. The purge gas is preferably a dry gas.

Specifically, the oxygen concentration measuring device 1 includes a blow device 41 that blows nitrogen gas. Specifically, the blow device 41 includes a compressor 42 and a nitrogen separation membrane 43. The compressor 42 sends air to the nitrogen separation membrane 43. The nitrogen separation membrane 43 separates nitrogen gas from air. The blow device 41 blows the nitrogen separated by the nitrogen separation membrane 43 as a purge gas. By using the nitrogen separation membrane 43, nitrogen gas can be obtained at low cost. A storage tank may be provided to temporarily store the produced nitrogen gas.

Further, the oxygen concentration measuring device 1 is configured to measure the gas flow rate supplied from the nitrogen separation membrane 43 and control the amount of air supplied to the nitrogen separation membrane 43 based on the flow rate. By controlling the amount of air supplied to the nitrogen separation membrane 43, it is possible to prevent a decrease in the nitrogen concentration in the nitrogen gas, and it is possible to continuously measure without interrupting the measurement even when purging the pipe. Become. The flow rate may be controlled automatically or manually.

The first pipe 23 is provided with a purge gas introduction port 23b and a purge gas discharge port 23c. The purge gas introduction port 23b is provided at the end of the measurement unit 10 of the first pipe 23, while the purge gas discharge port 23c is provided at the end of the first pipe 23 on the laser light emitting element 22 side. .. Nitrogen gas is sent from the blow device 41 to the purge gas introduction port 23b. The inserted nitrogen gas passes through the path 23a and is discharged from the purge gas discharge port 23c. As a result, the path 23a is set to a positive pressure, and the invasion of dust into the path 23a and the invasion of water vapor or the like into the path 23a suppress the fluctuation of the optical path.

The third pipe 33 is provided with a purge gas introduction port 33b and a purge gas discharge port 33c. The purge gas introduction port 33b is provided at the end of the measurement unit 10 of the third pipe 33, while the purge gas discharge port 33c is provided at the end of the third pipe 33 on the light receiving part 32 side. Nitrogen gas is sent from the blow device 41 to the purge gas introduction port 33b. The inserted nitrogen gas passes through the path 33a and is discharged from the purge gas discharge port 33c. As a result, the pressure inside the path 33a is set to positive, and the invasion of dust into the path 33a and the invasion of water vapor or the like into the path 33a suppress the fluctuation of the optical path.

A purge gas introduction port 24b is provided at the end of the second pipe 24 on the side of the first pipe 23. Nitrogen gas is sent from the blow device 41 to the purge gas introduction port 24b. The purge gas introduction port 24b is provided in a shape such that the supplied nitrogen gas is blown toward the measurement unit 10 side along the path 24a. Therefore, the purge gas introduced from the purge gas introduction port 24b flows into the measurement unit 10 via the second pipe 24.

A purge gas introduction port 34b is provided at the end of the fourth pipe 34 on the third pipe 33 side. Nitrogen gas is sent from the blow device 41 to the purge gas introduction port 34b. The purge gas introduction port 34b is provided in a shape such that the supplied nitrogen gas is blown toward the measurement unit 10 side along the path 34a. Therefore, the purge gas introduced from the purge gas introduction port 34b flows into the measurement unit 10 via the fourth pipe 34.

The purge gas introduced from the purge gas introduction ports 24b and 34b removes the dust in the second pipe 24 and the fourth pipe 34, and also removes the dust on the optical path of the laser beam L of the measuring unit 10.

In the present embodiment, the purge gas is continuously introduced into the purge gas introduction ports 23b, 24b, 33b, 34b (hereinafter, may be referred to as "continuous blow"). However, with only this continuous gas purging, there is a possibility that dust will invade the optical path of the laser beam L when the pressure in the measuring unit 10 fluctuates. In addition, the optical path of the laser beam may be closed due to the accumulation of dust or the like. In order to suppress these, it is conceivable to increase the amount of purge gas sent in from the purge gas introduction ports 23b, 24b, 33b, 34b. However, in that case, since the amount of purge gas used increases, the running cost of the oxygen concentration measuring device 1 increases. In addition, an increase in the amount of purge gas sent in may adversely affect the operation of the oxygen concentration measuring device 1.

Therefore, in the present embodiment, in addition to the continuous blow of the purge gas from the purge gas introduction ports 23b, 24b, 33b, 34b, if necessary, the blow of the purge gas is discontinuously referred to as "discontinuous blow". May).

Specifically, the calculation unit estimates the oxygen concentration in the measurement unit 10, and blows when the difference between the estimated value and the actually calculated oxygen concentration exceeds a predetermined concentration difference. Let the device blow the purge gas. The blown purge gas is sent to the purge gas introduction port 24c provided in the second pipe 24 and the purge gas introduction port 34c provided in the fourth pipe 34. As a result, dust on the optical paths of the paths 24a and 34a and the laser beam L of the measuring unit 10 is removed. Therefore, the oxygen concentration can be measured with high accuracy without increasing the flow rate of the purge gas that is continuously blown. Therefore, the oxygen concentration measuring device 1 has a low operating cost. In addition, it is possible to suppress the occurrence of adverse effects of the oxygen concentration measuring device 1 that may occur when a large amount of purge gas is continuously blown.

The method for estimating the oxygen concentration in the measuring unit 10 is not particularly limited. For example, the oxygen concentration in the measuring unit 10 can be estimated by a method as described in Japanese Patent Application Laid-Open No. 2016-205695. That is, the calculation unit may, for example, estimate the oxygen concentration in the measurement unit 10 from the amount of air discharged from the measurement unit 10, the amount of water vapor in the measurement unit, and the oxygen concentration in the air.

Hereinafter, the control of the discontinuous blow of the present embodiment will be described in detail with reference mainly to FIG.

First, in step S1, the calculation unit estimates the oxygen concentration in the measurement unit 10, and whether the difference between the estimated value and the actually calculated oxygen concentration is equal to or more than a predetermined concentration difference (set value). Judge whether or not.

In step S1, if the difference between the estimated value and the actually calculated oxygen concentration is equal to or greater than a predetermined concentration difference (set value), the process proceeds to step S2.

In step S2, the arithmetic unit causes the blow device to blow the purge gas discontinuously for a certain period of time. The flow rate of the purge gas at this time is preferably higher than the flow rate of the purge gas of the continuous purge, more preferably 5 times or more, and further preferably 10 times or more the flow rate of the purge gas of the continuous blow. However, if the flow velocity of the purge gas of the discontinuous blow is too high, the purge gas may excessively invade the measurement range, the gas to be measured may not substantially exist on the optical path, and the accumulated dust may be rolled up. The partition plate 25 and the partition plate 35 may be damaged. Therefore, the flow rate of the purge gas of the discontinuous blow is more preferably 20 times or less, and further preferably 15 times or less the flow rate of the purge gas of the continuous purge.

Next, in step S3, the calculation unit estimates the oxygen concentration in the measurement unit 10, and the difference between the estimated value and the actually calculated oxygen concentration is equal to or larger than the predetermined concentration difference (set value). Judge whether or not.

In step S3, if the difference between the estimated value and the actually calculated oxygen concentration is equal to or greater than a predetermined concentration difference (set value), the process proceeds to step S2.

In the present embodiment, the control unit performs these steps S1 to S3 continuously or periodically.

In this way, the calculation unit performs discontinuous blow when the difference between the estimated oxygen concentration in the measurement unit 10 and the calculated oxygen concentration is equal to or less than the predetermined concentration difference (set value). Stop. Therefore, the operating cost of the oxygen concentration measuring device 1 is further reduced.

Hereinafter, other examples of preferred embodiments of the present invention will be described. In the following description, members having substantially the same function as the first embodiment will be referred to by a common reference numeral, and the description thereof will be omitted.

(Second embodiment)
FIG. 3 is a schematic diagram of the oxygen concentration measuring device 1a according to the second embodiment. FIG. 4 is a flowchart showing the control of discontinuous blow according to the second embodiment.

The oxygen concentration measuring device 1a according to the present embodiment is configured so that the purge gas can be blown toward the measuring unit 10 side and the purge gas can be blown toward at least one of the emitting unit 21 and the light receiving unit 31. Therefore, it is different from the oxygen concentration measuring device 1 according to the first embodiment.

Specifically, the second pipe 24 is provided with a purge gas introduction port 24d in addition to the purge gas introduction port 24c configured so that the purge gas can be blown toward the measurement unit 10. The purge gas introduction port 24d is configured so that the purge gas can be blown toward the exit portion 21 side, that is, the partition plate 25 side.

The fourth pipe 34 is provided with a purge gas introduction port 34d in addition to the purge gas introduction port 34c configured so that the purge gas can be blown toward the measurement unit 10. The purge gas introduction port 34d is configured so that the purge gas can be blown toward the light receiving portion 31 side, that is, the partition plate 35 side.

As shown in FIG. 4, in this embodiment as well, step S1, step S2, and step S3 are performed in order as in the first embodiment. In this embodiment, in step S2, blow is performed from the purge gas introduction ports 24c and 34c. Therefore, in step S2, the purge gas is blown toward the measuring unit 10.

In this embodiment, if the difference between the estimated value and the actually calculated oxygen concentration in step S3 is equal to or greater than a predetermined concentration difference (set value), the process proceeds to step S4.

In step S4, the arithmetic unit causes the blow device 41 to blow the purge gas discontinuously for a certain period of time. In step S4, blow is performed from the purge gas introduction ports 24d and 34d. Further, in step S4, the purge gas is sprayed toward the emitting unit 21 and the light receiving unit 31 side. Therefore, dust is removed from the portion on the exit portion 21 side of the purge gas introduction port 24d of the path 24a. Specifically, for example, the dust adhering to the partition plate 25 is removed. Further, as the purge gas, dust is removed from the portion on the light receiving portion 31 side of the purge gas introduction port 34d of the path 34a. Specifically, for example, the dust adhering to the partition plate 35 is removed.

Next, in step S5, the calculation unit estimates the oxygen concentration in the measurement unit 10, and the difference between the estimated value and the actually calculated oxygen concentration is equal to or larger than the predetermined concentration difference (set value). Judge whether or not.

In step S5, if the difference between the estimated value and the actually calculated oxygen concentration is equal to or greater than a predetermined concentration difference (set value), the process proceeds to step S2.

In the present embodiment, the control unit performs these steps S1 to S5 continuously or periodically.

As described above, in the present embodiment, the calculation unit measures the purge gas in the blow device 41 when the difference between the estimated value and the calculated value of the oxygen concentration in the measurement unit 10 exceeds a predetermined concentration difference. Blow toward the unit 10 side, and then, when the difference between the estimated value and the calculated value of the oxygen concentration in the measuring unit 10 does not become less than or equal to the predetermined concentration difference within a predetermined time. , The blow device 41 blows the purge gas toward at least one side of the emitting unit 21 and the light receiving unit 31. Therefore, for example, it is possible to suppress a decrease in measurement accuracy due to dust adhering to the partition plates 25, 35 and the like. Therefore, the oxygen concentration in the measuring unit 10 can be measured with higher measurement accuracy.

1, 1a: Oxygen concentration measuring device 10: Measuring unit 21: Ejecting unit 22: Laser light emitting element 23: First pipe 23a: Path 23b: Purge gas introduction port 23c: Purge gas discharge port 24: Second pipe 24a: Path 24b: Purge gas introduction port 24c: Purge gas introduction port 24d: Purge gas introduction port 25: Partition plate 31: Light receiving unit 32: Light receiving element 33: Third pipe 33a: Path 33b: Purge gas introduction port 33c: Purge gas discharge port 34: Fourth Piping 34a: Path 34b: Purge gas introduction port 34c: Purge gas introduction port 34d: Purge gas introduction port 35: Partition plate 41: Blow device 42: Compressor 43: Nitrogen separation film L: Laser light

Claims (8)

The exit part that emits laser light and
A light receiving unit that faces the emitting unit via the measuring unit, receives the laser light emitted from the emitting unit and transmitted through the measuring unit, and detects the absorbance of the wavelength of the light absorbed by the oxygen molecule.
An arithmetic unit that calculates the oxygen concentration in the measurement unit from the absorbance detected by the light receiving unit, and
A blow device that blows purge gas onto the optical path of the laser beam, and
Equipped with
The blow device is configured to be able to blow the purge gas toward the measuring unit side and blow the purge gas toward at least one side of the emitting unit and the light receiving unit.
The calculation unit estimates the oxygen concentration in the measurement unit, and when the difference between the estimated value and the calculated oxygen concentration exceeds a predetermined concentration difference, the purge gas is supplied to the blow device. Blow toward the measuring unit side, and then, within a predetermined time, the difference between the estimated value of oxygen concentration in the measuring unit and the calculated oxygen concentration is equal to or less than the predetermined concentration difference. An oxygen concentration measuring device that causes the blow device to blow the purge gas toward at least one side of the exit portion and the light receiving portion . The calculation unit stops blowing the purge gas to the blow device when the difference between the estimated oxygen concentration in the measurement unit and the calculated oxygen concentration is equal to or less than the predetermined concentration difference. The oxygen concentration measuring device according to claim 1. The oxygen concentration measuring device according to claim 1 or 2, wherein the arithmetic unit estimates the oxygen concentration in the measuring unit from the amount of air discharged from the measuring unit, the amount of water vapor in the measuring unit, and the oxygen concentration in the air. The oxygen concentration measuring device according to any one of claims 1 to 3 , wherein nitrogen gas is used as the purge gas. The oxygen concentration measuring device according to claim 4 , further comprising a nitrogen separation membrane that separates the nitrogen gas used for the purge gas from air. The oxygen concentration measuring apparatus according to claim 5 , wherein the flow rate of air supplied to the nitrogen separation membrane is adjusted by the flow rate of the gas discharged from the nitrogen separation membrane. The emission unit that emits laser light and the emission unit that faces the emission unit via the measurement unit, receives the laser light emitted from the emission unit and transmitted through the measurement unit, and has the wavelength of light absorbed by oxygen molecules. Oxygen concentration measurement including a light receiving unit for detecting the absorbance, a calculation unit for calculating the oxygen concentration in the measuring unit from the absorbance detected by the light receiving unit, and a blow device for blowing purge gas on the optical path of the laser light. It is an oxygen concentration measurement method using a device,
The calculation unit estimates the oxygen concentration in the measurement unit, and when the difference between the estimated value and the calculated oxygen concentration exceeds a predetermined concentration difference, the purge gas is supplied to the blow device. Blow toward the measuring unit side, and then, within a predetermined time, the difference between the estimated value of oxygen concentration in the measuring unit and the calculated oxygen concentration is equal to or less than the predetermined concentration difference. A method for measuring an oxygen concentration, in which the blow device is made to blow the purge gas toward at least one side of the exit portion and the light receiving portion . The calculation unit stops blowing the purge gas to the blow device when the difference between the estimated oxygen concentration in the measurement unit and the calculated oxygen concentration is equal to or less than the predetermined concentration difference. The oxygen concentration measuring method according to claim 7 .

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