JPH05113391A - Gas concentration measuring device - Google Patents

Abstract

PURPOSE:To obtain the gas concentration measuring device constituted so as to enhance the detection accuracy of a sensor measuring the concn. of gas. CONSTITUTION:An on-off valve 9, a filter 6, an on-off valve 10 and a pump 11 are arranged to the sample gas supply pipeline 4 connecting a storehouse 1 and an oxygen densitometer 3 and, when the concn. of the gas in the storehouse 1 is measured, the on-off valves 9, 10 are opened to start the pump 11. The filter 6 is packed with an adsorbent 7 adsorbing combustible gas and the gas in the storehouse is supplied to the oxygen densitometer 3 while the combustible gas in said gas is adsorbed by the filter 6 to measure the concn. of oxygen in the gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas concentration measuring device, and more particularly to a gas concentration measuring device constructed so that the concentration of gas extracted from a storage can be accurately measured.

[0002]

2. Description of the Related Art Fresh food products such as vegetables and fruits are generally stored in a storage cabinet to maintain their freshness until shipment. In addition, for long-term storage of these stored materials, the inside of the storage is inactivated by setting it to a low temperature to the extent that the storage does not freeze, and the oxygen concentration in the storage is lowered to the necessary minimum, and further carbon dioxide is given to cause respiratory action. It is considered to be the best way to suppress this, and these kinds of studies have been continued these days. A storage method utilizing this phenomenon is called a CA (Atmosphere Controlled or Controlled Atmosphere) storage method.

In the storage device using this CA storage method, the minimum amount of oxygen (O ₂ ) is maintained in the storage and a minimum amount of carbon dioxide gas (CO ₂ gas) is put in, and the rest is nitrogen gas ( It is necessary to maintain the concentration ratio in the chamber at a constant value with an inert gas such as N ₂ gas).

In addition, depending on the type of fruits and vegetables,
Optimal O₂Gas and CO₂Gas and N₂Gas ratio decided
Since it is fixed, it must always be kept constant. However, before
As described above, the stored matter breathes, so
O₂Gas is consumed and CO ₂Gas is generated and
The concentration ratio changes. So, during the storage period,
The change in the gas concentration in the warehouse is monitored, and this is always constant.
It needs to be adjusted.

[0005] Therefore, the reservoir detects the CO ₂ concentration of the O ₂ sensor and-compartment for detecting the O ₂ concentration in the refrigerator CO ₂
The sensor is connected.

The control circuit controls the gas supply unit, the gas supply valve, and the exhaust valve so as to maintain a constant gas concentration according to the concentration detection signals from the O ₂ sensor and the CO ₂ sensor.
Therefore, due to the breathing action of fruits and vegetables in the storage,
_{When the 2} concentration and the CO ₂ concentration are out of the set ranges, the control circuit opens the gas supply valve and the exhaust valve, and supplies the gas with a concentration ratio according to the gas concentration in the storage from the gas supply unit to the storage, Exhaust the gas in the chamber to the atmosphere.

[0007]

A zirconia oximeter is an O ₂ sensor used in this type of device. This oximeter is configured to heat a hollow pipe made of zirconia ceramics to a high temperature and to flow a measurement gas through an internal passage, and a difference in O ₂ concentration between the atmosphere outside the hollow pipe and the measurement gas in the internal passage. Oxygen molecules pass through the hollow pipe and move to the inner passage side or the outside of the hollow pipe. The zirconia oxygen analyzer for detecting the O ₂ concentration in the measurement gas to output a current value proportional from the interior passage and the outside of the O ₂ concentration difference, that high oxygen side of the hollow pipe to the moving amount of oxygen to hypoxic side It is a thing.

In the storage device having the above structure, for example, in a gas concentration measuring device using a zirconia-type oxygen concentration meter as an O ₂ sensor, an organic combustible gas generated from fruits and vegetables is filled in the storage chamber, When the gas in the chamber containing the combustible gas is directly supplied to the O ₂ sensor, since the hollow pipe made of zirconia ceramic is heated, the oxygen in the measured gas reacts with the organic combustible gas. As a result, there is a problem that oxygen in the hollow pipe is reduced and the oxygen concentration cannot be measured.

Therefore, an object of the present invention is to provide a gas concentration measuring device which solves the above problems.

[0010]

According to the present invention, there is provided a gas concentration measuring device comprising a concentration sensor for detecting a gas concentration in a pipe for extracting gas in a storage, and a pipe connecting the storage and the concentration sensor. A filter for adsorbing the impure gas mixed in the gas extracted from the storage is provided in the passage.

[0011]

[Operation] A filter is provided in the middle of the pipe for extracting the gas in the storage to remove the impure gas mixed in the gas supplied to the concentration sensor so that the measurement output of the concentration sensor does not cause a measurement error due to the impure gas. To do.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first gas concentration measuring device according to the present invention.
An example is shown.

In FIG. 1, a storage 1 stores, for example, fresh food such as fruits and vegetables, and in order to keep the gas concentration in the storage at a constant value, a hermetically sealed structure in which a door (not shown) is highly sealed. Has become. Further, the storage 1 is provided with a refrigerating device (not shown) for storing fruits and vegetables at a low temperature.

Reference numeral 2 is an oxygen concentration measuring device for measuring the O ₂ concentration in the chamber, which is an oxygen concentration meter 3 comprising a zirconia O ₂ sensor.
Have. This oxygen concentration meter 3 has a sample gas supply line 4
It is connected to the storage 1 via.

Reference numeral 5 denotes a sample gas recirculation pipe, which recirculates the gas supplied to the oxygen concentration meter 3 into the chamber. Zirconia O ₂
The sensor is a concentration cell type oxygen sensor with stabilized zirconia as a diaphragm. In the case of this O ₂ sensor, for example, if a combustible gas (ethanol) generated by the breathing action of fruits and vegetables is mixed, oxygen reacts with the combustible gas and the oxygen concentration of 1% or less cannot be accurately measured due to the reason described above. It has such characteristics.

Reference numeral 6 is a filter, and an adsorbent 7 made of activated carbon is filled inside a cylindrical container 6a having ventilation holes (not shown) at both ends. The adsorbent 7 adsorbs only the combustible gas because the molecules of the combustible gas (ethanol) as an impure gas generated from fruits and vegetables are larger than the molecules of nitrogen and oxygen in the air.

A chuck 8 for holding both ends of the filter 6 is provided in the sample gas supply conduit 4 for extracting the gas in the refrigerator. Therefore, the filter 6 is the storage 1
The chuck 8 provided between the oxygen concentration meter 3 and the oxygen concentration meter 3 is connected to the sample gas supply conduit 4 to supply the gas in the refrigerator.

An opening / closing valve 9 made of an electromagnetic valve is provided in the pipe line 4 upstream of the filter 6, and an opening / closing valve 10 made of an electromagnetic valve is provided in the pipe line 4 downstream of the filter 6 and the inside of the refrigerator. A pump 11 for forcibly sucking gas is provided. still,
The on-off valves 9 and 10 are valves having a normally closed structure.

Therefore, when the pump 11 is started and the on-off valves 9 and 10 are opened, the gas in the storage 1 is supplied to the oxygen concentration meter 3 through the sample gas supply pipe line 4, and the O ₂ concentration is detected. , Through the sample gas recirculation line 5 to the inside of the refrigerator.

The open / close valves 9 and 10 are control circuits 1 to be described later.
It is opened and closed by the signal from 7, and opened only when measuring the concentration. Further, the pump 11 is normally stopped and is started only when the concentration is measured.

Since the above-described filter 6 is provided in the middle of the pipe line 4, the gas in the refrigerator passes through the filter 6 to remove the combustible gas and is supplied to the oxygen concentration meter 3. Therefore, the oxygen concentration meter 3 can constantly monitor the O ₂ concentration in the storage, and the inside of the storage 1 is designed so that the atmospheric pressure and the gas concentration ratio do not change due to the detection of the O ₂ concentration.

If the gas concentration in the chamber is measured for a long time, the adsorbent 7 of the filter 6 will eventually be saturated. Therefore, when the filter 6 is used for a predetermined period of time, the open / close valves 9 and 10 on the upstream and downstream sides are closed and removed from the chuck 8. Then, the filter 6 is replaced with a new one.

Therefore, the oxygen concentration meter 3 is always supplied with the gas from which the combustible gas has been removed, and the oxygen concentration meter 3 can accurately measure the oxygen concentration in the refrigerator.

An exhaust pipe line 12 and a gas supply pipe line 13 are connected to the storage 1. The exhaust pipe line 12 is provided with an exhaust valve 14 which is an electromagnetic valve.

The gas supply line 13 is a gas supply unit 15
And the storage 1 are grounded, and a gas supply valve 16 composed of an electromagnetic valve is disposed in the middle thereof. The gas supply unit 9 has a built-in PSA (Pressure Swing Adsorption) type nitrogen generator, and supplies a gas obtained by mixing O ₂ gas and N ₂ gas at a desired ratio to the storage 1 as described later.

A control circuit 17 controls the concentration of the gas supplied from the gas supply unit 15 so that the set gas concentration is maintained. Further, the control circuit 17 opens the exhaust valve 14 and the gas supply valve 16 when replacing the gas in the refrigerator.

FIG. 2 shows a second embodiment of the present invention. In FIG. 2, the same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 2, a pair of three-way electromagnetic valves 21 and 22 are arranged in the sample gas supply line 4, and a first filter 6A is arranged between the pair of three-way electromagnetic valves 21 and 22. ing. Further, a second filter 6B is arranged in the bypass pipe line 23 branched from the three-way solenoid valves 21 and 22.

That is, the upstream three-way solenoid valve 21 has ports A, B, and C in three directions, the port A is connected to the storage 1, and the port B is connected to the upstream end of the first filter 6A. , Port C is connected to the upstream end of the second filter 6B. Also, the downstream three-way solenoid valve 22 is port A
Is connected to the oxygen concentration meter 3, port B is connected to the downstream end of the first filter 6A, and port C is connected to the downstream end of the second filter 6B.

The first and second filters 6A and 6B are filled with the adsorbent 7 inside, and the pipes 4 and 23 are provided at both ends.
It is held by a chuck 8 connected to.

When measuring the gas concentration in the storage 1, the internal gas is initially supplied to the first filter 6A.

That is, the pair of three-way solenoid valves 21, 22 make ports A and B communicate with each other and shut off port C by a control signal from the control circuit 17. Therefore, the gas in the refrigerator is supplied to the first filter 6A through the upstream three-way solenoid valve 21, and the remaining gas in which the combustible gas is adsorbed in the first filter 6A is the downstream three-way solenoid valve. The oxygen concentration meter 3 is supplied via 22 to measure the O ₂ concentration.

When the first filter 6A is used for a certain period of time and becomes saturated, the three-way solenoid valves 21, 22 are switched,
Ports A and C communicate with each other, and port B is shut off. As a result, the gas in the storage is transferred from the three-way solenoid valve 21 to the bypass line 2
3 is supplied to the unused second filter 6B. Then, the gas from which the combustible gas has been removed by the second filter 6B is supplied to the oxygen concentration meter 3 from the three-way solenoid valve 22 on the downstream side.

Therefore, the first filter 6A which is saturated while the second filter 6B is in use is removed from the chuck 8 and replaced with a new filter or a filter in which the adsorbent is regenerated. Then, when the second filter 6B is used for a certain period of time, the three-way solenoid valves 21 and 22 are switched to communicate with the ports A and B again, and the port C is switched off so that the gas is supplied to the first filter 6A. To be done.

Therefore, the oxygen concentration meter 3 is always supplied with the gas from which the combustible gas has been removed, so that the concentration can be accurately measured even if the gas having the low oxygen concentration is supplied.

FIG. 3 shows a third embodiment of the present invention.

In the figure, the conduits 30 and 31 having one end connected to the storage 1 have the other ends at the first and second filters 6A and 6 respectively.
Connected to B. Further, the pump 11 is arranged in the sample gas supply pipeline 32, and the branch pipeline 3 is branched on the upstream side.
2a and 32b are connected to the downstream ends of the first and second filters 6A and 6B, and the downstream side is connected to the oxygen concentration meter 3.

The upstream end of the sample gas recirculation pipe 33 is connected to the oxygen concentration meter 3, and the branch pipes 33a and 33b branched on the downstream side are connected to the first and second filters 6A and 6B. ing.

Each branch pipe 32a, 32b, 33a, 33
On-off valves 34-37, which are electromagnetic valves, are provided in b, and each on-off valve 34-37 is normally closed (normally closed).
It has a structure and is switched to a valve open state by a control signal from the control circuit 17.

The pair of filters 6A and 6B of this embodiment are regenerated by desorbing the adsorbed gas while the other adsorbs the combustible gas. That is, the control circuit 17 controls the open / close valve 3
While the valves 4, 37 are open, the other on-off valves 35, 36 are closed. Then, after a certain time has passed, the on-off valves 34, 3
7 is closed and the other on-off valves 35 and 36 are opened.

For example, the opening / closing valves 34 and 37 are opened at the beginning of the operation of the gas supply unit 15. This allows
The gas in the refrigerator is sucked by the pump 11 and the first filter 6
After flowing into A, the combustible gas is removed, and the oxygen concentration meter 3 is supplied through the on-off valve 34.

The gas flowing out from the oxygen concentration meter 3 is used as an opening / closing valve 3.
It is supplied to the second filter 6B via 7. And
The gas supplied to the second filter 6B desorbs the molecules of the combustible gas adsorbed by the second filter 6B and returns to the inside of the refrigerator. Therefore, the second filter 6B is regenerated by the gas that is returned to the inside of the refrigerator.

When the first filter 6A is used for a certain period of time as described above, the opening / closing valves 34, 37 are closed and the other opening / closing valves 35, 36 are opened.

This time, the second filter 6B and the pump 11 are communicated with each other via the opening / closing valve 36. Therefore, the gas in the refrigerator flows into the second filter 6B in which the adsorbent 7 is regenerated, adsorbs the combustible gas, and is supplied to the oxygen concentration meter 3 via the opening / closing valve 36.

Then, the gas whose concentration is measured by the oxygen concentration meter 3 is supplied to the first filter 6A through the on-off valve 35. Therefore, the combustible gas adsorbed by the adsorbent 7 of the first filter 6A is desorbed and returned to the inside of the refrigerator. Therefore,
The adsorbent 7 of the first filter 6A is regenerated.

As described above, since the pair of filters 6A and 6B are alternately used and the unused filter can be regenerated by utilizing the reflux gas, it is not necessary to replace the filters 6A and 6B, and the maintenance is free. Therefore, the concentration measurement can be continuously performed for a long time.

In this embodiment, four on-off valves 34 to 37 are used.
Is provided to switch the first filter 6A and the second filter 6B, but instead of the on-off valves 34 to 37, the pipe lines 32 and 3 are provided.
It is also possible to provide a three-way solenoid valve for each of the three and switch them.

FIG. 4 shows a fourth embodiment of the present invention.

In the figure, the on-off valves 40,
41 is provided. In addition, the on-off valves 40, 41 and the first,
On-off valves 44 and 45 are arranged in exhaust pipes 42 and 43 branched from the pipe lines 30 and 31 between the second filters 6A and 6B.

The on-off valves 40, 41, 44, 45 are solenoid valves having a normally closed structure.

In this embodiment, the gas whose concentration has been measured by the oxygen concentration meter 3 is not returned to the inside of the chamber but is exhausted to the outside. That is, when the on-off valves 34 and 37 are opened, the conduit 30
The opening / closing valve 40 and the opening / closing valve 45 of the exhaust valve 42 are opened.

Therefore, the gas in the refrigerator is supplied to the first filter 6A through the on-off valve 40, and the gas from which the combustible gas is removed by the first filter 6A is the on-off valve 34.
Through the oxygen concentration meter 3.

Then, the gas whose concentration has been measured by the oxygen concentration meter 3 flows into the second filter 6B via the on-off valve 37. At this time, the opening / closing valve 41 on the downstream side of the second filter 6B is closed, and the opening / closing valve 45 of the exhaust pipe line 42 is opened.

Therefore, the gas flowing into the second filter 6B desorbs the gas adsorbed by the adsorbent 7 of the second filter 6B and is discharged to the atmosphere through the exhaust pipe line 42. As a result, the adsorbent 7 of the second filter 6B is regenerated.

When the first filter 6A is used for a certain period of time, on the contrary, the open / close valves 35, 36 and 41, 44 are opened and the others are switched to the closed state. Therefore, the gas in the refrigerator flows into the regenerated second filter 6B via the on-off valve 41 to adsorb the combustible gas. Then, the gas flowing in from the second filter 6B is supplied to the oxygen concentration meter 3 via the on-off valve 36 and the concentration is measured.

Further, the gas flowing out from the oxygen concentration meter 3 flows into the first filter 6A through the on-off valve 35,
The adsorbent 7 of the filter 6A is regenerated. Then, the gas desorbed from the gas adsorbed by the adsorbent 7 is discharged into the atmosphere through the opening / closing valve 44 provided in the exhaust pipe line 43.

As described above, the combustible gas adsorbed by the adsorbent 7 is discharged into the atmosphere without being returned to the inside of the compartment, and the combustible gas inside the compartment does not increase and becomes a constant value. Therefore, the usage time until the adsorbent 7 becomes saturated can be extended, the switching operation interval of the pair of filters 6A and 6B can be extended, and the concentration measurement can be continued for a long time.

In the above embodiment, the filter for removing the flammable gas (ethanol) in the gas is used, but the invention can be applied to remove other gases. In that case, instead of the adsorbent 7 made of activated carbon, another adsorbent such as silica gel, zeolite, or alumina is used according to the gas to be removed.

In the above embodiment, the gas concentration in the storage for storing fruits and vegetables has been described, but it is of course applicable to an apparatus for measuring the gas concentration in a storage for storing other than this. is there.

It goes without saying that the invention can also be applied to an apparatus having a sensor for measuring the gas concentration other than oxygen.

[0061]

As described above, the gas concentration measuring apparatus according to the present invention is provided with the filter for adsorbing the impure gas in the gas in the middle of the pipe for supplying the gas to the concentration sensor. Can be prevented from being lowered by the impure gas, and the gas concentration can be accurately measured. Therefore, while increasing the reliability when measuring the gas concentration in the storage where the storage that generates gas that interferes with the detection of the concentration sensor is stored, the gas concentration control in the storage based on the measurement result of the concentration sensor It has features such as accurate execution.

[Brief description of drawings]

FIG. 1 shows a schematic configuration diagram of a first embodiment of a gas concentration measuring device according to the present invention.

FIG. 2 is a schematic configuration diagram of a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a third embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a fourth embodiment of the present invention.

[Explanation of symbols]

 1 Storage 2 Gas Concentration Measuring Device 3 Oxygen Concentrator 4 Sample Gas Supply Pipeline 5 Sample Gas Reflux Pipeline 6 Filter 6A 1st Filter 6B 2nd Filter 7 Adsorbent 8 Chuck 11 Pump 15 Gas Supply Unit 17 Control Circuit 21 , 22 Three-way solenoid valve 34-37 Open / close valve 42, 43 Exhaust pipe line 44, 45 Open / close valve

Claims (1)

[Claims] 1. A gas concentration measuring device comprising a concentration sensor for detecting a gas concentration in a pipe for extracting gas in a storage, wherein the gas is extracted from the storage in the middle of a pipe connecting the storage and the concentration sensor. A gas concentration measuring device comprising a filter for adsorbing an impure gas mixed in the gas.