JP2008268154A - Method and apparatus for measuring dissolved gas concentration - Google Patents

Abstract

To provide a dissolved gas concentration measuring method and apparatus capable of accurately measuring the concentration of a gas dissolved in a liquid (solution) in a short time.
Gas partial pressure is measured by measuring a gas concentration by a gas detector by causing a liquid flow in which a gas is dissolved to act on a gas permeable membrane of a dissolved gas sensor and evaporating and separating the gas flow. The reference data to be stored is paired with the measurement elapsed time until it reaches an equilibrium state, and in the actual measurement of the gas concentration, the measured liquid 10 is accelerated by the water pump to a flow velocity equal to the liquid flow at the time of the reference data acquisition. In the middle of the actual measurement of the gas concentration detected by the gas detector by acting on the gas permeable membrane of the dissolved gas sensor, the specific concentration is obtained and compared from the actual measurement data and the reference data. Based on this, the dissolved gas concentration in the equilibrium state is estimated.
[Selection] Figure 3

Description

  The present invention relates to a dissolved gas concentration measuring method and apparatus for measuring the concentration of a gas (gas) dissolved in a liquid (solution).

  The dissolved gas sensor that measures the concentration (gas partial pressure) of the gas dissolved in the solution vaporizes and separates the gas dissolved in the solution with a gas permeable membrane (membrane), and the separated gas is a gas detector. Thus, the gas concentration is measured by converting into an electric signal.

JP 7-128223 A Japanese Patent Laid-Open No. 8-159943 JP 2001-348857 A JP 2002-214106 A JP 2005-195328 A

  In the gas concentration measurement method and apparatus for measuring the concentration of dissolved gas dissolved in a solution using such a dissolved gas sensor, the gas phase and liquid phase boundary material resistance generated at the interface of the gas permeable membrane is measured. Due to the existence, there is a problem that the permeation rate of the gas passing through the gas permeable membrane is low, and it takes an extremely long time (for example, about 11 hours) before the concentration of the dissolved gas can be accurately measured.

  In order to solve such a problem, a method has been proposed in which the measurement time of the dissolved gas concentration is shortened by increasing the flow rate of the solution acting on the gas permeable membrane of the dissolved gas sensor. However, in order to measure the concentration of gas dissolved in groundwater, a measurement device that incorporates such a dissolved gas sensor is suspended in the borehole to measure the concentration of gas dissolved in groundwater. When trying to increase the flow rate of groundwater acting on the gas permeable membrane, a large amount of groundwater moves in a narrow hole and disturbs the groundwater in the hole, resulting in a decrease in measurement accuracy (stabilization). There's a problem.

  One object of the present invention is to propose a dissolved gas concentration measuring method and apparatus capable of accurately measuring the concentration of a gas dissolved in a liquid (solution) in a short time.

  Another object of the present invention is to generate a flow rate of a solution to be applied to a gas permeable membrane of a dissolved gas sensor in a preferable state. Specifically, it is to reduce disturbance of the surrounding solution by increasing the flow rate of the solution acting on the gas permeable membrane.

In the dissolved gas concentration measuring method of the present invention, the liquid in which the gas is dissolved is allowed to act on the gas permeable membrane of the dissolved gas sensor to be vaporized and separated and converted into an electric signal by the gas detector in the dissolved gas sensor. In the dissolved gas concentration measurement method for measuring gas concentration,
In advance, the liquid flow in which the gas is dissolved is allowed to act on the gas permeable membrane of the dissolved gas sensor to be vaporized and separated, and converted into an electric signal by the gas detector in the dissolved gas sensor to detect the gas concentration. Perform the measurement until the gas partial pressure is in an equilibrium state and acquire the reference data to be held in combination with the measurement elapsed time.
In the actual measurement of the gas concentration, the flow rate of the liquid to be measured is increased to a flow rate equal to the liquid flow at the time of acquisition of the reference data by the water pump and is applied to the gas permeable membrane of the dissolved gas sensor to detect the gas in the dissolved gas sensor. In the middle of the actual measurement to detect the gas concentration by converting it into an electric signal by the vessel, the specific concentration is obtained from the actual measurement data and the reference data and compared, and when the two specific concentrations match, the dissolved in the equilibrium state based on the actual measurement data The gas concentration is estimated.

Further, the dissolved gas concentration measuring device of the present invention causes the liquid in which the gas is dissolved to act on the gas permeable membrane of the dissolved gas sensor to be vaporized and separated and converted into an electric signal by the gas detector in the dissolved gas sensor. In the dissolved gas concentration measuring device that measures the dissolved gas concentration,
In advance, the liquid flow in which the gas is dissolved is allowed to act on the gas permeable membrane of the dissolved gas sensor to be vaporized and separated, and converted into an electric signal by the gas detector in the dissolved gas sensor to detect the gas concentration. Perform the measurement until the gas partial pressure is in an equilibrium state and acquire the reference data to be held in combination with the measurement elapsed time.
In the actual measurement of the gas concentration, the flow rate of the liquid to be measured is increased to a flow rate equal to the liquid flow at the time of acquisition of the reference data by the water pump and is applied to the gas permeable membrane of the dissolved gas sensor to detect the gas in the dissolved gas sensor. In the middle of the actual measurement to detect the gas concentration by converting it into an electric signal by the vessel, the specific concentration is obtained from the actual measurement data and the reference data and compared, and when the two specific concentrations match, the dissolved in the equilibrium state based on the actual measurement data A control device for estimating the gas concentration is provided.

  The present invention can realize a dissolved gas concentration measuring method and apparatus capable of accurately measuring the concentration of a gas dissolved in a liquid (solution) in a short time.

  Moreover, this invention can generate | occur | produce the flow rate of the solution made to act on the gas permeable film of a dissolved gas sensor in a preferable state. Specifically, disturbance of the surrounding solution due to increasing the flow rate of the solution acting on the gas permeable membrane can be reduced.

In the dissolved gas concentration measuring method of the present invention, the liquid in which the gas is dissolved is allowed to act on the gas permeable membrane of the dissolved gas sensor to be vaporized and separated and converted into an electric signal by the gas detector in the dissolved gas sensor. In the dissolved gas concentration measurement method for measuring gas concentration,
In advance, the liquid flow in which the gas is dissolved is allowed to act on the gas permeable membrane of the dissolved gas sensor to be vaporized and separated, and converted into an electric signal by the gas detector in the dissolved gas sensor to detect the gas concentration. Perform the measurement until the gas partial pressure is in an equilibrium state and acquire the reference data to be held in combination with the measurement elapsed time.
In the actual measurement of the gas concentration, the reference is measured by a water pump in which a conical screw-type impeller is disposed in a conical pump chamber provided with an injection nozzle that opens toward the gas permeable membrane at the tip of the flow rate of the liquid to be measured. In the course of the actual measurement to detect the gas concentration by accelerating the gas flow membrane of the dissolved gas sensor and converting it to an electric signal by the gas detector in the dissolved gas sensor by accelerating the flow velocity equal to the liquid flow at the time of data acquisition, The specific concentration is obtained from the measured data and the reference data and compared, and when the two specific concentrations match, the dissolved gas concentration in the equilibrium state is estimated based on the measured data.

Further, the dissolved gas concentration measuring device of the present invention causes the liquid in which the gas is dissolved to act on the gas permeable membrane of the dissolved gas sensor to be vaporized and separated and converted into an electric signal by the gas detector in the dissolved gas sensor. In the dissolved gas concentration measuring device that measures the dissolved gas concentration,
In advance, the liquid flow in which the gas is dissolved is allowed to act on the gas permeable membrane of the dissolved gas sensor to be vaporized and separated, and converted into an electric signal by the gas detector in the dissolved gas sensor to detect the gas concentration. Perform the measurement until the gas partial pressure is in an equilibrium state and acquire the reference data to be held in combination with the measurement elapsed time.
For the actual measurement of the gas concentration, a conical pump chamber provided with an injection nozzle that opens toward the gas permeable membrane at the flow velocity of the liquid to be measured, and a conical screw-type impeller disposed in the pump chamber are provided. The flow rate is made equal to the liquid flow at the time of acquisition of the reference data by the water pump, and the gas permeation membrane of the dissolved gas sensor is made to act and converted into an electric signal by the gas detector in the dissolved gas sensor to change the gas concentration. In the middle of the actual measurement to be detected, a specific concentration is obtained from the actual measurement data and the reference data and compared, and when the two specific concentrations match, a control device is provided that estimates the dissolved gas concentration in the equilibrium state based on the actual measurement data. To do.

  FIG. 1 is a longitudinal side view of a dissolved gas sensor used in this embodiment.

  The dissolved gas sensor 1 includes a control circuit board 5 in which a gas detector 3, a temperature sensor 4 and a control circuit are mounted in a cylindrical container 2 in a watertight state.

  A gas permeable membrane (silicon separation membrane) 7 is installed on the end face of the container 2 on which a solution for detecting the concentration of dissolved gas is applied so as to be supported by a support 6 made of sintered metal, and on the inside thereof. A gas detector 3 for sensing gas that has passed through the gas permeable membrane 7 and the support 6 is disposed.

  As the gas detector 3, a thermal conductivity type detector is suitable for measuring the concentration of methane gas dissolved in a solution (water), but other types of detectors may be employed.

  The gas detector 3 and the temperature sensor 4 are connected to a control processing circuit board (control processing circuit) 5 and connected to a detection cable 9 through a waterproof connector 8.

  Since this dissolved gas sensor 1 is used for gas concentration measurement in a solution (groundwater) as deep as 1000 m, each component and its combination part can correspond to the high hydraulic pressure in such a solution. Configure as you can.

  As will be described in detail later, the dissolved gas sensor 1 is configured such that when a detection target solution 10 is allowed to act on the gas permeable membrane 7, the gas dissolved in the solution 10 is vaporized and separated by the gas permeable membrane 7. The gas detector 2 functions to detect the gas concentration by passing through the gas and reaching the gas detector 2. The dissolved gas concentration is determined by conversion from the gas partial pressure and temperature in the control processing circuit board 5 on the basis of Henry's law.

  FIG. 2 shows the measurement characteristics when the flow rate of the solution 10 applied to the gas permeable membrane 7 in the dissolved gas sensor 1 is changed, and shows the relationship between the elapsed time and the measured specific concentration. The solution 10 is water in which methane gas is dissolved.

  The characteristic curve a is characteristic curve d when the flow rate of the solution 10 acting on the gas permeable membrane 7 is 0 ml / min, the characteristic curve b is when the flow rate is 10 ml / min, the characteristic curve c is when the flow rate is 45 ml / min. Is when the flow rate is 90 ml / min.

  FIG. 3 is a side view of a dissolved gas concentration measuring device using the dissolved gas sensor, where (a) shows a longitudinal side view of the main part, and (b) shows a part of an outer cover (water-permeable cover). It is a partially opened side view shown.

  The dissolved gas concentration measuring apparatus 11 according to the first embodiment includes a dissolved gas sensor 1 and a water pump 16 in an elongated measurement container 15 constituted by a cylindrical water-permeable cover 14 whose both ends are closed by cone-shaped end covers 12 and 13. The pump drive motor 17 and the control box 18 are housed.

  The water-permeable cover 14 is configured to function so as to disperse a liquid flow through which the solution 10 flows in and out by a large number of water-passing holes 14a provided in a cylindrical peripheral wall to form a gentle internal / external flow liquid flow.

  The dissolved gas sensor 1 is fitted to a jacket 19 so that the gas permeable membrane 7 faces upward and is positioned at the lower part in the measurement container 15. The gas is passed through the jacket 19 by a pump drive motor 17 above the jacket 19. A water pump 16 for injecting the solution 10 toward the permeable membrane 7 is fitted. The unit of the dissolved gas sensor 1, the water flow pump 16, and the pump drive motor 17, which are integrally configured by the jacket 19 in this way, has the water flow rate so that a gap is interposed between the peripheral wall of the water flow cover 14. Install in the cover 14.

  The water flow pump 16 has a conical screw-type impeller 16c disposed in a conical pump chamber 16b provided with an injection nozzle 16a opening toward the gas permeable membrane 7 at the tip, and the impeller 16c is pump-driven. The solution 10 is sucked into the pump chamber 16 from the liquid absorption slit 19a formed in the upper part of the jacket 19 so as to communicate with the large-diameter side portion of the pump chamber 16b by being rotationally driven by the rotating shaft 17a of the motor 17. It is the structure which pressurizes toward the injection nozzle 16a of the front-end | tip of the pump chamber 16b. The flow of the solution 10 supplied to the spray nozzle 16a is stabilized by providing a rectifier 16d having a conical shape in the vertical direction at the tip of the impeller 16c.

  The injection nozzle 16 a makes it possible to realize the generation of a fast liquid flow of the solution 10 that acts on the gas permeable membrane 7 of the dissolved gas sensor 1 with a small amount of the solution 10.

  The solution 10 injected from the injection nozzle 16a of the water pump 16 and diffused by hitting the gas permeable membrane 7 of the dissolved gas sensor 1 passes through a drainage slit 19b provided in a lower part of the jacket 19 away from the upper part. Discharge.

  The control box 18 is built in so as to be positioned above the measurement container 15, and the detection cable 9 led out from the dissolved gas sensor 1 includes the dissolved gas sensor 1, the water pump 16, and the pump driven integrally by the jacket 19. The pump 17 is connected to the control box 18 by the pump control cable 20 through the gap between the outer periphery of the unit of the motor 17 and the water permeable cover 14, and the external connection cable 21 led out from the control box 18. Is extended so as to penetrate the cone-shaped end cover 12 and connect to the external (ground) main controller 22.

  Since the dissolved gas concentration measuring device 11 measures the gas concentration in a solution (groundwater) as deep as 1000 m, it can be adapted to the high liquid (water) pressure in such a solution. To do.

  The main control device 22 includes a power supply device 22a that supplies power to the control processing circuit board 5, the pump drive motor 17, and the control box 18, and an information processing device (small computer) 22b that executes measurement control and detection data processing.

  Next, a preferable flow rate of the solution 10 that acts on the gas permeable membrane 7 of the dissolved gas sensor 1 by the water pump 16 will be described.

  4 is a characteristic diagram showing the relationship between the applied voltage applied to the pump drive motor 17 and the flow rate of the solution 10 injected from the injection nozzle 16a of the water pump 16, and FIG. 5 shows the applied voltage applied to the pump drive motor 17. It is a characteristic view which shows the relationship of the flow velocity of the solution 10 injected from the injection nozzle 16a of the water flow pump 16, and the solution 10 is water in which methane gas is dissolved, respectively, and the opening diameter φ of the injection nozzle 16a is 2 mm and 4 mm. Shows the case.

  As shown in FIG. 4, the flow rate of the water 10 injected from the injection nozzle 16a of the water flow pump 16 increases as the applied voltage applied to the pump drive motor 17 increases, and the flow rate is as shown in FIG. The voltage increases as the applied voltage applied to the pump drive motor 17 increases.

  In this way, the water flow generating device that causes the water (solution) 10 having a small flow rate and a high flow rate to act on the gas permeable membrane 7 of the dissolved gas sensor 1 combines the conical pump chamber 16b and the conical screw type impeller 16c. A water flow pump 16 configured to pressurize the water 10 and inject it from the small-diameter injection nozzle 16a toward the gas permeable membrane 7 is suitable, and the opening diameter ψ at the tip of the injection nozzle 16a is about 2 to 4 mm. It is practical.

  Moreover, since such a water flow generator has a simple device configuration, it is easy to downsize the device, and it is also easy to ensure water pressure resistance.

  Such a dissolved gas concentration measuring device 11 increases the flow rate of water that acts on the gas permeable membrane 7 when measuring the concentration of gas that is suspended in a narrow borehole and dissolved in groundwater. However, since the liquid flow mitigating action of the water-permeable cover 10 also functions, a small amount of groundwater moves in a narrow hole, and a low water flow is sufficient. Therefore, the groundwater in the hole is disturbed and measurement accuracy becomes unstable. There is no such thing.

  Next, a dissolved gas measuring method using the dissolved gas concentration measuring device 11 will be described. The dissolved gas measuring method in this embodiment is a method for estimating the gas concentration (or gas partial pressure) in the solution 10 based on the detection data until the middle of the dissolved gas measurement using the dissolved gas concentration measuring device 11. This measurement (estimation) is performed with the assistance of a measurement processing program executed by the information processing device in the main control device 22.

  When the concentration of the gas dissolved in the solution 10 is measured by applying the liquid flow of the solution 10 to the gas permeable membrane 7 of the same dissolved gas sensor 1, the liquid flow of the solution 10 acting on the gas permeable membrane 7 is measured. Are identical, the relationship between the specific concentration of gas detected by the gas detector 3 (gas partial pressure ratio) and the measurement time is unambiguous regardless of the difference in dissolved gas concentration in the solution 10, as shown in FIG. A basic relationship. Here, the specific concentration and the partial pressure ratio indicate that the measurement (detection) value of the gas detector 3 is in an equilibrium state, that is, the gas concentration in the solution 10 is equal to the measurement (detection) concentration of the gas detector 3 and a steady state is reached. It is a value obtained by normalizing with the value at the time. Therefore, as shown in FIG. 7, reference data until the equilibrium state is obtained by the dissolved gas measuring device 11 in advance, and the actual measurement obtained from the actual measurement data up to the intermediate stage in the middle of the measurement when actually measuring. Compare the specific concentration with the reference specific concentration obtained from the reference data acquired in advance, and if they are equal, the gas concentration when the steady state is reached based on the detection characteristics of the reference data and the measured data up to the middle. Can be estimated.

  FIG. 8 is a block diagram of the method for measuring and estimating the dissolved gas in this way and the processing executed by the information processing device 22b in the main controller 22 to support the method.

  First, a process for acquiring reference data will be described.

Step S101
The water pump 16 is activated to continuously apply the liquid flow of the solution 10 toward the gas permeable membrane 7 of the dissolved gas sensor 1 in the dissolved gas concentration measuring device 11 under the same condition as the actual measurement.

Step S102
Detection data (gas concentration detection signal) is acquired from the dissolved gas sensor 1 at every predetermined elapsed time and stored in pairs with the elapsed time.

Step S103
The process branches after monitoring whether the detection data (detection gas concentration) has reached an equilibrium state (the concentration of the gas dissolved in the solution 10). When the detected data does not reach the equilibrium state, the process returns to step S102.

Step S104
When the detection data reaches the equilibrium state, the detection data held in step S102 is acquired and held as reference data.

Step S105
The operation of the water pump 16 is stopped and the acquisition of the reference data is finished.

  Next, actual measurement and estimation of the dissolved gas dissolved in the solution 10 will be described.

Step S201
A dissolved gas concentration measuring device 11 is introduced into a measured solution 10 for measuring a dissolved gas concentration, a water pump 16 is activated, and the solution is directed toward the gas permeable membrane 7 of the dissolved gas sensor 1 in the dissolved gas concentration measuring device 11. Ten liquid streams are applied continuously.

Step S202
Detection data (actually measured gas concentration detection signal) is obtained from the dissolved gas sensor 1 every predetermined elapsed time and is stored in pairs with the elapsed time.

Step S203
The specific concentration (measured specific concentration) of the detection data (actually measured gas concentration) is compared at the elapsed time equal to the reference specific concentration of the reference data (reference gas concentration) acquired and held in advance.

Step S204
The process branches after monitoring whether the specific concentration of the detection data matches the specific concentration of the reference data. If the two specific densities do not match, the process returns to step S202.

Step S205
When the specific concentration of the detection data and the specific concentration of the reference data match, the value of the actually measured gas concentration held is displayed. As will be described later, in order to secure a preferable estimation accuracy when estimating the measurement gas concentration, it is desirable to acquire the measured gas concentration signal until the specific concentration becomes 0.5 or more.

Step S206
Based on the obtained measured gas concentration, the measured gas concentration when the equilibrium state is reached is estimated and displayed and held.

Step S207
The operation of the water pump 16 is stopped, and the measurement and estimation of the dissolved gas concentration are finished.

It is a vertical side view of the dissolved gas sensor used in Example 1 of this invention. It is a measurement characteristic figure when changing the flow volume of the solution made to act on the gas permeable film of the dissolved gas sensor used in Example 1 of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a side view of the dissolved gas concentration measuring apparatus of Example 1 of this invention, (a) is a principal part vertical side view, (b) is a part opening side surface which opens and shows a part of water-permeable cover FIG. It is a characteristic view which shows the relationship between the applied voltage applied to a pump drive motor, and the flow volume of the solution injected from the injection nozzle of a water flow pump. It is a characteristic view which shows the relationship between the applied voltage applied to a pump drive motor, and the flow velocity of the solution injected from the injection nozzle of a water flow pump. It is a characteristic view which shows the relationship between the specific concentration (gas partial pressure ratio) of the gas which a gas detector detects when the liquid flow of the solution which acts on the gas permeable film of a dissolved gas sensor is the same, and measurement time. It is a figure which shows the concept of the density | concentration estimation method in the dissolved gas density | concentration measurement of Example 1 of this invention. It is a block diagram of the process which the information processing apparatus of the main controller in the dissolved gas concentration measuring apparatus of Example 1 of this invention performs.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Dissolved gas sensor, 2 ... Container, 3 ... Gas detector, 5 ... Control processing circuit board, 7 ... Gas permeable film, 10 ... Solution to be detected, 11 ... Dissolved gas concentration measuring apparatus, 14 ... Water-permeable cover, 14a DESCRIPTION OF SYMBOLS ... Water flow hole, 15 ... Measurement container, 16 ... Water flow pump, 16a ... Injection nozzle, 16b ... Pump chamber, 16c ... Impeller, 16d ... Rectifier, 17 ... Pump drive motor, 19 ... Jacket, 19a ... Liquid absorption Slit, 19b ... Drain slit, 22 ... Main control device, 22a ... Information processing device.

Claims (4)

A dissolved gas concentration measuring method for measuring a dissolved gas concentration by allowing a gas in which a gas is dissolved to act on a gas permeable membrane of a dissolved gas sensor to be vaporized and separated and converted into an electric signal by a gas detector in the dissolved gas sensor In
In advance, the liquid flow in which the gas is dissolved is allowed to act on the gas permeable membrane of the dissolved gas sensor to be vaporized and separated, and converted into an electric signal by the gas detector in the dissolved gas sensor to detect the gas concentration. Perform the measurement until the gas partial pressure is in an equilibrium state and acquire the reference data to be held in combination with the measurement elapsed time.
In the actual measurement of the gas concentration, the flow rate of the liquid to be measured is increased to a flow rate equal to the liquid flow at the time of acquisition of the reference data by the water pump and is applied to the gas permeable membrane of the dissolved gas sensor to detect the gas in the dissolved gas sensor. In the middle of the actual measurement to detect the gas concentration by converting it into an electric signal by the vessel, the specific concentration is obtained from the actual measurement data and the reference data and compared, and when the two specific concentrations match, the dissolved in the equilibrium state based on the actual measurement data A method for measuring a dissolved gas concentration, wherein the gas concentration is estimated.   2. The water pump according to claim 1, wherein a conical screw-type impeller is disposed in a conical pump chamber provided with an injection nozzle opening toward the gas permeable membrane at a tip. The dissolved gas concentration measurement method. A dissolved gas concentration measuring device for measuring a dissolved gas concentration by allowing a gas in which a gas is dissolved to act on a gas permeable membrane of a dissolved gas sensor to be vaporized and separated and converted into an electric signal by a gas detector in the dissolved gas sensor In
In advance, the liquid flow in which the gas is dissolved is allowed to act on the gas permeable membrane of the dissolved gas sensor to be vaporized and separated, and converted into an electric signal by the gas detector in the dissolved gas sensor to detect the gas concentration. Perform the measurement until the gas partial pressure is in an equilibrium state and acquire the reference data to be held in combination with the measurement elapsed time.
In the actual measurement of the gas concentration, the flow rate of the liquid to be measured is increased to a flow rate equal to the liquid flow at the time of acquisition of the reference data by the water pump and is applied to the gas permeable membrane of the dissolved gas sensor to detect the gas in the dissolved gas sensor. In the middle of the actual measurement to detect the gas concentration by converting it into an electric signal by the vessel, the specific concentration is obtained from the actual measurement data and the reference data and compared, and when the two specific concentrations match, the dissolved in the equilibrium state based on the actual measurement data A dissolved gas concentration measuring device, comprising a control device for estimating a gas concentration.   In Claim 3, the said water flow pump was provided with the conical pump chamber which provided the injection nozzle which opens toward the said gas permeable film at the front-end | tip, and the conical screw-type impeller arrange | positioned in the said pump chamber. Dissolved gas concentration measuring device characterized by that.

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