JP2005140652A - Diffusion scrubber type gas analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily remove gas bubbles staying in an upper space of an absorbent liquid holding part of a diffusion scrubber, and to conduct precise measurement not affected by the bubbles. <P>SOLUTION: This gas analyzer executes an operation for sucking out the bubbles by a syringe 24, when the bubbles are left in the upper space 16a after an absorbent liquid is filled in the absorbent liquid holding part 16. When the bubbles sucked out insufficiently by the syringe 24 remain, the remaining bubbles are moved from a measuring optical path by sucking the absorbent liquid by the syringe 24 or by delivering the once sucked absorbent liquid to conduct an operation to be returned to the upper space 16a, and are driven into a bubble reservoir formed in a position deviated from the measuring optical path. The measurement is thereby carried out without being affected by the bubbles. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a gas analyzer using a diffusion scrubber, and more specifically, a diffusion scrubber type that collects a gas component to be analyzed by the diffusion scrubber and measures a change in the optical characteristics of the absorbing solution dissolved therein by the diffusion scrubber. The present invention relates to a gas analyzer.

  Diffusion scrubbers are collected by separating only gas components and dissolving them in pure water or other liquids using the difference in diffusion coefficient between gas (gas) components and particles in sample gas such as the atmosphere. It is a kind of gas collecting means. In order to separate only the gas component, a filter made of porous polytetrafluoroethylene (PTFE) or the like is used.

  Conventionally, as a gas analyzer using such a diffusion scrubber, a gas component is collected in pure water or the like with a diffusion scrubber, and a solution of the gas component is introduced into a liquid chromatograph or the like for component analysis. It is common. However, there is a problem that such an analyzer is large and expensive. On the other hand, a gas analyzer that combines a diffusion scrubber and an LED colorimeter has been developed in recent years because it allows simpler measurement and the price of the device itself is low (for example, non-patented). Reference 1 etc.).

  The configuration of this conventional diffusion scrubber type gas analyzer will be described with reference to FIGS. That is, the diffusion scrubber 10 has a double structure of the outer cylindrical tube 11 and the inner cylindrical tube 12, and is between the liquid holding portion 16, which is a space in the inner cylindrical tube 12, the outer cylindrical tube 11, and the inner cylindrical tube 12. The partition wall that separates the gas flow part 13, that is, the peripheral wall of the inner tube 12, is made of, for example, porous polytetrafluoroethylene so that the gas component can pass therethrough. A gas introduction pipe 14 is provided at the upper part of the peripheral wall surface of the outer tube 11, and a gas outlet pipe 15 is provided at the lower part. The sample gas is supplied so as to flow from the top to the bottom or vice versa.

  A liquid supply pipe 17 is connected to the upper part of the peripheral wall surface of the inner tube 12, and a liquid discharge pipe 18 is connected to the lower part. The upper and lower end surfaces of the inner tube 12 are open, and transparent glass window members 19 and 20 provided with condensing lenses 19a and 20a are attached to the upper and lower end surfaces, respectively. An LED as the light emitting unit 21 is disposed outside the upper window member 19, and a photodiode as the light receiving unit 22 is disposed under the lower window member 20, and an inner tube is disposed between the light emitting unit 21 and the light receiving unit 22. A photometric path is formed substantially along the twelve central axes C.

  At the time of measurement, an absorption liquid in which a reagent that selectively causes a color development reaction with a gas component to be analyzed is stored in the liquid holding unit 16. In this state, when the sample gas is allowed to flow through the gas circulation part 13 for a predetermined time, the gas component in the sample gas passes through the micro holes in the peripheral wall of the inner tube 12 and enters the liquid holding part 16 and is collected by the absorbing liquid. The Since the absorption liquid is colored by the reaction between the gas component and the reagent, the light emitted from the light emitting unit 21 is allowed to pass through the absorption liquid, and the light that has received the specific absorption is detected by the light receiving unit 22. Absorbance is calculated based on the detection signal, and the concentration of the gas component is calculated based on the absorbance.

  In the diffusion scrubber as described above, the absorbing liquid is introduced into the liquid holding unit 16 from an empty state as a measurement preparation stage. At that time, it is difficult to completely expel the air in the liquid holding part 16, and bubbles may accumulate in the upper space 16a as shown in FIG. In addition, when the absorbing liquid is introduced into the liquid holding unit 16, air may be mixed and bubbles may accumulate. As a result, the presence of bubbles on the photometric path causes a part of the light to be scattered or absorbed, and the amount of light reaching the light receiving unit 22 is greatly reduced as compared with the case where there are no bubbles, thereby increasing the measurement accuracy. There was a problem of causing damage.

"Research Contents Environmental Measurement 1. Development of New Environmental Measurement Technology Using Diffusion Scrubber Method (4) Development of Automatic Continuous Measurement System for Air Polluting Gas Combining Diffusion Scrubber and LED Colorimeter", Applied Chemistry, Faculty of Science and Technology, Keio University Department of Environmental Chemistry, [Online], retrieved on November 6, 2003, Internet <URL: http://www.applc.keio.ac.jp/~tanaka/lab/hp4.html>

  The present invention has been made to solve such a problem, and the object thereof is to easily remove bubbles accumulated in the upper space of the liquid holding portion of the diffusion scrubber in a gas analyzer in which the diffusion scrubber and the photometry portion are combined. Therefore, it is possible to perform measurement with high accuracy without taking time for preparation for measurement and without being affected by bubbles.

In order to solve the above problems, the present invention provides a diffusion scrubber in which a liquid holding part that fills an absorbing liquid and a gas circulation part that circulates a gas to be analyzed are arranged via a partition wall through which a gas component can pass. A photometric part having a photometric path that passes in the vertical direction across the liquid holding part, and changes in optical characteristics of the absorbing liquid due to gas components collected in the absorbing liquid stored in the liquid holding part In the diffusion scrubber type gas analyzer that measures the light by the photometry unit,
A syringe connected to the upper space of the liquid holding unit, for sucking gas and / or liquid from the space, and discharging the sucked gas and / or liquid into the space;
A gas reservoir recess formed in a portion of the top surface of the liquid holding unit that is out of the photometric path;
It is characterized by having.

  In the diffusion scrubber type gas analyzer according to the present invention, the liquid holding part is first filled with the absorbing liquid before the measurement, but at that time, it is difficult to completely fill the liquid holding part with the absorbing liquid, and it remains in the upper space. Gas (usually air) may remain as bubbles. When such bubbles are present on the photometry path, basically, an operation of sucking out the bubbles with a syringe is performed. However, even if the bubbles do not disappear completely from the liquid holding unit, the bubbles move to the recesses and enter the photometry path. As long as it does not exist, the measurement will not be hindered. Therefore, the operation of sucking the liquid (absorbing liquid) from the upper space by the syringe or discharging the sucked liquid to return to the upper space is promoted to promote the movement of the bubbles, and the bubbles are removed from the photometry path. Move it into the recess.

  That is, in the diffusion scrubber type gas analyzer according to the present invention, it is only necessary to remove (move) the bubbles from the photometric path that hinders measurement, instead of completely removing the bubbles from the upper space of the liquid holding unit. Therefore, the bubble removal operation becomes very easy and can be completed in a short time. After removing the bubbles in this manner, the sample gas to be analyzed is circulated to the gas circulation part, the gas component in the gas is absorbed by the absorption liquid, and the measurement is performed by the photometry part. Of course, if possible, the bubbles may be directly sucked with a syringe and removed from the liquid holding portion.

  As described above, according to the diffusion scrubber type gas analyzer according to the present invention, it is possible to perform the measurement efficiently without taking time and effort for the preparation work for the measurement. In addition, since the bubbles can be reliably removed from the photometric path, highly accurate measurement can be performed without being affected by light scattering and absorption by the bubbles.

  A diffusion scrubber type gas concentration measuring apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 is a schematic longitudinal sectional view of a diffusion scrubber used in the gas concentration measuring apparatus of the present embodiment, FIG. 2 is an enlarged view of the upper part of the diffusion scrubber, FIG. 3 is an overall configuration diagram of the gas concentration measuring apparatus, and FIG. It is a flowchart which shows a procedure.

  In FIG. 1, the same or corresponding components as those shown in FIGS. 5 and 6 are denoted by the same reference numerals and description thereof is omitted. One of the features of the diffusion scrubber 10 according to the present embodiment is to suck out bubbles or absorbing liquid accumulated in the upper space 16a of the liquid holding unit 16, or in some cases, discharge the sucked absorbing liquid and return it to the upper space 16a. In addition, a syringe-like syringe 24 is connected to the upper portion of the inner tube 12 through a small communication tube 23. Another feature is that the shape of the glass window member 19 that closes the upper end surface of the inner tube 12 is different from the conventional one. That is, the lower surface of the window member 19 is a convex portion 19b that bulges from the portion corresponding to the photometric path toward the upper space 16a, so that the upper space 16a has an annular shape upward around the convex portion 19b. A recessed bubble reservoir 16b is formed.

  As shown in FIG. 3, the gas analyzer including the diffusion scrubber 10 includes an absorption liquid storage tank 30, an electromagnetic valve 31, and a waste liquid tank 32 as means for supplying or collecting the absorption liquid to the liquid holding unit 16. As a means for circulating the sample gas (in this case, the atmosphere) through the gas circulation unit 13, the three-way solenoid valve 33, the flow meter 34, and the pump 35 are provided. In addition, operations of the solenoid valves 31, 33, the pump 35, and the like are controlled. And a data processing unit 37 for receiving a light reception signal from the light receiving unit 22 and calculating a gas concentration based thereon. A part of the control unit 36 and the data processing unit 37 can be realized by operating a predetermined program in a general-purpose personal computer.

  A measurement procedure using the gas analyzer will be described with reference to FIG. In the initial state, it is assumed that the liquid holding unit 16 is empty. First, the liquid holding unit 16 is filled with a clean absorption liquid (that is, a gas component is not absorbed as will be described later) (step S1). That is, the electromagnetic valve 31 is opened by the control unit 36, and the absorbing liquid stored in the absorbing liquid storage tank 30 is injected into the liquid holding unit 16 through the liquid supply pipe 17. Then, the electromagnetic valve 31 is closed at an appropriate time. If necessary, the absorbing liquid may be sucked by a syringe (different from the syringe 24) on the drainage pipe 18 side to assist the absorbing liquid flowing into the liquid holding unit 16. Further, absorption or suction of the absorption liquid by a pump (different from the pump 35) may be used.

  If the liquid holding unit 16 is filled with the absorbing solution, the analysis operator visually checks whether the liquid holding unit 16 interferes with the measurement, that is, whether there are bubbles on the photometric path (step S2). . It is preferable that the diffusion scrubber 10 is detachable so that it is easy to check for the presence of bubbles by visual observation, and the upper and lower light emitting units 21 and light receiving units 22 are also detachable as a unit. In addition to visually confirming the presence or absence of bubbles, the light reception intensity by the light receiving unit 22 is actually checked, and when the light reception intensity is low, it is determined that the measurement light is scattered or absorbed by the bubbles. Good.

  When it is determined that there are bubbles on the photometry path by visual observation or other methods (Y in step S3), the analysis operator performs bubble removal by operating the syringe 24 (step S4). Specifically, when the amount of bubbles is large, the suction operation is performed with the syringe 24 to suck out the air in the upper space 16a. However, when aspirating rapidly with the syringe 24, a large amount of air is sucked into the liquid holding unit 16 through the peripheral wall surface of the inner tube 12, and there is a risk that bubbles will increase excessively in the liquid holding unit 16. In order to avoid such problems, it is necessary to perform suction by the syringe 24 at a slow speed.

  A considerable amount of residual air can be sucked out by the syringe 24. However, if some amount of bubbles remain in the upper space 16a, it is difficult to suck out the bubbles. Therefore, if the amount of remaining air is reduced to some extent, the syringe 24 is operated so as to move the remaining bubbles to the bubble reservoir 16b. In this case, not only the suction operation of the absorbing liquid by the syringe 24 but also the operation of discharging the absorbing liquid once sucked and returning it to the upper space 16a depending on the case, the remaining bubbles are projected. It moves from the lower surface of 19b to the bubble storage part 16b of the circumference | surroundings. As a result, as shown in FIG. 2, all the bubbles may be accommodated in the bubble reservoir 16b. Such an operation is much easier than completely sucking out bubbles.

  If it is determined from the result of the above operation or from the beginning that there are no bubbles on the photometric path (N in step S3), the measurement is started (step S4). That is, the pump 35 is operated by the control unit 36 or manually, and the gas outlet pipe 15 is connected to the pump 35 side by the electromagnetic valve 33. Then, the sample gas introduced through the gas introduction pipe 14 passes through the gas circulation part 13 with a predetermined flow rate. As a result, the gas component in the sample gas is dissolved in the absorption liquid and reacts with the reagent in the absorption liquid to produce a specific color. After circulating the sample gas for a predetermined time, for example, 1 hour, the measurement light from the light emitting unit 21 is allowed to pass through the absorption liquid, the passing light is detected by the light receiving unit 22, and the detection signal is sent to the data processing unit 37. . The data processing unit 37 measures the absorbance of light having a wavelength specific to color development, and calculates the concentration of the gas component from the absorbance. Alternatively, it is possible to measure a temporal change in gas concentration by performing measurement in parallel with the collection of gas components.

  It should be noted that the above embodiment is merely an example of the present invention, and it is apparent that appropriate modifications and corrections can be made in accordance with the spirit of the present invention. For example, the condensing lens 19a can be omitted depending on the types of LEDs and photodiodes used in the light emitting unit 21 and the light receiving unit 22. Further, the light emitting unit 21 and the light receiving unit 22 do not necessarily have to be provided vertically opposite to each other, and an optical path using an appropriate reflection optical system outside the photometric path passing through the liquid holding unit 16 in the vertical direction. It is good also as a structure which bends. Furthermore, the shape and structure of the diffusion scrubber are not limited to those described above, and can be appropriately modified within the scope of the present invention.

The schematic longitudinal cross-sectional view of the diffusion scrubber used with the gas concentration measuring apparatus by one Example of this invention. The enlarged view of the upper part of the diffusion scrubber of a present Example. BRIEF DESCRIPTION OF THE DRAWINGS The whole block diagram of the diffusion scrubber type gas concentration measuring apparatus of a present Example. The flowchart which shows the procedure of a measurement. The schematic longitudinal cross-sectional view of the diffusion scrubber in the conventional diffusion scrubber type gas concentration measuring apparatus. FIG. 6 is an enlarged view of the upper part of the diffusion scrubber of FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Diffusion scrubber 11 ... Outer cylinder pipe 12 ... Inner cylinder pipe 13 ... Gas distribution part 14 ... Gas introduction pipe 15 ... Gas outlet pipe 16 ... Liquid holding part 16a ... Upper space 16b ... Bubble reservoir part 17 ... Liquid supply pipe 18 ... Drainage pipes 19, 20 ... window member 19b ... convex part 21 ... light emitting part 22 ... light receiving part 23 ... communication pipe 24 ... syringe

Claims (1)

A diffusion scrubber in which a liquid holding part that fills the absorbing liquid and a gas circulation part that circulates the gas to be analyzed are arranged via a partition wall through which a gas component can pass, and photometry that passes in the vertical direction across the liquid holding part A diffusion scrubber type gas analyzer comprising: a photometric unit having a path; and measuring a change in optical characteristics of the absorbing liquid by a gas component collected in the absorbing liquid stored in the liquid holding unit by the photometric unit ,
A syringe connected to the upper space of the liquid holding unit, for sucking gas and / or liquid from the space, and discharging the sucked gas and / or liquid into the space;
A gas reservoir recess formed in a portion of the top surface of the liquid holding unit that is out of the photometric path;
A diffusion scrubber-type gas analyzer characterized by comprising:

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