JP2012042341A - Sample cell for gas analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sample cell for a gas analyzer, which allows an optical window and an inside wall of the cell to be easily cleaned and allows gas substitution to be quickly performed by causing gas introduced into a cell body from a gas inlet to flow to a gas outlet smoothly without staying.SOLUTION: The sample cell for a gas analyzer, through which sample gas is caused to flow from a gas inlet provided at one end of the cell toward a gas outlet provided at the other end, includes: a cylindrical cell body (11) having screw portions formed in end parts on both sides; and inlet-side and outlet-side window holders (14a and 14b) which hold optical windows (13a and 13b) made of an infrared-transmissive material and are attached so as to be engaged with screw portions (16a and 16b) of the cell body to seal up an end part on the gas inlet side and an end part on the gas outlet side. The inlet-side window holder (14a) is provided with a gas inlet pipe (12a), and the outlet-side window holder (14b) is provided with a gas outlet pipe (12b).

Description

  The present invention uses an infrared gas analyzer that measures the concentration of a desired gas component contained in a gas by utilizing the fact that light having a specific wavelength that is unique to various gases is absorbed when the infrared light passes through the gas. The present invention relates to a sample cell for a gas analyzer used in the above.

  As shown in FIG. 4, the conventional infrared gas analyzer 30 includes an infrared light source 31, an optical chopper 32, a sample cell 20 (hereinafter also referred to as “cell”), an infrared detector 33, and the like. The infrared light emitted from the infrared light source 31 becomes intermittent light by the light chopper 32 and enters the sample cell 20. Then, the infrared light is reflected inside the sample cell 20 and enters the infrared detector 33. At that time, since the amount of infrared absorption in the sample cell 20 changes according to the concentration of the component to be measured existing in the sample cell 20, the change is detected by an infrared detector 33 such as a mass flow sensor, and a concentration signal ( V) is output.

FIG. 5 shows a detailed configuration of the sample cell 20 incorporated in the single beam infrared gas analyzer 30 described above.
The sample cell 20 transmits light such as infrared rays, introduces a sample gas from a gas inlet pipe 22a provided in the cell body 21, and circulates the sample gas toward the gas outlet pipe 22b.

  The cell body 21 having a cylindrical shape is made of a metal such as stainless steel, for example, and window holders 24a and 24b are fitted to both ends thereof. Optical windows 23a and 23b made of an infrared transmitting material are bonded to the window holders 24a and 24b. Further, O-rings 25a and 25b are provided between the outer peripheral surfaces of the both end portions of the cell main body 21 and the window holders 24a and 24b to ensure airtightness.

  As described above, the sample cell 20 can be easily cleaned by removing the window holders 24a and 24b even if the inner wall of the cell body 21 is contaminated by dust or mist contained in the sample gas when used for a long period of time. It has a structure that can be done.

  As another infrared gas analyzer, for example, a double beam system described in Patent Document 1 is known. This infrared gas analyzer has two cells, and a sample gas (sample gas) containing a measurement target gas and a reference gas (reference gas) are alternately arranged at a constant cycle with respect to the first cell and the second cell. The influence of the drift due to the contamination of the cell can be canceled by calculating and processing the measurement signal that is supplied and output as an AC signal having a frequency corresponding to the gas switching period.

Japanese Utility Model Publication No. 53-166585

  By the way, in the infrared gas analyzer, since the amount of light received by the infrared detector 33 greatly affects the detector sensitivity of the analyzer, the inner diameter of the cell 20 is set to be relatively large (about φ25) so as to ensure a sufficient amount of light received. I was trying to do it. For this reason, it took time to introduce or replace the gas into the cell 20, and the 100% response time required about 30 seconds or more.

  In particular, the double beam infrared gas analyzer has an excellent feature that it can reduce the effect of changes in the reflectance of the inner surface of the cell due to dust, mist, and corrosive components contained in the sample gas. In spite of ensuring long-term stability in gas concentration measurement, it is difficult to quickly replace the gas in two cells, so it cannot be used for applications that require high-speed response. There was a problem that it could be used only for limited purposes.

  The present invention has been made in view of the above-described problems, and can easily clean the optical window and the inner wall of the cell, and the gas introduced into the cell body from the gas inlet does not stay. An object of the present invention is to provide a sample cell for a gas analyzer capable of promptly replacing a gas so as to smoothly flow to a gas outlet.

  The invention of claim 1 is a gas analyzer sample cell in which a sample gas is circulated from a gas inlet provided at one end of the cell to a gas outlet provided at the other end, and screw portions are provided at both ends. The formed cylindrical cell main body and an optical window made of a material that transmits the measurement light are held, and screwed with the threaded portion of the cell main body so that the gas inlet side end and the gas outlet side end An inlet side and an outlet side window holder attached so as to seal, a gas inlet pipe is provided close to the optical window in the inlet side window holder, and the outlet side window holder A gas outlet pipe is provided adjacent to the optical window.

  According to a second aspect of the present invention, in the sample cell for a gas analyzer according to the first aspect, the gas inlet pipe is disposed such that a central axis of the gas inlet pipe does not pass through a longitudinal axis of the cell body. It is characterized by.

  According to the first aspect of the present invention, the gas inlet pipe is provided near the optical window in the window holder on the inlet side, and the gas outlet pipe is provided near the optical window on the window holder on the outlet side. The inlet pipe and gas outlet pipe are placed close to the end face of the cell body (the inner surface of the optical window) to reduce the dead space that caused the gas to stay, allowing for quick gas replacement. Thus, the response speed of the gas analyzer incorporating this can be improved.

  According to the second aspect of the present invention, the gas introduced from the gas inlet pipe generates a vortex along the cell inner wall and efficiently pushes out the gas remaining in the cell, so that the responsiveness can be further improved. .

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows an example of the sample cell for gas analyzers by this invention, (A) is a longitudinal cross-sectional view which shows a part in cross section, (B) is a side view. It is a figure shown about the principal part for demonstrating the operation principle of this invention, (A) is a longitudinal cross-sectional view, (B) is a side view. It is a figure which shows the response characteristic of the infrared gas analyzer incorporating the sample cell by this invention. It is a figure which shows the outline | summary of the conventional infrared gas analyzer. It is a figure which shows the structure of the conventional sample cell for gas analyzers, (A) is a longitudinal cross-sectional view which makes a part cross section, (B) is a side view. It is a figure shown about the principal part of the conventional sample cell for gas analyzers, (A) is a longitudinal cross-sectional view, (B) is a side view.

Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.
FIG. 1 is a view showing an example of a sample cell for a gas analyzer according to the present invention.
As shown in the figure, a first (inlet side) window holder 14a and a second (outlet side) window holder 14b are provided at both ends of the cylindrical cell body 11. The first window holder 14a holds an optical window 23a made of a material such as CaF2 (calcium fluoride) that transmits infrared light as measurement light, and has an inner peripheral surface of the frame portion on the infrared light source side of the cell body 11. A female thread part 141a that is screwed with the external thread part 16a formed on the outer peripheral surface of the end part is formed, and the end part on the gas inlet side of the cell body 11 is sealed. Similarly, the second window holder 14b also holds an optical window 23b made of an infrared transmitting material such as CaF2, and is formed on the inner peripheral surface of the frame portion on the outer peripheral surface of the end of the cell body 11 on the infrared detector side. A female thread portion 141b that is screwed into the male thread portion 16b is formed, and seals the end of the cell body 11 on the gas outlet side.

  Reference numerals 15a and 15b denote O-rings for ensuring airtightness, respectively, between the inner peripheral surface of the first window holder 14a and the outer peripheral surface of the end of the cell body 11, and the inner periphery of the second window holder 14a. It is inserted between the surface and the outer peripheral surface of the end portion of the cell main body 11.

  And the through-holes 17a and 17b are provided in the surrounding wall of the 1st, 2nd window holders 14a and 14b, and the gas inlet pipe 12a and the gas outlet pipe 12b are fitted, respectively. The sample gas S or the reference gas R (for example, N2 or Air) is introduced from the gas inlet pipe 12a and flows toward the gas outlet pipe 12b provided at the other end.

  In the conventional cell, as shown in FIG. 6, the gas inlet pipe 22a is provided in the cell main body and is attached away from the optical window 23a serving as the end face of the cell, so that a dead space is formed in the vicinity of the optical window 23a. Is likely to occur. That is, the sample gas S or the reference gas R introduced into the cell body 21 from the gas inlet pipe 22a may be directed to the gas outlet side as indicated by an arrow 52 as shown in FIG. Some flow toward the optical window as shown. As a result, the gas introduced into the cell body 21 stays in the dead space, and the replacement of the sample gas S and the reference gas R is not performed quickly, so that the so-called gas replacement efficiency is lowered, and the gas analysis is performed. The response speed was slow.

  On the other hand, in the sample cell 10 according to the present invention, as shown in FIG. 2, the gas inlet tube 12a is provided in the window holder 14a, and the gas inlet tube 12a is brought as close to the end face side of the cell body 11 as possible. The dead space generated in the vicinity of the optical window 23a is reduced. Similarly, the gas outlet pipe 12b is also provided in the window holder 14b so as to reduce the dead space generated in the vicinity of the optical window 23b on the infrared detector side. Therefore, the gas introduced into the cell main body 11 flows smoothly toward the gas outlet pipe 12b as indicated by the arrow 61 without staying in the cell main body 11.

  In this embodiment, the main body cell 11 having an inner diameter of 14 mm and a length of 250 mm is used. The inner diameters of the gas inlet pipe 12a and the gas outlet pipe 12b are 2.5 mm. In this case, the distance between the central axis of the gas inlet pipe 12a and the inner surface of the optical window 13a and the distance between the central axis of the gas outlet pipe 12b and the optical window 13b are preferably set to 3 mm or less.

  Further, in the sample cell 10 according to the present invention, in particular, the gas inlet tube 12a orthogonal to the cell body 11 is gas in a parallel plane Z2 having a predetermined distance from the plane Z1 including the longitudinal axis of the cell body 11. It arrange | positions so that the center axis | shaft of the inlet pipe 12a may be located. Thus, by arranging the gas inlet pipe 12a so that its central axis does not pass through the longitudinal axis of the cell body 11, the gas introduced from the gas inlet pipe 12a has a circular cross section. As a result, a vortex flow 61 that spirally moves along the inner wall surface is generated, and the sample gas S or the reference gas R remaining in the cell body 11 before gas replacement is efficiently pushed out, and the responsiveness is further improved. The

  FIG. 3 is a diagram showing comparison data regarding response characteristics between an infrared gas analyzer incorporating the sample cell 10 according to the present embodiment and an infrared gas analyzer incorporating a conventional cell. As shown in FIG. 3, according to the present embodiment, it has been confirmed that the response time is shortened to about 1/2 when compared with the conventional cell, and the response characteristics have a significant effect. By suitably selecting the cell diameter and the cell length, the replacement of the sample gas, which conventionally required a response time of several tens of seconds, can be significantly reduced to about several seconds.

10: Sample cell 11: Cell body 12a: Gas inlet pipe 12b: Gas outlet pipe 13a, 13b: Optical window (infrared transmission window)
14a: first (entrance side) window holder 14b: second (outlet side) window holders 16a, 16b: threaded portion

Claims (2)

In the sample cell for the gas analyzer that circulates the sample gas from the gas inlet provided at one end of the cell toward the gas outlet provided at the other end,
Cylindrical cell body with threaded parts on both ends,
An inlet side that holds an optical window made of a material that transmits measurement light, and that is screwed into the threaded portion of the cell main body so as to seal the gas inlet side end and the gas outlet side end. A window holder on the exit side,
A gas inlet pipe is provided in the window holder on the inlet side in the vicinity of the optical window, and a gas outlet pipe is provided in the window holder on the outlet side in the vicinity of the optical window. Sample cell for analyzer. The sample cell for a gas analyzer according to claim 1,
The gas analyzer sample cell, wherein the gas inlet tube is arranged such that a central axis of the gas inlet tube does not pass through a longitudinal axis of the cell body.

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