KR20190014158A - Apparatus for detecting gas concentration using light filter - Google Patents

Abstract

The present invention relates to a gas detector using an optical filter that can selectively detect gas concentration at high sensitivity by a plurality of wavelength selection filters to measure the total organic carbons from a sample of a solution. The gas detector can selectively measure several gas concentrations by arranging a plurality of the wavelength selection filters which pass a light of wanted wavelength range, but reflect the light of remaining wavelength ranges. A gas detector of the related art reflects the light of a wanted wavelength range by positioning a plurality of wavelength reflection filters (optical filters) slanted at a certain angle on the same axis of an optical path to measure a quantity of light, but has a problem in that since the quantity of the light may be lost depending upon the sloped angle (reflective angle), and the number of the optical filters positioned along the same axis (the optical path) is increased as kinds of the wavelengths to be measured are increased, the quantity of the light reaching the optical filter positioned at the rearmost end. In contrast, the optical filter of the present invention is configured to absorb a wanted wavelength, and thus can reduce the optical loss caused by the reflective angle, similar to the related art. Also, the optical filter of the present invention reduces the number of the wavelength selection filters positioned on the same axis as the light source, it can reduce the loss of the amount of the light reaching the wavelength selection filter positioned at the rearmost end on the same axis. The present invention can increase the accuracy of analysis since the whole quantities of the incident light are used.

Description

[0001] The present invention relates to a gas detector using an optical filter,

The present invention relates to a gas detector using an optical filter, and more particularly, to a gas detector using an optical filter capable of measuring a concentration of a gas for measuring total organic carbon from a sample of an aqueous solution with high sensitivity and selectively using a plurality of wavelength selective filters Gas detector.

Due to the unusual climate change such as global warming, it is absolutely necessary to manage them due to the increase of green algae and water pollutants in rivers and lakes. In particular, there is a great need to strengthen management of organic matter to efficiently manage water quality.

At present, the index for evaluating water quality is changing politically from chemical oxygen demand (COD) to total organic carbon (TOC), and the tendency to use total organic carbon (TOC) as an indicator is not only in rivers and lakes, And so on. In addition, it has been expanded and activated all over the industrial fields including pharmaceuticals, which require the use of pure water, power generation processes in the semiconductor and boiler sectors, and cooling water.

In the US and other advanced countries in the world, in order to secure the high sensitivity of the total organic carbon (TOC) measuring device worldwide, it is necessary to use a hot-smelting method as an oxidation device for maximizing the oxidation efficiency, a supercritical calculation in the UV / persulfate method, And a fluidic sensing method using pressurized flow has been developed, and various technologies have been developed.

In recent years, it has been focusing on the development of detectors in order to save costs and to obtain high sensitivity. In the dual wavelength analysis method of existing single light, development of a measurement type detector having the same optical path by applying the Fabry-Perot (FPI) It is activated.

In Korea, gas detectors using electrochemistry and NDIR optics are being developed for CO2 analysis for total organic carbon measurement.

A non-dispersive infrared (NDIR) gas sensor is a system for measuring the gas concentration by measuring a light absorption rate with respect to a concentration by using a characteristic that a gas molecule absorbs light having a specific wavelength (infrared ray). That is, since specific gas molecules have a characteristic of absorbing only light of a specific wavelength band, the gas molecules are irradiated with light of a plurality of wavelengths, and only the light of the wavelength band absorbed by the gas molecules is filtered and filtered.

Since the non-dispersive infrared gas sensor merely attaches an optical filter that transmits only the wavelength to the photodetector, the system is simple and requires less cost than the dispersion system, and has advantages of high gas selectivity and high measurement reliability.

In the case of a non-dispersive infrared gas sensor, a more efficient measurement method for selecting and detecting only a specific wavelength according to an analytical substance is still required. Further, a plurality of analytical gas concentrations can be simultaneously measured using one reaction cell A measurement method is required.

The present invention provides a gas detector for measuring total organic carbon, which has a simple structure and can increase the photodetection sensitivity.

The present invention provides a gas detector capable of selectively measuring and simultaneously measuring a plurality of gas concentrations according to the kind of an analyte.

One aspect of the present invention is

A multi-wavelength light source unit for emitting light of a plurality of wavelength ranges;

A reaction cell located on an optical path to which the multi-wavelength light source is irradiated and into which a sample gas generated in the pretreatment device flows in and out;

An optical filter unit positioned at a rear end of the reaction cell and having a plurality of wavelength selective filters for transmitting light corresponding to at least one predetermined wavelength band and reflecting light at the other wavelength band; And

And a light detecting element for detecting a signal of light transmitted through the optical filter portion.

The gas detector of the present invention can arrange a plurality of wavelength selection filters that transmit light of a desired wavelength range and reflect light of the remaining undesired wavelength band so as to selectively measure and simultaneously measure a plurality of gas concentrations to be measured.

Conventionally, a plurality of wavelength reflection filters (optical filters) inclined at a specific angle are positioned on the same axis of the optical path to reflect light of a desired wavelength, and the amount of light is measured. However, depending on the tilt angle And the number of optical filters located along the same axis (along the optical path) increases as the number of types of wavelengths to be measured increases, so that there is a problem that the amount of light reaching the optical filter located at the rear end is decreased. On the contrary, since the optical filter of the present invention absorbs a desired wavelength, the optical loss according to the reflection angle can be reduced as in the prior art, and the optical filter of the present invention has a wavelength selective filter It is possible to reduce the loss of the amount of light reaching the wavelength selection filter located at the rear end on the same axis.

The present invention can increase the accuracy of analysis by using the amount of incident light as a whole.

1 is a conceptual diagram of a gas detector of the present invention.
Fig. 2 shows a light source section including a reflector.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. In addition, the terms described below are defined in consideration of the functions of the present invention, which may vary depending on the intention of the user, the operator, or the custom. Therefore, the definition should be based on the contents throughout this specification.

1 is a conceptual diagram of a gas detector of the present invention. Fig. 2 shows a light source section including a reflector. The gas detector of the present invention includes a light source portion 10, a reaction cell 20, a light filter portion 30, and a light detecting element 40.

The light source unit 10 can emit light in a plurality of wavelength ranges. The light source unit 10 may use any known multi-wavelength light source device without limitation. The light source unit may use an infrared lamp that emits light having a plurality of wavelengths. Referring to FIG. 1, the light source unit 10 may irradiate light of _n specific wavelength ranges (? ₁ , ...,? _N ).

Referring to FIG. 2, the gas detector may further include a reflector 50 surrounding an area except a surface corresponding to an optical path. The light energy irradiated from the light source through the reflector can be transmitted to the optical filter as much as possible.

The reaction cell 20 is located on the optical path through which the multi-wavelength light source is irradiated, and the sample gas generated in the pretreatment device 60 flows into the reaction cell 20.

Referring to FIG. 1, the irradiated multi-wavelength light passes through the reaction cell 20. The pretreatment apparatus 50 generates a gas containing carbon in the measurement sample (aqueous solution), for example, CO 2, CO, CH 4, and the like, and supplies it to the reaction cell 20.

The supplied sample gas flows into the reaction cell 20. The multi-wavelength light emitted from the light source unit is absorbed or scattered by the specific gas of the sample and is transmitted to the optical filter unit 30 located at the rear end of the reaction cell 150 .

For example, CO2 absorbs 4260nm, CH4 absorbs 3300nm, and CO absorbs 4640nm. Therefore, since the light sources of the specific wavelength band (4260 nm, 3300 nm, 4640 nm, 3800 nm (ref), etc.) irradiated by the light source unit are absorbed by the gas such as CO 2, the light intensity of the wavelength band reaching the optical filter is reduced. The amount of light reaching the optical filter and the photodetector element 40 is inversely proportional to the gas (molecule) concentration.

The temperature control unit 21 is attached to the outer surface of the reaction cell 20 to maintain a proper temperature in the reaction cell. A silicone rubber heater or the like may be used as the temperature regulating part 21. [

The optical filter unit 30 may be disposed at a rear end of the reaction cell, and may include a plurality of wavelength selective filters that transmit light corresponding to at least one predetermined wavelength band and reflect light of the remaining wavelength band.

More specifically, the optical filter unit 30 may include a first wavelength selection filter 31, a second wavelength selection filter 32, and a third wavelength selection filter 33.

The first wavelength selection filter 31 is positioned at the rear end of the reaction cell, and allows light of a predetermined wavelength band to pass through and reflects light of the remaining wavelength band.

The first wavelength selection filter 31 may be designed to pass a plurality of wavelengths. Referring to FIG. 1, the first selective wavelength filter may transmit light having a wavelength of? ₂ (3300 nm) and? ₃ (4260 nm).

The second wavelength selection filter 32 is positioned at the rear end of the first wavelength selection filter 31 and transmits light of a specific wavelength band among the lights having passed through the first wavelength selection filter 3, Can be reflected. Referring to FIG. 1, the second selective wavelength filter transmits light having a wavelength of? ₃ (4260 nm) and can reflect light having a wavelength of? ₂ (3300 nm).

The third selective wavelength filter (33) is disposed on the reflected light path of the first wavelength selective filter, and transmits the light of a specific wavelength band among the light reflected by the first wavelength selective filter . 1, the third selective wavelength filter 33 transmits light having a wavelength of? ₁ (3910 nm) and transmits light having wavelengths of? ₄ ,? _{5 ....} ? _N The light of a wavelength can be reflected. The third selection wavelength filter 33 may not be located on the same axis as the light source, the reaction cell, the first selection wavelength filter, and the second selection wavelength filter. For example, the third selection wavelength filter 33 may be disposed on the upper side of the first selection wavelength filter Can be located. Therefore, the optical filter of the present invention can reduce the number of wavelength selection filters located on the same axis as the light source, and thus can reduce the loss of the amount of light reaching the wavelength selection filter located at the rearmost stage.

The optical filter unit 30 may include another wavelength selection filter at the downstream of the first wavelength selection filter 31, the second wavelength selection filter 32, and the third wavelength selection filter 33.

For example, the optical filter unit may include a fourth wavelength selection filter positioned at a rear end of the second wavelength selection filter, transmitting light of a specific wavelength band among the light passing through the second wavelength selection filter, and reflecting light of the remaining wavelength band can do.

The optical filter unit further includes a fifth wavelength selection filter positioned at the downstream end of the second wavelength selection filter for transmitting light of a specific wavelength band among the light reflected by the second wavelength selection filter and reflecting light of the remaining wavelength band can do.

The optical filter unit 30 may include a wavelength reflection filter at the downstream of the first wavelength selection filter 31, the second wavelength selection filter 32, and the third wavelength selection filter 33, respectively.

The wavelength selection filter used in the present invention is a filter that transmits light corresponding to at least one predetermined wavelength band and reflects light of the other wavelength band. In addition, the wavelength reflection filter used in the present invention is a filter that reflects light corresponding to one predetermined wavelength band and transmits light of the other wavelength band.

As described above, the present invention can simultaneously and simultaneously measure a plurality of gas concentrations to be measured by arranging a plurality of wavelength selection filters. In addition, the present invention can simultaneously measure a plurality of gas concentrations by using a wavelength selection filter and a wavelength reflection filter at the same time.

The light detecting elements (40, 41, 42, 43) detect a signal of light transmitted through the light filter portion.

Referring to FIG. 1, each of the photodetecting devices 41, 42, and 43 detects the intensity of the received light, converts the intensity of the received light into an electrical signal, and transmits the electrical signal to the subsequent electrical circuit. As a result, the concentration calculation for the analyte can be performed in the downstream circuit. The concentration calculation can be performed by a known method. For example, the concentration of a specific gas molecule can be derived by the following equation (1) according to the Beer Lambert law.

Io: Initial light quantity emitted from the light source

I: The amount of light reaching the light detector is I,

L: travel distance of light

X: Concentration of gas molecules

a: a constant value determined by the light absorptance of each gas molecule, the light emission spectrum of the light source, the light detection spectrum of the photodetector, etc. (Note: a value usually set as a fixed value in the analysis of a non-dispersive infrared gas sensor).

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. Therefore, the scope of the present invention is not limited to the above-described embodiments, but should be construed to include various embodiments within the scope of the claims and equivalents thereof.

Claims (4)

A multi-wavelength light source unit (10) for emitting light of a plurality of wavelength ranges;
A reaction cell 20 located on an optical path to which the multi-wavelength light source unit is irradiated, into which a sample gas generated in the pretreatment unit flows in and out;
An optical filter unit 30 positioned at a rear end of the reaction cell and having a plurality of wavelength selective filters for transmitting light corresponding to at least one predetermined wavelength band and reflecting light of the other wavelength band; And
And a photodetector element (40) for detecting a signal of light transmitted through the optical filter section. The optical filter according to claim 1,
A first wavelength selection filter (31) located at the rear end of the reaction cell for transmitting light of a predetermined wavelength band and reflecting light of the remaining wavelength band;
A second wavelength selection filter (32) positioned at a downstream end of the first wavelength selection filter and transmitting light of a specific wavelength band among the light having passed through the first wavelength selection filter and reflecting light of the remaining wavelength band;
And a third wavelength selection filter (33) positioned at the downstream end of the first wavelength selection filter and transmitting light of a specific wavelength band among the light reflected by the first wavelength selection filter and reflecting light of the remaining wavelength band A gas detector using an optical filter. The optical filter according to claim 1,
A third wavelength selection filter positioned at a rear end of the second wavelength selection filter and transmitting light of a specific wavelength band among the light having passed through the second wavelength selection filter and reflecting light of the remaining wavelength band;
And a fourth wavelength selection filter positioned behind the second wavelength selection filter for transmitting light of a specific wavelength band among the light reflected by the second wavelength selection filter and for reflecting light of the remaining wavelength band. A gas detector using an optical filter. The gas detector according to claim 1, wherein the gas detector further comprises a reflector surrounding a region except a surface corresponding to an optical path.

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