JP2941762B2 - Dioxin analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analyzer for analyzing dioxins and their derivatives, which are harmful substances generated in incinerators.

[0002]

2. Description of the Related Art Dioxin has high toxicity in a very small amount, and development of a highly sensitive analytical method is desired. Therefore,
It is conceivable that a laser analysis method capable of high-sensitivity analysis will be applied.In recent years, it is possible to measure the spectrum of a chlorine-substituted product by combining a supersonic jet method and a resonance-sensitized multiphoton ionization method. Proposals have been made (C. Weickhardt, R. Zimmermann, U. Bosel, EWSchlag, Pap
id Commun, Mass Spectron, 7,198 (1993)). The detection limit of this method is at the ppb level, and the measurement results are shown in FIGS. 8 and 9. FIG. 9 is an enlarged view near 305 nm in FIG.

[0003]

However, the above-mentioned proposal is a method for analyzing a gas in which the spectrum is simplified by jetting a gas sample into a vacuum and instantaneously cooling the gas sample to near absolute zero. The detection limit of dioxin and its derivatives (hereinafter referred to as “dioxins”) is about ppb, and the actual analysis of dioxins requires concentration of 5 to 6 digits, which takes time and labor for detection. is there.

In the conventional manual analysis, it takes one to two months for the analysis result to be obtained. The daily generation of dioxins in the incinerator is measured, and the combustion control is performed as needed. It is difficult to drive to meet the appropriate regulation values.

[0005]

Means for Solving the Problems The invention of a dioxin analyzer according to claim 1 of the present invention which solves the above-mentioned problems comprises a means for directly collecting combustion gas containing dioxin and its derivative generated from an incinerator, A jetting means for jetting a collected gas containing the dioxin and its derivative into a vacuum chamber using a slit nozzle forming a rectangular supersonic jet flow, and irradiating a laser beam into the jetted supersonic jet flow, Direct analysis of dioxin in combustion gas with laser irradiation means for forming molecular ions in the process of resonance-sensitized ionization and time-of-flight mass spectrometer for analyzing dioxins and their derivatives of generated molecular ions It is characterized by doing.

The dioxin analyzer according to claim 2 is the dioxin analyzer according to claim 1, wherein
A slit nozzle for forming the rectangular jet flow includes a fixed slit portion and a moving slit portion which is opposed to the fixed slit portion and has a variable slit width.

The dioxin analyzer according to claim 3 is the dioxin analyzer according to claim 2, wherein
There is provided a return means for returning the moving slit portion so as to always maintain a predetermined interval.

According to a fourth aspect of the present invention, in the dioxin analyzer according to the first to third aspects, the jetting means for forming the supersonic jet stream comprises a jet of a rectangular jet stream. It is characterized by comprising airflow control means for controlling.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the dioxin analyzer according to the present invention will be described, but the present invention is not limited thereto.

According to the present invention, it is possible to directly sample a gas generated at the time of combustion in an incinerator through a filter, and to directly and quickly measure dioxins present in the sampled gas with high sensitivity. is there. As a result, dioxins in exhaust gas can be measured quickly and accurately, so that feedback can be immediately provided to combustion control,
It is possible to constantly monitor so as to perform combustion operation below the regulation value of dioxins.

FIG. 1 shows a schematic diagram of a dioxin analyzer according to the present embodiment. The dioxin analyzer according to the present embodiment uses the high temperature (about 800
C) means for cooling the gas with a cooler 11 and then removing dust components through a filter 12 to directly collect the gas;
A jetting means 14 for forming a supersonic jet stream by jetting a rectangular jet stream from the slit nozzle into the vacuum chamber 13 with the collected gas containing the dioxins, and a YAG laser 15 in the jetted supersonic jet stream. A laser irradiation means 19 for irradiating the excited dye laser beam 16 into the vacuum chamber 13 through the condenser lens 17 to form molecular ions 18 in the process of resonance-sensitized ionization, and dioxin of the generated molecular ions 18 And a time-of-flight mass spectrometer 20 for performing a class analysis. FIG.
Reference numeral 21 denotes KDP (potassium dihydrogen phospha).
te) crystal, 22 a pulse generator, 23 a pulse driver, 24 a preamplifier, 25 a digital oscilloscope, 26 an information processor, 27-29 electrodes, and 30 an ion detector.

In the above apparatus, the dye laser beam 16 is excited by the YAG laser 15 and the wavelength is
Set it to 1/2 and obtain an ultraviolet laser beam. The ultraviolet laser light is condensed by a condenser lens 17 and introduced into the vacuum chamber 13. On the other hand, the gas collected from the incinerator is
Then, the dust component is removed by the filter 12, and the dust component is conveyed to the pulse nozzle serving as the ejection unit 14.
The pulse generator 22 generates a TTL signal, controls the pulse driver 23, and drives the pulse nozzle for a predetermined time (200
(〜500 μs) to form a supersonic jet. A pulse signal is generated from the pulse generator 22 to control the YAG laser 15 so that a laser beam is irradiated when the molecules to be analyzed in the supersonic jet reach between the electrodes 27 and 28. It is. Since the laser is a pulse, introducing a sample during a time when the laser is not oscillating increases the load on the vacuum system and unnecessarily increases the amount of sample required for analysis, which is not preferable. Therefore, the sample can be introduced in a pulsed form in synchronization with the laser oscillation time.

The generated molecular ions 18 are applied to the electrodes 27, 2
An electric field is applied by the electron lens formed at 8, 29,
It is detected by the ion detector 30. In this system, since a time-of-flight mass spectrometer is configured, molecules having a low ionization potential are mixed, and even if ions are generated during the non-resonant ionization process, they are distinguished from the target molecule by the difference in mass number. It becomes possible. Since an electric signal proportional to the number of ions can be obtained in the ion detector 30, the electric signal is amplified by the preamplifier 24 and the digital oscilloscope 2
At 5, a mass spectrum can be observed. In order to perform processing of the mass spectrum, it is sent to the information processing device 26, where signal processing is performed.

Originally, it is possible to selectively ionize only by the wavelength of the laser. However, even if molecules having a low ionization potential are mixed to generate ions in the non-resonant ionization process, the present invention provides a time-of-flight type. Since the ions are detected using the mass spectrometer, accurate analysis is possible.

In the case of samples having different molecular weights, it is possible to discriminate immediately from the mass spectrum. In the case of the same molecular weight, the isomer can be distinguished by detecting the wavelength dependence of the ion signal of the target mass number in advance.

Here, a means for directly and quickly detecting dioxin with high sensitivity without improving the process of spouting a sample from a slit nozzle into a vacuum chamber according to the present invention and performing a process such as concentration will be described. .

Conventionally, as a method for improving the detection sensitivity, it is known to increase the degree of condensing of a laser beam condensing lens. However, such a method can sufficiently improve the detection sensitivity. Therefore, in the present invention, the detection sensitivity is improved by making the shape of the jet from the slit nozzle rectangular.

FIG. 2 is a schematic view of a slit nozzle for high sensitivity analysis according to the present invention. As shown in FIG. 2, the slit nozzle 31 has a rectangular ejection hole 31a,
The dioxin compound entrained in the helium gas forms a jet stream 33 in a vacuum chamber (not shown). In the present invention, the shape of the ejection hole 31a of the slit nozzle 31 is rectangular (L ₁ (= 20 in the figure) as shown in FIG.
mm) indicates the length of the slit opening in the longitudinal direction. ), The jet stream 33 to be jetted becomes a rectangular shape having a length L ₂ (50 mm) in the traveling direction of the irradiated laser beam 34 (see FIG. 3), and this region (the molecule shown by a broken line in FIG. 3). It is effectively ionized in the beam spread region). In FIG. 2, the laser beam 34 is irradiated in a direction perpendicular to the plane of the paper, and in FIG. In FIG. 2, reference numeral 35 denotes an ionization effective volume (hatched portion) which is an area where ions that can be actually detected exist. The ionization effective volume 35 is derived from the following equation, and is determined by the diameter of the laser beam and the ion permeable area of the mesh electrode.

[0019]

[Equation 1] ・ Total molecular number density N _total = 2.7 × 10 ¹⁹ / cc ・ Dioxin content C ・ Molecular number density in ionization effective volume V N = 10 ¹⁷ / cc ・ Ionization effective volume V = Laser beam assuming a value of photoionization efficiency E _i = 0.01 in diameter × the slit width (50cm) = 0.16cc · detection efficiency E _TOF = 0.5 · aromatics TOFMS, detectable by the laser beam 1 shot The expected number of dioxin molecules is as follows. Nd = C × N × V × E _i × E _TOF = C × 8 × 10 ¹³ pieces / cc As a result, if C = 10 ⁻¹⁴ = 0.01 ppt, it can be detected without concentration. Become.

Therefore, if the portion where the molecular beam 33 generated by the supersonic jet and the region where the laser beam 34 can be irradiated overlaps becomes large, the detection sensitivity will be improved.

Conventionally, as shown in FIG. 4, since the ejection hole 41 of the slit nozzle is of a pinhole type,
The jet stream to be ejected had an isotropic cone shape, and as a result, a large number of molecules not irradiated with the laser were generated. In contrast, the ejection shape of the jet stream (molecular beam) as in the present invention by a rectangular, it becomes possible to obtain a sufficient sensitivity. In the present embodiment, as described above, the dioxin content (C) = 10 ⁻¹⁴ = 0.01 pp
At t, detection was possible without concentration.
On the other hand, in the case of the conventional pinhole type, the dioxin content (C) = 5 ppt was required.

Further, as shown in FIG. 2, by providing an airflow suppressing member 32 on the gas ejection side of a slit nozzle 31 having a rectangular ejection hole 31a of the present invention, the molecular beam 33 is further reduced to a rectangular short axis. Spreading in the direction can be suppressed. As a result, compared with the case where the airflow suppressing member 32 is not provided, the number of molecules that are not irradiated with the laser sharply decreases,
The sensitivity can be further improved.

The mesh electrodes 36, 3 shown in FIG.
By making the shape of 7, 38, 39 and the shape of the ion detection MCP (Microchannel plate: Microchannel plate) which is the ion detector 40 into a rectangular shape, ions can be collected without waste, and furthermore, It is possible to achieve an improvement in sensitivity. FIG. 5 shows the ionization volume 35.
And the relationship between the mesh electrode 37. Laser beam 34
The ions ionized by the step 3 are rectangular mesh electrodes 3.
7 and is efficiently detected by a detector (not shown).

Next, in the slit nozzle, when the passage of the nozzle is blocked by dust components in the collected gas,
The means for responding when the required sensitivity cannot be obtained will be described.

FIG. 6 is a schematic view of a slit nozzle according to the present embodiment. As shown in FIG. 6, the slit nozzle 51 of the present embodiment has a fixed slit portion 53 fixed to the gas chamber 52 side and a slit width (s) that is opposed to the fixed slit portion 53 and is enlarged. And a movable slit portion 54 capable of performing the following operations.

The moving slit portion 54 is moved by a driving means (not shown) such as a stepping motor at the time of abnormality such as clogging of ash floating in the gas. The slit width is set so that it can always return to the slit width (s) at the time of ejecting the molecular beam. In the figure, reference numeral 55 denotes a holding portion, which is controlled by the pulse driver 23 shown in FIG.
(500-500 μs) to form a supersonic jet stream. Thus, the moving slit portion 5
By providing a return means such as a stepping motor which always returns so as to maintain a predetermined interval, it is possible to immediately return to a position where measurement can be performed after removing clogged dust components. In the present embodiment, the airflow suppression unit 56 is also provided to suppress the width of the molecular beam spread distribution. However, if the molecular beam spread width is within the target range, the airflow suppression unit 56 is used. Part 56
May be optional.

The occurrence of the abnormality may be sensed by the vacuum level measuring device provided in the vacuum chamber 13 (not shown), when the internal pressure is lowered (vacuum level raised) (abnormal: e.g. P = 10 ^{- The} operation may be stopped at ⁷ Torr or the like to remove dust components. For removing the dust component, a known removing means or method can be appropriately employed. For example, a clean carrier gas provided separately may be blown to remove the dust component.

FIG. 7 is a schematic view of a slit nozzle according to another embodiment, and is a front view from a jet port side, showing an opening and closing mechanism of the slit nozzle. As shown in FIG. 7, a slit nozzle 61 of the present embodiment has a fixed slit portion 62 fixed to a gas chamber (not shown) side, and a slit width (s) opposed to the fixed slit portion 62. And a movable slit portion 63 that can enlarge. Note that the holding portion 55 controlled by the pulse driver shown in FIG. 6 is not shown in FIG.

The moving slit portion 63 is normally pressed by a pressing means 64 such as a spring and abuts on the regulating member 65 to always maintain a slit width (s) at a predetermined interval. In the event of an abnormality or the like, the solenoid coil (not shown) is made differential, and the moving slit 63 is moved by a predetermined amount along the guide frame 65 for a predetermined time, so that the ejection port 6
Release 6. Thereafter, a clean gas such as an inert gas flows into the nozzle to eliminate the clogging inside the ejection port 66, and then releases the open state, whereby the moving slit portion 63 comes into contact with the regulating member 65, and a predetermined amount is released. After returning to the slit width, measurement can be immediately performed even after cleaning.

In the present embodiment, when dioxin in the combustion exhaust gas is analyzed, the exhaust gas is directly introduced into the pulse nozzle, and the sample is introduced in a pulse form. It is possible to reduce the sample volume by three orders of magnitude. When a sufficient vacuum system can be used, a continuous molecular beam can be used instead of a pulsed one.

[0031]

As described above, the dioxin analyzer of claim 1 directly collects the combustion gas containing dioxin and its derivative generated from the incinerator and the sample containing the dioxin and its derivative. A jet means for jetting a gas into a vacuum chamber using a slit nozzle that forms a rectangular supersonic jet stream, and a laser beam is irradiated into the jetted supersonic jet stream to generate a molecule in a resonance-sensitized ionization process. Laser irradiation means for forming ions,
Since it was provided with a time-of-flight mass spectrometer for analyzing the generated molecular ions of dioxin and its derivatives, so as to directly analyze dioxin in the combustion gas,
The jet stream to be jetted has a rectangular shape that is long in the traveling direction of the irradiated laser beam, and is effectively ionized in this region, enabling high-sensitivity measurement. As a result, high levels of dioxins mixed in the exhaust gas are obtained. Sensitivity direct analysis becomes possible, combustion can be controlled immediately, and response to dioxin emission regulations can be responded quickly.

The dioxin analyzer according to claim 2 is the dioxin analyzer according to claim 1, wherein
The slit nozzle that forms the rectangular jet flow has a fixed slit portion and a moving slit portion that is opposed to the fixed slit portion and has a variable slit width, so that the slit nozzle is clogged with dust components and the like. When you do
It can be opened immediately to remove dust components.

The dioxin analyzer of claim 3 is a dioxin analyzer of claim 2,
Since the moving slit section is provided with the returning means for returning so as to always maintain a predetermined interval, it is possible to immediately return to a position where measurement can be performed after removing the clogged dust component.

According to a fourth aspect of the present invention, in the dioxin analyzer according to the first to third aspects, the jetting means for forming the supersonic jet stream comprises a jet of a rectangular jet stream. By providing the airflow control means for controlling, the molecular beam can further suppress the spread in the rectangular short axis direction, and as a result, the number of molecules that are not irradiated with the laser is reduced as compared with the case where the airflow suppression member is not provided. It can be drastically reduced, and the sensitivity can be greatly improved.

Furthermore, by making the shape of the mesh electrode and the rectangular shape of the ion detector, ions can be collected without waste, and the sensitivity can be further improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a dioxin measuring device of the present invention.

FIG. 2 is a schematic view of a slit nozzle for high sensitivity measurement.

FIG. 3 is a front view of FIG. 2;

FIG. 4 is a schematic view of a conventional slit nozzle.

FIG. 5 is a diagram showing a relationship between an ionization effective volume and a mesh electrode.

FIG. 6 is a schematic view of a slit nozzle capable of freely moving a slit width.

FIG. 7 is a schematic view of another slit nozzle capable of freely moving a slit width.

FIG. 8 is a supersonic molecular jet spectrum diagram of a dioxin-derived compound.

FIG. 9 is a supersonic molecular jet spectrum diagram of a dioxin-derived compound.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Cooler 12 Filter 13 Vacuum chamber 14 Injection means 15 YAG laser 16 Dye laser beam 17 Condensing lens 18 Molecular ion 19 Laser irradiation means 20 Time-of-flight mass spectrometer 21 KDP 22 Pulse generator 23 Pulse driver 24 Preamplifier 25 Digital oscilloscope Reference Signs List 26 information processing device 27, 28, 29 electrode 30 ion detector 31a ejection hole 31 slit nozzle 32 airflow suppressing member 33 jet flow 34 laser beam 35 ionization effective volume 36, 37, 38, 39 mesh electrode 40 ion detector 51 slit nozzle 52 Gas chamber 53 Fixed slit part 54 Moving slit part 55 Holding part 56 Air flow suppressing part 61 Slit nozzle 62 Fixed slit part 63 Moving slit part 64 Pressing means 65 Guide frame 66 Spout s Tsu-wide

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ identification code FI H01J 49/40 H01J 49/40 (58) Investigated field (Int.Cl. ⁶ , DB name) G01N 27/62-27/70 H01J 49/00-49/48

Claims (4)

(57) [Claims] 1. A means for directly collecting combustion gas containing dioxin and a derivative thereof generated from an incinerator, and a slit nozzle for forming a rectangular supersonic jet stream from the collected gas containing dioxin and a derivative thereof. Jetting means for jetting into a vacuum chamber; laser irradiating means for irradiating a laser beam into the jetted supersonic jet stream to form molecular ions in the process of resonance-sensitized ionization; dioxin of generated molecular ions and its A dioxin analyzer comprising a time-of-flight mass spectrometer for analyzing derivatives and directly analyzing dioxin in combustion gas. 2. The dioxin analyzer according to claim 1, wherein a slit nozzle for forming the rectangular jet flow is opposed to the fixed slit portion and the movable slit portion having a variable slit width. A dioxin analyzer comprising: 3. The dioxin analyzer according to claim 2, further comprising a return means for returning the movable slit so as to always maintain a predetermined interval. 4. The method according to claim 1 , wherein
The dioxin analyzer according to any one of the preceding claims, wherein the ejection means for forming the supersonic jet flow includes an airflow control means for controlling a jet of a rectangular ejection flow.