CN110487887A - Chemical gas trace detector - Google Patents

Abstract

The invention discloses a chemical gas trace detector, which comprises an air inlet, an air outlet, a first air pump, a solenoid valve group, an air flow detector, a filter tube, a second air pump, a pressure detector, an ion drift spectrum detection unit and CPU. The present invention releases the ammonia gas dopant by arranging the ammonia salt component to reduce the interference of interfering gases in the air, thereby improving the accuracy of measurement and solving the problem of high misjudgment rate of ion drift spectrometers in the prior art; the present invention uses tritium As an ionization source, the ionization efficiency of the gas molecules to be detected is higher, and the ionization source is more convenient to handle after it is scrapped, and will not cause radioactive pollution.

Description

Chemical Gas Trace Detector

technical field

The invention relates to the technical field of analytical instruments and detection, and more specifically, to a chemical gas trace detector.

Background technique

Ion mobility spectrometry (IMS) was originally developed as an analytical technique in chemical laboratories. In recent years, this technology has been perfected and has been applied in many fields, including the monitoring of chemical warfare agents in the national military field, the monitoring of explosives in security departments at all levels, and the inspection of prohibited items such as drugs and narcotics by customs and airport entrance security inspection departments. monitoring and the monitoring of toxic and harmful gases by the environmental monitoring department. With the widening of the application range, IMS technology has aroused the research interest of experts from all over the world, so this technology has been continuously updated and developed.

Although the current ion drift spectrometer has developed rapidly, there are still some shortcomings:

1. Ion drift spectrometers basically use radioactive sources, the conventional one is Ni ⁶³ . When the instrument is eliminated or scrapped, it is difficult and expensive to deal with the radioactive source;

2. The measurement range of the substance concentration of the existing instrument is ppm, and the sensitivity is low.

3. The false alarm rate of existing instruments is high, about 30%.

4. The replacement rate of the consumables of the existing instruments is high and cumbersome, and the work needs to be stopped when replacing the consumables of the accessories.

Contents of the invention

In view of this, the present invention provides a chemical gas trace detector, comprising an air inlet, an air outlet, a first air pump, a solenoid valve group, a gas flow detector, a filter tube, a second air pump, a pressure detector, an ion drift Spectrum detection unit and central processing unit, wherein,

The air inlet is used to feed the gas to be measured, and communicates with the first air pump and the electromagnetic valve group respectively;

The gas outlet is used to discharge the detected gas and communicates with the first gas pump and the electromagnetic valve group respectively;

The first air pump communicates with the air inlet and the air outlet respectively;

The solenoid valve group is respectively communicated with the air inlet, the air outlet, the gas flow detector and the ion drift spectrum detection unit;

The gas flow detector is respectively connected with the electromagnetic valve group, the filter tube and the ion drift spectrum detection unit;

The filter tube communicates with the air flow detector and the second air pump respectively;

The second air pump communicates with the filter tube and the ion drift spectrum detection unit respectively, and the pressure detector and the ammonia salt component are arranged between the second air pump and the ion drift spectrum detection unit , the ammonia salt part is used to release ammonia as a dopant, and solid ammonia salt is placed in it, and a first check valve is provided at the outlet of the ammonia salt part;

The ion drift spectrum detection unit is respectively connected with the gas flow detector, the second gas pump, the solenoid valve group and the central processing unit, and is used to detect the gas to be measured to obtain an electronic signal of ion migration, and send it to the central processing unit;

The central processing unit is connected with the ion drift spectrum detection unit, and is used to receive the electronic signal of the ion migration and convert it into a spectrogram, and compare the spectrogram with the established data spectrum library. All spectrograms of the existing substances are compared to determine the composition of the gas to be measured.

Preferably, the ammonia salt component is a sleeve structure with the outlet, the outlet is provided with the first one-way valve, the sleeve structure includes an inner sleeve and an outer sleeve, the inner sleeve Sleeved in the outer sleeve, the bottom of the inner sleeve is provided with solid ammonia salt, the inner sleeve is provided with a second check valve near the outlet, and on the inner sleeve, the second A plurality of small holes are provided between the one-way valve and the first one-way valve.

Preferably, a fixing bracket is also included, and the fixing bracket is respectively fixedly connected with the outer wall of the non-open end of the inner cylinder and the inner wall of the non-open end of the outer sleeve.

Preferably, the filter tube includes a first filter tube and a second filter tube connected in series, and activated carbon is arranged in the first filter tube and the second filter tube.

Preferably, a display screen is also included, the display screen is connected to the central processing unit, and when the detected component content of the gas to be measured exceeds a preset threshold, a red highlight mark will be displayed on the display screen.

Preferably, both the first filter tube and the second filter tube are detachably connected.

Preferably, the ion drift spectrum detection unit includes an ionization source, a pulse grid and an ion collector, wherein

The pulse grid is located between the ionization source and the ion collector;

The ionization source ionizes gas molecules into positive ions and negative ions;

The ion collector includes a first electrode sheet and a second electrode sheet oppositely arranged, and the plane where the first electrode sheet and the second electrode sheet are located is perpendicular to the plane where the pulse grid is located.

Preferably, the ion drift spectrum detection unit further includes a signal amplifier, and the signal amplifier is electrically connected to the ion collector and the central processing unit, respectively.

Preferably, a tritium source is used as ionization source.

Preferably, the number of solenoid valves in the solenoid valve group is three.

Compared with the prior art, the chemical gas trace detector provided by the present invention at least achieves the following beneficial effects:

(1) The chemical gas trace detector of the present invention releases the ammonia gas dopant by setting the ammonia salt part, reduces the interference of interfering gas in the air, thereby can improve the accuracy of measurement, and solves the error of the ion drift spectrum instrument in the prior art The problem of high judgment rate;

(2) The chemical gas trace detector of the present invention adopts a tritium source as an ionization source, and the ionization efficiency of gas molecules to be detected is higher, and the ionization source is more convenient to handle after being scrapped, and will not cause radioactive pollution;

(3) In the chemical gas trace detector of the present invention, the ion drift spectrum detection unit measures the flight path of the ion by the electric field, and because the efficiency of the tritium source is higher, it is better for ionized ion discrimination, thereby reaching a higher ppb concentration detection level;

(4) The consumable material in the chemical gas trace detector of the present invention is a filter tube, and the first filter tube and the second filter tube are detachably connected, can be replaced in a short time, and are easy to use.

Of course, any product implementing the present invention does not necessarily need to achieve all the above-mentioned technical effects at the same time.

Other features of the present invention and advantages thereof will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

Fig. 1 is a schematic structural view of a chemical gas trace detector provided by the present invention;

Fig. 2 is the schematic diagram of the structure of ammonia salt parts in the chemical gas trace detector provided by the present invention;

Fig. 3 is a schematic structural diagram of the ion drift spectrum detection unit in the chemical gas trace detector provided by the present invention;

Among them, 1-air inlet; 2-air outlet; 3-first air pump; 4-solenoid valve group; 5-airflow detector; 6-filter tube; 7-second air pump; 8-pressure detector; 9- Ion drift spectrum detection unit; 11-ammonia salt component; 111-first one-way valve; 112-inner cylinder; 113-outer sleeve; 114-solid ammonia salt; 115-second one-way valve; 116-small hole; 117-Fixed frame; 91-Ionization source; 92-Pulse grid; 93-Ion collector; 931-First electrode sheet; 932-Second electrode sheet; 94-Ions drifting to the ion collector; 95-Signal amplifier .

Detailed ways

Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangements of components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.

The following description of at least one exemplary embodiment is merely illustrative in nature and in no way taken as limiting the invention, its application or uses.

Techniques, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such techniques, methods and devices should be considered part of the description.

In all examples shown and discussed herein, any specific values should be construed as exemplary only, and not as limitations. Therefore, other instances of the exemplary embodiment may have different values.

It should be noted that like numerals and letters denote like items in the following figures, therefore, once an item is defined in one figure, it does not require further discussion in subsequent figures.

1 to 3, the present invention provides a chemical gas trace detector, referring to FIG. Tube 6, second air pump 7, pressure detector 8, ion drift spectrum detection unit 9 and central processing unit.

The air inlet 1 is used to feed the gas to be measured, and communicates with the first air pump 3 and the electromagnetic valve group 4 respectively;

The gas outlet 2 is used to discharge the detected gas and communicates with the first gas pump 3 and the solenoid valve group 4 respectively;

The first air pump 3 communicates with the air inlet 1 and the air outlet 2 respectively;

The solenoid valve group 4 communicates with the air inlet 1, the air outlet 2, the air flow detector 5 and the ion drift spectrum detection unit 9 respectively;

The air flow detector 5 communicates with the solenoid valve group 4, the filter tube 6 and the ion drift spectrum detection unit 9 respectively; the filter tube 6 communicates with the air flow detector 5 and the second air pump 7 respectively;

The second air pump 7 communicates with the filter tube 6 and the ion drift spectrum detection unit 9 respectively, and a pressure detector 8 and an ammonia salt part 11 are arranged between the second air pump 7 and the ion drift spectrum detection unit 9, and the ammonia salt part 11 It is used to release ammonia gas as a dopant, and a solid ammonia salt 114 is placed in it, and the outlet of the ammonia salt component 11 is provided with a first one-way valve;

The ion drift spectrum detection unit 9 is respectively connected with the gas flow detector 5, the second gas pump 7, the solenoid valve group 4 and the central processing unit, and is used to detect the electronic signal of the ion migration of the gas to be measured and send it to the central processing unit;

The central processing unit is connected with the ion drift spectrum detection unit 9, and is used to receive the electronic signal of ion migration and convert it into a spectrogram, and compare the spectrogram with all the existing substances in the established data library Compare the spectrograms to determine the composition of the gas to be measured.

The central processing unit is not shown in FIG. 1 , and it can be understood that the electrical signal of the ion drift spectrum detection unit 9 can be sent to a central processing unit.

It can be understood that the gas to be tested enters the chemical gas trace detector from the gas inlet 1, and the solenoid valve group 4 has a solenoid valve, and the gas intake is controlled by the solenoid valve.

The detected gas is discharged through the gas outlet 2, and a solenoid valve is provided in the solenoid valve group 4, and the gas outlet is controlled by the solenoid valve.

It should be noted that only 15-20% of the incoming gas to be tested is used for detection, so the excess part can be discharged through the first gas pump 3 and the gas outlet 2 . In FIG. 1, L1 refers to the gas path discharged from the first air pump 3 and the gas outlet 2, and L2 refers to the gas path through which the intake air of the air inlet 1 enters the ion drift spectrum detection unit 9 through the solenoid valve.

The number of solenoid valves in the solenoid valve group 4 is three. One of them is used to control the gas intake, one of them is used to control the gas output, and one of them is used to control the gas to be measured to enter the ion drift spectrum detection unit 9 .

During each measurement, there will be residual substances in the instrument, which will lead to an increase in residual substances after long-term use. Therefore, after long-term use, in order to ensure the accuracy of the instrument, the instrument can be cleaned by backwashing when necessary. A large amount of air is introduced for flushing, which is conducive to maintaining high detection accuracy of the instrument. L3 in FIG. 1 is the gas path for backwashing the ion drift spectrum detection unit 9 .

In the present invention, the internal components of the equipment are more refined and modularized, and the gas circuit design in the device is optimized to reduce the gas circuit path, and a new ion drift spectrum detection unit 9 is used, so that the concentration of the detected substance can reach the ppb level.

Referring to Fig. 2, the ammonia salt component 11 is a sleeve structure with an outlet, the outlet is provided with a first one-way valve 111, the sleeve structure includes an inner sleeve 112 and an outer sleeve 113, and the inner sleeve 112 is sleeved on the outer sleeve 113 Inside, the bottom of the inner cylinder 112 is provided with a solid ammonia salt 114, and the inner cylinder 112 is provided with a second one-way valve 115 near the outlet, and on the inner cylinder 112, between the second one-way valve 115 and the first one-way valve 111 A plurality of small holes 116 are provided. When in use, the solid ammonia salt 114 releases ammonia gas, which first diffuses in the inner cylinder 112, then opens the second one-way valve 115, diffuses between the inner cylinder 112 and the outer sleeve 113 through the small hole 116, and opens it when it is to be used The first one-way valve 111 can release ammonia gas to the outside. A small amount of ammonia gas released each time is used as a dopant, but in order to maintain the internal ammonia concentration of the ammonia salt component 11, it is necessary to open the second check valve 115 to the outer sleeve 113 after each release of ammonia gas A certain amount of ammonia gas is released to ensure that the ammonia gas in the ammonia salt component remains at a certain concentration.

It can be seen from FIG. 2 that the ammonia salt component 11 also includes a fixing frame 117, which is fixedly connected to the outer wall of the non-opening end of the inner cylinder 112 and the inner wall of the non-opening end of the outer sleeve 113 respectively, so as to play the role of fixing and supporting the inner cylinder.

In addition, it can be seen from FIG. 2 that a cavity is formed at the bottom of the inner cylinder 112 for fixing the solid ammonia salt 114 .

Fig. 2 is a sectional view of the ammonia salt component 11, so there is a dotted line between the first one-way valve 111 and the second one-way valve 115 on the inner cylinder 112, which is used to indicate that the inner cylinder 112 is provided with a plurality of small holes, In fact, the inner cylinder 112 extends all the way to the opening of the outer sleeve 113 .

Since the first one-way valve 111 is provided at the outlet, only the ammonia gas can be discharged and the gas to be tested will not enter the ammonia salt component 11 .

The present invention utilizes Dopant ammonia salt technology, uses ammonia salt as the dopant of the instrument, greatly reduces the interference of conventional gases in the air to the instrument, reduces the false alarm rate of the instrument, and makes the false alarm rate reach <5%. The specific principles are as follows:

Ammonia salt part 11 is a very small part, mainly is to install a solid ammonia salt inside sleeve. There is a first one-way valve 111 at one end of the sleeve, which enables the ammonia gas released from the solid ammonia salt to be released outward in a small amount. Every time the instrument performs gas measurement, the ammonia salt component 11 can release a small amount of ammonia gas, which is doped in the gas to be measured. The ammonia salt component 11 is doped with a small amount of ammonia gas in each gas to be measured. Since N ₂ and CO ₂ are the most abundant in the air, on the ion drift spectrum, these gases with higher concentrations will form very high spectral peaks. The spectrogram will tend to be a straight line, which is difficult to display on the spectrogram, which will make it difficult to find the substance to be measured. The positioning value of ammonia gas on the spectrogram is 46, and the positioning value of high-concentration gases such as N ₂ and CO ₂ is less than 46. After doping ammonia gas, through processing, the display of gases below 46 is "shielded", so that further "Shielding" the high concentration of interfering gases allows the drift spectrum of other gases to be measured to be measured, greatly increasing the measurement accuracy of the substance to be measured.

In some optional embodiments, the filter tube 6 includes a first filter tube and a second filter tube connected in series, and activated carbon is arranged in the first filter tube and the second filter tube. Both the first filter pipe and the second filter pipe are detachably connected. Of course, three or more filter tubes 6 can also be set, and the more filter tubes 6, the better the filtering effect. The number of filter tubes should consider the actual demand and the overall power of the circuit equipment.

The filter tube 6 of the present invention uses activated carbon as the basic filter material. Compared with the filter tube 6 used in the prior art, the air path section and length are increased structurally, and the filtering effect can be improved.

Referring to Fig. 3, the ion drift spectrum detection unit 9 comprises an ionization source 91, a pulse grid 92 and an ion collector 93, wherein the pulse grid 92 is located between the ionization source 91 and the ion collector 93; the ionization source 91 ionizes gas molecules For positive ions and negative ions; the ion collector 93 includes a first electrode sheet 931 and a second electrode sheet 932 oppositely arranged, and the plane where the first electrode sheet 931 and the second electrode sheet 932 are located is perpendicular to the plane where the pulse grid 92 is located.

In some preferred embodiments, the present invention uses tritium as the ionization source 91, which has higher ionization efficiency, and after the instrument is scrapped, the half-life of tritium is short, and the tritium source is finally converted into environmentally friendly hydrogen after the half-life, which is convenient for disposal.

The ion drift spectrum detection unit 9 also includes a signal amplifier 95, and the signal amplifier 95 is electrically connected to the ion collector 93 and the central processing unit, respectively.

When the present invention needs to detect the gas to be measured, the detection process is as follows:

a. Ambient gas (gas to be detected) enters the instrument through the air inlet 1 through pumping;

b. The gas flow detector 5 will detect whether the inhaled gas to be tested meets the requirements of the instrument for gas flow;

c. The gas to be measured is filtered through the filter tube 6, and the filter tube 6 will filter the water vapor in the air and other interfering gases, so as to obtain relatively pure gas to be tested.

d. The pressure detector 8 will detect whether the gas to be tested meets the pressure requirements of the instrument;

e. The gas to be detected enters the ion drift spectrum detection unit 9, and finally outputs an electronic signal to the calculation processing module;

The gas to be detected enters the ion drift spectroscopy (IMS) detection unit, and the steps are as follows:

First, the gas molecules are ionized through the ionization source 91, and the gas molecules are ionized into positive and negative ions.

The ionized positive and negative ions then drift forward. A pulse grid is arranged inside the ion drift spectrum detection unit 9, and the pulse grid will switch according to a certain pulse frequency. Every time the pulse grid is turned on, a certain amount of ions will pass through;

After the ions pass through the pulsed grid, they drift in the electric field. The gas molecules of different substances have different ions after ionization. The ions with a large amount of ions are heavier, and the "friction force" is stronger than that of small molecules, so in the drift process Move at a slower speed. Based on the above factors, various ions finally reach the ion plate at different positions and times, thus forming different electrical signals to distinguish different substances.

After the ions fly, they land on the first electrode plate or the second electrode plate. Due to the different flight trajectories of different ions, the positions they reach on the electrode plates are also different, thus forming different electrical pulse signals. The electrical pulse signals are processed by the signal amplifier 95. The signal is amplified and finally enters the central processing unit for display.

f. The central processing unit (calculation processing module) will send the output electronic signal to the spectrogram (A substance spectrum) of the substance to be detected, and compare it with all the spectrograms of the existing substances in the established data library , if the material spectrum of A can be stably combined with the material spectrum of B in the data library, and it is finally confirmed after multiple measurement spectrum comparisons in a short period of time, then the substance A to be detected is determined to be B in the data library.

In some optional embodiments, the chemical gas trace detector also includes a display screen (not shown in the figure), and the display screen is connected to the central processing unit. When the component content of the detected gas exceeds the preset threshold , a red highlight will appear on the display.

Of course it can be understood that the chemical gas trace detector of the present invention includes a housing, the above-mentioned first air pump 3, solenoid valve group 4, air flow detector 5, filter tube 6, second air pump 7, pressure detector 8, ion Both the drift spectrum detection unit 9 and the central processing unit are arranged in the casing.

It can be seen from the above examples that the chemical gas trace detector provided by the present invention at least achieves the following beneficial effects:

(1) The chemical gas trace detector of the present invention releases the ammonia gas dopant by setting the ammonia salt part, reduces the interference of interfering gas in the air, thereby can improve the accuracy of measurement, and solves the error of the ion drift spectrum instrument in the prior art The problem of high judgment rate;

(2) The chemical gas trace detector of the present invention adopts a tritium source as an ionization source, and the ionization efficiency of gas molecules to be detected is higher, and the ionization source is more convenient to handle after being scrapped, and will not cause radioactive pollution;

(3) In the chemical gas trace detector of the present invention, the ion drift spectrum detection unit measures the flight path of the ion by the electric field, and because the efficiency of the tritium source is higher, it is better for ionized ion discrimination, thereby reaching a higher ppb concentration detection level in parts per billion;

(4) The consumable material in the chemical gas trace detector of the present invention is a filter tube, and the first filter tube and the second filter tube are detachably connected, can be replaced in a short time, and are easy to use.

Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and not intended to limit the scope of the present invention. Those skilled in the art will appreciate that modifications can be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims (10)

1. A chemical gas trace detector, characterized in that, comprises an air inlet, an air outlet, a first air pump, a solenoid valve group, a gas flow detector, a filter tube, a second air pump, a pressure detector, and ion drift spectrum detection unit and CPU, where, The air inlet is used to feed the gas to be measured, and communicates with the first air pump and the electromagnetic valve group respectively; The gas outlet is used to discharge the detected gas and communicates with the first gas pump and the electromagnetic valve group respectively; The first air pump communicates with the air inlet and the air outlet respectively; The solenoid valve group is respectively communicated with the air inlet, the air outlet, the gas flow detector and the ion drift spectrum detection unit; The gas flow detector is respectively connected with the electromagnetic valve group, the filter tube and the ion drift spectrum detection unit; The filter tube communicates with the air flow detector and the second air pump respectively; The second air pump communicates with the filter tube and the ion drift spectrum detection unit respectively, and the pressure detector and the ammonia salt component are arranged between the second air pump and the ion drift spectrum detection unit , the ammonia salt part is used to release ammonia as a dopant, and solid ammonia salt is placed in it, and a first check valve is provided at the outlet of the ammonia salt part; The ion drift spectrum detection unit is respectively connected with the gas flow detector, the second gas pump, the solenoid valve group and the central processing unit, and is used to detect the gas to be measured to obtain an electronic signal of ion migration, and send it to the central processing unit; The central processing unit is connected with the ion drift spectrum detection unit, and is used to receive the electronic signal of the ion migration and convert it into a spectrogram, and compare the spectrogram with the established data spectrum library. All spectrograms of the existing substances are compared to determine the composition of the gas to be measured. 2. The chemical gas trace detector according to claim 1, wherein the ammonia salt part is a sleeve structure, has the outlet, and the outlet is provided with the first one-way valve, The sleeve structure includes an inner sleeve and an outer sleeve, the inner sleeve is sleeved in the outer sleeve, the bottom of the inner sleeve is provided with solid ammonia salt, and the inner sleeve is provided with a A second one-way valve, and a plurality of small holes are arranged on the inner cylinder between the second one-way valve and the first one-way valve. 3. The chemical gas trace detector according to claim 1 or 2, characterized in that, it also includes a fixed mount, and the fixed mount is connected to the outer wall of the non-open end of the inner cylinder and the non-open end of the outer sleeve respectively. The inner wall is fixedly connected. 4. The chemical gas trace detector according to claim 1, wherein the filter tube comprises a first filter tube and a second filter tube connected in series, and the first filter tube and the second filter tube are provided with Activated carbon. 5. The chemical gas trace detector according to claim 1, further comprising a display screen, the display screen is connected with the central processing unit, and when the component content of the detected gas to be measured exceeds the preset When the threshold is reached, a red highlight will appear on the display. 6. The chemical gas trace detector according to claim 4, characterized in that, both the first filter tube and the second filter tube are detachably connected. 7. chemical gas trace detector according to claim 1, is characterized in that, described ion drift spectrum detection unit comprises ionization source, pulse grid and ion collector, wherein The pulse grid is located between the ionization source and the ion collector; The ionization source ionizes gas molecules into positive ions and negative ions; The ion collector includes a first electrode sheet and a second electrode sheet oppositely arranged, and the plane where the first electrode sheet and the second electrode sheet are located is perpendicular to the plane where the pulse grid is located. 8. The chemical gas trace detector according to claim 7, wherein the ion drift spectrum detection unit further comprises a signal amplifier, and the signal amplifier is electrically connected to the ion collector and the central processing unit respectively. 9. The chemical gas trace detector according to claim 1, characterized in that a tritium source is used as the ionization source. 10. The chemical gas trace detector according to claim 1, characterized in that, the number of solenoid valves in the solenoid valve group is three.