Automatic zero-calibration Fourier infrared gas analyzer and its analysis method

Abstract

The present invention belongs to the technical field of analytical detection, and particularly relates to an automatic zero-calibration Fourier transform infrared gas analyzer and its analysis method. The gas analyzer includes a sample gas analysis flow path composed of a sample gas sampling head, a bag filter, a three-pass filter, a sampling solenoid valve, a sampling pump, a flow meter, and an infrared gas cell connected in sequence; an air zero-calibration branch is connected between the sampling solenoid valve and the sampling pump, and the air zero-calibration branch includes an air sampling head, a condensation filter, a zero-calibration adsorption tube, and a zero-calibration solenoid valve connected in sequence; the zero-calibration adsorption tube includes a gas purification area, a CO2 absorption area, an activated carbon area, an ammonia removal area, and a molecular sieve area distributed in sequence along the air inlet direction, and both ends of each area are encapsulated with absorbent cotton. Through the coordinated cooperation of the bag filter, the three-pass filter, and the condensation filter, the present invention has a comprehensive adsorption effect, can adsorb particulate matters with different molecular sizes, and remove water vapor at the same time, which is beneficial to improving the detection accuracy of the analyzer and extending its service life.

Description

Technical Field

[0001] The invention belongs to the technical field of analysis and detection, and in particular relates to an automatic zero-calibration Fourier infrared gas analyzer and an analysis method thereof. Background Art

[0002] Fourier infrared analyzers are easily affected by factors such as ambient temperature, resulting in data drift. In order to obtain accurate concentration data, pure air needs to be introduced regularly to calibrate the instrument to zero. This process is often affected by the purity of the incoming air, and manual monitoring and zeroing are required. If the purity of the incoming air is high, an automatic zeroing mechanism can be set to reduce the labor cost of operation and maintenance. Currently, activated carbon is mainly used to adsorb impurity gases in the ambient air, but the removal degree is limited. After removal, the impurity content reaches the ppm level. In order to further improve the detection accuracy, the purity of the zeroing air still needs to be further improved. In addition, the degree of water removal of the incoming air also affects the detection accuracy.

[0003] In addition, since the detection working conditions are often around harsh environments such as chemical plants, smoke exhaust or sewage outlets, when sampling, the sample gas is mixed with particulate matter, the particle size of the particulate matter is at the micron level, and the size of gas molecules is at the micron level. The particles entering the analyzer are not conducive to gas detection and affect the test results. In serious cases, the analyzer may be damaged, which is not conducive to long-term and effective monitoring. Therefore, it is necessary to remove the particulate matter in the sample gas in advance. Summary of the invention

[0004] Based on the above-mentioned shortcomings and deficiencies in the prior art, one of the objects of the present invention is to at least solve one or more of the above-mentioned problems in the prior art. In other words, one of the objects of the present invention is to provide an automatic zero-calibration Fourier infrared gas analyzer and an analysis method thereof that meet one or more of the above-mentioned requirements.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0006] An automatic zero-calibration Fourier infrared gas analyzer comprises a sample gas analysis flow path formed by a sample gas sampling head, a capsule filter, a three-way filter, a sampling solenoid valve, a sampling pump, a flow meter and an infrared gas chamber connected in sequence;

[0007] Among them, an air zeroing branch is connected between the sampling solenoid valve and the sampling pump, and the air zeroing branch includes an air sampling head, a condensation filter, a zeroing adsorption tube and a zeroing solenoid valve connected in sequence;

[0008] The zero-adjusting adsorption tube comprises a gas purification zone, a CO2 absorption zone, an activated carbon zone, an ammonia removal zone and a molecular sieve zone which are sequentially distributed along the air intake direction, and both ends of each zone are respectively encapsulated by absorbent cotton.

[0009] As a preferred solution, the pore sizes of the CO2 absorption zone, activated carbon zone, ammonia removal zone and analytical sieve zone decrease in sequence.

[0010] As a preferred embodiment, the activated carbon zone is used to filter substances with a pore size greater than 50 nm, and the molecular sieve zone is used to filter substances with a pore size greater than 0.5 nm.

[0011] As a preferred embodiment, the ammonia removal zone is filled with anhydrous potassium dihydrogen phosphate.

[0012] As a preferred embodiment, the molecular sieve zone is filled with 5A molecular sieve.

[0013] As a preferred solution, the capsule filter uses a hydrophobic polytetrafluoroethylene filter membrane to filter particles larger than 0.2 μm.

[0014] As a preferred solution, the three-way filter is a columnar structure, the gas enters from the top and flows out from the side, and there is a drain port at the bottom, and the drain port is connected to a peristaltic pump;

[0015] The three-way filter uses a PE filter element to filter particles larger than 0.1μm.

[0016] The present invention also provides an analysis method for the automatic zero-calibration Fourier infrared gas analyzer as described in any of the above schemes, comprising the following steps:

[0017] S1, open the zeroing solenoid valve and close the sampling solenoid valve;

[0018] S2, start the sampling pump and collect the zero-point spectrum;

[0019] S3, close the zeroing solenoid valve and open the sampling solenoid valve;

[0020] S4, collecting the measurement spectrum of the sample gas to be measured, and calculating the measurement concentration of the sample gas to be measured based on the zero-point spectrum and the measurement spectrum;

[0021] S5. Determine whether the zero adjustment period has been reached; if so, go to step S1.

[0022] As a preferred solution, step S4 specifically includes:

[0023] S41. Calculate the absorbance based on the zero-point spectrum and the measured spectrum :

[0024] ;

[0025] in, is the zero-point spectrum, To measure the spectrum, is the preset absorbance spectrum of saturated water vapor at 40°, T is the condensation temperature of the condensation filter;

[0026] S42, based on the measured absorbance and the standard absorbance of the i-th sample gas to be tested and its corresponding standard concentration Calculate the measured concentration of the i-th sample gas to be tested :

[0027] ;

[0028] Among them, the proportional coefficient of the i-th sample gas to be tested is according to Calculated.

[0029] As a preferred solution, the proportionality coefficient Calculated by the least squares method.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The present invention has a comprehensive adsorption effect through the coordinated cooperation of the capsule filter, the three-way filter and the condensation filter, and can adsorb particles of different molecular sizes and remove water vapor at the same time, which is beneficial to improve the detection accuracy of the analyzer and extend the service life;

[0032] (2) The zero-adjustment adsorption tube of the present invention is sequentially distributed along the air intake direction with a gas purification zone, a CO2 absorption zone, an activated carbon zone, an ammonia removal zone and a molecular sieve zone. The gas purification zone causes an oxidation reaction of volatile substances in the air, thereby increasing their molecular size, which is beneficial to subsequent substance filtration; then, the CO2 in the air is absorbed, and substances with a pore size greater than 50 nm are filtered through activated carbon, and then anhydrous potassium dihydrogen phosphate is used as an ammonia removal agent, and finally, substances with a pore size greater than 0.5 nm are removed through a molecular sieve, thereby effectively improving the purity of the air;

[0033] (3) The present invention corrects the measured absorbance by combining the condensation temperature of the condensation filter and the preset absorbance spectrum of saturated water vapor at 40°, thereby effectively improving the accuracy of measuring the concentration of the sample gas to be tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 1 is a gas flow diagram of the automatic zero-calibration Fourier infrared gas analyzer of Example 1 of the present invention;

[0035] Figure 2 is a schematic cross-sectional structure diagram of a zero-calibration adsorption tube according to Example 1 of the present invention;

[0036] Figure 3 It is a flow chart of the analysis method of the automatic zero-calibration Fourier infrared gas analyzer of Example 1 of the present invention. DETAILED DESCRIPTION

[0037] In order to more clearly illustrate the embodiments of the present invention, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other accompanying drawings and other implementation methods can be obtained based on these accompanying drawings without creative work.

[0038] Embodiment 1:

[0039] like Figure 1 As shown, the automatic zeroing Fourier infrared gas analyzer of this embodiment includes a sample gas analysis flow path and an air zeroing branch; wherein, the light source and detector of the gas analyzer are not described in detail here, and reference may be made to the prior art.

[0040] Specifically, the sample gas analysis flow path includes a sample gas sampling head 1, a capsule filter 2, a three-way filter 3, a sampling solenoid valve 4, a sampling pump 5, a flow meter 6 and an infrared gas chamber 7 connected in sequence. Among them, an air zeroing branch is led out between the sampling solenoid valve 4 and the sampling pump 5, and the air zeroing branch includes an air sampling head 8, a condensation filter 9, a zeroing adsorption tube 10 and a zeroing solenoid valve 11 connected in sequence.

[0041] The zero-adjusting adsorption tube 10 of this embodiment is divided into five filling areas according to the air delivery direction. The first filling area is the air purification area, and the filling materials of the remaining areas are all physical filter layers. Figure 2 As shown, it specifically includes a gas purification zone 10a, a CO2 absorption zone 10b, an activated carbon zone 10c, an ammonia removal zone 10d and a molecular sieve zone 10e which are sequentially distributed along the air intake direction, and both ends of each zone are respectively encapsulated by absorbent cotton 10f. Among them, the pore sizes of the CO2 absorption zone, the activated carbon zone, the ammonia removal zone and the analytical sieve zone are successively reduced, which can improve the air filtration purity.

[0042] The above-mentioned gas purification zone is filled with existing conventional gas purifiers, which can oxidize conventional gases in the ambient air; the above-mentioned CO2 absorption zone is filled with CO2 absorbent for absorbing CO2 in the air; the above-mentioned activated carbon zone is used to filter substances with a pore size greater than 50nm, and the above-mentioned ammonia removal zone is filled with anhydrous potassium dihydrogen phosphate as an ammonia removal agent; the above-mentioned molecular sieve zone is filled with 5A molecular sieve for filtering substances with a pore size greater than 0.5nm.

[0043] The capsule filter of this embodiment adopts a disc-shaped design, with the inlet and outlet symmetrically distributed up and down. The specific structure can refer to the existing technology. It is small in size and light in weight, with a diameter of 64 mm and a filtration area of ​​20 cm 2 , 6mm pipe connection, using hydrophobic polytetrafluoroethylene PTFE filter membrane; ambient air can filter particles larger than 0.2μm through the capsule filter.

[0044] The three-way filter of this embodiment is made of glass with a columnar structure. Gas enters from the top and flows out from the side. There is a drain outlet at the bottom, which is connected to the peristaltic pump 12. The three-way filter adopts a PE filter element, which can filter particles larger than 0.1μm.

[0045] The drain port of the condensation filter 9 of this embodiment is connected to a peristaltic pump 13 for easy drainage.

[0046] Based on the filtration and dehumidification of the ambient air by the above-mentioned air zeroing branch, the purity of the zeroing air can be guaranteed, and automatic zeroing can be achieved without manual monitoring.

[0047] like Figure 3 As shown, the analysis method of the automatic zero calibration Fourier infrared gas analyzer of this embodiment includes the following steps:

[0048] (1) Open the zeroing solenoid valve and close the sampling solenoid valve;

[0049] (2) Start the sampling pump and collect the zero-point spectrum;

[0050] Specifically, after starting the sampling pump, wait for several minutes (e.g., 2 minutes) before collecting the zero-point spectrum;

[0051] (3) Close the zeroing solenoid valve and open the sampling solenoid valve;

[0052] (4) Collecting the measurement spectrum of the sample gas to be tested, and calculating the measurement concentration of the sample gas to be tested based on the zero-point spectrum and the measurement spectrum;

[0053] Specifically, the absorbance is first calculated based on the zero-point spectrum and the measured spectrum. :

[0054] ;

[0055] in, is the zero-point spectrum, To measure the spectrum, is the preset absorbance spectrum of saturated water vapor at 40°, T is the condensation temperature of the condensation filter;

[0056] Then, the absorbance was measured and the standard absorbance of the i-th sample gas to be tested and its corresponding standard concentration Calculate the measured concentration of the i-th sample gas to be tested :

[0057] ;

[0058] Among them, the proportional coefficient of the i-th sample gas to be tested is according to Calculated by least squares method;

[0059] (5) Determine whether the zero adjustment period has been reached; if so, go to step (1).

[0060] In order to verify the effectiveness of the analysis method of the above-mentioned automatic zeroing Fourier infrared gas analyzer, this embodiment analyzes and verifies three different types of gases to compare the measured concentrations before and after automatic zeroing. The results are shown in Table 1. The accuracy of the measured concentration after automatic zeroing is effectively improved by the analysis method of this embodiment.

[0061] Table 1 Measured concentrations of three different types of gases

[0062] .

[0063] Embodiment 2:

[0064] The automatic zero calibration Fourier infrared gas analyzer of this embodiment is different from that of Embodiment 1 in that:

[0065] The zero-adjusting adsorption tube can also add activated carbon and molecular sieve filling areas based on the actual application needs on the basis of the five filling areas, further improving the accuracy of air filtration and improving the cleanliness of the air;

[0066] For other structures, please refer to Example 1.

[0067] The above description is only a detailed description of the preferred embodiments and principles of the present invention. For ordinary technicians in this field, according to the ideas provided by the present invention, there will be changes in the specific implementation methods, and these changes should also be regarded as the protection scope of the present invention.

Claims

1. An analysis method of an automatic zero-calibration Fourier infrared gas analyzer, wherein the automatic zero-calibration Fourier infrared gas analyzer comprises a sample gas sampling head, a capsule filter, a three-way filter, a sampling solenoid valve, a sampling pump, a flow meter and an infrared gas chamber connected in sequence to form a sample gas analysis flow path; wherein, An air zeroing branch is connected between the sampling solenoid valve and the sampling pump, and the air zeroing branch includes an air sampling head, a condensation filter, a zeroing adsorption tube and a zeroing solenoid valve connected in sequence; the zeroing adsorption tube includes a gas purification area, a CO2 absorption area, an activated carbon area, an ammonia removal area and a molecular sieve area distributed in sequence along the air intake direction, and both ends of each area are respectively encapsulated by absorbent cotton, characterized in that the analysis method includes the following steps: S1, open the zeroing solenoid valve and close the sampling solenoid valve; S2, start the sampling pump and collect the zero-point spectrum; S3, close the zeroing solenoid valve and open the sampling solenoid valve; S4, collecting the measurement spectrum of the sample gas to be measured, and calculating the measurement concentration of the sample gas to be measured based on the zero-point spectrum and the measurement spectrum; S5, judging whether the zero adjustment period has been reached; if so, going to step S1; The step S4 specifically includes: S41. Calculate the absorbance based on the zero-point spectrum and the measured spectrum in, is the zero-point spectrum, To measure the spectrum, is the preset absorbance spectrum of saturated water vapor at 40°, T is the condensation temperature of the condensation filter; S42, based on the measured absorbance and the standard absorbance of the i-th sample gas to be tested and its corresponding standard concentration Calculate the measured concentration C of the i-th sample gas to be tested i : Among them, the proportionality coefficient k i according to Calculated.

2. The analysis method according to claim 1, characterized in that The proportionality coefficient k i Calculated by the least squares method.

3. The analysis method according to claim 1, characterized in that The pore sizes of the CO2 absorption zone, the activated carbon zone, the ammonia removal zone and the analysis sieve zone decrease in sequence.

4. The analysis method according to claim 2, characterized in that The activated carbon area is used to filter substances with a pore size greater than 50 nm, and the molecular sieve area is used to filter substances with a pore size greater than 0.5 nm.

5. The analysis method according to claim 1, 3 or 4, characterized in that: The ammonia removal zone is filled with anhydrous potassium dihydrogen phosphate.

6. The analysis method according to claim 1, 3 or 4, characterized in that: The molecular sieve zone is filled with 5A molecular sieve.

7. The analysis method according to claim 1, 3 or 4, characterized in that: The capsule filter adopts a hydrophobic polytetrafluoroethylene filter membrane to filter particles larger than 0.2 μm.

8. The analysis method according to claim 1, 3 or 4, characterized in that: The three-way filter is a columnar structure, gas enters from the top and flows out from the side, and there is a drain port at the bottom, which is connected to a peristaltic pump; The three-way filter uses a PE filter element to filter particles larger than 0.1μm.

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