A method and device for accurately measuring CO standard gas drift

Abstract

The invention discloses a method for accurately measuring the drift of CO standard gas. Firstly, a zero gas is mixed with mother gases of different concentrations by a dilution device to obtain standard gases of various concentrations, wherein the mother gas is a mixed standard gas of CO and CH4, and the zero gas does not contain CO and CH4. The concentration of CH4 in the standard gases of various concentrations is obtained by a gas concentration analyzer to infer the concentration of CO in the standard gases of various concentrations. Finally, a standard curve is established with the concentrations and indications of the standard gases of various concentrations, and the concentration of the CO primary standard gas is determined by the gas concentration analyzer to obtain the drift of the CO primary standard gas.

Description

Technical Field

[0001] The invention relates to the field of CO monitoring technology, and in particular to a method and a device for accurately measuring CO standard gas drift. Background Art

[0002] Carbon monoxide in ambient air mainly comes from industrial emissions, traffic emissions and incomplete combustion of organic fuels. The concentration of CO in urban atmosphere ranges from 300 to 500 ppb. In order to ensure the accuracy, comparability and traceability of data between different monitoring sites, the World Meteorological Organization has proposed a data quality target of 2 ppb for CO. The international comparison results show that Figure 1 As shown in the figure, since CO is unstable in high-pressure aluminum cylinders, its concentration will increase slowly. This phenomenon has become the key to restricting the accurate monitoring of CO. Specifically, the CO mass transfer system and CO 2 Similarly, the standard gas prepared by the weight method is used as the first-level standard gas for step-by-step measurement transfer. Since CO lacks stability in high-pressure aluminum gas cylinders, its first-level standard gas drifts, and the first-level standard gas prepared by the weight method cannot be repeatedly set, so its drift result cannot be identified, and the lower-level standard gas cannot be accurately revalued and the monitoring data cannot be corrected, which seriously affects the accuracy of CO monitoring data. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides an internal standard tracing method and device which can accurately measure the drift of CO standard gas.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] A method for accurately measuring CO standard gas drift comprises the following steps:

[0006] S1. Mix zero gas with mother gases of different concentrations through a dilution device to obtain standard gases of various concentrations. The mother gases are CO and CH 4 The mixed standard gas is N 2 As the matrix, zero gas is captured by the collector without CO and CH 4 ;

[0007] S2. Use gas concentration analyzer to set the concentration of various standard gases CO and CH at the same time. 4 concentration;

[0008] S3, CH 4 The response value of the primary standard gas on the gas concentration analyzer and the certificate value are used to establish a standard curve, and then the CH 4 The response value on the gas concentration analyzer is used to obtain CH in various concentrations of standard gases. 4 The certificate value of

[0009] S4, according to the CH 4 The response value and certificate value of the standard curve were used to establish the standard curve, and CO and CH 4 The ratio value of CO is used to obtain the certificate value of CO in standard gases with various concentrations;

[0010] S5. A standard curve is established based on the certified values ​​of CO in standard gases of various concentrations and the response values ​​on the gas concentration analyzer, and the response values ​​of the primary CO standard gas with different concentration gradients on the gas concentration analyzer are brought in to obtain the certified values ​​of the primary CO standard gas at different concentration gradients;

[0011] S6. The deviation between the original CO primary standard gas certificate value and the CO primary standard gas certificate value obtained in S5 is the drift of the CO primary standard gas.

[0012] Preferably, the gas concentration analyzer in S2 includes a gas analyzer for measuring CO and CH 4 High-precision gas concentration analyzer, CH 4 The concentration is measured by a high-precision methane constant value system, and the concentration of CO is calculated by the following formula:

[0013]

[0014] Where: C CO-D is the CO concentration in the standard gas, is CH in the standard gas 4 concentration, R is the CO and CH 4 Proportion.

[0015] Preferably, the dilution device includes a device for loading a zero gas cylinder and a first multi-channel valve box, as well as multiple mother gas cylinders and standard gas cylinders. The multiple mother gas cylinders are respectively connected to the gas inlet end of the first multi-channel valve box, the exhaust end of the first multi-channel valve box is connected to the first exhaust pipe, the zero gas cylinder is connected to the second exhaust pipe, the second exhaust pipe and the first exhaust pipe are both provided with mass flow meters, and are simultaneously connected to the gas injection pipe to form a dilution pipeline that cooperates with the multiple standard gas cylinders.

[0016] Preferably, the gas concentration analyzer further comprises a plurality of CO primary standard gas cylinders and CH 4 A primary standard gas cylinder, and a second multi-channel valve box, the air inlet end of the second multi-channel valve box are respectively connected to multiple standard gas cylinders, the first standard gas cylinder and the second standard gas cylinder, and the exhaust end is connected to a high-precision gas concentration analyzer to form a detection pipeline.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention prepares CO and CH 4Mix the standard gas and calculate the CO and CH 4 Concentration ratio, accurate determination of CH 4 The concentration can be accurately determined by using the newly prepared standard gas as the upper standard gas, and the first-level CO concentration can be set using the standard curve to monitor the drift of the first-level CO concentration.

[0019] 2. The present invention is based on the internal label tracer method using CH 4 Stability of the standard gas, establish CO and CH 4 concentration correlation, indirectly tracing the CO concentration to CH 4 concentration, and ultimately traceable to the gravimetric method. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the change in CO concentration since its preparation in July 2012;

[0021] Figure 2 This is the CO value traceability system framework;

[0022] Figure 3 It is a CO internal label tracer dilution device;

[0023] Figure 4 To pass CH 4 The standard curve drawn between the response value of the primary standard gas on the high-precision gas concentration analyzer and the certificate value;

[0024] Figure 5 The standard curve is drawn for the CO response value and the certificate value in various concentrations of standard gas. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0026] Example

[0027] The present application discloses a method and device for accurately measuring the drift of CO standard gas by preparing CO and CH 4 Mixed standard gas, based on CO and CH 4 The ratio of standard gas concentration can accurately determine CH 4 The concentration can be accurately determined by using the newly prepared standard gas as the upper standard gas, and the CO primary standard gas can be set using the standard curve to monitor the drift of the CO primary standard gas concentration.

[0028] Specifically, Figure 2 As shown, the value of CO primary standard gas is indirectly traced to CH 4A method for accurately determining the drift of CO standard gas comprises the following steps:

[0029] S1. Mix zero gas with mother gases of different concentrations through a dilution device to obtain standard gases of various concentrations. The mother gases are CO and CH 4 The mixed standard gas is N 2 As the matrix, zero gas is captured by the collector without CO and CH 4 ;

[0030] S2. Use gas concentration analyzer to set the concentration of various standard gases CO and CH at the same time. 4 The gas concentration analyzer includes a gas analyzer for measuring CO and CH 4 High-precision gas concentration analyzer 10, CH 4 The concentration is measured by a high-precision methane constant value system, and the concentration of CO is calculated by the following formula:

[0031]

[0032] Where: C CO-D is the CO concentration in the standard gas, is CH in the standard gas 4 concentration, R is the CO and CH 4 Proportion;

[0033] S3, CH 4 The response value of the primary standard gas on the gas concentration analyzer and the certificate value are used to establish a standard curve, and then the CH 4 The response value on the gas concentration analyzer is used to obtain CH in various concentrations of standard gases. 4 The certificate value of

[0034] S4, according to the CH 4 The response value and certificate value of the standard curve were used to establish the standard curve, and CO and CH 4 The ratio value of CO is used to obtain the certificate value of CO in standard gases with various concentrations;

[0035] S5. A standard curve is established based on the certified values ​​of CO in standard gases of various concentrations and the response values ​​on the gas concentration analyzer, and the response values ​​of the primary CO standard gas with different concentration gradients on the gas concentration analyzer are brought in to obtain the certified values ​​of the primary CO standard gas at different concentration gradients;

[0036] S6. The deviation between the original CO primary standard gas certificate value and the CO primary standard gas certificate value obtained in S5 is the drift of the CO primary standard gas.

[0037] like Figure 3As shown, the above-mentioned dilution device includes a device for loading a zero gas cylinder 1 and a first multi-channel valve box 2, as well as a plurality of mother gas cylinders 3 and a standard gas cylinder 4. The plurality of mother gas cylinders 3 are respectively connected to the gas inlet end of the first multi-channel valve box 2, and the exhaust end of the first multi-channel valve box 2 is connected to a first exhaust pipe. The zero gas cylinder 1 is connected to a second exhaust pipe. The second exhaust pipe and the first exhaust pipe are both provided with a mass flow meter 5, and are simultaneously connected to a gas injection pipe 6 to form a dilution pipeline that cooperates with the plurality of standard gas cylinders 4. The above-mentioned gas concentration analyzer also includes a plurality of CO primary standard gas cylinders 7 and CH for loading different concentration gradients. 4 The first-level standard gas cylinder 8 and the second multi-channel valve box 9, the air inlet end of the second multi-channel valve box 9 are respectively connected to multiple standard gas cylinders 4, the first standard gas cylinder 7 and the second standard gas cylinder 8, and the exhaust end is connected to a high-precision gas concentration analyzer 10 to form a detection pipeline.

[0038] The experimental process is as follows:

[0039] Three bottles of CO and CH 4 The mother gas 3 with different concentration ratios passes through the first multi-channel valve box 2 and the flow rate is precisely controlled by the mass flow meter 5. The flow rate of the zero gas 1 is precisely controlled by another mass flow meter 5. A series of CO / CH4 standard gases 4 with different concentrations are formulated through the flow ratio of the mother gas and the zero gas.

[0040] The second multi-channel valve box 9 is connected to the high-precision gas concentration analyzer 10 and the CO primary standard gas cylinder 7 and CH 4 The first-level standard gas cylinder 8 is set by a high-precision gas concentration analyzer 10. 4 concentrations, inferring a range of CO and CH 4 The concentration of standard gas 4 is then measured with a series of CO and CH 4 The concentration of the CO primary standard gas is determined by establishing a calibration curve based on the concentration and indication of the standard gas 4, thereby obtaining the drift of the CO primary standard gas.

[0041] Application Examples

[0042] The internal label tracer method was used to 4 Stability of the standard gas, establish CO and CH 4 concentration correlation, indirectly tracing the CO concentration to CH 4 concentration, and ultimately traceable to the gravimetric method.

[0043] CO in N 2 To ensure the stability of the matrix concentration in high-pressure aluminum bottles, three bottles with different concentrations and N 2 The high concentration of CH in the matrix 4 Mixed with CO as the mother gas, CH 4 The concentration and concentration ratio of CO are shown in Table 1:

[0044] Table 1 shows the concentration and ratio of CO and CH4 in the mother gas

[0045]

[0046] Zero gas does not contain CO after being captured by the collector. 4 The concentration is determined by a high-precision methane setting system By using the dilution device to change the flow ratio of the mother gas and the zero gas, a series of standard gases with different dilution ratios can be obtained, and the CO and CH concentrations can be determined simultaneously using a high-precision gas concentration analyzer. 4 , specifically, CH 4 The concentration is measured by a high-precision methane constant value system, and the CO concentration is calculated according to the following formula:

[0047]

[0048] Where: C CO-D is the CO concentration in the standard gas, is CH in the standard gas 4 concentration, R is the CO and CH 4 Proportion.

[0049] Different concentration gradients of CH 4 The concentration information of the primary standard gas and the CH 4 The concentration information is shown in Table 2 and Table 3 respectively:

[0050] Table 2 CH at different concentration gradients 4 Primary standard gas concentration information

[0051]

[0052] Table 3 CH in various concentrations of standard gases 4 Concentration Information

[0053]

[0054] CH 4 The standard curve is drawn by the response value of the primary standard gas on the high-precision gas concentration analyzer and the certificate value. Figure 4 As shown in the figure, y = 1.0028x + 0.005, CH 4 The response value on the high-precision gas concentration analyzer is substituted into the drawn standard curve y = 1.0028x + 0.005 to calculate CH 4 The certificate value of the dilution gas, among which the response value of CH4 primary standard gas on the high-precision gas concentration analyzer is shown in Table 4. 4 The response values ​​of the dilution gas are shown in Table 5.4 The certified values ​​of diluent gases are shown in Table 6:

[0055] Table 4CH 4 Primary standard gas concentration analyzer response value and certificate value

[0056]

[0057] Table 5 CH in various concentrations of standard gases 4 Gas concentration analyzer response value

[0058]

[0059] The standard gas CH 4 The response value on the high-precision gas concentration analyzer is substituted into the standard curve y=1.0028x+0.005 to calculate the standard gas CH 4 The certificate values ​​are shown in Table 6:

[0060] Table 6 CH in various concentrations of standard gases 4 Certificate Value

[0061]

[0062]

[0063] Through the CO and CH 4 The certificate value of CO in the standard gas is calculated by the ratio shown in Table 7:

[0064] Table 7 CO certificate values ​​of various concentrations of standard gases

[0065]

[0066] like Figure 5 As shown, the standard curve is drawn with the response values ​​of various concentrations of standard gases on the high-precision gas concentration analyzer and the certificate values ​​of CO. The response values ​​and certificate values ​​of CO on the gas concentration analyzer of various concentrations of standard gases are shown in Table 8:

[0067] Table 8 Response values ​​and certificate values ​​of standard gas CO at various concentrations

[0068]

[0069]

[0070] The standard curve of CO response value and certificate value of standard gas of various concentrations is y=0.9944x-1.2952. Substitute the response value of CO primary standard gas with different concentration gradients on the high-precision gas concentration analyzer into the standard curve. The calculated certificate value of CO primary standard gas is shown in Table 9:

[0071] Table 9 shows the response value and certificate value of CO primary standard gas

[0072]

[0073] The deviation between the calculated certificate value of the CO primary standard gas and the certificate value of the original CO primary standard gas on the high-precision gas concentration analyzer is the drift of the CO primary standard gas. For details, see Table 10:

[0074] Table 10 shows the concentration information of CO primary standard gas

[0075]

[0076] The certificate values ​​of the original CO primary standard gas on the high-precision gas concentration analyzer were 110.83ppb, 252.69ppb, 411.21ppb, 520.39ppb, and 660.52ppb, respectively. The deviations from the certificate values ​​of the CO primary standard gas in Table 9 are the drifts of the CO primary standard gas, which are 1.18ppb, 2.96ppb, 1.70ppb, 3.54ppb, and 5.33ppb, respectively, as shown in Table 10.

[0077] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for accurately measuring CO standard gas drift, characterized in that: The steps include: S1. Mixing zero gas with mother gas of different concentrations through a dilution device to obtain standard gas of various concentrations, wherein the mother gas is a mixed standard gas of CO and CH4, and is based on N2. The zero gas is captured by a capture agent and does not contain CO and CH4; S2. Using a gas concentration analyzer, the concentrations of the standard gases CO and CH4 of various concentrations are simultaneously determined; S3, establishing a standard curve with the response values ​​and certificate values ​​of the CH4 primary standard gas with different concentration gradients on the gas concentration analyzer, and substituting the response values ​​of CH4 in the standard gas with various concentrations on the gas concentration analyzer to obtain the certificate values ​​of CH4 in the standard gas with various concentrations; S4, establishing a standard curve according to the response values ​​and certificate values ​​of CH4 in the standard gas of various concentrations, and substituting the ratio values ​​of CO and CH4 in the standard gas of various concentrations into the standard curve to obtain the certificate values ​​of CO in the standard gas of various concentrations; S5. Establish a standard curve according to the certified values ​​of CO in the standard gas of various concentrations and the response values ​​on the gas concentration analyzer, and bring in the response values ​​of the primary standard gas of CO with different concentration gradients on the gas concentration analyzer to obtain the certified values ​​of the primary standard gas of CO at different concentration gradients; S6. The deviation between the original CO primary standard gas certificate value and the CO primary standard gas certificate value obtained in S5 is the drift of the CO primary standard gas.

2. The method for accurately measuring CO standard gas drift according to claim 1, characterized in that: The gas concentration analyzer in S2 includes a high-precision gas concentration analyzer (10) for measuring CO and CH4. The CH4 concentration of the standard gas is measured by a high-precision methane constant value system, and the CO concentration is calculated by the following formula: Where: C CO-D is the CO concentration in the standard gas, is the CH4 concentration in the standard gas, and R is the ratio of CO to CH4 in the mother gas.

3. The method for accurately measuring CO standard gas drift according to claim 2, characterized in that: The dilution device comprises a device for loading a zero gas cylinder (1) and a first multi-channel valve box (2), as well as a plurality of mother gas cylinders (3) and a standard gas cylinder (4). The plurality of mother gas cylinders (3) are respectively connected to the gas inlet end of the first multi-channel valve box (2), the exhaust end of the first multi-channel valve box (2) is connected to a first exhaust pipe, the zero gas cylinder (1) is connected to a second exhaust pipe, the second exhaust pipe and the first exhaust pipe are both provided with a mass flow meter (5), and are simultaneously connected to a gas injection pipe (6) to form a dilution pipeline that cooperates with the plurality of standard gas cylinders (4).

4. The method for accurately measuring CO standard gas drift according to claim 3, characterized in that: The gas concentration analyzer further comprises a plurality of CO primary standard gas cylinders (7) and CH4 primary standard gas cylinders (8) for loading different concentration gradients, and a second multi-channel valve box (9); the gas inlet end of the second multi-channel valve box (9) is respectively connected to the plurality of standard gas cylinders (4), the CO primary standard gas cylinders (7) and the CH4 primary standard gas cylinders (8), and the gas outlet end is connected to the high-precision gas concentration analyzer (10) to form a detection pipeline.

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