Benzene concentration detection method and device

Abstract

The invention relates to a benzene concentration detection method and device.The method is carried out through the benzene concentration detection device, the benzene concentration detection device comprises a filtering module and a gas sensor, the filtering module comprises a gas inlet, a gas outlet, a first branch and a second branch, the first branch and the second branch are connected with the gas inlet and the gas outlet, and the second branch comprises an interference gas filtering assembly; the gas sensor is connected with the gas outlet; the method comprises the following steps: controlling all to-be-detected gas to pass through a first branch, and obtaining a first response value measured by a gas sensor; according to the first flow distribution proportion, controlling part of the to-be-detected gas to enter the first branch, controlling the rest part of the to-be-detected gas to enter the second branch, and obtaining a second response value measured by the gas sensor; and determining the concentration of benzene in the to-be-detected gas according to the first response value and the second response value. By controlling the distribution proportion of the gas flow, the concentration of the benzene can be measured for multiple times, and the first response value and the second response value are obtained according to the multiple times of measurement, so that the concentration of the benzene is determined more accurately.

Description

Technical Field

[0001] The present application relates to the field of chemical technology, and in particular to a method and device for detecting benzene concentration. Background Art

[0002] Benzene is a common volatile organic compound that is widely found in the petrochemical, coating, solvent, pharmaceutical and other industries. Since benzene is carcinogenic and toxic, long-term exposure to high concentrations of benzene is seriously harmful to human health. Therefore, accurate and rapid detection of benzene concentrations in the environment is crucial to safeguard public health, industrial safety and environmental protection.

[0003] Currently, when a portable instrument (PID detector) is used to measure benzene in benzene series, a benzene filter tube is directly connected in front of the instrument. When the benzene series gas passes through the filter tube at a certain flow rate, the toluene, ethylbenzene, xylene and other gases in the benzene series will react with the strong acid and strong oxidant in the filter tube and be consumed, while benzene does not undergo a chemical reaction and can be detected by the PID through the filter tube.

[0004] However, the filter tube of this filtering method can only be used once. Discarding it during measurement will cause environmental pollution, and the one-time measurement method also affects the accuracy of the test results. Summary of the invention

[0005] The purpose of the present application is to provide a benzene concentration detection method and device, which controls the distribution ratio of the gas flow rate, obtains a first response value and a second response value based on multiple measurements, and thus determines the concentration of benzene more accurately.

[0006] The present application provides a benzene concentration detection method, which is performed by a benzene concentration detection device, the benzene concentration detection device comprising a filter module and a gas sensor, the filter module comprising an air inlet, an air outlet, a first branch connecting the air inlet and the air outlet, a second branch connecting the air inlet and the air outlet, the second branch comprising an interfering gas filter component; the gas sensor is connected to the air outlet; the method comprises:

[0007] Control all the gas to be tested to pass through the first branch, and obtain the first response value measured by the gas sensor;

[0008] According to the first flow distribution ratio, part of the gas to be measured is controlled to enter the first branch, and the rest of the gas enters the second branch, and a second response value measured by the gas sensor is obtained;

[0009] The concentration of benzene in the gas to be measured is determined according to the first response value and the second response value.

[0010] In one embodiment, determining the concentration of benzene in the gas to be measured according to the flow distribution ratio, the first response value and the second response value includes:

[0011] The concentration of benzene in the gas to be measured is determined according to the first flow distribution ratio, the known sensitivity of the gas sensor, the response baseline, the first response value and the second response value.

[0012] In one embodiment, the concentration of benzene in the gas to be measured is determined according to the first flow distribution ratio, the known sensitivity of the gas sensor, the response baseline, the first response value, and the second response value, and is calculated using the following formula:

[0013] C a =[(1+β1)(S2-S0)-β1(S1-S0)] / k a

[0014] Among them, β1 represents the first flow distribution ratio, C a represents the concentration of benzene, S1 represents the first response value, S2 represents the second response value, S0 represents the response baseline, k a Represents the sensitivity of the gas sensor.

[0015] In one embodiment, the benzene concentration detection method further includes:

[0016] According to the second flow distribution ratio, part of the gas to be measured is controlled to enter the first branch, and the rest of the gas enters the second branch, and a third response value measured by the gas sensor is obtained;

[0017] Wherein, determining the concentration of benzene in the gas to be measured according to the first response value and the second response value includes:

[0018] The concentration of benzene in the gas to be measured is determined according to the known sensitivity of the gas sensor, the first flow distribution ratio, the second flow distribution ratio, the first response value, the second response value and the third response value.

[0019] In one embodiment, the concentration of benzene in the gas to be measured is determined according to the known sensitivity of the gas sensor, the first flow distribution ratio, the second flow distribution ratio, the first response value, the second response value and the third response value, and is calculated using the following formula:

[0020] C a =[(1+β1)(S2-S0)-β1(S1-S0)] / k a

[0021] C a =[(1+β2)(S3-S0)-β2(S1-S0)] / k a

[0022] Among them, β1 represents the first flow distribution ratio, β2 represents the second flow distribution ratio, C arepresents the concentration of benzene, S1 represents the first response value, S2 represents the second response value, S3 represents the second response value, S0 represents the response base, k a Represents the sensitivity of the gas sensor.

[0023] In one embodiment, the first branch further includes a first flow sensor, and the second branch further includes a second flow sensor; the method further includes:

[0024] Acquire the flow rate of the first branch detected by the first flow sensor and the flow rate of the second branch detected by the second flow sensor;

[0025] A flow distribution ratio between the first branch and the second branch is determined according to the flow of the first branch and the flow of the second branch.

[0026] In one embodiment, the sensitivity and response baseline of the gas sensor are determined in the following manner:

[0027] Introducing clean gas into the filter module, controlling all the clean gas to pass through the first branch, and obtaining a response baseline of the clean gas measured by the gas sensor;

[0028] A sample gas with a known benzene concentration is introduced into the filter module, and the sample gas is controlled to pass through the first branch, and a sample response value of the sample gas measured by the gas sensor is obtained;

[0029] The sensitivity of the gas sensor is calculated based on the response baseline, known benzene concentration, and sample response value.

[0030] In one embodiment, when the interfering gas is completely filtered and benzene is partially filtered, the concentration of benzene in the gas to be measured is determined according to the first response value and the second response value, including:

[0031] Determine the benzene conversion rate based on the flow rate of the second branch;

[0032] The concentration of benzene in the gas to be measured is determined according to the benzene conversion rate, the first flow distribution ratio, the known sensitivity of the gas sensor, the response baseline, the first response value and the second response value.

[0033] In one embodiment, the concentration of benzene in the gas to be measured is determined according to the benzene conversion rate, the first flow distribution ratio, the known sensitivity of the gas sensor, the response baseline, the first response value, and the second response value, and is calculated using the following formula:

[0034]

[0035] Among them, β1 represents the first flow distribution ratio, ρ represents the benzene conversion rate, C a represents the concentration of benzene, S1 represents the first response value, S2 represents the second response value, S0 represents the response baseline, ka Represents the sensitivity of the gas sensor.

[0036] In one embodiment, when the interfering gas is partially filtered and benzene is not filtered, the concentration of benzene in the gas to be measured is determined according to the first response value and the second response value, including:

[0037] Determine the interference gas conversion rate according to the flow rate of the second branch;

[0038] The concentration of benzene in the gas to be measured is determined according to the interfering gas conversion rate, the first flow distribution ratio, the known sensitivity of the gas sensor, the response baseline, the first response value and the second response value.

[0039] In one embodiment, the concentration of benzene in the gas to be measured is determined according to the interfering gas conversion rate, the first flow distribution ratio, the sensitivity of the known gas sensor, the response baseline, the first response value and the second response value, and is calculated using the following formula:

[0040]

[0041] Among them, β1 represents the first flow distribution ratio, ρ represents the benzene conversion rate, and ρ a represents the interfering gas conversion rate, C a represents the concentration of benzene, S1 represents the first response value, S2 represents the second response value, S0 represents the response baseline, k a Represents the sensitivity of the gas sensor.

[0042] In one embodiment, when the interfering gas is partially filtered and the benzene is partially filtered, the concentration of benzene in the gas to be measured is determined according to the first response value and the second response value, including:

[0043] According to the flow rate of the second branch, the benzene conversion rate and the interfering gas conversion rate are determined;

[0044] The concentration of benzene in the gas to be measured is determined according to the benzene conversion rate and the interfering gas conversion rate, the first flow distribution ratio, the known sensitivity of the gas sensor, the response baseline, the first response value and the second response value.

[0045] In one embodiment, the concentration of benzene in the gas to be measured is determined according to the benzene conversion rate and the interfering gas conversion rate, the first flow distribution ratio, the sensitivity of the known gas sensor, the response baseline, the first response value and the second response value, and is calculated using the following formula:

[0046]

[0047] Among them, β1 represents the first flow distribution ratio, ρ represents the benzene conversion rate, and ρ a represents the interfering gas conversion rate, C arepresents the concentration of benzene, S1 represents the first response value, S2 represents the second response value, S0 represents the response baseline, k a Represents the sensitivity of the gas sensor.

[0048] In one embodiment, the interfering gas conversion rate satisfies the following characteristic curve:

[0049] ρ a =φ a (F2)

[0050] Among them, ρ a is the conversion rate of the interfering gas, F2 is the flow rate of the second branch, φ a is the characteristic curve of the interfering gas. Different characteristic curves correspond to different interfering gases.

[0051] The present application also provides a benzene concentration detection device, comprising:

[0052] A filter module, the filter module comprises an air inlet, an air outlet, a first branch and a second branch;

[0053] The first branch is connected to the air inlet and the air outlet;

[0054] The second branch includes an interfering gas filtering component, and the interfering gas filtering component is connected to the air inlet and the air outlet;

[0055] Gas sensor, the gas sensor is connected to the gas outlet.

[0056] In one embodiment, the benzene concentration detection device further includes:

[0057] The pump is connected to the gas sensor and is used for providing pressure to make the gas pass through the filter module and the gas sensor.

[0058] In one embodiment, the first branch includes:

[0059] A gas resistance component, one end of which is connected to the air inlet and the other end is connected to the air outlet, and is used to control and adjust the gas flow.

[0060] In one embodiment, the second branch includes:

[0061] A flow regulating component, one end of which is connected to the air inlet and the other end is connected to the interfering gas filtering component, and is used to control and adjust the gas flow.

[0062] In one embodiment, the first branch also includes: a first gas flow sensor, a gas resistance element and the first gas flow sensor are connected in sequence, the gas resistance element is connected to the air inlet, the first gas flow sensor is connected to the air outlet, and the first gas flow sensor is used to measure the gas flow of the first branch.

[0063] In one embodiment, the second branch also includes: a second gas flow sensor, a flow regulating component, an interfering gas filter component and a second gas flow sensor are connected in sequence, the flow regulating component is connected to the air inlet, the second gas flow sensor is connected to the air outlet, and the second gas flow sensor is used to measure the flow of the second branch.

[0064] In one embodiment, the first branch includes a vent pipe, one end of which is connected to the air outlet;

[0065] The second branch also includes a gas resistance component, the gas resistance component and the interference gas filter component are connected in parallel, and one end of the gas resistance component and the interference gas filter component are respectively connected to the gas outlet;

[0066] The device also includes: a three-way valve, a first end of the three-way valve is connected to the air inlet, a second end is connected to the first branch, and a third end is connected to the second branch. The three-way valve is used to control the flow direction of the gas.

[0067] The beneficial effects of the present application compared with the prior art are: the present application can control the distribution ratio of the gas flow in the first branch and the second branch, obtain the first response value of the first branch and the second response value of the second branch through multiple measurements, and calculate the concentration of benzene based on the obtained first response value and the second response value. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0069] Figure 1 It is a schematic diagram of a benzene concentration detection device provided in one embodiment of the present application;

[0070] Figure 2 This is a schematic diagram of the steps of a benzene concentration detection method provided in an embodiment of the present application;

[0071] Figure 3 This is a schematic diagram of a benzene concentration detection device scheme 1 provided in an embodiment of the present application;

[0072] Figure 4 This is a schematic diagram of a second embodiment of a benzene concentration detection device provided in an embodiment of the present application;

[0073] Figure 5 This is a schematic diagram of the detailed steps of the benzene concentration detection method provided in one embodiment of the present application;

[0074] Figure 6This is a schematic diagram of the sensitivity detection steps of a gas sensor provided in one embodiment of the present application;

[0075] Figure 7 This is a schematic diagram of a third filtering module solution provided in an embodiment of the present application.

[0076] The above drawings include the following reference numerals:

[0077] 1-filter module; 2-first branch; 3-second branch; 11-flow regulating component; 12-interference gas filter component; 13-second flow sensor; 14-gas resistance; 15-first flow sensor; 20-gas sensor; 30-pump; 40-three-way valve; 50-ventilation pipe. DETAILED DESCRIPTION

[0078] The terms “first”, “second”, “third”, etc. are only used for distinguishing descriptions and do not indicate the order of arrangement, nor can they be understood as indicating or implying relative importance.

[0079] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0080] In the description of the present application, it should be noted that the terms "inside", "outside", "left", "right", "up", "down", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the products of the present application are usually placed when in use. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present application.

[0081] In the description of this application, unless otherwise clearly specified and limited, the terms "set", "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements.

[0082] The present application provides a method for detecting benzene concentration. Figure 1 Schematic diagram of a benzene concentration detection device provided in one embodiment of the present application. Figure 1As shown, the method is carried out by a benzene concentration detection device, which includes a filter module 1 and a gas sensor 20, the filter module 1 includes an air inlet, an air outlet, a first branch 2 connecting the air inlet and the air outlet, a second branch 3 connecting the air inlet and the air outlet, and the second branch 3 includes an interfering gas filter component 12; the gas sensor 20 is connected to the air outlet; wherein the gas sensor 20 is used to obtain a response value of the gas passing through the first branch 2 or the second branch 3; by controlling the gas flow ratio of the two branches, it can be known that the proportion of the interfering gas reduced after the gas passes through the filter module 1; the principle of the interfering gas filter component 12 filtering benzene interfering substances is chemical reaction, adsorption, dissolution, thermal decomposition, selective catalytic reaction, etc.

[0083] In one embodiment, Figure 2 : is a schematic diagram of the steps of a benzene concentration detection method provided in an embodiment of the present application, such as Figure 2 As shown, the method includes:

[0084] Step S200: Control all the gas to be measured to pass through the first branch 2, and obtain the first response value S1 measured by the gas sensor 20; wherein the gas to be measured includes benzene and interfering gas, and the first response value S1 is the response value of all gases in the gas to be measured.

[0085] Step S210: Using a first flow distribution ratio, control part of the gas to be tested to enter the first branch 2, and the rest to enter the second branch 3, and obtain a second response value S2 measured by the gas sensor 20; wherein the first flow distribution ratio is set by the user based on experience.

[0086] Step S220: Determine the concentration of benzene in the gas to be tested according to the first response value S1 and the second response value S2.

[0087] In one embodiment, when the interfering gas is completely filtered and benzene is partially filtered, the concentration of benzene in the gas to be measured is determined according to the flow distribution ratio, the first response value S1 and the second response value S2, including: determining the concentration of benzene in the gas to be measured according to the first flow distribution ratio, the known sensitivity ka of the gas sensor 20, the response baseline, the first response value S1 and the second response value S2.

[0088] In one embodiment, Figure 3 : is a schematic diagram of a benzene concentration detection device scheme 1 provided in an embodiment of the present application, such as Figure 3 As shown, the second branch 3 also includes a flow regulating component 11, one end of the flow regulating component 11 is connected to the air inlet, and the other end is connected to the interfering gas filtering component, which is used to control the gas flow of the first branch 2 and the second branch 3.

[0089] Figure 4 This is a schematic diagram of a second scheme of a benzene concentration detection device provided in an embodiment of the present application. Figure 5FIG. 1 is a schematic diagram of the detailed steps of the benzene concentration detection method provided in an embodiment of the present application. Figure 4-5 As shown, the first branch 2 further includes a first flow sensor 15, and the second branch 3 further includes a second flow sensor 13; after step S200, after step S210, the following are also included:

[0090] Step S410: acquiring the flow rate of the first branch 2 detected by the first flow sensor 15 and the flow rate of the second branch 3 detected by the second flow sensor 13;

[0091] Step S420: Determine the flow distribution ratio between the first branch 2 and the second branch 3 according to the flow of the first branch 2 and the flow of the second branch 3.

[0092] in, Figure 6 Schematic diagram of the sensitivity detection steps of a gas sensor provided in an embodiment of the present application. Figure 6 As shown, the sensitivity k of the known gas sensor 20 is a And the response baseline is obtained by the following steps:

[0093] Step S500: close the flow regulating component 11, introduce clean gas into the first branch 2 and the gas sensor 20, remove the gas remaining in the first branch 2 and the gas sensor 20, measure and record the reading of the gas sensor 20, which is the clean gas response value S0; obtain the response baseline of the clean gas measured by the gas sensor 20;

[0094] Step S510: close the flow regulating component 11, and introduce a sample gas with a known benzene concentration into the first branch 2. After the sample gas with a known benzene concentration passes through the gas sensor 20, measure and record the reading of the gas sensor 20. The reading is the sample response value S of the sample gas with a known benzene concentration; wherein the benzene concentration is C a ;

[0095] Step S520: Based on the clean gas response value S0 and the benzene concentration C a Calculate the sensor sensitivity k a , the calculation formula is:

[0096]

[0097] Among them, S0 represents the response baseline, k a represents the sensitivity of the gas sensor 20, and S represents the response value of benzene gas with known concentration.

[0098] In one embodiment, the flow distribution is performed by the flow regulating component 11. If the flow distribution ratio is determined, the flow distribution ratio β1 is determined according to the first flow distribution ratio β1 and the known sensitivity k of the gas sensor 20. a, response baseline, the first response value S1 and the second response value S2, determine the concentration C of benzene in the gas to be tested a , calculated using the following formula:

[0099] S1-S0=k a C a +k x C x ; (2)

[0100] S2-S0=k a C a +k x C x2 ; (3)

[0101]

[0102] Combining formulas (1), (2), (3), and (4), we can obtain:

[0103] C a =[(1+β1)(S2-S0)-β1(S1-S0)] / k a ; (6)

[0104] Where β1 represents the first flow distribution ratio, C a represents the concentration of benzene, S1 represents the first response value, S2 represents the second response value, S0 represents the response baseline, k a represents the sensitivity of the gas sensor 20, C x is the original concentration of the interfering gas, C x2 is the concentration of interfering gas after filtration; k x is the sensitivity of the gas sensor 20 to the interfering gas x.

[0105] If the flow distribution ratio is not determined, the first flow sensor 15 is used to detect and obtain the flow of the first branch 2, and the second flow sensor 13 is used to detect and obtain the flow of the second branch 3;

[0106]

[0107] Combining formulas (1), (2), (3), and (5), we can obtain:

[0108]

[0109] Among them, C x is the original concentration of the interfering gas, C x2 is the concentration of interfering gas after filtration; k a represents the sensitivity of the gas sensor 20, F 22 is the flow rate of the second branch 3, F 21is the flow rate of the first branch 2, F 22 / F 21 is the flow distribution ratio, C a represents the concentration of benzene, S1 represents the first response value, S2 represents the second response value, S0 represents the response baseline, k a represents the sensitivity of the gas sensor 20 .

[0110] In one embodiment, the benzene concentration detection method further includes: when the clean response value (i.e., the response baseline) of the clean gas cannot be obtained, performing a third measurement, changing the control parameters of the flow regulating component 11, and if the flow distribution ratio is not determined, controlling part of the gas to be measured to enter the first branch 2 and the rest to enter the second branch 3 according to the determined second flow distribution ratio β2, and obtaining a third response value S3 measured by the gas sensor 20; the concentration C of benzene in the gas to be measured a , can be calculated by formula (8):

[0111] C a =[(1+β2)(S3-S0)-β2(S1-S0)] / k a ; (8)

[0112] Wherein, β2 represents the second flow distribution ratio, C a represents the concentration of benzene, S1 represents the first response value, S2 represents the second response value, S3 represents the third response value, S0 represents the response baseline, k a represents the sensitivity of the gas sensor 20 .

[0113] If the flow distribution ratio is not determined, the first flow sensor 15 is used to detect the flow of the first branch 2, and the second flow sensor 13 is used to detect the flow of the second branch 3; the concentration of benzene in the gas to be measured C a , can be calculated by formula (9):

[0114]

[0115] Among them, F 31 represents the flow rate of the first branch 2 and F 32 represents the flow of the second branch 3, C a represents the concentration of benzene, S1 represents the first response value, S2 represents the second response value, S3 represents the third response value, S0 represents the response baseline, k a represents the sensitivity of the gas sensor 20 .

[0116] The combined formulas (6) and (8) or (7) and (9) eliminate the unknown clean gas response value S0, and according to the known sensitivity k of the gas sensor 20, a, the second flow distribution ratio β2 or the flow F of the first branch 2 31 and the flow rate F of the second branch 3 32 , the first response value S1, the second response value S2 and the third response value S3, determine the concentration C of benzene in the gas to be tested a .

[0117] In one embodiment, when the interfering gas is completely filtered and benzene is partially filtered, for example, when the mixed gas containing the interfering gas passes through the filtering module 1, the interfering gas therein is completely catalytically oxidized, while benzene is not oxidized, step S220: determining the concentration of benzene in the gas to be tested according to the first response value S1 and the second response value S2 further includes:

[0118] The benzene conversion rate is determined according to the flow rate of the second branch 3; wherein, within a certain concentration and flow rate range, the oxidation of benzene can be regarded as being controlled by the catalyst surface chemical process, and its conversion rate ρ (variation range: 0-1) is independent of the benzene concentration, but is related to the gas flow rate passing through, satisfying the monotonic equation (10):

[0119] ρ=φ(F2); (10)

[0120] Among them, formula (5) can be corrected as

[0121] S2-S0=k a C a2 +k x C x2 ; (11)

[0122] Among them, F2 is the total flow of the two branches after part of the gas to be tested enters the first branch and the rest enters the second branch, C x2 is the concentration of interfering gas after filtration, k x is the sensitivity of the gas sensor 20 to gas X, C x2 Still satisfying equation (5), C a2 is the concentration of benzene after partial filtration, C a2 It can be expressed as:

[0123]

[0124] Combining formulas (2), (5), (10), and (11), we can obtain:

[0125]

[0126] or

[0127]

[0128] Where ρ is the benzene conversion rate, F 22is the flow rate of the second branch 3. When benzene passes completely, ρ = 0, F 21 is the flow rate of the first branch 2, F 22 / F 21 is the flow distribution ratio, C a represents the concentration of benzene, S1 represents the first response value, S2 represents the second response value, S0 represents the response baseline, k a represents the sensitivity of the gas sensor 20; through formula (13) or formula (14), according to the benzene conversion rate ρ, the flow rate F of the first branch 2 21 , the flow rate of the second branch 3 F 22 , the sensitivity k of the known gas sensor 20 a , response baseline, the first response value S1 and the second response value S2, determine the concentration C of benzene in the gas to be tested a .

[0129] In one embodiment, when the interfering gas is partially filtered and benzene is not filtered, for example, when the interfering gas (such as toluene) in the mixed gas can only be partially catalytically oxidized after passing through the catalyst of the filtering module 1, while benzene is not oxidized; step S220: determining the concentration of benzene in the gas to be measured according to the first response value S1 and the second response value S2 also includes:

[0130] According to the flow rate of the second branch 3, the conversion rate of the interfering gas is determined; wherein, within a certain concentration and flow range, the oxidation of toluene can also be regarded as being controlled by the chemical process on the catalyst surface, and the conversion rate of toluene ρ a (Variation range: 0~1) is independent of the toluene concentration, but is related to the gas flow rate passing through, satisfying the monotonic equation (10):

[0131] ρ a =φ a (F2); (15)

[0132] Among them, φ a (F2) is a characteristic curve obtained when the interfering gas (here, toluene) passes only through the second branch 3. Through this characteristic curve, the conversion rate of the interfering gas (here, the conversion rate of toluene) can be calibrated in advance;

[0133] Formula (4) can be modified as follows:

[0134]

[0135] Combining formulas (2), (3) and (16), we can obtain:

[0136]

[0137] or

[0138]

[0139] Among them, ρ a is the interfering gas conversion rate (here is the toluene conversion rate), F 22 is the flow rate of the second branch 3, F 21 is the flow rate of the first branch 2, C x2 is the concentration of interfering gas after filtration, k a represents the sensitivity of the gas sensor 20. When toluene is completely oxidized, ρ a =1, formulas (17) and (18) can be simplified to formula (5) (5A); according to the interfering gas conversion rate ρ a , the known flow distribution ratio or the flow F of the first branch 2 21 and the flow rate F of the second branch 3 22 , the sensitivity k of the known gas sensor 20 a , response baseline, the first response value S1 and the second response value S2, to determine the concentration of benzene in the gas to be tested.

[0140] In one embodiment, when the interfering gas is partially filtered and benzene is partially filtered, for example, when the interfering gas (such as toluene) and benzene in the mixed gas can only be partially catalytically oxidized after passing through the catalyst of the filtering module 1; step S220: determining the concentration of benzene in the gas to be tested according to the first response value S1 and the second response value S2 also includes:

[0141] According to the flow rate of the second branch 3, the benzene conversion rate and the interfering gas conversion rate are determined;

[0142] According to the benzene conversion rate ρ and the interfering gas conversion rate ρa, the first flow distribution ratio β1 or the flow rate F of the first branch 2 21 and the flow rate F of the second branch 3 22 , the sensitivity k of the known gas sensor 20 a , the response baseline, the first response value S1 and the second response value S2, and the concentration of benzene in the gas to be measured is determined according to formula (19) or (20):

[0143]

[0144] or

[0145]

[0146] Where, ρ is the benzene conversion rate, ρ a is the interfering gas conversion rate, F 22 is the flow rate of the second branch 3, F 21 is the flow rate of the first branch 2, F 22 / F 21 is the flow distribution ratio, β1 represents the first flow distribution ratio, Ca represents the concentration of benzene, S1 represents the first response value, S2 represents the second response value, S0 represents the response baseline, k a Represents the sensitivity of the gas sensor 20; in a catalytic reaction chamber with a fixed structure, corresponding to a specific catalyst and working temperature, the benzene conversion rate ρ and the interference gas conversion rate ρ a are not only related to their own reaction characteristics, but also related to the gas flow rate flowing through. They satisfy equations (10) and (15). This equation can be recorded as a characteristic reaction equation of different gases in the catalytic reaction chamber for subsequent use when needed.

[0147] In one embodiment, if there is only one interfering gas X in the gas to be measured, its response equation satisfies the relationship:

[0148]

[0149] or

[0150]

[0151] Among them, F 22 is the flow rate of the second branch 3, F 21 is the flow rate of the first branch 2, φ x (F 22 ) is the interference gas conversion rate, the known flow distribution ratio or the flow F of the first branch 2 21 and the flow rate F of the second branch 3 22 , ka is the sensitivity of the gas sensor 20, S x1 First response value, S x2 is the second response value, S0 is the response base (i.e., clean gas response value), C a2 is the concentration of benzene after partial filtration.

[0152] Among them, formulas (21) and (22) are characteristic response equations of gas X passing through the benzene concentration detection device at different flow rates, which are monotonic functions of flow rate F22 (or proportional valve control parameters). In the calibration stage, since different gases have different characteristic curves, the characteristic curves of gas X at different flow rates obtained by multi-flow measurement can be used to determine what kind of gas gas X is.

[0153] Furthermore, since the conversion efficiency of the gas passing through the catalyst is also a monotonic function of the reaction temperature, further measurements can be performed by adjusting the temperature of the catalytic reaction chamber to change the measurement state, and gas identification and measurement can also be performed by selecting different catalytic chamber temperatures.

[0154] In one embodiment, the present application also provides a benzene concentration detection device, such as Figure 1As shown, the device includes: a filter module 1 and a gas sensor 20, the filter module 1 includes an air inlet, an air outlet, a first branch 2 and a second branch 3; the first branch 2 connects the air inlet and the air outlet; the second branch 3 includes and interfering gas filter components 12 connected in sequence, the interfering gas filter component 12 is connected to the air inlet and the air outlet; the gas sensor 20 is connected to the air outlet.

[0155] Among them, the interfering gas filtering component 12 is a micro-reaction chamber or a catalytic reaction chamber, etc., and a catalyst or filtering material is arranged in the catalytic reaction chamber. The interfering gas filtering component 12 can selectively filter the gas, and the gas sensor 20 is a PID (Photoionization Detector), MOS (Metal-Oxide-Semiconductor), etc.

[0156] In one embodiment, the principle of filtering the interfering gas by the filter module 1 is a selective catalytic reaction. By selecting a suitable catalyst and reaction temperature, the mixed gas passes through the catalyst at a certain flow rate, so that toluene, ethylbenzene, xylene, etc. in the interfering gas can be completely oxidized, while benzene is basically not oxidized.

[0157] In one embodiment, if Figure 1 As shown, the benzene concentration detection device also includes: a pump 30, which is connected to the gas sensor 20 and is used to provide pressure to allow the gas to pass through the filter module 1 and the gas sensor 20; wherein the pump 30 is a micro air pump 30.

[0158] In one embodiment, if Figure 1 As shown, the first branch 2 includes a gas resistance element 14, one end of the gas resistance element 14 is connected to the air inlet, and the other end is connected to the air outlet, which is used to control and adjust the gas flow.

[0159] In one embodiment, if Figure 3 As shown, the second branch 3 includes a flow regulating component 11 , which is a proportional valve for controlling the flow of gas through the first branch 2 and the second branch 3 .

[0160] In one embodiment, if Figure 4 As shown, the first branch 2 also includes: a first gas flow sensor, a gas resistance element 14 is connected to the first gas flow sensor in sequence, the gas resistance element 14 is connected to the air inlet, the first gas flow sensor is connected to the air outlet, and the first gas flow sensor is used to measure the gas flow of the first branch 2; the second branch 3 also includes: a second gas flow sensor, a flow regulating component 11, an interfering gas filtering component 12 and a second gas flow sensor are connected in sequence, the flow regulating component 11 is connected to the air inlet, the second gas flow sensor is connected to the air outlet, and the second gas flow sensor is used to measure the flow of the second branch 3.

[0161] In one embodiment, the gas sensor 20 uses a PID sensor, the catalyst in the catalytic reaction chamber is PtRu (platinum ruthenium) or CeO2 (cerium oxide), the temperature is controlled to be 125°C, and the flow rate of the gas to be tested through the second branch 3 is controlled to be 50ml / min by the flow regulating component 11, and the flow rate through the first branch 2 is controlled to be 450ml / min. The selective detection of benzene in the benzene series can be achieved through formula (5).

[0162] In one embodiment, if Figure 1 As shown, the first branch 2 and the second branch 3 are connected to the first air inlet and the air outlet, one end of the gas sensor 20 is connected to the air outlet, and the other end is connected to the second air inlet; wherein, the first branch 2 is a gas resistance member 14, the second branch 3 is an interference gas filter assembly 12, the interference gas filter assembly 12 is a catalytic reaction chamber or a micro reaction chamber, and the gas sensor 20 is a pump-suction PID instrument; before use, calibrate the gas flow ratio through the two branches, set the reaction temperature as needed, control the gas to be tested to enter the pump-suction PID instrument through the second air inlet, and obtain the first response value; control the gas to be tested to enter the first branch 2 through the first air inlet according to the flow ratio set in advance, and the rest enters the second branch 3, obtain the first response value, and calculate the concentration of benzene by the following formula:

[0163] C a =[(1+β)(S2-S0) - β(S1-S0)] / k a ;

[0164] Among them, C a is the concentration of benzene; β is the gas flow ratio, S2 is the second response value, S1 is the first response value, S0 is the response value of clean gas passing through PID, k a is the sensitivity of the pump-suction PID instrument.

[0165] In one embodiment, Figure 7 Schematic diagram of filtering module scheme 3 provided in one embodiment of the present application, such as Figure 7 As shown, the first branch 2 includes a ventilation pipe 50, one end of which is connected to the air outlet; the second branch 3 also includes a gas resistance 14, the gas resistance 14 and the interference gas filter assembly 12 are connected in parallel, and one end of the gas resistance 14 and the interference gas filter assembly 12 are connected to the air outlet; the filter module 1 also includes a three-way valve 40 for controlling the flow direction of the gas; the first end of the three-way valve 40 is connected to the air inlet, the second end is connected to the first branch 2 (that is, connected to the gas resistance 14 and the other end of the interference gas filter assembly 12), and the third end is connected to the second branch 3.

[0166] Among them, the vent pipe 50 is an instrument gas path resistance component, which is used to adjust the resistance of the two branches, the interfering gas filter component 12 is a catalytic reaction chamber or a micro reaction chamber, and the gas sensor 20 is a pump-suction PID instrument. Before use, the gas flow ratio through the two branches is calibrated, and the three-way valve 40 is used to control the gas to be tested to pass through the instrument gas path resistance component and the pump-suction PID instrument in sequence to obtain the first response value; the three-way valve 40 is used to control the gas to be tested to enter the interfering gas filter component 12 according to the flow ratio set in advance, and the rest enters the gas resistance component 14 to obtain the second response value, and the concentration of benzene is calculated by the following formula:

[0167] C a =[(1+β)(S2-S0)-β(S1-S0)] / k a

[0168] Among them, C a is the concentration of benzene; β is the gas flow ratio, S2 is the second response value, S1 is the first response value, S0 is the PID zero point, k a is the sensitivity of the pump-suction PID instrument.

[0169] The benzene concentration detection device of the present application has a small size and low power consumption. By controlling the distribution ratio of the gas to be tested, the mixed gas component identification and concentration measurement can be realized. The device can be designed as an independent accessory and directly connected to an existing portable PID analyzer when used. The bypass design of the micro-reaction chamber or the catalytic reaction chamber does not affect the gas sampling speed of the existing portable instrument and has little impact on its performance parameters.

[0170] It should be noted that, in the absence of conflict, the features in the embodiments of the present application can be combined with each other. The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for detecting benzene concentration, characterized in that: The method is performed by a benzene concentration detection device, the benzene concentration detection device comprises a filter module and a gas sensor, the filter module comprises an air inlet, an air outlet, a first branch connecting the air inlet and the air outlet, a second branch connecting the air inlet and the air outlet, the second branch comprising an interfering gas filter assembly; The gas sensor is connected to the gas outlet; the method comprises: Controlling all the gas to be tested to pass through the first branch, and obtaining a first response value measured by the gas sensor; Controlling a portion of the gas to be measured to enter the first branch and the rest to enter the second branch at a first flow distribution ratio, and obtaining a second response value measured by the gas sensor; The concentration of benzene in the gas to be measured is determined according to the first response value and the second response value.

2. The method for detecting benzene concentration according to claim 1, characterized in that: Determining the concentration of benzene in the gas to be measured according to the flow distribution ratio, the first response value and the second response value includes: The concentration of benzene in the gas to be measured is determined according to the first flow distribution ratio, the known sensitivity of the gas sensor, the response baseline, the first response value, and the second response value.

3. The benzene concentration detection method according to claim 2, characterized in that: According to the first flow distribution ratio, the known sensitivity of the gas sensor, the response baseline, the first response value and the second response value, the concentration of benzene in the gas to be measured is determined and calculated using the following formula: C a =[(1+β1)(S2-S0)-β1(S1-S0)] / k a Where β1 represents the first flow distribution ratio, C a represents the concentration of benzene, S1 represents the first response value, S2 represents the second response value, S0 represents the response baseline, k a Represents the sensitivity of the gas sensor.

4. The method for detecting benzene concentration according to claim 1, characterized in that: Also includes: Controlling part of the gas to be measured to enter the first branch and the rest to enter the second branch at a second flow distribution ratio, and obtaining a third response value measured by the gas sensor; Wherein, determining the concentration of benzene in the gas to be measured according to the first response value and the second response value includes: The concentration of benzene in the gas to be measured is determined based on the known sensitivity of the gas sensor, the first flow distribution ratio, the second flow distribution ratio, the first response value, the second response value and the third response value.

5. The method for detecting benzene concentration according to claim 4, characterized in that: The concentration of benzene in the gas to be measured is determined based on the known sensitivity of the gas sensor, the first flow distribution ratio, the second flow distribution ratio, the first response value, the second response value and the third response value, and is calculated using the following formula: Wherein, β1 represents the first flow distribution ratio, β2 represents the second flow distribution ratio, C a represents the concentration of benzene, S1 represents the first response value, S2 represents the second response value, S3 represents the third response value, S0 represents the response base, k a Represents the sensitivity of the gas sensor.

6. The method for detecting benzene concentration according to claim 1, characterized in that: The first branch further includes a first flow sensor, and the second branch further includes a second flow sensor; the method further includes: Acquire the flow rate of the first branch detected by the first flow sensor and the flow rate of the second branch detected by the second flow sensor; A flow distribution ratio between the first branch and the second branch is determined according to the flow of the first branch and the flow of the second branch.

7. The method for detecting benzene concentration according to claim 2, characterized in that: The sensitivity and response baseline of the gas sensor are determined in the following manner: Passing clean gas into the filter module, controlling all the clean gas to pass through the first branch, and obtaining a response baseline of the clean gas measured by the gas sensor; Passing a sample gas with a known benzene concentration into the filtering module, controlling the sample gas to all pass through the first branch, and obtaining a sample response value of the sample gas measured by the gas sensor; The sensitivity of the gas sensor is calculated based on the response baseline, the known benzene concentration, and the sample response value.

8. The method for detecting benzene concentration according to claim 1, characterized in that: When the interfering gas is completely filtered and benzene is partially filtered, determining the concentration of benzene in the gas to be measured according to the first response value and the second response value includes: Determining the benzene conversion rate according to the flow rate of the second branch; The concentration of benzene in the gas to be measured is determined according to the benzene conversion rate, the first flow distribution ratio, the known sensitivity of the gas sensor, the response baseline, the first response value, and the second response value.

9. The method for detecting benzene concentration according to claim 8, characterized in that: The concentration of benzene in the gas to be measured is determined according to the benzene conversion rate, the first flow distribution ratio, the known sensitivity of the gas sensor, the response baseline, the first response value and the second response value, and is calculated using the following formula: Where, β1 represents the first flow distribution ratio, ρ represents the benzene conversion rate, C a represents the concentration of benzene, S1 represents the first response value, S2 represents the second response value, S0 represents the response baseline, k a Represents the sensitivity of the gas sensor.

10. The method for detecting benzene concentration according to claim 1, characterized in that: When the interfering gas is partially filtered and benzene is not filtered, determining the concentration of benzene in the gas to be measured according to the first response value and the second response value includes: Determining the interference gas conversion rate according to the flow rate of the second branch; The concentration of benzene in the gas to be measured is determined according to the interfering gas conversion rate, the first flow distribution ratio, the known sensitivity of the gas sensor, the response baseline, the first response value and the second response value.

11. The method for detecting benzene concentration according to claim 10, characterized in that: The concentration of benzene in the gas to be measured is determined according to the interfering gas conversion rate, the first flow distribution ratio, the known sensitivity of the gas sensor, the response baseline, the first response value and the second response value, and is calculated using the following formula: Wherein, β1 represents the first flow distribution ratio, ρ represents the benzene conversion rate, and ρ a represents the interfering gas conversion rate, C a represents the concentration of benzene, S1 represents the first response value, S2 represents the second response value, S0 represents the response baseline, k a Represents the sensitivity of the gas sensor.

12. The method for detecting benzene concentration according to claim 1, characterized in that: When the interfering gas is partially filtered and the benzene is partially filtered, determining the concentration of benzene in the gas to be measured according to the first response value and the second response value includes: Determining the benzene conversion rate and the interfering gas conversion rate according to the flow rate of the second branch; The concentration of benzene in the gas to be measured is determined according to the benzene conversion rate and the interfering gas conversion rate, the first flow distribution ratio, the known sensitivity of the gas sensor, the response baseline, the first response value and the second response value.

13. The method for detecting benzene concentration according to claim 12, characterized in that: The concentration of benzene in the gas to be measured is determined according to the benzene conversion rate and the interfering gas conversion rate, the first flow distribution ratio, the known sensitivity of the gas sensor, the response baseline, the first response value and the second response value, and is calculated using the following formula: Wherein, β1 represents the first flow distribution ratio, ρ represents the benzene conversion rate, and ρ a represents the interfering gas conversion rate, C a represents the concentration of benzene, S1 represents the first response value, S2 represents the second response value, S0 represents the response baseline, k a Represents the sensitivity of the gas sensor.

14. The method for detecting benzene concentration according to claim 13, characterized in that: The interfering gas conversion rate satisfies the following characteristic curve: r a =φ a (F2) Among them, ρ a is the conversion rate of the interfering gas, F2 is the flow rate of the second branch, φ a is the characteristic curve of the interfering gas. Different characteristic curves correspond to different interfering gases.

15. A benzene concentration detection device, characterized in that: include: A filter module, the filter module comprising an air inlet, an air outlet, a first branch and a second branch; The first branch connects the air inlet and the air outlet; The second branch includes an interfering gas filter component, and the interfering gas filter component is connected to the air inlet and the air outlet; A gas sensor is connected to the gas outlet.

16. The benzene concentration detection device according to claim 15, characterized in that: Also includes: A pump is connected to the gas sensor and is used to provide pressure to allow gas to pass through the filter module and the gas sensor.

17. The benzene concentration detection device according to claim 15, characterized in that: The first branch comprises: A gas resistance component, one end of which is connected to the air inlet, and the other end of which is connected to the air outlet, is used to control and adjust the gas flow.

18. The benzene concentration detection device according to claim 15, characterized in that: The second branch comprises: A flow regulating component, one end of which is connected to the air inlet, and the other end of which is connected to the interfering gas filtering component, is used to control and adjust the gas flow.

19. The benzene concentration detection device according to claim 17, characterized in that: The first branch also includes: a first gas flow sensor, the gas resistance element and the first gas flow sensor are connected in sequence, the gas resistance element is connected to the air inlet, the first gas flow sensor is connected to the air outlet, and the first gas flow sensor is used to measure the gas flow of the first branch.

20. The benzene concentration detection device according to claim 18, characterized in that: The second branch also includes: a second gas flow sensor, the flow regulating component, the interfering gas filtering component and the second gas flow sensor are connected in sequence, the flow regulating component is connected to the air inlet, the second gas flow sensor is connected to the air outlet, and the second gas flow sensor is used to measure the flow of the second branch.

21. The benzene concentration detection device according to claim 15, characterized in that: The first branch includes a vent pipe, one end of which is connected to the air outlet; The second branch further comprises a gas resistance element, the gas resistance element and the interference gas filter assembly are connected in parallel, and one end of the gas resistance element and the interference gas filter assembly are respectively connected to the gas outlet; The device also includes: a three-way valve, a first end of the three-way valve is connected to the air inlet, a second end is connected to the first branch, and a third end is connected to the second branch, and the three-way valve is used to control the flow direction of the gas.

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