Mixed gas detection device and detection method

Abstract

The present application discloses a mixed gas detection device and a detection method. The mixed gas detection device includes: a micro-catalytic chamber and a detection chamber. The micro-catalytic chamber is provided with a heating module and a catalytic material, and the catalytic material is provided on the heating module; the detection chamber is connected to the micro-catalytic chamber, and the detection chamber is provided with a detection element. The detection element is used to detect the relative response value of each gas component in the mixed gas to be tested after catalytic oxidation at different temperatures. The mixed gas detection device of the present application can be used for mixed gas component identification and concentration measurement, and is particularly used in the measurement of benzene in a benzene series mixed gas and has achieved application results. The mixed gas detection device of the present application can achieve miniaturization, low power consumption, high efficiency and rapid analysis, and has high detection accuracy.

Description

Technical Field

[0001] The present application relates to the technical field of gas concentration detection, and in particular to a mixed gas detection device and detection method. Background Art

[0002] Because benzene, toluene, and xylene often coexist, with benzene being the most toxic, practical applications require accurate benzene concentration measurement in environments where all three gases coexist. Since these three gases share similar chemical properties, multiple sensors with different characteristics must be assembled into an array for detection. However, this sensor structure is bulky, requires a large volume of gas for measurement, and the measurement results are heavily dependent on the sensor's stability and reliability. Advances in MEMS processing have enabled integrated designs and miniaturization of semiconductor and carbon nanotube sensors, but the performance stability of the sensing units themselves remains poor. Traditional, more stable and reliable gas sensors, such as electrochemical, photoionization, and NIDR, remain difficult to miniaturize. Therefore, a sensor structure is needed that can detect and analyze the composition of mixed gases. Summary of the Invention

[0003] The purpose of this application is to provide a mixed gas detection device and detection method, which analyzes the components of the mixed gas by measuring the sensitivity response value of each component in the mixed gas after catalytic oxidation at different temperatures. The device has a simple structure and high detection accuracy.

[0004] The embodiment of the present application is implemented as follows:

[0005] In a first aspect, the present application provides a mixed gas detection device, comprising:

[0006] A micro-catalytic chamber, wherein a heating module and a catalytic material are provided in the micro-catalytic chamber, and the catalytic material is provided on the heating module;

[0007] The detection chamber is connected to the micro-catalytic chamber. A detection element is provided in the detection chamber. The detection element is used to detect the relative response value of each gas component in the mixed gas to be tested after catalytic oxidation at different temperatures.

[0008] In one embodiment, the mixed gas detection device further includes:

[0009] The flow control mechanism is connected to the micro-catalytic chamber and is used to control the flow of the mixed gas entering the micro-catalytic chamber.

[0010] In one embodiment, the flow control mechanism includes:

[0011] an air resistance regulating assembly connected to the inlet of the microcatalytic chamber; and

[0012] A power source is connected to the air resistance adjustment component.

[0013] In one embodiment, the flow control mechanism includes:

[0014] The mass flow control component is connected to the inlet of the microcatalytic chamber.

[0015] In one embodiment, the catalytic material is a nano-catalytic material.

[0016] In one embodiment, the detection element is one of PID, FID, and MOS.

[0017] In a second aspect, the present application provides a mixed gas detection method, comprising:

[0018] The heating module controls the micro-catalytic chamber to reach different preset temperatures, wherein the heating module is coated with a catalytic material;

[0019] Continuously introduce the mixed gas to be tested into the testing chamber;

[0020] At different preset temperatures, the detection element detects the mixed gas to be tested after catalytic oxidation at different preset temperatures, and obtains the relative response value of each gas component in the mixed gas to be tested.

[0021] In one embodiment, before the heating module controls the micro-catalytic chamber to reach different preset temperatures, the method further includes:

[0022] The flow control mechanism controls the mixed gas to be tested to enter the micro-catalytic chamber and the detection chamber according to a preset flow value.

[0023] In one embodiment, the heating module controls the micro-catalytic chamber to reach different preset temperatures, including:

[0024] The heating module controls the micro-catalytic chamber to reach different preset temperatures at preset increasing temperature values according to a first heating mode, wherein the preset temperatures include a preset temperature lower limit value and a preset temperature upper limit value;

[0025] Among them, the preset temperature lower limit value is used to indicate that the most active gas among the components of the mixed gas to be tested that need to be detected at the current temperature is only partially converted under the current test conditions, and the remaining gas components are not converted; the preset temperature upper limit value is used to indicate that the most stable gas among the components of the mixed gas to be tested that need to be detected at the current temperature is only partially converted or fully converted under the current test conditions.

[0026] In one embodiment, the heating module controls the micro-catalytic chamber to reach different preset temperatures, including:

[0027] The heating module controls the micro-catalytic chamber to reach different preset temperatures at a constant heating rate according to the second heating mode.

[0028] Compared with the prior art, the present invention offers the following advantages: the mixed gas detection device can be used to identify mixed gas components and measure their concentration, particularly effectively measuring benzene in benzene-based mixed gases. The mixed gas detection device also achieves miniaturization, low power consumption, high efficiency, and rapid analysis with high detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. 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 relevant drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 A schematic structural diagram of a mixed gas detection device provided in one embodiment of the present application;

[0031] Figure 2 A flow chart of a mixed gas detection method provided in one embodiment of the present application;

[0032] Figure 3 A schematic diagram of the relative response values of isobutylene, toluene, xylene, and benzene after passing through a 1% Pt / Mn2O3 nanocatalyst at different conversion temperatures provided in an embodiment of the present application;

[0033] Figure 4 for Figure 3 The relative response value change spectrum of isobutylene, toluene, xylene and benzene after passing through Pt / Mn2O3 nanocatalyst at different conversion temperatures;

[0034] Figure 5 A schematic diagram of the conversion rates of CO, formaldehyde, and alcohol on 1% Ag / CeO2 at different conversion temperatures provided by another embodiment of the present application;

[0035] Figure 6 A schematic diagram of the relative response values of CO and HCHO at different conversion temperatures provided in an embodiment of the present application;

[0036] Figure 7 for Figure 6 The relative response change value spectrum of CO and HCHO at different conversion temperatures.

[0037] icon:

[0038] 1-Mixed gas detection device; 11-Micro-catalytic chamber; 111-Heating module; 112-Catalytic material; 12-Detection chamber; 121-Detection element; 13-Flow control mechanism. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0040] Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and should not be understood as indicating or implying relative importance.

[0041] The technical solution of this application will be clearly and completely described below with reference to the accompanying drawings.

[0042] Please refer to Figure 1 , which is a structural schematic diagram of a mixed gas detection device 1 provided in the present application, the mixed gas detection device 1 includes: a micro-catalytic chamber 11, a detection chamber 12 and a flow control mechanism; wherein, a heating module 111 and a catalytic material 112 are provided in the micro-catalytic chamber 11, and the catalytic material 112 is provided on the heating module 111. The detection chamber 12 is connected to the outlet of the micro-catalytic chamber 11, and a detection element 121 is provided in the detection chamber 12, and the detection element 121 is used to detect the relative response value of each gas component in the mixed gas to be tested after catalytic oxidation at different temperatures. The flow control mechanism 13 is connected to the inlet of the micro-catalytic chamber 11, and is used to control the flow of the mixed gas entering the micro-catalytic chamber 11.

[0043] In one embodiment, heating module 111 is a heater with a heating and temperature-raising function, preferably a MEMS (Microelectro Mechanical Systems) heater. MEMS heaters can rapidly and programmably raise and lower the temperature. During experiments, the MEMS heater structure can be optimized based on the desired temperature control requirements, temperature control speed, stability, and catalyst loading.

[0044] In one embodiment, the flow control mechanism 13 includes: an air resistance adjustment component and a power source, wherein the air resistance adjustment component is connected to the inlet of the micro-catalytic chamber 11; and the power source is connected to the air resistance adjustment component. The structure of the air resistance adjustment component adopts the structure of the prior art and is not further described here.

[0045] In another embodiment, the flow control mechanism 13 includes a mass flow control element connected to the inlet of the microcatalytic chamber 11. The mass flow control element can be a mass flow controller, and the structure of the mass flow controller adopts the structure of the prior art and is not repeated here.

[0046] In one embodiment, the catalytic material 112 is a nano-catalytic material, which is applied evenly on the surface of the MEMS micro-heater.

[0047] In one embodiment, the detection element 121 is a highly sensitive sensor responsive to the mixed gas to be detected, such as a PID (Photo Ionization Detector), a FID (Flame Ionization Detector), or a MOS (Metal Oxide Semiconductor). A PID sensor is preferred, but electrochemical, infrared, semiconductor, or combustion gas sensors may also be used.

[0048] In one embodiment, the microcatalytic chamber 11 can be replaced with a multi-channel pipeline, each channel can filter or adsorb different gas components, and can also change the composition of the gas to be measured passing through the pipeline by designing different chemical and electrochemical reactions. In one analysis process, the gas passes through at least two of the channels and completes at least two measurements.

[0049] Please refer to Figure 2 , which is a flow chart of a mixed gas detection method provided in an embodiment of the present application, the method adopts Figure 1 The mixed gas detection device 1 shown utilizes the different decomposition temperatures of isobutylene, benzene, toluene, and xylene on a catalyst. Before entering the detection chamber 12 for detection, the mixed gas first undergoes partial oxidation at different temperatures in a microcatalytic chamber 11, and then enters the detection chamber 12 for measurement. Because different substances undergo catalytic oxidation at different temperatures, the composition of the gas changes after passing through the microcatalytic chamber 11. This change is related to the gas composition, catalyst, and reaction temperature. This relationship can be used to analyze the composition of the mixed gas. The mixed gas detection method specifically includes steps S210-S240:

[0050] Step S210 : The flow control mechanism 13 controls the mixed gas to be tested to enter the micro-catalytic chamber 11 and the detection chamber 12 according to a preset flow value.

[0051] In this step, the flow control mechanism 13 can control the amount of mixed gas entering the micro-catalytic chamber 11 and the detection chamber 12. When the mixed gas is introduced into the micro-catalytic chamber 11 and the detection chamber 12, the flow control mechanism 13 can control the flow according to a fixed flow rate as a preset flow rate value, so that the introduced gas passes through the micro-catalytic chamber 11 and the detection chamber 12 in sequence at a fixed flow rate and empties the micro-catalytic chamber 11 and the detection chamber 12. The fixed flow rate value can be controlled according to the specific needs of the experiment.

[0052] Step S220 : The heating module 111 controls the micro-catalytic chamber 11 to reach different preset temperatures, wherein the heating module 111 is coated with a catalytic material 112 .

[0053] In this step, as mentioned above, the heating module 111 is preferably a MEMS micro heater, which controls the temperature of the micro catalytic chamber 11 through a program within one analysis cycle so that the temperature inside the micro catalytic chamber 11 reaches different preset temperatures.

[0054] In one embodiment, the heating module 111 controls the micro-catalytic chamber 11 to reach different preset temperatures with preset increasing temperature values according to the first temperature rising mode. The preset temperatures include a preset temperature lower limit value and a preset temperature upper limit value.

[0055] In this embodiment, the first temperature increase mode is a step-by-step temperature increase mode, which controls the microcatalytic chamber 11 to reach different preset temperatures using preset temperature increments. For example, the temperature increments may be 10°C, 20°C, or 30°C. Both the preset temperature increments and the preset temperature can be designed based on the composition characteristics of the mixed gas to be measured, experimental requirements, and the like.

[0056] Among them, the preset temperature lower limit value is used to indicate that the most active gas among the components of the mixed gas to be tested that need to be detected at the current temperature is only partially converted under the current test conditions, and the remaining gas components are not converted; the preset temperature upper limit value is used to indicate that the most stable gas among the components of the mixed gas to be tested that need to be detected at the current temperature is only partially converted or fully converted under the current test conditions.

[0057] In one embodiment, the heating module 111 can control the microcatalytic chamber 11 to reach different preset temperatures at a constant heating rate according to the second heating mode. For example, the temperature can be increased at a rate of 10°C to 100°C / min. The preset temperature increment and the preset temperature can also be designed based on the composition characteristics of the mixed gas to be tested, experimental requirements, etc.

[0058] In this embodiment, the second temperature rising mode is a constant rate temperature rising mode, that is, the micro-catalytic chamber 11 is controlled to reach different preset temperatures at a constant temperature rising rate.

[0059] Step S230: continuously introducing the mixed gas to be tested into the detection chamber 12 .

[0060] In this step, the mixed gas to be tested is introduced into the detection chamber 12 at a fixed flow rate through the flow control mechanism 13 .

[0061] Step S240: At different preset temperatures, the detection element 121 detects the mixed gas to be tested after catalytic oxidation at different preset temperatures, and obtains a relative response value of each gas component in the mixed gas to be tested.

[0062] In this step, the detection element 121 continuously records the analysis period and detects the mixed gas to be tested after catalytic oxidation at different preset temperatures to obtain the relative response value of each gas component in the mixed gas to be tested.

[0063] As described in step S220, in the step heating mode, the steady-state response of the gas at different temperatures constitutes a plurality of response equations, and the sensitivity of different gases at each temperature is calibrated in advance; the simultaneous equations are solved to calculate the concentration of each component gas; and then, at different temperatures, the PID sensor is used to detect the relative response value of each gas component in the mixed gas to be tested after catalytic oxidation at different preset temperatures. This is because the response characteristics of the PID sensor at different temperatures can be used to identify the gas components.

[0064] In the constant rate heating mode, different heating and cooling ranges and speeds can form different response characteristic spectra; the response characteristics of different gases can be calibrated and recorded in advance for gas component identification and concentration calculation; neural network algorithms are used to identify gases and calculate gas concentrations.

[0065] The above two embodiments provide methods for identifying each gas component in the mixed gas to be measured and algorithms for calculating gas concentrations under two heating modes, respectively.

[0066] The mixed gas detection method provided by this application was used for experiments and has been applied. The specific application cases are as follows: in the laboratory, the mixed gas to be tested is selected as a benzene series mixed gas, and the heating module 111 in the micro-catalytic chamber 11 is selected as a platinum microheater, and the heating area size is 200×200μm. The catalytic material 112 uses 1% Pt / Mn2O3 or Pt / CeO2 nanocatalyst. When used, the catalytic material 112 is evenly coated on the surface of the above-mentioned microheater. The detection part 121 in the detection chamber 12 uses a PID sensor. When the platinum microheater is heated and heated, the conversion rate of the benzene series mixed gas at different temperatures is calculated under the catalytic oxidation action of 1% Pt / Mn2O3. The calculation results are shown in Table 1.

[0067] Table 1 Conversion rate of mixed gas after catalysis by 1% Pt / Mn2O3 catalyst at different temperatures

[0068] temperature Isobutylene Toluene p-Xylene benzene 160 50％ 20％ 16％ 5％ 170 81％ 30％ 22％ 10％ 180 95％ 50％ 34％ 19％ 190 98％ 68％ 50％ 30％ 200 99％ 88％ 65％ 50％ 210 99％ 95％ 76％ 65％ 220 99％ 97％ 89％ 74％ 230 99％ 98％ 95％ 88％ 240 99％ 99％ 99％ 95％

[0069] Before detection, the gas flow into the micro-catalytic chamber 11 and the detection chamber 12 is controlled at a fixed flow rate by the flow control mechanism 13. For example, the gas flow control range is 20 to 60 ml / min, and the preferred fixed flow value is 60 ml / min. The temperature range for heating the platinum micro heater is 160°C to 240°C. The temperature is increased in a step-by-step heating mode through the temperature control program, that is, at 160°C to 240°C, the temperature is increased in steps of 10°C per temperature point, and the temperature is kept constant for 3 minutes after the temperature stabilizes. In fact, the MEMS micro heater can reach the preset temperature within 1 minute. In actual application, the best temperature control curve can be selected according to the response speed of the micro heater and the sensor.

[0070] In this embodiment, the benzene series mixed gas to be tested is controlled to be passed into the micro-catalytic chamber 11 at a flow rate of 60 ml / min, and the platinum micro-heater is heated at the same time. After undergoing partial catalytic oxidation by 1% Pt / Mn2O3 at different temperatures, the isobutylene, toluene, xylene, and benzene mixed gas enters the detection chamber 12, and the relative response values of isobutylene, toluene, xylene, and benzene are detected by the PID sensor.

[0071] Please refer to Figure 3 , using the different response values of the PID sensor to different gas components at different temperatures, the relative response values of isobutylene, toluene, xylene, and benzene through 1% Pt / Mn2O3 nanocatalysis were obtained. As can be seen from the figure, at 80°C, the relative response value of isobutylene is lower than that of the other three substances, while the response values of toluene, xylene, and benzene are relatively close, and they cannot be clearly distinguished for the time being. However, as the temperature continues to rise, the response values of the four components are all decreasing, and the degree of decrease of each component is different, indicating that the higher the temperature, the greater the difference in the response degree of different substances. When the temperature approaches 240°C, the response values of the four substances are all close to 0, indicating that the current PID sensor can no longer detect multiple components in the mixed gas. Therefore, the mixed gas detection method of the present application can distinguish different gas components in the mixed gas.

[0072] Considering the relative response value change of isobutylene, toluene, xylene and benzene after passing through 1% Pt / Mn2O3 nanocatalyst at different conversion temperatures, the following graph can be obtained: Figure 4 ,Depend on Figure 4 It can be seen that the response spectra of the four gases are very different, and the spectra can be used for pattern recognition. Figure 3 The concentrations of four gases can be calculated using an intelligent algorithm.

[0073] In the above embodiment, the platinum microheater adopts a step heating mode. Of course, the step heating mode can also be modified to a constant rate heating mode, and the PID sensor response value and its differential curve throughout the heating process are used to identify the gas components and calculate the concentration.

[0074] In another application case, the mixed gas to be tested is selected as CO, formaldehyde, and alcohol, and the catalytic material 112 is selected as 1% Ag / CeO2. The catalytic material 112 is coated on a 200um×200um micro heater. After catalytic oxidation with 1% Ag / CeO2, the conversion rate of each component is as follows: Figure 5As shown. At around 10°C, CO begins to catalytically decompose, formaldehyde has been oxidized and the conversion rate is 10%, but alcohol does not begin to oxidize until around 60°C, when alcohol begins to catalytically decompose. At 150°C, formaldehyde has basically completed catalytic decomposition, with a conversion rate of 100%, and CO has completed partial catalytic decomposition, with a conversion rate of 98%. At 200°C, CO has completed catalytic decomposition, with a conversion rate of 100%, but alcohol has only completed partial catalytic decomposition, with a conversion rate of around 50%.

[0075] In the range of 10℃~100℃, after the mixed gas is introduced into the micro-catalytic chamber 11, the sensor response value obtained by measuring with the electrochemical sensor is as follows: Figure 6 shown. Figure 6 In the range of 0°C to 100°C, as the temperature rises, the initial response value of alcohol on the electrochemical sensor is larger, but the change in its response value is very small. Although the initial response value of formaldehyde is lower than that of alcohol, its response value changes more significantly as the temperature rises. CO has the lowest initial response value, and its response value changes less significantly as the temperature rises. Therefore, the method of this application can also distinguish the different gas components in a mixed gas of CO, formaldehyde, and alcohol.

[0076] In the range of 0℃~100℃, the reaction characteristics of electrochemical sensors to CO and HCHO are as follows Figure 7 As shown ( Figure 7 This feature can be used to identify the presence of formaldehyde and carbon monoxide in a gas mixture.

[0077] If you're measuring formaldehyde concentration in an environment, and you know the only interference is from carbon monoxide and alcohol, you can choose three measurement temperatures: room temperature (generally less than 30°C) plus two additional temperatures, such as 40°C and 80°C. Since alcohol isn't catalytically decomposed at these three temperatures, and CO and formaldehyde have different conversion rates at these temperatures, you can quickly calculate the concentrations of the three gases in the environment using simultaneous equations.

[0078] The mixed gas detection device 1 provided in this application can be used to identify the components of mixed gases and measure their concentrations, and has been particularly effective in measuring benzene in mixed gases containing benzene series. The mixed gas detection device 1 provided in this application enables miniaturization, low power consumption, high efficiency, and rapid analysis with high detection accuracy.

[0079] It should be noted that, unless there is any conflict, the features in the embodiments of this application can be combined with each other.

[0080] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A mixed gas detection method, characterized in that: The method is performed by a mixed gas detection device, the device comprising: a micro-catalytic chamber, wherein a heating module and a catalytic material are provided in the micro-catalytic chamber, wherein the catalytic material is provided on the heating module; a detection chamber connected to the micro-catalytic chamber, wherein a detection element is provided in the detection chamber, wherein the detection element is used to detect the relative response value of each gas component in the mixed gas to be tested after catalytic oxidation at different temperatures; the method comprises: The heating module controls the micro-catalytic chamber to reach different preset temperatures, wherein the heating module is coated with a catalytic material; Continuously introduce the mixed gas to be tested into the testing chamber; At different preset temperatures, the detection element detects the mixed gas to be tested after catalytic oxidation at different preset temperatures, and obtains the relative response value of each gas component in the mixed gas to be tested.

2. The mixed gas detection method according to claim 1, characterized in that: Also includes: The flow control mechanism is connected to the micro-catalytic chamber and is used to control the flow of the mixed gas entering the micro-catalytic chamber.

3. The mixed gas detection method according to claim 2, wherein: The flow control mechanism comprises: an air resistance regulating assembly connected to the inlet of the microcatalytic chamber; and A power source is connected to the air resistance adjustment component.

4. The mixed gas detection method according to claim 2, characterized in that: The flow control mechanism comprises: The mass flow control component is connected to the inlet of the microcatalytic chamber.

5. The mixed gas detection method according to claim 1, characterized in that: The catalytic material is a nano-catalytic material.

6. The mixed gas detection method according to claim 1, characterized in that: The detection element is one of PID, FID and MOS.

7. The method according to claim 2, characterized in that Before the heating module controls the micro-catalytic chamber to reach different preset temperatures, the method further includes: The flow control mechanism controls the mixed gas to be tested to enter the micro-catalytic chamber and the detection chamber according to a preset flow value.

8. The method according to claim 1, characterized in that The heating module controls the micro-catalytic chamber to reach different preset temperatures, including: The heating module controls the micro-catalytic chamber to reach different preset temperatures at preset increasing temperature values according to a first heating mode, wherein the preset temperatures include a preset temperature lower limit value and a preset temperature upper limit value; Among them, the preset temperature lower limit value is used to indicate that the most active gas among the components of the mixed gas to be tested that need to be detected at the current temperature is only partially converted under the current test conditions, and the remaining gas components are not converted; the preset temperature upper limit value is used to indicate that the most stable gas among the components of the mixed gas to be tested that need to be detected at the current temperature is only partially converted or fully converted under the current test conditions.

9. The method according to claim 1, characterized in that The heating module controls the micro-catalytic chamber to reach different preset temperatures, including: The heating module controls the micro-catalytic chamber to reach different preset temperatures at a constant heating rate according to the second heating mode.

Images