Gas sampling apparatus and method

Abstract

A gas sampling device and method includes a cylindrical chamber comprising a closed top and a closed bottom, an opening in the top and a vent in the wall of the chamber near the closed bottom, a fan in the opening for drawing in atmospheric air and creating positive pressure in the chamber to expel air through the vent, a set of sensors in the chamber including a methane sensor, a hydrogen sensor, a liquefied petroleum gas sensor, a temperature sensor, a pressure sensor, and a humidity sensor, and a controller and a power supply operatively connected to the sensors and the fan for controlling the fan and the sensors to collect sensor data.

Description

Technical Field

[0001] In one aspect, this disclosure generally relates to gas sampling apparatus and methods, and particularly to methane detection apparatus and methods. Background Technology

[0002] Current electrochemical sensors suffer from two main problems. First, they lack a direct mapping function that converts the sensor output voltage into effective gas concentration units (such as parts per million). Second, they exhibit cross-sensitivity and temperature dependence to other gases. This cross-sensitivity refers to the change in resistance when other gases, not the primary focus, are present. Improved sensor devices that address these issues are desirable. Summary of the Invention

[0003] In one aspect, this disclosure relates to methods for quantifying emission-related methane concentrations and providing real-time monitoring for leak detection in various settings, such as, but not limited to, oilfields, landfills, water treatment plants, and residential areas.

[0004] In another aspect, this disclosure relates to a gas sampling device comprising a cylindrical chamber including a closed top and a closed bottom, an opening in the top and a vent in the chamber wall near the closed bottom, a fan in the opening for drawing in atmosphere into the chamber and creating positive pressure within the chamber to expel air through the vent, a set of sensors in the chamber including a methane sensor, a hydrogen sensor, a liquefied petroleum gas sensor, a temperature sensor, a relative humidity sensor, and a pressure sensor, and a controller and a power supply operatively connected to the sensors and the fan for controlling the fan and sensors to collect sensor data. For example, an environmental sensor such as the ENS 160 can be used, which quantifies air quality carbon dioxide (CO2) and volatile organic compound (VOC) concentrations. In another aspect, the gas sampling device may include a pressure sensor and an air quality sensor. In yet another aspect, in the gas sampling device, the controller also includes a processor with stored instructions for processing the sensor data and providing a methane concentration value. In another aspect, the gas sampling device includes instructions for adjusting the resistance of a methane sensor in response to trends in the methane concentration value. In yet another aspect, the gas sampling device also includes a second methane sensor, wherein the resistance of the second methane sensor is adjustable.

[0005] In another aspect, this disclosure relates to a method for generating a methane concentration value, comprising the steps of: providing readings from a methane sensor, providing readings from a hydrogen sensor, providing readings from a liquefied petroleum gas sensor, providing a temperature reading from a temperature sensor, providing a relative humidity reading from a humidity sensor, and providing an atmospheric pressure reading from a pressure sensor; and using a processor and the readings to generate a methane concentration value. In yet another embodiment, the readings from the sensors are resistance readings, and the methane concentration value is expressed in parts per million (ppm).

[0006] Other advantages of this teaching may become apparent to those skilled in the art after reading this specification. Attached Figure Description

[0007] Embodiments of the invention will be described with reference to the accompanying drawings, wherein like reference numerals denote like parts, and wherein:

[0008] Figure 1 This is a perspective view of a gas sampling device according to an embodiment of the present invention;

[0009] Figure 2 It comes from Figure 1 An exploded view of the top of the device;

[0010] Figure 3 It comes from Figure 1 An exploded view of the bottom of the device;

[0011] Figure 4 yes Figure 1 A side view of the device;

[0012] Figure 5 It is along Figure 4 A partial cross-sectional view taken by line BB;

[0013] Figure 6 It is along Figure 4 A cross-sectional view taken by line AA;

[0014] Figure 7 It is a circuit diagram of the electrical components divided into three parts (ESP 32, sensors, and external peripherals);

[0015] Figure 8 It is a circuit diagram of electrical components used in variable resistor circuits;

[0016] Figure 9 It comes from the use of Figure 1 Exploded view of the bottom of the outdoor cover of the equipment;

[0017] Figure 10 It indicates that it is used for operation. Figure 1A flowchart of one embodiment of the software steps of the device;

[0018] Figure 11 This is an exploded perspective view of a gas sampling device according to another embodiment of the present invention;

[0019] Figure 12 yes Figure 11 A top view of the gas sampling equipment;

[0020] Figure 13 It is along Figure 12 The cross-section of line BB, in which the device is rotated 90 degrees counterclockwise;

[0021] Figure 14 It is along Figure 12 The cross-section of line BB, in which the device is rotated 90 degrees counterclockwise, shows the airflow;

[0022] Figure 15 yes Figure 11 A partial cross-sectional view of the gas sampling equipment; and

[0023] Figure 16 yes Figure 11 A partial cross-sectional view of the lower part of the gas sampling device. Detailed Implementation

[0024] Various apparatuses or processes are described below to provide examples of embodiments of each claimed invention. The embodiments described below do not limit any claimed invention, and any claimed invention may cover a different process or apparatus than those described below. The claimed invention is not limited to an apparatus or process having all the features of any of the apparatuses or processes described below, nor is it limited to the common features of the multiple or all of the apparatuses described below. The apparatuses or processes described below may not be embodiments of any claimed invention. Any invention disclosed in the apparatuses or processes described below but not claimed in this document may be the subject of another protection tool (e.g., a continuation of a patent application), and the applicant, inventor, or owner does not intend to waive, deny, or publicly offer any such invention through the disclosure in this document.

[0025] In one embodiment, the present invention relates to a device, sometimes referred to herein as an "air retainer," for sampling air and calculating the concentration of methane (CH4) in the air, taking into account certain environmental conditions. (See first for reference...) Figure 1The following description first refers to the housing, generally indicated by 2, used in the device of the present invention, without reference to the various sensors and electronic devices housed in the device. The housing 2 includes a central housing 4, an annular cover 6, and a base plate 8. The central housing 4 has a closed top 10 with a central circular opening 12. A threaded ring 14 extends from the top 10. The annular cover 6 has a well, generally indicated by 16, whose walls 18 gradually taper to the central circular opening, generally indicated by 20, in the annular cover 6. A concave threaded ring 22 is provided on the underside of the annular cover 6 for receiving the threaded ring 14, thereby threading the annular cover 6 to the housing 4. When the annular cover 6 is fixed to the housing 4, the circular opening 20 is substantially aligned with the circular opening 12. The base plate 8 includes a wall 22 with a vent 24. The base plate 8 is detachably fixed to the bottom of the housing 4, and a threaded ring 26 engages with a thread 28 inside the housing 4. In one embodiment, the housing 4 defines a chamber generally indicated by 30. Those skilled in the art will understand that the volume of the chamber 30 can be enlarged or reduced according to the teachings of the present invention.

[0026] Now for reference Figure 4 , Figure 5 and Figure 6 This describes the various sensors and electronic components housed within the housing 4. The fan 31 is located within the circular opening 12. For simplicity, the fan 31 is only... Figure 2 As shown in the diagram, a set of sensors 32, 34, 36, 38, and 40 are located inside the central housing 4. Sensor 32 is an MQ4 methane gas sensor, which is a metal oxide semiconductor type sensor for detecting the concentration of methane gas in the air, and serves as the primary methane gas sensor in the device of this invention. A Figaro TGS 2611 sensor can also be used. Sensor 34 is an optional second MQ4 methane gas sensor, which serves as a secondary methane gas sensor in this device and is used for calibration of the primary MQ4 sensor 32.

[0027] Sensor 36 is used to measure the concentration of hydrogen in the air [X] H2 The MQ8 hydrogen sensor. Sensor 38 is used to measure the concentration of liquefied petroleum gas in the air [X]. LPG A liquefied petroleum gas (LPG) sensor. Sensor 40 is used to measure air temperature [X]. T Relative humidity [X] H2O ] and atmospheric pressure [X P The BME 280 sensor is described. Those skilled in the art will understand that sensors 32 to 40 can be located in different positions within housing 2. Furthermore, separate temperature, humidity, and atmospheric pressure sensors can be used instead of the single-unit BME 280 sensor.

[0028] The MQ4, MQ8, and LPG sensors feature a chemically selective layer that reacts (changing the sensor's resistance) upon contact with the specific gas being measured. The MQ4 sensor also includes a resistor that allows each side of the sensor to be tuned to have more or less selectivity to changes in gas concentration.

[0029] The integrated circuit board 46 is located on the base plate 47 of the base disk 8 and is operatively connected to, for example, Figure 7 and Figure 8 The electrical components of the device of the present invention are shown in the circuit diagram. The electrical components are divided into three parts: "ESP 32," which is a system-on-a-chip (SoC) microcontroller including Wi-Fi and Bluetooth wireless capabilities and a dual-core processor, and used in the device of the present invention to handle all computing and communication between the device and the Internet; "sensors," which are sensors 32 to 40; and "external peripheral devices." ESP 32 includes software code for performing the various operations and processing steps described in this specification.

[0030] In one embodiment, if desired, the device of this invention can be connected to a DC or AC power supply by attaching a buck converter to a 6V source, followed by a bridge rectifier and a 5V regulator. The device can be portable and moved to any desired location to sample air in various locations, or it can be installed in a fixed location for field measurements.

[0031] For outdoor use, the air retainer can be utilized by attaching a cover 48 instead of the annular cover 6 and changing the mode to outdoor use. Cover 48 includes a cover 50 and a ring 52 with an air inlet 54. In this embodiment, air is drawn into the chamber 30 via the air inlet 54. In some embodiments, the chamber 30 is made of an insulating material, such as fiberglass or reinforced plastic / ceramic fiber. Cover 48 and housing 4 can be made of renewable plastics, such as polypropylene (PP), which provides insulation and rain protection. Furthermore, in another embodiment, the device can use one or more heating pads within the chamber 30 to maintain an optimal internal temperature.

[0032] In one embodiment, the volume of chamber 30 is 0.7725, and fan 31 generates 0.042 m³ during operation. 3An airflow of [ / min] is used to draw the air to be sampled from outside the device into chamber 30 through openings 12 and 20. Chamber 30 inherently secures the device because the sensors are housed within it. The sampled air is then further pushed downwards into chamber 30 by fan 31 and gravity, where it contacts sensors 32 to 40, and then exits chamber 30 via vent 24. The passage of the sampled air through chamber 30 causes mixing, which facilitates sampling of the air by sensors 32 to 40. In another embodiment, a humidity filter (not shown) may be placed in opening 12 such that the intake air passes through the filter before entering chamber 30. Filtering the intake air can increase the lifespan of one or more sensors 32 to 40 within chamber 30.

[0033] In one embodiment of this device, sensors 32 to 40 simultaneously perform their respective measurements per second (1 Hz). Chamber 30 is filled with sampled air when sensors 32 to 40 begin collecting their respective measurements, provided the internal volume of chamber 30 is equal to the amount of sampled air displaced within chamber 30 per second. Sensor collection may begin after the first second of fan activation, or after another suitable time delay between fan activation and sensor sampling. In other embodiments, other suitable time intervals between measurements may be used.

[0034] For optimal results, the device should be placed within a three-meter radius of the air source. Sources further away will take longer to be displaced by the fan 31 in chamber 30, but will still be operational. In operation, in one embodiment, the sampling sequence begins by turning on the fan 31 and drawing the air to be sampled from the surrounding area into chamber 30. After one second, the sampled air is mixed inside chamber 30, and sensors 32 through 40 simultaneously perform their respective measurements. When the measurement is complete, the software in ESP 32 processes the pressure, humidity, and temperature readings from sensor 40 and increases or decreases the resistance of one or both of MQ4 sensors 32 and MQ4 sensors 34 to calculate the most accurate sensitivity. In another embodiment, sensors 32 and 34 can be tuned to a high sampling / high sensitivity mode using the signal-to-noise ratio (SNR), calculated using equation (1) below or any other model described in this disclosure, divided by the standard deviation over the time interval τ. This SNR from the rotating MQ4 sensor is compared to the SNR from the static MQ4 sensor. Similarly, the SNR from both the MQ8 and MQ6 sensors can be calculated using only millivolt (mV) readings to determine any cross sensitivity.

[0035] In one embodiment, the internal volume of the chamber 30, defined by its radius and height, depends on the airflow of the fan 31, as described in equation (2): (2).

[0036] Due to the aforementioned dependence, during measurement, the air inside the chamber is fully mixed, but also mixed with air drawn in from the surrounding air. The volume is identified using the model of Equation (2), and given the concentration of the gas (CH4), its mass and emissions (measured as mass per unit time) can then be calculated. In one embodiment, the use of a cylindrical chamber also maximizes the volume while minimizing the surface area and the materials required for assembly. In other embodiments, air is sampled from other parts of the chamber (i.e., the bottom, left, or right side of chamber 30).

[0037] In one embodiment, the model described by equation (1) is used to process data acquired simultaneously by sensors 32 to 40 (data transmitted and processed remotely by the device itself or via a network) to generate a methane concentration reading. In one embodiment, [y CH4 The [value] can be used to warn of elevated methane levels, as explained in further detail below. This warning can be used, for example, to issue an alarm or to shut down certain equipment or systems. (1).

[0038] Equation (1) adjusts the cross-sensitivity of methane sensors 32 and 34 to gases other than methane, and also adjusts the temperature dependence of methane detector 32 and methane sensor 34. Equation (1) is used to measure methane [X] in millivolts obtained from the respective sensors. MQ4 ], hydrogen [X H2 ] and liquefied petroleum gas [X LPG The measured sensor values ​​and the measured relative humidity [X] H2O Atmospheric pressure [X] P ] and temperature [X T The value is used to calculate the methane concentration value y. CH4 The coefficient β used in equation (1) o The value up to β8 was not measured and will be discussed in the example below. In one embodiment, the resistance value [X] is... MQ4Resistor The initial selection is based on the initial temperature, pressure, and humidity readings collected at the start of methane concentration sensing emissions (see Table 1). In another embodiment, equation (1) is solved once or multiple times to generate an additional methane concentration [y]. CH4 The value depends on the methane concentration [y] obtained using equation (1). CH4 The trend of the value [X] is then used to adjust the resistance value accordingly. MQ4Resistor In one embodiment of this method, the methane concentration [y] obtained from equation (1) per time interval τ is examined. CH4To check if it is constant, the resistance on the secondary MQ4 sensor 34 is adjusted according to the consistency in Table 1 to correspond to the resistive load corresponding to temperature, pressure, and relative humidity. If the secondary sensor 34 detects a statistically significant change in methane concentration relative to the primary methane sensor 32 with its resistance not modified after its resistance is adjusted, the resistance of the primary sensor 32 is changed to match the resistance of the secondary methane sensor 34. The resistance value of the primary MQ4 sensor 32 is adjusted [X]. MQ4Resistor There are three possible scenarios: (i) if the concentration has a constant trend, and the second MQ4 sensor 32 obtains a statistically significant measurement using another resistance value; (ii) if the trend is increasing, the other resistance value provides better accuracy; and (iii) if the trend is decreasing, the other resistance value provides a more accurate measurement, as shown in Table 1.

[0039]

[0040] Table 1. Initial resistance values ​​based on environmental conditions

[0041] By way of example, equation (1) is solved using the following readings from sensors 32 to 40: MQ4 = 878.0 mV, LPG = 1664.0 mV, hydrogen = 419.0 mV, pressure = 99862.0 Pa, relative humidity = 72.42, temperature = 9.69°C, resistance = 20.05 KΩ, and the coefficient β from Table 2. o The value up to β8. In one embodiment, the coefficient can vary within the range provided in the “Range Coefficient” column of Table 2.

[0042]

[0043] Table 2. Coefficients and Range

[0044] Using the numbers above and solving equation (1), the generated methane concentration is 20.53 parts per million (ppm). In one embodiment, a concentration of 20.53 ppm implies a moderate risk of methane gas leakage. In one embodiment, the device is specifically designed to differentiate readings into six categories: 0–5 ppm standard concentration, 5 ppm–20 ppm low leakage risk, 20 ppm–100 ppm medium risk, 100 ppm–1000 ppm high risk, 1000 ppm–5000 health risk, and 50000 ppm explosion risk. Figure 10 The present invention provides an operational flowchart of one embodiment of the device.

[0045] This device and method were tested and cross-validated using data collected from a central steam plant, and the inventors determined that equation (1) is the preferred model (minimum outcome variance and minimum bias). However, the air retainer and the variables it can measure (e.g., electrochemical sensor measurements, ambient values, and resistance values) allow for the use of alternative models to provide methane concentration. These alternative models include models incorporating simple decision trees involving predictors and the following models: Simple multivariate regression, y CH4 = β1X H2O + β2X H2 + β3X LPG + β4X T + β5X P + β5X MQ4 + β6X Resistor ; Multinomial regression, y CH4 = β1X H2O (a) + β2X H2 (b) + β3X LPG (c) + β4X T (d) + β5X P (e) + β5X MQ4 (f) + β6X Resistor (g) , Where a...g is some real number; A model with certain transformations, y CH4 = f(β1X H2O + β2X H2 + β3X LPG + β4X T + β5X P + β5X MQ4 + β6X Resistor ), Where f is any function; The artificial neural network model comprises multiple layers that assign weights to measurements from various environmental conditions and MOX sensors using training data. A genetic algorithm (GA) is then employed for iterative optimization to derive the optimal approximation.

[0046] refer to Figures 11 to 16In another embodiment, sensors 32 to 40 are housed in a housing 55 having an open top and an open bottom, and tapering towards the open bottom. The housing 55 functions the same as chamber 30 and is nested within housing 4. The nested housing 55 within housing 4 provides greater insulation for sensors 32 to 40. A battery 58 is located at the bottom of base disk 8. An integrated circuit board 46 is located on battery 58 and is operatively connected to, for example... Figure 7 and Figure 8 The electrical components of the device of the present invention are shown in the circuit diagram, and are described in relation to other embodiments of the invention. A cover 56 is placed on the battery 58 and the integrated circuit board 46. The cover 56 may be made of silicon or other suitable malleable material.

[0047] Arrow 60 indicates the path and direction of air as it is drawn into the device through the circular opening 20 in the annular cover 6 and into the housing 55, then exits from the bottom of the housing 55. Some of the air leaving the housing 55 contacts the cover 56, is heated by heat from the integrated circuit board 46, and conventionally rises into the space between the walls of the housing 55 and the housing 4 to help insulate the chambers in the housing 55 and help keep the sensors 32 to 40 warm, while some air exits the device through the vent 24. This air circulation also helps cool the integrated circuit board 46.

[0048] While the teachings herein include illustrative embodiments and examples of some aspects of the invention, this description is not intended to be limiting. Therefore, various modifications to the illustrative embodiments and other embodiments of the invention will likely be apparent to those skilled in the art upon referring to this description. Accordingly, the appended claims are intended to cover any such modifications or embodiments.

[0049] All publications, patents and patent applications mentioned herein are incorporated by reference in their entirety to the same extent as each individual publication, patent or patent application is specifically and individually incorporated by reference in its entirety.

Claims

1. A gas sampling device, characterized in that, include: A cylindrical chamber includes a closed top and a closed bottom, an opening in the top and a vent in the wall of the chamber near the closed bottom, a fan in the opening for drawing in air into the chamber and creating positive pressure in the chamber to expel air through the vent, a set of sensors in the chamber including a methane sensor, a hydrogen sensor, a liquefied petroleum gas sensor, a temperature sensor, an atmospheric pressure sensor, and a relative humidity sensor, and a controller and a power supply operatively connected to the sensors and the fan for controlling the fan and the sensors to collect sensor data.

2. The gas sampling device according to claim 1, characterized in that, The controller also includes a processor with stored instructions for processing the sensor data and generating methane concentration values.

3. The gas sampling device according to claim 2, characterized in that, The storage instructions include instructions for using the sensor data and solving equations to generate the methane concentration value. ， in, [y CH4 [X] represents the methane concentration value. H2O [X] is the relative humidity value from the relative humidity sensor. MQ4 [X] is a measurement from the methane sensor. H2 ] is a measurement from the hydrogen sensor, [X LPG ] is the measurement value from the liquefied petroleum gas sensor, [X P [X] is the measured atmospheric pressure value from the atmospheric pressure sensor. T ] is the measured temperature value from the temperature sensor, β o Up to β8 are the coefficient values, and [X] MQ4Resistor [] is the resistance value.

4. The gas sampling device according to claim 3, characterized in that, The storage instructions also include instructions for repeating the step of using sensor data from fresh sensor readings one or more times to generate the methane concentration value.

5. The gas sampling device according to claim 4, characterized in that, The storage instructions also include instructions for adjusting the resistance of the methane sensor in response to the trend of the generated methane concentration value over the time interval.

6. The gas sampling device according to claim 5, characterized in that, It also includes a second methane sensor.

7. The gas sampling device according to claim 6, characterized in that, The storage instructions also include instructions for adjusting the resistance of the second methane sensor to correspond to a resistive load corresponding to the measured values ​​of temperature, pressure, and relative humidity.

8. The gas sampling device according to any one of claims 1 to 7, characterized in that, It also includes an air quality sensor.

9. A method for generating a methane concentration value, characterized in that, Includes the following steps: It provides readings from the methane sensor, readings from the hydrogen sensor, readings from the liquefied petroleum gas sensor, temperature readings from the temperature sensor, relative humidity readings from the humidity sensor, and atmospheric pressure readings from the pressure sensor. The processor is used, and the readings are used to generate a methane concentration value.

10. The method according to claim 9, characterized in that, The readings from the methane sensor, the hydrogen sensor, and the liquefied petroleum gas sensor are resistance readings.

11. The method according to claim 9 or 10, characterized in that, The methane concentration value was calculated by solving an equation. ， in, [y CH4 [X] represents the methane concentration value. H2O [X] is the relative humidity value from the relative humidity sensor. MQ4 [X] is a measurement from the methane sensor. H2 ] is a measurement from the hydrogen sensor, [X LPG ] is the measurement value from the liquefied petroleum gas sensor, [X P [X] is the measured atmospheric pressure value from the atmospheric pressure sensor. T ] is the measured temperature value from the temperature sensor, β o Up to β8 are the coefficient values, and [X] MQ4Resistor [] is the resistance value.

12. The method according to claim 11, characterized in that, It also includes the step of solving the equation once or multiple times using fresh readings from the sensor to generate one or more additional methane concentration values.

13. The method according to claim 12, characterized in that, It also includes adjusting the resistance of the methane sensor in response to the trend of the methane concentration value over a time interval.

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