WO2025118061A1

WO2025118061A1 - Gas sampling device and method

Info

Publication number: WO2025118061A1
Application number: PCT/CA2024/000017
Authority: WO
Inventors: Sebastian IBARRA MENDEZ
Original assignee: Individual
Current assignee: Individual
Priority date: 2023-12-04
Filing date: 2024-12-04
Publication date: 2025-06-12
Anticipated expiration: 2026-06-04

Abstract

A gas sampling device and method including a cylindrical chamber comprising a closed top and a closed bottom, an opening in the top and air vents in the wall of the chamber proximate to the closed bottom, a fan in the opening for drawing atmospheric air into the chamber and creating positive pressure in the chamber to expel air through the air vents, a set of sensors in the chamber, the sensors comprising a methane sensor, a hydrogen sensor, a liquified petroleum gas sensor, a temperature sensor, a pressure sensor, and a humidity sensor, and a controller and a power source operably connected to the sensors and the fan for controlling the fan and sensors for the collection of sensor data.

Description

GAS SAMPLING DEVICE AND METHOD

FIELD

[0001] In one of its aspects, the present disclosure relates generally to gas sampling devices and methods, and methane detection devices and methods in particular.

BACKGROUND

[0002] Current electrochemical sensors have two main problems. First, they do not come with a direct mapping function that converts the voltage that the sensor outputs to a valid unit of concentration for gas (such as parts per million). Second, they have cross-sensitivities to other gases and temperature dependence. This cross-sensitivity -is the -variation in resistance when other gases that are not the main focus are present. An improved sensor device that addresses these problems would be desirable.

SUMMARY

[0003] The present disclosure, in one aspect, relates to methods used to quantify methane concentrations which are related to emissions and provide real-time monitoring for leak detection in different settings such as but not limited to oil extracting sites, landfills, water treatment plants and residential dwellings.

[0004] The present disclosure, in another aspect, relates to a gas sampling device including a cylindrical chamber including a closed top and a closed bottom, an opening provided in the top and air vents provided in the wall of the chamber proximate to the closed bottom, a fan in the opening for drawing atmospheric air into the chamber and creating positive pressure in the chamber to expel air through the air vents, a set of sensors in the chamber, the sensors including a methane sensor, a hydrogen sensor, a liquified petroleum gas sensor, a temperature sensor, a relative humidity sensor, and a pressure sensor, and a controller and a power source operably connected to the sensors and the fan for controlling the fan and the sensors for the collection of sensor data. For example, an environmental sensor such as ENS160 that quantifies air quality carbon dioxide (CO2) and volatile organic compounds (VOC) concentrations can be used. In a further aspect, the gas sampling device can include a pressure sensor and an air quality sensor. In a further aspect, in the gas sampling device the controller further includes a processor with stored instructions for processing the sensor data and providing methane concentration values. In a still further aspect, in the gas sampling device, the stored instructions further include instructions for adjusting the resistance of the methane sensor in response to a trend in the methane concentration values. In a still further aspect, the gas sampling device further includes a second methane sensor wherein the resistance of the second methane sensor is adjustable.

[0005] The present disclosure, in another aspect, relates to a method of generating a methane concentration value including the steps of providing a reading from a methane sensor, providing a reading from a hydrogen sensor, providing a reading from a liquified 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 generating, using a processor, a methane concentration value using the readings. In a still further embodiment, the readings from the sensors are resistance readings and the methane concentration value is expressed in units of parts per million.

[0006] Other advantages of the present teachings may become apparent to those of skill in the art upon reviewing the present specification.

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0009] FIG. 2 is an exploded view from the top of the device of FIG. 1 ;

[0010] FIG. 3 is an exploded viewfrom the bottom of the device of FIG. 1 ;

[0011] FIG. 4 is a side view of the device of FIG. 1 ;

[0012] FIG. 5 is a partial section view taken along line B-B of FIG. 4;

[0013] FIG. 6 is a cross-section view taken along line A-A of FIG. 4; [0014] FIG. 7 is a circuit diagram for the electrical components divided into three parts: ESP32, sensors and external peripherals;

[0015] FIG. 8 is a circuit diagram for electrical components for the variable resistor circuit;

[0016] FIG. 9 is an exploded view from the bottom of an outdoor lid for the device of FIG.1 ;

[0017] FIG. 10 is flow chart denoting one embodiment of software steps for operating the device of FIG. 1 ;

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

[0019] FIG. 12 is a top view of the gas sampling device of FIG. 11 ;

[0020] FIG. 13 is a cross-section along line B-B of FIG. 12, with the device turned counterclockwise 90 degrees;

[0021] FIG. 14 is a cross-section along line B-B of FIG. 12 with the device turned counterclockwise 90 degrees, showing air flow;

[0022] FIG. 15 is a partial section view of the gas sampling device of FIG. 11 ; and

[0023] FIG. 16 a partial section view of a lower section of the gas sampling device of FIG. 11.

DETAILED DESCRIPTION

[0024] Various apparatuses or processes will be described below to provide an example of an embodiment of each claimed invention. No embodiment described below limits any claimed invention and any claimed invention may cover processes or apparatuses that differ from those described below. The claimed inventions are not limited to apparatuses or processes having all of the features of anyone apparatus or process described belowor to features common to multiple or all of the apparatuses described below. It is possible that an apparatus or process described below is not an embodiment of any claimed invention. Any invention disclosed in an apparatus or process described below that is not claimed in this document may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicants, inventors or owners do not intend to abandon, disclaim, or dedicate to the public any such invention by its disclosure in this document.

[0025] In one embodiment, the present invention relates to a device, also sometimes referred to herein as "AirKeeper", for sampling the air and calculating the concentration of methane (CH₄) in air taking into account certain environmental conditions. Referring initially to FIG. 1 , a housing indicated generally at 2 for the device of the present invention is initially described below without reference to various sensors and electronics that are housed in the present device. Housing 2 includes a central housing 4, a ring cap 6 and a base disk 8. Central housing 4 has a closed top 10 with a central circular opening 12 provided in top 10. A threaded ring 14 extends from top 10. A well indicated generally at 16 is provided in ring cap 6 with a wall 18 of well 16 tapering to a central circular opening indicated generally at 20 in ring cap 6. A recessed threaded ring 22 is provided on the underside of ring cap 6 for receiving threaded ring 14 for threaded engagement threaded ring 14 for securing ring cap 6 to housing 4. When ring cap 6 is secured on housing 4, circular opening 20 substantially aligns with circular opening 12. Base disk 8 includes a wall 22 with air vents 24 provided in wall 22. Base disk 8 is removably secured to the bottom of housing 4 with a threaded ring 26 engaging threads 28 on the inside of housing 4. In one embodiment, housing 4 defines a chamber indicated generally at 30. It will be understood by persons skilled in the art that the volume of chamber 30 can be scaled up or scaled down in accordance with the teachings of the present invention.

[0026] Various sensors and electronic components housed in housing 4 are now described with reference to FIGs 4, 5 and 6. A fan 31 is located in circular opening 12. Fan 31 is only shown in FIG. 2 for simplicity. Aset of sensors 32, 34, 36, 38, and 40 are located inside central housing 4. Sensor 32 is an MQ4 methane gas sensor which is a metal oxide semiconductor type sensor for detecting methane gas concentration in air, and serves as the main methane gas sensor in the device of the present invention. A Figaro TGS2611 sensor can also be used. Sensor 34 is an optional second MQ4 methane gas sensor which serves as a secondary methane gas sensor in the present device and is used for calibration of main MQ4 sensor 32.

[0027] Sensor 36 is an MQ8 hydrogen sensor for measuring hydrogen concentrations in air [XH2] Sensor 38 is a liquified petroleum gas (LPG) sensor for measuring liquified petroleum gas concentrations in air [XLPG]. Sensor 40 is a BME280 sensor for measuring air temperature [XT], relative humidity [XH2O], and atmospheric pressure [XP]. It will be understood by those skilled in the art that sensors 32 to 40 can be situated at various locations in housing 2. In addition, individual temperature, humidity and atmospheric pressure sensors can be used in place of the single combined BME280 sensor.

[0028] MQ4, MQ8 and LPG sensors have a chemical selective layer that reacts (changes the resistance of the sensor) upon coming into contact with the particular gas being measured. MQ4 sensors also include resistors that allow for each side of an MQ4 sensor to be adjusted to be more or less selective to changes in gas concentration,

[0029] An integrated circuit board 46 is located on floor 47 of base disk 8 and is operably connected to the electrical components of the device of the present invention as shown in the circuit diagrams of FIG. 7 and FIG. 8. The electrical components are divided into three parts: "ESP32" which is a System on a Chip (SoC) microcontroller that includes Wi-Fi and Bluetooth wireless capabilities and dual-core processor and is used in the device of the present invention to handle all the computations and communications of the device with the internet, "sensors" which are the sensors 32 to 40, and "external peripherals". The ESP32 includes software code for carrying out the various operational and processing steps described in the present specification.

[0030] In one embodiment, the device of the present invention design can be connected either to a DC power source or an AC power, if necessary, by attaching a step-down converter to 6v and then a bridge rectifier as well as 5v regulator. The present device can either be portable and movable to any desired location to sample air in various locations or alternatively installed in a stationary position for taking in-situ measurements.

[0031] For outdoor use, the AirKeeper can be utilized by attaching a lid 48 instead of ring cap 6 and changing the mode to outdoor usage. Lid 48 includes a cap 50 and a ring 52 with air intakes 54. In this embodiment, air is drawn into cbamber.30 via air intakes 54. In certain embodiments, chamber 30 is made from an insulated material such as fiberglass or reinforced plastic/ce ramie fiber. Lid 48 and housing 4 can be made of recyclable plastic such as polypropylene (PP) which provides insulation and protection from the rain. Additionally, in another embodiment, the present device can maintain an optimal internal temperature with the use of one or more heating pads in chamber 30.

[0032] In one embodiment, chamber 30 has a volume of 0.7725 and fan 31 when in operation generates an airflow of 0.042m³/min to draw air to be sampled from outside the present device through openings 12 and 20 and into chamber 30. Chamber 30 makes the device intrinsically safe because sensors are housed within chamber 30. The sampled air is then pushed by fan 31 and gravity further down into chamber 30 where the sampled air contacts sensors 32 to 40 and then exits chamber 30 via air vents 24. The passage of sampled air through chamber 30 results in mixing of the sampled air which aids sampling of the sampled air by sensors 32 to 40. In another embodiment, a humidity filter (not shown) can be placed in opening 12 such that intake air passes through the filter before entering chamber 30. Filtering the intake air can increase the lifespan of one more sensors 32 to 40 in chamber 30.

[0033] In one embodiment of the present device, sensors 32 to 40 make their respective measurements simultaneously each second (1 Hz). VVth the inner volume of chamber 30 equal to the amount of sampled air displaced in chamber 30 per second, chamber 30 is filled with sample air by the time sensors 32 to 40 start collecting their respective measurements. Sensor collection can start after the first second of the fan being switched on, or upon another suitable time delay between fan start-up and sensor sampling. In other embodiments, other suitable time intervals between measurements can used.

[0034] For optimal results, the device should be placed within a radius of three meters of a gas source. Sources further away will take longer to be displaced by fan 31 in chamber 30 but are still operable. In operation, in one embodiment, a sequence of sampling starts with fan 31 being turned on and drawing air to be sampled from the surroundings Into chamber 30. After one second, the sample air becomes mixed inside of chamber 30 and sensors 32 to 40 take their respective measurements simultaneously. As the measurements are done, the software in the ESP32 processes the pressure, humidity, and temperature readings from sensor 40 and either increases or decreases the resistance of one or both of MQ4 sensors 32 and 34 to calculate the most accurate sensitivity. In another embodiment, sensors 32 and 34 can be adjusted to high sampling/high sensitivity mode using a signal to noise ratio (SNR), that is, using a mean CH4 computed with equation (1) below or any of the other models described in this disclosure, divided by a standard deviation over a time interval 7. This SNR from a rotatory MQ4 sensor is compared with the SNR from a static MQ4 sensor. Likewise, it is possible to compute a SNR from MQ8 and MQ6 sensors using only the readings in millivolts (mV) to determine any cross-sensitivity.

[0035] In one embodiment, the inner volume of chamber 30 defined by its radius and height has a dependence on the airflow of fan 31 as described in Equation (2):

[0036] As a result of the above dependence, air inside the chamber is fully mixed at the time of taking measurements but it is also mixed with air drawn from air surrounding the present device. By using the model of Equation (2) to identify the volume and given the concentration of the gas (CH 4), it is then possible to compute its mass and emissions (measured in mass per unit of time). In one embodiment, the use of a cylindrical chamber a Iso maximizes the volume while minimizing the surface area and required material for assembly. In other embodiments, air from other parts of the chamber (r.e. bottom, left or right face of chamber 30) are sampled.

[0037] In one embodiment, data acquired simultaneously by sensors 32 to 40 are processed (either by the present device itself or the data transmitted across a network and processed remotely) using a model described by Equation (1) to produce a methane concentration reading. In one embodiment the [y_CH4 ] value can be used to warn of an elevated methane, leve La s-further. detailed below. Such a warning can be used to for example sound an alarm or shut down the operation of certain equipment or systems.

[0038] Equation (1) adjusts for cross-sensitivities in methane sensors 32 and 34 to gases other than methane, and also adjusts for the temperature dependence of methane sensors 32 and 34. Equation (1) is used to calculate yew which is a methane concentration value using the measured sensor values in millivolts for the sensors for methane [XMQ], hydrogen [X_w] and liquified petroleum gas [Xz.rc] obtained from the respective sensors, as well as measured relative humidity [XH2O], atmospheric pressure [X_P] and temperature [XT] values. Coefficients β o to β₈ used in Equation (1) are not measured and are discussed in the example below. In one embodiment, resistor value [XMQ4Reszszor] is initially chosen based on initial temperature, pressure and humidity readings taken at the beginning of a methane concentration sensing session (see Table 1). In another embodiment, equation (1) is solved one or more additional times to generate additional concentration of methane [yCH4] values and resistor value [XMQ4Resisor] is subsequently adjusted accordingly depending on the trend of the concentration of methane [yCH4] values obtained using Equation (1). In one embodiment of the present method, the concentration of methane [yCH4 ] obtained from Equation (1) per time interval T is checked to see if it is constant and the resistor on the secondary MQ4 sensor 34 is adjusted to correspond to the resistance load that corresponds to the temperature, pressure and relative humidity according to the concordances in Table 1. If the second sensor 34, once its resistor is adjusted, detects a statistically significant change in methane concentration with respect to the main methane sensor 32 whose resistance has not been modified, then the resistance of the main method sensor 32 is changed to match that of the secondary methane sensor 34. There are three possible instances where the resistor value [XMQ4Resistor] of the main MQ4 sensor 32 would be adjusted: (i) if the concentrations have a constant trend and the second MQ4 sensor 34 catches a statistically significant measurement with another resistor value, (ii) if there is a trend going up in which another resistor value would provide a better accuracy, and (iii) if there is a trend going down in which another resistor value would provide more precise measurements as specified in Table 1 .

Table 1 . Initial Resistor Value based on Environmental Condition

[0039] By way of an 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, and Temperature = 9.69°C, resistor = 20.05KOms and values for coefficients p0 to p8 from Table 2. In one embodiment, coefficients can be varied within the ranges provided in the “Range Coefficient" column of Table 2.

Table 2. Coefficients and ranges

[0040] Using the above values and solving Equation (1) results in a generated methane concentration of 20.53 parts per million (ppm). In one embodiment, a concentration of 20.53 ppm means there is a medium risk of a methane gas leak. In one embodiment, the present device is specially designed to differentiate readings from six categories 0 - 5ppm normal concentrations, 5ppm - 20ppm low-risk of leak, 20ppm - 100ppm medium-risk, 100ppm - 1000ppm high-risk, 1000ppm - 5000 health risk, 50,000 ppm explosivity risk. An operational flowchart for one embodiment of the present device is provided in FIG.10.

[0041] The present device and method were tested and cross-validated using data collected from a central steam plant, and the present inventor has determined that Equation (1) is the preferred model (lowest result variance and smallest bias). However, the AirKeeper and the variables it is able to measure (e.g. electrochemical sensor measurements, environmental values, and resistor values) allow for the use of alternate models to provide methane concentrations. These alternative models include a model comprising simple decision trees involving predictors, and the following models:

• Simple Multivariate Regression yCH4 = β1 XH2O + P2XH2 + β3XLPG + P4XT + β5 Xp + β 5XMQ4 + β6XResiStor

• Polynomial Regression

where a...g are some real number

• Model with some transformation yCH4 = f(β1XH2O + β2XH2 + β3XLPG + β4XT + β5Xp + β5XMQ4 + β6XResistor) where f is any function

• An artificial neural network model comprises multiple layers that assign weights to various environmental conditions and the measurements of MOX sensors, leveraging training data. Concurrently, a genetic algorithm (GA) is employed to iteratively optimize and derive the best approximation. [0042] Referring to Figures 11 to 16, in another embodiment, sensors 32 to 40 are housed in a housing 55 which has an open top and an open bottom and tapers towards the open bottom. Housing 55 serves the same function as chamber 30 and nests inside housing 4. Nesting housing 55 inside 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 operably connected to the electrical components of the device of the present invention as shown in the circuit diagrams of FIG. 7 and FIG. 8 and described with respect to other embodiments of the invention. A cover 56 is placed over battery 58 and integrated circuit board 46. Cover 56 can be made of silicon or other suitable malleable material.

[0043] Arrows 60 indicate the path and direction of air as it is drawn into the device through circular opening 20 in ring cap 6 and into housing 55, then out the bottom of housing 55 where some of the air exiting housing 55 contacts cover 56, is warmed by heat from integrated circuit board 46 and rises by convention into the space between the walls of housing 55 and housing 4 to help insulate the chamber in housing 55 and help keep sensors 32 to 40 warm, while some of the air exits the device through air vents 24. The circulation of air also helps to cool integrated circuit board 46.

[0044] While the teaching herein includes illustrative embodiments and examples of some aspects of an invention, the description is not intended to be construed in a limiting sense. Thus, various modifications of the illustrative embodiments, as well as other embodiments of the invention, may be apparent to persons skilled in the art upon reference to this description. It is therefore contemplated that the appended claims will cover any such modifications or embodiments.

[0045] All publications, patents, and patent applications referred to herein are incorporated by reference in their entirety to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference in its entirety.

Claims

What is claimed is:

1. A gas sampling device comprising: a cylindrical chamber comprising a closed top and a closed bottom, an opening in the top and air vents in the wall of the chamber proximate to the closed bottom, a fan in the opening for drawing atmospheric air into the chamber and creating positive pressure in the chamber to expel air through the air vents, a set of sensors in the chamber, the sensors comprising a methane sensor, a hydrogen sensor, a liquified petroleum gas sensor, a temperature sensor, an atmospheric pressure sensor, and a relative humidity sensor, and a controller and a power source operably connected to the sensors and the fan for controlling the fan and sensors for the collection of sensor data.

2. The gas sampling device of claim 1 , wherein the controller further comprises a processor with stored instructions for processing the sensor data and generating a methane concentration value.

3. The gas sampling device of claim 2, wherein the stored instructions comprise instructions for using the sensor data and solving equation

where

[yCH ] is a concentration of methane value, [XH2O] is a relative humidity value from the relative humidity sensor. [XMQ4] is a measured value from the methane sensor. [XH2] is a measured value from the hydrogen sensor, [X PG] is a measured value from the liquified petroleum gas sensor, [X_P] is a measured atmospheric pressure value from the atmospheric pressure sensor, [XT] is a measured temperature value from the temperature sensor, p_; to β8 are coefficient values, and [XMQ4Reststor] is a resistor value, for generating the methane concentration value.

4. The gas sampling device of claim 3, the stored instructions further comprising instructions for repeating, one or more times, the step of generating the methane concentration value using sensor data from fresh sensor readings.

5. The gas sampling device of claim 4, the stored instructions further comprising instructions for adjusting a resistance of the methane sensor in response to a trend over a time interval in the generated methane concentration values.

6. The gas sampling device of claim 5, further comprising a second methane sensor.

7. The gas sampling device of claim 6, the stored instructions further comprising instructions for adjusting the resistance of the second methane sensor to correspond to the resistance load that corresponds to the measured values for temperature, pressure and relative humidity.

8. The gas sampling device of any one of claims 1 to 7, further comprising an air quality sensor.

9. A method of producing a methane concentration value comprising the steps of: providing a reading from a methane sensor, providing a reading from a hydrogen sensor, providing a reading from a liquified 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 generating, using a processor, a methane concentration value using the readings.

10. The method of claim 9, wherein the readings from the methane, hydrogen and liquified petroleum sensors are resistance readings.

11 . The method of claim 9 or claim 10, wherein the methane concentration value is calculated by solving equation,

where

[yCH4 ] is a concentration of methane value, [XH2O] is a relative humidity value from the relative humidity sensor, [XMQ4] is a measured value from the methane sensor, [XH2] is a measured value from the hydrogen sensor, [XLPG] is a measured value from the liquified petroleum gas sensor, [XP] is a measured atmospheric pressure value from the atmospheric pressure sensor, [XT] is a measured temperature value from the temperature sensor, β_o to β8 are coefficient values, and [XMQ4 Resistar] is a resistor value.

12. The method of claim 11 , further comprising repeating, one or more times, the step of solving the equation using value using fresh readings from the sensors to generate one or more additional methane concentration values.

13. The method of claim 12, further comprising adjusting a resistance of the methane sensor in response to a trend over a time interval in the methane concentration values.