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Methane detectors are crucial for monitoring efficiency and safety in a large variety of applications. This article illustrates why infrared (IR) sensors are the favored choice for the detection of methane.
As recently as 30 years ago, canaries were still used by miners to warn them of high levels of methane or carbon monoxide present in the mine. Luckily, sensor technology has now moved on, and there is an ever-increasing number of choices for gas detection.1,2
Gas detectors that can quantify and detect environmental and industrial gases such as methane, carbon monoxide, and carbon dioxide play a key role in ensuring the efficiency and safety of a wide scope of applications and processes.
Gas Detectors are Widely Used to Monitor Methane Concentrations and Detect Leaks
Mainly consisting of methane, natural gas is used widely in power generation. Methane is a greenhouse gas, it is highly flammable, and can form explosive mixtures in air. Detecting leaks is crucial during natural gas extraction, transportation, and power generation, as methane leaks can have devastating results.2-4
In the chemical industry, production of methanol, syngas, acetic acid and other commodity chemicals rely on methane gas sensors to confirm that processes are operating efficiently and safely. Measuring atmospheric levels of methane is also becoming more vital for monitoring changing environmental conditions that could affect human health and the environment.2-4
Commercially Available Gas Detection Technologies
There is a wide range of commercially available methane gas detectors and sensors, all with their advantages and disadvantages:
- Electrochemical sensors
Electrochemical sensors reduce or oxidize the methane at an electrode to create a current, which is utilized to determine the concentration of gas. Due to the contact between the electrode and the atmosphere, chemical contamination and corrosion can happen, so electrochemical sensors need replacing often. 4-6
- Flame ionized detectors (FIDs)
FIDs employ a hydrogen flame to ionize the methane gas. The ionized gas conducts an electrical current, which is calculated to establish the gas concentration. Although FIDs are accurate and fast, they need an open flame, the presence of a hydrogen source, and a clean air supply which means FIDs are unsuitable for some applications.4,5
- Catalytic sensors
Catalytic sensors catalyze the reaction between oxygen and methane, resulting in heat generation and an adjustment in resistance in the sensor, from which the methane concentration can be measured. Although catalytic sensors are robust and inexpensive, the presence of oxygen is essential to operate and they are susceptible to contamination, poisoning, and sintering. Frequent calibration and replacement is required as a result.5-7
- Semiconductor sensors
In a similar manner to catalytic sensors, semiconductor sensors react with methane, causing a change in resistance that is used to calculate the gas concentration. In common with catalytic sensors, semiconductor sensors are prone to contamination and poisoning.5,6,8
- IR sensors
IR sensors utilize an IR beam to detect and measure any gases that are present in the atmosphere. Although infrared sensors are a little more expensive than some other sensors, they are long-lasting and robust. As a result, infrared sensors have become the dominant technology for detecting a range of gases.4-6,9,10
IR Sensors are the Technology of Choice for Methane Detection
Nondispersive infrared sensors (NDIR) sensors typically consist of an IR source, an IR detector, a sample chamber, and a light filter. Usually, a second chamber which contains a reference gas runs in parallel to the sampling chamber.
IR light is administered to the detector through the atmospheric sampling chamber. The methane gas present in the sampling chamber absorbs light at specific wavelengths. A filter in front of the detector blocks out light that is not at the chosen wavelength, so the detector measures the attenuation at the specified wavelength only, which is utilized to ascertain the concentration of methane present.9,10
IR sensors have many advantages over other gas detection technologies: They have a fail-safe system which is built-in, which comes from the fact that small signals represent high concentrations of gas, while in other sensors small or no signal means zero or low gas concentrations. If the detector fails or becomes obscured, IR radiation will not be registered, which will trigger an alarm.
NDIR sensors can also be more precise than methods that need the gas mixture to be burnt. In some instances, NDIR sensors can even permit the detection of one flammable gas component whilst another is present. Although, this does create a limitation that users cannot determine whether a gas mixture is flammable or not.
IR detectors don’t interact with the methane gas, unlike other available types of sensors. The gas and any contaminants in the atmosphere only interact with a light beam. As a result, the detector is shielded from damage and has a long lifespan.4,5,9,10
IR detectors give accurate results and fast response times, which is also common with other sensors. While semiconductor, catalytic, electrochemical sensors, and FIDs all need the target gas to be present in concentrations below the lower explosion limit, IR sensors can calculate gas concentrations of 0-100% accurately. They do not require external gases or oxygen for operation. 4,5,9,10
IR sensors have some disadvantages; they can be affected adversely by adjustments in pressure and temperature.5 Nonetheless, advanced IR sensors now produce pressure and temperature compensation, meaning durable and reliable sensors with minimal drawbacks. IR sensors are now the chosen detection method for methane and other industrially and environmentally relevant gases.11
Edinburgh Sensors Gascard NG for Reliable Gas Detection
Figure 1: Gascard NG from Edinburgh Sensors. Image credit: Edinburgh Sensors. Edinburgh sensors, a leading supplier of high-quality gas sensing solutions, provides a comprehensive range of NDIR sensors for reliable carbon dioxide, carbon monoxide, and methane detection.12,13
The Gascard NG is a gas sensor made for simple integration by original equipment manufacturers (OEMs) into a wide variety of systems to give reliable and accurate calculations of carbon dioxide, carbon monoxide and methane gas concentrations.14
Some IR sensors suffer from the effects of pressure or temperature, but the Gascard NG incorporates considerable pressure and temperature correction to guarantee accurate results in many environments.14 The Gascard NG is utilized for methane detection in a variety of research, environmental and industrial applications including pollution monitoring,15,16 agricultural research,17,18 chemical processes,19,20 and many more.
References and Further Reading
- ‘Evolution of Gas Sensors in the Mining Industry’ https://www.azosensors.com/article.aspx?ArticleID=12
- ‘Handbook of Modern Sensors: Physics, Designs, and Applications’ — Fraden J, Springer, 2010.
- ‘Monitoring Methane’ — Patel P, ACS Central Science, 2017.
- ‘Instruments for Methane Gas Detection’ — Thomas S, Haider NS, International Journal of Engineering Research and Applications, 2014.
- ‘The selection and use of flammable gas detectors’ http://www.hse.gov.uk/pubns/gasdetector.pdf
- Explosive atmospheres. Gas detectors. Selection, installation, use and maintenance of detectors for flammable gases and oxygen (BS EN 60079-29-2:2015) — British Standards Institution, 2015.
- ‘Solid State Gas Sensing’ — Comini E, Faglia G, Sberveglieri G, Springer, 2008.
- ‘Forty Years of Adventure with Semiconductor Gas Sensors’ — Mizsei J, Procedia Engineering, 2016.
- ‘Non-Dispersive Infrared Gas Measurement’ — Wong JY, Anderson RL, IFSA Publishing, 2012.
- ‘Handbook of Gas Sensor Materials: Properties, Advantages and Shortcomings for Applications Volume 1: Conventional Approaches’ — Korotcenkov G, Springer, 2013.
- ‘A Survey on Gas Sensing Technology’ — Liu X, Cheng S, Liu H, Hu S, Zhang D, Ning H, Sensors, 2012.
- ‘Edinburgh Sensors’ https://edinburghsensors.com/about/about-us/
- ‘Methane Gas Sensing Solutions’ https://edinburghsensors.com/search-by-gas/methane/
- ‘Gascard NG’ https://edinburghsensors.com/products/oem/gascard-ng/
- ‘Calibration of a cluster of low-cost sensors for the measurement of air pollution in ambient air’ — Spinelle L, Gerboles M, Villani MG, Aleixandre M, Bonavitacola F, Sensors, 2014.
- ‘The development and trial of an unmanned aerial system for the measurement of methane flux from landfill and greenhouse gas emission hotspots’ — Allen G, Hollingsworth P, Kabbabe K, Pitt JR, Mead MI, Illingworth S, Roberts G, Bourn M, Shallcross DE, Percival CJ, Waste Management, 2018.
- ‘Interchangeability between methane measurements in dairy cows assessed by comparing precision and agreement of two non-invasive infrared methods’ —Difford GF, Lassen J, Løvendahl P, Computers and Electronics in Agriculture, 2016.
- ‘The time after feeding alters methane emission kinetics in Holstein dry cows fed with various restricted diets’ — Blaise Y, Andriamandroso ALH, Beckers Y, Heinesch B, Muñoz EC, Soyeurt H, Froidmont E, Lebeau F, Bindelle J, Livestock Science, 2018.
- ‘Effect of active thermal insulation on methane and carbon dioxide concentrations in the effluent of a catalytic partial oxidation reactor for natural gas conversion to synthesis gas’— Al-Musa A, Shabunya S, Martynenko V, Kalinin V, Chemical Engineering Journal, 2015.
- ‘Syngas Production from Propane-Butane Mixtures using a High-Voltage Atmospheric Pressure Discharge Plasma’ — Alenazey FS, Al-Harbi AA, Chernukho AP, Dmitrenko YM, Migoun AN, Zhdanok SA, Heat Transfer Research, 2016.
This information has been sourced, reviewed and adapted from materials provided by Edinburgh Sensors.
For more information on this source, please visit Edinburgh Sensors.