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The detection of toxic gas emissions, such as carbon monoxide (CO), carbon dioxide (CO2) and methane (CH4), which can be achieved through various applications and processes, is imperative for ensuring the safety of all working personnel. In addition to safety concerns, these types of gas detectors can also be used to improve efficiency of certain chemical industrial processes that produce syngas, methanol, acetic acid and other chemicals.
While natural gas can be exploited in these industries to generate power, the leakage of greenhouse gases like methane could cause catastrophic events, of which can include explosions, severe injuries and even death to nearby workers. It is therefore critical that the potential leakage of these types of harmful gases is closely monitored during extraction and transportation processes in facilities that utilize these gases of power generation.
The Limitations of FIDs
Although traditional detectors, such as flame ionization detectors (FIDs), are accurate and rapid in their ability to detect and determine gas concentrations, these detectors often require the presence of a hydrogen source, open flame and clean air supply to function properly. As a FIDs may be unsuitable for certain applications, therefore requiring the need for other gas detection sensors to be employed instead.
Catalytic Sensors
Catalytic gas sensors are capable of directly detecting methane concentrations by measuring the change in resistance that occurs as a result of heat generated following the reaction between methane and oxygen. In doing so, catalytic sensors initiate the reaction between methane and oxygen. Since catalytic sensors require the presence of oxygen to function, they are therefore vulnerable to potential personnel poisoning, sintering and contamination. Although catalytic sensors are robust and generally inexpensive tools, they are often require regular calibration and part replacement.
Semiconductor Sensors
Similar to catalytic sensors, semiconductor-based sensors detect the change in gas concentration by measuring the change in resistance that occurs in the presence of methane. Semiconductor sensor, like catalytic sensors, are also prone to contamination and poisoning.
Electrochemical Sensors
These sensors detect gas concentration by measuring the current produced by oxidizing or reducing methane at an electrode. Electrochemical sensors also require frequent replacement due to the contamination and corrosion that occurs as a result of the contact between the electrode and the environment.
Infrared (IR) Sensors
Infrared (IR) sensors detect and measure the concentration of the gases through the use of an IR beam. Nondispersive IR (NDIR) sensors consists of an IR source, sample chamber, light filter and an IR detector, along with a reference gas that is present in another chamber. When exposed to methane gas, a specific wavelength of IR light, which is directed through the sample chamber, is absorbed by the methane. The attenuated signal is subsequently measured by the detector and quantified in order to accurately determine the methane concentration.
As compared to the aforementioned devices, IR sensors are not prone to chemical contamination or poisoning, which is attributed to their non-contact nature. As a result, IR sensors are robust and long lasting options. Furthermore, IR sensors are equipped with a fail-safe mechanism that alarms the user when the sensor fails or becomes obscured. The non-contaminating nature, robustness, accuracy and ability of IR sensors to detect multiple gases, has allowed these tools to emerge as a powerful gas detection technology. IR sensors have been used as a preferred method of gas detection for detecting methane and various other gases that are industrially and environmentally relevant.
Advancements in IR Gas Sensors
While earlier generation IR sensors were adversely affected by temperature and pressure, the new generation of IR sensors provide compensation for temperature and pressure effects, thereby making them increasingly reliable and durable. For example, Gascard NG by Edinburgh Sensors, which is a leading supplier of high-quality gas sensing solutions, provides users with an accurate and reliable measurement of CO, CO2 and CH4 concentrations. Due to the extensive temperature and pressure correction provided by the Gascard NG, this sensor can be used in a variety of applications, of which include research laboratories, industries, agriculture and environmental applications, such as pollution monitoring.
References
- “Air Monitoring, Measuring and Emissions Research” – The United States Environmental Protection Agency
- “Using an Infrared Sensor (IR Sensor) for Reliable Methane Gas Monitoring” – Edinburgh Sensors
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