As infrared detectors simplify emissions tracking processes, laser absorption spectroscopy is helping to address an escalating methane problem.
MARK NAPLES, UMICORE COATING SERVICES
Ensuring that air quality is safe for humans and other forms of life is one of the most pressing challenges facing the world today. The average person will inhale ~79,250,000 gallons of air in their lifetime. Simply walking a city street, a person will likely inhale millions of potentially harmful particles, potentially with each lungful of air.
Although the toxicity of the air around us has been a known issue for centuries, global energy demands are growing, and the effect of air pollution on the environment and public health is reaching a
crisis point. Across the energy sector, businesses are grappling to reduce pollution stemming from their operations.
Governments around the world are enacting increasingly strict legislation. As these regulations mount, the need for technology that can monitor the air is more important than ever.
Undetected leaks can lead to environmental dangers and costly losses for companies. Laser absorption spectroscopy (LAS) can help detect these leaks quickly to limit the harm. Courtesy of Shutterstock.
Demand is also increasing for high-performance photonics systems that enable detections of trace amounts of gases. Certain tools, such as the technique of laser absorption spectroscopy (LAS), are essential to improve data collection efforts, thereby helping businesses to identify leaks and maintain regulatory compliance. Combined with advancements in connected sensor networks, photonics techniques, especially those in the IR, are apt to provide industries with the tools needed to begin investing in a more sustainable future.
A clear set of challenges
The colorless and odorless nature of many gases causes many gas leaks to go undetected. The vastness of the networks of pipelines and storage infrastructure that most businesses in the oil, gas, and other relevant sectors operate further challenge these companies and their employees to identify and act on leaks. This increases the risk of serious workplace incidents that can lead to injury and/or death.
Accurate measurements obtained via on-the ground detection will be instrumental to setting and meeting global targets on emissions reduction and supporting the energy sector in mitigating its massive environmental impact.
At the same time, these undetected emissions also present a problem for the well-being of the environment, with methane, in particular, recognized as a significant contributor to poor air quality. Largely, the intense heat-trapping potential that methane possesses is a cause for this threat. Although methane lasts for much less time in the atmosphere than other greenhouse gases, including carbon dioxide — around 12 years as opposed to hundreds — it possesses a much higher potential for global warming. Since preindustrial times, the concentration of methane in the atmosphere has risen by ~2.5×, reaching a record high in 2019.
Coated filters are essential in a variety of applications, including those supporting clean air quality measures and those targeting greenhouse gas reductions. Courtesy of Umicore.
As it relates to detection, challenges range from logistical to technical. For example, a lack of concrete and up-to-date data on the scale of air contamination from energy sector emissions is likely to limit the effectiveness and accuracy of preventative actions. Targeting the best places for investments and/or regulations becomes challenging when the global map of emissions is inaccurate.
As a result, increasing the quality of data, especially that which companies themselves gather, is imperative. Accurate measurements obtained via on-the-ground detection will be instrumental to setting and meeting global targets on emissions reduction and supporting the energy sector in mitigating its massive environmental impact.
Still, these solutions must also account for the number of sources, especially in the energy sector, where gas emissions occur. Super-emitting events, such as pipeline or storage tank failures, can lead to 10,000 kg or more of methane escaping in only 1 h1. Flaring and venting represent other common sources of methane, with some businesses often burning off large quantities of gas if they believe they cannot sell the gas for sufficient profit. And smaller-scale emissions, such as valve leaks, are often more difficult to track; much of the monitoring technology in use today is incapable of providing sufficient information about these types of leaks, which is due in part to the frequency of smaller-scale leaks. Satellite monitoring can routinely capture super-emitting events, whereas lower profile events require a more localized network of on-the-ground solutions.
Finally, the atmospheres in the energy sector can also present a problem for detection. Extreme temperatures and high humidity can influence sensor accuracy, as can oxygen-rich or oxygen-deficient atmospheres. Such conditions may contribute to sensor poison, contamination, or corrosion. Also, the presence of ambient moisture may result in lasting leaks in undersea pipelines, or in particularly humid environments that are inherently difficult to detect. Similarly, accidental leaks experienced during fossil fuel production and transport often represent an area of oversight, since these leaks are difficult to account for.
Infrared detection
From electrochemical sensors to flame-ionized detectors, industry currently benefits from a plethora of available choices when it comes to mitigating emissions. Combining devices and methods ranging from point detectors to drones ensures that businesses have access to a suite of low-cost, high-performance monitoring systems.
Amid these choices, the most effective solutions are in the IR.
Gas detection technology can broadly be split into two categories — point detectors and area detectors — with point detection being increasingly deployed by industry. Point detectors use a single detector location in which the detected source, such as a gas cloud, interacts with the sensor. In addition to IR point sensor solutions, catalytic, solid-state, and electrochemical point sensing also find use in gas sensing deployments.
Fundamentally, optical gas detection
equipment is used to measure the amount of light at specific wavelengths — namely, the wavelength where hydrocarbon molecules absorb light, and wavelengths where no absorption takes place. IR laser absorption spectroscopy (IR-LAS) exploits this methodology, passing IR beams through a sampling chamber containing a filter that blocks any light from undesired wavelengths from reaching a detector. Passing the light through the sample gas causes the wavelength’s intensity to reduce, and the other wavelength is unaffected. Comparing the ratio of the two signals yields information on the gas concentration that is present.
Valve leaks are difficult to locate, because current monitoring systems fall short of providing the data needed to find and respond to these leaks. Recent improvements in the cost and scalability of laser absorption spectroscopy (LAS) could provide a solution. Courtesy of Shutterstock.
This technology enables rapid, accurate detection and quantification of gases in the atmosphere in the parts-per-billion range. Further, other types of sensors may require the target gas to be present in concentrations below the lower explosive limit. IR sensors effectively measure concentrations of any strength, without requiring oxygen or external gases.
Enhancing potential
Recent advancements in LAS have raised its potential as a potent tool for gas detection. Newer iterations of instruments feature a laser diode mounted on a thermoelectric (or Peltier) cooler, which enables the laser’s wavelength to be tuned to match the specific absorption wavelengths of select molecules. Exploiting the high-frequency resolution of the diode sources results in enhanced sensitivity. This means that the detectors register the interaction between gas molecules and light on the order of parts per billion. Compared with other sensors, these detectors provide faster, more accurate results.
IR technology is also much more flexible than alternative solutions. Catalytic, electrochemical, and semiconductor sensors require gases to be present in concentrations below the lower explosive limit. Also, users can deploy current instruments and devices in a range of challenging environments commonly encountered across oil and gas infrastructure. These include oxygen-rich and/or oxygen-deficient locations. Such devices require little sensor calibration and are functionally immune to sensor poison, contamination, and corrosion.
Sensor fusion offers another range of benefits: Users may choose to combine real-time measurements from IR gas detectors with systems, including GPSs and geographic information systems, to expand functionality. This results in an interconnected detector network that provides immediate insights into where leaks occur, to facilitate the chance to perform quick and effective maintenance.
Coating technology
Thin-film technology helps unlock the optimal performance in optical systems. The sophistication of this technology is also rapidly increasing, owing to heightened demand for advanced IR detectors.
Thin-film technology helps unlock the optimal performance in optical systems. The sophistication of this technology is also rapidly increasing, owing to heightened demand for advanced IR detectors.
The performance (and ultimately the function) of thin films relies on how electromagnetic radiation interacts at different wavelengths with a deposited functional layer. Multiple alternating layers are used to create a filter, and these layers are made up of high- and low-refractive index material on a glass substrate. Controlling the deposition of these coatings enables the precise tailoring of thin-film properties, and experts in this technology are capable of deposition ranging from a fraction of a nanometer to several micrometers in thickness.
Using LAS devices alongside IR filters, operators can ensure an ideal signal-to-noise ratio and high selectivity for the wavelength being used. This grants these coated filters use in a range of applications, supporting air quality and greenhouse gas reduction targets.
Improving understanding
Importantly, the use and increased adoption of LAS underscores a technological shift. Even more importantly, this shift does not have to come at a great cost to oil and gas producers. Data published by the International Energy Agency last year, for example, estimates that ~80 million tons of methane emissions could be prevented by deploying technologies that exist today at no cost to businesses.
In fact, in many cases, action on methane could even prove to be profitable. Improving leak detection enables immediate repair work, which itself results in less wasted gas, which could be resold.
The favorable changes in cost and scalability of LAS technology are helping to address these issues. As these devices become increasingly cost-effective and convenient, mass IR sensing deployment at a hyperlocal level is no longer a pipe dream.
Meet the author
Mark Naples is managing director at Umicore Coating Services. He has nearly two decades of experience working across the optics,
sensing, and imaging industries; email:
[email protected].
References
1. Wood Mackenzie (Nov. 2023). Mission invisible: tackling the oil and gas industry’s methane challenge, https://www.woodmac.com/horizons/oil-and-gas-methane-challenge.