Methane Gas Visualization Using Infrared Imaging System and Evaluation of Temperature Dependence of Methane Gas Emissivity

Abstract

Infrared (IR) camera has been used widely in the industry to visualize gases that cannot be seen by the naked eye or a visual camera. The use of an infrared camera for gas imaging offers several advantages such as faster locating of gas leaks and easier understanding on how the gas travels and disperses. In addition, several types of infrared cameras have the capability to measure the temperature of target objects especially solid body objects. However, this facility has not been applied for measurement of gas temperature due to complex analysis on the physics of infrared imaging and some uncertainties related to the radiation heat transfer processes during temperature measurement that have not been well understood. The objective of this research is to make use of the infrared or thermal imaging system to provide a concise temperature distribution of a methane gas plume presented in the infrared image. However, the current technology in infrared imaging cannot provide the true temperature of a gas plume because the emissivity value is always assumed as unity, and the actual emissivity value of the gas is not integrated in the camera’s algorithm. The visualization of dispersed liquefied natural gas (LNG) vapor from LNG spills on the ground using a midwave thermal camera is presented in this work. Two types of infrared cameras were used: Amber Radiance 1 and GasFindIR, also known in industry as hydrocarbon camera. The infrared images or thermograms show that several factors affecting the temperature measurement are weather conditions, wind rose, atmospheric attenuation due to the presence of other radiation absorbing gases along the optic path, and gas emissivity. Gas emissivity is the main uncertainty in gas temperature measurement using thermal cameras. This research proposed a method to correct the gas temperature measured by a thermal camera by applying the emissivity factor calculated from a theoretical analysis on methane gas emissivity using the band absorption method. The study demonstrates that methane gas emissivity is a strong function of gas temperature; however, the effect of optical depth is insignificant. Because in this work, the infrared camera is used to visualize the LNG vapor, temperature dependence of methane emissivity at temperatures 110−300 K is evaluated and presented in this paper.

In situ temperature measurements in microwave-heated gas-solid catalytic systems. Detection of hot spots and solid-fluid temperature gradients in the ethylene epoxidation reaction

“…Each molecule has a specific absorption range within the infrared spectrum and IR cameras can detect the absorptive and 12 emissive characteristics of these gas molecules. When the detection range of the IR camera can be tuned to a narrow spectral region where the target molecules display a strong absorption, then the gas can be visualized 22 , i.e., in this case the gas influence will not be negligible, and this provides a basis to determine the gas temperature. For this, the emission and absorption characteristics of the gas cloud must be known, at the operation temperatures of interest.…”

“…To this end, we will make use of the fact that gases that present absorption and emission in the infrared range (there are many examples, including water, CO 2 or ethylene) can be detected with a thermographic camera. The procedure is well known and in fact is currently used for the detection of leaks in industrial pipes [22][23] . Matters, however, get much more complex when the temperature of a gas has to be determined by measuring through a partially transparent window and through different atmospheres, plus the interference of any surfaces in view within the optical path.…”

Review of Optical Thermometry Techniques for Flows at the Microscale towards Their Applicability to Gas Microflows

“…The IR imaging technique has been widely employed in gases for leak detection [61,62] and to measure temperature. For example, Safitri and Mannan [63] have detected the leak and studied temperature by directly measuring the IR signal of methane gas, which is the major constituent in liquefied natural gas (LNG). The aim of this study was to determine the concentration and temperature of LNG vapor plumes generated by spills of LNG on concrete and water (in an open environment).…”