Undiscovered gas leaks, known as fugitive emissions, in chemical plants and refinery operations can impact regional air quality and present a loss of product for industry. Surveying a facility for potential gas leaks can be a daunting task. Industrial leak detection and repair programs can be expensive to administer. An efficient, accurate and cost effective method for detecting and quantifying gas leaks would both save industries money by identifying production losses and improve regional air quality. Specialized thermal video systems have proven effective in rapidly locating gas leaks. These systems, however, do not have the spectral resolution for compound identification. Passive FTIR spectrometers can be used for gas compound identification, but using these systems for facility surveys is problematic due to their small field of view. A hybrid approach has been developed that utilizes the thermal video system to locate gas plumes using real time visualization of the leaks, coupled with the high spectral resolution FTIR spectrometer for compound identification and quantification. The prototype hybrid video/spectrometer system uses a sterling cooled thermal camera, operating in the MWIR (3-5 μm) with an additional notch filter set at around 3.4 μm, which allows for the visualization of gas compounds that absorb in this narrow spectral range, such as alkane hydrocarbons. This camera is positioned alongside of a portable, high speed passive FTIR spectrometer, which has a spectral range of 2 - 25 μm and operates at 4 cm<sup>-1</sup> resolution. This system uses a 10 cm telescope foreoptic with an onboard blackbody for calibration. The two units are optically aligned using a turning mirror on the spectrometer's telescope with the video camera's output.
A highly mobile passive remote sensing FT-IR spectrometer has been designed and built. It is based on the patented Turbo FT interferometer from D&P Instruments, and was developed for the U.S. EPA in Research Triangle Park, NC. The purpose of the work is to remotely sense, detect, and identify gaseous emissions in the field. The sensor can operate from AC power or on-board battery power.
The Turbo FT is a rotary high speed Fourier Transform Infra-Red (FT-IR) spectrometer capable of operating in the rugged environments of the field. This sensor was built for 4 cm-1 resolution and 25 scans per second with a dual element MWIR/LWIR (2-16 micrometer) single pixel detector. An auto-calibrating blackbody accessory was built in, and automated real-time chemical detection software was developed. This feature allows quick calibration and facilitates the remote detection of target gas clouds. This paper will discuss the system specifications, preliminary sensor performance, and results from initial testing.
Airborne longwave infrared (LWIR) hyperspectral imagery was utilized to detect and identify gaseous chemical release plumes at sites in southern Texas. The Airborne Hyperspectral Imager (AHI), developed by the University of Hawai’i, was flown over a petrochemical facility and a confined animal feeding operation on a modified DC-3 during April, 2004. Data collected by the AHI system was successfully used to detect and identify numerous plumes at both sites. Preliminary results indicate the presence of benzene and ammonia and several other organic compounds. Emissions were identified using regression analysis on atmospherically compensated data. Data validation was conducted using facility emission inventories. This technology has great promise for monitoring and inventorying facility emissions, and may be used as means to assist ground inspection teams to focus on actual fugitive emission points.
Conference Committee Involvement (1)
Remote Sensing of Aerosol and Chemical Gases, Model Simulation/Assimilation, and Applications to Air Quality
13 August 2006 | San Diego, California, United States