Finding fugitive emissions

The control and management of fugitive emissions is becoming even more important for safety compliance, and the techniques used to identify them are becoming more accurate. Sean Ottewell reports.

Cameras equipped with infrared (IR) technology are quickly becoming an essential tool in the chemical manufacturing and other industries in the detection of fugitive emissions - the leaks in pipe connections and seals that are difficult to detect.
Although use of the IR cameras is only just becoming a requirement of the US Environmental Protection Agency (EPA), LyondellBasell began using the technology in 2005. The initial results from their use in ground and aerial surveys at the Channelview and La Porte, Texas, plants and also at the plants in Morris and Tuscola, Illinois, were very promising and IR cameras are now an important part of plant equipment at the company's sites (Fig. 1).
The use of IR cameras enables the company to pinpoint the exact location of leaks that might have remained hidden using traditional fugitive monitoring techniques. In only minutes, an operator can aim, pan and zoom as far as several hundred feet away from an area and check for leaks without having to move. Traditional methods for identifying fugitive emissions required placement of an instrument probe directly on the component, which is a challenge for components high in a pipe rack.
Another advantage is the detection of particularly elusive emissions that leak from corrosion beneath insulation. These leaks have historically been a challenge and many times impossible to pinpoint because the vapours often exit at points a considerable distance from the source point. The IR camera can very easily detect the source of these leaks by simply following the trail of the hydrocarbon plume.

Law enforcement

The Dutch Environmental Protection Agency (DCMR) is using a FLIR GF320 optical gas imaging camera from French company FLIR Advanced Thermal Solutions to help with inspection and law enforcement in and around the port of Rotterdam where many chemical companies are located.

The tasks of the DCMR include regulation of all the industries in the area and monitoring and assisting authorities on developing environmental policy. The DCMR issues permits to virtually all of the 22,000 enterprises in the area and carries out more than 9000 inspections to monitor compliance with the permit conditions.

Earlier field studies found that emissions for volatile organic compounds (VOCs) in the area were 3-4 times that reported by the industries present.

After comparing several techniques Rob van Doorn, technical manager of the DCMR and his colleagues opted for the FLIR GF320 optical gas imaging camera. "The external consultants we had hired previously utilised technologies like solar occultation flux (SOF) and differential absorption light detection and ranging (DIAL). Although these techniques are robust and can quantify the emissions these technologies are very expensive to purchase, they are unwieldy, requiring large trucks to carry the equipment, and also complicated to use, requiring a lot of training to be used effectively. In comparison the GF-Series camera is a much more affordable solution. It is also compact, lightweight, portable, and it is very easy to use, requiring very little training," he said.

So the initial focus for using the camera will be on inspecting storage tanks, vapour recovery units, and VOC handling activities of refineries and storage and handling facilities. The camera will be used to develop a standard and solid working method that can be used as a law enforcement tool.

The US National Energy Technology Laboratory (NETL) is using a range of techniques including near IR and thermal IR to detect and monitor fugitive emissions of carbon dioxide stored in geologic formations.

By providing an accurate accounting of stored carbon dioxide and a high level of confidence that the carbon dioxide will permanently remain in storage, these efforts can help ensure the technical soundness and economic viability of carbon sequestration, a technology that is critical to meeting the national goal of reduced greenhouse gas emissions.

Migration pathways

To identify possible carbon dioxide migration pathways, NETL scientists are investigating surface and near-surface characteristics by combining satellite and aerial photography with remote sensing, ground-penetrating radar, and ground-based measurements. In co-operation with regional sequestration partnerships, long- and short-term carbon dioxide monitoring is being conducted at depleted oil wells, saline aquifers, and coal-bed methane test sites.

For example, using ground-penetrating radar, NETL found extremely low levels of carbon dioxide leakage associated with subsurface thinning and faulting under the sandy soil at the West Pearl Queen, New Mexico, depleted oil well sequestration test site. NETL registered similar low levels of leakage using several techniques to monitor the Frio saline aquifer sequestration test site near Houston, Texas.

Tracer compounds

A novel technique NETL used at both the West Pearl Queen and Frio sites to monitor sequestered carbon dioxide is to add chemically inert perfluorocarbon tracer compounds to the carbon dioxide stream being sequestered, and then detect any resulting tracer emissions in soil-gas at extremely low concentrations. NETL developed the protocol for tracer detection and quantification, the soil sampling pump, and several sampling systems.

Other NETL-developed techniques are capable of monitoring fugitive emissions of non-carbon dioxide greenhouse gases such as methane.

Perfluorocarbon tracers in a syringe pump located in the back of the NETL van are being added to carbon dioxide as it is injected underground at the Frio saline aquifer sequestration test site near Houston, Texas.