Applications of Laser-Based Sensors for Environmental Protection - Monitoring and Testing
Gas Detection in the Environment: refer to different laser-based applications in the environment.
SO2 causes acid rain when it reacts with nitrogen oxide. It is generated during fuel combustion at power plants and other industrial facilities. For this reason SO2 emissions are restricted and need to be monitored.
Formaldehyde has been used in consumer and industrial products since the beginning of the 19th century. Currently the annual formaldehyde production accounts for 21 million tons. About 50 % are processed as adhesives in pressed wood panels. In 2004 formaldehyde has been classified carcinogenic by the International Agency for Research on Cancer. Since then formaldehyde concentrations have been strictly controlled in the production process as well as in the finished product. Laser-based measurement systems are required to detect the maximum levels of 0.01 ppb (USA) and 2 ppb (EU).
Ecologists are worried about the melting of permafrost soils in the northern hemisphere. Greenhouse gases like CO2 or CH4 that are stored in the soil might be released in this case. Another, less observed, thread comes from the evaporation and condensation of large water vapor volumes. A laser-based hygrometer for mobile field applications has been developed. It measures water vapour in situ and at low concentrations. An airborn approach for monitoring climate processes is the use of a multi-wavelength H2O-Differential Absorption Lidar. It examines the whole troposphere and lower stratosphere simultaneously.
NH3 is added in combustion processes to reduce emissions of the flue gas NOx. The two compounds will react to uncritical N2 and H2O. To avoid any corrosive or environmental effects from overuse, the gas volume needs to be continuously monitored.
Ethane is a by-product of methane emissions. The ethane ratio varies between methane emissions from thermogenic and biogenic sources. This allows differentiating oil and gas reserves from those of livestock, landfills, wetlands or stagnant water. Studies are executed on behalf of the US Environmental Protection Agency to quantify methane emissions caused byincreased natural gas exploration and production in the US. A newly developed ethane spectrometer delivers 1 second ethane measurements with sub-ppb precision in an ethane-methane mixture.
Greenhouse gas effects and climate change have triggered global emission monitoring of pollutants like methane. Methane is one of the Earth’s most important atmospheric gases. It is, to a large extend, responsible for the accelerating greenhouse effect. The global warming potential of methane is about 30 times higher than that of CO2 based on a 100 year scale. Studies are executed on behalf of the US Environmental Protection Agency to quantify the methane emissions caused by the increased natural gas exploration and production in the US.
Ethane is an important greenhouse gas that has a critical impact on climate change. Emissions are related to fossil fuel and biofuel consumption, biomass combustion and natural gas losses. Trace gas detection of ethane is an important tool to monitor greenhouse gases.
Continuous monitoring of contents like CO2 or CH4 concentrations is essential for the efficiency of high-temperature processes in e. g. incinerators, furnaces or petrochemical refineries. Managing the CO2 content in combustion processes simultaneously reduces greenhouse gas emissions. This is also relevant for energy generating industries like coal burning power plants.
Leaks of CH4 may cause dangerous situations and are hard to locate precisely. Hence, maintenance of underground pipelines produces high costs. CH4 leaks are also an important source for greenhouse gases. With TDLAS a strong tool is available to manufacture portable leak detectors.
CO is a major element in high temperature processes. Optimizing CO concentration in flue gas increases combustion efficiency. Simultaneously, it reduces greenhouse gas emissions. CO detection at long wavelengths like 2.8 μm and 4.3 μm uses stronger vibrational absorption features than the shorter wavelength ranges. This effect increases the sensitivity of the detector and allows using measurement set ups with short path lengths.