50 AIRMONITORING


The CI Analytics CI SMART LASER software processes and integrates at very high frequency to give stable measurements for long periods of time.


Figure N. 2 C.I. Analytics Laser laboratory unit


(European Space Agency) observed an environmental quality improvement and a reduction up to 20-30% of NO2


emissions


throughout the pandemic early stages. Monitoring before and after the lockdown demonstrated large fluctuations of the gases due to Covid-19 in countries with high infection rates such as China, Spain, France, Italy and USA (NASA & ESA, 2020) [4,5,6]. There may be a correlation that has not as yet been identified.


On a global scale, intensive research has been conducted to evaluate the impact of the pandemics in the environment. For instance, a study carried out at Rio de Janeiro, Brazil, where the partial lockdown effects were analyzed resulted in changes of the CO levels with a significant reduction (30.3-48.5%) [7]. In Delhi, an Asian megacity with a population close to 16.8 million inhabitants, they experienced important changes in the air quality during the lockdown. Amid the most common pollutants, NO2


52.68%, whereas, CO emissions decreased 30.35% during the 24th March to 14th April, 2020 shutdown. The same study concluded a general 40 to 50 % improvement in air quality when comparing the emissions with the preceding year [8].


The challenge analysing environmental pollutants


With continued improvements in industrial processes and more stringent environmental regulations, many industrial applications require fast and accurate analytical methods. In general, industrial analyzers use gas chromatography, electrochemical, optical and mass spectrometry techniques to measure trace contaminants and key species.


Gas chromatography (GC) is the most widely used technology and provides simultaneous, sensitive detection of several species. However, GC requires frequent calibration, operational consumables (e.g., carrier gases and column replacements), hands-on maintenance, and is often too slow for active industrial process control (e.g. measurement every 2–4 minutes). Although electrochemical sensors are inexpensive, they typically cannot provide the necessary accuracy (often due to cross-interferences) and fast measurement time for industrial applications and emission monitoring.


Mass spectrometry provides very sensitive detection of multiple species, but is expensive and insufficiently robust for process control and emissions monitoring needs. Conventional optical methods (e.g. NDIR and FTIR) can quantify several species and provide fast time response, but also require frequent calibration and exhibit substantial cross-interferences between species.


Recent advances in small and compact monochromatic laser diodes and high reflective multi-pass cavities mirrors have resulted in instrumentation that meets sensitive and accurate detection requirements. Thus, compared to conventional sensors, analyzers based on laser absorption spectrometry technology provide fast (> 1 Hz), sensitive and accurate readings in complex gas mixtures with minimal calibration or drift.


Laser technology


Laser absorption spectroscopy has become the foremost used technique for quantitative assessments of atoms and molecules in the gas phase. Laser-based techniques have a great potential for detection and monitoring of constituents in gas phase. They combine a number of important properties, e.g. a high sensitivity and a high selectivity with non-intrusive and remote sensing capabilities. Miniaturized and affordable new optical components (laser, cavity, and mirrors) yield to small, compact and cost-effective product for different applications in field, continuous emission monitoring, laboratory or process measurements.


The principle of the technique relies on a light beam from a


tuneable laser passing through a gas sample and then being focused onto a detector. Typically, telecommunications-grade, near-infrared (1200 – 2000 nm) diode lasers and InGaAs detectors are used due to their robustness, availability and cost. The laser wavelength is tuned over a small range (typically 0.5 nm) by varying its injection current or laser temperature. This can be done by a laser controller (dual laser current and temperature control). Specific molecules absorb IR light at particular laser frequencies, resulting in a decrease in transmitted intensity at those frequencies. The measured transmission trace can then be converted to an absorption spectrum, and the integrated area under the absorption peak can be directly related to the concentration of the targeted species via Beer’s Law.


levels decreased C.I. Analytics Laser


The new CI Analytics laser-based analyzer is designed for high precision and accurate trace gas measurements at ppm and ppb levels. High sensitivity and selectivity (interference-free) make this analyzer a robust analytical instrument suitable for stable operation in laboratories, continuous emission monitoring, industrial process or any stringent environment. With the combination of stable laser, multi-pass cavity, 24 bits analog to digital data conversion and processing software, lower detection limits can be achieved in few seconds compared to conventional TDL and associated techniques.


Applications , acetylene (C2


The C.I. Analytics laser laboratory analyzer can measure H2 NH3


H2 S, CO2


emission narrow band makes it very selective to these impurities. Table N.1 presents the Low Detection Limits (LDL) for some impurities:


Table N.1 LDL table for C.I. Analytics Laser Gas


Range


impurity H2


S NH3 CO2 C2 H2


(Minimum- Maximum) 0-30 ppm 0-5ppm 0-30ppm 0-400ppm 0-5%


0-100ppm , ) and mixtures with no interference. The laser


Figure N.5 1 ppm of Ammonia in pure nitrogen, measured in 1 second. Top graph shows nitrogen background in blue (No absorption) and transmitted intensity in red with presence of Ammonia. The bottom graph in orange is the absorption peak which is obtained by subtracting transmitted light from sample cell to the background signal. Vertical axis is an arbitrary unit and horizontal axis wavelength around center value.


Conclusion LDL


Response time for LDL


1ppb 15 seconds 6ppb 30 seconds 66ppb 1 second 150 ppb 15 seconds 100 ppb 1 second 1 ppb 1 second


C.I. Analytics new Laser analyzer offers an analytical solution for trace gas monitoring. Whether to comply with environmental standards or to control process efficiencies, CI. Analytics Laser analyzer is a versatile automatic unit designed to respond in a fast and appropriate way to the analytical needs of a changing world.


References


[1] https://www.activesustainability.com/climate-change/link- between-climate-change-air-pollution/


[2] https://www.iass-potsdam.de/en/output/dossiers/air-pollution- and-climate-change


[3] https://www.canada.ca/en/environment-climate-change/ services/air-pollution/pollutants/common-contaminants.html


[4] S. Muhammad et al., COVID-19 pandemic and environmental pollution: A blessing in disguise?/ Science of the Total Environment 728 (2020) 138820


[5] https://earthobservatory.nasa.gov/images (2020)


[6] https://www.esa.int/Applications/Observing_the_Earth/ Copernicus/Sentinel-5P (2020)


[7] G. Dantas et al., The impact of COVID-19 partial lockdown on the air quality of the city of Rio de Janeiro, Brazil / Science of the Total Environment 729 (2020) 139085


[8] S. Mahato et al., Effect of lockdown amid COVID-19 pandemic on air quality of the megacity Delhi, India / Science of the Total Environment 730 (2020) 139086


Figure N.3 Laser transmitted intensity (top graph) and absorption peak (bottom graph) NH3


sample gas at different concentration levels from 0


to 1 ppm. Vertical axis is an arbitrary unit and horizontal axis wavelength around center value.


Author Contact Details Babacar Diop and Lorena Torres • 2085 Industrial blvd., Chambly, QC J3L 4C5, Canada • Tel +44 450 658 4965 • Email: info@cianalytics.ca • Web: cianalytics.com


IET ANNUAL BUYERS’ GUIDE 2020/21 WWW.ENVIROTECH-ONLINE.COM Figure N.4 1ppm of acetylene (C2H2 ) in nitrogen and in ethylene. Absorption


peak is obtained by scanning the laser around the central absorption wavelength. Vertical axis is an arbitrary unit and horizontal axis wavelength around center value.


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