Modern industrial plants are typically required by law to measure and report the quantities of certain chemicals that they release to the atmosphere. As environmental regulations become increasingly stringent and ubiquitous, more plants worldwide will need adequate process analysis to guarantee compliance.

Government agencies such as the EPA and EEA have rigid criteria for Continuous Emissions Monitoring (CEM) systems. Stipulations include the mandatory monitoring of emissions of SO2, NOX (generic term for nitrogen oxides including NO and NO2), CO, CO2, and O2, as well as strictly regulated reporting of these chemicals’ concentrations.

While reducing emissions is a pressing environmental issue, it typically poses no direct financial benefit for the plant yet requires purchasing and servicing expensive equipment. Clearly, an ideal CEM system provides reliable compliance at minimal cost. The OMA CEMS is a fully integrated powerhouse, monitoring dynamic concentrations of various emitted chemicals with a single system.

While this solution leads its class in multi-component accuracy, it remains cost-effective by virtue of low-maintenance solid state design, competitive pricing, and high scalability for your exact analysis needs. The painless, economical route to environmental compliance and public social responsibility begins as soon as your OMA emissions monitoring solution is installed.

Concept: Spectrophotometer Principle of Operation

This article explains the principle of operation behind the nova II UV-Vis/SW-NIR Spectrophotometer, the detector used in many of our analyzers.

The key difference between a spectrophotometer and conventional photometers is that photometers use 'non-dispersive' methods whereby measurement wavelengths are physically isolated using filters. For measuring multiple components, this will require the photometer to employ a moving part (filter wheel) or multiple line source lamps. By contrast, our spectrophotometer is solid state and has a single light source.

Fig 5.10

The Path of the Light Signal

The measurement cycle of the nova II is virtually instantaneous, but it is helpful to explain it in stages:

1. The white light signal originates in the pulsed xenon light source.
2. The signal travels via fiber optic cable to the entry point of the flow cell, where a collimator narrows the light beam. The signal travels directly across the flow cell path length, interacting with the continuously drawn process sample fluid.
3. Now containing the distinct absorbance imprint of the current chemical composition in the sample, the signal exits the flow cell on the opposite end through a collimator and travels via fiber optic cable to the spectrophotometer inside the analyzer enclosure.
4. The holographic grating physically separates (disperses) the signal into its constituent wavelengths, focusing each wavelength onto a corresponding photodiode within the 1024-element diode array.
5. The light intensity spectrum measured by the diode array is processed by the analyzer CPU. The absorbance spectrum is calculated and visualized by plotting lost light intensity at each wavelength due to the process sample interactions.

From xenon lamp to diode array, the entire cycle occupies a few milleseconds and involves no moving parts.

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