The CEM500 is an extractive online gas analyser dedicated to Continuous Emission Monitoring.
This new model is based on a 2048 pixels CCD (charge-coupled device) giving a higher resolution (0.1 nm) and a longer lamp life time (3 years) It is based on UV spectroscopy that brings a higher sensitivity than infra-red and gives the possibility to measure several gases simultaneously. A high selectivity is achieved by a fast Fourier transform (FFT) on the absorbance spectrum for all the gases having a periodic structure like NH3, SO2, NO and others. All the internal gas circuit is heated at 190°C to admit directly hot and humid combustion gases. The CEM500 is presented in a IP65 wall mounted enclosure. This model may include a heated sampling pump as an option.
MAIN METHOD : UV SPECTROSCOPY
- Several gases can be measured simultaneously thanks to the UV spectroscopy method by using different wavelengths and algorithms. For gases with a periodic absorption spectrum such as NH3, SO2, NO, CS2 or acetylene, an algorithm based on FFT (Fast Fourier Transform) guarantees a very good selectivity of measurement. The solid-state design due to the UV spectroscopy gives a high reliability of the measuring system with quite no maintenance.
- The UV lamp is a xenon flash lamp with a high lifetime and without thermal effect that may generate measurement drift.
- The gas flow cell has two quartz windows to transmit the UV light through the measured gas. The standard path length of the flow cell is 240 mm.
- The spectrograph is based on a concave grating to minimize the optical parts and the spectrum is read on a 2048 pixel CCD with a resolution of 0.1nm.
- A zero is done automatically on zero air or nitrogen with an adjustable period (if possible every 2 or 4 hours but once per day remains acceptable).
- The absorbance spectrum is calculated from the reference spectrum acquired during the zero step.
A colour touch screen display interface allows the user to easily navigate through a number of screens that are used to set and check all of the operating conditions of the instrument. A protective film limits the risk to damage the surface of the touch screen, especially against solvent and corrosive liquid.
Recorded data and diagnostic files for each parameter can be downloaded to memory stick thanks to a USB port. This allows to collect easily these files on site without using a computer. The files are in text format and can be directly imported to Excel® for graphic charts.
Several gases can be measured in a same analyser if the sample gas composition is compatible with the selected algorithms and wavelengths. The analyser gives high measurement selectivity thanks to the recognition of the specific UV absorption spectrum of gases by using proprietary algorithms. For Denox applications, special algorythms allow to measure NH3 in a 0-10 ppm range with high level of SO2 up to 1200 ppm like on coal power plants.
An internal measurement of temperature and pressure of the sample is performed. A ratio related to the ideal gas law is applied on the measured value to compensate the effects of temperature and pressure. More…