CEM500 Online Gas Analyser

Description

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 throught 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.

Parameter Range* (ppm) Range* (mg/m3) Typical Repeatability Detection Limit
NH3
Ammonia 0-10 ppm
0-100 ppm
0-1000 ppm 0 – 7 mg/m3
0 – 70 mg/m3
0 – 700 mg/m3 0.05 ppm at 10 ppm
0.1 ppm at 100 ppm
0.5 ppm at 1000 ppm 0.1 ppm
NO
Nitrogen Oxide 0-2000 ppm 0 – 2500 mg/m3 1 ppm at 1000 ppm 3 ppm
SO2
Sulfur Dioxide 0-1000 ppm 0 – 3000 mg/m3 2 ppm at 1000 ppm 0.5 ppm
H2S
Hydrogen Sulfide 0-500 ppm 0 – 750 mg/m3 0.5 ppm at 500 ppm 0.5 ppm
NO2
Nitrogen Dioxide 0-2000 ppm 0 – 4000 mg/m3 10 ppm
C6H6
Benzene 0-100 ppm 0 – 300 mg/m3
C7H8
Toluene 0-30 ppm 0 – 100 mg/m3
C8H10
Xylene 0-30 ppm 0 – 150 mg/m3
NCL3
Nitrogen Trichloride 0-100 ppm 0 – 500 mg/m3