EXM500-L Online Gas Analyser

Description

The EXM500-L is an extractive online gas analyser for Continuous emission monitoring (CEMS).
It is specifically dedicated to the new low level emission Regulations known as 50/30/5/3 (50 mg/Nm3 NOx, 30 mg/Nm3 SO2, 5 mg/Nm3 particles, 5 μg/Nm3 mercury) anda lso to chemical processes requiring low values of H2S. This new model is based on a multi-path flow cell of 1200 mm coupled to a high resolution spectrograph (0.1 nm) using an ultra-sensitive 2048 pixels CCD (charge-coupled device). It gives a high sensitivity and a longer lamp life time (3 years). The uv spectroscopy brings a higher sensitivity than Infra-red spectroscopy and also gives the possibility to measure several gases simultaneously on the same Spectrograph.

Optical principle – Main method : UV spectoscopy
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 1200 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.