The EXO (EXtractive Optical PM Monitor) for CEMS is a continuous particulate emissions monitoring system (PM-CEMS) designed for accurate dust measurement in wet and condensing process environments. Ideal for applications downstream of wet scrubbers, the EXO uses extractive, isokinetic sampling with a heated probe to eliminate moisture before measurement. Its advanced optical forward scattering technology delivers reliable, continuous particulate concentration readings, while the integrated touchscreen interface provides real-time data in mg/m³ or 4–20 mA outputs. Supplied in a robust weatherproof enclosure, the EXO offers dependable performance for industrial stack emissions monitoring and supports compliance with environmental monitoring requirements.
Technical Description – EXO Dust Monitor for Wet Gases
EXO system is designed to continuously measure the concentration of dust particles inside industrial stacks. It is an ideal solution for emission monitoring in wet conditions, for example after wet scrubbers or in condensing environments.
EXO PM-CEMS consists of a heated sampling probe, optical XO sensor module, and an integrated touchscreen graphical user interface , which are housed in a weather-proof powder-coated steel enclosure that is mounted on a frame. In a complete installation, the probe is inserted inside a stack perpendicular to the airflow using a flange. An external sample air blower supplies air to an ejector chamber at the end of the sampling line, creating a vacuum effect that draws flue gas through the internal piping of the device and ejects it back into the stack.
During operation, the probe continuously extracts a gas sample, which is heated to vaporize any moisture. The remaining particles are directed through the measurement chamber of the optical XO sensor module. Light from an LED is directed through the particle stream, which causes the light to scatter. A scattered light detector captures the scattered light and determines the particle concentration in the gas sample from the amount of scattered light. The underlying method is called “optical forward scattering”.
The device must be calibrated to the process conditions after installation using a standard reference method.
The user interface displays the measurement results as mg/m3 or 4-20 mA values.
A Closer Look
EXO is used in wet processes where the dust particles are bound into water droplets or other liquids. Dust particles are bound into droplets in steam saturated (flue) gases where the temperature is below the dew point.
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