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 The Continuous Emissions Monitoring System, using the extractive dilution technique, is the most widely used method for continuous emission monitoring of SO2 and NOX. It is also ideal for use in monitoring CO, CO2, H2S and NH3.and can be combined with a zirconium oxide sensor for the continuous measurement of O2. The extractive dilution system can be installed in a drivable van, in a caravan or in a permanently sited air conditioned shelter.
Ecotech’s extractive dilution systems are used by most of the Power Stations within Australia as well as many other industrial companies such as BHP, CSBP & Farmers, TIWEST & Pilkington Glass to name just a few.
Theory of Operation
The extractive dilution system is based on extracting a small sample of gas from the stack, removing particulates by a proprietary filter and then accurately diluting the sample with clean dry zero air (air free of the gases to be measured) thus reducing the dew point so as to prevent condensation of water vapour and acid mist. The diluted sample is then sent down unheated umbilical lines to the base of the stack where it is analysed by high precision analysers. Due to the high sensitivity of these analysers, dilution doesn’t influence measurement accuracy negatively. In fact, accuracy is improved over other systems since water vapour cannot condense and remove part of the sample.
Calibration
Calibration of the system is achieved effectively by sending span or zero gas directly to the stack through the probe controller/pump module up the umbilical and directly into the centre of the probe filter. This effectively displaces the stack gas, so that the entire system samples the calibration gas. This scheme provides a true calibration of the full system under working conditions. Because excess calibration gas is vented to the stack, even stack pressure effects are tested. This method of calibration eliminates the need to know the dilution ratio as the analysers are adjusted to read the span gas concentration directly.
Brochure
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