Measuring gas velocity in a duct as a specific function of a pressure-balance-type probe in an isokinetic dust...

A probe of the pressure-balance type has been developed and used as part of an automatic isokinetic dust sampler. The aerodynamic characteristic of the probe was studied in order to determine the gas velocity when using this probe at its location in the duct. Such an anemometric function of the probe, together with an automatic control and logging of sampling parameters, maintains the isokinetic conditions during the sampling of dust-carrying gas and permits the online and in situ continuous measurement of the gas velocity (with uncertainty at the same level as that of typical standard methods). This eliminates the necessity to use separate standard gas velocity sensors that disturb the aerosol movement at the entrance of the aspiration nozzles of dust probes. This in turn ensures a high representativeness of the aerosol aspiration. While being in compliance with the international standards, dust sampling trains equipped with the pressure-balance-type probe with an anemometric function are more accurate from the point of view of the determination of the dust content of flue gases.