2008 Volume 43 Issue 1 Pages 9-22
Recently, in studies on measuring methods of dust emitted from stationary sources, special attention has been paid to PM10/PM2.5 particulates from the point of view of their effect on human beings. Measurements with the use of current source PM10/PM2.5 samplers are based on isokinetic sampling with a constant suction flowrate, which is difficult to carry out in the case of gas velocity variations that, in turn, producs large measurement errors.
With the objective of finding an easy and accurate measurement method of source PM10/PM2.5 emissions, an automatic sampling system that combines a changeable inlet diameter nozzle with a PM10/PM2.5 impactor and microcomputer for automatic sampling systems has been developed and tested.
The results from the characteristics investigation using test particles and in-situ field tests indicate that this source PM10/PM25 measurement system is applicable for isokinetic sampling with a constant flowrate. At the same time, several basic characteristics and critical points were clarified through the measurements using the PM10/PM2.5 impactor.
1) The tested source PM10/PM2.5 measurement system gave an instantaneous response to sudden changes in the velocities of test gases, indicating that PM10/PM2.5 measurements are easily carried out through isokinetic sampling with a constant flowrate.
2) Assembly and disassembly of the PM10/PM2.5 impactor, exchange of the classifier plate and the collection plate (plane filters), etc., were easily achieved during in-situ measurements.
3) In the case of fly-ash as the test particle, the amount of coarse particles taken in through anisokinetic sampling changed considerably, but the collection ratio of PM10 and PM2.5 remained almost constant in relation to the sampling error. On the other hand, particles re-entrained from the PM10-2.5 collection plate were accompanied by the downstream flow, and collected into the PM2.5 collection section. This caused a concentration error, and may have resulted in an increase of the PM2.5 measured value.
4) Re-entraining on the flat filter paper was not observed for dust in the combustion flue gas.
