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NIRE Annual Report
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1996

Measuring Method of Condensed Dust from Stationary Sources

Air Quality Measurement Division
Atmospheric Environmental Protection Department
Objectives
The compliance rate with the environmental quality standard for suspended particulate matter (SPM) has stayed low level (50-60%) in Japan. As one of the causes that the compliance rate could not be improved, it is inferred that the current authorized method (JIS Z 8808) for measuring source dust can not accurately estimate substances emitted from stationary sources which might change to SPM in the ambient air, so-called condensed particulate matter (CPM).
This research aims at providing a better assessing method for discharged particulate matter including CPM.
Results
To establish a measuring method for the condensed dust in hot flue gas, three kinds of the sampling system, such as a direct cooling type with air (D-A type), an indirect cooling type with water (I-W type) and a direct cooling type with water (D-W type), were developed and tested using A-heavy oil combustion furnace. Components of each measuring system, such as an in-stack dust sampler (Type 1), a cooling device and an out-stack dust sampler (Type 2), are fundamentally equal except for the cooling method to generate CPM.
Figure 1. shows a comparison of results obtained by three types of dust samplers. Total dust concentration was significantly different among the three types. The concentration was highest in the D-W type and lowest in the D-A type. The D-W collected a lot of CPM, about 5.6 times higher than the dust of the current authorized method. On the other hand, the I-W type and D-A type collected about 2.5 and 2 times, respectively. The sample gas temperature of the three types was approximately 55, 30 and 25°C, respectively.
In the case of the D-A type and I-W type, the ratio of CPM in total dust was about 0.7, while the ratio in the I-W type was larger than in the D-A type because of drain. In the case of the I-W type, the sample gas was cooled enough compared with the D-A type and the other gas components were also absorbed in the drain. However, the ratio in the D-W type was about 0.85 because of the temperature drop of the sample gas and absorption of other gas components.
From these results, it is estimated that the condensed dust generation depends mainly on the temperature drop of the sample gas. The prominent factors affecting the temperature drop are the temperatures and flow rates of the sampled gas and the dilution air, the volume of the dilution and mixing tube, and the cooling capacity of the circulating or bubbling water.


Selected Publication
1) Study on Measuring Method for condensed particulate matter discharged from Stationary Sources, Proc. of 10th World Clean Air Congress, 61, 1995

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