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OPTICAL INSTRUMENT FOR IN-STACK MONITORING OF PARTICLE SIZE
Citation:
Wertheimer, A. AND M. Trainer. OPTICAL INSTRUMENT FOR IN-STACK MONITORING OF PARTICLE SIZE. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/2-79/032 (NTIS PB292751), 1979.
Description:
A new light scattering instrument for in-situ measurements of particulates in the 0.2 to 10.0 micrometer diameter size range is described. Two modes of scattering are used, each with two wavelengths of light, to generate five size fractions by volume from a distribution of particulates. One mode measures polarized light scattered in two orthogonal orientations at an angle of 90 degrees to the optical probe beam. The second mode measures light scattered in near forward angles (4 to 11 degrees). Both modes allow the extraction of size data when particles of different sizes are present simultaneously in the sensing region. These principles have been incorporated into a prototype portable stack monitor, consisting of a 1.5 meter long, 9 cm diameter insertable probe capable of withstanding temperatures up to 260C. The optical signals are carried through fiber optic cables contained in the probe. An arc source and silicon photodetectors are outside the stack at the end of the probe, while a digital microprocessor analyzes the set of measurements and calculates the size fractions. The microprocessor, an air purge system, the lamp power supply, and a digital printer are housed separately from the probe for ease of installation and service. The completed instrument was tested on coal-fired fly ash particulates in the laboratory at a stationary source simulator facility and in the field at a coal-fired power plant. Results and comparisons with other sizing techniques are presented.