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Instrument Design and Process Interface
Figures 1, 2, 3,and 4
summarize the basic methodology of this
in situ optical scattering instrument,
which has been described in detail in many
publications, with the key ones listed under
Available Publications along with
several PDF files describing applications.
Figure 1 shows a schematic of the PPC probe,
while Figures 2,3, and 4 summarize the basic
light scattering methodology for this single
particle counting instrument. The
primary advantage of this approach is the
use of a relatively simple optical geometry,
coupled with a mathematical algorithm to
cover a wide range of particle sizes and
concentrations. The simpler optical
geometry allows greater flexibility and
robustness for challenging applications at
high temperatures and pressures in plant
process operations.
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Figure 1. Schematic Diagram of
Particle Concentration, Size, Velocity (PPC) probe.
Probe is enclosed within 9.5 cm dia. water-cooled jacket
(not shown) and test section is inserted up to 2 meters
into a 10 cm diameter boiler access port. Measurements
are obtained by laser light scattering from particles
suspended in the boiler gas flow as they pass through
the 3cm by 9cm water-cooled test section
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Figure 2. Schematic of the optical
configuration for a single beam PPC. The standard PPC
uses a split illumination beam to form two sample
volumes in one instrument to measure over a wide size
range from 0.3 – 100 micrometers and concentrations up
to 106 particles per cm3.
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Figure 3. This figure shows that
PPC is a single particle counting instrument. As a
particle passes through the sample volume at the focus
of Figure 2, a scattering pulse is seen by the
detector. The signal processor measures the peak
height, Ap (related to the particle size and
particle trajectory through the beam), and also measures
the pulse width, Δt. Using the Gaussian beam invariance
principle, the particle velocity can then be derived
from the measurement of the pulse width, peak height,
and known discriminator level, At.
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Figure 4. This schematic close up of the particle
sample volume shows that the same size particle can give
different scattering amplitudes for the same size particle,
depending on the random particle trajectory. PPC uses a
unique mathematical deconvolution algorithm to “unscramble”
this statistical effect (similar to medical CAT
scanning) to extract the true particle size distribution
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For
information regarding the Process Particle Counter (PPC)
contact:Donald Holve, Ph.D.
dholve@processmetrix.com
voice: (925)
460-0385
x116
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