Chemical Engineering August 2016 - 70

isting APC system utilizes a venturi
scrubber with 10-in. w.c. pressure
drop to limit particulate-matter emissions
to 0.08 grains/dry std. ft3 (gr/
dscf). The fan that drives the system
is equipped with a 75-hp motor. A
higher particulate matter emissionremoval
efficiency is now required to
limit emissions to 0.02 gr/dscf. Two
options can be considered: Downsize
the venturi throat and increase
the pressure drop on the venturi system
to 60-in. w.c. to improve particulate
removal, or replace the venturi
with a baghouse filter. Table 2 shows
the power required for the current
system, as well as the two options.
In this example, it is clear that the
baghouse has significant power savings
compared to the high-pressure
drop venturi. The same would be the
case for an IWS, should a wet system
be desired.
What might have been the right
choice years ago - a low-pressure
drop venturi - is now the
wrong choice, based on lowered
particulate limits and energy cost
for applications with high loading
of fine particles. With proper bag
selection and maintenance, many
baghouses are capable of limiting
stack emissions to 0.01-0.02
gr/dscf range, allowing for tighter
regulations and for reduced total
annual emissions.
Closing thoughts
When selecting new APC or upgrading
old, look first at your regulatory
limits, then factor in the characteristics
of the fume, and all the pollutants
that must be controlled. Then
select candidate systems, and estimate
capital and operating costs
before making your final, wellinformed
choice.
n
Edited by Suzanne Shelley
References
1. McGowan, Thomas F., D. Coughlin, B. Axon, T.
Wechsler and J. Santoleri, VOC Emission Controls
for the CPI, Chem. Eng., February 2007.
2. McGowan, T., Chief Editor, " Biomass and Alternate
Fuels Systems: An Engineering and Economic
Guide, " AIChE/John Wiley & Sons, 2009, ISBN: 9780-470-41028-8.
Associate Editors Brown, M., Bulpitt,
W., and Walsh Jr.
3. McGowan, Thomas F., Charting a Path for Costeffective
NOx Control, Chem. Eng., October, 2004.
4. U.S. EPA AP-42, Emission Factors; by chapter and
fuel type (www.epa.gov/ttn/chief/ap42/ch01/) and
by industry (www.epa.gov/ttn/chief/ap42/).
5. McGowan, Thomas F., VOC and Air Toxics Control by
Oxidation and Other Methods, Air Pollution Control,
September 2014.
6. McGowan, Thomas F., Oxidizers for Control of VOCs
and Other Air Toxics: Application and Design, Process
Heating, October 2013.
7. " Industrial Ventilation: A Manual of Recommended
Practice for Design, " 28th Ed., www.acgih.org/
Author
Thomas F. McGowan is president
and founder of TMTS Associates
Inc. (399 Pavillion St., Atlanta, GA
30315; Phone: 404-627-4722;
Email:
tmtsassociates1000@
mindspring.com; www.tmtsassociates.com),
a firm that specializes
in thermal systems and airpollution
control.
He was
previously employed by RMT/Four
Nines, the Georgia Tech Research Institute, and Particulate
Solid Research, Inc. McGowan has 40 years of experience
in air-pollution control, filtration, combustion,
and bulk-solids handling. He holds an M.S.Ch.E. from
Manhattan College in New York City, and an M.S. in
industrial management from Georgia Tech.
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Chemical Engineering August 2016

Table of Contents for the Digital Edition of Chemical Engineering August 2016
