vvEPA
United States
Environmental Protection
Agency
Municipal Environmental Researc
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-097 July 1981
Project Summary
Compatibility of Source
Separation and Mixed-Waste
Processing for Resource
Recovery
Louis Soldano, Stephen C. James, and Charles Miller
This report evaluates whether
source separation and mixed-waste
processing of municipal solid waste
are compatible approaches for
recovery of materials and energy in the
same community or region. Existing
source separation programs and
mixed-waste processing facilities
were analyzed to develop typical
options for assessment. Among the
issues addressed are changes in
production of useful energy from a
mixed-waste processing facility; air
and water pollution; residual solid
waste; employment; operator profit-
ability; total solid waste collection
costs; and quantities of recycled
materials.
This Project Summary was develop-
ed by EPA's Municipal Environmental
Research Laboratory, Cincinnati, OH,
to announce hey findings of the
research project which is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Are source separation and mixed-
waste processing (MWP) of municipal
solid wastes compatible approaches for
recovery of materials and energy in the
same community or region? With
source separation, salable materials
(currently aluminum, ferrous metals,
paper, and glass) are segregated from
wastes at the point of discard for collec-
tion and processing. With MWP,
collected, mixed municipal wastes are
centrally processed to convert the mixed
wastes into energy and, if possible, to
separate recyclable material. The basic
difference between the two approaches
is that source separation requires the
separation of wastes by the house-
holder whereas MWP relies on machin-
ery.
Conflicts may arise between the two
methods, however. Both may overlap in
recovering a single material from the
waste stream Supporters of source
separation claim to recover the highest
economic value, operators of MWP
facilities claim that separation of certain
materials reduces the energy content of
the solid waste and causes financial
loss to plants that require a fixed
amount of waste to break even Mutual
benefits can be seen where source
separation allows a larger amount of
waste to be processed and increases
equipment life by reducing abrasive
materials. Conflicts may be the result of
poor coordination rather than inherent
conflicts
Procedure
Resource recovery was analyzed from
the viewpoint of the mixed-waste plant
operator, the municipality, and the
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nation. For each viewpoint, specific
issues that would be most important are
identified—energy materials conserva-
tion, environmental impacts, economic
impacts, and institutional/technical
impacts. This assessment was conduc-
ted for a hypothetical community with
solid waste data equal to national
averages.
Scenarios were based on five source
separation options: high-efficiency
multi-material recovery, low-efficiency
multi-material recovery, high-efficiency
newsprint recovery, low-efficiency
newsprint recovery, and beverage con-
tainer recovery.
The following MWP alternatives and
possible combinations were addressed:
unprocessed combined waterwall
combustion and ferrous recovery
(UWCG); combined processed water-
wall combustion and ferrous recovery
(PWCF); refuse-derived fuel and ferrous
recovery (RDFF), and modular incinera-
tion without ferrous recovery (Ml). MWP
facilities options were a fixed capacity
plant, a variable-sized plant with a fixed
service area, and a fixed capacity plant
with an expandable service area.
The hypothetical community,
Baselyn, has approximately 100,000
people in a major metropolitan area
producing 200 tons of solid waste per
day. The city's sanitation department
collects solid waste from all
households. There is a materials
processor who buys newspaper for
$30/ton, corrugated paper for $60/ton,
high-grade paper for $70/ton, and
mixed glass and cans for $10/ton.
For a "Fixed Service Area" of five
communities like Baselyn producing
1,000 tons/day of waste, it may be
economical to reduce plant size or
collect waste from an outside area to
make up for reduction in waste because
of source separation. For "Variable
Plant Size," it is assumed that the
service area generates 1,000 tons/day
of waste but alters the plant size to
correspond to the waste remaining after
source separation.
At present, the source separation
programs discussed for Baselyn recover
as much as 5 percent of the waste
although as much as 10 percent can be
recovered. The reason for this gap is
that the waste generator has few incen-
tives to recycle materials because the
market prices fluctuate widely.
Six common methods of source sepa-
ration are recycling centers, separation
of office paper, separation of corrugated
paper, separate collection of newsprint
and other paper, separate collection of
various materials, and beverage con-
tainer deposits.
Although the value to large commer-
cial establishments of separating high-
grade office paper varies, it does have
good prospects for being economically
feasible Recovery rates for separated
corrugated paper are high because of
ease of physical separation and because
recovery reduces mixed-waste collec-
tion costs to commercial establish-
ments. Separate collection of newsprint
and other paper depends on
participating residents who place
newsprint at the curbside in separate
containers. Many of these programs
have been well received. Separate
collection of various materials is less
common than single material programs
because of the burden of separating and
storing several different materials until
collection day. Beverage container
deposits, including mandatory deposit
systems, place responsibility on the
resident and can achieve recovery rates
as high as 90 percent. Each of the above
options, except recycling centers, was
evaluated for Baselyn.
Source Separation Options
For high-efficiency multi-material
recovery, ordinances required resi-
dents to separate their waste into mixed
paper, clear glass and cans, mixedglass
and cans, and remaining waste;
scavenging of separated materials was
prohibited. This option cost Baselyn
$982/day but provided revenues of
$546/day. Eliminating 35.1 tons of
waste reduced landfill disposal costs
from $8,890 to $7,330/day. If MWP
was used, costs were reduced from
$7,770 to $6,406/day. Baselyn was
contractually required to supply the
MWP operator with all remaining
wastes.
This source separation program
extended the 20-year life of the county's
landfill by 3.6 years, lowered pollution
emissions during the production
process, and slowed resource depletion.
Low-efficiency multi-material
recovery is similar to the case above
except that participation is voluntary
and there is no program for recovery of
office or corrugated paper wastes. In
this option, residents were asked to
separate wastes into only three com-
ponents—mixed papers, mixed bottles
and cans, and remaining waste. The
cost of the source separation program
was $513/day and revenues were
$303/day. The source separation pro-
gram reduced total disposal cost by
$394/day with landfill and by
$322/day with MWP. Because Baselyn
had no ordinance to enforce source
separation by residents, the city and
intermediate processors were reluctant
to enter into any long-term contract.
As in the first case, the county's land-
fill life was extended, but for only a little
more than a year. This option had little
effect on the groundwater pollution
from the landfill and only small reduc-
tions in pollution emissions for MWP.
Two other options are high- and low-
efficiency newsprint recovery—
mandatory and voluntary. The
mandatory program resulted in a 60
percent recovery; the voluntary pro-
gram, 20 percent. The high-recovery
program cost $503/day with total
revenues of $270/day. Net disposal
cost was reduced $167/day for landfill
and $117/day for the MWP plant. In low
recovery, there are revenues of
$90/day. In addition to the advantage of
initial simplicity, the most important
effect of these programs is a slight
reduction in landfill requirements.
Beverage container recovery resulted
from state legislation rather than local
initiative. The program was operated by
the private sector, and waste reduction
was approximately 11.8 tons/day. This
recovery provided a net energy of
102 X 109 joules/day. The mandatory
deposit option would extend landfill life
slightly but would greatly reduce road-
side litter.
Mixed-Waste Processing
Alternatives
MWP energy can be recovered as
electricity, hot water or steam, or fuel.
Inorganic materials usually recovered
include ferrous metals, glass cullet,
aluminum, and nonferrous metals.
Organic materials recovered can be
converted to compost, animal feed, or
chemical industry feedstocks.
Unprocessed combined waterwall
combustion and ferrous recovery
(UWCF) consists of mass burning of
collected mixed waste in a thick bed on a
moving grate in a waterwall furnace.
The ash is quenched before passing
over a magnetic separator, where
ferrous material is recovered and the
residue is sent to a landfill.
Combined processed waterwall
combustion and ferrous recovery
(PWCF) is the same as UWCF except
that the waste is shredded and sepa-^
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rated into light and heavy fractions. The
light fraction, a higher quality fuel than
combined waste, is burned. The heavy
fraction is passed through a magnetic
separator and the residue is sent to a
landfill. More waste can be handled this
way than in a UWCF.
Refuse-derived fuel production and
ferrous recovery (RDFF) is similar to
PWCF except that the light fraction is
processed into a fuel than can be used
on or off site.
Modular incinerators without ferrous
recovery (Ml) can be batch type or
continuous feed type. Since the typical
size is less than 50 tons/day, over 20
units would be required to handle 1,000
tons/day.
Areas of Concern
Energy
An analysis of the source separation
options used in Baselyn showed that
variations of the BTU content resulting
from source separation to be small and
well within the range of variation
expected in raw municipal waste. For a
fixed service area, source separation
reduces both the percent and total
amount of BTU recovery. For an ex-
panded area, the total BTU recovery for
each waste processing option is propor-
tional to the BTU content/pound of the
MWP stream.
Environmental Impacts
Environmental issues are emissions
to air and water pollution from landfills.
This analysis assumed that source
separation and ferrous recovery were
not contaminated. Calculations were
based on 1,000 tons/day of mixed
waste.
Although air emissions for each type
of facility must be made on site-specific
bases, emissions for each combination
of options are reported. In general,
paniculate emissions were high
enough to present potentially signifi-
cant problems for all combined alterna-
tives involving MWP facilities.
Residuals to landfills for each option
were reported; the separation options
extended the life of the landfill. Low
newsprint option extended it 1.5
percent, and high multi-material sepa-
ration extended it 1 7.6 percent. Greater
extensions, up to 86.3 percent, can be
attained by coupling source separation
.with MWP alternatives.
The magnitude of water pollution
indicative of the amount of water
discharged from the facility was
reported. Source separation alone
caused few changes in the major
environmental problems of landfills,
i.e., pollution of surface and
groundwater resulting from leaching.
MWP residuals created less leachate so
that problem was greatly reduced.
Considering the pollution to air and
water, no MWP alternative is clearly
superior.
Economic Impacts
Typical contract provisions between
operators of MWP plants and munici-
palities include long terms, guaranteed
tonnages, guaranteed payment, estab-
lished fees, and adjustments to fees. In
considering the economics of MWP
facilities, the quality and quantity of the
source separation option will change
revenues and cause higher costs per ton
because of plant under-utilization. In
the expanded service area, the only
source separation scheme that has
more than a minor effect on processing
costs is the removal of beverage con-
tainers. Removing glass and metals
reduces processing costs.
The effects of source separation and
MWP are also considered in overall
employment, railroad freight rates,
influence on local decisions, savings on
solid waste disposal costs, and
reduction in fuel import needs.
Viewpoints
The Plant Operator's
Viewpoint
The operator of a MWP facility has the
objectives of receiving enough process-
able waste, recovering the cost of
operation, marketing, and realizing a
profit. The operator's concern with
source separation is its effect on the
quantity and quality of waste sent to the
MWP plant.
For the operator, source separation
offers both potential risks and benefits.
Risks include reduction in supply of
waste, lower profits, and difficulties in
financing the plant. Potential benefits
are lower maintenance costs when
unwanted materials are removed and
the possibility of securing additional
quantities of waste for the plant. One
problem with opening a MWP facility is
that is may force local entrepreneurs to
lose their source of supply and cease
operations Source separation then be-
comes a part of the issue of "flow con-
trol," i.e., the ownership of wastes and
the legal rights of political jurisdictions
to specify where and how their wastes
are disposed MWP operators must
address the issues of reliability of supply,
profitability, cost of private financing,
and whether source separation will
inhibit recycled materials purchasers
from committing themselves.
The Municipal Viewpoint
Municipal officials seek to dispose of
the community's solid waste in the most
economical and environ mentally accep-
table manner possible. The energy used
in collecting and transporting source
separated materials and remaining
mixed wastes is a relatively small frac-
tion of the energy available in the mixed
waste. Use of source separation options
reduces emissions from trucks and
landfill requirements. Either source
separation or MWP may require
municipal actions with significant
financial, legal, employment, tax, and
political implications. The primary issue
from the municipal standpoint is the
effect of source separation on the
economics of collection, transportation,
and disposal of mixed solid waste
The National Viewpoint
From the national viewpoint,
interests in resource recovery include
reducing fuel imports, conserving valu-
able material resources, and improving
environmental quality. The national
environmental issues are reduction of
the amount of waste and provisions for
proper solid waste disposal. Because
landfill sites are becoming more difficult
to obtain and the regulations governing
them are becoming more stringent, any
action reducing landfill requirements
should be considered. Pollution
occasioned by coal mining, processing,
and transporting will be eliminated in
situations where MWP energy recovery
is substituted.
Conclusion
With proper planning, there is no
inherent incompatibility in any combi-
nation of source separation options and
MWP alternatives. As a matter of fact,
analysis showed that combining any
source separation option with any MWP
> US GOVERNMENT PRINTING OFFICE 1981 -757-01Z/7ZZO
-------
alternative will result in positive or
neutral impacts. In all cases, combina-
tions are available that result in a
greater net benefit than implementing
any one separately.
The full report was submitted in ful-
fillment of Contract No. 68-02-2645 by
Gilbert Associates, Inc., Resource Plan-
ning Associates, and Crystal Planning
and Communications, Inc., under the
sponsorship of the U.S. Environmental
Protection Agency.
This Project Summary was authored by Louis Saldano, who is with the Munici-
pal Environmental Research Laboratory, and Stephen James and Charles
Miller, who are also the EPA Project Officers (see below).
The complete report, entitled "Compatibility of Source Separation and Mixed-
Waste Processing for Resource Recovery," was authored by M. G. Klett, W. H.
Fischer, B. N. Murthy, H. H Fiedler, L M. O/iva, and R Crystal
The above report (Order No. PBS 1-213 480, Cost. $ 15.50, subject to change) will
be avaiiab/e only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone. 703-487-4650
EPA Project Officer Stephen James can be contacted at:
Municipal Environmental Research Laboratory
U. S. Environmental Protection Agency
Cincinnati, OH 45268
EPA Project Officer Charles Miller can be contacted at:
Resource Recovery Branch
Office of Solid Waste
U S. Environmental Protection Agency
Washington, DC 20460
United States Center for Environmental Research
Environmental Protection Information
Agency Cincinnati OH 45268
Official Business
Penalty for Private Use S300
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-------
United States
Environmental Protection
Agency
Environmental Sciences Research
Laboratory
Research Triangle Park NC 2771 1
Research and Development
EPA-600/S2-81-096 Aug 1981
Project Summary
Modification of Optical
Instrument for In-Stack
Monitoring of Respirable
Particle Size
A. L Wertheimer
A light scattering instrument for in-
situ measurements of participates in
the 0.2 to 20 micrometer diameter
size range is described, and field test
results are presented. The instrument
is a modified version of a prototype
built during a prior EPA contract.
Number 68-02-2447. The upper limit
of the size response has been extended
from 10 to 20 micrometers, and several
component and packaging changes
have been incorporated to make the
unit more suited to stack paniculate
survey applications. Low forward
angle and 90° polarization dependent
scattering is employed to make the
measurements.
The completed instrument was tested
at a coal-fired electric power generat-
ing facility. During the test a cascade
impactor was used as a referee device
and both instruments were run side by
side in the outlet duct of the electro-
static precipitator.
The results show an excellent cor-
relation between the two instruments
with regard to the identification of a
1//m diameter peak in the particle size
distribution. A second peak around 20
fjm was defined by the optical instru-
ment, but could not conclusively be
confirmed through the impactor data.
The optical instrument handled well
during the field test and was delivered
to EPA for additional testing.
This Project Summary was devel-
oped by EPA's Environmental Sciences
Research Laboratory, Research Tri-
angle Park, NC, to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
A prototype real-time in-situ monitor
was developed and constructed on EPA
Contract 68-02-2447 to measure particle
size distribution of respirable particles
in the 0 2 to 10 /urn range. The purpose
of this project was to add a channel to
cover the 15 (jrr\ size range so as to
include the upper cut-off of the inhalable
particulate emissions from stationary
sources.
The addition of the large particle
channel required a series of changes in
the optical and electronic assemblies of
the original instrument. In the process
of incorporating these changes,the
latest available components were se-
lected and packaging improvements
were made, resulting in an instrument
optimally suited for survey work and
stack paniculate analyses. The new
instrument measures the size distribu-
tion in the 0.2 to 20 /um range in five size
fractions, using a low power helium
neon laser light source
The modified prototype instrument
was tested at a coal-fired electric gen-
-------
erating plant. Referee measurements
were made with a cascade impactor.
Both instruments reported a strong
peak in particle size around one /jm in
diameter.
Procedure
Principles of Operation
The instrument was designed by
using simple diffraction theory for the
low angle forward scattered light, and
rigorous Mie theory for the light scattered
at 90° to the probe beam. By adding high
angle scattering capabilities, the use of
light scattering for particle analysis can
be extended to the sub-micrometer size
range.
The stack particulate monitor mea-
sures the light scattered by particles
passing through a 2.5 cm by 36 cm slot
at the end of a 152 cm (5 foot) long
probe. The light source is a 2 milliwatt
helium neon laser, which emits a co-
herent beam at 0.6328 //meters. The
scattered light signals are proportional
to the volumes of particulate material
present in each of five size fractions. Six
scattered light readings are taken at
precisely determined angles. The light
signals are acquired through fiber optic
cables and transmitted to detectors
located in the transceiver. A digital
microprocessor calculates a five chan-
nel, volume-by-size histogram, covering
the size range from 0.2 /urn to 20 /urn.
Modification of the Prototype
Modification of the original instru-
ment to add a 1 5/um channel involved a
number of significant changes. When
appropriate, these changes were made
so as to accommodate improvements
suggested from field trial experience
with the first unit. The pertinent aspects
of the new design are discussed in the
following paragraphs.
The xenon arc source was replaced by
a low power (2 milliwatt) helium-neon
laser, which provides better collimation
of the source, and eliminates a trouble-
some electrical transient starting prob-
lem. A slightly larger collection lens
system was designed to accommodate a
wider range of forward scattering angles.
However, the 90° collection system
used in the earlier unit remains the
same.
A beam alignment sensor was added
to the tip of the probe to monitor any
thermally induced shifts. Through ports
accessible from the rear of the probe,
the beam can be aligned in or out of the
stack by maximizing the reading on a
meter adjacent to the adjustment ports.
A Z-80 microprocessor system re-
placed the original 8008 based elec-
tronics. The new system allowed for
rapid and efficient implementation of
the hardware and software changes
required in modifying the unit The new
electronics is much more compact than
the earlier version, and is combined
with a small digital printer in a 20 pound
transportable electronics console. A
second, smaller box, contains the elec-
tronics power supply, packaged sepa-
rately to avoid heat build-up on the
control console box.
A summary of operational character-
istics of the prototype is shown in Table
1. The measurement time can be set by
the user and ranges from 5 seconds to
12 minutes. Immediately following the
data collection, the size distribution is
printed out at the console.
Calibration
The calibration process involved
several steps and used a variety of
materials. To properly fill the sample slot
region under operating conditions sim-
ulating a flowing gas stream, an aerosol
test chamber was constructed in the
laboratory
The major steps of the calibration
process are outlined here.
(1) During assembly, the light collect-
ing apertures were checked for
alignment and adjusted to insure
that the correct angles were being
measured
• (2) Di-octyl phthalate (OOP), a trans-
parent liquid with an index of
1.49, was dispersed as a droplet
suspension in the aerosol test
chamber by a Phoenix Precision
Aerosol Generator. This created a
well-controlled size and loading of
particles in the 0.2 to 3 fjm size
range From the measured signal
levels and knowledge of the load-
ings, detector gain adjustments
were made to accommodate a
uniform distribution of particles at
40 parts per billion.
(3) The collection geometry and fiber
transmission product at each
angle was determined by measur-
ing fresh, filtered cigarette smoke.
Because the majority of the par-
ticulate volume is well below one
fjm in diameter, the forward
scattering pattern does not change
with particle size. A correction
constant is thus defined for each
scattering angle, based on t
difference between scattered lighi
strengths observed and those
predicted by theory.
Results
Laboratory Tests
As a check for consistency, the instru-
ment was then used to measure the
aerosol distributions employed to cali-
brate it Figure 1 shows the filtered
cigarette smoke distribution, indicating
a large percentage of the material in the
0.3 /jm size channel, while Figure 2
shows the measured and manufacturer's
specifications for the OOP aerosol
suspension. In both cases, agreement
between expectation and observation is
quite good.
To further check the performance and
calibration, two other materials were
run, burning red phosphorous, and solid
glass spheres. The red phosphorous is
used for tactical smoke screens, but no
referee data was available. The instru-
ment readings indicated roughly equal
amounts of material in the 0.3 and 1 0
/jm size channels. This is consistent
with its intended tactical use since par-
ticles in this size range are the most
efficient scatters per unit volume and
thus provide good obstruction.
The solid glass spheres, from Potters
Industries, Inc., were used to check
performance of the larger size channels.
The spheres are specified as "3 to 10
micron" size, but no additional data was
provided or available. No material is
reported in the 0.3 fjm channel, as
expected, and most of the material is in
the 3.5 or 7 5 fjm region. The material
reported in the 15 fjm channel may be
caused by clumping of the beads due to
electrostatic charges introduced in the
suspension process. Microscopic exam-
ination of a bead sample collected
during the test confirmed this, showing
occasional clumping.
Field Test Performance
During July, 1980, the prototype
instrument was tested at an east coast
coal-fired electric power generating
station. L&N personnel used the proto-
type instrument to measure particle size
distribution m a duct leading to the
smoke stack. Personnel from Northrop
Services, Inc., Environmental Science
(NSI-ES), participated in the tests,
taking data with a cascade impactor,
and provided the necessary data analysis
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able 1. Operational Characteristics of Stack Paniculate Monitor
Size Range (Particle Diameter)
Size Discrimination
Mode of Operation
Loading Range
Measurement Time
Duct Velocity
Duct Temperature
Instrument Temperature
Power Requirements
Probe Dimensions
Sample Slot Dimensions
Transceiver-Probe Assembly
Control Console
Electronics Power Supply
Blower
Probe Material
0.2 to 20.0 fjm
Five volume fractions with centers at 0.3, 1,0,
3.5, 7.5, 15 fjm
Low angle forward scattering and 90°
polarization dependent scattering
0.01 to 1.0 grams of material/meter3 (.023
to 2.3 grams/ft3) or 4 to 400 parts/billion by
volume (with s.g. of 2.5}
Signal integration time selectable from 5
seconds to 12 minutes (including a 6-minute
position)
1.5 to 18 meters/second (5-60 feet/second)
260° C maximum (500° Fj
2° Cto43° C(35to 110° Fj
One 20A, 115 volt, 60 Hz outlet
Physical Specifications
152 cm long (60 inches) by 9 cm diameter
(3'/4 inches)
25 x 36 cm (1 x 14 inches)
203 x 25 x 25 cm. 31.8 kg (80 x 10 x 10 inches,
70 pounds)
38 x 41 x 25 cm, 9.1 kg (15 x 16 x 10 inches,
20 pounds)
23 x 41 x 25 cm, 6.4 kg (9 x 16 x 10 inches,
14 pounds)
74 x 48 x 43 cm, 22.7 kg (29 x 19 x 17 inches,
50 pounds)
Type 316 Stainless Steel (except for optical
components)
for that method. Six separate data sets
were collected over two days. One set of
data from each day is presented here.
All testing was performed at the
outlet of the electrostatic precipitators
and prior to the final exhaust fan. The
testing section was a vertical flow duct,
approximately 32 1/2 ft. wide by 7 ft.
deep. Sampling ports are located hori-
zontally across the wide side of the duct.
Each port is a 6-mch diameter flanged
pipe, approximately 14 in. long. Two
adjacent ports were selected as test
points A summary of the stack condi-
tions appears in Table 2.
All aerodynamic particulate sizing
was performed using a University of
Washington Mark III Cascade Impactor
and necessary support equipment. Prior
to actual source testing, all in-stack
atmospheric measurements necessary
for isokinetic and other calculations
were recorded. Velocity head and stack
differential pressure measurements
were peformed using a type "S" pilot.
In-stack temperatures were measured
using a thermocouple system attached
to the end of the pitot tube. Velocity
profile measurements were made up to
4.5 ft. into the duct at both test ports,
with the impactor sampling conducted
at the point of both average velocity and
close proximity to the optical instrument.
The point used for sampling was ap-
proximately the mid-point of the duct or
4 ft from the lip of the port flange.
The impactors were preheated to
stack temperature before sampling to
avoid moisture condensation within the
impactor body. The duration of each test
was varied according to the stack opacity,
knowledge thatthiscoal unitwaswithm
particulate emissions standards, and
the visual inspection of the previous
80-
70
50-
40-
30-
20-
10-
.3 1.0 35 75 15
^
Figure 1.
Calibration run
cigarette smoke
using
impactor test. Sample runs varied from
20 to 40 minutes in length.
Several hours were required to make
the preliminary measurements before
the impactors were inserted.
The prototype optical particle size
monitor was prepared within approxi-
mately one hour. All electrical cables
were connected and the instrument
was turned on to warm-up the electron-
ics. The optical alignment of the unit
was adjusted using the external meter.
The stack velocity, measured for the
impactor runs, was used to set the
purge flow rate on the blower. To facili-
tate insertion and removal from the
stack during the tests, a suspension rail
designed and built previously for this
unit by NSI-ES was erected. A typical
sample run lasted 6 minutes, and sev-
eral runs were made during the impactor
sample collection period.
On the first sampling day the boiler
unit was operating at maximum output.
On the second day, the boiler was
operating at reduced output, and the
particulate emissions were distinctly
lower, dropping from around 0.02g/Nm3
the first day, to 0.007g/Nm3 the second,
as measured by the impactor.
Results for both optical and inertial
instruments are shown in Figures 3 and
4, plotted as histograms of volume
fraction per unit log interval of particle-
size The optical data in each figure are
indicated by the cross hatched histogram,
while the impactor data are shown as
the heavier outlined histogram. Varia-
tions in the individual.channel widths
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30-,
SO-
70-
60-
| 50-
40"
§?
30-
20-
10-
Measured
Manufacturer's
Spec.
— -,
Table 2. Stack Conditions During Field Test
Figure 2.
3 1.0 35 7.5 15
Calibration using dibutyl
phthalate aerosol from
Phoenix generator
are due to the different principles
involved in measuring the particle
distribution
The impactor data, provided by NSI-
ES, were derived by plate weighings and
computer assisted data reduction. A
material density of 2.5g/cm3 was as-
sumed, and the channel edges were
based on the aerodynamic separation
properties of the individual stages of the
impactor.
During each impactor run, continuous
optical data measurements were made.
The histograms shown are compiled
from the time weighted average of the
sequential optical data, which involved
from 5 to 8 optical runs, depending on
the length of the impactor run. The
boundaries of the optical histogram are
determined by the instrumental response,
as calculated from scattering theory.
Discussion
The optical and inertial measurements
agreed in some significant respects. In
all runs both instruments reported a
significant size fraction to be around
one fjm in diameter with, in most cases,
substantial reductions in the amount of
material above the one /urn size. The
optical instrument consistently indi-
cated a good deal of material in its
largest size channel, which made the
distribution appear bimodal. This could
not be definitely confirmed by the
impactor data available, although im-
pactor runs from some tests show a
Stack gas velocity:
Stack gas temperature:
Gas pressure.
Direct/on of flow:
45 to 50 feet/second
230 to 300° F
-2 inches of Hg
Vertical downward
leveling off of the distribution, and run 4
does indicate a secondary peak in its
largest particle channel
The general agreement between the
two methods is good. The size response
question could well be resolved through
further testing at other sites. There
were some relatively minor technical
problems, but none that should prevent
the optical instrument from being used
in other field tests. At the conclusion of
this test, the prototype stack paniculate
monitor and its associated equipment
were turned over to the EPA.
Conclusions and
Recommendations
The primary goal of this work was to
modify and test a prototype optical stack
particulate monitor by the addition of a
channel responding to particles in the
15 /jm size range. This was successfully
accomplished Tests m the laboratory
showed results that agreed with ex-
pected size distributions of several
40-
sample materials which were in the 0.2
to 20 /urn size range of the instrument.
The field tests, conducted at a coal fired
electric utility plant, provided size distri-
bution data which were in excellent
agreement with results reported by a
referee inertial impactor. An additional
advantage with the optical instrument is
that size distribution data are computed
and displayed immediately upon the
conclusion of the signal collection
sequence.
A secondary goal of this project was to
improve the reliability and portability of
the instrument to make it more suitable
for stack survey work. The modified
prototype unit is lighter and smaller
than the original, and the operational
improvements, such as ease of align-
ment and reliability of operation, were
demonstrated during the field trial.
There may be some value in develop-
ing an on-site technique to provide the
opera tor with a quick means of checking
the calibration of the unit Although
Run No. 1
Impactor
Optical Sizer
.2
1 2 5
Diameter, D(/jm)
10 20
Figure 3.
Particle size vs volumetric concentration distribution during Day 1 of
the field test
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50-i
0,~ ,
30-
O
< 20-
10-
Run No. 4
Impactor
Optical Sizer
1 2
Diameter, D(/jm)
20
Figure 4. Particle size vs. volumetric concentration distribution during Day 2 of
the field test
there are no moving parts in the proto-
type which would affect the calibration,
some form of indicating calibration
status is desirable.
Another area for future consideration
is modification of the electronics to
optimize the gain for loadings at or
below the originally specified range of
0.01 toO.1 grams/meter3.Thiscould be
done by changing the feedback resistors
at the detector board and trimming the
electrical offsets to lower values.
In its present form, however, this type
of instrument should prove to be very
useful for field survey work for analysis
of size distributions from stationary
sources. Recommendations for future
work involve additional field trials at
sites with different types of fuel, clean-
up devices, and loading conditions. To
gain confidence in this type of instru-
mentation, measurements with referee
sizing instruments should be taken in
parallel
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