United States Office of Air Quality EPA-450/3-83-012
Environmental Protection Planning and Standards May 1983
Agency Research Triangle Park NC 27711
Air
Control
Techniques
for Organic
Emissions from
Plywood
Veneer Dryers
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EPA-450/3-83-012
Control Techniques for Organic Emissions
from Plywood Veneer Dryers
Emission Standards and Engineering Division
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air, Noise, and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina
October 1982
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This report has been reviewed by the Emission Standards and Engineering Division of the Office of Air Quality
Planning and Standards, EPA, and approved for publication, Mention of trade names or commercial products is not
intended to constitute endorsement or recommendation for use. Copies of this report are available through the Library
Services Office (MD-35), U.S. Environmental Protection Agency, Research Triangle Park, N C. 2771 1, or from
National Technical Information Services, 5285 Port Royal Road, Springfield, Virginia 22161.
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TABLE OF CONTENTS
Chapter
1 Introduction
Sources and Types of Emissions
2.1 Product Characterization
2.2 Industry Profile
2.2.1 Markets
2.3 Trends
2.4 Processes and Their Emissions
2.4.1 Green Processes
2.4.2 Veneer Drying
2.4.3 Veneer Preparation, Layup, and Gluing
2.4.4 Plywood Finishing
2.4.5 Technological Changes
2.5 References
Emission Control Techniques 3-1
3.1 Introduction 3-1
3.2 Veneer Dryer Emission Control 3-1
3.2.1 Met Scrubbing 3-1
3.2.1.1 Multiple Spray Chambers 3-2
3.2.1.2 Combination Packed Tower and
Cyclonic Collectors 3-2
3.2.1.3 Sand Filter Scrubbers 3-4
3.2.1.4 Ionizing Viet Scrubbers 3-4
3.2.2 Incineration 3-6
3.2.2.1 Boiler Incineration 3-5
3.2.2.2 Incineration in a Fuel Cell .... 3-8
3.2.2.3 Catalytic Incineration 3-12
3.2.3 Low-Temperature Drying 3-12
3.2.4 Control of Fugitive Dryer Emissions .... 3-12
3.3 Panel Sander Emission Control Techniques 3-13
3.3.1 High-Efficiency Cyclones 3-14
3.3.2 Fabric Filters 3-14
3.4 Conclusions 3-15
3.5 References 3-15
n
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TABLE OF CONTENTS (continued)
Chapter
Cost of Emissions Control
4.1 Introduction . . .
4.2 Model Plants . . .
4.3 Costs
4.4 References ....
Environmental Impact . . . ,
5.1 Air Pollution Impact .
5.2 Water Pollution Impact
5.3 Solid Waste
5.4 Energy Impact
5.5 References
Test .Methods and Test Results 6_1
5.1 Veneer Dryer Test Methods 6-1
5.1.1 Oregon Department of Environmental Quality
(ODEQJ Method 7 6-1
6.1.2 Washington State University (VJSU) Method . . 6-3
6.1.3 EPA Method 25 6-6
6.1.4 Combination EPA Method 5X and EPA
Method 25 6-8
6.2 Plywood Sander Test Method 6-8
6.3 Results of Emission Testing 6-11
6.3.1 Veneer Dryers 6-11
6.3.1.1 Uncontrolled Emissions 6-11
6.3.1.2 Emission Tests of Control Devices . 6-16
6.3.2 State Regulations Applicable to Plyv/ood
Plants 6-25
6.3.2.1 Veneer Dryer Control Evaluation . . 6-25
6.3.3 Plywood Sanders 6-25
6.4 References 6-29
IV
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LIST OF TABLES
Number Page
2-1 Plywood Production by State and Region, 1980 2-2
2-2 Employment Statistics—Softwood Veneer and Plywood . . . 2-5
4-1 Parameters for Model Plant 1 4-4
4-2 Parameters for Model Plant 2 4-5
4-3 Parameters for Model Plant 3 4-6
4-4 Parameters for Model Plant 4 4-7
4-5 Parameters for Model Plant 5 4-3
4-5 Parameters for Model Plant 6 4-9
4-7 Summary of Model Plant Parameters 4-10
4-3 Capital Costs of Control Options for Model Plants
With Steam-Heated Dryers 4-14
4-9 Capital Costs of Control Options for Model Plants
'Jitn Direct-Fired Dryers 4-15
4-10 Annual Operating Costs of Control Options for Model
Plants With Steam-Heated Dryers 4-17
4-11 Annual Operating Costs of Control Options for Model
Plants with Direct-Fired Dryers 4-13
4-12 Annualized Costs of Control Options for Plants With
Steam-Heated Dryers 4-19
4-13 Annualized Costs of Control Options for Plants
With Direct-Fired Dryers 4-20
4-14 Capital Costs of Complete Plywood Plants 4-22
4-15 Annualized Direct Costs of Complete Plywood Plants . . . 4-23
5-1 Estimated Air Pollution Impacts of Control Options
for Model Plants 5-2
5-2 Estimates of Electrical Energy Consumption of Model
Plants 5-5
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LIST OF TABLES (continued)
Number Page
6-1 Emission Tests of Uncontrolled Veneer Dryers Drying
Douglas Firs 6-12
6-2 Distribution Between Terpene Emissions and Other
Emissions 6-14
5-3 Total Organic Emissions Tests of Uncontrolled
Veneer Dryers 6-15
6-4 Emission Data for Wet Scrubbers on Veneer Dryers .... 6-17
6-5 Emission Data for Sandair Filter Systems on Veneer
Dryers 6-13
6-6a Results of EPA Tests of a Boiler Incineration System—
Particulate and Condensible Organic Emissions ...... 6-19
6-6b Results of EPA Tests of a Boiler Incineration System—
Particulate and Condensible Organic Emissions 6-20
6-7a Results of EPA Tests of a Boiler Incineration
System—Total Organic Emissions (Metnod 25) at
Veneer Dryer Exhaust 6-21
5-7b Results of EPA Tests of a Boiler Incineration
System—Total Organic Emissions (Method 25) at
Veneer Dryer Exhaust 6-22
6-3a Results of EPA Tests of a Boiler Incineration
System--Total Organic Emissions (Method 25) at
Boiler Exhaust 6-23
6-3b Results of EPA Tests of a Boiler Incineration
System—Total Organic Emissions (Method 25) at
Boiler Exhaust 6-24
6-9 Tests Showing Emission Reductions Achieved by
Lowering Dryer Temperatures 6-25
5-10 Summary of State of Oregon Regulations for
Plywood Manufacturing 6-27
5-11 Emissions From Plywood Sanders with Product
Recovery Cyclones 6-23
VI
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LIST OF FIGURES-
Number n
- P^ge
2-1 Softwood plywood production by region, 1960-1980 .... 2-8
2-2 Process flow diagram for veneer and plywood
production ..................... 2_n
2-3 Two-zone longitudinal -flow dryer ............ 2-13
2-4 Wet end of a steam-heated longitudinal -flow dryer .... 2-15
2-5 Three-zone, twelve-section jet dryer .......... 2-16
2-6 Cross section of a steam-heated jet dryer ........ 2-17
3-1 Georgia-Pacific emission eliminator ........... 3,3
3-2 Rader SandAir filter .................. 3_5
3-3 Wood-fired dryer system with partial incineration
in a fuel cell .................... 3_g
3-4 Hood-fired system with complete incineration of dryer
exhaust in a fuel cell ............. .... 3-n
3-b Fabric filter system for control of sanderdust
emissions ......... 0 rc
...... * .......... o-lb
6-1 Oregon Department of Environmental Quality Method 7
sampling train _
5-2 Washington State University (1972) sampling train .... 6-4
6-3 Modified EPA Method 25 sampling train .......... 6_7
6-4 Simplified schematic of nonmethane organic anal/zer
(Method 25) .................. _
6-5 Modified EPA Method 5X/25 sampling train ....... . 5.
10
vn
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1.0 INTRODUCTION
This document summarizes information gathered by the U.S. Environ-
mental Protection Agency (EPA) on the control of emissions from softwood
plywood manufacturing. The primary sources of emissions from this
industry are veneer dryers and panel sanders. Veneer dryers emit con-
densible and noncondensible organic compounds and minor quantities of
particulate matter. The rate of uncontrolled condensible and noncon-
densible organic compound emissions from a veneer dryer is a function of
test method, wood characteristics (species, moisture content, etc.), and
dryer operating conditions (temperature, speed, etc.). As an example of
the magnitude of total organic emissions from a plywood plant, National
Council of the Paper Industry for Air and Stream Improvement, Inc.,
(NCASI) staff measurements of total organic emissions from uncontrolled
Southern pine veneer dryers showed average Method 25 emissions rates of
13.7 g/m2 as C1( 9.5-mm basis (2.8 lb/1,000 ft2, 0.375-in. basis) on
fresh cut veneer. For a representative new Southern plywood plant with
three dryers producing 17.2 x 106 m2/yr, 9.5-mm basis (185 x 106 ft2/yr,
0.375-in. basis) of plywood, total organic emissions would be 235 Mg/yr
(259 ton/yr). Panel sanders produce particulate emissions at a rate
depending on the final product. Approximately 18 to 20 percent of all
softwood plywood production is sanded.
The industry is largely located in the Northwest and South. Veneer
dryer emissions are controlled in some Northwestern States, notably
Oregon, by a variety of wet scrubbing and incineration schemes. In the
South, where industry growth is expected to concentrate, all but a few
dryers are uncontrolled. Panel sanders are controlled by fabric filtra-
tion in most States, although high-efficiency cyclones may meet emissions
standards in some Southern States.
1-1
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The remainder of this report details the sources and types of
emissions from the plywood industry, the types and costs of emissions
control techniques, environmental impacts associated with these control
techniques, and available emissions test data.
1-2
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2. SOURCES AND TYPES OF EMISSIONS
2.1 PRODUCT CHARACTERIZATION
Plywood is a product composed of layers of wood veneer glued together
with an adhesive, usually a synthetic resin. The grain of each successive
layer is placed at right angles to give the product strength in two
directions. A veneer, or ply, is a thin sheet of wood, peeled or sliced
from a log. Softwood plywood is constructed using veneers, including
the face ply, from coniferous or needlebearing trees. Wood species used
in softwood plywood manufacture include Douglas fir, White fir, hemlock,
Ponderosa pine, Southern pine, and redwood. Hardwood veneer drying and
sanding are not considered in this document because emissions from these
processes are insignificant compared to emissions from softwood processes.
Softwood plywood is used for roof decks, exterior sheathing, plywood
siding, all-weather wood foundations, and rough flooring in housing
construction. It is also used in light industrial roofs, heavy tongue-
and-groove commercial floor systems, and furniture.1 There are about 50
to 60 different grades of softwood plywood, and many mills produce more
than one type of plywood.2
2.2 INDUSTRY PROFILE
The majority of plants in the softwood plywood industry are located
in the Pacific Northwest (Oregon, Washington, and California), with the
second-largest concentration in the Southeast. In 1980, softwood plywood
production totalled 1.53 billion m2, 9.5-mm basis (16.5 billion ft2,
3/8-in. basis).3 Of this total, 0.28 billion m2, 9.5-mm basis (3.0
billion ft2, 3/8-in. basis), constituted sanded plywood production.
This plywood production rate is a 16-percent decrease from the 1.85-
billion m2, 9.5-mm basis (20.0-billion ft2, 3/8-in. basis), production
rate of 1978. Table 2-1 shows the number of producing units in each
State together with production by State and region.
2-1
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TABLE 2-1. PLYWOOD PRODUCTION BY STATE AND REGION, I9604
(billion m2, 9.5-mm basis)
Region and State
Northwest
Oregon
Washington
Cal i fornia
Southeast
Louisiana
Texas
Alabama
M i s s i s s i p i
Arkansas
Georgia
North Carolina
South Carolina
Florida
Virginia
Oklahoma
Maryland
Inland
Montana
Idaho
TOTAL
Industry production Percent
Units (m2 x 109/yr) of U.S. total
72
23
6
14
10
9
6
7
6
5
4
1
1
1
1
4
5
0.574
0.123
0.029
0.115
0.139
0.085
0.086
0.073
0.069
0.050
0.034
0.011
0.009
0.009
0.005
0.053
0.048
1.515
48.0
37.9
8.1
1.9
45.3
7.6
9.2
5.6
5.7
4.8
4.6
3.3
2.2
0.7
0.6
0.6
0.3
6.7
3.5
3.2
-100.0
2-2
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In January 1980, an estimated 267 facilities were manufacturing
softwood plywood and veneer in the continental United States. Of this
number, 65 plants produced only veneer, while 202 plants produced either
plywood alone or both plywood and veneer. By January 1982, many mills
were closed, either temporarily or permanently.
The top five firms accounted for 40.5 percent of production in
1972 and for 47.5 percent of production in 1979.3 The top 20 firms
accounted for approximately 70.9 and 75.2 percent of production in 1972
and 1979, respectively.3 Therefore, industry leaders gained market
share largely at the expense of small firms.
Most recent growth in new plants has occurred in the South. Also,
the apparent industry trend has been toward greater capacity among new
plants. Consequently, Southern plants are generally newer and have
larger capacities than do Northwestern plants. In 1979, an average
Northwestern plant produced 8.36 million m2, 9.5-mm basis (90 million
ft2, 3/8-in. basis), of softwood plywood. The average Southeastern
plant produced 11.9 million m2, 9.5-mm basis (128 million ft2, 3/8-in.
basis), of softwood plywood in 1979.
Data are not available on the ages of individual plants. Most
Northwestern plants are 30 years old, whereas most Southeastern plants
are less than 15 years old. Plants close periodically and are fre-
quently rebuilt because of change of wood supply or change of ownership.
Production at single sites may continue for decades (e.g., the McCleary
Washington plant was built in 1912)6 or may be terminated after a few
months.
Many companies in the softwood plywood industry are vertically
integrated. Weyerhaeuser, Crown Zellerbach, Union Camp, Georgia-Pacific,
Southwest Forest Industries, and International Paper all own timber
stands that supply logs for plywood manufacture.7 These companies have
an advantage over firms that must purchase timber on the open market
because stumpage costs have jumped almost 75 percent since 1978, to
nearly $400 per 1,000 board feet.8 St. Regis, Champion, Potlatch, Boise
Cascade, Louisiana-Pacific, and Willamette supply over half their raw
material needs from their own timberlands.9
2-3
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In 1979, the softwood plywood industry employed approximately
46,100 workers. States leading employment are Oregon, Washington,
Texas, and Louisiana, accounting for 67 percent of total industry
employment in 1977.10
Employment statistics for the years 1972 through 1977 are given in
Table 2-2. The table shows total establishments and employees, wages,
hours, and production workers. It lists figures for value added by
manufacture, materials cost, and shipment.
2.2.1 Markets
A number of factors affect the U.S. plywood market. It appears
that over the next few years, oriented strand boards and waferboard will
be used increasingly as plywood substitutes.4 In fact, it is estimated
that nonveneer panel production may be up to 0.232 billion m2, 9.5-mm
basis (2.5 billion ft2, 3/8-in. basis), in the coming years.4
International activities moderately impact U.S. production. The
United States imports softwood plywood mainly from Canada and Mexico,
though not to any significant extent. Softwood sales overseas account
for some 5 percent of U.S. production. Because U.S. companies have
gained agreements in the growing international markets and because
potential competitors (Scandinavia and U.S.S.R.) do not have sufficient
wood or plant capacity, U.S. production should expand in the future to
serve the export market.4
The pricing of softwood plywood products depicts a classic case of
price elasticity of demand: many market variables affect the price of
softwood products, making them price sensitive. Even a small price
decrease can increase product demand, which in turn fosters an increas-
ingly competitive industry.
Demand determinants for the softwood plywood market comprise a
variety of factors, the primary factor being the number of forecasted
housing starts. During the forecast period, veneer panel use is esti-
mated at 520 m2 per single-family unit and 300 m2 per multifamily unit.
These estimates reflect the expectation that new uses like wood founda-
tions and structural panel floors will replace concrete walls and slab
floors. These new uses will offset lost plywood use resulting from the
2-4
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TABLE 2-2. EMPLOYMENT STATISTICS—SOFTWOOD VENEER AND PLYWOOD9 10
All establishments
Yearb
1972 Census
1973 ASM
1974 ASM
1975 ASM
1976 ASM
1977 Census
Companies Total
(No.) (No.)
121
(NA)
(NA)
(NA)
(NA)
129
232
(NA)
(NA)
(NA)
(NA)
256
With 20
employees
or more
(No.)
225
(NA)
(NA)
(NA)
(NA)
224
All employees
Number Payroll
(1,000's) ($ millions)
43.7
45.5
42.8
41.1
45.0
46.2
403.6
442.2
421.1
438.6
537.8
634.6
Industry was defined or redefined for 1972 Census of Manufacturers, so
^ In annual survey of manufacturers (ASM) years, data are estimates based
i differ from a canvass of all establishments.
en r
Production workers
Number Hours Wages
(1,000's) (millions) ($ millions)
39.9
41.3
38.5
36.7
40.5
41.9
85.3
87.7
78.1
75.0
84.5
89.0
356.5
388.7
363.3
377.5
468.0
556.9
Value Cost of Value of
added by materials shipments
manufacture ($ mil- ($ mil-
($ millions) lions) lions)
935.4
1.097.2
832.0
850.3
1.304.2
1.583.7
data are available only for years shown.
on a representative sample of establishments
1.071.3
1,283.5
1,299.8
1,386.5
1,880.5
2,231.1
($ millions)
2,011.5
2,365.1
2,123.8
2,243.5
3,164.1
3,804.8
canvassed annually and may
For the census, a company is defined as a business organization consisting of one establishment or more under common ownership or control.
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trend toward constructing smaller units with more common walls. Mobile
homes add to the residential volume. Structural panel use is expected
to grow in this market as the trend toward more double-wide units con-
tinues. Use per unit is expected to increase from 38 m2 to 80 m2 on the
average.4
The second-largest market for structural panels is the homeowner
market, about two-thirds of which is for structural additions, altera-
tions, and property improvements. This category includes garages,
storage sheds, privacy screening, patios, and planters. The remainder
of the homeowner market includes such miscellaneous uses as furniture,
shelving, toys, games, pet shelters, temporary closures, paneling, and a
host of other applications. The homeowner market is expected to continue
to increase at a 2- to 3-percent rate each year, reflecting population
growth, continued, strong upgrading of houses, and additional activity.
Diverse industrial uses constitute the third-largest structural
panel market. The two largest use areas are materials handling (pallets,
bins, crates, and industrial shelving) and transportation (truck bodies,
bus floors, rail car liners, and recreational vehicles). All-veneer
structural panels dominate the industrial markets and are expected to
continue to do so, especially in materials handling and transportation
equipment areas.
Nonresidential consumption constitutes the fourth-largest structural
panel market. Plywood used in building construction and in concrete
forming accounts for 90 percent of the nonresidential market. Auxiliary
applications include signs, barricades, workhorses, bench shoring,
retaining walls, and highway sound barriers. Applications such as sound
barriers and retaining walls have potential for substantial growth.
Overall, nonresidential uses are forecast to expand gradually at 1 to 2
percent per year.4
2.3 TRENDS
The softwood plywood industry has shown a highly variable but
consistently increasing production pattern over the past three decades.
Some product lines recently have expanded while others have nearly
disappeared because of competition from substitutes or changing consumer
tastes.
2-6
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Production trends over the last 20 years are shown in Figure 2-1,
which shows softwood plywood production by region.4 Note that Southern
production increased from zero to 45.3 percent of the national total
during that time. Until 1981, Southern production had increased every
year except for 1974. Western-and inland production generally has
fluctuated around a base level, increasing less consistently than Southern
production has.
While softwood plywood production has increased gradually over the
past decade, it has not matched the 11-percent annual rate established
from 1945 to 1968. During the past decade, the industry has expanded
production by adding or replacing veneer dryers in existing plants and
by building new greenfield plants. Because drying capacity is a limiting
factor in many plants, additional drying capacity has automatically
increased total production capacity. Most of the new plants have been
constructed in the Southeast.
The rapidly increasing timber and plywood production in the Southeast
and South should continue to increase well into the 1980's. Timber
supply has been a primary factor in development of the Southern pine
plywood industry. Because they have been assured timber availability
from private holders of timberland, many firms have expanded capacity by
building mills in the South rather than by increasing capacity in a
region controlled by public timber management.
In 1980 and 1981, producers cut prices to move wood, a strategy
that proved only marginally successful. The underlying problem is a
depressed housing market, which in 1981 closed many Western mills, some
permanently.
Many plants are now operating in the red. Some are able to continue
operating only with parent company subsidies through the current recession.
This subsidization is partly due to the fact that some companies need
wood chips from their plywood mills as raw materials for their paper
mills.
Energy and mineral resource shortages could be considered a poten-
tial boon to the plywood industry. Plywood comes from a renewable
resource and can be manufactured with far less energy than can most
other building materials.
2-7
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8-Z
Production, m2 X 108 per year
T|
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The plywood industry traditionally has used short-term market
conditions and production costs as principal factors in deciding to
build new plants or to close existing ones. As a net effect, rapid
plant turnovers have had a major impact on the number of new plants.
Also, most plants close periodically because of wood supply, product
line, or owner changes.
However, the size of individual plants has increased over the past
few years, especially for new, integrated softwood plywood plants.
Incorporation of plywood or veneer facilities into total wood production
complexes (which is occurring in large forest industry corporations)
will be reflected in increased stability and continued upgrading of
individual plants. It is estimated that existing veneer dryers undergo
major reconstruction or modification every 15 years.11 There are
presently no known plans for new plywood plants, though once recovery
from the housing slump commences, this situation might change.
Existing softwood plywood capacity at 2.27 billion m2, 9.5-mm basis
(24.4 billion ft2, 3/8-in. basis), is sufficient to meet increased
softwood plywood demand through 1986, which is predicted to be 1.89
million m2, 9.5-mm basis (20.3 billion ft2, 3/8-in. basis).5 However,
past trends indicate that new plants will be built to replace plants
that close or to seek a larger market share by offering a more econ-
omically produced product. From 1977 to 1979, production in the South
increased 12 percent, where it appears most new growth in the plywood
industry will occur. Annual plywood production may reach 2.4 billion
m2, 9.5-mm basis (26.5 billion ft2, 0.35-in. basis), by 1995. The above
predictions must be used with caution because of the current economic
s1ump.
2.4 PROCESSES AND THEIR EMISSIONS
Four processes used to produce plywood are listed below:
Green process—log conditioning, followed by peeling into
green veneer;
Veneer drying;
Veneer patching and grading, layup and gluing, and pressing to
make plywood; and
Sizing and finishing of the plywood.
2-9
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Figure 2-2 is a generalized flow chart for these processes.
2.4.1 Green Processes
Continual low-level emissions of volatile wood components occur
throughout the lives of softwood trees. These emissions continue when
the live trees are cut and during the veneer drying process; the emission
rate increases as temperature and wood surface area increase. Volatile
components—primarily terpenes--are estimated at 20 g/m2, 9.5-mm basis
(4 lb/1,000 ft2, 0.375-in. basis), of product for freshly cut Southern
pines.12 By the time green veneer has been prepared for drying, this
component has decreased significantly. Most studies of terpene loss
from wood indicate rapid loss from logs or thin sheets of wood within I
to 8 weeks after cutting.13 14 1S Georgia-Pacific experience indicates
that logs lose approximately 6 percent of total weight in wood moisture
during a typical 3-week log storage period.16
After delivery to a west coast plywood facility, the logs are
stored in a pond or piled on a prepared surface called a cold deck. The
latter storage method requires water spraying in warm periods to prevent
log deterioration. In the South, logs usually come directly from the
woods to an open log yard. Pond storage is almost never used, and water
spraying is only used if prolonged storage is anticipated. Next, logs
are debarked and cut into specifically sized blocks. The bark is recov-
ered and used for fuel.
The next operation at most plants is log conditioning—treating the
logs with heat and moisture—for which hot water vats or spray chambers
are used. At some mills, softwoods are peeled cold without such con-
ditioning.
Veneer can be cut from logs by several methods. Essentially, all
softwood veneer is cut by peeling or rotary cutting. Other methods are
used primarily for decorative cuts for face veneer and for special
effects with certain woods. Softwood veneer is cut to thicknesses
ranging from 2.5 to 8.0 mm (0.1 to 0.313 in.).
After the veneer is peeled, it is brought as a semicontinuous
ribbon through automatic clippers and cut to size before drying. These
machines automatically detect and clip out unacceptable sections of
2-10
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LOG
STORAGE
DEBARKER
LOG
CONDITIONER
VENEER
CUTTER
VENEER OPERATION
PLYWOOD OPERATION
VENEER
DRIER
VENEER
PREPARATION
GLUE
LINE
PRESS
FINISHING
Figure 2-2. Process flow diagram for veneer and plywood production.
2-11
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veneer. The green veneer is then sorted according to size, wood species,
and veneer grade and whether it is heartwood or sapwood. This sorting
is necessary before the veneer can be dried because different types of
wood require different drying conditions. Sorting is the last step
before drying.
Byproducts of veneer cutting are log cores, wood chips, and veneer
scraps suitable only for chipping. Conveyance of coarse material leads
to negligible air emissions, while conveyance of fine material can lead
to particulate emissions.
2.4.2 Veneer Drying
Freshly cut veneer must be dried before it can be glued and pressed
into plywood. A veneer dryer is a heated chamber with layers of rolls
(typically four to eight) to carry the veneer. Heat transferred to the
wood by hot gases circulating in the dryer causes the veneer to dry to a
low moisture content. This final moisture content is typically 2 to 5
percent for Douglas firs and 3 to 8 percent for Southern pines.17
Two methods of heating veneer dryers are indirect (steam) and
direct heat. With steam heat, the dryer is separate from the boiler,
which produces steam to heat the internal coils in contact with dryer
air. With direct heat, hot combustion gases provide the energy neces-
sary to dry the veneer. Direct-fired dryers are fueled with either gas
or wood. In gas-fired dryers, combustion occurs at a burner inside the
dryer, and the heated air is circulated to the veneer with fans. In
wood-fired dryers, air is heated outside the dryer by combustion of wood
fuel. Combustion gases are mixed with recirculating dryer air in a
blend box and transported into the dryer.
Dryers are also characterized by the method used to circulate hot
air to the veneer sheets. Longitudinal-flow dryers may have one to
three zones; a two-zone longitudinal-flow dryer is shown in Figure 2-3.
A zone is the portion of a dryer that has a self-contained air circula-
tion system, as shown in Figure 2-4; air circulates through a longi-
tudinal zone parallel to veneer movement. The air is moved by cen-
trifugal fans located at one end of the zone. In a steam-heated longi-
tudinal dryer, air flows past steam coils in the upper plenum, through a
2-12
-------
\
Steam coils
Air flow
J
1.8 m (typical)
Figure 2-3. Two-zone longitudinal-flow dryer.18
-------
delivery manifold at the end of the zone, and down into the various
decks containing moving veneer.18 The air is collected in another
manifold at the opposite end of the zone before it reaches the cen-
trifugal fans. Steam coils also are installed among the veneer decks in
the drying portion of the dryer. In most direct-heated systems, instead
of steam coils, hot gases generated outside the dryer supply the required
heat. In the gas-fired dryers currently used, a gas burner located on
the upper plenum supplies heat.
Over 90 percent of the new dryers installed in the last 5 years are
jet-impingment-type dryers (jet dryers).19 20 Figure 2-5 shows a three-
zone jet dryer, where hot air is directed onto the veneer surface through
jets or holes in horizontal plenums. The jets of hot air effectively
transfer moisture from the wood by disturbing boundary layers on the
veneer surface. These dryers generally have higher green end temperatures
and more control zones than do longitudinal dryers. Jet dryers may be
direct fired or steam heated. Figure 2-6 shows a cross section of a
steam-heated jet dryer. In a jet dryer, one side of the unit is under
positive pressure. The condition of door seals on this side of the
dryer partially determines the extent of fugitive emissions. All dryers
are equipped with baffles at each end to minimize infiltration or leakage
while allowing veneer movement.
Emissions from dryer stacks vary according to dryer type. Some of
the emissions from gas-fired dryers are unburned methane and other
low-molecular-weight hydrocarbons.21 Because they emit combustion
gases, wood-fired dryers may emit more organics than do gas-fired and
steam-heated veneer dryers. However, a wood-fired dryer may have fewer
overall organic emissions than a steam-heated veneer dryer and the
associated wood-fired boiler do because some dryer organics may be
destroyed by high temperatures in the blend box or combustion unit.
Dryer emissions also vary according to type of wood in the dryer. For
example, on the basis of mass emissions per production unit, drying
Ponderosa pine veneer may yield over twice the emissions from drying
Douglas fir veneer.21
2-14
-------
i
Direction of
Veneer Flow
Air Flow
IN3
I
cn
HP
BOO 6—TT
n 6 n 6=S
a o o
ft n a
«> o n n a
a—g ? g
_2—o—a—o—a_
OOP—a_
a o o o e
o oooo
0 Q Q o o
0 o Q cTo
0606'
Q Q Q Q Q
Q Q Q Q Q
Q 0
Q O
008
o o a
OOP 5~5~
066
6 4
9 O O 0
Q O n Q O
Figure 2-4. Wet end of a steam-heated longitudinal-flow dryer.20
-------
IV)
1
1— '
CT>
n n r
i
,-MQ-f
h
ORS-%
rf
\
n
n
n
n
n n
(TYPICAL)
NOTE: No scale
DOORS
Figure 2-5. Three-zone, twelve-section jet dryer.
-------
CENTRIFUGAL FAN
BANK OF
FINNED
STEAM
COILS
NOTE: No scale
Figure 2-6. Cross section of a steam-heated jet dryer.
2-17
-------
Stack damper setting directly influences the amount of organic
material vented from a veneer dryer, as well as dryer operating efficiency.
In the high wet bulb temperature method,22 23 24 25 the dampers are set
to reduce the volume of air exhausted and to raise the humidity in the
dryer. The desired wet bulb temperature is typically about 66° C. Some
dryers, particularly jet dryers in the South, are operated with the
stack dampers in the closed position (although some air is exhausted
through built-in openings in the dampers). Heat loss is reduced and
heat transfer to the veneer is increased in dryers operated by the high
wet bulb temperature method. Advantages include: (1) more even
veneer moisture content, (2) higher production, (3) lower fuel costs,
(4) less chance of overdrying, (5) less chance of dryer fires, and
(6) lower capital cost of air pollution control equipment.25 When dryer
vents are closed, the static pressure in the dryer is increased, causing
higher fugitive emissions out dryer ends and through any leaks in
the dryer shell. Therefore, the condition of door and roll seals
becomes very important on a dryer operated in the high wet bulb tempera-
ture mode. Fugitive emissions are discussed further in Chapter 3.
The primary emissions from veneer dryers are organic aerosols and
gaseous organic compounds. A small amount of wood fiber also is emitted.
The organic material is a mixture of compounds driven from the wood by
steam that forms within the wood when moisture in the veneer is heated.
These materials are in gaseous form until cooled to below approximately
150° C, at which time an aerosol begins to form.26 At ambient air
temperatures, a vapor fraction remains, while the remainder of the
material is an aerosol. Douglas fir and Loblolly pine veneer both
showed high gaseous fractions (greater than 80 percent) in a recent
Washington State University study.26 The vapor fraction at 21° C
consists mainly of monoterpenes (C10H16) in various combinations, depend-
ing on the wood species. The most common monoterpenes are a-pinene,
p-pinene, camphene, A3-carene, and limonene. The predominant monoter-
pene, a-pinene, is the major component of commercial turpentine and
occurs in many volatile oils.26 The aerosol fraction at 21° C probably
contains additional monoterpene.20 However, the bulk of this complex
2-18
-------
mixture consists of compounds of higher molecular weights than the
monoterpenes. The compound groups identified include resin acids
(notably abietic), fatty acids, and neutral sesqui- and di-terpene
compounds, all of which have at least 15 carbon atoms.21 26 Detailed
gas chromatograph-mass spectrometer analyses of condensible organic
emissions from several wood species are available.26 The relative
abundance of vapor/aerosol fractions in dryer emissions varies according
to wood type but also depends on measurement technique.21 26
Emissions rate data for veneer dryers are summarized in Chapter 6.
At least four different test methods have been used to quantify dryer
emissions, and the resulting data are not always comparable because of
differences in physical configurations, condenser temperatures, and
analytical schemes. Chapter 6 contains a description of test methods
that is useful in interpreting the veneer dryer emissions data below.
Emissions vary from dryer to dryer. With the same test method (Oregon
Method 7), condensible emissions for Douglas fir alone have been measured
at from 1.3 to 14 g/m2, 9.5-mm basis (0.26 to 2.86 lb/1,000 ft2, 0.375-in.
basis) at different steam-heated dryers.
Limited sampling by Washington State University (WSU) indicates
that the noncondensible fraction equals or exceeds the condensible
fraction of emissions from Douglas firs. The study strongly suggests
that noncondensible emissions make up 80 percent of Southern pine
emissions.26 An extensive 1972 study by WSU found Douglas fir conden-
sible emissions to average approximately 4.4 g/m2, 9.5-mm basis (0.9
lb/1,000 ft2, 0.375-in. basis). Noncondensible emissions from Douglas
firs were reported to be much lower, but calculation errors were later
discovered. Corrected, noncondensible Douglas fir emissions from the
1972 study average 2.0 (sapwood) to 4.0 (heartwood) g/m2, 9.5-mm basis
(0.4 to 0.8 lb/1,000 ft2, 0.375-in. basis).2? Condensible emissions
from Southern pines are estimated from this report to be approximately
4.0 g/m2, 9.5-mm basis (0.8 lb/1,000 ft2, 0.375-in. basis). Noncon-
densible Southern pine emissions averaged approximately 11 g/m2, 9.5-mm
basis (2.3 lb/1,000 ft2, 0.375-in. basis), after corrections for cal-
culation errors.27 Thus, the ratio of noncondensible to condensible
2-19
-------
emissions calculated from the 1972 WSU study data are in line with those
reported in the 1981 WSU report. Exact agreement would not be expected
because of differences in test methods (see Chapter 6).
2.4.3 Veneer Preparation, Layup, and Gluing
Plywood consists of sheets of veneer bonded by layers of glue. Dry
veneer is inspected, clipped, and spliced as needed. Steps in the layup
process are veneer preparation, layup or gluing, and pressing. Knot
holes are plugged, and the veneer is regraded as necessary to prepare
sheets for layup.
Different plywood products require different glues to bond the
veneer sheets. Approximately 98 percent of the softwood plywood pro-
duced in this country is made with phenol-formaldehyde resins.
Glue is applied to the plywood, which is moved in loose layers to
the pressing area. Many glues must stand for a few minutes before
pressing. Pressing requires 2 to 7 minutes, depending on the panel
thickness. Phenol-formaldehyde glues are steam pressed at temperatures
ranging from 132° to 174° C and at pressures up to 1,030 kPa (150 psi).29
During pressing and when the presses are released, some gaseous organics
may be emitted from unreacted monomers. These fugitive emissions have
been considered only in terms of their in-plant effects. Their presence
requires adequate venting to protect worker health and to eliminate
odors.
2.4.4 Plywood Finishing
The last step in plywood preparation is trimming and finishing.
The plywood is trimmed by stationary circular saws, which remove up to
25 mm (1 in.) on each side to produce even-edged sheets. Then the
plywood sheets may be sanded on one or both faces, depending on the
final product. Only 18 to 20 percent of all plywood is sanded. During
sanding, the sheets move on a conveyor through enclosed automatic sanders,
which are cleared continuously of sanderdust by pneumatic collectors
located above and below the plywood.
Mills may produce one or several grades or classifications of
plywood; the amount of plywood sanded varies from none at some plants to
the entire production at others. The depth of cut, or amount of material
2-20
-------
sanded from each plywood face, varies widely with product. Dust from
sanding and trimming operations is transferred by pneumatic systems to
cyclone collectors, in addition to which many plants have installed
baghouses. Sanderdust and sawdust are valuable byproducts and are used
as fuel for boilers or direct-fired combustion units.
2.4.5 Technological Changes
Although Douglas firs traditionally have been used in softwood
plywood manufacture, technological innovations have allowed the use of
other softwoods: hemlocks, spruces, White firs, red cedars, and Southern
pines. Trees of these species are smaller in diameter than is the
coastal Douglas fir. A lathe was developed to accommodate logs with
diameters as small as 20.3 to 25.4 cm (8 to 10 in.).30
In 1964, the jet veneer dryer replaced the roller dryer as most
effective. The new jet dryers enabled output volume to double, while
the number of employees necessary remained constant or decreased.30
Other technological changes that increase productivity include
automatic clipping of veneer sheets, panel knot hole patching with hot
plastic, and automatic high-speed hot press loading, curing, and
unloading.31 ^
2.5 REFERENCES
1. Industry and Trade Administration, U.S. Department of Commerce.
U.S. Industrial Outlook 1979. January 1979. p. 40.
2. 1980 Directory of the Forest Products Industry. San Francisco,
Miller Freeman Publications, 1980.
3. Letter from Emery, J. A., American Plywood Association, to
McCarthy, J. M., Research Triangle Institute. January 13, 1982.
Comments on draft Control Techniques Document.
4. Anderson, R. Regional Production and Distribution Patterns of the
Softwood Plywood Industry. American Plywood Association. Economic
Report E 31. Tacoma, Washington. June 1981.
5. U.S. Environmental Protection Agency. Economic Analysis of Proposed
Effluent Guidelines. The Timber Processing Industry (Hardboard,
Wood Preserving, Plywood and Veneer). EPA-230/ 1-73-029. August
1973. p. 70.
2-21
-------
6. Bellas, Carl. Industrial Democracy and the Worker Owned Firm New
York, Praeger Publishers. 1972. p. 105.
7. Value Line Investment Surveys. Arnold Bernhard & Company New
York, August 8, 1980. p. 937, 940, 943, 953, 954, 956.
8. Reference 8, p. 931.
9. Reference 8, p. 932, 934, 945, 951, 957.
10. Bureau of the Census, U.S. Department of Commerce. 1977 Census of
Manufacturers—Industry Series. MC 77-1-24B. June 1980. p. 24B-11.
11. Telecon. Erb, K., American Plywood Association, with Chessin,
Robert L., Research Triangle Institute. July 29, 1981. Reconstruc-
tion of existing veneer dryers.
12. Franklin, E. C. Phenotypic and Genetic Variation of Sulfate Navel
Stores Yields in Loblolly Pine. (Presented at TAPPI Forest Biology
Conference. San Francisco. April 1974.) p. 99.
13. Springer, E. L. Losses During Storage of Southern Pine Chips.
TAPPI. 59:126. April 1976.
14. Hajng, G. J. Outside Storage of Pulpwood Chips. TAPPI. 49:97A
October 1966. —
15. Cowling, E. G., et al. Changes in Value and Utility of Pulpwood
During Harvesting, Transport, and Storage. TAPPI. 57:120.
December 1974.
16. Letter from Mortensen, D. K., Georgia-Pacific Corporation, to
McCarthy, J. M., Research Triangle Institute, January 31, 1983.
Comments on draft Control Techniques Document.
17. Letter from Emery, J. A., American Plywood Association, to McCarthy,
J. M., Research Triangle Institute. December 1981. Comments on
draft BID chapters.
18. Vranizan, J. M. Veneer Dryers—Typical Construction, Operations,
and Effluent Abatement Possibilities. (Presented at Air Pollution
Control Association. Eugene. November 17, 1972.)
19. Telecon. Chessin, R., Research Triangle Institute, with Oehling,
N., Coe Manufacturing Company. October 8, 1980. Information about
veneer dryers.
20. Browning, B. L., ed. The Chemistry of Wood. New York, Interscience
Publishers, 1963. p. 318.
2-22
-------
21. Monroe, F. L. , et al. Investigation of Emissions from Plywood
Veneer Dryers, Revised Final Report. Washington State University
Pullman, Washington. February 1972.
22. Corder, S. E. Energy Use in an Industrial Veneer Dryer. Plywood
Research Foundation. Tacoma, Washington. September 1975.
23< iC?r?!o'J; E-n yePtilatl'n9 Ver>eer Dryers. Forest Products Journal.
13:449-453. October 1963.
24. Erb, Carl. Dryers and Veneer Drying. American Plywood Association
Tacoma, Washington. DFPA Technical Report No. 112, Part I. December
1975. 13 p.
25. Laity W. W. , G. H. Atherton, and J. R. Welty. Comparisons of Air
and Steam as Veneer Drying Media. Forest Products Journal. 24:21-29.
26. Cronn, DR., et al . Study of the Proposed and Chemical Properties
or Atmospheric Aerosols Attributable to Plywood Veneer Dryer
Emissions-Final Report to American Plywood Association. Washington
State University. Pullman, Washington. June 1981.
27. Telecon. McCarthy, J. M. , Research Triangle Institute, with
Dallons, V., NCASI. March 24, 1983.
28. Letter from Blosser, R. 0., National Council of the Paper Industry
^Ar- aStream ImProvement, Inc., to Farmer, J. , U.S. Environmental
Protection Agency. January 19, 1983. Comments on draft Control
Techniques Document.
29. Lambuth^ A. ^ ^Adhesives in the Plywood Industry. Adhesive Age.
30. Farris, M. R. The Veneer and Plywood Industry: Above Averaae
Productivity Gains, Monthly Labor Review. Bureau of Labor
Statistics, U.S. Department of Labor. September 1978. p. 28.
31. Industry and Trade Administration, U.S. Department of Commerce,
U.S. Industrial Outlook 1974. January 1974. p. 54.
2-23
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3. EMISSION CONTROL TECHNIQUES
3.1 INTRODUCTION
Controlling emissions from plywood veneer dryers begins with
maintaining door seals, dryer skins, tops, and baffles; proper balancing
of air flows; and use of end-sealing sections to minimize fugitive
emissions.1 Stack emissions from plywood veneer dryers and panel sanders
can best be controlled by add-on equipment. The strategy for reducing
veneer dryer emissions has centered on removal of the organic aerosol
component to reduce plume opacity. Wet scrubbing and incineration are
the most common control techniques for veneer dryers. Fabric filtration
represents current technology for control of sanderdust emissions; but
sufficient blowout panels, halon deluge systems, spark detectors, and
abort gates must be added to mitigate the fire hazard.1
3.2 VENEER DRYER EMISSION CONTROL
3.2.1 Wet Scrubbing
The most common technology for veneer dryers is wet scrubbing, for
which several types of equipment are available. In each case, a water
spray is introduced into the dryer exhaust stream, resulting in cooling
and condensing of organic material. Water vapor may condense onto the
organic aerosol,2 and the resulting droplets are large enough to be
removed by cyclonic collectors, filters, or mist eliminators. Organic
material that remains in the vapor phase escapes collection and reaches
the atmosphere. Therefore, wet scrubbing will have a low organic
emissions removal efficiency if applied to veneer dryer emissions with
high gaseous fractions.
Scrubbers employing a number of different collection mechanisms
have been used to control veneer dryer emissions. Representative
3-1
-------
examples of these collector types are described In the following subsec-
tions. These systems have only been used at Northwestern plants. No
systems have been installed at plants drying Southern woods.
3.2.1.1 Multiple Spray Chambers. The Burley Scrubber, the most
common wet scrubbing device used today, employs three to five spray
chambers in series.1 The five-chamber model contains a final demisting
zone where a high-speed centrifugal fan removes droplets. The three-
chamber model, which is currently being marketed, requires no fan and
has an operating pressure drop of only 62 to 124 Pa (0.25 to 0.50 in.
water). The three-zone unit is reported to meet Oregon's 10 percent
opacity limit on dryer exhausts that have moisture contents of at least
24 percent by volume.2 This device is designed to treat the exhaust
from a single steam-heated or gas-fired dryer and generally is installed
above the dryer. Chapter 6 contains the results of emissions tests of
Burley Scrubbers and several other wet-scrubbing devices. The removal
efficiency of Burley Scrubbers for particulate and condensible emissions
generally is less than 50 percent. From recent Oregon Department of
Environmental Quality (ODEQ) Method 7 tests, ODEQ reports that this
scrubber can limit particulate and condensible emissions to 3.2 g/m2,
9.5-mm basis (0.65 lb/1,000 ft2, 0.375-in. basis), for Western woods.3
3.2.1.2 Combination Packed Tower and Cyclonic Collectors. An
example of a combination packed tower and cyclonic collector is the
Georgia-Pacific Emission Eliminator (now marketed by Coe Manufacturing
Company), which consists of a spray section followed by a bank of 2 to
12 cyclones in parallel and a packed spray tower.4 5 The packed tower
may be equipped with fiber-pad mist eliminators. A schematic diagram of
the system is given in Figure 3-1. Georgia-Pacific Emission Eliminators
have been installed to treat the exhausts of from one to three steam-
heated or direct-fired veneer dryers. Because of their size, the units
are installed outside of the buildings housing the dryers. Overall
pressure drop across such a system is approximately 2,860 Pa (11.5 in.
water) without the mist eliminator and 4,850 Pa (19.5 in. water) with
the mist eliminator.4 Emission test results for these units are given
in Chapter 6. Removal efficiencies for particulate and condensible
3-2
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EXHAUST FROM
PACKED TOWER
EXHAUST -*-
FROM
DRYERS
PRE-TREATiNG
SPRAY
SECTION
FILTER -H F
PUMP-H P
it
POLISHING
SECTION
PAFTTICLES,
PITCH, 4
WATER
Figure 3-1. Georgia-Pacific Emission Eliminator.6
3-3
-------
organic emissions have been measured through ODEQ Method 7 at up to
59 percent without the mist eliminator and up to 91 percent with the
mist eliminator. ODEQ reports that these units with mist eliminators
can limit particulate and condensible emissions to 1.2 g/m2, 9.5-mm
basis (0.25 lb/1,000 ft2, 0.375-in. basis), for steam-heated and gas-
fired dryers; 1.6 g/m2, 9.5-mm basis (0.35 lb/1,000 ft2, 0.375-in.
basis), for wood-fired dryers with fuel moisture content less than
20 percent; and 1.8 g/m2, 9.5-mm basis (0.40 lb/1,000 ft2, 0.375-in.
basis), for wood-fired dryers with fuel moisture content of 20 percent
or greater.3
Various simple wet-scrubbing devices have been installed on
Northwestern veneer dryers in the past 10 years. Most of these wet
scrubbers never have received widespread use. Emission reductions of
these units are not expected to be better than those of the Burley and
Georgia-Pacific scrubbers without mist eliminators.7 Emissions data for
two units, the Buchholz Scrubber and the Leckenby Scrubber, are given in
Chapter 6.
3.2.1.3 Sand Filter Scrubbers. The Rader SandAir Filter is a
device incorporating a wet-scrubbing section followed by a wet-sand
filter and mist eliminator. Figure 3-2 is a schematic diagram of the
system. The Rader SandAir Filter has been installed at more than six
plywood plants in the Northwest.8 Existing systems treat the exhaust
from two or more steam-heated dryers. The larger particulate material
is removed in the scrubber, while a portion of the remaining organic
material is collected in the filter bed or the mist eliminator. A water
spray carries the condensed material through the filter bed to a separa-
tion system. The design pressure drop of the SandAir unit is approxi-
mately 4,500 kPa (18 in. water). Emission data for this device are
summarized in Chapter 6. The results indicate that up to 90 percent of
particulate and condensible organic material (as defined by ODEQ Method 7)
may be removed by the SandAir system.
3.2.1.4 Ionizing Wet Scrubbers. Ionizing wet scrubbers have been
under development as veneer dryer emission control devices for several
years. Several Ceilcote Ionizing Wet Scrubbers have been installed on
dryers in the Northwest.9 The Ceilcote unit has four main collection
3-4
-------
Figure 3-2. Rader SandAir filter.8
3-5
-------
features: (1) a water spray; (2) packed towers; (3) electrostatic
collection plates; and (4) a mist eliminator. One packed tower is
placed on each side of the collection plates. Ceilcote makes both
single- and dual-stage units, the dual-stage units having two sets of
collection plates placed in series. Although no emission data have been
published showing removal efficiencies of full-scale units, a pilot unit
demonstrated 57 to 84 percent removal of particulate and condensible
organic emissions as measured by ODEQ Method 7.10 ODEQ has summarized
several tests of exhausts from full-scale units. The agency's conclusion
is that Ceilcote units can limit particulate and condensible emissions
to 1.2 g/m2, 9.5-mm basis (0.25 lb/1,000 ft2, 0.375-in. basis), for
steam-heated and gas-fired dryers; 1.6 g/m2, 9.5-mm basis (0.35 lb/
1,000 ft2, 0.375-in. basis), for wood-fired dryers with fuel moisture
content less than 20 percent; and 1.8 g/m2, 9.5-mm basis (0.40 lb/
1,000 ft2, 0.375-in. basis), for wood-fired dryers with fuel moisture
content of 20 percent or greater.3 Ionizing wet scrubbers have only
been used on wood-fired and gas-fired dryers.
3.2.2 Incineration
Veneer dryer emissions are controlled at some locations by incinera-
tion in wood-fired boilers or furnaces. The entire exhaust flow from a
steam-heated veneer dryer sometimes can be sent to a boiler, while only
a portion of the exhaust from a direct-fired dryer is normally returned
to the furnace or fuel cell. At least one Southern plant has direct-
fired dryers with exhaust gas recycle to the furnace, but no such systems
have been tested for emissions removal. Boiler incineration of veneer
dryer emissions has not been demonstrated on a Southern pine veneer
dryer. However, Georgia-Pacific11 reports problems with ducting any type
of Southern pine dryer exhaust for any distance because of condensation.
Condensation often occurs in the dryer, so insulation is of little value.
In such cases, steam tracing of the ducts may be a viable alternative,
although it has not been demonstrated in this application.
3.2.2.1 Boiler Incineration. Boiler incineration systems have
been installed in at least 13 plants in the Northwest.12 With this
method, dryer exhaust is used as combustion air in the boiler. Dryer
3-6
-------
exhaust can be introduced as underfire air and/or overfire air. The
most sophisticated systems involve automatic distribution of dryer
exhaust as overfire and underfire air, according to steam demand.12
Because no additional combustion device is required in boiler
incineration, the main capital expenditures are for ductwork, fans,
pressure controllers, and boiler oversizing or modifications. All ducts
are heavily insulated to prevent condensation of dryer emissions.
Boiler modifications include installing water-cooled grates as well as
ports for introducing dryer exhaust.12 Dryer exhaust has been ducted to
boilers located over 350 m from the dryer.13
Several generalizations can be made about boiler incineration
systems. Furnace temperatures of 1,190° C (2,000° F) or greater are
found in most wood-fired boilers.14 Residence times for fuel in the
furnace section are on the order of 2.5 s for spreader-stoker boilers,
but combustion air residence time may be less for these and dutch-oven
boilers. These temperatures and residence times are above the minimum
requirements for thermal destruction of hydrocarbons.15 Therefore,
destruction efficiency may be largely a function of the turbulence or
degree of mixing in the high-temperature area of the boilers. Boiler
designs provide for a high degree of mixing to promote combustion of
volatile materials from the fuel. Temperature and residence time con-
siderations support the potential for a high, overall removal rate of
total veneer dryer emissions (perhaps greater than 90 percent) by boiler
incineration. However, at least two attempts to measure the destruction
efficiency of these systems for total organic emissions have been unsuc-
cessful. A removal rate for condensible organic material of approximately
70 percent was suggested by the results of one test (see Chapter 6). A
wet-scrubbing device on the boiler exhaust may be required to meet a
high level of emissions reduction.
Boiler incineration may not be a viable control technique for
certain existing plants. The combined dryer exhaust volume for a typical
plywood mill approaches the capacity of the plant boiler to accept
combustion air. In some cases, that capacity may be exceeded. For
example, newer boilers that are designed to operate efficiently on
3-7
-------
relatively low excess air might be unable to accept the exhaust volume
from all dryers. For this reason also, new boilers might have to be
oversized to accommodate the system.
3.2.2.2 Incineration in a Fuel Cell. The technology for heating
dryers with wood-waste fuel has developed considerably in the last 10
years. The process involves burning fuel in a furnace or fuel cell and
using the hot combustion gases as an energy source for the dryer. A
portion of the dryer exhaust gas is returned to a blending zone of the
furnace or to a blend box and is mixed with the hot combustion gas
before being returned to the dryer. Combustion gases must be blended
with dryer gases because combustion gases are too hot for direct injec-
tion to the dryer. Figure 3-3 is a schematic diagram of a typical
system. The amount of dryer exhaust that reaches the blend box varies
among systems.16 1? 18 Systems that recycle a large fraction of the
dryer exhaust (e.g., 65 percent) typically have blend box exit tempera-
tures of 427° C (800° F). When a smaller fraction of dryer exhaust is
recycled (e.g., 35 percent), blend box exit temperatures are typically
621° C (1,150° F). High-temperature ductwork and insulation are needed
in the latter case.
At least three types of systems currently are available.16 17 18
In the most common system, dry wood-waste is burned in a cyclonic burner
that is designed to hold wood particles in the burner until combustion
is complete. Ambient air is introduced as combustion air. Hot combustion
gases from the burner are mixed with dryer exhaust in a blend box and
are returned to the dryer. Blend box exit temperatures are 427° to
649° C (800° to 1,200° F).
In a second type of wood-fired system, wet or dry wood-waste is
burned in a pile furnace. Combustion air consists of ambient air and
(typically) exhaust from the dry end of a veneer dryer. Dryer exhaust
is introduced at various points in four combustion chambers, including
the primary chamber containing the wood pile. Temperatures range from
approximately 982° to 1,093° C (1,800° to 2,000° F) at the primary
chamber to 427° C (800° F) at the final chamber exit.19
3-8
-------
To Dryer(s)
Exhaust
Return to Furnace
CO
Dryer(s)
427° - 649° C
Blending
Zone
Burner
Air
Wood
Fuel
Furnace
Figure 33. Wood-fired dryer system with partial incineration in a fuel cell.
-------
Finally, a direct-fired system is used in which wet or dry wood-
waste is introduced into a fluidized furnace. Ambient air is used as
combustion air. Combustion products at approximately 871° to 982° C
(1,600° to 1,800° F) are mixed with the dryer return flow in a blend
box; the resulting mixture is ducted to the dryer at 427° to 649° C
(800° to 1,200° F).19
Emissions data for wood-fired veneer dryer systems are given in
Chapter 6. The fate of the condensible organic material is masked by
the inorganic particulate (ash) load characteristic of direct-fired
systems. Existing data do not indicate the percent of pollutants removed
in the blend box. In such systems, inorganic particulate matter (ash)
may settle out in the dryer or impinge on the veneer surface, whereas
organic material may be partially destroyed in the blend area. The
exhaust from wood-fired veneer dryer systems is sometimes further con-
trolled by high-efficiency wet-scrubbing devices such as the Georgia-
Pacific Emission Eliminator or the Ceilcote Ionizing Wet Scrubber.
EPA experience suggests that incineration of all dryer exhaust in a
fuel cell or furnace could be achieved in wood-fired systems. Figure 3-4
is a conceptual diagram of such a system. Ambient air would be heated
to required dryer temperatures in a high-temperature air-to-air heat
exchanger by hot furnace exhaust gases. A portion of the dryer exhaust
gases would be used as combustion air for the wood fuel, and another
portion (perhaps 40 percent) would be recycled to the dryer. Maintaining
a fuel cell exhaust temperature of 760° to 871° C (1,400° to 1,600° F)
and providing sufficient residence time should achieve organic emissions
removal efficiencies of greater than 90 percent. The disadvantages of
this system include the need to modify currently available burner designs,
increased difficulty in balancing air flows due to one or more additional
fans and control dampers, and potentially increased fuel requirements.
Balancing problems would tend to be more severe for systems involving
multiple dryers, while additional fuel requirements would be crucial for
plants that are marginally self-sufficient in fuel (e.g., layup plants).
It is stressed that this is a conceptualized system and that the required
technology (especially burner technology) may not currently exist.
3-10
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Exhaust
Ambient Air
Dryer(s)
Heat Exchanger
Wood
Fuel
Burner
760° - 870° C
Furnace
Figure 3-4. Wood fired system with complete incineration of dryer exhaust
in a fuel cell.
-------
3.2.2.3 Catalytic Incineration. Pilot studies have been conducted
on a catalytic incineration system for veneer dryer exhausts. In tests
of a unit handling 0.065 stdmVs (138 stdft3/min) at 259° C (499° F) and
316° C (601° F), the emissions reduction was 93 percent, as measured by
ODEQ Method 7,20 and there were no visible emissions (except for steam).
At 183° C (361° F), the emissions reduction was 84 percent and blue haze
emissions went above 10 percent opacity. Major disadvantages of this
system are the need for supplementary fuel and plugging of the catalyst
bed. No sales of the system have been made because it is costly compared
to the Burley scrubber.1
3.2.3 Low-Temperature Drying
Dryer emissions on a per-unit-of-production basis may be reduced by
lowering dryer temperatures. This procedure reduces veneer production
rates, because longer drying times are required at lower temperatures.
Low-temperature drying may only be feasible at facilities that have
excess drying capacity, an uncommon situation. Maintaining the required
air circulation rates in the dryer may substantially increase the elec-
trical energy costs per unit of production. In tests of three dryers,
particulate and total organic emissions (as measured by a Washington
State University method) were reduced by lowering dryer temperatures
(see Chapter 6). Emission reductions varied greatly, with the highest
reduction being 74 percent.21
3.2.4 Control of Fugitive Dryer Emissions
Fugitive emissions can comprise a significant portion of the total
emissions from a veneer dryer. The main factors affecting the quantity
of fugitive emissions are the type of dryer, the condition of door seals
and end baffles, and stack damper settings. In the Northwest, stack
dampers generally are set to maintain a desirable moisture level inside
the dryers. Damper settings also can be used to balance the air flows
within a dryer and, thus, to minimize energy loss. This is especially
true for longitudinal dryers, for which it is desirable to maintain
neutral pressure at dryer ends by means of the dampers. In the South,
dampers are set in the closed position on many jet dryers. Even with
the dampers closed, 1.5 to 4 m3/s of exhaust gas may escape through the
annuli between dampers and stack walls of a three-zone jet dryer.
3-12
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However, material balance calculations show that in such dryers the
evaporated water alone would result in exhaust rates of approximately
3 rnVs. The emissions that do not leave through stack exhausts must
escape as fugitive emissions through the doors, skins, and ends of the
dryers. In-plant observations indicate that fugitive emissions may be
significant, but quantitative measurements of fugitive emissions are not
available.
Control techniques for minimizing fugitive emissions include
maintenance of door seals, dryer skins, tops, and end baffles; proper
balancing of air flows (considering the effect of damper settings on
internal dryer pressure); and use of end-sealing sections. Dryer doors
can be sealed and shimmed as necessary to eliminate visible emissions
caused by leaks. New seals are usually needed only every 2 years;
however, quarterly inspection and maintenance of seals may be reasonable
because of the energy losses and emissions associated with leaking
doors.1 22 Maintenance of skins and tops consists of applying insulating,
sealing material where feasible and replacing those portions when other
methods are no longer adequate.
End-sealing sections are pressurized sections added to a dryer to
prevent emissions and energy loss from the ends of a dryer or to prevent
infiltration of cold air into the dryer. End seal sections may be
positively or negatively pressurized. No available data show the
effectiveness of end seal sections in controlling fugitive emissions.
One vendor, who regularly installed end seal sections with scrubbers,
finds that another method of sealing dryer skins and doors is more
effective than are end seal sections.2 A sealing compound is used on
the dryer skins and doors, and in conjunction dryer operation is evalu-
ated to maximize dryer efficiency. However, at least one dryer vendor
is considering seal sections on the green ends of jet dryers as a means
of reducing total exhaust flow.23
3.3 PANEL SANDER EMISSION CONTROL TECHNIQUES
Uncontrolled plywood panel sander emissions are emissions that pass
through a primary product recovery cyclone. These cyclones have tradi-
tionally been large, conventional units with diameters typically 3.0 m
3-13
-------
(10 ft). However, in some cases, two separate cyclones have been
installed to handle the sanderdust from the tops and bottoms of the
panels.24
3.3.1 High-Efficiency Cyclones
With increasing State pressure to control sanderdust emissions,
installation of high-efficiency cyclones, either as single units or in
banks of smaller cyclones, has replaced installation of a single, con-
ventional cyclone. A typical bank of cyclones consists of four cyclones
that are in parallel and empty the collected material into a single
hopper.25 The advantage of high-efficiency cyclones is high removal
efficiency without a baghouse. Emissions data from sanderdust cyclones
are relatively abundant; however, the input rate to the cyclone has been
determined in relatively few tests (see Chapter 6). Removal efficiencies
for sanderdust cyclones that had been tested averaged from 94 to 99.5 per-
cent. The dimensions of these cyclones are not known. These removal
efficiencies are high, considering the particle size distribution of
sanderdust. Plywood sanderdust size is reported to be between 10 and 80
pm (99.8 percent by weight) with a mean particle size of 22 nm on a
count basis.26
3.3.2 Fabric Filters
When new sanders are installed in the Southern States, fabric
filter systems (baghouses) or high-efficiency cyclones will be used.
Figure 3-5 is a cutaway view of a type of fabric filter system often
used to control sanderdust emissions. If current practices continue,
new sanders in the Pacific Northwest probably will be controlled by
single cyclones (achieving perhaps 94 to 99 percent removal) followed by
a fabric filter system. The exact percent removal of these systems
cannot be calculated because inlet loadings generally are not measured.
However, baghouse emissions from plywood sanding operations are typically
0.009 g/stdm3 (0.004 gr/stdft3).28 This figure corresponds to 99.9 per-
cent removal of emissions from a touch sanding system operating at a
moderate rate (0.25 mm depth of cut, 2,100 m2/h of surface area sanded).
While this high removal is suggested by existing data, average removal
through the life of the system may be limited to 99 percent. Given the
3-14
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REVERSE AIR
PRESSURE SLOWER DRIVE MOTOR AIR MANIFOLD
CLEAN
AIR
OUTLET
OUTER ROW
REVERSE AIR
MANIFOLD
FABRIC
FILTER TUBES
HEAVY DUST
DROPOUT
MIDDLE ROW
REVERSE AIR
MANIFOLD
PRE-CLEANING
BAFFLE
Figure 3-5. Fabric filter system for control of sanderdust emissions.27
3-15
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choice, some firms elect to try to meet State emission limits using only
high-efficiency cyclones because of the explosion hazard of baghouses.
3.4 CONCLUSIONS
Boiler incineration appears to be the best control technique for
emissions from steam-heated dryers, based on temperature and residence
time considerations. Incinerating a portion of dryer emissions in a
fuel cell in conjunction with high-efficiency wet scrubbing of the
remaining emissions appears to be the best existing technique for
controlling emissions from wood-waste-fired dryers. High-efficiency
scrubbing appears to be the best control technique for gas-fired dryers.
Further emissions testing is needed, particularly on Southern dryers, to
establish removal rates for each of these control techniques.
Control of emissions from plywood sanding operations can best be
achieved by baghouses in conjunction with primary collectors (cyclones).
Overall removal rates of greater than 99 percent can be achieved.
3.5 REFERENCES
1. Letter from Bosserman, P. B., Oregon Department of Environmental
Quality, to McCarthy, J. M., Research Triangle Institute.
November 29, 1982. Comments on draft Control Techniques Document.
2. Telecon. McCarthy, J. M., Research Triangle Institute, with
Potter, G., Burley Industries. February 19, 1981. Wet-scrubbing
devices.
3. Bosserman, D. B. Controls for Veneer and Wood Particle Dryers.
Oregon Department of Environmental Quality. Portland, OR.
(Presented at the Air Pollution Control Association, Pacific
Northwest International Section Annual Meeting. Spokane.
November 3, 1981.)
4. Tretter, V. J., Jr. Plywood Veneer Dryer Emission Control Systems.
Georgia-Pacific Corporation. Atlanta, GA. (Presented at the
Annual Meeting of the Air Pollution Control Association. Portland.
June 27-July 1, 1976.) 17 p.
5. Telecon. McCarthy, J. M., Research Triangle Institute, with
Hammes, D. A., Georgia-Pacific Corporation. February 19, 1981.
Wet-scrubbing devices.
6. Letter and attachments from Hammes, D. A., Georgia-Pacific
Corporation, to McCarthy, J. M., Research Triangle Institute.
March 2, 1981. Response to request for cost data.
3-16
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7. Oregon Department of Environmental Quality, Air Quality Control
Division. Veneer Dryer Control Device Evaluation, Supplemental
Report. Portland, OR. December 14, 1976.
8. Letter and attachments from Hirsch, J., Rader Companies, Inc., to
McCarthy, J. M., Research Triangle Institute. February 24, 1981.
Response to request for information on sand filters.
9. Telecon. McCarthy, J. M. , Research Tn angle Institute, with Frega,
V., The Ceilcote Company. February 19, 1981. Ionizing wet
scrubbers.
10. Letter and attachments from Wellman, E. A., BWR Associates, to
McCarthy, J. M., Research Triangle Institute. December 22, 1980
Veneer dryer emission data.
11. Letter from Mortensen, D. K., Georgia-Pacific Corporation, to
McCarthy, J. M., Research Triangle Institute, January 31, 1983.
Comments on draft Control Techniques Document.
12. Telecon. McCarthy, J. M., Research Triangle Institute, with Hagel
P. M., P. ^M. Hagel and Associates, Inc. June 2, 1980. Boiler
incineration of veneer dryer exhaust.
13. Letter and attachments from Bartels, H. H., Champion International
Corporation, to McCarthy, J. M., Research Triangle Institute.
September 17, 1980. Response to request for information on boiler
incineration systems.
14. Telecon. McCarthy, J. M., Research Triangle Institute, with
McBurney, B., McBurney Corporation. January 21, 1981. Boiler
incineration systems.
15. Memorandum from Mascone, D. C., EPA, to Farmer, J. R. , EPA.
June 11, 1980. Thermal incineration performance for NSPS.
16. Research Triangle Institute. Trip Report on Visit to Boise-Cascade
Corporation, Albany, OR. Research Triangle Park, NC. September 2,
1980.
17. Sullivan, Paul. Direct-Fired Wood Waste Combustion Systems In-
Modern Plywood Techniques, Proceedings of the Fifth Plywood Clinic
White, V. S. (ed.). San Francisco, Miller Freeman Publications
1977. p. 59-65.
18. Research Triangle Institute. Trip Report on Visit to Boise-Cascade
Corporation, Moncure, NC. Research Triangle Park, NC. August 28,
1980.
19. Letter and attachments from Emery, J. A., American Plywood
Association, to McCarthy, J. M., Research Triangle Institute
December 16, 1981. Industry comments on draft documents.
3-17
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20. Mick, Allan. Current Participate Emissions Control Technology for
Particleboard and Veneer Dryers. Mid-Willamette Valley Air
Pollution Authority. Salem, OR. (Presented at the Meeting of the
Pacific Northwest International Section of the Air Pollution
Control Association. Seattle. November 28-30, 1973.).
21. Monroe, F. L., W. L. Bamesberger, and D. F. Adams. An Investigation
of Operating Parameters and Emission Rates of Plywood Veneer Dryers--
Final Report. Washington State University. Pullman, WA. July
1972. 50 p.
22. Research Triangle Institute. Trip Report on Visit to Timber
Products Company, Medford, OR. Research Triangle Park, NC.
September 23, 1980.
23. Telecon. McCarthy, J. M., Research Triangle Institute, with
McMahon, I. J. , Coe Manufacturing Company. November 20, 1980.
Veneer dryers.
24. Telecon. McCarthy, J. M., Research Triangle Institute, with Fick, 0.
International Paper Company. October 31, 1980. Plywood sanders.
25. Telecon. Chessin, R., Research Triangle Institute, with Tice,
G. W., Georgia-Pacific Corporation. December 18, 1980. Plywood
sanders.
26. Tretter, V. J., R. C. Sherwood, and A. H. Mick. Technology for the
Control of Atmospheric and Waterborne Emissions from Plywood and
Lumber Manufacture. Georgia-Pacific Corporation. Portland, OR.
(Presented at the Annual Meeting of the American Institute of
Chemical Engineers. Chicago. November 1976.) 17 p.
27. Letter and attachments from Wai us, M., Carter-Day Company, to
Chessin, R. L., Research Triangle Institute. February 11, 1981.
Response to request for information on sanderdust control systems.
28. O'Dell, F. G., et al. Pacific Northwest Emission Factors Manual.
Air Pollution Control Association, Pacific Northwest International
Section. 1974. p. F-3.
3-18
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4. COST OF EMISSIONS CONTROL
4.1 INTRODUCTION
Costs for controlling emissions from veneer dryers include capital
and operating expenditures. Costs vary depending upon a number of
factors, including plant age, plant layout, type of processing
equipment, operational parameters, and geography and climate. This
chapter presents emissions control costs for six model plants believed
to be representative of existing plywood facilities and new plants
likely to be built in the next 5 to 10 years.
Two basic types of control techniques are used by the industry:
thermal incineration and wet scrubbing. The cost difference between a
boiler incineration system and an efficient scrubbing system such as a
Georgia-Pacific, Ceilcote, or Sandair scrubber is not great for some
plants. A company decision regarding an emissions control system is
thus based only partially on cost.
4.2 MODEL PLANTS
Softwood veneer dryers (hereafter called veneer dryers) and panel
sanders are the plywood production processes that have potentially
significant emissions. Hardwood veneer drying and sanding are not
considered in this document because emissions from these processes are
insignificant compared to emissions from softwood processes.
All of the model plants represent either new dryers and sanders
installed in existing plants or new plywood plants. This is done for
the sake of example and does not imply that the control techniques
presented herein cannot be applied to existing process equipment. In
general, the capital costs of retrofitting emissions controls to existing
process equipment will be higher than the capital costs of installing
the control systems with new process equipment. However, in the case
4-1
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of boiler incineration, boilers that are already operated with high
excess air may require lower capital costs for modification than the
incremental capital cost of oversizing a new boiler to accept veneer
dryer emissions. The possibility also exists that a boiler may not
have sufficient capacity to accept veneer dryer emissions and must be
determined on a case-by-case basis.
The majority of veneer dryers built in the last 5 years currently
are jet-impingement-type dryers (jet dryers), a trend expected to
continue.1 Coe Manufacturing Company and Irvington-Moore Company are
the primary manufacturers of jet dryers. Coe, which dominates the
industry in dryer sales, sold approximately 80 new jet dryers to U.S.
plants between 1976 and 1981.2 Most of these units are in plants in
the Southern States, where virtually all growth in the softwood plywood
industry will occur. However, single dryers may be sold to plants in
other areas to replace old dryers or to add to existing plant capacities.
Veneer dryers may be classified according to their source of heat
energy. Steam-heated (indirect-heated) dryers are the more common
type of dryer. The air in these units is heated as it passes over
internal steam coils. Direct-fired dryers are heated by hot gases of
combustion from the burning of natural gas or wood fuel. As reflected
in the model plants, wood-waste (sanderdust, plywood trim waste, and
hogged bark) will be the predominant fuel for new direct-fired dryers.
Veneer dryers are designed according to the number of drying
sections needed to achieve a desired drying rate. Drying sections are
typically 1.8 to 2.1 m (6 to 7 ft) long; the number of sections per
dryer ranges from 6 to 26.
New sanders are expected to be high-speed, wide-belt units capable
of light or full sanding. Operation of these sanders will vary among
plants because some plants sand all panels while others sand only a
small fraction of the panels produced.
Model plants are used for cost analysis of emissions control
techniques. These plants are believed to be representative of new
dryers and sanders that would be installed at a wide range of plywood
mills, both existing mills and those likely to be built. Following a
4-2
-------
detailed discussion of these model plants, emissions control costs for
each one are presented.
The six model plants described in Tables 4-1 through 4-6 and
summarized in Table 4-7 include new veneer dryers and new plywood
sanders. Model Plant 1 consists of a new, 16-section, steam-heated
jet dryer and a new panel sander. This dryer is typical of new dryers
installed in Western mills, but such units sometimes are installed in
Southern mills.3 For example, such a dryer might be built to replace
one or two older dryers in a small- to medium-sized Western plant or a
small Southern plant that produces 7.4 to 9.3 x 106 m2/yr, 9.5-mm
basis (80 to 100 x IQS ftVyr, 0.375-in. basis). This existing plant
might employ 250 persons and operate 6,370 h/yr. Model Plant 2 includes
a wood-fired jet dryer whose production rate equals that of Model
Plant 1. Such a dryer is representative of a unit that might be
installed at a small- to medium-sized Western plant or a small Southern
plant using wood-fired dryers. This existing plant might have the
same production rate, operating hours, and number of employees as does
the existing plant described for Model Plant 1.
Model Plants 1 and 2 include new sanders that are assumed to
operate 5,500 h/yr. This might be the case in a mill that sands a
high percentage of its products.
Model Plant 3 consists of a new, 20-section, steam-heated jet
dryer and a plywood sander. This model plant contains a dryer of the
size likely to be installed at existing Southern plywood mills. Such
an existing plant might be a medium-sized mill producing a total of
13.9 x 1Q6 m2/yr> 9_5_mm basis (150 x 1Q6 ft.2/yrj o.375-in. basis);
operating 6,370 h/yr; and employing 300 persons. Model Plant 3 contains
a plywood sander that operates 2,000 h/yr or about one shift per day.
Western plants installing plywood sanders are required to install
baghouses on new sanders. However, Southern plants that install
sanders might install high-efficiency cyclones rather than baghouses.
While some Southern plants do not produce sanded panels, sanders are
expected to be installed where a market exists for sanded plywood.
The number of panels sanded at a Southern mill seldom exceeds 50 percent
of total production.4
4-3
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TABLE 4-1. PARAMETERS FOR MODEL PLANT 1
Description: A single steam-heated dryer and a single plywood sander
Veneer dryer to be controlled:
Number of units
Type
Production
Annual operating time
Exhaust flow rate
Exhaust temperature,
uncontrolled .
Uncontrolled emissions
Sanders to be controlled:
Number of units
Type
Production
Annual operating time
Exhaust flow rate
Exhaust temperature
Uncontrolled emissions
New 16-section, steam-heated jet dryer
4.7 x I06 mVyr (51 x 106 ft2/yr) final
product; 5.9 x 106 mVyr (63 x 1Q6
ft2/yr) through dryer
6,370 h
4.72 stdnrVs (10,000 stdftVmin)
wet basis
163° C (325° F)
28 Mg/yr (31 ton/yr)
Wide-belt panel sander
6.9 x 106 mVyr (74 x 106 ft2/yr)
5,500 h
14.2 stdnrVs (30,000 stdft3/min)
wet basis
21° C (70° F)
39.3 Mg/yr (43.3 ton/yr)
aVeneer dryer production rates are given on a 9.5-mm (0.375-in.)-thickness
basis. Production through dryer includes 10 percent redry and 10 percent
fall-down losses.
Total particulate and condensible organic emissions are based upon the
best available information for Douglas fir. Some other Western species
are known to have lower emission rates. Southern softwoods (various pine
species) may have higher emission rates.
cSander production is based on a Western mill that sands both sides of the
plywood.
Particulate emissions controlled by high-efficiency cyclones.
4-4
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TABLE 4-2. PARAMETERS FOR MODEL PLANT 2
Description: A single wood-fired dryer and a single plywood sander
Veneer dryer to be controlled:
Number of units
Type
Production
Annual operating time
Exhaust flow rate
Exhaust temperature,
uncontrolled
Uncontrolled emissions
Sander to be controlled:
Number of units
Type
Production
Annual operating time
Exhaust flow rate
Exhaust temperature
Uncontrolled emissions
New 12-section, wood-fired jet dryer
4.74 x io6 mVyr (51 x 106 ftVyr) final
product; 5.9 x io6 mVyr (63 x
ftVyr) through dryer
6,370 h
7.55 stdmVs (11,000 stdftVmin)
wet basis
163° C (325° F)
37 Mg/yr (41 ton/yr)
Wide-belt panel sander
6.9 x io6 mVyr (74 x io6 ftVyr)
5,500 h
14.2 stdmVs (30,000 stdftVmin)
wet basis
21° C (70° F)
39.3 Mg/yr (43.3 ton/yr)
aVeneer dryer production rates are given on a 9.5-mm (0. 375-in. )-thickness
basis Production through dryer includes 10 percent redry and 10 percent
tali-down losses.
Total particulate and condensible organic emissions are based upon the
best available information for Douglas fir. Some other Western species
are known to have lower emission rates. Southern softwoods (various pine
species) may have higher emission rates.
°n a Western m111 that sands ^th sides of the
Particulate emissions controlled by high-efficiency cyclones.
4-5
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TABLE 4-3. PARAMETERS FOR MODEL PLANT 3
Description: A single steam-heated dryer and a single plywood sander
Veneer dryer to be controlled:
Number of units
Type
Production
Annual operating time
Exhaust flow rate
Exhaust temperature,
uncontrolled ,
Uncontrolled emissions
Sander to be controlled:
Number of units
Type
Production
Annual operating time
Exhaust flow rate
Exhaust temperature
Uncontrolled emissions
New 20-section, steam-heated jet dryer
5.9 x 106 mVyr (64 x 106 ftVyr) final
product; 7.3 x 106 m2/yr (79 x 106
ftVyr) through dryer
6,370 h
6.13 stdmVs (13,000 stdftVmin)
wet basis
163° C (325° F)
35 Mg/yr (38 ton/yr)
Wide-belt panel sander
3.3 x 106 m2/yr (36 x io6 ftVyr)
2,000 h
14.2 stdmVs (30,000 stdftVmin)
wet basis
21° C (70° F)
11.0 Mg/yr (12.1 ton/yr)
aVeneer dryer production rates are given on a 9.5-mm (0.375-in.)-thickness
basis. Production through dryer includes 10 percent redry and 10 percent
fall-down losses.
Total particulate and condensible organic emissions are based upon the
best available information for Douglas fir. Some other Western species
are known to have lower emission rates. Southern softwoods (various pine
species) may have higher emission rates.
GParticulate emissions controlled by high-efficiency cyclones.
4-6
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TABLE 4-4. PARAMETERS FOR MODEL PLANT
Description: A single veneer dryer and a single plywood sander
Veneer dryer to be controlled:
Number of units
Type
Production
Annual operating time
Exhaust flow rate
Exhaust temperature,
uncontrolled ,
Uncontrolled emissions
Sander to be controlled:
Number of units
Type
Production
Annual operating time
Exhaust flow rate
Exhaust temperature
Uncontrolled emissions
New 15-section, wood-fired jet dryer
5.9 x 106 m2/yr (64 x 106 ftVyr) final
product; 7.3 x 106 m2/yr (79 x 106
ft2/yr) through dryer
6,370 h
9.91 stdmVs (14,000 stdftVmin)
wet basis
163° C (325° F)
46 Mg/yr (51 ton/yr)
Wide-belt panel sander
3.3 x 106 mVyr (36 x 106 ftVyr)
2,000 h
14.2 stdmVs (30,000 stdftVmin)
wet basis
21° C (70° F)
11.0 Mg/yr (12.1 ton/yr)
Veneer dryer production rates are given on a 9.5-mm (0.375-in.)-thickness
basis. Production through dryer includes 10 percent redry and 10 percent
fall-down losses.
Total particulate and condensible organic emissions are based upon the
best available information for Douglas fir. Some other Western species
are known to have lower emission rates. Southern softwoods (various pine
species) may have higher emission rates.
'Particulate emissions controlled by high-efficiency cyclones.
4-7
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TABLE 4-5. PARAMETERS FOR MODEL PLANT 5
Description: A new plywood plant with three steam-heated dryers and a
single plywood sander
Plywood production: 17.2 x 106 m2/yr, 9.5-mm basis
(185 x 106 ftVyr, 0.375-in. basis)
Plant annual operating time: 6,370 h
Number of employees: 350
Land area: 0.20 km2 (50 acres)
Veneer dryers to be controlled:
Number of units
Type
Production3
Annual operating time
Exhaust flow rate
Exhaust temperature,
uncontrolled ,
Uncontrolled emissions
Sander to be controlled:
Number of units
Type
Production
Annual operating time
Exhaust flow rate
Exhaust temperature
Uncontrolled emissions
New steam-heated jet dryers, 58
sections total
17.2 x 106 mVyr (185 x 106 ftVyr) final
product; 21.1 x 106 mVyr (228 x 106
ftVyr) through dryer
6,370 h
17.5 stdmVs (37,000 stdftVmin)
wet basis
163° C (325° F)
101 Mg/yr (111 ton/yr)
Wide-belt panel sander
3.3 x 106 m2/yr (36 x 106 ftVyr)
2,000 h
14.2 stdmVs (30,000 stdftVmin)
wet basis
21° C (70° F)
11.0 Mg/yr (12.1 ton/yr)
aVeneer dryer production rates are given on a 9.5-mm (0. 375-in. )-thickness
basis. Production through dryer includes 10 percent redry and 10 percent
fall-down losses.
bTotal particulate and condensible organic emissions are based upon the
best available information for Douglas fir. Some other Western species
are known to have lower emission rates. Southern softwoods (various pine
species) may have higher emission rates.
cParticulate emissions controlled by high-efficiency cyclones.
4-8
-------
TABLE 4-6. PARAMETERS FOR MODEL PLANT 6
Description: A new plywood plant with three wood-fired dryers and a
single plywood sander
Plywood production: 17.2 x 106 m2/yr, 9.5-mm basis
(185 x 1Q6 ft2/yr, 0.375-in. basis)
Plant annual operating time: 6,370 h
Number of employees: 350
Land area: 0.20 km2 (50 acres)
Veneer dryers to be controlled:
Number of units
Type
Production3
Annual operating time
Exhaust flow rate
Exhaust temperature,
uncontrolled
Uncontrolled emissions
Sander to be controlled:
Number of units
Type
Production
Annual operating time
Exhaust flow rate
Exhaust temperature
Uncontrolled emissions0
New wood-fired jet dryers, 43
sections total
17.2 x io6 mVyr, 9.5-mm basis (185 x
106 ftVyr, 0.375-in. basis) final
product; 21.1 m2/yr (228 x io6 ft2/
yr) through dryer
6,370 h
28.3 stdmVs (39,000 stdftVmin)
wet basis
163° C (325° F)
134 Mg/yr (148 ton/yr)
Wide-belt panel sander
3.3 x io6 mVyr (36 x io6 ft2/yr)
2,000 h
14.2 stdmVs (30,000 stdftVmin)
wet basis
21° C (70° F)
11.0 Mg/yr (12.1 ton/yr)
pnH Produc^on ratf are 9ive" on a 9.5-mm (0.375-in. )-thickness
fan-down kisses™ ^ 1ncludes 10 Percent redrV and 10 Percent
Total particulate and condensible organic emissions are based upon the
best available information for Douglas fir. Some other Western species
are known to have lower emission rates. Southern softwoods (various pine
species) may have higher emission rates.
Particulate emissions controlled by high-efficiency cyclones.
4-9
-------
TABLE 4-7. SUMMARY OF MODEL PLANT PARAMETERS
Vpnppr rtrv^r *« he controlled
Veneer dryers
Model
1
2
3
4
5
6
Number
of units
1
1
I
1
3
3
Tvoe
Steam-heated
Wood- f i red
Steam-heated
Wood- fired
Steam-heated
Wood- fired
106 i«2/yr 106 ftVvr
4.7
4.7
5.9
5.9
17.2
17.2
51
51
64
64
185
185
Exhaust
std«3/s
4.72
7.55
6.13
9.91
17.5
28.3
flow rate
stdftVmin
10.000
11,000
13,000
14,000
37,000
39,000
Uncontrollgd
emissions
Mg/yr
28
37
35
46
101
134
ton/yr
31
41
38
51
111
148
Plywood sander to be controlled
Sanded plywood
production
106 raz/yr
6.9
6.9
3.3
3.3
3.3
3.3
106 ftVyr
74
74
36
36
36
36
Exhaust
stdmVs
14.2
14.2
14.2
14.?
14.2
14.2
flow rate
stdftVmin
30,000
30,000
30,000
30,000
30,000
30.000
Uncontrollgd
emissions
Mg/yr
39.3
39.3
11.0
11.0
11.0
11.0
ton/yr
43.3
43.3
12.1
12.1
12.1
12.1
aAnmial operating time is 6.370 h. As final plywood product; a 9.5-mm (0.3/5-in.)-thickness basis is used
^articulate condensible organic emissions.
cParticulate emissions from product recovery cyclone.
-------
Most of the parameters of Model Plant 4 are identical to those of
Model Plant 3 except that Model Plant 4's veneer dryer is a wood-fired
unit. Model Plant 4 might be installed at an existing Southern plant
that uses direct-fired rather than steam-heated dryers. The parameters
describing such an existing plant are assumed to be the same as those
given for the existing plant that installs the affected facilities
comprising Model Plant 3.
Model Plant 5 is representative of a new Southern plywood plant.
A typical new plant heating with steam will contain three dryers
having a total of 58 sections. Although the number of drying sections
requested by different companies varies, most new plants using steam
are expected to be large mills containing 55 to 60 drying sections.5
New plants of this size will have plywood production rates of approxi-
mately 17.2 x io6 mVyr, 9.5-mm basis (185 x 106 ftVyr, 0.375-in.
basis). Some plywood companies plan new plants based on lower
production rates; many of these plants are overdesigned for the
original, lower production and have rates approaching those given
above.5 Direct-fired dryers require fewer sections than do steam-
heated dryers to achieve comparable drying rates. This difference is
considered in the presentation of Model Plant 6, which is representative
of a new plant that will use wood-fired dryers. Sanders are expected
to be installed at new plants where a market exists for sanded plywood.
In such cases, however, most of the plant's panels probably will not
be sanded, as indicated in Model Plants 5 and 6. Sander parameters
are identical to those of Model Plants 3 and 4.
New plywood mills generally are designed to operate continuously
5 days/wk and 50 wk/yr. Veneer dryers, however, are expected to
operate additional hours each week and a total of about 6,370 h/yr.6
The drying rates of the new veneer dryers in Model Plants 1
through 6 can be achieved only with new jet dryers.5 Drying rates per
section vary among Western plants because several species of wood are
used and because Douglas fir heartwood and sapwood have different
drying properties. Production rates in Tables 4-1 through 4-7 are
intended to represent typical conditions at both Southern and Western
4-11
-------
plants. Because sanding rates vary greatly, depending on the product
mix of individual plants, it is difficult to establish a typical
production rate for sanders. A Western mill, Model Plant 1 or 2,
typically will sand both sides of the plywood at a rate of 420 panels/h.
Tables 4-1 and 4-2 provide an estimate of 5,500 h/yr sanding time for
Model Plants 1 and 2. The sanding rates in Tables 4-3 through 4-6 are
based on touch sanding of one side of each panel at a rate of approxi-
mately 560 panels/h. At 2,000 h/yr annual operating time, each sander
would be operated one shift per day. The sanding rates are believed
to be representative of new sanders in Southern plants.
Tables 4-1 through 4-7 give uncontrolled particulate and
condensible emissions for the dryers and sanders in the six model
plants. Total VOC emissions are probably two or more times condensible
emissions but are not presented because total organic emissions factors
have not been firmly established. Uncontrolled particulate and
condensible emissions from steam-heated dryers are estimated using a
5.9-g/m2, 9.5-mm basis (1.2-lb/l,000 ft2, 0.375-in. basis). This
average value is obtained from data collected through ODEQ Method 7
(see Section 6) and is based for the most part on Douglas fir. Douglas
fir is an important softwood and has an emissions factor between the
low values of true firs and the higher values of pines. For wood-fired
dryers, baseline emissions are considered equivalent to uncontrolled
emissions because certain dryer systems in the South and other areas
of the United States may have no emissions control because of rela-
tively low blend box temperatures of approximately 427° C (800° F).
Uncontrolled particulate and condensible emissions from direct-fired
dryers are estimated at 7.8 g/m2, 9.5-mm basis (1.6 lb/1,000 ft2,
0.375-in. basis).7 Veneer dryers and emissions control systems are
discussed in more detail in Chapters 2 and 3.
Emissions for the sanders in Model Plants 1 and 2 are based upon
an average cutting depth in Western mills of 0.9 mm (0.035 in.), the
combined depth for both sides.7 An emissions estimate for these
plywood sanders is 5.72 g/m2 (1.17 lb/1,000 ft2). Emissions for the
plywood sanders in Model Plants 3 through 6 are estimated at 3.1 g/m2
4-12
-------
of sanded plywood (0.67 lb/1,000 ft2). This emissions rate was derived
from an average sanding depth of 0.5 mm (0.02 in.), which corresponds
to typical sanding of only one side at a Southern mill. Sanderdust
emissions are assumed to be 99 percent controlled, which is the control
level of a high-efficiency cyclone. This assumption is made because
virtually all States require the use of high-efficiency cyclones as a
minimum.
4.3 COSTS
Veneer dryer and sander emissions control costs in 1981 dollars
are provided for Model Plants 1 through 6. These costs are budget-
level estimates, accurate to ±30 percent for the model plants under
consideration. Caution should be used when the costs in this section
are applied to specific plants. Neither boiler incineration nor wet
scrubbing has been used on full-scale Southern veneer dryers, nor have
these technologies been tested adequately in the South on pilot-scale
units. Emissions from Southern pines may be more difficult to control
by scrubbing than emissions from Western woods are. Furthermore,
control costs are site specific and vary greatly depending on
differences in plant and boiler design, production parameters, wood
species, and other factors. Table 4-8 gives the installed capital
costs for wet scrubbing and boiler incinerator systems for steam-heated
dryers in Model Plants 1, 3, and 5. Boiler incinerator capital costs
are more likely to show wide variation from plant to plant. Boiler
incineration costs for a new plant (Model Plant 5) in Table 4-8 include
approximately $280,000 (1981 dollars) additional costs for the plant
boiler, which might have to be oversized or otherwise modified.
Boiler incineration costs do not include costs for steam tracing of
ducts from dryers to boiler. Steam tracing might be necessary in
plants drying pine (e.g., Southern plants) to prevent a fire hazard
from the buildup of pitch inside ducts.
Table 4-9 shows the estimated capital costs for wet scrubbing
control of direct-fired dryers. Two scrubbing units probably would be
required for a system the size of Model Plants 5 and 6. Partial
incineration in a furnace or blend box presently is part of all
4-13
-------
TABLE 4-8. CAPITAL COSTS OF CONTROL OPTIONS FOR MODEL PLANTS
WITH STEAM-HEATED DRYERS
Model
plant
number
1
3
5
2,3,5
Number
of devices
control led
Veneer
1 dryer
1 dryer
3 dryers
Plywood
1 sander
Control option
dryers
Wet scrubbing
Boiler incineration
Wet scrubbing
Boiler incineration
Wet scrubbing
Boiler incineration
sanders
Fabric filtration
Installed
cost
($l,000's)a
210
156
235
192
480
614
125
a
Mid-1981 costs. Include costs of ducts, miscellaneous equipment, and
boiler modification.
4-14
-------
TABLE 4-9. CAPITAL COSTS OF CONTROL OPTIONS FOR MODEL PLANTS WITH
DIRECT-FIRED DRYERS
Model
plant
number
2
4
6
2,4,6
Number
of devices
controlled
1 dryer
1 dryer
3 dryers
1 sander
Control option
Veneer dryers
Wet scrubbing
Wet scrubbing
Wet scrubbing
Plywood sanders
Fabric filtration
Installed
cost
($l,000's)
215
240
520
125
4-15
-------
direct-fired systems and, therefore, no costs are assigned to such an
arrangement. Installed capital costs of fabric filtration devices for
plywood sanders also are given in Tables 4-8 and 4-9. Blowout panels
are included in these costs. The need for halon deluge systems, spark
detectors, etc., is site specific, depending on insurance requirements.
Additional fire prevention systems will increase the capital cost of
the fabric filtration device, but the total cost with such systems
generally will be less than twice the cost shown.
Annual operating costs for steam-heated dryers, direct-fired
dryers, and sanders are presented in Tables 4-10 and 4-11, respectively.
Electricity costs are based on a charge of $0.04/kWh. Labor costs are
based upon a Bureau of Labor Statistics (Department of Labor) estimate
of $10.30/h as the average hourly rate for plywood mill workers.8
Overhead is based on a 60-percent rate of maintenance and labor costs.
Maintenance costs are estimated according to type of control device.
Tables 4-12 and 4-13 provide annualized costs and an estimated
cost-effectiveness of pollutant removal. Dryer and sander control
costs are included. The assumed particulate/condensible removal
efficiency for boiler incineration (90 percent) is based on engineering
judgment of a removal efficiency that could be expected in a well-
designed and operated system; testing of actual systems has not
successfully quantified a removal efficiency. However, use of this
removal efficiency leads to a pollutant removal rate (mass basis) that
may be conservative (lower than actual) because total organic emissions
are believed to be two or more times as high as particulate/condensible
organic emissions for most wood species of interest (see Chapter 6).
An overall removal efficiency of 80 percent of particulate and
condensible organic emissions is expected from high-efficiency wet
scrubbers with mist eliminators used on steam-heated or direct-fired
dryers. Partial incineration of the dryer exhaust stream in a hot
(650° C or greater) fuel cell can be used in conjunction with a high-
efficiency wet scrubber. This type of system is not listed in Table
4-13 because neither the particulate (inorganic)/condensible emissions
split nor the removal efficiencies in the fuel cell can be estimated
reliably.
4-16
-------
TABLE 4-10. ANNUAL OPERATING COSTS OF CONTROL OPTIONS FOR MODEL PLANTS WITH STEAM-HEATED DRYERS
MnHpl
plant
number
1
3
5
1
3,5
Number of
veneer
affected
facilities
1
1
3
-
-
Control option
Veneer
Wet scrubbing
Boiler incineration
Wet scrubbing
Boiler incineration
Wet scrubbing
Boiler incineration
Plywood
Fabric filtration
Fabric filtration
Electricity
dryers
14
9
18
11
53
33
sanders
11
4
Annual operating
($l,000's)
Maintenance
and labor
35
26
35
28
70
49
25
10
costs
Overhead
21
17
21
18
42
26
15
6
Total
70
52
74
57
165
108
51
20
-------
TABLE 4-11. ANNUAL OPERATING COSTS OF CONTROL OPTIONS FOR MODEL PLANTS WITH DIRECT-FIRED DRYERS
00
Model
plant
number
2
4
6
2
4,6
Number of
veneer
dryer
affected
facilities
1
1
3
-
-
Annual operating costs
($l,000's)
Control option
Veneer
Wet scrubbing
Wet scrubbing
Wet scrubbing
Plywood
Fabric filtration
Fabric filtration
Electricity
dryers
23
30
85
sanders
11
4
Maintenance
and labor
35
35
70
25
10
Overhead
21
21
42
15
6
Total
79
86
197
51
20
-------
.-- — — " • »••"> • i»«i- wi i i^iisj i ui\ i i_nn i o n j. i ri o 1 cnrl ncnlCU UK I en O
Model
plant Affected
number facilities Control option
1 1 dryer Wet scrubbing
Boiler incineration
3 1 dryer Wet scrubbing
Boiler incineration
5 3 dryers Wet scrubbing
Boiler incineration
1 1 sander Fabric Alteration
3,5 1 sander Fabric filtration
Assumed
control
efficiency
(X)
80
90
80
90
80
90
99. 9d
99. 9d
ff Overall Total
effectiveness of Annual i zed annual i zed
pollutant removal ' capital costs Direct costs costs
(Mg/yr) (ton/yr) ($l,000's) ($l,000's) ($l,000's)
23
25
27
31
81
91
35
10
Veneer dryers
25
28
30
34
89
100
Plywood sanders
39
11
46
34
51
42
104
133
27
27
70
52
74
57
165
108
51
20
116
86
125
99
269
241
78
47
Overall cost
per unit for .
pollutant removal
($/Mg) ($/ton)
5,000
3,400
4,600
3,200
3,300
2,600
2,200
4,700
4,600
3,100
4,200
2,900
3,000
2,400
2,000
4,300
. ^ — ._ —.__ .„,.„ ^a,, ,n^Mjui tv* \jy uui_u MGtnou /.
These values are subject to considerable uncertainty for reasons discussed in the text.
administrative costs. Ten-year life is assumed at 12 percent cost of capital
Overall efficiency of cyclones and fabric filters.
-------
TABLE 4-13. ANNUALIZED COSTS OF CONTROL OPTIONS FOR PLANTS WITH DIRECT-FIRED DRYERS
Number of Assumed
Model veneer dryer control
plant affected efficiency
number facilities Control option (%)
2
4
6
' 2
ro
o
4,6
1 Wet scrubbing 80
1 Wet scrubbing 80
3 Wet scrubbing 80
Fabric filtration 99. 9d
Fabric filtration 99.9
Overall Total Overall cost
effectiveness of . Annualized . annualized per unit for
pollutant removal ' capital costs Direct costs costs pollutant removal
(Mg/yr) (ton/yr) ($l,000's) ($l,000's) ($,1000's) ($/Mg) ($/ton)
Veneer dryers
30 33
37 41
107 118
Plywood sanders
35 39
10 11
47
52
113
27
27
79
86
197
51
20
126 4,200
138 3,700
310 2,900
78 2,200
47 4,700
3,800
3,400
2,600
2,000
4,300
Condensible organic emissions as measured by ODEQ Method 7.
These values are subject to considerable uncertainty for reasons discussed in the text.
Includes 4 percent for taxes, insurance, and administrative costs. Ten-year life is assumed at 12 percent cost of capital
(capital recovery factor equals 0.177).
Overall efficiency of cyclones and fabric filters.
-------
Chapter 3 discussed a hypothetical system that would incinerate
the entire exhaust stream from a direct-fired dryer. This system is
not included in the cost tables because of uncertainty about the fate
of inorganic particulates in the system and the costs associated with
research and development and furnace or burner modification needed.
Overall costs of pollutant removal in Tables 4-12 and 4-13 also
depend on the emissions factor used in the calculations. Emissions
factors vary greatly with species, but most testing has been done on
Douglas fir plywood. NCASI staff measurements of total organic
emissions from Southern pine veneer dryers9 showed average Method 25
emissions rates of 13.7 g/m2 as Clf 9.5-mm basis (2.8 lb/1,000 ft2,
0.375-in. basis) on fresh cut veneer and 10.7 g/m2 as C1} 9.5-mm basis
(2.2 lb/1,000 ft2, 0.375-in. basis) on veneer that had been cut 24 to
48 hours before drying. These limited data indicate that Southern
pine species may emit two or more times the 5.9 g/m2, 9.5-mm basis
(1.2 lb/1,000 ft2, 0.375-in. basis) assumed in this report, mostly as
noncondensible organics. The boiler incineration costs per unit
pollutant removed in the tables may be conservative (higher than
actual) by a factor of two or more for Southern and Western pines and
may be conservative even for Douglas firs, because considerable
fugitive emissions and noncondensible stack emissions were not
accounted for in previous tests of this species.
Relative capital and operating costs of emissions control compared
to entire plant costs can be determined from information in Tables 4-14
and 4-15. Complete plywood plant capital costs are presented in
Table 4-14. Model Plants 1 through 4 are existing mills that could be
replaced today for the costs presented, for the given total production.
The complete plywood mill would be expected to have annualized direct
costs shown in Table 4-15. The capital costs for control equipment
may be up to about 23 percent of capital costs of the veneer dryer and
21 percent of costs of the plywood sander. Capital costs for veneer
dryer emission control equipment are approximately 1 to 2 percent of
those costs for complete plywood plants; capital costs of sander
emission control systems are less than 1 percent of complete plant
4-21
-------
TABLE 4-14. CAPITAL COSTS OF COMPLETE PLYWOOD PLANTS10
I
ro
ro
Model
plant
number
I
2
3
4
5
6
New or
existing
plant
E
E
E
E
N
N
Number
of new
veneer dryers
1
1
1
1
3
3
Total plant
production
(m2 x 106/yr)
7.4
7.4
13.9
13.9
17.2
17.2
Capital costs
of new model
veneer dryer(s)
($l,000's)
1,120
1,080
1,400
1,350
4,060
3,920
Capital
cost of
plywood sander
($l,000's)
600
600
600
600
600
600
Capital cost
of new
plywood plant
or replacement
cost of
existing plant
($l,000's)
17,450
17,000
31,700
30,900
41,100
39,400
N = new plant.
E = existing plant.
alncludes the cost of new dryer(s) and sander.
-------
I
ro
CJ
TABLE 4-15. ANNUALIZED DIRECT COSTS OF COMPLETE PLYWOOD PLANTS10
($l,000's)
Model
plant
number
1
2
3
4
5
6
Utilities
390
390
650
650
860
860
Labor
3,700
3,700
4,800
4,800
6,300
6,300
Overhead
2,200
2,200
2,900
2,900
3,800
3,800
Raw
materials--
logs
6,000
6,000
10,500
10,500
14,000
14,000
Other
materials
and supplies
2,200
2,200
4,000
4,000
5,00
5,000
Total
14,490
14,490
18,050
18,050
29,960
29,960
-------
costs. Total annualized costs of veneer dryer or sander emission
control are less than 1 percent of total annualized plant costs in
each case.
4.4 REFERENCES
1. Telecon. Oehling, N., Coe Manufacturing Company, with Chessin,
R. L., Research Triangle Institute. October 8, 1980. New veneer
dryers.
2. Letter from McMahon, I. J. , Coe Manufacturing Company, to Chessin,
R. L., Research Triangle Institute. October 29, 1980. Followup
to telephone conversation of October 8, 1980, with N. Oehling.
3. Telecon. Erb, C., American Plywood Association, with McCarthy,
J. M., Research Triangle Institute. March 19, 1981. New veneer
dryers.
4. Telecon. Johnson, A. T., Georgia-Pacific Corporation, with
McCarthy, J. M., Research Triangle Institute. December 23, 1980.
Plywood sanders.
5. Telecon. McMahon, I. J., Coe Manufacturing Company, with McCarthy,
J. M., Research Triangle Institute. November 20, 1980. Sizes
and production rates of new plywood plants.
6. Letter from Erb, C., American Plywood Association, to McCarthy,
J. M., Research Triangle Institute. February 2, 1982. Production
rates of plywood mills.
7. Letter and attachment from Emery, J. A., American Plywood
Association, to McCarthy, J. M., Research Triangle Institute.
December 16, 1981. Comments on draft chapters.
8. Bureau of Labor Statistics. Employment and Earnings. August
1981.
9. Letter and attachment from Blosser, R. 0., National Council of
the Paper Industry for Air and Stream Improvement, Inc., to
Farmer, J., U.S. Environmental Protection Agency. January 19,
1983. Comments on draft Control Techniques Document.
10. Letter and attachments from Hobart, J., J. E. Sirrine Company, to
McCarthy, J. M., Research Triangle Institute. July 22, 1981.
Costs of plywood mills.
4-24
-------
5. ENVIRONMENTAL IMPACT
The following subsections discuss the air, water, solid waste,
and energy impacts of various types and levels of emission control.
The bases for estimating environmental impacts are the model plant
parameters, as discussed in Chapter 4, and the control efficiencies
that are presented in Chapter 3.
5.1 AIR POLLUTION IMPACT
The impact on emissions of particulate and condensible organic
material (as defined by ODEQ Method 7) that results from various
control options is estimated. Actual emissions from veneer dryers may
be higher than those estimated in the following discussion because
fugitive emissions are not included. All dryers have fugitive
emissions, but those emissions have not been defined quantitatively.
All emission figures used in this chapter represent vented or control-
lable organic compounds.
Table 5-1 outlines the control options and provides estimates of
emission reductions for each of the six model plants. Separate results
are presented for steam-heated and direct-fired dryers because separate
control technologies are required to reduce emissions from the two
types of dryers. Steam-heated dryers are compatible with incineration
of the exhaust stream in the plant boiler. Direct-fired dryers can
recycle a portion of their exhaust stream to a furnace or blend box to
remove organic compounds from that stream. The remaining exhaust
gases can be controlled most efficiently by a wet scrubber. These
estimates may be subject to considerable error because removal
efficiencies and emission factors are not firmly established.
Secondary environmental impacts are defined as impacts that are
not normally associated with an uncontrolled facility but that result
5-1
-------
TABLE 5-1. ESTIMATED AIR POLLUTION IMPACTS OF CONTROL OPTIONS FOR MODEL PLANTS
Model plant number
Steam-heated dryers
1
3
5
Direct-fired dryers
2
4
6
Plywood sanders
1,2
3-6
Affected
facilities
1 dryer
1 dryer
3 dryers
1 dryer
1 dryer
3 dryers
1 sander
1 sander
28
35
101
37
46
134
39.3
11.0
Annual emissi
I
Baseline
(31)
(38)
(111)
Baseline
(41)
(51)
(148)
Basel ine
(43.3)
(12.1)
onsa under each control
(Mg/yr [ton/yr])
II
80% removal d
5.6 (6.2)
7.0 (7.6)
20.2 (22.2)
80% removal d
7.4 (8.2)
9.2 (10.2)
26.8 (29.6)
99.9% removal d
3.9 (4.3)
1.2 (1.3)
option
III
90% removal d
2.8 (3.1)
3.5 (3.8)
10.1 (11.1)
aFor veneer dryers—emissions are estimates of particulate and condensible organic compounds
(ODEQ 7); for sanders, emissions are estimates of particulate.
bControl Option I--for veneer dryers, no removal equipment;
--for sanders, high-efficiency cyclonic collectors.
Control Option II—for steam-heated dryer, high-efficiency wet scrubbers;
--for direct-fired dryer, high-temperature blend box with wet scrubbing.
--for sanders, high-efficiency cyclonic collectors and fabric filtration.
Control Option III—for steam-heated dryers, boiler incineration.
cModel plants consist of two types of processing units: veneer dryers and plywood sanders. Each
of these processes has separate control options.
dRemoval efficiencies have not been firmly established. The estimates may be subject to considerable
error.
-------
after addition of pollution control equipment. No measurable secondary
impact to the air is expected from any of the control options. Control
Option II for both steam-heated dryers and for direct-fired dryers
will add moisture to the air because they include wet scrubbing of the
exhaust stream. Control Option III involves incineration, which adds
carbon dioxide and carbon monoxide to the atmosphere. However, the
additional carbon dioxide and carbon monoxide do not add significantly
to the amount of these compounds that otherwise would be emitted by
the boiler. All steam-heated dryers are expected to have a correspond-
ing boiler at the plant, and from engineering calculations, dryer
exhausts and boiler air requirements generally are compatible.
5.2 WATER POLLUTION IMPACT
EPA regulations require softwood plywood plants to have zero-
discharge systems.1 Wet scrubbers separate collected pitch and water
and add water as needed to replace water lost to the atmosphere.
Collected pitch is burned in a boiler or landfilled. To operate
efficiently, wet scrubbers may treat and discharge their recirculated
water after an excess amount of pitch has accumulated in the water
supply, but this practice currently is not common in the plywood
industry. If necessary, this recirculated water may be treated in the
existing wastewater treatment system. Because of existing regula-
tions, the potential impact of the regulatory alternatives requiring
wet scrubbing is minimal. Boilers and wood-fired fuel cells used as
incinerators have no wastewater discharges that can be attributed to
their use as veneer dryer emission control devices.
5.3 SOLID WASTE
The only regulatory alternatives that result in accumulated solid
waste are those requiring wet scrubbing devices. In such devices, the
heavier organics generally are removed from recirculated water as a
wet sludge. This sludge may contain up to 13 kg/h (29 Ib/h) of organic
material at a large plywood plant such as Model Plant 5. This rela-
tively small amount of material can be destroyed by its injection into
the boiler at a steam-heated plant, although direct-fired plants may
have to dispose of the sludge in a landfill or in the plant's wastewater
5-3
-------
treatment system. Sander dust collected from plywood sanders is not
considered solid waste. This material is used as fuel in almost all
plants.
5.4 ENERGY IMPACT
Most plywood plants use nonfossil (wood) fuel as the main source
of heat energy. Over 50 percent, by weight, of a plywood plant's raw
materials (logs) are not suitable for producing veneer. A portion of
this material is used as fuel for boilers and furnaces. Therefore,
many existing plywood mills and virtually all new mills are self-
sufficient in fuel energy. Notable exceptions are existing veneer
plants that purchase peeled veneer and other plants using gas-fired
dryers.
Fuel consumption of the steam-heated model plants (dryers) is
estimated based on a steam requirement of 9,530 kg steam/1,000 m2,
9.5-mm basis (1,950 Ib steam/1,000 ft2, 0.375-in. basis). Fuel
consumption by the direct-fired model plants (dryers) is assumed to be
approximately the same as that of the steam-heated plants of correspond-
ing production rates. Annual fuel consumption estimates are: Model
Plants 1 and 2, 90 TJ or 85 x 109 Btu; Model Plants 3 and 4, 110 TJ or
100 x 109 Btu; and Model Plants 5 and 6, 320 TJ or 300 x 109 Btu.
While new plants will be built, most of this new production will
be at the expense of. existing production in other geographic areas.
National fuel energy demand for this industry will not change signifi-
cantly due to growth. National fuel energy demand essentially will
not change due to increased use of control devices since none of the
control options for dryers and sanders require additional fuel.
Plywood mills consume electrical energy from outside sources.
Table 5-2 gives estimates of electrical energy use of the six model
plants. The electrical energy impact of the control options is rela-
tively insignificant in each case. For example, a large plywood plant
producing 17.2 x 106 m2/yr, 9.5-mm basis (185 x 1Q6 ft2/yr, 0.375-in.
basis), might consume 72 TJ/yr (20 x 106 kWh/yr), while the additional
electrical energy required for the fans associated with wet scrubbing
of all three dryers would be approximately 2.6 TJ/yr (0.72 x 106 kWh/yr),
5-4
-------
TABLE 5-2. ESTIMATES OF ELECTRICAL ENERGY CONSUMPTION OF MODEL PLANTS'
en
i
on
Mode] plant number
Steam- heated dryers
1
3
5
Direct- fired dryers
2
4
6
Plywood sanders
1-6
Affected
facilities
1 dryer
1 dryer
3 dryers
1 dryer
1 dryer
3 dryers
1 sander
Energy consumption by.control
(TJ/yr)D
I
No
emission control
9
11
31
No
emission control
7
9
26
Baseline
1.0
II
80% removal
10
12
34
80% removal
8
10
29
99.9% removal
1.4
option
III
90% removal
10
12
34
Model plants consist of two types of processing units: veneer dryers and plywood sanders.
of these facilities has separate regulatory alternatives.
D0ne TJ (terajoule) equals 109 J.
Each
-------
During the next decade, a new trend toward (regeneration of electricity
at large new mills may develop. If this trend occurs, the increase in
electrical energy consumption from fossil-fuel burning, nuclear, or
hydroelectric power plants may be less than that indicated above.
5.5 REFERENCES
1. Telecon. Williams, Richard, Effluent Guidelines Division, U.S.
Environmental Protection Agency, with McCarthy, J. M., Research
Triangle Institute. May 19, 1980. Water discharge regulations.
5-6
-------
6. TEST METHODS AND TEST RESULTS
This section discusses test methods that have been used to measure
emissions from plywood veneer dryers and plywood sanders and presents
the results of selected source tests. The choice of test method is
important when emissions from veneer dryers are evaluated because of
the types of compounds emitted. As discussed in Chapter 2, veneer
dryer emissions consist of a particulate fraction (mainly wood fines
and ash), a condensible fraction (mainly compounds of 15 or more
carbon atoms), and a noncondensible fraction (mainly terpenes of 10
carbon atoms). The choice of condenser temperature in the sampling
train determines where the condensible/noncondensible split occurs
among the various organic compounds entering the train. Different
tests of emissions from the same wood species have shown widely varying
condensible to noncondensible ratios, probably for this reason.1 The
mass fractions of condensible and noncondensible emissions also differ
among wood species; e.g., some tests have shown that emissions from
Loblolly pine dryers contain more than 85 percent terpenes, while some
tests have shown that emissions from White fir dryers contain less
than 20 percent terpenes.1 This situation is further complicated by
the need for isokinetic sampling after wet scrubbers because some of
these organic compounds condense in such control devices. A combina-
tion of test methods is required to obtain separate measurements of
the noncondensible and condensible materials.
6.1 VENEER DRYER TEST METHODS
5'1'1 P.regon Department of Environmental Quality (ODEO) Method 7
ODEQ Method 7 is essentially a modified U.S. Environmental Protec-
tion Agency (EPA) Method 5.2 The sampling train is shown in Figure 6-1.
6-1
-------
FILTER
[ 3LJ IMPINGER
FILTER THERMOMETER
u c=> ,—^CHECK VAL
NOZZLE
PITO
TUBE
Figure 6-1. Oregon Department of Environmental Quality Method 7 sampling train.2
6-2
-------
The major modification to the Method 5 sampling train is the addition
of an unheated backup filter between the third and fourth impingers .
whose purpose is to collect organic aerosols not collected within the
impingers. An optional modification is the exclusion of the filter
normally located in the heated chamber preceding the impingers.
However, when the filter is used, the glass cyclone also is included,
the purpose of the combination being to eliminate wood fiber or ash
particulate matter.
Sampling is performed in accordance with EPA Method 5 procedures.
The sample is recovered from the impingers when sample-exposed surfaces
and the filter support frit(s) are rinsed with acetone, although a
water rinse is sometimes used also. Each filter is removed and placed
in individual petri dishes. A chloroform-ethyl ether procedure iden-
tical to that originally proposed for Method 5 is used to extract the
condensible organics from the impinger water samples.3 The extract
and the glassware acetone rinses are evaporated separately at 21° C
(70° F) or less, desiccated for 24 hours, and weighed. Following
organic extraction, the impinger water is evaporated at 104° C (220° F),
desiccated for 24 hours, and weighed. The backup filter and fourth
impinger1s silica gel also are weighed. The amount of condensible
organics is determined when residuals are totaled. Emission concentra-
tions are determined according to EPA Method 5 calculation procedures.
The greatest potential problem with ODEQ Method 7 is sample loss,
which is most likely to occur during sample transfer, extraction, and
extraction solvent evaporation. Even the high-molecular-weight organics
have a finite vapor pressure at normal room temperatures, so some loss
may occur. Some of the monoterpenes are collected within the impingers
and on the filter at typical sampling train temperatures. However,
they are lost during evaporation procedures.
6.1.2 Washington State University (WSU) Method
The WSU Method was developed in the early 1970's (sampling began
in July 1970) under joint sponsorship of the Plywood Research Foundation
and EPA. Figure 6-2 depicts the sampling train. The sample probe is
an unheated glass tube with a fritted glass filter fitted in the
6-3
-------
DIAGRAM OF
CONDENSER
STACK
EMISSION
PROBE
CONDENSER
IN DEWAR
GLASS -
FRIT
CTl
VENEER
DRYER
STACK
VACUUM
GAUGE
OUTLET
SMALL PORTION
OF STACK GASES
DELIVERED TO THA
FOR VOLATILE
HYDROCARBON
ANALYSIS
VACUUM
PUMP
DEWAR
W/ICE WATER BATH
CLAMPED TO EDGE
OF STACK
STOPPER
INLET
SAMPLE COLLECTION
RESERVOIR
MOST SAMPLED
STACK GAS
EXHAUSTED HERE
TOTAL HYDROCARBON
ANALYZER
"AFTER CONDENSER"
GAS CHROMATOGRAPIC
SAMPLES TAKEN HERE
Figure 6-2. Washington State University (1972) sampling train.4
-------
upstream end to preclude wood fibers entering the sample stream. It
is connected to a spiral condenser maintained at 21° to 27° C (70° to
80° F) in an ice bath. The condenser design provides lengthy contact
between the sample stream and the cold surfaces and has a large
reservoir to collect the condensed organics and water vapor. The
exhaust stream temperature from the condenser is approximately 21° C
(70° F). Eventually, a filter was located at the condenser exit to
collect any escaping aerosols. A vacuum pump, rotameter, vacuum
gauge, and total hydrocarbon analyzer (THA) complete the sampling
train. The THA is used to measure the volatile (noncondensible)
organic fraction.
Sampling is performed anisokinetically at a single point within
the stack. Following sampling, collected organics are transferred
from the condenser into sample bottles and acetone is used as a rinse
agent. The probe also is rinsed with acetone and the rinse combined
with that from the condenser. In the laboratory, a Rinco evaporating
apparatus is used to evaporate the water and acetone from the condensed
organic fraction. The apparatus' rotating flask is maintained at 40°
±5° C (104° ± 9° F) in a water bath heated by an electrical hotplate.
The pressure within the flask is held at 91 to 95 kPa (27 to 28 in.
Hg) vacuum until the water and acetone have evaporated, leaving a
pitchy, resinous, varnish-like residue. Total residue weight is
determined after a 3-hour stabilization period. This weight is used
in conjunction with rotameter readings, sample times, and stack volu-
metric flow data to determine condensible organic emissions.
The THA measurements of total organic concentration data in
terms of equivalent parts per million, volume basis hexane are recorded
during the test. A time-weighted average concentration is determined
and the volatile emission rate calculated with stack flow parameters.
Comparative analytical tests of the WSU Method and an ODEQ test
method (an experimental procedure that formed the basis for ODEQ
Method 7) indicated a loss of condensible material during the Rinco
apparatus evaporation procedure of the former. The evaporating
temperature-40° ± 5° C (104° ± 9° F)-coupled with the low pressure-91
6-5
-------
to 95 kPa (27 to 28 in. Hg)--vacuum apparently causes volatilization
of some of the heavier organics and any of the lighter monoterpenes in
the condensate. Volatilization of the monoterpenes would be expected
based on vapor pressure curves for these compounds.2 These vapor
pressure data tend to indicate that, at normal stack temperatures of
163° C (325° F) and higher, the monoterpenes will exist in a vapor
state. However, at condenser (or impinger) temperatures, the vapor
pressures of the monoterpenes are reduced significantly. Therefore, a
significant fraction should be condensed and collected. Heating the
samples increases the vapor pressure, which causes the accompanying
loss of volatilized fraction. The loss by evaporation is intensified
by the apparatus' low absolute pressure. The driving force for
attaining equilibrium cannot be achieved. A similar situation exists
with ODEQ Method 7, but the loss should not be as great because
evaporation is performed at ambient temperature and pressure. Following
initial stack testing according to the WSU Method, correction factors
were developed (based on limited data) to account for loss of condensed
material. The location of the THA also may have been a source of
error in the WSU testing in the early 1970's. Adsorption losses may
have occurred between the condenser and the analyzer.2
6.1.3 EPA Method 25
EPA Method 25--Determination of Total Gaseous Nonmethane Organic
Emissions as Carbon: Manual Sampling and Analysis Procedure—is
essentially an extension of the Los Angeles Air Pollution Control
District (LAAPCD) Total Combustion (or Carbon) Analysis technique
developed to determine compliance with the District's Rule 66 organic-
solvent regulation.
A sample is withdrawn anisokinetically from the emission gas
stream through a chilled condensate zone by means of an evacuated
gas-sampling tank.5 Figure 6-3 shows an EPA Method 25 sampling train
modified for sampling veneer dryer emissions. The water-ice bath
condenser, not a standard component of the Method 25 train, was added
by EPA to prevent ice crystals from blocking the dry ice condenser.
Analytical results obtained from independent analyses of the condensate
6-6
-------
cr>
SWAGELOK
CONNECTORS
VACUUM
GAUGE
FLOW
RATE
CONTROLLER
ON/OFF FLOW
VALVE
QUICK r~|
CONNECT "I'
COHOENSATE TRAP
Figure 6-3. Modified EPA Method 25 sampling train.'
EVACUATED
SAMPLE
TANK
-------
traps and evacuated tank fractions are combined to determine total
gaseous nonmethane organics. After sampling, the organic contents of
the condensate trap are catalytically oxidized to carbon dioxide
(C02), which is collected quantitatively in an intermediate tank. An
aliquot is then taken, reduced to methane, and measured by a flame
ionization detector (FID). A portion of the sample collected in the
evacuated sample tank is injected into a gas chromatographic column to
separate the nonmethane organics from the inherent carbon dioxide,
carbon monoxide, and methane. The nonmethane fraction after elution
is oxidized catalytically to C02) reduced to methane, and measured by
FID. Figure 6-4 is a simplified schematic of the analysis procedure.
6.1.4 Combination EPA Method 5X and EPA Method 25
During two source tests, EPA has used a sampling train consisting
of EPA Method 5X (modified EPA Method 5) and one or more EPA Method 25
trains.6 7 Figure 6-5 is a schematic of this sampling system. The
Method 25 trains sample a slip stream from behind the initial Method 5X
filter. Thus, both Method 5X and Method 25 samples are taken isokinet-
ically. EPA Method 5X is similar to EPA Method 5 and ODEQ Method 7,
the major exception being that the probe and front filter are maintained
at 177° ± 14° C (350° ± 25° F). This temperature is approximately the
average veneer dryer exhaust temperature; the filter at this temperature
excludes from the Method 25 samples only organic matter that condenses
at or above 177° C (350° F). Standard Method 25 and ODEQ 7 analytical
procedures are used on the samples collected.
This sampling and analysis system provides estimates of both
particulate plus condensible organic emissions (Method 5X) and total
organic emissions (Method 25). These results are not comparable
because Method 25 measurements include the noncondensible material
while Method 5X does not. Method 5X has the same potential problem
with loss of sample during analysis discussed for ODEQ Method 7.
6.2 PLYWOOD SANDER TEST METHOD
EPA Method 5 is the test method applicable to sanders. Few
sanderdust control systems have been tested to show removal efficiency.
6-8
-------
CARRIER GAS
CALIBRATION STANDARDS
SAMPLE TANK
INTERMEDIATE
COLLECTION
VESSEL
(CONDITIONED TRAP SAMPLE)
BACXFLUSH
NON-METHANE
ORGANICS
HYDROGEN
COMBUSTION
A/a
Figure 6-4. Simplified schematic of nonmethane organic analyzer (Method 25).5
6-9
-------
cr>
i
SLIPSTREAM TO 4
METHOD 25 TRAINS
i
2
3
4
5
6
7
8
9
10
11
12
13
14
Ib
16
17
NOZZLE
PROBE
FILTER HOLDER
I IE AT LI) FILTER BOX
IMP INKER ICE BAIII
UMBILICAL CORD
VACUUM GAUGE
MAIN VALVE TO PUMP
PUMP
BYPASS VALVE
DRY GAS METER
ORIFICE AND MANOMETER
PI TOT TUBE AND MANOMETER
THERMOCOUPLE READOUT
FLEXIBLE 1EFION SAMPLE LINE
BACK-UP FILTER HOLDER
THERMOCOUPLES
Figure 6-5. Modified EPA Method 5X/25 sampling train.7
-------
Participate loads from sanders often are calculated from the plywood
feed rate and the depth of cut due to sanding. Emission rates after
control devices can then be measured with EPA Method 5.
6.3 RESULTS OF EMISSION TESTING
6.3.1 Veneer Dryers
6.3.1.1 Uncontrolled Emissions. Table 6-1 presents the results
of tests of uncontrolled veneer dryers drying Douglas fir. The data
represent particulate and condensible organic emissions as measured by
ODEQ Method 7 or EPA Method 5X. The wide variation in emissions even
for the same wood species illustrates the difficulty in defining
emissions factors for plywood veneer dryers. Some of this variation
is probably due to differences in the extent of unmeasured, fugitive
emissions among the dryers tested. The average emission rate for the
seven tests of steam-heated dryers is 5.9 g/m2, 9.5-mm basis (1.2
lb/1,000 ft2, 0.375-in. basis). The average emission rate for the
seven tests of gas-fired dryers is 5.4 g/m2, 9.5-mm basis (1.1 lb/
1,000 ft2, 0.375-in. basis); these tests also show wide variation in
emission factors.
The average emission rate of particulate and condensible matter
for six tests of wood-fired veneer dryers in Table 6-1 is 5.13 g/m2,
9.5-mm basis (1.05 lb/1,000 ft2, 0.375-in. basis). Operating condi-
tions for these systems are not known, and this average may not be
typical of the industry. The American Plywood Association estimates
that a more reasonable average emission factor is 7.8 g/m2, 9.5-mm
basis (1.6 lb/1,000 ft2, 0.375-in. basis).10
EPA measured uncontrolled organic emissions by using EPA Method 25
at two mills drying predominantly Douglas fir. The sampling train was
as illustrated in Figure 6-5. Results of these tests are discussed in
Subsection 6.3.1.2. Uncontrolled emissions for these two tests aver-
aged 4.3 and 5.4 g/m2 as Ci, 9.5-mm basis (0.87 and 1.1 lb/1,000 ft2
as GI, 0.375-in. basis).
WSU conducted extensive testing of uncontrolled veneer dryers in
the early 1970's.4 Problems in the WSU test method were discovered
near the end of the testing program. Correction factors were
6-11
-------
TABLE 6-1. EMISSION TESTS OF UNCONTROLLED VENEER DRYERS DRYING DOUGLAS FIRS6 7 8 9
CT>
Particulate condensible organic emissions
No. Heat Exhaust flow rate
of dryers source (stdmVs) (stdftVmin)
1
1
1
1
1
4
3
1
1
1
1
1
1
1
1
1
1
-
~
a9.5-mm
Steam
Steam
Steam
Steam
Steam
Steam
Steam
Natural
gas
Natural
gas
Natural
gas
Natural
gas
Natural
gas
Natural
gas
Natural
gas
Wood
Wood
Wood
Wood
Wood
(0.375-in.)
6.28
3.35
2.41
3.35
8.12
5.80
11.5
7.08
9.01
7.32
9.47
2.12
4.06
3.63
14.4
15.8
2.45
5.10
4.32
basis.
13,300
7,100
5,100
7,100
17,200
12,300
24,300
15,000
19,100
15,500
20,060
4,500
8,600
7,700
30,400
33,500
5,200
10,800
9,150
Stack
temperature
149
94
176
182
190
154
-
158
160
160
152
183
176
179
129
121
163
-
-
Concentration
Veneer production (g/stdm3 (gr/stdft3
(1,000 m2/h) (1,000 ft2/h) dry) dry)
0.39
0.31
0.34
0.22
0.19
3.22
2.63
0.59
0.67
0.59
0.67
0.66
0.53
0.94
1.58
1.38
0.56
1.30
1.18
4.2
3.4
3.7
2.7
2.1
34.7
28.3
6.4
7.2
6.4
7.2
7.1
5.7
10.1
17.0
14.9
6.0
14.0
12.7
0.105
0.04
0.39
0.07
0.11
0.375
0.368
0.06
0.07
0.23
0.15
0.39
0.27
0.09
0.17
0.05
0.38
0.522
0.247
0.046
0.02
0.17
0.03
0.05
0.164
0.161
0.026
0.029
0.101
0.068
0.173
0.12
0.039
0.075
0.024
0.167
0.228
0.108
Rate3
(g/m2) (lb/1,000 ft2)
6.11
1.27
9.88
3.28
13.89
2.57
5.82
2.54
3.18
10.27
7.82
4.35
7.33
1.61
5.48
2.25
6.11
7.38
3.3
1.25
0.26
2.02
0.67
2.84
0.525
1.19
0.52
0.65
2.1
1.6
0.89
1.5
0.33
1.12
0.46
1.25
1.51
0.67
-------
established for certain wood species based on limited comparisons to
ODEQ test results (tests performed with a preliminary version of Method 7).
While wide variations were observed among dryers tested, average
participate and condensible organic emission rates for Douglas fir and
Ponderosa pine are estimated at 4 and 10 g/m2, 9.5-mm basis (0.9 and
2.1 lb/1,000 ft2, 0.375-in. basis). Noncondensible organic emissions
from these two species, as measured by THA, are estimated at 0.3 and
1.5 g/m2, 9.5-mm basis (0.07 and 0.3 lb/1,000 ft2, 0.375-in. basis);
noncondensible organic emissions from Southern pine (species unknown)
are estimated from the early WSU data at 1.5 g/m2, 9.5-mm basis (0.3
lb/ft2, 0.375-in. basis). As previously discussed, these data may be
in error because of sample loss in the train.
In 1981, a WSU team again sampled a series of uncontrolled veneer
dryers using a similar collection technique for condensible emissions,
but analysis was by gas chromatography/mass spectroscopy. Stainless
steel collection cannisters and analysis by gas chromatography were
used for the condensible fraction. Table 6-2 summarizes data on the
split between terpene emissions and other uncontrolled stack emissions
collected during this study. The noncondensible organic fraction
exceeds the condensible fraction for most stacks in Table 6-2, in
contrast to results obtained during the earlier WSU studies. Noncon-
densible organic emissions from Douglas fir and Loblolly pine, for
example, compose more than 80 percent of total emissions from these
woods in Table 6-2. Veneer production rates are not available for the
1981 WSU study, so emission factors cannot be calculated from these
data. Results suggest that earlier total emission rate estimates by
other methods may be low.
The National Council of the Paper Industry for Air and Stream
Improvement, Inc. (NCASI) recently has conducted EPA Method 25
emissions tests on a number of uncontrolled veneer dryers. Results
will be published in a technical bulletin, which is presently in draft
form. Table 6-3 summarizes the preliminary test results. Emissions
factors reported are 1-hour average values when the dryer was operating
at full capacity on the species specified and are not adjusted for the
6-13
-------
TABLE 6-2. DISTRIBUTION BETWEEN TERRENE EMISSIONS AND
OTHER EMISSIONS1
Wood
Douglas fir
White fir
White fir
Larch
Larch
Loblolly pine
Loblol ly pine
Short leaf
pine
Short leaf
pine
Slash pine
Stacks sampled
1 of 5 (middle)
1 of 6 (middle)
(2 of 4, 1 of 2
green end and 1
of 2 dry end)
2 of 5 (green and
dry)
1 of 6 (middle)
3 of 3
2 of 5 (middle and
dry)
2 of 3 (green and
dry)
2 of 3 (green and
dry)
3 of 3
Minimum9
terpenes
(%)
82
16
41C
93
48
86C
93C
56C
62C
42C
Maximum Total emissions
nonterpene measured '
(%) (kg/h) (Ib/h)
13
82
59d
7
52
14d
17d
44d
38d
58d
0.710
0.090
0.037
6.94
1.46
5.63
1.98
2.72
1.27
2.38
1.56
0.199
0.082
15.3
3.21
12.4
4.37
6.00
2.80
5.25
Calculated from summation in Ib/h of only stacks sampled for each dryer.
These are total dryer emissions only if all dryer stacks were sampled.
"Not including alpha-pinene observed in the condensate or filtrate samples.
Including alpha-pinene observed in the condensate and filtrate samples.
6-14
-------
TABLE 6-3.
o>
I
Heat source Species
— —
stea|n Douglas fir sap
Douglas fir heart
Douglas fir mixed
Douglas fir &
hemlock
Lodgepole pine
Loblolly & short-
leaf pine
Douglas fir redry
Wood-residue
direct-fired
Douglas fir sap
Douglas fir heart
Douglas & white fir
Hemlock & white fir
:j~^ * " - ~^;============^^
Mill
A
A
E
E
D
D
F
F
F
E
A
G
G
A
M
M
L
J
J
Exhaust
Exhaust rate
temperature dstdm3/
(°C) 1,000 m2
182
177
154
154
151
157
154
157
160
161
157
178
163
163
158
159
172
163
163
152
157
157
157
157
21,900
11,000
16,900
17,400
7,400
7,700
7,800
13,800
16,300
17,500
14,700
16,800
16,900
16,400
3,700
4,800
9,700
42,400
25,300
20,800
31,400
31,400
31,400
27,300
dstdft3/
1,000 ft2
71,700
36,000
55,500
57,200
24,200
25,100
25,700
45,200
53,500
57,500
48,200
55,000
55,400
53,800
12,200
15,600
31,800
139,000
83,000
68,400
103,000
103,000
103,000
89,500
Organic emissions
(
g/m2
10.3
5.4
5.9
5.4
4.9
5.9
5.9
4.9
7.8
8.3
4.4
9.8
16.6
18.6
13.2
15.1
0.1
19.0
11.7
4.4
2.0
3.4
4.4
5.4
tas Ln4 )
lb/1,000 ft2
2.1
1 i
1 2
1.1
1.0
1 2
1 2
1.0
1 6
1.7
0.9
2.0
3 4
3 8
2 7
3.1
0.03
3.9
2.4
0.9
0 4
0 7
0 9
1.1
-------
percent redry. Normally about 10 to 20 percent of the veneer must be
redried. Emissions factors for redry are very low compared to green
veneer. Daily average emissions factors should be adjusted to compen-
sate for the amount of redry or would be calculated based on daily net
production.11
6.3.1.2 Emission Tests of Control Devices. QDEQ Method 7 is the
only test method that has been used extensively on exhaust streams
from veneer dryer emission control devices. Tables 6-4 and 6-5 present
emission data for several types of wet scrubbers, which are described
in more detail in Chapter 2. Removal efficiencies of up to 90 percent
of particulate and condensible organic emissions (as measured by ODEQ
Method 7) have been reported for certain high-efficiency wet scrubbers
that incorporate mist eliminators into equipment design.
Results of an EPA source test of four steam-heated veneer dryers
controlled by a wet scrubber were inconclusive. The system tested was
a spray tower/cyclone scrubber without a mist eliminator. Removal
efficiency for particulate and condensible organic emissions (as
measured by EPA Method 5X) varied from 6 to 29 percent in three runs,
averaging only 16 percent. The removal efficiency for total organic
emissions (as measured by EPA Method 25) ranged from less than zero to
14 percent in three runs, averaging less than zero. While it is
possible for organic material to be stripped from scrubber water by
exhaust gases, it is not likely to have occurred consistently through-
out the week of testing. Some of the error is attributed to the
difficulty in applying Method 25 to wet, partially condensed exhaust
streams such as scrubber outlets. Analytical results from three
laboratories that split Method 25 samples on this source test showed
wide variation, although all three showed negative removal efficiencies
across the scrubber.
Attempts to test boiler incineration systems also have been
inconclusive. Results of EPA sampling of such a system treating
emissions from three steam-heated veneer dryers are given in Tables
6-6 through 6-8. These data indicate but do not confirm the proba-
bility that removal efficiency of condensible organic compounds was
6-16
-------
TABLE 6-4. EMISSION DATA FOR WET SCRUBBERS ON VENEER DRYERS12 13 14
I
I—'
•-J
Particulate and
condenslble organic emissions'1
System
Five-stage Burley
Scrubber without
mist eliminator
Georgia-Pacific
Emission Elimi-
nator without
mist eliminator
Georgia-Pacific
Emission Elimi-
nator with
mist eliminator
Leckenby Scrubber
Buchholz Scrubber
__™
Test
or run
number
1
2
3
4
1
2
3
4
5
6
1
2
3
4
6
1
1
2
3
4
Exhaust
(stdm'/s)
l.X
1.35C
6.18CC
6.14C
4.18
7.93
10 0
7.50
7.79
5.00
5.24
7.74
1 42
2.50C
2.42C
1.58C
1.39°
flow rate
(stdftVmin)
2,580C
2,980C
2,750C
2,860C
13,100°
13.000C
8,650
16,800
21,400
15.900
16,500
10,600
11,100
8,050
16,400
3,000
5,300C
5,130C
3,340C
2,940C
Number (1
and type .
of dryers
1/2 (D.ST)
1/2 (0,S1)
1/2 (G,S1)
1/2 (G,S7>
4 (ST)
4 (ST)
1 (GA)
1 (GA)
4 (ST)
4 (ST)
2 (GA)
2 (GA)
1 (GA)
1 (6A)
1 (GA)
2 (GA)
<1 (G,ST)
<1 (G,ST)
<1 (O.ST)
<1 (O.ST)
2/3 (G and D)
2/3 (G and D)
1/3 (G)
1/3 (G)
Veneer production
,000 mVh, (1,000 ftVh
9.5-mm 0.375-tn
basis) basis)
1 92
1 06
1.21
1.83
2.08
2.38
1.10
1 99
0.99
1.27
-
-
-
-
"
1.28
1.05
1.05
1.05
20.7
11.4
13.0
19.7
22.4
25 6
11.8
21.4
10.7
13.7
-
-
-
-
-
13.8
11.3
11.3
11.3
Temperature
Inlet
175
176
167
168
155
153
169
153
160
134
128
159
155
113
137
-
-
-
-
64 (G)
139 (01
69 (G)
134 (0)
128 (G)
126 (G)
Outlet
65
61
68
67
79
77
67
70
59
62
62
58
62
52
58
_
-
-
-
60
58
60
63
Inlet
concentration
g/stdm3, (gr/stdft3,
dry) dry)
0.757
0 627
0.565
0.492
0.268
0.236
0.223
0 390
0 245
0 250
0.180
0.130
0.313
0.538
O.OB5
0 526
0 160
0 183
0.124
0.310
0 104
0.096
0 202
0 329
0.331
0.274
0.247
0 215
0 117
0 103
0.0975
0.17
0 107
0 11
0.079
0 059
0.137
0.235
0.037
0.23
0 070
0.080
0.054
0.137
0.0454
0 042
0.0881
0.144
Outlet
concentration Removal
(g/stdm1, (gr/stdft1, efficiency
dry) dry) (%)
0 350
0.373
0 295
0 341
0.110
0.124
0.108
0.160
0.114
0 130
0 026
0.015
0.083
0.181
0 046
0.032
0.126
0.126
0 078
0.158
0 072
0.058
0.089
0 198
0 153
0 163
0 129
0 149
0.048
0 054
0 047
0 07
0.050
0.057
0.0112
0 0067
0.0361
0.079
0 014
0.02
0.055
0.055
0 034
0 069
0.0315
0 0252
0. 0390
0.0864
54
40
48
31
59
48
52
59
53
48
86
89
74
66
62
91
21
31
37
50
31
40
56
40
0 = dry end.
G = green end.
ST = steam-heated dryer(s).
GA = natural-gas-fired dryer(s)
aAs measured by ODEQ Method 7.
In some cases, only the emissions from certain stacks passed through the control device
Dry basis Other flow rate values are on a wet basis
-------
CO
TABLE 6-5. EMISSION DATA FOR SANDAIR FILTER SYSTMES ON VENEER DRYERS8 12 15
Particulate and
condensible organic emissions1'
lest
or
run
num-
ber
1
?
3 .
4d
5
6
7
ft
9
Exhaust
(stdm3/s)
2.49
7.31
7.88
(11-0)
(11-0)
(11.0)
(11.0)
(11.0)
(11.0)
flow rate
(stdftVmin)
5,270C
15,500C
16,700C
(23,400)
(23,400)
(23,400)
(23,400)
(23,400)
(23,400)
.. . Temperature3 ,,
Number (° C)
of dryers Inlet
2 (GA) 132
3 (ST) 137
3 (ST) 143
3 (ST) (163)
3 (ST) (163)
3 (ST) (163)
3 (ST) (163)
3 (ST) (163)
3 (ST) (163)
Outlet
65
53
53
(65)
(65)
(65)
(65)
(65)
(65)
Veneer production Inlet
,000 m2/h, (1,000 ft2/h, concentration
9.5-mm 0.375-in. (g/stdm3, (gr/stdft3.
basis)
3.66
2.38
1.92
2.64
2.34
1.84
1.99
basis)
39.4
25.6
20.7
28.4
25.2
19.8
21.4
dry)
0.220
0.378
0.378
0.39
0.40
0.41
0.37
0.40
0.21
dry)
0.096
0.165
0.165
0.17
0.17
0.18
0.16
0.17
0.092
Outlet
concentration
(g/stdm3, (gr/stdft3,
dry)
0.025
0.183
0.172
0.08
0.11
0.07
0.08
0.06
0.07
dry)
0.011
0.0802
0.0753
0.035
0.048
0.031
0.035
0.026
0.031
Removal
(%)
88
51
54
79
72
83
78
85
67
GA = natural-gas-fired dryer(s).
ST - steam-heated dryer(s).
aValues in parentheses are estimated.
bAs measured by ODEQ Method 7.
cDry basis. Other flow rate values are on a wet basis.
dTests 4 through 9 were run on the same unit. In tests 4 through 6, the filter depth was 50 percent greater than the
design depth.
-------
TABLE 6-6a. RESULTS OF EPA TESTS OF A BOILER INCINERATION SYSTEM--
PARTICULATE AND CONDENSIBLE ORGANIC EMISSIONS7
(Metric Units)
— ~ ~
Kun number
Date
Emission point
Sample volume (dry stdrn3)0
Stack gas flow rate
(dry stdm3/min)
Stack temperature (° C)
Stack gas moisture (% by
volume)
Isokinesis (X)
Wet fan AP (mm H20)
Average opacity (X)
Production rate (1,000 m2/h)d
CTl
tl. Particulate/condensible emissions
g/dry stdm3
kg/ 1,000 m2
NA - not applicable.
1
9/21/81
Dryers Boiler^
1.41
677
157
15.1
112
NA
NA
2.
0.341
13.9
4.73
1.10
1,120 ~
217
17.4
104
18.5
16
94
0.238
16.1
5.48
3
9/23/81
Dryers Boiler 2
1-31 1.04
728 1,090
160 216
11.7 19.2
99.6 101
NA 12.7
NA 8
2.68
0.391 0.245
17.1 16.1
6.38 6.01
4a
9/24/81
Dryers Boiler 2
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
0.86
957
159
15.2
95.5
14.0
9
NA
0.291
16.7
NA
5a
9/24/81
Dryers Boiler ?
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
0.92
918
170
21.2
106
23.9
10
NA
0.343
18.9
NA
6
9/25/81
1.18
660
159
11.2
99.7
NA
NA
0.357
14.1
6.24
1.08
1,130
218
18.3
101
14.0
9
2.26
0.188
12.7
5.62
Average
1.30
688
159
12.7
104
NA
NA
2
0.363
15.0
5.78
1.07
1,120
217
18.3
102
15 0
10
63
0.224
14 9
5 69
Boiler background emission test.
^Average does not include boiler background emission tests.
Standard conditions are 760 am Hg at 20° C.
On 9.5-M basis, includes trim factor; does not account for redry material.
-------
TABLE 6-6b. RESULTS OF EPA TESTS OF A BOILER INCINERATION SYSTEM—
PARTICULATE AND CONDENSIBLE ORGANIC EMISSIONS7
(English Units)
Run number
Date
Emission point
Sample volume (dry stdfta)c
Stack gas flow rate 23
(dry/stdfta)c
Stack temperature (° F)
Stack gas moisture (X by
volume)
Isokinesis (%)
Wet tan AP (in. II20)
^ Average opacity (X)
0 Production rate (I. 000 ft*/h)d
Particulate/condensible emissions
g/dry stdft3
Ib/h
lb/1,000 ft2*1
1
9/21 /ft 1
Dryers
48.5
,900
315
15.1
112
NA
NA
31.
0.153
31.4
0.99
Boiler 2 Dry*
38.
39,700
422
17.
104
0.
16
7
0
35
1
9 46.
25,700
320
4 11.
99.
73 NA
NA
104 0.
4 3/.
.12 1
3
9/23/81
^? Boiler 2 1
1 36.6
38.500
421
7 19.2
6 101
0.50
8
28.8
175 0.107
8 35.4
31 1.23
4a
9/24/81
Dryers Boiler 2
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
30.5
33,600
317
15.2
95.5
0.55
9
NA
0.127
36.9
NA
5a
9/24/81
6
9/25/81
Dryers Boiler 2 Dryers
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
32.
32.400
338
21.
106
0.
10
NA
0.
41.
NA
6 41.8
23.300
322
2 11.2
99.7
94 NA
NA
24
150 0. 156
9 31.1
1.28
Averaqe
Boiler 2 Dryers Boi ler i
38.
40.000
424
18.
101
0.
9
.3
0.
28.
1.
0 45.
24,300
319
3 12.
104
55 NA
NA
082 0.
1 33.
16 1.
9 37.8
39,400
422
7 18.3
102
0.59
10
28.3
161 0.098
4 33.0
19 1.17
NA = not applicable.
a8oiler background emission test.
Average does not include boiler background emission tests.
Standard conditions are 29.92 in. Hg at 68° F.
dOn 3/B-in. basis, includes tri« factor; does not account for redry material.
-------
en
ro
TABLE 6-7a. RESULTS OF EPA TESTS OF A BOILER INCINERATION SYSTEM—TOTAL
ORGANIC EMISSIONS (METHOD 25) AT VENEER DRYER EXHAUST7
(Metric Units)
Run number
Date
Stack gas flow rate
(dry stdm3/min)a
Stack temperature (° C)
Stack gas moisture (% by
volume)
Production rate (1,000 roz/h)b
Analysis laboratory
Total organic emissions0
ppm (Ct)
g/dry stdm3 (C,)
kg/h (Ct)
kg/1,000 m2 (C5)
136
9/21/81 9/23/81 9/25/81 Average
677 728 660 688
157 160 159 12.7
15.1 11.7 11.2 12.7
2.94 2.68 2.26 2.63
TRC NCASI TRC NCASI TRC NCASI TRC NCASI
1,577 543 734 729 647 726 986 666
0.788 0.270 0.367 0.364 0.323 0.362 0.493 0.332
32.0 . 11.0 16.0 16.3 12.8 14.3 20.3 . 13.9
(12.6)° (13.8)°
10.9 . 3.74 5.97 6.08 5.66 6.33 7.51 . 5.38
(4.29)a (5.25)d
TRC = TRC Environmental Consultants, Inc.
NCASI = National Council for Air and Stream Improvement.
aStandard conditions are 29.92 in. Hg at 68° F.
On 3/8-in. basis, includes trim factor; does not account for redry material.
Emissions calculated and reported as Ct. Does not include front half results from Method 5X sample.
One data point from Test Run 1 not considerea representative. Parenthetical values are approximations based on
other test runs.
-------
I
no
TABLE 6-7b. RESULTS OF EPA TESTS OF A BOILER INCINERATION SYSTEM—TOTAL ORGANIC
EMISSIONS (METHOD 25) AT VENEER DRYER EXHAUST7
(English Units)
Run number 1 3 o
Sa?e 9/21/81 9/23/81 9/25/81
Stack gas flow rate 23,900 25,700 23,300
(dry stctavVrain)
Stack temperature (° F) 315 320 322
Stack gas moisture (% by 15.1 11.7 11.2
volume)
Production rate (1,000 m2/h)b 31.7 28.8 24.3
Analysis laboratory TRC NCASI TRC NCASI TRC NCASI
Total organic emissions
ppm (C,) 1,577 543 734 729 647 726
gr/dry stdft3 (Ct) 0.344 0.118 0.160 0.159 0.141 0.158
lb/h (d) 70.5 . 24.3 35.3 36.0 28.2 31.6
(27.7)d
lb/1,000 ft2 (d) 2.22 . 0.765 1.22 1.22 1.16 1.30
(0.87)°
Average
24,300
319
12.
28.
TRC
986
0.215
44.8 .
(30.4)d
1.58 H
(1.08)°
7
3
NCASI
666
0.145
30.3
1.10
TRC = TRC Environmental Consultants, Inc.
NCASI = National Council for Air and Stream Improvement.
aStandard conditions are 29.92 in. Hg at 68° F.
bOn 3/8-in. basis, includes trim factor; does not account for redry material.
Emissions calculated and reported as C,. Does not include front half results from Method 5X sample.
dOne data point from Test Run 1 not considered representative. Parenthetical values are approximations based on
other test runs.
-------
TABLE 6-8a. RESULTS OF EPA TESTS OF A BOILER INCINERATION SYSTEM--
TOTAL ORGANIC EMISSIONS (METHOD 25) AT BOILER EXHAUST7
(Metric Units)
fTl
ro
CO
Run number 1 3
Date 9/21/81 9/23/81
Stack gas flow rate 1,120 1,090
(dry stdm3/min)a
Stack temperature (° C) 217 216
Stack gas moisture (% by 17.4 19.2
volume
Production rate (1,000 m2/h)e 2.94 2.66
Analysis laboratory TRC NCASI TRC NCAS1
Total organic emissions
ppm (C,) 741 23.3 1,175 146
g/dry stdm3 (C,) 0.371 0.011 0.586 0.073
kg/h (C,) 25.0 0.785 38.4 4.77
kg/1,000 ra2 (C,) 8.50 0.267 14.3 1.78
4a
9/24/81
957
159
15.2
NA
TRC NCASI
744 173
0.371 0.087
21 3 4.95
NA9 NA9
5a
9/24/81
918
170
21.2
NA
TRC NCASI
1,425 120
0.712 0.060
39.2 3.28
NA9 NA9
6 Average
9/25/81 (1, 3, 6)
1,130 1,120
218 217
18.3 18.3
2.26 2.63
TRC NCASI TRC NCASI
755 71.1 890 80.1
0.378 0.034 0 445 0 039
25.7 2.41 29 / 2.66
11.4 1 07 11.4 1.04
Average*"
(4, 5)
938
165
18.2
NA
TRC NCASI
1,085 14/
0.541 0 0/4
30.3 4.12
NA9 NA9
NA = not applicable.
aBoiler background emission test.
Average does not include boiler background emission test.
cAverage of boiler background emission tests.
dStandard conditions are 29.92 in. at 68° F.
On 3/8-in. basis, includes trim factor; does not account for redry material
Results not corrected for C02 interference. See Section 5.3.2.5 (Adjustments will be made to the data in the final report).
9Boiler load increased near the end of Run 4 and maintained at increased load during Run 5
-------
TARIF 6-8b RESULTS OF EPA TESTS OF A BOILER INCINERATION SYSTEM-TOTAL ORGANIC EMISSIONS
lABLb b BD. (METHOD 25) AT BOILER EXHAUST7
(English Units)
CT>
1
ro
_ .,.._,=. -.i_-._-_ .-._^-.^=--,--=^^— =---=-
Date 9/21/81
Stack gas flow.rate 39,700
(dry stdft3)0
Stack temperature (° F) 422
Stack gas moisture (% by 17.4
volume
Production rate (1,000 ft2/h)e 31.7
Analysis laboratory TRC NCASI
Total organic emissions
ppm (C,) 741 23.3 1,
g/dry stdfLJ (C,) 0.162 0 005
Ib/h (C,) 55. 0 1.73
lb/1,000 ft2 (C,} 1 74 0.055
_..,- -^ ------- - =- ^- =--= __., -
9/23/81 9/24/81 9/24/81
38,500 33,800 32,400
421 317 338
19.2 15.2 21.2
28.8 NA NA
TRC NCASI TRC NCASI TRC NCASI
175 146 744 173 1,425 120
0.256 0.032 0.162 0.038 0.311 0026
84.6 10.5 47.0 10.9 86.3 7.23
2.94 0.365 NA9 NA9 NA9 NA9
6 Average
9/25/81 (1, 3, 6)
40,000 39,400
424 422
18.3 18.3
24.3 28 3
TRC NCASI TRC NCASI
755 71 1 890 80.1
O.l6b 0.015 0 194 0.017
56.5 5.31 65.6 5.85
2.32 0.219 2 32 0.213
Average0
(4, 5)
33,100
328
18.2
NA
IRC NCASI
1,085 147
0.236 0 032
67.2 9 08
NA9 NAIJ
NA = not applicable.
IRC = TRC Environmental Consultants, Inc.
NCASI = National Council for Air and Stream Improvement.
aBoiler background emission test.
bAverage does not include boiler background emission test.
GAvcrage of boiler background emission tests.
dStandard conditions are 29.92 in. at 68° f.
eOn 3/8-in. basis, includes trim factor; does not account for redry material
Results not corrected for C02 interference See Subsection 5.3 2.5 (Adjustments will be made to the data in the final report.)
9Boiler load increased near the end of Run 4 and maintained at increased load during Run 5.
-------
greater than 70 percent. However, Method 25 analytical results showed
such variation between laboratories that calculation of removal effi-
ciencies is not valid. The cause of the sampling and/or analytical
problems of this test is not known. ODEQ has attempted to test boiler
incineration systems at three plants using a THA, but a volatile
organic compound (VOC) removal efficiency (60 percent) could only be
calculated for one plant.16
Emission reductions reportedly can be achieved by drying veneer
for longer times at lower temperatures than normally used. Table 6-9
gives the results of emission tests on dryers where internal tempera-
ture (and thus stack temperatures) were lowered.
6-3-2 State Regulations Applicable to Plywood Plants
Oregon is the only State that has emission regulations that apply
specifically to the plywood industry. Table 6-10 summarizes these
regulations. The State's reference test method (Oregon Department of
Environmental Quality Method 7) measures organic aerosols as particu-
late.
The State of Washington and some local agencies in Washington use
general regulations which are applicable to all industry to limit
emissions from plywood plants. Visible emissions are limited to an
opacity of 20 percent, and paniculate matter is limited to a concen-
tration of 0.23 g/dry stdm3 (0.1 gr/dry stdft3).
Other locations limit emissions from this industry only with an
opacity standard that is applicable to all industry, typically 20 to
40 percent.
6'3'2-1 ^neer Dryer Control Evaluation These emissions consist
of condensible and noncondensible organics and a small amount of
filterable particulates. Although some losses occur during analysis,
ODEQ 7 appears to be the most reasonable procedure for measuring
condensible organics and filterable particulates. The procedure could
be satisfactory to evaluate the performance of wet scrubbers and wet.
electrostatic precipitators (ionizing wet scrubbers).
6-3.3 Plywood Sanders
Few data exist that show removal efficiencies of plywood sander-
dust emission control systems. Only exit streams sometimes are tested,
6-25
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cr>
I
en
TABLE 6-9 TESTS SHOWING EMISSION REDUCTIONS ACHIEVED BY LOWERING
DRYER TEMPERATURES4
Test
" a
number
1
2
3
4
5
6
Dryer type
Steam, longitudinal flow
Steam, longitudinal flow
Gas, jet- impingement
Gas, jet- impingement
Gas, longitudinal flow
Gas, longitudinal flow
Damper
setting
Open
Closed
Open
Closed
Open
Closed
Reduction in par-
Average ticulate and organic
Stack temperatures temperature emissions per
( C) v,«r(ii^+ir.nD nm't nf n if nrli ir t i nn
Green end
145
128
156
122
167
137
184
151
156
130
164
140
i \_ vj v* w w i i t |—
Dry end (° C) (%)
156
146 14 25
179
138 38 74
182
149 32 11
180
152 30 -91 (increase)
172
143 28 18
195
153 33 34
^Douglas fir heartwood was dried in each test.
Based on the reported stack temperatures.
cAs measured by a WSU method consisting of a participate train followed by a flame ionization detector.
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TABLE 6-10. SUMMARY OF STATE OF OREGON REGULATIONS
_ ___ FOR PLYWOOD MANUFACTURING
Veneer dryers
Opacity: 10 percent design opacity
10 percent average operating opacity
20 percent maximum opacity
Participate limitations for wood-fired dryers:
If fuel has mo1sture
basis) "1n- ^ wei'9ht ^ <20 percent
7, • Jf fuel has moisture
basis) .375-in. by weight of >20 percent
(c) In addition to (a) and (b) above, 0.4 g/kg of steam generated
Other emission sources (excluding veneer dryers and boilers)
Participate limitations:
35-in. ba,,s)
6-27
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TABLE 6-11. EMISSIONS FROM PLYWOOD SANDERS WITH PRODUCT RECOVERY CYCLONES16 1?
CT)
ro
CD
Test
or run
number
1
2
3
4
5
6e
Exhaust
(stdnrVs)
11.6
10.5
9.16
10.3
19.7
15. 7f
Production refers
bln1et 1
flow rate
(stdftVmin)
24,600
22,200
19,400
21,900
41,800
33,200f
Sanded production3 Depth
(1,000 m2/h)
2.90
2.90
-
0.45
-
-
to the surface area of one
loadings were calculated
based on prod
(1,000 ft2/h) (mm)
31.2 0.64
31.2 0.64
-
4.8
-
-
side of the panels
of cut
(in.)
0.025
0.025
-
-
-
-
Particulate
concentration
exiting
the cyclone
(g/stdm3)
0.14
0.18
0.37
0.087
0.357
0.044
(gr/stdft3)
0.061
0.078
0.16
0.038
0.156
0.019
Removal b
efficiency
(%)
>99
>99
-
>94
94
99.5
Mean
outlet particle
size (urn)
Size
-
6.4C
6.2C
49. Od
7-°d
19. Od
Range
-
4-12
3-15
-
-
-
-
that reach the sander.
uction data, depth-of-cut
data, or changes in panel
weight during
sanding.
Measured on a count basis.
Measured on a weight basis.
eAverage of three tests on a bank of four cyclones.
Dry basis. Other flow rate values are on a wet basis.
-------
and fabric filter systems often are assumed to be in compliance without
testing. Table 6-11 summarizes test data for plywood sanderdust cyclones
for which inlet parti cul ate loading can be estimated. These data
indicate that high-efficiency cyclones can achieve 99 percent removal
of plywood sanderdust. Actual removal rates vary according to type of
wood sanded, presence or absence of sawdust (sawdust is sometimes
ducted to the same cyclone as sanderdust), particulate loading rates,
and equipment design.
6.4 REFERENCES
1. Cronn, D. R. , M. J. Campbell, L. Bamesberger, and S. Truitt
Study of the Physical and Chemical Properties of Atmospheric
Aerosols Attributable to Plywood Veneer Dryer Emissions
Washington State University. Pullman, WA. Final Report to
American Plywood Association. June 1981.
2. Brackbill, E. A. Review of Candidate Sampling and Analysis
Procedures for the Determination of Plywood Veneer Dryer Organic
r?1SS^f; IRC En^>onmental Consultants, Inc. Wethersfield,
CT. EPA Contract 68-02-2820. May 21, 1981.
3. Federal Register. 36 FR 159. August 17, 1971.
4. Monroe F. L ,_W. L. Bamesberger, and D. F. Adams. An Investiga-
tion of Operating Parameters and Emission Rates of Plywood Veneer
WaShington State University. Pullman, WA.
5. Federal Register. 44 FR 194. October 3, 1980.
?' W" oi A B:/wkbi11' J- H- Powe11' E' A" Pearson> and
jr el P^ood/Veneer Emission Test Report, Georgia-Pacific
Conn cnt! ^ngfield, O^gon, June 1981/ TRC Environmental
Consultants, Inc. East Hartford, CT. EPA Emission Measurement
Branch Report 81-PLY-4, Contract No. 68-02-3543. December 1981.
p V J" H' Powe11' E- A- Pe^on, and
P1ywood/Veneer Emission Test Report, Champion
can f ?°^ 2reg°n' SePtember 1981- TRC Environmental
Consultants, Inc. East Hartford, CT. EPA Emission Measurement
Branch Report 81-PLY-2, Contract No. 68-02-3543. May 1982
8' MerteLand1atMaChmentS from Wellman. E- A., BWR Associates, to
McCarthy, J. M. , Research Triangle Institute. December 22 1980
Veneer dryer emission data. '
6-29
-------
9. Grimes, Gary. Direct-Fired Drying—the Hybrid Unit. Control in
the Forest Products Industry. SWF Plywood Company. Medford, OR.
(Presented at the Pollution Control Seminar for the Northwest
Forest Industries. Portland. April 5, 1978.) 13 p.
10. Letter and attachments from Emery, J. A. , American Plywood Asso-
ciation, to McCarthy, J. M., Research Triangle Institute.
December 16, 1981. Comments on draft chapters of plywood report.
11. Letter and attachment from Blosser, R. 0. , National Council of
the Paper Industry for Air and Stream Improvement, Inc. , to
Barry, J. C., U.S. Environmental Protection Agency. March 8,
1983. Draft study of Organic Compound Emissions from Veneer
Dryers and Means for their Control.
12. Oregon Department of Environmental Quality, Air Quality Control
Division. Veneer Dryer Control Device Evaluation, Supplemental
Report. December 14, 1976.
13. Tretter, V. J., Jr. Plywood Veneer Dryer Emission Control Systems.
Georgia-Pacific Corporation. Atlanta, GA. (Presented at the
Annual Meeting of the Air Pollution Control Association. Portland.
June 27-July 1, 1976.) 17 p.
14. Mick, Allan. Current Particulate Emissions Control Technology
for Particleboard and Veneer Dryers. Mid-Willamette Valley Air
Pollution Authority. Salem, OR. (Presented at the Annual Meeting
of the Pacific Northwest International Section of the Air Pollution
Control Association. Seattle. November 28-30, 1973.)
15. Letter and attachments from Hirsch, J., Rader Companies, Inc., to
McCarthy, J. M., Research Triangle Institute. February 24, 1981.
Response to request for information on sand filters.
16. Bosserman, P. B. Controls for Veneer and Wood Particle Dryers.
Oregon Department of Environmental Quality. Portland, OR.
(Presented at the Annual Meeting of the Pacific Northwest Inter-
national Section of the Air Pollution Control Association.
Spokane. November 3, 1981.)
17. Letter and attachments from Tice, G. W., Georgia-Pacific Corpora-
tion, to McCarthy, J. M., Research Triangle Institute. March 9,
1981. Sanderdust emission control data.
18. Letter and attachments from Willhite, P. T., Del Green Associates,
to McCarthy, J. M., Research Triangle Institute. March 18, 1981.
Sanderdust emission control data.
19. Memorandum from McCarthy, J. M., Research Triangle Institute, to
Vincent, E. J., EPA. August 13, 1981. Minutes of meeting with
American Plywood Association.
6-30
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TECHNICAL REPORT DATA
(rtease read Instructions on the reverse before completing}
T£ — - .
1 REPORT NO.
I EPA-450/3-83-012
|4. TITLE AND SUBTITLE
Control Techniques for Organic Emissions from
Plywood Veneer Dryers
7. AUTHOR(S)
9. PERFORMING ORGANIZATION NAME AND ADDRESS ~ ~~
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Emission Standards and Engineering Division (MD-13)
Research Triangle Park, North Carolina 27711
12. SPONSORING AGENCY NAME AND ADDRESS ~~
15. SUPPLEMENTARY NOTES
This document summarizes information gathered by the U.S. Environmental
Protection Agency (EPA) on the control of emissions from softwood plywood
manufacturing. It is intended to inform Regional, State, and local air
pollution control agencies about technology for abatement of these emissions.
Information is given on environmental impacts and costs of control.
KEY WORDS AND DOCUMENT ANALYSIS
b. IDENTIFIERS/OPEN ENDED TERMS
Air Pollution Control
Air Pollution
Plywood
Pollution Control
Volatile Organic Compounds (VOC)
13. DISTRIBUTION STATEMENT
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
0. SECURITY CLASS (Thispage)
nciassified
3. RECIPIENT'S ACCESSION-NO
5. REPORT DATE
May 1983
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO
10. PROGRAM ELEMENT NO.
11 CONTRACT/GRANT NO.
68-02-3056
3. TYPE OF REPORT AND PERIOD COVERED
4. SPONSORING AGENCY CODE
EPA/200/04
c. COS AT I Field/Group
EPA Form 2220-1 (9-73)
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