Acurex Pr-,ect 7510
NEW SOURCE PERFORMANCE
STANDARDS AND NATIONAL EMISSION
STANDARDS FOR HAZARDOUS
AIR POLLUTANTS
Plywood-Veneer Manufacturing Source
Category Survey
Kirk Willard, Larry Waterland, Craig Fong
Acurex Corporation
Energy & Environmental Division
Route 1, Box 423
Morrisville, North Carolina 27560
February 1980
Prepared for
EPA Project Officer — Thomas M. Eibb
EPA Lead Engineer — Greg Gasperecz
Environmental Protection Agency
Research Triangle Park
North Carolina 27/11
Contract 68-02-3064
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oSif
Acurex Project 7510
NEW SOURCE PERFORMANCE STANDARDS AND NATIONAL EMISSION STANDARDS
FOR HAZARDOUS AIR POLLUTANTS
Plywood-Veneer Manufacturing Source
Category Survey
Kirk Willard, Larry Waterland, Craig Fong
Acurex Corporation
Energy and Environmental Division
Route 1, Box 423
Morrisville, North Carolina 27560
February 1980
Prepared for
EPA Project Officer ~ Thomas M. Bibb
EPA Lead Engineer ~ Greg Gasperecz
Environmental Protection Agency
Research Triangle Park
North Carolina 27711
Contract 68-02-3064
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TABLE OF CONTENTS
Section Page
1 SUMMARY 1-1
1.1 Product Use 1-1
1.2 Industry Location 1-2
1.3 Production 1-2
1.4 Industry Growth . 1-3
1.5 Industrial Processes 1-3
1.6 Industry Emissions 1-3
1.7 Emission Controls 1-5
1.8 State Regulations 1-5
1.9 Sampling Methods 1-6
1.10 Surmiary 1-6
2 INTRODUCTION 2-1
3 CONCLUSIONS AND RECOMMENDATIONS 3-1
3.1 Conclusions 3-1
3.2 Recommendations 3-4
3.2.1 Standards Recommended 3-4
3.2.2 Activities Not Requiring Standards 3-6
4 DESCRIPTION OF INDUSTRY 4-1
4.1 Source Category 4-1
4.1.1 Industry Description 4-1
4.1.2 Production and End Use 4-2
4.2 Industry Production 4-7
4.2.1 Past and Current Production 4-7
4.2.2 Projected Production and New Sources 4-7
4.3 Veneer and Plywood Manufacturing Processes .... 4-14
4.3.1 Green Process 4-17
4.3.2 Veneer Drying 4-21
4.3.3 Gluing and Pressing 4-30
4.3.4 Sizing and Finishing 4-34
5 AIR EMISSIONS DEVELOPED FROM THE PLYWOOD INDUSTRY ... 5-1
5.1 Plywood Plant and Process Emissions 5-1
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TABLE OF CONTENTS (Continued)
Section Page
5.1.1 Air Emissions Developed From Veneer Drying
Operations 5-2
5.1.2 Air Emissions Developed From Gluing and
Pressing Operations 5-7
5.1.3 Air Emissions Developed From Plywood Sanding
and Trimming Operations 5-7
5.1.4 Summary of Emission Factors for the
Plywood Industry 5-10
5.2 Total National Emissions From the Plywood
Industry 5-14
5.2.1 Total National Emissions From Veneer Dryers . . 5-14
5.2.2 Total National Emissions From Sanding and
Trimming Operations 5-15
5.2.3 National Emissions From Other Plywood
Industry Processes 5-17
5.2.4 National Emissions Projected for 1985 With
and Without NSPS 5-18
6 EMISSION CONTROL SYSTEMS 6-1
6.1 Current Control Technology 6-2
6.1.1 Veneer Dryer Emission Control 6-2
6.1.2 Particulate Control of Fine Wood Residue .... 6-14
6.2 Alternative Control Techniques 6-19
6.2.1 Low Temperature Drying 6-19
6.2.2 Wet Electrostatic Precipitators 6-20
6.3 Candidate "Best Systems" of Emission
Reduction 6-21
6.3.1 Veneer Dryer Emission Control 6-21
6.3.2 Sanders, Saws, and Pneumatic Dry
Fine Solids Conveying 6-22
7 EMISSIONS DATA FOR THE PLYWOOD MANUFACTURING
INDUSTRY 7-1
7.1 Available Test Data for the Plywood
Manufacturing Industry 7-1
7.1.1 Emission Test Data From Veneer Dryers 7-2
7.1.2 Emissions Data from Gluing and Pressing
Operations 7-15
7.1.3 Emissions Test Data From Sanding and
Trimming Operations 7-16
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TABLE OF CONTENTS (Concluded)
Section Page
7.1.4 Available Test Data Summary 7-23
7.2 Sample Collection and Analysis 7-23
7.2.1 EPA Reference Methods 7-23
7.2.2 Organic Aerosol Emission Sampling and
Analysis Methods 7-26
7.2.3 Volatile Organic Emissions Sampling and
Analysis Methods 7-31
7.2.4 Summary 7-32
8 STATE AND LOCAL EMISSION REGULATIONS 8-1
8.1 Regulatory Framework 8-1
8.2 State of Oregon Regulations for Veneer and
Plywood Manufacturing 8-2
8.3 Particulate Matter Regulations
from Other States 8-3
8.4 Hydrocarbon Emissions 8-6
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LIST OF ILLUSTRATIONS
Figure Page
4-1 Annual Plywood Production 4-8
4-2 Process Flow Diagram for Veneer and Plywood
Production 4-16
4-3 Gas-fired Longitudinal Dryer 4-24
4-4 Four Control Zone Jet Dryer 4-25
4-5 Steam- and Gas-heated Jet Dryer 4-25
6-1 Open Spray Tower 6-6
6-2 Packed-bed Scrubber 6-7
6-3 Venturi Scrubber 6-8
6-4 Cyclone Separator 6-16
6-5 Typical Pulse Jet Fabric Filter Configuration 6-18
6-6 Sander Particulate Control System 6-24
7-1 Washington State University Sampling Train 7-27
7-2 Oregon DEQ Organic Aerosol Sampling Train 7-30
7-3 Proposed EPA Reference Method 25 Sampling Train . . . . 7-32
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LIST OF TABLES
Table Page
3-1 Emission Estimates for 1985 for Plywood-Veneer
Industry With and Without NSPS 3-3
4-1 Softwood Plywood and Veneer 4-4
4-2 Hardwood Plywood and Veneer 4-5
4-3 New Source Softwood Production 4-12
5-1 Surmiary of Emissions Test Results for Veneer Dryers
Compared to AP-42 Guidelines and the Oregon
State Implementation Plan 5-6
5-2 Suirmary of Particulate Emissions Test Results for
Air Conveying Systems Compared to AP-42 Guidelines and
the Oregon State Implementation Plan 5-11
5-3 Emission Factors from Various Plywood
Manufacturing Processes 5-12
5-4 Total National Emissions Levels 5-16
6-1 Veneer Dryer Emission Control Costs 6-3
7-1 Test Data From Veneer Drying Operations 7-3
7-2 Test Data From Veneer Drying Operations 7-7
7-3 Test Data From Veneer Drying Operations 7-8
7-4 Emission Data Summary From Various Control Devices
Used on Veneer Dryer Operations 7-10
7-5 Emission Data From Various Control Devices Used on
Veneer Dryer Operations 7-12
7-6 Emissions Data for Hogged Fuel Boiler
Incineration as a Control Device 7-14
7-7 Characterization of Extractable Composition of
Douglas Fir 7-14
7-8 Composite Field Data for Cyclones Tested by the
Tennessee Division of Air Pollution Control 7-17
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LIST OF TABLES (Concluded)
Table Page
7-9 Field Test Data for the Performance of Cyclones
from the Canadian Provincial Pollution Control
Board 7-19
7-10 Test Data Summary, National Emissions Data System
for the State of Georgia 7-20
7-11 Performance of Baghouses as Reported by the
Canadian Provincial Pollution Control Board 7-24
7-12 EPA Reference Methods Applicable to the Plywood
Manufacturing Industry 7-25
3-1 State of Oregon Regulations for Veneer and Plywood
Manufacturing for Particulate Matter and Organic
Aerosol 8-2
8-2 State and Local New Source Particulate Regulations
Applying to the Plywood and Veneer Industries 8-4
8-3 State and New Source Hydrocarbon Regulations
Applying to the Plywood and Veneer Industry 8-7
v i i i
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SECTION 1
SUMMARY
Plywood is composed of layers of wood veneer bonded together with
glue. The grain direction of successive layers is set at right angles to
give strength to the product in two directions. The veneer which makes up
the ply is thin wood sheet, peeled or sliced from a log. According to its
face layer composition, plywood is classified as either softwood or
hardwood. Softwood plywood consists of veneers, including the face ply,
of wood from coniferous or needle-bearing (i.e., softwood) trees; whereas
hardwood plywood has a face ply of wood from deciduous or broad-leaf
(i.e., hardwood) trees.
1.1 PRODUCT USE
Softwood plywood is extensively used for roof decks, exterior
undersiding, and rough flooring in single- and multiple-family housing
construction. It is also used in the commercial and industrial sectors
for all-weather wood foundations, heavy tongue and grooved commercial
plywood floor systems, and light industrial roofs. Miscellaneous other
uses include other structural applications and furniture.
Uses for hardwood plywood include exterior siding, interior wall
panels, kitchen and bathroom cabinets, laminated block flooring, and flush
doors. Much wood furniture, both household and office, is manufactured of
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hardwood plywood. Miscellaneous other uses include such applications as
boats, skate boards, shoe heels, and tool handles.
1.2 INDUSTRY LOCATION
Nationally, there were approximately 182 softwood plywood plants in
operation during 1977 and 1978. The hardwood plywood industry had
approximately 165 plants in operation during the same period. The
majority of softwood plywood plants are located on the Pacific Coast:
Oregon, Washington, and California, with the second largest concentration
in the Southeastern United States. The hardwood plywood industry consists
primarily of numerous small plants located in states east of the
Mississippi River with smaller concentrations in the Pacific Coast states
already mentioned and the Southwest: Arkansas, Texas, and Louisiana.
1.3 PRODUCTION
2
In 1978, softwood plywood production totaled 1.81 billion m ,
9.5-nrn thickness plywood production basis (19.5 billion ft , 3/8-inch
basis). This continued consecutive yearly increases since 1974 and was up
3 percent from 1977. The estimated value of shipments for softwood
plywood for 1977 was $3.55 billion.
2 ?
In comparison, 0.137 billion m , 9.5-mri basis (1.48 billion ft ,
3/8-inch basis), of hardwood plywood was produced in 1977. The total
value of shipments, including interplant transfers, amounted to
$468 million for 1977.
Softwood plywood production has increased gradually over the past
decade, but not at the 11 percent per annum rate established from 1945 to
1968. Hardwood plywood production has remained essentially constant over
the past 10 years.
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1.4 INDUSTRY GROWTH
Based on several reliable sources, the softwood plywood industry is
expected to grow at 2.7 percent per year over the next few years.
Projections for hardwood plywood production are for essentially no growth
through 1985 and minimal growth (-1 percent per year) over the period 1985
to 2000.
1.5 INDUSTRIAL PROCESSES
For both softwood and hardwood plywood, three different types of
plants exist: veneer plants, plywood layup plants, and combination
plants. In veneer plants, the raw material is logs or wood slabs and the
final product is dried or green (undried) veneer. The product veneer may
be shipped to a plywood layup plant to make plywood. Combination plants
have both veneer production and plywood layup operations on a single site.
Unit operations in veneer plants include log conditioning, debarking,
veneer cutting and clipping, and veneer drying if dried veneer is the
final product. Plywood layup plants' unit operations include veneer
drying if green veneer is received, veneer inspection and repair, plywood
layup and gluing, pressing, and trimming and finishing. Combination
plants have all the above unit operations.
1.6 INDUSTRY EMISSIONS
Some emissions occur during all steps of veneer and plywood
processing. These emissions are either insignificant for new sources or
unmeasured in all processes except for veneer drying and plywood sawing
and sanding. Nonfossil fuel boilers (NFFB) were eliminated from the scope
of this study since a separate new source performance standard (NSPS) is
being developed for them. Fugitive gaseous compounds comprised mostly of
monoterpenes are dissipated from greenwood continuously from the felling
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of trees through veneer manufacture and drying. Approximately 85 percent
of the live trees terpenes are volatilized in the woods, in transit,
during storage or handling before veneer drying.
Veneer drying is done primarily in combination plants or softwood
plywood layup plants. Occasionally, veneer plants have dryers,
particularly if the veneer is hardwood. Typical uncontrolled emission
factors for gaseous organic compounds and aerosol (condensible) organic
2
compounds from a veneer dryer are 0.75 g/m , 9.5-mm thick plywood
(1.53 lbs/10,000 ft2, 3/8-inch basis) and 4.54 g/m2, 9.5-mm basis
(9.28 lbs/10,000 ft2, 3/8-inch basis), respectively. Nationwide current
annual emissions of gaseous organics from veneer dryers total 1950 metric
tonnes (2150 short tons), while aerosol organic compounds annual emissions
total 7390 metric tonnes (8130 short tons). Waste incineration and
fugitive emissions add 182 metric tonnes (200 short tons) of gaseous
organics and 455 metric tonnes (500 short tons) of aerosol organics.
Dry trim sawdust and sanding dust are produced and transported only
in plywood layup plants and combination plants. Approximately 680,000
metric tonnes (750,000 tons) of fine, dry wood dust is produced and
handled each year. Typical uncontrolled emission factors from sawing and
sanding operations are 3.2 g/m2, 9.5-mm basis (6.6 lbs/10,000 ft2,
3/8-inch basis). Uncontrolled emissions are defined as those downstream
of a primary collector (cyclone).
Uncontrolled emissions from conveying green material and other
non-sander residues are estimated at 0.23 g/m2, 9.5-mm basis
(0.47 lbs/1000 ft , 3/8-inch basis). Nationwide annual emissions of
particulate from all plywood and veneer processes are 6660 metric tonnes
(7330 short tons) excluding organic aerosols.
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1.7 EMISSION CONTROLS
Control technologies currently exist for sawing and sanding dust and
associated pneumatic transport and for veneer dryer gaseous and aerosol
organic compound emissions. Cyclones followed by fabric filters represent
current technology practiced in many newer plants for control of saw and
sander dust. Properly operated, removal efficiencies approaching
99 percent can be realized. Veneer dryer emissions are currently
controlled in a limited number of plants by filtration devices, wet
scrubbers, and incineration. Removal efficiencies are typically
approximately 50 percent for wet scrubbers and similar control devices for
organic aerosols only. No information was found for gaseous organic
compound removal efficiencies. Control efficiencies by incineration are
in excess of 95 percent for both gaseous and organic aerosol compounds.
The "best system" of pollution control is incineration by boiler for
steam-fired dryers. "The best system" for direct-fired dryers would be
incineration of 50 percent of the exhaust gas with treatment of the other
50 percent by wet scrubber. Incineration for veneer dryer emissions is
considered best as it reduces all of gaseous organic, organic aerosol, and
wood fiber particulates. Other systems do not effectively reduce gaseous
organics.
Combination cyclone/fabric filter units are considered "best" for
sawing and sander dust pneumatic transport systems for particulate
control. No significant secondary environmental impacts result from
either of these "best systems."
1.8 STATE REGULATIONS
Oregon is currently the only state with regulations specific to the
plywood industry. Veneer dryer visible emissions are limited to an
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average of 10 percent opacity with a maximum of 20 percent opacity while
2
total plant veneer dryer emissions are limited to 4.9 g/m , 9.5-mm basis
(1 lb/1000 ft , 3/8-inch basis). Other states base emission limits for
their plywood plants on general regulations, most of which are based on
process weight rate.
1.9 SAMPLING METHODS
Currently, the only proven method of sampling veneer dryer emissions
is the State of Oregon Department of Environmental Quality (DEQ) Method 7.
This method consists of isokinetically collecting organic aerosols on a
heated glass filter backed up by a cooled glass filter. The sampling
train is essentially an EPA Method 5 train with a filter (the cooled
filter) between the third and fourth impingers. This method does not
measure gaseous organic emissions.
Proposed EPA Method 25 is currently under consideration for
determining gaseous organic emissions as volatile organic compounds
(VOC). However, it is presently under technical and economic feasibility
evaluation. All other emissions from the plywood industry can be measured
by existing EPA Reference Methods.
1.10 SUMMARY
As a result of this study, New Source Performance Standards are
recommended for development as follows.
• Veneer drying with either direct-fired dryers (gas or wood dust)
or indirect- (steam) fired dryers
• Dry material removal and conveying
In addition, the following wee concluded:
• No emissions of the plywocd industry were considered sufficiently
hazardous to warrant NESHAP^
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• If the agency concurs with the above recommendations, a specific
EPA Method will have to be developed to define VOC emissions from
veneer dryers
• Based on existing data, direct-fired veneer dryers drying
Ponderosa pine may have to be allowed a higher emission rate than
that for other species
• Hardwood species have only been tested in conjunction with
softwood drying and will require verification of existing
emissions data
All other emissions sources in the plywood industry, except for
boilers, appear to be negligible. Nonfossil fuel boilers will be
regulated separately.
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SECTION 2
INTRODUCTION
The Clean Air Act (CAA), as amended in 1977, mandates the
Environmental Protection Agency (EPA) to protect health and welfare by
establishing National Ambient Air Quality Standards (NAAQS's) for the
specified criteria pollutants. In order to aid in attaining and
maintaining NAAQS's, EPA regulates emissions from new sources by
promulgating New Source Performance Standards (NSPS's). Section 111 of
the CAA calls for issuance of emission standards for new and modified
sources which may contribute significantly to air pollution, the emissions
from which could endanger public health or welfare. The standards must
reflect the best degree of control as satisfactorily demonstrated to EPA,
taking cost, energy, and non-air environmental impacts into account.
The Congress of the United States has mandated a list of sources and
schedule for the review of NSPS promulgation. The Office of Air Quality
Planning and Standards (OAQPS) is reviewing the industries on this list
for possible standard setting. This document, which is referred to as a
source category survey, is the first step in the process of setting an
NSPS for the plywood and veneer manufacturing industries. Its primary
purpose is to verify the need for a standard and to determine the
availability of data required to set a standard.
Plywood is an assembly of several layers of thin wood (veneer), in
alternating grain directions, which are glued together with an adhesive.
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? 2
About 2.0 billion m (21.7 billion ft ) of plywood (9.5 mm or 3/8 in.
2
basis) will be manufactured in the U.S. in 1979. Another 0.37 billion m
(4 billion ft ) of hardwood veneer will be imported. The industry is
concentrated in the Northwest and the Southern states. Most new plants
are being constructed in the South.
The industry being studied includes veneer preparation and the
manufacture of plywood from veneer. Logging operations supplying the
veneer mills are not reviewed in this document, nor are production
processes that use the waste from plywood manufacture, such as
particleboard or hardboard manufacture. The purpose of this document is
to verify the need for setting a standard and to determine the
availability of data required for the plywood industry itself. Due to
this, only processes unique to this industry are reviewed. These specific
processes are:
• Green process, including log conditioning, peeling or slicing
into veneer, and veneer sizing
• Veneer drying and preparation
• Plywood layup, including gluing and pressing
• Sizing and finishing of the plywood
• Conveying of materials, including boiler feed, green waste and
dry dust transport
The necessary information for the source category survey was gathered
through the following activities:
• Literature review and personal contact
— Industry characterization, production and growth: Major
information sources used were the two plywood trade
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associations, the American Plywood Association and the
Hardwood Plywood Manufacturers Association
-- Process description: Major information sources used were the
literature and the trade associations
— Emission data: Major information sources used were studies
done by Washington State University for trade associations
and the EPA. A literature review was also performed, and
relevant state regulatory agencies were queried.
-- Control technologies: Major information sources used were
the literature, the control device manufacturers and users,
and State and regional EPA offices
— Regulations: Major information sources used were a
compilation of relevant Federal documents, plus phone surveys
of State agencies in 10 states with heavy concentration of
the plywood industry
• Site visits: These were made to the Champion International plant
at Lebanon, Oregon, the Willamette Industries plant at Sweet
Home, Oregon, and Georgia Pacific plants at Springfield and
Eugene, Oregon, and Dudley, North Carolina. These visits
assisted in the assessment of:
— Process description
— Emission data
— Control technologies.
On the basis of the above data, an estimate of future industry growth, new
sources, national emissions, and control effectiveness has been made.
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SECTION 3
CONCLUSIONS AND RECOMMENDATIONS
3.1 CONCLUSIONS
The plywood and veneer industry is a healthy manufacturing industry
that is expected to continue growing at a 2.7 percent per year rate from
2 ?
the current 2.0 billion m , 9.5-rmn basis (21.7 billion ft , 3/8-inch
basis) annual production. All new added capacity since 1965 has been
added in the South and Southeast while the Northwest, the biggest
producing area, and other areas have retained constant production only by
2 2
replacing closed mills. Some 0.65 billion m (7.94 billion ft ) of
9.5-mm plywood is expected to be produced in 1985 by new mills built or
reconstructed after 1979. Three types of manufacturing plants are
included, veneer only, plywood lay-up only and plywood-veneer plants. For
2 7
softwood plants each type currently averages 10 million m (110 million ft )
of capacity. Hardwood plants are usually smaller by an order of magnitude.
Some emissions occur during all steps of veneer and plywood
processing. However, these emissions are either very minor or unmeasured
in all processes except for veneer drying or plywood sanding and sawing.
Boiler emissions will be covered under the Non-Fossil Fuel Boiler NSPS.
Waste incinerators (teepee burners) are rapidly being phased out and are
not expected to be built for any new plants. Veneer drying is mostly
carried out in plywood-veneer plants or softwood plywood layup plants.
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Veneer plants occasionally have dryers, more commonly if the veneer is
hardwood. Estimated emissions of 1950 metric tonnes (2150 short tons) of
gaseous organic compounds and 7390 metric tonnes (8130 short tons) of
aerosol organic compounds are emitted annually.
Sander dust and dry trim sawdust are only produced and transported in
plywood layup-only and plywood-veneer plants. Approximately 682,000
metric tonnes (750,000 tons) of dry fine wood dust is produced and handled
each year. This material is composed of larger particles than most
combustion generated particulate.
Control technologies now exist for sander and saw dust and their
pneumatic transport lines. Cyclones which remove the solids from transfer
air are backed up with fabric filters in many newer plants. The only
other emission currently controlled is veneer dryer exhaust which in some
instances is incinerated, filtered or wet scrubbed for aerosol organic
pollutant removal. Incineration is the best control technique for this
source, and essentially eliminates the organic emissions.
Available emission data are sufficient to estimate the magnitude of
emission impact. However, only a few source surveys have been completed
and reported for plants within the industry segment. Disagreements on
emission levels are comrion due to a variety of sampling and analytical
techniques that have been used for dryer emissions.
The total emission reduction potential for 1985 is shown on
Table 3-1. If both gaseous and aerosol organics are defined as VOC, then,
as the table shows, an emission reduction potential of 3660 metric tonnes
(4030 short tons) per year is estimated for organics, and 460 metric
tonnes (500 short tons) for particulate. If organic aerosol is regarded
as particulate, then the emission reduction potential for VOC is
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Table 3-1. EMISSION ESTIMATES FOR 1985 FOR PLYWOOD-VENEER INDUSTRY WITH
AND WITHOUT NSPS
Pollutant
Metric tonnes (short tons)
Current control3
Best control
Emission
reduction
potential
Gaseous organic
compounds
Aerosol organic
compounds
Particulate matter
(PM)
2810 (3090)
9080 (9990)
6320 (6960)
1920 (2110)
6310 (6940)
5860 (6460)
890 (980)
2770 (3050)
460 (500)
Gaseous plus
aerosol organic
defined as VOC
VOC
PM
11890 (13080)
6320 (6960)
8230 (9050)
5860 (6460)
3660 (4030)
460 (500)
Aerosol organic
defined as PM
VOC
PM
2810 (3090)
15400 (16950)
1920 (2110)
15400 (16950)
890 (980)
3230 (3550)
aCurrent control based on existing SIP's.
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890 metric tonnes (980 short tons) per year while particulate emission
reduction potential is 3230 metric tonnes (3550 short tons) per year.
3.2 RECOMMENDATIONS
3.2.1 Standards Recommended
New source standards are recommended for veneer drying operations at
veneer, plywood layup, and plywood-veneer plants and for sander and
sawdust pneumatic transfer lines.
The largest uncontrolled emission of this industry is the condensible
aerosol organic material emitted from wood during drying. It is
recomnended that this material be regulated along with gaseous organic
compounds. Measurement methods suggested are the Oregon DEQ Method 7 for
aerosol organic material followed by EPA Method 25 for gaseous organic
materials. Total organics would comprise the sum of these two fractions.
Effective control of process emissions might require different
standards for the two types of veneer drying, steam heated and direct
fired systems. It is recormiended that standards be developed based on the
following demonstrated techniques:
Dryers
Steam heated Exhaust ducting to boiler
Direct fired 50 percent of exhaust recirculated
to firing unit
50 percent of exhaust ducted to a
scrubber
Dry fine residue conveyance Fabric filtration
Technology now exists and is used within the industry to control emissions
in this manner.
A generalized cost of pollutant removal was developed based on a
veneer dryer incineration system completed in early 1979 at Champion
International s, Lebanon, Oregon plant. By amortizing equipment over
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20 years, an estimated removal cost of $0.73/kg (SO.33/lb) for total
organic compounds was calculated. Based on this, in 1985 the total cost
to the industry would be $2.6 million (1979 dollars) compared to total
sales estimated to be $5.7 billion (1979 dollars). Costs based on a
5-year amortization would be $1.30/kg ($0.59/lb).
In recommending to proceed with standards development for veneer
dryers, it is realized that the emission reduction potential in 1985 for
total organics (3660 metric tonnes) is relatively small in comparison to
other industrial processes. In addition, the costs to achieve this
potential emission reduction (about $1.00/kg organic removed) are
relatively high. However the recommendation to proceed also considers
that the region projected to realize the bulk of new plywood plant growth
(the South) currently does not regulate veneer dryer emissions through
State or local regulations.
The recommendation to proceed with standards development for sander
and sawdust emissions also recognizes that potential emission reductions
of particulate in 1985 (460 metric tonnes) are relatively low. Further,
many new plants currently being built will employ baghouse control of all
dry waste outlet points to preclude, or to respond to, the PSD review
process. Still, the recommendation to proceed with standards development
is based on the perceived need to insure that new plants are built to
incorporate rather straight forward and effective control of these
particulate emissions.
No other pollutants are currently considered sufficiently hazardous
to warrant NESHAPS.
A major difficulty exists for monitoring or compliance testing.
Emissions from veneer dryers can be quite variable throughout an operating
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day, however representative sampling of pollutants is not a major
problem. Rather it is that no simple, continuous, verified sampling and
analysis method for gaseous organic compounds is available. Measurement
of aerosol organics as a cooled particulate, as done by Oregon DEQ Method
7, has been extensively used. However, a separate sample and analysis
must then also be made for the gaseous organics. The proposed EPA Method
25 could be used for these emissions but does have the disadvantage of
higher cost and complicated equipment. Further EPA Method 25 will have to
be verified on veneer dryer emissions.
Data exist that suggest direct fired dryers operating on Ponderosa
pine may not be able to attain as low an organic level as other species by
normal incineration of 50 percent of the dryer recirculated exhaust with
scrubbing of the other 50 percent. If higher emissions are verified an
exception may have to be established. In addition, only softwood species
have been included in current emission factors. Hardwood species have
only been tested in conjunction with softwood drying and will require
determination of emission factors.
Table 3-1 showed estimated emissions levels for 1985 with and without
recommended NSPS. Values were determined from current emissions estimates
as discussed in Section 5.2, new source production estimates as developed
in Section 4.2, and NSPS levels based on demonstrated technology. Current
control levels reflect current SIP's.
3.2.2 Activities Not Requiring Standards
Several emission sources from the plywood and veneer industry do not
need standards developed. The emissions from all these sources, except
for boilers and waste incinerators, appear to be negligible. Emissions
3-6
-------
data are lacking, but site visits confirmed that emissions from these
sources appear to be minor amounts of gaseous organic compounds or rapidly
settling residue particles.
In veneer manufacturing it is reconmended that the green veneer
operations of log conditioning, debarking, veneer cutting, handling, and
storage not be regulated. It is recommended that for air drying
operations standards not be developed.
The plywood operations of layup and finishing need not be regulated;
although emissions are perceivable no data were available and the total
quantity of emissions appeared negligible. Plywood layup includes glue
preparation and application as well as hot and cold pressing.
Other processes in the plywood and veneer industry which do not
require standards include coarse material conveying, incinerators, and
residue disposal. No substantial emission data are available for material
conveying other than fine dry sanderdust and sawdust, which are
recommended for standards as noted above. Waste fuel fired boilers are
significant pollution sources. They will be covered, however, under the
nonfossil fuel-fired boiler New Source Performance Standard. Waste
incinerators are also significant pollution sources, but none are expected
to be included in new plants.
3-7
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SECTION 4
DESCRIPTION OF INDUSTRY
4.1 SOURCE CATEGORY
4.1.1 Industry Description
Plywood is a product composed of layers of wood veneer glued together
by means of an adhesive, which is usually a synthetic resin.* The grain
direction of successive layers is set at right angles to give strength to
2
the product in two directions. The final product is used for both
construction and decorative purposes.
Plywood is classified as either hardwood or softwood, according to
its face layer composition. Hardwood plywood is generally used for
decorative purposes and has a face ply of wood from a deciduous or broad
leaf (i.e. hardwood) tree. In most cases, softwood plywood is used for
construction or structural purposes and the veneers are of wood from
coniferous or needle bearing (i.e. softwood) trees.
Veneer is the thin wood sheet of uniform thickness comprising the
layers of a plywood sheet. Currently more than 90 percent of all veneer
is produced by peeling or rotary cutting in a veneer lathe. When a log
or "bolt" of wood is rotary cut, it is centered between two chucks on a
lathe. The bolt is then turned against a knife that extends across the
length of the lathe. A thin sheet of veneer is continuously peeled from
3
the log as it turns. Prior to the cutting of veneer, most wood species
require steaming or hot water heating; this improves the cutting
4-1
-------
properties of the wood. It is the hardness or density of the species that
determines the degree of conditioning necessary prior to the cutting of
the veneer. However, some species such as Douglas fir are generally
peeled cold from logs known as peeler blocks. The green veneer coming
from the lathe is cut, spliced, and dried to uniform moisture levels
4
before it is further processed into plywood.
A large assortment of woods are used in the manufacture of the
veneers used in the production of plywood. A high percentage of the
veneer produced in the Northwestern U.S. is manufactured from Douglas fir,
with lesser quantities of veneer made from True firs, Ponderosa pine,
Hemlock, and other species. In the Southeast U.S., Southern pine is the
3
predominant raw material.
4.1.2 Production and End Use
This section discusses the production and end-use aspects of the
plywood veneer industry. Plywood plants can be classified into three
generic types: veneer plants, plywood layup plants, and combined
plywood-veneer plants. Nationally, there were approximately 182 softwood
plywood plants of all types in operation during 1977 and 1978. A great
majority of these are plywood veneer plants which produce veneer for their
own purposes.^ Still, large amounts of dried or green (undried) veneer
are sold to plywood mills or furniture or panelling factories. The
hardwood plywood industry had approximately 165 plants in operation during
1976 and 1977. Of these, many laid up their own veneer, but traditionally
much of the hardwood veneer is sold dried to other plywood mills.
The largest concentration of softwood plywood and veneer plants is
located on the Pacific Coast, specifically Oregon, Washington, and
Northern California, while the majority of the hardwood plywood is
4-2
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produced in the Southeastern states. The hardwood plywood industry
predominantly consists of a large number of small plants distributed
widely over the Eastern U.S. Softwood plywood plants are also scattered
in the South, but the greatest number of plants is located in the
Northwestern U.S.
2
In 1978, softwood plywood production totalled 1.81 billion m ,
p
9.5-rmi basis (19.5 billion ft , 3/8-inch basis). This continued a
consecutive yearly increase in production since 1974 and was 3 percent
more than in 1977. The estimated value of softwood plywood shipments in
c 2
1977 was $3,548 million. In comparison, 0.137 billion m
2
(1.48 billion ft ) of hardwood plywood was produced in 1977. This was
2
considerably less than the highest yearly rate of 0.20 billion m
(2.20 billion ft ) in 1972 but an increase of 8 percent from that
reported for 1976. The total value of shipments, including interplant
transfers, amounted to $468 million in 1977, which is 12 percent more than
the $416 million reported for 1976.^
Tables 4-1 and 4-2 present statistical data by state for the softwood
and hardwood industries, respectively. Included are the number of
manufacturers, number of employees, volume of production, and value of
shipments. The number of plants is not shown in these tables. Table 4-2
gives volume of production for hardwood plywood by geographical region.
This was necessary because of the lack of readily available statistical
data providing production numbers by state.
A brief description of the end uses of plywood products follows for
each industry. For both hardwood and softwood, the availability of timber
for the plywood industry is a critical factor and plant operations are
dependent on basic supply and demand economics. Other problems facing the
4-3
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Table 4-1. SOFTWOOD PLYWOOD AND VENEER8
No. of
manuf acturers
No. of
employees
Volume of
production
Value of
shipments
State
Total
no.
No. with 20
or more
employees
1,000 unless
general
range given
Million m2
(million ft?),
9.5-mm basis
Million
do 11ars
Alabama
5
5
EE
85.9 (924.9)
(D)
Arkansas
7
7
1.7
82.2 (884.5)
77.9
Colorado
1
1
AA
5.8 ( 63.0)
(D)
California
15
14
2.5
47.4 (510.7)
91.4
Florida
3
3
CC
10.7 (114.8)
(0)
Georgia
4
4
1.0
69.8 (751.7)
47.4
Idaho
6
6
EE
52.0 (560.3)
(D)
Louisiana
10
10
2.2
143.0 (1539.2)
103.8
Mississippi
7
7
EE
87.1 (937.5)
(0)
Montana
4
4
CC
63.6 (684.7)
(0)
No. Carolina
11
9
1.0
43.3 (465.8)
32.0
Oklahoma
1
1
AA
7.3 ( 78.7)
(D)
Oregon
108
106
19.8
764.2 (8226.4)
971.2
So. Carolina
1
1
BB
49.5 (533.0)
CD)
Texas
4
4
EE
132.6 (1427.6)
(D)
Virginia
3
3
3B
16.8 (180.5)
(D)
Washington
33
32
FF
193.6 (2084.2)
(0)
NA = not available
(D) * withheld to avoid disclosing figures for individual companies
AA = 150 to 249 employees
8B = 250 to 499 employees
CC » 500 to 999 employees
EE = 1,000 to 2,499 employees
FF » 2,500 employees and over
4-4
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Table 4-2. HARDWOOD PLYWOOD AND VENEER8
State
No. of
manufacturers
No. of
employees
Volume of
production
Value of
shipments
Total
no.
No. with 20
or more
employees
1,000 unless
general
range given
Million m2
(million ft2),
9.5-nm basis
Mil lion
dollars
Alabama
21
13
0.9
S
15.1
Arkansas
8
5
AA
S
(0)
California
18
9
1.2
W
74.7
Florida
7
7
0.4
S
17.3
Georgia
15
11
EE
S
(0)
Illinois
4
2
AA
NC
(D)
Indiana
23
20
2.3
NC
66.7
Kentucky
7
4
0.6
S
25.1
Louisiana
8
5
AA
S
(0)
Maine
4
3
CC
NE
(D)
Michigan
7
5
0.4
NC
9.0
Mississippi
9
7
0.6
S
12.2
New York
14
6
CC
NE
(D)
No. Carolina
67
54
3.8
S
113.6
Ohio
4
1
AA
NC
(0)
Oregon
18
9
EE
W
(0)
Pennsylvania
5
4
0.4
NE
9.4
So. Carolina
24
21
2.0
S
59.3
Tennessee
10
10
0.9
S
49.5
Texas
7
2
BB
S
(0)
Vermont
4
4
CC
NE
(D)
Virginia
22
14
2.0
S
97.2
Washington
14
8
1.9
U
50.0
West Virginia
5
4
0.3
S
6.5
Wisconsin
21
17
EE
NC
(0)
NA * not available NE ¦ Northeast 12.95 (139.4)
(D) = withheld to avoid disclosing figures for NC ¦ Northcentral 29.17 (314.0)
Individual companies S * South 154.88 (1667.2)
AA * 150 to 249 employees W « West 66.03 (710.7)
88 = 250 to 499 employees
CC ® 500 to 999 employees
EE = 1,000 to 2,499 employees
FF * 2,500 employees and over
4-5
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plywood industry are the advancing costs of labor, energy, and general
operati ons.
4.1.2.1 Softwood Plywood. Softwood plywood is extensively used for
roof decks and rough flooring in the construction of single- and
g
multiple-family housing. It is also used in the commercial and
industrial sectors for all weather wood foundation, heavy tongue and
g
grooved comnercial plywood floor systems, and light industrial roofs.
Miscellaneous other uses include other structural materials and furniture.
The general high level of residential construction during the first
three quarters of 1978, coupled with a very active economy earlier in the
year, made 1978 nearly duplicate 1977. Softwood plywood producers are
promoting semi-industrial and nonresidential construction applications of
softwood plywood, with special emphasis on the end-use plywood items
mentioned in the previous paragraph.
4.1.2.2 Hardwood Plywood. Uses for hardwood plywood include
exterior siding, interior wall panels, kitchen and bathroom cabinets,
laminated block flooring, and flush doors. Much wood furniture —
household and office alike — is manufactured of hardwood plywood.
Miscellaneous other uses include plywood in boats, aircraft, recreational
vehicles, tennis rackets, skis, hockey sticks, golf club heads, table
tennis paddles, skate boards, musical instruments, shoe heels, die boards,
bed rails, tool handles, and containers.^
The hardwood plywood market remained strong in 1978 primarily due to
the active furniture manufacturers and flooring demand. A tight supply
situation for nearly all species plagued the industry in mid-year and
current demand far exceeds available supply.
4-6
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4.2 INDUSTRY PRODUCTION
This section discusses the production characteristics of this
industry and explains the base for projecting new capacity.
4.2.1 Past and Current Production
The plywood/veneer industry has shown a highly variable, but
consistently increasing, production pattern over the past 3 decades.
Certain product lines have recently expanded, while others have nearly
disappeared because of competition from substitutes or change in consumer
taste. Figure 4-1 shows the total output for softwood plywood over
20 years and for hardwood over the past 10 years.
p
U.S. production of hardwood plywood peaked in 1972 at 0.20 billion m
(2.2 billion ft^) but has flucuated near 0.16 billion (1.7 billion ft^)
per year for the past decade.** Softwood production has continued to
increase, but not at the 11 percent per year rate realized between 1945
and 1968.
International activities have a moderate impact on U.S. production.
Softwood sales overseas account for some 5 percent of U.S. production,
11 12
while hardwood imports are 2-1/2 times U.S. production. ' Only
production within the U.S. has been included in the figures in this
report. Since U.S. companies have gained agreements in the growing
international markets and potential competitors (Scandanavia and U.S.S.R.)
do not have sufficient wood or plant capacity, U.S. production should
12
expand in the future to serve the export market.
4.2.2 Projected Production and New Sources
New plywood production has been estimated based on data from six
13
sources: (1) past growth of industry segments, (2) American Plywood
Association long term forecast (1977 to 1986),^ (3) announced new
4-7
-------
o
(XI
Softwood
O APA Long Term Estimate
(about 2.5% except for
during recessing)5
X Acurex Composite Estimate
(2.7%, including the 1980
recession and response)
Hardwood
C^^^oPcOqqqqo X
1960 1970 1980 1990
Year
Figure 4-1. Annual plywood production.
-------
plants,^ (4) specific company announced growth plans,16 (5) raw
material availability trends,16 and (6) projected international
11 12
markets. '
A composite annual production increase of 2.7 percent per year was
selected for softwood. This projected increase is continuous, although
there should be a downturn in 1980 and recovery in 1981. Projections for
2
hardwood production were assumed to be a no-growth 0.16 billion m
(1.7 billion ft^) for 1985 and 0.186 billion m^ (2.0 billion ft^)
for 2000.
Several trends within the industry are readily apparent. The
Northwestern wood base will diminish between 1980 and 1995, then it should
increase.16 All future increases are expected to result from wood
produced on private land. Both timber and plywood production in the
Southeast and South have been rapidly increasing; this trend will continue
well into the 1980's. Most new plants will be large units built by forest
industry companies. Examples are the announced International Paper
Company's (IP) mills in Arkansas, Louisiana, East Texas, South Carolina,
15
and Mississippi. Production capacity at IP will increase by
p p
250 percent in 3 years up to 0.1 billion m (1.1 billion ft ) in 1981.
Expansion of plywood production will not keep pace with veneer
production, since demand for cost-effective products that combine veneer
with particleboard, hardwood, or other materials has increased rapidly in
recent years. Inexpensive imported veneer will help balance U.S.
production of the two products.
The number of new plants that an industry will build in the near
future can be estimated by adding the number needed for increased product
demand to the number of replacements needed for deteriorating plants in
4-9
-------
operation. If existing plants are replaced at definite intervals and are
all similar in size, the estimation is quite simple. For many industry
segments the size of individual plants has been gradually increasing for
economic reasons (management, permits, and planning expenses all being
more site related than production dependent) and because the life of
larger plants is longer. These factors also hold true for the plywood-
veneer industry, however, this industry exhibits one significant
difference. The plywood veneer industry has traditionally used short-term
market conditions and production costs as the principal factor in deciding
to build new plants or close existing ones. As a net effect, rapid plant
turnovers have a major impact on estimated numbers of new plants. Most
plants close periodically and frequently they are completely rebuilt
because of fire, change of wood supply, product line, or owner. Thus, a
new mill is difficult to identify unless it is a totally new facility at a
new site. Production at single sites may continue for many decades (such
as at the currently operating plant in McCleary, Washington, built in
1912) or be terminated after only a few months. For illustration, the
following example is given. In 1966 the softwood plywood industry
produced 5 percent more plywood than in the previous year, continuing a
23 year trend of increased production, averaging 10 percent per year. But
the softwood industry ended that year with four less producing units than
it began. This change came from:
• Eighteen "new sources"
— Two were rebuilt/reopened mills
— Sixteen were new mills
4-10
-------
Twenty-two mill closures
— Eleven were permanently closed, including two new mills that
operated only a few months
— Eleven were reopened later
Thus, while the 184 operating units were joined by 16 new plants, closures
(including 2 plants that operated only a few months) lowered the active
number to 180.
The size of individual plants has been increasing over the past few
years, especially for new integrated plywood-veneer plants. Incorporation
of plywood or veneer facilities into total wood production complexes
(which is occurring in large forest industry corporations) will be
reflected in the stability of individual plants and their continued
upgrading. Therefore, the development of predicted new source numbers
should be based more on evaluation of individual plant characteristics,
history, and expected life or needs than on past average size and life.
As noted above, new softwood capacity is projected to increase at
2.7 percent per year for the next decade, but the combination of new and
rebuilt plant openings will exceed this rate because of numerous plant
closures due to poor economic return, change of product or wood supply, or
burning down.
No new sources for hardwood veneer and plywood are assumed for 1985.
Existing capacity is sufficient and plant locations are adequate for any
increased demand for which wood is available (currently demand is
exceeding wood supply).
New sources of softwood veneer and plywood are assumed to have
parallel capacity. Table 4-3 summarizes projected new plant numbers and
production for 1985 for the softwood plywood industry.
4-11
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Table 4-3. NEW SOURCE SOFTWOOD PRODUCTION
(billion m2, 9.5-mm basis (billion ft2, 3/5-in. basis))
Production
in new sources
Replacement
capacity^
Total new source
production^
Year
Total
production
Added
capacity3
Case I
Case II
Case I
Case II
1979
1.88
(20.2)
0.05
(0.54)
0.09
(1.01)
0.05
(0.55)
0.14
(1.55)
0.10
(1.01)
1985
2.20
(23.7)
0.32
(3.50)
0.60
(6.48)
0.33
(3.54)
0.92
(9.98)
0.65
(7.04)
aAdded capacity — 2.7 percent annual growth in total industry capacity
bCase I — closure and replacement of 5 percent of plants of average size
(10 million m2 each)
Case II — closure and replacement of 5 percent of plants of small size
(5.6 million m2 each)
-------
Based on data from the 132 plants (representing 43 percent of U.S.
production) in Oregon, the average sized plants are as follows:^
Annual production,
million m2 (million ft2)
Veneer plants
Plywood layup plants
Plywood/veneer plants
Average
10 (110)
10 (110)
10 (110)
Small
5.6 (60)
5.6 (60)
5.6 (60)
Large
12 (130)
12 (130)
18.6 (200)
Data from the American Plywood Association indicates the average
production of all U.S. softwood plywood mills is also 10 million m per
13
year. Two scenarios are presented with differences based on the size
of old plants that closed. Under both scenarios, added new capacity is
based on a production increase of 2.7 percent per year, and replacement
capacity is based on 5 percent replacement. The latter value is composed
of 2.5 percent of the plants closing each year (average for the last 5-
and last 10-year periods) and 2.5 percent rebuilt or unit retrofitting.^
Modifications of existing plants will produce new sources such as new
veneer dryers but no estimation of additional equipment has been made.
Five percent replacement is also equivalent to twice the IRS asset
guidance period of 10 years (20 years life s 5 percent/yr).
Case I was computed for closures of average size plants and
replacement plants of equal total capacity using the typical large size
2 2
units of 12 million m (130 million ft )/yr. New plants built
since 1976 are typically 10 to 14 million m^ (110 to 150 million ft^)/yr.^
4-13
-------
Case II assumes plant closures affect the smallest units only, averaging
2 2
5.6 million m /yr {60 million ft /yr) while replacement plants are
large size units of equivalent total capacity. Generally plants closed in
the past have been smaller than replacements since the average plant size
2 7
has increased from 6.7 to 10 million m /yr (72 to 110 million ft /yr)
2
during the past 10 years, and from 4.6 to 10 million m /yr (50 to
2 13
110 million ft /yr) during the past 20 years.
Under Case I, 0.32 billion m^/yr (3.5 billion ft^/yr) of added new
2 2
capacity and 0.60 billion m /yr (6.5 billion ft /yr) of replacement capacity
will be built from 1979 to 1985. Case II predicts 0.33 billion m^/yr
o
(3.54 billion ft /yr) of replacement capacity will be built. Values for
calculations in this report were based on the second case.
4.3 VENEER AND PLYWOOD MANUFACTURING PROCESSES
This section describes veneer and plywood manufacturing processes and
the potential air pollutants from them. Each of the primary processes
used for debarking, veneer cutting, veneer drying, and plywood layup can
be accomplished by several differing systems. The specific system used
will influence the type and quantity of air pollutants produced. Air
pollutant emissions are described qualitatively in this section;
quantitative emissions data are discussed in Section 5. The focus of this
section is on descriptions of the processes themselves and on the
consequences of different process choices on air pollutant emissions.
Plywood manufacture involves two generic operations: veneer
preparation and plywood layup. For veneer preparation the "aw material
consists of logs or wood slabs and the product is green (undried) or dry
veneer. Veneer is produced by peeling or slicing the logs or slabs,
producing the thin sheets of wood, typically about 2.4 m (8 ft) wide and
4-14
-------
between 0.6 urn (1/40 in.) and 9.5 ran (3/8 in.) thick. After cutting the
veneer is usually clipped to about 1.2 by 2.4 m (4 by 8 ft) veneer sheets
or smaller, less than 1.2 by 2.4 m (less than 4 by 8 ft) veneer strips.
Plywood layup consists of gluing dried veneer into multilayer sheets,
with veneer stacked in layers of alternating fiber orientation. The
veneer drying process can be associated with either one of the veneer
preparation or plywood layup operations.
Some plants produce veneer only and ship it to separate layup
plants. Both green and dry veneer is shipped. Conversely some plants lay
up plywood only and thus purchase all their veneer. Such plants may
purchase both green and dry veneer, drying the green veneer on site.
Integrated plywood plants perform both veneer preparation and plywood
layup, though a spectrum of possibilities exists in these plants also.
Some plants produce all the veneer they use and use all the veneer they
produce. Others produce (and sell) excess veneer. Still others purchase
a portion of the veneer they lay up.
In the following discussion, the material flow from roundwood (logs)
to finished plywood will be described as it takes place at a single
combined plant complex. There are four generic processes in producing
plywood:
• Green process — log conditioning, then peeling or slicing into
green veneer
• Veneer drying
§ Veneer preparation, gluing, and pressing — veneer patching and
grading, layup, and gluing and pressing to make plywood
• Sizing and finishing of the plywood
Figure 4-2 shows a generalized flowsheet for these processes.
4-15
-------
VENEER OPERATION^
PLYWOOD OPERATION
Figure 4-2. Process flow diagram for veneer and plywood production.^
4-16
i
-------
4.3.1 Green Process
Making green veneer involves two main steps -- log storage and
preparation, and veneer cutting. Throughout the green process a continual
low level emission of volatile wood components occurs. This emission
initiates upon cutting of live trees and increases moderately in rate with
temperature or wood surface area increases. These volatile components,
primarily terpenes, amount to 104 kg/1000 m^, 9.5-mm basis (21.2 lb/10^ ft^,
18
3/8-inch basis) of product for fresh cut Southern pine. By the time
green veneer has been prepared for drying, this component has decreased to
approximately 16.2 kg/1000 m^, 9.5-mm basis (3.3 lb/10^ ft^,
3/8-inch basis).^ Most reports of studies on the loss of terpenes from
wood indicate a rapid loss from logs or thin sheets of wood within the
20 21 22
first 1 to 8 weeks after cutting.' ' Thus, the emission is
dispersed over both forests and manufacturing plants and is not easily
contained.
4.3.1.1 Log Storage and Preparation. The first step begins when the
logs are delivered to the wood yard where they are stored. Sometimes logs
are stored in a pond, but usually they are stored on a cold deck (piled on
a prepared surface). The latter storage method requires water spraying in
warm periods to prevent log checking.
In the next log preparation step, logs are debarked and cut into
blocks of the correct length. The types of debarkers conmonly used are:
t Drum barkers: cylindrical metal shells rotating on their long
axes. Logs are fed in and their tumbling and rolling dislodges
the bark. Water sprays may be used to reduce dust, thaw wood, or
aid the debarking by loosening the bark.
4-17
-------
• Ring barkers: rotating rings with several radial arms. Each arm
is equipped with a tool for scraping off bark. Ring barkers
handle only one log at a time.
• Cutterhead barkers: a cylindrical cutterhead which rotates
parallel to the axis of the logs which are fed through the unit.
This operation uses no water.
• Hydraulic barkers: high pressure water jets blast bark from a
log. They require large quantities of water and generate waste
water with a low solids volume. These types of barkers are
slowly being phased out since they are principally used on large
diameter logs.
The bark removed by these processes is conveyed to other portions of
the plant where it is generally used for fuel.
Logs are cut into blocks in sizes that fit into the veneer cutters.
Circular saws are typically used for this operation. While blocks up to
3.6 m (12 ft) are sometimes cut, most blocks are cut long enough to
prepare 2.4 m (8 ft) veneer. Blocks are cut 100 to 150 mm (4 in. to
6 in.) wider than the intended size of the veneer.
The next step in veneer cutting is log conditioning. Logs are
conditioned by heat and moisture. There are two methods of conditioning
logs: (1) by directing steam onto the logs in a steam vat, or (2) heating
the logs in a hot water vat that is heated directly with live steam or
indirectly through heating coils. Steam vats generally have higher
heating rates and thermal gradients than hot water vats and can only be
used on species that do not rupture with rapid temperature increases.
Woods that are dense, and therefore hard to cut, require long,
low-temperature conditioning. Some hardwoods, such as poplar, cottonwood
4-18
-------
and some conifers, can be cut satisfactorily without conditioning. A
typical soak time in a hot water bath 330°K (150°F) is 12 to 18 hours
23
for Douglas fir.
4.3.1.2 Veneer Cutting. Veneer can be cut from logs by one of four
methods. The vast majority of veneer (90 percent) is cut by peeling or
¦i
rotary cutting. The other three methods are primarily used for
decorative cuts for face veneer and for special effects with certain woods.
Rotary veneer cutting is done on a lathe. A peeler log or bolt of
wood is centered on the lathe, and the log is turned against a knife
extending the length of the lathe. This peels a sheet of thin veneer from
the log as it turns. A core which is several (10 or more) cm thick
remains on the lathe after the veneer is peeled off. Typically, such
cores are further processed to framing lumber at a studmill or chipped for
pulping.
During the 1960's, high-speed, small-log handling equipment was
introduced, enabling an expansion of the southern pine plywood industry,
and allowing economic utilization of second growth Douglas fir in the
Northwest. The small-log systems handles several small logs at a time.
The cores from small-log peelers are typically 10 cm (4 in.) in diameter,
while cores from the old peelers range up to 45 cm (18 in.). This
high-speed equipment can handle logs as small as 20 cm (8 in.) diameter.^
Another method of cutting veneer is the slicer, or stationary knife.
This method is primarily used for high quality hardwood face veneers. The
log is not "peeled", rather, it moves up and down under the slicer. Many
parallel cuts are made through the log, leaving no wasted core.
4-19
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Stay log cutters consist of a metal knife mounted off-center to a
rotary lathe. It cuts half-rounds from the log, and is considered a face
veneer technique.
A very small amount of veneer is sawed with a thin-bladed circular
saw. Thi.s method is only used for making special effects on valuable face
veneer hardwoods.
Veneers are cut to thicknesses ranging from 0.6 to 9.5 mm (1/40 to
3/8 in.). Most rotary cut veneers are either 3.6, 3.2, 2.5, 1.7 or 1.3 mm
(1/7, 1/8, 1/10, 1/15 or 1/20 in.) thick. Sliced veneer is 1.3 to 0.6 mm
(1/20 to 1/40 in.) thick and sawn veneers range from 6.3 to 0.8 mm (1/4 to
1/32 in.).19
After the veneer is peeled, it is brought through green clippers and
cut to size before drying. The clippers are large knives which cut 1.2-m
(4-ft) segments out of the continuous ribbon of green veneer. If there
are too many defects in a section of veneer a shorter section of veneer
containing the defects is cut free. Usually, the clippers are equipped
with infrared scanners that detect the defects (voids) and control the
clippers' actions — cutting regularly at 1.2-m (4-ft) intervals for good
veneer, and more often for veneer with voids (a knot or rot size greater
than 38 mn (1-1/2 in.) diameter).
The veneer is then sorted by size, wood species, heartwood or
sapwood, and veneer grade (including veneer unsuitable for plywood). This
sorting is done by hand and is necessary before the veneer can be dried,
because different veneers require different drying conditions. Sorting is
the last process step before drying.
4-20
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Side products of veneer cutting are log cores, wood chips, and wood
only suitable for chipping. The cores are often trimmed and sold as
lumber, the chips and dust are used for hog fuel, or pulp, hardboard, or
particleboard production.
These materials are conveyed around the plant by pneumatic or direct
displacement. Dust and chipped wood are often conveyed pneumatically
while coarse material is conveyed by direct displacement: belts, gravity
chutes, bucket lifts, etc. This coarse material includes log trim, bark,
veneer clippings, veneer cores, rejected veneer, roundings and spur trim.
Conveyance of coarse material leads to negligible air emissions while
conveyance of fines can lead to particulate emissions. Emissions from
pneumatic systems are discussed in Section 5.
2
For a typical veneer mi 11/plywood plant making 10 million m
p
(110 million ft ) of plywood on a 9.5-rmi (3/8-in.> basis per year, each
day 304,000 kg (670,000 lb) of logs are processed, which form 127,000 kg
(280,000 lb) of plywood. For these logs, 176,000 kg (46,400 gal) of water
3
are used in log conditioning. No significant air pollutants are likely
24
to be emitted from this process.
4.3.2 Veneer Drying
Freshly cut veneer is too wet to glue. It must be dried before being
assembled into plywood. The vast majority (over 99 percent) of veneer is
dried in veneer dryers. Some cheap, low-grade veneer, destined for use in
crate manufacturing, is occasionally air-dried. In air drying, veneer is
3
simply placed in stacks that allow good circulation of air.
Veneer dryers generally consist of a long heated chamber with layers
of belts (typically five) carrying the veneer. Heat transferred to the
wood by air circulating in the dryer causes the veneer to dry to a low
4-21
-------
moisture content. The moisture content of the wood at the end is the "set
24
point" of the dryer and can range from 1 to 10 percent.
There are two general methods of heating veneer dryers; steam
(indirect) and direct heat application. In steam heating, a boiler
separate from the dryer produces steam that heats dryer coils in contact
with dryer air. In direct heat dryers the combustion heated gas comes
into direct contact with the veneer. Direct heat dryers are almost always
either gas- or wood-fired. In gas-fired direct heat dryers, the
combustion takes place on a burner close to the dryer chamber, and the
heated air is circulated to the veneer with fans. In a wood-waste-fired
direct heat dryer, air is heated outside the dryer by wood-waste-fired
combustion. The combustion gas is mixed with recirculation dryer air in a
blend box and circulated into the dryer.
Direct-fired and steam-heated dryers can have either longitudinal or
cross-directional circulation of air. In longitudinal circulation, fans
blow the air the length of a drying zone. In cross-directed air flow, the
air is circulated across the wood at a 90° angle from its travelling
direction.
Dryers are divided into control zones. Each control zone is a
portion of the dryer that can stand by itself, with its own air
circulating system and heating system. Each zone contains several
sections, 1.6 or 1.8 m (5.25 or 6 ft) long. Each section is defined by
its own side door for dryer access. There are typically 6 to 12 sections
25
in a zone. Dryers typically have two to four control zones, followed
by a separate cooling zone in which ambient air is drawn across the veneer
to cool it before exiting the dryer.
4-22
-------
A longitudinal gas-fired dryer is shown in Figure 4-3. It has two
control zones. The temperature in the first control zone (green end) will
be higher than the temperature in the second zone, since green wood can
tolerate higher temperatures. In each zone, a portion of the air is
exhausted from the stack each time the air is recirculated. The amount of
air exhausted depends on the damper setting of the dryer.
A steam-heated longitudinal dryer has the same basic design as the
gas-fired dryer, with a bank of finned heating coils in the upper plenum
replacing the gas firing. Not enough heat can be imparted to the air
through these reheater banks, so steam coils are also placed along the
decks of the conveyer.
Jet (cross-flow) dryers differ from longitudinal dryers in that the
air stream is directed to the wood through horizontal plenums (placed at a
90° angle to the direction of veneer flow) impinging directly on the
wood through jets. Jet dryers usually have hotter green end temperatures
and more control zones than longitudinally fired dryers. They require
less fuel for the same drying, but more electric energy to power the
fans. Incoming air temperatures are approximately 533°K (500°F), and
air leaving the veneer and on its way back to the recirculating fan is
436°K (325°F).25 Cooling zones have a separate air supply. Jet
dryers can be steam heated or direct-fired. If they are steam heated,
however, there are no steam coils near the decks of the conveyer, because
that is where the gas jet plenums are located. Therefore, many more
heating coils must be added to the heating bank of the dryer. Figure 4-4
shows a four control zone jet dryer and the air flow in a typical zone.
25
Figure 4-5 shows steam-heated and gas-heated jet dryers.
4-23
-------
Figure 4-3. Gas-fired longitudinal dryer.26
-------
4*
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ro
cn
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i
ft
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Figure 4-4.
26
Four control zone jet dryer.
-------
Figure 4-5. Steam
and gas-heated jet dryer. ^
-------
In a wood-fired, direct-fired veneer dryer, powdered wood fuel is
burned, and postcombustion gases come from the burner at temperatures
approximately 1590°K (2400°F). Some of the air circulating in the
dryer is mixed with these hot gases in the blend box; blend box
temperatures are approximately 920°K (1200°F). The high temperatures
in the blend area allows the oxidation of some of the hydrocarbons emitted
from the wood.27 Some wood-fired veneer dryers use the exhaust from the
26
. . ^ ac an air inlet stream to the wood combustor.
veneer drying process as an air =»»..*
L i. „_4.e „« an incinerator for the hydrocarbons in the
The wood combustor acts as an incinera w
veneer dryer vent stream.
Wood drying times depend on the species of wood, whether the wood is
heartwood or sapwood, the thickness of the veneer, the drying "set point",
and the dryer type. For 1.6 mm (1/16 in.) veneer passing thrugh a
17-section dryer, Douglas fir heartwood will take about 4-1/2 minutes and
sapwood will take about 8 to 9 minutes. At the other extreme hemlock can
take 16 minutes for heartwood and 31 minutes for sap*,od.24
When the veneer is dried, the veneer dryer vent can emit several air
pollutants. Organic aerosol and gaseous organic compounds are the major
emission. A small amount of particulate, mostly wood fiber, is also
emitted. The organic aerosol is derived from the hydrocarbons distilled
from the wood. Most of the gaseous organics (such as monoterpenes) are
also derived from the wood, but some unburned methane can also be emitted
from gas dryers.
There are also fugitive emissions from veneer dryers. These
emissions are of two types.
• Leakage of vent-type emissions around the dryer section doors and
the dryer entrance and exit openings
4-27
-------
• Emissions due to the accidental burning of wood in dryer fires
The amount of hydrocarbons vented depends on:
• The type of dryer
• The type of wood dried
• Dryer operating conditions, including damper setting and the
condition of the door seals
• The skill of the operator in preventing overdrying of the wood
Sampling data taken from veneer dryer stacks are presented in Section 5.
This section discusses the general effects of the conditions listed above
on veneer dryer emissions.
Leakage of gases around the dryer door seals can be a significant
fugitive emission. The amount of leakage depends on the maintenance of
the door seals and the type of dryer. Door seals are frequently damaged
by splinters of wood being forced into them when the doors are closed.
Proper maintenance can alleviate this problem. Jet dryers have more
leakage around door seals than longitudinal dryers because the doors on
the "positive pressure" side of the dryer are always under pressure.
oc
Maintenance is especially important for these doors.
Dryer fires are an intermittent source of fugitive emissions.
Splinters and knots fall out of the veneer while it is in the dryer and
fall to the floor. This combustible material remains on the floor,
collecting in areas of low air velocity near the dryer doors. Leaks of
fresh air into the dryer at the doors lead to fires. Such fires can be
prevented by proper maintenance of dryer doors, periodic cleaning of
dryers, and installation of wet lines on the dryer floor.
4.3.2.1 Dryer Type. Emissions from the dryer vent can vary
according to dryer type. Steam-heated dryers, for example, usually have
4-28
-------
less emissions from the dryer vents than gas fired-dryers. Some of the
19
emissions from the gas-fired dryers are unburned methane. The vents
of wood-fired dryers emit more organics than the vents of gas- and
steam-fired veneer dryers, because the postcombustion gases are also
emitted. However, the wood-fired dryers have less overall organic
emissions than emitted from a steam heated veneer dryer vent and the
associated wood-fired boiler combined, since some organics are destroyed
27
by the high temperatures in the blend box or combustion unit.
Available data do not show any differences in vent emissions between
longitudinal and jet dryers.
4.3.2.2 Wood Type. The type of wood dried has a large effect on the
organic emissions exiting from the veneer dryer vent. Organic emissions
from Hemlock and White fir are lower than emissions from Ponderosa pine,
19
Douglas fir, and White pine. Heartwood and sapwood from the same tree
will have different organic emission rates, as well as different drying
times.
4.3.2.3 Dryer Operating Conditions. The temperature and retention
time of wood in a dryer affect the evolution of organics. Overdrying and
drying at overly hot temperatures tend to increase the organic emissions
as well as increase the chance of fires.
Another significant variable is the damper setting. The air in
dryers constantly recirculates with only a fraction vented to the
atmosphere. This reduces the fuel costs of dryer operation. The damper
setting controls this rate of exit and also has a very noticeable effect
on the organic emission rate. A dryer operated with dampers open has a
high flow volume with low organic concentration. A dryer operated with
dampers closed has higher organic content, but a lower total amount of
4-29
-------
2 19
organics emitted per m of plywood. The dryer which operates with
dampers closed tends to accumulate pitch balls, as the condensible organic
compounds condense within the dryer.
4.3.2.4 Operator Skill. There are wide variations in operator skill
and alertness. Some veneer dryer operators are very aware of changes from
heartwood to sapwood, from species to species, as the veneer goes through
the mill. They keep tables and charts and constantly adjust heat and
damper settings to maximize dryer efficiency. Other operators take up to
half an hour to respond to changes in species and overdry much more wood.
Since overdrying and haphazard heat and damper settings can cause
increased organic emissions, dryer operating skill is an important
19
criterion.
4.3.3 Gluing and Pressing
All plywood consists of sheets of veneer bonded together by layers of
glue. This section describes the formation of plywood from dried veneer.
The steps in this process are:
• Veneer preparation
• Layup with gluing of the veneer
• Pressing
4.3.3.1 Veneer Preparation. The veneer coming from the green
clipper is sized into approximately 1.2, 0.9, 0.6, and 0.3 m (4, 3, 2 and
1 ft) wide pieces, and sorted by grade and type of wood (species, and
heartwood versus sapwood). After the veneer is dried, it is reinspected,
clipped, spliced, knot holes plugged, redried, and regraded as necessary
to make sheets ready for layup. Occasionally a coating is added to veneer
before layup. This coating can be plain or oiled paper. Some plywood
plants purchase two-ply plywood and add further layers of veneer to it.
4-30
-------
No significant emissions are caused by these veneer preparation
steps. Most of the preparation work is mechanical, giving rise to small
amounts of dust formation. Some glue is used during splicing, but the
quantities are small compared to those in use at glue-up.
4.3.3.2 La.yup and Gluing. Different plywood products use different
glues to bond the wood together. Most exterior plywoods are made with
phenol-formaldehyde resins; over 90 percent of all plywoods are made with
these resins. Some me1 amine-formaldehyde resins are also used for
exterior plywood. Interior hardwood panels are made with
urea-formaldehyde resins. Phenol-formaldehyde resins are used to make
interior softwood panels. Some-protein based glues are also used.^'2^
Glue application requirements change with changes in the types of
logs available. For example, West Coast glue use has increased from 0.31
to 0.33 kg/m2 (63 to 67 lbs/1000 ft2) to 0.35 to 0.36 kg/m2 (73 to
75 lb/1000 ft2) of 9.5 rim (3/8 in.) plywood to offset the increased
roughness of veneer from smaller diameter logs being peeled. Southern
pine plywoods require 0.04 to 0.06 kg (10 to 15 lb) more glue per m2 of
9.5 mm (3/8 in.) plywood because of the glue absorption characteristics of
this species. Plywood glues will continue to evolve as different needs
arise and as glue raw materials fluctuate in price. Gap-filling glues and
glues which make a better adhesive bond to overdried or overaged wood are
28
currently under development.
Glues are available both as ready-to-use resins stored in tanks or as
resins which are mixed onsite. Not all glues are available as
ready-to-use glues, and some plywood plants prefer their own mix of
resins, extenders, and dispersants. Therefore, glue mixing at plywood
4-31
-------
plants remains an important part of the plywood manufacturing process
28
despite the availability of ready-to-use glues.
Glue is mixed in glue-lofts, where either high-shear impeller mixers
or rotating paddle mixers mix tanks of glue. The trend is toward fewer
and larger glue batches being made so that one shift of gluemaking will
28
supply three shifts of plywood manufacture. Increased shelf life of
mixed glues has led to this trend. Phenol resins require heat to cure;
urea resins can be cold-cured, but require acid. These glue-mixing
operations could give rise to fugitive formaldehyde or phenol emissions.
There are no published data on the extent of such emissions, but they are
generally considered to be minor.
Glue is spread onto the veneer by hand-fed hard-roll spreaders or by
automatic soft-roll spreaders, spray lines or curtain coaters. The
hard-roll spreaders coat two sides of a piece of veneer destined for core
use; these coated pieces are laid on top of the face piece, and the back
piece is added by hand. Soft-roll spreaders, spray-lines, and curtain
coaters generally coat only one side of a piece of veneer, so a face piece
and the center piece or both face pieces must be coated separately to form
standard three-ply plywood. The person doing core layup using a two-sided
hard-roll spreader takes veneer pieces of different sizes (0.3, 0.6, or
0.9 by 1.2 m — 1, 2, or 3 by 4 ft) to make up a 1.2 by 2.4 m (4 by 8 ft)
section of plywood. The automated plywood coaters and layup require 1.2 m
(4 ft) wide veneer sections to begin operation, so the core veneer is
29
spliced or sewn to this width. Otherwise, smaller cross strip pieces
are laid on face veneer by hand, with glue applied to each face veneer
sheet. Glue overspray in automated lines is generally collected for
4-32
-------
reuse. Some automated spray lines are vented to atmosphere under vacuum,
24
therefore becoming a possible source of fugitive organics.
Ninety-eight percent of the softwood plywood made in this country
will be made with phenol-formaldehyde glues and 2 percent with protein
glues. The amount of glue that will be used on this plywood is 0.3 to
0.4 kg/m^ (60 to 80 lb/1000 ft^) of 9.5 m (3/8 in.), plywood
? 9
equivalent.
Urea-formaldehyde glues were used in over 90 percent of the hardwood
plywood, which is intended for interior use. The remainder of the
hardwood plywood is used for exterior products and is glued with
30
phenol-formaldehyde, or melamine glues.
Two-thirds of the plywood production in the West is done by hand
spreader, while the majority of southern plywood plants are
automated. Cleanup of glue mixes and spreaders can cause water
pollution problems. However, negligible air pollution is expected from
this phase of plywood production.
4.3.3.3 Pressing. The loose layers of plywood with applied glue are
then moved to the pressing area. Urea-formaldehyde glues are pressed at
ambient temperature. Phenol-formaldehyde glues are steam pressed at
temperatures ranging from 390° to 420°K (240° to 300°F) and
pressures to 1030 kPa (150 psi). Phenol-formaldehyde glues are also
sometimes pre-pressed at ambient temperature, before steam pressing. Some
glued plywood must be clamped after pressing, and many glues must stand
for a few minutes before pressing. Pressing itself takes from 2 to
1 minutes, depending on the type of glue.
During pressing and when the presses are released, there are some
gaseous organic emissions from uncured resin bonds. With urea-formaldehyde
4-33
-------
glues, formaldehyde is released; with phenol-formaldehyde glues, phenol is
no on
released, * These releases are fugitive and have only been
considered in terms of their effects within the plant, i.e., adequate
venting is provided to protect workers' health and eliminate nuisance
odors. There are no sampling data available on these compounds outside
the vents.
4.3.4 Sizing and Finishing
The last step in plywood preparation is trimming and finishing. The
plywood is trimmed to produce even-edged sheets and may be sanded on one
or both sides. Both of these processes produce dust, which is collected
by a pneumatic system and routed to at least a cyclone and sometimes a
baghouse for collection.
The wood dust is produced in automatic sanders and by trim saws.
Automatic sanders are enclosed boxes through which the plywood moves on a
conveyer. The box is continuously cleared of sawdust, with pneumatic
systems above and below the plywood. Plywood trimmers are stationary
circular saws that trim up to 25 mm (1 in.) on a side from the plywood to
produce sized, even-edged sheets. The saw has about a 1.5 mm (1/16 in.)
kerf, and the sawdust is conveyed away by a vacuum system similar to that
used in the sander.
The sawdust is transferred and collected in cyclones sometimes with
secondary baghouses. The collected material is used for for boiler fuel.
Sampling results for the exhaust from these cyclones and baghouses are
discussed in Section 5.
Coarse mill residue, as dicussed earlier, is used for raw material,
fuel, or decorative bark. Occasionally a plant will simply incinerate the
waste to reduce its volume. Old "wigwam" or "teepee" burners exist at a
4-34
-------
few veneer mills and do emit significant air pollutants. However, State
and local regulations and increasing residue value have both discouraged
use of these systems. No such incinerators are expected to be built at
new sources.
4-35
-------
REFERENCES
1. Ellis, E. McGraw-Hill Encyclopedia of Science and Technology,
Vol. 14, McGraw-Hill, New York. 1971. p. 619.
2. Bradly, G., et al. Materials Handbook, 11th edition. McGraw-Hill,
New York. 1977. p. 600.
3. Development Document for Effluent Limitation Guidelines and New
Source Performance Standards for the Plywood, Hardboard and Wood
Preserving Segment of the Timber Products Processing Point Source
Category. EPA 440/1-74-023a. April 1974.
4. Reference 1, p. 18-19.
5. Anderson, R. G. Long Term Forecast of Plywood Demand 1977-1986.
American Plywood Association. September 1977.
6. Current Industrial Reports — Softwood Plywood. U.S. Department of
Commerce. Bureau of the Census Report No. MA-24H(78)-1. October
1979.
7. Current Industrial Reports — Hardwood Plywood. U.S. Department of
Commerce, Bureau of the Census Report No. MA-24F(77)-1. August 1978.
8. 1972 Census of Manufacturers, Vol. III. Area Statistics. U.S.
Department of Commerce, Bureau of the Census. August 1976.
9. U.S. Industrial Outlook 1979. U.S. Department of Commerce.
January 1979. p. 40-41.
10. Hardwood Plywood Stock Panels. Hardwood Plywood Manufacturers
Association Brochure.
11. Hardaway, 0. T. Hardwood Plywood in Demand. Timber Processing
Industry Journal. 3:39-41. December 1978.
12. Lewis, B. J. Softwood Plywood Industry Challenged Admidst Growth.
Timber Processing Industry Journal. 2:34-38. December 1978.
13. American Plywood Association. Softwood Plywood Production
Statistics. Tacoma, Washington. Management Bulletin No. FA-200.
April 10, 1979.
14. 1979 Directory of the Forest Products Industry. San Francisco,
Miller Freeman Publishers, 1979. p. 772.
15. Dixon, R. Garden Plant is First Step in IP Plywood, Lumber Expansion
Program. Plywood & Panel Magazine. September 1979. p. 14-15.
4-36
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16. Millard, H. K. Trip Report of November 12, 1979 visit to American
Plywood Association Members Panel, Eugene, Oregon. Acurex
Corporation. Mountain View, California. November 28, 1979.
17. Howard, J. 0. and B. A. Hiserote. Oregon's Forest Products Industry
1976. U.S. Department of Agriculture. Portland, Oregon. Forest
Service Resources Bulletin PNW-79. 1978.
18. 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.
19. Monroe, F. L., et al. Investigation of Emissions from Plywood Veneer
Dryers. Final Report for the Plywood Research Foundation, Tacoma,
Washington, and EPA (Contract CPA-70-138). February 1972.
20. Springer, E. L. Losses During Storage of Southern Pine Chips.
TAPPI. 59:126. April 1976.
21. Hajng, G. J. Outside Storage of Pulpwood Chips. TAPPI. 49:97A.
October 1966.
22. Cowling, E. B., et al. Changes in Value and Utility of Pulpwood
During Harvesting, Transport, and Storage. TAPPI. 57:120.
December 1974.
23. Waterland, L. Trip Report of November 13, 1979 visit to Georgia
Pacific Plywood Plant, Springfield, Oregon. Acurex Corporation.
Morrisville, North Carolina. November 30, 1979.
24. Personal communication resulting from site visits, Larry Waterland
and Kirk Willard. Acurex Corporation, Mountain View, California.
25. Vranizan, J. M. Veneer Dryers, Typical Construction, Operation and
Effluent Abatement Possibilities. (Paper presented at 1972 Annual
Meeting of the Pacific Northwest Internation Section Air Pollution
Control Association. November 17, 1972.)
26. Communication from Champion Building Products to Kirk Willard, Acurex
Corporation, Mountain View, California. November 26, 1979.
27. Grimes, G. Direct Fired Drying — The 'Hybrid' Unit. Paper
presented to the Pollution Control Seminar for the Northwest Forest
Industries, Portland, Oregon, April 5, 1978.
28. Lambuth, A. L. Adhesives in the Plywood Industry. Adhesive Age.
38:21-26. April 1977.
29. Personal communication, Carl Erb of American Plywood Association,
December 5, 1979.
30. Personal communication, Clark McDonald, Hardwood Plywood
Manufacturing Association, December 6, 1979.
4-37
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SECTION 5
AIR EMISSIONS DEVELOPED FROM THE PLYWOOD INDUSTRY
This section presents a discussion of test data compiled for this
source survey. The test data presented in Section 7 are synthesized so
that emission factors are obtained and national annual emissions levels
calculated. The discussion of the synthesis of data is categorized with
respect to the particular plywood manufacturing process. The emission
factors and emission levels are then projected, and comparisons between
projected emissions under current State Implementation Plans (SIP1s) and
those under more stringent controls implemented by developing a New Source
Performance Standard (NSPS) are presented.
5.1 PLYWOOD PLANT AND PROCESS EMISSIONS
As discussed in Section 4, the potential emissions from plywood
manufacturing may originate from the following sources:
• Log green handling, peeling, and conveying
• Veneer drying
t Layup, gluing and pressing
• Sanding and triirening
Of these various manufacturing processes, fugitive sawdust, bark, and
wood chips generated from log green handling and peeling operations is
generally minor.* Fugitive emissions of gaseous wood terpenes occurs
throughout the green wood handling and storage operations but at a low
5-1
-------
rate and at several locations. Emissions from layup, gluing and pressing
processes consist of fugitive gaseous organic vapors resulting from the
evaporation of adhesive components. Thus, of these four process
categories, the two primary sources of emissions from plywood
manufacturing are from veneer drying, and from sanding, and trimming
operations. Section 7.1 of this Source Survey presents the data found for
the various manufacturing processes. This subsection synthesizes the data
of Section 7.1.
5.1.1 Air Emissions Developed From Veneer Drying Operations
The major pollutants emitted from veneer dryers are organic aerosols
derived from wood sugars, resins, and resin acids, and gaseous organic
compounds comprised mostly of monoterpenes. The organic aerosol
constituents typically form the "blue haze" plumes associated with certain
uncontrolled veneer dryers in the Pacific Northwest. As discussed in
Section 4.3.1, losses of wood terpenes occur throughout the green wood
operations. Of the total amount of emitted material (approximately
10,000 metric tonnes (9100 short tons) per year) only about 15 percent or
1500 metric tonnes are emitted in a confined location — the veneer
dryers. All other emissions are dispersed over wide areas including
forest, transport lanes, and log or veneer storage locations. Since the
continuous emitted material cannot be practically contained, it is not
further discussed.
Section 7.1.1 presents data from several veneer dryer tests. The
most extensive series of tests were conducted by Washington State
University (WSU) on 14 veneer dryers located in the Pacific Northwest and
2
southern U.S. These tests were the first to record wood type and
plywood production rate, and measure fractions of organic emissions and
5-2
-------
opacity. Other test data cited in Section 7.1.1 include test results from
3
the SWF plywood "hybrid" unit. This system uses the exhaust gases of a
veneer dryer as primary and secondary combustion air for a direct
wood-fired dryer. The data are included for information only. The
initial WSU tests being the most extensive and best documented serve as
the baseline for determining emissions factors.
In a subsequent, second series of tests WSU investigated the effects
4
of stack damper setting on veneer dryer emissions. Because stack
damper setting was changed and the effect on veneer dryer emissions
determined, a process other than normal or baseline operation was used.
Consequently, inclusion of such data in determining an overall emission
factor would not represent normal veneer dryer operation, and is not done
here.
The SWF test results assess the effects of a control technology on
veneer dryer emissions. The tests do show that substantial reductions
in organic and particulate emissions can be realized by the recirculation
of veneer dryer flue gas. However, the data do not represent that of
normal veneer dryer operation and are hence excluded in the determination
of an emission factor here.
WSU found that veneer dryer emissions consist of small quantities of
solid particulate matter (generally less than 4.6 mg/Nm^ —
0.002 grains/scf) and organic compounds. WSU denoted two categories of
hydrocarbons — hermiterpene hydrocarbons (qaseous) and diterpenes
(condensible). The condensible diterpenes are termed organic aerosols in
this source survey.
The initial WSU study concentrated on the nature of organic compounds
emitted from veneer dryers. The method used WSU in their initial study
5-3
-------
for the sample collection arid subsequent analysis of both gaseous and
condensible hydrocarbons was a glass condenser system with a backup
filter, followed by a total hydrocarbon analyzer (THA). In a second study
on veneer dryers by WSU (data shown in Section 7.1.1) to evaluate the
impact of stack damper setting on emissions, concern was raised as to the
2
potential inaccuracies in the procedures used. Work was conducted to
compare or generate equivalence factors between the WSU system and an
approved EPA Method 5 train (the Research Appliance Company's
"Staksamplr") using an organic solvent extraction technique. Contrary to
the existing belief at the time of the WSU tests, not all of the material
emitted from veneer dryers was being measured, either by the glass
condenser or by the THA. Organics not caught by the condenser would be
ostensibly detected by the THA. However, when a glass fiber filter was
inserted in the WSU train, THA response was unchanged from that obtained
without the filter. Material was caught on the filter, material that
5
apparently eluted no THA response. The Oregon Department of
Environmental Quality (DEQ) and the American Plywood Association were
satisfied with the quantitative results of the initial WSU sampling train
and the cost-effective method of analysis. This WSU methodology was
subsequently modified and adopted by the Oregon DEQ as their Method 7,
prior to the promogulation of EPA Method 5 and the findings of the
sampling and analysis discrepancy.
From these comparison results, it was concluded that the data
reported in the initial study for the organic aerosols or condensible
organic fraction should be multiplied by factors from 1.06 to 2.19
2
depending on the wood species. These factors have been applied to the
emission factors adopted in this report.
5-4
-------
Table 5-1 shows a comparison between corrected WSU emission factors,
AP-42 guidelines and the SIP from the State of Oregon. AP-42 guidelines
address the level of emissions for total hydrocarbon compounds and their
fractions. The State of Oregon SIP only delineates acceptable emissions
in terms of nominal and maximum stack opacities and total particuate
allowable on a production basis identified by fuel moisture content.
Section 10.3.2 of AP-42 bases these emission factors on the unfactored
original WSU data. As previously discussed, the original WSU data must be
factored to account for differences in organic aerosol content due to
sampling and analysis technique.
Also noted in Table 5-1 are the characterizations of the gaseous and
aerosol fractions of the organic compounds emitted from veneer dryers.
No test data were found on hardwood veneer dryers. At present,
hardwood plywood production represents less than 10 percent of total
plywood production. Until tests can be conducted on hardwood veneer
dryers, it is assumed that hardwood dryer emission factors are the same as
those from softwood dryers, even though they are certainly lower.
Section 7.1.1 also discusses test data for various control devices
evaluated and currently under evaluation by the State of Oregon and its
various agencies. The initial data indicate a range of control
efficiencies of veneer dryer emissions from 26 to 98 percent for the
particulate fraction as reported by the Mid-Willamette Valley Air
Pollution Authority (MWVAPA).^ Further data reported by the Oregon OEQ
show control efficiencies from 43 to 87 percent on the removal of the
P
condensible or aerosol fraction including particulate. Extensive
onsite visits of plants implementing control devices were made in this
survey. Discussions with users of various systems indicated that
5-5
-------
Table 5-1. SUMMARY OF EMISSIONS TEST RESULTS FOR VENEER DRYERS COMPARED TO
AP-42 GUIDELINES AND THE OREGON STATE IMPLEMENTATION PLAN
Pollutant
Uncontrolled
emission
Characteristics
Reference
AP-42
emission factor6(*)
SIP-Oregon controlled
emission factor'
Gaseous organic
compounds
0.75 g/m2
(1.53 lb/104 ft2)
-Pinene
3-Carene
2
1.1 kg/103 in2 (4)
(2.1 lb/104 ft2)
NA
Aerosol organic
compounds
4.54 g/m2
(9.28 lb/104 ft2)
corrected for
sampling and
analysis differences
abietic-plmonic acids,
sesquiterpenes,
fatty acids, resin
esters, resin,
resin alcohols
2.4
1.9 kg/103 m2 <4)
(3.6 lb/104 ft2)
NA
Total organic
compounds
5.29 g/m2
(10.81 lb/104 ft2)
NA
3.0 kg/103 m2
(5.7 lb/104 ft2)
NA
Particulate (2)
4.6 g/Nm3
(0.002 grain/scf)
Fine wood fiber
2,4
NA
3-7 9/n»2 (3) ,
(7.5 lb/104 ft2)
7.3 g/in2 (4i
(15.0 lb/104 ft2)
Opacity
23%
2
NA
10% Design
10% Average
20% Maximum
Notes:
Units expressed oh a kilogram/1000 m2 of 9.5 nm plywood basis (standard units as lb/10,000 ft2 on a 3/8 inch plywood
basis)
(1) — As cited in AP-42
(2) — "Condensibles" plus particulates as measured by DEQ Method 7 -- Reference 8
(3) — For fuel having a moisture content of less than 20 percent
(4) — For fuel having a moisture content of greater than 20 percent
-------
nominally, a 50 percent control efficiency was seen for the majority of
the systems.^ This assumption coincides with the data presented in
Section 7.1. This control efficiency will be used to evaluate the impact
of existing control on national emission levels presented in Section 5.2.
5.1.2 Air Emissions Developed From Gluing and Pressing Operations
As discussed in Section 7.1.2, the pollutants emitted from plywood
gluing and pressing operations are quite small. The emissions from these
operations are from the phenol-, melamine-, and urea-formaldehyde
adhesives used to produce specific end-use plywood.**
It has been noted by manufacturers that fugitive emissions do exist.
Odors have been noticed from glue mixing, spreading, and spraying
operations. Prepressing has no emissions. Pressing at process
temperatures from 283° to 420°K has both an odor and visible emission.
This is ducted and vented outside for moisture control. Both the
Formaldehyde Institute and Battelle NW Research are studying emissions
from urea-formaldehyde. The Chemical Industry Institute of Toxicology has
19
found animal nasal cancer from formaldehyde exposure. Emission
results from panel pressing were stated as 0.2 to 0.3 ppm free
formaldehyde found in the plant area when using ammonia processes.*"^
Several agencies, companies and manufacturers were contacted during
this source survey for test data regarding this process source
emission.*^ To this date, no emissions tests have been conducted.
Moreover, no regulations currently exist regarding this industrial
process. Consequently, no emission factor can be generated.
5.1.3 Air Emissions Developed From Plywood Sanding and Trimming
Operations
The major emission from plywood sanding and trimming processes is dry
wood particulate consisting of wood chips, sander dust and hogged plywood
5-7
-------
trimmings. The majority of the wood waste is captured and transported by
a pneumatic conveying system for collection by cyclones or multiclones.
It is then used as raw material for particleboard, paper pulp, and
waste-fired boiler fuel. Some 99.8 percent (weight basis) of the
particulate is in the 10 to 80 micron size range with a mean particle size
g
of 22 microns on a number basis.
The data presented in Section 7.1.3 represent those currently
available. In all of the test data found, no method of sampling and
analysis of emission sources was given nor was the production rate, or
wood type. It was difficult to determine if techniques similar to EPA
test methodology had been used. However, it is reasonable to suspect,
based on general descriptions, that ASME methods regarding the
determination of relative humidity, duct velocity, temperature and
particulate loading were followed.
Generally, all sanding and trimming process facilities use a cyclone
or similar control device, sometimes in series with a baghouse if
compliance cannot be met with a cyclone alone. For the purposes of this
source survey, uncontrolled emissions will be considered those emissions
from the outlet of the cyclone. The exhaust air from fabric filter
collectors is termed as controlled emissions.
The Tennessee Division of Air Pollution Control tests presented in
15
Table 7-7 show inlet particulate grain loading data to cyclones.
Many of the cyclones tested had measured inlet loadings of greater than
3 3
200 g/Nm while others had less than 30 g/Nm . Typical outlet
loadings of Q.07g/Nm would indicate a cyclone efficiency of greater
than 99.95 percent in the case of high inlet particulate loading
conditions. Variations in cyclone inlet particulate loading are due to
5-8
-------
the intermittant loading of the cyclone because of process demands. For
example, total pneumatic conveying of material occurred during the peak of
the process. Waste rates noted are the time averaged feed rate to the
cyclones. Measured cyclone discharge rates were subject to the same
problems of varying process operation.
A statistical treatment of these tests by Acurex personnel,
accounting for intermittant process operation, yields a composite inlet
3
particulate loading in excess of 22 g/Nm , a composite outlet
3
particulate loading of 0.07 g/Nm for an average efficiency of
99.7 percent. In comparison to nominal cyclone efficiencies of around
95 percent, the tested cyclone efficiency is high. However, a cyclone
3
outlet particulate 0.07 g/Nm is reasonable when compared to typical
3 9
user reported outlet loading of 0.09 g/Nm . Calculated average
particulate loading from data supplied by the tests conducted by the
Georgia Department of Natural Resources for uncontrolled emissions to a
0 1g
control device is 0.13 g/Nm . Small diameter cyclone clusters
(multiclones) have demonstrated excellent collection efficiencies at
3 17
outlet particulate loadings of 0.11 g/Nm . Based on all published
3
field test data, a particulate loading of 0.10 g/Nm is calculated by
statistical averaging for uncontrolled emissions from the primary
collection device.
Very limited test data were published by the Canadian Provincial
18
Pollution Control Board on fabric filter collectors. Again, no
information regarding sampling and analysis methodology, production rate,
wood type or duct velocity was cited. Of the data presented, the average
0
outlet particulate loading from the baghouses tested was 0.014 g/Nm .
3
Compared to the 0.009 g/Nm generally agreed as typical for fabric
5-9
-------
13
filters, this tested loading is relatively high. In comparing the
inlet particulate loading to that of the outlet, this would indicate a
fabric filter collector efficiency of only 86 percent. Most manufacturers
of collectors are quoting efficiencies of 99.9 percent or better.
However, in many of the tests, the particulate loading was lower than the
maximum resolution of the sampling train (i.e., lower than 0.002
g/Nm3). Such an outlet loading would suggest a fabric filter efficiency
of 98 percent. Consolidating the data would indicate a level of control
of 0.002 g/Nm3 for a fabric filter. Consistent with that reported by
3
users of baghouses for sanding and trimming operations, 0.002 g/Nm is
used in the evaluation of controlled national emission levels.
A summary of the emission factors estimated for each control device,
compared to AP-42 guidelines and State of Oregon air quality control
standards is shown in Table 5-2. In examining the particulate emission
factor from cyclone outlet test data, it can be seen that this controlled
emission factor is less than the AP-42 guidelines for other or composite
waste particulate. The maximum AP-42 emission factor is noted for
sanderdust, wood chips from trimmings, and other process wood waste
particulates. A particulate grain loading from fabric filter collectors
of 0.002 g/Nm3 is well below that of the AP-42 guideline of
0.126 g/Nm3.
5.1.4 Summary of Emission Factors for the Plywood Industry
A tabulation of the pollutant emission factors used in determining a
national emissons level for the primary sources identified from the
plywood manufacturing industry is shown in Table 5-3.
As discussed in Section 5.1.1, veneer dryer emission factors were
generated from WSU test data. These factors have been corrected for the
5-10
-------
Table 5-2. SUMMARY OF PARTICULATE EMISSIONS TEST RESULTS FOR AIR CONVEYING SYSTEMS
COMPARED TO AP-42 GUIDELINES AND THE OREGON STATE IMPLEMENTATION PLAN
Control
dev ice
Uncontrolled
emissions at
device Inlet
Controlled
emissions at
device outlet
Reference
AP-42
emission
factor
sanderdust6(1)
AP-42
emission
factor
other® (2)
Oregon state
implementation plan'
Cyclone
Fabric filter
22 g/Nm3
(9.6 grains/scf)
0.10 g/Nm3
(0.044 grains/scf)
0.10 g/Nm3
(0.044 grains/scf)
0.002 g/Nm3
(0.001 grains/scf)
14,15
17
0.126 g/Nm3
(0.055 gr/scf)
or
2.3 kg/hr
(5 lb/hr)
0.07 g/Nm3
(0.03 gr/scf)
or
0.91 kg/hr
(2 lb/hr)
4.9 g/m^ of product
(1.0 lb/1000 ft2)
of product
[for average size plant
all cyclones
5.7 kg/hr
(12.5 lb/hr)]
Notes: 1. Guideline for waste directly fed into cyclone.
2. Guideline for sanderdust, wood chips, trimmings and other process waste particulate.
-------
Table 5-3. EMISSION FACTORS FROM VARIOUS PLYWOOD MANUFACTURING PROCESSES
Process source
category
Pollutant constituent
Emission factor
uncontrolled, 9.5-mm
(3/8-inch) plywood basis
Pollutant characteristics
Veneer drying
hardwood and
softwood
Volatile organic
compound
Aerosol organic
compound
Total organic
compounds
0.75 g/ra2 , o
(1.53 lb/10^ ft2)
[direct fired has additional
0.88 g/m2
(1.8 lb/10^ ft*)]
4.54 g/m2
(9.28 lb/10^ ft?)
5.29 g/m2
(1.08 lb/103 ft2)
-pinene
3-carene
Abietic-piinaric acids
sesquiterpenes, fatty
acids, resin esters,
resin alcohols
Particulate
4.6 mg/Nm^
(0.002 grains/scf)
Fine wood fiber
Sanding and
trimming operations
for hardwood and
softwood
Cyclone inlet
Cyclone outlet
fabric filter inlet
Fabric filter outlet
323 g/m2
(66 lb/1000 ft2)
3.2 g/m2
(0.66 lb/1000 ft2)
0.064 g/m2
(0.013 lb/1000 ft2)
Mood sanderdust, sawdust
Wood dust
Wood dust
Green material and
other non-sander
residues
Cyclone inlet
Cyclone outlet
930 g/in2
(190 lb/1000 ft2)
0.23 g/m2
(0.05 lb/1000 ft2)
Chipped wood, trimming
hogged material
-------
differences in sampling and analysis techniques discovered after
publication of the initial field test data. The factors are expressed in
terms of grams of pollutant emitted per square meter of 9.5-mm plywood on
a production basis. Since the factors are dependent on wood species, the
ratio of wood used was estimated and a composite factor developed. Wood
species usage was taken from U.S. Forest Service report data for the
19
Northwest and assumed to be Southern pine for the South.
Field test data and emission factors from both industry and
regulating air control agencies are conmonly expressed as particulate
grain loading for cyclones and fabric filters from sanding and trimming
operations. As discussed in Sections 5.1.3 and 7.1.3, test data were not
correlated to plywood production rates at the subject facility.
To determine an emissions factor for particulate from sanding and
trimming operations based on production requires that assumptions be made
on the industry as a whole. Two separate approaches were developed.
The first approach was based on pneumatic air requirements. The
total number of plants in operation was evaluated for 1978. This was
combined with the average total number of operating hours per plant
considering days of plant shutdown. This was combined with the air
requirements for each plant to pnuematically convey wood waste material,
inclusive of sander dust, sawdust, planer chip, and hogged trimming
sources. A total air requirement on an annual basis for all process
plants was thus arrived at for the year 1978. Finally, total air required
on a g/m of 9.5-irm plywood basis was calculated based on hardwood and
softwood production for 1978.
The second approach was based on the amount of dry wood dust
pneumatically transported. Residues generated were estimated from total
5-13
-------
19
wood material balances and production rates. This was divided into
dry fine material (sander and saw dust) and green wood and bark. All dry
fine material was assumed to be pneumatically conveyed and separated by
cyclones (99 percent effective). In addition, 11 percent of the green
residue was assumed to be chipped and pneumatically transferred; the
remaining green residue was assumed to be transported by direct
displacement. Cyclone effectiveness was selected at 99.97 percent for
green material.^" The results of these calculations are reflected in
Table 5-3.
It should be noted that these emission factors were derived from
available field test data. Many tests were conducted without the use of
proven and demonstrated sampling and analysis techniques. However, being
that these factors are based on field test data, they provide a basis for
estimating the national emissions level.
5.2 TOTAL NATIONAL EMISSIONS FROM THE PLYWOOD INDUSTRY
The total national emissions from the plywood industry for each major
manufacturing process are presented in this section. The methods of
estimating these emissions are also discussed. The emissions factors
presented in Section 5.1 are used with annual plywood production rates to
attain these emission estimates.
5.2.1 Total National Emissions From Veneer Dryers
The total national emissions from veneer dryers are based on
estimated softwood and hardwood produced in the current year of 1979. In
1979, the U.S. total production for softwood plywood is estimated to be
1.86 billion m^ (20.2 billion ft^) on a 9.5-mm production basis. The
U.S. total production for hardwood plywood will is estimated at
2 o
0.14 billion m (1.5 billion ft ) on a 9.5-mm production basis. Using
5-14
-------
2
the emission factor of 5.29 g/m , as derived in Section 5.1.1, and a
? p
total U.S. production estimate of 2.01 billion m (21.7 billion ft )
of 9.5-mm plywood, a total of 10,630 metric tons (11,700 short tons) would
be emitted as uncontrolled organic emissions on an annual basis. Of this,
approximately 9,125 metric tons (10,040 short tons) would be classified as
aerosol "condensible" organic compounds. Approximately 1,510 metric tons
(1660 short tons) would constitute the gaseous fraction of organic
compounds. Fugitive emissions are estimated to add 5 percent more organic
compounds.
By comparison, AP-42 guidelines would place the national emissions
level at 6,818 metric tons for total organics. In comparing these factors
with Oregon's SIP at 90 metric tons for low moisture fuel (less than
20 percent) and 180 metric tons for high moisture content fuel (greater
than 20 percent) as delineated by the SIP, the uncontrolled national
emissions are extremely high.
Emissions with the use of current control technology for veneer
dryers were calculated for two types of control. First, 50 percent of the
aerosol organic compounds were considered removed for veneer produced in
the State of Oregon using controls in place on dryers in that State as
noted in Section 5.1.1. Secondly, direct-fired dryer veneer production
2 o 1ft
with exhaust recirculation, 0.07 billion m (0.75 billion ft ),
was assumed to remove 45 percent (90 percent total organic control
efficiency for the treated 50 percent of the exhaust) of the gaseous and
aerosol organics. The results are presented in Table 5-4.
5.2.2 Total National Emissions From Sanding and Trimming Operations
The total national emissions from sanding and trimming operations is
^so based on 1979 estimated softwood and hardwood production. Emission
5-15
-------
Table 5-4. TOTAL NATIONAL EMISSIONS LEVELS
(metric tonnes (short tons))
Pollutant
Current
Emissions
1985
Emissions
Source
Uncontrolled
Current
Technology
Current
Technology
NSPS
voc
Dryer
—Veneer
--Oirect-Fired Fuel
Fugitive 4 Incinerators
Total
1510
355
182
2045
(1650)
(390)
(200)
(2250)
1455
318
182
1955
(1600)
(350)
(200)
(2150)
2170
440
200
2810
(2390)
(480)
(220)
(3090)
1340
380
200
1920
(1470)
(420)
(220)
(2110)
Aerosol Organic Compounds
Dryers
Fugitive
Total
9125
455
9580
(10040)
(500)
(10540)
6936
455
7391
(7630)
(500)
(8130)
8550
540
9090
(9400)
(590)
(9990)
5770
540
6310
(6350)
(590)
(6940)
PM
Sanders
Conveying Other
Wood/8ark
Miscellaneous
Total
6509
491
518
7618
(7160)
(540)
(680)
(8380)
5555
491
618
6664
(6110)
(540)
(680)
(7330)
5200
580
540
6320
(5720)
(640)
(600)
(6960)
4740
580
540
5860
(5220)
(640)
(600)
(6460)
5-16
-------
19
factors (primarily from a materials inventory in the Northwest)
correlated to a production basis were used. Approximately 682,000 metric
tonnes (750,000 short tons) are generated as dry wood waste from sanding
and trimming alone. This constitutes fine material fed into plant
cyclones. As previously discussed, the defined uncontrolled emission is
that of the outlet of the cyclone. Approximately 6,510 metric tons
(7,160 short tons) of wood particulate would be emitted as uncontrolled
from a cyclone. With a fabric filter in series, approximately
130 metric tons (140 short tons) of material would be emitted to the
atmosphere.
By comparison, control by the Oregon SIP would allow 11,960 metric
tons (10,850 short tons) of wood particulate to be emitted to the
atmosphere on an annual basis. The results are tabulated in Table 5-4.
Based on a material balance developed by the USFS for 1976, coarse
wood residues and bark that are generated would amount to approximately
14 million metric tonnes (15.5 million short tons) dry weight in 1979.^
After deduction of material that is removed whole (i.e., 65 percent of
cores) or conveyed by belt systems only an estimated 2.0 million metric
tonnes (2.2 million short tons) of residues are chipped and pneumatically
conveyed as other residues. Since such material is collected well by
cyclones (emissions of 0.25 kg/metric tonne fed or 0.5 lb/ton), no
additional control is practiced. Total annual emissions were calculated
at 490 metric tonnes (540 short tons).
5.2.3 National Emissions From other Plywood Industry Processes
A familiar part of small primary wood processing plants has been a
cone shaped metal waste wood incinerator called a "teepee" or "wigwam"
burner. Although such units are still used in some locations, their
5-17
-------
number has been greatly reduced. In the past 10 years they have decreased
19
from being found at a majority of plants to only 10 percent.
Markets for wood and bark residue have removed their necessity to the
extent that none are expected at new mills. Existing sources are
estimated to incinerate half of the unused excess residue or 63,000 metric
tonnes (69,000 tons). Half of this is assumed burned under uncontrolled
incineration (emission factors of 14 kg/tonne (28 lb/ton) of particulate
and 3 kg/tonne (6 lb/ton) of gaseous organic) while the other half is
burned in air recirculated incinerators (emission factors of 2.8 kg/tonne
(5.7 lb/ton) of particulate matter and 0.5 kg/tonne (1 lb/ton) of gaseous
19
organic).
Other miscellaneous and fugitive emissions include an estimated
organic aerosol and gaseous organic component of 5 percent of veneer dryer
emissions. This material seeps out of dryer cracks, doors, or ends and
escapes along with glue press emissions through ceiling vents.
The current particulate emission factors based on materials loading
also corresponds well with the average state regulation process weight
2 2
basis emission limit of 4.9 g/m (1 lb/1000 ft') for the industry's
2
average sized plant (10 million m per year). At this size plant,
10.5 kg are processed per hour and national emissions would be
9,900 metric tonnes (10,850 tons).
5.2.4 National Emissions Projected for 1985 With and Without NSPS
Projected total particulate emissions from the plywood veneer
industry were based on emissions from sanding and trimming operations,
pneumatic conveying of green wood materials and fugitive sources.
Fugitive and green wood conveying emissions were considered to continue
discharging at uncontrolled rates. An estimated 15 percent of current
5-18
-------
sander dust cyclones now have baghouses; a similar percentage of new
sources should also use baghouses. A telephone survey of new plants built
or expanded in 1979 indicated that several did have fabric filters in
addition to cyclones and other were using multiclones. Thus, new sources
are projected to use baghouses (15 percent) or multiclone separation (85
percent of production) for sanderdust emission control.
Estimated emission values for 1985 were developed using the following
criteria based on current best practices and industry trends.
• Old source emission factors remained the same as 1979; production in
2 ?
old sources decreased from 2.0 billion m (21.7 billion ft ) to
1.7 billion m^ (18.4 billion ft^) per year
2 ?
t New sources — production of 0.65 billion m (7 billion ft ) in
the South and Southeast as developed in Section 4.2
• Dryer gaseous organic and aerosol organic compounds emissions for new
sources calculated at 1.44 g/m^ (2.95 lb/10^ ft^) and
4.55 g/m^ (9.31 lb/104 ft^) respectively, based on Southern
o
pine usage. Fugitive emissions were estimated at 5 percent, as
was done for 1979 values, and were assumed unchanged by NSPS.
Current technology assumed no veneer exhaust control as all new
sources would be located in states which have no dryer limitations
now or planned. NSPS technology assumed that steam heated units have
their exhaust incinerated in boilers that have 99 percent removal of
organic pollutants; direct fired units would have their emissions
controlled with 50 percent being incinerated in the fuel cell
(90 percent destruction) and 50 percent being treated in a typical
scrubber. The scrubber would remove half of the aerosol organic
compounds but none of the gaseous organic. For new dryers, 80
5-19
-------
percent would be steam heated and 20 percent would be direct
fired, afraction estimated for retrofits and new sources
13
developed in 1979. Direct fired units also produce gaseous
organic from the fuel.
• Dry sander and sawdust emissions were calculated as uncontrolled
emissions (cyclone outlet) on the same basis as for old sources —
3.22g/m2 (0.66 lb/10^ ft2). Current technology emission
levels were calculated assuming 15 percent fabric filtration
subsequent to cyclones and 85 percent multiclone use at
0.87 g/m2 (0.018 lb/10^ ft2). NSPS levels were calculated
for all plants using fabric filters.
• Green material, other residue and miscellaneous emissions were
calculated with the same uncontrolled rates as for existing old
sources as identified above. No NSPS control is expected for
these minor sources.
The suimiarized emission values for 1985 were presented on Table 5-4.
5-20
-------
REFERENCES
1. O'Dell, F. G., et al. Pacific Northwest Emission Factor Reference
Manual. Air Pollution Control Association. June 1974.
2 Monroe, F. L., et al. Investigation of Emissions from Plywood Veneer
Dryers. Final Report for the Plywood Research Foundation, Tacoma,
Washington, and EPA (Contract CPA-70-138) February 1972.
3. Grimes, G. Direct Fired Drying -- The "Hydrid" Unit. SWF Plywood
Co. Medford, Oregon. April 5, 1978.
4. Monroe, F. L., et al. An Investigation of Operating Parameters and
Emission Rates of Plywood Veneer Dryers. Final Report No. 72/1-61
for the Plywood Research Foundation, Tacoma, Washington. July 1972.
5. Reference 2, p. 114.
6. Compilation of Air Pollutant Emission Factors (Second Edition). U.S.
EPA. AP-42. April 1973.
7. State of Oregon, Department of Environmental Quality. Oregon
Administrative Rules. Chapter 340, Div. 25.
8. State of Oregon, Department of Environmental Quality, Air Quality
Control Division. Veneer Dryer Control Device Evaluation,
Supplemental Report. December 14, 1976.
9. Mick, A. Current Particulate Emissions Control Technology for
Particleboard and Veneer Dryers. Paper presented to 1973 meeting of
the Pacific Northwest International Section of APCA, November 1973.
10. Waterland, L. R. Trip Report of November 13, 1979 visit to Georgia
Pacific, Springfield and Prairie Road, Oregon, plants. Acurex
Corporation. Morrisville, North Carolina. November 30, 1979.
11. Lambuth, A. L. Adhesives in the Plywood Industry. Adhesives Age.
38:21-26. April 1977.
12. Formaldehyde Linked to Cancer in Laboratory Rats. Forest
Industries. 106(13):75. December 1979.
13. Willard, H. K. Trip Report of November 12, 1979 meeting with
American Plywood Association Members, Eugene, Oregon. Acurex
Corporation. Mountain View, California. November 28, 1979.
14. Willard, H. K. Trip Report of November 15, 1979 meeting with
Department of Environmental Quality, Portland, Oregon. Acurex
Corporation. Mountain View, California. December 3, 1979.
15. Walton, J. W., et al. Air Pollution in the Woodworking Industry.
Paper presented at the 68th Annual APCA Meeting. June 1975.
5-21
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16. Georgia Department of Natural Resources, Environmental Protection
Division, Air Quality Control Section. Point Source Report. NEDS.
December 1975.
17. Tretter, V. J. Technology for the Control of Atmosphere and
Waterborne Emissions from Plywood and Lumber Manufacture. Presented
to 68th Annual AIChE Meeting, Chicago, Illinois. November 1976.
18. Canadian Provincial Pollution Control Board. Data presented at
Public Inquiry on Pollution Control Practices in the Forest Products
Industry. March 2, 1976.
19. Howard, J. 0. and B. A. Hiserote. Oregon's Forest Products
Industry. 1976 USDA Forest Service Resource Bulletin PNW-79. 1978.
p. 69.
5-22
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SECTION 6
EMISSION CONTROL SYSTEMS
Controlling air pollutant emissions from the manufacture of plywood
and veneer can be accomplished through changes in the manufacturing
operations or processes, or through the use of add-on emission control
equipment. The principles of these potential process changes and the
design and operation of pollution control equipment are presented in this
section.
As noted in Section 5, two major emission sources exist in the
plywood and veneer manufacturing processes. Pollution control practices
applied to these sources can be surmiarized as follows:
• Veneer dryer — organic/particulate emissions controlled in a few
plants
• Sanding, trimming and dry waste pneumatic transport — emissions
controlled with cyclones; cyclone separator emissions
occasionally controlled
The veneer dryer controls have been applied to meet state or local
regulatory agency visibility requirements.
Control systems can be classified into four types: cyclones,
filters, wet scrubbers, and incinerators. Cyclones and fabric filters are
primarily used to control sander and trim sawdust. Cyclones are simple
and reliable, but their efficiency is low for particles below
6-1
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20 microns.^" Fabric filters cost more than cyclones to install and to
operate, and require more maintenance, but offer greater collection
efficiencies. Wet scrubbers, incinerators, and various filtration systems
are used in many different configurations to control organic aerosol
emissions from veneer dryers. Detailed descriptions of current and
prospective control systems are discussed below.
6.1 CURRENT CONTROL TECHNOLOGY
The systems described in this section are currently being used in
production plants.
6.1.1 Veneer Dryer Emission Control
Present control strategy to reduce veneer dryer emissions has been
primarily focused on the removal of the organic aerosol component to
reduce plume opacity in response to local visibility regulations. The
controls presently in use can be classified into three types: filtration,
wet scrubbing, and incineration. Most of the concepts for reducing dryer
emissions have included process modifications directed toward reducing the
discharge volume flowrate (m /s) of emitted gases. Some have used heat
recovery steps, while others have achieved a reduction in consumption of
primary fuel through a total systems approach. As most systems are custom
designed, the general concepts behind filtration, wet scrubbing, and
incineration are first discussed and then specific systems are detailed.
Data from limited sources are presented in Table 6-1 to provide a
qualitative concept of control costs. Each entry represents input from a
single company or may represent an average for several mills within a
2
single corporation. Tables 7-4, 7-5, and 7-6 list the operating
characteristics of the veneer dryer emission control systems currently in
use.
6-2
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Table 6-1. VENEER DRYER EMISSION CONTROL COSTS2
Cost 1977 dollars
Equipment type
Capital
Operating
Maintenance/effectiveness
Filters
$120,000
(200 hp fan, pump)
Wet Scrubbers
(Water)
(Caustic foam)
$100,000
$120,000
$10,240/yr
Weekly maintenance and
2 to 3 months blade
replacements
1/4 man-month/mo.
(Intermediate)
$250,000
($14,400/m3/s)
$15,000/yr
70>6 efficient
(did not meet Oregon
requirements)
(With Brink)
$300,000
($18,000/m3/s)
$30,000/yr
95% collection
efficiency, fouling
problems
Incinerators
$250,000
Ooes not meet Oregon
requirements
as a single source
6-3
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6.1.1.1 Filtration. Filtration applied to veneer dryer emissions
generally combines initial water spray cooling of the stack gas followed
by collection of the condensed droplets on a filter medium such as a glass
fiber mat or a sand bed. In mat filters, the condensed droplets migrate
through the filter as the filter loads, necessitating a secondary droplet
or mist collector. Moving filter beds present a fresh filter surface; the
speed of the filter movement is adjusted to optimize collection while
minimizing droplet breakthrough. Filter material is usually not recycled
2
in these systems.
Sand bed filters accumulate the condensed droplets on the bed face
(usually horizontally fed). Gas flows across the bed face. Gravity
conveys the pitch-water condensate through the bed to a separation basin
below. Separated water is recycled while the pitchy condensate is removed
when cool.
6.1.1.1.1 Aero-Vac Scrubber, Aero-Vac Systems, Corvallis,
3
Oregon. The Aero-Vac scrubber uses a water bath to condense and
agglomerate the organic aerosol fraction. Wetted dacron filter bags are
used to collect the condensed material. The air to cloth ratio is about
2.5 cm/s (5:1 ft/min). A proprietary chemical is added to the water,
which is recirculated to the bath and filter bags in order to keep the
organic material in solution.
The Aero-Vac Scrubbing unit has been installed at the Brand-S Plywood
plant in Corvallis, Oregon. No emissions data were available.
6.1.1.1.2 Rader Sand Filter, Rader Co., Inc., Portland, Oregon.**
The Rader Sand Filter (previously the Becker Sand Filter) is an adaptation
of sand filters used in water treatment. Gases from the veneer dryer pass
6-4
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through a preconditioning water spray into a sand bed where the water
pitch-organic fraction flows down the sand bed face and out a port to a
separation basin below. The bed is periodically backwashed with air and
water to remove the collected material. The pitch-organic fraction is
drawn off for barrel storage (it is burnable) while the water at 310°K
(120°F), is recycled to the spray system.
The Rader Sand Filter is installed at the Willamette Industries
Plywood Plants in Sweet Home, Oregon and Dallas, Oregon. The capital cost
of the Sweet Home dryer control was $250 to $300 K (1979 dollars). No
emissions data could be obtained for this plant. Emissions data from the
Dallas plant are surmiarized in Tables 7-4 and 7-5.
6.1.1.2 Scrubbing Systems. Wet scrubbers have come into relatively
common use on the West Coast to control veneer dryers. At least 19 types
of units are installed in Oregon, Washington, and Northern California.
Scrubbers are add-on units which require little or no modification to
the operation of the veneer dryers. They remove the organic aerosol
fraction from the exhaust gas stream by effecting contact between the gas
stream and a liquid. The primary mechanism for particulate collection in
wet scrubbers occurs by impaction on water droplets. Droplet impaction
increases the effective particle size, facilitating removal. Scrubbers
are designed to cause the gas-liquid contact in various ways. Some of the
more common designs are shown schematically in Figures 6-1, 6-2, and 6-3.
The three scrubber designs are shown in order of energy levels necessary
to operate them:
• Low energy — spray tower
• Medium energy — packed column
• High energy — venturi scrubber
6-5
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LIQUOR
DISTRIBUTOR
CLEAN GAS OUTLET
3* LIQUOR
INLET
Figure 6-1. Open spray tower.
6-6
-------
TRAY TUBE
LIQUOR
DISTRIBUTOR
OIRTY GAS
INLETS
t
CLEAN GAS OUTLET
a
-DE-ENTRAINMENT
SECTION
7
sd|
*AAAAAA
" / V t
j
) t
'LIQUOR
INLET
SCRUBBER
PACKING
PACKING
SUPPORT
GRID
J- LIQUOR
DRAIN
Figure 6-2. Packed-bed scrubber.
6-7
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DIRTY GAS
INLET
MAKEUP 4
LIQUOR -
INLET «H
LIQUOR
DISTRIBUTION
WEIR
CLEAN GAS OUTLET
DE-ENTRAPMENT
SECTION
VENTURI
SECTION
LIQUOR TO
RECIRCULATION
PUMP AND DISPOSAL
Figu"? 5-3. Venturi scrubber.
6-8
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A scrubber's removal efficiency is directly related to the energy
required to operate that scrubber. The required operating pressure drop
varies inversely as the dust-particle size for a given collection
efficiency, or, for a given dust particle size, collection efficiency
increases as operating pressure drop increases. Current wet scrubbers on
veneer dryers range from simple single- stack, low pressure drop, spray
chamber type systems to sophisticated high pressure drop units. Each of
the systems in current use will be discussed briefly below.
6.1.1.2.1 Burlev Industries Scrubber. Burley Industries. Coos Bay,
3 5
Oregon. ' The Burley Industries scrubber is a simple spray chamber
device designed to handle a single dryer exhaust stack. No additional
fans are needed since the pressure drop through the scrubber is on the
order of 0.25 to 0.50 kPa (1 to 2 in. WG). Caustic is added to the
recirculated water for pH control.
Burley scrubbers are currently the most common design applied to
veneer dryers. Ninety-four percent of all veneer dryer scrubbers in the
country today have been designed by 8urley. Sixty-five units have been
sold to date. Emissions data for a standard scrubber are presented in
Table 7-5.
6.1.1.2.2 Air Guard Scrubber, Brizard Construction Company, Areata,
California. The Air Guard unit uses spray nozzles and a scrubber
chamber to cool and condense veneer dryer hydrocarbon emissions. Spray
droplets are separated from the cooled exhaust gases. Spray water is
recirculated and caustic is added for pH control.
The Air Guard units are installed in Northern California at
Cloverdale Plywood, Sierra Pacific Fiberboard, and Simpson Timber Company,
Areata, California. No emissions data were available. Continuation of
6-9
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this line of scrubbers is uncertain, since the Brizard Construction
Company recently went out of business.
6.1.1.2.3 Buchholz Foam Generator, Buchholz Industries, Portland,
OregonIn the Buchholz scrubbing system, the veneer stack gases are
cooled by evaporation of water passed through a sodium base foam. The
gases pass over a steel grate, while a caustic solution flows over the
grate in the opposite direction. The gases and solution mix to generate a
bubbly foam. The gases cool and the organic aerosol condenses to droplet
size particles.
The sequence of bursting and re-forming bubbles creates turbulence in
the gases contained within the bubbles and brings the tiny droplets of
condensed material into contact with the bubble surface. As the organic
material is soluble in the caustic solution, the tiny droplets dissolve
into the caustic solution at the bubble wall. The foam is then separated
into a liquid, which is recirculated, and a gas, which is discharged to
the atmosphere.
Buchholz systems have been installed at the Publishers' Paper plywood
plant and the Multnomah Plywood plant, both in Portland, Oregon.
Publishers Paper is currently out of business and the Multnomah plant was
sold to the Murphy Company. Emissions data from the Multnomah plant are
summarized in Tables 7-4 and 7-5.
6.1.1.2.4 Leckenby Scrubber, Leckenby Company, Seattle,
3 6
Washington. ' The Leckenby system utilizes a spray section ahead of
the scrubber for gas cooling and conditioning. The small self-contained
unit can be attached to a veneer dryer stack. Pitch is decanted from the
scrubber water and disposed. The clarified water is recirculated.
6-10
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The leckenby system is installed at Champion International's Seattle
plywood mill and at Puget Sound Plywood in Tacoma, Washington. Emissions
data for the Leckenby scrubber are given in Table 7-4.
6.1.1.2.5 Georgia-Pacific Scrubber and Demister, Georgia-Pacific
3 8
Corporation, Portland, Oregon. ' The Georgia-Pacific scrubbing system
consists of a water spray section, high efficiency cyclone separators, a
packed tower scrubber, and an optional Brink demister unit. The exhaust
gases from multiple veneer dryers are run through insulated ducting to a
central spray section. After cooling and organic aerosol agglomeration in
this section, the gases pass through a high efficiency cyclone section
where large particles are removed. A fan blows the cyclone exhaust into a
tower, the bottom section of which is packed with polypropylene pall
rings. The top section is designed to accommodate a Monsanto Enviro-Chem
Brink Mist Eliminator system. Water and pitch from the tower and cyclones
drain into a separation tank. After separation, the water is recycled
through a filter and pumped back through the spray section.
Georgia-Pacific's scrubber has been installed at their Springfield
and Prairie Road Plants. At the Prairie Road plant, the Brink Mist
Eliminator has been removed because of fouling problems. Emissions data
for this plant are presented in Tables 7-4 and 7-5.
6.1.1.3 Incineration Systems. Incineration systems are occasionally
used to control emissions from veneer dryers. If a boiler or other
combustion device is located near a veneer dryer, and if this combustion
device can handle the volume of exhaust gases (5 to 10 m /s, or 10,000
to 20,000 acfm), the veneer dryer emissions can be incinerated.9 This
is done by using the veneer dryer exhaust gases as combustion air in the
combustion unit.
6-11
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Two general types of incineration systems exist: exhaust gas recycle
and once-through systems. The first type is applicable only to
direct-fired systems. It uses wood waste as its primary fuel source to
burn the organic emissions from the dryers. A portion of the dryer
exhaust gases are cycled through the wood-fired burner, then back to the
dryer, with a bypass controlled to maintain the desired moisture content
in the dryer. This system has the advantage of both incinerating the
dryer emissions and saving the sensible heat from the dryer vent gas by
using it as combustion air. However, only about half of the dryer gas can
be circulated through the burner system, as this is all that can be used
for combustion and combustor exit gas temperature control. Sometimes the
unrecirculated portion of the dryer gas is scrubbed.
The second type of incineration system is the once-through or add-on
method where the gases from the dryer are passed through the incinerator
and discharged directly to the atmosphere. This system is applicable to
steam-heated dryers. In most systems, the vented dryer gases are used as
combustion air (either overfire or underfire) in the steam-generating
boiler. The sensible heat of the dryer gas is again preserved by using it
as combustion air.
Other systems in this category include thermal or catalytic
incineration even though these systems do not recover the sensible heat in
the dryer exhaust. All systems reportedly can meet a 10 percent opacity
standard. Each of these incineration systems will be discussed briefly.
6.1.1.3.1 Boiler Incineration.^'^ Veneer dryer exhaust emissions
can be incinerated by ducting these off-gases to the plant boiler.
Recovery of the sensible heat of the dryer gas is accomplished by using
these gases as combustion (overfire or underfire) air on the boiler.
6-12
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These systems have the advantage of low capital cost and minimal operating
costs but can be limited in the amount of dryer gas that can be
incinerated by low boiler combustion air requirements.
At the Champion International plant in Lebanon, Oregon,^ veneer
dryer exhaust streams are fed into the power boiler (a dutch oven boiler
design). Fuel includes hogged fuel (bark and wood), dry trim, veneer
clipping and sanderdust from the plywood plant. This system had a capital
cost of $500,000 and requires 2 man-days/week plus $10,000 per year for
its operation. One 75-kW (100-hp) fan is in continual operation. The
available emissions data are presented in Tables 7-4 and 7-6.
3
6.1.1.3.2 Agnew Environmental Products, Grants Pass, Oregon. The
Agnew system uses a portion of the dryer gas as combustion air for a
hogged-fuel-fired heater which supplies dryer direct heat. Thus, it
differs from the above in that hogged fuel is used in a dryer burner
instead of in a boiler.
The Agnew system is installed at 4-Ply, Inc. in Grants Pass, Oregon.
No emissions data were obtained.
6.1.1.3.3 Enerqex System.6 Energex burners are compact woodwaste
burners which can be used to supply heat to veneer dryers. The principal
function of these units is to save on fuel costs, as they replace
gas-fired heating systems in veneer dryers. Up to 50 percent of the
exhaust gas from the dryer is used as combustion air for the burners,
thereby incinerating the organic material. The exhaust gases from the
burners are sent to the veneer dryer as its heat supply. Since part of
the exhaust gas does not pass through the burner, incineration of all
dryer organic emissions is incomplete, but the organic fraction discharged
to the atmosphere is significantly reduced.
6-13
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The Energex system is installed at SWF Plywood in Grants Pass,
Oregon. The available emissions data are presented in Table 7-4.
6.1.1.3.4 Moore Lo-Em System, Moore-Oregon, North Portland,
g
Oregon. The Moore Lo-Em system burns pulverized wood waste to
incinerate the organic fraction of the exhaust gases from veneer dryers.
A portion of the dryer exhaust gas is passed through a stainless steel
plenum which is heated to between 810° to 920°K (1,000° to 1,200°F).
This heats the dryer exhaust and incinerates the organic components.
Makeup air is drawn into the dryer gas recirculation system to replace the
exhaust gases discharged through an exhaust stack.
The Moore Lo-Em system is installed at Boise Cascade Corporations'
Sweet Home plant and at Lane Plywood in Eugene, Oregon. The available
emissions data are presented in Table 7-4.
6.1.1.3.5 Catalytic Incinerator, Coe Manufacturing Company,
Portland, Oregon.^ Pilot sized catalytic afterburners have been used
to control veneer dryer emissions. Catalyst temperatures are controlled
by a natural-gas-fired burner and a plenum chamber is provided to ensure
mixing of the gas stream before injection through the catalyst. Low
pressure drops occur across this system, but additional energy is required
to raise the gas temperature.
The Catalytic Incineration system has been installed at the Champion
International plant in Lebanon, Oregon, but is no longer in use.
Emissions data from a single dryer zone with catalytic afterburner are
given in Tables 7-4 and 7-5.
6.1.2 Particulate Control of Fine Wood Residue
Sanding and trimming operations in plywood plants generate large
quantities of sawdust. This dust is generally collected and used in
6-14
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combination with other plant dry waste as dryer or boiler fuel. Pneumatic
transfer systems are used to capture the dust at the sanders and trim saws
and transport it to the cyclones. Sometimes a baghouse is used in series
with the cyclones. Air volumes of 9.4 to 18.8 m /s (20,000 to
40,000 acfm) are used in present day plants to capture dust at sanding and
g
trimming machines. Descriptions of both fabric filters and cyclones
are presented below.
6.1.2.1 Cyclones. Cyclones use centrifugal force to separate the
dust from the air stream transporting it in a pneumatic transfer system.
As shown in Figure 6-4, the dry wood waste and sawdust enter the top of
the cyclone. The tangential inlet (or inlet guide vane) spins the air
stream in a helical path down the inside of the cyclone. Particles in the
air stream are forced to deviate from a straight path as they rotate about
the cyclone axis. The linear momentum causes the particles to move toward
the cyclone walls. As they reach the walls, their velocity is decreased
by drag so that gravity and the downward motion of the air stream can
carry them to the bottom for collection. As the air stream approaches the
bottom, it changes direction and goes toward the discharge in a return
vortex. Because of the characteristics of cyclone separation (primarily
dependent on cyclone diameter), many small cyclones work better than a few
large cyclones.
Virtually all pneumatic dust conveying systems from sanders and trim
saws are controlled with one or more cyclones. For this reason, cyclones
are considered part of the sanding and trimming processes in this report.
Consequently, as noted in Section 5, uncontrolled emissions from these
processes are defined as those from typical cyclones.
6-15
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Figure 6-4. Cyclone separator.
6-16
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Small diameter cyclone clusters have demonstrated excellent
sander/trim sawdust collection efficiencies. The pressure drop for such
systems ranges between 0.9 and 2.5 kPa (3.5 to 10 in. WG) and typical
3 9
emission rates are less than 115 mg/Nm (0.05 gr/scf). Cyclones also
have the advantage of low maintenance; reliabilities approach 100 percent.
Fire and explosion problems exist but damage can be quickly repaired.
Cyclones have one significant limitation; as particle size drops,
cyclone collection efficiencies diminish. This results in a minimum
outlet grain loading attainable. Consequently, cyclones are not useful as
a final collection device for fine particulates. To more effectively
collect sander and trim sawdust, cyclones can be used as a precleaner for
the more efficient baghouse.
6.1.2.2 Fabric Filters. To increase sander and trim sawdust
collection and comply with stringent local regulatory requirements,
baghouses are often used in series with cyclones for dry material
collection. Baghouses consist of an arrangement of bags (fabric filters)
suspended in a structural housing.
Fabric filters collect particles from a gas stream by impingement on
a filter surface. Particles accumulate on the fabric forming a "cake"
that becomes an effective part of the filtering medium. When the cake
becomes too thick, an excessive pressure drop results. Thus, the filter
must be cleaned periodically. Cleaning methods include shaking, pulsing,
or reverse air flow. These operations loosen the caked dust, which then
falls into a hopper beneath the bags and is conveyed for disposal. A
fabric filter unit is shown in Figure 6-5.
6-17
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Figure 6-5. Typical pulse jet fabric filter configuration.
6-18
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Operating experience with fabric filters has shown that collection
efficiencies generally exceed 99 percent. This collection efficiency is
attained with a typical air to cloth ratio of 3:1 cm/s (6:1 ft/min). To
insure good operation, air to cloth ratios should not exceed 5:1 cm/s
(10:1 ft/min). The only major drawback with the use of fabric filters on
sander and trim sawdust is the danger from fires and explosions. This
hazard can be minimized by adequate fire protection systems installed as
9
an integral part of the dust collection system.
Base installed fabric filter costs are usually in the range of $1,000
to $4,000 per mVs ($0.50 to $2.00 per acfm) in 1975 dollars.^ These
costs will vary in proportion to the size of the filter and with respect
to the kind and the arrangement of fabric and cleaning apparatus. Total
installed costs, including the required ancillary equipment, may be 1.1 to
10 times the base cost of the fabric filter.
6.2 ALTERNATIVE CONTROL TECHNIQUES
Two alternative control techniques designed primarily for veneer
dryers will be discussed in this section. Both systems, low-temperature
drying, and wet electrostatic precipitators (ESP's), have been used to a
limited extent in experimental situations, but they have not been
developed into commercially sold emission control systems.
Alternative control techniques for sanderdust emissions have not been
studied extensively. Systems combining cyclones and baghouses have proved
both effective and economical.
6.2.1 Low Temperature Drying
Drying temperatures can be reduced to an approximate range of
410° to 420°K (280° to 300°F) in order to control veneer drying
emissions. By lowering the drying temperature, the amount of organic
6-19
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evolved is reduced. At sufficiently low drying temperatures, the organic
load of the exhaust is low enough to meet 20 percent maximum opacity
limits. Data do not exist that show the amount of actual gaseous organic
compounds exhausted by this technique, however. To compensate for the
reduced drying temperature, increased air circulation rates and drying
time are required. This results in reduced production and increased power
costs to drive circulating fans. Overall, the technique's success is
dependent on closely controlling the dryer temperatures, which is
difficult to effect. The major advantage of this system is low cost.
Dryer temperature reduction requires little increase in fuel costs and
small capital expenditures compared with emission control equipment.*'
One technique currently in use employs additional changes:
• Dryer air is circulated parallel to the flow of the veneer
• The moisture content of the dried veneer is increased by about 50
percent to a range of 6 to 8 percent.0
The increased veneer moisture content necessitates changing glues in the
plywood layup operation.
6.2.2 Wet Electrostatic Precipitators
Wet ESP's have been used to a limited extent for both sanderdust and
veneer dryer emission control. They were originally abandoned as a viable
control technique because of reliability problems and high costs, but
advances in the state of the art may now have overcome these difficulties.
Wet ESP's use an electrostatic field to separate charged particles
from the gas stream. The process occurs Ui three steps:
• Charging, where the particle passes through a region of ionized,
electronegative gas and takes on an electrostatic charge
6-20
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• Collection, where the charged particle migrates toward, and
collects on, a grounded metal surface
• Removal, where the layer of agglomerated particulate is flushed
off the collector surface.
The reason ESP's of the wet rather than dry design are used involves the
physical characteristics of the collected particles; veneer dryer organic
aerosols stick to the electrode. Rapping (used in dry ESP's) will not
remove these particles. Wet ESP's also diminish the possibility of fires
or explosions.
The collection efficiency of the ESP is related to the time of
particle exposure to the field, the strength of the field, and the
resistivity of the particle. These factors can be optimized in a
precipitator designed for a given application to produce good collection
efficiencies with plume opacity of less than 5 percent for veneer
dryers. No data are available on other dryer exhaust parameters
affected by this technique.
6.3 CANDIDATE "BEST SYSTEMS" OF EMISSION REDUCTION
The "best systems" to control emissions of dry waste from sanders and
trim saws, and of organics from veneer dryers will be discussed in this
section. Other process emissions are uncontrolled due to insignificant
pollutant quantity. The criteria used to select a "best system" include
effectiveness, commercial or demonstrated availability, cost, and
reliability. All systems chosen have been used in production plants.
6.3.1 Veneer Dryer Emission Control
Of the available veneer dryer control methods, incineration is
considered the "best" control method. One major advantage places
incineration above other control systems. Other systems, such as
6-21
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scrubbers, by design remove primarily only the organic aerosol and
particulates; incineration has the potential to reduce both the gaseous
and aerosol organic components.
One of two types of incineration control systems should be used
depending on the veneer dryer heat source. For steam-heated dryers, the
dryer gas is ducted to the boiler. Boiler systems include both
retrofitted boilers and ones newly designed for accepting dryer exhaust.
In the Champion International plant in Lebanon, Oregon, dryer gas from six
3
veneer dryers is fed to the boiler at an average rate of 20 m /s
(43,000 cfm).^ For direct-fired dryers, the dryer gas is ducted to the
wood-fired heat cell. As the heat cell cannot accept all of the dryer
gas, some must be vented. At the Georgia-Pacific Prairie Road Plant, this
vented exhaust flows to the plant's scrubber system to improve emission
control.^
As noted in Section 6.1, several different incineration systems are
currently marketed. Installed production models number considerably less
than scrubbing systems. The primary reason for this is the scrubber's
extensive use in other industries for pollution control that facilitated
their application to the plywood industry. Cost figures, though, tend to
indicate that for plants with suitable physical relationships between
existing dryers and boilers, incinerators may be the lowest cost type
installation.
6.3.2 Sanders, Saws, and Pneumatic Dry Fine Solids Conveying
The predominant method for collecting sander and trim sawdust and
other fine solid dry material is pneumatic removal. The best system for
solids removal from transfer air is a combination of cyclone and
baghouse. This system has proved both effective and economical; it is
6-22
-------
considered by both state agencies and the industry to be the "best
system". Other methods, including wet ESP's, have been used
experimentally but reliability and cost problems have prevented extensive
commercialization of these systems.
Figure 6-6 diagrams a standard system employing a primary cyclone in
conjunction with a baghouse. The system works as follows:
1. Sander and trim sawdust or other dry fine material is
pneumatically collected and transported from the source location
to the primary cyclone
2. The cyclone removes particles greater than approximately 15 to 20
microns
3. The remaining particulate matter is transported pneumatically to
the baghouse
4. The baghouse removes virtually 99+ percent of the remaining
wooddust discharging the clean air to the atmosphere
5. The fabric filters are cleaned either periodically or continually
by reverse cycling of the air
6. The filter's accumulated dust (its mass increased through
agglomeration) is pneumatically recycled back to the cyclone.
This feature is optional. Other systems remove collected dust
from the baghouse separately.
Experience within the plywood industry with such systems is
relatively extensive. Cyclones and baghouses together are frequently used
for new plants whenever dry particulate emissions need to be controlled.
The only major drawback of these systems is the danger from fire and
explosions especially in the baghouse. As noted previously, this hazard
can be minimizes by adequate fire protection systems installed as an
integral part of the dust collection system.
6-23
-------
PNEUMATIC
TRANSFER OF
SAWDUST AND
WOOD WASTE
MATERIAL
DISCHARGE
Figure 6-6
t
P
—
1
t_
P:
\|
--
J
—
L
'EFFLUENT
AIR BYPASS
CLEAN AIR
DISCHARGE
FILTERING
CYCLE
particulate control system.
-------
REFERENCES
1. Edminsten, N. G. Controlling Particulate Emissions from Wood
Particle Dryers. (Paper presented at the 1976 Annual Meeting of
Pacific Northwest International Section Air Pollution Control
Association. Anchorage. September 15-17, 1976.)
2. Adams, D. F. Veneer Dryer Emissions and Control Systems. Washington
State University. Pullman, Washington. June 29, 1977.
3. Tretter, V. J. Jr. Plywood Veneer Dryer Emission Control Systems.
(Paper presented at 69th Annual Meeting of Air Pollution Control
Association. Portland. June 27-July 1, 1976.)
4. Willard, H. K. Trip Report of November 14, 1979 visit to Willamette
Industries, Sweet Home, Oregon. Acurex Corporation. Mountain View,
California. December 3, 1979.
5. Telecon. Murphy, G., Acurex Corporation, Mountain View, California,
with Burley Industries, Coos Bay, Oregon. November 2, 1979.
6. Burkart, A. Veneer Drier Emissions Control Systems. Oregon
Department of Environmental Quality. June 1975.
7. Telecon. . Murphy, G., Acurex Corporation, Mountain View, California,
with Bucholz Industries, Portland Oregon. November 2, 1979.
8. Waterland, L. R. Trip Report of November 13, 1979 visit to
Georgia-Pacific Corporation, Springfield, Oregon. Acurex
Corporation. Morrisville, North Carolina. November 30, 1979.
9. Tretter, V. J. Jr., et al. Technology for the Control of Atmospheric
and Waterborne Emissions from Plywood and Lumber Manufacture. (Paper
presented to 68th Annual AIChE Meeting. Chicago. November 1976.)
10. Willard, H. K. Trip Report of November 14, 1979 visit to Champion
International Corporation, Lebanon, Oregon. Acurex Corporation.
Mountain View, California. November 28, 1979.
11. Mick, A. Current Particulate Emission Control Technology for
Particleboard and Veneer Dryers. (Paper presented to 1973 meeting of
the Pacific Northwest International Section Air Pollution Control
Association. Seattle. November 28-30, 1973.)
12. The Fabric Filter Manual. Charles E. Billings, ed. Mcllvaine Co.
Northbrook, Illinois. 1975.
6-25
-------
SECTION 7
EMISSIONS DATA FOR THE PLYWOOD MANUFACTURING INDUSTRY
This section presents available test data assembled during this
source survey. Test data for various plywood manufacturing processes are
presented and categorized with respect to the particular manufacturing
process. The validity of the data is discussed. A discussion of the
various sampling and analysis procedures as applicable to this process
industry is also presented. Test data presented in this section were used
in Section 5 to determine a national emissions level for each
manufacturing process category.
7.1 AVAILABLE TEST DATA FOR THE PLYWOOD MANUFACTURING INDUSTRY
Some limited test data were found in test reports published by state
and local air pollution control agencies, EPA documents, and publications
from the plywood industry and its trade organizations. Other relevant
data were obtained through extensive literature searches. EPA regional
offices, state and local air pollution control offices, universities, and
private companies were also contacted. The primary source of information
was trade organization prepared field test reports. The data presented in
this subsection are categorized with respect to the particular
manufacturing process. Major sources of potential emissions were
discussed in detail in Section 4 and to a lesser degree in Section 5.
7-1
-------
7.1.1 Emission Test Data From Veneer Dryers
The most extensive series of tests to date were conducted by
Washington State University (WSU).1 Tests were conducted on nine
Pacific Northwest and five Southern plywood veneer dryers in 1970 under a
grant from the Plywood Research Foundation and the EPA. Both gas- and
steam-heated, jet and longitudinal dryers drying 11 wood species were
tested. Visual observations of equivalent opacity were measured. Amounts
of both gaseous and aerosol organics emitted from the dryers were sampled
and analyzed in 51 separate tests. Over 700 gas chromatograms were
recorded. Table 7-1 tabulates the WSU test results.
Emission factors were calculated for gaseous, condensible and total
organic compounds on a gram per square meter basis. WSU defined gaseous
and condensible fractions based on their sampling methodology. This is
discussed in Section 7.2. Data presented in Table 7-1 and all subsequent
tables presenting test data are reported in the original units used in the
test reports. Emission factors are also parenthetically noted in English
units on data sunrmaries.
3
From this study, WSU calculated dryer emission factors as 4.6 mg/Nm
of particulate as wood fiber (0.002 grains per dry scf), 0.73 g of gaseous
organic and 1.9 g of condensible organic, for a total of 2.63 g total
2 ?
organic per m on a 9.5-mm production basis (5.4 lb/10,000 ft of
3/8-inch production basis plywood) for steam-heated dryers. Gas-heated
dryer emissions were 4.6 mg/Nm particulate as wood fiber (0.002 grains
per dry scf), 2.98 g of gaseous organic and 1.07 g of condensible matter
for a total of 4.05 g total organic per m of 9.5-mm plywood
(8.3 lb/10,000 ft^ of 3/8-inch production basis). Besides the variable
parameters of dryer process operation, organic emission factors were
7-2
-------
Table 7-1. TEST DATA FROM VENEER DRYING OPERATIONS
Tests conducted by: Washington State University for the Plywood Research
Foundation and EPA Contract No. CPA-70-138, 1970.1
Test method used: WSU method
Dryer type: Steam heated Operating opacity: 20%
Dryer
ref.
No.
Wood
species
Dryer
production,
ft2 of 3/8-
inch per hr
Organics, lb/10,000 ft2
produced
No. of
tests
Gaseous
Condensible
Total
9
Doug, fir sap
6580
N/D
5.13
5.13
2
12
Doug, fir sap
3474
N/D
3.29
3.29
2
12
Spruce sap
3912
N/D
3.43
3.43
2
15
Doug, fir heart
11,970
1.85
3.48
5.34
1
15
Doug, fir sap
9267
0.74
4.54
5.29
1
15
Pond, pine sap
8245
2.95
8.02
10.97
1
15
Hemlock sap
9060
0.39
1.14
1.53
1
15
Larch sap
8867
0.34
3.40
3.74
1
15
White pine sap
9860
1.09
6.13
7.22
1
19
Doug, fir heart
16,386
0.38
2.44
2.83
2
19
Doug, fir sap
6636
0.63
5.73
6.36
2
27
White fir sap
6218
0.03
0.51
0.54
2
28
Doug, fir heart
10,475
0.36
3.72
4.09
3
28
Doug, fir sap
6439
0.51
4.54
5.05
3
31
Southern pine sap
9004
2.63
3.13
5.76
6
32
Southern pine sap
13,400
1.65
6.33
7.98
4
35
Southern pine sap
8833
4.83
2.71
7.55
2
Total of sources tested: 11
Mo. of different wood species: 9
Total no. of tests for this reference: 43
7-3
-------
Table 7-1. Concluded
Tests conducted by: Washington State University for the Plywood Research
Foundation and EPA Contract No. CPA-70-138, 1970.1
Test method used: WSU method
Dryer type: Gas fired Operating opacity: 20%
Dryer
ref.
No.
Wood
species
Dryer
production,
ft2 of 3/8
inch per hr
Organics, lb/10,000 ft2
produced
No. of
tests
Gaseous
Condensible
Total
36
Southern pine sap
8195
1.62
4.05
5.67
5
37
Southern pine sap
10,100
3.99
2.26
6.25
2
23
Doug, fir sap
5054
10.37
4.05
14.41
3
24
Doug, fir sap
47 7 5
7.43
0.56
7.99
1
25
Doug, fir sap
5432
4.80
2.50
7.31
2
26
Doug, fir other
5038
2.02
1.54
3.57
2
Total of sources tested: 4
No. of different wood species: 2
Total no. of tests for this reference: 8
7-4
-------
reported to vary due to dryer configuration (jet or longitudinal), wood
species types and fuel burned. A statistical treatment of the data from
all dryers tested by WSU gave average emission factors for total organics
at 2.80 g per of 9.5-irm plywood (5.7 lb/10,000 ft^ of 3/8-inch
plywood) with average condensible emissions at 1.76 g, and average gaseous
organics at 4.56 g per m^ (3.6 lb and 2.1 lb per 10,000 ft^ of
3/8-inch plywood).*
WSU also concluded that due to the large variations in dryer
operating variability and condition, variations in stack opacity, water
vapor content and total organics emitted from the stack resulted. The
most important variable was stack damper setting. A dryer operated with
stack dampers open would have a high volume of gas flow, low plume opacity
and generally lower gaseous and condensible concentrations. However, for
a dryer operated with stack dampers nearly closed, production was higher,
gas volume flowrate lower, plume opacity higher, gaseous and condensible
organic concentrations higher but total organics based on production lower.
In support of this, WSU conducted additional testing on one
steam-heated and two gas-fired dryers during the drying of Douglas Fir
heartwood. These Pacific Northwest dryers were tested under various
operating conditions to determine the degree that their organic emission
rates could be controlled by varying dryer temperature and stack damper
settings.
By setting stack dampers for low velocity, low exhaust volumes,
higher dryer temperature, and higher dryer gas moisture content, higher
dryer gas specific heat and available heat were realized. Visible water
plume and higher stack opacities as well as an increase in stack organic
concentrations were the result. However, production rate also increased
7-5
-------
2
up to 10.6 percent. Therefore, total emissions per m of 9.5-mm plywood
were less than for high volume damper setting operation. Conversely,
dryers with high exit velocities (10 m/s and higher) had a visible water
plume and very little visible blue haze. An increased volume flow out of
the stack resulted in a higher air exchange rate within the dryer per unit
time. This increase in dilution air caused a corresponding reduction of
water and organic concentrations in the stack. Therefore, the opacity of
stack plumes were reduced by opening stack dampers. Opacities as low as
zero percent were occasionally had. However, dryer temperature was
reduced and therefore production rate was decreased relative to low damper
2
setting operating conditions. Thus, organic emissions reported as g/m
of 9.5-mm plywood were highest on dryers with dampers open. The composite
results of these tests are shown in Table 7-2. Large variations in
results were due not only to differences in damper setting but also to
interruptions in veneer feedrate and discontinuities in dryer operation.
Wood fiber particles were the only true particulates found in the
stack at stack temperatures. Of the 15 samples taken, grain loadings of
2.3 to 34 mg/Nm^ (0.001 to 0.015 gr/scf) were reported.
Shown in Table 7-3 are veneer dryer emissions data for SWF Plywood
3
Company, a subsidiary of Southwest Forest Industries. SWF operates 16
dryers located throughout Oregon. Ten of these dryers are fired by direct
wood-fired systems. In these systems wood waste (sander dust and trim) is
fired in suspension, or in moving or fixed grate fluid bed burners. Off
gases of combustion are applied directly to the drying process without the
use of a secondary heat transfer medium. Exhaust gases from the dryer are
recirculated to the burner as primary or secondary combustion air. Gases
may also be routed to plant boilers for primary or secondary air. In such
7-6
-------
Table 7-2. TEST DATA FROM VENEER DRYING OPERATIONS
Tests conducted by:
Test method used:
Dryer type:
Washington State University for the Plywood Research
Foundation, 1972.2
WSU method Operating opacity: 20*
Steam and gas composites not delineated by test
Dryer
Reference
Number
Wood
species
Dryer
production,
ft2 of 3/8
inch per hr
Organics lb/10,000 ft2
produced
Number
of
tests
Gaseous
Condensible
Total
40
Douglas fir heart
5,651
0.80
2.91
3.72
3
40
Douglas fir heart
9,559
0.59
1.08
1.67
3
41
Douglas fir heart
6 , 359 to 10,108
0.64
4.07
4.71
3
41
Ponderosa pine
5 410
1.26
5.62
6.88
3
42
Douglas fir heart
10,414
0.77
1.76
2.53
3
42
Ponderosa pine
6,912
0.49
2.81
3.31
3
43
Douglas fir heart
6,727 to 9,859
0.58
3.61
4.19
2
44
Douglas fir heart
6,635
0.56
4.28
4.84
3
50
Douglas fir heart
19,461
0.72
4.14
4.86
2
51
Douglas fir heart
16,876 to 19,814
0.54
4.18
4.73
2
51
Douglas fir heart
17,452
0.54
4.37
4.92
2
52
Douglas fir sap
8,505
0.52
5.90
6.42
2
52
Douglas fir heart
19,051
0.34
4.03
4.37
2
53
Douglas fir heart
14,515
0.72
2.90
3.62
2
54
Douglas fir heart
14,968
0.32
0.81
1.13
2
60
Douglas fir heart
33,730
0.42
1.46
1.88
2
60
Hemlock
14,969
0.67
1.65
2.32
2
61
Douglas fir heart
37,048
0.21
1.85
2.06
2
62
Douglas fir heart
37,601
0.21
1.65
1.86
2
63
Douglas fir heart
27 , 924
0.24
1.44
1.69
2
64
Douglas fir heart
32,071
0.18
1.04
1.23
2
Total number of sources tested: 15 Number of different wood species:
Total number of tests for this reference: ^ . A
Note: Large variations in damper settings and stack gas flowrates used as
variable parameters to effect effluents in each test.
7-7
-------
Table 7-3. TEST DATA FROM VENEER DRYING OPERATIONS
Tests conducted by: The SWF Plywood Company, Medford, Oregon^
Test method: EPA method 5
Dryer type: Prototype hybrid unit ~ Wood fired with flue gas
recirculation to burner, demonstration tests
Date of tests: October 1976 No. of tests: 2
Production rate: 14,000 ft2/hr
Wood type: Douglas Fir Sap
Inlet
Return
(recirculate)
Atmosphere
Temperature, °R
1,367
760
760
Flow, sfcm
17,812
8,670
13,481
CO2, percent
5.45
4.3
4.3
H2O, percent
15.2
19.8
19.8
gr/scf
0.1495
0.183
0.183
Total particulate, Ib/hr
22.64
13.60
21.15
Particulate produced: 1.51 lb/10,000 ft2, 3/8 in.
Date of tests: December 1977 No. of tests: 3
Production rate:- 12,680 ft2/hr
Wood type: Various soft and hardwood
Inlet
Return
(recirculate)
Atmosphere
Temperature °R
1,329
801
817
Flow, scfm
18,761
10,111
10,405
CO2, percent
3.37
2.3
2.3
H2O, percent
8.6
12.1
12.1
gr/scf
0.1013
0.0952
0 . 0952
Total particulate, lb/hr
16.35
8.16
8.49
Particulate produced: 0.67 lb/10,000 ft2, 3/8 in.
7-8
-------
systems, up to 50 percent of the exhaust gases are kept in recirculation
and used as combustion air. Thus, organic emission factors from such
systems are substantially lower as reflected in the emission factors shown
in Table 7-3 for organic aerosol (particulate).
The Mid-Willamette Valley Air Pollution Authority (MWVAPA) compiled
test results conducted by various plywood and particleboard/hardboard
industries using several control devices.4 Shown in Table 7-4 are the
results of their survey. The data show the effects of control devices on
veneer dryer emissions. Such results provide a baseline for estimating
controlled dryer emissions.
Later, the Oregon Department of Environmental Quality (DEQ) compiled
5
test data on various control devices. The results of their survey are
shown in Table 7-5. A number of candidate control devices were tested and
the information represents the best summary of available control
techniques to date.
Shown in Table 7-6 are emission data for veneer dryer emissions
routed to a hogged fuel boiler as primary and secondary air. The results
show comparisons between boiler performance and organic emissions with and
without veneer dryer stack recirculation to a hogged fuel boiler.
7.1.1.1 Organic Emissions Characterization. The compounds emitted
as gaseous organic and organic aerosol range from alpha-Pinene to
trans-Anethole. Drew and Plyant in 1966, identified approximately six
major compounds by ethylene glycol extractions of various wood
species.^ A suitmary of their findings is presented in Table 7-7.
In a separate study, over 700 gas chromatograph (GC) analyses were
performed by Washington State University during their 1970 study.1 GC
analyses for the gaseous hydrocarbons in the stack gas from 13 dryers
7-9
-------
Table 7-4. EMISSION DATA SUMMARY FROM VARIOUS CONTROL DEVICES USED
ON VENEER DRYER OPERATIONS4
Pressure [lrop
Particulate Concentration
Average Product ion
Dryer
Flow Rate
Acrons System
Gr/SCF
Efficiency
Opacity 1
Mo-le 1
Type
Control Tqulpmcnt
SCFM
In. W.iler (..iuqo in Out
«
In Out
nstalled
Steal*
American Air Filter Kinpactor
1,800
33.5
.065 .013
37
40 6
Steam
American Air Filter Kinpactor
and glass fiber demistor
3 ,000
27
.142 .049
65
28 5
Steam
Baker Filter
JJ5
25-40
.138 .02
85
50 » 0
Steam
Buchholz Toam System
405
2-3
.086 .010*
88
Brown Plume
Steam
Dupont Catalytic Afterburner
11)
2
.086 .014 <36V*F)
84
3/74|
140
.099 .0067 (499* F)
93
136
. 134 .0087 (601' F)
93
NG
Energex Burner
6,130
.0B4» 12* C02
¦s 0
7/73
NG
G-P Scrubber
11.000
151
.137 .036
74 '
55 5-20
7/73
NC
Johns-Manvl 1 le lleath
265
17-29
0.144 .018
87
60 -5
272
17-29
0.0789 .0019
98
20 '5
250
17-29
0.0779 .0017
98
20 "5
Steam
Leckenby
3,000
151
.070 .0551
21
-10
.080 .055*
31
•10
.054 .014-
37
>10
.137 .0692
48
-10
NG
Moore Lo-Em
3,415
.0946 .0944}
160] 5-25
7/73
3,200
.093 .0701
25
2/73
Seversky Electrostatic Preclp.
700
1.3
.004
f 0
1,300
3.6
.007
20
Steam
Weyco Condenser
Pilot
< 5
51
Red Plume
12/741
Steam
Hheelabrator
13,000
16
.048 .035
26
22
10/72
14.6
.016 Run 11
7
14.6
.015 Nun 12
20
NG
Wasteco Incinerator
7.760
.108 e 12* co2
9/71
Steam
Hogfuel Boiler Incineration
73,100
.115 « 1|« C02*
10
2/73
Steam
Temperature Reduction
20-40
Steam
Tompet.il ute flr'iluction
.004-.009
(19751
• Not Standard PNW!i;-ArCA S-8-2 Tc3t Method
1 .Correct «-d fur dilution Jir, aroen o nd
2 .1»» y *»ful
J .Not < or r «snl tt'Sts
t | ost i m.i t «* v.i 1 in*
-------
Table 7-4. Concluded
Dryer
Type Control Eguipw>ent
Pressure Drop Particulate Concentration
Flow Rate Across System Gr/SCF
SCFH In- Water G»uqe In Out
Efficiency
Average Opactly
Out
Heil
Hell
Heil
Harding
Heil as
Maerican Air Filter Kinpactor
American Air Filter Roto-Cline
toerican Air Filter Venturl
Scrubber
Koch MultiVenturi Flexitray
Scrubber
Temperature Reduction
2,375
1,1(0
• 32
1.400
17.220 • 112*F
Stack Tenperati
35
151
27
«.S
.144
.106
.053
.594
.0)4
.05*
.014
.233
.0122
76
1521
79
61
50-60 14
20 5
60-7C 20-25
"¦10
1. Not concurrent testa
2. High vdluae Method
I | estimated value
-------
Table 7-5. EMISSION DATA FROM VARIOUS CONTROL DEVICES USED ON
VENEER DRYER OPERATIONS5
Condenslble hydrocarbons
Removal
Inlet Outlet efficiency
Sysltn.
Burley Scrutber(5-sUge)
flowrate
SCOFH
Dryers
per
System
1/2(0)*
Prod.
Ft*/hr
3/B"
Temp.
Inlet
•F
Ter,.p.
Outlet
•F
Opacity
gr/SDCF
lb/hr
lb/1000
ft2 3/8"
qr/SDCF
lb/hr
lb/1000
ft2 3/8"
Conden-
slble
2576
20,700
347
149
1.6
0.331
7.31
0.353
0.153
3.38
0.163
53.8)
m/o denliter
2975
'/2(D)*
U ,400
348
141
?x-.:
0.274
6.99
0.613
0.163
4.16
0.365
40.5)
43 2
Roseburg Lumber Co.
2749
l/2(G)*
13,000
332
155
i.i
0.247
5.82
0.449
0.129
3.04
0.235
47.E)
Dlllard
2btl
1/2(G)-
19.700
334
152
i.i
0.215
5.27
0.2oB
0.149
3.65
o.ue
?C.7\
H)7/
3682
2/3(G i
D)*
13,024
148/
H.2
.40
) *
j
0.G0G2/
0.0(^6
0.0136/
1.97
0.145
0.0315
1.43
0.103
30.6)
|
Buchnoli Scrubber
1649/
3481
3342
2/3(6 t
0)«
1/3(6)*
11,310
11,310
106/
273
262
137
140
)
)
)5I
)
)
)
0.C057/
0.0591
0.0CB1
0.095/
1.76
2.52
0.164
0.223
0.0252
0.0390
1.11
1.12
0.098
0.059
40.4)
)41.7
)
55.7)
\
P1l*aj'n1e Ply«.otd, K1lv
-------
Table 7-5. Concluded
atalytic Burner
Plywood Corp., Lebanon
Sandair Filter
fttc Industries, Dallas
Flowrate
SCDFH
1952
2155
2163
Dryers
per
System
1
1
1
Prod.
Ftvhr
Temp.
T«p.
Inlet
Ojtlet
3'8"
OF
OF
Catalyst
OF
6041
500
555
6041
450
455
6041
360
440
Opacity qr/SDCf
0
0
15539 3
16656 3
280
290
128
128
0.165
0.165
Condenslble Hydrocarbons
Volatile Hydrocarbons*
as methane
Removal Efficienc
Inlet
lb/hr
lh/1000
Ft* 3/8"
qr/SOCF
Outlet
lb/hr
lb/1000
Ft' 3/8"
PPHV
Inlet
lb/hr
lb/mo
Ft? 3/3"
PP'IV
Ojtlet
Is/hr
lb/1033
Ft2 3/8"
Condenslble Vola
UQ
103
112
0.56
0.54
0.62
0.093
0.039
0.113
52
62
94
0.25
0.32
0.52
0.043
0.053
0.136
i
t
21.97
0.558
0.0802
10.68
0.271
33
1.30
0.033
36
1.42
0.035
51.4
21.97
0.476
0.0753
10.75
0.233
71
3.00
0.065
SI
2.<5
0.153
54.4
CJ
Test method : S-8-2 developed by the PNWIS-APCA S-8 Source Test Committee.
Date of tests: 11/76
*Volatile hydrocarbons except methane used as methane
-------
Table 7-6. EMISSIONS DATA FOR HOGGED FUEL BOILER INCINERATION AS A
CONTROL DEVICE5
Bo i 1 er
Particulate
@ 12 percent CO2
Flowrate,
dscfm
Steam
production,
Ib/hr
Pinenes,a
ppm
Ib/hr
+
gr/dscf
Ib/hr
0.115
16.0
27,631
24,000b
6.2 7.0
7.9
0.214
32.9
30,194
47,000b
5.2 1.8
4.5
0.030
4.3
20,909
18,000c
10.0 1.6
5.2
0.206
34.6
21,381
45,000c
7.4 2.8
4.7
Dryer
—
--
22,000
—
6.4 1.6
4.8
Average of two sets of simultaneous tests.
aPinene concentrations measured at different time than particulate.
Emission rates for pinenes assume same flow as during particulate tests,
bwith dryer.
cWithout dryer.
Table 7-7. CHARACTERIZATION OF EXTRACTABLE COMPOSITION OF DOUGLAS FIR6
Components
Douglas Fir (OR),
percent
Light hydrocarbons
1.2
-Pinene
52.0
Camphene
3.0
-Pinene
3.6
Dipentenes
14.4
Pine oils
20.4
7-14
-------
showed that alpha-Pinene was the major monoterpene except for Ponderosa
pine where delta-3-Carene was the major constituent. Alpha-Pinene
accounted for 75 to 90 percent of the monoterpene emission for Douglas
fir, 55 to 65 percent for Southern pine, and 40 to 50 percent for
Ponderosa pine. Their data showed that the monoterpene composition of the
stack gas was characteristic of the wood species dried. The condensed
organic fraction analyses identified abietic-pimaric acids,
sesquiterpenes, fatty acids, resin esters, and resin alcohols.
7.1.2 Emissions Data from Gluing and Pressing Operations
Relative to pollutants emitted from veneer dryers, the emissions from
plywood gluing and pressing operations appear quite small. The
emissions from these operations are largely fugitive organics from
evaporation of the glue binder in glue spreading and pressing processes.
Typical adhesives used in plywood gluing are based on thermosetting
synthetic resins. In particular, phenol-formaldehyde and
melamine-formaldehyde are used to glue all exterior grade plywood though
phenol-formaldehyde predominates. Urea-formaldehyde resins are used to
make virtually all interior hardwood panels. Phenolic resins are used to
produce the majority of interior softwood panels for structural
purposes.8 Evaporation from gluing processes and periodic washing of
glue spreaders is minor.
Vapor emissions from the hot press during plywood adhesive cure also
4. w „ cinm'ficant source of emissions. Phenolic adhesives
appear not to be a significant iuu'
emit very little organic vapors. It has been noted that even the amount
of formaldehyde evolved from urea adhesives during cure is relatively low.
To date, no tests have been performed quantitatively assess the air
emissions from this plywood manufacturing process.
7-15
-------
7.1.3 Emissions Test Data From Sanding and Trimming Operations
The major emission from plywood sanding and trimming operations is
particulate in the form of wood dust. It has been generally estimated
that approximately 0.5 kg of sander dust may result from every square
Q
meter of plywood produced. The sources of emissions are rough sanding,
planing, and trimming operations. The particulate matter produced
consists of wood dust and chips. Pneumatic transfer systems are used to
capture the particulate. The particulate is then conveyed to a control
device such as a cyclone, multiclone or baghouse. The particulate is low
in moisture content and is used as material for either boiler fuel or
particleboard raw material.
The number of emissions tests on sanding, planing, and trimming
pneumatic conveying systems is limited. The Tennessee Division of Air
Pollution Control published composite field test results for wood cyclones
shown in Table 7-8.^ The Canadian Provincial Pollution Control Board
tested discharge rates of cyclones from various wood waste sources.^
The results of those tests are shown in Table 7-9. Test parameters such
as production rate, product, and test methodology were not noted in any of
these tests.
The Georgia Department of Natural Resources identified and tested
various point sources from two Georgia Pacific plywood facilities and one
1 O
Champion Building Products plywood facility within Georgia. These
tests do not include any control device and represent nominal inlet grain
loading data to a primary cyclone. The test data are sumnarized in
Table 7-10. No information was given as to the point source product
production rate. Emissions are noted on an annual basis and are compared
to total allowable particulates within Georgia.
7-16
-------
Table 7-8. COMPOSITE FIELD DATA FOR CYCLONES TESTED BY THE TENNESSEE
DIVISION OF AIR POLLUTION CONTROL10
Cyclone
reference
number
Volumetric
discharge,
dry scfm
Waste rate
cyclone inlet,
lb/hr
Type of waste
Inlet grain
loading,
gr/scfm
Measured outlet
grain loading,
gr/scfm
Measured
particulate
discharge rate,
lb/hr
Time averaged
visible emission
evaluation,
time average
C « B
1,989
2084
Green sawdust
122
0.055
0.941
0
0 # 4
4,144
100
Sawdust
2.82
0.033
0.121
1.21*
F # 5
4,656
1050
Sawdust, sander
dust, lathe and
hog waste
26.3
0.029
1.16
NA
E # C
4,670
130
Shaper waste
and sawdust
2.44
0.005
0.213
1.39*
0 # 6
6,210
200
Sawdust
3.76
0.004
0.214
0.30*
0 #2
7,572
1000
Planer waste
117
0.027
1.76
2.0*
F I 7
8,052
1950
Sawdust, sander
dust, lathe and
hog waste
28.25
0.065
4.49
NA
L # K
8,156
1400
Sawdust
20.03
0.036
2.48
9.83*
L # I
8,233
225
Sawdust
3.19
0.019
1.38
5.38*
D # 2 9,630 696 Planer waste 8.43 0.047 3.85 NA
-------
Table 7-8. Concluded
Cyclone
reference
number
Volumetric
discharge,
dry scfm
Waste rate
cyclone inlet,
lb/hr
Type of waste
Inlet grain
loading,
gr/scfm
Measured outlet
grain loading,
gr/scfm
Measured
particulate
discharge rate,
lb/hr
Time averaged
visible emission
evaluation,
time average
0 # 1
9,880
500
Sawdust
5.90
0.035
2.99
3.75X
0 # 5
10,119
1200
Sawdust
13.84
0.026
2.25
2.31%
0 # 3
10,327
1500
Sawdust
16.95
0.046
4.03
9.85X
L # B
10,730
75
Sawdust
0.82
0.006
0.596
0
L # £
14,721
725
Planer waste
5.75
0.029
3.66
9.29X
-------
Table 7-9. FIELD TEST DATA FOR THE PERFORMANCE OF CYCLONES FROM THE
CANADIAN PROVINCIAL POLLUTION CONTROL BOARD 11
Location
Material
conveyed
Discharge
average
emission,
gr/scf
% of tests over
0.050 gr/scf
BCFP, Victoria
Sander dust
0.059
66
Sander dust
0.036
0
Sawdust
0.109
100
Planer shavings
0.020
0
Crown Zellerbach
Sander dust
0.053
60
Fraser mills
Sander dust
0.0254
100
Hog fuel
0.056
50
BCFP Mackenzie
Planer shavings
0.012
0
Chip fines
0.001
0
Chips
0.001
0
Sawdust
0.001
0
Nicola Valley
Chips
0.001
0
Chips
0.006
0
Richmond Plywood
Sander dust
0.046
33
Fraser River'
Shavings
0.030
20
PIaning
Chips
0.015
0
Can for,
Not reported
0.005
0
Stave Lake
Not reported
0.017
0
Not reported
0.006
0
7-19
-------
Table 7-10. TEST DATA SUMMARY, NATIONAL EMISSIONS DATA SYSTEM
FOR THE STATE OF GEORGIA^2
Plant
Source
Flowrate,
cfm
Particulates,
tons/yr
tested allowable
Hours of
operati on
per year
Estimated
control
efficiency
ta leu lated
grain loading
gr/scf
GA Pacific
Monti cello
Plywood
sander
4,437
1
4
2000
99.9
0.026
GA Pacific
Monticello
Plywood
sander
no. 204
33,176
17
46
2000
98.9
0.060
GA Pacific
Monticello
Panel board
sander
no. 201
4,394
2
2
2000
85.0
0.053
GA Pacific
Monticello
Plywood
trim
no. 214
4,400
5
11
2000
99.9
0.133
GA Pacific
South
Durand
A & B
conveying
system
10,000
92
109
4160
99.9
0.611
GA Pacific
South
~urand
A & 8
conveying
system
1,000
92
109
4160
99.9
5.16
GA Pacific
South
Durand
Low press
conveyor
9,600
33
34
4160
99.9
0.193
GA Pacific
South
Durand
D sys low
press
conveyor
9,600
33
34
4160
99.9
0.193
GA Pacific
South
Durand
FR hog &
saw
system
2,440
4
40
4160
99.9
0.092
GA Pacific
South
Durand
E sys. A
sander
1
36 , 000
2
25
4160
99.9
0.0031
7-20
-------
Table 7-10. Continued
Particulates,
Hours of
Estimated
Calculated
Flowrate,
tons/yr
operation
control
grain loading,
PI ant
Source
cfm
tested
allowable
per year
efficiency
gr/scf
GA Pacific
Sys. F
42,000
4
40
4160
99.9
0.005
South
hogged
Durand
trim
GA Pacific
ER sys
1,390
2
25
4160
99.9
0.081
South
high press
Durand
conveyor
GA Pacific
Pine bark
9,000
1
1
5616
99.9
0.005
Savannah
conveyor
GA Pacific
Plyvood
45,000
1
1
5616
99.9
0.001
Savannah
trimming
conveyor
GA Pacific
Sanding
4,500
2
2
5616
99.9
0.018
Savannah
conveyor
GA Pacific
Sander dust
45,000
1
1
2496
99.9
0.002
Savannah
conveyor
GA Pacific
Sander dust
3,000
1
1
2496
99.9
0.031
Savannah
conveyor
GA Pacific
Sawdust
20,000
1
27
6240
99.9
0.002
Savannah
collector
GA Pacific
Sawdu st
5,000
3
3
6240
99.9
0.022
Savannah
conveyor
GA Pacific
Sander dust
30,000
1
35
6240
99.9
0.001
Savannah
collector
GA Pacific
90,000
1
1
6240
99.9
0.0004
Sander dust
Savannah
conveyor
GA Pacific
Sander dust
3,000
1
1
6240
99.9
0.012
Savannah
conveyor
GA Pacific
8,000
1
4
2080
99.9
0.014
Sawdu st
Savannah
collector
GA Pacific
Chip loading
7,760
27
46
4680
99.9
0.173
Savannah
system
7-21
-------
Table 7-10. Concluded
Plant
Source
Flowrate,
cfm
Particulates,
tons/yr
tested allowable
Hours of
operation
per year
Estimated
control
efficiency
Calculated
grain loading,
gr/scf
GA Pacific
Savannah
Chip loading
system
6,984
4 7
624
99.9
0.214
Champion
building
prod,
waycross
Sander dust
collector
26,600
16 21
4160
95.0
0.034
Champion
building
prod,
way cross
Dry waste
conv. no.2
34,500
2 3
416
90.0
0.033
Champion
building
prod,
way cross
Dry waste
conv. no.l
34,500
15 33
416
90.0
0.244
7-22
-------
Table 7-11 shows sparse data on baghouses as presented by the
Canadian Provincial Pollution Control Board.11 In most tests,
measurable emissions were below that of the maximum resolution of the
sampling train. No information on sampling technique, measured air
volume, and plant production for these tests were available.
7.1.4 Available Test Data Summary
The data presented in this section represents all data assembled
during the course of this source survey. Many tests were conducted prior
to the promogulation of EPA reference test methods. In the majority of
tests, no information was found as to the sampling method, wood type,
production rate or other test data.
A discussion of the validity of the presented test data and the
subsequent use in determining process category emissions factors and a
national emissions level is found in Section 5.
7.2 SAMPLE COLLECTION AND ANALYSIS
This section sunmarizes the available methods for sample collection
and analysis of air pollutant emissions from the plywood manufacturing
industry.
7.2.1 EPA Reference Methods
EPA reference methods exist for most of the different types of
emissions that may result from the various unit operations of the plywood
manufacturing industry. Table 7-12 lists applicable EPA reference methods
and the species measured. The sampling and analysis methodologies of
these methods are described in 40 CFR 60.344: Appendix A.
With the exception of aerosol organic compounds, the above methods
provide sampling and analysis methodology for all important emission types
generated by the plywood manufacturing industry. The next section
7-23
-------
Table 7-11. PERFORMANCE OF BAGHOUSES AS REPORTED BY THE CANADIAN
PROVINCIAL POLLUTION CONTROL BOARD'1
Average emission,
gr/scf
Maximum emission,
gr/scf
Sauder doors
Baghouse 1
<0.001
<0.001
Baghouse 2
0.001
0.001
BCFP, Delta Plywood
0.001
0.001
MacMillan Bloedel
Particle Board
Baghouse 1
0.001
0.001
Baghouse 2
0.001
0.001
MBX-10
0.022
0.031
7-24
-------
Table 7-12. EPA REFERENCE METHODS APPLICABLE TO THE PLYWOOD
MANUFACTURING INDUSTRY
Method
Title
Species mesaured
1
Sample and Velocity Traverses for
Stationary Sources
None
2
Determination of Stack Gas Velocity and
Volumetric Flowrate (Type S Pi tot Tube)
None
3
Gas Analysis for Carbon Dioxide, Oxygen,
Excess Air, and Dry Molecular Weight
COg, O2
4
Determination of Moisture in Stack Gases
H20
5
Determination of Particulate Emissions from
Stationary Sources
Particulate matter
7
Determination of Nitrogen Oxide
Emissions from Stationary Sources
NO2
9
Visual Determination of the Opacity of
Emissions from Stationary Sources
None
10
Determination of Carbon Monoxide Emissions
from Stationary Sources
CO
17
Determination of Particulate Emissions from
Stationary Sources -- In-stack Filtration
Method
Particulate matter
25
Determination of Total Gaseous Nonmethane
Organic Emissions as Carbon: Manual
Sampling and Analysis Procedure (Proposed)
Volatile organic
compounds
7-25
-------
discusses efforts to date in developing a sampling and analysis method for
organic aerosol emissions from the veneer dryers used in the plywood
manufacturing industry.
7.2.2 Organic Aerosol Emission Sampling and Analysis Methods
Upon leaving an operation, evaporated organics may either remain in
the vapor state or condense to form a fine particulate. That which
remains in the vapor state has been termed gaseous organic in this report,
while the condensed phase has been termed organic aerosol. Gaseous
organics generally consist of low molecular weight compounds, while
aerosol components are usually higher molecular weight compounds. It is
important to note, though, that it is the sampling and analysis method
used which really defines what is reported as gaseous or aerosol organic
in a given test given. The next sections describe methods used to
quantify both gaseous and aerosol components emissions from veneer dryers.
7.2.2.1 Washington State University Method. Early in the 1970's,
WSU, under sponsorship of the Plywood Research Foundation and the EPA,
attempted to develop a method to measure the condensible organics
emanating from veneer driers.* This method consisted of developing a
sampling train for the collection of the condensible fraction of the
organic emissions and specifying an analytical procedure for the collected
sample. It was based on ASME and IGCI procedures which had been used
earlier by private concerns. The sampling train used is shown in
Figure 7-1. The WSU method also predated the previously discussed EPA
reference methods.
The sample probe was a glass tube with a fritted glass filter at the
upstream end to eliminate wood fibers. The probe led to a glass
condenser kept at 294° to 300°K (70° to 80°F) in an ice bath. The
7-26
-------
Figure 7-1. Washington State University COC sampling train.
-------
condenser was designed to provide a long contact time with the heat
exchanger and had a large reservoir to collect the condensed water and
organics. A vacuum pump, a rotameter, and a vacuum gauge completed the
sampling train.
The analytical procedure for the aerosol organic component began by
using acetone to transfer the collected sample from the condenser to
sample bottles. Upon receipt of the samples in the lab, a Rinco
evaporating apparatus was used to evaporate water and acetone from the
condensed organic samples. The rotating flask of the apparatus was kept
at 313° + 5°K (103° +9°F) in a water bath heated with an
electrical hotplate under 91 to 95 kPa (27 to 28 in. Hg) vacuum until the
water and acetone had evaporated leaving a pitchy, resinous, varnish-like
residue. The total weight was taken after a 3-hour stabilization period.
This weight was used along with data from rotameter readings and
sampletimes to determine the amount of condensible organics emitted from
2
the stack in units of pounds per hour, lb per 10,000 ft of 3/8-inch
plywood produced, and lb per 1,000 cfm exhausted from the dryer.
7.2.2.2 Sampling and Analytical Inaccuracies. Before completion of
the initial study using the WSU method, questions were raised concerning
the comparability or equivalence between that method and a typical EPA
Method 5 train (the Research Appliance Company "Staksamplr") using an
organic solvent extraction analysis technique.^ Comparison of the two
methods in sampling the same emissions yielded the following information
as to the inaccuracies inherent in the WSU method:
• The condenser in the WSU sampling train did not collect all the
condensibles
7-28
-------
• The evaporation procedure used in the WSU method allowed some of
the collected condensible organic to evaporate
Consequently, the WSU method did not give true values for the amounts of
condensible organics under the tested conditions in the initial study.
7.2.2.3 Oregon Department of Environmental Quality Method 7.
Shortly following the WSU tests in the early 1970's the State of Oregon,
DEQ devised an isokinetic method for measuring condensible organics.*3
It was this method that was used to determine the inaccuracies of the WSU
method as previously discussed. The DEQ Method 7 sampling train is shown
in Figure 7-2. The probe, collection devices, and metering system are the
same as those for EPA Method 5 except:
• A cyclone and/or heated filter may be installed in the sample
line just prior to the impingers if significant quantities of
solid particulate matter are present.
• An unheated glass filter is placed between the third and fourth
impingers.
The sample is collected from the impingers by rinsing all sample
exposed surfaces including the glass filter frits with acetone. The
filter(s) is(are) removed and placed in petri dishes.
The condensible organics in the impinger water are extracted from the
water using a chloroform-ether extraction. The extract is then evaporated
at 294°K (70°F) or less, desiccated for 24 hours, and weighed. The
remaining impinger water following extraction is evaporated at 378°K
(220°F), desiccated for 24 hours, and weighed. The acetone rinse from
all sample exposed surfaces is evaporated at 294°K (70°F) or less,
desiccated for 24 hours, and weighed. The filter(s) and the silica gel
from the fourth impinger are desiccated at 294°K (70°F) for 24 hours
7-29
-------
Figure 7-2. Oregon DEQ organic aerosol sampling train.^
7-30
-------
and weighed. The amount of condensible organic is then determined by
totaling the above residuals and along with data from the dry gas meter,
sample times, etc., the rate of condensible organics emitted from the
stack can be determined in any appropriate units.
7.2.3 Gaseous Organic Emissions Sampling and Analysis Methods
WSU initially used a Total Hydrocarbon Analyzer (THA) for the
analysis of gaseous organic components. WSU defined a gaseous organic as
all components measured by the THA, which had sampled gas that had passed
through the WSU aerosol organic train. The THA continuously monitored
gaseous organic during the duration of the tests. Any organic material
not collected in the condenser would be detected by the THA. These data
were calculated as equivalent hexane. The Oregon DEQ also adopted this
method along with methodology for aerosol organic compound analysis
techniques.
Because different compounds of the same molecular weight have
different boiling points, different response factors will be recorded by
the THA through its flame ionization detector. Consequently, it is
difficult to accurately measure gaseous organics on a consistent basis.
As a result of these differences in the response of the THA, EPA has
proposed Method 25 to analyze gaseous organics as carbon through
conversion to methane.
7.2.3.1 Proposed EPA Reference Method 25. Currently under
consideration by EPA for the determination of gaseous organic emissions is
14
proposed EPA Reference Method 25. Gaseous organics determined by
Method 25 will be defined as VOC. This method consists of
anisokinetically drawing an emission sample from the stack through a
7-31
-------
chilled condensate trap by means of an evacuated gas collection tank. The
proposed sampling train is shown in Figure 7-3.
TANK
Figure 7-3. Proposed EPA Reference Method 25 sampling train.
After sampling, the organic contents of the condensate trap are
oxidized to carbon dioxide (CC^) which is quantitatively collected in an
evacuated vessel; a portion of the CC^ is reduced to methane and
measured by a flame ionization detector (FID). Thus Total Gaseous
Nonmethane Organic (TGNMO) is determined as methane.
7.2.4 Summary
Early tests on a method developed by Washington State University from
ASME and IGCI procedures proved to have inadequacies in both sampling and
analysis. The current status of that method is not known.
7-32
-------
The Oregon DEQ Method 7 is currently a recommended method in that
State for the measurement of aerosol organic compound. Several other
states have adopted it for that purpose also.
EPA is currently evaluating the technical and economic feasibility of
proposed Reference Method 25.
7-33
-------
REFERENCES
1. Monroe, F. L., et al. Investigation of Emissions from Plywood Veneer
Dryers. Final Report for Plywood Research Foundation, Tacoma,
Washington, and EPA (Contract CPA-70-138). February 1972.
2. Monroe, F. L., et al. An Investigation of Operating Parameters and
Emission Rates of Plywood Veneer Dryers. Final Report No. 72/1-61 for
the Plywood Research Foundation, Tacoma, Washington. July 1972.
3. Grimes, G. Direct Fired Drying ~ The "Hybrid" Unit. SWF Plywood Co.
Medford, Oregon. April 5, 1978.
4. Mick, A. Current Particulate Emissions Control Technology for
Particleboard and Veneer Dryers. (Paper presented at the 1973 meeting
of the Pacific Northwest International Section of APCA. Seattle.
November 1973.)
5. State of Oregon, Department of Environmental Quality, Air Quality
Control Division. Veneer Dryer Control Device Evaluation, Supplemental
Report. December 14, 1976.
6. Drew, J. and G. D. Plyant, Jr. Turpentine from the Pulpwood of the
United States and Canada. TAPPI. 49:430. October 1966.
7. Water land, L. R. Trip Report of November 13, 1979 visit to
Georgia-Pacific Corporation, Springfield, Oregon. Acurex Corporation.
Morrisville, North Carolina. November 30, 1979.
8. Lambuth, A. L. Adhesives in the Plywood Industry. Adhesives Age.
38:21-26. April 1977.
9. Supplement No. 3 for Compilation of Air Pollutant Emission Factors
(Second Edition). U.S. EPA. July 1974.
10. Walton, J. W., et al. Air Pollution in the Woodworking Industry.
(Paper presented at the 68th Annual APCA Meeting. June 1975.)
11. Canadian Provincial Pollution Control Board. (Presented at the Public
Inquiry on Pollution Control Practices in the Forest Products
Industry. March 2, 1976.)
12. Georgia Department of Natural Resources, Environmental Protection
Division, Air Quality Control Section. Point Source Report, National
Emissions Data System. December 1975.
13. State of Oregon, Department of Environmental Quality, Air Quality
Control Division. Source Sampling Manual. January 1976, revised April
14. Determination of Total Gaseous Nonmethane Organic Emissions as Carbon:
Manual Sampling and Analysis Procedure. U.S. EPA. Draft Report.
April 1979.
7-34
-------
SECTION 8
STATE AND LOCAL EMISSION REGULATIONS
8.1 REGULATORY FRAMEWORK
Major and new sources, must meet the requirements set forth by the
Clean Air Act Amendments of 1977. In areas in attainment of the National
Ambient Air Quality Standards for particulate matter and ozone, major new
sources are required to install the Best Available Control Technology
(BACT). Determined on a case-by-case basis, BACT controls are the best
currently demonstrated ones for a particular sourc-j type. In areas which
are not in attainment of a National Ambient Air Quality Standard, a major
new source must meet the Lowest Achievable Emission Rate (LAER). LAER may
be a substantially stricter requirement than BACT, since LAER allows
little consideration of economics. BACT and LAER are enforced through the
permitting process. Major new sources, then, may be controlled more
strictly through the permitting process than by the regulations listed
here.
States have particulate and opacity regulations that apply to
industrial processes, and a few states have organic pollutant
regulations. These regulations would apply to the plywood and veneer
plants within their jurisdiction. Only Oregon has regulations
specifically for the plywood and veneer industries. Section 8.2 presents
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Oregon's regulations and Section 8.3 gives the applicable rules for other
states.
3.2 STATE OF OREGON REGULATIONS FOR VENEER AND PLYWOOD MANUFACTURING
Table 8-1 summarizes the State of Oregon regulations for veneer
dryers and for other emission sources. Oregon considers organic aerosol
as measured by Oregon DEQ Method 7 to be particulate. For veneer dryers,
opacity has been the main regulatory tool although specific particulate
limitations are also used.
Table 8-1. STATE OF OREGON REGULATIONS FOR VENEER AND PLYWOOD MANUFACTURING
FOR PARTICULATE MATTER AND ORGANIC AEROSOLS
Veneer Dryers
Opacity: 10 percent design opacity
10 percent average operating opacity
20 percent maximum opacity
Particulate limitations for wood-fired dryers:
(a) 3.7 g/m2 Veneer dried (3/8" basis)
(0.75 lbs/1000 ft2) if fuel has moisture content
by weight of 20 percent
(b) 7.3 g/m2 Veneer dried (3/8" basis)
(1.5 lb/1000 ft2) if fuel has moisture content
by weight of 20 percent
(c) In addition to (a) and (b) above, 0.4 g per kg of steam
generated
More restrictive limitations can be placed on particular plants
in special problem areas.
Other Emission Sources (excluding boilers)
Particulate limitations:
4.9 g/m2 Plywood or veneer production
(1 lb/1000 ft2) (3/8" basis)
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Provision for stricter regulation of the Portland, Eugene-Springfield
and Medford Air Quality Monitoring Areas are incorporated into the
regulations. Stricter regulations may be required in the future to attain
or maintain the ambient air standards or to protect the public health or
welfare.
8.3 PARTICULATE MATTER REGULATIONS FROM OTHER STATES
Two types of particulate regulations apply to plywood and veneer
plants. One type is the opacity regulation which specifies the limitation
on visible emissions from a plant. The other type limits the particulate
matter generated during industrial processing and is based on the weight
per hour of input material or on the concentration of particulates in the
exhaust gas. The particulate regulations may apply to virtually any phase
of plywood and veneer manufacturing, including sawing, chipping and drying.
Table 8-2 summarizes the particulate and opacity regulations in
pertinent states. Note that although the regulations do vary from state
to state, many states have adopted essentially the same regulations.
Organic aerosols are usually considered to be particulate matter.
The sampling methods used to measure particulate matter may or may not
measure the organic aerosols. Method 5 does measure part of the aerosol
especially if the back half of the unit is included. The particulate
regulations are more effective in limiting emissions from plywood plants
in states which collect a greater fraction of the organic aerosol as
particulate matter. A few states — for example, Iowa and Montana — add
the back half analysis of a Method 5 sample; most states do not.
Since a specific regulation may be quite complicated or have numerous
exemptions, the reader should refer to the regulation as adopted in order
to determine its applicability to a particular plant. Table 8-2
sumriarizes and provides an overview of the regulations, but since the
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Table 8-2. STATE AND LOCAL NEW SOURCE PARTICULATE REGULATIONS
APPLYING TO THE PLYWOOD AND VENEER INDUSTRIES
State
Visible emissions
Process emissions,
rated for process weight of 10 Mg/hr
(equivalent to industry average per plant of
10 million m^/yr)
Alabama
20* opacity; 60* opacity for more
than 3 minutes in any 60 minutes
None beyond lot line
Class 1 counties: 0.22 Mg/hr
Class 2 counties: 0.20 Mg/hr
Arizona
40* opacity
0.20 Mg/hr
Arkansas
20% opacity
Cal iforni a
Del Norte,
Humbolt,
Sonoma
40* opacity
Up to 0.018 Mg/hr and 0.46 g/dscm
So. Coast AQMD
20* opacity
Up to 0.014 Mg/hr; pp to 0.023 g/dscm
Shasta County
-
<0.025 Mg/hr and 0.46 g/dscm
Siskiyou
40* opacity
0.065 Mg/hr and 0.69 g/dscm
Tehama
40* opacity
<0.042 Mg/hr and 0.69 g/dscm
Amador,
Tuolumne
20* opacity
0.021 Mg/hr and 0.045 to 0.23 g/dscm
Colorado
20* opacity; 40* opacity for no
more than 3 minutes In any hour
during process modification or
cleaning of control equipment
0.22 Mg/hr
FT ori da
201 opacity
0.22 Mg/hr
Georgia
40% opacity; 60* for 3 minutes 1n
half hour
0.20 Mg/hr
Idaho
20* opacity
0.20 Mg/hr
111 i no is
30* opacity; 60* for no more than
8 minutes in any 60 minute period
0.23 Mg/hr
Indi ana
Dearborn 30* opacity
Dubois, Vigo and Wayne Counties
Other Counties: 40*
0.20 Mg/hr
(Particulate concentration must be
<0.11 mg/kg gas at standard conditions)
Iowa
40* opacity
0.20 Mg/hr; (can impose 0.23 g/dscm (0.1 gr/dscf)
in nonattainment areas)
Kentucky
0.22 Mg/hr
Lou is i ana
20* opacity (some exceptions)
0.20 Mg/hr
Maine
40* opacity except for 5 minutes in
one hour or IS minutes 1n 3 hours
0.22 Mg/hr
Maryland
No visible emissions
(some exceptions)
0.068 g/dscm (0.03 gr/dscf)
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Table 8-2. Concluded
State
Visible emissions
Process emissions,
rated for process weight of 10 Mg/hr
(equivalent to Industry average per plant of
10 mi 11i on m'/yr)
Michigan
20* opacity; 40* for no more than
3 minutes in arty hour, for more
than 3 occasions in any 24 hours
0.20 Mg/hr
(can Impose exhaust gas limit of 1.1 kg/hr)
Minnesota
20* opacity; 40* for any 4 minutes
1n half hour period plus
4 minutes at 60*
99.7* control
94 or greater mg/dscm depending on gas volume
Mississippi
40* opacity
0.20 Mg/hr
Missouri
40* opacity for existing equipment;
20* opacity for new equipment;
60* for 6 minutes 1n any
60 minute period
0.20 Mg/hr
Montana
20* opacity
0.20 Mg/hr
New Hampshire
20* opacity
0.20 Mg/hr
New Jersey
20* opacity
94 mg/dscm on 99* collection efficiency
New York
See regulation for specifics.
North Carolina
20* opacity except for no more than
5 minutes in any 24 hour period
(some exemptions provided up
to 40* opacity)
0.20 Mg/hr
Ohio
20* opacity except 60* opacity for
3 minutes 1n any 60 minutes period
0.20 Mg/hr
Oklahoma
20* opacity except 60* opacity for
no more than 5 minutes in any
60 minute Interval or 20 minutes
In any 24 hour period
0.20 Mg/hr
Oregon
See Section 8.2
See Section 8.2
Pennsylvani a
20* opacity except 3 min.
1n any one hour; 60* opacity
at any time
94 mg/dscm 1f E ¦ 460,000 dscm/m1n
where E » effluent gas volume
South Carolina
0.20 Mg/hr
Tennessee
20* opacity except 5 minutes 1n
one hour or 20 minutes In 24 hours
0.22 Mg/hr
Texas
20* opacity except for 5 minutes
in any 60 minute Interval or
6 hours in any 10 day period
0.029 Mg/hr
Vermont
60* opacity; 20* opacity except
for 6 minutes In any hour
0.14 g/dscm
Virginia
20* opacity except for 2 6 minute
intervals 1n any one hour
0.20 Mg/hr
Washington
20* opacity
0.23 g/dscm (0.1 gr/scf).
Some local areas: 0.12 g/dscm (0.05 gr/scf)
West Virginia
20* opacity; 40* for 5 minutes 1n
any hour
See regulation for details
Wisconsin
20* opacity
0.20 Mg/hr
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regulations have been simplified somewhat, for the sake of clarity, it may
not indicate all the details of a specific regulation.
Also note that the process weight regulations are usually written in
terms of grams per hour of particulate matter allowed for the kilograms
per hour of input material processed. Thus, to determine the emission
limitation based on square meters (3/8-in. basis) of input wood, the
density of the wood is needed. For example, the density of Southern pine
is about 0.6 dry. Thus, a plywood plant in a Class II county in Alabama
9 9
manufacturing 10 million m (110 million ftr) per year of Southern
pine plywood will have a limitation of 12.5 kg (27.5 lb) particulate
O
matter per hour. The 10 million m /yr corresponds to a process volume
of 2267 m2 (24,400 ft2), 9.5-mm basis, or 13,000 kg (28,600 lb)/hr.
The allowable emission rate is 5.5 g of particulate matter per mc of
Southern pine plywood. An emission limitation, then, depends on the wood
being processed.
8.4 HYDROCARBON EMISSIONS
Table 8-3 summarizes the organic compound ("hydrocarbon") regulations
in pertinent states which apply to plywood and veneer plants. Only a few
states have such regulations at present.
These limitations regulate hydrocarbon including those from veneer
dryers. The organic aerosol emissions may instead be regulated under the
particulate regulations of the state. See Section 8.3 for further
discussion of regulation of the organic aerosols. Specific requirements
on organic emissions have not been carried to the point that controls are
required on dryer emissions.
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Table 8-3. STATE AND NEW SOURCE HYDROCARBON REGULATIONS
APPLYING TO THE PLYWOOD AND VENEER INDUSTRY
State
11 lino is
3.63 kg/hr (8 Ib/hr) or 85% control
Indiana
85% control if emit 45.4 kg/yr
(100 ton/yr) of hydrocarbon
Mary!and
6.8 kg/day (15 lb/day) or 85% control
Wisconsin
In Southeastern Wisconsin AQCR:
1.4 kg/hr (3 lb/hr) or 6.8 kg/day
(15 lb/day) or 85 % control
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