United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600 2-79-008
iry 1979
Research and Development
xvEPA
Raw Wasteload
Characteristics of the
Hardboard Industry
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution-sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-79-008
January 1979
RAW WASTELOAD CHARACTERISTICS OF THE HARDBOARD INDUSTRY
by
Victor J. Gallons
Industrial Pollution Control Division
Industrial Environmental Research Laboratory
Con/all is, Oregon 97331
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
-------
DISCLAIMER
This report has been reviewed by the Industrial Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
-------
FOREWORD
When energy and material resources are extracted, processed, converted,
and used, the related pollutional impacts on our environment and even on
our health often require that new and increasingly efficient pollution
control methods be used. The Industrial Environmental Research Laboratory-
Cincinnati (lERL-Ci) assists in developing and demonstrating new and improved
methodologies that will meet these needs both efficiently and economically.
Characterization of an industry's raw wasteloads (in this instance
from the hardboard industry) and identification of process conditions that
affect the raw waste load provides information useful in controlling those
wastes by process modification. Regulatory agencies can also use the in-
formation to assess the progress of the hardboard industries in controlling
their wastes. The Food and Wood Products Branch, lERL-Ci, can be contacted
for further information on the subject.
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati
m
-------
ABSTRACT
Raw waste loads from the hardboard industry are characterized. Factors
that affect the raw waste load are studied. The raw waste load is most
strongly affected by the wood cooking conditions. More of the wood is
dissolved at the higher pressures and temperatures found in production of
smooth on one side (SIS) board, which results in higher raw waste loads for
smooth on two sides (S2S) production. Additional wood is dissolved in the
hot press in the production of SIS board. Refining of the wood results not
only in production of solids, but also in production of wood fines that add
to the raw waste load.
Recycling of Whitewater and press pit waters reduces the quantity of dis-
charge from a hardboard mill. Raw waste loads are also decreased. Dissolved
solids, suspended solids, and the temperature in the Whitewater increase with
increased recycling. The change in the raw waste load and Whitewater charac-
teristics are most dramatic when nearly all the process waters are being
recycled.
IV
-------
CONTENTS
Foreword • . iii
Abstract iv
Figures vi
Tables viii
Acknowledgments x
1. Introduction 1
2. Summary and Conclusions 2
3. Recommendations 3
4. Literature Survey 4
5. Comparison of Pollution Loads Resulting From Use of
Different Wood Species 31
6. Effects of White Water Recycle i 62
References 79
Appendices
A. Digester Pressure, Temperature, Time, and Recovery Data 81
B. Test Results From Digester Cooks 89
C. Data Collected at Evans Products Corporation 92
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FIGURES
Number Page
1 Diagram of an SIS hardboard mill 5
2 Diagram of an S2S hardboard mill 6
3 White water concentration vs. discharge flow 17
4 Discharge of dissolved solids vs. discharge flow 18
5 Raw waste load variation for several hardboard mills 29
6 Digester temperature vs. digester pressure 34
7 Grams soluble BOD vs. cook temperature, aspen 35
8 Grams soluble BOD vs. cook temperature, oak 36
9 Grams soluble BOD vs. cook temperature, Douglas fir 37
10 Grams soluble BOD vs. cook temperature, plywood trim 38
11 Grams soluble BOD vs. cook temperature, southern yellow pine. ... 39
12 Grams soluble COD vs. cook temperature, aspen 40
13 Grams soluble COD vs. cook temperature, oak 41
14 Grams soluble COD vs. cook temparature, Douglas fir 42
15 Grams soluble COD vs. cook temperature, plywood trim 43
16 Grams soluble COD vs. cook temperature, southern yellow pine. ... 44
17 Yield vs. cook temperature, aspen 45
18 Yield vs. cook temperature, oak 45
19 Yield vs. cook temperature, Douglas fir 47
20 Yield vs. cook temperature, plywood trim 48
21 Yield vs. cook temperature, southern yellow pine 49
vi
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FIGURES (Continued)
Number Page
22 Total dissolved solids vs. cook temperature, aspen 50
23 Total dissolved solids vs. cook temperature, oak 5.1
24 Total dissolved solids vs. cook temperature, Douglas fir 52
25 Total dissolved solids vs. cook temperature, plywood trim 53
26 Total dissolved solids vs. cook temperature,
southern yellow pine 54
27 Long term BODs for hardboard mill wastewater 58
28 Frequency of occurrence of dissolved solids loadings 65
29 Discharge of suspended solids vs. white water discharge 67
30 White water suspended solids concentration
vs. white water discharge 68
31 White water dissolved solids concentration
vs. white water discharge 70
32 Discharge of dissolved solids vs. white water discharged 71
33 Discharge of COD vs. discharge 72
34 Discharge of BOD vs. discharge 73
35 BOD discharged from final settling pond Vs. effluent flow 75
36 % BOD removal vs. effluent flow 76
37 Suspended solids discharged from final settling pond
vs. effluent flow 77
38 Suspended solids in effluent/BOD input
vs. effluent flow 78
vn
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TABLES
Number Page
1 Basic Hardboard; Classification of Hardboard By
Surface Finish, Thickness, and Physical Properties ........ 9
2 Prefinished Hardboard Paneling, Physical Properties
of the Hardboard Substrate ................... 10
3 Hardboard Siding, Physical Properties
and Maximum Linear Expansion ................... 11
4 Water Use and Quality in a Hardboard Mill ............. 13
5 Composition of North American Woods (% Extractive-Free Wood). ... 22
6 Major Carbohydrate Polymer Components of Hemicelluloses ...... 24
7 Softening Temperatures of Some Wood Species ............ 25
8 Cooking Conditions at Various Mills ................ 28
9 BODs Resulting from Different Wood Species
Cooked at Various Pressures ................... 30
10 Moisture Content and Size Distribution of Chips .......... 33
11 Suspended Solids Data ....................... 55
12 Mill Cooking Data and Corresponding Soluble
COD and BOD Loadings ....................... 56
13 Average Experimental COD and BODs Loadings
for Each Wood Species ...................... 57
14 Comparison of Mill BODs to Predicted BODs ............. 60
15 Comparison of Mill Dissolved Solids Loadings
to Predicted Dissolved Solids Loadings .............. 61
16 Process Water Composition ..................... 64
vm
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TABLES (continued)
Number £531
B-l Test Results From Digester Cooks 89
C-l White Water Solids Data 92
C-2 Press Pit Solids Data 93
C-3 Cyclone Dissolved Solids Data 94
C-4 White Water BOD Data 95
C-5 Press Pit BOD Data 96
C-6 Soluble COD Data 97
C-7 Total COD Data 98
C-8 Process Water Solids Composition 99
IX
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ACKNOWLEDGMENTS
This report would not have been possible without the contributions and
assistance of several people. I wish to extend my appreciation to the fol-
lowing for their assistance during the conduct of the project.
Dr. Henry Tu, Director of Product Quality, Evans Products Corporation,
for providing access to the Evans Products Hardboard mill, help in setting
up sampling stations, collecting samples, keeping us informed of process
changes, and providing results of company sampling and waste treatment
records.
Al Ewing, EPA, for his help in setting up the initial sampling program
at Evans Products and help in laboratory analysis.
Mark McElroy, EPA, for his assistance in contacting hardboard mills to
gather process information, arranging for shipment of wood chips to Con/all is,
and help in laboratory analysis.
Dr. Walt Bublitz, Forest Products Research Lab, Oregon State University,
for advice on setting up chip cooking experiments.
Jerry Hull, Forest Products Research Lab, for his excellent operation
of cooking experiments, helpful suggestions, and diligence in doing a good
job.
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SECTION 1
INTRODUCTION
Hardboard production by the wet process often results in large flows
of strong waste streams. The waste streams contain dissolved and suspended
solids resulting from processing of wood. In-plant control of the quantity
and quality of the raw waste load is predicated upon knowledge of factors
affecting the raw waste loading origin, factors affecting the raw waste load
during subsequent processing of the pulp, and the effect of process condition
changes on product quality. The effects of raw waste load control measures
on product quality and production costs must be fully accounted for.
Many variables cause raw waste loadings from hardboard mills to differ
between mills. The variables include the wood species used, whether or not
the wood is debarked, the product being manufactured, the steaming time and
pressure used, the amount of Whitewater recycle, whether or not the pulp
is washed, and the additives and retention aids used.
Each of the variables has a particular role in determining the raw
waste load from a hardboard mill. The amount of pollutants released into
the manufacturing process water is influenced by the severeness of the
cooking.The cooking time and pressure are determined by the wood species used
and the product desired. Each type of wood reacts differently to the cooking
step and releases different quantities of pollutants. Use of wood that has
not been debarked adds 45% to 50% to the raw waste load (2,3) . Other
variables modify the raw waste load. An increase in the amount of Whitewater
recycled can reduce the amount of pollutants reaching the effluent.
Increased retention of finely divided wood on the mat by use of polymers and
retention aids reduces the raw waste load. Some additives have a BOD of
their own and their use increases the raw waste load.
Many hardboard mills are reducing their raw waste load by recycling
their process water to ultimately eliminate discharges of all process waters.
The resultant high concentration of dissolved wood constituents in the
process waters may cause problems in maintaining board quality standards.
The causes and solutions to these board quality problems are being sought.
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SECTION 2
SUMMARY AND CONCLUSIONS
A literature survey indicated that several hardboard mills have
attempted to recycle their process waters to eliminate all contaminated
discharges and have met with varying degrees of success. Several mills have
achieved complete closeup of their process water systems. Other mills have
experienced product quality and operating problems once the dissolved solids
concentration in the white water reached a specific level. The most common
product quality and operating problems encountered are board sticking on the
hot press, loss of board strength, slow drainage of water from the mat,
and high water adsorption of the finish board.
Raw waste loads differ from mill to mill and show considerable variation
within a single mill. Laboratory work was undertaken to determine the
dependence of raw waste loads on the cooking conditions and the species of
wood used. Raw waste loads increased dramatically as the steaming pressure
and/or steaming time was increased. Different wood species produced different
raw waste loadings. Wood species generating the highest raw waste loadings
are often the least severely cooked in industry thus reducing differences
in raw waste loading due to different wood species. Production of S2S
board generally uses more severe cooking conditions than SIS production and
thereby generates a larger raw waste loading.
Studies were also undertaken to investigate the benefits derived from
partial closure of a hardboard process water system. Reductions in waste-
water flow from a hardboard mill resulted in some BOD removal, largely due
to increased suspended solids' capture on the mat. There was little reduction
of soluble BOD until flows were reduced to less than 6.6 I/kg (1437 G/Ton)
pulp. Reduction in flow improves the efficiency of in-place effluent
treatment systems. Reduction in quantities of BOD and suspended solids
discharged occurred when flows to the biological treatment were reduced,
thereby increasing residence time the discharge of BOD and suspended solids
was decreased.
Complete recycle of mill process waters may be possible in situations
where the dissolved solids loading to the Whitewater system is low, as is
the case in most SIS mills. When high dissolved solids loadings are
delivered to the white water system, as in S2S mills, evaporation of the
excess white water should be considered as a means of eliminating the
effluent. Evaporation of wastewater from a hardboard mill can be made
profitable at very high dissolved solids loadings to the white water
system through sales of the evaporator concentrate as a molasses sub-
stitute in animal feeds.
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SECTION 3
RECOMMENDATIONS
Complete closure of process water systems at hardboard mills is being
accomplished. Not all hardboard mills will be able to achieve complete
closure of their process water systems because of high dissolved solids
production during cooking and refining and, consequently, high dissolved
solids contents in their white water systems. A better understanding of
the causes of board quality problems would be beneficial to mills encounter-
ing product quality problems while attempting to close their process water
systems. Methods of reducing board sticking in the hot press that don't
affect the board surface qualities need to be developed. An understanding
of the mechanisms of board strength loss at higher white water recycle needs
to be developed. Problems of slow water drainage from the mat, high water
adsorption by the board, and poor dimensional stability of the board result-
ing from high white water dissolved and suspended solids content need to be
solved.
The effects of reducing cooking times and temperatures on product quality
and energy consumption should be investigated. The necessity of a shive-
free surface on S2S board is doubtful. If there is no effect on board
strength, swelling, or water adsorption properties, there is no reason to
maintain the severe cooking conditions.
For mills planning on evaporation of wastewater, more efficient pulp
washing systems are required. A transfer of technology from the chemical
pulping industry may be possible. The possibility of using reverse osmosis
or ultrafiltration technology to increase evaporator feed concentrations at
low cost should be investigated. A system to use digester blow steam for
evaporation of wastewater should be developed.
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SECTION 4
LITERATURE SURVEY
THE HARDBOARD INDUSTRY
There are 16 manufacturers of wet process hardboard in the United States.
Six hardboard mills are operated in conjunction with insulation board mills.
Hardboard produced in conjunction with insulation board mills is smooth on
both sides (S2S board). One mill produces S2S board without the production
of insulation board. Production of S2S board is accomplished by what is
referred to as the wet/dry process. The remaining nine hardboard mills
produce hardboard that is smooth on one side and has a screen pattern on the
back side (SIS board). Figures 1 and 2 diagram an SIS a-nd an S2S hardboard
mill respectively.
Wood Supply
The hardboard industry derives its wood from a number of sources. Most
hardboard mills in the north central section of the United States use round-
wood. Mills in the east and south parts of the country use a combination of
roundwood and wood residue. Hardboard mills in the west use primarily wood
residue from either sawmills or plywood mills.
There is a trend toward use of more wood residue in the hardboard
industry. The demand for roundwood by lumber and plywood mills is increasing
the cost of roundwood. The demand for chips by paper mills is making chips
scarce. Some mills are experimenting with whole tree chips and forest
residues. The use of lower quality wood usually results in a lower quality
product. It is likely that hardboard mills built in the future will be built
in conjunction with other wood products processing to ensure a steady supply
of raw material.
The wood may be processed with the bark still attached or debarked.
When barking is convenient, as with roundwood, the bark is normally removed
and disposed of by incineration. Bark processed with the wood disintegrates
into fine material in the cooking and refining process. Some of the bark
fines go into the product and some end up in the effluent. Sometimes round-
wood or chips are washed to remove dirt.
F i ber P re parat i on
There are three methods of preparing fiber for the manufacture of hard-
board: (1) thermomechanical, (2) explosion process, and (3) stone ground
wood. All of these methods use some degree of preheating the chips or wood.
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CHIPS
1
DIGESTER
STEAM
DEFIBERATOR
CYCLONE
•*• STEAM
OPTIONAL
RAFINATOR
STOCK CHEST
MAT
FORMATION
WIRE DRAIN
SUCTION BOXES
PRESS ROLLS
WHITE WATER
CHEST
DISCHARGE
HOT PRESS
I
-*- VAPOR
DISCHARGE
BOARD
Figure 1. Diagram of an SIS hardboard mill
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CHIPS
DIGESTER
STEAM
DEFIBERATOR
CYCLONE
-*-STEAM
RAFINATOR
WASHER
FRESH
WATER3
-*- DISCHARGE
STOCK CHEST
MAT
FORMATION
WIRE DRAIN
SUCTION BOXES
PRESS ROLLS
WHITE WATER
CHEST
DISCHARGE
DRYER
VAPOR
HOT PRESS
II
-*-VAPOR
BOARD
Figure 2. Diagram of an S2S hardboard mill
-------
Heated wood is softer and will break down into pulp with less fiber breakage
than cold wood. The longer fibers contribute to an increased strength of the
board formed.
In the thermomechanical process chips are heated with steam in either a
continuous or batch reactor. In a continuous reactor the chips are fed to
the pressurized chamber with a screw. If the moisture content of the wood
is high, water is squeezed out of the wood and drained away from the digester
area. If dried wood residue is being used, water may be added to the digester
along with the chips to keep the moisture content of the wood high enough to
prevent scorching in the refining process. The chips are heated for 2 minutes
to 15 minutes with 6.8 atm (100 psig) to 13.6 atm (200 psig) steam, depending
upon the type of wood being used and the product being produced. The chips
are then passed through rotating disc refiners. The chips may or may not be
refined at the cooking pressure. The chips are then blown into a cyclone to
separate the steam from the fiber. The steam is partially condensed in the
cyclone by a water spray which serves to wash the pulp out of the cyclone.
If the pulp is not washed from the cyclone, bridging occurs and the cyclone
becomes plugged.
Some mills bypass the cyclone and blow directly to the stock chest, or
have specially designed cyclones wherein the pulp is removed mechanically
from the cyclone to prevent pulp bridging.
In the explosion process chips are heated with 40 atm (600 psig) steam
for one minute. The pressure is then increased to 68.1 atm (1000 psig) for
5 seconds whereupon the contents of the digester are suddenly released to
atmospheric pressure. The sudden reduction of pressure causes the chips to
explode into individual fibers or fiber bundles. The pulp is then refined
to insure all shives and fiber bundles are reduced to pulp.
Pulp is produced by the stone ground wood process at one hardboard mill
which also produces insulation board. Preparation of fiber by the stone
ground wood process is common in the insulation board industry. No preheat-
ing of the wood is used. Conventional pulp wood grinders are used with
coarse burred artificial stones of 16 to 25 grit with various patterns.
Roundwood is hydraulically forced against the rotating stone and reduced to
fiber. Water is sprayed on the stone to wash the fiber away and to keep the
stone cool.
Washing of the pulp sometimes follows refining. Pulp washing is used
to improve consistency control later in the operation and to remove excess
dissolved solids which may result in surface flaws in the board. Washing is
commonly accomplished on deckers which are rotating, wire covered cylinders
that dip into a pulp slurry. A vacuum pulls water through the screen. Pulp
is pulled out of the vat on the screen and then removed from the screen by
a doctor blade.
Board Formation
After dilution to 1.5% consistency, the pulp enters the head box of
the fourdrinier machine. A urea formaldehyde, phenolic formaldehyde, or
-------
other thermo setting resin is added to the pulp either prior to pulp storage
or just prior to entering the head box. Waxes and starches are sometimes
added for sizing. Alum is added to help retain the resin on the board.
Sulfuric acid is added for pH control to precipitate the resin.
The fourdrinier machine is similar to those used in the paper industry.
It consists of a moving screen onto which pulp is delivered at a steady rate
and thickness by theheadbox. On the first portion of the screen water is
allowed to drain from the pulp. Further water is removed by a vacuum under
the screen. Press rolls then squeeze water out of the pulp mat until a
consistency of about 27% is achieved. Then the mat is trimmed and cut into
section of either 2.44 m (8 ft) or 4.88 m (16 ft) long, depending upon the
size of the press.
Most SIS board is overlayed with a finely refined pulp just prior to
the vacuum dewatering section. The overlay is to provide a smooth, shive-
free surface. Some S2S mills put a layer of fine material on the bottom of
the mat as well as an overlay so that both sides of the board will have high
quality surfaces.
Further processing of the board differs from mill to mill depending on
the type of board being produced. For SIS board the mat is placed on screen
backed cauls and is fed directly to the hot press. Water is pressed out
under 34 atm (500 psig) pressure at a temperature of 200°C to 300°C (392°F
to 572°F) to a board consistency of about 40 to 55% solids. The remaining
water is evaporated from the board. About 20 to 50% of the water in the mat
going to the hot press is evaporated; the remainder is discharged. Hot
pressing of the board causes the lignin in the wood to plasticize and melt
together and the thermosetting resins added earlier in the process to set.
In the manufacture of S2S hardboard, the mat is dried prior to hot
pressing, placed on smooth platens and fed to the hot press. There is no
effluent from the hot press in S2S board manufacturing.
The boards are sent to a rehumidifying chamber and heat cured for
several hours. After heat treatment the boards are trimmed to size and sent
to the finishing department. Finishing is essentially a dry process causing
no effluent.
PRODUCTS
Hardboard mills produce either SIS or S2S board of various densities
and thicknesses. These products are used for a wide range of applications:
interior wall paneling, exterior siding, automotive door paneling, T. V.
cabinets and furniture, base for tile panels, concrete forms, and
non-conductor material for electrical equipment.
The American Hardboard Association published a set of voluntary product
standards to establish nationally recognized dimensional and quality require-
ments for various hardboard products (4). Products are listed in three
categories: basic hardboard, prefinished hardboard paneling, and hardboard
siding, each with its own product quality standards. Tables 1, 2, and 3 list
8
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TABLE 1. BASIC HARDBOARD; CLASSIFICATION OF HARDBOARD BY SURFACE FINISH,
THICKNESS, AND PHYSICAL PROPERTIES*
Class
1
Tempered
2
Standard
3
Service-tempered
4
Service
5
Industrialite
Surface
SIS
SIS
and
S2S
SIS
and
S2S
SIS
and
S2S
SIS
and
S2S
S2S
SIS
and
S2S
S2S
Nominal
thickness
_.
inch
1/12
1/10
1/8
3/16
1/4
5/16
3/8
1/12
1/10
1/8
3/16
1/4
5/16
3/8
1/8
3/16
1/4
3/8
1/8
3/16
1/4
3/8
7/16
1/2
5/8
11/16
3/4
13/16
7/8
1
1-1/8
3/8
7/16
1/2
5/8
11/16
3/4
13/16
7/8
1
1-1/8
Water resistance
(max av per panel)
Water absorption j Thickness
based on weight 1 . swelling
SIS J ~S2S J SIS 1 S2S~"
percent
30
20
15
12
10
8
8
40
25
20
18
16
14
12
20
18
15
14
30
25
25
25
25
25
-
25
25
25
:
percent
25
20
18
12
11
10
40
30
25
25
20
15
12
25
20
20
18
30
27
27
27
27
18
15
15
12
12
12
12
12
25
25
25
22
22
20
20
20
20
20
percent
25
16
11
10
8
8
8
30
22
16
14
12
10
10
15
13
13
11
25
15
15
15
15
15
\
20
20
20
-
percent
20
16
15
11,
10
9
30
25
18
18
14
12
10
22
18
14
14
25
22
22
22
22
14
12
12
9
9
9
9
9
20
20
20
18
18
16
16
16
16
16
Modulus of
rupture
(minav
per panel)
psi
7000
__ _
5000
4500
3000
2000
Tens
(min 2
Parallel
to
surface
psi
3500
2500
2000
1500
1000
lie strength
v per panel)
Perpendicular
to
surface
psi
150
100
100
75
35
*Tab1e is from reference 4,
-------
TABLE 2. PREFINISHED HARDBOARD PANELING, PHYSICAL PROPERTIES OF THE
HARDBOARD SUBSTRATE*
Mass
i
Tempered
2
Standard
3
Service-tempered
4
Service
Nominal
thickness
inch
1/8
3/16
1/4
1/8
3/16
1/4
1/8
3/16
1/4
1/8
3/16
1/4
Water resistance
{max av per panel)
Water absorption
based on weight
percent
20
18
12
25
25
20
Thickness
swelling
Modulus of
rupture
(minav
per pane!)
percent j psi
16 |
15 ! 7000
11
18 !
18
14
25 22
20
20
30
27
27
18
14
25
22
22
5000
4500
3000
Tensile strength
(minav per panel)
Parallel
to surface
psi
3500
Perpendicular
to surface
psi
150
i
;
2500
2000
1500
100
100
75
*Table is taken from reference 4.
-------
TABLE 3. HARDBOARD SIDING PHYSICAL PROPERTIES
AND MAXIMUM LINEAR EXPANSION*
Physical properties
Property
Percent water absorption
based on weight (max av
per panel)
Percent thickness swelling
(max av per panel)
Weatherability of substrate
(max swell after 5 cycles), in
Sealing quality of primer coat
Weatherability of primer coat
P ii|Uirement
Primed 15
Unprimed 20
Primed 10
Unprimed 15
0.010 & no objectionable
fiber raising
No visible flattening
No checking, erosion, or flaking
Nail-head pull-through, Ib
(minav per panel)
150
Lateral nail resistance, Ib
(min av per panel)
150
Modulus of rupture
(min av per panel) psi
Hardness (min av per panel), Ib
Impact (min av per panel), in
1800 for V8&7/,6-ir)ch-thick
siding
3000 for Vx- inch- thick siding
450
9.0
Moisture content,c percent
2.0-9,0 incl., and not more
than 3 percent variance
between any two boards in
any one shipment or order.
Maximum linear expansion
Type of
siding
Lap
Panel
Thickness
range
inches
0.325-0.375
over 0.376
0.220-0.265
0.325-0.375
over 0.376
Maximum linear
expansion
percent
0.38
0.40
0.36
0.38
0.40
*Table is taken from reference 4.
11
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some of the more basic product quality specifications for each of the
categories, respectively. Further standards specify surface finishes,
dimensions and tolerances, squareness, edge of straightness, moisture
content, flame resistance, scrape adhesion, humidity resistance, and stain
resistance.
WATER RECYCLE
Water Use
Hardboard mills use large quantities of water to transport pulp and
form the product. Smaller water uses are numerous, and add up to a large
flow. Water uses and inputs to a hardboard mill are delineated as follows.
Raw Material--
Chips and sawdust contain between 0 to 50% moisture (total weight
basis). Chips and sawdust derived from plywood mill residues contain
between 0 and 30% moisture, depending upon their origin and subsequent
exposure to weather. Sawdust from kiln dry lumber contains about 30%
moisture. Fresh chips contain about 50% moisture.
Steam and Impregnation Water--
Live steam is added directly to the digester cooking the chips. Some
of the steam condenses during heating of the chips and some condenses
in the cyclone when contacted with cyclone wash water. If the chips are
dry, some water is added to the digester to prevent scorching of the chips.
Cyclone--
Water is sprayed into the cyclones to wash the pulp into the stock
chests. Without the water spray the pulp is likely to bridge over the
outlet and plug the cyclone. Water used for cyclone wash is either
freshwater or recycled white water. If the mill blows directly to the
stock chest or is equipped with mechanical pulp removal from the cyclone,
there is no water use at this point.
Stock Dilution Water--
Pulp leaves the cyclone at about 5% consistency and must be further
diluted before formation of the board. Recycled white water is most
commonly used for dilution water, although freshwater is sometimes
substituted to control the white water temperature when board formation
problems occur or when there is insufficient white water available.
Consistency Regulator Water--
Consistency regulators control dilution of pulp to the consistency
required for board formation of about 2.5%. Freshwater is often used by
consistency regulators because of its assured continual supply. Recycled
white water is more often used for consistency regulators.
Overlay Dilution Water—
Some of the pulp from the stock chest is further refined for use
as an overlay on the already formed mat. Water used to dilute the overlay
stock to about 1% consistency can be recycled white water.
12
-------
Broke Dilution Water--
Broke is continuously produced by trimming the mat prior to its going
to the hot press. System upsets and grade changes produce intermittent
broke which is diluted and pumped back to the stock chest. Normally white
water is used for broke dilution; however, when the entire mat is going
to broke as in grade changes, insufficient white water may be available
and freshwater is added.
Shower Water--
Water is sprayed on the fourdrinier screens and press screens to wash
away debris and prevent buildup of solids. Freshwater is often used for
screen washing, although filtered white water can be used. Large fibers
and particles in unfiltered white water will plug spray nozzles. The
presence of fines in re-used white water does not hinder screen washing
and the higher temperature is sometimes helpful. Screen wash waters are
often added to the white water.
Vacuum Seal Water--
A small amount of freshwater is used to insure a seal in the vacuum
pumps. This water must be of high quality to prevent corrosion of the
vacuum pump, and must be of low temperature.
Pump Gland Water--
Water low in suspended solids content is used on pump glands.
Chemical Make-up Water--
Freshwater is used to make-up chemical additives to the pulp system;
alum, sulfuric acid, and resins account for most of this chemical make-
up water.
Water Quality
Quantities and qualities of water used through a hardboard mill
are listed in Table 4. Water usage will vary from mill to mill, depending
upon moisture content of the chips and the amount of white water recycle
practiced.
TABLE 4. WATER USE AND QUALITY IN A HARDBQARD MILL
Water use
I/kg
Flow
(Gal/Ton)
Quality*
Boiler water
Chemical make-up
Cyclone spray
Impregnation water
Consistency regulator
and dilution water
Overlay dilution water
0.32-0.55
0.07-0.09
0-17.4
0-0.81
0.07-2.29
0-3.68
(70-120)
(15-20)
( 0-3800)
( 0-200)
15,000)
0-800)
very good
good
low
low
low
low
13
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TABLE 4. (continued)
Water use
Shower wash
Vacuum seal
Pump gland
Broke repulping
Hoses and miscellaneous
I/kg
0.91-1.84
4.50
32.17
2.29-4.60
0.18-0.36
Flow
(Gal /Ton)
(200-400)
(1000)
(7000)
(500-1000)
(40-80)
Quality*
medium
good
good
low
medium
*Definition of water quality: very good, deionized or softened water;
good, freshwater; medium, filtered white water; low, unfiltered white water.
Water Discharges
Water is discharged from hardboard production at various process
locations. In some mills the various discharges are collected into the
white water system, in others they are discharged separately to the
sewers. Discharge locations are listed as follows.
Screw Water--
When chips have high moisture contents, in the range of 50% or
greater, moisture is squeezed from the chips in the screw feed to the
digester. Screw water has a low dissolved solids content, but usually
contains chips, slivers, and other solid material.
Cyclone Steam--
Noncondensed steam from cooking and refining escapes from the cyclone.
Normally a water spray in the cyclone condenses much of the steam. Some
mills do not use a cyclone, or do not have a spray in their cyclone, and
much of the steam will escape.
Excess White Water--
Overflow from the white'water chest is discharged directly to the
sewers. The amount and quality of the overflow depends upon the amount of
recycle practiced.
Shower Water--
Shower water is often added to the white water, but is sometimes
discharged separately. Normally it has a low dissolved solids content
but contains fibers and fines washed from the screens. When filtered
white water is used for shower water, it has characteristics similar to the
white water.
Wash Water--
Some mills, usually those producing S2S board, wash the pulp to
remove dissolved solids after it comes out of the refiner. This wash
water containing dissolved solids, colloidal material, and fibers is
discharged directly to the sewer.
14
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Dryer Vapor—
In production of S2S board the mat is dried prior to the hot press.
The water contained in the mat leaving the tipple is vaporized and vented
to the atmosphere.
Press Pit Effluent--
In production of SIS board, water is squeezed from the mat when the
hot press is rapidly closed. About 70% of the water in the mat is pressed
from the board. A screened platen allows for the water to freely drain
from the mat giving SIS board its characteristic screen back appearance.
This water is often the lowest quality water in the mill as it contains
oil drippings from the press, fiber, and trash from problem boards.
Press Steam--
The remaining water in the mat in either SIS or S2S production is
vaporized in the hot press and is vented to the atmosphere.
Pump Gland Water—
Pump gland water is often added to the white water, but is sometimes
discharged separately.
Vacuum Seal Water--
Vacuum seal water is often added to the white water, but is sometimes
discharged separately.
White Water Recycle
Most mills presently recycle over half of their white water. Various
degrees of white water recycle are evidenced by the range of discharge
from 45.9 liter/kilogram (10,000 gal/ton) to 2.6 liter/kilogram (930 gal/
ton). The total flow of white water to the white water tank at various
mills including shower water, pump gland, and vacuum seal water, is between
50 to 80 liter/kilogram (12,000 to 19,000 gal/ton).
Opportunities for reuse of white water and press pit water are
numerous. The most obvious, and easiest to install, is to use white
water for all cyclone sprays, pulp dilution water, consistency regulators,
and for broke dilution. To achieve full white water utilization for
these processes some additional white water storage tanks may be required
to supply white water when demanded. Numerous saveall devices can be used
to upgrade the white water quaTity so that it may be used for shower water
without causing operational problems.
Solids Buildup—
During cooking and refining of the chips, soluble, colloidal, and
finely divided material are released into the aqueous pulp medium. Other
15
-------
water soluble materials are added through resin and chemical additions.
When recycle is practiced, the soluble material in the water drained
from the mat is returned to the incoming pulp causing an increase in
the concentration. Some of the soluble material is carried out with the
water in the mat. A material balance will show that with increasing
recycle, the concentration of solids in the white water will increase.
Figures 3 and 4 show the white water dissolved solids concentration
vs. discharge flow, and discharge of dissolved solids vs. discharge flow,
respectively as derived from a mass balance. The systems represented are
an SIS mill where the press pit water is returned to the white water, and
an S2S mill. No washing of the pulp is assumed in both situations. A
dissolved solids loading to the white water system was assumed to be-09 kg/kg
pulp, corresponding to a 90% yield pulp. Figures 3 and 4 show that when
recycle is increased and the discharges decrease, the white water concen-
tration increased and the solids sewered decreased. Significantly
little increase in white water concentration or little decrease in solids
discharged occurs until about 90% of the white water is recycled. Recycle
of the remaining 10% of the white water causes significant increases
in white water concentrations and significant decreases in solids dis-
charged.
.Host American mills operate with discharges. .of more than 22 1/kq
pulp (4800 gal/ton). There appears to be plenty of opportunity to decrease
the quantity of discharge; however, as the white water dissolved solids
concentration increases, problems with board quality and other mechanical
difficulties begin to occur. The concentration at which these problems
begin to occur varies from mill to mill, and the problem causing the limi-
tation is different for each mill.
The limiting concentration of dissolved solids in the white water
will depend upon whether SIS or S2S board is being made. Assuming that
the board quality deterioration is dependent upon the quantity of dissolved
solids in the board, probably S2S boards cannot tolerate as high a dissolved
solids concentration in the white water as can SIS boards. In S2S
production all of the dissolved solids contained in the water in the mat
leaving the tipple area becomes permanently part of the board when dried.
In SIS production about 50 to 80% of the dissolved solids contained in
the water in the mat leaving the tipple area are removed with the water
upon squeezing in the hot press. At identical white water dissolved
solids concentration S2S board will contain more soluble materials than
will SIS board. The higher solids concentrations in the S2S board is
more likely to cause product quality problems than would be encountered
in SIS production. To maintain the same dissolved solids content in the
board the S2S mill has to discharge twice as muQh water as the SIS
mill. The quantity of dissolved solids in the effluent would be the
same for both types of mills.
The concentration of suspended solids in the white water does not
increase in the same manner as do dissolved solids when recycling is
increased. Suspended solids are selectively removed from the white water
by filtration during draining of the mat, which removes most of the larger
16
-------
0
6 8 10 12 14 16 18 20 22 24 26 28
DISCHARGE FLOW, L/Kg o.d.b.
Figure 3. White water concentration vs. discharge flow.
-------
00
i
o
CO
0
I- 6 8 10 12 14 16 18 20 22
DISCHARGE FLOW, L/Kg o.d.b.
Figure 4. Discharge of dissolved solids vs. discharge flow.
24 26 28
-------
particles and fillers. Colloidal particles are not so easily removed and
will increase in concentration in the white water as recycling is
increased unless a flocculating agent is added to the white water system.
A flocculating agent such as alum will increase the particle size,
rendering them filterable or possibly attach the colloidal material to
the fibers. Most mills already use alum to precipitate resins. A buildup
of sulfates from alum additions to a closed system may result in decreased
retention of resins. The double negative charge of the sulfate ion
could impair the affirnnty of the alum for the resin and fibers.
Effects of White Water Recyle on Board Quality
Numerous reports of board quality problems have been reported in
the literature when hardboard mills attempt to recycle greater quantities
of white water. Problems that occur most often are sticking in the hot
press, and loss of board strength. Other problems reported are alter-
ation of specific board properties, such as dimensional stability,
discoloration, and leaching of solubles from boards in use.
Press Stieking--
Sticking of the board to platens in the hot press is often the first
problem encountered when recycle is attempted. When the white water
dissolved solids concentration exceeds about 3.5%, sticking is prone
to occur. Gross clinging of the board to the hot press platen is seldom
experienced. Pinpoint sticking is more often encountered, which disrupts
the smooth continuity of the board surface.
Release agents are often used to reduce sticking of the board to
platens in the hot press. The most common release agent is a wax emulsion
that is lightly sprayed on the surface of the mat just prior to the tippe
area. Other proprientory release agents are also used, especially if the
hardboard is to be painted for its intended use. These release agents
are capable of preventing sticking in the hot press until the white
water dissolved solids concentration exceed 7% (1). The highest reported
white water concentration where sticking is not a problem is 10% dissolved
and suspended solids (2).
Another method of reducing sticking in the press is to lower the
press temperature (3). Lowering the press temperature may be the only
method available to S2S mills to reduce press sticking because the back
side, of S2S board cannot be sprayed with a release agent. Lowering the
press temperature has the disadvantage of requiring a longer press cycle
time.
Temperature—
\
The heat added to the hardboard process in the cooking stage normally
leaves the process in the effluent. With increasing recycle, heat is
19
-------
retained in the system in the form of higher white water temperature. _ The
white water temperature increases until some equilibrium temperature is
reached. Temperatures as high as 70°C have been reached.
High white water temperatures can cause high temperatures and humid-
ities around the forming line, especially in the summer, making working
conditions uncomfortable. Condensation of moisture on cold surfaces,
such as cold water lines, causes dripping of water around the forming
line.
These problems can be prevented if adequate measures are taken. The
area around the forming line can be well ventilated to keep temperatures
and humidities down. The white water can be cooled with heat exchangers
to tolerable levels.
Board Strength--
Some attempts at increasing white water recycle have been thwarted
by decreases in board strength properties, modulus of rupture (MOR) in
particular. The cause of the strength loss has not been determined, one
theory is discussed below.
When recycle is practiced white water chemistry changes; acidity
increases. The increased acidity and lower pH may cause the resins to
prematurely set or not react at all causing a weak board to be formed.
High white water temperatures may cause the thermosetting resins to
prematurely set. If the resins set before the board reaches the hot press
it will not assist in binding fibers together.
Water Absorption--
The greater amount of fines and dissolved solids content of the board
due to high recycle levels may lead to an increase in board water ab-
sorption. Water absorption sites are much more readily accessible in the
small amorphous colloidal particles and dissolved solids than in the
crystalline structure of the fibers. Wood celluloses and hemicelluloses
are highly hygroscopic, and readily exchange moisture with the air upon
humidity changes.
Dimensional Stability--
When wood adsorbs water it expands. The increase in water adsorption
of hardboard produced with a high degree of white water recycle thereby
decreases the dimensional stability of the board. Dimensional stability
is especially important for hardboard siding products.
Bleedout--
Dissolvable materials in boards may leach out of the board if the
board should get wet. Uneven wetness of the board may cause discoloration
of the board. Bleedout may be a problem when hardboard is used around
sinks or showers.
Color--
Sugars in the board are subject to scorching and burning in the hot
press. When a high degree of recycle is practiced a darker board color
20
-------
is noticed, which is partially due to scorching in the hot press and partially
'due to the higher wood extractives content of the boards.
Corrosion--
The higher dissolved solids and acidity and the lower pH found in
mills that practice high degrees of recycle are conducive to high
corrosion rates. Most hardboard mills use stainless steel piping throughout
the mills and should not be bothered by harsher white water chemistry.
Replacement of other metal parts exposed to white water with stainless
steel should minimize corrosion.
Decay--
Free sugars in the hardboard are an inviting food source for various
fungus and biota. Dry rot will attack hardboard if the moisture content
is about 15%. Boards with a high dissolved solids content will rot
twice as fast as those,with low sugar contents (5). Termites are attracted
by the high sugar content.
CHEMICAL REACTIONS DURING HARDBOARD PRODUCTION
Composition of Wood
Wood is composed of lignins, celluloses, hemicelluloses, wood extrac-
tives, and small quantities of other materials. Most wood compounds
are insoluble in water. Table 5 lists the compositions of various wood
species and their hot water solubilities. Hardwood and softwoods vary
significantly in composition, mainly in respect to their hemicellulose
content. Softwood contains between 5 to 13% pentosans, whereas hardwoods
contain between 17 to 32% pentosans. Table 6 shows differences in hardwood
and softwood carbohydrate polymers.
The area near the cell wall contains most of the hemicellulose. The
fibers (cell walls) are held together with lignin. Between the lignin
and cell walls, lignin and hemicellulose are closely intermingled. Relative
solubilities of these wood components are different.
Chemi ca1 Reacti ons
When wood is heated hydrolysis of acetyl groups connected to the
hemicellulose occurs, as evidenced by a drop in pH in an aqueous medium.
With the decrease in pH, hydrolysis of hemicellulose increases. The
product of hydrolysis is acetic acid. The drop in pH at a constant cooking
time is more pronounced as the cook temperature increases. The pH drops
rapidly at temperatures above 160°C (320°F) (6).
The lowering of the pH within the wood causes hydrolysis of the
hemicellulosesfand celluloses to sugars or oligosaccharides. Hydrolysis
of the hemicellulose and cellulose material proceeds at different rates.
The rate of hydrolysis is also temperature dependent. Above 140°C (284°F)
dissolution of hemicelluloses becomes rapid, and above 150°C (302°F)
the rate of dissolution of cellulose increases (7). Below 150°C (302°F)
21
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TABLE 5. COMPOSITION OF NORTH AMERICAN WOODS
(% EXTRACTIVE-FREE WOOD)
INJ
ro
Species
Hardwoods:
Trembling aspen
(Populus tremuloides)
Beech
(Fagus grandifolia)
White birch
(Betula papyrifera)
Yellow birch
(Betula lutea)
Red maple
(Acer rubrum)
Sugar maple
(Acer saccharum)
Sweetgum
(Liquidambar
styraciflua)
White elm
(Ulmus americana)
Southern red oak
(Quercus falcata)
Yellow poplar
Sycamore
Glucan
57.3
47.5
44.7
46.7
46.6
51.7
39.4
53.2
40.6
--
49.0
Mannan
2.
2.
1.
3.
3.
2.
3.
2.
2.
-
1.
3
1
5
6
5
3
1
4
0
-
6
Galactan
0.8
1.2
0.6
0.9
0.6
0.1
0.8
0.9
1.2
--
1.1
Xylan
16.
17.
24.
20.
17.
14.
17.
11.
19.
20.
16.
0
5
6
1
3
8
5
5
2
0
0
Arabinan
0.4
0.5
0.5
0.6
0.5
0.8
0.3
0.6
0.4
—
10.0
Uronic
anhydride Acetyl lignin
3.3 3.4 16.
4.8 3.9 22.
4.6 4.4 18.
4.2 3.3 21.
3.5 3.8 24.
4.4 2.9 22.
23.
3.6 3.9 23.
4.5 3.3 23.
20.
25,
3
1
9
3
0
7
7
6
9
0
.0
Solubility in
hot water
Ash % of wood
0.2
0.4
0.2
0.3
0.2
0.3
0.2
0.3
0.8
--
0.6
3.0
--
__
4.0
-_
4.4
2.0
3.6
_.
0.2
—
-------
TABLE 5. COMPOSITION OF NORTH AMERICAN WOODS (Continued)
(% EXTRACTIVE-FREE WOOD)
Species
SOFTWOODS:
Balsam fir
(Abies balsamea)
Eastern white-cedar
(Thuja occidental is )
Eastern hemlock
(Tsuga canadensis)
Jack pine
(Pinus banksiana)
White pine
(Pinus strobus)
Loblolly pine
(Pinus taeda)
Glucan
46.8
45.2
45.3
45.6
44.5
45.0
Douglas-fir
(Pseudotsuga taxifolia)43.5
taxifolia) 43.5
Black spruce
(Picea mariana)
White spruce
(Picea glauca)
Tamarack
(Larix laricina)
47.9*
46.5
46.1
Mannan
12.4
8.3
11.2
10.6
10.6
11.2
10.8
10.5
11.6
13.1
Galactan
1
1
1
1
2
2
4
1
2
.0
.5
.2
.4
.5
.3
.1
--
.2
.3
Xylan
4.8
7.5
4.0
7.1
6.3
6.8
2.8
8.0
6.8
4.3
Arabinan
0.5
1.3
0.6
1.4
1.2
1.7
2.7
_-
1.6
1.0
Uronic
anhydride
3.4
4.2
3.3
3.9
4.0
3.8
2.8
4.1
3.6
2.9
Acetyl
1.5
1.1
1.7
1.2
1.3
1.1
0.8
1.1
1.3
1.5
Lignin
29.4
30.7
32.5
28.6
29.3
27.7
31.5
28.0
27.1
28.6
Solubility in
hot water
Ash % of wood
0.2
0.2
0.2
0.2
0.2
0.3
0.4
0.4
0.3
0.2
__
3.7
3.7
4.5
1.8
5.6
..
2.9
-------
TABLE 6. MAJOR CARBOHYDRATE POLYMER COMPONENTS OF HEMICELLULOSES
Polymer
Relative amount present
Softwoods
Hardwoods
4-0-Methyglucuronoxylan acetate
4-0-Methylglocuronoarabinozylan
Glucomannan
Glucomannan acetate
Galactoglucomannan acetate
Arabinogalactan
Small or none
Medium
Nil
Large
Small
Trace to medium
Very large
Trace
Small
Small
Nil
Nil
very little hydrolysis and dissolution of cellulose occurs.
of hemicelluloses begins at about 140°C (284°F).
Solubilization
The amount of cellulose solubllized depends upon the amount of
hemicelluloses present. For hardwood, where the hemicellulose content
is high, the cellulose removal during cooking is quite low. On the other
hand, where the original hemicellulose level is low, as in softwoods, the
degradation of celluloses upon cooking is much greater (7).
Richter's work (7) showed different yields for different wood species
at identical cooking conditions. White birch had the lowest yield
whereas Douglas fir, western hemlock, spruce, and gumwood had similar
yields at identical cooking conditions. Gran showed the differences in
yield for birch and beech at identical cooking conditions (3).
Bornardin reported that the yield of wood is a logarithmic function
of time (8). He also reported that the material removed from black
gumwood by water hydrolysis at 160°C (320°F) consisted of about 55%
hemicelluloses. The remainder of the materials removed were extractives,
lignin, and decomposition products.
The solubility of wood in hot water is not a good indication of how
much of the wood will be solubilized at fiberboard cooking conditions,
but is mainly a measure of the water soluble extractives content. In the
solubility test, insufficient time or temperature is available for signi-
ficant degradation of the hemicelluloses and celluloses. In the hardboard
mill most of the water soluble materials result from the degradation of
hemicellulosic materials.
Softening of Lignin with Heat
When wood chips are heated the lignin and hemicelluloses between
the cell walls becomes soft, beginning at specific temperatures referred to
as the glass point. During cooking the lignin is heated to the glass
point so the fibers can be easily separated upon refining. At temperatures
24
-------
below the glass point the wood fractures through the outer layer of the
secondary cell wall when refined. At temperatures above the glass point
the wood fractures through the lignin layers between the cells when
refined. When wood has been fiberated above the glass point the fibers
will be coated with a layer of lignin (12). When these lignin coated
fibers are pressed together under heat and pressure such as during hot
pressing of hardboard, the lignin remelts and the fibers are glued back
together in a new pattern.
Steamed wood passes through two softening regions. Table 7 shows
these softening regions for several species of wood (13). • The lower
temperature softening region is thought to be due to degradation of bonding
between the lignin and cellulose; that is, solubilization of the hemi-
celluloses during the steaming process. The higher temperature softening
region is thought to be due to the softening of the lignin. In practice,
the transition between refined spruce fractured in the cell wall or fractur-
ing in the cell wall or fracturing between the cell walls during refining
occurs between 120-135°C (248-275°F) (12).
TABLE 7. SOFTENING TEMPERATURES OF SOME WOOD SPECIES
Wood species
Aspen
Birch
Spruce
Lower transition
temperature, °C
60 -
60 -
80 -
140
150
170
% of
change
50
60
20
Higher transition
temperature, C°
180 -
180 -
170 -
230
240
240
% of
change
50
40
80
Several minutes are required to heat the entire chip to a uniform
temperature. For most chips 2 minutes of heating is all that is necessary.
If the chips are not uniformly heated shives>are likely to occur because
the center of the chip won't break into fibers because it is too hard.
The number of shives is also a function of the cook temperature; more
shives appear at lower cooking temperatures. The number of shives in the
final pulp can be reduced by increasing the refining energy, i.e., by
bringing the plates closer together.
White Water Composition
As indicated by the previous section, the composition of the white
water in a hardboard mill should contain a large portion of dissolved
cellulosic materials in the form of simple sugars or as water soluble
oligosaccharides. The ratio of the types of sugar compounds present is
dependent upon the types of wood being processed and the cooking conditions
used. Where hardwoods are being cooked a high content of pentosans should
be found. When soft woods are being cooked the pentosan fraction should
be lower and the hexosan content higher.
25
-------
Analyses of the dissolved substances in the Masonite process (cooked)
at 275°C (527°F) from a coniferous wood showed a composition of 70% carbo-
hydrates, 10% lignin, and 20% organic resins. The carbohydrates were 35%
pentosans, mostly xylans, and 65% hexosans (3). Analysis of the dissolved
substances in a mill using an Asplund defiberator (cooked at 180°C (356°F))
on beech showed a composition of 75% carbohydrates, a few percent lignin
type materials, and about 10% acetic acid. Eighty percent of the carbo-
hydrates were pentosans, mainly xylans, and 20% hexosans (3). Analysis on
Aspuland process white water resulting from Douglas fir cooked at 180°C
(356°F) showed 44% of the dissolved materials were carbohydrates. Twenty two
percent of the carbohydrates were pentosans, mostly arabinose, and the re-
mainder hexosans, mainly mannose, and galactose. Glucose, a decomposition
product of cellulose, was only 15% of the carbohydrates (9). The low
glucose content indicates minimal dissolution of the cellulosic content
of the wood.
Another mill cooking Douglas fir at 166°C (330°F) reports that of
the free carbohydrates in the combined discharge from the mill, 58% is
arabinose, 15% xylose and the remainder hexosan sugars, largely mannose.
Galactose is present mostly as a polymerized carbohydrate. There was
practically no glucose present (15).
Effects on Hardboard of Hemicenulose Removal From Raw Material
Rot Potential —
Dry rot, or fungal attack, begins on wood when the mositure content
of the wood is above 15%. Hardboard, being essentially wood, also begins
to rot at this moisture content and is seldom used in applications where
they will receive much moisture. Exceptions are uses in shower stalls,
outside sheathing, or in applications where inadequate vapor barrier pre-
cautions have been taken.
The hemicellulose content of wood is responsible for a portion of
its water adsorption characteristics from air. Hemicellulose has an amorphous
structure and can easily adsorb water. The cellulose portion of wood is
crystalline in nature and water molecules have difficulty in penetrating
the crystalline structure. Consequently, the equilibrium water concentration
in hardboard that has had a high degree of hemicellulose removal during
production is about 70% that of wood. Removal of hemicelluloses reduces
the amount of water moisture the board can hold and thereby reduces the
•dry rot potential.
A study of decay of hardboards showed that some fungi and molds attacked
the hemicellulose portion of the wood first, then when the hemicellulose
content had been reduced to about 12%, began to attack the cellulosic material
of the wood. Other molds and fungi attacked the celluloses and hemicelluloses
indiscriminately (10). Removal of hemicelluloses reduces the susceptibility
of hardboard to rot (5).
26
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Dimensional Stability—
When wood absorbs water it swells. As described in the previous section
the amount of water a board can adsorb is in part controlled by its hemicellu-
lose content. Hardboard with a high hemicellulose content will expand
and contract more than a board with a low hemicellulose content.
Because higher cooking temperatures prior to refining reduce the hemi-
cellulose content of the board, water adsorption and dimensional stability
of the board can be directly related to the chip cooking pressure. Reduction
of the cooking pressure from 8 atm (118 psig) to 3 atm (44 psig) increases
the 24 hr submersion water adsorption by 16% (11). Correspondingly, thick-
ness swelling increases by 33%. There is little change in water adsorption
or swelling thickness above 8 atm cooking pressure. Changes in relative
humidity from 90% to 30% resulted in an 8% higher dimensional change in
thickness swelling and a 4% higher dimensional change in sheet direction
swelling for boards produced with pulp cooked at 3 atm (44 psig) as compared
to that cooked at 8.5 atm (124 psig) (11).
Board Strength--
Back and Larson reported some loss in internal bonding strength (Z
strength) when chips used in making hardboard were cooked at low pressures
(11). Z strength is related to the amount of refining and to the shive
content of the pulp. The tensile strength was reported to be unaffected
by the cooking pressure.
RAW WASTE LOAD VARIABILITY
Two subjects are covered by the term raw waste load variability: dif-
ference in raw waste loads between mills, and variation of the raw waste load
from any one mill. The former results from differences in operation between
mills, and the latter results from changes occuring within a mill. The
causes of raw waste load variations, either between mills or within a mill,
are difficult to determine. Some possible causes of raw waste load variation
are discussed in the following text.
Differences Between Mills
Many variables cause raw waste loadings from hardboard mills to differ.
These include the wood species used, whether or not the wood is debarked,
the product being manufactured, the steaming time and pressure used, the
amount of white water recycle, whether or not the pulp is washed, and the
additives and retention aids used. Each of the variables has a particular
role in determining the raw waste load from a hardboard mill. The amount
of pollutants released into the manufacturing process water is influenced
by the severeness of the cooking. The cooking time and pressure are
determined by the wood species used and the product desired. Each type of
wood reacts differently to the cooking step and releases different quantities
of pollutants. Use of wood that has not been debarked adds 45% to 50% to the
raw waste load (3, 2) and other variables modify the raw waste load. An
increase in the amount of white water recycled can reduce the amount of
pollutants reaching the effluent. Increased retention of finely divided wood
on the mat by use of polymers and retention aids reduces the raw waste load.
27
-------
Some additives have a BOD of their own and their use increases the raw
waste load.
Figure 5 is a monthly average raw waste BOD variability plot for 7
U.S. hardboard mills. Mills A, B, C, and E produce SIS hardboard, whereas
mills D and F produce S2S hardboard, and mill G produces both SIS and S2S
hardboard. Mills F and 6 wash their stock. Mills A, D, and E process chips
that have bark included. Cooking conditions for the mills are listed in
Table 8.
TABLE 8. COOKING CONDITIONS AT VARIOUS MILLS
Mill
A
B
C
D
E
F
G
Wood Species
Hardwood and softwood chips
Douglas fir plywood trim
Douglas fir plywood trim
Pine, hardwood, FRC
Aspen
Hardwood
Hardwood
Digester Pressure
Atm (psig)
10 (140-150)
8.5 (120-130)
6.5 (96)
10.2 (150)
6.8 (100)
10.2 (150)
10.2 (150)
12.2 (180)
Time
min.
2.5
2-3
3
8-14
6-12
1.5-2.5
1.5-4
2
Board
SIS
SIS
SIS
S2S
S2S
SIS
S2S
S2S
Isacson and Back reported on pulp yields using various materials and
cooking conditions and the corresponding BOD's produced, as shown in
Table 9.
Determining which of the many factors or combination of factors listed
affects the raw waste load is a difficult task. More information about
each of the factors listed needs to be gathered before a clear understanding
is attained about why raw wastes differ from mill to mill.
Raw Waste Load Variability Within a Mill
Figure 5 also shows that there is considerable monthly variation in
the raw waste loading from any particular mill; day to day variation can be
greater. Mill variations can be either long term variations, as expected
in monthly averages, or short term variations expressed by daily averages.
Causes for each type of variation are likely different, but accumulation
of short term variations can lead to long term variations.
28
-------
200
150
•
-Q
-o 100
6
-------
TABLE 9. BODs RESULTING FROM DIFFERENT WOOD
SPECIES COOKED AT VARIOUS PRESSURES
Raw Material
40% Spruce
40% Pine
20% Birch
70% Pine
30% Birch
100% Barked Birch
70% Pine
30% Birch
Sawmill slabs, pine
Sawmill slabs, pine
Pine logs
Pine saw mill slabs
Softwood, 20% bark
Steam Pressure Time
Atm (psig) min
10
12
13
13
11
12
13
13
11
(147)
(176) 3
(191) 4
(191)
(161)
(176)
(191)
(191)
(161)
BOD
kg/t (Ib/Ton)
29.4 (58.8)
21.4 (42.80)
43.2 (86.4)
44.6 (89.2)
44.8 (89.6)
38.4 (76.8)
43.2 (86.4)
33.1 (66.2)
30.0 (60.0)
Short term variations may result from a number of process changes and
upsets. Daily changes in the nature of the wood supply can cause changes
in the way the wood is processed. Changes in the thickness of the board
being produced result in different retentions of suspended solids in the
mat. Other process fluctuations can also result in short term variation.
Long term changes may result from factors such as length of storage
of chips, season the wood was harvested, wood bark content, or changes
in product orders. When wood is stored for long periods of time the chances
for fungal degradation of the cellulose is increased. Degraded cellulose
is likely to be water soluble and thereby contribute to the raw waste loading,
Further study of causes of long and short term raw waste load variation
is required.
30
-------
SECTION 5
COMPARISON OF POLLUTION LOADS RESULTING
FROM USE OF DIFFERENT WOOD SPECIES
An experiment was designed to determine differences in raw waste
loading due to processing different wood species and due to the product
manufactured. Pollution loadings resulting from processing each of several
wood species at different cooking conditions corresponding to those in
use in the hardboard industry were determined. The relative importance
of wood species processed and the product produced in determining the raw
waste load are compared.
BACKGROUND
When chips are preheated in the hardboard process two reactions take
place, a softening of the lignin material that holds the individual fibers
together, and hydrolysis of the hemicellulose. Thermal softening of the
lignin reduces the amount of energy required to refine chips to pulp.
Softening of the lignin is a reversible process. The lignin will harden
when the chips are cooled. The temperature at which softening occurs when
the chips are heated differs among wood species.
Although not as pronounced an effect as the softening of the lignin,
hydrolysis of the hemicellulose produces a permanent softening of the chips.
The hemicelluloses are hydrolyzed into low molecular weight, water soluble
molecules. About half of the soluble material found in a hardboard mill
effluent is hemicellulosic material (3, 4, 5). The remaining material
consists of extractives, lignin, and organic acids resulting from the decompo-
sition of wood components. Hydrolysis of cellulose does not occur below
170°C (338°F) (6).
Because of these differences in the softening temperature of the wood
and rates of decomposition, mills using different species of wood will
preheat chips to different temperatures and for,different durations. Oak
breaks down more rapidly than do other species of wood, and when cooked
too long produces a slow draining pulp. Other types of wood are more.resis-
tant to thermal softening and degradation and require more severe cooking
conditions.
Cooking conditions are largely determined by the degree of cooking
required to produce a pulp suitable for the manufacture of the type or
grade of hardboard being produced. A major difference exists in the cooking
31
-------
conditions used in the manufacture of SIS and S2S hardboard. Other product
quality factors also influence the cooking conditions used.
SIS boards are normally produced by forming a thick mat of coarsely
refined fiber and overlaying the mat with a thin layer of finely refined
fiber. The overlay produces a high quality, shive free, smooth surface.
Since the majority of the board can contain shives, the fiber in the bulk
of the board does not need to be finely refined. Coarse refining requires
less energy than fine refining, so cooking conditions need not be as thorough.
Most S2S production processes do not use an overlay to produce a smooth
surface on both sides of the board. The whole of the board is made from *
the same stock. The fibers throughout the board are highly refined so
that the surface is shive free. To keep refiner energy consumption at
a minimum, the chips need to be thoroughly softened. Thoroughly softened
chips call for higher preheating pressures.
Other factors affect steaming times and pressures used at a particular
mill. Formation and drainability are affected by refining conditions.
More severe cooking conditions may permit less usage of drying oils and
resins. Press cycles are shorter for boards made from more severely cooked
chips. Longer steaming times are required for frozen chips during winter
months.
EXPERIMENTAL PROCEDURE
A questionnaire was sent to all U.S. hardboard manufactures to determine
typical wood species mixes, cooking conditions and products made that are
relevant in the hardboard industry. Aspen, southern yellow pine, Oregon
white oak, Douglas fir, and Douglas fir plywood trimmings were chosen as
representative of the wood used by hardboard mills throughout the United
States.
Samples of chips used at several mills were shipped to Corvallis.
Oak chips were prepared by chipping freshly cut oak logs. Size distributions
determined in a Williams Classifier, and moisture contents determined on
a total weight basis of the chips are presented in Table 10. The moisture
content of the plywood trimmings is higher than oven dry because the chips
were stored in an outside pile and subjected to rainfall.
For the tests, bark-free chips were screened on a Williams Classifier
to sizes inclusive of 5-29 mm. Each species was steamed in a batch digester
at pressures ranging from 6.8 to 13.6 atm (100 to 200 psig) for 2 to 10
minutes. After steaming, all chip samples were refined in a bauer refiner at
gap setting of .25 mm (0.010 inch) and a speed of 1755 rpm. All condensate
from the digester, refining and wash water, and pulp were diverted to pit
where water samples and consistencies were taken. Water was separated from
the pulp by drainage through a 32 mesh screen. The water samples were ana-
lyzed for total solids, dissolved solids, soluble chemical oxygen demand,
total chemical oxygen demand, soluble biological oxygen demand, total bio-
logical oxygen demand, and pH. The consistencies, out volume, and initial
chip weights were used to determine yields.
32
-------
TABLE 10. MOISTURE CONTENT AND SIZE DISTRIBUTION OF CHIPS
Southern Douglas Plywood
Species Aspen Oak Yellow Pine' Fir Trimmings
Moisture content 48.1% 36.5% 48.6% 42.4% 27.9%
Size distribution
through - retained on
in. in.
1-1/8
7/8
5/8
3/8
7/8
5/8
3/8
3/16
9.4%
27.9%
47.4%
15.4%
52.4%
34.6%
12.2%
1.4%
23.0%
36.4%
33.7%
6.9%
6.4%
22.7%
45.6%
25.4%
4.3%
9.0%
32.3%
54.4%
EXPERIMENTAL RESULTS
When the test results were plotted against pressure considerable scatter
of data was evident. Checking the recorded temperature of the cooks showed
some deviation of the cook temperature from the theoretical temperature
of the steam at the set pressure. Actual temperatures were always lower
than theoretical temperatures as shown in Figure 6. The lower temperatures
were due to the partial pressure exerted by the volatile wood components
and air remaining in the chips. The digestor was flushed with steam prior
to the cooks to reduce -the effects of the partial pressure of air. When
data were plotted against the recorded temperature, trends became better
defined.
A test showed that no statistically significant relationship exists
between suspended solids and either time or pressure at the 90/ confidence
level. There were differences in the amount of suspended solids between
individual wood species. Suspended solids averages and standard deviations
for each species are listed in Table 11. Also listed are values for the
average chemical oxygen demand of the suspended solids along with standard
deviations.
The quantity of suspended solids that reaches the effluent is dependent
upon retention of the suspended solids on the forming wire. Retention
of suspended solids on the wire is governed by the thickness of the board
(COT)! The raw waste losing due to the dissolved solids content of the
33
-------
200
CO
THEORETICAL
120 140 160 180
DIGESTER PRESSURE PSIG
200
Figure 6. Digester temperature vs. digester pressure.
-------
160 170 180 190
COOK TEMPERATURE °C
Figure 7. Grams soluble BOD vs. cook temperature, aspen.
35
-------
350
300
cj- 250
T3
6
o> 200
ID
Q
O
CO
150
100
50
160 170 180 190
COOK TEMPERATURE °C
Figure 8. Grams soluble BOD vs. cook temperature, oak,
36
-------
350
300
•
* 250
T>
•
O
200
IO
Q '50
O
GO
en 100
50
D
IO m in
2 min
U
160 170 180 190
COOK TEMPERATURE °C
Figure 9. Grams soluble BOD vs. cook temperature, Douglas fir.
37
-------
-
•
o
350
300
250
200
IO
Q 150
O
m
rn 100
50
160 170 180 190
COOK TEMPERATURE °C
Figure 10. Grams soluble BOD vs. cook temperature, plywood trim.
38
-------
350
300
°r 250
200
in
Q
O
00
50
en 100
50
IO min
A 2 min
\
160 170 180 190
COOK TEMPERATURE °C
Figure 11. Grams soluble BOD vs. cook temperature, southern yellow pine.
39
-------
2 mm
r2 =.95
160 170 180 190
COOK TEMPERATURE °C
Figure 12. Grams soluble COD vs. cook temperature, aspen.
40
-------
160 170 180 190
COOK TEMPERATURE °C
Figure 13. Grams soluble COD vs. cook temperature, oak.
41
-------
350
300
°: 250
•O
*
o
o» 200
0 150
O
O
rn 100
50
IO min
r2=.97
5 min
r2 =.88
2 min
\
I
160 170 180 190
COOK TEMPERATURE °C
Figure 14. Grams soluble COD vs. cook temperature, Douglas fir.
42
-------
350
300
250
200
in
Q
O
O
10 min
r2 = .88.
160 170 180 190
COOK TEMPERATURE °C
Figure 15. Grams soluble COD vs. cook temperature, plywood.
43
-------
350
300
250
200
1C
Q 150
O
O
> 100
50
10 m in
r2 =.96
5 min
r2 =.95
2 min
r2 =.99
1
160 170 180 190
COOK TEMPERATURE °C
:igure 16. Grains soluble COD vs. cook temperature, southern yellow pine.
44
-------
100 -
Q
_l
LU
160
170 180 190
COOK TEMPERATURE °C
Figure 17. Yield vs. cook temperature, aspen.
45
-------
100-
Q
_J
UJ
70 H-
I
160 170 180 190
COOK TEMPERATURE °C
Figure 18. Yield vs. cook temperature, oak.
46
-------
100
Q
90
80
70
2 min
r2 = .97
5 min
r2 = .86
D
IO min
160 170 180 190
COOK TEMPERATURE °C
Figure 19. Yield vs. cook temperature, Douglas fir.
47
-------
00
LL)
>-
90
80
70
2 min
I
160 170 180 190
COOK TEMPERATURE °C
Figure 20. Yield vs. cook temperature, plywood trim.
48
-------
100
90
UJ
80
70
2 min
2 = LOO
1
160 170 180 190
COOK TEMPERATURE °C
Figure 21. Yield vs. cook temperature, southern yellow pine.
49
-------
170 180 190
COOK TEMPERATURE °C
Figure 22. Total dissolved solids vs. cook temperature, aspen.
50
-------
170 180 190
COOK TEMPERATURE °C
Figure 23. Total dissolved solids vs. cook temperature, oak.
51
-------
Q 350
LJ
O
Q 300
O
cr.
to
Q
O
to
Q
UJ
CO
Q
O
250
200
100
50
160 170 180 190
COOK TEMPERATURE °C
Figure 24. Total dissolved solids vs. cook temperature, Douglas fir.
52
-------
160
170 180 190
COOK TEMPERATURE °C
Figure 25. TotaFdissolved solids vs. coo-k temperature, plywood trim.
53
-------
Q 350
LU
O
Q 300
O
o:
Q_
CO
Q
o
CO
Q
LU
O
CO
CO
<
o
250
200
100
50
I
I
I- 160 170 180 190
COOK TEMPERATURE °C
Figure 26. Total dissolved solids vs. cook temperature, southern yellow pine.
54
-------
effluent remains approximately constant as the amount of recycle is increased.
TABLE 11. SUSPENDED SOLIDS DATA*
Wood Species Average
SS
pulp
Aspen 63
Standard Average Standard
Deviation CODSS Deviation
of SS
g/Kg pulp
14
g/Kg of CODSS
pulp g/Kg pulp
104 26
Average
BODss
g/Kg
pulp
14
Standard
Deviation
of BODSS
g/Kg pulp
in
Southern yellow
pine
Plywood trim
Douglas fir
Oak
63
82
95
180
14
22
28
29
110
133
151
261
33
32
50
78
8
3
20
24
13
5
13
27
*A11 values as mg/1
Because the quantities of suspended solids being produced and reaching
the effluent are affected by process variables other than cooking time
and pressure, their influence on the raw waste are not determined in this
study. The raw waste loads described in this paper are due to the soluble
portions only. Inclusion of suspended solids waste load only increases
scatter of the data. Soluble 6005 as grams per kilogram oven dry pulp
produced vs. temperature at several lengths of cooks are presented in Figures
7 through 11. Soluble CODs as grams per kilogram oven dry pulp produced
vs. temperatures, and yields vs. temperatures at several lengths of cooks
are presented in Figures 12 through 16 and 17 through 21, respectively.
Figures 22 through 26 show the quantities of dissolved solids released from
the wood during cooking and refining.
A non-linear regression analysis was used to plot the constant time lines
on the plots. The data fit well to the formula: Pollutant = A + B*exp(-C/T).
The parameter "A" represents the level of pollutants that would be released
with no cooking of the chips. T is the cook temperature and C is a constant
for each wood species and cooking time. Correlation coefficients (r^)
were all greater than 0.85 for COD and 0.80 for yields; correlations were
not determined for BOD. Scarcity of data for some BOD5 regression analyses
would have resulted in perfect correlation and thereby be misleading. BOD5
data were more scattered than data for other parameters.
Yields were calculated by four different methods: (1) by dividing
the original dry weight of wood minus the total dissolved solids by the
original dry weight of wood, (2) by dividing pulp consistency times the
55
-------
volume by the original dry weight of wood, (3) by dividing the pulp consistency
by the pulp consistency plus the concentration of total dissolved solids,
(4) and by dividing the weight of the collection of all fiber produced
by the original dry weight of the wood. Methods 1 and 3 were in close
agreement, whereas method 2 showed considerable scatter and method 4 gave
consistently lower results. Summation of the concentration of dissolved
solids and the consistency showed an overall experimental recovery of 1003
grams (2.21 Ib) material for each 1000 grams (2.20 Ib) dry wood processed.
The yield reported is the consistency in the press pit divided by the sum
of the consistency and the total dissolved solids.
Results of the survey conducted as part of this project, plus additional
information from the forest products industry, are listed in Table 12.
Experimental values for soluble COD and BODs are shown for the typical
cooking conditions used by the hardboard industry.
TABLE 12. MILL COOKING DATA AND CORRESPONDING SOLUBLE COD AND BOD LOADINGS
Soluble Soluble
Pressure Time COD BOD5
Mill Product psig min g/kkg g/kkg
Aspen
1 SIS 140 2 72 38
2 SIS 150 2 78 41
3 SIS 180-185 0.75 78 38
4 S2S 180-185 2-2.5 120 70
Oak
1 SIS 100 3-4 120 60
2 S2S 100 15-25 225-300 150
Southern yellow pine
1 S2S 150 8-14 120-130 90
2 S2S 175-200 5-6 140-190 75
Douglas fir
1 SIS 95-120 3-5 85-120 55-75
2 SIS 95 3-3.5 85 60
3 S2S 200 2.66 160 95
Plywood trim
1 SIS 120-130 3-4 82-90 38
56
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DISCUSSION
BOD is not as reliable an indicator of raw waste loading as COD
thtnfa? loarHatnrthf""t °I th: B°D data" A1SO the BOD do*s not measure
the total load to the waste treatment system. In Figure 27 an extendpd
time BOD on a hardboard mill's effluent shows that the ultimate BOD
approached the COD which was 2680 mg/1 for the press pit, and 5350 mq/1
for the white water. After 5 days only 60% of the BOD from the press
pit was utilized and only 40% of the BOD from the white water was utilized
The press pit water contained 288 mg/1 suspended solids and the white
water contained 1250 mg/1 suspended solids. Because BOD is not a good
indicator of the total load to the waste treatment system, is subject
to scatter and other inadequacies of the BOD tests, COD is a better
indicator of raw waste loads resulting from the use of different wood
species.
The data can be separated into two distinct groups corresponding
to SIS production or S2S production as shown in Table 13. BOD values
and COD values for the SIS board were consistently lower than those
for the S2S board. Differences in pollutional loading between individual
species are apparent in the data for both SIS and S2S boards, with the
S2S board having the greatest variation. The ranking of wood species
for the quantity of pollutants released is the same for both SIS and
S2S boards.
TABLE 13. AVERAGE EXPERIMENTAL COD AND BOD.- LOADINGS FOR EACH WOOD SPECIES
b
Wood Species
Aspen
Plywood trim
Southern yellow pine
Douglas fir
Oak
SS
g/kg
66
84
63
96
185
COD
SIS
75
85
--
95
120
g/kg
S2S
120
—
145
160
225
BOD5
SIS
39
38
--
63
60
g/kg
S2S
70
—
82
95
150
The ranking of wood species in Table 11 is not according to which
species inherently has more pollution producing potential in a hardboard
mill. When the wood species are compared at constant cooking conditions
the ranking is different. For example, at 8.84 atm (130 psia) for 5
minutes, the ranking from highest to lowest COD loading is southern
yellow pine, plywood trim, aspen, Douglas fir, and oak. The ranking
in Table 11 results from the particular cooking conditions used in the
mills for each wood species. Woods that have a potential of causing
high pollution loading may rank low on Table 13 because the .. +.
wood softens at less severe conditions and/or the mills are making an attempt
to reduce their pollution load by reducing the severity of cooking conditions.
57
-------
-------
The mill reporting the lowest cooking pressure for aspen (SIS)
\yec™]*ffo,rt to reduce its pollution load by reducing the cooking
time. This mill reduced Us raw waste load by 25% by reducing the cooking
time from 4 to 2 minutes. Most mills using aspen cook their chips for
2 minutes or less, whereas mills using other species of wood cook their
chips for 3 minutes or more. It is because aspen is cooked for a shorter
time than other wood species that the raw waste load from aspen is lower.
The high value for the raw waste load from oak from a SIS mill
is also an anomaly. The mill that reported the cooking conditions for
oak does not normally use oak, but did so when other wood was not available,
using equipment normally used for another wood species and not attempting
to optimize or shorten the cooking time. The long time used to cook
oak at the S2S mill is probably also unnecessary. Time required to
homogeneously heat a chip is seldom more than 3 minutes.
The degree to which the severity of cooks could be reduced has
not been explored. Factors such as increased refining energy, board
strength, board dimensional stability, board water absorption, swelling
thickness, and pulp shiye content need to be explored. Black and Larson
(2) have taken a preliminary look at these factors. A reduction in
cooking time appears most possible in S2S board production. The limit
to shortening the cooking time in S2S production is the time at which
the production of shives reaches an unacceptable level. Severe cooking
is used to ensure that no shives appear on the board surface. Shives
are likely to occur when the chips are not homogeneously heated.
If those mills that have not already done so were to reduce the
severity of their cooks by as much as their product specifications will
allow, the raw waste loads within each classification (SIS or S2S) would
probably be closer to each other. There would be little variation in
raw waste loads between SIS mills using different species of wood.
Raw waste loads from S2S mills would probably have greater variation
between mills producing S2S board from different wood species. The difference
in loading between SIS and S2S mills would also be much less if the
severity of cooks were reduced.
Special note should be taken of the results for Douglas fir and
Douglas fir plywood trimmings. Douglas fir chips produce a substantially
higher raw waste load than Douglas fir plywood trimmings. The plywood
trimmings contain an alkaline phenolic glue, have a smaller size distri-
bution, have a lower moisture content, and have a processing history.
The glue should have minimal effect on the raw waste load as it makes
up very little of the chip mass. The pH of the solution apparently
played no part since there was no difference in the pH's of the liquid
resulting from cooks of other species. If the size of the chips was
responsible for the difference, one would expect a higher raw waste
load from the samples with the smaller chips. The opposite occurred.
To check if the differences in the moisture content of chips was
the cause of the differences in raw waste loadings, further experimentation
was performed. Two samples of Douglas fir taken from the same batch
59
-------
of chips used earlier in this study were dried, one to 35% moisture
and the other to 25% moisture. The 2 samples were then cooked at 8.8 atm
(130 psia) for 5 minutes and processed by the methods used in the experimen-
tal work reported on in this paper. The results showed no difference
from earlier cooks of Douglas fir at the same pressure and time. Drying
of the chips has no effect on the raw waste load from a hardboard mill.
The effect on the raw waste load of drying the chips to oven dryness
has not been investigated. Plywood trimmings would have been dried
to oven dryness in earlier processing.
The most likely reason that the raw waste loading from plywood
trim was lower than that from Douglas fir is the previous processing
history of the plywood trimmings. The exact history of the plywood
trimmings could not be traced because the mill from which the chips
were obtained has a large number of sources for its wood supply. In
the plywood process round wood is often heated in a hot water bath or
steamed. Part of the soluble material present in the wood is leached
into the water bath or condensate. By the time plywood trimmings reach
a hardboard mill, a portion of the water soluble materials that contribute
to the raw waste load have been removed from the wood.
Comparison of Results to Mill Values--
Raw waste BOD averages from Figure 4 are listed in Table 14 with
predicted BODc values. Considerable differences between mill BOD data
and experimental BODs data exist.
TABLE 14. COMPARISON OF MILL BODs TO PREDICTED BODs
Mill
B
C
E
G
Wood Species
Plywood trim
Douglas fir
Aspen
Aspen
Mill BOD5
Kg/t pulp
57
61
115
225
Predicted 6005
Kg/t pulp
44
96
49
70
Predictions of dissolved solids loadings to hardboard mill white
water systems were compared to measured values for three mills as shown
in Table 15.
All of the predicted dissolved solids values are between 17% and
20% higher than the measured values. The lower measured values are pro-
bably due to precipitation of tannin materials onto the board when the
pH is lowered and alum added.
60
-------
TABLE 15. COMPARISON OF MILL DISSOLVED SOLIDS LOADINGS TO PREDICTED
DISSOLVED SOLIDS LOADINGS
Wood Species
Aspen
Plywood trim
Southern yellow pine
Cook
Temperatures
OC
165
175
187
Cook
Time
Min
2
3
5
Predicted
Dissolved
Solids
Kg/KKq
60
70
130
Measured
Dissolved
Solids
Kg/KKg
50
60
no
All chips used in the experiment were fresh chips. No attempt was
made to quantify increases in raw waste load due to aging of the chips.
For instance, if chips were used that had been stored in a pile and had
undergone fungal and thermal degradation, the raw waste load would surely
be higher than shown in this study.
CONCLUSION
Significant differences existing in the raw waste load resulting
from the manufacture of hardboard can be related to either the production
of SIS or S2S board and to the wood species used. Actual loads from hard-
beard mills deviate from the experimentally determined values because
of process variations such as the amount of recycle. A reduction in
excessively severe cooking conditions at some mills could reduce the S2S
average raw waste load. Differences in the soluble raw waste load between
wood species used is of smaller magnitude than differences for SIS and
S2S production. Suspended solids in the raw waste load proved to be
independent of the cooking conditions but highly dependent on the species
of wood used. The quantity of suspended solids reaching the effluent is
partially regulated by the amount of white water recycle and the use of
retention aids.
61
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SECTION 6
EFFECTS OF WHITE WATER RECYCLE
Evans Products, Corvallis, Oregon, invited EPA personnel in the
wood products research section to monitor water characteristics within
the Evans Products hardboard mill while the company made process changes
to decrease water usage by increasing recycle of white water. EPA's
role was that of collecting and analyzing samples.
METHOD
Water use was measured throughout the mill at all locations by
both EPA and mill personnel. Effluent flows from the white water tank,
press pit, and total effluent were measured. Flow from the white water
tank was measured by recording the level in the tank. Excess white
water overflowed through a twelve-inch diameter pipe. The flow from
the white water tank at any tank level was calibrated by filling the
tank with the overflow pipe plugged, then pulling the plug and measuring
the level at short time intervals. The slope of the line resulting from
plotting the level-time data is the flow at any particular tank level.
The resulting curve was cross checked by adding a known flow of water
to the tank with all other exits blocked. The calibration curve flows
came quite close to the known flows. The slope of the calibration curve
fit very well to the theoretical flow equations for flow into a circular
pipe.
Flow from the press pit area was measured by calibration of the
pump capacity volumes by dumping a known flow into the press pit for
a day when no production was taking place. The pump was operated by
a level control switch. The total amount of time the pump was on that
day was automatically recorded. By recording the amount of time the
pump was on during production, the flow could be determined.
Flow from the aerated lagoon settling pond was determined by measure-
ment of the pond level. The pond drained through a V notch weir.
Other water flows in the mill were calculated by collection of
the total flow for a set amount of time and measuring the volume, or
by consistency measurements and water balances.
The white water and press pit flows were sampled. Composite samples
were taken from the white water system by a Hydragard sampler. The
sampler took a 100 ml sample about every 15 minutes. The Hydragard
sampler operates by blowing the contents of a sample chamber into the
62
-------
collection chamber with air on a set time interval. When the air pressure
ceases, the sample chamber fills up with liquid again. The press pit
was sampled with a dip-stick type sampler. The sampler periodically
dipped a pipe with a stop at one end and hole in the top into the water
stream. When the pipe returns to its normal position, the collected
sample flows to a collection bottle.
The collected samples were analysed for total BOD, soluble BOD,
total COD, soluble COD, suspended solids, dissolved solids, and volatile
dissolved solids.
In addition, grab samples were collected at various process locations.
Samples were taken out of the head box, wire drain, press rolls, overlay
and cyclone.
Extent of White Water Recycle
Closing up of the white water system was approached on a step-by-
step basis. First, freshwater usage at the cyclones was replaced by
white water. Then the consistency regulators were tied into the white
water system. The system was run for several months in this mode to
record any changes.
Next the freshwater to the secondary refiner that prepared finely
reformed pulp for the overlay was converted to white water usage. Then
the shower water was connected to the white water system. This brought
the percent recycle to nearly 90%.
The remaining freshwater usages were at the freshwater feed to
the digester (steaming chamber), vacuum pump seal water, and some high
pressure showers. These were not converted to white water usage because
of feared abrasion in the close tolerance high pressure pump for the
digester feed and in the close tolerance vacuum pumps.
OBSERVATIONS AND RESULTS
Data obtained from this study were from both company records and
EPA tests. The data was analysed to attempt to determine the causes
of raw waste load variation, process water compositions, effects of
process water recycle on process conditions and effluent loading, and
the effects of decreasing flows on the waste water treatment system.
Waste Load Variation
Production records were compared with raw waste loadings and flows.
Raw waste loads and flows showed no dependence upon the thickness of
board being produced. Flows of excess white water also did not depend
upon the production for the day. During days of low production the
Fourdrinier machine was operated as normal, with the unused mat going
to broke. Water discharges are dependent on water reuse practices rather
than production dictates.
63
-------
Measurements were made of the quantity of dissolved solids entering
the white water system from the cyclone and of the quantity of dissolved
solids being discharged from the mill. Figure 28 shows the frequency
of occurrence of quantities of dissolved solids loaded to the white water
system and quantities of dissolved solids discharged. The figure illustrates
that nearly all of the effluent raw waste load is due to variations in
the refining process or wood supply. The two high points on the line
for dissolved solids loading from the cyclone came at a time when the
wood was being cooked for a longer time than normal.
Processes Water Composition
Evans Products took samples of process water at various locations
throughout the mill. These samples were analysed for suspended solids,
dissolved solids, non-volatile dissolved solids, sugars, and tannins.
The results of the investigation are shown in Table 16, as % sugars,
% tannins and % unaccounted for material in the volatile portion of the
dissolved solids.
TABLE 16. PROCESS WATER COMPOSITION
Location
x*
%
Sugars
s* n*
%
Tannins
X s n
% %
Unaccounted for
X
%
Cyclone
Plywood trim
before recycle
Oak before recycle
Oak after recycle
Stock chest
Head box
Fourdrim'er
roller sections
Vacuum
Press rolls
White water tank
Hot press pit
60.0
75.1
74.8
72.5
78.4
72.1
78.1
74.9
71.9
62.1
2.7
3.8
5.8
21.4
5.2
6.2
3.1
6.9
5.2
9.2
3
2
5
3
10
4
2
4
n
9
14.7
14.5
13.5
10.7
13.4
14.1
15.2
15.5
13.3
19.7
0.5
3.3
2.3
8.8
1.2
1.4
—
1.2
1.4
3.8
2
2
5
2
10
4
1
9
12
9
15.9
10.4
11.7
16.8
8.2
13.9
6.7
9.6
14.8
18.2
X-mean, s-standard deviation, n-number of samples
64
-------
CTl
cn
.Q
•
T5
d
<£>
Q
150
\ 100
o> 90
^ 80
-------
A difference between the proportion of sugars in the water between
the cyclones using plywood trim and the cyclone using oak is apparent.
The portion of sugars in the cyclones was 75.1% for oak and 60.4% for
Douglas fir. These differences became obscure once recycling of white
water to the cyclone sprays was installed.
The composition of the white water changed throughout the processes.
Variations in the sugar concentration occurred at various locations along
the forming line. The proportion of tannins in the liquid phase increased
along the forming line. The composition of the hot press discharge was
considerably different. The proportion of sugars significantly decreased
while the proportion of tannins and unaccounted for materials increased.
An explanation for this is either that more material was released from
the wood due to the pressure and temperature, or that the soluble wood
sugars were charred due to the high temperatures encountered. A material
balance about the hot press showed there was little or no change in the
quantity of dissolved sugars due to hot pressing. The amount of dissolved
tannins present increased by about 58%, and the amount of unidentified
soluble material present in the press pit water increased by about 50%
when the board passed through the hot press. There was a 25% increase
in total materials dissolved after passing through the hot press. The
material balance indicates that more materials are dissolved from the
fibers during hot pressing, and that if any sugars are dissolved, they
or an equivalent amount of sugars were degraded or oxidized.
Effects of Increased Recycle on Water Properties
Suspended Solids—
As the amount of recycle was increased, the quantity of suspended solids
going to the effluent decreased as shown in Figure 29. When the white
water discharge was between 20.9 to 29.2 Kl/KKg (5000 to 7000 gal/Ton),
suspended solids in the raw effluent averaged 28.8 Kg/KKg (57.6 Ibs/Ton).
After a reduction in flow to 10.4 to 18.8 Kl/KKg (2500 to 4500 gal/Ton),
suspended solids in the raw effluent dropped to 16.4 Kg/KKg (32.8 Ibs/Ton).
Further reduction of flow to 4.2 to 10.4 Kl/KKg (1000 to 2500 gal/Ton)
resulted in 9.1 Kg/KKg (18.2 Ibs/Ton) suspended solids in the raw effluent.
The concentration of suspended solids in the white water increased after
less than 12 Kl/KKg (50,000 gal/Ton) white water was discharged, as shown
in Figure 30.
A change in the nature of the suspended solids in the white water
occurred as more white water was recycled. Settleable solids dropped
from an average of 840 mg/1 to nil. This reduction in settleable solids
is attributed to the increased overall retention of larger solids due
to repeated passes through the fiber mat. The nature of the solids in
the press pit effluent remained unchanged when recycling was increased.
Most of the suspended and settleable solids in the press pit effluent
originate from blown board or other mishaps in the pressing process,
and from dust and fibers from handling of the pressed boards.
66
-------
-Q
•
TJ
o
D>
50 -
O WHITE WATER SS
• PRESS PIT SS
CTi
Q
LU
CD
O
CO
Q
CO
Q
O
CO
Q
LU
Q
LU
Q_
CO
40
30
20
0
0
o 8
o o
o
o
o
o o
GO
O o O O
6
I
5 10 15 20 25 30 35
WHITE WATER DISCHARGED KI/KKg o.d.b.
Figure 29. Discharge of suspended solids vs. white water discharge.
40
-------
00
o>
e
^ 3000
0
1-
cr
h-
LU
Z 2000
o
0
CO
Q
l
•
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^ 1000
Q
LU
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CO
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0
—
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o
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o
80 § o o o
o o o o° Q) g8 o
0 0 °
o o
0
1 1 1 1 1 1 1 1
0 5 10 15 20 25 30 35 40
WHITE WATER DISCHARGED Kl KKg o.d.b.
Figure 30. White water suspended solids concentration vs. white water discharge.
-------
Dissolved Solids—
An increase in the amount of recycle causes in increase in the total
dissolved solids concentration. A material balance yields the equation
Cm =_L describing the relationship between the white water concentration
Wm+E
(Cm) and the quantity of effluent (E). L is the loading of dissolved
organic solids to the white water system and Wm is the water contained
in the mat. The equation does not include the press pit discharge. Data
taken at Evans Products fit very well to this equation, as shown in Figure
31, with a correlation-coefficient of 0.96. Three data points were excluded
from the correlation because hog fuel containing bark was being processed
at the time, significantly increasing the dissolved solids loading to
the white water system. The quantity of dissolved solids going to the
effluent is shown in Figure 32.
As a side note, the loading of dissolved solids to the white water
system as predicted using data obtained in the comparison of pollution
loads resulting from different species of wood was 73 g/Kg pulp (146
Ib/Ton). The loading found in the measurements in Evans Products white
water system was 61 g/Kg (122 Ib/Ton) pulp. The difference may be caused
by precipitation of some of the tannins dissolved during cooking by addition
of alum. Alum is added to help precipitate waxes. Many of the tannins
dissolved are phenolic compounds.
Chemical Oxygen Demand (COD) —
One of the objectives of increasing the amount of recycle is to
decrease the raw waste loading to the treatment system. The total mill
raw waste load COD was plotted as a function of total mill discharge in
Figure 33.
Figure 33 shows that the quantity of soluble COD discharged changes
very little as the amount of recycle of white water increases. The total
COD, including the contribution due to suspended solids, decreases with
increasing recycle. BODs raw waste loads behaved similarly, as shown in
Figure 34, except that the Total BODs was not as responsive to the increase
in recycle. The BOD5 of suspended solids does not exert itself until
later in the BOD test, sometime after the 5 day time allotment in the
test.
Temperature—
Temperatures rose from about 42°C (108°F) to about 65°C (150°F)
in the head box when recycle was increased from about 50% recycle to
about 90% recycle. This temperature rise was not enough to cause any
noticeable problems.
Board Quality Changes--
Increasing the white water did not change the board strength or
dimensional stability. A decrease in water adsorption was noticed, so
use of a starch additive to lower water adsorption was discontinued.
No sticking on the hot press occurred.
69
-------
o>
£
<
r-
Z
LL!
O
Z
O
O
CO
Q
Ii
O
CO
Q
UJ
>
O
CO
CO
8000
7000
6000
5000
4000
3000
2000
Q 1000
D.S. Concentration =
Wm + E
L=dissolved solids from cyclone = 61 Kg/KKg
Wm = water in the mat = 2.68KI/KKg
E= white water discharge
i O
5 10 15 20 25 30 35
WHITE WATER DISCHARGED KI/KKg o.d.b.
40
Figure 31. White water dissolved solids concentration vs. white water discharge.
-------
-Q
•
T3
•
O
O>
150
g 125
Q
UJ
g 100
<
1 75
Q
O
CO
CO
0
O WHITE WATER TDS
• PRESS PIT TDS
r2= O.22
5 10 15 20 25 30 35
WHITE WATER DISCHARGED KI/KKg o.d.b.
40
Figure 32. Discharge of dissolved solids vs. white water discharged.
-------
180
•
_Q
T3 I6°
O
o> 140
\ 120
100
Q
UJ
O
a:
80
60
o
C/)
Q 40
Q
O 20
O
0
0
O TOTAL COD
A SOLUBLE COD
A
00
A
°
o°0
03
A A AA
8
A
A
10 15 20 25 30 35
TOTAL DISCHARGE KI/KKg o.d.b.
40
45
Figure 33. Discharge of COD vs. discharge.
-------
Co
180
<
JD
"O
d
en 140
\ 120
m
\^
Q 100
UJ
1 8°
I 6°
CO
Q 40
Q
0 20
GO
n
o
o
o
o
0 0
o o cPo
0 0 o
^ o
o
—
—
1 I 1 1 1 1 I 1
10 15 20 25 30 35
TOTAL DISCHARGE KI/KKg o.d.b.
40
45
Figure 34. Discharge of BOD vs. discharge.
-------
EFFECTS OF RECYCLE ON THE WASTE TREATMENT SYSTEM
Evans Products treats its waste water by primary settling, aeration
in a lagoon, and by final settling. Primary settling consists of two
ponds in series with capacities of about 9.5 million liters (2.5 million
gallons) each. Sludge is periodically pumped to a sludge drying basin
when the settling ponds become filled. The aeration basin holds about
37.8 million liters (10.0 million gallons), and has 5 aerators with a
combined total of 268 Kilowatts (360 horsepower). The final settling
pond also holds 18.9 million liters (5.0 million gallons). Sludge
is pumped from the settling lagoon when the suspended solids in the ef-
fluent becomes too high.
This waste treatment pond also receives waste water from a battery
separator plant which is largely cooling water. The battery separator
plant began to recycle its process and cooling water about a year after
the hardboard plant had completed its recycle program. Since the battery
separator plant waste water contains much less BOD than the hardboard mill,
it mainly acted as a dilutant to the hardboard mill waste.
As recycle in the hardboard mill is increased, the BOD loading to
the treatment system does not decrease substantially until 80 to 90%
recycle is obtained. However, the total organic raw waste load, as measured
by the COD, does decrease with increasing recycle. The waste treatment
system largely benefits from the reduced flow. Increased detention time
in the aeration basin allows more time for biological degradation of
the wastes and thereby results in increased treatment efficiency. Reduction
of the raw waste load results in an additional improvement of the effluent
quality. Figure 35 shows the BOD of the effluent following the final
settling pond at various flows. Figure 36 shows the percent BOD removal
for the different flows.
Suspended solids are not substantially decreased by the longer detention
time in the aeration basin. Suspended solids removal is improved in
the final settling pond because of the increased detention time. Some
improvement in the final suspended solids discharged results from the
lower loading of suspended so'lids and organic materials to the lagoon.
Figure 37 shows effluent suspended solids as a function of flow. Figure
38 shows that the reduction in suspended solids in the treated effluent
is not due to a reduction of input BOD, but is due to improved settling
in the final lagoon.
74
-------
2000
en
o
Q
\
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Q
LU
O
01
<
X
O
C/)
in
Q
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1500
1000
500
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A APR- J UN
X JUL-SEP
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o
A
A
D
8
A
0 0
A<0 A A X
4in DA ^ x
# X
I 1 I I
0
Figure 35.
FLOW MI/D
BOD discharged from final settling pond vs. effluent flow.
-------
CT)
100
_l
> 80
0
2>
LU
* 60
Q
O
CO
40
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0^
on
D A \ X XX
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A APR-JUN °
X JUL-SEP
D OCT-DEC
I I 1 1 I I
0
12345
FLOW MI/D
Figure 36. % BOD removal vs. effluent flow.
-------
SUSPENDED SOLIDS
DISCHARGED Kg/Day
_ ro o
0 O C
o o c
o o o c
0 JAN-MAR n A
A APR-JUN
X JUL-SEP Q QA ° ^
D OCT-DEC A <&° £0 X
^ * A yD
fl n A v
x
^ i i i i i
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FLOW MI/D
Figure 37. Suspended solids discharged from final settling pond vs. effluent flow.
-------
CO
1 .V
h-
ZD
Q_
5 0.8
Q
O
5 0.6
1—
1
LU
3 0.4
U_
u_
UJ
^ 0.2
—
CO
n
0 JAN -MAR
A APR-JUN
X JUL-SEP o
A
D OCT-DEC A m A
0 ° °
A^b A ^ AA.
fl ^A A
AD Q x X
0 °
D X
D X x
A A
X v/
X
X
1 1 1 1 1 1
0
3 4
FLOW MI/D
figure 38. Suspended solids in effluent/BOD input vs. effluent flow.
-------
REFERENCES
1. Panak, J. "Reduced Consumption of Water in the Manufacture of Wood
Fiber Building Boards by the Wet Process." Drevo 25, No 6-1512
156. June 1970.
2. Selander, Stig D. "Report on the Totally Closed White Water System
at the Wet Process Fiberboard Mill in Casteljalou, France." 2nd
International Congress on Industrial Waste Water and Wastes. Stock-
holm. February 47, 1975.
3. Gran, G. "Wastewater from Fiberboard Mills." Pure and Applied Chemistry,
29:13. 1972.
4. "Product Standards for Today's Hardboard." American Hardboard Associa-
tion. Nov. 1973.
5. Personal Communication with 0. B. Eustis, Abitibi Corp. Alpena, MI.
6. Mitheb, B. B., Webster, 6'. H., and Rapson, W. H. "The Action of
Water on Cellulose Between 100 and 225°C." TAPPI 40:1. 1957.
7. Richter, George A. "Some Aspects of Prehydrolysis Pulping." TAPPI,
39:7. 1956.
8. Barnardin, Leo J. "The Nature of the Polysaccharide Hydrolysis in
Black Gumwood Treated with Water at 160°C." TAPPI, 41:9. 1958.
9. Unpublished EPA data.
10. Merrill, W., French, D. W., and Hassfeld, R. L. "Effects of Common
Molds on Physical and Chemical Properties of Wood Fiberboard, Part
II of a Series of Wood Fiberboard Studies." TAPPI, 48:8. 1965.
11. Black, Ernst L., Larson, Stig A. "Increased Pulp Yield as a Means
of Reducing the BOD of Hardboard Mill Effluent." Svensk Papperstiding,
75:723. 1972.
12. Atack, D. "On the Characterization of Pressurized Refiner Mechanical
Pulps." Svensk Papperstiding, 75:89. 1972.
13. Baldwin, S. H. and Goring, D. A. I. "The Thermoplastic and Adhesive
Behavior of Thermomechanical Pulps from Steamed Wood." Svensk Papper-
stiding, 71:646. 1968.
79
-------
14. Blecken, H. G., and Nichols, T. M. "Capital and Operating Costs of
Pollution Control Equipment Modules—Vol. II--Data Manual." EPA-R5-
73-023b. July 1973.
15. Minelli, M. P. "Factors Affecting Slime Accumulation in Fiberboard
Mill Process Water." A thesis submitted to Oregon State University,
June 1976.
80
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APPENDICES
APPENDIX A. DIGESTER PRESSURE, TEMPERATURE, TIME, AND RECOVERY DATA
Department of
Forest Products
Oregon
, .State .,_
University
Corvallis, Oregon 97331
December 29, 1975
Mr. Victor Dallons
Industrial Treatment & Control
200 SW 35th Street
Corvallis, OR 97330
Dear Vic:
Enclosed are the tabulated data for the wood steaming experiments which
we performed for you under Project F-818-100. We ran the experiments as
closely as possible according to the schedule in your letter of July 31,
1975. Briefly, the various chip and wood samples were steamed at the
indicated pressure in our 2-pound digester for the specified time, and
the effluents were delivered to you for BOD and other analyses. We deter-
mined the resulting yields from these treatments, and this is the only
test which we performed in our lab on the products (solid or liquid) of
the experiments.
We subjected the yield data to multiple regression analysis, with the
results given in the accompanying table. Combining all 70 experiments
in one pool, both pit yields and flatbox yields have poor correlation
with the 3 independent variables, steaming time, temperature (actual or
recorded), and pressure.* Pressure was the most significant variable for
prediction of pit yield, closely followed by temperature, while steaming
time was the most significant variable for flatbox yield. In view of the
low overall multiple correlation coefficients (.27 and .20 respectively),
little significance should be attached to these relationships.
Originally, both theoretical and recorded temperatures were included in
the regression analysis. Since the pressures and theoretical tempera-
tures were perfectly correlated (r=l), there was no value in keeping both
variables in the analysis, and the theoretical temperature was dropped
out.
81
-------
By analyzing the data for each wood sample individually, the regressions
become more meaningful.** The (r2)'s generally improve to a maximum of
.76 for aspen, although the r^ for plywood trim is only .27. With some
exceptions, steaming time generally rates secondary in importance to
steaming pressure in terms of influencing the yields, and again the tem-
perature follows the pressure closely in terms of influence. Since the
pressure and temperature are so closely correlated, and the pressure pre-
cedes the temperature in the regression analysis, the apparent significance
of the temperature is lower than it might otherwise be.
In summary, we can state that, within the ranges of the independent variables
tested, temperature seems a bit more influential in determining yield than
time. Steam pressure and temperature are highly correlated, but it seems
most likely that it is the temperature that is responsible for loss of wood
substance in these experiments rather than the steam pressure per se. While
the pressure may be important in promoting penetration of moisture into the
wood, the temperature of the steam is the factor that determines the rate
of breakdown and ultimate solution of woody material into the aquepus
effluent.
If you have further questions on this, please do not hesitate to contact us.
It has been a pleasure working with you on this project, and we hope that
we may conduct future cooperative work on other projects.
Yours truly,
Walter J. Bublitz
Associate Professor
Pulp and Paper
klm
enc.
cc: Resch
Hull
Currier
** Only pit yield was thus analyzed, since flatbox yield showed poorer
correlation with independent variables from the pooled analysis.
82
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Multiple Regression Data for Digester Yields
Yield data
from
Species
# of tests
Flat-
box
All
70
Pit
All
70
Pine
14
Douglas
fir
14
Oak
14
Plywood
trim
14
Aspen
14
Simple Correlation With:
X(l)
X(2)
X(3)
-.31
-.31
-.29
Multiple Correlation
r2
Regression
B(0)
B(l)
B(2)
B(3)
"t" Value,
t(l)
t(2)
t(3)
.20
-.26
-.45
-.41
(All) :
.27
-.11
-.59
-.59
.37
-.58
-.46
-.45
.59
-.33
-.79
-.75
.73
-.37
-.02
-.03
.28
Coefficients :
131.5
-1.22
-.067
-.084
Regression
-2.8
-.37
-.20
56.8
-.693
-.185
.178
331.7
-.398
.222
-.760
86.3
-1.17
-.123
.074
163.4
-.730
-.039
-.212
Coefficients:
-2.3
-1.5
.62
-.58
+ .36
-.55
-3.1
-.90
.23
-2.0
-.27
-.61
-207.5
-.323
-.494
1.06
-.67
-1.4
1.3
-.34
-.84
-,86
.76
220.5
-.504
-.064
-.338
-1.1
-.46
-1.0
Independent Variables:
X(l) Steaming time, minutes
X(2) Steaming pressure, psi^
X(3) Steaming temperature, °F
83
-------
F"
^TOonpaF^:
COOK
HO.
42
26
24
12
25
52
39
28~A
15
44
68
13
37
55
COX
TIHE
MM
•f-f-f-f * If 4f
2
2
2
C.
5
5
5
5
5
5
18
18
18
13
COOK
PRESS.
PSIG
rT'fTy'T T^M^T1
108
139
168
289
188
188
138
168
288
288
188
138
168
288
TEHPERfiTURE
DEGREES F
THEO. fiCTURL
333
356
378
383
338
338
356
378
338
388
338
356
378
388
r TT ^^*P TT T"l*
(1)
348
363
378
333
332
348
363
376
379 .
332
358
356
379
TTMC
— • — ilnhj
TO
PRESS.
8.58
8.75
8.75
125
8.58
8.58
8.75
188
158
1.17
8.58
8.58
8.92
8.75
MINUTES-
TO
REFINER
3.5
4.5
3.5
3.5
4.5
3.8
3.5
3.8
4.3
3.5
3.5
4.9
3.5
3.8
ip&fHa&sfW
IN
PIT
4c.t#*#*$$#
16
14
17
15
17
13
IS
16
13
17
17
13
16
13
CONSISTENCY, V.
ON IN
SCREEN PIT
6.22
6.69
6.54
6.43
6.68
6.99
6.78
5.72
5.99
7.12
7.97
6.58
5.95
5.91
6.82
7.16
6.85
6.69
7.88
6.71
6.88
6.82
6.63
6.71
8.18
6.85
6.62
5.78
|!Trt PI •>
ilCLU> /.-••
FROM FROH
PIT FLRT60X
93. 1 93. 6
97.7
93.5
91.3
96.6
915
9Z8
93.1
98.5
916.
1116
93.5
98.4
78.8
95.3
89.9
82.7
97.6
92.6
87.9
84.6
81 4
83.2
181. 2
84.8
84.9
77.8
RERflRKS
ECORO. 1
DUPLICflTE COOKS
DUPLICflTE COOKS
REFER! COOK
DUPLICflTE COOKS
DUPLICBTE COOKS
^
-------
ClO LJ G L_ Fl S F" I 1R
I-M I'-i-f-.y^-l'^-r^T^TT'^y'r^^^^^T^'I^T-^^rT-f'T^^^-T^T^^T^^t^^-J^^T'^T'-i^^^
COOK 030K TEMPERfiTURE TIME, MINUTES CONSISTENCY, Z —YIELD, Z-
COOK
HO.
TIME
MIN.
PRESS.
PSIG
DEGREES F
THEO.
fiCTUflL
TO
PRESS.
TO
REFINER
IN
PIT
ON
SCREEN
IN
PIT
FROM FROM
PIT FLfiTBftX
REMfiRKS
^^'f^r^'lr1""''1""0"^****'"**''"'^^
7
53
78
27
17
03 -~
cn .H>
22
35
IS
45
54
23
2
33
2
2
2
2
2
5
5
5
5
19
19
19
19
18
169
139
168
169
289
199
139
160
298
199
138
138
160
209
338
356
370
379
388
338
356
379
38-3
338
356
355
379
388
328 9.42 18 17 6.42 7.13 97.3 911
348
363
363
366
333
(1)
355
378
331
348
348
363
372
0.83
1.88
188
188
0.59
8.92
108
1.59
9.67
0.67
8.75
117
125
3.3
3.3
3.5
15
3.5
4.3
4.3
3.8
2.3
3.3
3.5
4.0
4.0
22
15
18
20
16
22
18
18
16
21
17
17
17
6.28
5.93
5.59
6.57
6.23
6.76
5.93
5.32
5.79
6.33
6.53
5.29
4.72
6.99
6.74
6.38
6.55
6.36
6.78
6.53
6. 16
6.89
6.61
6.79
5.81
5.33
95. 4 91 9
9Z 9 85. 8
87. 1 87. 3
89. 4 89. 7
86. 8 90. 4
92. 5 87. 0
89. 1 86. 4
84. 0 76. 8
81 9 86. 1
S8. 3 87. 5
92. 7 84. 9
79. 3 76. 3
72. 8 78. 2
DUPLICaTE COOKS
DUPLICflTE COOKS
TEMP. RECORD. PROS.
DUPLICflTE COOKS
DUPLICflTE COOKS
m'm*****'!^^*^
-------
s_» Fl K
CD
COCK
NO.
•l-iri^fc-L-t-J
4 -A
18
33
21
61-A
41
•43
S3
28
1
S6
53
16
4S
. .j.^..
"T Tf T'rTvl
COOK
TI?E
HIM.
2
2
2
2
5
5
5
5
5
5
18
18
18
18
*******
•^Hr T^T-I* -r •!*•!
YTCI Pi *'
itLU^ f»
FffiM FROM
PIT FLfiTBOX
r- r-r -i • -r-r- T* • T* - t-i--^ - r • i •• r™ r -T- r- r • r1 • T •-!• • i
REMfiRKS
^•^^^••^•*ii-l-iiii-,l-i*i-i-*i*^^
8.42
8.83
0.75
117
0.33
0.67
8.67
108
188
8.32
0.25
8.58
1.88
125
3.8
3.5
3.8
3.5
3.3
3.5
3.8
3.3
3.5
4.8
Z8
3.5
4.8
3.3
15
22
13
IS
15
17
17
17
IS
17
17
17
17
14
5.68
5.72
5.83
5.87
5.66
5.52
5.43
4.77
5.38
4.33
5.23
(1)
4.82
4.23
5. 97 81 5 86. 4
6.19
6. 83
5.57
6.41
6.17
6.83
5.38
5.68
5.88
6.16
5.33
5.53
5.14
83. 3 88. 5
8Z 3 86. 3
76. 1 77. 5
87. 5 85. 7
84. 1 84. 2
S3. 1 84. 3
73. 4 71 1
77. 6 78. 6
68. 2 68. 3
84. 1 73. 3
73. 4 (1)
76. 2 74. 5
78. 2 78. 2
REPEflT COOK
WJPLICflTE COOKS
OUPLICHTE COOKS
DUPLICRTE COOKS
DUPLICfnE COCKS
^TIEE DESTROY Sftf.
Mrtfr^^m*M°fcM'*^m4^^^^
-------
F> L_ V" 1*1 O O O T IR I M
,..^,..J , .,_,..,.
COCK
NO.
•^-^••IC^WP^
57-A
43-A
24
3
59-A
00
•^J f
6
47
S7
59
68 -a
3
18
14
•!••»"»« r-r-f 't 'i
COOK
TIHE
BIN.
1t^"rirf'fri"i
2
2
w
2
2
5
5
5
5
18
18
18
18
18
*•»' 'j'-i-i'-i-i'T-t-r-i
COOK
PRESS.
F3IG
188
138
169
288
288
198
138
163
288
189
1%
138
168
288
TEMPERHTURE
DEGREES F
THEO.
r|^^.^^^-J«J.^
338
356
378
388
388
338
356
378
388
333
338
356
378
383
flCTUflL
332
351
365
378
381
332
351
364
3?8
332
332
349
362
376
ir~r*F •r-rTV T*i*t
.--rTtMr
i IltC
TO
PRESS.
8.25
8.42
8.92
158
1.33
8.50
0.83
8.83
125
8.33
8.25
9.58
8.58
133
*1vT»-fwT~>^-P-T*-I"l
j MINUTES"
TO
REFINER
3.3
3.8
4.8
3.5
3.8
3.8
4.5
3.8
3.8
3.8
3.3
4.8
3.5
4.3
P-Ii-rf-lcT-i^T'T
IN
T-f -i— !-i*-i«i* • !"P*P'I« Tf l"f— r— 1" I"l"t
CONSISTEHCV, Z
ON IH
. iiTri r-, •>-
fiLLl/J Im
FROM FROM
PIT SCREEN PIT PIT FLflTBOX REHflRKS
li4uMt4Q)[4i4c4f4!4E4i4i4aMt^^
14 6.28 6.?3 91.5 88.3
13
18
38
18
13
21
16
17
15
14
28
13
14
6.87
6.9?
6.33
7.83
6.56
7.48
6.92
7.88
6.42
6.52
6.39
5.82
6.32
7.84
7.53
6.57
7.32
6.99
7.67
6.47
7.83
6.73
6.89
7.81
6.12
6.82
96. 1 91 4
182. 8 97. 8
89. 7 85. 2
99. 9 89. 3
95. 4 98. 5
104. 7 90. 2
89. 3 91 4
95. 6 84. 2
91 9 93. 8
94. 8 89. 5
95. 7 89. 8
83. 5 88. 8
S3. 1 84. 9
RE PERT CCOJC
DUPLICfiTE COOKS
DUPLICfflE COOKS
DUPLICBTE COOKS
DUPLICATE QMS
-------
COOK
HO.
11
48
58-A
43
32
29
51
56-4
38
9
S4
5
31
DM
TIRE
2
2
2
2
2
5
5
5
5
19
19
13
19
18
COOK
PRESS.
PSIG
189
188
139
168
288
198
138
169
288
198
138
168
208
288
F*yTT)T'P-f'T-T^**'ft-y)H[-T-E'T
TEHPERflTURE
DEGREES F
THEQ. RCTUfiL
333
338
356
379
388
333
356
379
383
338
356
378
388
388
332
332
349
345
372
332
349
363
376
332
337
362
368
373
Tf^f^-fft-f-^H-f
TfMF
— i int,*
TO
PRESS. R
8.67
8.42
8.92
188
117
9.42
8.67
168
125
8.58
8.75
125
117
142
**********>!
^^jf,^-f^fHj-Jf
HINUTES-
TO
EFINER
3.5
2.5
3.9
3.5
3.5
4.8
3.3
3.5
3.5
4.8
3.8
4.5
4.3
T^P-T^P-IW^-T-T-T"
IN
PIT
]fc********
12
19
15
14
16
16
15
18
18
28
14
28
21
3.5 14
em**************
y-^-T ,»,lT..y^ gl,fr.T-T^-T..T-7Wfrjlwr.^v.
CONSISTENCV, Z
GH IN
SCREEN PIT
^M=m****+*******
6. 92 7. 29
6.53
6.63
6.28
6.32
6.73
6.52
6.88
5.46
6.82
5.92
5.53
5.29
5.32
**********
6.91
6.68
6. 98
6.31
7.28
7.15
6.67
5.43
7.73
6.69
5.62
5.47
5.69
*********
T~rMwM>-T"T^wM-
P-f^T-T-T-T-T"?1
TJiwr-lwr-T~T-T-^-T"T-THr--T-T-T4-T*'f-T-lT^-T.
FROM FROM
PIT FLRTBOX REMflRKS
**4^4*M-***^*****^^******+**-^+****-+**
98. 3 96. 9 DUPLICflTE COOKS
94.3
98.5
94.2
86.1
98.3
97.6
918
74.1
185.5
913
75.5
74.7
77.7
**********
96.5
89.9
93.8
88.8
93.7
98.2
88.3
76.6
94.4
84.9
77.4
77.3
72.5
4******4
DUFUCRTE COOKS
DUPLICATE COOKS
DUPLICflTE COCKS
*****-****:M*i!********4
-------
APPENDIX B. TEST RESULTS FROM DI6ESTOR COOKS
TABLE B-l. TEST RESULTS FROM DIGESTER COOKS
t-p
TDS
VDS NVDS SS TS BODr
BOD,
COD.
COD,
PH
Aspen
2-100
2-130
2-160
2-200
5-100
5-130
5-160
5-200
10-100
10-130
10-160
10-200
2-100
10-200
Southern
Yellow Pi
2-100
2-130
2-160
2-200
5-100
5-130
5-160
5-200
10-100
10-130
10-160
10-200
5-100
5-200
Loading, g/Kg
56
66
69
126
73
94
151
264
78
116
229
284
57
219
ne
52
63
79
107
53
91
101
171
55
97
142
191
52
153
47
52
48
116
56
77
133
247
70
99
206
260
46
200
41
49
71
98
45
81
36
157
44
90
124
181
40
142
11
14
21
10
17
21
17
17
8
13
23
25
11
19
11
7
9
9
8
10
15
13
10
7
18
10
12
10
62
57
68
46
76
59
57
64
74
57
50
60
103
53
85
71
63
44
59
65
40
80
47
57
81
76
67
47
122
123
145
172
155
153
209
327
162
275
354
163
272
142
138
146
155
116
157
127
271
101
158
238
276
119
192
27
18
84
41
56
97
178
75
139
188
41
41
28
49
58
26
71
36
89
123
44
98
66
39
95
49
66
no
187
84
143
209
49
49
46
62
31
40
73
46
68
116
135
55
105
53
66
73
149
70
104
165
289
81
138
299
333
60
303
51
64
90
111
57
101
111
192
60
100
140
217
66
171
151
151
235
219
165
196
279
382
194
227
377
428
212
420
180
194
194
192
163
208
191
360
140
214
298
348
181
227
6.36
6.53
6.36
6.06
6.23
5.41
6.39
4.71
4.68
5.27
4.62
6.45
5.52
6.65
6.57
6.08
6.50
6.22
5.93
6.70
5.68
4.68
6.12
6.54
5.45
6.61
6.09
89
-------
TABLE B-l. TEST RESULTS FROM DIGESTER COOKS (Continued)
t-p TDS VDS NVDS SS TS BOD$ BODT COD$ CODT pH
Oak
2-100
2-130
2-160
2-200
5-100
5-130
5-160
5-200
10-100
10-130
10-160
10-200
5-130
5-160
Douglas
2-100
2-130
2-160
2-200
5-100
5-130
5-160
5-200
10-100
10-130
10-160
10-200
2-160
10-130
Loading, g/Kg
92
120
170
266
92
177
235
338
153
229
275
357
179
243
Fir
67
80
152
141
100
106
141
175
120
138
227
212
101
134
68
103
147
248
68
167
216
296
144
207
257
336
166
245
57
67
126
119
92
94
135
163
109
123
182
209
86
120
24
17
22
17
24
10
19
41
9
14
18
21
13
13
10
13
22
22
9
13
6
13
10
15
46
8
15
14
196
205
230
173
196
174
126
158
170
184
196
228
163
174
91
75
146
86
117
71
96
111
124
52
77
135
72
73
296
333
430
465
296
373
384
544
323
412
514
656
362
417
166
155
320
226
220
178
251
314
248
196
331
375
173
207
50
312
103
50
152
166
102
157
245
121
61
87
71
97
85
77
74
147
58
94
61
159
160
61
170
247
107
160
267
139
63
102
82
110
102
108
123
176
72
115
130
129
186
290
130
202
272
377
175
272
308
410
207
298
79
97
152
155
108
121
161
192
129
155
233
249
116
161
391
423
523
626
391
366
440
648
369
475
638
834
444
542
216
218
322
277
296
229
335
389
312
256
354
509
223
274
6.20
6.03
4.87
5.25
5.12
4.89
4.95
4.57
4.32
4.59
4.68
5.68
6.70
6.24
6.40
5.92
6.62
5.43
6.44
5.84
6.16
5.64
6.12
6.28
90
-------
TABLE B-l. TEST RESULTS FROM DIGESTER COOKS (Continued)
t-p
Plywood
2-100
2-130
2-160
2-200
5-100
5-130
5-160
5-200
10-100
10-130
10-160
10-200
10-100
2-200
TDS
Trim
60
72
73
92
70
71
92
115
61
92
109
135
71
83
VDS
NVDS
SS
TS
Loading,
51
62
63
52
62
76
105
45
80
90
118
58
56
9
10
10
18
9
16
10
16
12
19
18
13
16
116
128
109
88
64
67
61
74
89
87
78
73
59
61"
177
205
188
183
134
140
148
199
153
188
193
219
131
144
BODS
g/Kg
39
47
44
44
31
56
75
58
39
46
BODT
44
54
52
36
37
53
80
59
45
50
CODS
72
80
84
126
79
72
104
137
77
96
110
151
86
97
CODT
252
267
263
250
182
178
200
258
213
229
245
281
179
185
pH
6.54
6.32
6.47
6.95
6.47
6.00
6.37
6.16
6.54
6.11
6.53
6.40
91
-------
APPENDIX C. DATA COLLECTED AT EVANS PRODUCTS CORPORATION
TABLE C-l. WHITE WATER SOLIDS DATA
Date
3/19/74
3/20/74
3/21/74
3/26/74
3/27/74
3/28/74
4/02/74
4/03/74
4/04/74
4/09/74
4/10/74
4/11/74
4/16/74
4/17/74
4/18/74
4/24/74
4/25/74
12/20/74
2/05/75
2/12/75
2/19/75
3/05/75
3/12/75
3/19/75
4/02/75
4/23/75
6/04/75
Excess
White Total
Water Dissolved
Flow Solids
MGD mg/1 Ibs/day
.51
.59
.53
.63
.57
.59
.57
.54
.58
.61
.60
.60
.63
.65
.69
.73
.65
.43
.39
.22
.45
.25
.18
.11
.14
.2
.18
__
2384
2128
2638
2039
1920
2115
4366
3650
2202
3163
1968
2029
1825
1822
1570
1770
3482
3098
6006
2102
4588
6296
7636
7148
5218
5736
11730
9406
13860
9692
9447
10054
19662
17655
11202
15828
9847
1066
9893
10484
9558
9595
12487
10076
11020
7880
9566
9452
7005
8346
8704
8610
Volatile
Dissolved
Solids
mg/1 Ibs/day
_ _
-_
1747
2318
1775
1669
1851
4070
3357
1967
2813
1727
1792
1529
1524
1336
1520
3019
2856
5120
1896
3916
5524
6776
6136
4616
--
__
--
7722
12179
8438
8212
8799
18329
16238
10007
14076
8641
9415
8289
8770
8134
8239
10827
9289
9394
7116
8165
8292
6216
7164
7699
—
Non-Volatile
Dissolved
Solids
mg/1 Ibs/day
__
--
382
320
264
251
264
296
293
235
350
240
236
296
218
234
250
463
242
886
206
672
772
860
1012
602
--
__
--
1688
1681
1255
1235
1255
1333
1417
1196
1751
1200
1240
1605
1715
1425
1355
1660
787
1626
773
1401
1159
789
1182
1004
--
Suspended
Solids
mg/1 Ibs/day
803
641
1880
1186
1632
1380
969
1244
944
1206
1199
1490
973
984
934
776
993
869
892
1135
1040
1534
1185
2154
2667
708
1204
3415
5154
8310
6231
7758
6790
4606
5602
4566
6135
6000
7456
5112
5334
5374
4724
5383
3116
2901
2082
3903
3198
1779
1976
2114
1173
1807
92
-------
TABLE C-2. PRESS PIT SOLIDS DATA
Date
3/19/74
3/20/74
3/21/74
3/26/74
3/27/74
3/28/74
4/02/74
4/03/74
4/04/74
4/09/74
4/10/74
4/11/74
4/16/74
4/17/74
4/18/74
4/24/74
4/25/74
12/20/74
2/05/75
2/12/75
2/19/75
3/05/75
3/12/75
3/19/75
4/02/75
4/23/75
6/4/75
White
Water
Flow
MGD
.51
.59
.53
.63
.57
.59
.57
.54
.58
.61
.60
.60
.63
.65
.69
.73
.65
.43
.39
.22
.45
.25
.18
.11
.14
.2
.18
Total
Dissolved
Solids
mg/1 Ibs/day
2603
2722
2911
2460
2441
3086
2929
822
2581
3094
2967
2874
2362
2724
2505
2605
2335
3995
2202
4640
2256
4992
8212
6426
7470
5440
—
911
953
1019
861
854
1080
1025
288
903
1083
1039
1006
827
954
876
911
817
1398
770
1624
780
1572
2875
2249
2615
1904
- -
Volatile
Dissolved
Solids
mg/1 Ibs/day
2025
—
2618
1913
2221
2841
2624
576
2357
2846
2684
2626
2158
2355
2257
2340
2115
3601
1988
4188
2088
4356
7374
5722
6534
4654
— ~
709
__
916
670
111
994
918
202
825
996
939
919
755
824
790
819
740
1260
696
1466
730
1525
2581
2003
2287
1629
— _
Non-Volatile
Dissolved
Solids
mg/1 Ibs/day
578
-_
293
298
220
245
305
246
224
284
609
246
204
369
248
265
220
394
214
452
168
636
838
704
936
786
""" — *
202
— _
102
104
77
86
107
86
78
99
213
86
71
129
87
93
77
138
75
158
59
272
293
246
327
275
"
Suspended
Solids
mg/1 Ibs/day
180
312
451
891
235
236
401
246
174
349
300
206
507
214
231
266
260
158
826
6692
144
188
88
299
332
221
189
63
109
158
312
82
83
140
86
61
122
105
72
177
75
81
93
91
55
289
2343
50
66
31
105
116
77
r f
66
93
-------
TABLE C-3. CYCLONE DISSOLVED SOLIDS DATA
Date
4/09/74
4/10/74
4/16/74
4/17/74
4/24/74
4/25/74
5/01/74
1/31/75
2/04/75
2/05/75
2/12/75
3/05/75
3/19/75
4/02/75
4/16/75
4/23/75
4/30/75
6/04/75
Cyclone
Dissolved
mg/1
1988
3687
2275
2420
2060
1880
2170
2748
4348
4420
7518 1
5966 1
9166 1
9044 1
4660
6768 1
6814 1
7150 1
Total
Solids
g/kg
34.7
64.4
39.7
42.3
36.0
32.8
37.9
48.0
75.9
77.2
31.3
04.2
60.0
57.9
81.4
18.2
19.0
24.8
Cyclone Spray
Dissolved Solids
mg/1 g/kg
0
0
0
0
0
0
0
1898
2412
3098
6006
4588
7636
7148
3386
5218
5676
5736
0
0
0
0
0
0
0
28.6
36.4
46.7
90.5
69.1
115.1
107.7
51.0
78.6
85.5
86.4
Dissolved Solids
Loading to Cyclone
g/kg
34.7
64.4
39.7
42.3
36.0
32.8
37.9
19.4
39.6
30.5
37.1
35.0
45.0
50.2
30.3
39.5
33.4
38.4
94
-------
TABLE C-4. WHITE WATER, BOD DATA
Date
3/20/74
3/21/74
3/27/74
3/28/74
4/03/74
4/04/74
4/10/74
4/11/74
4/17/74
4/18/74
4/24/74
4/25/74
12/20/74
2/05/75
2/19/75
3/05/75
4/02/75
4/23/75
Flow
.51
.53
.57
.59
.54
.58
.60
.60
.65
.69
.73
.65
.43
.39
.45
.25
.14
.2
BOD,
rag/l
1525
1518
1487
1262
1438
1462
1232
1305
1867
1747
963
1502
2925
1675
1285
2488
3287
3188
Total
1 bs/day
6486
6710
7069
6210
6476
7072
6165
6530
1012
10053
5862
8142
10489
5448
4823
5187
3838
5318
BOD,
mg/1
—
1162
—
1298
--
1470
—
1035
--
1507
—
894
1890
1675
1060
2256
2821
2962
Soluble
1 bs/day
__
5136
—
6387
--
7111
--
5179
—
8672
—
4846
6778
5448
3978
4704
3294
4941
95
-------
TABLE C-5. PRESS PIT, BOD DATA
Date
3/20/74
3/21/74
3/27/74
3/28/74
4/03/74
4/04/74
4/10/74
4/11/74
4/16/74
4/18/74
4/24/74
4/25/74
4/29/74
12/20/74
2/05/75
2/19/75
3/05/75
4/02/75
4/16/75
4/23/75
4/30/75
BOD,
mg/1
1525
1532
1430
1735
1517
1542
1362
1650
1438
1838
1292
1500
1400
2730
2075
1440
2385
3028
2016
2930
2290
Total
1 bs/day
534
536
500
605
531
540
477
577
503
643
452
525
490
955
726
504
835
1060
706
1028
801
BOD, Soluble
mg/1 1 bs/day
—
1525
—
1642
--
1405
—
1085
--
1865
—
1433
--
2070
1700
1365
3090
1942
1965
2963
2250
—
534
--
575
—
492
--
380
--
653
--
501
--
724
595
478
1081
680
688
1037
787
96
-------
TABLE C-6. SOLUBLE COD DATA
Date
3/19/74
3/20/74
3/21/74
3/26/74
3/27/74
3/28/74
4/02/74
4/03/74
4/04/74
4/09/74
4/10/74
4/11/74
4/16/74
4/17/74
4/18/74
4/24/74
4/25/74
12/20/74
2/05/75
2/12/75
2/19/75
3/05/75
3/12/75
3/19/75
4/02/75
4/23/75
White Water
Flow
MGD
.51
.59
.53
.63
.57
.59
.57
.54
.58
.61
.60
.60
.63
.65
.69
.73
.65
.43
.39
.22
.45
.25
.18
.11
.14
.2
White
COD
mg/1
3355
2640
2640
2560
2510
2270
2560
2990
2865
2570
2420
2220
2150
2040
1990
1650
1590
3520
3776
6370
3555
5130
8137
9425
8539
6115
Water
COD
Ibs/day
14270
12990
11669
13450
11932
11169
12170
13465
13858
13074
12109
11108
11296
11058
11451
10045
8619
12623
12281
11687
13341
10696
12215
8644
9970
10199
Press
COD
mg/1 1
4165
2146
2258
2247
1210
4570
4210
3900
3630
4440
'4150
3900
3310
3350
3330
2830
2750
4380
4930
8100
2600
6537
7783
8448
9368
6843
Pit
COD
bs/day
1458
751
790
787
424
1600
1474
1365
1271
1555
1453
1365
1158
1173
1164
991
963
1533
1726
2836
910
2289
2724
2957
3279
2395
Total
COD
Ibs/day
15728
13741
12459
14237
12356
12769
13644
14830
15129
14629
13562
12473
12454
12231
12615
11036
9582
14156
14007
14523
14251
12985
14939
11601
13249
12594
97
-------
TABLE C-7. TOTAL COD DATA
Date
3/19/74
3/20/74
3/21/74
3/26/74
3/27/74
3/28/74
4/02/74
4/03/74
4/04/74
4/09/74
4/10/74
4/11/74
4/16/74
4/17/74
4/18/74
4/24/74
4/25/74
1/20/75
2/05/75
2/12/75
2/19/75
3/05/75
3/12/75
3/19/75
4/02/75
4/23/75
White Water
Flow
MGD
.51
.59
.53
.63
.57
.59
.57
.54
.58
.61
.60
.60
.63
.65
.69
.73
.65
.43
.39
.22
.45
.25
.18
.11
.14
.2
White
COD
mg/1
5500
4260
4650
4680
5090
4570
4680
4490
6420
4670
4790
4720
4320
4050
3680
2670
3300
4770
,6250
8985
4890
8206
11370
13820
14590
7856
Water
COD
Ibs/day
23400
21000
20600
24600
24200
22500
22300
20200
31100
23800
24000
23600
22700
22000
21200
16255
17900
17100
20300
16500
18400
17109
17068
12678
17035
13103
Press
COD
mg/1 1
3930
4620
4960
4690
--
5090
4690
4545
4120
5015
4670
4350
4540
4020
3840
3460
3240
4640
9147
17000
3810
6925
7783
8965
9989
6885
Pit
COD
bs/day
1376
1618
1737
1642
__
1783
1642
1592
1443
1756
1635
1524
1590
1408
1345
1212
1135
1625
3204
5954
1334
2424
2724
3138
3496
2409
Total
COD
Ibs/day
24776
22618
22300
26200
--
24300
23900
21800
32500
25600
25600
25100
24300
23400
22500
17500
19000
18700
23500
22459
19734
19533
19792
15816
20531
15512
98
-------
TABLE C-8. PROCESS WATER SOLIDS COMPOSITION
vo
Board Suspended
Date Thickness solids
(in) Location (mg/1)
10/14/74 1/4
10/21/74 1/4
10/30/74 1/4
11/12/74 1/8
11/18/74 1/8
Cyclone L
Cyclone S
Head Box
W.W. Chest
Baby Rolls
1st Big Roll
1st sec. ,
Fordrineer
Hot Press #1
Hot Press 12
2nd Headbox
#3 Vat
W.W. Pit
3rd Sue. Box
Press Roll Sect
2nd Pan
Fourdrinier
roller section
Pit under
roller section
1st Pan of
Press Rolls
2nd Pan of
Press Rolls
Hot Press
Pit #2
White Water
Stock Chest
Head Box
W.W. from
roller sec.
Suction Box
880
1714
1850
781
894
872
834
174
272
2550
1878
972
454
. 820
1104
798
154
1290
1562
92
1082
1824
2590
1272
10
Dissolved
sol ids
(mg/1)
2202
5588
2452
2254
1726
1828
2494
3494
3338
1428
3514
2680
1476
1996
2018
3404
424
1480
1302
1468
2218
3466
2732
2612
202
Non-Volatile
solids Sugars
(mg/1) (mg/1)
332
60
142
108
134
146
230
252
452
204
818
284
156
288
434
314
32
258
246
158
288
1084
348
348
76
1490
4350
1650
1650
1175
1285
1750
2160
2000
860
1800
1810
1060
1250
1260
2100
210
800
790
850
1400
2240
1975
1760
54
Tannins Sugars
(mg/1) %
305
682
353
341
244
276
355
587
137
157
335
201
241
259
385
36
184
182
323
287
407
300
308
13
67
77
71
76
73
76
77
61
59
51
67
80
73
79
68
53
65
74
51
63
94
82
77
.7
.8
.4
.9
.8
.4
.3
.8
.9
.2
.5
.3
.2
.5
.0
.6
.5
.8
.2
.1
.0
.8
.7
Tannins
% pH Comments
13.9
12.2
15.3
15.9
15.3
16.4
15.7
16.8
4.5
12.5
15.2
14.1
16.4
12.5
9.2
15.0
17.2
22.0
12.9
17.0
12.6
13.6
55
3
4
4
4
5
5
5
4
5
3
5
5
5
5
5
6
.1 Plytrim
.8 Oak
.5
.6
.5
.4
.2
.2
.8
.3
.6
.1
.7
.3
.2
.2
.2
5.0
4.9
5.5
6.
4.
4.
5.
0
7
7
9
-------
TABLE C-8. PROCESS WATER SOLIDS COMPOSITION (Continued)
o
o
Board Suspended
Date Thickness solids
(in) Location (mg/1)
11/19/74
11/25/74
11/26/74
11/27/74
11/27/74
12/05/74
12/12/74
12/18/74
12/19/74
1/28/75
1/8
1/8
1/8
1/8
1/8
1/4
1/8
1/4
3/16
3/16
3/16
1/8
Cyclone, M
Cyclone, S
Broke
Overlay Slurry
W.W. Chest
Head Box
W.W. Chest
(comp. )
Head Box
Hot Press
1st Head Box
W.W. Chest
(comp.)
Cyclone, M
Head Box
W.W. Chest
(comp. )
Hot Press
W.W. Composite
Head Box
Press Rolls,
Baby
Hot Press
Cyclone, M
W. W. Pit
Head Box
Cyclone M
Press Roll
Hot Press
W. W. Pit. Comp
Cyclone S
Cyclone M
Head Box
White Water,
Comp
Press Rolls
Hot Press
996
890
1768
3398
486
1806
644
1926
288
2210
1376
1072
2356
1246
182
1654
2366
1354
260
630
756
3926
1544
1496
178
.1252
1624
2382
2404
1242
1634
200
Dissolved
sol ids
(ing/1 )
2102
5846
996
1478
2718
2888
3308
4180
3510
4250
4102
5706
3590
6304
3218
4178
4216
2638
3860
5288
3886
3498
4906
1392
3614
2880
5500
4514
2470
2694
1520
2790
Non-Volatile
solids Sugars
(mg/1) (mg/1)
212
218
158
404
450
516
466
494
318
666
454
736
550
1612
456
640
772
544
874
778
638
576
754
254
716
546
290
876
362
390
214
266
1370
5500
820
1100
1725
1910
2050
2630
2230
2950
2850
4080
2600
4000
1950
2710
2220
1650
2350
3500
2400
2185
2880
900
1560
1660
3950
2480
1550
1560
1004
1270
Tannins Sugars Tannins
(mg/1) % '-,
276
460
160
146
273
293
309
438
591
480
454
616
418
670
544
521
487
318
793
673
407
352
443
153
520
317
661
601
301
324
21?
491
72.5
97.7
97.9
102.0
76.1
80.5
72.1
71.4
69.7
82.3
78.1
82.1
85.5
85.3
70.6
76.6
79.0
78.8
78.7
77.6
73.9
74.8
69.4
79.1
53.3
71.1
75.8
63.2
73.5
67.7
76.9
50.3
14.6
8.2
19.1
14.0
12.0
12.4
10.9
11.8
18.5
13.4
12.5
12.4
13.8
14.3
19.7
14.7
14.1
15.2
26.6
14.9
12.5
12.0
10.7
13.4
17.9
13.6
12.7
16. 5
14.3
14.1
16.6
19.5
pH Comments
4.9
3.6
4.8
5.0
4.6
4.6
4.6
4.5
4.6
4.4
4.6
4.8
5.3
5.2
5.5
5.9
5.0
5.0
5.7
5.2
5.6
4.9
5.1
5.2
8.1
5.9
4.7
5.5
5.7
5.8
5.6
5.8
D.F.
Oak
Recycle
of White
Water In
Cyclone
Started
11/25/74
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TABLE C-8. PROCESS WATER SOLIDS COMPOSITION (Continued)
Board Suspended
Date Thickness solids
(in) Location (mg/1)
1/21/75
1/14/75
1/07/75
1/8 Cyclone M
1/8 Cyclone S
Head Box
White Water,
Comp
Press Roll , S
Hot Press
1/8 Cyclone, M
Head Box
Roller Sec.
Press Rolls
White Water
( Comp . )
Hot Press
1/8 White Water
(Comp.)
Head Box
Cyclone, M
Hot Press
Roller Section
Press Rolls
974
2014
1822
1398
1548
224
1504
2728
354
1432
1412
198
1296
1946
1548
206
288
1072
Dissolved
solids
(mg/D
4700
5196
2972
2708
1548
2876
4032
2228
2098
1181
2372
3266
2224
2160
3600
2806
2086
914
Non-Volatile
solids Sugars
(rng/1) (mg/1)
1048
622
504
476
264
284
1572
618
392
242
432
616
272
524
1108
1080
626
94
2810
3100
2040
1485
830
1460
2550
1295
1120
681
1330
1960
1410
1275
2220
1800
1370
637
Tannins Sugars
(mg/1) %
609
577
363
301
209
603
545
209
248
195
276
642
254
248
415
639
297
114
76.9
67.8
82.7
66.5
64.6
56.3
103.7
80.4
65.7
72.5
68.6
74.0
72.2
77.9
92.8
104.0
93.8
77.7
Tannins
16.7
12.6
14.7
13.5
16.3
23.3
13.0
14.5
20.8
14.2
24.2
1.3.0
15.2
17.3
37.6
20.3
13.9
pH Comments
4.6
4.0
3.8
4.2
4.2
4.7
5.2
5.4
4.4
4.9
5.1
4.5
6.1
5.6
5.0
5.8
5.7
6.2
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TECHNICAL REPORT DATA
(Please read Iiiztmctions on the reverse before completing/
1 . RE3O3T NO.
EPA-600/2-79-008
4. TITLE AND SUBTITLE
Raw Wasteload Characteristics of the Hardboard
Industry
6. PERFORMING ORGANIZATION CODE
3. RECIPIENT'S ACCESSION'NO.
5. REPORT DATE
January 1979 issuing date_
7. AUTHOR(S)
Victor J. Dallons
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Industrial Pollution Control Division
Industrial Environmental Research Laboratory
Corvallis, Oregon 97331
10. PROGRAM ELEMENT NO.
1BB610: 01-05
11. CONTRACT/GRANT NO.
Inhouse
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Lab.
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 1*5268
- Cinn, OH
13. TYPE OF REPORT AND PERIOD COVERED
Final 6/75-12/77
14. SPONSORING AGENCY CODE
EPA/600/12
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Rav waste loads from the hardboard industry are characterized. Factors that affect
the raw waste load are studied. The raw waste load is most strongly affected by the
wood cooking conditions. More of the wood is dissolved at the higher pressures and
temperatures found in production of smooth on one side (SIS) board, which results in
higher raw waste loads for smooth on two sides (S2S) production. Additional wood is
dissolved in the hot press in the production of SIS board. Refining of the wood
results not only in production of solids, but also in production of wood fines that
add to the raw waste load.
Recycling of Whitewater and press pit waters reduces the quantity of discharge from
a hardboard mill. Raw waste loads are also decreased. Dissolved solids, suspended
solids, and the temperature in the Whitewater increase with increased recycling. The
change in the raw waste load and,Whitewater characteristics are most dramatic when
nearly all the process waters are being recycled.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSAT1 Field/Group
Extraction
Biochemical oxygen demand
Water reuse, hardboard
industry, total suspen-
ded solids, Whitewater ,
waste effluents
13B
13. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
112
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
102
•t* U. S. GOVERNMENT PRINTING OFFICE: 1979 — 657-060/1586
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