Environmental Protection Technology Series
INVESTIGATION OF REUSE POTENTIAL
OF ASH FROM PAPERMILL SLUDGES
Industrial Environmentai Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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RESEARCH REPORTING SERIES
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Protection Agency, have been grouped into nine series. These nine broad cate-
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EPA-600/2-77-123
July 1977
INVESTIGATION OF REUSE POTENTIAL
OF ASH FROM PAPERMILL SLUDGES
by
Allan M. Springer
Duane W. Marshall
National Council of the Paper Industry
for Air and Stream Improvement, Inc.
Central-Lake States Regional Center
Kalamazoo, Michigan 49008
Isaiah Gellman
National Council of the Paper Industry
for Air and Stream Improvement, Inc.
New York, New York 10016
Grant No. EPA-R-803348-01
Project Officer
Victor J. Dallons
Industrial Pollution Control Division
Industrial Environmental Research Laboratory-Cincinnati
Corvallis, Oregon 97330
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Industrial Environ-
mental Research Laboratory, U.S. Environmental Protection Agency,
and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the U.S.
Environmental Protection Agency, nor does mention of trade names
or commercial products constitute endorsement or recommendation
for use.
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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 more 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.
"Investigation of Reuse Potential of Ash From Papermill Sludges"
is a product of the above efforts. Two techniques for
recovery of filler from fine papermill high ash sludges,
screening and wet oxidation, were evaluated for their technical
feasibility. The alternative of screening the sludge and using
the material passing through the screen as recovered filler
was investigated in cooperation with two mills. The wet
oxidation scheme appears technically feasible. The screening
alternative would probably have to incorporate a bleaching
step before it would be deemed acceptable. The technical
feasibility of oxidative bleaching was demonstrated.
For further information regarding this report contact the
Food and Wood Products Branch, Industrial Pollution Control
Division, Industrial Environmental Research Laboratory—Ci,
Cincinnati, Ohio 45268.
David G. Stephan
Director
Industrial Environmental Research Laboratory—Ci
Cincinnati, Ohio
111
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ABSTRACT
Two techniques for recovery of filler from fine papermill
high ash sludges, screening and wet oxidation, were evaluated for
their technical feasibility. The alternative of screening the
sludge and using the material passing through the screen as
recovered filler was investigated in cooperation with two mills.
The screening for recovery of filler was conducted at the mill
site. Then the material was shipped to Western Michigan Univer-
sity where selected grades incorporating the recovered filler
were manufactured. The paper manufactured was shipped to Roches-
ter Institute of Technology where it was printed on their web
offset press. The grades simulated were found lacking only in
that the brightness of the paper was from four to seven points
lower than grades made with virgin filler. The wet oxidation
alternative was evaluated in a similar manner with a cooperating
mill. The wet oxidized, recovered fillers only slightly lowered
the brightness of the sheet simulated and gave an increase in
opacity in exchange. The wet oxidation scheme appears techni-
cally feasible. The screening alternative would probably have
to incorporate a bleaching step before it would be deemed accept-
able. The technical feasibility of oxidative bleaching was
demonstrated.
IV
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CONTENTS
Foreword iii
Abstract iv
List of Figures vi
List of Tables vii
Acknowledgments ix
I Conclusions 1
II Recommendations 3
III Introduction 4
IV Evaluation of Screening as a Recovery Alternative 8
for a Mill Manufacturing Coated Fine Paper
V Discussion of Results from Evaluation of 13
Screening as an Alternative for Filler
Recovery from High Ash Sludge for Reuse in
Coated Fine Paper
VI Evaluation of Screening as a Recovery Alternative 21
for a Mill Manufacturing Uncoated Fine Paper
VII Discussion of Results 26
VIII Bleaching of Screened, Recovered Filler 36
IX Plausible Screening System to Recover Filler 39
X Evaluation of Filler Recovered by Wet Oxidation 47
XI Discussion of Results for Use of Wet Oxidized 50
Recovered Filler as a Filler Pigment
XII Potential of Wet Oxidized, Recovered Filler as a 56
Possible Coating Pigment
XIII References 58
XIV Appendices 59
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LIST OF FIGURES
Number Page
1 Full Scale Pigment Recovery System 6
2 Diagram of Possible Scheme for Mill Installation 40
3 Case I Primary Clarifier Sludge Utilization 44
Bleaching System
4 Acid Demand of Wet Oxidized Pigment 51
5 Particle Size Distribution of Wet Oxidized 57
Recovered Filler
1-A Foam Flotation: Time vs. % Filler Purity and 67
Recovery
2-A Screening - The Effect of Screen Mesh and 69
Consistency on Purity and Recovery
VI
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LIST OF TABLES
Number Page
1 Screening Characteristics for Filler Recovery 14
for Reuse in Coated Fine Paper
2 Physical and Optical Properties of Coating 15
Base Sheet
3 Coated Offset Sheet Physical Properties 17
4 Coated Offset Sheet Optical Properties 18
5 Coated Offset Sheet Laboratory Printing Tests 18
6 Coated Offset Sheet Printing Results 20
7 Comparison of Laboratory Screening vs. Mill 27
Site Screening of Conventional High Ash Sludge
8 Uncoated Offset Model Machine Trial Retention 28
Values
9 Uncoated Offset Sheet Physical Properties 29
10 Uncoated Offset Sheet Optical Properties 31
11 Uncoated Offset Sheet Laboratory Printing 32
Properties
12 Evaluation of Web Offset Printed Samples 34
13 Printing Sharpness of Sequential Samples 35
14 Conditions for Bleaching 37
15 Bleaching Results 38
16 Bleaching Conditions for Mill Reclaiming 46
Clarifier Sludge by Processing Through Bleach
Plant
Vll
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LIST OF TABLES
(continued)
N limber Page
17 Characteristics of Filler Recovered by Wet 50
Oxidation of Deinking Sludge
18 Retention Characteristics of Wet Oxidized 52
Recovered Filler
19 Wet Oxidized, Recovered Filler Uncoated Offset 53
Paper Physical Properties
20 Wet Oxidized, Recovered Filler Uncoated Offset 54
Paper Optical Properties
21 Wet Oxidized, Recovered Filler Uncoated Offset 54
Paper Printing Properties
22 Uncoated Offset Sheet Printing Results 55
1-A Recovered Filler Purities from Centrifugal 64
Separation Deinking Sludge
2-A Recovered Filler Purities from Centrifugal 65
Separation Conventional Sludge
3-A Summary of High Ash Sludge Laboratory Recovery 66
Technique Data - Purity
4-A Summary of High Ash Sludge Laboratory Recovery 66
Technique Data - Recovery
5-A Brightness Results 70
6-A Abrasion Results by Flat Disc Method 70
7-A Hand Sheet Properties Modification (Conventional) 72
8-A Hand Sheet Properties Modification (Deinking) 73
1-D Printing Sample Evaluation by Use of 1-5 Grading 83
System
viii
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ACKNOWLEDGMENTS
The Project Engineer, Dr. A.M. Springer, wishes to acknow-
ledge the following organizations and their personnel, particu-
larly those cited, whose assistance and cooperation was indis-
pensable to the conduct of this study:
Allied Paper Company
Bergstrom Paper Company
Consolidated Paper Company
Fletcher Paper Company
Mr. F. Harrison
Mr. L. Stoeffler
Mr. M. Smith
Mr. J. Stiegemeyer
Mr. Ken Maves
Dr. I Sanborn
Mr. P- Cox
Mr. R. Lau
Mr. D. Rucks
Mr. J. Uttermark
Mr. Ed Grys
Rochester Institute of Technology Mr. R. McAllen
Western Michigan University
Zimpro Inc.
Mr. H. Warren
Mr. C. Schuster
Mr. K. Many on
Dr. W.E. Rayford
Mr. Bernard Flynn
Mr. Chuck Soukup
The efforts of the NCASI technician staff, especially the
help of Mr. T. Arnson, Mrs. D. Trainer and Mr. J. Marks, and the
secretarial assistance of Mrs. E. Kavelman was most appreciated.
The guidance provided by the NCASI technical staff, namely
Dr. I. Gellman, Mr. R. Blosser and Mr. D. Marshall, was also
appreciated.
Finally, the support of this study by the Office of Re-
search and Development of the United States Environmental Pro-
tection Agency, and the assistance provided by the Project Offi-
cer, Mr. V. Dallons, is gratefully acknowledged.
IX
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SECTION I
CONCLUSIONS
Fractionation of the high ash sludge from the primary clari-
fier of a fine paper manufacturing operation by use of a vibra-
ting screen results in a reusable high filler content fraction,
which passes through the screen, and a high organic material
content fraction, which is retained on the screen. The high or-
ganic content fraction becomes amenable to incineration, should
circumstances dictate. Fifty to seventy-five percent of the
sludge may be reclaimed in the high ash fraction as possible
reusable material and would result in a parallel decrease in the
mass of sludge requiring disposal.
In recovery of fillers in the paper manufacturing process,
selection of screen mesh and feed rate are specific to each mill
due to the varying nature of the sludges and the tolerance of
the mill's grade structure to contamination introduced with the
recovered materials. In the course of this study, a mill manu-
facturing coating base stock opted for a 100-mesh screen whereas
the mill making uncoated fine paper opted for a 230-mesh screen.
Less organic contamination is associated with the use of a finer
screen mesh. However,- a smaller amount of material is recovered.
Based upon pilot work, the screened, recovered filler did
not affect the physical properties of the sheet made in this
study when used to partially replace virgin filler. The highest
level of replacement observed was 83 percent of the filler clay,
constituting 68 percent of the total filler. The screened,
recovered filler did not (a) affect the printing properties of
the sheet in the grades examined, (b) increase the dirt count of
the sheets or (c) adversely affect the filler retention charac-
teristics of the pilot paper machine. Moreover, the recovered
materials have abrasive properties comparable to normal filler
grade clay utilized in the paper industry.
Utilization of screened, recovered filler led to an increase
in opacity of the sheets. The 50-lb (74 gm/m2) coated offset
grade gained 3.6 points in the base stock and 1.8 points in the
final coated product. The 50-lb (74 gm/m2) uncoated offset sheet
gained 1.2 points and the 30-Ib sheet (44 gm/m2), 0.4 points.
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Utilization of screened, recovered filler, however, did ad-
versely affect the brightness of the sheets. For the 50-lb
(74 gm/m2) coated offset grade, this amounted to 7 points in the
coating base sheets; 4 points in the final coated sheet. For the
uncoated offset sheet, it amounted to 4.6 points for the 50-lb
(74 gm/m2) sheet and 0.8 of a point for the 30-lb (44 gm/m2)
sheet. All sheets reflected deteriorating brightness, with dif-
ferences in magnitude attributable to utilization of (a) differ-
ent sludges, (b) differing media for screening, (c) different
levels of addition of the recovered filler and (d) different
blends of filler materials. Subsequent study indicates that oxi-
dative bleaching techniques have potential for brightening
screened, recovered filler.
Wet oxidation produces a reusable filler material from high
ash sludges. Fillers recovered by wet oxidation did not
(a) harm the physical properties of the sheet, (b) increase the
dirt count of the sheet, or (c) adversely affect the printing
properties of the sheet at addition levels employed in this
study. Futhermore, tests of the wet oxidized, recovered filler
indicated it to be no more abrasive than normal filler clay.
The wet oxidized, recovered filler from the sludge evalu-
ated imparted 2.6 points lower brightness to the sheet but gave
an increased 4.9 points of opacity. From the standpoint of
product brightness, wet oxidation would have to be considered
superior to separation by screening. However,- the wet oxidized,
recovered filler from the sludge evaluated has a buffer effect
and consumed several times as much acid in controlling the pH
to 4.5 during the machine trial as did No. 2 coating clay when it
was used as filler. In comparison with No. 2 coating clay,
titration of the wet oxidized filler from pH 7 to pH 4.5 required
48 times the quantity of sulfuric acid.
The screening alternative looked more promising than wet
oxidation for the conventional mill (nondeinking) but would not
be feasible for the deinking mill due to the low brightness of
the recovered product. The wet oxidation alternative would
appear workable on either type of sludge but involves a good deal
higher capital investment cost than the screening.
The wet oxidized, recovered filler was preliminarily evalu-
ated as a coating pigment. The evaluation showed that this
material would be unsuitable as a coating pigment due to its
heterogeneous nature, lower brightness, particle size distribu-
tion, and dispersion difficulties.
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SECTION II
RECOMMENDATIONS
This study has addressed the technical feasibility for
recovery of filler materials from high ash sludges and subse-
quent reuse in the paper manufacturing process. Though separa-
tion techniques employed herein involved screening and wet oxida-
tion, efforts were not made to optimize either. As a consequence
alternative screening devices besides the Sweco vibrating screen,
as well as alternative wet oxidation processes, should be evalu-
ated for their relative merits as a means for filler recovery
from clarifier underflow.
Remaining to be quantified are the operational and economic
implications of filler recovery on a larger scale continuous
basis. Alternative means for filler recovery warrant further
evaluation on a continuously operating pilot plant scale at an
actual mill site. Elements of such further study would appro-
priately include such issues as how the variable nature of the
clarifier underflow would affect properties of the recovered
filler and how much equilization capacity would be required to
dampen variation of those properties. It could also address the
issue of system dependability and the effect of recovered filler
addition to a full scale paper machine system. Cost analysis
would appropriately follow to determine the economic feasibility
of filler recovery by screening or wet oxidation in an overall
residuals management program.
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SECTION III
INTRODUCTION
Among the solids which are accumulated in the treatment of
wastewaters of pulp and paper origin are those lost from the
papermaking process and subsequently separated during primary
clarification. Land disposal is the largest single method prac-
ticed in the pulp and paper industry for disposal of these
sludges. Sludges with ash contents exceeding 50 percent are
commonly associated with the manufacture of (a) deinked pulp and
paper and (b) integrated and nonintegrated fine papers. In the
absence of by-product recovery opportunities, land disposal
remains the only feasible method of disposing of these sludges.
Of the mills which must deal with the disposal of high ash
sludges, more than 100 are located in or adjacent to metropolitan
areas where land available for solid waste disposal is limited.
Combined with declining land availability in restricting the
practice of land disposal are declining public acceptance and
increasingly stringent regulation. Thus, an impetus for develop-
ment of by-product approaches is clearly suggested.
This problem was identified as early as 1951 when the Kala-
mazoo River Improvement Company (a group of six paper companies
in southwestern Michigan practicing deinking) initiated work
under the direction of Dr. A. H. Nadelman to develop alternative
solutions to the problem (1). Two approaches were pursued: the
first to convert sludge into a product which could be reused on
site in the papermaking operation, and the second to study the
possibility of other industrial uses of the sludge. Two pro-
cesses for sludge modification were investigated and included:
(a) drying and powdering and (b) calcining and ball milling the
sludge.
The calcined product was of adequate brightness for reuse in
the papermaking process, though agglomerated. As a consequence,
it was necessary to pulverize the reclaimed material with a ball
mill. Though promising from the standpoint of appearance, the
final product, when evaluated for abrasiveness with the Valley
abrasion tester (2), was found to be more than 10 times as
abrasive as commercial clay, thus down-grading its desirability
as a paper filler material. The material was also evaluated for
use as a filler pigment in rubber products and asphalt tile and
found to function satisfactorily. However, for those
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applications the cost of calcining and ball milling made the
recovered fillers more expensive than virgin filler.
Attention was, therefore, given to other techniques for
recovering the filler, including electrophoretic separation and
flotation. Electrophoresis seemed an unlikely alternative since
the cost of electrical power needed to do the separation was
more than the value of the product produced. Flotation, however,
was shown to have some potential for making a partial separation,
but experiments were not carried far enough to reach a definite
conclusion.
In early 1962, S. D. Warren Company began development work
in the field of sludge incineration and arrived at a viable sys-
tem for their fine paper mills which they felt would economically
dispose of their primary high ash sludge while generating from
it a usable paper filler material. A full scale system, which
was constructed and operated under an EPA demonstration grant,
is shown in Figure 1. It consisted of (a) a centricleaner system
to remove grit, (b) vacuum filters to dewater the sludge, (c) a
shredder to break up the cake, (d) a rotary kiln to incinerate
the sludge and (e) a pulverizer classifier to break up the incin-
erated product (3). It was observed that if the kiln temperature
was below 1500°F (816°C), the product did not achieve the desired
brightness. However, if the kiln temperature exceeded 1600°F
(871°C), the product was exceedingly abrasive, even after pulver-
ization. By maintaining kiln temperatures between 1500 to 1550°F
(816 to 843°C) with a 90-minute detention time, a product could
be obtained which had a G.E. brightness of 84 to 85 percent.
Moreover, it was only two to five times as abrasive as normal
filler clay. Full scale paper machine trials employing the
recovered filler were subsequently conducted, and the paper was
commercially printed with no difficulties encountered. Based
on 1971 prices, the recovered filler was estimated to cost
$50/ton to produce. In comparison, virgin filler cost only $38/
ton and was not plagued with the abrasive properties. However,
the costs associated with solid waste disposal at specific mill
sites would warrant inclusion in the economic balance. Because
of the abrasive properties of fillers recovered by incineration,
alternative techniques for recovery of filler material from
high ash sludge continued to warrant investigation, again with
the aim of providing a product which could be reused at the mill
as a paper filler material. As a result, in 1973 the National
Council of the Paper Industry for Air and Stream Improvement
(NCASI) studied four separation techniques under laboratory con-
ditions to attempt recovery of filler from high ash sludge.
These included (a) foam flotation, (b) centrifugal separation
(centricleaning), (c) screening and (d) wet oxidation. The
capability of each was judged on the basis of (a) the degree of
separation (proportion of the recovered product which is filler),
(b) recovery (the proportion of the original filler in the sludge
which is recovered) and (c) brightness of the final product in
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SLUDGE
2.5% SOLIDS
CENTRI CLEANERS
CONSISTENCY &
REGULATOR
DILUTION
TANK
PULVERIZER
CLASSIFIER
POLYMER INJECTION
V
REJECTS TO
SECONDARY TREATMENT
2.2 MGD
FILTRATE TO
SECONDARY
TREATMENT
SLUDGE CONVEYOR
SHREDDER
11
\u-— -
__ — - —
BULK
STORAGE
— • — -
mi
L
WAT
i
V
SLURRY
TANK
Figure 1. Full scale pigment recovery system.
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comparison to the original sludge. Appendix A contains the re-
sults of these tests as well as details of the experiments. Two
high ash sludge samples were studied: one from a fine paper mill
practicing deinking and one from a mill not deinking, which will
be termed a conventional mill. The recovered fillers were eval-
uated for abrasiveness by a modification of the flat disc method
(4,5) and found to be nonabrasive. Based upon this evaluation,
the screening and wet oxidation techniques showed most promise.
Further demonstration of the acceptability of filler materials
recovered by these techniques for reuse in the paper manufactur-
ing process required pilot plant scale trials. To that end, it
was proposed to evaluate on pilot scale paper manufacturing
equipment the technical feasibility of reusing filler materials
recovered by the screening of sludges from two fine paper mills
and the wet oxidation of a third sludge generated at a fine
paper mill employing deinking. In the course of doing so, the
screening alternative was evaluated for both coated and uncoated
grades of web offset printing paper, whereas the wet oxidation
alternative was evaluated only for uncoated web offset printing
paper.
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SECTION IV
EVALUATION OF SCREENING AS A RECOVERY
ALTERNATIVE FOR A MILL MANUFACTURING COATED FINE PAPER
EXPERIMENTAL DESIGN
The overall experimental design involves simulating on a
model paper machine production of grades of pape^ similar to
those produced at cooperative mills, using both virgin and
reclaimed fillers, and testing the papers to distinguish property
changes due to reclaimed filler content. In evaluating the po-
tential use of recovered fillers in the manufacture of coated
fine paper, a cooperative mill chose from its grade structure a
high volume grade felt to be capable of accepting recovered fil-
ler as part of its furnish. In the normal production of this
particular grade, all of the filler normally employed in the
sheet enters in the coated broke. Thus, recovered filler addi-
tion would increase the ash content of the grade.
Utilizing virgin material provided by the mill, manufacture
of coated fine paper was simulated on a 24-in. (0.6 m) pilot
fourdrinier paper machine at Western Michigan University (WMU)
at the normal ash level of 5 percent, as well as a higher 8 per-
cent level representative of the ash content associated with
projected use of recovered fillers. These sheets were compared
with a similarly manufactured sheet containing a combination of
virgin filler at the 5 percent level and sufficient recovered
filler to increase the ash content to 8 percent, thereby simu-
lating the way in which the mill would utilize the recovered
filler.
The rolls of paper manufactured were shipped to the cooper-
ating mill to be coated and supercalendered. The coated paper
was subsequently evaluated for its physical and optical proper-
ties and shipped to Rochester Institute of Technology for print-
ing on a commercial four-color web offset press.
SCREENING PROCEDURE
The screening was accomplished at the research and develop-
ment center of the cooperating mill using a 30 in. (0.76 m)
diameter Sweco vibrating screen. The primary clarifier sludge
8
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was trucked from the mill in drums, diluted to 2 percent, and
screened using a 100-mesh sieve.
Mill personnel had previously conducted studies varying the
mesh size from 325 mesh to 100 mesh. Initial examination of the
recovered fillers for brightness and dirt speck content suggested
that the separation effected by the 100-mesh screen would result
in an acceptable quality material for the intended end use.
Apparently a significant proportion of the dirt and grit were
preferentially retained on the screen with the more highly fi-
brous organic fraction, allowing a more selective passage of
filler components through the sieve.
Furthermore, the 100-mesh screen had the added advantages
of (a) allowing a higher throughput rate, 2 to 3 gpm (7.6 to
11.4 &/m) and (b) recovering a larger fraction of the clarifier
underflow as reusable material. The recovered fraction, which
passed through the screen, amounted to 50 to 75 percent of the
total sludge. Seventy to eighty-five percent of the possible
filler was recovered. The recovered filler was thickened by
settling and decanted to approximately 5 to 8 percent solids.
In addition, it was treated with a biocide, 125 mg/S, Dowicide G,
to prevent bacterial degradation during subsequent shipment to
Western Michigan University- There it was refrigerated upon
arrival.
PILOT PAPER MACHINE TRIAL
The major raw materials for the pilot machine trial were
provided by the cooperating mill. The groundwood pulp was
dewatered on a large vacuum screen to approximately 18 percent
solids and packed in polyethylene lined 55-gallon (210 I) drums
for shipment. Pulp degradation was prevented by addition of
Rx-28. The softwood kraft pulp was shipped in dry lap form to
Western Michigan University. The starch (Cato 16) and No. 2
coating clay were shipped in dry form in 100-lb (45.4 Kg) bags.
Coating clay was utilized because in the mill the ash content in
the grade comes from addition of coated broke.
A run with a 1-day machine trial was devoted to each of
three conditions designed to simulate (a) the usual manner in
which the selected grade was produced in the mill, (b) the way
the grade would be manufactured if recovered fillers were to be
incorporated and (c) a control where the recovered filler was
replaced by virgin filler.
In each case, the furnish was held constant throughout the
run at 45 percent groundwood and 55 percent softwood kraft. The
softwood kraft was refined from 660 Canadian Standard Freeness
to 600 Canadian Standard Freeness (CSF) in a beater. The pres-
sure was then taken off the bed, and the groundwood was added
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and reslushed. The starch was cooked at 200°F (93°C) for 30
minutes at 6 percent solids and diluted to 3 percent solids for
metering to the machine. The clay, recovered filler, and starch
were metered in continuously to a mix tank just before the head-
box.
Distinctions between the various trials merit mention. Dur-
ing the first trial, the starch was metered in to give 1.75 per-
cent starch. The No. 2 coating clay was slurried at 70 percent
solids, diluted to 15 percent solids, and metered in at a rate
to give 5 percent ash in the sheet. In the second trial, the
starch feed rate was increased to give 2.25 percent starch, but
the virgin clay feed rate remained at the previous day's level.
The recovered filler, at 3 percent consistency, was metered in
at a sufficient rate to result in a final ash level in the sheet
of 8 percent. In the final trial on the third day, the starch
level was left fixed at the previous day's level. However,
recovered filler was not used and the feed rate of virgin filler
was increased to yield an ash content of 8 percent. The recov-
ered filler was replaced exactly with virgin filler.
Throughout the trials the basis weight was held constant at
45 lb/3300 ft2 (66.6 gm/m2) . The alum level was maintained at
30 Ib/ton (15 Kg/metric ton) . All water used in the trial was
deionized. Hardness was added back to' give 200 grains (3420 mg/
£) . The headbox temperature was maintained at 95QF (35°C) , and
headbox pH was adjusted continuously with sulfuric acid to give
a pH of 4.5 to 4.7. The sheet was not internally sized nor was
a size press used. Three nips were used in the calender stack.
The dandy roll was not used. The final sheet moisture was con-
trolled to 3 percent ± 0.5 percent.
During the run, the basis weight and moisture were con-
trolled by the machine's Accu-ray system. Four times during each
day's run 30-ft (9.1 m) paper samples were collected and stored
in a constant temperature and humidity control testing laboratory
for later evaluation. Concurrently control tests for basis
weight, caliper, ash, and Scott Bond were conducted. The col-
lected paper samples were subsequently cut every 2 feet (0.6 m)
for a length of 20 feet (6.1 m) to provide 10 segments for test-
ing each of the physical, optical and printing properties of
interest. For each test, a strip from each of the 10 samples
was evaluated. The 20-ft (6.1 m) length was selected on the
basis of the basis weight fluctuation cycle which the model
paper machine exhibits. In addition, 8 minutes prior to -the
taking of the paper samples, water samples were collected from
the headbox, first tray white water and total wet end overflow.
Water sample analyses, in conjunction with those conducted on
the paper samples, were used to calculate retention values.
10
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COATING TRIAL
Each day three to four 30-in. (0.76 m) diameter rolls of
paper 24 in. (0.6 m) wide were made. These rolls were wrapped
and shipped to the cooperating company for coating. Upon ar-
rival, the rolls from each trial were rewound into large master
rolls and trimmed to a 20-in. (0.5 m) width for use on the pilot
blade coater. All rolls were coated'using the coating formula-
tion commercially applied on the simulated grade. It consisted
of 100 parts dry weight of clay, and 15 parts dry weight of cal-
cium stearate. The pilot blade coater was operated at a speed
of 1000 fpm (305 m/min). The coated paper was supercalendered
to meet a gloss specification of 50 ± 2. Samples of the coated
paper were taken for testing of the physical and optical proper-
ties. The rolls of paper were then rewound into two composite
rolls containing paper from each of the three test conditions.
These rolls were wrapped and shipped to Rochester Institute of
Technology for further assessment of printing properties.
PRINTING TRIAL
The composite rolls consisted of a leader of paper manufac-
tured commercially by the mill, followed by segments from each of
the three test conditions. In doing so, the rationale was to get
the press set up and running on the commercial paper and then
print at the same conditions the pilot paper machine manufactured
paper. The printing was accomplished with a GOSS Commercial
30-in. (0.76 m) , four-color perfecting press equipped with a
brush dampening system. The four colors run in sequence were
cyan (tack 14.2), magenta (tack 12.0), yellow (tack 10.0) and
black (tack 8.2). The press speed was controlled at 600 fpm
(183 m/min), and the temperature of the web out of the drier
ranged from 200 to 350°F (93 to 177°C). There appeared to be
little difference in the runability of the different components
of the composite rolls. The printed samples were evaluated both
by printing experts from the cooperating company and by Dr. E.W.
Rayford of Western Michigan University. Dr. Rayford's comments
on the printed samples are also included in Appendix B. He was
asked to evaluate a series of number-coded samples on ink hold-
out, strikethrough, printing smoothness, pick resistance, fiber
rise, sharpness and showthrough on a scale of 1 to 5: 1 - poor,
2 - fair, 3 - average, 4 - good, 5 - excellent. Results can be
found on Table 6.
LABORATORY PHYSICAL, OPTICAL AND PRINTING TESTS
The paper was evaluated using methods commonly practiced in
the paper industry. Following is a listing of the various tests
performed and the method used for each. With the one exception,
they are either Technical Association of Pulp and Paper Industry
,Standard Methods (6) or Useful Methods (7).
11
-------
Basis Weight
Caliper
Tensile
Stretch
Sheffield Porosity
Sheffield Smoothness
Mullen
Tear
Fold
Brightness
Opacity
Gloss
IGT
K & N Ink
Wax Pick
Dirt Specks
Hiding Power
T410
T411
T494
T457
UM524
UM518
T403
T414
T511
T452
T425
T480
T499
UM553
T459
T437
(described below)
Hiding power is a control test which is used to monitor
printing showthrough. The sample of interest is solidly printed
on one side using No. 4 black printing ink (I.P.I.) at a con-
stant speed of 0.4 m/sec by means of the IGT printability tester
AC2. The sample is allowed to dry three hours and the brightness
of the nonprinted side is taken. The brightness of a nonprinted
sample is also measured, and the corresponding percent reduction
in brightness due to the printing on the opposite side is calcu-
lated as:
HP = 100(1 -
Original _ Opposite Side
Brightness Printed Brightness,
Original Brightness
12
-------
SECTION V
DISCUSSION OF RESULTS FROM EVALUATION OF SCREENING AS AN
ALTERNATIVE FOR FILLER RECOVERY FROM HIGH ASH SLUDGE FOR
REUSE IN COATED FINE PAPER
SCREENING
Characteristics of the screening process and the recovered
material is shown in Table 1. The pilot scale screening trials
conducted at the cooperating mill achieved filler recoveries
(ignition loss compensated ash recoveries) on the order of 70 to
85 percent; whereas, the laboratory results on a conventional
sludge (nondekining) suggested potential filler recovery of 91.5
percent. This difference in recovery is probably due to the
difference in composition of the two sludges evaluated. The
cooperating mill's sludge had a high groundwood content, making
it very hydrous. Possibly it was harder to separate the fillers
from the hydrous groundwood particles. The conventional sludge
studied under laboratory conditions did not contain any ground-
wood. It would follow that the differing composition and proper-
ties of primary clarifier sludges among individual mills would
require screening trials on a site-specific basis to determine
their filler recovery potential.
PHYSICAL AND OPTICAL PROPERTIES OF COATING BASE SHEET
Table 2 lists the physical and optical properties of the
uncoated base sheet for the three trial conditions. For compari-
son, the mill-manufactured base sheet properties are also listed.
The column labeled "5% Control" represents simulation of the
mill-manufactured grade. Comparing these two on a physical and
optical properties basis, one would conclude that they are sig-
nificantly different from one another on many of the properties.
The column labeled "8% Control" was to simulate the effect
of increasing the ash content to the level of the sheet associ-
ated with reuse of the recovered filler. A comparison of results
of the 5 and 8 percent virgin filler additions indicates increas-
ing the ash had a negligible effect on the physical and optical
properties.
13
-------
Table 1. SCREENING CHARACTERISTICS FOR
FILLER RECOVERY FOR REUSE IN COATED FINE PAPER
Parameter
Mill site data
Feed consistency (%)
Feed ash content (%)
Feed rate (gpm)/(1/min)
Screen diameter (in.)/(cm)
Mesh
Recovered ash content (%)
Purity (%)
Total solids recovered (%)
Filler recovery (%)
Brightness (% elrepho)
Solids loading rate (lb solids/
min ft2)/(Kg/minm2)
2
38.2
2-3/8-11
30/76
100
54.5
64.1
50-75
70-85
56.7
.07-.! Ib/min ft /
.3-.5 Kq/m2 min
Note: For comparison, brightness of No. 2 filler
clay is 80 to 82.
14
-------
Table 2. PHYSICAL AND OPTICAL PROPERTIES
OF COATING BASE SHEET
Properties
Basis weight ,
(lb/3300 ft2)/(gm/in )
Ash (%)
Caliper (.001 in.) /(mm)
Opacity (TAPPI)
Felt brightness
(% elrepho)
Wire brightness
(% elrepho)
Smoothness (Sheffield)
Porosity (HOP)
MD Tensile (Kg)
CD Tensile (Kg)
Mullen (PSI)/(kPa)
Mullen ply bond (PSI)/
(kPa)
MD Tear (g)
CD Tear (g)
MD Fold (number)
CD Fold (number)
MD Stretch (%)
CD Stretch (%)
MD TEA (KgdrO/m2,)
CD TEA (Kg(m)/nr)
Dirt specks
First pass retention (%)
Overall retention (%)
5%
Control
47.0/69.6
4.4
5.0/0.13
90.3
68.4
68.6
171
120
9.6
5.1
20.7/143
172/1180
62
75
157
25
1.72
3.6
3.4
4.4
554
64.2
79.0
8%
Control
45.2/66.9
8.0
4.8/0.12
89.7
70.4
70.4
171
131
8.3
4.7
16.8/116
168/1160
62
75
111
17
1.71
3.4
2.9
3.8
413
65.4
76.9
Recov-
ered
filler
45.8/67.8
8.6
4.7/0.12
93.3
62~Tja
163. 4la
177
96
8.5
4.4
16.6/114
175/1200
55 a
65 a
84
15
1.74
3.4
3.1
3.7
428
66.0
76.8
Mill
manuf .
base
sheet
46.3/68.5
3.7
4.1/0.10
90.6
72.5
73.4
97
81
11.0
3.9
18.6/128
185/1270
46
62
157
18
1.5
2.4
3.3
2.2
384
—
—
ai [Significantly lower than 8% control sample
' 'at 99.5% confidence as indicated by a t te
test.
15
-------
The column designated "Recovered filler" reflects the prop-
erties of the sheet made employing recovered filler to increase
the ash content, thus simulating the way it would be utilized in
the mill. The best basis for direct comparison with this sheet
is the 8 percent control. The boxed values in the recovered
filler column are statistically lower than the 8 percent control
values. The apparent small loss in tear is not of practical con-
sequence; however, the drop in brightness of the product is.
The drop of 7.6 points in felt side brightness and 7.0 points in
wire side brightness is of real concern. This loss in brightness
caused by the recovered filler suggested the necessity for
bleaching of the recovered filler prior to reuse and prompted
the additional investigation of that option, discussed later in
this report. It should be noted also that the brightness of all
of the sheets made at Western Michigan University are lower than
the products made at the mill. This was due to the preserved
.groundwood discoloring during storage prior to
However, loss of brightness was accompanied by the gain of
3.6 points in opacity. The gain in opacity may be related to the
presence of other filler materials besides clay in the recovered
filler material. It is interesting to note that the dirt speck
count did not significantly increase when utilizing the recovered
filler, although all values are very high due to the groundwood
content of the product.
The first pass and overall retention values, also reported
in Table 2, demonstrate that utilization of recovered filler
does not appear to have changed the retention characteristics on
the machine.
COATING
The physical properties of the coated offset sheets are
summarized in Table 3. There does not appear to be any signifi-
cant deterioration in the physical properties of the sheet due
to either the addition of the recovered filler or increase in
ash content. Unlike results reported for the uncoated sheet, a
difference in tear between the sheet containing the recovered
filler and that containing exclusively virgin filler was not
apparent. The result reported on the coated sheet was substan-
tiated by additional tests, inclusive of mill testing, and is
felt to be the^ more reliable.
The optical properties of the coated offset sheet are sum-
marized in Table 4. The brightness of the sheet containing the
recovered filler is 4 points lower than the 8 percent control,
and its opacity is 1.8 points higher. Thus, the loss in bright-
ness of 7.0 to 7.6 points in the base sheet is dampened in the
coated product. However, it remains questionable whether the
16
-------
Table 3. COATED OFFSET SHEET PHYSICAL PROPERTIES
Summary
Physical properties
Coat wt (lb/3300 ft2)/
( gm/m2 )
a
Caliper (.001 in) /(mm)
a
MD Tensile (Kg)
a
CD Tensile (Kg)
a „
MD TEA (Kg(m)/nr)
a ~
CD TEA (Kg(m)/m )
a
MC Stretch (%)
a
CD Stretch (%)
a
Porosity (Sheffield)
a
Porosity (HOP)
a
Smoothness (Sheffield)
a
Mullen Q?SI)/(kPa)
a
MD Tear (gm)
a
CD Tear (gm)
a
MD MIT fold (number)
a
CD MIT fold (number)
a
5%
Control
6.15/
9.10
0.10/
0.15
3.79/
0.096
O.ll/
0.003
11.95
0.61
5.91
0.29
4.04
0.53
3.84
0.72
1.75
0.16
2.9
0.38
|28.0|a
0.6
216
22
53.2
7-8
22. 5/
155
2.2/
15.4
57.8
4.2
72.9
3.3
254
83
40.8
11.3
8%
Control
6.17/
9.13
0.13/
0.19
3.73/
0.095
0.13/
0.003
10.0
0.90
5.90
0.23
3.41
0.77
3.97
0.46
1.50
0.22
2.9
0.25
33.8
0.9
204
33
40.1
6.5
19. 6/
135
1.8/
12.5
59.6
3.8
73.8
5.2
184
76
29.1
11.5
Recov-
ered
filler
6. OS/
8.95
0.16/
0.24
3.66/
0.093
0.12/
0.003
11.1
0.46
5.61
0.26
3.31
0.41
4.25
0.46
1.61
0.15
3.3
0.27
31.8
2.3
215
20
48.7
5.6
19. 4/
134
1.8/
12.1
57.7
5.3
69.2
3.7
201
58
26.7
13.0
Mill
manuf .
sheet
6.10/
9.03
0.58/
0.86
3.55/
0.090
O.ll/
0.003
33.9
0.61
5.07
0.32
4.22
0.44
2.77
0.36
1.57
0.10
2.4
0.23
33.9
0.6
182
25
49.7
12.2
20. 1/
138
1.6/
10.7
49.8
6.2
62.0
3.0
186
62
25.2
9.51
Significantly different from recovered filler sample at
99.5% confidence as indicated by a t test.
17
-------
Table 4. COATED OFFSET SHEET OPTICAL PROPERTIES
Summary
Optical properties
Brightness (% elrepho)
a
Opacity (TAPPI)
0
Gloss (75°)
a
5%
Control
72.2
0.21
94.3
0.31
49.2
5.3
8%
Control
73.3
0.13
94.6
0.29
48.5
2.2
Recovered
filler
|69.3|a
0.22
DEO]*
0.26
47.5
3.2
CPI
73.7
0.16
94.7
0.20
50.6
2.7
indicates significantly different from control at
99.5 confidence level as indicated by a t test.
Table 5. COATED OFFSET SHEET, LABORATORY PRINTING TESTS
Laboratory printing
tests
IGT Pick (#6 ink)
o
K & N ink (% reduction)
a
Hiding power
a
Fiber rise W/F
B = blisters
(0 = poorest, 4 = best)
285°
255°
230°
5%
Control
92
12.0
19.6
1.3
0.98
0.015
•
1-0
1-0
3-1
8%
Control
88
8.1
20.2
1.5
0.98
0.005
1-0
1-0
3-1
Recovered
filler
88
5.1
20.4
1.9
0.99
0.004
1-0
2-0
3-1
CPI
94
5.5
22.4
3.2
0.97
0.008
1-0
2-1
3-1
1 8
-------
mill could, under present marketing conditions, tolerate this
degree of brightness loss.
The laboratory printing tests for the coated sheet are
given in Table 5, and there appears to be no significant differ-
ence in the laboratory printing properties. The printing trial
conducted at the Rochester Institute of Technology upon rolls of
coated paper composited from those produced under the various
manufacturing conditions allowed determination under uniform
printing conditions of whether the type of paper affected print
quality. Four signatures selected at random for each condition
were submitted to a printing specialist for his independent
evaluation. He was asked to grade each signature on a scale of
1 to 5 for 7 printing properties. The scale was: 1 - poor,
2 - fair, 3 - average, 4 - good, 5 - excellent. The printing
properties he was asked to judge were gloss, ink holdout, strike-
through, printing smoothness, pick resistance, fiber rise, ink
spread and showthrough. The specialist was not aware of the
origin of the samples or purpose of the evaluation until after
the evaluation was completed. His detailed comments are given in
Appendix B. The results of his independent evaluations are tab-
ulated in Table 6.
All three test conditions from the pilot paper machine trial
were rated as essentially identical. Thus, it appears that the
recovered filler does not affect printability significantly. The
mill-manufactured paper was graded lower on the properties of ink
holdout, printing smoothness and showthrough but superior in its
lack of fiber puffing.
Printing experts at the cooperating mill examined the print-
ing quality and reached the similar conclusion that there was
little difference among the three conditions from the pilot trial
at WMU. However, a difference between these and the commercially
produced paper was cited. This difference was mostly due to the
color difference between the papers: the commercial paper was a
more blue-white; whereas, the pilot plant paper had a cream
color.
19
-------
Table 6 . COATED OFFSET SHEET PRINTING RESULTS
Sample
8R
Recov- 8R
ered
Filler 8R
8R
8V
8% 8V
Control
8V
8V
5V
5% 5V
Control
5V
5V
CW
Mill cw
Manufac-
tured cw
Paper
CW-P
(Gloss)
Ink
holdout
4
4
4
2
4
4
3
4
4
4
4
4
3
3
3
2
Strike-
through
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
Printing
(smoothness)
mottle
4
4
4
4
4
4
4
4
4
4
4
4
3
3
3
3
Pick
resis-
tance
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
Fiber
Rise
(puffing)
4
4
4
4
4
4
4
4
4
4
4
4
3
5
5
5
Ink
spread
(sharpness)
4
4
4
4
4
4
4
4
4
4
3
4
3
4
4
2
Show-
through
4
4
4
4
4
4
4
4
4
4
4
4
3
3
3
3
Total
28
28
28
26
28
28
27
28
28
28
27 "
28
23
26
26
24
Aver-
age
27.5
21. IS
21. IS
2^.75
to
o
1. Poor
2. Fair 3. Average 4. Good 5. Excellent
-------
SECTION VI
EVALUATION OF SCREENING AS A RECOVERY ALTERNATIVE
FOR A MILL MANUFACTURING UNCOATED FINE PAPER
EXPERIMENTAL DESIGN
A mill selected from its grade structure two grades which
were high volume items and would be likely candidates for plans
to utilize the recovered filler. It was felt that a heavy grade,
which had a basis weight of 50 lb/3300 ft2 (74 gm/m2), would
probably be able to utilize the recovered filler with little
difficulty. In addition a 30 lb/3300 ft2 (44 gm/m2) grade was
chosen as a more critical test of the recovered filler in recog-
nition of long range industry trend toward lighter weight fine
papers. It was intended that the recovered filler be tested as
a partial replacement for virgin filler clay. The mill had such
a diverse grade structure, some products of which the recovered
filler would not be suitable for, that no single virgin filler-
recovered filler blend condition emerged as likely to be princi-
pally utilized. However, practical experimental conditions
suggested that recovered filler clay be added directly to the
beater during the model machine run and that virgin clay be con-
tinuously metered in at a rate necessary to maintain the desired
ash level. The screening was conducted at the mill site and the
recovered filler shipped to WMU where the two grades were simu-
lated on the pilot paper machine. The grades were simulated
using virgin filler exclusively and utilizing recovered filler
in combination with virgin clay. Properties of the paper pro-
duced were evaluated by NCASI personnel. The rolls produced were
evaluated by NCASI personnel. The rolls produced were subse-
quently rewound at the cooperating mill before shipment to
Rochester Institute of Technology for printing evaluation on a
four-color commercial web. offset press.
SCREENING PROCEDURE
The screening was accomplished on site at the cooperating
mill utilizing an unused 30-in. (0.76 m) Sweco vibrating screen.
Primary sludge at 10 to 12 percent consistency was hauled from
the site of the primary clarifier in half-full 55-gallon (210 I)
drums, diluted at the screen installation to 5 to 6 percent
21
-------
using a drum pump and mixed manually. The screen was equipped
with a 230-mesh stainless steel screen and fed at a rate of 3 to
5 gpm (11.4 to 18.9 £/min). At the rate of 5 gpm (18.9 A/min),
the screen became flooded and one occasionally had to stop to
allow the screen to clear itself.
The solids content of the material passing the screen, as
recovered filler, was 3 to 3.5 percent solids and amounted to
approximately 50 percent of the total sludge fed the screen.
Considering only the ash fraction as being the component of
interest, 65 to 67 percent of the total ash or filler was recov-
ered. The material passing through the screen was 88 percent
filler and only 21 percent organic matter, as calculated from an
ash measurement, compensating for 15 percent ignition loss. This
material passing through the screen was predominantly filler.
The screening was conducted over a 1-week period by both
mill and NCASI personnel. The recovered filler was allowed to
settle, decanted, consolidated to a minimum number of drums and
shipped by truck to WMU. At the conclusion of each day's
screening and again prior to shipment to WMU, the drums of
recovered filler were treated with 500 ml of formaldehyde to pre-
vent bacterial decomposition. Upon arrival at WMU, the drums
were all adjusted to 6 percent consistency by addition of city
water and treated with an additional 500 ml of formaldehyde per
drum.
PILOT PAPER MACHINE TRIAL
The two mill grades simulated during the WMU pilot paper
machine trial were a 30 lb/3300 ft2 (44 gm/m2) Bible-type paper
and a 50-lb (74 gm/m2) offset sheet. Two days of machine time
were devoted to each grade. The first day the grade was produced
using virgin filler clay; the second day screened, recovered
filler was substituted for a portion of virgin material.
The furnish for the 30-lb (44 gm/m2) sheet consisted of 40
percent Canadian bleached softwood kraft, 20 percent bleached
hardwood kraft, 20 percent semi-bleached softwood kraft and 20
percent broke, which was supplied by the cooperating mill. The
pulp was refined in the beater to 250 to 300 Canadian Standard
Freeness. Added to the beater after refining, expressed as per-
cent of O.D. pulp weight, were 5 percent titanium dioxide, 12
percent filler clay and 0.8 percent alum. In addition, dyes
provided by the cooperating mill were added to tint the paper a
cream color. The pH was controlled on the machine to 4.8 to
5.0 with sulfuric acid. The sheet was sized by continuous addi-
tion of Neuphor emulsified rosin size at a rate equal to 2 Ib/ton
of paper (1 Kg/metric ton). The size was added to a mixing
chamber just prior to the headbox. The dandy roll was used and
22
-------
three nips were used in the calender stack. The sheet was also
externally starch-sized in the size press. The starch, Clinton
753B, had been previously batch cooked at 10 percent for use in
the size press. The size press temperature was held at 140° to
150°F (60 to 66°C), and the pickup rate was about 65 Ib/ton of
product (32 Kg/metric ton).
The initial headbox temperature selected was 110°F (43°C),
and a retention aid (Dow CP7) was fed at a rate of 1/2 Ib/ton
(0.25 Kg/metric ton). These two parameters had to be modified
during the first hour of running the machine due to bad sheet
formation. The sheet was overflocculated and blotchy, so the
retention aid was stopped and the temperature dropped to approx-
imately 70°F (21°C). This solved the formation problem. Addi-
tional filler clay, at 15 percent solids consistency, was metered
into the system to maintain the ash content in the sheet at a
desired 15 percent level. An additional 9 percent clay was
metered in this manner. In the absence of a retention aid, the
achievement of such a level in a lightweight grade sheet with
the prescribed furnish on the WMU pilot machine required a 9 per-
cent trim clay addition.
During the second day of running, recovered filler material
was substituted for the virgin clay added to the beater. How-
ever, use of virgin filler was continued for the supplemental
trim clay- The magnitude of trim clay addition was such that
filler materials constituted 57 percent of the clay or 46 percent
of the total filler contained in the 30-lb (44 gm/m^) sheet.
2
The furnish for the 50-lb (74 gm/m ) sheet consisted of 40
percent southern bleached softwood kraft, 27 percent southern
bleached hardwood kraft and 33 percent broke supplied by the
mill. The pulp was refined in a beater to 250 to 300 Canadian
Standard Freeness. Three percent titanium dioxide, 14 percent
filler clay, 0.8 percent alum, expressed as weight of O.D. pulp,
were added after refining; dye also was added and mixed in to
give the sheet a bluish-white cast.
The pH of the furnish to the machine was controlled contin-
uously with sulfuric acid to 4.6. The sheet was internally sized
with Neuphor emulsified rosin size at a level of 2 Ib/ton (1 Kg/
metric ton), and a retention aid (Dow CP7) was added to the mix
tank prior to the headbox at a level of 2 Ib/ton (1 Kg/metric
ton). Three nips were taken in the calender stack, and the dandy
roll was utilized. The sheet was externally sized with starch
through use of the size press, which was operated under condi-
tions similar to those associated with the lightweight sheet.
The starch used was the same as for the 30-lb (44 gm/irr) grade
and was prepared in a similar manner. The pickup rate was
approximately 50 Ib/ton of product (25 Kg/metric ton). Final
sheet moisture was controlled to 4 percent.
23
-------
During the first day's run of the 50-lb (74 gm/m2) sheet no
trim clay was added, but during the second day's run, the ash
level of the sheet was maintained by adding a 15 percent slurry
of filler clay to the mix chamber prior to the headbox. This
addition represented 2.35 percent of the filler added with the
final sheet ash controlled to 15 percent ± 1. During the second
day's run on the 50-lb (74 gm/m2) sheet, the filler added in the
beater was replaced by screened, recovered filler. Thus, during
the run containing the recovered filler, 83 percent of the clay
was recovered filler and 68 percent of the total filler in the
sheet was recovered filler. A daily sampling routine of collect-
ing four sets of paper and white water samples per day was fol-
lowed similar to that described in the coated fine paper model
machine run.
The rolls of paper from the four 1-day machine trials were
wrapped and shipped to the cooperating mill, where they were
rewound into four composite rolls, two of which were of the
lightweight grade and two of the heavy- Each composite roll was
half made with virgin filler and half with recovered filler.
Rewinding problems were encountered with the lightweight paper
which consisted of a series of breaks due to pin holes and dirt
in the paper. However, these problems were observed in both
sheets made with and without recovered fillers and as a result,
could not be attributed to the presence of reclaimed material.
The composite rolls were then shipped to Rochester Institute of
Technology for printing.
LABORATORY PHYSICAL, OPTICAL AND PRINTING TESTS
The procedures used are in common practice in the paper
industry and are described in detail in the section on testing
procedures for the coated fine paper evaluation, Section IV of
this report.
PRINTING TRIAL
The printing was accomplished using a GOSS Commercial 38-
in., four-color perfecting press equipped with a brush-dampening
system. The four colors used were yellow, magenta, cyan and
black, and they were applied in that order. The printing speed
was controlled at 520 to 540 fpm (158 to 165 m/min) and the web
temperature leaving the dryers varied from 220°F to 290°F (104
to 143°C). The hot air temperature varied from 400°F to 490°F
(204 to 254°C).
2
The press was made ready using a roll of 50 lb/3300 ft
(74 gm/m2) mill-manufactured paper. When the press exhibited
satisfactory printing conditions, it was run for an additional
3000 impressions before a composite roll, consisting of equal
proportions of the 50-lb (74 gm/m2) control sheet and the 50-lb
24
-------
o
(74 gm/nr) recovered filler sheet was spliced in and printed.
Two breaks occurred during the rnn of the roll of mi11-manufac-
tured paper and one each during the sections of composite roll
containing the control and recovered filler.
A roll of 35 lb/3300 ft2 (52 gm/m2) mill-manufactured paper
was run next as a made-ready roll for printing of a composite
roll of the 30-lb (44 gm/m2) paper manufactured on the pilot
paper machine. The cooperating mill did not have an extra roll
of the 30-lb (44 gm/m2) grade which simulated in the pilot trial
so the 35-lb (52 gm/m2) roll was substituted. The 35-lb (52 gm/
m2), mill-made paper left a white deposit on the yellow blanket,
and two breaks were experienced during the printing of this roll.
Three breaks occurred in the subsequent printing of the 30-lb
(44 gm/m2) composite roll, two during the course of running the
section containing only the virgin filler and one during the
segment containing recovered filler. The second composite roll
of 30-lb (44 gm/m2) paper was run next, and only one break, dur-
ing the portion containing the recovered filler, was encountered.
2
The final roll printed was the second 50-lb (74 gm/m )
basis weight composite roll, and it ran without any breaks.
The frequency of breaks was undoubtedly detrimental to
quality of the printed sheets. In the course of the trial, the
occurrence of breaks diminished as the press crew gained experi-
ence in the printing of the grades of paper under study. Fur-
thermore, to prevent breaks, sheet tension had been progressively
decreased over duration of the trial.
Each roll or segment of a roll was printed with greater
than 3500 impressions. Plate wear was observed at the end of
the printing trial after only 60,000 impressions but it is not
possible to say whether this was due to the paper or the stop-
start nature of the press operation.
After the press had reached steady state, the different
papers printed were sampled every 500th impression by taking 10
signatures. These signatures were packaged and shipped to
Western Michigan University for evaluation. From these signa-
tures, five samples from each condition were selected at random
and submitted to an impartial printing expert at Western Michi-
gan University for evaluation based upon seven printing pro-
perties. These included ink holdout, strikethrough, showthrough,
printing smoothness, ink spread, printing sharpness and pick
resistance. The samples were judged on a scale of 1 - poor,
2 - fair, 3 - average, 4 - good, 5 - excellent.
In addition to the samples from each manufacturing condi-
tion, a set of sequential samples were submitted for evaluation
of whether plate wear significantly affected printing sharpness
as the run progressed.
25
-------
SECTION VII
DISCUSSION OP RESULTS
The cooperating mill in this segment of the study was one
whose sludge had been evaluated in the initial laboratory test
program. Table 7 is a comparison of the screening results
obtained under laboratory and field conditions. The purity of
the screened product decreased only slightly, while the percent-
age of the filler which was recovered decreased significantly -
In the laboratory study it was found at a constant solids loading
rate to the screen that variation in sludge consistency over a
range from 0.1 to 3 percent did not affect the recovery effi-
ciency- However, it is conceivable that such a trend would not
extend to the 6 percent consistency utilized in the field evalu-
ation. Going further, a comparison of respective mass loading
rates, expressed as pounds of dry solids/minute per ft2, indi-
cates that the screen under field conditions was loaded at least
an order of magnitude more heavily than under laboratory condi-
tions. This likely contributed to the lower filler recovery
efficiency and corresponds with the field observation that the
screen at times appeared overloaded and took on a flooded appear-
ance .
The high feed rate to the screen was chosen under field con-
ditions in order to complete the screening operation in suffi-
cient time to permit the previously scheduled installation of new
equipment by the host mill. The product recovered, however,
provides a more critical test of the recovered filler's potential
usefulness since it is less pure than the material recovered
under laboratory conditions.
In the 50-lb (74 gm/m2) sheet, reclaimed filler materials
constituted 87 percent of the filler clay, which corresponds to
68 percent of the total filler in the sheet. In the 30-lb (44
gm/m2) sheet, 57 percent of the filler clay was replaced with
recovered filler, representing 46 percent of the total filler.
The lower percentage of total filler replaced is due to the
addition of titanium dioxide to each sheet. Its level of addi-
tion was not altered by substitution of filler grade clays with
recovered filler. The 30-lb (44 gm/m2) sheet contained a higher
percentage of titanium dioxide and exhibited less brightness
loss.
26
-------
Table 7. COMPARISON OF LABORATORY SCREENING
VS MILL SITE SCREENING OF CONVENTIONAL HIGH ASH SLUDGE
Parameter
Original sludge ash content (%)
Consistency of feed (%)
Total solids recovered (%)
Filler recovered (%)
Purity of product (% of recov-
ered material which is filler)
Feed rate to screen (gpm)/(l/m)
Screen diameter (in.)/(m)
Screen mesh
Solids loading rate to screen
(Ib solids/min ft2)/Kg/min m2)
Abrasiveness (mg)
Brightness (% elrepho)
Laboratory
data
-
0.1-3.0
-
98
92
0.2 to 4.8/
0.6 to 18.0
18/0.46
230,325
0.023/0.112
-
-
Mill
site
data
55
5-6
50
65-67
88
3 to 5/
11 to 19
30/0.76
230
0.25-0.51/
1.22-2.49
4.2
66.5
27
-------
The first pass and overall retention values experienced dur-
ing the pilot machine runs are summarized in Table 8. It would
appear from the data that the retention conditions were not sig-
nificantly influenced by the substitution of recovered filler
clay for virgin filler clay in either of the grades simulated.
Table 8. UNCOATED OFFSET MODEL MACHINE TRIAL
RETENTION VALUES
Sheet produced
2
30-lb (44 gm/m ) control sheet
2
30-lb (44 gm/m ) recovered filler
sheet
2
50-lb (74 gm/m ) control sheet
2
50-lb (74 gm/m ) recovered filler
sheet
First pass ,
29.5
28.3
51.0
54.0
Overall,
67.0
65.0
76.5
77.0
The physical properties of the sheets made during the pilot
machine run are listed in Table 9 along with the samples of mill-
manufactured paper which were utilized during the printing trial.
In comparing the control sheet to that containing recovered
filler, the figures boxed in the recovered filler column are
statistically significantly different from the control. However,
none of the differences are of sufficient magnitude to be of
practical concern. Thus, the use of recovered filler does not
seem to have an adverse effect on the physical properties. Spe-
cial note should be taken that the dirt speck level of the sheets
containing the recovered filler did not significantly increase.
The optical properties of the sheets are summarized in
Table 10, and It appears that the brightness is adversely
affected by the addition of the recovered filler. The 30-lb
(44 gm/m2) sheet lost 0.8 points and the 50-lb (74 gm/m2) sheet
lost 4.6 points. The 50-lb (74 gm/m2) sheet with the recovered
filler gained 1.2 points in opacity. It is doubtful whether a
mill could tolerate 4.5 points loss in brightness. As a conse-
quence, if the recovered filler is to be utilized, it would have
to be used in a smaller percentage or would have to be bleached
prior to. use. Possible techniques for bleaching are discussed
later in this report.
The laboratory printing test results are summarized in
Table 11. No differences were noted between the control samples
and samples containing the recovered filler. In general, the
28
-------
Table 9. UNCOATED OFFSET SHEET PHYSICAL PROPERTIES
Test
Basis wt (lb/3300 ft2)/
( gm/m2 )
a
Caliper (.001 in.) /(mm)
a
Porosity (SHeffield)
a
Smoothness (Sheffield)
a
MD Tear (gm)
a
CD Tear (gm)
0
Mullen (PSI)/(kPa)
a
MD Fold (%)
a
CD Fold (%)
a
Paper sample
30-lb
(44 gm/m2)
Control
30. 8/
45.6
0.6/
0.9
2.46/
0.062
0.04/
0.001
161
16
167
11
26.6
3.0
30.4
4.1
11. 5/
79.2
1.5/
10.3
8.1
3.0
5.5
1.5
3U-1JD
(44 gm/m )
Recovered
filler
|29. 7|a /
44.0
0.6/
0.9
|2.35|a/
0.060
0.04/
0.001
147
13
163
8.5
24.4
2.0
31.0
2.0
10. 7/
73.7
1.4/
9.6
7.7
3.5
4.4
0.9
Jb-lD
(52 gm/nr)
Mill
manuf .
35. 6/
52.7
0.3/
0.4
3.19/
0.081
0.07/
0.002
84.5
11.5
168
7.7
37.1
2.1
52.6
4.1
13. 7/
94.4
1.3/
9.0
26.7
8.9
10.8
3.7
50-lb
(74 gm/nr)
Control
50. 6/
74.9
0.3/
0.4
3.80/
0.097
0.05/
0.001
122
13
196
11
67.4
3.3
81.6
5.5
16. 4/
113.0
1.3/
9.0
17.4
4.5
8.2
2.3
t>U-lJD
(74 gm/m2)
Recovered
filler
50. 3/
74.4
0.3/
0.4
3.84/
0.098
0.05/
0.001
| 100|a
7
193
12
66.0
3.0
74.4
3.6
16. 3/
112.3
1.5/
10.3
14.0
3.6
8.3
1.9
i>U-lt»
(74 gm/m2)
Mill
manuf.
58. 8/
87.0
0.21/
0.3
3.88/
0.099
-
94.8
10
220
19
47.4
1.8
54.4
1.6
19. 4/
133.7
3.3/
22.7
7.6
1.8
5.3
1.5
NJ
VD
Statistically different from the control at 99.5% confidence level as
indicated by a t test.
-------
Table 9. UNCOATED OFFSET SHEET PHYSICAL PROPERTIES
(Continued)
Test
Sizing (Hercules-sec)
a
Dirt Specks
a
MD Tensile (Kg)
a
CD Tensile (Kg)
o
MD TEA (Kg(m)/m )
a 7
CD TEA (Kg(m)/m )
a
MD Stretch (%)
a
CD Stretch (%)
a
Ash (%)
Paper sample
30-lb
(44 gm/m )
Control
8.9
0.5
5.94
1.9
6.2
0.6
3.17
0.4
1.89
0.4
4.32
0.8
1.5
0.2
4.3
0.5
15.3
30-lb 2
(44 gm/m )
Recovered
filler
10.6
3.0
16.1
7.9
6.3
0.9
3.16
0.3
2.38
0.6
4.32
0.7
1.5
0.2 „
J3TTIa
0.6
15.5
35-lb 2
(52 gm/m )
Mill
manuf.
157
58
25.6
5.8
8.6
0.6
4.3
0.3
1.9
0.4
2.3
0.3
1.0
0.1
1.9
0.2
14.6
50-lb „
(74 gm/m )
Control
95.2
45
11.8
4.2
8.2
0.9
4.4
0.7
6.3
1.2
3.7
0.7
1.8
0.2
4.6
0.8
16.3
50-lb ~
(74 gm/m )
Recovered
filler
83.7
25
12.3
4.3
8.5
0.8
4.2
0.5
6.8
1.8
4.5
1.0
1.9
0.2
4.9
0.8
16.5
50-lb -.
(74 gm/m;
Mill
manuf .
148
36
23.7
8.3
12.9
1.1
4.72
0.2
3.5
0.5
3.09
0.6
0.9
0.1
1.9
0.3
16.4
I [Statistically different from the control at 99.5% confidence level as
^indicated by a t test.
-------
Table 10. UNCOATED OFFSET SHEET OPTICAL PROPERTIES
Optical
properties
Brightness (G.E.)
a
Opacity (TAPPI)
a
30-lb
(44 gm/m )
Control
78.6
0.25
81.0
1.0
30-lb
(44 gm/m )
Recovered
filler
177.81
0.30
81.4
1.3
35-lb
(52 gm/rn )
Mill
manuf .
77.7
0.22
85.6
1.1
50-lb 9
(74 gm/m )
Control
86.2
0.33
93.1
0.6
50-lb
(74 gm/in )
Recovered
filler
rsTTel a
0.42
194. 3|a
0.6
50-lb
(74 gm/m)
Mill
manuf .
78.3
0.30
91.1
0.5
u>
Statistically different from control at 99.5 confidence level as indicated
by a t test.
-------
Table 11. UNCOATED OFFSET SHEET LABORATORY PRINTING PROPERTIES
Test
Wax pick: Wire side
Felt side
Hiding power
a
IGT Pick (cm/sec)
a
Velocity viscosity
product (xlO+ gm/sec )
a
K & N Ink (% reduction)
a
Paper sam
30-lb 2
(44 gm/m )
Control
14
16
76.1
1.3
129.8
20
10.7
1.7
50.8
1.6
30-lb
(44 gm/m )
Recovered
filler
14
16
75.9
2.0
129.3
15
10.6
1.2
53.0
1.7
35-lb -
(52 gm/m )
Mill
manuf .
10
20
89.4
0.2
115.0
7.9
9.5
0.6
52.9
2.0
pie
50-lb
(74 gm/m )
Control
14
14
91.9
0.4
100.9
11
8.3
0.9
54.2
1.0
50-lb
(74 gm/ni )
Recovered
filler
14
14
93.0
0.7
106.5
8.5
8.8
0.72
53.3
0.9
50-lb
(74 gm/m )
Mill
manuf.
16
11
95.1
-
129.0
14
10.6
1.2
55.0
2.1
U)
to
-------
breaks previously cited hampered the printing with the conse-
quence that overall printing quality achieved was not very good.
Though the printing expert was unaware of which samples
were associated with which grades of paper, it was obviously
easy to distinguish the heavy basis weight sheets. His detailed
comments are given in Appendix C. Table 12 summarizes the re-
sults of his evaluation. Each trial condition had five signa-
tures evaluated. For the 50-lb (74 gm/m2) grade, the sheets con-
taining recovered filler were judged superior to the control on
ink holdout, strikethrough, and printing sharpness. It compared
very well to the mill-manufactured paper. For the 30-lb (44 gm/
m2) grade, the sheet containing the recovered filler rated poorer
than the control on printing smoothness and sharpness but they
differ by only 1 point in their overall rating. Both the control
and the sheet containing the recovered filler rated below the
mill-manufactured paper but this was probably due more to the
basis weight difference between the 30- and 35-lb (44 and 52 gm/
m2) sheets than to any other factor.
Considering all of the printing results as a whole, it would
appear that the recovered filler addition was not a prime factor
in affecting printing properties. It was the opinion of the
printing expert that varying press conditions were the prime
factor, even though the trial design was set up to minimize this.
During the printing trial, plate wear was observed and to
see if this significnatly influenced the printing characteris-
tics, a set of sequential samples arranged in the order in which
the printing was done was submitted to the printing expert for
evaluation. These samples consisted of an early signature and a
late signature from the printing of each individual paper condi-
tion. From an examination of the results shown in Table 13, it
is apparent that although the printing sharpness did vary
throughout the run, there is not a trend to relate it to plate
wear.
33
-------
Table 12. EVALUATION OF WEB OFFSET PRINTED SAMPLES
d)
r— |
04
<0
rn
CN
6 *
rH g H 3
O >H n)
m ** S g
^ Aver
CN T3
g 0) H
J3 \ M CD
rH g 0) rH
1 & > rH
O O -r)
in ^f o m
— »p^ Aver
CN
grH
iQ ^^ O
7 &£
^^ c!
m ^* O"
r- u _
^> Avg
CN
,Q \ «H
•H g rH 3
1 &rH C
m «H (d
m CN S g
in _
^- Avg
CN "O
g 0) H
,Q\ M 0)
rH g 0) H
O O -H
n sr O «w
— '05 Avg
-•*
grH
rQ ^»* O
1 &-P
0^4
G
CO ** O
-* Avg
4J
3
O
13
H
O
,cj
^
cj
M
4
4
4
3
4
3.8
4
4
4
4
3
3.8
3
3
3
3
3
3
3
3
2
2
3
2.6
1
1
1
1
1
1
1
1
1
1
1
I A
3
0
M
X!
-P
[5
O
c/>
2
2
3
2
2
to ; 'O
CQ : n)
tn 0) d)
C C 0)
•H A rH
-P -P -P
C O -P
•H O O
H g g
d, tn ^^
4
4
4
4
4
2.2 4
4
4
4
4
3
3.8
3
3
3
2
3
2.8
3 ' 2
3 i 2
2
2
3
2.6
1
1
1
1
1
1
1
1
1
1
1
1 ' 1
1
2
3
2.0
1
1
1
1
1
1
1
1
1
1
1
1
4
4
4
4
4
4
4
4
4
4
4
4
4
3
4
3
2
3.2
4
3
2
3
4
3.2
4
3
3
4
4
3.6
j^
p.
CO
^
G
i— i
4
4
4
4
5
4.2
4
3-4
4
4
4
4
3
4
3
4
2-3
3.4
4
4
4
3
3
3.6
3
4
3
3
4
3.4
4
4
4
3
2
3.4
CQ
cn en
G 0)
•H (3
•P Pu
Cti
ri
•H (0
QJ W
Lt. ink 4
Lt. ink 4
Lt. ink 4
Lt . ink 4
Lt. ink 4
4
/
4
4
(U
o
c
m
CQ
U tn
•H
EH (tl
27.0
28.2
23.6
21.2
16.6
5
5
5
5
2 5
17.6
2 | 5
2.6 5
Grading Scale:
1 - poor, 2 - fair, 3 - average, 4 - good
5 - excellent
34
-------
Table 13. PRINTING SHARPNESS
OF SEQUENTIAL SAMPLES
Sample
Number
Al
A2
Bl
B2
Cl
C2
Dl
D2
El
E2
PI
P2
Gl
G2
HI
H2
11
12
Jl
J2
Kl
K2
High-
lights
3
4
4
3
1
2
1
2
2
3
1
2
1
1
2
2
2
1
1
2
3
3
Middle-
tones
1
4
3
2
2
2
1
1
3
3
1
3
1
1
1
1
1
2
1
3
2
3
Shadow
areas
1
4
3
2
1
3
1
1
2
2
1
2
1.
2
1
1
2
2
1
2
2
2
Average
2
4
3-4
2-3
1
2-3
1
1
2
2
1
2
1
1
2
1-2
2
2
1
2-3
2
3
Grading scale:
1 - poor, 2 - fair, 3 - average,
4 - good, 5 - excellent
35
-------
SECTION VIII
BLEACHING OF SCREENED, RECOVERED FILLER
The chief drawback to the use of the screened, recovered
filler appears to be its low brightness. This phenomena was
observed in all three grades of paper manufactured incorporating
the screened, recovered filler. There are a variety of bleaching
techniques which might be of value in restoring the brightness
of the recovered filler. Sodium hydrosulfite is commonly used in
the clay industry to bleach its clays. As a result, it was eval-
uated over a variety of conditions on the screened sludge used
in the manufacture of the uncoated offset sheets. The tempera-
ture was varied from 150 to 200°F (66 to 93°C). The concentra-
tion of Na2$204 was varied from 5 to 20 percent, and the EDTA
level from 0.5 to 2 percent. The best condition appeared to be
1 percent EDTA and 15 percent sodium hydrosulfite for 1 hour at
180°F (82°C), but this resulted in only a 3-point gain in bright-
ness . This 3-point gain would only increase the brightness from
70 to 73 and probably would not be enough to overcome the degra-
dation of final sheet brightness.
A variety of other bleaching techniques common to the paper
industry were also evaluated under severe bleaching conditions
on two high ash sludges from conventional mills which were not
deinking. These techniques included borohydride, chlorination,
hypochlorite, chlorine-water system at pH 5, chlorine dioxide
and peroxide. The bleaching conditions are summarized in Table
14, and the results given in Table 15. It appears that all of
the oxidative techniques have the ability to brighten the sludge,
with peroxide showing the greatest capacity- Thus, bleaching
may provide an alternative to the brightness loss difficulty.
Economic comparison of the various options warrants further
evaluation.
36
-------
Table. 14. CONDITIONS FOR BLEACHING
Experimental
parameters
Consistency
PH
Time
Temperature
% Chemical
Additional chem-
ical
Post treatment
Types of Bleaching
Boro-
hydride
2% SS
10
100 min
room
2
Chlori-
nation
2% SS
1-2
1 hr
room
6.59% avCl
Thiosul-
fate
Hypo-
chlorite
2% SS
11-12
2 hrs
room
10% avCl
Thiosul-
fate
CK>2
2% SS
3.5-6.0
5 hrs
160°F(71°C)
1.2
Thiosul-
fate
Chlorine -
H20 pH 5
2% SS
5
1 hr
room
10% avCl
Thiosul-
fate
Peroxide
2% SS
10-11
1 hr
160°F(71°C)
1.5% of
100% chem-
ical
5% Na2Si03
1% Mg SO4
S02 wash
U)
-------
Table 15. BLEACHING RESULTS
Type
of
bleaching
No bleaching
Borohydride
Chlorination
Hypochlorite
Chlorine - H20 pH 5
Chlorine Doxide
Peroxide
Brightness, % Elrepho
A
Sludge
70.5
70.0
74.2
75.9
77.5
76.8
77.3
B
Sludge
50.0
52.0
67.4
56.2
64.4
55.6
70.9
Note:
Sludge A originated at the same mill
from which sludges used in the uncoated
fine paper evaluation were taken.
Sludge B originated at a small fine
paper/specialty mill. Originally low
brightness of the sludge is attribut-
able to excessive clarifier residence
time.
38
-------
SECTION IX
PLAUSIBLE SCREENING SYSTEM TO RECOVER FILLER
If a mill were to employ screening to recover filler from
their high ash sludge as a sludge volume reduction technique,
the flow schematic might be the one shown in Figure 2. The pri-
mary clarifier underflow is fed through a consistency regulator
to a screening device. Sludge components which pass the screen
are sent to a mix tank with sufficient residence time to dampen
recovered filler quality variations. The mix tank might also
function as a tank in which to do any bleaching, if necessary.
From the mix tank the material would flow to the mill for addi-
tion at the usual point where filler is added in the system,
such as a blend chest.
There are many facets in designing a filler recovery system
to which the previously discussed trials and data do not speak.
However, if one were to make recommendations from the data con-
tained in this report, as far as the consistency fed the screen,
about 3 percent would be a good figure on which to control.
As far as screen types are concerned, the Sweco vibrating
screens which were used in these studies worked well, but there
are other alternatives commercially available which might be
considered. A trial was attempted using the Sweco concentrator
rather than their normal flat vibrating screen and it gave very
poor recovery efficiencies when tested. The screen retained most
of the filler as well as the fiber.
The mesh of the screen to be employed depends on how much
contamination the grades run can tolerate. A 320-mesh screen
gives a very pure product. Employing a more open mesh would
result in more contamination but a greater throughput rate and
associated reduction in required screening surface area. Life
of the screen is a factor of consideration as well.
Explicit size and design criteria for the equalization
chamber is elusive. Equalization required would be dependent
upon the mill's grade structure and frequency of grade changes.
The more changes and wider the variety, the longer will have to
be the equalization chamber to dampen these out.
39
-------
PRIMARY
CLARIFIER
>£>
O
MATERIAL RETAINED
TO DISPOSAL
SCREEN-
ING
DEVICE
MATERIAL
PASSING
THE
SCREEN
WATER
CO
0:1-
LUZ
_)•-«
-10
M Q_
-10
Q
O Q
EQUALIZATION CHAMBER
AND/OR BLEACHING
CHAMBER
Figure 2. Diagram of possible scheme for mill installation.
-------
For" a small specialties mill, the screening of the primary
clarifier sludge might not be the route to follow. There it
would likely be preferable to go back into the mill, catch the
losses close to the point of origin, and reuse them immediately -
For example, one source of filler loss to the sewer is from the
cleaner rejects. One specialty mill is currently using 325-mesh
Sweco vibrating screen to recover the filler from this source by
taking the material passing through the screen and sending it
back to the headbox fan pump (8). No adverse effect on product
quality has been observed. However, it is important not to send
the screen accepts back to the primary cleaner intake. Other-
wise, the cleaner system will be overloaded with filler. This
scheme has a particularly -good return on investment where Ti02 is
being used as filler. It is a good illustration of isolating the
loss at the source point and immediately reusing it.
MILL EXPERIENCES INCORPORATING PRIMARY CLARIFIER HIGH ASH
SLUDGE INTO A BLEACHING SEQUENCE
Case I (9)
A fine paper mill producing 485 tpd (440 metric tpd) of a
mix of bond, offset, book publishing and reprographic papers,
when confronted with the 1974 pulp shortage, decided to reacti-
vate a portion of a dormant three-stage bleach plant to process
100 tpd (91 metric tpd) of semi-bleached hardwood pulp which had
been manufactured at another location. The pulp would be
bleached in a hypochlorite stage to achieve an 84 to 86 bright-
ness . At this same time it was decided to reclaim the 10 tpd
(9.1 metric tpd) of primary clarifier sludge which the mill
produced by blending it with the semi-bleached pulp prior to the
thickener preceding the hypochlorite stage. The bleaching con-
ditions used in the hypochlorite stage were 10 percent stock con-
sistency, 2-hour detention time, calcium hypochlorite to give
3 percent available chlorine, 0.5 percent sulfamic acid, 120°F
(49°C) and pH 7 to 8. These bleaching conditions worked fine on
the pulp alone, but on the sludge pulp combination it was found
to give a brightness of less than 80 G.E. Upon investigation in
the laboratory it was found that the primary clarifier sludge by
itself could not be bleached above 55 G.E. brightness. A strict
blending of 10 tons (9.1 metric tons) of 55 brightness sludge
with 100 tpd (91 metric tpd) of 85 brightness pulp should give
an 82 brightness product which would have been acceptable, but
this additive relationship did not hold, and it was found exper-
imentally that only 5 tpd (4.5 metric tpd) of sludge could be
utilized if the brightness level were to be maintained.
A second difficulty with the sludge was that the ash frac-
tion was retained poorly on the thickener so a fair portion of it
returned via the thickener filtrate overflow to the clarifier,
thus producing a dead load in the loop between the thickener
41
-------
and the clarifier. A third difficulty which the sludge caused
was plugging of the centricleaners which followed the hypochlor-
ite stage. After the hypochlorite stage, the stock is diluted
to 1 percent, sent through three stages of centricleaners,
pumped to a vacuum washer and then pumped to the paper mill. The
rejects from the third stage centricleaners are sent over a Bauer
Hydrasieve and trucked to a land fill. This acts as the purge of
material from the system. The filtrate from the hydrasieve was
sent back to the clarifier. The mill lived with the above diffi-
culties and utilized about half of its primary clarifier sludge
from July through November of 1974. At this time the operations
were suspended because the extra bleached pulp capacity was not
needed.
After this experience an economic analysis indicated that
it would be advantageous to continue recovery of the clarifier
sludge even if fully bleached pulp or broke were used as a car-
rier instead of semibleached pulp. It must be kept in mind that
there were no capital investment costs, only operating costs of
utilizing existing equipment which was available in the inactive
bleach plant.
Before pursuing this, however, efforts were made to trace
down and alleviate some of the problem areas. The primary clari-
fier was fed by total mill effluent, storm sewers, roof drains,
septic tank leachings, boiler house sewers, and backwash from
the water treatment plant sand filters. By daily monitoring of
laboratory bleached brightness of the clarifier sludge, it was
observed that when storm runoff was present, poor brightness of
the bleached sludge resulted. When the intake water was very
turbid, a lot of filter backwash was in the primary clarifier
sludge and this caused lower brightness. This amounted to 1 ton
(0.9 metric ton) of silt in 10 tons (9.1 metric tons) of sludge
where normally there would be 500 Ibs (227 Kg) of filter back-
wash in 10 tons (9.1 metric tons) of sludge. The mill negotiated
with the state for permission to place the filter backwash back
in the water intake basin, and this feed stream was taken out of
the primary clarifier. This resulted in an average increase of
10 G.E. points in sludge bleachability moving from an average
of 55 to an average of 65.
The storm sewer runoff was still a problem, but it was
determined that it would be a problem only 25 percent of the time
and moving the coal piles and rerouting storm runoffs so they
would not drain to the clarifier would bring this sufficiently
under control.
Laboratory studies showed that addition of a chelating
agent before bleaching could increase the brightness an addi-
tional 3 points. In practice it would be too costly to do this
on a full scale, but it was felt that perhaps iron in the boiler
42
-------
blow-down water was the source of this and an alternate way to
dispose of this stream is being sought.
To solve the loss of filler on the first washer it was
decided to apply the sludge through a drilled pipe to the surface
of the washer after the pulp mat was formed. This brought the
solids loss problem under control.
To solve the centricleaner plugging problem it was thought
that placing an 1/8-in. (0.32 cm) opening vibrating-type Johnson
screen prior to the clarifier sludge surge tank and placing a
pressure-type centriscreen prior to the centricleaners would
alleviate this problem. These are possible future refinements
of their existing system.
The sludge bleaching recovery system illustrated in Figure
3 was operated for most of the month of June. Forty tpd (36.4
metric tpd) of fully bleached pulp was fed to a thickener prior
to the hypochlorite retention tower. This thickener had been
the caustic washer of the inactive bleach plant. Ten tpd (9.1
metric tpd) of sludge were fed into the chlorination tower of
the inactive bleach plant and treated with calcium hypochlorite
to a level of 3 percent available chlorine. The chlorination
tower was run as a short retention, completely mixed system at
ambient temperature. The sludge was fed through showers to the
face of the caustic washer and then into the hypochlorite tower
with the pulp. Calcium hypochlorite, to give 0.5 percent avail-
able chlorine on the pulp, was added to the hypochlorite tower.
The stock consistency in the tower was 10 percent; 4 hours de-
tention time was utilized at a 120°F (49°C) temperature and a
pH of 7 to 8.
The stock-sludge mixture was diluted with papermill white
water and sent to the centricleaners. After the centricleaners,
it was thickened on a vacuum washer and sent to the paper mill
for utilization. The centricleaners still had plugging problems
but the solids loss problem and the brightness problem were
brought under control. The sludge processed in this fashion did
not appear to cause any problems when utilized in the mill.
Further modification of the system to include screening devices
to solve the centricleaner plugging problem is anticipated.
This system or some alternate scheme will be in use in the
near future at this mill to recover their primary clarifier
sludge.
Case II (10)
A pulp and paper mill producing 500 tpd (455 metric tpd)
of fine paper (book, bond, offset, ledger, duplicator, repro-
graphic, etc.) and 650 tpd (590 metric tpd) of bleached soda
pulp is reusing its primary clarifier sludge by sending it back
43
-------
CLARIFIER
REJECTS TO
LAND FILL
VIBRATING
SCEEE1
\[
CaOC*
/STOCK
4 *
V/YYYYYY-YYYTrrv
^
S
/
10% SLURRY
f
CaOCfc
RETENTION
V, TOWER
^
CAUSTIC
TOWER
BLEACHED STOCK
CAUSTIC WASHER
FILTRATE
SEWER
TO MILL
SEWER
PAPER MACHINE
WHITE WATER
Figure 3. Case I primary clarifier sludge utilization bleaching system.
-------
through the bleach plant. This mill has a separate sewer system
for the pulp mill and bleach plant areas. The sewer stream,
whose solids are reclaimed, consists of the papermill sewer, wet
lap machine sewer, storm sewer.- and flexographic printing opera-
tion sewer. These streams are fed through a 1/2-in. (1.3 cm) bar
screen, to a 1/8-in. (0.32 cm) bar screen and then into a 60-mesh
sidehill screen, which reclaims much of the pulp solids. The
filtrate passing the screen is sent to two highly over-loaded
settling primary clarifiers, whose overflow goes to the city
sewage treatment plant. The clarifier underflow is combined with
the solids recovered from the sidehill screen and sent to a
chest where they are blended with mill colored broke. The com-
bined clarifier underflow and sidehill screen accepts consist
of approximately 50 percent ash which contains titanium dioxide,
talc, clay, and hydrated silica. This blend is then shipped to
the brown stock surge tank prior to the chlorination stage. The
approximate proportion of material processed through the CEHD
bleach plant is 600 tpd (546 metric tpd) virgin pulp, 15 tpd
(13.6 metric tpd) clarifier and sidehill screen sludge and 10 tpd
(9.1 metric tpd) colored broke. The approximate bleaching con-
ditions employed are given in Table 16. No overt change in the
bleaching chemical demand was noticed when the clarifier sludge
was introduced. The mill had been reclaiming the sidehill
screen-captured material for approximately 20 years and has been
utilizing the clarifier underflow in this manner for a year and
a half.
The only problem which has been noted is an increase in the
dirt count in the final paper product during periods of heavy
rainfall. Most of the dirt is usually taken out in the Radiclone
system in the bleach plant, but in heavy rainfall periods this
purge is insufficient. The stock out of the bleach plant is used
to manufacture all of the grades commonly produced by the mill.
The only grade in which it caused difficulty was a perforator
base paper grade which had a low ash requirement. Since ash was
already present in the pulp coming from the bleach plant, virgin
pulp had to be substituted.
45
-------
Table 16. BLEACHING CONDITIONS FOR MILL RECLAIMING
CLARIFIER SLUDGE BY PROCESSING THROUGH BLEACH PLANT
Conditions
Detention time (min)
Consistency (%)
Temperature (°F)/(C°)
PH
Chemical (wt % Of
O.D. pulp)
C
27
3
90/32
2.0-2.5
3% avg cS,
C*,2
E
17.1
8
140-150/60-66
10.0-11.0
1% '
NaOH
H
81.5
8
120/49
8.5-9.5
3% avg cH
CaOCJl
D
326
8
160/71
3.0-3.5
0.5% avg cH
cao2
OS
635 tpd (580 metric tpd) through plant
-------
SECTION X
EVALUATION OF FILLER RECOVERED BY WET OXIDATION
EXPERIMENTAL DESIGN
The overall experimental design involved the cooperating
fine paper mill practicing deinking, picking from its grade
structure a high volume 50 lb/3300 ft2 (74 gm/m2) uncoated offset
sheet which was to be simulated on the pilot paper machine at
Western Michigan University- This grade was to be manufactured
using virgin filler material and then made with the filler com-
pletely replaced with wet oxidized, recovered filler. The wet
oxidized, recovered filler was obtained by the mill's having
shipped drums of their dewatered clarifier sludge to a commercial
wet oxidation equipment supplier (Zimpro, Inc.) for processing.
The paper produced was tested for its physical and optical prop-
erties, rewound at the cooperating mill, and shipped to a nearby
commercial printer for a printing evaluation.
WET OXIDATION PROCEDURE
Dewatered primary clarifier sludge was placed in 55-gallon
(210 H) drums by the cooperating mill and shipped to Zimpro, Inc.
in Rothschild, Wisconsin for wet oxidation. The material was
reslurried and processed through their pilot plant at a tempera-
ture of 600°F (316°C) and a retention time of one hour. This
resulted in a pressure in the reaction chamber of approximately
3000 psi (21000 kPa). The solids fraction, after being wet
oxidized, appeared very similar to virgin filler. The liquid
fraction had a distinct yellowish tint to it. As a result, the
solids fraction was washed by allowing it to settle, decanting
the liquid and reslurrying in tap water. This process was re-
peated several times to ensure removal of the yellow supernatant.
The material was concentrated to 15 percent solids and shipped
to Western Michigan University in plastic-lined, 55-gallon (210 £)
drums.
The wet oxidation condition of one hour at 600°F (316°C) is
as severe an oxidation condition as the processor had ever
observed. At the time of the trial, they had developed experi-
ence with high ash sludges from five different plants. To ob-
tain a satisfactory high-brightness product the temperature
47
-------
conditions generally ranged from 482°F to 600°F (250°C to 316°C).
The conditions needed to achieve a satisfactory product is some-
thing which will have to be determined on each individual sludge.
Again, the sludge utilized in this study was the most difficult
case that had been encountered, requiring the most intensive of
conditions to achieve high brightness.
PILOT PAPER MACHINE TRIALS
The pilot paper machine at Western Michigan University was
utilized to make a 50 lb/3300 ft2 (74 gm/m2) sheet from a furnish
consisting of 40 percent bleached softwood kraft and 60 percent
bleached hardwood kraft refined to 300 Canadian Standard Freeness
with a Claflin refiner.
The sheet was filled to a level.of 15 percent ash using
No. 2 coating clay on the first day of a 2-day trial, and wet
oxidized, recovered filler on the second day. The sheet was
rosin sized at a level of rosin addition of 8 Ib/ton (4 Kg/metric
ton) and alum addition of 10 Ib/ton (5 Kg/metric ton) . The pH
on the machine was kept at 4.5 using sulfuric acid.
The headbox temperature was kept at 110°F (43°C) and a re-
tention aid, Kato 15 cationic starch, was metered in at a mix
tank prior to the headbox at a level of 10 Ib/ton (5 Kg/metric
ton). The dandy roll was run on the machine and three nips were
taken in the calender stack.
The sheet was sized externally by use of the size press.
Penford 280 ethylated starch was used at 6 to 7 percent solids
and the size press temperature kept at 140°F (60°C).
The machine was run 7 hours manufacturing paper for the
control sample which contained the No. 2 coating clay as filler
and 6 hours manufacturing paper for the wet oxidized, recovered
filler sheet.
When starting to run the recovered filler sheet, problems
were encountered with pH control on the machine. The acid
strength had to be increased several fold in order to compensate
for the demand imposed by the wet oxidized, recovered filler.
This will be explained further in the discussion of results.
During each day's run, four 30-ft (9.1 m) lengths of paper
were.taken for later evaluation. Samples of the headbox, first
tray water, and wet end overflow were taken also in order to
establish retention characteristics.
48
-------
PRINTING TRIAL
The printing trial was conducted at Banta Corporation in
Neenah, Wisconsin. An American Type Founders, four-color, blan-
ket-to-blanket, perfecting offset press was utilized. The color
sequence used was blue, red, yellow, black. The paper surface
temperature was kept at 190°F (88°C) after the dryers. The
printing speed was 700 to 800 fpm (215 to 245 m/min). The press
had a cloth dampening system.
The test paper was printed at the end of a regular commer-
cial run. The plates had 23,000 impressions on them at the start
of the trial. A roll of the control paper was printed with about
2500 signatures. A roll of paper containing the wet oxidized,
recovered filler was subsequently printed with approximately the
same number of signatures. One hundred signatures were randomly
collected from each roll and shipped back to Western Michigan
Unviersity for evaluation. From these 200 signatures, 5 from
each condition were randomly selected and submitted to a printing
expert for evaluation of 5 printing properties: holdout, strike-
through, showthrough, smoothness and sharpness. They were eval-
uated on a scale of 1 - poor, 2 - fair, 3 - average, 4 - good,
5 - excellent.
LABORATORY PHYSICAL, OPTICAL AND PRINTING TESTS
The same set of tests were used as were discussed in
Section IV of this report.
49
-------
SECTION XI
DISCUSSION OF RESULTS FOR USE OF
WET OXIDIZED, RECOVERED FILLER AS A FILLER PIGMENT
The wet oxidized, recovered filler appears and acts very
much like a normal clay slurry. Characteristics are shown in
Table 17. It was handled and metered during the pilot machine
trials in the same manner as a clay slurry. The only difficulty
which arose was with pH control on the machine. pH control
proved impossible until the acid strength was increased several
fold. To check the magnitude of this acid demand, as compared
to a sample of No. 2 coating clay, a 25 ml sample of wet oxidized
recovered filler slurry was titrated with .IN sulfuric acid from
its pH of 7 to the pH 4.5 used in the pilot machine trials. From
Figure 4 it is apparent that the recovered filler consumes about
48 times as much acid as normal No. 2 coating clay. This calcu-
lates out to 2.73 x 10 equivalents of acid/gm of wet oxidized,
recovered filler. The acid demand of the wet oxidized, recovered
filler at pH 4.5 will be an additional cost to be born. This
problem can be avoided by running at neutral conditions. The
increased acid demand may have been due to calcium carbonate
being present in the wet oxidized, recovered filler.
Table 17. CHARACTERISTICS OF FILLER RECOVERED BY
WET OXIDATION OF DEINKING SLUDGE
Parameter
Original sludge ash content (%)
Oxidized sludge ash content (%)
Oxidized sludge purity (%)
Brightness (% elrepho)
Abrasion (mg)
Pilot data
45.0
85.0
100.0
81.4
6.4
Table 18 gives the retention characteristics for each day of
the pilot machine run. There does not appear to be a significant
difference in the retention behavior of the wet oxidized, recov-
ered filler as compared to No. 2 coating clay.
50
-------
NO, 2 COATING CLAY
WET OXIDIZED
FILLER
Figure 4. Acid demand of wet oxidized pigment.
51
-------
Table 18. RETENTION CHARACTERISTICS OF
WET OXIDIZED RECOVERED FILLER
Control sheet
Wet oxidized recovered
filler sheet
First pass
73.1
74.4
Overall
83.6
84.8
The physical properties of the sheets made during the pilot
trial and a sample of the mill-manufactured paper which was being
simulated are given in Table 19. Only MD TEA was significantly
different from the control at the 99.5 confidence level and is
not far enough out of line to be of practical concern. Note
also that the dirt count did not increase significantly.
The optical properties of the sheets are listed in Table 20.
The sheet containing recovered filler lost 2.6 points in bright-
ness but gained 4.9 points in opacity- This kind of a trade of
opacity for brightness could probably be tolerated. The increase
in opacity may be due to the presence of titanium dioxide in the
recovered filler; whereas, there was none at all present in the
control sheet. Analysis of the wet oxidized, recovered filler
showed it to contain about 1 percent Ti02 which would account
for about half of the opacity increase.
The laboratory printing properties are given in Table 21.
The only difference between the control sheet and the sheet con-
taining the recovered filler is in the test for hiding power
where the increased opacity of the sheet containing the recovered
filler manifests itself.
The paper was shipped to a commercial printer and printed on
a four-color ATF perfecting web offset press. One roll of paper
containing the wet oxidized, recovered filler was run as was a
roll of the control. The results of the printing evaluation are
presented in Table 22. The print quality was very uniform and
the wet oxidized pigment sheet compared well to the control
sheet, rating better than the control on showthrough. The
printing expert's detailed comments are contained in Appendix D.
- 52
-------
Table 19. WET OXIDIZED, RECOVERED FILLER UNCOATED
OFFSET PAPER PHYSICAL PROPERTIES
1
Physical properties
Basis weight (lb/3300 ft2)/
( gm/m2 )
a
Caliper (.001 in) /(mm)
a
Porosity (Sheffield)
a
Smoothness (Sheffield)
a
MD Tensile (Kg)
a
CD Tensile (Kg)
a
MD Tensile factor
a
CD Tensile factor
a
MD Stretch (%)
a
CD Stretch (%)
a
MD TEA (Kg(m)/m )
a ~
CD TEA (Kg (m) /m )
a
Mullen (PSI)/(kPa)
a
MD Tear (gm)
a
CD Tear (gm)
a
MD MIT fold (number)
a
CD MIT fold (number)
a
Dirt specks
a
Control
51.8/76.7
1.1/1.6
3.80/0.097
0.0 /0.002
117
3.1
125
15.2
10.0
0.35
5.65
0.30
0.13
0.005
0.073
0.004
1.82
0.15
3.79
0.59
3.55
0.36
5.02
1.1
18.3/126
1.5/10.3
58.4
5.6
63.5
4.2
62.9
35.1
21.5
6.4
45.0
Recovered
filler
51.4/76.1
1.1/1/6
3.85/0.098
0.10/0.003
115
6.7
121
21.2
9.16
0.62
5.38
0.22
0.12
0.009
0.070
0.003
1.63
0.14
4.10
0.47
|2.88| a
0.38
5.24
0.73
17.4/120
0.95/6.5
59.3
4.0
67.9
5.1
60.2
17.1
18.9
4.6
58.8
13.4 9.1
Mill
Made
46.5/68/8
1.4/2.1
3.55/0.090
0.05/0.001
102
6.1
153
27.8
9.39
0.79
6.23
0.28
0.136
0.008
0.09
0.004
1.64
0.18
4.23
0.46
2.94
0.49
6.32
0.95
20.5/141
2.1/14.5
48.4
3.4
49.0
4.3
100.4
27.5
63.8
15.7
—
—
Statistically different from the control at 99.5%
confidence level as indicated by a t test.
53
-------
Table 20. WET OXIDIZED, RECOVERED FILLER
UNCOATED OFFSET PAPER OPTICAL PROPERTIES
Optical properties
Brightness
a
Opacity (TAPPI)
a
Units
% Elrepho
Control
82.5
0.15
85.4
0.52
Recovered
filler
(HIl]a
0.17
[9073] a
0.59
Mill
Made
77.7
0.39
89.6
0.45
Statistically different from control at 99.5
confidence level as indicated by a t test.
Table 21. WET OXIDIZED, RECOVERED FILLER
UNCOATED OFFSET PAPER PRINTING PROPERTIES
Lab printing properties
Wax pick
a
K & N Ink
a
Hiding power
a
WP (x 10 4) gm/sec2
a (x lO*)
Hercules size (sec)
a
IGT Pick (cm/sec)
(Polybutene oil 822 poise) a
Control
12.1
0.45
48.4
4.25
0.87
0.028
9.7
0.82
58.6
21.2
118
10.9
Recovered
filler
11.1
0.80
52.3
5.09
|0.93a
0.007
10.0
1.17
77.6
10.9
122
14.0
Mill
made
13.2
0.83
44.4
6.48
0.90
0.014
21.7
2.1
76.7
15.2
264
26
Statistically different from control at 99.5
confidence level as indicated by a t test.
54
-------
Table 22. UNCOATED OFFSET SHEET PRINTING RESULTS
01
Sample
R 1
8 R 2
-H -P
*& c3
•« 1 R 3
O tn
4j Q. R 4
0)
* R 5
C 6
H C 7
0
]j C 8
c:
u C 9
CIO
(Gloss)
Ink
holdout
2
2
2
2
2
2
2
2
2
2
Strike-
through
3
2
2
2
2
2
2
2
2
2
Printing
(smoothness)
mottle
3
3
3
3
3
3
3
3
3
3
Ink
spread
(sharpness)
3
3
3
3
3
3
3
3
3
3
Show-
through
2
2
2
2
2
1
1
1
1
1
Total
12
12
12
12
12
11
11
11
11
11
5. Excellent 4. Good 3. Average 2. Fair
1. Poor
-------
SECTION XII
POTENTIAL OF WET OXIDIZED, RECOVERED FILLER
AS A POSSIBLE COATING PIGMENT
When the recovered filler obtained by wet 'oxidation was
dried, repulverized using a mortar and pestle, and pressed into
a pellet, it had an elrepho brightness of 81.4 percent. This is
about equal to the brightness of filler grade clays but 5 to 6
points lower than conventional No. 2 coating clay. Its lower
brightness would be its first drawback as a coating pigment.
The cooperating mill contracted with the Institute of Paper
Chemistry to have particle size distributions run on the recov-
ered filler. These are shown in Figure 5. Its distribution lies
between that of a No. 2 coating clay and a filler clay. Seventy-
four percent of the recovered clay is less than 2 um where a
No. 2 coating clay has 81 percent less than 2 ym.
The recovered fillers dispersing agent requirement was
determined using a modification of TAPPI Procedure T648, using
sodium hexametaphosphate. It did not readily disperse even when
treated with excessive quantities of the dispersant.
Hercules viscometer rheograms taken on the wet oxidized,
recovered filler at 40 percent solids showed it required about
four times the shear stress to get the material to shear as com-
pared to No. 2 coating clay at the same solids level.
The wet oxidized, recovered filler is a mixture of all of
the inorganic material which was in the deinking sludge before
wet oxidation. Transmission electron photomicrographs done at
Western Michigan University illustrate this most readily. The
recovered filler contained kaolin clay, calcium carbonate, titan-
ium dioxide and other unidentifiable material.
It seems unlikely that this material would be suitable as
a coating pigment due to its heterogeneous nature, lower bright-
ness, particle size distribution and dispersion difficulties;
but it is suitable as a filler clay substitute.
56
-------
ioo-
in
-o
80
60
LJU
U
o;
ai
o_
40
20
NO, 2 COATING CLAY
FILLER CLAY
WET OXIDIZED RECOVERED
FILLER
Q| i i i—i—i—i L
_L
J L
50 30 20 10 6432 1.0 0.8
EQUIVALENT SPHERICAL DIAMETER/ MICRONS
0.2
0.1
Figure 5. Particle size distribution of wet oxidized recovered filler.
-------
SECTION XIII
REFERENCES
1. A Study of Practical Approaches to Utilization of Solids
from Deinking Mill Waste. NCASI Technical Bulletin No. 67.
June 1954.
2. MacDonald, J.P., and J.W. Kenney. Abrasiveness Test for
Paper Fillers. TAPPI, 32, No. 11. November 1949.
3. Sludge Material Recovery System for Manufacturers of Pig-
mented Papers. Water Pollution Control Research Series.
12040 FES 07/71.
4. Frank, R.D., and F.C. Schmutz. A Proposed Test for Abra-
siveness of Pigments and Paper Fillers. TAPPI, 43, No. 7.
July 1960.
5. The Relation Between Process Water Quality Characteristics
and Its Reuse Potential in Combination Board Mills, Part
III, Procedures for Determining Water Quality Characteris-
tics in Paper and Board Manufacturing Water Reuse Programs.
NCASI Technical Bulletin No. 282. September 1975.
6. TAPPI Testing Procedures. Technical Assosication of the
Pulp and Paper Indsutry, Atlanta, Georgia.
7. Useful Methods. Technical Association of the Pulp and Paper
Industry, Atlanta, Georgia.
8. Personal Communications. E. Grys, Technical Director,
Fletcher Paper Company, Alpena, Michigan.
9. Personal Communications. James E. Flynn, Manager Technical
Services, Lock Haven, Pennsylvania.
10. Personal Communications. T. Collins, Research Chemist,
Hammermill Paper Company, Erie, Pennsylvania.
58
-------
SECTION XIV
APPENDICES
Page
A. Laboratory Evaluation of Recovery Techniques 60
B. Details of Printing Trial and Evaluation for 74
Coated Fine Paper Samples
C. Details of Uncoated Web Offset Printing Trial and 76
Printing Evaluation
D. Details of Printing Evaluation of Uncoated Web 82
Offset Samples from Wet Oxidized Recovered Filler
Trial
59
-------
APPENDIX A
LABORATORY EVALUATION OF RECOVERY TECHNIQUES
EXPERIMENTAL PROCEDURE
The experimental design for this laboratory project was
divided into three main parts. The first was to compare four
methods of recovering an acceptable filler grade clay from high
ash primary paper sludge. These four methods were centrifugal
separation, foam flotation, screening and wet oxidation. The
second part of the design was to evaluate the fillers recovered
from each method. The percent filler, brightness and abrasive-
ness were determined in this evaluation. The final part was to
make up handsheets for the two most promising techniques. These
sheets were tested for their optical, strength and sizing pro-
perties .
The high ash primary sludges used in this project were from
two different paper mills, both making printing and bond grades
of paper. However, one mill was involved in deinking operations
and the other was not. Enough of both types of sludges were
stored in a refrigeration unit so that all of the recovery meth-
ods could be evaluated from the same sludge.
Recovery Methods
All of the recovery method trials were done at Western
Michigan University and were run on both types of sludges.
Centricleaning—
The centrifugal separation was done using a No. 600 3-inch
(7.62 cm) Bauer Centricleaner. The inlet pressure and back
pressure were kept constant at 50 and 5 psig (340 to 34 kPa)
respectively. The sludge was diluted to two consistencies, 0.1
percent and 0.5 percent. Both the accepts and the rejects from
the cleaner were analyzed.
Foam Flotation—
The foam flotation work was done in a Fegergran Lab Flota-
tion machine made by WEMCO (Western Machinery 'Company) . The
surfactant, its concentration and the sludge conditioning had
been predetermined by work done by Prakasha Misra for his Senior
Thesis in conjunction with the NCASI. The surfactant was a
60
-------
partially soluble, cationic quaternary ammonium chloride,
Kemamine Q-6502, which is produced by Humko Products. Enough
sludge to yield 20 grams dry suspended solids was put into a
Waring Blender and broken up for 5 minutes. Next the pH was
adjusted to 6.5 using dilute NaOH or H2S04. The concentration
of the surfactant was 0.75 percent of the 20 grams suspended
solids. The surfactant was added to the pH adjusted sludge and
then mixed well in the Waring Blender for 5 minutes at low speed.
Finally, the sludge was put in the flotation cell and diluted to
approximately 0.70 percent solids. The air flow to the cell was
regulated to maintain a small bubble size and a supporting layer
of foam on the surface. The flotation cell was run for 3 to 4
minutes and then the volume of both the froth and the tailings
were measured and analyzed.
Screening—
The separation of the filler from the fiber by simple
screening was accomplished with 18-inch SWECO vibrating screen.
The sludges were diluted to 0.1, 0.4, 1.0, 2.0 and 3.0 percent
solids. The sludge was placed over the vibrating screen at a
constant dry solids loading of .04 pounds per minute (18 gm/min).
Two screen mesh sizes, 230 and 325, were used at all five of the
percent solids levels. The weight setting on the bottom of the
motor was kept at 20° so that the fiber would go out across the
screen rather than spiraling around the screen which tends to
trap the fillers. Samples from the overflow and the flowthrough
were analyzed.
Wet Oxidation—
The final method used to recover the fillers was wet oxida-
tion. The sludge was diluted to 2 to 3 percent solids. One
liter was poured into the stirred reactor built by Autoclave
Engineers and sealed. Next, enough oxygen was added to bring
the pressure up to 500 psig (3400 kPa). The conventional sludge
was brought up to 600°F (316°C) and held there for 10 minutes.
The maxium pressure that developed during these cooks was 2900
psig (20,000 kPa). The deinked sludge had to be heated up to
620°F (327°C) for 30 minutes before complete oxidation took
place. A maximum pressure of 3400 psig (23,000 kPa) was re-
corded during the deinked cooks. After the bomb had cooled off,
it was vacuumed out and the contents analyzed.
Analysis of Recovered Fillers
The recovered fillers were analyzed using the following
tests.
Percent Filler or Ash Content—
The ash content was determined following TAPPI Standard
Method T-113. A 15 percent loss of filler from ignition in the
muffle furnace was assumed in all of the calculations.
61
-------
Percent
A modification of TAPPI Standard Method T-439 m-60 was used
to find percent Ti02 of the recovered filler. This modification,
which originated at Du Pont, uses potassium pyrosulfate to fuse
the sample before it is put into solution.
Brightness—
A brightness pad was formed in a Buchner funnel, dried and
then measured for brightness using the elrepho brightness tester.
The brightness was reported percent elrepho. For the wet oxida-
tion filler and the standard water-washed clay filler, a special
disc was made due to the fact the dried fillers on the filter
paper cracked badly.
Abrasion—
The flat disc method proposed by Frank and Schmitz, modified
by the NCASI (4,5) was used to find the relative abrasiveness
of solutions. A felt wrapped around an abrading block which was
mounted in a drill press was placed in contact with a bronze
disc and rotated while the filler slurry was circulated over the
disc. The relative loss of weight of the disc measures the abra-
sion tendency of the material.
Handsheet Procedures
These samples of recovered fillers from the screening and
wet oxidation method were used to make up laboratory handsheets.
These were compared to sheets made with ones using a standard
water-washed Kaolin filler clay. The filled sheets contained
20 percent clay addition and no addition of Ti02 to give a target
filler content of about 10 percent filler in the final handsheet.
All of the handsheets were made on the Noble and Wood handsheet
machine with target basis weight of 60 gm/m^. The furnish, 60
percent bleached softwood kraft and 40 percent bleached hardwood
kraft, was refined in a Valley beater until Canadian Standard
Freeness of 350 was reached. The sheets were sized with 1.0
percent rosin and 2 percent alum. The pH in the mixing tank and
in the sheet mold kept close to 4.5 with dilute sulfuric acid.
They were conditioned overnight in a constant temperature and
humidity room, then the following tests were run on them:
TAPPI Standard Method Test
410 Basis weight
411 Caliper
452 Brightness (elrepho)
425 Opacity
494 Tensile
494 % Stretch
494 Tensile energy absorption
403 Brust (Mullen)
62
-------
TAPPI Standard Method Test
414 Tear (internal)
511 Fold (MIT)
413 Ash Content
Sizing - Hercules
499 IGT Pick
TAPPI Useful Method K and N Ink
553 Hiding power
From the ash content of the handsheet, one pass filler re-
tention was calculated. The tensile factor was calculated by
dividing the tensile by the basis weight.
DISCUSSION OF RESULTS
Centrifugal Separation
Although centricleaners are quite widely used in the paper
industry as a method to separate solids from fibers, their appli-
cation as a filler recovery method did not prove to be fruitful.
From Tables 1-A and 2-A it can be seen that the maximum increase
in percent filler was only 8 to 10 percent. Also, the inconsis-
tency in which the two sludges behaved seemed to bring out the
ineffectiveness of the centricleaners. The conventional sludge
had a maximum purity in the first pass rejects at 0.5 percent
solids while the deinked sludge had its maximum purity in the
accepts after four passes through the cleaners at 0.1 percent
solids. The fillers used in the handsheets were those recovered
in the first pass rejects at 0.5 percent solids for both sludges.
Foam Flotation
From previous work done, it was found that 90 to 92 percent
of the filler materials could be recovered with purity increase
of 17 to 18 percent or a total purity of 75 to 80 percent. The
work done on flotation for this project was also aimed at these
figures but with a different flotation cell. The Fergergran
laboratory flotation cell was a larger unit and it did not have
the exact control over the bubble size that the previously used
cell had. However, we did match results very closely as the
figures of Tables 3-A and 4-A point out. The conventional
sludge had a purity of 75 percent and a recovery of 90 percent.
The deinked sludge was somewhat lower with a purity of 61.5 and
a recovery of 70.5. The main variable with the Fergergran cell
was the length of time that each batch should be run, because
the purity decreased with time. By taking samples at 1-minute
intervals, the purity and recovery was found throughout the
transition of a flotation run. Figure 1-A is a plot of purity
63
-------
Table 1-A. RECOVERED FILLER PURITIES FROM
CENTRIFUGAL SEPARATION DEINKING SLUDGE
Centricleaner Pass
Raw sludge
At 0.5% solids
1st pass: accepts
1st pass: rejects
2nd pass: accepts
2nd pass: rejects
3rd pass: accepts
3rd pass: rejects
4th pass: accepts
4th pass: rejects
At 0.1% solids
1st pass: accepts
1st pass: rejects
2nd pass: accepts
2nd pass: rejects
3rd pass: accepts
3rd pass: rejects
4th pass: accepts
4th pass: rejects
Total
solids %
28.5
0.38
1.59
0.38
0.88
0.36
0.69
0.35
0.58
0.11
0.52
0.11
0.20
0.10
0.15
0.10
0.13
Ash,
%
45.0
53.5
34.4
51.8
33.9
53.8
39.3
54.2
41.5
52.7
27.0
55.9
38.1
57.0
43.7
57.9
50.1
Filler,
%
52.9
62.9
40.5
61.0
39.9
63.3
46.2
63.7
48.8
62.0
31.8
65.7
44.9
67.1
51.4
68.1
59.0
Fiber,
%
47.1
37.1
59.5
39.0
60.1
36.7
53.8
36.3
51.2
38.0
68.2
34.3
55.1
32.9
48.6
31.9
41.0
64
-------
Table 2-A. RECOVERED FILLER PURITIES FROM
CENTRIFUGAL SEPARATION CONVENTIONAL SLUDGE
Centricleaner pass
Raw sludge
At 0.5% solids
1st pass: accepts
1st pass: rejects
2nd pass: accepts
2nd pass: rejects
3rd pass: accepts
3rd pass: rejects
4th pass: accepts
4th pass: rejects
At 0.1% solids
1st pass : accepts
1st pass: rejects
2nd pass: accepts
2nd pass: rejects
3rd pass: accepts
3rd pass: rejects
4th pass: accepts
4th pass: rejects
Total
solids %
4.91
0.40
2.52
0.40
0.94
0.39
0.64
0.40
0.57
0.11
0.72
0.11
0.20
0.10
0.16
0.09
0.13
Ash,
%
55.0
49.4
61.8
49.3
46.2
49.5
45.4
49.0
48.6
51.9
53.3
52.9
44.0
54.1
45.4
53.5
48.8
Filler,
%
64.7
58.2
72.7
58.0
54.3
58.3
53.4
57.6
57.2
61.1
62.7
62.3
51.8
63.7
53.5
62.9
56.4
Fiber,
%
35.3
41.8
27.3
42.0
45.7
41.7
46.6
42.4
42.8
38.9
37.3
37-7
48.2
36.3
46.5
37.1
42.6
65
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Table 3-A. SUMMARY OF HIGH ASH SLUDGE
LABORATORY RECOVERY TECHNIQUE DATA - PURITY
(% of product which is filler material)
Separation
technique
Original sludge
Centricleaning
Screening
Foam flotation
Wet oxidation
Conventional
s ludge
%
48.0
72.7
91.5
75.5
100.0
De inking
sludge
%
52.9
62.9
76.5
61.5
100.0
Table 4-A. SUMMARY OF HIGH ASH SLUDGE
LABORATORY RECOVERY TECHNIQUE DATA - RECOVERY
(% of filler in original sludge which is recovered)
Separation
technique
Centricleaning
Screening
Foam flotation
Wet oxidation
Conventional
sludge
%
1.5
97.7
90.5
100.0
Deinking
s ludge
%
98.3
97.3
70.5
100.0
66
-------
90--
% RECOVERY OF FILLER
% PURITY OF FILLER
• i®-
~®—
TIME IN MINUTES
Figure 1-A. Foam flotation: time vs. % filler
purity and recovery
-------
and recovery versus time. From this figure, it was decided that
a batch run would be 3 to 4 minutes long.
Screening
Figure 2-A summarizes all of the work done with the SWECO
vibrator screen. It shows how the recovery for both sludges was
very high with 96 percent minimum and that the 325-mesh and 230-
mesh lines were almost the same. This means the 230-mesh screen
was just as effective as the 325-mesh screen for the recovery of
the filler. An analysis of variance was run to find out if the
percent solids, mesh size or their interaction significantly
affected the purity and the recovery.
At a 95 percent confidence level, neither the mesh size nor
their interaction affected the purity or the recovery. However,
as the percent solids increased, the purity also increased.
Although recovery decreased slightly with increasing solids, it
was not significant at a 95 percent confidence level.
Wet Oxidation
The conditions for wet oxidation were chosen to ensure a
complete oxidation of all fibrous materials. At these extreme
conditions, the purity and recovery were both 100 percent.
Summary of Separation Results
A final summary of the methods of recovering filler materi-
als from high ash primary sludge is shown in Tables 3-A and
4-A. Wet oxidation and screening have high recovery for both
types of sludges. The purity of the deinked sludge was lower
than the conventional sludge in every method except wet oxida-
tion. The centricleaners and vibrating screen were much easier
unit operations to run. Because of its high recovery with either
sludge, good purity and ease of operation, screening appeared to
be the best method to recover the filler material from the
sludge.
In Table 5-A the brightnesses of the recovered filler for
both sludges is listed. When these were compared to a standard
filler clay which has a brightness of 81 to 82 percent elrepho,
it was decided that the recovered filler would probably cause
some loss in sheet brightness when employed.
Abrasiveness
One of the main concerns in reusing the filler was that the
filler would become more abrasive. From Table 6-A it can be
seen that the fillers from wet oxidation were more abrasive than
the filler from the other methods. However, the relative
68
-------
10
% FILLER RECOVERY
FOR BOTH
FILLER PURITY OF
CONVENTIONAL SLUDGE
DEINKED - MESH
DEINKED - MESH 230
CONVENTIONAL MESH 325 O
CONVENTIONAL MESH 230 «
% FILLER PURITY OF DEINKED SLUDGE
-—- __»— —
®
CONSISTENCY OF SLUDGE
Figure 2-A. Screening. The effect of screen mesh and
consistency on purity and recovery.
-------
Table 5-A. BRIGHTNESS RESULTS
(Elrepho)
Separation tech .
Raw sludge
Centricleaners
Screening
Flotation
Wet oxidation
De inking
50.8
54.5
56.0
50.6
73.5
Conventional
63.0
61.1
71.3
71.7
71.7
Table 6-A. ABRASION RESULTS BY FLAT DISC METHOD
Sample
Filler grade clay
Filler grade clay
Centricleaned sludge
Screened sludge
Foam floated sludge
Wet oxidized sludge
Slurry
consistency
%
10
6
6
10
6
10
De inking
wt loss
(mg/disc)
7.1
6.3
1.4
4.1
1.3
6.4
Conventional
wt loss
(mg/disc)
7.1
6.3
1.0
4.2
2.4
7.0
70
-------
abrasiveness of the filler from any of the methods was not
greater than a normal filler grade clay.
Effect of Screened and Wet Oxidized Recovered Filler on
Physical and Optical Properties of Hand Sheets
Contained in Tables 7-A and 8-A are the results of handsheet
tests made employing filler recovered by the screening and wet
oxidation techniques for the conventional and the deinking mill
sludges. The blocked figures are numbers which were shown to be
statistically lower than the control at a 99.5 percent confidence
level using the t test. The only property of practical concern
which changed was the brightness. The screened, recovered filler
caused a drop of 3.6 points for the conventional sample and 10.9
points for the deinking sample. The 3.6 drop in brightness may
be able to be tolerated but certainly not the 10.9 drop. Thus,
it appears that from a laboratory handsheet viewpoint, screening
for filler recovery may be a possibility for a mill not practic-
ing deinking. Wet oxidation will be the route a deinking mill
will probably have to pursue. None of the other physical or
optical properties tested seem to be affected.
71
-------
Table 7-A. HAND SHEET PROPERTIES MODIFICATION
(conventional)
Property
Basis wt. (G/M2)
Caliper (.0*01 in.) /(mm)
Brightness (elrepho)
Opacity (TAPPI)
Tensile (Kg)
Tensile factor (Kg M2/gm)
Stretch (%)
Tear (gm)
Mullen (PSI)/(kPa)
Fold (number)
Hercules size (sec)
Filler (%)
Retention (%)
IGT Pick
Hiding power
K & N Ink (% red.)
Control
64.6
5.41/0.137
72.5
83.6
7.98
0.125
2.64
52.8
22.6/156
21
66.5
9.4
46.9
255
0.77
46.3
Screened
64.4
5.38/0.137
|68.9| a
87.6
7.99
0.126
2.62
48.0
24.3/167
30
35.9
10.9
54.6
245
0.87
50.8
Wet-oxidized
[6374] a
5.22/0.133
73.4
85.4
7.59
0.119
2.54
56.8
25.8/178
34
118.5
11.4
56.9
245
0.85
53.3
Significantly different from control at 99,
confidence.
72
-------
Table 8-A. HAND SHEET PROPERTIES MODIFICATION
(deinking)
Property
Basis wt. (G/M2)
Caliper (.001 in.) /(nun)
Brightness (elrepho)
Opacity (TAPPI)
Tensile (Kg)
Tensile factor (Kg M/gm)
Stretch (%)
Tear (gm)
Mullen (PSI)/(kPa)
Fold (number)
Hercules size (sec)
Filler (%)
Retention (%)
IGT Pick
Hiding power
K & N Ink (% red.)
Control
64.6
5.41/0.137
72.5
83.6
7.98
0.125
2.64
52.8
22.6/156
21
66.5
9.4
46.9
255
0.79
46.3
Screened
[63T7]a
5.39/0.137
|61. 6|a
92.1
7.52
0.117
2.42
48.8
23.7/163
27
72.7
12.1
60.6
255
0.93
47.5
Wet-oxidized
HsTTsl a
5.28/0.134
75.2
89.1
7.50
0.122
2.16
55.2
20.0/138
13
77.1
10.9
5.4
230
0.88
54.8
Significantly different from control at 99
confidence.
73
-------
APPENDIX B
DETAILS OF PRINTING TRIAL AND EVALUATION
FOR COATED FINE PAPER SAMPLES
ASSESSMENT OF PRINTING QUALITY OF COATED OFFSET PRINTED
SAMPLES CONDUCTED BY E.W. RAYFORD
The absence of standards upon which the characteristics of
printability of the test sheets could be based, limits the com-
prehensiveness of this evaluation. In this case, the separate
test sheets were evaluated one against the other in an attempt to
arrive at comparative values.
The primary difficulty encountered in the evaluation was
the poor quality of the printing. Sharpness and gloss were two
of the characteristics to be evaluated. Close examination with
10X, 12X and 30X glasses revealed more than minimal differences
in these two characteristcis between the samples. Color, gloss
and sharpness are a function of the amount of ink laid on the
sheet. Inspection revealed visible differences in ink coverage
and color. Not knowing the printing sequence of the samples, I
was unable to determine whether the differences were due to pa-
per factors or press problems. After determining that there was
little difference in the amount of showthrough and strikethrough
between the samples, and that the printing quality was markedly
different on the back sides of some of the samples, I decided to
run a series of densitometer readings on the four process colors.
These curves showed wide latitudes in color control on the press.
Correlations can be drawn between the amount of ink on the sheet
and the differences in penetration and gloss, and printing
sharpness.
Examination of the slur gauges also reveals press problems.
Good dot hardness and sharpness is most often a result of good
press conditions. Evidence of the word "slur" o^all of the
samples indicates less than optimum printing quality. Examina-
tion of both highlight and shadow dots under a 30X glass indi-
cates soft, mushy and slurred dot formation, particularly on the
blue and black. This would result in.a lack of printing sharp-
ness and halftone quality.
74
-------
A certain amount of scumming is apparent on many of the
samples. I think this can also be attributed to press conditions
rather than to paper factors.
The mis-register also lowers the quality of the printed job
and the determination of fine detail.
After making close examinations of both sides of each sam-
ple, and close comparisons between the samples, keeping in mind
the lack of uniformity of press control, I found no major differ-
ences in the printability of the samples. Samples 14, 17 and 26
were less opaque; and samples 21, 23 and 26 in particular, lacked
sharpness in the halftones. There were little apparent differ-
ences in strikethrough, mottle, pick resistance, fiber puffing
and blister, and ink spread. These were all considered to be
satisfactory. Opacity was considered to be somewhat low in all
samples where there was no backup, particularly samples 23
through 26, bvit showthrough was not evident when backed up with
light colors.
One characteristic noticed was the softness of the samples
and the lack of resistance to tear in handling.
In my opinion, the printing characteristics of all of these
samples were satisfactory, and that most of the objectionable
qualities found in the printing were due to press conditions.
However, whether or not these conditions could be controlled to
a closer degree on the press using these papers cannot be ascer-
tained from these samples, but should be determined from the
reports of the press conditions and paper runability.
75
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APPENDIX C
DETAILS OF UNCOATED WEB OFFSET PRINTING TRIAL
AND PRINTING EVALUATION
ASSESSMENT OF PRINTING QUALITY OF UNCOATED FINE PAPER PRINTED
SAMPLES CONDUCTED BY E.W. RAYFORD
An honest and genuine attempt was made to evaluate the
printing qualities of the thirty-five samples submitted to me.
Because of wide variation in the quality of the printing and ink
coverage, I feel the evaluation of the printing quality of the
paper is subject to some question.
The differences, in my opinion, were due more to printing
quality and press condiitons than to paper characteristics. Of
course, there is a big difference between most of the printing
qualities of the lightweight stocks and the heavier weight
stocks.
Because of the imposition of the backup forms, evaluation
of some qualities were limited. The solid color bars were backed
up by another bar of the same color; the black halftones were
backed up by the GRETAG Control Bar; large color areas, screens
and process were backed up by large color areas. Therefore,
strikethrough and showthrough were confined to limited areas.
The amount of strikethrough, showthrough and lack of ink holdout
was in most cases, directly related to the amount of ink
applied. Color density could be expected to be greater in the
color bars because of being backed up by the same color, parti-
cularly in the lighter weight stocks.
Printing sharpness was evaluated in the half tones and the
screened areas. Because of the large differences in ink cover-?.
age, evidence of plate wear and breakdown, and other printing
factors, I think sharpness was more a condition of printing
quality than paper quality. An additional twenty-two samples
were added to the original thirty-five to give me a better exam-
ple of plate image breakdown, but because these samples too,
were randomized, they had no more meaning than the original
thirty-five. Where ink coverage was light and the plate new,
sharpness was good in all categories, highlights, mid-tones and
shadows. As the run progressed, all areas got progressively
76
-------
worse, particularly when ink coverage was heavier. It was also
noted to deteriorate more in the shadow areas where dot structure
disappeared entirely in some areas.
A special effort was made to evaluate the printing sharpness
in the halftones on the additional samples which were used to
assess the importance of plate wear on printing. Highlights,
midtones and shadows were evaluated, and recorded individually
as well as the average overall sharpnes. It should be noted
that there was little, if any difference noted between these
samples and the other thirty-five samples. The same faults, too
little or too heavy ink coverage, dot breakdown and loss of
shadow dot detail, slur and scum are all evident in various sam-
ples . Densitometer readings were recorded for the black on these
samples in an attempt to relate the amount of ink coverage with
printing sharpness. No densitometer readings were recorded for
the other three colors on these samples.
As a whole, I would say printing sharpness was poor, except
in a few cases. However, these conditions were noted to be sim-
ilar on all paper samples, with the difference between weights
again being noted.
Printing smoothness or mottle was evident in the blue on all
samples, and in the black on some samples where the ink coverage
was heavy. The other colors were good.
Ink spread was noted on the head of the red color bar in
some cases, and on the tail of this same color bar on others. It
was noted on the tail of the black bar on several samples. Also,
the dot structure of the screens was noted to be soft on many
samples. This could be a condition of ink spread or dot slur.
The SLUR gauges were noted as being bad on many samples.
Ink coverage was very inconsistent, both between samples,
and in many cases, within a sample. In some cases, coverage
was very light, the paper showed through the ink so badly that
no evidence of solid coverage was apparent. On these samples,
sharpness was rated accordingly higher. Ink coverage can be
noted on the densitometer charts.
There was a good deal of black ink transfer on the other
colors caused by press rollers. There was also scumming evident.
This made taking densitometer readings in some areas impractical.
Register is bad on many of the process samples, and is also
evident in the back-up of the Control Strip.
In my opinion, the average quality of the printing is low,
but I think this is due to press conditions and problems as
similar faults are evident on all of the different types of
paper, the exception being between the lightweight papers and
77
-------
the heavier papers. Quality, overall, is lower on the lighter
weight samples.
There was little, if any, evidence of fiber pick on any of
the samples.
In all cases, the lightweight and the heavier weight samples
were separated for evaluation, but samples within the separate
weights were randomized. The charts are sequential for ease of
recording. (See Table 11 in "Discussion of Results" Section.)
Densitometer Readings
Macbeth RD-100
Densitometer readings were taken in several areas: on the
solid patch of the Control Strip, in the center of the solid
color square, and on the left end, center and right end of the
solid color bar. As the yellow GRETAG color patch, the color
square and the left end of the solid color bar are all in line
of press travel, these densitometer readings were the same.
However, by moving the aperture about one and one-half inches to
the right, a much higher reading was obtained. This difference
is noted between the columns marked GRETAG and Color Bar, left
on the yellow.
Also, differences in color values could be obtained on all
colors by moving the aperture fractions of an inch. Therefore,
a special effort was made to read the same respective area on all
colors on all samples (except as noted above on the yellow).
Areas marked NG could not be recorded, either because the
area was contaminated with another color, mostly black, or
showthrough of mis-register on the lighter samples made the
reading meaningless.
78
-------
DENSITOMETER READINGS
Sample
number
1.
2.
3.
4.
5.
6.
7.
8.
9.
.10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
Yellow
0)
n n a
So u
•H 41
tr o id
w o o
0.82
0.82
0.82
0.80
0.82
0.87
0.90
0.88
0.86
0.87
0.86
0.90
0.90
0.92
0.90
0.87
NG
0.88
0.86
NG
0.92
0.93
0.92
0.94
0.94
0.92
0.92
0.88
0.87
0.85
0.92
0.90
Color bar
4>
Si
2
0.84
0.88
0.86
0.87
0.86
0.92
0.93
0.94
0.92
0.90
0.88
0.92
0.90
0.94
0.90
0.86
0.90
0.98
0.90
0.89
0.94
0.95
0.94
0.94
0.98
0.95
0.98
0.96
0.94
NG
NG
Magenta
0)
M M X
id o u
P i— 1 4J
O1 o id
w o a
0.93
0.94
0.99
1.04
1.04
1.14
1.12
1.10
0.98
1.04
0.95
1.01
1.02
1.00
0.98
1.12
1.11
1.15
1.10
1.04
0.99
1.00
1.02
0.98
1.00
1.08
1.06
1.06
1.10
1.07
1.04
Color bar
4>
tr o id
M u a
1.20
1.21
1.22
1.18
1.15
1.19
1.18
1.24
1.16
1.14
1.06
1.14
1.01
1.14
1.16
1.22
1.20
1.16
1.18
1.20
1.20
1.28
1.26
1.21
1.25
1.16
1.23
1.24
1.30
1.25
1.02 1.25
1.04 1.24
Color bar
4J
O id
M o a
1.U4
1.02
Color bar
4>
,£2
tr>
•H
K
l.Ub
1.11
1.07
1.10
1.02
1.18
1.22
1.20
1.10
1.14
1. 30
1.35
1.38
1.38
1.34
1.34
1.30
1.32
1.34
1.38
1.21
1.20
1.28
1.29
1.26
1.46
1.38
1.44
1.42
1.34
1.39
1.41
GRETAG - HIT
Color control
system
rH
iH
d)
U.U2
0.82
0.82
0.80
0.82
0.87
0.90
0.88
0.86
0.86
0.86
0.88
0.90
0.92
0.90
0.87
0. 88
0.88
0.86
0.88
0.92
0.93
0.92
0.94
0.94
NG
NG
NG
NG
NG
NG
0.90
id
4J
C
O
O1
id
u.uy
0.88
0.90
0.92
0.97
1.08
1.06
1.07
0.92
0.98
0.86
0.94
0.94
0.96
0.94
1.06
1.06
1.04
1.10
1.06
0.96
0.94
NG
0.96
0.99
0.98
1.01
NG
NG
NG
0.96
1.00
"
l.l/
1.11
1.13
1.14
1.15
1.15
1.10
1.14
1.11
1.06
1.02
1.10
1.12
1.04
1.04
1.16
1.06
1.11
1.16
1.14
1.12
1.14
1.18
1.12
1.14
1.07
1.22
1.18
1.20
1.17
1.18
1.14
^
o
id
1-1
1.00
1.02
1.00
1.00
1.04
1.32
1.26
1.33
1.20
1.22
1.25
1.28
1.28
1.28
1.26
1.34
1.35
1.32
1.32
1.36
1.20
1.20
1.40
1.32
1.28
1.39
1.42
1.41
1.36
1.32
1.40
1.50
-------
DENSITOMETER READINGS
(continued)
Sample
number
33.
34.
35.
Highes
Lowest
Range
Yellow
o>
v< M .c
n) O (J
3 rH 4J
O1 o m
U) U 0
0.90
0.93
0.94
0.94
0.80
Color bar
4J
M-l
a
1.04
1.06
1.04
1.08
0.91
i<
Cente
1.08
NG
NG
1.10
0.98
&
tj>
•rH
«
0.96
0.99
0.98
0.99
0.84
0.. 80-1. 10
Magenta
0)
fc M £
ra o o
3 H 4J
tr o it
en u a
1.00
1.02
1.05
1.15
0.93
Color bar
.u
H-l
3
0.95
1.01
0.96
1.14
0.86
M
Cente
.
1.08
1.20
1.18
1.24
0.99
-P
D>
2
1.06
1.10
1.14
1.17
0.86
0.86-1.24
Cyan
H
3
1.18
1.05
1.00
1.18
0.91
u
Cente
1.24
1.14
1.12
1.36
1.02
0.91-1.30
jj
•&
•H
K
1.21
1.10
1.12
1.22
0.98
Black
01
^ M j:
n) O u
3 rH 4J
tj< 0 <8
u> u o,
1.4S
1.47
1.46
1.48
1.00
Color bar
4-1
IM
3
1.33
1.24
' 1.40
1.34
0.91
n
Cente
1.44
1.55
1.54
1.56
1.14
4J
•a
a
1.40
1.50
1.41
1.50
1.06
0.91-1.56
GRETAG - RIT
Color control
system
2
Yello
NG
NG
NG
0.94
0.80
0.14
id
4J
01
I
0.98
NG
1.00
1.10
0.86
0.24
n)
&
1.24
1.06
1.04
1.24
1.07
0.17
Black
1.47
1.34
1.46
1.50
1.00
0.50
-------
DENSITOMETER READINGS
oo
Sequen-
tial
Samples
Sample
number
Al
A2
Bl
B2
Cl
C2
Dl
D2
El
E2
Fl
F2
Gl
G2
HI
H2
11
12
Jl
J2
Kl
K2
Highest
Lowest
Range
Yellow
Q
w
§
o
o
s
EH
o
2
Magenta
Q
W
§
o
U
s
o
2
Cyan
Q
W
o
U
3
EH
o
2
Black
(!)
nJ O O
3 H -P
tT< O (U
C/) O fit
Ma
1.35
1.31
1.26
1.24
1.40
1.24
1.40
1.42
1.52
1.44
1.48
1.44
1.50
1.40
1.44
1.43
1.48
NG
1.45
1.40
1.43
1.52
1.24
Color bar
-P
m
0)
0.86
1.20
1.26
M
1.17
1.32
1.22
1.26
1.34
1.46
1.44
1.34
1.28
1.34
1.36
1.24
1.30
1.34
1.16
1.22
1.20
1.16
1.46
0.86
H
0)
-P
d)
u
1.14
1.27
1.32
M
1.16
1.34
1.36
1.40
1.34
1.54
1.54
1.54
1.50
1.60
1.46
1.53
1.60
1.56
1.32
1.46
1.51
1.48
1.60
1.14
p
-H
«
0.94
1.23
1.30
1.18
1.19
1.32
1.21
1.41
1.41
1.38
1.40
1.52
1.34
1.46
1.38
1.42
1.56
1.47
1.22
1.28
1.39
1.38
1.56
0.94
0.86-1.60
GRETAG - RIT
Color control
system
>
O
H
*
Q
W
§
o
U
$
EH
o
2
i m
tri-p
S
-------
APPENDIX D
DETAILS OF PRINTING EVALUATION OF UNCOATED
WEB OFFSET SAMPLES FROM WET OXIDIZED RECOVERED FILLER TRIAL
I
ASSESSMENT OF PRINTING QUALITY OF UNCOATED WEB OFFSET
PRINTED SAMPLES CONDUCTED BY E.W. RAYFORD
A lack of standards limits the evaluation of these test
sheets. The uncoated samples also appeared to have very similar
properties of printability. All of the colors except black are
screened, and most of them are arrived at through a combination
of two or more screened colors; therefore, mottle, spread, and
printing sharpness were more easily determined using the black
printed areas.
Printing sharpness is satisfactory on all of the samples.
Again, there is evidence of soft, mushy screen patterns but this
was found to be similar on all of the samples. There was little
evidence of ink spread into the unprinted areas.
Gloss was considered to be low on all colors except the
black where it was judged to be satisfactory. There is evidence
of scumming throughout the samples, more so on the black than
on the other colors. This was attributed to press conditions
such as ink-water balance (this could also be a factor in the
low gloss) , counter etching of the plate, or other plate or
press factors. The higher gloss of the black and the larger
amount of scumming could be a result of a heavier ink flow.
Printing smoothness was considered to be average for a
base sheet such as this.
Opacity was considered to be poor. The amount of show-
throught is objectionable, even when backed up. Samples 6
through 10, the control samples, were considered to be slightly
worse than samples 1 through 5, the recovered filler samples.
There is evidence of strikethrough on all of the samples.
The amount of strikethrough and the lack of opacity and gloss
would, in my opinion, determine ink holdout to be only fair.
The printability of these sheets was considered to be sat-
isfactory except in the areas of strikethrough and showthrough.
82
-------
Table 1-D. PRINTING SAMPLE EVALUATION
BY USE OF 1-5 GRADING SYSTEM
Sample
1
2
3
4
5
6
7
8
9
10
(Gloss)
Ink
Holdout
2
2
2
2
2
2
2
2
2
2
Strike
Through
2
2
2
2
2
2
2
2
2
2
Printing
(Smoothness)
(Mottle)
3
3
3
3
3
3
3
3
3
3
Ink
Spread
(Sharpness)
3
3
3
3
*
3
3
3
3
3
3
Show
Through
2
2
2
2
2
1
1
1
1
1
83
-------
1. RtPOHT NO.
_ EPA-600/2-77-123
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing:)
2.
3. RECIPIENT'S ACCESSION-NO.
-: TITLE AND SUBTITLE
INVESTIGATION OF REUSE POTENTIAL OF ASH FROM
PAPERMILL SLUDGES
5. REPORT DATE
July 1977 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR13)
Allan M. Springer, Duane W. Marshall, Isaiah
Cellman
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
National Council of the Paper Industry for Air
and Stream Improvement, Inc.
Central-Lake States Regional Center
Kalamazoo, Michigan 49008
10. PROGRAM ELEMENT NO.
1BB610
11. CONTRACT/GRANT NO.
EPA-R-803348-01
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Lab.-Cin., OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA/600/12
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Two techniques for recovery of filler from fine papermill high ash
sludges, screening and wet oxidation, were evaluated for their technical!
feasibility. The alternative of screening the sludge and using the I
material passing through the screen as recovered filler was investigated
in cooperation with two mills. The screening for recovery of filler
was conducted at the mill site. Then the material was shipped to
Western Michigan University where selected grades incorporating the
recovered filler were manufactured. The paper manufactured was
shipped to Rochester Institute of Technology where it was printed on
their web offset press. The grades simulated were found lacking only ir
that the brightness of the paper was from four to seven points lower
than grades made with virgin filler. The wet oxidation alternative
was evaluated in a similar manner with a cooperating mill. The wet
oxidized recovered fillers only slightly lowered the brightness of the
sheet simulated and gave an increase in opacity in exchange. The wet
oxidation scheme appears technically feasible. The screening alterna-
tive would probably have to incorporate a bleaching step before it
would be deemed acceptable. The technical feasibility of oxidative
bleaching was demonstrated.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Sludge, clay minerals, refractories,
kaolin, opacifiers, fillers, paper-
making, paper mills, book paper,
oxidation, screening, separation,
vibrating screens, recovery,
reclamation
Fine paper,
Wet oxidation
13/B,H
11/B
07/A
13. DISTRIBUTION STATEMENT
Release To Public
19. SECURITY CLASS (This Report)
Unclassified
94
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
84
* ui GWBtfaexr ™Dmne omcE an- 757-ffl56/646»
------- |