Utilization of Lime-mud
As a Filler in Paper Making
By
Hazem S. Ahmed
Qena Paper Industry Company
Under Supervision of
Prof. Abd El-Aziz. A. Said Prof. Aref M. A. Aly
Chemistry Department
Faculty of Science,
Assiut University
Outline
 Introduction
 Aim of the work
 Experimental
 Results and discussion
 Conclusion
Introduction
LIME-MUDE DEFFINITION
Lime mud is a waste byproduct
generated by pulp and paper mill
industry, and collected from the
kraft pulping chemicals recovery
process.
Bagasse
 the most fibrous raw material available and
suitable for paper making in Egypt, is the
sugarcane residue after sugar extraction.
 The ultimate goal of chemical pulping is to liberate
cellulosic fibers by lignin removal (delignification)
without degrading or removing fibers.
 Pulp plant consists of four main processes as follow
1st
• pulping
2nd
• washing
3rd
• Screening
4th
• Bleaching
Pulping
In the Kraft pulping
process, bagasse mixed
with aqueous cooking
liquor “white liquor”
composed mainly of
sodium hydroxide (NaOH)
and sodium sulfide (Na2S),
in pandia under pressure
and temperature
conditions to separate the
cellulosic fiber from the
natural lignins
washing
Washing filters
economically remove the
maximum amount of
dissolved organic and
soluble inorganic material
present with pulp mass
with the minimum
amount of fresh or reused
processed water, to
prevent any interference
with bleaching or
papermaking chemicals
screening
Screening systems
are installed to
selectively remove
certain constituents
from a pulp feed, so
that the accepted
pulp is more
suitable for the
paper making
bleaching
is the chemical
treatment of
cellulosic fibers to
increase
brightness by
decolorizing or
dissolving the
colored
components in
pulp, principally
lignin to increase
the visual quality
Paper Machine
Bleached pulp
mixed in a furnish
with wood pulp
and other
chemical additives
(filler, dye,
retention aid,
AKD, starch) to
produce the paper
roll
Return back to washers in pulp plant
 The filtrate of washers called black liquor.
 black liquor contains, aside from the original white
liquor chemicals, lignins and other organic matter.
 Black liquor supplied to recovery plants to recover and
recycle the costly pulping chemicals .
 the black liquor is concentrated in multiple-effect
evaporators .
Evaporators
Black liquor delivered as a concentrated fuel
to a “chemical recovery boiler.”
 recovery boiler combusts the organics under unique
oxidizing/reducing conditions to a molten inorganic
ash (“smelt”) consisting primarily of Na2S and Na2CO3.
 The smelt is drained from the recovery boiler and
quenched in water to create the “green liquor.”
 The green liquor is delivered to the “slakers” to initiate
conversion of the dissolved Na2CO3 into NaOH
required in the white liquor.
 This slaking process utilizes calcium oxide CaO to
convert Na2CO3 into NaOH via the following two
consecutive reactions:
Recovery boiler
Slaking process
 CaO(s) +H2O→Ca (OH)2
 Na2CO3(aq)+Ca(OH)2→2NaOH(aq)+CaCO3(s)
 CaCO3 is the lime mud waste produced from
chemicals recovery in pulp and paper manufacture.
Experimental
 Lime-mud obtained from the recovery plant was dried and
then the alkali loss was measured. It was subjected to full
chemical analysis, particle size determination and optical
properties. The study included the effect of washing with
hot water at different temperatures on the removal of alkali
loss and dissolved silica then another full chemical analysis
was conducted.
 The study was also performed on the effect of grinding
process on the particle size distribution using constant
volume and changing the time of grinding.
 The optical properties which include: brightness, opacity,
scattering coefficient were determined as well.
Results and Discussion
Lime-mud obtained from the recovery plant was
subjected to full chemical analysis, particle size
determination and optical properties.
SiO2
4.85
Al2O3
Fe2O3
CaO
MgO
Na2O
K 2O
SO3
TiO2
P2O5
L.O.I
0.01
0.03
51.13
0.01
1.45
0.01
0.39
0.01
0.11
40.95
% on diameter 2µm
Alkali losses as Na2O
brightness
14.970 %
1.45%
85
AVAILABILITY TO USE AS FILLER?
 From results in the table we can see that we are facing
three problems to use lime-mud as filler in
papermaking as follow
Brightness must be increase to about 90% iso
2. Removing of alkali losses and dissolved silica
1.
3.
Particle size must be 2µm and its portion is
about 70%
Alkali losses and dissolved silica removal
 The effect of washing with hot water at different
temperatures on the removal of alkali loss and
dissolved silica was carried out then, full chemical
analysis was conducted.
 The best results achieved when washing was carried
out at 90°C.The alkali losses decreased to 0.55% and
silica decreases to 3.5%.
 The washing filtrate will be used in quenched of smelt
to obtained the green liquor.
temperature
Loss as
Na2O%
SiO2
3.5
60°C
70°C
80°C
90°C
1.45%
0.86%
0.84%
0.55%
Al2O3
Fe2O3
CaO
MgO
Na2O
K 2O
SO3
TiO2
P2O5
0.01
0.02
54.39 0.01
0.55
0.01
0.01
0.01
0.1
L.O.I
41.28
Particle size distribution
Relation between time of grinding and particle size
Particle size distribution
Relation between time of grinding and particle size
Raw sample direct from
the filter
Drying and grinding
for1 min
Washed, drying and
grinding
Washed, drying and grinding
CaCO3
for10 min
for 5 min
15.0891
4.2952
Diameter on 10% µm
0.3985
0.3876
Diameter on 50% µm
15.0891
4.2952
Diameter on 90% µm
29.4304
10.3031
% on diameter 2µm
14.970 %
% on diameter 3µm
median µm
0.5762
0.2179
0.5762
Filler sample
0.5208
1.6230
0.1771
0.7684
0.5208
1.6230
9.3428
6.3470
32.741 %
70.515 %
71.764 %
73.178%
15.717 %
39.730 %
74.356 %
77.788 %
95.119%
% on diameter 4µm
16.679 %
47.549 %
77.443 %
82.387 %
99.417%
% on diameter 5µm
17.925 %
55.917 %
80.262 %
86.45 %
90.993
95.903
2.8552
2.0094
% on diameter 10µm
Mean µm
15.7194
Brightness iso
85
d98 (top cut)
5.2788
90.2
18.1890
3.6730
1.97
95.7
97.8%
12.474
6.9733
Brightness increase
 Reason for brightness decrease due to black spots in
the lime-mud.
 Black spots are formed through combustion of sulpher
compounds in the boiler.
 A new filtration method was adopted to the green
liquor before the slaking process to remove the black
spots.
 Brightness increases after this step from 85% iso to
95.7% iso.
Pilot scale
Paper making research plant
 Two sets of paper sheets were made in the research
plant.
 1st set using the same furnish in the paper machine
using exported calcium carbonate as filler
 2nd set using the same furnish in the paper machine
using treated lime mud sample as filler
 Optical and mechanical properties were measured
optical and mechanical properties for paper sheets, where sample1, is paper sheets made by using exported calcium carbona
Calcium
Carbonate
Treated Lime-mud
66.03
62.94
µ
400
390
BULK
cc/g
1.51
1.55
MOISTURE
%
6.67
5.88
TENSILE INDEX
Nm/g
53.97
58.64
BREAKING LENGTH
METER
5500
5980
TEAR INDEX
mNm2/g
7.27
7.01
73.93
71.52
3.93
3.98
40.06
40.56
227
206
SUBSTANCE
THICKNESS
g/m2
TEAR FACTOR
BURST INDEX
Kpa m2/g
BURST FACTOR
Air permeance
ml/min
OPACITY (ptg)
%
80.89
78.73
Sc COEFFICIENT
m2/kg
36.99
34.15
YELLOWNESS
%
5.96
4.65
Conclusion
 Tests made in this study showed that lime-mud after
washing and drying is an important source of crude
carbonate which (due its chemical properties and
natural potential) can be used in paper making
industry as a filler in coated paper with the following
superior properties:
1. Chemical content (loss) and drigs removed.
2. Brightness is suitable for papermaking
3. Lime-mud particles size becomes smaller and
percent of 2 µm increases gradually with increasing
time and become more suitable for paper making.
Thank you for your attention