kraft and mechanical pulpsbiorefinery.utk.edu/technical_reviews/fiber engineering.pdf · lab...
TRANSCRIPT
Fiber Engineering
Importance of carboxyl (acid) groups on pulps.• Main group responsible for surface and bulk charge of kraft
fibers.
• Important for pulp swelling.
• Increase pulp fiber softness and collapsibility.
• Improve pulp strength properties.
• Improve beatability.
• Capable of ion-exchange reactions.
Fiber Engineering
Two methods developed for measurement of surface and bulk acid groups:
1. UV/VIS measurement of iodide counterion released from electroneutralization reaction – attempting to make it an automated measurement
2. On-line HSGC measurement of carbon dioxide released from acid/base reaction of HCl and carboxylates
Fiber Engineering
It has been found that O and EOP increase overall acid levels, but D sequences tend to decrease it
00 .010 .020 .030 .040 .050 .060 .070 .08
BS O
D(EOP )ODE
D (EOP )DE
D (EOP)DED
[CO
OH
], m
mol
/g p
ulp
0102030405060708090100
TAPPI B
rightness
[C O O H]B rig h tn ess
BS Kappa =26
OD(EOP)D Mill Tensile Strength and Bulk/Surface Acid Groups.
50
55
60
65
70
75
80
85
90
95
100
Refere
nce C
ookBro
wn StockO2 F
eedO2 W
asher M
atD0 M
at(E
OP) Mat
D1 Mat
(R1-3
)*
D1 Transfe
r (R1-3)
*D1 M
at (R
4)*
D1 Transfe
r (R4)*
Stage
Tens
ile In
dex
0
20
40
60
80
100
120
Aci
d C
onte
nt, µ
eq/g
Tensile IndexBulk AcidSurface Acidx10
Fiber Engineering
OD(EOP)D Mill Loss in Fiber Strength
130
135
140
145
150
155
160
165
170
Referen
ce C
ookBro
wn StockO2 F
eed
O2 Was
her M
atD0 M
at(E
OP) Mat
D1 Mat
(R1-3
)*
D1 Tran
sfer (
R1-3)*
D1 Mat
(R4)*
D1 Tran
sfer (
R4)*
Stage
Zero
Spa
n Te
nsile
Inde
x
Fiber Engineering
Fiber Engineering
• Primary losses in OD(EOP)D Mill fiber strength from digester, and O2 stages, and to a lesser extent, across the (EOP) stage.
0%Lab reference cook
-15.6%Bleached Hi-D pump (R4)-18.6%D1 washer mat (R4)-16.8%Bleached Hi-D pump (R1-3)-15.6%D1 washer mat (R1-3)-14.4%(EOP) washer mat-10.2%D0 washer mat-13.2%O2 washer mat
-8.4%O2 Feed-6.6%Brown stock washer mat
% Loss in ZST
Composite Samples
Fiber Engineering
Fiber Length and Curl from OD(EOP)D Mill Pulps
00.020.040.060.08
0.10.120.140.160.18
0.2
Lab R
efere
nce C
ookBro
wn StockO2 F
eed
O2 was
her mat
D0 was
her mat
(EOP) w
asher
mat
D1 was
her mat
(R1-3
)*
Bleach
ed H
i-D pum
p (R1-3
)*
D1 was
her mat
(R4)*
D1 Hi-D
pump (R4)*
LW C
url I
ndex
22.12.22.32.42.52.62.72.82.93
LW F
iber
Len
gth,
mm
Curl Index Curl Index, PFI refined LW Fiber Length LW Fiber Length, PFI refined
Fiber Engineering
Fiber Length and Curl from Mill D(EOP)D Pulps
0.040.060.08
0.10.120.140.160.18
0.2
Lab R
efere
nce c
ook
Knotte
r Fee
d
BS Was
her L
ine 2 M
at
Pre-was
her Fe
ed
Pre-was
her Disc
harge
D0 was
her fee
d
D0 was
her disc
harge
(EOP) s
tage f
eed
(EOP) w
ash fe
ed
(EOP) w
ash disc
harge
D1 fee
d before
ClO2
D1 fee
d after
ClO
2
D1 was
h feed
D1 was
h discharg
e*
Bleach
ed pulp to
Hi-D
LW C
url I
ndex
2
2.2
2.4
2.6
2.8
3
3.2
LW L
engt
h, m
m
Curl Index Curl Index, PFI refined Fiber Length Fiber Length, PFI refined
• Across the whole bleach plant, there is a loss in bulk acid group content and a potential decrease in bonding capability. Combined with fiber strength loss, this leads to an overall lossin tensile strength.
• Largest single stage loss in bulk acid groups are in chlorine dioxide stages (D0 and D1) due in part to HexA loss. Need to examine further the effect of D stage conditions on acid groups.
• The capability to add or retain acid groups in the bleach plant would provide a means to better tailor fiber properties.
Fiber Engineering
• Loss in fiber strength (zero span) across bleach plant with greatest loss in O2 stage and smaller loss in (EOP) stage. Previous work indicated that O2 stage loss is more of a function of mechanical treatment than chemical conditions. (Allison, et al. 1998) This needs to be investigated further.
• Significant curl imparted to Mill C pulps in oxygen stage with little additional increase in other stages.
• Only small effect on curl in Mill D bleach plant despite MC processing. (Potentially equipment related)
Fiber Engineering
Fiber EngineeringResearch Objectives for Subtask III
1.Understand the mechanism of bond strength in TMP sheets by clarifying the morphological factors which hinder strong bond formation.
2.Understand the bond enhancement mechanism of reinforcement fibers.
Fiber Engineering
632.842.20.3829.61092592
303.126.00.2623.03951762
86.212.40.2217.0679883
TEA Index(mJ/g)
TensileIndex(Nm/g)
SheetDensity(g/cm3)
FinesContent
(%)CSF (ml)
SpecificEnergy
Consumption(kWh/t)
Description of Previous Slide
Specific energy consumption: 883 kWh/t
• Majority of the long fibers keep S1 layer
• S1 layer keeps the cross section squared
• The pulp has abundant shives
Fiber Engineering
Fiber Engineering
1762 kWh/t
Specific energy consumption: 1762 kWh/tMore fibers lose the S1 layerSquared fibers (cross section) are still notable
Fiber Engineering
2592 kWh/t
Specific energy consumption: 2592 kWh/t
Majority of long fibers lost the S1 layer
Fibers appear more collapsible
Fiber Modification/Fiber-Fiber BondingResults from Enhancement of Fiber-Fiber Bonding
883 kWh/t 2592 kWh/t
Fines Morphology
Fines consist of peeled S1 layer, cut fibers, ray cells, fibrils, pit borders, etc
Fines of peeled S1 layer are fibrillated and flattened with intensive refining
Fines appear more conformable
Effect of refining energy input on handsheet (60 g/m2) structure
• Thick-walled fibers are resistant to collapse regardless of refining energy
• Thin-walled fibers tend to collapse more with increased refining
• Reduction of caliper appears be largely dependent on the flattening of thin-walled fibers
Fiber Engineering
Fiber Engineering
Two newsprints, made of black spruce and southern pine TMPs, were compared to understand how pulp morphology affects the structure of commercial products
Structure of newsprints made ofblack spruce and southern pine TMPs
1.6840.03429.7Black Spruce Newsprint
1.5780.04431.1Southern
Pine Newsprint
Fiber Length (mm)Curl IndexFine Content
(%)
Fiber Engineering
375.419.5445.963.348.2Black
Spruce Newsprint
393.317.1343.050.549.2Southern
Pine Newsprint
TEA Index,
CD, mJ/g
Tensile Index,
CD, Nm/g
TEA Index,
MD, mJ/g
Tensile Index,
MD, Nm/g
Basis Weight g/m2
Fiber Engineering
Cross Sections of Newsprints (high density area)
Southern Pine Black Spruce
Fiber Engineering
Description of Previous Slide
• Both thin-walled and thick-walled fibers are notably deformed and collapsed by calendering in dense areas
• Black spruce has more fibers in cross section than southern pine*
*compared at the same basis weight
Fiber Modification/Fiber-Fiber BondingResults from Enhancement of Fiber-Fiber Bonding
Cross Sections of Newsprints (low density area)
Southern Pine Black Spruce
Fiber Engineering
fines
Southern Pine Newsprint
Thin-walled fibers are less collapsed in the low density areaThick-walled fibers are uncollapsed
There is noticeable difference in location of fines between southern pine and black spruce newsprintsSouthern pine newsprint: fines are filtered at the pocket of coarse fiber network at low density area fewer fines are located in high density areasBlack spruce: fines are more or less uniformly distributed
• Bonded areas in southern pine and black spruce newsprints, as visualized by vapor phase osmium coating, are notable as the dark areas (areas of bond breakage)
• Southern pine newsprints seem to have fewer bonded areas than black spruce
Fiber Engineering
