- •Recovered Paper and Recycled Fibers
- •Isbn: 3-527-30999-3
- •Introduction
- •Isbn: 3-527-30999-3
- •Isbn: 3-527-30999-3
- •2006, Isbn 3-527-30997-7
- •Volume 1
- •Isbn: 3-527-30999-3
- •4.1 Introduction 109
- •4.2.5.1 Introduction 185
- •4.3.1 Introduction 392
- •5.1 Introduction 511
- •6.1 Introduction 561
- •6.2.1 Introduction 563
- •6.4.1 Introduction 579
- •Volume 2
- •7.3.1 Introduction 628
- •7.4.1 Introduction 734
- •7.5.1 Introduction 777
- •7.6.1 Introduction 849
- •7.10.1 Introduction 887
- •8.1 Introduction 933
- •1 Introduction 1071
- •5 Processing of Mechanical Pulp and Reject Handling: Screening and
- •1 Introduction 1149
- •Isbn: 3-527-30999-3
- •Isbn: 3-527-30999-3
- •Isbn: 3-527-30999-3
- •Isbn: 3-527-30999-3
- •Introduction
- •Introduction
- •Isbn: 3-527-30999-3
- •1 Introduction
- •1 Introduction
- •1 Introduction
- •1 Introduction
- •1 Introduction
- •1 Introduction
- •150.000 Annual Fiber Flow[kt]
- •1 Introduction
- •1 Introduction
- •Introduction
- •Isbn: 3-527-30999-3
- •Void volume
- •Void volume fraction
- •Xylan and Fiber Morphology
- •Initial bulk residual
- •4.2.5.1 Introduction
- •In (Ai) Model concept Reference
- •Initial value
- •Validation and Application of the Kinetic Model
- •Inititial
- •Viscosity
- •Influence on Bleachability
- •Impregnation
- •Impregnation
- •Impregnation
- •Impregnation
- •Impregnation
- •Impregnation
- •Impregnation
- •Impregnation
- •Impregnation
- •Impregnation
- •Introduction
- •International
- •Impregnation
- •Influence of Substituents on the Rate of Hydrolysis
- •140 116 Total so2
- •Xylonic
- •Viscosity Brightness
- •Xyl Man Glu Ara Furf hoAc XyLa
- •Initial NaOh charge [% of total charge]:
- •Introduction
- •Isbn: 3-527-30999-3
- •Introduction
- •Isbn: 3-527-30999-3
- •Introduction
- •Introduction
- •Isbn: 3-527-30999-3
- •In 1950, about 50% of the global paper production was produced. This proportion
- •4.0% Worldwide; 4.2% for the cepi countries; and 4.8% for Germany.
- •1150 1 Introduction
- •1 Introduction
- •1 Introduction
- •Virgin fibers
- •74.4 % Mixed grades
- •Indonesia
- •Virgin fibers
- •Inhomogeneous sample Homogeneous sample
- •Variance of sampling Variance of measurement
- •1.Quartile
- •3.Quartile
- •Insoluble
- •Insoluble
- •Insoluble
- •Integral
- •In Newtonion liquid
- •Velocity
- •Increasing dp
- •2Α filter
- •0 Reaction time
- •Increasing interaction of probe and cellulose
- •Increasing hydrodynamic size
- •Vessel cell of beech
- •Initial elastic range
- •Internal flow
- •Intact structure
- •Viscosity 457
- •Isbn: 3-527-30999-3
- •1292 Index
- •Visbatch® pulp 354
- •Index 1293
- •1294 Index
- •Impregnation 153
- •Viscosity–extinction 433
- •Index 1295
- •1296 Index
- •Index 1297
- •Inhibitor 789
- •1298 Index
- •Index 1299
- •Impregnation liquor 290–293
- •1300 Index
- •Industries
- •Index 1301
- •1302 Index
- •Index 1303
- •Xylose 463
- •1304 Index
- •Index 1305
- •1306 Index
- •Index 1307
- •1308 Index
- •In conventional kraft cooking 232
- •Visbatch® pulp 358
- •Index 1309
- •In prehydrolysis-kraft process 351
- •Visbatch® cook 349–350
- •1310 Index
- •Index 1311
- •1312 Index
- •Viscosity 456
- •Index 1313
- •Viscosity 459
- •Interactions 327
- •1314 Index
- •Index 1315
- •Viscosity 459
- •1316 Index
- •Index 1317
- •Xylose 461
- •Index 1319
- •Visbatch® pulp 355
- •Impregnation 151–158
- •1320 Index
- •Index 1321
- •1322 Index
- •Xylan water prehydrolysis 333
- •Index 1323
- •1324 Index
- •Viscosity 459
- •Index 1325
- •Xylose 940
- •1326 Index
- •Index 1327
- •In selected kinetics model 228–229
- •4OMeGlcA 940
- •1328 Index
- •Index 1329
- •Intermediate molecule 164–165
- •1330 Index
- •Viscosity 456
- •Index 1331
- •1332 Index
- •Impregnation liquor 290–293
- •Index 1333
- •1334 Index
- •Index 1335
- •1336 Index
- •Impregnation 153
- •Index 1337
- •1338 Index
- •Viscose process 7
- •Index 1339
- •Volumetric reject ratio 590
- •1340 Index
- •Index 1341
- •1342 Index
- •Index 1343
- •1344 Index
- •Index 1345
- •Initiator 788
- •Xylose 463
- •1346 Index
- •Index 1347
- •Vessel 385
- •Index 1349
- •1350 Index
- •Xylan 834
- •1352 Index
Initial value
[% ow]a
powers const
[k2]
pre-exp
[Ac]
corr.
Factor [fc]
EA
[OH– ]a [HS– ]b [kJ mol–1]
L1 9.0 0.00 0.06 0 0.1 1.5 50
L2 19.0 0.48 0.39 0 0.1 1.2 127
L3 1.5 0.20 0 0 4.7·10–3 1 127
C1 3.0 0.10 0 0 0.06 6 50
C2 4.1 1.00 0 0.22 0.054 2 144
C3 36.4 1.00 0 0.42 6.4·10–4 0.4 144
GM1 12.8 0.10 0 0 0.06 6 50
GM2 2.5 1.00 0 0.22 0.054 2 144
GM3 4.5 1.00 0 0.42 6.4·10–4 0.4 144
AX1 1.1 0.10 0 0 0.06 6 50
AX2 1.6 1.00 0 0.22 0.054 2 144
AX 3 4.5 1.00 0 0.42 6.4·10–4 0.4 144
a) over-dried wood
222 4 Chemical Pulping Processes
Validation and Application of the Kinetic Model
_ Prediction of delignification in the case where [OH– ]is changed.
After an initial impregnation stage, the course of delignification during a constant
composition cook with a L/W ratio of 41:1 at a very low alkali concentration of
[OH– ]= 0.1 M and [HS– ]= 0.28 M was determined [33]. After a cooking time of
approximately 220 min, the cooking liquor is replaced with a high-alkalinity liquor
of [OH– ]= 0.9 M and [HS– ]= 0.28 M. In a second run, the cook was run at a high
[OH– ]concentration of 0.9 M prior to a change to a very low alkali concentration
of [OH– ]= 0.1 M. Figure 4.33 shows that the presented model developed by
Andersson et al. is able to predict both scenarios very precisely [7].
0 100 200 300 400
0,1
1
10
[OH-] = 0.1 M [OH-] 0.1 to 0.9 M
[OH-] = 0.9 M [OH-] 0.9 to 0.1 M
lignin trend (dashed) for step decrease in [OH-] from 0.9 to 0.1 M
lignin trend (solid) for step increase in [OH-] from 0.1 to 0.9 M
Lignin on wood [%]
time [min]
Fig. 4.33 Model predictions of an autoclave cooking scheme.
The effect of changing [OH– ]from 0.1 to 0.9 M and 0.9 to
0.1 M in the residual phase in two cooks at constant
[HS– ]= 0.28 M and maximum cooking temperature of 170 °C.
Data from Lindgren and Lindstrom [33].
_ Prediction of the unbleached pulp quality of softwood kraft pulping
and the course of EA-concentration using a conventional
batch process.
The wood raw material consisted of a mixture of industrial pine (Pinus sylvestris)
and spruce (Picea abies) chips in a ratio of about 50:50. The chips were screened in
a slot screen, and the fraction passing a plate having 7-mm round holes and
retained on a plate with 3-mm holes were used. Bark and knots were removed by
hand-sorting. The mean (SD) thickness of the chips was 3.5 1.5 mm; the corresponding
mean length of the chips was 25.4 6.5 mm. The chips had a dry content
of 49.5% and were stored frozen. The cooking trials were carried out in a 10-L
4.2 Kraft Pulping Processes 223
digester with forced liquor circulation. The digester was connected to three pressurized
preheating tanks, which allowed precise simulation of a large-scale operation.
In addition, dosage volumes, temperatures and H-factors were monitored
and recorded on-line. The digester and pressurized tanks were heated by steam
injection and/or a heat exchanger in circulation and/or an oil-filled jacket. Dry
wood chips (1700 g) were charged, followed by a short steaming phase (7 min,
0.2 g water g–1 wood, final temperature 99 °C). Subsequently, the white liquor with
an average temperature of 90 °C was added to a total L/W ratio of 3.7–3.8:1. The
effective alkali charge (EA) of 19% was kept constant. The sulfidity varied slightly
in the range between 35 and 39% (see Tab. 4.24). The conventional batch cooking
procedure was characterized by a heating-up time of 90 min and a H-factor- controlled
cooking phase at constant temperature. The cooking phase was terminated
by cold displacement from bottom to top using a washing filtrate at 80 °C comprising
an EA concentration of 0.2 mol L–1, a sulfidity of 65% (equals to [HS– ]of
0.19 mol L–1) and a dry solid content (DS) of approximately 10%. The time–temperature
and time–pressure profiles are shown schematically in Fig. 4.34.
Finally, the pressure was released to fall to atmospheric by quenching with cold
water. Two series of H-factors in the range between 800 and 1400 were investigated
at two different cooking temperatures, 170 °C and 155 °C. Further details
concerning the experimental conditions and the results are summarized in
Tab. 4.24.
00:00 01:00 02:00 03:00 04:00
80
100
120
140
160
180
Pressure [bar]
temperature (top) temperature (bottom)
Temperature [. C]
time [hh:mm]
0
2
4
6
8
10
pressure
Fig. 4.34 Time–temperature (top/bottom) and time–pressure
profiles of a selected laboratory kraft cook using conventional
batch technology (cook labeled CB 414).
224 4 Chemical Pulping Processes
4.2 Kraft Pulping Processes 225
Tab. 4.24 Conditions and results of pine/spruce kraft cooking experiments.
Comparative evaluation of experimental and calculated values (according to [16]).
Label Maximum
temperature
[°C]
Time at max.
temperature
[min]
L/W
ratio