- •Isbn: 3-527-30999-3
- •Introduction
- •Isbn: 3-527-30999-3
- •1072 1 Introduction
- •Isbn: 3-527-30999-3
- •Inventor of stone groundwood. Right: the second version
- •1074 2 A Short History of Mechanical Pulping
- •In refining, the thinnings (diameter 7–10cm) can also be processed.
- •In mechanical pulping as it causes foam; the situation is especially
- •In mechanical pulping, those fibers that are responsible for strength properties
- •Isbn: 3-527-30999-3
- •In mechanical pulping, the wood should have a high moisture content, and the
- •In the paper and reduced paper quality. The higher the quality of the paper, the
- •1076 3 Raw Materials for Mechanical Pulp
- •1, Transversal resistance; 2, Longitudinal resistance; 3, Tanning limit.
- •3.2 Processing of Wood 1077
- •In the industrial situation in order to avoid problems of pollution and also
- •1078 3 Raw Materials for Mechanical Pulp
- •2, Grinder pit; 3, weir; 4, shower water pipe;
- •5, Wood magazine; 6, finger plate; 7, pulp stone
- •Isbn: 3-527-30999-3
- •4.1.2.1 Softening of the Fibers
- •1080 4 Mechanical Pulping Processes
- •235 °C, whereas according to Styan and Bramshall [4] the softening temperatures
- •Isolated lignin, the softening takes place at 80–90 °c, and additional water
- •4.1 Grinding Processes 1081
- •1082 4 Mechanical Pulping Processes
- •1, Cool wood; 2, strongly heated wood layer; 3, actual grinding
- •4.1.2.2 Defibration (Deliberation) of Single Fibers from the Fiber Compound
- •4 Mechanical Pulping Processes
- •Influence of Parameters on the Properties of Groundwood
- •In the mechanical defibration of wood by grinding, several process parameters
- •Improved by increasing both parameters – grinding pressure and pulp stone
- •In practice, the temperature of the pit pulp is used to control the grinding process,
- •In Fig. 4.8, while the grit material of the pulp stone estimates the microstructure
- •4 Mechanical Pulping Processes
- •4.1 Grinding Processes
- •Is of major importance for process control in grinding.
- •4 Mechanical Pulping Processes
- •4.1.4.2 Chain Grinders
- •Is fed continuously, as shown in Fig. 4.17.
- •Initial thickness of the
- •4 Mechanical Pulping Processes
- •Include:
- •Increases; from the vapor–pressure relationship, the boiling temperature is seen
- •4 Mechanical Pulping Processes
- •In the pgw proves, and to prevent the colder seal waters from bleeding onto the
- •4.1 Grinding Processes
- •In pressure grinding, the grinder shower water temperature and flow are
- •70 °C, a hot loop is no longer used, and the grinding process is
- •4 Mechanical Pulping Processes
- •Very briefly at a high temperature and then refined at high
- •4.2 Refiner Processes
- •4 Mechanical Pulping Processes
- •Intensity caused by plate design and rotational speed.
- •4.2 Refiner Processes
- •1. Reduction of the chips sizes to units of matches.
- •2. Reduction of those “matches” to fibers.
- •3. Fibrillation of the deliberated fibers and fiber bundles.
- •1970S as result of the improved tmp technology. Because the key subprocess in
- •4 Mechanical Pulping Processes
- •Impregnation Preheating Cooking Yield
- •30%. Because of their anatomic structure, hardwoods are able to absorb more
- •Is at least 2 mWh t–1 o.D. Pulp for strongly fibrillated tmp and ctmp pulps from
- •4 Mechanical Pulping Processes
- •4.2 Refiner Processes
- •1500 R.P.M. (50 Hz) or 1800 r.P.M. (60 Hz); designed pressure 1.4 mPa
- •1500 R.P.M. (50 Hz) or 1800 r.P.M. (60 Hz); designed pressure 1.4 mPa;
- •4.2 Refiner Processes
- •4 Mechanical Pulping Processes
- •In hardwoods makes them more favorable than softwoods for this purpose. A
- •4.2 Refiner Processes
- •Isbn: 3-527-30999-3
- •1114 5 Processing of Mechanical Pulp and Reject Handling: Screening and Cleaning
- •5.2Machines and Aggregates for Screening and Cleaning 1115
- •In refiner mechanical pulping, there is virtually no such coarse material in the
- •1116 5 Processing of Mechanical Pulp and Reject Handling: Screening and Cleaning
- •5.2Machines and Aggregates for Screening and Cleaning
- •5 Processing of Mechanical Pulp and Reject Handling: Screening and Cleaning
- •5 Processing of Mechanical Pulp and Reject Handling: Screening and Cleaning
- •5.3 Reject Treatment and Heat Recovery
- •55% Iso and 65% iso. The intensity of the bark removal, the wood species,
- •Isbn: 3-527-30999-3
- •1124 6 Bleaching of Mechanical Pulp
- •Initially, the zinc hydroxide is filtered off and reprocessed to zinc dust. Then,
- •2000 Kg of technical-grade product is common. Typically, a small amount of a chelant
- •6.1 Bleaching with Dithionite 1125
- •Vary, but are normally ca. 10 kg t–1 or 1% on fiber. As the number of available
- •1126 6 Bleaching of Mechanical Pulp
- •6.2 Bleaching with Hydrogen Peroxide
- •70 °C, 2 h, amount of NaOh adjusted.
- •6.2 Bleaching with Hydrogen Peroxide
- •Is shown in Fig. 6.5, where silicate addition leads to a higher brightness and a
- •Volume (bulk). For most paper-grade applications, fiber volume should be low in
- •Valid and stiff fibers with a high volume are an advantage; however, this requires
- •1130 6 Bleaching of Mechanical Pulp
- •6.2 Bleaching with Hydrogen Peroxide
- •Very high brightness can be achieved with two-stage peroxide bleaching, although
- •In a first step. This excess must be activated with an addition of caustic soda. The
- •Volume of liquid to be recycled depends on the dilution and dewatering conditions
- •6 Bleaching of Mechanical Pulp
- •6 Bleaching of Mechanical Pulp
- •Is an essential requirement for bleaching effectiveness. Modern twin-wire presses
- •Is discharged to the effluent treatment plant. After the main bleaching stage, the
- •6.3 Technology of Mechanical Pulp Bleaching
- •1136 6 Bleaching of Mechanical Pulp
- •Isbn: 3-527-30999-3
- •7.3 Shows the fractional composition according to the McNett principle versus
- •1138 7 Latency and Properties of Mechanical Pulp
- •7.2 Properties of Mechanical Pulp 1139
7.3 Shows the fractional composition according to the McNett principle versus
the yield of various pulps. The amount of long fibers in mechanical pulps (fraction
McNett R28) increases in the range SGW, RMP, TMP, CTMP more to the
debit of the middle fraction than of the fines fraction.
The bonding ability of mechanical pulp fractions can vary widely, as shown in
Fig. 7.4 [41]. The high bonding ability of middle fractions is clear.
1138 7 Latency and Properties of Mechanical Pulp
Fig. 7.3 Comparative fractional composition of various pulps
according to the McNett principle [40].
Fig. 7.4 Tensile index versus apparent density for the coarse
fiber fraction, middle fraction and fines fraction of different
mechanical pulps (according to Mohlin [41]).
Mechanical pulps typically form bulky sheets with high light scattering
(Fig. 7.5). Thus, it is possible to produce paper with acceptable stiffness and opacity
at a considerably lower basis weight by using a mechanical pulp than a chemical
pulp. When compared at the same freeness levels, TMP normally has the
highest bulk and CTMP the lowest bulk of mechanical pulps. With regard to the
mechanical pulps in Fig. 7.5, groundwood pulps usually exhibit the best optical
properties (Fig. 7.5, below), whereas TMP and CTMP exhibit the best strength
properties (Fig. 7.5, left and right). Because of their good strength properties,
these mechanical pulps require less reinforcement pulps when manufacturing,
7.2 Properties of Mechanical Pulp 1139
Fig. 7.5 Tensile index, tear index, and light-scattering
coefficient of different pulps depending on freeness [42].
for example, LWC paper. This compensates their lower light-scattering power and
makes their use economically viable.
Hoglund et al. [43] have compared the same types of mechanical pulps with
chemical pulps according to their strength properties. The mechanical pulps were
from spruce wood (SGW, RMP, TMP, and CTMP), and the chemical pulps from
pine were either unbleached (USB) or semi-bleached (SBK). The possible property
fields for these pulps are illustrated in Figs. 7.6–7.8.
Strength properties increased in the range SGW, RMP, TMP, CTMP, USB, and
SBK. The tear resistance of CTMP pulps was close to that of unbleached chemical
pulp USB (Fig. 7.6). The tensile index of CTMP covered large parts of the semibleached
chemical pulp SBK and unbleached chemical pulp USB, but at lower
apparent densities (Fig. 7.7). When considering the light-scattering coefficient,
1140 7 Latency and Properties of Mechanical Pulp
7.2 Properties of Mechanical Pulp
Fig. 7.6 Tear resistance versus tensile index for various
mechanical pulps compared with chemical pulps.
Fig. 7.7 Tensile index versus apparent density for various
mechanical pulps compared with chemical pulps.
SGW had the highest values, followed by RMP and TMP. The light-scattering
coefficient of CTMP was in the same range as TMP, but at higher levels of tensile
index. The chemical pulps had the lowest light-scattering coefficient, and could be
distinguished by type (USB or SBK) (Fig. 7.8).
1141
7 Latency and Properties of Mechanical Pulp
Fig. 7.8 Light-scattering coefficient versus tensile index for
various mechanical pulps compared with chemical pulps.
Selected properties from different mechanical pulps, made from Norway spruce
and compared at freeness level 40 mL, are listed in Tab. 7.1. General quality
requirements of mechanical pulp for use in LWC and SCA grades are detailed in
Tab. 7.2.
Tab. 7.1 Properties of mechanical pulps for printing paper
grades (Norway spruce, CSF 40mL).
Parameter Unit Groundwood Pressure
groundwood
TMP
Minishives % 0.1 0.1 <0.1
Coarse fibers (R14) % 1 3 10
Long fibers (P14/R28) % 11 22 30
Fines (P200) % 38 33 30
Fiber length mm 0.65 0.85 1.5
Apparent density kg m–3 520 510 500
Gurley s 150 200 250
Tensile index Nm g–1 35 43 52
Tear index mNm2 g–1 3.2 4.2 7.2
Scott Bond J m–2 280 320 250
Light scattering coefficient m2 kg–1 75 72 60
Brightness % 65 64 62
1142
References
Tab. 7.2 General quality requirements of mechanical pulp for use in LWC and SCA grades.
Pulp grade SGW PGW TMP TMP
Paper grade Unit SC/LWC SC/LWC SC LWC
Freeness mL 30–40 30–40 30–40 40–50
Shives content % <0.05 <0.05 <0.05 <0.05
Coarse fibers (R14) % <1.0 <1.0 <7.0 <3.0
Long fibers (P14/R28) % 10–15 14–20 28–33 22–27
Fines (P200) % >36 >32 >28 >28
Apparent density kg m–3 450–500 440–500 450–520 450–500
Tensile index Nm g–1 >40 >45 >50 >50
Tear index mNm2 g–1 >3.5 >4.5 >7.0 >6.5
Light-scattering coefficient m2 kg–1 >70 >68 >58 >58
1143
References
1 vdp Verband Deutscher Papierfabriken
e.V.
2 Sittauer, H.L., Friedrich Gottlob Keller,
Leipzig, 1982.
3 Goring, D.A.J., Thermal softening of
lignin, hemicellulose and cellulose.
Pulp Paper Mag. Can., 1963; 64(12):
T517–T527.
4 Styan, G.E., Bramshall, A.E., Ligninsolvation
improves mechanical pulp
processing. Pulp Paper Can., 1979;
80(1): 74–77.
5 Luhde, F., Temperature within the
grinding zone. Part 1. Pulp Paper Mag.
Can., 1959; 60(9): T269–T271.
6 Suttinger, R., The Technology of the Wood
Grinding Process. Heidenheim: Voith
Forschung und Konstruktion, Nr. 26,
1979.
7 Steenberg, M.B., Nordstrand, A., Production
and dissipation of frictional
heat in the mechanical wood grinding
process. Tappi J., 1962; 45(4): 333–336.
8 May, W.D., Atack, D., A laboratory study
of a new mechanical pulping process.
Pulp Paper Mag. Can., 1965; 66(8):
T422–T435.
9 Atack, D., Pye, I.T., The measurement
of grinding zone temperature. Pulp
Paper Mag. Can., 1964; 65(9): T363–
T376.
10 Atack, D., Mechanics of Wood Grinding
Trend. The Activities of the Pulp and
Paper Research Institute of Canada,
Report No. 19, 1971: 6–11.
11 Powell, F.G., Luhde, F., Logan, K.C.,
Super groundwood by grinding. Pulp
Paper Mag. Can., 1965; 66(8): T399–
T406.
12 Aario, M., Haikkala, P., Lindahl, A.,
Pressure grinding – a new process for
mechanical pulping. Wochenbl. f. Papierfabr.,
1978; 106(19): 723–730.
13 Pietarila, V., Mitchell, G., Haikkala, P.,
Tuominen, R., PGWat high temperatures
and pressures. International
Mechanical Pulping Conference,
Vancouver, Canada, Preprints, CPPA,
Montreal, 1987: 19.
14 Pasanen, K., Peltonen, E., Haikkala, P.,
Liimatainen, H., Experiences using
super-pressurized groundwood at a
Finnish supercalender paper mill.
Tappi J., 1991; 74(12): 63.
1144 7 Latency and Properties of Mechanical Pulp
15 Murtola, C., Peltonen, E., Industrial
pressure grinding at low shower water
temperatures in a paper mill. PTSTUD-
Symposium Technology of Chemical
and Mechanical Pulp 1995, PTS Verlag
Munchen, 1995.
16 Valmet, Groundwood Systems, Pressure
Groundwood, Tampere, 1996.
17 Tuovinen, O., Liimatainen, H., Fibers,
fibrils and fractions – an analysis of
various mechanical pulps. Pap. Puu,
1994; 76(8): 508–515.
18 Asunmaa, P., The selection, process
flowcharts, optimization and results
obtained from the new PGW-S mill
at the Kaukas Oy Voikkaa paper mill in
Finland. Annual Meeting CPPA Montreal,
Proceedings, 1993: B71.
19 Giertz, H.W., Different qualities of
groundwood, refiner mechanical pulp
and thermomechanical pulp, Wochenbl.
f. Papierfabr., 1976; 104(19): 736–737.
20 Atack, D., Heitner, C., State of the art of
chemimechanical wood pulping processes
for printing paper. Das Papier,
1982; 36(10A): V114–V127.
21 Beatson, R., Heitner, C., Atack, D.,
Factors affecting the sulphonation
of spruce. J. Pulp Paper Sci., 1984: 10(1):
J12.
22 Suttinger, K., Analysis of energy
consumption in mechanical pulping.
Wochenbl. f. Papierfabr., 1979; 107(2):
40–43.
23 Strauss, J., Screening by classifying – a
more and more important process in
stock preparation. Zellstoff und Papier,
1981; 30(4): 170–176.
24 Ammala, A., Fractionation of thermomechanical
pulp in pressure screening
– an experimental study on the classification
of fibres with slotted screen
plates. Acta Universitatis Oululensis,
Technica, C156, 2001 (Thesis).
25 Papermaking Science and Technology.
Book 5, Mechanical Pulping. Fapet Oy
Helsinki 1999: 270.
26 Yu, C.J., DeFoe, R.J., Fundamental
study of screening hydraulics. Part 1:
Flow patterns at the fed-side surface of
screen baskets. Mechanism of fiber mat
formation and remixing. Tappi J., 1994;
77(9): 767–782.
27 Niinimaki, J., On the fundamentals of
pressure screening – an experimental
study of conditions and phenomena in
the screen basket. Acta Universitatis
Oululensis, Technica, C124, 1998 (Thesis).
28 Bliss, T., Screening in the Stock Preparation
System. Stock Preparation Short
Course, Atlanta, GA, USA, Proceedings,
1990: 59–75.
29 Kleinhappel, S., Lipponen, J., Jussila, T.,
Groundwood pulp quality improvements
with economical benefit by
improved screening efficiency. International
Mechanical Pulping Conference,
Ottawa, Canada, Proceedings, 1995:
267–270.
30 Schmidt, G., Schempp, W., Krause, T.,
Wasserlosliche Holzschliffbestandteile,
Analyse und Auswirkung bei der Papierherstellung.
Das Papier, 1990; 44(10A):
V49–V55.
31 Roick, T., Schmidt, G., Schempp, W.,
Storstoffe in Holzstofffiltraten: Identifizierung,
Veranderungen im Verlauf der
Bleiche, analytische Beurteilung der
Wirkung von Bekampfungsmitteln.
Wochenbl. f. Papierfabr., 1994; 122(12):
506–509.
32 Roick, T., Schempp, W., Krause, T.,
Holzstoff-Feinstoffe: einige Ursachen
ihrer schlechten Bleichbarkeit. Das
Papier, 1991; 45(10A): V23–V26.
33 Melzer, J., Stabilitat von Natriumdithionit
in wassrigen Losungen. Wochenbl.
f. Papierfabr., 1990; 118(22): 925–931.
34 Ellis, M.E., Hydrosulfite (dithionite)
bleaching. In: Pulp Bleaching, Principles
and Practice. Tappi Press, Atlanta, 1996:
500–501.
35 Fischer, K., Vergilbung von Hochausbeutezellstoff.
Das Papier, 1990;
44(10A): V11.
36 Suss, H.U., Del Grosso, M., Schmidt,
K., Hopf, B., Options for bleaching mechanical
pulp with a lower COD load.
Appita Annual Conference, Proceedings,
2001.
37 Htun, M., Engstrand, P., Salmen, L.,
The implication of lignin softening on
latency removal of mechanical and chemimechanical
pulps. J. Pulp Paper Sci.,
1988; 14(3): 109–112.
References 1145
38 Karojarvi, R., Nerg, H., Latency in pressure
groundwood. International Mechanical
Pulping Conference, Vancouver,
Canada, Proceedings, 1987: 25–28.
39 Blechschmidt, J., About latency behavior
of mechanical pulps. Zellstoff und
Papier, 1976; 25(10): 293–298.
40 Sundholm, J., What is mechanical pulping?
In: Papermaking Science and Technology.
Book 5, Mechanical Pulping. Fapet
Oy Helsinki, 1999: 17–21.
41 Mohlin, U.-B., Properties of TMP fractions
and their importance for the quality
of printing papers. Part 1: Large variations
in properties within fractions are
observed. Svensk. Papperstidn., 1980; 16:
461–466.
42 Heikkurinen, A., Leskela, L., The character
and properties of mechanical
pulps. In: Papermaking Science and
Technology. Book 5, Mechanical Pulping.
Fapet Oy Helsinki 1999: 395–413.
43 Hoglund, H., Modified thermomechanical
pulp in newsprint furnishes. International
Mechanical Pulping Conference,
Helsinki, Proceedings Vol. III,
1977: 17B.