- •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
4.2 Refiner Processes
Somewhat later, Sunds Defibrator (today Metso) developed the RGP CD (= conical
disc) system. Conical-disc refiners have a single-disc refining gap followed by
a conical refining gap inside one refiner housing (Fig. 4.30).
The latest developments on the market are cylindrical refiners; the Papillon™
(Andritz) (Fig. 4.31) incorporates the advantages of hollaender beating with the
continuous refiner principle. Also available are multiconical refiners; an example
is the TriConic® (Pilao) (Fig. 4.32), which is a medium-angle, double-flow conical
refiner with a low refining intensity and low no-load.
Fig. 4.27 The single-disc refiner (Metso RGP 268).
Fig. 4.28 The double-disc refiner (Metso RGP 68DD).
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4 Mechanical Pulping Processes
Fig. 4.29 The twin-refiner TwinFlo™ (Andritz).
Fig. 4.30 The conical-disc refiner (Metso RPG 82 CD).
Fig. 4.31 The cylindrical refiner Papillon™ (Andritz), with an
open housing for plate change.
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4.2 Refiner Processes 1107
Fig. 4.32 The multiconical refiner TriConic® (Pilao). Left: Refiner
with an open housing. Right: TriConic®; upper diagram,
principle of operation; lower diagram, plate design.
Fig. 4.33 Double disc refiner concept.
1 and 2, Rotating discs; 3, active parts
of the discs (refiner plates); 4, entrance
area into the refining zone; 5, outlet from
the refining zone; 6, chip feed.
4 Mechanical Pulping Processes
The working principle of mechanical pulp refiners is explained by means of the
double disc concept in Fig. 4.33. The pulp is treated between two refiner discs,
enters in the center at the shaft, and passes the discs from center to side. Refining
plates constructed from high-strength steel and with different profiles are
mounted on the refiner discs, which are pressed together hydraulically. The refining
gap has an important influence on mechanical pulp quality.
An overview of the design of selected refiner types is provided in Tab. 4.3.
Tab. 4.3 Characteristics of selected large-size refiner types.
Refiner type Characteristics
RGP 268 SD Single-disc refiner (Metso)
Motor size 15 MW, disc diameter 1728 mm (68 in), rotational speed
1500 r.p.m.
RGP 68 DD Double-disc refiner (Metso)
Motor size 30 MW, disc diameter 1730 mm (68 in), rotational speed
1500 R.P.M. (50 Hz) or 1800 r.P.M. (60 Hz); designed pressure 1.4 mPa
RGP 82 CD Conical-disc refiner (Metso)
Motor size 30 MW, disc diameter 2080 mm (82 in), rotational speed
1500 R.P.M. (50 Hz) or 1800 r.P.M. (60 Hz); designed pressure 1.4 mPa;
refining surface 3.2 m2
Twin 66 Twin refiner (Andritz)
Motor size 24 MW, nominal disc diameter at 1800 r.p.m.: 1680 mm (66 in)
Papillon CC-600 Cylindrical refiner with center feed (Andritz)
Motor size 2000 kW, diameter of refining area 600 mm, idle load 160 kW
TriConic Type
RTC 6000
Multiconical refiner (Pilao)
Motor size 880–1470 kW, throughput 200–1800 t day–1
Refiner plates are the “heart” of the refining process. The type of refiner plate
design chosen is specified for a certain pulp quality and depends on the requirements
of the paper machine. These depend on the type of paper produced and on
the control strategy of the paper machine. Varying refiner positions (1st stage, 2nd
stage, reject) also require different refiner plate designs. Refiner plate designs are
always under further development, and some selected examples of actual plate
design are illustrated in Fig. 4.34. Bi-directional refiner plates are standard in
TMP production, and perform independently of the direction of rotation of the
refiner. Turbine™ segments are the latest development by Metso Paper for the
conical disc refiner RGP 82 CD (see Fig. 4.30); this system operates at low pressure
during chip defibration stage, and this results in improved optical properties
of the refined pulp.
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