- •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
1069
II
Mechanical Pulping
Jurgen Blechschmidt, Sabine Heinemann, and Hans-Ulrich Suss
Handbook of Pulp. Edited by Herbert Sixta
Copyright © 2006 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim
Isbn: 3-527-30999-3
©2006 WILEY-VCHVerlag GmbH&Co .
Handbook of Pulp
Edited by Herbert Sixta
1
Introduction
Jurgen Blechschmidt and Sabine Heinemann
There are two technological principles to produce paper pulp from wood, namely
mechanical processes or chemical processes. Whereas in chemical pulping the
yields are only about 45–55%, mechanical pulping uses about 80–95% of the fiber
wood. Whilst this represents a source for the economic potential of mechanical
pulps, the higher yield results in certain unfavorable properties compared to
chemical pulp. Thus, fromthe sameportion ofwood, a double quantity of mechanical
pulp is produced compared to chemical pulp. The increasing demand for paper and
board has led to a permanent increase in mechanical pulp production (Fig. 1.1).
Fig. 1.1 Worldwide development of mechanical pulp production [1].
Among the total amount of paper pulp produced, mechanical pulp accounts for
about 20%.
Although mechanical pulping is a thermomechanical process, chemical processes
may also play a certain role. The mechanical defibration of wood is carried
out in two different ways (Fig. 1.2), namely as a grinding process or as a refining
process. The following definitions have been formulated for the products of those
processes:
1071
Handbook of Pulp. Edited by Herbert Sixta
Copyright © 2006 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim
Isbn: 3-527-30999-3
_ Mechanical pulp: this is manufactured by mechanical defibration
using a variety of mechanical procedures.
_ Stone groundwood: this is manufactured from round logs in a
grinder.
_ Refiner mechanical pulp: this is manufactured by the mechanical
defibration of wood chips in a disc refiner.
Fig. 1.2 An overview of the basic mechanical pulping procedures.
1072 1 Introduction
1073
2
A Short History of Mechanical Pulping
Jurgen Blechschmidt and Sabine Heinemann
Along with the development of mankind there has been an ever-increasing
demand for writing materials. It is said that papermaking was invented in China
in the year 105 AD and, after a long journey, the procedure arrived in Europe in
1144 (Spain) and finally in Germany in 1390 (Nuremberg). When Gutenberg
invented letterpress printing in 1445, to replace hand-written books with printed
books, the demand for paper increased immensely. During this evolution, the raw
materials used for paper have ranged from rags to hemp, and from flax and cotton
as well as worn-out hemp ropes.
Up until the end of the eighteenth century, paper was only made by hand, but
in 1799 Nicolas-Louis Robert developed the first papermaking machine in France
(Fig. 2.1).
Fig. 2.1 Papermaking machine, developed in 1799 by N.-L. Robert (1761–1826).
At about in the same time, in 1805, Bramah invented the cylinder machine in
England, and as a result of these inventions paper production was subsequently
increased during the following years. The problem was that this increased production
resulted in an increasing lack of raw materials.
In 1843, the Saxon weaver Friedrich Gottlob Keller (Fig. 2.2) successfully developed
the mechanical defibration of wood to produce groundwood. "Because this
Handbook of Pulp. Edited by Herbert Sixta
Copyright © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim