- •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
- •Introduction
- •Xylosec
- •Xylan residues
- •Viscosity
- •Introduction
- •Viscosity
- •Viscosity
- •Introduction
- •Initiator Promoter Inhibitor
- •Viscosity
- •Viscosity
- •Viscosity
- •Introduction
- •Viscosity
- •Introduction
- •Intra-Stage Circulation and Circulation between Stages
- •Implications of Liquor Circulation
- •Vid Chalmers Tekniska
- •Introduction
- •It is a well-known fact that the mechanical properties of the viscose fibers
- •Increase in the low molecular-weight fraction [2]. The short-chain molecules represent
- •Isbn: 3-527-30999-3
- •In the cooking process or, alternatively, white liquor can be used for the cold
- •Is defined as the precipitate formed upon acidification of an aqueous alkaline solution
- •934 8 Pulp Purification
- •8.2 Reactions between Pulp Constituents and Aqueous Sodium Hydroxide Solution 935
- •Is essentially governed by chemical degradation reactions involving endwise depolymerization
- •80 °C [12]. Caustic treatment: 5%consistency ,
- •30 Min reaction time, NaOh concentrations:
- •8.2 Reactions between Pulp Constituents and Aqueous Sodium Hydroxide Solution
- •80 °C is mainly governed by chemical degradation reactions (e.G. Peeling reaction).
- •Investigated using solid-state cp-mas 13c-nmr spectroscopy (Fig. 8.4).
- •Indicates cleavage of the intramolecular hydrogen bond between o-3-h and o-5′,
- •8 Pulp Purification
- •Interaction between alkali and cellulose, a separate retention tower is not really
- •In the following section.
- •3% In the untreated pulp must be ensured in order to avoid a change in the supramolecular
- •8.3 Cold Caustic Extraction
- •Xylan content [%]
- •8 Pulp Purification
- •Is calculated as effective alkali (ea). Assuming total ea losses (including ea consumption
- •Xylan content [%]
- •8.3 Cold Caustic Extraction
- •120 °C (occasionally 140 °c). As mentioned previously, hce is carried out solely
- •Involved in alkaline cooks (kraft, soda), at less severe conditions and thus avoiding
- •8.4Hot Caustic Extraction 953
- •954 8 Pulp Purification
- •120 Kg NaOh odt–1, 90–240 min, 8.4 bar (abs)
- •8.4Hot Caustic Extraction 955
- •956 8 Pulp Purification
- •Into the purification reaction, either in the same (eo) or in a separate stage
- •960 8 Pulp Purification
- •8.4.1.5 Composition of Hot Caustic Extract
- •8.4Hot Caustic Extraction 961
- •Isbn: 3-527-30999-3
- •Xyloisosaccharinic acid
- •Inorganicsa
- •Inorganic compounds
- •Value (nhv), which better reflects the actual energy release, accounts for the fact
- •968 9 Recovery
- •It should be noted that the recycling of bleach (e.G., oxygen delignification) and
- •9.1 Characterization of Black Liquors 969
- •9.1.2.1 Viscosity
- •9.1.2.3 Surface Tension
- •9.1.2.5 Heat Capacity [8,11]
- •9.2 Chemical Recovery Processes
- •Is described by the empirical equation:
- •9 Recovery
- •Vent gases from all areas of the pulp mill. From an environmental perspective,
- •9.2.2.1 Introduction
- •In the sump at the bottom of the evaporator. The generated vapor escapes
- •Incineration, whereas sulphite ncg can be re-used for cooking acid preparation.
- •9 Recovery
- •Values related to high dry solids concentrations. The heat transfer rate is pro-
- •9.2 Chemical Recovery Processes
- •9.2.2.3 Multiple-Effect Evaporation
- •7% Over effects 4 and 5, but more than 30% over effect 1 alone.
- •9.2 Chemical Recovery Processes
- •Increasing the dry solids concentration brings a number of considerable advantages
- •9.2.2.4 Vapor Recompression
- •Is driven by electrical power. In general, vapor coming from the liquor
- •Vapor of more elevated temperature, thus considerably improving their performance.
- •9 Recovery
- •Is typically around 6 °c. The resulting driving temperature difference
- •Is low, and hence vapor recompression plants require comparatively large heating
- •Vapor recompression systems need steam from another source for start-up.
- •9 Recovery
- •Its temperature is continuously falling to about 180 °c. After the superheaters,
- •In the furnace walls, and only 10–20% in the boiler bank. As water turns into
- •9.2.3.1.2 Material Balance
- •Is required before the boiler ash is mixed. In addition, any chemical make-up
- •In this simplified model, all the potassium from the black liquor (18 kg t–1
- •Values for the chemicals in Eq. (11) can be inserted on a molar basis, equivalent
- •9.2 Chemical Recovery Processes
- •Input/output
- •9 Recovery
- •9.2.3.1.3 Energy Balance
- •In the black liquor, from water formed out of hydrogen in organic material, and
- •9.2 Chemical Recovery Processes
- •9.2.3.2 Causticizing and Lime Reburning
- •9.2.3.2.1 Overview
- •9.2.3.2.2 Chemistry
- •986 9 Recovery
- •Insoluble metal salts are kept low. Several types of filters with and without lime
- •Is, however, not considered a loss because some lime mud must be
- •988 9 Recovery
- •In slakers and causticizers needs special attention in order to avoid particle disintegration,
- •9.2 Chemical Recovery Processes 989
- •Ing disks into the center shaft, and flows to the filtrate separator. There, the white
- •9.2.3.2.4 Lime Cycle Processes and Equipment
- •It is either dried with flue gas in a separate, pneumatic lime mud dryer or is fed
- •990 9 Recovery
- •Its temperature falls gradually. Only about one-half of the chemical energy in the
- •9.2.3.3.2 Black Liquor Gasification
- •Inorganics leave the reactor as solids, and into high-temperature techniques,
- •In the bed. Green liquor is produced from surplus bed solids. The product gas
- •992 9 Recovery
- •Incremental capacity for handling black liquor solids. The encountered difficulties
- •10% Of today’s largest recovery boilers. When the process and material issues are
- •9.2 Chemical Recovery Processes 993
- •9.2.3.3.3 In-Situ Causticization
- •Is still in the conceptual phase, and builds on the formation of sodium titanates
- •9.2.3.3.4 Vision Bio-Refinery
- •Into primary and secondary recovery steps. This definition relates to the recovery
- •994 9 Recovery
- •Is largely different between sulfite cooking bases. While magnesium and
- •Introduction
- •In alkaline pulping the operation of the lime kiln represents an emission source.
- •Isbn: 3-527-30999-3
- •Is by the sophisticated management of these sources. This comprises their collection,
- •Ions, potassium, or transition metals) in the process requires the introduction
- •Industry”. Similarly guidelines for a potential kraft pulp mill in Tasmania [3]
- •Initially, the bleaching of chemical pulp was limited to treatment with hypochlorite
- •In a hollander, and effluent from the bleach plant was discharged without
- •In a heh treatment and permitted higher brightness at about 80% iso (using
- •Increasing pulp production resulted in increasing effluent volumes and loads.
- •10.2 A Glimpse of the Historical Development 999
- •It became obvious that the bleaching process was extremely difficult to operate in
- •In a c stage was detected as aox in the effluent (50 kg Cl2 t–1 pulp generated
- •1% Of the active chlorine is converted into halogenated compounds (50 kg active
- •In chlorination effluent [12] led to the relatively rapid development of alternative
- •1000 10 Environmental Aspects of Pulp Production
- •10.2 A Glimpse of the Historical Development
- •In 1990, only about 5% of the world’s bleached pulp was produced using ecf
- •64 Million tons of pulp [14]. The level of pulp still bleached with chlorine
- •10 000 Tons. These are typically old-fashioned, non-wood mills pending an
- •In developed countries, kraft pulp mills began to use biodegradation plants for
- •10 Environmental Aspects of Pulp Production
- •Indeed, all processes are undergoing continual development and further improvement.
- •Vary slightly different depending upon the type of combustion unit and the fuel
- •10.3Emissions to the Atmosphere
- •Volatile organic
- •In 2004 for a potential pulp mill in Tasmania using “accepted
- •10 Environmental Aspects of Pulp Production
- •Is woodyard effluent (rain water), which must be collected and treated biologically
- •10.4 Emissions to the Aquatic Environment
- •Is converted into carbon dioxide, while the other half is converted into biomass
- •Into alcohols and aldehydes; (c) conversion of these intermediates into acetic acid and
- •10 Environmental Aspects of Pulp Production
- •In North America, effluent color is a parameter which must be monitored.
- •It is not contaminated with other trace elements such as mercury, lead, or cadmium.
- •10.6 Outlook
- •Increase pollution by causing a higher demand for a chemical to achieve identical
- •In addition negatively affect fiber strength, which in turn triggers a higher
- •Introduction
- •2002, Paper-grade pulp accounts for almost 98% of the total wood pulp production
- •Important pulping method until the 1930s) continuously loses ground and finds
- •Importance in newsprint has been declining in recent years with the increasing
- •Isbn: 3-527-30999-3
- •Virtually all paper and paperboard grades in order to improve strength properties.
- •In fact, the word kraft is the Swedish and German word for strength. Unbleached
- •Importance is in the printing and writing grades. In these grades, softwood
- •In this chapter, the main emphasis is placed on a comprehensive discussion of
- •1010 11 Pulp Properties and Applications
- •Is particularly sensitive to alkaline cleavage. The decrease in uronic acid content
- •Xylan in the surface layers of kraft pulps as compared to sulfite pulps has been
- •80% Cellulose content the fiber strength greatly diminishes [14]. This may be due
- •Viscoelastic and capable of absorbing more energy under mechanical stress. The
- •11.2 Paper-Grade Pulp 1011
- •Various pulping treatments using black spruce with low fibril
- •In the viscoelastic regions. Fibers of high modulus and elasticity tend to peel their
- •1012 11 Pulp Properties and Applications
- •11.2 Paper-Grade Pulp
- •Viscosity mL g–1 793 635 833 802 1020 868 1123
- •Xylose % od pulp 7.3 6.9 18.4 25.5 4.1 2.7 12.2
- •11 Pulp Properties and Applications
- •Inorganic Compounds
- •11.2 Paper-Grade Pulp
- •Insight into many aspects of pulp origin and properties, including the type of
- •Indicate oxidative damage of carbohydrates).
- •In general, the r-values of paper pulps are typically at higher levels as predicted
- •Is true for sulfite pulps. Even though the r-values of sulfite pulps are generally
- •Is rather unstable in acid sulfite pulping, and this results in a low (hemicellulose)
- •11 Pulp Properties and Applications
- •Ing process, for example the kraft process, the cellulose:hemicellulose ratio is
- •Increases by up to 100%. In contrast to fiber strength, the sheet strength is highly
- •Identified as the major influencing parameter of sheet strength properties. It has
- •In contrast to dissolving pulp specification, the standard characterization of
- •Is observed for beech kraft pulp, which seems to correlate with the enhanced
- •11.2 Paper-Grade Pulp
- •11 Pulp Properties and Applications
- •Is significantly higher for the sulfite as compared to the kraft pulps, and indicates
- •11.2 Paper-Grade Pulp
- •Xylan [24].
- •11 Pulp Properties and Applications
- •11.2 Paper-Grade Pulp
- •11 Pulp Properties and Applications
- •Introduction
- •Various cellulose-derived products such as regenerated fibers or films (e.G.,
- •Viscose, Lyocell), cellulose esters (acetates, propionates, butyrates, nitrates) and
- •In pulping and bleaching operations are required in order to obtain a highquality
- •Important pioneer of cellulose chemistry and technology, by the statement that
- •11.3 Dissolving Grade Pulp
- •Involves the extensive characterization of the cellulose structure at three different
- •Is an important characteristic of dissolving pulps. Finally, the qualitative and
- •Inorganic compounds
- •11 Pulp Properties and Applications
- •11.3.2.1 Pulp Origin, Pulp Consumers
- •Include the recently evaluated Formacell procedure [7], as well as the prehydrolysis-
- •11.3 Dissolving Grade Pulp
- •Viscose
- •11 Pulp Properties and Applications
- •11.3.2.2 Chemical Properties
- •11.3.2.2.1 Chemical Composition
- •In the polymer. The available purification processes – particularly the hot and cold
- •11.3 Dissolving Grade Pulp
- •In the steeping lye inhibits cellulose degradation during ageing due to the
- •Is governed by a low content of noncellulosic impurities, particularly pentosans,
- •Increase in the xylan content in the respective viscose fibers clearly support the
- •11.3 Dissolving Grade Pulp
- •Instability. Diacetate color is measured by determining the yellowness coefficient
- •Xylan content [%]
- •11 Pulp Properties and Applications
- •Xylan content [%]
- •11.3 Dissolving Grade Pulp
- •11.3 Dissolving Grade Pulp
- •Is, however, not the only factor determining the optical properties of cellulosic
- •In the case of alkaline derivatization procedures (e.G., viscose, ethers). In industrial
- •11.3 Dissolving Grade Pulp
- •Viscose
- •Viscose
- •In order to bring out the effect of mwd on the strength properties of viscose
- •Imitating the regular production of rayon fibers. To obtain a representative view
- •11 Pulp Properties and Applications
- •Viscose Ether (hv) Viscose Acetate Acetate
- •Xylan % 3.6 3.1 1.5 0.9 0.2
- •1.3 Dtex regular viscose fibers in the conditioned
- •11.3 Dissolving Grade Pulp
- •Is more pronounced for sulfite than for phk pulps. Surprisingly, a clear correlation
- •Viscose fibers in the conditioned state related to the carbonyl
- •1038 11 Pulp Properties and Applications
- •In a comprehensive study, the effect of placing ozonation before (z-p) and after
- •Increased from 22.9 to 38.4 lmol g–1 in the case of a pz-sequence, whereas
- •22.3 To 24.2 lmol g–1. The courses of viscosity and carboxyl group contents were
- •Viscosity measurement additionally induces depolymerization due to strong
- •11 Pulp Properties and Applications
- •Increasing ozone charges. For more detailed
- •11.3 Dissolving Grade Pulp
- •Is more selective when ozonation represents the final stage according to an
- •11.3.2.3 Supramolecular Structure
- •1042 11 Pulp Properties and Applications
- •Is further altered by subsequent bleaching and purification processes. This
- •Involved in intra- and intermolecular hydrogen bonds. The softened state favors
- •11.3 Dissolving Grade Pulp
- •Interestingly, the resistance to mercerization, which refers to the concentration of
- •11 Pulp Properties and Applications
- •Illustrate that the difference in lye concentration between the two types of dissolving
- •Intensity (see Fig. 11.18: hw-phk high p-factor) clearly changes the supramolecular
- •11.3 Dissolving Grade Pulp
- •Viscose filterability, thus indicating an improved reactivity.
- •11 Pulp Properties and Applications
- •Impairs the accessibility of the acetylation agent. When subjecting a low-grade dissolving
- •Identification of the cell wall layers is possible by the preferred orientation of
- •Viscose pulp (low p-factor) (Fig. 11.21b, top). Apparently, the type of pulp – as well
- •11 Pulp Properties and Applications
- •150 °C for 2 h, more than 70% of a xylan, which was added to the cooking liquor
- •20% In the case of alkali concentrations up to 50 g l–1 [67]. Xylan redeposition has
- •11.3 Dissolving Grade Pulp
- •Xylan added linters cooked without xylan linters cooked with xylan
- •Viscosity
- •In the surface layer than in the inner fiber wall. This is in agreement with
- •11 Pulp Properties and Applications
- •Xylan content in peelings [wt%]
- •Xylan content located in the outermost layers of the beech phk fibers suggests
- •11.3.2.5 Fiber Morphology
- •11 Pulp Properties and Applications
- •50 And 90%. Moreover, bleachability of the screened pulps from which the wood
- •11.3.2.6 Pore Structure, Accessibility
- •11.3 Dissolving Grade Pulp
- •Volume (Vp), wrv and specific pore surface (Op) were seen between acid sulfite
- •11 Pulp Properties and Applications
- •Irreversible loss of fiber swelling occurs; indeed, Maloney and Paulapuro reported
- •In microcrystalline areas as the main reason for hornification [85]. The effect of
- •105 °C, thermal degradation proceeds in parallel with hornification, as shown in
- •Increased, particularly at temperatures above 105 °c. The increase in carbonyl
- •In pore volume is clearly illustrated in Fig. 11.28.
- •11.3 Dissolving Grade Pulp
- •Viscosity
- •11 Pulp Properties and Applications
- •Increase in the yellowness coefficient, haze, and the amount of undissolved particles.
- •11.3.2.7 Degradation of Dissolving Pulps
- •In mwd. A comprehensive description of all relevant cellulose degradation processes
- •Is reviewed in Ref. [4]. The different modes of cellulose degradation comprise
- •11.3 Dissolving Grade Pulp
- •50 °C, is illustrated graphically in Fig. 11.29.
- •11 Pulp Properties and Applications
- •In the crystalline regions.
- •11.3 Dissolving Grade Pulp
- •Important dissolving pulps, derived from hardwood, softwood and cotton linters
- •11.3 Dissolving Grade Pulp 1061
- •Xylan rel% ax/ec-pad 2.5 3.5 1.3 1.0 3.2 0.4
- •Viscosity mL g–1 scan-cm 15:99 500 450 820 730 1500 2000
- •1062 11 Pulp Properties and Applications
- •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
- •75 Mm thickness, is much thinner than that of a concrete pulp stone, much
- •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
- •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
960 8 Pulp Purification
0 10 20 30 40 50
0.0
0.2
0.4
0.6
0.8
DCM extractives, %
Energy, kWh/odt
Fig. 8.24 Course of dichloromethane (DCM) extractives in
fully bleached softwood dissolving pulps as a function of
energy input in a Frotapulper [35,36].
8.4.1.5 Composition of Hot Caustic Extract
Hot caustic extract contains a large amount of low molecular-weight hydroxycarbonic
acids,with glucoisosaccharinate as the main component, derived frompurification of
softwood sulfite pulp [37]. A typical extract composition is shown in Tab. 8.4.
Tab. 8.4 Typical composition of hot caustic extract [37].
Compounds % of solids as sodium Salts
Chloridea 3.3
Formate 17.0
Acetate 3.4
Glucoisosaccharinate 27.0
Other Hydroxy acids 38.0
“Complex” acids 11.3
a. C stage preceding HCE treatment.
The combined saccharinic acids and other hydroxy acids constitute about 65%
of the hot caustic extract. These compounds are readily biodegradable in a wastewater
treatment plant. However, the COD load is significant and calculates to
about 180 kg odt–1, assuming an average yield loss of about 15% on bleached pulp
across the stage (150 kg carbohydrates/odt . 1.185 kg COD/kg carbohydrates). As
8.4Hot Caustic Extraction 961
a consequence, several sulfite dissolving pulp mills have recently installed evaporation
plants and recovery furnaces (soda boiler) to concentrate and burn the filtrates
from hot caustic extraction. To date, no products are prepared from the thick
liquor, mainly because of the high costs to isolate, purify, and modify the saccharinic
acids. Reintjes and Cooper have proposed a scheme to utilize these compounds
where the acids are lactonized and converted to amides; they may then be
further processed to anionic and nonionic surfactants by reaction with chlorosulfonic
acid or ethylene oxide [37].
8.4.2
MgO as an Alternative Alkali Source
The main disadvantage of using NaOHas an alkali source forHCE is that the evaporated
caustic extract cannot be recycled to the spent sulfite liquor (SSL) of a Mg-based
cooking process due to the formation of low-melting Na-Mg eutectic mixtures. Thus,
efforts were undertaken to investigate the possibility of using Mg(OH)2 as an alkali
source for hot caustic extraction, as this enables the combined recovery of hot caustic
extract and Mg-based SSL [38]. As known fromweak bases such as sodiumcarbonate,
sodium sulfite and others, a higher temperature than is used for NaOH is required
for the purification. The time and temperature of MgO-based HCE (EMgO)
are the two main parameters that determine the degree of purification, rather
than the Mg(OH)2 charge. Charges higher than 15 kg odt–1 have no effect on purification,
due mainly to the low solubility of Mg(OH)2 in aqueous solution.
130 140 150 160 170
91
92
93
94
95
120 min 240 min at temperature
R18 content [%]
Temperature [.C]
Fig. 8.25 R18 content of a hardwood sulfite
pulp (HW-S) as a function of temperature during
hot caustic extraction using MgO as a
base, at two different reaction times [39]. HW-S
for 120 min reaction time: kappa number 6.2,
viscosity 640 mL g–1, 91.0%R18; HW-S for
240 min reaction time: kappa number 9.9, viscosity
600 mL g–1, 90.9%R18.
962 8 Pulp Purification
Figure 8.25 illustrates the successful use of MgO to obtain degrees of purification
sufficiently high for the production of viscose staple fiber pulps. The main
drawback when using MgO is the high temperature needed to achieve the necessary
purification. Another problem may be to achieve homogeneous distribution
of Mg(OH)2 within the pulp suspension in order to obtain a uniform pulp quality.
The prolongation of retention time from 120 to 240 min may reduce the temperature
by almost 10 °C, while maintaining the same R18 content. Moreover, the
MgO-based hot caustic extraction appears to be more selective than the conventional
system, with a specific yield loss of only 2.4% per 1% increase in R18
(Fig. 8.26).
91 93 95 97
70
75
80
85
90
95
100
E
MgO
- 240 min E
NaOH
E
MgO
- 120 min
Purification Yield [%]
R18 content [%]
Fig. 8.26 Purification yield as a function of R18 content for
MgO- and NaOH-based hot extraction processes of a hardwood
sulfite pulp (HW-S) [39]. Pulp substrate and conditions:
EMgO according to Fig. 8.25; ENaOH according to Fig. 8.18.
References 963
References
1 Hermans, P.H., The analogy between
the mechanism of deformation of cellulose
and that of rubber. J. Phys. Chem.,
1941; 45: 827–836.
2 Avela, E., et al., Sulfite pulps for HWMfibres.
Pure Appl. Chem., 1967: 289–301.
3 Sixta, H., et al., Evaluation of new organosolv
dissolving pulps. Part I: Preparation,
analytical characterization and viscose
processability. Cellulose, 2004; 11:
73–83.
4 Rydholm, S.A., Pulping Processes. Malabar,
Florida: Robert E. Krieger Publishing
Co., Inc., 1965: 992–1023.
5 Richter, G.A., Production of high alphacellulose
wood pulps and their properties.
Tappi, 1955; 38(3): 129–150.
964 8 Pulp Purification
6 Hempel, K., Solubility of cellulose in
alkalies and its technical significance.
Przeglad Papierniczy, 1949; 5: 62–69,
73–81.
7 Shogenji, T., H. Takahasi, K. Akashi,
The cold alkaline purification of sulfite
pulp. Use of ion-exchange resin for the
analysis of waste liquor and some information
on alkali consumption. J. Jap.
Tech. Assoc. Pulp Paper Ind., 1952; 6:
201–211.
8 Wilson, K., E. Ringstrom, I. Hedlund,
The alkali solubility of pulp. Svensk. Papperstidn.,
1952; 55: 31–37.
9 Ranby, B.G., The mercerization of cellulose.
II. A phase-transition study with
X-ray diffraction. Acta Chim. Scand.,
1952; 6: 116–127.
10 Ranby, B.G., The physical characteristics
of alpha-, beta- and gamma-cellulose.
Svensk. Papperstidn., 1952; 55:
115–124.
11 Corbett,W.M., J. Kidd, Some aspects of
alkali refining of pulps. Tappi, 1958;
41(3).
12 Sixta, H., A. Schrittwieser, Alkalization
of hardwood dissolving pulps. R&D
Lenzing AG: Lenzing, 2004: 1–10.
13 Saito, G.-I., The behaviour of cellulose
in solutions of alkalies. Kolloid-Beihefte,
1939; 49: 365–366.
14 Saito, G.-I., The behaviour of cellulose
in solutions of alkalies. I. Cross-sectional
swelling of fibers of different celluloses
in sodium hydroxide solutions
at different temperatures. Kolloid-Beihefte,
1939; 49: 367–387.
15 Bartunek, R., The reactions, swelling
and solution of cellulose in solutions of
electrolytes. Das Papier, 1953; 7:
153–158.
16 Dobbins, R.J., Role of water in cellulosesolute
interactions. Tappi, 1970; 53(12):
2284–2290.
17 Sixta, H., et al., Characterization of
alkali-soluble pulp fractions by chromatography.
In 11th ISWPC. Nice, France,
2001.
18 Sartori, J., Investigations of alkaline
degradation reactions of cellulosic
model compounds. In Institute of
Chemistry. University of Natural
Resources and Applied Life Science:
Vienna, 2003: 134.
19 Mais, U., H. Sixta, Characterization of
alkali-soluble hemicelluloses of hardwood
dissolving pulps. In ACS Symposium
Series, 2004: 94–107.
20 Krassig, H.A., Cellulose: Structure, Accessibility
and Reactivity. Polymer Monographs.
M.B. Huglin, Ed. Vol. 11. Gordon
and Breach Science Publishers,
1993: 258–323.
21 Sixta, H., Comparative evaluation of
TCF bleached hardwood dissolving
pulps. Lenzinger Berichte, 1999; 79:
119–128.
22 Fink, H.-P., J. Kunze, Solid state 13C
NMR studies of alkalization of hardwood
dissolving pulps. Fraunhofer,
Institut fur Angewandte Polymerforschung:
Golm, 2003: 1–5.
23 Fink, H.-P., B. Philipp, Models of cellulose
physical structure from the viewpoint
of the cellulose I → cellulose II
transition. J. Appl. Polym. Sci., 1985;
30(9): 3779–3790.
24 Fink, H.-P., et al., The composition of
alkali cellulose: a new concept. Polymer,
1986; 27(6): 944–948.
25 Fink, H.-P., et al., The structure of
amorphous cellulose as revealed by
wide-angle X-ray scattering. Polymer,
1987; 28(8): 1265–1270.
26 Fink, H.-P., et al., 13C-NMR studies of
cellulose alkalization. Cellulose and Cellulose
Derivatives, Physico-chemical
Aspects and Industrial Applications.
J.F. Kennedy, G.O. Williams, L. Piculell,
Eds. Woodhead Publishing Ltd: Cambridge,
1995: 523–528.
27 Hinck, J.F., R.L. Casebier, J.K.Hamilton,
Dissolving pulp manufacturing. In Sulfite
Science & Technology. J.K.O. Ingruber,
P.E. Al Wong, Eds. TAPPI, CPPA:
Atlanta, 1985: 213–243.
28 Borgards, A., A. Lima, H. Sixta, Cold
caustic extraction of various hardwood
dissolving pulps. Internal Report, R&D
Lenzing AG, 1998.
29 Sears, K.D., J.F. Hinck, C.G. Sewell,
Highly reactive wood pulps for cellulose
acetate production. J. Appl. Polym. Sci.,
1982; 27(12): 4599–4610.
30 Leugering, H.-J., Zur Kenntnis der Zellstoffveredelung
durch Heissalkalisierung.
Das Papier, 1953; 7(3/4): 47–51.
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31 Meller, A., Studies on modified cellulose.
I. The alkali stability of oxidized,
hydrolyzed, and methanolized cellulose.
Tappi, 1951; 34: 171–179.
32 Samuelson, O., C. Ramsel, Effect of
chlorine and chlorine dioxide bleaching
on the copper number, hot-alkali solubility,
and carboxyl content of sulfite cellulose.
Svensk. Papperstidn., 1950; 53:
155–163.
33 Yaldez, R., H. Sixta, Hot caustic extraction
of sulfite dissolving pulps. Internal
Report, R&D Lenzing AG, 1998.
34 MacLeod, J.M., L.R. Schroeder, b-d-(glucopyranosyl)-
d-glucose-3.6-anhydro-4-Omethyl-
d-glucose, and d-glucose.
J. Wood Chem. Technol., 1982; 2(2):
187–205.
35 Lindahl, J.A.I., Process and apparatus
for the deresination and brightness
improvement of cellulose pulp. Mo och
Domsjo Aktebolag: US Patent, 1981.
36 Assarsson, A., et al., Control of rosininduced
complications in pulp. Przeglad
Paperniczy, 1982; 38(2): 53–55.
37 Reintjes, M., G.K. Cooper, Polysaccharide
alkaline degradation products as a
source of organic chemicals. Ind. Eng.
Chem. Prod. Res. Dev., 1984; 23: 70–73.
38 Sixta, H., T. Gerzer, W. Muller, Verfahren
zur Veredelung von Zellstoffen.
Osterreichische Patentanmeldung,
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39 Sixta, H., Hot caustic extraction of hardwood
sulfite pulp with MgO as a base.
Internal Report, R&D Lenzing AG,
2002.
967
9
Recovery
Andreas W. Krotscheck, Herbert Sixta
9.1
Characterization of Black Liquors
9.1.1
Chemical Composition
Kraft black liquor contains most of the organic compounds removed from the
wood during the cook and the inorganic chemicals charged, mainly in the form of
salts with organic acids. A major portion part of the extractives removed from the
wood during kraft pulping is, however, not included in the black liquor solids.
The volatile wood extractives such as low molecular-weight terpenes are recovered
from the digester relief condensates (turpentine). The resin and fatty acids, as
well as some neutral resins (e.g., b-sitosterol), are suspended in the diluted black
liquor (in the form of stable micelles). During the course of black liquor evaporation,
when a concentration of 25–28% of total solids is reached, these extractives
are separated from the aqueous phase as “soap skimmings”. Crude tall oil is
obtained from the soap skimmings after acidification with sulfuric acid. The composition
of the tall oil is described elsewhere [1].
The remaining kraft black liquor contains organic constituents in the form of
lignin and carbohydrate degradation products. The composition of the spent
liquor depends greatly on the wood species, the composition and amount of white
liquor charged, the unbleached pulp yield, and the amount of recycled bleach filtrates
(predominantly from the oxygen delignification stage). During kraft pulping,
lignin and a large part of carbohydrates mainly derived from hemicelluloses,
are degraded by alkali-catalyzed reactions. Thus, the organic material of the black
liquor consists primarily of lignin fragments (mainly high molecular-mass fragments)
and low molecular-weight aliphatic carboxylic acids originating from wood
carbohydrates. The approximate composition of a black liquor from birch and
pine kraft cooks is shown in Tab. 9.1.
Organic material also contains minor amounts of polysaccharides mainly derived
from xylan (part of “Other organics” in Tab. 9.1). Quite recently, it was
shown that black liquor from Eucalyptus globulus kraft cooking contains substantial
amounts of dissolved polysaccharides (BLPS = black liquor dissolved polysaccharides)
[4]. BLPS represent about 20% of the total dissolved and/or degraded
wood polysaccharides. The major component of BLPS is xylan, with a molecular
Handbook of Pulp. Edited by Herbert Sixta
Copyright © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim