Holik H. (ed.) Handbook of Paper and Board

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(elementary chlorine free) pulps compared with the conventionally bleached

pulps.

The quality of pulp depends on the kind of wood used. Softwood pulps have

longer fibers, resulting in higher strength, whereas hardwood pulps with shorter

fibers for instance produce a more uniform sheet. Paper containing only chemical

pulp as the fiber component is called wood-free paper, i.e. it has only a low residual

lignin content.

Sulfate pulps have distinctly higher strength than sulfite pulps, especially if they

are unbleached. That is why unbleached sulfate pulps are mostly used in papers

with high strength demand such as corrugated board, packaging papers, or techni-

cal papers. Highly bleached pulps are used in high-quality printing papers.

The dominant process of semi-chemical pulping is the neutral sulfite semi-

chemical process (NSSC), with sodium or ammonium sulfite as the digestion

chemicals. The pulp yield is in the range 70–80% depending on the wood species,

most commonly hardwood species like birch, beech, maple, oak and eucalyptus.

This pulp is used for fluting production – often as the sole component in fur-

nish.

2.1.3

Mechanical Pulp

Mechanical pulp is produced from wood by mechanical defibration. Different

processes are in use:

• Stone groundwood (SGW) is produced by the mechanical defibration of round

wood logs by a grinding stone.

• Refiner mechanical pulp (RMP) is obtained by mechanical defibration of wood-

chips in a refiner and is carried out without pre-treatment. Defibration takes

place under atmospheric pressure. The wood chips are defibrated at tempera-

tures of about 100 °C, mostly in two stages with consistencies of 20 to 30 % in

the second stage.

• In the refiner process with thermal pre-treatment (TMP), wood chips are treated

with steam at 110 °C to 130 °C for 2 to 5 min before they are defibrated under

high pressure.

• In the refiner process with chemical pre-treatment (CTMP/CMP), wood chips

are impregnated with chemicals before they are mechanically defibrated in the

refiner under high pressure of about 3 bar or at atmospheric pressure, mainly in

two stages.

The CTMP and CMP processes differ in the intensity of the chemical treatment

and the yield. The yield of softwood CTMP is about 91% to 96%. CMP is more

heavily chemically treated and therefore has more the character of a chemical pulp,

i.e. higher strength properties at a cost of lower light-scattering coefficient (see

Table 2.2). For hardwood, the yield of CMP can decrease to 80%.

During mechanical defibration, lignin is plasticized and remains in the pulp.

This is the reason for the lower strength properties but higher light-scattering

2 Raw Materials for Paper and Board Manufacture22

coefficient and opacity compared to chemical pulp. The residual lignin in mechan-

ical pulps results in a poorer and less stable brightness level. Mechanical pulps

cannot be brightened by oxidative and reductive bleaching to the same extent as

chemical pulps as only negligible delignification takes place compared to the

bleaching of chemical pulp.

Paper grades that contain pulp produced by mechanical or chemimechanical

processes are referred to as wood-containing papers. Mechanical pulps are mainly

used in short-life printing papers, hygienic papers and board.

A comparison of some of the main characteristics of chemical and mechanical

pulps: yield, BOD (biological oxygen demand), grinding or refining energy (in the

case of chemical pulp for final pulp preparation), freeness, tensile index and light

scattering coefficient, is given in Table 2.2. The yield decreases from 97 % for SGW

to 40% for chemical pulp (kraft type) and the effluent impact increases i.e. the

biological oxygen demand increases. Specific energy consumption is lower for

conventional chemical pulps than for chemimechanical pulps but chemical con-

sumption is higher.

Freeness is measured as about 100 ml for (fines-containing) stone groundwood

(SGW) and 780 ml for chemical pulp with high long-fiber content.

Chemical pulps have a higher strength potential (tensile index) but lower light

scattering ability.

Light scattering values are given for the pulp before undergoing additional me-

chanical treatment. Post-refining of mechanical pulp increases the light scattering

coefficient whereas refining of chemical pulp decreases this property.

Table 2.2 Characteristics of mechanical, chemimechanical and

chemical pulps.

Pulp type Mechanical pulp Semi-

chemical

Chemical

pulp

SGW TMP CTMP CMP pulp

Yield % 97 95 90 80 70 60 40

biological

oxygen demand

(BOD)

kg t

–1

10 20 50 100 200

grinding or

refining energy

kWh t

–1

1200 2200 2500 1000 500 200 100

freeness CSF ml 100 120 200 400 600 800

tensile index Nm g

–1

30 40 50 60 70 80 100

light-scattering

coefficient

–1

65 60 50 40 30

2.1 Fibrous Materials 23

2.1.4

Recovered Paper, Recycled Fibers

Hans-Joachim Putz

2.1.4.1 Role of Recovered Paper in the Paper and Board Industry

In the past chemical pulp was the most important raw material for paper produc-

tion, but now this has been replaced by recovered paper. 158 million tons of this

raw material were used globally in 2002. This volume exceeds the total volume of

woodpulp, i.e. chemical pulp (117 million tons) and mechanical pulp (36 million

tons) [1]. These figures show that recycled fibers play a very important role today in

the global paper industry as a substitute for virgin fiber pulps.

Figure 2.1 shows the global increase in recovered paper usage, compared to

paper production since 1961. Globally the use of recovered paper increased by

approximately 5.8% annually whereas annual paper production growth was only

3.6%.

The paper industry is the exclusive relevant user of recovered paper as a secon-

dary raw material – at least in terms of material recycling. Various recovered paper

processing systems with mechanical and chemical unit processes prepare recycled

fibers for the production of paper and board grades. These processing systems use

different recovered paper grades that contain either chemical or mechanical fibers

or, mainly, an undefined mixture of both. Some paper and board grades can be

made from recycled fibers exclusively. This includes paper grades such as corrugat-

ing medium and testliner or newsprint in Europe. For newsprint and other grades

blends of recycled and virgin fibers are also used. The proportion of recycled fibers

Fig. 2.1 Global development of recovered paper utilization

and paper production (1961–2002) [1–5].

2 Raw Materials for Paper and Board Manufacture

in the raw material furnish can vary from about 5% for fine papers to 100%

depending on the paper grade or geographic region.

Figure 2.2 shows the largest recovered paper consuming countries. They used in

total 122 million tons in 2002 corresponding to 77% of the global recovered paper

consumption.

2.1.4.2 Main Definitions for Statistics

Consideration of recovered paper use and recovery of used paper products requires

definitions. Statistical definitions can be related to the world, a continent, a country

or a certain region (e.g. Europe) or to a certain category of paper products (e. g.

graphic papers or newsprint). Differentiation is given by three statistical parame-

ters:

• Recovered paper utilization rate, in percent, is the amount of recovered paper

used as raw material in the paper industry, in tons, divided by paper production,

in tons, on an annual basis, multiplied by 100.

• Recovery or collection rate, in percent, is the amount of collected recovered

paper for material recycling, in tons, divided by paper consumption, in tons, on

an annual basis, multiplied by 100.

• Recycling rate, in percent, is the amount of recovered paper used as raw material

in the paper industry, in tons, divided by paper consumption, in tons, on an

annual basis, multiplied by 100.

Fig. 2.2 The 12 largest recovered paper consuming countries

in the world (2002) [1].

2.1 Fibrous Materials

From these definitions it becomes obvious that the utilization rate is related to

recovered paper usage in paper production, whereas the recovery rate is related to

the amount of collected paper related to paper consumption. Both rates can be

affected directly either by the paper industry by the use of more or less recovered

paper in paper production or by the waste management industry collecting more

or less recovered paper from the paper consumed. The recycling rate is a more

theoretical value putting recovered paper usage in relation to paper consumption.

A high level of recovered paper usage in paper production combined with strong

net paper export rates will result in a high recycling rate, which has to be satisfied

by recovered paper imports from abroad.

Recovered paper utilization rates globally and nationally may be used for com-

parison. Such statistics can give, however, a false impression of the recycling activ-

ities in different countries as the following discussion explains. The range of na-

tional utilization rates extends globally from 5% to more than 100 %. Figure 2.3

shows the 12 largest papermaking countries, accounting for almost 80% of the

global paper production in 2002 of 331 million tons. Simultaneously, they con-

sumed about three quarters of the world’s recovered paper volume. Heading the

list are South Korea, Germany, Indonesia and Japan with utilization rates above

61%. The lowest utilization rates are for Finland and Sweden. This is because

more than 80% of their paper production is exported due to their low population

figures and related low level of national paper consumption.

Fig. 2.3 Utilization rates of recovered paper of the 12 largest

papermaking countries in the world (2002) [1].

2 Raw Materials for Paper and Board Manufacture

Figure 2.4 shows the utilization rate for the three largest paper production re-

gions in the world where the paper industry uses 85% of the global recovered

paper volume: Asia, Europe and North America. Paper production in these three

regions is between 90 and 100 million tons each, resulting in recovered paper

utilization rates of roughly 57% in Asia, 47 % in Europe and 38 % in North

America.

2.1.4.3 Utilization Rates for Different Paper Grades

Utilization rates for different countries should not be compared without further

comment. It is important to know the structure of the production program of the

different national paper industries in the main product categories of packaging

papers and board, graphic papers, household and hygiene papers as well as spe-

cialty papers because the utilization rates for these product segments differ sig-

nificantly.

In Fig. 2.5 for the CEPI countries the recovered paper utilization by the main

paper categories is presented and additionally the utilization rates are given. The x-

axis is a summarizing ordinate representing the total paper production in the

CEPI countries of 91 million tons, subdivided into the production of the various

paper categories. The broader a single paper category, the larger the paper produc-

tion (for example, the biggest category, with 34 million tons, is other graphic pa-

pers). For each paper product category (e.g. newsprint) the used recovered paper

Fig. 2.4 Recovered paper utilization rate and paper production

in Asia, the CEPI countries

and North America (2002) [1].

CEPI countries are all EU countries plus the Czech Republic,

Hungary, Norway, the Slovak Republic and Switzerland.

2.1 Fibrous Materials 27

volume is shown on the y-axis. In the circles the corresponding recovered paper

utilization rate is given. It becomes obvious that the highest volume of recovered

paper is used in the production of case materials (19.2 million tons). The second

highest recovered paper utilization rate of 73% is in newsprint with a volume of

7.4 million tons. In the other paper categories between 2.0 and 4.4 million tons of

recovered paper are used, resulting in recovered paper utilization rates between

9% and 61 %.

Traditionally, packaging papers and board have the highest recovered paper utili-

zation rate. In the CEPI countries this ratio has reached almost 75%. Demanding

quality specifications have to be fulfilled by these recycled fiber-based paper and

board grades to ensure trouble-free converting, for example, to corrugated board

boxes or folding boxes and adequate functional characteristics of the finished prod-

ucts. Occupying second place is the utilization rate of household and hygiene

papers (61%). Due to high yield losses in the flotation and washing steps, the

proportion of recycled fibers in hygiene paper is not higher than 40% on average.

The figure of 40% deinked pulp comes from about 60% yield of about 65 % utiliza-

tion rate. The group of other papers, comprising gypsum liners, special papers for

waxing, insulating and roofing, achieve a 51% utilization rate in the CEPI coun-

tries, but there are also many specialty paper grades such as cigarette paper, filter

paper, or banknote paper which never can use recycled fibers.

Finally, the level of the utilization rate for graphic papers is only 23%. Due to the

wide spectrum of the paper grades produced, a distinction is necessary for this

product segment because newsprint has reached a level of 73%. The utilization

rate of the other graphic papers averages only 9%. Included among these other

graphic papers are wood-containing and woodfree papers that are coated or un-

coated. Some use 100% recycled fiber furnish, e.g. recycling copy papers.

Fig. 2.5 Recovered paper utilization by paper grades in the

CEPI countries (2002) [6].

2 Raw Materials for Paper and Board Manufacture

2.1.4.4 Resources of Recovered Paper

Before using recovered paper for paper production its recovery is necessary. Re-

sources of recovered paper are in general collection from industrial enterprises

(e.g. printing houses), business operations (e.g supermarkets) or offices and from

private households and small commercial enterprises. Whereas the recovery of

used paper from industry, business operations and offices has a long history and

can be easily managed, recovery of used paper from private households is more

complex. Additional recovered paper resources cannot be expected in the first cate-

gory, because these paper grades mainly belong to the so-called “pre-consumer”

grades, are of high quality and are already almost 100% recovered. Collected paper

from private households is “post-consumer” recovered paper which is usually

mixed and always requires a sorting process.

As far as national recycling activities are concerned, an assessment of the paper

recovery rates of different countries is more relevant than a comparison between

national recovered paper utilization rates. Figure 2.6 shows the collection rates vs.

the utilization rates of recovered paper in the CEPI countries. The bubble size is

equivalent to the tonnage of recovered paper used in each country. Due to in-

tensified collection in each country the average rose from 41% in 1991 to 56%,

corresponding to a total volume of recovered paper of 46 million tons in 2002. It

becomes obvious that the highest collection rates in the CEPI countries are by

Germany, Switzerland, the Netherlands, Norway, Sweden and Austria, whereas the

highest utilization rates are reached in Ireland, Denmark, Spain, Greece, the

United Kingdom and Hungary. The largest tonnages of recovered paper are used

in Germany, France, Italy, the United Kingdom and Spain.

The maximum paper recovery rate in an industrialized country with a well-

developed infrastructure is about 80% [7]. This theoretical limit of the recovery rate

Fig. 2.6 Recovered paper utilization and collection rates vs.

utilization rate in CEPI countries (2002) [1].

2.1 Fibrous Materials

occurs since approximately 20% of the used paper products are not collectible,

because they are contaminated, long living products or are destroyed by disposal or

burning. This includes hygiene paper, specialty paper products, long-life paper

products, papers used in industrial applications, and papers used for other pur-

poses in private homes such as fuel or compost material. Considering the theoret-

ical recovery rate of 80%, the recovery rate of 75 % already achieved in 2002 in

Germany is equivalent to a paper collection efficiency of about 94%. Collecting

additional used paper is probably not economically feasible.

At the global level, no data are available for the different sources of collection

systems of recovered paper by tonnage. In Europe, CEPI has conducted recovered

paper surveys which found, for 2002, the following five sources of recovered pa-

per:

• Recovered paper from households: 38%

• Recovered paper from trade and industry: 33%

• Recovered paper from converting and printing: 15%

• Recovered paper from offices: 10%

• Recovered paper from unsold newspapers and magazines: 4%.

The recycling rate was introduced by CEPI for the first time as the relation between

recovered paper utilization and paper and board consumption. Related to the con-

sumption of paper and board the figure indicates the internal material recycling of

recovered paper in a country or a region, so long as no net import of recovered

paper occurs. Nevertheless, recycling rates close to 100% indicate that either a

large amount of recovered paper is imported or a high volume of produced paper

and board is exported. Figure 2.7 shows the development of the recycling rates in

the CEPI countries from 1991 with an increase of 2.2% p. a. until 2002, when it

was approaching 52.7% and it should reach 56 % in 2005, far from the theoretical

or practical limit.

Fig. 2.7 Development of recycling rate and recovered paper

utilization in the CEPI countries (1991–2002) [6].

2 Raw Materials for Paper and Board Manufacture

2.1.4.5 Lists for Recovered Paper Grades

Globally no common list of recovered paper grades exists. A European Standard

was established in 2001 by CEN (European Committee for Standardization) as EN

643 for Europe [8]. All recovered paper grades are classified into the following five

groups:

• Ordinary grades

• Medium grades

• High grades

• Kraft grades

• Special grades.

Recovered paper grades are generally not defined by physically verifiable quality

characteristics. Instead, the naming of recovered paper in the list uses one of the

following criteria:

• Places of occurrence, such as supermarket corrugated paper and board (1.04)

• Former paper grades of which the recovered paper consists, such as mixed mag-

azines and newspapers (1.10)

• Mixed categories such as mixed sorted papers and boards (1.02).

Globally and in Europe, the use of deinked pulp (DIP) in newsprint dominates

(55%–65 %), followed by hygiene papers (20 %–15%) and printing and writing

papers (about 12%). Therefore, another very important paper grade in Europe

describes a wood-containing recovered paper mix, commonly used for deinking. It

is called “Sorted graphic paper for deinking” (1.11) and originates primarily from

household collections.

The complete list of recovered paper grades is published in the Annex of Volume

I and is available also on the website of GesPaRec (www.altpapier-rohstoff.de).

Recovered paper grade lists are not comparable between Europe, USA and Asia.

Therefore recovered paper grades are summarized very often in the following four

groups:

• Mixed grades: comprising always a mixture of various paper and board grades

used for the production of packaging paper and board.

• Corrugated and kraft grades: comprising predominantly packaging paper and

board grades used for the production of packaging paper and board. The term

OCC is also very often used for this recovered paper grade and stands for “old

corrugated containers”.

• Deinking grades: comprising exclusively graphic paper grades used – after a

deinking process – predominantly for the production of graphic and tissue pa-

pers.

• High grades: comprising predominantly white lightly printed graphic papers

and board (very often woodfree), recovered by separate collection and therefore

relatively clean.

2.1 Fibrous Materials 31