MANUFACTURING PROCESS OF TISSUE PAPER
FROM RECOVERED PAPER
Authors: Enma Pérez Chacón, Sebastián O. Pérez Báez, Juan A. Peña Quintana and Mª
de la Concepción F. Ling Ling
Dpto. de Ingeniería de Procesos - E.T.S.I.I. Universidad de Las Palmas de Gran Canaria.
Abstract
The aim of this paper is to design a plant in order to obtain tissue paper from recovered
paper.
Keywords: tissue paper, recovered paper, manufacturing process.
1. Introduction
The great development of paper is due to the relationship utility/price that has allowed it
to assert over other materials in several uses but, above all, to the fact that it is a natural,
recyclable and biodegradable product, very important aspects in a society worried about
the environmental damage and the maximum exploitation of the resources. The
consumption of paper may be considered indicative of the growth rate of a country, as it
is a product closely linked to culture, education, communication, commerce, transport,
health and hygiene.
Within the properties that allow to define paper, one of the most used is grammage,
which is defined as the mass of the paper surface unity expressed in grams per square
metres, this measure is very important because the regulation of the paper pulp in the
machine depends on it. Besides, the paper trade is carried out in terms of this property.
Among the numerous kinds of paper that exist in the market, there are the ones known
as tissue, within which a wide range of low grammage sheets are included. The sanitary
tissue, to which this paper refers, includes facial and toilet tissues, towels and paper
napkins. Tissues are single-use products, which guarantees an optimum level of
hygiene, The main functions of these types of paper are to protect, to absorb, to clean
and to dry.
In Spain, the consumption of this kind of paper in the year amounted to 513.600 tons,
that confronted with the sum of 284.300 tons in 1996, it means an increase of 81%.
With regard to the growing consumption of paper carried out by the society, it is
necessary to have available big quantities of raw material that allow to satisfy the
demand; this is the reason why it is important the recovery and reuse of the paper and
corrugated cardboard wastes that are daily generated.
2. The sustainable cycle of paper
All paper plants recover their own wastes and most of them, for many years, have had
as a total or partial raw material the so-called old, recovered, used paper or simply scrap
paper. Nowadays it is more frequent to refer to this raw material as secondary fibres.
The interest for the use of recovered paper is due to several reasons:




Economic reasons. The recovered paper used as raw material is generally
cheaper.
Lack of space in the landfills. Paper and corrugated cardboard are a very
important constituent in the content of domestic rubbish : 50% in USA.
40% in Europe and, finally, 30% in Spain. The reuse of paper and
corrugated cardboard wastes implies a reduction of the volume occupied in
the landfills.
Ecological reasons. The raw material for the paper industry is paper pulp
that is generally obtained from the trees. Although the industry encourages
the reforestation, some people have presented it as one of the main agents
of its destruction. Motivated by this propaganda, some consumer groups
wish to use recycled papers.
Legal reasons. Due to the previous causes, some countries have included
in their legislation the obligatoriness for some kinds of papers to be
manufactured with, at least, a certain amount of recycled fibres.
3. The industrial paper sector in the Canary Islands
According to the National Classification of Activities in 1993 (SNCA-93), the paper
sector is divided into two big groups:
a)


Paper industry (SNCA 21), which is subdivided into:
Manufacturing of paper pulp, paper and corrugated cardboard.
Manufacturing (transformation) of paper and corrugated cardboard
articles.
b) Edition, graphic arts and reproduction of engraved base (SNCA 22), that
comprises:
 Edition of books, magazines, newspapers, etc.
 Printing, binding, etc..
Due to the differences that exist between industrial processes, as well as their settlement
in the Canary Islands, these are going to be classified into three different groups:
 Manufacturing of paper and corrugated cardboard.
 Transformation of paper and corrugated cardboard.
 Graph arts.
According to what has been published by the Canarian Government, through its
Consejería de Política Territorial y Medio Ambiente (Territorial policy and
Environment), among all of them, only the two last groups are present in the
archipelagoThe sector of pulp and paper manufacturing is inexistent in the Canary
Islands, this is an aspect that has to be considered from the point of view of wastes
generation and management because the absence of this type of installations blocks the
possibility of carrying out a local recycling process of recovered paper that has to be
exported to the mainland or to the international market.
This is the reason why, in this paper, it is proposed the design of a plant for
manufacturing tissue paper from a raw material totally composed by recycled material.
The selection of the type of paper that is going to be manufactured has been based on
the study of the figures of importation to the Canary Islands, and according to these
data, tissue paper is the kind of paper whose importation implies the greatest expenses
to the archipelago.
This proposal pretends to pay special attention in evaluating the possibility for
producing tissue paper within the framework of respect to the environment, that is to
say, obtaining it only from recycled material, with a minimizing of water and energy
consumption, as well as the optimisation of the waste management, not only for
reducing them, but also to integrate them in the adequate or reusing circuits.
This last objective is reinforced by the European Directive 1999/31 about waste
disposal and its statal application through Decree 1481/2001, in which is included the
need for avoiding valuable wastes to arrive at landfills starting from this present year.
The manufacturing process of tissue paper from scrap paper includes a series of stages.
It is fundamental for paper fibres to be recovered without any damage, so that the
physical, chemical and optical qualities will be equivalent to those present in the paper
obtained from virgin fibres.
The manufacturing of tissue paper and, in general, of any kind of paper can be divided
into three main stages:
Pulp preparation
Paper preparation
Handling or converting
In this paper, it has been chosen to integrate jointly pulp and paper preparation. The first
one includes the pulp preparation circuit: its aim is to obtain a homogeneous pulp with
characteristics adequate for the paper desired to be obtained as product. The main
objectives of this first stage are raw material purification and pulp whitening. These
operations are always carried out trying to obtain the maximum recovery and reuse of
the process water and the thickening of the generated rejections.
4.- Process effluent treatment
In the development of the recycling process of paper in order to obtain tissue paper, two
main objectives are necessary to take into account: firstly, losses have to be minimized
and, secondly, the plant effluents have to be treated in order to keep the environmental
impact to a minimum and, above all, non-polluting. All the operations whose purpose is
to close the process will produce a double benefit: a more efficient use of the resources
and a reduction of the polluting charge. So, the most effective way to reduce losses is
the recirculation and reuse of the waters. Despite the fact that the internal installations
of the process water treatment are taken into account in the pulp preparation section as
well as in the paper preparation one, it is considered necessary the installation of a
sedimentation stage of the waters in order to allow, on the one hand, the maximum
amount of treated water to incorporate again to the process so that the water cycle will
be closed to a maximum, thus, optimising the consumption of fresh water and, on the
other hand, the optimisation of the unavoidable waste with a maximum respect to the
environment.
The pollutants present in the effluent of the paper recycling plant come fundamentally
from the additives that the raw material contains, that is to say, the recovered paper. The
additives are normally non-fibrous in their manufacture in order to give the product the
characteristics that it must show; it is used additives such as alumina, gluing agents,
mineral charges, starches and colourings. These are extracted from the manufacturing
process through the water, thus generating the suspended solids and the BOD typical of
the effluent.
The additives mostly used in the paper industry, Table I, constitute the process water
pollutants of the recycling process.
Table I., Additives mostly used in the paper industry
Additive
Application
Alumina
To control pH, to fix additives on the fibers, to
increase retention
Gluing agents (resins)
To control penetration of liquids
Dry resistance agents To communicate rigidity and tearing resistance
(starches)
Humidity
resistance To communicate humidity resistance (wipes)
resins
Charges (kaolin, talc)
To improve optical and printing properties
Colouring
matters To give the desired colour
(colourings, pigments)
Retention aids
To improve retention of fines and charges
Fibre deflocculants
To improve sheet formation
Antifoaming agents
To improve drainage and sheet formation
Drainage aids
To increase drainage on the fabric
Optical whiteners
To improve the apparent whiteness
The gluing process is applied to a great amount of paper types in order to give
resistance to the penetration of fluids. Starches, which are the gluing agents par
excellence, are glucose polymers that are obtained from different plants; these are the
main cause of the characteristic BOD of the effluent. Charges are finely divided white
mineral particles that are added to the paper manufacturing compositions in order to
improve the physical and optical properties of the sheet. Nearly all the colourings used
in the paper industry are organic compounds (minerals are not frequent), that are rarely
eliminated from paper; which is carried out in the whitening process is a change of
colour in them by varying the bonds between carbons through oxidation.
It is considered a press to reduce the humidity of the rejections before carrying them to
the landfill sites and a clarifier to reduce the content of suspended solids of waters
before disposing them to the sewerage system of the industrial area.
Thus, in this case, it has been chosen to include only the physical-chemical treatment
(primary) of the purifying plant that usually comes with every paper industry. It has to
be pointed out that, although the design of an entire wastewater plant would have been a
better solution, it has not been considered within this project because it is not included
in its goals.
The primary treatment will consist in a settling process that, apart from separating the
suspended particles which are heavier than water by gravity action (and a small part of
BOD), will allow to obtain a sludge with such a solids concentration that it could be
handled and treated easily. Although flotation by dissolved air is other alternative for
the primary treatment, it has been chosen the sedimentation by gravity because of the
advantages that it shows: it is relatively insensitive to the variations of flow and solids
concentration, it needs little attention and maintenance and its operation presents a low
cost.
In the circuit of pulp preparation, it is carried out all the different operations that are
going to produce a homogeneous pulp with adequate characteristics. The main
objectives for this first stage are the purification of the raw material (separation and
elimination of the ink and the rest of pollutants from the fibres) and the whitening of the
pulp. These operations are carried out with the maximum recovery and reuse of the
process water and the adequate thickening of the generated rejections. Three stages of
purification allow the separation of the impurities from the pulp. The first stage consists
in a centrifugal purification of the thick pulp where the pollutants with a bigger specific
weight are separated by leaving them after the first vast purification realized in the
disintegration system. The second stage is a purification by holes and slots at a lesser
consistency in which the polluting particles are classified by their shape, eliminating
those with flat shape (purification by holes) and those with three-dimensional shape
(purification by slots). Finally, the centrifugal purification will be in charge of
separating the impurities of small size according to their specific weight. The first stage
has a great separation efficiency; it is the rejection of each one which passes to the
following stage, while the accepted part goes back to the previous stage.
The deinking process is fundamentally carried out through the flotation mechanism as it
shows a water consumption much lesser than the washing method, in the same way that
an efficiency between 80-95% and greater potential capacity to reduce the content of
sticky substances originated by adhesive products nonsoluble in water. Nevertheless,
they pass with the part accepted in the previous stages of purification and this is the
reason why a dispersion stage is added before the whitening. With all these disposal
stages, it is assured adequate separation efficiencies that guarantee the correct operation
of the paper machine. The chemical products used are alkali, oxidant agents and a
tensoactive agent such as a sodium soap or a synthetic detergent whose purpose is to
carry out two functions: one as a foaming product, and the other one as a collector.
The rejections of the deinking plant are constituted by charges, fibres, fines and inks
into equal parts. This rejection is discharged as an alkaline effluent, pH between 8,5 and
10, with some features such as: suspended solids: 1000-4000 mg/L; BOD5: 10 kg/ton
(500-600 mg/L); COD: 23 kg/ton (1100-1600 mg/L).
The total amount of wastes that are generated throughout the manufacturing process of
cellulose and paper is classified in the European Catalogue of Wastes (ECW) as nonhazardous. The management policy of the sector with respect to the process wastes
consists, firstly, in its minimization through the quality control of the raw material and
improvements in the manufacturing process and, secondly, in its recycling or energetic
valorisation.
The average rate of generation of deinking sludges is of 20% in solid matter on
recovered paper used as a raw material and a ratio of 25% in solid matter on the
obtained product. There are different ways to valorise the deinking sludges that
maintain a common objective: to convert the wastes in resources. This is the reason why
it is applied several techniques and wastes management lines in agricultural sectors, in
the industry as a raw material or alternative fuel, (ceramic and cement sectors), as in the
energetic valorisation.
References
ASOCIACION NACIONAL DE FABRICANTES DE PASTA, PAPEL Y CARTÓN
(ASPAPEL), Informe medioambiental. 2002. El ciclo sostenible del papel
ASOCIACIÓN ESPAÑOLA DE NORMALIZACIÓN Y CERTIFICACIÓN (AENOR)
UNE-EN-643 2002
AEPO Ingenieros consultores S.A. y Trazas Ingeniería S.L. 2001. Estudio de
composición y caraterización de las basuras urbanas en la Comunidad Autónoma de
Canarias
Instituto Canario de Estadística (ISTAC) www.istac.rcanaria.es
Plan Integral de residuos de Canarias. Decreto 161/2001. Viceconsejería de Medio
Ambiente del Gobierno de Canarias
McKinney , R.W,J, 1995. Technology of paper recycling. Chapman and Hall
Smook, G.A. 1990. Manual para técnicos de pulpa y papel. Tappi Press
García Hortal, J.A. 2001 Fundamentos del destintato por flotación (I). Condiciones
químicas. Ingeniería Química
García Hortal, J.A. 2001. Fundamentos del destintado por flotación (II). Proceso de
destintado. Ingeniería Química
Colom Pastor, J.F. y Torres López A.L. 1992. El destintado del papel. Escuela Técnica
Superior de Ingenieros Industriales de Tarrasa. Universidad Politécnica de Cataluña
Celulosa e papel. Tecnología de fabricación del papel Vol. II 1998. Deparatamento de
divulgación de IPT