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DE LA FACULTAD DE INGENIERÍA
REVISTA TÉCNICAREVISTA TÉCNICA
Patrimonio del Estado Zulia e
interés Cultural desde 2001
Fecha de Construcción:
1954-1958
Diseño: Arquitecto Carlos Raúl
Villanueva, con elementos
novedosos de adaptación
climática.
Policromía de la obra: Artista
Zuliano Victor Valera.
VOLUMEN ESPECIAL 2019 No.1
Rev. Téc. Ing. Univ. Zulia. Volumen Especial, 2019, No. 1, pp. 154-262
Rev. Téc. Ing. Univ. Zulia. Volumen Especial, 2019, No. 1, 181-186
Obtaining and characterization of pellets based on walnut
shells, waste paper and paperboard
Y. Pérez1 , A. González1* , J. Castillo1 , P. Oliveira2 , A. Sánchez1 , C. Pichara3
1Department of Industrial Processes, Universidad Católica de Temuco, Rudecindo Ortega 02950, Temuco, Chile.
2 Núcleo de Investigación en Bioproductos y Materiales Avanzados, Universidad Católica de Temuco,
Rudecindo Ortega 02950, Temuco, Chile.
3Department of Administration and Economics, Faculty of Legal, Economic and Administrative Sciences,
Universidad Católica de Temuco, Chile.
*Corresponding author: agonzalez@uct.cl
https://doi.org/10.22209/rt.ve2019a05
Recepción: 20/06/2019 | Aceptación: 03/11/2019 | Publicación: 01/12/2019
Abstract
Spite of continuously deforestation in Chile in the last 40 years, the production of combustion pellets is increased,
being the main producer Ecomas. For this study, it was testedwalnut and wheat shells, waste paperboard and waste Kraft
paperas raw materials for17 formulations of pellets. Only 8 formulations were successful for pellet production. The 8 pellets
obtained and Ecomas pellet were compared according to ash and moisture content and heating value (HHV). The pellets
obtained indicated a better HHV and moisture content but a higher ash content than Ecomas pellet. Moreover, 8 pellets and
Ecomas pellet were compared with the set values inEuropean Norm EN 14961-2, indicating that pellets 5 and 6, meet the EN
14961-2. In view of the results achieved, the mixtures used in this study could considered as promising raw material for the
production of combustion pellets with similar characteristics as commercial pellet Ecomas.
Keywords: Pellets, walnut shells, wheat shells, waste paperboard, EN 14961-2
Obtención y caracterización de Pellets basados en cascaras
de nueces, residuos de cartón y papel
Resumen
A pesar de la continua deforestación en Chile en los últimos 40 años, la producción de pellets para la combustión se
ha ido incrementando, siendo el principal productor Ecomas. Para este estudio, se propusieron 17 formulaciones basadasen
cáscara de nuez y trigo, desecho de cartón y papel Kraft para la obtención de pellets. Sólo 8 formulaciones fueron exitosas
para la producción de pellets, las cuales fueron comparadas con el pellet de Ecomasmediante el contenido de cenizas y
pero un mayor contenido de cenizas. Además, los 8 pellets y el de Ecomas fueron comparados valores establecidos en la
norma europea EN 14961-2, observando que el pellet de Ecomas, y el pellet 5 y 6 cumplen con EN 14961-2. En vista de
los resultados obtenidos, las mezclas utilizadas (5 y 6) podrían considerarse como una potencial materia prima para la
producción de pellets con características similares al pellet comercial Ecomas.
Palabras clave: Pellets, cáscaras de nuez, cáscaras de trigo, cartón residual, EN 14961-2
Rev. Téc. Ing. Univ. Zulia. Volumen Especial, 2019, No. 1, pp. 154-262
182 Pérez y col.
Introduction
There is a growing interest in substituting
fossil fuels by renewable energies[1]. Pellets have
received increasing attention not only for their potential
as renewable energy but also to be considered a clean
(reduction of particulate matter emissions by up to 50%)
and affordable source [2-3]. Combustion pellets are a
standardized solid biofuel of cylindrical shape, whose
production is obtained by pressing the organic material.
Their manufacturing provides an enhancement in the
handling and storage and lower transport costs [4].
attractive Latin-American country for investments in
pellet mills, offering the best results between availability
of biomass, annual yields and low investment risk [5].
However, wood demand for pellets production could
affectsustainability and management of forest by
deforestation, detecting in Chile a continuously decrease of
tree cover [6-7]. In this sense, investigation on alternative
raw materials for pellets production is necessary to
decrease pressure on natural resources.
Chilean government is becoming increasingly
aware of the high level of air pollution caused by residential
and high moisture content. Since 2016, the regional
governments carried out a heating and wood policy
which includes incentives to increase the regional use of
combustion pellets, being the most commercialized pellet
by Ecomas Company with 80% of national combustion
pellets production [8-12]. Therefore, it is expected an
increase on combustion pellets demand and consequently
also on the pressure on wood.
This studyfocus on obtaining pellets composed
by walnut and wheat shells, waste paperboard and Kraft
paper with similar characteristics to commercial pellet
from Ecomas. Resulting and Ecomas pellets will be
characterized according to European norm EN 14961-2.
Materials and Methods
Materials
The raw materials for the present studywere
and the other two from solid household wastes: waste
Characterization of raw materials
Previous to the characterization, the four raw
materials were milled (Retsch Mill, ZM200) at 6000
rpm equipped with a 500 µm sieve. The structural
analysisconsisted of a quantitative method based on
gravimetric analysis to estimate extractives (TAPPI T-264
Hoffer method), hemicellulose and lignin (Klason method)
[13-14].The moisture (M) and ash content (A) was
determined as the residue left after thermal treatment
of raw materials at 105 °C and 575 ± 2.5 °C for 3.5 h in a
heating value (HHV) was carried out using a Parr 6200
calorimetric bomb.
Formulationsproposal and pelletizing
It was proposed 17 formulations with different
process. The formulation was based on the availability
and HHV of raw materials (Figure 1). Moreover, sodium
lignosulfonate between 4 and 10% (w/w) was added to
enhance binding effect among the raw materials during
pelletizing.
Figure 1. Proposed formulations with the raw materi-
als of this study and the sodium lignosulfonate (Na-L) as
binder agent.
A pelletizer machine (Hund Model) was
continuously operated at 100 kg/h (steady state), and
temperature between 80 and 85°C to obtain 3 kg of each
formulation. Between each batch, it was added Na-L for 5
min to avoid contamination. After pelletizing, the pellets
were cooled to room temperature in suitable equipment.
Posterior, the pellets are sieved and the smaller particles
are again inserted in the process as raw materials. The
product that meet the desired dimension are stored in
sealed plastic bags and protected from direct light.
Rev. Téc. Ing. Univ. Zulia. Volumen Especial, 2019, No. 1, pp. 154-262
183Obtaining and characterization of pellets based on walnut shells
Characterization of pellets
Among the formulations, those that visually
met the desired dimensions were characterized and
compared with Ecomas pellet. The characterization
included: (i) moisture content, (ii) average length
and diameter determined by measuring with caliper
(randomly selected), (iii) bulk density determined by
pellets, (iv) ash content by
furnace, (v) the compressibility strength of the pellets
bythe determination of the force at break (Compression
Tester Egeo)and (vi) the determination of HHV using Parr
6200 calorimetric bomb[15-16].
Results and Discussion
Characterization of the raw materials
The quality of the pellets for thermochemical
conversion utilization depends on the physical-chemical
(Table 1 and 2) of the raw materials. Therefore, inquiry
about chemical composition of raw materials from the
present study, would be information about their potential
to form pellets.
Table 1. Moisture content and HHV for raw
materials used in this study.
Samples M*
(%)
HHV*
(MJ/kg)
References
consulted
WaS 8.1 ± 0.7 19.6 ± 1.1
[17-18]
WsS 10.9 ± 0.2 18.3 ± 1.0
WP 5.4 ± 0.7 17.8± 1.3
WKP 5.0 ± 1.4 16.6± 1.1
Range reported 4-10 15.8-32.0
*M: Moisture, HHV: Higher heating value
Table 1 provides the resultsof moisture content
and HHV. Both properties were compared with data
values are in the range reported for such raw materials.
value of moisture content which could be attributed to
the presence of hemicellulose, because the presence of
this structure promotes water absorption. For pelletizing
it is preferred a low content of water to improve the
resistance of the pellets to crumbling effect. Nevertheless,
the presence of water during pelletizing is necessary for
the development of intermolecular forces between the
particles from raw materials. In addition, the HHV is also
affected by a high moisture content. The higher the value
of moisture, the lower the amount of energy produced
and therefore the lower the quality of the resulting pellet.
However, according to the literature reviewed, the effect
understood, acting water as binder and also as lubricant
[19].
Due to almost all values of moisture content
were below 10%, it was decided to desist from the drying
pre-treatment before pelletizing process. Moreover, it is
expected that the high temperature in pelletizer machine,
and the friction between the mixture of raw materials and
reduction of the moisture content of resulting pellets by
evaporation.
Regarding HHV, all raw materials showed values
to the high HHV. Authors reported that there are a positive
the higher value of lignin content.
The chemical composition based on the
structural composition of raw materials are illustrated
in Table 2, indicating that obtained values are within
the values reported in literature [17]. The percentage
values than 11%. The presence of extractables in the raw
pelletizing and the pellet quality, favoring the crumbling
values of cellulose, due to these materials come from the
Table 2. Chemical composition of raw materials and ash
content for all raw materials tested, expressed in percent-
age (% w/w).
Samples Extractables Hemicellulose Cellulose Lignin Ash
WaS 11.7 5.4 27.0 46.5 1.2
WsS 9.2 46.5 8.6 21.7 3.3
WP 14.2 0 75.8 0 4.8
WKP 13.5 0 69.8 0 11.8
Range*
reported 8.5-14.1 0-48.0 8-80 0-32.0 1.0-10.4
*References consulted for range reported: [17-18, 21-22]
The percentage of hemicellulose was higher for
hemicellulose content[23]. The amount of lignin reached
to a better structural stability of the resulting pellets. In
case of the ash content, almost raw materials evidenced a
which could imply a high ash content for the resulting
Rev. Téc. Ing. Univ. Zulia. Volumen Especial, 2019, No. 1, pp. 154-262
184 Pérez y col.
Obtaining ofpellets from proposedformulations
The current study found that from all
formulations tested (Figure 1), only 8 formulations were
possible for pellet production (Formulations 1 to 8). The
formulations without addition of the binder agent (Na-L)
failed. Moreover, pellets (Formulations 9 to 17), observing
a strong crumbling effect in the resulting pellets.
Figure 2. Photos of the obtained pellets with the formula-
tions 1 to 8.
In Figure2 is showed the photos of the
formulations with a successful pelletizing process. These
8 formulations are composed by all raw materials. This
result indicate that the contribution of lignocellulosic
materials, cellulosic materialsand small addition of Na-
L, favors the bonding of particles by intermolecular
attractive forces (e.g. hydrogen bonds).
The characterization of the pelletsare illustrated
in Table 3.All pellets revealed adequate levels of moisture
content, heating value and bulk density(> 550 kg/
m3). Pellets obtained presented similar diameter and
lengths to Ecomas pellets. Regardingmoisture content,
pelletsshowed values(< 2%) lower than Ecomas pellet.
It was observed that the higher the mass contribution
content in the resulting pellets, which could be attributed
to the high water content of both raw materials. The
providing an increase in HHV.
From the results, it also detected that the ash
content in the pellets tends to increase with an increasing
of the Na-L dose. Moreover, the ash content values in the
pellets are higher than the value of Ecomas pellet, but
lower than the value set in the standard norm.
of the pellet, providing an increase in HHV. In addition, an
HHV for the pelletsobtained. This statement corroborate
study carried out by Demirbas [20]. It is clear, that both
values are of great concern for the combustion process in
domestic stoves. From these results, could be suggested
that combustion would generate low particulate matter
emissions.
Regarding the compressibility strength, the values were
reported by Puig-Arnavat et al. [19]. This parameter
behaves with similar trend as the ash content, showing
values between 3.5 and9.1 kN.
In order to enable a better visualization (Figure 3), the
values of HHV, moisture, bulk density and ash content
of all pellets were compared with the set values for the
standard norm EN 14961-2[24].
Figure 3. Comparison on moisture and ash content, HHV,
bulk density among the pellets obtained, Ecomas pellet
and the set values by EN 14961-2[24].
Among the pellets obtained, the moisture con-
Rev. Téc. Ing. Univ. Zulia. Volumen Especial, 2019, No. 1, pp. 154-262
185Obtaining and characterization of pellets based on walnut shells
Table 3. Results from the characterization of the pellets obtained from formulations 1 to 8.
Pellets Diameter
(mm)
Length
(mm)
M*
(%)
HHV*
(MJ/kg)
A*
(%)
BD*
(kg/m3)
Compressibility
Strength (kN)
16 ±0.1 21 ±0.3 0.04 ±0.03 20.2 7.0 ±0.19 556 ±0.02 5.2 ±0.02
26 ±0.2 21 ±0.2 1.88 ±0.05 17.4 5.0 ±0.23 590 ±0.02 6.2 ±0.01
36 ±0.3 23 ±0.3 0.27 ±0.04 20.4 7.9 ±0.05 586 ±0.02 6.21 ±0.01
46 ±0.1 23 ±0.1 0.75 ±0.04 18.2 5.2 ±0.17 579 ±0.02 6.0 ±0.01
56 ±0.1 27 ±0.2 0.29 ±0.01 21.3 6.7 ±0.18 619 ±0.02 9.1 ±0.02
66 ±0.2 25 ±0.1 0.41 ±0.02 18.5 5.5 ±0.21 607 ±0.02 6.2 ±0.01
76 ±0.2 21 ±0.1 0.45 ±0.02 18.8 6.2 ±0.13 586 ±0.02 6.1 ±0.01
86 ±0.2 17 ±0.1 0.55 ±0.02 18.4 4.3 ±0.22 584 ±0.02 3.5 ±0.02
Ecomas 6 ±0.09 25 ±0.1 6 ±0.01 17.9 0.2 ±0.15 640 ±0.2 11.2 ±0.01
*M: moisture content; HHV: higher heating value; A: ash content
tent of all pellets were below 15 % and 6%, corresponding
to EN 14961-2 and Ecomas pellet. In case of ash content,
all pellets obtained meet the EN 14961-2, whereas regard-
ing bulk density only pellet 5 and 6 presented similar val-
ues as the set value of EN 14961-2. Regarding HHV, only
pellet 2 was below the set value of EN 14961-2 (18 MJ/
kg). The other pellets showed an increase of 11 and 16%
compared with Ecomas pellet and the EN 14961-2[24].
These preliminary results (Table 3 and Figure 3) indicates
that pellet 5 and 6 are suitable and could compete in the
regional pellet market with Ecomas pellet. Moreover, both
pellets meet EN 14961-2[24]. Therefore, the formulations
could be recommended for the pellets production.
However, the authors are convinced
that the results obtained in this research are the
Further experimentalinvestigations are needed to
improvethepelletizing process.
Conclusions
for the development of the pellet market in the Chilean
region “La Araucania”. The evidence suggests that walnut
shells, wheat shells, waste paperboard and waste Kraft
paper are potential raw materials for the production of
pellets. In addition, the obtaining of pellets based on these
raw materials could present a high potential to improve
directly from the results, pellets 5 and 6 meet EN 14961-
2 and present higher values of the parameter tested
compared with the current commercial pellet Ecomas.
Acknowledgements
The authors thank the Engineering Faculty
of Universidad Católica de Temucoand in special, PhD.
Patricia Oliveira for the support during production
of pellets, and the support of FONDECYT under grant
11150088.
References
[1] Tauro R., García C.A., Skutsch M., Masera O.: The
potential for sustainable biomass pellets in Mexico:
An analysis of energy potential, logistic costs and
market demand. Renew. Sust. Energ. Rev. Vol. 82,
(2018) 380-389.
[2] Arteaga-Perez L.E, Vega M., Rodríguez L.C., Flores
M., Zaror C.A., Casas L.Y.: Life-cycle assessment of
coal-biomass based electricity in Chile: focus on
Vol. 15, (2015) 29-81.
[3] ThomsonH., LiddellC.: The suitability of wood
pellet heating for domestic households: A review
of literature. Renew. Sust. Energ. Rev. Vol. 42,
(2015) 1362-1369.
[4] Alarcón M., Santos C., Cevallos M., Eyzaguirre R.,
Ponce S.: Study of the mechanical and energetic
properties of pellets produce from agricultural
biomass of quinoa, beans, oat, cattail and wheat.
Industry and Trade Study. International Energy
Agency (IEA). IEA Bionergy (2017).
(2017). https://www.wri.org/blog/2017/10/
global-tree-cover-loss-rose-51-percent-2016
(accessed on 08-10-2018).
[7] Miranda A., Altamirano A., Cayuela L., Lara A.,
Gonzàlez M.: Native forest loss in the Chilean
biodiversity hotspot: revealing the evidence”. Reg.
Environ. ChangeVol. 1, (2017) 285-297.
Rev. Téc. Ing. Univ. Zulia. Volumen Especial, 2019, No. 1, pp. 154-262
186 Pérez y col.
[8] Ministerio del Medio Ambiente del Gobierno
de Chile (MMA). “Informe del Estado del Medio
Ambiente” (2011).
stated preference methods to design cost-effective
subsidy programs to induce technology adoption:
An application to a stove program in southern
Chile. J. Environ. Manage. Vol. 132, (2014) 346-
357.
from a pilot program to induce stove replacements
in Chile: design, implementation and evaluation.
Environ. Res. Lett. Vol. 12, (2017) 1150011.
convertirse en el combustible del futuro” (2016).
http://www.corma.cl/corma-al-dia/biobio/el-
el-combustible-del-futuro (accessed on 12-05-
2016).
[12] Unidad de Desarrollo Tecnológico de la Universidad
de Concepción (UDT). Producción de pellets
en Chile y tecnologías de combustión, (2013).
http://www.mma.gob.cl/1304/articles-55266_
PresentacionPellets.pdf (accessedon 12-15-2016).
[13] Technical Association of the Pulp and Paper
Industry (TAPPI): T 264 cm-07. Preparation of
[14] Technical Association of the Pulp and Paper
Industry (TAPPI). TAPPI Test Methods 2000 –
2001. TAPPI Press. Atlanta, United States, (2000).
[15] EN 15103. Biocombustibles sólidos. Determinación
de la densidad a granel. (2009).
[16] EN 14774-2. Determinación del contenido de
humedad. Método de secado en estufa. Parte 2:
[17] Romero-UscangaE., Montero-AlpírezG.,
Toscano-PalomarL., Pérez-PelayoL., Torres-
RamosR.,Beleno-CabarcasM.T.: Determinación
de los principales componentes de la biomasa
lignocelulósica; celulosa, hemicelulosa y lignina de
biológico. Conference: XVII Congreso Internacional
en Ciencias Agrícolas, Agricultura sustentable: Uso
proceso de incineración con generación de energía.
Información tecnológicaVol. 20, (2009) 105-112.
[19] Puig-Arnavat M., Shang L., Sárossy Z., Ahrenfeldt
J., Henriksen U.B.: From a single pellet press to a
bench scale pellet mill-Pelletizing six different
biomass feedstocks. Fuel Process. Technol. Vol.
142, (2016) 27-33.
and heating values of biomass.Energ. Convers.
Manage.Vol. 42, (2001) 183-188.
[21] Gonzalvo S., Nieves D., Ly J., Macías M., Carón M.,
Martínez V.: Algunos aspectos del valor nutritivo
de alimentos venezolanos destinados a animales
monogástricos. Livestock Res.Vol. 13, (2001).
structure and properties. Elsevier, Amsterdam, the
Netherlands (2008) p. 201-224.
[23] DöringS.: Biomass types for pellet production. In
Power from Pellets. Springer Verlag, Berlin, (2013)
p. 13-30.
[24] UNE-EN 14961-2:2012. “Solid biofuels - Fuel
for non-industrial use”. https://www.une.
org/encuentra-tu-norma/busca-tu-norma/
norma/?c=N0049135(accessed on 12-05-2016).
REVISTA TECNICA
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UNIVERSIDAD DEL ZULIA
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Esta revista fue editada en formato digital y publicada
en Diciembre de 2019, por el Fondo Editorial Serbiluz,
Universidad del Zulia. Maracaibo-Venezuela
Volumen Especial, 2019, No. 1, pp. 154 - 262_______________
