Pelletization of Carbonized Wood Using Organic Binders with

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Biofuels and Biomass

Pelletization of carbonized wood using organic binders with biomass gasification residue as additive XIN DAI, Sarut Theppitak, and Kunio Yoshikawa Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b03372 • Publication Date (Web): 10 Dec 2018 Downloaded from http://pubs.acs.org on December 16, 2018

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Energy & Fuels

Pelletization of carbonized wood using organic binders with biomass gasification residue as additive Xin Dai*, Sarut Theppitak, Kunio Yoshikawa School of Environment and Society, Tokyo Institute of Technology G5-8, 4259 Nagatsuta, Midori-Ku, Yokohama 226-8502, Japan. Keywords: pelletization; carbonized wood; binder; biomass gasification residue; tar.

ABSTRACT: Integrating carbonization and pelletization becomes an attractive technology for energy usage of biomass resources. But challenges still remain for the densification of carbonized biomass. Firstly, the pellet quality by using lignin, starch and polyvinyl alcohol (PVA) as binder was compared. PVA performed the best both on the pellet strength and hydrophobicity. Furthermore, a new pelletization method by using organic binders coupled with additives was suggested to enhance the pellet strength. The strength of PVA pellet increased by employing the biomass gasification residue (BGR) as additive. Mechanism of the influence of the binder and the BGR additive to the pellet quality was discussed. Overall, applying PVA as a binder and BGR as additive could be an adequate method to produce carbonized pellet with high quality. Using BGR as additive for pelletization gives a chance to reduce the binder usage and also provides a good disposal method of the BGR.

wood will cause a low gasification efficiency.3 The

1. INTRODUCTION

optimum temperature for wood gasification is below 700

In order to build a more sustainable society, renewable biofuels can be a kind of substitutes for fossil fuels. For

oC.

example, wood is considered as a clean source of energy,

gasification temperatures are required. Thus, wood will be

featured with low nitrogen, sulphur, and ash contents as

over-oxidized in the gasifier.4 Moreover, the formation of

well as low carbon dioxide emission. Efficient wood

condensable tars during the wood gasification process will

conversion technologies are still in need of development.

block the pipe lines or damage the down-stream

Compared

equipment.

with

pyrolysis

and

direct

combustion,

However in the practical applications, a higher

gasification is the most efficient process.1 There are still a

Carbonization, which can be defined as mild pyrolysis in

lot of challenges in the gasification process because of

an inert atmosphere, can enhance the energy properties of

unsatisfied fuel properties of woody biomass. Firstly, the

the raw wood. Feedstock with higher bulk and energy

raw wood has relatively low bulk and energy densities, high

densities can be further produced by a following

moisture content, which make the on-site delivery, storage

densification process. These processes are important not

and usage complex.2 Secondly, high O/C ratios of the raw

only for benefiting the transportation and storage, but also

1

ACS Paragon Plus Environment

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Page 2 of 14

ensuring the stable gasification process for fixed bed

the tar during thermal conversion process. Inorganic

gasifiers. A downdraft gasifier is featured with its easy

reagent such as sodium hydroxide can be used for

fabrication and operation which makes it suitable for small

pelletization to soften the remained lignin in torrefied

scale application.5 Main challenges for a downdraft gasifier

biomass. But it caused the high hygroscopicity of the

are blocking, channeling, bridge and so on, especially for

pellet.18

feedstock with low bulk density.6 Low bulk density of

The goal of this research is to achieve a low die

feedstock will restrict the flow of fuel bed thus result in

temperature pelletization of carbonized woody biomass

bridging.7 Also small particles generated from the breaking

with high pellet quality and low tar generation potential. A

of feedstock in the fixed bed gasifier will lead to high

new method by using binders coupled with additives was

pressure loss. Therefore, there are a huge need for the

suggested in this research. By adding suitable additives, we

densification of carbonized woody biomass. Challenges are

can achieve higher pellet quality with similar or less binder

still remained for the densification. Woody biomass

usage. Polyvinyl alcohol (PVA) is a kind of water-soluble

contains a large amount of lignin which can act as a binder

synthetic polymer which has relatively high tensile

during the densification. The glass transition of lignin has

strength that can be used in textiles, composite synthesis

a strong impact on the pelletizing properties.8 After

and others areas.19-21 In some industries have been using

carbonization, the structure of lignin changed, which will

PVA as a crosslinking agent to produce biomass

increase the glass transition temperature of

Because of

biocomposites.22 In this research, the properties of pellets

the relatively high glass transition temperature of the

using PVA, lignin and starch as a binder were compared.

carbonized biomass, there is a narrow process window for

Binders can further improve the quality of pellets by the

the pellet production with a good

quality.10

it.9

Pelletization of

development of solid bridge between particles. However,

carbonized woody biomass by the moisture conditioning

the tar generation during the gasification process which

at high die temperature is reported.11, 12 In this case, a die

caused by the reintroduced organic binder has been

temperature over 170 oC is required, which causes a high

overlooked for a long time. Especially for an updraft fixed

risk of firing and dust explosion. It also made the operation

bed gasifier, the tar generated from the pyrolysis zone

difficult and increased the production cost.13

could be one of the main sources of the tar content in the syngas. The usage of organic binders should be reduced in

Some studies have explored the pelletization of torrefied

regards to the economy or to the tar issues.

biomass by using binders. Starch and lignin are two of the most widely used binder which can improve the quality of

It could be a solution to strengthen the polymer films of

torrefied pellet.14 Another method is to introduce raw

binder by adding fly ash additive.23 Walter Christopher

biomass materials as a binder during pelletization.

Wilfong, et al. achieved pelletization of immobilized amine

Xiaopeng Bai, et al. used the peanut shell as the binder

CO2 sorbents by utilizing Poly (vinyl chloride) binder and

source during the densification of torrefied wheat straw

coal fly ash additive. The physical interlocking of large

and the best densification condition was identified with

sorbent particles by small fly ash particles can increase the

the 15% peanut shell and 10% water content with the die

strength of the pellet.24 But for thermal conversion usage it

temperature of 120

oC.15

The main composition of peanut

may cause the fusion problem or reduce the process

shell are lignin, cellulose and hemicellulose which can act

efficiency. Recently, with the development of biomass

as binders during densification. Saw dust is another

gasification technology, a large amount of solid residue

effective binder for densification.16 Compared with starch

which is called biomass gasification residue (BGR) in this

and lignin, raw biomass binder have similar binder quality

research was produced. BGR have low content of ash and

but lower price.17 But the raw biomass could be a source of

high content of amorphous carbon which can be used as

2


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Energy & Fuels

feedstock for gasification.25 How to dispose this kind of

thoroughly. The concentration of the binder and water is

residue appropriately is still a problem for the biomass

presented by eq 2. In this study, about 0.25 g of feedstock

gasification process. To our best understanding it is the

was used to make one pellet. The compress pressure was

first time to use BGR as additive for the pelletization of

set at 100 MPa with the die temperature of 100 oC. In this

carbonized woody char. Firstly this could be an attractive

research, BGR was collected from a pilot scale updraft

method to reuse BGR as fuel thus increase the whole

fixed-bed gasifier using carbonized woody pellet as

energy efficiency of the biomass gasification process.

feedstock. The temperature distribution in the gasifier

Secondly it could be a solution to increase the quality of

from the drying layer to the combustion layer was around

carbonized woody pellet by adding BGR as an additive.

200 oC to 1000 oC. During gasification, feedstock was

2. EXPERIMENTAL SECTION

discharged from the bottom grate of the gasifier which was collected as BGR. The detail of the gasification process was

2.1. Carbonization Method. Sawdust of Japanese cedar

described in the previous work.27 Before making pellets,

was used as feedstock for the carbonization. Sawdust was

biomass gasification residue was crushed and sieved. The

firstly sieved into uniform particle size ranged from 0.5 mm

BGR particles whose size is less than 1.0 mm were collected

to 1.0 mm and then kept at 105 oC over night for drying

and kept at 105 oC oven over night for drying. The additive

before the carbonization. The carbonization was achieved

amount of BGR is defined as eq 3.

by a lab-scale fixed-bed carbonizer. Nitrogen was purged into the reactor for 10 minutes to keep the feedstock under

C binder/water 

an inert atmosphere before increasing the temperature.

Wbinder/water  100% （Wbinder  Wchar  WBGR )

(2)

The carbonization underwent from 300 oC to 450 oC with the interval of 50 oC. The holding time was fixed at 1 hour.

C BGR

Table 1 shows the fuel characterization of the raw and the carbonized wood char. Higher heating value (HHV) is



WBGR  100% （WBGR  Wchar  Wbinder )

(3)

calculated by eq 1.26

where Wbinder, Wchar, Wwater and WBGR represent the added amount of the binder, the char, water and the

HHV  0.3491C  1.1783H  0.1005S  0.1034O  0.0211A (MJ/kg)

biomass gasification residue, respectively.

(1)

2.3. Pellet Characterization. The strength of the pellet where C, H, O, N, S, and A represent the weight

was measured by using a tablet strength tester. The tester

percentage of carbon, hydrogen, oxygen, nitrogen, sulfur

was equipped with two identical flat steel plates. One plate

and ash contents of the material, respectively.

was fixed in the base and the other one was attached to the

2.2. Pelletization Method. The densification of

upper moving crosshead. A pellet was placed horizontally

carbonized char was carried out by a press machine which

on the bottom plate, while the moving crosshead moved

is able to operate at various loading forces. A cylinder with

slowly. The maximum load to break the pellet was

the inner diameter of 6.55 mm and the length of 60 mm

recorded. The strength of single pellet is calculated by

with a piston of 6.50 mm diameter was installed on the

using the maximum breaking force (N) divided by the

press machine to make a single pellet. The cylinder was

length (mm) of the pellet. The volume density was

wrapped by a heating tape with a thermocouple and a

calculated by using the weight of the pellet dived the

temperature controller, to preheat the cylinder to a certain

volume.

temperature (also called the die temperature). Firstly,

A humidity chamber with the humidity of 75% was

wood char was mixed with a binder at different ratios. After

prepared by supplying saturated sodium chloride solution

that, 26% of water was added into the feedstock and mixed

3


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in a desiccator. The pellet was put on the holder of the

huge decrease of oxygen and hydrogen contents, whilst the

desiccator and the weight of single pellet was recorded at

carbon content increased. A lower O/C ratio can bring a

a certain period of time. Moisture uptake is represented by

higher gasification efficiency, and, with the change of C, H

using the weight of moisture (g) absorbed by one pellet

and O, the higher heating values (HHV) of raw cedar wood

divided by the weight of the pellet at the beginning.

increased apparently from 19.51 MJ‧kg-1 to 32.32 MJ‧kg-1. It

A scanning electron microscope (SEM: S-5200 (Hitachi),

can be said that the carbonization can be used as an

1 kV) analysis was conducted to study the morphological

effective technology to improve the fuel property of raw

structure of the pellet. A small notch was created in the

biomass.

middle of the pellet and then the pellet was divided into

The pyrolysis experiment was conducted to study the tar

half. A slice of the sample was collected from the fracture

generation potential of carbonized wood char. Pyrolysis

section for the SEM observation.

temperature was set at 600 oC. The tar production of wood char carbonized at four carbonization temperatures, 300

2.4. Pyrolysis Method. Heavy tar produced from

oC,

pyrolysis of wood char or pellet was measured in this

350 oC, 400 oC and 450 oC, was 11.1%, 3.7%, 3.0% and

research. A fixed bed reactor was used for the pyrolysis.

1.7%, respectively. Lignin, cellulose and hemicellulose are

About 5 g of feedstock was put into the reactor. Before the

the main sources of tar during gasification.28 When the

pyrolysis, nitrogen was purged for 10 min in order to ensure

carbonization temperature is over 300 oC, large amount of

an inert condition in the reactor. The pyrolysis

cellulose and hemicellulose decomposed and the structure

temperature was set at 600 oC and the holding time was 30

of remained lignin is changed by the dehydrations.11

min. Four impingers containing 100 mL isopropanol each

Consequently, the tar generation potential of carbonized

was used for the tar collection. After the sampling, all

char will be reduced. From this point, the carbonization

isopropanol in each impinger was collected together and

could be an effective method for tar reduction.

then evaporated by a rotary evaporator. The residue after

3.2. Influence of Carbonization Temperature on

evaporation was defined as heavy tar. The tar production

Pellet Quality. Many works have been done for the

is calculated by using the weight of tar (g) generated during

densification of wood char which carbonized at lower

the pyrolysis divided by the total weight of the supplied

temperature. Because of the decomposition and the

feedstock (g).

structure change of natural binders in the raw biomass, a

3. RESULTS AND DISCUSSION

decreasing of the pellet quality was observed by increasing the carbonization temperature from 250 oC to 300 oC.8 It

3.1. Basic Fuel Properties of Wood Char. The

caused the failure of the pelletization when the

proximate and ultimate analysis results are presented in

carbonization temperature increased to 300 oC with the die

Table 1. The results show that the final carbonization

temperature of 100 oC.29 A different trend was observed in

temperature had a great impact on the fuel characteristics

the pelletization of the severely carbonized wood char

of wood char. During the carbonization, water was reduced

(carbonized at the temperature from 300 oC to 450 oC) with

from the raw wood by drying and dehydrations. The

9.09% of PVA addition as a binder, and the die

hydroxyl groups in the feedstock also decreased by the

temperature of 100 oC in this research. The density and the

decomposition and the structure change of lignin,

strength of the pellet using the char produced at different

cellulose and hemicellulos. As a result, there was a trend of

carbonization temperatures are shown in Figure 1. The

decreasing the volatile matter and increasing the fixed

strength of the pellet increased from 2.72 N‧mm-1 to 24.02

carbon as the carbonization conditions became severe.

N‧mm-1 when the carbonization temperature increased

From the ultimate analysis, we can see that there was a

from 350 oC to 450 oC. The glass transition temperature of

4


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Energy & Fuels The pellet with the binder concentration of 9.1% was

lignin increased with the increase of the carbonization temperature. When it is higher than the die temperature,

used

for

the

hydrophobicity

experiment.

The

lignin cannot act as a binder. At the same time, the elastic

hydrophobicity of pellets was presented by the moisture

nature of lignin which can be indicated by the modulus of

uptake rate. It can be seen from Figure 2(b), PVA binder

elasticity (MOE) will decreases by increasing the thermal

showed the best hydrophobicity quality, especially for the

It can be concluded that the

first 8 hours. After 8 hours exposure, the moisture uptake

increase in the carbonization temperature thus reduce the

of pellets made from lignin, PVA and starch binders were

elastic nature of lignin which can enhance the pellet

7.5%, 6.1% and 6.9%, respectively. The smooth surface of

quality significantly in this carbonization temperature

the pellet with PVA binder might prevent the moisture

range. There was a slight decrease of the pellet strength

uptake. The final moisture uptake amount of PVA, starch

treatment

from 3.40

temperature.30

N‧mm-1

to 2.72

N‧mm-1

and lignin pellets were 8.1%, 8.3% and 8.6% respectively,

when the carbonization It can be say,

after 24 h exposure at 75% relative humidity. The

that the deterioration of the binder property of lignin by

equilibrium moisture content of spruce char after 310 oC

increasing

this

carbonization is about 2% which is much lower than the

temperature range. In other words, the benefit from the

pellet with binders.11 Such difference is highly related to the

decrease of MOE by increasing the temperature cannot

hydrophilic of the binder used in the pellet. PVA pellet

compensate the side effect caused by the binder loss.

showed a better hydrophobicity than starch and lignin

Compared with the increase of the strength, the density of

pellet.

temperature increased from 300 the

oC

temperature

is

to 350

oC.

dominant

in

the pellet was not significantly increased by increasing the

The pellet with the binder concentration of 9.1% was

carbonization temperature. That may due to more pore

used for the pyrolysis experiment to determine the tar

structure of char generated at a higher carbonization

generation potential of pellet. Tar production from PVA,

temperature.

starch and lignin pellet were 7.5%, 6.5% and 4.0%

3.3. Influence of Binders on Pellet Quality. The

respectively, while the tar production from the cedar char

compressive strength of the pellets made from cedar char

carbonized at 450℃ was 1.7%. The lignin binder, showed

with different binders is shown in

lower tar production compared to other binders. That may

Figure 2(a). The highest strength was achieved at the

be related to the higher thermal stability of lignin under

highest binder content group for both lignin and PVA.

600 oC condition. One of the reason for carbonization is to

While for the starch, it was achieved at 9.1% concentration

reduce tar generation potential of raw feedstock during

group. This indicates that an appropriate quantity of

gasification. For purpose of pelletization, the reintroduce

binder is needed to make a strong pellet. A huge

of binder enhanced the tar generation potential of

differences of pellet strength was observed by using

carbonized pellet. Efforts should be made to reduce the

different binders. The best strength achieved by lignin,

usage of binder to prevent the tar generation caused by

PVA and starch were 3.58 N‧mm-1, 26.32 N‧mm-1 and 14.86

binders.

carbonized at 450

oC

N‧mm-1, respectively. During the pelletization binder

3.4. Biomass Gasification Residue as an Additive. In

softens and flows between adjacent particles which formed

order to produce pellet with high quality as well as less

the solid bridge by

hardening.31

Strength of solid bridge

binder usage, a new pelletization method which using

was determined by binder type which act as one of the

binder coupled with additive was employed in this

main factor on pellet strength. In regarding to the strength,

research. BGR was added as an additive to increase the

PVA is much better than lignin and starch.

strength of the pellet with the PVA binder. The proximate and ultimate analysis results of BGR are shown in Table 1.

5


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Page 6 of 14

BGR was composed of 83.6 %wt of fixed carbon and

d display the structure feature of particle agglomeration of

15.3 %wt of volatile matter. It can be used for gasification

9.1% PVA binder pellet without BGR. Because of the

with a high gasification reactivity and a low tar generation

angular structure of the char particles, a large amount of

potential. Different amount of BGR was added to each

gaps were created thus reduced the contact area between

binder concentration group with the water concentration

particles. The significant gaps and voids between the

of 26.0%. The result of the strength test is shown in Figure

adjacent particles could be the reason which reduced the

3 a. The strength of the pellets was enhanced by BGR

hardness of the carbonized pellet.35, 36 SEM image of BGR is

addition for each PVA concentration group. For the 4.9%

shown in Figures 4 e and f. It is noteworthy that there are

and 9.1% PVA group, the highest strength was achieved

lots of fine and less regular particles in BGR additives.

when the BGR content was 8.7% and 8.3%, with the

Particle agglomeration in the pellet with 9.1% of PVA

to 20.11

binder and 8.3% of BGR is shown in Figures 4 g and h. As

N‧mm-1,

shown in Figure 4 g, less angular BGR particles can fill the

respectively. For the 12.9% PVA concentration group, the

spaces between larger wood char particles. In Figure 4 h, it

highest strength was achieved at the BGR content of 4.3%

can be seen that smaller BGR particles can be gathered

with the strength of pellets increasing from 26.32 N‧mm-1

together with binder and attached on the surface of char

to 35.27 N‧mm-1. It can be concluded that BGR can be a

particles that will reduce the distance between adjacent

good additive from the pellet strength basis as well as its

particles. As a result, the gaps between char particle can be

good fuel properties and low tar generation potential. The

reduced by adding BGR and the contact area between

pelletization with BGR additive can reduce the binder

adjacent particles increased. This also can be proved from

usage therefore to reduce the cost and minimize the side

the changes of the density after adding BGR. It can be seen

effect from binder addition.

from Figure 3 b, that the density of the single pellet

strength of pellets increased from 11.08 N‧mm-1

and from 22.34

N‧mm-1

N‧mm-1

to 27.86

3.5. Binding Mechanism. It is important to understand

increased after adding of BGR that means the void in the

the bonding mechanisms between biomass particles in a

pellet reduced. Therefore, more solid bridge generated and

pellet to produce high quality products. Nalladurai Kaliyan

the strength of the pellet increased. Nevertheless, the less

and R. Vance Morey concluded that during the densification

angular property of BGR particles may reduce the

of corn stover and switchgrass, the bonding between

mechanical interlocking force between particles which is

particles was mainly created by solid bridges.32 It is also

not in favor of the pelletization, especially for the low

reported by other researchers that the solid bridge plays a

binder does group.

key role during the densification of raw biomass.33 During

It can be concluded that the angular structure of

the densification of raw biomass, a natural binder such as

carbonized wood char during the densification created

lignin flows and inter-diffuses between adjacent particles,

noteworthy voids in the pellet. That hindered the

and after hardening, the solid bridge was formed.34 For the

development of solid bridge and reduced the strength of

densification of carbonized biomass, binders could be

the pellet. Although the binder type has a significant

introduced to compensate the loss of natural binders after

impact on the pellet strength by influencing the solid

carbonization.17, 18

bridge force, adding additives such as BGR to increase the

The SEM figure of the carbonized char made from 450 oC

contact area between adjacent particles could be another

carbonization is shown in Figures 4 a and b with different

important method to increase the quality of carbonized

magnification ratios. A hollow structure can be observed.

pellet. Using high quality binder, such as PVA, coupled

During the densification, char is broken up into small

with the addition of specific amount of BGR can produce

angular particles and compressed together. Figures 4 c and

the carbonized wood pellet with high quality.

6


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Energy & Fuels

4. CONCLUSIONS

[2] Kumar, L.; Koukoulas, A. A.; Mani, S.; Satyavolu, J. Integrating Torrefaction in the Wood Pellet Industry: A Critical

A higher carbonization temperature are chosen to

Review. Energy Fuels 2017, 31 (1), 37-54.

achieve a better pellet quality and a lower tar generation potential. The pellet using the PVA binder showed a higher

[3] Prins, M. J.; Ptasinski, K. J.; Janssen, F. J. J. G. From coal to

strength and hydrophobicity than the ones using the

biomass gasification: Comparison of thermodynamic efficiency.

traditional lignin and starch binders. PVA can be a kind of

Energy 2007, 32 (7), 1248-1259.

suitable binder to produce carbonized wood pellet with a

[4] Prins, M. J.; Ptasinski, K. J.; Janssen, F.J.J.G. More efficient

high strength. Tar generation potential from binders was

biomass gasification via torrefaction. Energy 2006, 31 (15), 3458-

identified which suggested that we would better to reduce

3470.

the organic binder usage in regards to the tar reduction.

[5] Reed T, Das a. Handbook of Biomass Downdraft Gasifier

The angular shape of carbonized wood particles limited the

Engine Systems; Solar Energy Research Institute (SERI): Golden,

formation of solid bridge from a binder. To address this

CO, 1988; Vol. SERI/SP-271-3022.

issue, a new pelletization method was suggested. Additive

[6] Susastriawan, A. A. P.; Saptoadi, H.; Purnomo. Small-scale

was added with binder. BGR was used as an additive to

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produce carbonized pellet with high strength along with

and Sustainable Energy Reviews 2017, 76, 989-1003. [7] Akay, G.; Jordan, C. A. Gasification of Fuel Cane Bagasse in

less binder usage. It is also an attractive option for the

a Downdraft Gasifier: Influence of Lignocellulosic Composition

recovery of BGR.

and Fuel Particle Size on Syngas Composition and Yield. Energy &

AUTHOR INFORMATION

Fuels 2011, 25 (5), 2274-2283. [8] Stelte, W.; Clemons, C.; Holm, J. K.; Ahrenfeldt, J.;

Corresponding Author

Henriksen, U. B.; Sanadi, A. B. Fuel Pellets from Wheat Straw: The

*Tel: +81-45-924-5507. Fax: +81-45-924-5518.

Effect of Lignin Glass Transition and Surface Waxes on Pelletizing

*E-mail: [email protected].

Properties. BioEnergy Res. 2012, 5 (2), 450−458.

Notes

[9] Nanou, P.; Huijgen, W. J. J.; Carbo, M. C.; Kiel, J. H. A. The

The authors declare no competing financial interest.

role of lignin in the densification of torrefied wood in relation to

ACKNOWLEDGMENTS

the final product properties. Biomass Bioenergy 2018, 111, 248-262.

This work has been supported by Innovative Science and

[10] Rudolfsson, M.; Stelte, W.; Lestander, T. A. Process

Technology Initiative for Security (Ministry of Defence,

optimization of combined biomass torrefaction and pelletization

Japan). We would like to thank the Chinese Scholarship

for fuel pellet production–A parametric study. Applied Energy

Council (CSC) for the financial support under the Grant No.

2015, 140, 378-384.

201608050031. The authors thank Suzukakedai Materials

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Analysis Division, Technical Department, Tokyo Institute of

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Technology, for ultimate analysis.

residence time on continuous torrefaction of spruce wood. Fuel Process. Technol. 2015, 134, 387-398.

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Page 9 of 14 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels pellets obtained from different woody and non woody biomasses.

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Carrasco, J. E. Study on the effects of raw materials composition and pelletization conditions on the quality and properties of

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Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 14

Table 1. Proximate and ultimate analysis of raw cedar wood, wood chars produced at different pyrolysis temperatures and BGR C

O

H

N

S

H/Ca

Unit

%

%

%

%

%

Raw

48.69

44.72

6.13

0.16

0.01

1.51

300 oC

72.85

18.95

4.56

0.27

0.14

350 oC

77.01

16.71

4.02

0.34

400 oC

82.18

12.57

3.62

450 oC

84.74

9.45

BGR

87.81

7.36

O/Ca

HHV

Ash

VM

FC

MJ‧kg-1

%

%

%

0.69

19.51

0.3

84.5

15.2

0.75

0.20

28.83

0.4

42.9

56.7

0.14

0.63

0.16

29.87

0.4

37.9

61.7

0.31

0.15

0.53

0.11

31.64

0.6

32.5

66.9

3.18

0.39

0.10

0.45

0.08

32.32

0.7

27.2

72.1

1.80

0.59

0.14

0.25

0.06

32.00

1.1

15.3

83.6

a: atomic ratio.

10


Page 11 of 14

35

800 750

698.59

650

550

492.92

460.48

25

24.02

510.71

-1

-3

600

20

500 15

450 400

7.15

350 300

3.40

10 5

2.72

250 200 280

300

320

340

360

380

400

420

440

460

0

Carbonization Temperature (oC)

Figure 1. Quality of pellet using the char produced at different carbonization temperatures.

11


Strength (N¡¤ mm )

30

700

Density (kg¡¤ m )

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Energy & Fuels 30

10

26.32 22.34

(a)

(b)

20

14.86 11.08 10

7.57

6.36

Moisture uptake (%)

8

Strength (N·mm-1)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 14

6

4 PVA Starch Lignin

2

3.58 1.82 1.59 0

0

4.9% 9.1% 12.9%

4.9% 9.1% 12.9%

4.9% 9.1% 12.9%

Lignin

PVA

Starch

0

5

10

Time (h)

Figure 2. Influence of the binder type on the strength (a) and the hydrophobicity (b) of pellets.

12


15

20

25

Page 13 of 14

a

40

740

710.7 714.9 715.2 698.6

b

720

20

PVA (%)

709.1 703.6

665

680

665.5

646.8 660

628.3 640 620

10 BGR (%)

710.7

689.6

700

30

Density (kg‧ m-3)

Strength (N·mm-1)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

0

4.7 4.9

8.7 16.0

0

4.5

8.3 15.4

9.1

0

4.3

8.0 14.8

12.9

600

BGR (%)

0

8.7

4.7

PVA (%)

16.0

4.9

Figure 3. Influence of BGR to the strength (a) and the single pellet density (b) of PVA pellet.

13


0

8.3

4.5 9.1

15.4

0

4.3

8.0

12.9

14.8

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

a

c

b

d

e

g

f

h

Page 14 of 14

Figure 4. SEM images of a, b: 450 oC carbonized char; c, d: agglomeration of char with PVA binder; e, f: BGR; g, h: agglomeration of char with PVA binder and BGR.

14


Pelletization of Carbonized Wood Using Organic Binders with

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