Optimizing the Pyrolysis Process and Modelling the Caloriﬁc Value of

Sawdust Charcoal as Composing Materials of Quality Briquettes

Musabbikhah

, Samsul Bakri

Mechanical Engineering Department, Akademi Teknologi Warga Surakarta

Accounting Department, Universitas Widya Mataram Jogjakarta

Keywords:

Optimization, Pyrolysis, caloriﬁc value, sawdust charcoal, model, briquettes.

Abstract:

This study aims to optimize the pyrolysis process and build caloriﬁc value model of sawdust charcoal as

composing materials of quality briquettes to fulﬁll the need of renewable fuels. The results showed that the

caloriﬁc value of sawdust increased by 2344 Cal/g after pyrolysis. The optimum conditions of caloriﬁc value

were achieved at drying temperature parameters of 60°C, pyrolysis temperature of 600°C, holding time of

120 minutes, and particle size of 100 mesh. The linearity test results between the value of R, R Square, and

Adjusted R Square of the caloriﬁc value showed there is a strong correlation between drying temperature,

pyrolysis temperature, holding time, and particle size. Based on validation test, the caloriﬁc value model

showed that the residual normality distribution (P-value) was > 0.05 which did not form a certain pattern

on the assumption of homoscedasticity, no multicollinearity (T OL > 1; V IF < 10) and the DW value was

between the speciﬁed range. The model was declared valid. Based on the feasibility test model, P-value was

(0.000) < α (0.05). This means the model of proper caloriﬁc value was reliable to be used to predict the

sawdust charcoal caloriﬁc value.

1 INTRODUCTION

Energy demand is increasing every year with increas-

ing population. One of the main energy sources

needed by humans is the energy source from fossils.

The availability of this fossil energy source will grad-

ually run out, so that it becomes a serious problem be-

cause it cannot be renewed. High dependency on fos-

sil resources combined with the need to reduce CO

emissions due to the climate change force people to

utilize renewable energy sources, including biomass.

Biomass is a renewable energy source required to

meet the energy needs, and is also used for carbon

neutrality as a means of preventing climate change.

Vargas (Vargas-Moreno et al., 2012) states that ad-

vanced societies have replaced the use of fossil fuels

with biomass. Wisakha (Wisakha, 2015) explains that

biomass is able to produce continuous heat, therefore

it can be used to replace fossil fuel. One of the renew-

able energy from biomass as a constituent material for

briquettes is sawdust (Lela et al., 2016).

Pyrolysis is needed by sawdust used to make bri-

quettes. Pyrolysis is a thermal degradation process of

solids in the absence of oxygen which allows the oc-

currence of several thermochemical conversion path-

ways so that the solid changes into gas, liquid, then

back to its solid form (Blasi, 2008). Furthermore,

Basu (Basu, 2013) explains that the pyrolysis reaction

from biomass is as follows:

CnHmOp

∑

liquid → CxHyOz +

∑

gasCaHbOc +

O +C (1)

Heat pyrolysis (thermolysis) decomposition is of

organic matter, such as coal heated more than 300

C°without atmospheric air. The selection of biomass

materials to produce carbon is based on the avail-

ability of materials, costs and the ability to be con-

verted into porous carbon powder after carbonization

(Kalyani and Anitha, 2013). In this study, the qual-

ity of sawdust charcoal is in terms of caloriﬁc value

which indicates the energy contained in the fuel per

unit mass of fuel (cal/g). This research is in accor-

dance with the development of solid bio-fuel using a

wood pellet model (Giacomo and Taglieri, 2013).

The research conducted (Lela et al., 2016) con-

cerning the physical, mechanical and thermal proper-

ties of sawdust briquettes is used as a reference for

fuel quality. The optimal value obtained for the bri-

quette making process parameters is the compression

strength of 588.6 KN, sawdust mass of 46.66% and

drying temperature of 22 C°. Based on the mathemat-

Musabbikhah, . and Bakri, S.

Optimizing the Pyrolysis Process and Modelling the Caloriﬁc Value of Sawdust Charcoal as Composing Materials of Quality Briquettes.

DOI: 10.5220/0009882402630267

In Proceedings of the 2nd International Conference on Applied Science, Engineering and Social Sciences (ICASESS 2019), pages 263-267

ISBN: 978-989-758-452-7

263

ical model, the optimal values generated are caloriﬁc

values increased to 17.41 MJ/kg, ash content de-

creased to 6.62% and maximum compressive strength

is of 149.54 N/mm2. Research on sawdust briquettes

was also carried out by (Stolarski et al., 2013) which

showed that the highest caloriﬁc value in sawdust bri-

quettes was 18.144 MJ/kg. Moreover, sawdust bri-

quettes have an effect of 0.40% on ash content.

2 MATERIAL AND METHOD

2.1 Material

The material used in pyrolysis is sawdust powder

from teak wood.

2.2 Method

Data collection of pyrolysis process and caloriﬁc

value refers to orthogonal L9(3)4 arrays. The in-

dependent variables used in the study were drying

temperature, pyrolysis temperature, holding time, and

particle size. The dependent variable to determine

the quality of sawdust charcoal is the caloriﬁc value.

The method for optimizing pyrolysis parameters is

Taguchi, while for modelling of caloriﬁc value is mul-

tiple linear regression model (MLRM) analysis.

3 RESULTS AND DISCUSSION

The effect of level factor differences on the sawdust

charcoal caloriﬁc value which has the highest aver-

age caloriﬁc value of 6231 cal/g was achieved at dry-

ing temperatures of 60 C°, pyrolysis temperature of

600 C°, holding time of 120 minutes, and particle

size of 100 mesh. The caloriﬁc value is inﬂuenced

by water content and carbon content. This study is

in line with the research of (Sundaram et al., 2016)

which states the water content of the particles changes

with the variation of drying time in ﬂuidized bed dry-

ing. The same study was also carried out by (Wilk

et al., 2016) who stated that the carbonization of wood

residue into charcoal occurred during the low temper-

ature process.

3.1 Normality Test

The normality test of the Sawdust Charcoal caloriﬁc

value variable uses a signiﬁcance level of α = 0.05

and the Shapiro-Wilk statistical test shows that P −

value = 0.915. Therefore, H0 is accepted. It means

that Caloriﬁc value of sawdust charcoal variables are

normally distributed and are presented in Figure 1 and

Figure 2.

Figure 1: Normality Test of caloriﬁc value.

Figure 2: Normality Test of caloriﬁc value (extension).

a Lilliefors Signiﬁcance Correction

3.2 ANOVA

Based on ANOVA calculations, the four variables

namely drying temperature, pyrolysis temperature,

holding time, and particle size have a signiﬁcant in-

ﬂuence on the sawdust charcoal caloriﬁc value with

the percentage value of the contribution consecutively

is 7.877%; 54.77%; 11.534%; and 25.817%. In this

case, the pyrolysis temperature has the greatest inﬂu-

ence on the sawdust charcoal caloriﬁc value because

the higher the pyrolysis temperature is, the lower the

water content and the higher the caloriﬁc value. The

results of this study was in line with the research of

(Mandala et al., 2016) which states that pyrolysis tem-

perature is varied from 200 C°to 500 C°and in using

the random wood powder size, there is 29% bio-oil

yield occurs at a temperature of 400 C°.

3.3 Optimization

The optimum conditions of caloriﬁc value on sawdust

charcoal obtained were material drying temperature

of 60 C°, pyrolysis temperature of 600 C°, holding

time of 120 minutes, and particle size is of 100 mesh

as shown in Figure 3 and Figure 4. The difference in

mean values between factor effects is shown in Figure

5 and Figure 6. Research on optimization using the

Taguchi method was also conducted by ((Azadi et al.,

2011) and (Roy, 2010).

ICASESS 2019 - International Conference on Applied Science, Engineering and Social Science

264

space

Figure 3: Optimum condition of caloriﬁc value.

Figure 4: Optimum condition of caloriﬁc value (extension.).

Figure 5: Factor Effects of caloriﬁc valu.

Figure 6: Factor Effects of caloriﬁc value (extension).

The average sawdust caloriﬁc value obtained be-

fore pyrolysis was 3887 cal/g, and after pyrolysis the

average sawdust charcoal caloriﬁc value was 6231

cal/g. The effect of drying and pyrolysis are very sig-

niﬁcant in increasing the sawdust caloriﬁc value. This

sawdust charcoal has fulﬁlled the Indonesia National

Standard so that sawdust charcoal is suitable as a high

quality briquette maker. This study is in accordance

with the results of (Wilk et al., 2016) which used py-

rolysis of wood waste material by varying carboniza-

tion temperatures of 230, 260 and 290 C°and car-

bonization times of 0.5, 1.0 and 1.5 hours. The same

study was also carried out by (Al-Refaie et al., 2010)

who explained that the HHV from torreﬁed samples

increased with increasing temperature. The highest

HHV was found at 26.09 MJ/kg obtained at 60 min-

utes and 300 C°.

3.4 Building a Caloriﬁc Value Model

Linearity test is a procedure to ﬁnd out whether linear

data distribution is or not. The relationship of the re-

sponse variable sawdust charcoal caloriﬁc value and

predictor variables is shown in Figure 7 and Figure 8.

Figure 7: Relation between independent variable and

caloriﬁc value

Figure 8: Model Summary

Based on Figure 8, the value of R=0.935 shows a

fairly close degree of linear relationship between the

response variable of the caloriﬁc value and the pre-

dictor variable. The R Square=0.875 and Adjusted R

Square=0.852 showed that 85.2% of the variance in

the caloriﬁc value variable can be explained by the

independent variable. Meanwhile, St. Error=1.682

states the magnitude of the variance of the regression

model. Thus, there is a linear relationship between the

variables sawdust charcoal caloriﬁc value with drying

temperature, pyrolysis temperature, and holding time

and particle size. This modelling research is in accor-

dance with the results of (Sundaram et al., 2016) that

describe the process of drying materials using tem-

perature variations of 55, 60 and 65 C°; speeds of 2.2,

2.4 and 2.6 m/s and moisture content of 27.5, 30 and

32.5% of the total weight.

Optimizing the Pyrolysis Process and Modelling the Caloriﬁc Value of Sawdust Charcoal as Composing Materials of Quality Briquettes

265

3.5 Overall Test (Model Feasibility)

The feasibility test of multiple regression models at

the level of signiﬁcance: α0.05 using the F test is

shown in Figure 9 and Figure 10. Based on ANOVA

in Figure 9, P-value (0.000) < α (0.05). H0 is re-

jected, meaning the sawdust charcoal caloriﬁc value

model is suitable for use.

Figure 9: ANOVA

Figure 10: ANOVA

(Extension).

a Dependent Variable: caloriﬁc value (cal/g)

b Predictors: (constant), drying temperature (°C),

pyrolysis temperature (°C), holding time (min-

utes) and particle size (mesh)

3.6 Coefﬁcient Feasibility Test

The coefﬁcient feasibility test is used to determine the

level of feasibility of the independent variable coefﬁ-

cients in the formation of a model of caloriﬁc value.

The output of the coefﬁcient feasibility test of the

sawdust charcoal caloriﬁc value is presented in Fig-

ure 11 and Figure 12.

Figure 11: Coefﬁcient feasibility test

space

Figure 12: Coefﬁcient feasibility test

(extension).

a Dependent Variable: caloriﬁc value (cal/g)

Based on Figure 11 and 12, all the independent

variables in the model signiﬁcantly affect the sawdust

charcoal caloriﬁc value variable. The mathematical

model to predict sawdust charcoal caloriﬁc value as

a function of drying temperature, pyrolysis tempera-

ture, holding time and particle size are:

Y (cal/g) = 4708.58–33.23X

+ 42.71X

5.70X

+ 12.32X

(2)

Based on the above equation (2), the higher of

pyrolysis temperature, holding time and particle size

are signiﬁcant to the higher the caloriﬁc value. This

happens because the higher the pyrolysis tempera-

ture, the higher the water content lost, the material

becomes dry so that the water content becomes low

and the carbon is bound as high which results in a

high caloriﬁc value. The results of this study is in

accordance with (Lela et al., 2016) which states that

the mathematical model and optimal value produces a

caloriﬁc value increased to 17.41 MJ/kg, ash content

decreased 6.62% and maximum compressive strength

of 149.54 N/mm

. The same study was alsocarried

out by (Al-Refaie et al., 2010) which explained that

the optical mal parameter design with regression tech-

nique and grey relational analysis. Research on op-

timization and regression modelling were also con-

ducted by (Vishwakarma et al., 2012).

3.7 Model Validation

Residual analysis is a way to validate the sawdust-

charcoal caloriﬁc value model. The results of resid-

ual analysis summary to determine the validity of

the response model to the sawdust charcoal caloriﬁc

value is presented in Figure 13. The model validation

test results show that the residual normality distribu-

tion (P-value) is 0.563> 0.05, no particular pattern is

formed on the assumptions of homoscedasticity, no

multicollinearity (T OL > 1;V IF < 10) and the DW

value is in the range of 0.878<1.456 <1.514.

ICASESS 2019 - International Conference on Applied Science, Engineering and Social Science

266

space

Figure 13: Residual normality test of caloriﬁc value.

Figure 14: Residual normality test of caloriﬁc value (exten-

sion).

Based on Figure 13 and Figure 14, it can be con-

cluded that the sawdust charcoal caloriﬁc value model

has met the eligibility requirements, and model vali-

dation, so that the resulting model is declared feasible

and valid and can be used to predict the sawdust char-

coal caloriﬁc value. The drying and pyrolysis treat-

ment has a positive effect on increasing the caloriﬁc

value. It is proved because the initial sawdust caloriﬁc

value of 3887 cal/g increased to 6231 cal/g after dry-

ing and pyrolysis. Therefore, there was an increase in

the caloriﬁc value of 2344 cal/g.

4 CONCLUSIONS

The optimum condition of the pyrolysis process

which can increase the caloriﬁc value of sawdust is

the drying temperature of 60 C°, the pyrolysis temper-

ature of 600 C°, holding time of 120 minutes, and par-

ticle size of 100 mesh. The linearity test results show

that the value of R; R Square; and Adjusted R Square

at the caloriﬁc value to have a strong correlation with

drying temperature, pyrolysis temperature, holding

time, and particle size. The result caloriﬁc value

model is

Y(cal/g) = 4708.58–33.23X1 + 42.71X2 +

5.70X3 + 12.32X4. The validation test results of the

heat value model show that the residual normality dis-

tribution (P-value)> 0.05 does not form a certain pat-

tern on the assumption of homoscedasticity, no mul-

ticollinearity (TOL> 1; VIF <10) and the DW value

is within the speciﬁed range so the model is declared

valid. The model feasibility test results in a P-value

(0.000) < α (0.05) so that the caloriﬁc value model

is declared feasible and can be used to predict the

caloriﬁc value of sawdust charcoal to produce a qual-

ity briquette.

ACKNOWLEDGEMENTS

This research was funded by the Directorate Gen-

eral of Research and Development, Ministry of Re-

search, Technology and Higher Education for the pe-

riod 2017-2019.

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Optimizing the Pyrolysis Process and Modelling the Caloriﬁc Value of Sawdust Charcoal as Composing Materials of Quality Briquettes

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