International Forum for Green Asia 2020

Production of Fuel Pellet and Coke from Heavy Oil and Bio-char Mixture ofVarious Blending Ratios
Aditya Wibawa1, Xiangpeng Gao2, Jun-ichiro Hayashi1
12Interdisciplinary Graduate School of Engineering, Kyushu University
School of Engineering and Information Technology, Murdoch University

Abstract
Bio-chars for pellets are affected by pyrolysis temperatures and binder. Thus, controlling for thesetwo variables can produce an ideal product with engineered properties - "designer bio-pellet." Thepotential for designer bio-char pellets stems from its ability to combine the properties of pyrolysis
bio-char, which is rich in nutrients and alkalis, with heavy oil products another from pyrolysis which
will also be rich in carbon and energy. In this study, raw material from rice straw was pyrolysis, its
products are heavy oil HO and char. The HO and char are mixed at different ratios (100%, 75%,50%, 25%, and 12.5%), pelletized (diameter 14.1 mm), and then undergo heat in mold at different
temperatures (80 °C, 140 °C, and 200 °C) to create test chars. Blending pellets are tested for energy
characteristics, pellet tensile strength (TS), and elemental composition. The results showed that themixed HO/char had different tensile strength in each mixture, the maximum TS of rice straw 400 °C
with a mixture ratio of 100%. The blending HO/char at 100% had a high in ash content and highenergy content (HHV), and also lower in the moisture uptake. Structurally, blending HO/charpellets resemble bituminous coal. Although the bio-char/char pellet mixture degrades faster in
combustion, mixing HO/char for pellets and coke production can alleviate some energy conversion
application problems, and be obtained co-firing with bituminous coal.
Keywords: pellets, energy conversion, pyrolysis, heavy oil and char, blending
1. Introduction
Agricultural residues are abundant andwidely distributed in the many countries. The
traditional treatment methods such as open
burning, pulverization, and return to the field,
causing environmental pollutions and leave aconsiderable amount of energy unutilized.
Researches regarding the efficient andenvironmentallyfriendlytreatment
ofagricultural residues have gained increasing
attention in the past decades. Manytechnologies turn agricultural biomass into
thermal energy or bio-products.
Pyrolysis is the main step of biomass
gasification, and the formulation ofcondensable organic products, which isgenerally called tar, while carbon-rich residues
are called bio-char.[1] In this study briquettes

were made from a mixture of biochar and its
heavy oil/ tar.
2. Experimental Section
Rice straw (RS) was pyrolyzed in ahorizontal auger reactor, which is popular in thebiomass pyrolysis, with temperatures of 400 °C,
450°C and 500 °C. The details of the reactor arereported elsewhere.[2] The bio-oil wascondensed at the reactor downstream with asilica fiber made aerosol filter (150 °C) andthree condensers (0, −40, and −70 °C,respectively) in series. Heavy oil (HO) and biooil have been mixed by dissolving acetone.
Prior to evaporation at a temperature of 60 °C,
a mixture of HO/Char was stirred at stirring rateof 170 rpm for overnight.
The palletization process was5

International Forum for Green Asia 2020
performed using hydraulic press consists ofstainless steel cylindrical interior diameterand length are 14.10mm and 28mm,respectively. Approximately 1 g of powderwas filled inside the hole, compacted to apressure of 128 MPa for holding time 8 min
at 200 °C. After the pressure release, themold was cooled down naturally to ambient
temperature. The briquette heat for thecarbonization at atmospheric flow of N2 at
the rate of 3 oC /min to 1000 oC where thetemperature held for 10 min.

energy densification are great, and the small
blending ratio or more char provided low energy
densification, it was due to the heavy oil is richin volatile and also high density, conversely theHO is contained greater of carbon content. Otherimpacts also occur on the ash content, the higher
the blending ratio of HO/char gives a low ashcontent, while the small blending ratio generates
high the ash content.
40
RS 400RS 500RS 450RS 450RS 400RS 500

Energy desification [GJ/M3]

3. Results and Discussion
The yields and distribution of pyrolytic
products are presented in Fig 1. Incorporating
HO into char results in considerable increase in
the yield of solid fuel (i.e., HO/char mixture),from 34.4 - 40 wt% for char only to 41 - 50 wt%
for mixture of HO and char. The two concepts,(i) char as a sorber for HO capture and(ii) HO as a binder for char briquetting, havebeen successfully demonstrated.

11351030

92587

Ash content (wt% adb)

1220
100%

75%

50%

25%

12.5%

mixing ratio, % of R (MHO/Mchar)

Yield (wt% of biomass feedstock, dry)

100Fig 2. Energy densification and ash content ofchar

80

60

As discussed above, the noticeable
synergies always occur under conditions of ahigher mixing ratio condition. This due to thesufficient quantity of HO in the mixture isneeded to offer plenty of carbon donors.

CharHOWate

40LO
NCG

202raw sample

1.8
1.6

0
H/C (atomic ratio)

400450500
Pyrolysis Temperature (°C)

Fig 1. Yield of char, heavy oil (HO), water, lightoil (LO) and non-condensable gases (NGC) frompyrolysis of rice straw (RS)

1.4

HOPeat1.2
1 Bituminous

Brown

0.8

Lignitecoal

0.6char

0.4

HO/charSemi anthracite

0.2

Fig. 2 presents the energy densification ofblending of HO/char generated from RS at
400 °C, 450 °C and 500 °C. It was found thatsome synergetic effects on energy densification.
In the under higher blending ratio conditions, the000.1

0.2
0.3
O/C (atomic ratio)

0.4

Fig. 3 Van Kreven diagram of blending ratio
60.5

International Forum for Green Asia 2020
uptake. In addition, suggest the pellets high of
mixing ratio can be stored safely in humid
environment for long time [3].
This section also explores theoptimized pyrolysis temperature andHO/Char mixing ratio for production of fuelpellets and coke from rice straw pyrolysis.
In practice, pyrolysis of rice straw at given
temperature produces certain amounts ofHO and char, with the mass ratio ofHO/Char being R (0.22, 0.26 and 0.26 for400, 450 and 500 °C, respectively). It has
been previously demonstated that biomass
feedstock itself is also an excellent sorber fo
HO capture. Therefore, if fuel sorbers filledwith char and rice straw are applied, it ispractically feasible to produce HO/Char
mixtures at any ratios lower than R. To
determine the optimized HO/Char blending
ratio, HO and char produced from pyrolysisof rice straw at 400, 450, and 500 °C wereblended at different ratios (100%, 75%, 50%,25%, and 12.5% of R.

Fig.3 It shows the Van Krevelen plot ofpyrolyzed rice straw and shows the changes in
H/C and O/C atoms used to determine the levelof maturation of pyrolysis products. The van
Krevelen diagram also provides information
about differences in the composition of elements(C-H-O). The Van Krevelen diagram shows thatthe characters obtained from the pyrolysis of ricestraw HO and char have a ratio of H/C and O/C
which is much lower than raw rice straw. Thisshows the gradual loss of hydrogen and oxygenand char enrichment of carbon. In this figure thecomposition of blending HO/char shows thatH/C and O/C are very close to Bituminous coal.
It's clear that blending HO/char compared tobituminous coal contains more oxygen.
Fig.4 shows the measured moisture uptakeof pellets RS-400 at 25 °C and 80% relative
humidity. It was observed that the pellets
reached saturation in about 10 h. The
hydrophobicity improved when the HO/charhigh mixing ratio and long residence time wereused, with RS-400 100% exhibiting the lowest
moisture content, at around 3.8%.

R = MHO/Mchar.eq (1)7RS-400
RS-450RS-500675TS [MPa]moisture uptake (%)

654432

3100%
75%
50%
25%
12.5%

21

10100%

75%

50%

25%

12.5%

mixing ratio, % of R (MHO/Mchar)

00500

1000

1500

2000

Fig 5. Tensile strength (TS) of briquetting fuelExposure time (min)Fig. 4 Moisture uptake of pellets RS-400

pellets from HO/Char with temperature of 200°C

Among the mixing ratio of HO and char,
the high hydrophobicity of the pellets due to theHO intercalation, which is the hygroscopicityof bio-char played of preponderant in moisture

Tensile strength (Ts) is critical for thebriquettes because soft hardness might lead tobreakage during transportation and handlingprocesses. In the present study, the mechanical7

International Forum for Green Asia 2020

HO/Cha blending ratio as percentage of R

properties of the briquette pellets were evaluatedin terms of their tensile strength, as illustrated inFig. 5. As expected, all pellets showed relative
low tensile strength, the strongest pellet withtensile strength 6.3 MPa is produced at pyrolysis
temperature of 400 °C, hot briquettingtemperature of 200 °C and the HO/Char
blending ratio of 100% of R (0.22 g HO/g Char).
All mixing ratios are more strength than
without heavy oil and the surface was muchsmoother, that indicating the interval between
particles which are considered heavy oilrecrystallizing after the drying process and solid
forming to bind the particle. After briquetting athigh temperature, consistency of polymerized
serving as a glue. The surface was muchsmoother, indicating the interval between
particles.
As illustrated in Fig 6, the highest TSof 19.9 MPa has been achieved for cokeproduced at the same process conditions as
those for fuel pellets. There is a strong bond
between HO/Char before the release ofvolatiles at the carbonization temperature.

4. Conclusions
In this work, typical agricultural
biomass, rice straw was briquettes under
different mixing ratio of HO and char to obtain
fuel pellets and coke. The hydrophobicity ofpyrolyzed char pellets increased withincreasing the mixing ratio. High mixture
HO/Char pellets exhibited increased tensile
strength and density. The mixing ratio 100%
has higher TS around 6.3, the increased TS due
to strengthening from HO. The same blending
and briquette conditions as pellets, coke has atensile strength with an average of three times
stronger than pellets. The coke is sufficient tobecome metallurgical coke.
Acknowledgment
The author would like acknowledgment to
the member of Hayashi and Kudo Laboratory,
Azka Mori and Ashik, who has taken the timeand taught using several equipments and also
make discussion with me.
References
1) Zhou, H., Meng, A., Long, Y., Li, Q., Zhang, Y.
Renew. Sustain. Energy Rev. 2014, 36, 107-122.
2) Kudo, S.; Sugiyama, K.; Norinaga, K.; Li, C.Z.; Akiyama, T.; Hayashi, J.-i. Fuel 2013, 103,64−72.
3) Zhu, Y.; Si, Y.; Wang, X.; Zhang, W.; Shao, J.:
Yang, H.; Chen, H.. Energy & Fuels 2018, 32,11538-11546.

12.5%

80 °C
140 °C
200 °C

25%

50%

Email: wibawa.aditya.645@s.kyushu-u.ac.jp
75%

100%

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TS (MPa)Fig 6. TS of coke from HO/Char mixture ofpyrolysis 400 °C8