Proceedings of International Forum for Green Asia 2019
5th International Exchange and Innovation Conference on Engineering & Sciences (IEICES 2019)

GA10 / P22
Production of Fuel Pellet from the Mixture of Heavy Oil and Biocharwith a variety of Blending Ratios
1

Aditya Wibawa1, Xiangpeng Gao2, Jun-ichiro Hayashi1
Interdiciplinary Graduate School of Engineering, Kyushu University 2 School of Engineering and Information
Technology, Murdoch University
Email: wibawa.aditya.645@s.kyushu-u.ac.jp

Abstract: Pyrolysis is a proved technology that converts biomass into bio-oil and biochar. The heavy portion of bio-oil,termed as heavy oil (HO), is sticky and responsible for coking problems during bio-oil upgrading. However, sticky HO
can be an excellent binder for pelletizing biochar. When a sorber filled with biochar is applied, HO can be effectively
captured by biochar. Furthermore, if another sorber filled with biomass feedstock is employed, it is practically feasible
to tune the blending ratio of HO and char to produce HO/Biochar pellets of optimized properties. In this study, a typicalagricultural residue in Japan, rice straw, was pyrolyzed at 400, 450, and 500 °C in an auger reactor to produce HO andbiochar, with a HO/biochar mass ratio of R for a given temperature. The resulting HO and biochar were then mixed atdifferent ratios (100%, 75%, 50%, 25%, and 12.5% of R), and pelletized at different temperatures (80 °C, 140 °C, and200 °C) to produce HO/biochar pellets. The pellets were tested for energy density, tensile strength (TS), and elementalcomposition. The results showed that the mixed HO/char had different tensile strength, and the maximum TS ofHO/biochar pellets were found from 100% R of HO/biochar mixture from 400 °C pyrolysis. The blending HO/char at
100% had a high in ash content and high energy content (HHV), and also lower in the moisture uptake
Keywords: pellets, energy conversion, pyrolysis, heavy oil and char, blending
INTRODUCTION
Rice straw is one of the most abundant agriculturalresidues in Japan. The traditional treatment methods suchas open burning, pulverization, and return to the field,
causing environmental pollutions and leave aconsiderable amount of energy unutilized. Researches
regarding the efficient and environmentally friendly
treatment of agricultural residues has gained increasing
attention in the past decades. Many technologies turn
agricultural biomass into thermal energy or bioproducts.
Pyrolysis is the main step of gasification, and theformulation of condensable organic products, which is
generally called tar, while carbon-rich residues are calledbiochar.[1] In this study briquettes were made from a
mixture of biochar and its heavy oil/ tar.

transportation and handling processes. In the present
study, the mechanical properties of the briquette pellets
were evaluated in terms of their tensile strength, asillustrated in fig. 1. As expected, all pellets showed
relative low tensile strength, with RS-400 100% R
mixture having the highest tensile strength of 6.3 MPa.
7RS-400
RS-450RS-5006TS [MPa]

543
2
1

EXPERIMENTAL SECTION
Rice straw (RS) was pyrolyzed in a horizontal auger
reactor, which is popular in the biomass pyrolysis, attemperatures of 400, 450 and 500 °C. The details of thereactor are reported elsewhere. [2] The bio-oil wascondensed at the reactor downstream with a silica fiber
made aerosol filter (150 °C) and three condensers (0, −40,and −70 °C, respectively) in series. Heavy oil (HO) andbio-oil have been mixed by dissolving acetone. Prior toevaporation at a temperature of 60 °C, a mixture ofHO/Char was stirred at a stirring rate of 170 rpm forovernight.
The pelletization process was performed using
hydraulic press consists of stainless steel cylindricalinterior diameter and length are 14.10 mm and 28mm,respectively. Approximately 1 g of powder was filled
inside the hole, compacted to a pressure of 128 MPa forholding time 8 min at 200 °C.

0100%

75%

50%

25%

12.5%

mixing ratio, % of R (MHO/Mchar)

Fig 1. Tensile strength of pellets
All mixing ratios are more strength than without
heavy oil and the surface was much smoother, thatindicating the interval between particles which areconsidered heavy oil recrystallizing after the drying
process and solid forming to bind the particle.
Subsequent to briquetting at high temperature,
consistency of polymerized serving as a glue. The surface
was much smoother, indicating the interval between
particles.
Fig. 2 presents the energy densification of blendingof HO/char generated from RS at 400 °C, 450 °C and500 °C, it was found that some synergetic effects onenergy densification. In the under higher blending ratio
conditions, the energy densification are great, and thesmall blending ratio or more char provided low energy
densification, it was due to the heavy oil is rich in volatile
and also high density, conversely the HO is contained
greater of carbon content. Other impacts also occur on

RESULTS AND DISCUSSION
Tensile strength (TS) is critical for the briquettes
because soft hardness might lead to breakage during- 25 -the ash content, the higher the blending ratio of HO/char
gives a low ash content, while the small blending ratio
generates high the ash content.

400 100% exhibiting the lowest moisture content, ataround 3.8%.
Among the mixing ratio of HO and char, the highhydrophobicity of the pellets due to the HO intercalation,
which is the hygroscopicity of bio-char played of
preponderant in moisture uptake. In addition, suggest thepellets high of mixing ratio can be stored safely in ahumid environment for a long time [3].

40
RS 400RS 500RS 450RS 450RS 400RS 500351030925876moisture uptake (%)

11Ash content (wt% adb)

Energy desification [GJ/M3]

1220

7100%

75%

50%

25%

12.5%

mixing ratio, % of R (MHO/Mchar)

54
3

100%
75%
50%
25%
12.5%

21Fig 2. Tensile strength of pellets

00

As discussed above, the noticeable synergies
always occur under conditions of a higher mixing ratio
condition. This due to the sufficient quantity of HO in themixture is needed to offer plenty of carbon donors.
2H/C (atomic ratio)

HO1 Bituminous

Brown coalLignite0.80.6

char

0.4
0.2

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.

HO/char

Semi
anthracite

000.1

0.20.30.4

2000

CONCLUSIONSIn this work, typical agricultural biomass, rice straw
was briquettes under different mixing ratio of HO andchar to obtain pellets. High mixture HO/char pellets
exhibited increased tensile strength and density. The
mixing ratio 100% has higher TS around 6.3, theincreased TS due to strengthening from HO. The
hydrophobicity of pyrolyzed char pellets increased withincreasing the mixing ratio.

Peat

1.2

1500

Fig. 4. Moisture uptake of pellets RS-400

1.6
1.4

1000

Exposure time (min)rawsample

1.85000.5

O/C (atomic ratio)

Fig. 3. Van Kreven diagram of blending ratio
Fig.3 It shows the Van Krevelen plot of pyrolyzed
rice straw and shows the changes in H/C and O/C atoms
used to determine the level of maturation of pyrolysis
products. The van Krevelen diagram also provides
information about differences in the composition ofelements (C-H-O). The Van Krevelen diagram showsthat the characters obtained from the pyrolysis of ricestraw HO and char have a ratio of H/C and O/C which ismuch lower than raw rice straw. This shows the gradualloss of hydrogen and oxygen and char enrichment ofcarbon. In this figure the composition of blending
HO/char shows that H/C and O/C are very close toBituminous coal. It's clear that blending HO/charcompared to bituminous coal contains more oxygen.
Fig. 4 shows the measured moisture uptake ofpellets RS-400 at 25 °C and 80% relative humidity. It wasobserved that the pellets reached saturation in about 10 h.
The hydrophobicity improved when the HO/char highmixing ratio and long residence time were used, with RS- 26 -