The Production of a Liquid Fuel from Coke Oven By-product Gas and Biomass
and the Establishment of a Method for the Use in advanced chemical applications
コークス副生ガス／バイオマスによる液体燃料化と化学原料化高度利用法の構築
Yukihiko Okumura, National Institute of Technology, Maizuru College
1. INTRODUCTION
Studies of the effective use of by-products and the effective use of waste energy in thesteel making process are important for the advanced chemical applications and for the
reduction of carbon dioxide retention. The present study examines two approaches tothe intensive use of large amounts of by-product gas and by-product liquid as chemical
raw materials in the coke production process. Some examples of by-productliquid-components obtained from coal are naphthalene, tar pitch, creosote oil,anthracene, phenol, and cresol [1]. These products are distinct from the chemical raw
materials obtained from oil (organic synthetic chemical components) i.e., the products
obtained from coals have unique chemical characteristics [2]. For example, rarecomponents, such as indene and fluorene, are contained in coal tar (not found in oil).
Indene is useful as a starting material for producing resin modifiers and medicines [3].
Optical properties including heat resistance and refractive index can be improved byincorporating indenes into resin. (Cardo structural skeleton incorporated orthogonal to
the resin main chain.) By incorporating fluorene-skeleton into the resin, the following
characteristics can be imparted to it [4]: compatibility between high refractive indicesand low birefringence, heat resistance, high glass-transition point, and low dielectric
constant. The aforementioned rare components are used to increase the functionality ofresins such as polycarbonate, polyester, and polyimide. At present, more advanced
applications of functional raw materials obtained from coal tar are constantly being
studied.
In the present study, the effects of the heating rate and the coal type on the yields ofuseful by-product components are first examined to intensively use chemical raw
materials (research objective-(1) in Fig. 1). In a national project of Japan, the heating
rate in newly-built coke ovens is rapidly increased, in addition a large amount of nonor slightly-coking coal is mixed with caking coal in the SCOPE21 [5], (the Super CokeOven for Productivity and Environmental Enhancement Toward the 21st Century).
Since ~60% of other coal is replaced with conventional coal types [5], the compositionof by-products may vary from the by-products obtained in the past. Multiple coaltypes have been used for coke, and the use of non-caking coal has steadily expanded－ 47 －

Use in advanced chemical applications(Functional materials)
(1)

Coal

By-product liquid ＋By-product gas
(tar)
Coke

Steel production(2)
Production of liquid fuel withbiomass using waste heat
(low temperature)

Fig. 1 Background and objectives ((1), (2))
for use in the future steel industry. Therefore, the effect of coal type on the yield of
volatile matter (by-product liquid and gas components) must be elucidated. Although
the yield of volatile matter is higher in fast pyrolysis than in slow pyrolysis [6],[7], nostudy has reported on the components and their increased or decreased amounts indetail. To achieve research objective-(1), we quantitatively investigated the effect of theheating rate on the yield of the volatile matter.
Next, as shown in research objective-(2) in Fig. 1, we propose a process in which thecoke oven by-product gas is mixed with biomass, and a solid–gas reaction is facilitatedat medium to low temperatures (in the temperature range of waste heat) to convert the
mixture to CO and H2. The technology of producing liquid fuel can contribute to thedensification of fuel and the intensive use in automotive fuels and industrials. The
addition of biochar is expected to facilitate the production of CO-rich gas (C + CO2 →2CO) and provide the ideal CO/H2 ratio for the Fischer-Tropsch (FT) synthesis. The
methane gas can reform by the reaction (CH4 + H2O = CO ＋ 3 H2) at medium
temperature (in the temperature range of waste heat) using steam. Liquid fuel can beproduced from the synthesized gas (H2 + CO) obtained from the above reactions
through dry refinement and the FT synthesis. The present study first examines amethod to increase the gasification rate of biochar that determines the overall
gasification rate. (The gasification rate of biochar is particularly important in a
low-temperature range.) In summary, the present study elucidates the following two
points:(1) The gasification reaction rate represented by Arrhenius plot
(2) The enhancement of the char gasification reaction at low temperatures using acatalyst [Development of the constituent technology to facilitate gasification at
low temperatures]－ 48 －

2. RESEARCH OBJECTIVE-(1)[ The Yield and Composition of By-product Gas and Liquid from Coal Pyrolysis ]2.1 Experimental Apparatus and Method
The thermogravimetric analyzer (Fig. 2: TGD9600, ALVAC) was used in thisresearch objective-(1). A coal sample (Table 1, 100mg, under 100mesh) is placed in aplatinum cell (height: 10mm, diameter: 8mm) in an argon atmosphere, and the coalis pyrolyzed by an infrared gold image furnace. When the maximum temperature of1273 K is reached (ref. Table 2), the applied voltage is interrupted, thereby stopping
the heating, and then the sample is abruptly cooled. Since radiation can pass
unimpeded through Ar, the entrainment gas remains relatively cool and quenches
the chemical reactions among the primary products as they are expelled.
The yields were defined as follows:
Total yield of volatile matter, Ytotal V.M.:

Ytotal V.M. ＝(M sample－M char ) /M sample‥ (1)Tar yield, Ytar :Ytar ＝M tar /M sample‥‥‥‥ (2)M shows a weight, and Mtar is calculated from the change in the weight of the filterin the tar trap before and after each experiment.
Total yield of gas, Ytotal gas :Ytotal gas ＝(M sample－M char－M tar ) /M sample‥ (3)Here, the following equation holds:

Ytotal V.M. ＝Ytar + Ytotal gas‥‥‥‥ (4)In case of the tar component analysis, the impingers (Figure 3) were used in stead of
the tar trap in Figure 2. The tar is transported by the carrier gas Ar and collected by
the impinger. The first layer of the impinger contains isopropyl alcohol solvent cooledby dry ice and the second layer contains acetone solvent cooled similarly (194.15K). In
order to make the cooling process of the structure efficient, marbles (glass beads)
were placed in the structure to increase the surface area of the bubbles formed.
For the tar-component analysis, a Shimadzu gas chromatograph–massspectrometer (GCMS-QP2010 Ultra) was used. Rtx-5MS and helium were selected as
the column and carrier gas, respectively. The temperature of the sample vaporizationchamber was set at 280°C. The analysis was conducted by increasing the column
oven temperature gradually as follows: 40°C (retention time: 5 min) -> temperature
increase at 10°C/min -> 320°C (retention time: 5 min). This procedure was carried out
in the high-precision control mode, in which the carrier gas was provided at a

－ 49 －

GC-8A

Sampling bag
GC （TCD,FID）

Ribbon heater

Flow meter

Biomass sample
Infrared gold image furnace
Quartz glass tube

Cooling waterand ice

Tar trap

Pressure gauge
Vacuum gauge

Ar gas cylinder
Control unit ofthermo balance
Vacuum pump

Fig.2

PC

Fig.3

Outline of experimental
apparatus

Experimental apparatus andimpinger

Table 1 Coal properties
Ultimate analysis(wt%, d.a.f.)
C
H
O
N
S

Elemental composition
Proximate analysis (wt%)
H/C
O/C
VM
FC
ASH MOIST.

A-coal (SS011,IND)

73.1

0.0

40.65

45.19

1.58

12.58

0.837

0.213

B-coal (SS071, IDN)

76.2 5.4 16.0 1.8 0.53

39.87

45.02

5.81

9.30

0.850

0.157

C-coal(SS024, USA)78.5 5.8

D-coal (SS002 , AUS)

5.1

20.8 1.0
13.5 1.7

0.48

38.08

50.06

7.14

4.72

0.887

0.129

81.2

6.1 10.6 1.6

0.58

38.04

45.20

14.52

2.24

0.901

0.098

E-coal (SS003, AUS)

82.9

4.7 10.2

1.8

0.31

28.44

60.00

8.56

3.00

0.680

0.092

F-coal (SS007, AUS)

83.8

5.3

8.9

1.3

0.66

31.60

51.10

15.00

2.30

0.759

0.080

G-coal (SS035, AUS)

88.3

5.1

4.5

1.6

0.48

18.33

65.93

14.54

1.20

0.693

0.038

H-coal (SS037, CHN)

90.6

4.2

3.4

1.3

0.4

8.49

73.40

16.54

1.57

0.556

0.028

(1)-coal (SS015 ,COL)

80.7 5.9

11.2

1.6

0.63

35.30

53.50

8.30

2.90

0.877

0.104

(2)-coal (SS027, CHN)

80.6 4.9

12.8

1.0

0.68

27.66

56.89

10.24

5.21

0.730

0.119

(3)-coal (SS028, AUS)

80.8 4.8

12.2

1.9

0.29

26.79

60.07

7.98

5.16

0.713

0.113

I-coal (SS048, AUS)

84.0 5.4

7.9

1.9

0.71

29.00

53.92

15.73

1.35

0.772

0.071

II-coal (SS022, ZAF)

83.4 4.8

9.2

2.0

0.61

26.40

57.09

13.73

2.78

0.690

0.083

III-coal (SS021, ZAF)

84.4 4.7

8.5

1.9

0.46

24.10

59.07

14.43

2.40

0.668

0.076

１-coal (SS050, AUS)

82.7 5.4

9.4

1.9

0.56

29.92

54.00

14.16

1.92

0.784

0.085

２-coal (SS058, CHN)

82.7 5.4

9.9

1.6

0.49

33.07

53.55

10.76

2.62

0.784

0.090

３-coal (SS036, AUS)

87.0 5.4

5.5

1.7 0.46

19.22

57.42

22.17

1.19

0.745

0.047

４-coal (SS064, CHN)

88.3 4.7

5.2

1.5 0.29

18.32

65.89

14.28

1.51

0.636

0.044

５-coal (SS067, CHN)

89.6 4.6

4.2

1.6 0.16

16.12

67.89

14.29

1.69

0.610

0.035

Table 2 Pyrolysis conditions
Atmospheric gas
Heating rate [K/s]
Maximum temperature [K]Holding time [s]Ar
0.5 - 20.0
1273
0.0

Pressure [MPa]0.1 (1.0atm), 1.06

－ 50 －

constant linear velocity (40 cm/s). Trial experiments were repeated to refine the peakseparation, and the split ratio was determined to be 20. Fifty two types of tar
components were quantified by using an internal standard method, which isconsidered to be the most accurate method. The calibration curve was prepared byusing concentrations at three points; acetone was used as the solvent of the mixed
standard samples. The quantities of the other 54 species of tar components were
determined by using semiquantitative analysis based on the peak-area value of thetotal ion chromatogram (TIC) for Toluene-D8.
2.2 Experimental Results and Discussion
2.2.1 The composition and yield of pyrolysates generated during a rapid heating
rate corresponding to that of SCOPE21
Figure 4 shows the volatile product yields of C-coal (see Table 1) as arepresentative example. The tar yield at atmospheric pressure increased withincreasing heating rate, while the gas yield (obtained from Ytotal gas = Ytotal V.M. – Ytar
in Fig.4) hardly changed. Under high pressure, Ytotal V.M. and Ytar were suppressed.
The total volatile matter yield exceeds the proximate analysis value, which is shownby the alternate long and short dashed lines in Fig. 4, at a heating rate of 5 K/s (P=0.1MPa). The liquid color of the collected tar changed to dark-brown upon
Volatile yield ( wt% , g /g-coal,daf ×100)

increasing the heating rate. (Fig.5)
60
Ytotal V.M. (0.1MPa)

C-coal50
40

Ytotal V.M. (1.06 MPa)30

Tmax =1273K

20

Ytar (0.1MPa)100(a) 0.5K/s, (b) 5K/s,

Ytar (1.06 MPa)

0

10
20
Heating rate ( K/s )(c) 20K/s

Fig.5 Appearance of collected tar (1atm)

Fig.4 Effect of heating rate on first-pyrolysis yield
2.2.2 Effect of heating rate on tar component yield
Figure 6 shows the GC-MS chromatograms of the tar under the atmosphericpressure. The distinct high peaks of benzene, styrene, and indene are clearlyobserved on the left-hand side, and the peaks of heterocyclic tar components up to
the 6-membered ring are observed on the right-hand side at 20K/s (Fig.6(a)). At a

－ 51 －

slow heating rate, however, the chromatogram is composed chiefly of the peaks oftar with up to 4-membered rings (Fig.6(b)).
Figures 7 and 8 show the results of the detailed study of the tar components.
Approximately 110 peaks with high intensities were analyzed to identify thechemical species involved. The analysis quantitatively specified the chemical
species contained in 32 wt% of tar. (The chemical species contained in 43wt% of tar
were identified by including semi-quantitative analyses.)

Figure 7 shows thedetected number of only quantified chemical species, indicating that aromatichydrocarbons of 1- to 2-membered-ring were formed in large numbers, while 5- to
6-membered ring components were formed in relatively small numbers. Figure 8
shows the collected amounts of the tar species. The formation of benzene andtoluene were much higher than that of other chemical species. The high-yield
polycyclic aromatic hydrocarbon species with more than 3-membered rings wereacenaphthene, phenanthrenea, and fluorene.
Figure 9 shows how the yield of each component varies with heating rate inpyrolysis. From Fig.9(a), the yields of primary pyrolysis components, including
benzene, styrene, indene, naphthalene, and PAHs (3–5 rings), rapidly increase withincrease in the heating rate. The amount of aromatic hydrocarbons increases withincreasing heating rate. The yields of toluene and xylene do not increase much withincrease in the heating rate (Fig. 9(b)). On the other hand, at a slow heating rate theyields of straight-chain saturated hydrocarbons such as octane and phenol (OHgroup) increased. (Fig.9(c)) In addition to the above analysis, we investigated themolecular components and their structures of the tar by valuating FTIR (Fig.10:
infrared absorption intensity data). Infrared absorption spectroscopy allows us to
conduct qualitative and quantitative analyses of the functional groups present in thetar by observing the stretching and torsional behaviors of tar molecules. (Thespectrometer has been used for analyzing asphalt and heavy oil [8].) In this study, IR
spectrometer (IR μs spectrometer, Spectra-Tech Co. LTD, detection range: 4000–650
cm−1; measurement mode: transmission method; resolution: 8 cm−1; and accumulation
number: 1024) was employed. The absorption peak in the vicinity of 3050 cm−1 isattributable to the C=C bonds or aromatic rings, and that in the vicinity of 2920
cm−1 is attributable to -CH2- and -CH3- groups.

The peak in the vicinity of 1460

cm−1 is derived from the CH group. We evaluate the composition ratio of aromatichydrocarbons including unsaturated aliphatic hydrocarbons to saturated aliphatichydrocarbon in directly collected tar. Specifically, the change in the tar components
with a heating rate ranging from 0.5 to 20 K/s was examined by determining the－ 52 －

(a) Tar components at rapid heating rate detected by GC-MS (20K/s, 1atm)(b) Tar components at slow heating rate detected by GC-MS (0.5K/s, 1atm)
Fig.6

Effect of heating rate on first-pyrolysis product

SDCHCG: Saturated Direct Chain Hydrocarbon GroupUSDCHCG: Unsaturated Direct Chain Hydrocarbon Group
USCHCG: Unsaturated Cyclic Hydrocarbon GroupThe number of components

11
10
9
8

ＳＳ024

HR = 0.5-20K/s
Tpyro = 1000℃

7
6
5
4
3
2
1
0

Fig. 7 Detected chemical species according
to molecular configuration. (1atm)

Fig. 8－ 53 －

Yield of major chemical species ofpyrolysis tar. (5.0K/s, 1atm)

(a) increasing component(b) middle behavior(c) decreasing component
Fig.9 Effect of heating rate on tar-component yield (Coal type:SS024, Use in impinger, 1 atm)
δCH
2900 cm -1

0.2

νCH

A 3050 / A 2920

νC-O

Absorbance

3000cm -1

SS024
0.1MPa1.0 ata
0.1

10.6 ata
1.06MPa
0
0
4000

3000

2000

1500

Wave numbers (cm-1)

Fig.10 FTIR analysis of tar (20K/s, 1 atm)

1020

Heating rate ( K/s )1000

Fig.11

Effect of heating rate on moleculecomponent of tar

integrated intensity ratio A3050/A2920. The higher the intensity ratio, the greater is therelative amount of aromatic hydrocarbons contained in tar components in the sample.
Figure 11 shows the dependence of the integral intensity ratio A3050/A2920 on theheating rate. The results reveal that the relative amount of aromatic hydrocarbon
components (i.e. polycyclic structures) tends to increase with increasing heating rate.
A similar tendency was observed even under high pressure, although the effectobserved under high pressure is smaller than that under atmospheric pressure.
2.2.3 Effect of coal type on tar component
We discuss the effect of coal type on the yields of tar components based on thepyrolysis experiment using 19 different coal types ranging from lignite tosemi-anthracite coal. Table 1 shows the properties of the coals used for these－ 54 －

experiments. A to H coals with different carbon contents (wt%) were used. Coals(1)-(3), I-III, and 1-2 were included for the specific reason that bituminous coal tar
yields differ considerably depending on the coal type. Coals (1) and (3) were included
for comparison with Coal D, as they have identical carbon contents. Similarly, Coal
I-III was included for comparison with Coal F, and Coals 3 and 5 were included forallowing carbon content interpolation between Coals F and G, and between Coals G
and H, respectively.
As a result, even when the carbon contents of the coals were almost the same, theiryield of volatile matter were significantly different（Fig.12）. Therefore, these yields
need to be systematically organized using an indicative physical value. Here, we
adopted the atomic ratio H/C for this purpose（Fig.13）. We have shown that Ytotal V. M.
and Ytar in many coals can be predicted by determining the H/C ratio. In other words,

Ytotal V. M. and Ytar in many coals can be predicted by determining the H/C ratio. Below,
we formulate predictive equations for the total volatile matter, and tar yields byapplying the least-squares approximation to the yield data for various coals. (R shows
the multiple correlation coefficient. )Y total V.M = 109×(H/C)－47.0[wt%]

Y tar =30.4×(H /C)－14.0 [wt%]‥‥(5)( R2 =0.837 )‥‥(6)( R2 = 0.576)

Here, the yields of CH4, C2H4, CO, CO2, C2H4 (Fig.14) are shown as:

Y H2 =0.506×(H/C) + 1.73‥‥ (7)( R2 = 0.018 )CH4[wt%]：Y CH4 =6.63×(H/C) －0.839‥‥ (8)( R2 = 0.611 )CO[wt%]：Y CO = 75.6×(O/C) －0.0284‥‥ (9)( R2 = 0.873 )CO2[wt%]：YCO2 =39.7×(O/C) －1.06‥‥(10)( R2 = 0.852 )C2H4[wt%]：

YC2H4 = 20.7×(H/C) －12.0‥‥(11)( R2 = 0.641 )0.1MPa 1.06MPa

60

B

A

D
C

FI

(1)

40

(2)
(3)

20

II

E III

(2)

75

80

G

I

(1)

0

YtotalVM
Y tar

(3)

II

III

85

H

90

Carboncontent (wt%,
Carboncontent(wt%,daf)
daf )Fig.12

Effect of coal type on total yield of
volatile matter and tar yield.

－ 55 －

Released Volatile matter (daf, wt%)

H2 [wt%]：

80

,
,
60 ,
,
40 ,
20
0
0.6

Fig.1388.3-89.6 (wt%C, daf)
83.4-84.4
82.7-82.9
80.6-81.2
Others

V.M.

Tar

0.7
0.8
Atomic ratio H / C ( - )0.9Changes in the volatile yields
with atomic ratio H/C (1 atm)

Fig.14 Dependence of gas yields on atomic ratio (20K/s, 1 atm)
M. Maroto-Valer et al.[9],[10] investigated more than 15 coal types using 13C NMR(Carbon-13 Nuclear Magnetic Resonance) spectroscopy and suggested that thecomposition ratio of the aromatic compounds in each coal type decreases linearly withan increase in the H/C ratio. In the Progress DOE (United States Department ofEnergy) Report, Zilm et al.[11] suggested that the structure parameters of coals (i.e.,
the aliphatic-to-aromatic ratio) can be determined from the H/C ratio using 13C NMR.
Because the aliphatic-to-aromatic ratio can be determined using the H/C ratio [14],Ytar could also be determined using the H/C ratio.
Figure 15 shows the effect of raw coal property on the yields of the functional tar
components: benzene, toluene, and xylene (BTX). The yields of BTX components
increased with increasing H/C ratio. In agreement with the results of Fig. 13,
proportional increase of BTX components were observed.
Fig. 16 and 17 show the yields of two chemical raw materials, indene and fluorene,that can be used for advanced applications such as in medicines and resin
modifiers[3] and as a functional raw material[4], respectively. As shown in Fig. 16,
the yield of indene increases proportionally with the H/C ratio. However, as shown in
Fig.17, that of fluorene increases considerably only for coals with a high H/C ratio.
Furthermore, the yield of the normal chain saturated hydrocarbon, octane, shows asimilar tendency. We revealed that both the yields of functional tar components
increase for coal types with a high H/C ratio.
Finally, the yields of PAHs are discussed. Though not shown in figure, polycyclicaromatic components with 4- to 5-membered rings such as fluoranthene, dibenzo
anthracene and benzopyrene etc. were observed, and polycyclic components with 6- ormore-membered rings such as indenopyrene, and benzoperylene etc. were also
observed. There is no correlation between H/C and PAHs yield (Fig.18) except in thecase of polycyclic components with 3-membered ring (phenanthrene and anthracene－ 56 －

etc.), because the PAHs changes into soot and cokes (agglomerate components fromYieldamountof tar ofcomponent
Collected
tar component(g/g-coal（mg/L
Solv.) wt%)
daf×100,

liquid-tar to solid) are generated [12],[13].

1.8
180
1.6
160
1.4
140
1.2
120

P = 0.1MPa
HR = 20K/s
Tmax=1273K

Benzene

1.4ｗｔ％

100
1.0
80
0.8

Toluene0.6
60

0.8ｗｔ％

0.4
40m,p-Xylene

20
0.2
0.0
0
0.5

0.6

0.7

0.8

0.9

0.2ｗｔ％
1.0

Atomic ratio H/C

Fig.15

Effect of pressure on released
volatile matter in various coalranks (20K/s, 1 atm)

Fig.16

Effect of coal ranks on yield ofindene(for use in medicines andresin modifiers)

2.１ ガス化の実験
Fig.17

Effect of coal ranks on functional Fig.18
tar components(Fluorene:for use in organic EL
polymer skeletons, Octane: liquid
fuel for engine)

Effect of coal ranks on theyield of indenopyrene

As mentioned above, the variation in the yield with respect to an increased heating
rate and the effect of coal type can be shown quantitatively in the research
objective-(1).

－ 57 －

3. RESEARCH OBJECTIVE-(2)[Rapid Gasification of Biomass Feedstock at Low Temperatures]
3.1 Development of the Constituent Technologies
The rapid gasification of biochar at temperatures below approximately 600 °C is
important to establish a system in which the by-product gas can be modified to a
CO-rich gas and for which the FT synthesis is available using biomass at thetemperature of the waste heat from a coke oven. However, the antagonistic conditionsof low temperature and rapid gasification are difficult to attain simultaneously [14].
The pyrolysis rate of biomass is much faster than the gasification rate of char, and theoverall conversion rate of biomass is controlled by the gasification reaction rate ofchar in the region of the endothermic reaction. For research objective-(2), a study to
drastically increase the gasification reaction rate at low temperatures was performed
with an alkali catalyst directly supported onto the char at 0, 2, 6, 10, or 20 wt%. The
details of this study are described in the following section.
3.2 Experimental Apparatus and Method(Preparation of biochar sample and gasification method)
The wheat straw (≒3.0 mm), rice straw(≒3.0 mm), rice husk, and Douglas-fir(1.0 4.0 mm) were used in this study. Tables 3 and 4 show the results of ultimate andproximate analyses, respectively. The ash content increased in the order Douglas-fir
chip < wheat straw < rice straw < rice husk (see Table 4). The chars were sifted toobtain samples with nearly same diameters and lengths. Chars were prepared with
rapid heating rate in an argon environment. The pyrolysis conditions are shown in
Table 5.
The chars produced by the pyrolysis process described in before were gasified using
the thermobalance shown in Fig. 2 (ALVAC 9600). The gasification kinetic rates ofgrass and woody biomass-derived char have been revealed by measuring the rate ofweight loss during its reaction with CO2 as a function of temperature（Table 6,
800/900/1000℃, 0.1MPa） [15],[16]．Gasification rate was determined using Eq. (8)based on the random pore model [17],[18].
Table 3 Ultimate analysis

Douglas fir

H/C

C

1.31

52.10

Wheat straw 1.53

47.88

Ultimate analysis [daf wt%]
H
O
N
5.70
6.10

42.10
45.50

Table 4 Proximate analysisS

HV (d.b.) [J/g]VM

Proximate analysis [wt%]FC
AshMoist.

0.006

Douglas fir

19600

82.6

12.1

0.3

5.0

0.31

0.210

Wheat straw

17050

70.8

18.3

5.1

5.8

0.10

Rice straw

1.57

47.55

6.23

45.67

0.48

0.070

Rice straw

15520

65.5

16.6

11.1

6.8

Rice husk

1.52

48.94

6.21

44.46

0.34

0.050

Rice husk

14320

58.4

14.5

18.4

8.7

－ 58 －

Table 5 Char-preparation experiment.
Exposure gas

Temp.(K)Pressure(MPa)Heating rate (K/s)

Holding time(min)

Ar

1073

0.1

10

0

Table 6 Gasification experiment
Gasification Temp (K)Gasifing agent Flow rate (ml/min)1073, 1173, 1273

CO2

400

Pressure (MPa)0.1（Atmospheric pressure）

dX
 K p 1  X  1   ln(1  X )dt‥‥ (8)

Solving Eq. (8) analytically, we obtain K pt X  1  exp   K p t 1 
4  ‥‥ (9)

Transforming Eq. (9) and taking logarithms on both sides of the transformed
equation, we rewrite Eq. (10) as2

K p ln(1  X ) Kp tt
4‥‥ (10)

The gasification rate constant Kp and pore structure parameter ψ can be derived bydetermining the intercept and gradient of the straight line of -ln(1−X)/t versus t given
by Eq. (10)
3.3 Method for directly supporting the catalyst on char samples
A catalyst (i) is supported on the raw biomass or (ii) is directly supported on thechar. In general, a catalyst is supported on the raw biomass. However, a large amountof alkali metal (K, Ca, etc.) supported on the raw biomass may volatilize together
with the pyrolysates during the pyrolysis reaction [19]. Therefore, we attempt toprevent the catalyst from scattering by adopting method (ii), above. Herein, we
describe the direct method of supporting a catalyst on char. (This is new type of
supporting method.) The raw biomass was pyrolyzed with conditions as describedabove. The raw biomass char sample was immersed in potassium acetate solution([CH3COOK] aq = 0.2 mol/L). The water present in the solution was evaporated at
105°C so that all the K components in the solution could be supported on the char [19].

－ 59 －

(In a basic research, a raw biomass sample is immersed in a catalyst solution, as
mentioned above. In an actual plant, char is isolated from the raw biomass and acatalyst solution is sprayed onto the isolated char). The weight ratio ofchar-supported K catalyst was calculated using next equation.
Weight ratio of char-supported K= (weight of supported K) / (weight of char + weight of supported K)‥‥ (11)

Similarly, the biomass char sample was immersed in a 0.025-mol L-1 Fe(II) acetate
solution (Fe(II) acetate; Wako. Co.). The water present in the solution was evaporated
at 105°C so that all the Fe components in the solution could be supported on the char;this procedure is known as the evaporation drying method.
3.4 Experimental Results and Discussion
3.4.1 Effect of directly supported catalyst on rate-enhancement
The effect of a catalyst on the gasification rate is described below. From Fig. 19, thegasification rate of woody biomass can be improved remarkably by using potassium
supported on char; a small amount of potassium (approximately 2 wt%) is sufficient
to enhance the gasification of woody biomass char, which originally contains less ash,by three to four times or more. When the support ratio of K is 10 wt%, therate-enhancement ratio is greater than 10. Here, the rate-enhancement ratio is
calculated using the following equation: Rate enhancement = t/tK
where t and tK are the time required for carbon conversion from 0.0 to 1.0 for the raw
biomass char and the K-supporting biomass char, respectively. In Fig.20, the1

K: 10wt% K: 2.1wt%
0.8
Support effect0.6
Douglas fir (raw biomass char)
0.4

Douglas fir(K-supported char)

0.2
0

0

200

400

Time tFig.19T gasific = 900 [℃]
Pgasific = 0.1 [MPa]

600

800

[s]

Effect of supported-K on carbon
conversion rate
(Douglas-fir char: 900℃)－ 60 －

Carbon conversion X [ - ]Carbon conversion X [ - ]1

Supported
effect0.8

Rice straw (raw biomass char)
0.6

Rice straw(K supported char)

0.4

T gasific = 900 [℃]
Pgasific = 0.1 [MPa]

0.2
0
0

Fig.20

200

400

600

Time t

800

[s]

1000

1200

Effect of supported-K on
gasification rate
(Rice straw char: 900℃)

variation in X with time is compared between raw and rice straw chars. It is clearthat when the amount of supported K is approximately twice the ash content of raw
biomass, the gasification time would be 1/5 times that in the case of raw char.
Figures 21 - 23 show the Arrhenius plots. The temperature dependence ofgasification rate of K-supported chars indicates that the gasification can be activatedover the whole measured temperature range. In addition, in the case of K-supported
wheat straw char (Fig.22), rapid gasification (approximately Kp ≈ 0.1/min) can beachieved at a low temperature of 650°C. From the viewpoint of the overall
gasification process, the supported potassium significantly enhances the gasification
rate; hence, the FT synthesis system can be downsized and the gasification conditions
can be eased from higher temperature restriction.

Supporteffect

800℃

750℃

1

0.1

K support
ratio：2.1wt%

Douglas fir charRawbiomass
Douglasfir char

0.01

0.001

K-supported char:2.1wt%

0.000750.75

0.000850.85

1/T

Fig.21

Pgasific=0.1[MPa]K-supported char: 10wt%

Wheat straw char
0.01

Wheat
straw char
Raw biomass
Wheat
straw (supported
K)
K-supported
char
0.00090.9

1/T

Fig.22

900℃

800℃

Rice straw char

700℃

K support ratio：10.0wt%

Rice
Rawstraw
biomass char
Rice
K-supported
straw (supported
char
K)

0.001

0.8
0.00080.9
0.0009

1/T

Fig.23

1.0
0.001
1/T

[1/K×1000]

Effect of supported-K on gasification rate
(Rice straw char）－ 61 －

0.0011
1.1

Effect of gasifying temperatureon structure parameter(Wheat straw char)

0.1

0.01

0.001
1.0

1/T
[1/K×1000]

Pgasific=0.1[MPa]

1

650℃

0.1

0.00080.8

Effect of supported-K on
gasification rate
(Douglas-fir char)

700℃

K support ratio：10.0wt%

1[1/K×1000]

10

800℃

Pgasific=0.1[MPa]0.001

0.00095
0.95

1/T

900℃

10

K support ratio：10.0wt%

Gasification rate Kp [1/min]

Gasification rate Kp [1/min]

900℃

Gasification rate Kp [1/min]

1000℃

10

As shown in Fig. 21, in the case of wooden biomass (Douglas fir), the rate constantfor gasification of the biochar, Kp, with a small K-support ratio of 2.1 wt% was 1.5 - 4times that of the raw biomass char. When the K-support ratio was 10 wt%, the valueof Kp for the biochar was 20 - 25 times that of the raw biomass char. As seen in Fig. 23,
the temperature dependence of gasification rate of K-supported rice straw charindicates an increase in the gasification rate owing to the catalyst with decreasing
temperature and a decrease in the activation energy (i.e., the degree of slope).
3.4.2 Effect of the support ratio on rate-enhancement
Figures 24 and 25 show the gasification rates (Douglas-fir) of the K-supportingchar and the Fe-supporting char, respectively. The gasification rate Kp of thecatalyst-supporting char increased as the support ratio increased. The rate constantfor gasification of the char on which 10 wt% of K was supported (K10) wasapproximately 300 times that of the deashed char (K0). However, when more than 10
wt% of K was supported, the gasification rate tended to be saturated. For the
Fe-supporting char, although the gasification rate slightly increased as the support
ratio increased, the gasification rate Kp of the char was markedly lower when Fe was
supported than when K was supported. The gasification rates Kp of the char on which
23 wt% of Fe was supported (Fe23) at 900ºC and 1000ºC were approximately 3.3 and10 times, respectively, that of the deashed char (Fe0). Comparing Fig. 24 with Fig. 25
revealed that the gasification rate of (K10) was approximately 90 times that of Fe10.
Therefore, when K was directly supported on the char, the gasification rate at low
temperatures could be drastically enhanced.
At present, the mechanism for the catalytic gasification has been elucidated basedon the physical support morphology [22]. Here, the impregnation state of the catalyst
in the char is investigated using a scanning electron microscope (i.e., cross-sectional
analysis by EDS). Of course, there exist differences in this effect of each type ofcatalyst originally [20], [21].
For the K-supporting char, K was impregnated into the char, and the amount of K
increased as the support ratio increased (not shown in the figure). Additionally, thecrystal structure of K could not be confirmed. (I.e., in the char with a K-support ratio
below 10 wt%, K was evenly distributed in the char. When the K-support ratio wasabove 20 wt%, K was locally concentrated in the char. There is a threshold value of K
that must be supported on the char to achieve a homogeneous concentration.）
For the Fe-supporting char, Fe was difficult to impregnate into the char and that alarge number of Fe crystals (α-FeOOH, α-Fe2O3) were laminated on the char surface.

－ 62 －

For a char with a high support ratio, the excess supply of Fe on the char surface
during the initial gasification stage decreased the number of active sites, which
consisted of Fe and the char. Moreover, because the Fe crystals laminated on the charsurface were easily detached from the surface as gasification advanced, the Fe
catalyst could not function effectively.

Fig.24

Effects of the Fe support ratio on
the CO2 gasification rate

Fig.25

Effects of the K support ratio on
the CO2 gasification rate

4. CONCLUSION
The present study proposes a method to increase the yield of functional chemical
raw materials in order to use in advanced chemical applications (research
objective-(1)). Specifically, based on the results of (I) and (II) below, selecting a coaltype with a high H/C ratio and performing fast pyrolysis for the selected coal were
found to be important to obtain functional chemical raw materials. (I) The yields ofthe primary pyrolysis components such as benzene, styrene, indene, and naphthalene
increase drastically with increasing heating rate. In addition, the yield of 3- to
6-membered-ring tar components (polycyclic aromatic hydrocarbons: PAHs) increases
with increasing heating rate. (II) The tar yield increases linearly with the H/C ratio.
Especially, the yield of indene, which can be used as a functional raw material,
increased proportionally with increasing H/C ratio. Whereas, the yield of fluorene,
which can be used to enhance resin functionality, increased only for coals with a high
H/C ratio.
In the research objective-(2), this study aimed to realize the rapid gasification ofbiochar at low temperatures in order to produce liquid fuel from the by-product gas
and biomass in the temperature range of waste heat. The experimental results show

－ 63 －

that the high gasification rate of biomass char is appeared i.e., approximately 10
times higher than that of the raw biochar by directly supported catalyst. When using
grass biochar on which potassium is directly supported, rapid gasification can be
carried out at approximately 650°C. (When wheat straw is used, a gasification rate ofKp ≈ 0.1/min can be achieved.)
ACKNOWLEDGMENT
This research was financially supported by the JFE 21st Century Foundation．The
author is grateful to all those who have supported this study.
REFERENCE[1] Schobert, H.H. et al., Fuel 81 (2002) 15–32.
[2] Li, C. et al., Resources, Conservation and Recycling 54 (2010) 905-915.
[3] Coal Science and Coal Technology, Ed. Japan Institute of Energy, ISBN:
978-4-339- 06629-6, Corona Publishing Co. Ltd. (2013) 71-73.
[4] Dai Z. et al., European Polymer Journal 45 (2009) 1941–1948.
[5] Tanizawa K.，“Establish SCOPE type new coke oven battery at NSSMC Nagoya
works”，Proc. the 52nd Conference on Coal Science, The Japan Institute ofEnergy (2015), ii-vii[6] Cai H.-Y. et al., Fuel 75 (1996) 15-24.
[7] Gibbins-Matham J., Kandiyoti R., Energy Fuels 2 (1988) 505-511.
[8] Guillen M.D. et al., Fuel 74 (1995) 1595-1598.
[9] Maroto-Valer M. et al., Fuel 77 (1998) 783-785.
[10] Maroto-Valer M. et al., Fuel 77 (1998) 805-813.
[11] Zilm K., Advanced Solids NMR Studies of Coal Structure and Chemistry, Report

No. DOE/PC/95227-5, United States Department of Energy, 1998.
[12] Ledesma E.B. et al., Fuel 79 (2000) 1801-1814.
[13] Wijayanta A.T. et al., Fuel 93 (2012) 670-676.
[14] Hayashi J.，Journal of Chemical Engineering of Japan (The Society of Chemical

Engineers). Vol.76, No.4 (2012) , 190-192.
[15] Okumura Y., Journal of the Japan Institute of Energy, Vol.90, No.2 (2011),
122-131.
[16] Okumura Y. et al., Proc. Combustion Institute, Vol.32, Issue 2 (2009), 2013–2020.
[17] Bhatia S. K. et al., Carbon, Vol.34, Issue 11 (1996) 1383-1391.
[18] Zhang Y. et al., Fuel, Vol.87 (2008), pp.475–481.
[19] Davidsson, K.O. et al., Fuel, Vol.81 (2002) 137-142.

－ 64 －

[20] Mitsuoka K. et al., Fuel Processing Technology, Vol.92 (2011) 26–31.
[21] Huang Y. et al., Biotechnology advances, Vol.27 (2009) 568-572.
[22] Okumura Y. et al., “A consideration on mechanism of enhancement of gasification
rate of biomass char diagnosed by cross section of supported catalysts ”, Proc. the24th Annual Meeting of Japan Institute of Energy, No.3-2-1 (2015), pp.72-73.
[23] Hanaoka T. et al., Journal of Thermal Science and Technology, Vol.9, No.2 (2014),
DOI: 10.1299/jtst.2014jtst0006.

－ 65 －