平成 27年度
博士学位論文
Novel Utilization of Biomass for Activated Carbon Preparation and Catalytic Gasification
バイオマスを活用した新しい活性炭製造法及
びガス化法の開発
Boodsakorn Kongsomart (ブーサコン コンソムアート)
Novel Utilization of Biomass for Activated Carbon Preparation and Catalytic Gasification
バイオマスを活用した新しい活性炭製造法及
びガス化法の開発
by
Boodsakorn Kongsomart
A dissertation submitted to Graduate School of Engineering, Gunma University
For the Degree of Doctor of Engineering
Department of Environmental Engineering Science
Graduate School of Science and Technology
Gunma University
2016
Evaluation Committee
Professor Takayuki Ohshima, Chair
Faculty of Engineering, Gunma University, Japan
Professor Tomohide Watanabe, Vice-Chair
Faculty of Engineering, Gunma University, Japan
Professor Shinji Katsura, Vice-Chair
Faculty of Engineering, Gunma University, Japan
Associate Professor Reiji Noda, Vice-Chair
Faculty of Engineering, Gunma University, Japan
Professor Takayuki Takarada, Vice-Chair
Faculty of Engineering, Gunma University, Japan
I
Abstract
Biomass is an attractive material that much attention as renewable energy sources due to
their low-cost and environmental friendly. Biomass comprises organic compounds of carbons,
can reduce CO2 in the atmosphere by photosynthesis. Among various conversion
technologies, pyrolysis and gasification are one of the most attractive methods for biomass
utilization. In this research, the biomass ash as a catalyst prepared by combustion process for
the production of activation carbons (ACs) was investigated.
In Chapter 2 the effects of catalyst (chemical reagent and biomass) on specific surface
area and yield of activated carbon from biomass were investigated. CaCO3 and Ca(OH)2 are
catalysts in chemical activation. Chicken dropping compost is biomass as a catalyst to
compare the effect with chemical reagent. Activated carbon preparation was performed at
1000oC under N2 gas ambient. With increasing the amount of catalyst added, the specific
surface area was increased. The specific surface area of activated carbon reached the range
between 200 and 1100 m2g-1.
In Chapter 3, the preparation of the activated carbon (ACs) from teak sawdust (TS)
biomass mixed with chicken dropping compost ash (CCA) and empty fruit bunch ash
(EFBA) as activating agents were studied. The carbonization was done in pure N2 and
N2/CO2 stream gases by temperature range between 600 to 1000°C. The concentration of
CO2 in N2/CO2 gas was varied from 2 to 10%. The specific surface area (SSA) of TS mixed
with CCA (1:1 wt%) carbonized at 1000°C in N2 and N2/2%CO2 gas ambient was 930 and
1094 m2g-1, respectively. Larger SSA of carbonization in N2/2%CO2 gas ambient is due to
the reaction between CO2 gas and the carbon content in TS during pyrolysis. This can
II
increase pores and widen the pore size in ACs. Finally, the EFBA is more efficient in
increasing the SSA up to 30% compared to the CCA with the same process conditions.
In Chapter 4, the catalytic effects of two different biomass-derived ash catalysts, chicken
dropping compost ash (CCA) and empty fruit bunch ash (EFBA) on the performance of CO2
gasification of Loy Yang brown coal (LY) char were studied. The CO2 gasification was done
at temperatures between 650 to 800oC. It was found that the reaction rate was strongly
dependent on the temperature and the carbon conversion increases by increasing the CO2
gasification temperature. By using LY mixed with 10 wt% of EFB ash (EFBA), the maximum
char conversion of 1.0 with a high gasification rate was obtained when CO2 gasification was
carried out at 800oC for 30 min. Finally, the EFBA is more efficient in catalytic activity
compared to the CC ash (CCA) under the same conditions.
III
Table of contents
Abstract ..................................................................................................................................... I
Table of contents .................................................................................................................... III
Table of Figures ................................................................................................................... VIII
Table of Tables ...................................................................................................................... XI
Chapter 1. Introduction .......................................................................................................... 1
1.1 Current status of world energy consumption .............................................................. 1
1.2 Types of energy source ............................................................................................... 3
1.2.1 Fossil fuels ............................................................................................................. 3
1.2.2 Renewable energy .................................................................................................. 4
1.2.1.1 Biomass ...................................................................................................... 4
1.2.1.2 Geothermal energy ..................................................................................... 4
1.2.1.3 Hydroelectric power ................................................................................... 5
1.2.1.4 Wind energy ............................................................................................... 5
1.2.1.5 Solar energy ................................................................................................ 5
1.2.1.6 Solar thermal system .................................................................................. 5
1.3 World energy production ............................................................................................ 6
1.3.1 Oil ........................................................................................................................... 6
1.3.2 Coal ........................................................................................................................ 7
1.3.3 Natural gas .............................................................................................................. 8
IV
Table of contents (con't)
1.3.4 Biomass .................................................................................................................. 8
1.3.5 Nuclear ................................................................................................................... 8
1.4 Energy related issues ................................................................................................. 10
1.4.1 Global warming .................................................................................................... 10
1.4.2 Fossil fuel combustion .......................................................................................... 10
1.5 Technology development for power generation cost ................................................ 11
1.6 Biomass conversion technology ................................................................................ 12
1.7 Methods of biomass conversion ................................................................................ 14
1.7.1 Direct fired or conventional steam boiler ............................................................. 15
1.7.2 Co-firing ............................................................................................................... 16
1.7.3 Pyrolysis ............................................................................................................... 16
1.7.4 Gasification .......................................................................................................... 17
1.8 Description of the process ......................................................................................... 18
1.9 Pyrolysis process technology .................................................................................... 20
1.9.1 Slow pyrolysis ...................................................................................................... 20
1.9.2 Fast pyrolysis ........................................................................................................ 20
1.9.3 Flash pyrolysis ...................................................................................................... 21
1.10 Activated carbon ....................................................................................................... 22
1.10.1 Activation process .............................................................................................. 24
V
Table of contents (con't)
1.10.2 Carbonization ..................................................................................................... 24
1.10.3 Activation ........................................................................................................... 26
1.10.4 Applications of activated carbon from lignocellulosic biomass ........................ 27
1.10.4.1 Removal of SO2 ....................................................................................... 27
1.10.4.2 Removal of NO2 ....................................................................................... 29
1.11 Catalytic gasification ................................................................................................. 29
1.12 Interesting biomass used in this experiment ............................................................. 32
1.13 Relevant research ...................................................................................................... 33
1.14 Objective of this study ............................................................................................... 35
References ................................................................................................................................ 36
Chapter 2. Activated carbon from biomass using chemical reagents ............................... 42
2.1 Introduction ............................................................................................................... 42
2.2 Experimentals ............................................................................................................ 43
2.2.1 Materials ............................................................................................................... 43
2.2.2 Experimental set-up .............................................................................................. 44
2.2.3 Sample preparation ............................................................................................... 45
2.2.4 Characterization of the activated carbons ............................................................ 45
2.3 Results and discussion ............................................................................................... 45
2.4 Summary ................................................................................................................... 49
References ............................................................................................................................ 50
VI
Table of contents (con't)
Chapter 3. Preparation of activated carbons from teak sawdust using chicken dropping
compost and empty fruit bunch ............................................................................................ 52
3.1 Introduction ............................................................................................................... 52
3.2 Experimentals ............................................................................................................ 53
3.2.1 Raw materials ....................................................................................................... 53
3.2.2 Sample preparation ............................................................................................... 54
3.2.3 Characterization of the activated carbons ............................................................ 55
3.3 Results and discussion ............................................................................................... 55
3.3.1 Preparation of ACs from TS mixed with CCA activating agent .......................... 55
3.3.1.1 Effects of CCA activating agent ................................................................ 55
3.3.1.2 Effects of ash to biomass weight ratio ....................................................... 56
3.3.1.3 Effects of carbonization gas ambient using CCA activating agent ............ 58
3.3.1.4 Effects of carbonization temperature using CCA activating agent
on CO2 gas ................................................................................................. 59
3.3.1.5 Effects of CO2 concentration in carbonization process using CCA
activating agent .......................................................................................... 62
3.3.2 Comparison of CCA and EFBA activating agents ............................................... 63
3.4 Conclusions ............................................................................................................... 65
References ................................................................................................................................ 66
VII
Table of contents (con't)
Chapter 4. Catalytic effects of biomass on Loy Yang brown coal gasification ................ 70
4.1 Introduction ............................................................................................................... 70
4.2 Experimental ............................................................................................................. 72
4.2.1 Materials ............................................................................................................... 72
4.2.2 Catalytic gasification ............................................................................................ 73
4.3 Results and Discussion .............................................................................................. 73
4.3.1 Characteristic of biomass ash ............................................................................... 73
4.3.2 Effect of gasification temperature on LY char conversion .................................. 76
4.3.3 Effects of biomass ash contents ............................................................................ 76
4.3.4 Effect of biomass-derived ash type ...................................................................... 78
4.3.5 Comparison of chemical reagent with ash ........................................................... 81
4.4 Conclusions ............................................................................................................... 84
References ................................................................................................................................ 85
Chapter 5. Conclusions .......................................................................................................... 88
Acknowledgements ................................................................................................................ 90
Publication lists ...................................................................................................................... 92
Author biography .................................................................................................................. 94
VIII
Table of Figures
Figure 1-1. World energy consumption from 1908 to 2030. ..................................................... 2
Figure 1-2. Historical and forecast data on global oil production in 1859 to 2100. .................. 6
Figure 1-3. Historical and forecast data on global coal production in 1900 to 2100. ................ 7
Figure 1-4. Global coal reserves in 2012. .................................................................................. 7
Figure 1-5. World gas productions. ........................................................................................... 9
Figure 1-6. Development of global biomass use by main world regions from 1990 to 2010. .. 9
Figure 1-7. Global warming mechanism ................................................................................. 10
Figure 1-8. CO2 emission from fossil fuel combustion by section and fuel type in 2006. ...... 11
Figure 1-9. Learning curves for power generation technologies up to 2030. .......................... 12
Figure 1-10. Sources of biomass for conversion to energy. .................................................... 13
Figure 1-11. Renewable nature of biomass conversion into energy. ....................................... 13
Figure 1-12. Thermochemical processes for biomass conversion. .......................................... 15
Figure 1-13. Schematic reaction zones of wood pyrolysis ...................................................... 18
Figure 1-14. Reaction paths of biomass pyrolysis. .................................................................. 18
Figure 1-15 Pyrolysis process technology. .............................................................................. 21
Figure 2-1. Schematic diagram of pyrolysis process used in this experiment. ........................ 44
Figure 2-2. Specific surface area of biomass char after pyrolysis in N2 gas ambient at 1000°C.
.................................................................................................................................................. 46
Figure 2-3. Specific surface area of activated carbon obtained from different types of biomass
mixed with various types of catalyst at the ratio of 1.0. ....................................... 47
Figure 2-4. Specific surface area of activated carbon obtained from different types of biomass
mixed with various types of catalyst at the ratio of 3.0. ....................................... 48
IX
Table of Figures (con't)
Figure 2-5. Activated carbon yield of activated carbon obtained from different types of
biomass mixed with various types of catalyst at the ratio of 1.0. ......................... 48
Figure 2-6. Activated carbon yield of activated carbon obtained from different types of
biomass mixed with various types of catalyst at the ratio of 3.0. ......................... 49
Figure 3-1. Specific surface area of TS and TS mixed with CCA. .......................................... 56
Figure 3-2. Specific surface area and yield of ACs with different CCA to biomass weight
ratio. ...................................................................................................................... 57
Figure 3-3. Adsorption isotherm of ACs with different CCA to biomass weight ratio. .......... 58
Figure 3-4. Specific surface areas of the ACs from TS prepared in pure N2 and N2/2%CO2
gas ambient at the carbonization temperature of 1000oC. .................................... 59
Figure 3-5. Specific surface area and ACs yield obtained from carbonization process in
N2/2%CO2 gas ambient by varied the carbonization temperature from 600 to
1000oC. ................................................................................................................. 60
Figure 3-6. Pore size distribution obtained from carbonization process with N2/2%CO2 gas
ambient at different carbonization temperatures. ................................................. 61
Figure 3-7. Specific surface area and ACs yield with different CO2 concentration in N2/CO2
gas ambient at 600oC. ........................................................................................... 63
Figure 3-8. Specific surface area of ACs from TS mixed with CCA and EFBA by varied the
ash/biomass weight ratio from 0.6 to 1.0 and carbonized in different gas ambient
at 1000oC. ............................................................................................................. 64
Figure 3-9. Pore size distribution of ACs from TS mixed with CCA and EFBA with the
ash/biomass weight ratio of 1.0 and carbonized in N2 gas ambient at 1000oC. ... 65
X
Table of Figures (con't)
Figure 4-1. XRD patterns of EFBA. ........................................................................................ 75
Figure 4-2. XRD patterns of CCA. .......................................................................................... 75
Figure 4-3. CO2 gasification profiles of LY char. ................................................................... 77
Figure 4-4. CO2 gasification profiles of LY1 char at different EFBA contents of 2 to 10 wt%.
.............................................................................................................................. 77
Figure 4-5. CO2 gasification profiles of LY1 char (10 wt% of EFBA). .................................. 79
Figure 4-6. CO2 gasification profiles of LY2 char (10 wt% of CCA). .................................... 79
Figure 4-7. XRD patterns of LY1 char (10 wt% of EFBA) after CO2 gasification. ................ 80
Figure 4-8. XRD patterns of LY2 char (10 wt% of CCA) after CO2 gasification. .................. 80
Figure 4-9. Effect of gasification temperature on the conversion of LY char with and without
mixing with 10 wt% of EFBA and 10 wt% of CCA. ........................................... 81
Figure 4-10. Comparison of conversion of LY1 char (10 wt% of EFBA) and LY3 char of
(10 wt%) of K2CO3) at 700°C. ............................................................................. 82
Figure 4-11. Comparison of conversion of LY2 char (10 wt% of CCA) and LY4 char of
(10 wt%) CaCO3) at 700°C. ................................................................................. 82
Figure 4-12. XRD patterns of LY1 char (10 wt% of EFBA) and LY3 char
(10 wt% of K2CO3) after gasification at 700°C. .................................................. 83
Figure 4-13. XRD patterns of LY2 char (10 wt% of CCA) and LY4 char
(10 wt% of CaCO3) after gasification at 700°C. .................................................. 83
XI
Table of Tables
Table 1-1 Total ultimately recoverable conventional oil resources. .......................................... 6
Table 1-2 Formation of different products from various types of pyrolysis ............................ 22
Table 1-3 Type of pyrolysis in relation to operating processes and products with greater yield.
.............................................................................................................................. 22
Table 1-4 Ultimate and proximate analysis of lignocellulosic biomass used for air pollution
control. .................................................................................................................. 25
Table 1-5 Various activation conditions for preparation of lignocellulosic chars. .................. 27
Table 1-6 Preparation method and adsorption capacity of various activated carbons from
lignocellulosic biomass. ....................................................................................... 28
Table 1-7 Characteristics of activated carbon used for removal of SO2. ................................. 28
Table 1-8 The preparation conditions and characteristics of activated carbon for removal of
NO2. ...................................................................................................................... 29
Table 1-9 The most important char-gas reactions and its effective catalysts. ......................... 30
Table 2-1 Proximate and ultimate analysis of raw materials ................................................... 44
Table 3-1 Proximate and ultimate analysis of the teak sawdust .............................................. 54
Table 3-2 Composition of metal oxide in CCA and EFBA ..................................................... 55
Table 3-3 Parameters of the activated carbon obtained from the carbonization process ......... 60
Table 4-1 Proximate and ultimate analysis of the Loy Yang brown coal ................................ 73
Table 4-2 Elements of biomass ash ......................................................................................... 74
Chapter 1
Introduction
Energy is an essential physical substance to perform work for human being. The energy
is useful for the economic, technology, social, which can improve our quality life. The
various forms of energy such as heat, light, electrical, etc. are obtained from the conversion
of the fuel. The utilizing of energy, fuel has converted numerous times before it reaches to
the point-of-use such as household, factory, department store and automotive.
Typically, the energy source can be categorized into three groups (1) fossil fuel, (2)
nuclear-powered source and (3) renewable energy. The fossil fuels are in the form of coal,
petroleum, and natural gas. The nuclear-powered source can be produced by nuclear fission
or nuclear fusion reaction. In case of renewable energy sources, the energy can be converted
from solar, wind, hydroelectric, geothermal power and biomass. According to the
International Energy Agency (IEA), the global energy consumption has grown up doubled in
the past 50 years related to the increasing of the world population. It was predicted that 88%
of world energy will be consumed from the fossil fuels in 2030.
Not only the energy shortage which might occurs in the near future, the energy related
issues, especially the global warming should be considered. Therefore, the new methods to
produce energy, especially from renewable energy resource with sustainable and
environmental friendly, are developing.
1.1 Current status of world energy consumption
Nowadays, the main energy consumption is fossil fuels including oil, gas, and coal. The
fossil fuels consumption will reach 10 gigatons of oil equivalent (Gtoe) per year with 1.6 tons
of oil equivalent (toe) as energy consumption per occupant. According to IEA research, the
2
primary energy consumption has grown by 49% but the CO2 emission was also increased by
43% during past two decades (1984–2004) [1-3]. The average annual increasing of energy
consumption and CO2 emission was 2% and 1.8%, respectively. Moreover, the world energy
consumption is predicted to increase up to 70% in 2030 as the graph shown in Fig. 1-1. The
world gross inland consumption (GIC) shows that oil still represents the largest share of the
energy source (34%) in 2030.
It was predicted that the global energy that obtains from renewable sources including
hydropower, geothermal energy wind, solar and hydropower energy will reach 8% of total
world energy requirements in 2030. This prediction is lower than 13% of the energy utilizing
that observed in 2000 due to the continuous decline of biomass consumption in Asia and
Africa. However, the evolution of the share of renewables in total energy consumption in
Europe countries is highest progression among other industrialized regions.
Figure 1-1. World energy consumption from 1908 to 2030.
3
1.2 Types of energy source
In this section, the types of energy source including fossil fuels, renewable energies, and
nuclear-powered source will be briefly introduced.
1.2.1 . Fossil fuels [4-8]
The fossil fuels are the energy source that obtained from the remains of ancient plants and
animals, which accumulated in the geologic over hundreds of millions of years. Those
organic materials are acts like hydrocarbon-containing natural resources. After those natural
buried substances are reacting with the heat and pressure in the earth's crust, it can be
converted to the form of coal, crude oil, natural gases and heavy oils.
Coal is formed by the decomposing of remained plants by using high atmospheric
pressure and high temperature through the calcification process. Based on the different types
of the nature sources, more than 1,200 different compositions of coal are available.
The natural gas is one form of fossil fuels that commonly found at the inner layers of
earth or at the surface of the petroleum reservoirs. Among the natural gases, methane is the
environmental friendly compared to the other forms of fossil fuel that normally used for
household purpose.
Petroleum is transformed by the remains of oceanic plants and bacteria over million years.
This type of fossil fuel is consumed around 40% of the world demand of energy.
Crude petroleum is used to produce various types of distillate fuels such as kerosene, jet
fuel and so on. Moreover, the by-products of the petroleum distillation can be used in plastic
production.
Although the fossil fuels are useful energy resource, the utilizing of fossil fuels is one of
the largest sources to emit the carbon dioxide (CO2) to the atmosphere. The accumulation
layer of CO2 in the atmosphere can reflect the UV radiation to the ground and it also can trap
the heat, which is the root cause of greenhouse effects that contributes to global warming.
4
1.2.2 Renewable energy
The renewable energy is the clean energy that considering using instead of conventional
fossil fuels. The sources of renewable energy from natural are rain, sunlight, wind, waves,
tides, and geothermal heat. Typically, the renewable energy can be applied in four
applications; (1) electricity generation, (2) air and water heating/cooling, (3) rural energy
services, and (4) motor fuels. In this section, six types of renewable energy sources including
biomass, geothermal energy, hydroelectric power, wind energy, solar energy, and solar
thermal systems will be introduced.
1.2.1.1 Biomass [9-10]
Biomass is a carbon-based biological material that derived from plant-based materials,
which is a living or recently living organisms. Biomass is a substance that composed with a
mixture of organic molecules including hydrogen, oxygen, nitrogen, alkali, alkaline earth,
and heavy metals. The metal components in biomass are found in the form of functional
molecules called porphyries, which include chlorophyll that contains magnesium.
1.2.1.2 Geothermal energy [11-13]
Geothermal energy is an energy that release from the earth’s core. The high temperature
around 5000°C of the earth’s core can melt the outer layers of mantle and become magma.
When the rain water seeps down through the cracks of geological, it will react with
superheated of the magma or the hot rocks beneath. Then the rain water that suddenly heated
at the magma surface will vaporized and release back to the earth surface in the form of high
pressure vapor. An example of the utilizing of geothermal energy at the earth surface is hot
springs (or called geysers).
5
1.2.1.3 Hydroelectric power [14-15]
Hydroelectric power is the form of electricity that generated by the movement of water
stream on the hills and mountains that that eventually move down to the lower ground level
by gravity force. The movement of water pass through the turbine blades can generate
electricity. The cycling of rain fall and melting snow make the hydropower is the cheapest
and most clean fuel renewable source.
1.2.1.4 Wind energy [16]
Wind energy is generated by converting wind flow through the wind turbines. The wind
turbines convert the force of the wind to propel an electric generator to create electricity. The
multiple wind turbines can be installed on-shore (land) and off-shore (sea) to generate the
electricity grid.
1.2.1.5 Solar energy [17-18]
The solar energy is an energy source that can be used to produce electricity. The heat and
photons in the sunlight is reacts with the surface of semiconductor device called Photovoltaic
(PV) cell. The photons and sunlight energy is collected by the PV cell and convert to
electricity that can keep in the battery for further utilization.
1.2.1.6 Solar thermal system [19-20]
Solar thermal electric energy is the energy that utilizing the sunlight to heat up the fluid
or gas in the heat engine to rotating the motor. The heat engine such as steam engines and gas
turbines has efficiency around 30 to 40%, which can produce megawatts of power.
6
1.3 World energy production
1.3.1 Oil
The majority of oil production comes from different offshore area such as West
Siberia, Persian Gulf region, East Siberia, Caspian Sea, South America, and Gulf of Mexico.
Table 1-1 estimates that the average world conventional oil ultimately recoverable resources
(URR) is 510 Bt. Figure 1-2 shows that by the end of the 21st century, world cumulative oil
production will reach 4700 to 5000 Bt.
Table 1-1 Total ultimately recoverable conventional oil resources.
Indicator Bt %
Cumulative production 165 32
Reserves 162 32
Undiscovered resources 183 36
Ultimately recoverable oil resources 510 100
Figure 1-2. Historical and forecast data on global oil production in 1859 to 2100.
7
1.3.2 Coal
Figure 1-3 shows that the global coal production predicted by IPGG is around 10 to
12 Btpa in the year of 2030 to 2040. The limits to growth in global coal production are
related to the environmental restrictions and depletion of the coal resource base. However,
United States of America (USA) and Russia reserves coal more than 50% of the total world
coal reserves (395 Bt). Those countries plan to increase their coal production in the 21st
century. Figure 1-4 show that the world coal reserves (431 Bt) except USA and Russia, will
produce about 10 to 11 Bt by 2060. Therefore, many countries are increasing their
investments in exploration of high-grade coal resources. [21]
Figure 1-3. Historical and forecast data on global coal production in 1900 to 2100.
Figure 1-4. Global coal reserves in 2012.
8
1.3.3 Natural gas
Figure 1-5 show the increasing of the world gas production from 1975 to 2025. The
OECD region shows the increasing of gas production of 3% between 2000 and 2025. It was
predicted that OECD will produce more than 40% of the world’s total gas production in 2025.
However, the CIS region also produce one third of the gas production, which is almost
equally allocated to OECD. Moreover, ten largest gas producers across the different
continents will support more than 80% of the world’s total natural gas production in 2030. [22]
1.3.4 Biomass [23]
Figure 1-6 shows that OECD Europe has increased the global sharing of bioenergy
demand from 6 to 10%, while China decreased their sharing from 22 to 16%. Among the
different types of biomass, wood fuel such as pellets, fuel wood and charcoal, and biodiesel,
palm oil, bioethanol are the most widely used and commercial. The volume of trading the
wood products that used as energy has reached 1 EJ in 2011. This amount is equal to 2% of
the total use of biomass energy around the world. The wood pellets is the largest biomass
products that has been traded (130 PJ) in 2011. The mainly wood pellets are based on
sawdust and wood residues as feedstock. Moreover, the bioethanol which exported from
Brazil (48%), USA (6%), and France (6%) are more than half of the global market.
1.3.5 Nuclear [24]
In 2005, the 442 nuclear power plants in global with a total capacity around 370 GWe
produced 16% of the world total electricity power consumption (2626 TWh). Among the
worldwide, USA has the largest number of reactors while France using nuclear power as a
main source for electricity generation. It was predicted that the nuclear power plants in global
will have a capacity between 279 and 740 GWe in 2030.
9
In Japan, nuclear power is the main source for electrical generation. Therefore, more than
55 nuclear reactors are currently operated to produce 40% of total national electricity
consumption. However, the plans for construction of new reactors in Japan have been scaled
down due to the safety consideration after the disaster at Fukushima nuclear power plant. In
China, nine reactors are in operation and 40 new reactors will be installed to support a total
capacity of 41 to 46 GWe by 2020.
Figure 1-5. World gas productions.
Figure 1-6. Development of global biomass use by main world regions from 1990 to 2010.
10
1.4 Energy related issues
1.4.1 Global warming [25-26]
Global Warming is one of the most severe problems in global due to the increasing of
average surface temperature of the atmosphere. By burning the fossil fuels, various types of
gases such as carbon dioxide (CO2), carbon monoxide (CO), methane, nitrous oxide are
released to the atmosphere. It was found that increasing small amount of carbon dioxide
(CO2) in atmospheric can cause a substantial increase in the Earth’s surface temperature. The
mechanism of CO2 emissions from and trap heat to escape from Earth atmosphere are shown
in Fig. 1-7. As we know that the earth’s temperature is going to increase due to huge
consumption of fossil fuels in the next century. Therefore, the reduction of the emission of
CO2 to the atmosphere should be decreased to prevent the disaster from the greenhouse
effects.
1.4.2 Fossil fuel combustion
During the combustion of fossil fuels such as petroleum, natural gas, and coal to produce
energy, the carbon content such as CO2 that stored in fossil fuels is emitted to the atmosphere.
Figure 1-8 shows that the petroleum supplied the largest portion of domestic energy demands,
accounting of 47 % of total fossil-fuel-based energy consumption in 2006. In contrast, coal
and natural are taken account of 27 and 26 % of total fossil fuel consumption, respectively.
Figure 1-7. Global warming mechanism. [25]
Sunlight Sunlight
Earth Earth
Greenhouse gas
Greenhouse gas
Sea Sea Land Land
11
Figure 1-8. CO2 emission from fossil fuel combustion by section and fuel type in 2006 [27].
1.5 Technology development for power generation cost [28]
Besides the limits of natural sources of fuels that might be affects to its prices in the
future due to mismatch of demands and supply and the CO2 emission from the fuel
combustion process that generate the greenhouse effects, the development of alternative
energy technologies is required. The projection of technology development that is consistent
with historic trends is shown in Fig. 1-9.
To describe the enhanced technology performance, the conversion efficiency, total
investment cost and operation cost are changed. The hybrid approach is applied to the
technology development to estimate the amount of research that necessary to bring about
accelerated technological progress rather than the issue of higher R&D investments. This can
be used to determine the focusing technology policies to provoke technological development.
Note: Electricity generation also includes emissions of less than 0.5 Tg CO2 Eq. from
geothermal-based electricity generation.
12
Figure 1-9. Learning curves for power generation technologies up to 2030.
1.6 Biomass conversion technology
Biomass is the most abundant and renewable organic resources that comprises of all
biological materials. The biological waste (dead biomass) can be used for producing the
energy such as electricity and heat or used for an indirect source of energy such as fuels. The
living organisms or their components such as algae, microorganisms and enzymes can be
used to produce energy using biofuels cells. Figure 1-10 shows various sources of biomass
that can be used for biomass conversion into energy. In the total process of biomass
conversion to energy, including the purpose of energy generation and environmental cleanup
is accomplished.
Inve
stm
ent [
Euro
/kW
]
Cumulative installed capacity [MW]
13
Figure 1-10. Sources of biomass for conversion to energy.
Figure 1-11. Renewable nature of biomass conversion into energy.
The factor of timeframe is one important parameter that should be considered for the
renewable of the energy source. For example, the energy from the fossil fuels such as coal,
oil, and natural gas take million years to renew. Beyond the fossil fuels, sunlight is an
infinitely abundant renewable source of energy. Therefore, it is very interesting to reduce the
time frame that required to converted sunlight into usable energy.
14
Among those renewable energy sources, biomass such as plants and trees are
excellent sources. Those biomasses can be considered as perpetual capable utilizing
photosynthesis to continuously tapping the energy from sunlight and converting it into
carbon-rich compounds as the mechanism shown in Fig 1-11.
Figure 1-11 shows the carbon that released into the atmosphere from burning process
of biomass can returns to the biomass by photosynthesis. After that, it is converted into
carbon-rich compounds for reconversion into energy. The photosynthesis process can
produce carbon positive, which is the carbon neutral unlike fossil fuel. For example, the
remaining CO2 in the atmosphere from the burning process of fossil fuel increases the total
amount of CO2. However, the conventional sinks such as trees and soils cannot absorb large
amount of CO2 in the atmosphere.
Therefore, it is necessary to reduce the global CO2 emissions by using the effective
energy generation technologies, which generates carbon negative. Based on various
technologies, Bioenergy with carbon capture and storage (BECCS) method are expected to
obtain net negative carbon emissions in global. This carbon capture and storage (CCS)
technology can release of CO2 into the atmosphere and redirect it into geological storage area.
Beyond the BECCS and CCS technology, high solar efficiency cultivation is an alternative
method to achieve carbon negative.
1.7 Methods of biomass conversion [28-32]
The technologies of biomass conversion can be classified into primary and secondary
conversion technologies. The primary conversion technologies such as combustion,
gasification and pyrolysis are directly convert the biomass into heat or other convenient form
of energy carrier such as (1) gases (methane and hydrogen), (2) liquid fuels (methanol and
ethanol), and (3) solids (char). The secondary technologies convert these primary conversion
15
products into the desired form of energy product such as transportation fuel or electricity. The
different thermochemical conversion processes are given in Fig. 1-12.
Figure 1-12. Thermochemical processes for biomass conversion.
The thermochemical processes involve high temperature and high pressure processing
of biomass. The combustion process to generate heat and/or power such as direct fried
(conventional steam boiler) and co-firing is done by heating the biomass in the excess oxygen
ambient. Those techniques are accounting for over 97% of the world’s bioenergy production.
The other processes such as pyrolysis and gasification are the heating process in the presence
of controlled oxygen to produce liquid fuels, heat and power.
1.7.1 Direct fired or conventional steam boiler
The direct fired or conventional steam boiler is the technique to covert the woody
biomass to the energy. In a direct-fired system, biomass is feed into the bottom parts of the
boiler, which connected to the air supply. When the biomass feedstock is burned, the hot
16
combustion gases are generated and pass through a heat exchanger. In this step, the water is
boiled and become a high pressure water steam that can use to rotate the turbine to generate
the electricity by driving the electricity generator.
To improve the efficiency of the direct fried process, the starting biomass is dried and
the size is reduced by Pelletization process. The size of pelletized (briquetted) biomass that
was reduced by mechanical process can improve the handling and the combustion
characteristics of biomass. For much more efficiency, the heat generated by the exothermic
process of combustion to power the generator can also be used to regulate temperature of
buildings and plant.
1.7.2 Co-firing
Co-firing is the simplest method to convert the biomass to energy by burning two
different types of materials at the same time. For example, the mixing of woody (15 wt%)
with biomass such as willow and switch grass can reduce the materials cost. The advantages
of adding small portion of biomass in coal boiler is to decrease the nitrogen and sculpture
oxides, which causes the formation of various types of air pollutions such as smog, acid rain
and ozone. Moreover, small amount of CO2 is released into the atmospheres. Therefore, the
co-firing method is low cost, more efficiency, cleanly and sustainable renewable energy.
1.7.3 Pyrolysis
Pyrolysis is an attractive method overcome the solid biomass due to it can convert
solid biomass into a transportable and easily stored fuel. In pyrolysis, the residues biomass
from nature such as wood residuals, and biogases, is inserted to high temperatures vacuum
chamber in the absence of oxygen resulting the generation of pyrolysis oil (bio oil), chars, or
singes. The advantage of pyrolysis process is that ash or energy did not generated during
transformation. The types of biomass is significantly effects the efficiency of pyrolysis
17
method. For example, straw and other agro-residues are important as an energy sources.
However, straw has high ash content which causes problems in pyrolysis.
1.7.4 Gasification
Gasification is a high efficiency process that can convert biomass into combustible
gases. There are two kinds of gasification process called direct gasification and indirect
gasification. Direct gasification process uses the combustion of air or oxygen to generate heat
through exothermic reactions. Indirect gasification process can transfer heat to the reactor
from the outside. The burned gas by-products can produce the heat for industrial and house
and it can use for mechanical or electrical power purposes. The conversion efficiencies
obtained from gasification is between 60 to 90%. Moreover, the gas can also use to produce
synthetic fuels.
Biomass gasifies can be categorized to updraft and downdraft. In case of updraft unit,
biomass is fed from the top of the reactor and air is injected into the bottom of the fuel bed.
By this setting, the efficiency of updraft gasifies can increase up to 90%. However, the gas
must be cooled before usage in the internal combustion engines due to the formation of tars.
Therefore, updraft unit is normally used for direct heat applications. Among those
gasification processes, the fluidized bed technology has a higher throughput due to its
superior heat and mass transfer with good uniform temperatures that creates faster rate of
reaction. Furthermore, the fluidized bed technology has better fuel moisture utilization
compared to the others gasification techniques.
18
1.8 Description of the process [30, 32]
Thermochemical conversion of biomass such as pyrolysis, gasification and
combustion is the most promising technologies for energy production. In this section, the
details of pyrolysis process will be introduced. Pyrolysis is one of the thermochemical
conversion processes that decompose the organic materials at elevated temperature as the
schematic shown in Fig. 1-13. Note that the oxygen did not participate into the pyrolysis
process. When the temperature is below 400°C, the pyrolysis process is defined as
carbonization which can produce charcoal, liquid fuels (heavy and light oils) and fuel gas.
However, when the pyrolysis temperature increases to 1000°C, a complete gasification of
biomass has occurred.
Figure 1-13. Schematic reaction zones of wood pyrolysis [30]
Figure 1-14. Reaction paths of biomass pyrolysis.
19
Figure 1-14 shows the reaction paths of biomass pyrolysis. In this reaction, the solid
materials are transformed into liquid and gas fractions with low to medium calorific value.
The calorific value is combines with synthesis gas (CO, H2 and CH4) and other low
molecular weight hydrocarbons. The liquid fraction that contains water and organic
compounds with low to medium molecular weight is called Tar. A solid carbonaceous
portion is called Char. Therefore, the advantages of pyrolysis are the capability to use wide
variety of materials and it can produce lower emissions of nitrogen oxides and sulphur
compared with other technologies. Moreover, the energy recovery of pyrolysis process can
reaches up to 70%. [33]
Typically, the by-products that obtain from pyrolysis reaction can be classified into
three groups called (1) synthesis gas, (2) tar, and (3) char. The synthesis gas is compose of
primarily of hydrogen, carbon oxides (CO and CO2), and gaseous hydrocarbons such as
methane. The calorific value of synthesis is around 13 to 15 MJ/Nm3.
Second, tar is the liquid product in the form of condensable organic (bio-oil) that
obtain from pyrolysis. The oily liquid portion consists of two phases called aqueous phase
and non-aqueous phase. An aqueous phase is an organic compounds containing oxygen with
a low molecular weight. A non-aqueous phase is an insoluble organic compound with a high
molecular weight such as aromatic.
Char is a solid carbon residue with low ash content. The density of char is 150 to 300
kg/m3 and it has a relatively high PCI (30 MJ/kg). Typically, char is used as a fuel to power
the pyrolysis process. Char also can be used for drying the biomass before putting it into the
reactor. Char is stable and complex for handling and does not degrade biologically.
20
1.9 Pyrolysis process technology [32-35]
Bio-oil from pyrolysis process can be used instead of conventional fuel oil and diesel
for electricity generation equipment such as furnaces, boilers and turbines. The utilizing of
pyrolysis is shown in Fig. 1-15. Based on the process parameters (reaction temperature,
heating rate, residence time) and products, pyrolysis can be categorized into three groups; (1)
slow pyrolysis, (2) fast pyrolysis and (3) flash pyrolysis.
1.9.1 Slow pyrolysis
Slow pyrolysis is typically occurs at reaction temperature over 400°C with long
residence time of 4 to 8 mins. The heating rate of 1 to 5°C/sec is typically used to balance
and stabilize the reactions. By using this optimized condition, large amount of gaseous phase
of the products will be obtained because of the complete secondary reactions. When the
process temperature increased from 400°C to 700°C, the final char yields and liquid products
decreased due to increasing of volatiles from tar. The maximum value of liquid products can
be obtained at the temperature of 550°C. That means, slow pyrolysis is subjected to the
secondary reactions which generates small amount of liquid products but generates large
amount of gas products.
1.9.2 Fast pyrolysis
Fast pyrolysis is typically occurs at reaction temperature between 500 to 950°C with
very short residence time of 1 to 5 s. The heating rate of fast pyrolysis is 100 to 300°C/sec.
The purpose of short residence time is to reduce the formation of intermediate products and
also increase the yield of tar up to 80 wt% of dry biomass. When the residence time is too short
(< 1 s), an incomplete depolymerization of biomass has occurred. Moreover, the liquid product is
21
Figure 1-15. Pyrolysis process technology.
not homogeneous due to the contribution of instability of bio-oil. To produce a high heating rate,
the cool down pyrolysis vapors should be very rapidly to obtain more stable product. To produce a
high heating rate, smaller homogenous particles are necessary. The small homogeneous particles
are often pre-treated with mechanical grinders. The fast pyrolysis is very interesting technology
because the produced liquid fuel is more dense and easier to handle.
1.9.3 Flash pyrolysis
Flash pyrolysis is a pyrolysis with high heating rate more than 1000°C/s and short
residence times of 0.1 to 1 sec. solid and volatile components. When the temperature is
between 450 to 750°C, more than 80 wt% of liquid fraction can be achieved. When the
temperature is higher than 750°C, the gas production can reach 80 wt% of the weight of the
products by using high speed reaction. The flash pyrolysis process has less tar and the
calorific value of gas increases around 5 to 10%. Table 1-2 and Table 1-3 show the summary
of different types of pyrolysis.
22
Table 1-2 Formation of different products from various types of pyrolysis [35]
Technique Process conditions By products
Temperature (°C) Residence time (s) Liquid Gas Char
Slow pyrolysis 400 Very long 30% 35% 35%
Intermediate
pyrolysis 500 10 to 20s 50% 30% 20%
Fast pyrolysis 500 > 2s 75% 13% 12%
Table 1-3 Type of pyrolysis in relation to operating processes and products with greater yield.
Pyrolysis type Residence
time
Temperature
(°C) Heating rate Products
Carbonisation Days 400 to 500°C Very slow Char
Slow pyrolysis 4 to 8 min 400 to 700°C 1 to 5 °C/s Gas
Fast pyrolysis 1 to 5 sec 500 to 950°C 100 to 300 °C/s Tar
Fast-liquid
pyrolysis < 1s 450 to 750°C > 1000°C/s Tar
Fast-gas pyrolysis < 1s > 750°C > 1000°C/s Gas
1.10 Activated carbon [36-40]
Activated carbons (ACs) are carbon with highly microporous structure, high specific
surface areas (SSA) and good adsorption properties. ACs allows the gas/liquid access into
internal pore surface and high degree of surface reactivity. ACs is an attractive material use
in various applications such as wastewater treatment, harmful gases removal in the air and
solvent recovery and ground water improvement. Nowadays, the agricultural by-products
23
have proved to be promising raw materials for the production of ACs because of their
availability at a low-cost, renewable and environmental friendly.
Lignocellulosic biomass is one of abundant agricultural wastes to produce ACs that
used for water and air pollution treatment. The advantages of ACs from lignocellulosic
biomass over the ACs from fossil sources are less emission of CO2 due to its carbon-neutral
cycle in the conversion process, reduce the amount of abundantly agricultural wastes and low
cost. Generally, the main components of lignocellulosic biomass are comprises with cellulose,
hemicellulose and lignin. Among those components, lignin is identified as the useful
component for the adsorption process due to the rich carbon content in lignin. Note that the
worldwide production of lignin-based biomass is 40 to 50 million tons per year.
ACs with high adsorption capacity can be produced from numerous sources of
lignocellulosic biomass such as coconut shell, durian shell, hazelnut shell, rubber seed shell,
palm kernel shell, almond shell, cotton stalks, plum stones, rice husk, pistachio-nut shell,
walnut shell, wood, etc. Lignocellulosic ACs can be used for chemical processes, petroleum
refining, waste water treatment, air pollution treatment and volatile organic compounds
(VOC) adsorption. Moreover, ACs obtained from Lignocellulosic provides an effective way
for gas phase applications such as for purification, separation, deodorization, storage and
catalysis.
To produce the ACs, the carbonization or pyrolysis process is firstly requires to
converse the char from biomass. In this process step, moisture and volatile compounds are
removed from the biomass. After the char producing, ACs can be fabricated using three
different processes: physical activation, chemical activation and physiochemical activation.
Physical activation is related to the gas-activating agents such as steam and CO2. The
chemical activation involves the presence of chemical agents such as metal oxide, alkaline
24
metal and acid. After the activation process, ACs with high porosity, large surface area and
high pore volume can be obtained.
1.10.1 Activation process
In the present days, the carbonization of lignocellulosic biomass to produce ACs is
widely study. Typically, the carbonization was done at the temperature below 800oC in the
absence of oxygen ambient. After that, the activation process is required to increase the
surface area and pore volume of ACs. There are two different activation processes called
physical activation and chemical activation.
1.10.2 Carbonization
The carbonization process is a thermal decomposition process that can eliminate a
non-carbon species and thus enrich the carbon content in carbonaceous material. The initial
porosity of char that obtained from carbonization process is still comparatively low.
Therefore, the porosity of char in activation process should be further developed due to the
products of this process step are significantly effect on the final product.
Among the carbonization process parameters such as heating rate, nitrogen flow rate
and the residence time, the carbonization temperature is the most important parameter.
Normally, high carbonization temperatures in the range between 600 to 700oC can reduce the
yield of char but can increase the liquid and gases release rate. Higher temperature is
preferred to obtain high quality char due to an increasing of amount of ash and fixed carbon
content with lower amount of volatile matter. Unfortunately, high carbonization temperature
can also decrease the yield due to the reduction of primary decomposition of biomass, the
decreasing of residence times of primary vapors inside the cracked particle and secondary
decomposition of char residue at high temperature. Moreover, high carbonization
25
temperatures also increase ash and fixed carbon content due to the decreasing of volatile
matter.
Char with a high fixed carbon content is requires for producing ACs. Low
volatilization with a high char yield can be obtained by using low carbonization heating rates
of 10 to 15oC/min. The low heating rate increases the dehydration and improves the
stabilization of the polymeric components [2-3]. However, the microporosity of char is
independent to the precursor composition and the carbonization heating rate. Table 1-4 shows
the proximate and ultimate analysis of several lignocellulosic biomass materials. It was found
that the carbonization is an important process to develop the initial pore structure in the char.
This can be explained by the release of volatile compounds from the carbon’s matrix.
Regarding to the pore development in the char has a great influence on the pore
characteristics of subsequently ACs production, the carbonization parameters should be taken
into account prior to activation process.
Table 1-4 Ultimate and proximate analysis of lignocellulosic biomass used for air pollution
control.
26
1.10.3 Activation
The activation process is use to increase the pore volume by increase the diameter of
pores, and thus increasing the porosity of ACs. ACs can be performed by three different
methods: physical activation, chemical activation and physiochemical activation (a
combination of physical and chemical activation). Physical activation use steam or CO2 while
the chemical activation uses various chemicals. The preparation of ACs from lignocellulosic
precursors by using various activation conditions is shown in Table 1-5. In the activation
process, unorganized carbon is removed during the first stage. Hence, the exposing of lignin
to the activating agents can lead to the development of micro-porous structure. In the second
stage of the reaction, the existing pores are widened and large size pores are formed. The
walls between the pores are simultaneously burnt-off. Completely burnt-off the wall of the
pores can increases the transitional pores and macro-porosity but also decreases the volume
of micro-pores. Therefore, the extension of burn-off carbon material is an important
parameter in activated carbon production.
During activation, the temperature is typically set between 800 to 1000oC to increase
the porosity and surface area of lignocellulosic carbon. In the physical activation, steam is
more effective than CO2 due to the smaller molecule of water can diffuse within the porous
of char faster than CO2 molecule. Therefore, steam activation is two or three times faster than
CO2 at the same conversion process. By using the steam, ACs with a relatively high surface
area compared to CO2 can be produced.
In the chemical activation, various chemical agents such as ZnCl2, H3PO4, KOH and
NaOH are used to develop the porosity. Generally, the chemical activation is takes place at
the temperature of 300 to 500oC, which is lower temperature than physical activation. The
dehydration and degradation mechanism of chemical agents can improves the development of
pore in carbon structure by using shorter treatment duration compared to physical activation.
27
Table 1-5 Various activation conditions for preparation of lignocellulosic chars.
In addition, the chemical activation process can form the ACs with larger surface area
with smaller ranges of micro-porosity compared to physical activation process. Furthermore,
the carbon yield of chemical activation is higher than that of physical activation.
1.10.4 Applications of activated carbon from lignocellulosic biomass
The rapid development in industrial activities that follows the growth of the world
population severely degraded the air quality due to high amount of pollutant emissions to
atmosphere. Therefore, air pollution control is a crucial step to achieve a sustainable energy
development. Currently, scrubbing gaseous pollutants using the adsorption method by
adsorbents such as ACs is widely used due to it has a suitable pore size in the micropore
region (< 2 nm) for gas adsorption and it has a large surface area for rapid reaction. A
summary of gaseous pollutants removal by various lignocellulosic ACs such as SO2, NOx,
H2S, volatile organic compounds (VOCs) and CO2 is presented in Table 1-6.
1.10.4.1 Removal of SO2
SO2 is the main precursors for acid rain generation, which is the most serious global
environment problem. The utilizing of ACs for SO2 adsorption through physical adsorption
and chemical adsorption takes a several advantages compared to the earlier methods. The
28
utilizing of metal oxides components in ACs that impregnated with the chemicals method to
remove SO2 from coal and oil combustion exhaust has been studied.
Table 1-6 Preparation method and adsorption capacity of various activated carbons from
lignocellulosic biomass.
Table 1-7 Characteristics of activated carbon used for removal of SO2.
29
1.10.4.2 Removal of NO2
The ACs with high porous structure that obtained from Lignocellulosic biomass is
widely used for minimizing the emission of NO2 gas. In addition, the surface chemistry that
defines by the type, number and chemical arrangement of heteroatoms on their surface are
considering. The dry adsorption process has better adsorption capacity compared to other
method due to the reaction mechanism is significantly changed and difficult to control in the
water. The micropores of activated carbon produced under optimum condition contributed up
to 96% of total pore volume. Preparation conditions and characteristics of activated carbon
for removal of NO2 are summarized in Table 1-8.
1.11 Catalytic gasification [41]
The gasification reaction is the important parameter to the catalytic or inhibiting
effects of the mineral matter in coals and chars. It is well known that a number of inorganic
elements present in coal/char have potential effects on the rates of gasification reaction on the
coal/char surface and in the gas phase. The reactions in the gas phase are contributed to ash
particles, whereas the reaction on or inside the reacting coal/char particles are contributed by
the dispersed minerals in the coal/char body. Generally, the alkali, alkaline earth, and
transition metals are the most effective catalysts for char-gas reactions as shown in Table 1-9.
Table 1-8 The preparation conditions and characteristics of activated carbon for removal of NO2.
30
Table 1-9 The most important char-gas reactions and its effective catalysts.
Reaction Effective catalysts
Char-oxygen Fe, Co, Ni
Char-steam K, Na, Ni
Char-carbon dioxide K, Na, Li, Ni, Co, Fe, Ca
Char-hydrogen K, Ni
When a catalytic effect is significant, the rate expression is depends on the presence
or absence of catalysts. To isolate such effects, kv and ks is determined by Eq. 1-1:
kv = Zvkvt and ks = Zskst (1-1)
Where kv and kst are the true rate constants of a reaction, and Zv and Zs represent the
effect of catalysis. The correct values of true rate constants are extremely difficult to
determine. However, the presence of a trace of solid or gaseous impurity is a significant
effect on the measured rate. Therefore, the rate expression shows in Eq. 1 is useful. As we
know that catalysts or impurities effects on the pre-exponential factor, kv0, and also the
activation energy, E, of carbon-gas reactions. Therefore, the values of E in carbon-CO2 and
carbon-O2 reaction systems have decreased due to the presence of catalytic minerals in coal.
The catalytic effects on the values of Zv and Zs for a given catalytic mineral are
depend on four factors; (1) The chemical form of the catalyst, (2) The physical form of the
catalyst, (3) The amount of catalyst, and (4) The temperature of reaction.
Thus Fe, Co, and Ni is effective catalysts in their elemental states or when they are
transformed to the elemental states during reaction. However, Potassium (K) and sodium
(Na) is the most effective in the form of carbonates and least effective as phosphates. Among
31
the oxides of iron and other transition metals, the stoichiometry of deficient oxides is better
catalyzes in C-CO2 and C-H2O reactions. This means, FeO or Fe3O4 is a better catalyst than
Fe2O3 in the same reactions.
Among the salts of those metals, the organic salts like oxalates, acetates, and citrates
show superior catalytic effects than those of the inorganic salts. This is because the former
group of salts yields finer subdivision and dispersion of the metal ions inside the body of the
reacting solid particles. The catalytic activity can be decreased by increasing the size of the
dispersed catalyst particles. The activity increases with an increase in the amount of catalyst
(or impurity) and then reaches the saturation point. However, larger amount of catalyst is not
an appreciable effect.
It was reported that the reduction of agglomerating tendency of caking coals can be
obtained by treatment of coals with Na2CO3 and/or K2CO3 (15 wt%) solutions at 700oC. It
was found that the rate of gasification is proportional to the concentration of the impregnated
potassium. It was also demonstrates that the agglomeration of coal can prevent by
impregnation of CaO into coal before gasification process due to the increasing of coal/char
reactivity and hydrocarbon yields in the gasifier.
It is believed that impurities decrease the CO/CO2 ratio in the C-O2 reaction, because
the impurities catalyze the secondary CO à CO2 reaction, without significantly affecting the
primary reaction, C à CO. This is because the CO and H2 are inhibitors of C-CO2 and C-
H2O reactions. However, this reaction is true only for un-catalyzed reactions. If the reactions
are catalyzed by oxides of Ni, Co, or Fe, then the CO, and H2 may act as promoters.
Therefore, the promoters might reduce the oxides of Ni, Co, and Fe. Moreover, if the process
temperatures are suitable, they can be changed to metallic states, which are the most effective
catalysts for gasification reactions. By using the same mechanism, steam may also act as a
promoter for these reactions, since it produces H2 and CO with carbon or char.
32
1.12 Interesting biomass used in this experiment [42-44]
In this experiment, three types of biomass including Chicken dropping compost (CC)
from Japan, Empty fruit bunch (EFB) from Malaysia and teak sawdust (TS) from Thailand
were studied. The EFB from Malaysia is the interesting biomass due to the large amount of
oil palm biomass about 30 million tons is produced each year. The remained agricultural
waste from the oil palm industry that can be used as renewable biomass is approximately
17.08 million tons a year. The EFBs with a relatively wet material (moisture content about 65
to 70 wt%) constitute 9% of the total oil palm industry.
In case of Teak sawdust (TS), it is the biomass that obtained from Thailand. In
Thailand, around 350 to 700 million tons of TS were produced a year. This material is very
attractive for carbon source. The chicken dropping compost (CC) from Japan is also
interesting materials due to it can produce up to 13 million tons per year. However, the
utilizing of CC is not suitable due to the pollution of air, soil, and ground water. The
summarized data of those interesting materials are shown in Fig. 1-16.
Figure 1-16. Interesting biomass used in this experiment.
Teak sawdust (Thailand)
(c)
Empty fruit bunch (Malaysia)
(a) (b)
Chicken dropping compost (Japan)
33
1.13 Relevant research
Garcia et. al. [45] studied low cost activated carbons with high surface area by
chemical activation using KOH at 700oC from the bamboo and residues from shells of the
fruits. The high porosity with surface areas ranging from 850 to 1100 m2/g was obtained. The
average pore width centered in the super micro-pores in the range of 1.3 to 1.8 nm. The
electrochemical performance of the activated carbons shows specific capacitance values at
low current density (1 mA/cm2) as high as 161 F/g in the shell of fruit activated carbon. This
is due to the presence of pseudo capacitance derived from surface oxygenated acidic groups
identified in this activated carbon.
Okman et.al. [46] studied the effects of activation reagents, reagent concentrations
and carbonization temperatures. It was found that lowest ACs yields were obtained at 800oC
for both K2CO3 (100 wt%) and KOH (100 wt%) reagents. By using the temperature of 800oC,
By using K2CO3 (50 wt%) and KOH (25wt%), microporous ACs with the highest specific
surface area of 1238 and 1222 m2g-1 were obtained at 800oC.
Sudaryanto et.al. [47] reported by using the cassava peel with KOH activation reagent
at the carbonization temperature of 750oC, the maximum specific surface area of 1600 m2/g
with pore volumn of 0.7 cm3/g were obtain at impregnation ratio of 5:2.
Lua et.al. [48] studied on the preparation and characterisation of effective adsorbents
from pistachio-nut shells. The optimum pyrolysis conditions was obtained at the temperature
of 500oC/2 hrs with a heating rate of 10oC/min. Under this pyrolysis condition, ACs with a
maximum BET surface area of 778 m2/g were obtained.
Kim et.al. [49] also studied the effects of the pyrolysis ambient including N2/CO2
without cooling, N2/CO2 with cooling and direct CO2 on the specific surface area of ACs. It
was reported that surface areas of biochars obtained by intermediate pyrolysis at 500 and
800oC were 107 and 249 m2/g, respectively. The maximum surface area of microporous ACs
34
(≤ 1 nm) of 1126 m2/g was obtained by carried out the process in N2/CO2 gas ambient without
cooling method at a final activation temperature of 900oC/1 hour.
Zhou et.al. [50] studied the effects of Na2CO3 catalyst on coal pyrolysis and
gasification of bituminous char. It was found that the activation energy of catalytic coal
gasification using Na2CO3 (10 wt.%) is 31.5 kJ.mol-1, which is less than that of non-catalytic
coal gasification. Therefore, Na2CO3 can improve the kinetics of coal gasification with CO2.
Kopyscinski et.al. [51] investigated the interactions of K2CO3 with ash-free brown
coal in N2 or CO2 atmospheres at 700 °C. The X-ray diffraction (XRD) analysis confirmed
that the evaporation of potassium is negligible because the K2CO3 does not exist in N2 and
CO2 atmospheres at 700°C. It was found that the CO2 gasification rate can be increased by
holding the ash-free coal mixed with K2CO3 in N2 prior to switching to the reaction gas. This
means, the catalyst reduction is necessary for a fast char conversion.
Perander et.al. [52] studied the catalytic gasification of Ca and K. It was found that
the gasification rate of the char linearly increased with an increasing of the concentration of
Ca or K. The catalytic activity of Ca was higher than K at the beginning of char gasification.
However, the catalytic effect of Ca decreased earlier than the catalytic effect of K. This might
related to the formation of CaCO3 and K2CO3 layer on the char surface.
35
1.14 Objective of this study
The conversion of biomass and coal as a renewable energy sources on the
thermochemical process to produce energy and fuels is considered. The conversion process
with low temperature, less pollution, and fewer effects to the global-warming issues
compared to existing fossil fuel is required.
The preparation of activated carbons (ACs) from agricultural by-products has attracted
much attention due to their low-cost, renewable and environmental friendly. Low temperature
coal gasification by metal species has been also studied in order to develop the coal
utilization with high efficiency. Many extensive works had been performed to investigate the
catalysts such as alkali and alkaline earth metals (AAEMs). However, the cost of purchasing
chemical catalysts is expensive. Therefore, it is necessary to identify inexpensive biomass as
a catalyst that will improve the surface area of ACs and reactivity of gasification.
The objective of this research is to study the novel utilization of biomass-derived ash for
ACs preparation and catalytic gasification. Two types of biomass-derived ashes including
chicken dropping compost ash (CCA) and empty fruit bunch ash (EFBA) was used as a
catalyst.
In ACs preparation, five different types of biomass that are abundant in Asia including
teak sawdust (TS), bagasse (BG), cypress (CP), palm kernel shell (PKS) and empty fruit
bunch (EFB) were used as a feedstock for pyrolysis to produce activated carbon. The specific
surface area of ACs that using CCA and EFBA was also compared with the process that
utilizing chemical reagents (CaCO3 and Ca(OH)2).
Moreover, the utilizing of different sources of catalyst on Loy Yang brown coal (LY)
char by CO2 gasification including CCA and EFBA biomass-derived ashes and K2CO3 and
CaCO3 chemical reagents were compared. Furthermore, various process parameters included
char conversion, reaction rate, gasification temperature were investigated.
36
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Chapter 2
Activated carbon from biomass using chemical reagents
2.1 Introduction
Biomass is an organic matter on earth that obtained from plant and animal growth in the
form of plant residues and organic wastes from animal and human. The variety of biomass is
depends on both seasonally and geographically across the world. Biomass can be prepared by
harvest, collect, assemble, compress, transport, and then stored for further use. The estimates of
the biomass weight that the approximate annual worldwide fixation of carbon from all sources is
around 200x109 tons. The utilizing of biomass from agricultural wastes is to convert it into
activated carbon (ACs).
ACs is the form of carbon with small and low-volume porosity in micro-pores and meso-
pores, which typically used as adsorbent materials due to its high surface area. ACs can produce
from different residual biomass utilizing physical or chemical activation processes and used in a
various applications such as separation and purification technologies.
The preparation of ACs from agricultural by-products with low-cost is considering in the
view of economic and environmental impacts. First, low-cost agricultural waste such as residual
biomass with low ash and high volatile content has converted to be useful and valuable
carbonaceous adsorbents. The preparation of ACs from lignocellulosic biomass can be obtained
by three factors; (1) the porosities and surface of the biomass to produce adsorbent, (2) the low
cost and the possibility for mass production, and (3) the waste disposal problem with the
addition of value added products.
Activated carbons can be produced by the conventional partial gasification of the char
either with steam, CO2 or a combination of steam and CO2. Generally, the physical activation
that comprises with two-step process including the carbonization of a carbonaceous material and
the activation of char at elevated temperature. The activation process is typically carried out in
43
the oxidizing gases ambient such as steam, CO2 or a combination of steam and CO2. The
gasification reaction can remove the carbon atoms and produce a wide range of predominantly
micro-pores that can produce a porous ACs.
In case of chemical activation process, the carbonization was done at in a single step. The
precursors are mixed with dehydrating chemicals such as H3PO4, ZnCl2, K2CO3, NaOH or KOH.
The advantages of chemical activation are included the single step activation with low activation
temperatures and short activation time. The chemical activation process has higher yields and
better porous structure compared to physical activation process. Moreover, the chemical agents
in the chemical activation process did not form tar and it also can reduce the production of other
volatile products. The main disadvantage of chemical activation process is the washing step.
This washing step is time consuming due to the necessary of completely remove the activation
agent from the carbon.
2.2 Experimental
2.2.1 Materials
Carbon source in this section has five types of biomasses including teak sawdust (TS)
from Thailand, cypress (CP) from Japan, bagasse (BG), empty fruity bunch (EFB), and palm
kernel shell (PKS) from Malaysia. The particle size of TS is between 0.25 to 0.50 mm while the
particle size of other materials is between 0.5 to 1.0 mm.
The proximate and ultimate analyses of the initial material are shown in Table 2-1. The
volatile matter and ash content were measured by a thermo gravimetric analyzer (TGA 701,
Leco Co., Ltd.). The content of C, H, N and O elements were determined using an elemental
analyzer (TruSpec CHN, version 100, Leco Co., Ltd) and the content of sulfur element was
44
Table 2-1 Proximate and ultimate analysis of raw materials
Sample Proximate analysis Ultimate analysis
Volatile
matter
Ash Fixed
carbon
C H N O
(diff)
TS 76.8 0.8 2.4 49.8 3.8 1.8 44.6
CP 79.0 0.4 20.6 47.1 8.9 0.4 43.6
BG 83.4 2.5 14.1 46.2 5.6 0.4 47.8
PKS 74.6 1.2 24.2 52.0 5.0 0.4 42.6
EFB 80.6 2.7 16.7 45.3 5.5 0.5 48.7
analyzed by sulfur analyzer (Leco SC-432, Leco Co., Ltd). Five types of biomasses used in this
experiment were dried at 107oC for 1 hour before mixed with catalyst. Biomass is chicken
dropping compost (CC). Chemical reagent including calcium hydroxide (Ca(OH)2) and calcium
carbonate (CaCO3) and were used as a catalyst. It was dried at 107oC for 1 hour before using.
2.2.2 Experimental set-up
The experimental apparatus of the pyrolysis in this study is shown in Figure 2-1. The set-
up mainly consists of a horizontal fixed bed reactor.
Figure 2-1. Schematic diagram of pyrolysis process used in this experiment.
Slow pyrolysis
Holding time: 30 min
Heating rate: 10 to 20°C/min
45
2.2.3 Sample preparation
Biomasses were mixed with 3 different catalysts, Ca(OH)2, CaCO3 and CC. The ratios of
chemical catalyst/biomass were mixed at 1.0 and 3.0. The mixtures were replaced to a horizontal
fixed bed reactor. The char was produced by slow pyrolysis in a ceramic crucible at 1000oC for
30 min. The slow pyrolysis in a fixed bed reactor was done in different gas ambient including
pure N2 gas ambient by using the heating rate of 10°C/min.
To remove the catalyst in samples, the char samples were put in the magnetic stirrer that
contained 1M of HCl at 70oC for 2 hrs. In this process, catalyst was converted to water-soluble
Metal-Cl thus easily removed from char. After that, the carbon samples were rinsed with
deionized water and filtered until the pH is 7. Then, the ACs were obtained by heating the
carbon samples in an oven at 107oC for 24 hrs.
2.2.4 Characterization of the activated carbons
The SSA, pore size distribution and N2 adsorption isotherm were characterized by
nitrogen adsorption and desorption at -196oC using Brunauer-Emmett-Teller (BET) and
micropore analysis (MP) methods (BELSORP-max, Japan), respectively. Note that all samples
were degassed at 300oC for 3 hrs before the adsorption in N2 gas ambient.
2.3 Results and discussion
The results in Fig. 2-2 show specific surface area (SSA) of raw materials used in this
experiment. After pyrolysis in N2 gas ambient at 1000°C, the SSA was 200 m2/g for TS, BG,
PKS, and EFB due to normal characteristics of biomass. However, the SSA of CP has increased
to 500 m2/g. This might related to the own specific properties of CP, which still cannot be
explained.
46
TS CP BG PKS EFB0
200
400
600
800
1000
1200
14001000°C in N2
Spec
ific
surf
ace
area
[m2 /g
]
Biomass char
Figure 2-2. Specific surface area of biomass char after pyrolysis in N2 gas ambient at 1000°C.
The results in Fig. 2-3 shows the specific surface area (SSA) of activated carbon obtained
from different types of biomass mixed with various types of catalyst at the ratio of 1.0. The SSA
of TS, CP, BG, and EFB after mixed with various types of catalyst has similar values, while the
PKS has lower SSA compared to the other biomass. This is because the PKS is a hard biomass,
therefore the catalyst may not react to the PKS surface to increase pore. By adding the CaCO3
catalyst, the SSA of all types of biomass is higher compared to Ca(OH)2 and CC catalyst. This
means the CaCO3 is an effective catalyst to activate the biomass to ACs with high SSA. By
using the catalyst to biomass ratio of 1.0, the average SSA of various types of biomass is in the
range of 600 to 883 m2/g.
Typically, calcium atom (Ca) in the CaCO3 was deposited into the structure of porous
materials during pyrolysis by a mechanism called “pore blocking effect”. In this mechanism, a
discrete inorganic compound (calcium atom) is capable to form an intercalation compounds with
carbon by penetrating through an adjacent carbon layer and inserting into a graphite-like
structure. The similar mechanism caused by different additives deposited on the porous materials
has been widely reported [2, 16-18]. The pore blocking effect is widely used to describe the
47
TS CP BG PKS EFB0
200
400
600
800
1000
1200
1400Catalyst/biomass: 1/1
CaCO3
Ca(OH)2
CC
Spec
ific
surf
ace
area
[m2 /g
]
Types of biomass
Figure 2-3. Specific surface area of activated carbon obtained from different types of biomass
mixed with various types of catalyst at the ratio of 1.0.
decreasing of textual parameters. Nevertheless, washing out the Ca from the porous materials is
a simple way to substantially high porosity from micropores.
The results in Fig. 2-4 show that when the catalyst to biomass ratio has increased to 3.0, the
SSA of various types of biomass has increased to 807 to 1082 m2/g. This means, increasing of
catalyst in the process can increases the SSA. Moreover, the utilizing of CC catalyst with
catalyst to biomass ratio of 3.0, the SSA of CC catalyst has increased and comparable to CaCO3.
This might due to large amount of high porous carbon that still available in the CC. The CC
catalyst that contains fixed carbon and high porous of fixed carbon can be obtained after
pyrolysis process. Therefore, the fixed carbon in the CC catalyst can increase the total amount of
biomass in the reaction.
The results in Fig. 2-5 show the ACs yield obtained from different types of biomass mixed
with various types of catalyst at the ratio of 1.0. It was found that the ACs yield of CaCO3
catalyst has lower than Ca(OH)2 and CC catalyst, respectively. The EFB biomass with high SSA
has ACs yield around 10%. When the catalyst to biomass ratio has increased from 1.0 to 3.0, the
48
ACs yield has decreased from 10 to 0.9% in case of CaCO3 and Ca(OH)2 catalyst as the results
in Fig. 2-6.
TS CP BG PKS EFB0
200
400
600
800
1000
1200
1400Catalyst/biomass: 3/1
Spec
ific
surf
ace
area
[m2 /g
]
Types of biomass
CaCO3
Ca(OH)2
CC
Figure 2-4. Specific surface area of activated carbon obtained from different types of biomass
mixed with various types of catalyst at the ratio of 3.0.
TS CP BG PKS EFB0
5
10
15
20
25
30Catalyst/biomass: 1/1
Act
ivat
ed c
arbo
n yi
eld
[%]
Types of biomass
CaCO3
Ca(OH)2
CC
Figure 2-5. Activated carbon yield of activated carbon obtained from different types of biomass
mixed with various types of catalyst at the ratio of 1.0.
49
TS CP BG PKS EFB0
5
10
15
20
25
30Catalyst/biomass: 3/1
Act
ivat
ed c
arbo
n yi
eld
[%]
Types of biomass
CaCO3
Ca(OH)2
CC
Figure 2-6. Activated carbon yield of activated carbon obtained from different types of biomass
mixed with various types of catalyst at the ratio of 3.0.
2.4 Summary
Various types of biomasses including teak sawdust (TS), cypress (CP), bagasse (BG),
empty fruity bunch (EFB), and palm kernel shell (PKS) was used to produce activated carbon.
Among various types of catalysts, CaCO3 has higher specific surface area with lower activated
carbon yield compared to Ca(OH)2 and chicken compost (CC). This is because the pore-
blocking effects of Ca atoms and also the carbon content in the CaCO3. When the catalyst to
biomass ratio has increased from 1.0 to 3.0, the SSA of various types of biomass has increased
to 807 to 1082 m2/g. This means, increasing of catalyst in the process can increases the SSA.
50
References
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[6]. X. Xu, J.M. Andresen, C. Song, B.G. Miller, A.W. Scaroni, Novelpolyethyleneimine
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[10]. N.A. Fathy, B.S. Girgis, L.B. Khalil, J.Y. Farah, Utilization of cotton stalks-biomass waste
in the production of carbon adsorbents by KOH activation for removal of dye contaminated
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[11]. P. Sugumaran, S.V. Priya, P. Ravichandran, S. Seshadri, Production and characterization of
activated carbon from banana empty fruit bunch and delonix regia fruit pod, J. Sustainable
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51
[12]. E. Taer, L.M. Deraman, I.A. Talib, A. Awitdrus, S.A. Hashmi, A.A. Umar, Preparation of
a highly porous binderless activated carbon monolith from rubber wood sawdust by a multi-
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[13]. A.N.A. El-Hendawy, A.J. Alexander, R.J. Andrews, G. Forrest, Effects of activation
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Chapter 3
Preparation of activated carbons from teak sawdust using chicken dropping
compost and empty fruit bunch
3.1 Introduction
In recent years, agricultural by-products are generally used as feedstock in fuel
combustion. However, recycling agricultural waste as combustion fuel still lacks of profit and
efficiency. Agricultural waste especially biomass is commonly used as raw materials to produce
various value-added products in solid, liquid and gaseous forms from various conversion
processes [1-4]. This is because biomass has high carbon content and is low-cost, renewable and
environmental friendly. Among solid products, activated carbons (ACs) are the most attractive
material due to its high microporous structure, high specific surface area (SSA) and good
adsorption properties. The properties of ACs are excellent for various applications such as
wastewater treatment, pollutant removal, solvent recovery, color removal and ground water
improvement [5-9].
Typically, ACs can be produced by chemical activation and physical activation. The
chemical activation method requires a single step of carbonization at a relatively low
temperature between 400 to 700oC in the presence of chemical agents. The physical activation
method is a thermal activation process that consists of carbonization of a precursor and the
activation of a resolution char in the presence of some activating agents [10-12]. Generally, carbon
dioxide (CO2) and steam (H2O) are preferred as activating gases due to the controllability of the
oxidation process compared with O2 and air [13].
In the past, synthesis chemicals such as KOH, ZnCl2, H2SO4, NaOH and K2CO3 were
used as activating agents. However, the by-products from synthesis activating agents are harmful
and it can contaminate the surrounding environment [14]. Therefore, some research groups
53
reported that the ACs with large SSA can be produced by using natural activating agents
obtained from agricultural wastes [5-6]. Unfortunately, much agricultural waste such as rice
straw, wheat straw, pinewood and olive tree wood have SiO2 as its main component (40 to 95%)
[15]. Hence, utilizing agricultural waste still requires significant amounts of synthesis activating
agents to produce ACs.
This paper focuses on the utilizing of two different agricultural wastes including chicken
dropping compost ash (CCA) and empty fruit bunch ash (EFBA) as natural activation agents
instead of synthesized chemicals. The low cost ACs production from teak sawdust (TS) was
used as the carbon source. The effects of various parameters including the ash/biomass weight
ratio, the concentration of CO2 in reaction gas and the reaction temperature to the SSA, yield of
ACs, adsorption volume, pore size and N2 adsorption isotherm of the prepared ACs were
investigated.
3.2 Experimentals
3.2.1 Raw materials
Teak sawdust (TS) from Thailand with particle size of 0.25 to 0.50 mm was used as the
raw material. The proximate and ultimate analyses of the initial material are shown in Table 3-1.
The volatile matter and ash contents were measured by thermo gravimetric analyzer (TGA 701,
Leco Co., Ltd.). The content of C, H, N and O elements were determined using an elemental
analyzer (TruSpec CHN, version 100, Leco Co., Ltd) and the content of sulfur element was
analyzed by sulfur analyzer (Leco SC-432, Leco Co., Ltd). The TS was dried at 107oC for 1 hour
before mixed with biomass ashes.
54
Table 3-1 Proximate and ultimate analysis of the teak sawdust
Proximate analysis (%wt) Ultimate analysis (%wt, daf)
Moisturear Volatiled Ashd Fixed carbonb C H N S Ob
7.48 76.77 0.83 22.40 50.02 9.49 0.29 0.12 40.08
ar: as-received, d: air-dried basis and b: by difference
The chicken dropping compost (CC) was obtained from Kinsei Sangyo Co., Ltd., Japan.
The CCA was prepared by TGA in oxygen gas ambient with temperature variations from 500 to
815oC with the heating rate of 10oC/min and stabilized at 815oC for 30 min. The CCA was then
cooled down to room temperature and was kept for further use. The empty fruit bunch (EFB)
was obtained from Chemical Engineering Department, Universiti Teknologi Petronas, Malaysia.
Note that the preparation condition of EFBA is similar to the process condition used for CCA.
3.2.2 Sample preparation
TS was mixed with two different biomass ashes, CCA and EFBA. Both CCA/TS and
EFBA/TS weight ratio were varied from 0.6 to 1.0 and the mixtures were replaced to a
horizontal fixed bed reactor. The char was produced by slow pyrolysis in a ceramic crucible at
600 to 1000oC for 30 min. The slow pyrolysis in a fixed bed reactor was done in different gas
ambient including pure N2 and N2/CO2 gas ambient by using the heating rate of 10oC/min.
To remove the ash components in CCA and EFBA, the char samples were put in the
magnetic stirrer that contained 1M of HCl at 70oC for 2 hrs. In this process, metal oxide was
converted to water-soluble Metal-Cl thus easily removed from char. After that, the carbon
samples were rinsed with deionized water and filtered until the pH is 7. Then, the ACs were
obtained by heating the carbon samples in an oven at 107oC for 24 hrs.
55
3.2.3 Characterization of the activated carbons
The SSA, pore size distribution and N2 adsorption isotherm were characterized by
nitrogen adsorption and desorption at -196oC using Brunauer-Emmett-Teller (BET) and
micropore analysis (MP) methods (BELSORP-max, Japan), respectively. Note that all samples
were degassed at 300oC for 3 hrs before the adsorption in N2 gas ambient.
3.3 Results and discussion
3.3.1 Preparation of ACs from TS mixed with CCA activating agent
3.3.1.1 Effects of CCA activating agent
Fortunately, CCA and EFBA contains low amount of SiO2 component (< 20%) as the
information shown in Table 3-2. The composition of CCA contains high amount of calcium
oxide, CaO (∼ 85%) and the composition of EFBA contains high amount of potassium oxide,
K2O (∼ 77%). Therefore, CCA and EFBA are very interesting activating agents to produce ACs
without using any synthesized chemicals in the activating process. Figure 3-1 shows the SSA of
TS and ACs obtained from TS mixed with CCA activated with N2 gas stream at 1000oC. By
adding the CCA catalyst, the SSA of TS has increased from 192 to 930 m2g-1. This means the
CCA is an effective catalyst to activate the TS to ACs with high SSA.
Table 3-2 Composition of metal oxide in CCA and EFBA
Biomass ash Metal oxide composition (wt%, dry basis)
K2O SiO2 CaO P2O5 Fe2O3 SO3
CCA 11.06 1.27 84.65 2.58 0.29 0.14
EFBA 76.94 18.17 3.46 0 1.01 0.16
56
0
200
400
600
800
1000
TS+CCATSType of biomass
Spec
ific
surf
ace
area
[m2 g
-1]
Figure 3-1. Specific surface area of TS and TS mixed with CCA.
Typically, calcium oxide (CaO) in the CCA was deposited into the structure of porous
materials during pyrolysis by a mechanism called “pore blocking effect”. In this mechanism, the
ash that contains a discrete inorganic compound (calcium atom) is capable to form an
intercalation compounds with carbon by penetrating through an adjacent carbon layer and
inserting into a graphite-like structure. The similar mechanism caused by different additives
deposited on the porous materials has been widely reported [2, 16-18]. The pore blocking effect is
widely used to describe the decreasing of textual parameters. Nevertheless, washing out the CaO
from the porous materials is a simple way to substantially high porosity from micropores.
3.3.1.2 Effects of ash to biomass weight ratio
The results in Fig. 3-2 show the evolution of ACs produced by slow pyrolysis using the
TS mixed with CCA. The amount of activation agent mixed with CCA and TS was varied at the
weight ratio of 0.6 to 1.0. It was found that when the ash to biomass weight ratio has increased
57
from 0.6 to 1.0, the SSA has increased from 684 to 930 m2g-1 and carbon yield of ACs has
decreased from 18.9 to 13.1%, respectively.
The decrease of ACs yield by increasing the ash to biomass weight ratio can be explained
by the reaction rate of metal elements with the char and volatile matter. By using high ash to
biomass weight ratio, the activation of TS has increased and the by-products can be quickly
diffused out from the particles surface during activation process [19]. Therefore, the gasification
of carbon atom surface becomes predominant that leads to decrease the weight loss and ACs
yield. Figure 3-3 exhibits the N2 adsorption isotherm of ACs obtained from carbonization
process in N2 gas stream with different ash to biomass weight ratio. The appearance of isotherm
clearly shows the Type I, which is the characteristic of microporous materials [20].
0
200
400
600
800
1000
1200
1.00.80.6
N2 ambient
Sp
ecifi
c su
rfac
e ar
ea [m
2 g-1]
SSA ACs yield
Ash/biomass weight ratio
0
10
20
30
40 Activated carbon yield [%
]
Figure 3-2. Specific surface area and yield of ACs with different CCA to biomass weight
ratio.
58
0 0.2 0.4 0.6 0.8 1.00
200
400
600
800
N2 ambient
Ash/Biomass weight ratio1.00.80.6
Relative pressure [P/P0]
Ads
orpt
ion
volu
me,
Va [m
3 g-1
]
Figure 3-3. Adsorption isotherm of ACs with different CCA to biomass weight ratio.
3.3.1.3 Effects of carbonization gas ambient using CCA activating
agent
The results in Fig. 3-4 show that the main effect of gasification with N2/2%CO2 gas is the
creation and widening of the existing pores. This can improve the adsorption properties such as
SSA. By using N2/2%CO2 activation at 1000oC, the SSA of TS has increased from 196 to 600
m2g-1. The increasing of SSA can be explained by the “burn off” reaction. In the burn off
reaction, CO2 reacts with carbon to produce CO during the thermal activation by reaction
mechanism in Eq. 1. The CO2 can increase an amount of the activating gas in the reaction.
Moreover, it can enhance the bulk mass transfer of the CO product from the burn off reaction [21].
C+CO2 à 2CO ΔH = +159 kJ/mol (1)
59
0
200
400
600
800
1000
N2/2% CO2N2Carbonization gas ambient
Spec
ific
surf
ace
area
[m2 . g
-1]
Figure 3-4. Specific surface areas of the ACs from TS prepared in pure N2 and N2/2%CO2
gas ambient at the carbonization temperature of 1000oC.
3.3.1.4 Effects of carbonization temperature using CCA activating
agent on CO2 gas
The results in Fig. 3-5 show the SSA and ACs yield obtained from TS and TS mixed
with CCA using carbonization process with N2/2%CO2 gas ambient at various carbonization
temperatures. When the carbonization temperature has increased from 600 to 1000oC, the SSA
has increased from 400 to 1094 m2 g-1 but the ACs yield has decreased from 24.4 to 6.3%,
respectively. By using the combination of chemical and physical activation, the SSA of ACs is
higher than the one that obtained from chemical activation. Table 3-3 shows the characterization
parameters of the ACs obtained from the carbonization process including yield of activated
carbon (Yacs), SSA, volume of microporous (Vmicro), total volume of ACs (Vtotal) and average
diameter of ACs (Davg). The volume of microporous has increased by increasing the activation
temperature.
60
Figure 3-5. Specific surface area and ACs yield obtained from carbonization process in
N2/2%CO2 gas ambient by varied the carbonization temperature from 600 to 1000oC.
Table 3-3 Parameters of the activated carbon obtained from the carbonization process
Sample Carbonization
temperature
[oC]
Gas
ambient
CCA
to TS
ratio
YAcs
[%]
SSA
[m2g-1]
Vmicro
[cm3g-1]
Vtotal
[cm3g-1]
Davg
[nm]
AC1 1000 N2 0.6 13.6 684 0.33 0.48 2.80
AC2 1000 N2 0.8 10.7 820 0.40 0.55 2.67
AC3 1000 N2 1.0 7.0 1006 0.42 1.15 2.55
AC4 600 N2/2%CO2 1.0 24.4 400 0.16 0.34 2.39
AC5 600 N2/5%CO2 1.0 23.6 482 0.22 0.36 2.94
AC6 600 N2/10%CO2 1.0 21.8 554 0.22 0.40 3.21
AC7 800 N2/2%CO2 1.0 13.7 897 0.43 0.57 2.30
AC8 1000 N2/2%CO2 1.0 6.3 1093 0.51 0.63 2.31
61
Figure 3-6. Pore size distribution obtained from carbonization process with N2/2%CO2 gas
ambient at different carbonization temperatures.
Figure 3-6 show the pore size distribution of ACs obtained from carbonization process
with N2/2%CO2 gas ambient at different carbonization temperatures. When the carbonization
temperature has increased from 600 to 1000oC, the pore size distribution of ACs decreased from
0.7 to 0.5 nm, respectively. However, the pore size distribution of ACs in the range of 0.8 to 1.0
nm has increased as the carbonization temperature increased.
The carbonization is a complex reaction process that includes the decomposition of
organic matter and the elimination of volatile matter in the remaining products. At the
carbonization temperature of 450oC, the volatile matter start to accumulate in the particles
undergoes the first cracking, which can generate pores on the materials surface. When the
carbonization temperature is higher than 450oC, the volatile matters start to escapes from the
particles undergoes the secondary cracking. It can form carbon to deposit on the char thus
blocking the developed pore and leads to decrease the surface area of microspore [22]. The
0 0.4 0.8 1.2 1.6 2.00
1000
2000
3000
4000
5000
6000
dVp/d
(dp)
Pore size [nm]
1000°C800°C600°C
2% CO2 ambient
62
continuous of secondary cracking at higher carbonization temperature can collapse the
micropores size of 0.4 to 0.7 nm and generate the bigger pore with the size of 0.8 to 1.2 nm.
The dependence of SSA, ACs yield and pore size distribution on the carbonization
temperature can be explained by the burn off mechanism. The products burn off at low
carbonization temperature is smaller than the high carbonization temperature. Therefore, the
amount of volatile matter in the products that was obtained from high carbonization
temperatures is smaller than the one that obtained from low carbonization temperature. The loss
of volatile materials was related to the high SSA of ACs [23-24].
3.3.1.5 Effects of CO2 concentration in carbonization process using
CCA activating agent
The effects of N2/CO2 gas ratio to the SSA and the yield of ACs using the CCA
activation agent at 600oC were investigated. In this experiment, the CO2 concentration of
N2/CO2 gas was varied from 2 to 10%. The results in Fig. 3-7 show that when the CO2
concentration has increased from 2 to 10%, the SSA has increased from 400 to 555 m2g-1.
However, the ACs yield has decreased by increasing the CO2 concentration. This means, higher
CO2 concentration is more efficient in removing the volatile matters from the activating mass.
This can be explained by the reaction between carbon and CO2 in the activation process. The
carbon was removed and then exposed to the aromatic carbon sheets to the action of CO2 gas [25-
27]. Based on the results in Fig. 3-7, it can be predicted that if the CO2 concentration is less than
2%, SSA trends to decreases and ACs yield trends to increases, respectively. In contrast, if the
CO2 concentration is excessively increases, the burn off reaction will be strongly occurred.
Therefore, the CO2 could react with all of carbon in TS and the ACs products will not remain
after carbonization process.
63
Figure 3-7. Specific surface area and ACs yield with different CO2 concentration in N2/CO2
gas ambient at 600oC.
3.3.2 Comparison of CCA and EFBA activating agents
Figure 3-8 show the comparison of the SSA of ACs obtained from TS mixed with CCA and
TS mixed with EFBA at different ash/biomass weight ratio. The carbonization was done in
different gas ambient at 1000oC. By using an EFBA activating agent, the SSA has higher
compared to CCA activating agent. This is related to the different composition of EFBA that
contains potassium oxide (K2O) and CCA that contains calcium oxide (CaO) as shown in Table
3-2. The ACs with high SSA can produce from biomass that contains the potassium compound.
This could be explained by the carbon gasification of CO2 by-product to the decomposition of
potassium compound.
0 2 4 6 8 10 120
200
400
600
800
1000
1200
at 600°C
Sp
ecifi
c su
rfac
e ar
ea [m
2 g-1]
SSA ACs yield
CO2 concentration [%]
0
10
20
30
40 Activated carbon yield [%
]
64
600
800
1000
1200
1400
1.0 (N2/2% CO2)1.0 (N2)0.8 (N2)0.6 (N2)
TS + CCATS + EFBA
Carbonization gas ambient
Spec
ific
surf
ace
area
[m2 g
-1]
Figure 3-8. Specific surface area of ACs from TS mixed with CCA and EFBA by varied the
ash/biomass weight ratio from 0.6 to 1.0 and carbonized in different gas ambient at 1000oC.
Moreover, high SSA obtained from potassium compound can be attributed to the particle
reaction of the potassium with the cellulose in biomass [28]. Due to the ionic strength of calcium
cation being weaker than potassium cation, the catalytic activity during pyrolysis of calcium is
less than potassium. Moreover, the combination of chemical activation and physical activation
process can increase the SSA of TS by the reaction of metal oxide and CO2 gas.
Finally, the pore size distribution of the activated carbon obtained from TS mixed with
CCA and TS mixed with EFBA is shown in Figure 3-9. The pore size of ACs was varied from
0.4 to 2.0 nm. The maximum volume (means of normal distribution) of the pore size was located
at 0.5 nm. Therefore, the average pore size of the ACs obtained from TS mixed with CCA and
TS mixed with EFBA were 0.5 nm.
65
0 0.4 0.8 1.2 1.6 2.00
2000
4000
6000
8000TS + CCATS + EFBA
dVp/d
(dp)
Pore size [nm]
Figure 3-9. Pore size distribution of ACs from TS mixed with CCA and EFBA with the
ash/biomass weight ratio of 1.0 and carbonized in N2 gas ambient at 1000oC.
3.4 Conclusions
Activated carbon (ACs) can be produced from teak sawdust
(TS) mixed with two different biomass activation agents including chicken dropping compost
ash (CCA) and empty fruit bunch ash (EFBA). The specific surface area (SSA) of ACs over
1000 m2g-1 can be obtained for both CCA and EFBA after physical activation process in
N2/2%CO2 gas ambient at 1000oC. However, the potassium compound (K2O) in EFBA has more
efficiency to increase the SSA compared to the calcium compound (CaO) in CCA.
66
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Chapter 4
Catalytic effects of biomass on Loy Yang brown coal gasification
4.1 Introduction
In recent years, carbon dioxide (CO2) is the primary greenhouse gas that is emitted
through human activities such as the combustion of fossil fuels from transportation and
industrial process. The CO2 gas in the atmosphere acts like radiative active gas, which
radiates energy in all directions. Part of this radiation is directed towards the earth surfaces,
thus warming it. This process is the fundamental cause of the greenhouse effect, which has an
impact to the global climate change [1]. To meet emission limitations of CO2, the novel
technologies that limit the fossil fuel processing is necessary to be developed. Among
important technologies, gasification process is found to be promising for dealing with the
commercial-scale release of CO2.
It is well known that the gasification is a series of processes producing synthesis gas such
as H2 and CO from carbonaceous materials. Over the past several years, the concept of
polygeneration gasification technology that combines power generation with chemical
production from synthesis gases were considered. Therefore, most of current research works
focus on the increasing of gasification process performance. As presented elsewhere, the
pressurized CO2 enriched gasification of coal is considered as competitive to conventional
gasification technology [2].
In coal gasification, the first stage starts with a rapid de-volatilization, leaving a char
mainly composed of carbon. The second stage is the gasification of a nascent char that can be
converted to fuel gas [3-5]. The fuel gas can be used instead of synthetic biofuel for feeding
gas engines and gas turbines. The most important heterogeneous reaction, which takes place
71
during the gasification process, is the carbon conversion by reaction mechanism shown in
Eq. 4-1.
C + CO2→2CO (4-1)
It was reported that the catalytic gasification technique has more efficiency to improve
the reaction rate and the conversion efficiency by using lower reaction temperature compared
to conventional gasification techniques [6-9]. Generally, the coal gasification with CO2 is a
high temperature process but low temperature gasification is desired to reduce the total
process cost. Therefore, the use of catalysts has been proposed for low temperature
gasification to overcome the slow reaction rate of carbon with CO2. The previous works
reported that hydroxide, oxide of alkaline and alkaline earth metal (AAEM), transition metal
salts, and partial transition metals are effective catalysts on coal char gasification. AAEM
catalysts are mostly used as effective catalysts [10-14].
For catalytic gasification of low rank coals, the mineral matters from catalyst such as
sodium and calcium occur as cations during the gasification process that associated with
carbonaceous matrix. By heating coals into the temperature range of 400°C or above, the
carboxyl groups are destroyed and left the associated cations behind the resulting char that
leads to the formation of highly dispersed metals. Those highly dispersed metals composing
mineral matter in the carbonaceous matrix can be used as a catalyst to increase the
gasification rate.
For the sub-bituminous char, the catalytic effects due to mineral matter content were
detected up to 1060oC. However, the current gasification temperature is too high to meet the
economic point-of-view [15]. Fortunately, the iron-loaded on activated carbon or carbon black
has high activity in the CO2 gasification that yields the rapid gasification. Both steps in the
72
oxidation and reduction of iron species proceeded very fast. However, the key step for the
CO2 gasification is the oxidation step of iron metal in the redox cycle [16].
This paper focuses on the utilizing of Loy Yang brown coal (LY) as natural starting
material for CO2 gasification. The char conversion of LY mixed with two different types of
ash was measured to investigate the catalytic effect of the ash. The two ash samples were
prepared from chicken dropping compost (CC) and empty fruit bunch (EFB). The effects of
various parameters including the type of catalyst and gasification temperature on the char
conversion profile of the CO2 gasification process were investigated.
4.2 Experimental
4.2.1 Materials
Loy Yang brown coal (LY) from Australia, which contains low ash content with the size
between 0.5 to 1.0 mm, was used as a raw material. The proximate and ultimate analyses of
the LY are shown in Table 4-1. The moisture, volatile matter and ash contents were measured
by a thermogravimetric analyzer (TGA 701, Leco Co., Ltd.). The content of C, H, N and O
elements were determined using an elemental analyzer (TruSpec CHN, version 100, Leco Co.,
Ltd). The LY was dried in an oven at 107°C for 1 hour before mixed with biomass ashes. The
moisture content of LY was 18 wt%.
In this experiment, two types ash prepared from empty fruit bunch (EFB) from Malaysia
and chicken dropping compost (CC) from Japan with the size between 0.5 to 1.0 mm were
used as catalysts. The chicken dropping compost ash (CCA) and empty fruit bunch ash
(EFBA) were prepared by TGA in O2 gas with temperature ramping from 500 to 815°C.
After heating up to 815ºC, the temperature was maintained for 30 min, then cooled down to
room temperature.
73
Table 4-1 Proximate and ultimate analysis of the Loy Yang brown coal
Proximate analysis
(wt%, dry basis)
Ultimate analysis
(wt%, dry basis)
Volatile matter Ash Fixed carbon C H N O (diff)
52.36 0.93 46.71 63.79 7.01 0.62 28.58
4.2.2 Catalytic gasification
LY sample was mixed with two different biomass ashes, CCA and EFBA, and two
different chemical reagents, K2CO3 and CaCO3. In this experiment, the designations of LY
mixed with EFBA, LY mixed with CCA, LY mixed with K2CO3 and LY mixed with CaCO3
are LY1, LY2, LY3, and LY4, respectively.
The coal char was produced by TGA at maximum heat treatment of 650 to 800oC for 30
min. The heating rate was at 100oC/min under pure Ar gas atmosphere. The samples were
continuously gasified under a CO2 gas ambient for 2 hours. The initial char mass of dry ash
free (m0) and the instantaneous of char mass of dry ash free (mt) were calculated by
subtraction the weight of initial char mass (w0) and the weight of instantaneous char mass
(wt) that obtained from TGA with the weight of ash (wa). Hence, the char conversion (Xch)
can be calculated by using the fraction of weight loss as shown in the Eq. 4-2 given below;
𝑋!! =!!!!!!!
= (!!!!!)!(!!!!!)(!!!!!)
(4-2)
4.3 Results and Discussion
4.3.1 Characteristic of biomass ash
Forest residues and wood wastes represent a large potential resource for long-term
renewable energy. In general EFB and CC are abundant in Malaysia and Japan, respectively.
Generation of EFB and CC amounts to 19 and 13 million tons per year, respectively.
74
Table 4-2 Elements of biomass ash
Biomass ash Elemental composition (wt%, dry basis)
K Si Ca P Fe S Cl
EFBA 62.1 15.7 7.5 - 1.4 1.3 10.9
CCA 10.0 0.7 83.3 2.4 1.5 0.6 -
Fortunately, EFBA and CCA contain low amount of Si component (< 20 wt%) as the
information shown in Table 4-2. EFBA contains high amount of potassium, K (∼ 62 wt%)
and CCA contains high amount of calcium, Ca (∼ 83 wt%). Therefore, EFBA and CCA are
very interesting catalysts for catalytic gasification. After ash preparation, the biomass ash was
characterized by X-ray diffraction (XRD) method. For EFBA, the potassium was observed in
the form of potassium chloride (KCl) and potassium sodium calcium phosphate
(KNaCa2(PO4)2) as shown in Fig. 4-1. On the other hand, the calcium in CCA was observed
in the form of calcium hydroxide (Ca(OH)2), calcium silicate hydrate (CaSiO3H2O) and
Calcic ferrite (CaFe4O7) as shown in Fig. 4-2.
The presence of metal complex compounds after ash preparation in Figs. 4-1 and 4-2
might be explained by the following mechanism. During the preparation of CCA by
combustion under O2 atmosphere at 815°C for 30 min, many complex chemical reactions
occurred. Therefore, the exact mechanism of the compounds formation cannot be explained.
However, the results in Table 4-2 show that the main components of CCA include various
metal elements such as K, Si, Ca, P, Fe and S. These elements in CCA, especially Ca (83.3
wt%), K (10 wt%) and Fe (1.5 wt%), reacted with oxygen during the combustion process and
formed complex compounds such as calcium hydroxide (Ca(OH)2), calcium silicate hydrate
(CaSiO3H2O) and Calcic ferrite (CaFe4O7) as the XRD patterns shown in Fig. 4-2. The
75
presence of potassium sodium calcium phosphate (KNaCa2(PO4)2) from EFBA also might be
explained by the similar mechanism.
10 20 30 40 50 60 70 80 90
Inte
nsity
[arb
. uni
t]
2θ [degree]
EFBAx
•
•
x
• xx x
•: KNaCa2(PO4)2
x: KCl
Figure 4-1. XRD patterns of EFBA.
10 20 30 40 50 60 70 80 902θ [degree]
Inte
nsity
[arb
. uni
t]
CCA
•ο
•ο
x
x
ο: CaFe4O7
•: CaSiO3H2Ox: Ca(OH)2
Figure 4-2. XRD patterns of CCA.
76
4.3.2 Effect of gasification temperature on LY char conversion
The gasification temperature is one of the most important parameters to control the
gasification rate and conversion [17-20]. In this experiment, the gasification temperature was
varied at 650, 700, 750 and 800oC. The CO2 gasification profiles of LY char are shown in
Fig. 4-3. It was found that when the gasification temperature increased from 650 to 800oC,
the char conversion at 120 min gradually increased from 0.1 to 0.4.
4.3.3 Effects of biomass ash contents
The results in Fig. 4-4 show that when the EFBA content of LY1 char in catalytic
gasification increased from 2 to 10 wt%, the char conversion increased due to the catalytic
effect of potassium. This trend may be attributed to increase in the interaction between active
metal and char surface with increase in EFBA content. The catalytic effect of potassium for
EFBA-catalyzed CO2 gasification of LY char can be explained by the redox mechanism.
Under gasification conditions, the oxidation and the reduction occur concurrently. The
catalytic reduction involves a series of reaction in catalyst.
During gasification process, the completely reduced group is readily decomposed to
free potassium, sodium and calcium metals, which are easily vaporized at the gasification
temperatures. After the reduction process was completed, the catalyst was oxidized by CO2
and the gasification process was initialized. The active metal ions are connected to the
carboxylic and phenolic groups to form active sites on coal surface to perform the catalytic
activity [21-23].
77
0 30 60 90 1200
0.2
0.4
0.6
0.8
1.0LY char
Con
vers
ion
[-]
Time [min]
650°C700°C750°C800°C
Figure 4-3. CO2 gasification profiles of LY char.
0 30 60 90 1200
0.2
0.4
0.6
0.8
1.0
700°C
LY charLY1 char (2 wt%)LY1 char (5 wt%)LY1 char (10 wt%)
Con
vers
ion
[-]
Time [min]
Figure 4-4. CO2 gasification profiles of LY1 char at different EFBA contents of 2 to 10 wt%.
78
4.3.4 Effect of biomass-derived ash type
The catalytic CO2 gasification profiles of LY1 char (10 wt% of EFBA) and LY2 (10
wt% of CCA) char at various gasification temperatures are shown in Figs. 4-5 and 4-6,
respectively. It was found that the catalytic gasification rate and conversion are dependent on
the type of biomass-derived ash added to char as a catalyst. The conversion of both LY1 char
and LY2 char reached 100% when the gasification temperature was 800oC. This means that
the catalytic activity is strongly dependent on the reaction temperature and a high gasification
temperature is required to obtain a high conversion rate.
The results in Fig. 4-3 show that the char conversion of pure LY was very low. However,
the char conversion of LY1 (10 wt% of EFBA) linearly increased at the beginning stage and
then asymptotically decreased towards the end of the reaction as shown in Fig. 4-5. When the
gasification temperature is higher than 700oC, the char conversion reached the maximum
value (1.0). Increasing the gasification temperature from 750 to 800oC can decrease the
duration time to reach the maximum conversion from 60 to 30 min. It was confirmed that the
reaction rate is strongly dependent on the gasification temperature.
The results in Fig. 4-6 show the conversion of LY2 char (10 wt% of CCA). The char
conversion of LY2 increased twice compared to that of pure LY at gasification temperatures
between 650 to 700oC. When the reaction temperature is higher than 750oC, the char
conversion reached the maximum value (1.0). The increasing of char conversion of LY2 (10
wt% of CCA) with temperature might be related to the formation of crystalline layer of Ca on
char surface and the adsorption of CO2 by Ca(OH)2 before the CO2 gasification occurs.
The results in Figs. 4-7 and 4-8 show then XRD patterns of LY1 char (10 wt% of EFBA)
and LY2 char (10 wt% of CCA), respectively. It was found that after the gasification process,
the components of raw materials remained by comparing these results with the results shown
in Figs 4-1 and 4-2, respectively.
79
0 30 60 90 1200
0.2
0.4
0.6
0.8
1.0C
onve
rsio
n [-
]
Time [min]
LY1 char (10 wt%)
650°C700°C750°C800°C
Figure 4-5. CO2 gasification profiles of LY1 char (10 wt% of EFBA).
0 30 60 90 1200
0.2
0.4
0.6
0.8
1.0
Con
vers
ion
[-]
Time [min]
LY2 char (10 wt%)650°C700°C750°C800°C
Figure 4-6. CO2 gasification profiles of LY2 char (10 wt% of CCA).
80
10 20 30 40 50 60 70 80 90
•
xxx
x • xIn
tens
ity
[arb
. uni
t]
2θ [degree]
LY1 char (10 wt%)
•: KNaCa2(PO4)2
x: KCl
650°C700°C750°C800°C
•
Figure 4-7. XRD patterns of LY1 char (10 wt% of EFBA) after CO2 gasification.
10 20 30 40 50 60 70 80 90
800°C750°C700°C650°C
•
Inte
nsit
y [a
rb. u
nit]
2θ [degree]
LY2 char (10 wt%)
•x
ο
ο: CaFe4O7
•: CaSiO3H2O
x: Ca(OH)2xο
Figure 4-8. XRD patterns of LY2 char (10 wt% of CCA) after CO2 gasification.
81
600 650 700 750 800 8500
0.2
0.4
0.6
0.8
1.0
Con
vers
ion
[-]
Temperature [°C]
LY charLY1 char (10 wt%)LY2 char (10 wt%)
Figure 4-9. Effect of gasification temperature on the conversion of LY char with and without
mixing with 10 wt% of EFBA and 10 wt% of CCA.
The result in Fig. 4-9 shows the effect of gasification temperature on the char
conversion of LY without ash, LY1 (10 wt% of EFBA) and LY2 (10 wt% of CCA). It was
found that the char conversion rate of LY without mixing ash (LY char) is lower than that of
the LY mixed with ashes. This means that when LY is mixed with the ashes, the efficiency of
conversion increased. The conversion rate increased when the gasification temperature
increased. Moreover, LY1 char (10 wt% of EFBA) has higher reactivity than LY2 char (10
wt% of CCA).
4.3.5 Comparison of chemical reagent with ash
The results in Figs. 4-10 and 4-11 show the comparison of char conversion with
biomass ashes and chemical reagents at 700°C. Fig. 4-10 shows the LY1 char (10 wt% of
EFBA) is more effective in char conversion compared to the LY3 char (10 wt% of K2CO3)
when the gasification time is longer than 30 min. However, the char conversion of LY3 char
82
(10 wt% of K2CO3) is slightly higher than LY1 char (10 wt% of EFBA) when the gasification
time is shorter than 30 min. On the contrary, the conversion of LY4 char (10 wt% of CaCO3)
is similar to LY2 char (10 wt% of CCA) as shown in Fig. 4-11.
0 30 60 90 1200
0.2
0.4
0.6
0.8
1.0
700°C
Con
vers
ion
[-]
Time [min]
LY1 char (10 wt%)LY3 char (10 wt%)
Figure 4-10. Comparison of conversion of LY1 char (10 wt% of EFBA) and LY3 char (10
wt% of K2CO3) at 700°C.
0 30 60 90 1200
0.2
0.4
0.6
0.8
1.0
Con
vers
ion
[-]
Time [min]
LY2 char (10 wt%)LY4 char (10 wt%)
700°C
Figure 4-11. Comparison of conversion of LY2 char (10 wt% of CCA) and LY4 char (10
wt% of CaCO3) at 700°C.
83
10 20 30 40 50 60 70 80 90
: K2CO3
♦
Inte
nsity
[arb
. uni
t]
2θ [degree]
700°C
LY3 char (10 wt%)
LY1 char (10 wt%)
∇: KCl
∇•♦ ∇
♦ ∇∇ ∇
♦: KNaCa2(PO4)2
Figure 4-12. XRD patterns of LY1 char (10 wt% of EFBA) and LY3 char (10 wt% of
K2CO3) after gasification at 700°C.
10 20 30 40 50 60 70 80 90
∗: CaCO3
Inte
nsity
[arb
. uni
t]
2θ [degree]
∗ ∗∗ ∗∗
∗
∗
LY2 char (10 wt%)
LY4 char (10 wt%)
ο: CaFe4O7
•: CaSiO3H2Ox: Ca(OH)2
ο•
ο
700°C
•x x
Figure 4-13. XRD patterns of LY2 char (10 wt% of CCA) and LY4 char (10 wt% of CaCO3)
after gasification at 700°C.
84
The high efficiency of EFBA can be explained by using XRD patterns shown in Fig.
4-12. The reason may be attributed that EFBA might be able to generate more effective atom
(K, Na, Ca) than K2CO3 chemical reagent. Therefore, the char conversion is higher than
K2CO3 chemical reagent. In case of CCA, the Ca atom in CaCO3 chemical reagent can absorb
CO2 similar with Ca(OH)2. Therefore, carbon conversion of chemical reagent is similar with
ash as the XRD patterns shown in Fig. 4-13.
4.4 Conclusions
The effects of two different biomasses catalysts including chicken dropping compost
(CC) and empty fruit bunch (EFB) to the performance for the CO2 gasification process
utilizing of Loy Yang brown coal (LY) were investigated. By adding CC ash (CCA) and EFB
ash (EFBA), the CO2 gasification rate and conversion of the LY has increased. The catalytic
activity has shown at the low temperature from 700ºC. Furthermore, the EFBA is more
efficient in increasing the catalytic activities compared to the CCA with the same conditions.
85
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88
Chapter 5
Conclusions
Activated carbon from biomass by pyrolysis with and without catalysts in fixed bed
reactor was studied. The various types of catalysts that contained from nature and chemical
reagent was compared on specific surface area, activated carbon yield, and pore size
distribution. Catalytic gasification from coal also was studied. We have focuses on the
utilizing of Loy Yang brown coal (LY) as natural starting material for CO2 gasification. The
carbon conversion of LY char was catalyzed by using two different biomasses including
chicken dropping compost (CC) and empty fruit bunch (EFB).
In chapter 2, various types of biomasses including teak sawdust (TS), cypress (CP),
bagasse (BG), empty fruity bunch (EFB), and palm kernel shell (PKS) was used to produce
activated carbon. Among various types of catalysts, CaCO3 has higher specific surface area
with lower activated carbon yield compared to Ca(OH)2 and chicken compost (CC). This is
because the pore-blocking effects of Ca atoms and also the carbon content in the CaCO3.
When the catalyst to biomass ratio has increased from 1.0 to 3.0, the SSA of various types of
biomass has increased to 807 to 1082 m2/g. This means, increasing of catalyst in the process
can increases the SSA.
In chapter 3, activated carbons (ACs) can be produced from teak sawdust
(TS) mixed with two different biomass activation agents including chicken dropping compost
ash (CCA) and empty fruit bunch ash (EFBA). The specific surface area (SSA) of ACs over
1000 m2g-1 can be obtained for both CCA and EFBA after physical activation process in
N2/2%CO2 gas ambient at 1000oC. However, the potassium compound (K2O) in EFBA has
more efficiency to increase the SSA compared to the calcium compound (CaO) in CCA.
89
In chapter 4, the effects of two different biomass-derived ash catalysts, chicken dropping
compost ash (CCA) and empty fruit bunch ash (EFBA), on the performance of the CO2
gasification of Loy Yang brown coal (LY) were investigated. By mixing LY with CCA and
EFBA, the CO2 gasification rate and conversion of the LY increased. It was shown that the
catalytic activity starts to become prominent at the temperature of 650°C. Furthermore, the
EFBA is more efficient in increasing the catalytic activity compared to the CCA under the
same conditions.
90
Acknowledgements
Foremost, the author would like to express my sincere gratitude to my principal
supervisor Prof. Takayuki Takarada for his continuous support, study and research, for his
patience, motivation, enthusiasm, immense knowledge and fruitful discussion during my
doctoral course. His guidance helped me in all the time or research and writing of this thesis.
The author was much appreciated and respected to him for given the valuable chance to study
abroad in Japan. The most precious things that I obtained from him during these three years
were the carefully think about the originality of the research work and also the good logic to
organize the thesis and publication story.
Beside my supervisor, the author would like to thanks the rest of my thesis
committees: Prof. Takayuki Ohshima, Prof. Tomohide Watanabe, Prof. Shinji Katsura and
Associate Prof. Reiji Noda for their encouragement, insightful comments, and hard questions
during my intermediate presentation and final thesis defense that are valuable for the future
research work. The author also would like to thanks Osaka Gas Co., Ltd. and JST-MOST
project, Japan for their financial support on this research.
The author would like to thanks all the members of Takarada’s laboratory for their
support, especially Associate Prof. Naokatsu Kannari for discussion during the Doctoral
course. The author would like to appreciate to Mrs. Miyoko Kakuake, Mrs. Mayumi Tanaka,
Mrs. Kumiko Sakamoto and Mrs. Yumi Kojima, the secretariats of Takarada’s laboratory to
support me and taken care about my living in Japan. Furthermore, the author would like to
thanks Mr. Hoshino for his kindly support the financial for the living expenses and take care
for a warmly meeting and party every month.
Last but not least, the author would like to thanks my family: My parents, Mr.
Bumrung Kongsomart and Mrs. Somsri Kongsomart, for giving birth to me at the first place
91
and support me spiritually throughout my life. My older sisters, Mrs. Parada Boonchoowong
and Mrs. Chadasa Klinsukon. Thanks all of my friends and Thai students in Kiryu, Gunma
(Japan) who give me laugh and relax from the stress and pressure during these three years.
Without their support, the goal to achieve the Doctoral degree from Gunma University was
not success.
Boodsakorn Kongsomart
Gunma University, Kiryu, Japan
01 February 2016
92
Publication lists
Journal Publication (2)
[1] B. Kongsomart, L. Li and T. Takarada, “Preparation of activated carbons from teak
sawdust using chicken dropping compost and empty fruit bunch”, International Journal
of Biomass & Renewables, vol. 4 (2), pp. 1–7 (2015).
[2] B. Kongsomart , N. Kannari and T. Takarada, “Catalytic effects of biomass-derived ash
on Loy Yang brown coal gasification”, International Journal of Biomass &
Renewables (In-press).
International conferences (7)
[1] B. Kongsomart and T. Takarada, “Preparation of activated carbon and catalytic coal
gasification using biomass ash”, The 17th International Conference on Clean Coal
Technologies (CCT2015), Poland (2015).
[2] B. Kongsomart, B. Tsedenbal, N. Kannari and T. Takarada, “Preparation of activated
carbon from teak sawdust by using chicken dropping compost ash as an activation
agent”, The 13th China-Japan symposium on coal and C1 chemistry, China (2015).
[3] B. Kongsomart, B. Tsedenbal, N. Kannari and T. Takarada, “Preparation of activated
carbon from teak sawdust with empty fruit bunch ash”, The 13th China-Japan
symposium on coal and C1 chemistry, China (2015).
[4] B. Kongsomart, B. Tsedenbal, S. Komatsu, N. Kannari and T. Takarada, “Low
temperature catalytic gasification of brown coal using chicken droppings”, The 13th
China-Japan symposium on coal and C1 chemistry, China (2015).
93
[5] B. Kongsomart, B. Tsedenbal, S. Komatsu, N. Kannari and T. Takarada, “Low
temperature catalytic gasification of brown coal using empty fruit bunch”, The 13th
China-Japan symposium on coal and C1 chemistry, China (2015).
[6] B. Kongsomart, L. Liuyun, S. Komatsu, N. Kannari and T. Takarada, “Low temperature
catalytic gasification of brown coal using biomass”, The 2015 ICCS&T/ACSE,
Australia (2015).
[7] T. Takarada, B. Kongsomart and B. Tsedenbal, “Low temperature pyrolysis and
gasification of biomass and brown coal using catalysts from natural product”, The 5th
International Conference on the Characterization and Control of Interfaces for
High Quality Advanced Materials and the 51st Summer Symposium on Powder
Technology (ICCCI 2015), DI-13, p. 137, Japan (2015).
Domestic conferences (4)
[1] B. Kongsomart and T. Takarada, “Preparation of activated carbon from biomass using
chicken compost”, The SCEJ 79th Annual Meeting, Japan, J207, p. 625 (2014).
[2] B. Kongsomart and T. Takarada, “Synthesis of activated carbon from biomass using
agricultural waste ash by pyrolysis,” The 23rd Annual Meeting of Japan Institute of
Energy, Japan, 3-7-2. pp. 114-115. (2014).
[3] B. Kongsomart, L. Liuyun, N. Kannari and T. Takarada, “Catalytic CO2 gasification of a
brown coal using biomass ash as a catalyst”, The 24th Annual Meeting of Japan
Institute of Energy, Japan (2015).
[4] B. Kongsomart, N. Kannari and T. Takarada, “Utilization of chicken dropping compost
for activated carbon preparation and catalytic gasification”, The 1st SEOULTECH-GU
Joint Seminar on Cooperation of Politics and Technology (CPT-1), Japan, P-17, p. 61
(2016).
94
Author biography
Boodsakorn Kongsomart was born on February 25th, 1986 in Saraburi (Thailand). She
received the Bachelor of Science (Industrial Chemistry) and Master of Science (Industrial
Chemistry) from Chiang Mai University (CMU), Thailand 2007 and 2012, respectively. She
was an exchange student of Gunma University (Japan) in 2012. Her current research topic
during doctoral course is related to activated carbon and catalytic gasification process.