ABSTRACT
Five coal samples from Odagbo (Kogi State), Owukpa (Benue State), Ezimo (Enugu State),
Amansiodo (Enugu State) and Inyi (Enugu State) weresubjected to proximate analysis,
ultimate analysis, calorific value determination, petrographic and thermogravimetric
analysis to determine their suitability for power generation. Tests were carried out at the
laboratories of Advanced Coal Technology, South Africa (now Bureau Veritas Testing and
Inspections South Africa, BV-TISA) and the Institute of Applied Materials of the
University of Pretoria. Based on analysis of results of tests carried out, Amansiodo coal is a
bituminous, low sulphur and medium ash coal; while Owukpa coal is a sub-bituminous A,
low sulphur, low ash coal rich in huminites. In addition, Odagbo coal is a sub-bituminous
B, medium sulphur, low ash coal rich in huminites; Ezimo coal is a sub-bituminous C, low
sulphur, high ash coal; while Inyi coal is a sub-bituminous C, low sulphur, high ash
coal.Between Odagbo and Owukpa sub-bituminous coals, Owukpa has a lower ignition
temperature (283.63oC) due to its higher volatile matter content (39.1%). However, Ezimo
sub-bituminous coal, which has a lower volatile matter (31.1%) unexpectedly has the same
ignition temperature as Owukpa (283.63oC) due to its higher liptinite content (7.2%) when
compared with that of Owukpa (2.9%). The five (5) coal samples analysed can be used for
power generation using circulating fluidised bed combustion (CFBC) technology due to its
tolerance of a widevariety of coals and particle sizes. Amansiodo coal is suitable for power
generation using pulverised coal combustion technology based on comparison of its gross
calorific value (27.48MJ/kg), ash content (8.6%), inherent moisture content (5.4%), sulphur
content (0.92%), etc with requirements published by coal-fired power plant operators.
Gross calorific values, inherent moisture and contents of Odagbo, Owukpa, Ezimo and Inyi
sub-bituminous coals make them largely suitable for pulverized coal combustion when
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compared with the coal fuel used for the Genessee Phase 3 power station in Canada. The
ease of combustion of the coal samples in decreasing order is Odagbo, Owukpa, Inyi,
Ezimo and Amansiodo. The ignition temperatures of the coals increase with decreasing
volatile matter content, their calorific values are strongly correlated with the fixed carbon,
elemental carbon, volatile matter and hydrogen contents in decreasing order.
TABLE OF CONTENTS
Title Page ——————————————————————————————– i
Declaration Page ———————————————————————————– ii
Certification Page ———————————————————————————– iii
Acknowledgement ——————————————————————————— iv
Abstract ———————————————————————————————– v
Table of Contents ———————————————————————————— vii
List of Appendices ———————————————————————————– xi
List of Figures ————————————————————————————— xii
List of Tables —————————————————————————————- xiii
List of Plates —————————————————————————————— xv
CHAPTER ONE: INTRODUCTION
1.1 Background of the Study —————————————————————– 1
1.2 Statement of the Problem —————————————————————– 7
1.3 The Present Research ——————————————————————— 8
1.4 Aim andObjectives ————————————————————————8
1.5 Significance of the Research ————————————————————–9
viii
CHAPTER TWO: LITERATURE REVIEW
2.1 Previous Researchon Nigeria Coals ————————————————— 11
2.2 Review of Theoretical Basis for Coal Analysis ————————————–13
2.2.1 Coal classification ————————————————————————–13
2.2.2 Coal utilisation ——————————————————————————16
2.3 Characterisation of Coal —————————————————————–21
2.3.1 Proximate analysis ————————————————————————-24
2.3.2 Ultimate analysis —————————————————————————25
2.3.3 Calorific value ——————————————————————————-26
2.3.4 Petrographic analysis ———————————————————————–26
2.3.5 Thermogravimetric analysis —————————————————————33
2.3.6 Bases for reporting coal analysis ——————————————————— 34
2.4 Fundamentals of Coal Combustion —————————————————-35
2.4.1 The effect of coal macerals on combustion ———————————————37
2.4.2 Reactivity Index (RI) ———————————————————————–38
2.5 Influence of Coal Properties on Power Plant Design ——————————-39
2.6 Power Generation from Low Grade Coals ——————————————-44
2.7 Coal Beneficiation ————————————————————————-46
2.8 Research Gap —————————————————————————— 47
CHAPTER THREE: MATERIALS AND METHODS
3.1 Coal Samples ——————————————————————————48
3.2 General Sample Preparation ———————————————————–48
3.3 Proximate Analysis ———————————————————————–52
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3.3.1 Moisture content ————————————————————————— 52
3.3.2 Volatile matter —————————————————————————— 52
3.3.3 Ash content ———————————————————————————- 53
3.3.4 Fixed carbon ——————————————————————————— 54
3.4 Ultimate Analysis ————————————————————————–54
3.5 Determination of Calorific Value ——————————————————56
3.6 Determination of Total Sulphur Content ———————————————57
3.7 Petrographic Analysis ——————————————————————–58
3.8 Thermogravimetric Analysis ————————————————————61
3.9 Ash Composition Analysis ————————————————————–62
3.10 Ash Fusion Temperature Analysis —————————————————-63
3.11 Correlation Coefficient between some Properties and Calorific Value ——- 64
of Coal
CHAPTER FOUR: RESULTS AND DISCUSSIONS
4.1 Proximate Analysis ————————————————————————65
4.2 Ultimate Analysis ————————————————————————–66
4.3 Calorific Value —————————————————————————– 66
4.4 Ash Analyses ——————————————————————————-67
4.5 Petrographic Analysis ——————————————————————-69
4.6 Thermogravimetric Analysis ————————————————————69
4.7 Correlation of Some Properties and the Calorific Value of the Sampled —— 75
Coals
4.8 Discussion of Results ——————————————————————— 76
x
4.8.1 Proximate analysis ————————————————————————-76
4.8.2 Ultimate analysis —————————————————————————78
4.8.3 Petrographic (PGA) and thermogravimetric (TGA) analyses ———————— 78
4.8.4 Correlation of properties ——————————————————————- 80
4.8.5 Ranking of analysed coal samples using ASTM classification criteria ————- 80
4.8.6 Ash and sulphur classification of analysed coal samples —————————– 81
4.8.7 Suitability of analysed coal samples for pulverised coal-fired power generation — 82
4.8.8 Suitability of analysed coal samples for circulating fluidized bed combustion —- 84
(CFBC) power generation
CHAPTER FIVE: SUMMARY, CONCLUSIONS AND RECOMMENDATIONS
5.1 Summary ———————————————————————————- 86
5.2 Conclusions ——————————————————————————–87
5.3 Recommendations ———————————————————————— 88
REFERENCES ————————————————————————————-89
APPENDICES ————————————————————————————– 96
CHAPTER ONE
INTRODUCTION
1.1 Background of the Study
Access to energy, especially electricity, is a driving force for economic and social
development (Samboet al., 2009). Energy is a key factor in industrial development and in
providing vital services that improve the quality of life. Traditionally, energy has been
regarded as the engine of economic progress. Limited access to energy is a serious
constraint to development in the developing world, where the per capita use of energy is less
than one sixth that of the industrialised world(IAEA, 2005).It is widelyaccepted that there is
a strong correlation between socio-economic development and theavailability of energy.
The electricity demand in Nigeria far outstrips the current epileptic supply. Nigeria is faced
with acute electricity supply problems, which is hindering its development notwithstanding
the availability of vast natural resources in the country (Sambo et al., 2009). There are
currently 23 grid-connected generating plants in operation in the Nigerian Electricity Supply
Industry (NESI) with a total installed capacity of 10,396.0 MW and available capacity of
6,056 MW. Most generation is thermal based, with an installed capacity of 8,457.6 MW
(81% of the total) and an available capacity of 4,996 MW (48% of the total). Hydropower
from three major plants accounts for 1,938.4 MW of total installed capacity and an available
capacity of 1,060 MW (KPMG Nigeria, 2013). Total power generation as at 11 December,
2014 stands at 3,385.9 MWe as displayed on the website of the Federal Ministry of Power
(http://www.power.gov.ng).
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The Nigerian government, in a bid to fix this problem, has developed a roadmap for power
sector reform in Nigeria. Some parts of the roadmap read as follows (The Presidency,
Federal Republic of Nigeria, 2010):
“In view of the high capital costs and long lead times required to develop
commercial power generation through solar, wind, nuclear and biomass, the
Federal Government will focus its development efforts on hydro, coal and
natural gas …the Federal Government is committing to focus on electricity
generation in three areas, namely: Hydro, Coal and Natural Gas, of which the
latter represents the largestresource for fuel-to-power… Nigeria will largely
rely on hydro, coal and natural gas for generation of much of its power over
the next decade”.
From the foregoing, it is apparent that coal will play a significant role in the effort to achieve
the much-needed improvement in electricity generation in Nigeria.
Coal is a solid, brittle, combustible, carbonaceous rock formed by the decomposition and
alteration of vegetation by compaction, temperature and pressure. It varies in colour from
brown to black and is usually stratified (Speight, 2005). Coal accounts for 41% of the
world‟s energy source for electricity generation. This is distantly followed by gas (21%),
hydro (16%), nuclear (13%), oil (5%) and other renewables (3%). Coal is the key fuel for
generating electricity on almost all continents, with almost all developed and developing
countries relying on coal for the stable and secure supply of electricity (World Coal
Association, 2012).The 2011 Electricity information published by the International
3
EnergyAgency (IEA) showing the percentage contribution of coal for electricity generationin
some countries is listed in Table 1.1.
Table 1.1: Coal in Electricity Generation
Country Coal usage for
electricity (%)
Country Coal usage for
electricity (%)
Botswana 100 Zimbabwe 46
Mongolia 96 USA 45
South Africa 93 Germany 42
Poland 88 United Kingdom 29
PR China 78 Turkey 28
Australia 77 Japan 23
Kazakhstan 75 Netherlands 21
India 68 Vietnam 18
Czech Rep. 56 Russia 16
Morocco 50 Canada 15
Denmark 49 France 5
Source: World Coal Association, 2012
Coal also provides an affordable and reliable source of electricity generation. A Comparison
of electricity generation costs across international studies (US$/MWh) is shown in Table 1.2.
This proves that coal still remains the cheapest source of electricity in the world today.
Table 1.2: Comparison of Electricity Generation Costs across International Studies (US$/MWh)
Source
Researching Organisation
IEA/NEA
(2005)
CBO
(2008)
EC
(2008)
EPRI
(2008)
House of Lords
(2008)
MIT
2009
Coal 28 – 75 56 52 – 71 64 82 62
Gas 44 – 69 58 65 – 78 80 78 65
Nuclear 33 – 74 73 65 – 110 73 90 84
Biomass 54 – 109 n/a 104 – 253 80 180 n/a
Hydro 69 – 262 n/a 45 – 240 n/a n/a n/a
Wind 50 – 156 n/a 97 – 181 91 146 – 162 n/a
Solar PV 226 – 2031 n/a 674 – 1140 n/a n/a n/a
Source: World Coal Association, 2012
IEA/NEA: International Energy Agency/Nuclear Energy Agency, CBO: Congressional Budget Office, EC: European Commission, EPRI:
Electric Power Research Institute, MIT: Massachusetts Institute of Technology
The proportion of electricity generated from coal is currently on the increase. Under the
International Energy Agency‟s reference scenario, annual electricity generation from coal
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could more than double between 2004 and 2030. Even the alternative scenario of lower
growth shows almost a 58% increase in annual coal-generated electrical units over the same
period. Table 1.3 shows data from the reference scenario.
Table 1.3: World Electricity Generation from Major Fuels, IEA Reference Scenario
Fuel
Year 2004 2015 2030
Total
Generation
TWh % share TWh % share TWh % share
17, 408 100 24, 816 100 33, 750 100
Coal 6, 917 39.7 10, 609 42.8 14, 703 43.6
Oil 1, 161 6.7 1, 195 4.8 940 2.8
Gas 3, 412 19.6 5, 236 21.1 7, 790 23.1
Nuclear 2, 740 15.7 3, 108 12.5 3, 304 9.8
Hydro 2, 809 16.1 3, 682 14.8 4, 749 14.1
Renewables
(excluding hydro)
369 2.1 986 4.0 2, 264 6.7
Source: International Energy Agency, 2007
Developing economies have a particularly strong dependency on coal for power production,
and the rate of growth in coal‟s contribution to electricity supply in these countries will be
greatest, as Table 1.4 shows.
Table 1.4: Developing Countries Electricity Generation from Major Fuels,IEA Reference Scenario
Source
Year 2004 2015 2030
Total
Generation
TWh % share TWh % share TWh % share
5, 754 100 10, 749 100 17, 001 100
Coal 2753 47.8 5659 52.6 8979 52.8
Oil 580 10.1 670 6.2 616 3.6
Gas 983 17.1 1955 18.2 3389 19.9
Nuclear 142 2.5 322 3.0 523 3.1
Hydro 1239 21.5 1928 17.9 2827 16.6
Renewables
(excluding hydro)
56 1.0 215 2.0 668 3.9
Source: International Energy Agency, 2007
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Available data show that coal of sub-bituminous grade occurs in about 22 coal fieldsspread
in over 13 States of the Nigerian Federation. Table 1.5 shows the existing/potential coal
mines in Nigeria (Kibiya, 2012).
Table 1.5: Existing/Potential Coal Mines/Sites in Nigeria
S/N Mines Location State Type of Coal *Estimated
reserves
*Proven
Reserves
Mining method
1 Okpara Mine Enugu Sub- Bituminous 100 24 Underground
2 Onyeama Enugu Sub- Bituminous 150 40 Underground
3 Ihioma Imo Lignite 40 N.A Open-cast
4 Ogboyoba Kogi Sub- Bituminous 427 107 Opencast/Underground
5 Ogawashi Azagba/
Obomkpa
Delta Lignite 250 63 Opencast/Underground
6 Ezimo Enugu Sub- Bituminous 156 56 Opencast/Underground
7 Inyi Enugu Sub- Bituminous 50 20 Opencast/Underground
8 Lafia/Obi Nasarawa Bituminous
(Cokable)
156 21.42 Opencast/Underground
9 Oba/Nnewi Anambra Lignite 30 N.A Underground
10 Afikpo/Okigwe Ebonyi/Imo Sub- Bituminous 50 N.A Underground
11 Amansiodo Enugu Bituminous
(Cokable)
1000 N.A Underground
12 Okaba (Odagbo) Kogi Sub- Bituminous 250 3 Opencast/Underground
13 Owukpa Benue Sub- Bituminous 75 75 Open
14 Ogugu/Awgu Enugu Sub-Bituminous N.A N.A Underground
15 Afuji Edo Sub- Bituminous N.A N.A Underground
16 Ute Ondo Sub- Bituminous N.A N.A Underground
17 Doho Gombe Sub- Bituminous N.A N.A Underground
18 Kurumu Gombe Sub- Bituminous N.A N.A Underground
19 Lamja Adamawa Sub- Bituminous N.A N.A Underground
20 Garin maigungu Bauchi Sub- Bituminous N.A N.A Underground
21 Gindi Akwati Plateau Sub- Bituminous N.A N.A Underground
22 Jamata Koji Kwara Sub- Bituminous N.A N.A Underground
The proven reserves so far in the country are 639 million tonnes while the inferred reserves
are about 2.75 billiontonnes, consisting approximately of 49% sub-bituminous, 39%
bituminous and 12%lignitic coals. Up to the early 1960s, coal productionwas significant and
dominated the commercial energy supply. It was also thepredominant source of energy for
rail transportation and electricity generation (The Presidency, Federal Republic of Nigeria,
2003). Coal presently does not contribute to Nigeria‟s electricity generation. Of the new
Source: Kibiya, 2012 * Expressed in Million Tonnes
6
generation stations under construction, only the Oji River Power Plant with a planned
capacity of 20MW, is coal-fired (Sambo et al., 2009).
With the development of cleaner coal utilisation technologies such as Carbon Capture and
Storage (CCS), coal has shedthe toga of being called a “dirty fuel”. The International Energy
Agencydescribes CCS as “one of themost promising options for mitigatingemissions in the
longer term” while theIntergovernmental Panel on ClimateChange (IPCC) concluded that
CCSwas among the technologies with thelargest economic potential to reduceemissions from
electricity generation (World Coal Institute, 2008).
Nigeria has made a commitment to pursue vigorously a comprehensive programme
ofresuscitation of the coal industry and promote effective utilisation of coal for
complementing the nation’s energyneeds (The Presidency, Federal Republic of Nigeria,
2003). The Federal Government of Nigeria has awarded contracts for the provision of
consultancy services for feasibility studies, detailed engineering design and drafting of
contract documents for the development and construction of coal-fired power plants to be
located in Enugu, Benue, Kogi and Gombe States (Ogbu, 2011). In addition, the Federal
Government of Nigeria, in 2013, signed a Memorandum of Understanding with HTG/Pacific
Energy Company Limited, with substantial technical partnership with Chinese experts, for a
$3.7 billion coal-to-power projectscripted to provide an initial 1,200 MW power plant to be
built at Enugu, using coal from the Ezimo mine (Adetayo, 2013).
7
With vast supplies of coal and against the backdrop of severe shortages in much needed
supply of electricity, it is inevitable that Nigeria must move from rhetoric to concrete action
in the development and addition of coal-fired electricity to the nation‟s electricitysupply mix.
1.2 Statement of the Problem
With a conservative peak load forecast of 8,900MW and an average generation of less than
4,000MW, the resultant massive load shedding has made Nigeria an unattractive
environment for existing and prospective manufacturers. Manufacturers operating in Nigeria
spend a weekly average of N1.8 billion on diesel to run their electric power generating sets
(Iba, 2011). In addition, it is claimedby the Manufacturers Association of Nigeria (MAN)
that an estimated 60 million Nigerians now own power generating sets for their electricity,
while the same number of people spend a staggering N1.56 trillion ($13.35m) to fuel them
annually. This is besides private power generation by industrial consumers, which is almost
at the same level (Energy Commission of Nigeria, 2009). These reports paint a vivid picture
of the problem bedeviling the country.
1.3 The Present Research
This research coveredthe characterisationof coal from five deposits in Nigeria which include
Odagbo (Kogi State), Owukpa (Benue State), Ezimo (Enugu State), Amansiodo (Enugu
State) and Inyi (Enugu State). Estimated reserves of these deposits are 250, 75, 156, 1000
and 50 milliontonnes, respectively (Kibiya, 2012). Analysis carried out include
8
determination of Proximate Analysis, Calorific Value, Ultimate Analysis, Ash Composition,
Ash Fusion Temperature (in oxidising and reducing atmospheres),petrographic analysis and
thermogravimetric analysis.
1.4 Aim and Objectives
The aim of this research is to characterise coalsfrom five deposits in Nigeria which include
Odagbo (Kogi State), Owukpa (Benue State), Ezimo (Enugu State), Amansiodo (Enugu
State) and Inyi (Enugu State), thereby enriching the repository of existing data on properties
of Nigerian coals and make a strong case for the utilisation of these coals in power
generation.
The specific objectives of the research are:
(i) To carry out proximate, ultimate and ash composition analyses of the coal
samples.
(ii) The determination of calorific value of the coal samples.
(iii)To determine ash fusion temperature (in oxidising and reducing atmospheres) of
the coal samples.
(iv) To carry out petrographic and thermogravimetric analyses of the coal samples.
(v) To compare results of the above analyses with reference values of coal properties
for power generation in order to determine the suitability of the coal samples for
power generation.
1.5 Significanceofthe Research
9
The quality of the coal used affects most of the costs associated with coal-fired power plants.
Proper evaluation of the combustion performance of the coal to ensure optimum utilisation
and minimum costs is therefore essential.
This research will help determine the suitability of some Nigerian coals for use in coal-fired
power plants, not only in Nigeria, but as an export commodity to other coal-consuming
countries around the world. This will assist the potential investor in Nigeria‟s power sector to
make a decision on areas of the coal‟s performance that may be suspect,requiring further
investigation by a larger-scale form of testing (pilot-scale simulation or full-scale testing)
and also serve as a justification for investment in such a larger-scale testing.
The significance of this research is further underscored by the present dependence of Nigeria
on natural gas- and hydro-powered electricity.The unreliability of natural gas supply due to
frequent disagreement over appropriate pricing and pipeline vandalism and the susceptibility
of hydro-electric power to weather has made the inclusion of coal-fired electricity into
Nigeria‟s electricitygeneration mix imperative. The argument for nuclearpower has been
punctured by recent safety concerns arising from the Fukushima nuclear disasteras raised in
the website of Green Peace International (http://www.greenpeace.org).
With world industrial giants such as the United States of America, Peoples Republic of
China, Germany, Australia, India and South Africa among countries heavily dependent on
coal for electricity generation, Nigeria cannot exclude itself from benefitting from this
resource which it has been richly endowed with.
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