ABSTRACT
In the quest for search of suitable coal deposits for power generation, the qualities of
four Nigerian coal samples from Kurumu (Gombe State), Garin-maiganga (Bauchi
State), Gindi-akwati (Plateau State) and Ogboyoba (Kogi State) deposits were analysed
to assess their suitability for power generation. The coal samples were subjected to
proximate analysis, ultimate analysis, calorific value determination, thermogravimetric
analysis, ash fusion temperature analysis, ash composition analysis and auto-ignition
temperature determination. Tests were carried out in Nigerian Geological Survey
Agency, Kaduna and Beijing University of Technology (BUT), China. From the results
of these analyses, Kurumu coal deposit was found to be a sub-bituminous, low ash and
low sulphur coal. Garin-maiganga coal deposit was found to be a sub-bituminous,
medium ash and low sulphur coal. Gindi-akwati coal deposit was found to be a lignitic,
high ash and low sulphur coal while Ogboyoba coal deposit was found to be a subbituminous,
low ash and low sulphur coal. Kurumu, Garin-maiganga and Ogboyoba coal
deposits with calorific values of 25.71MJ/kg, 23.37MJ/kg and 24.78MJ/kg respectively,
can be used for power generation using the integrated gasifier combustion cycle clean
coal technology. However, Gindi-akwati coal deposit with a calorific value of
11.56MJ/kg can be used for power generation using circulating fluidised bed combustion
technology due to its tolerance of a wide variety of coals. The self-ignition temperature
and ease of combustion of the coal samples in decreasing order of their volatile ratio is
Gindi-akwati (0.58), Garin-maiganga (0.49), Ogboyoba (0.48) and Kurumu (0.47).
TABLE OF CONTENTS
Title page……………………………………………………………………….. i
Declaration……………………………………………………………….…….. ii
Certification…………………………………………………………………….. iii
Acknowledgement……………………………………………………………… iv
Abstract………………………………………………………………………… v
Table of contents……………………………………………………………….. vi
List of figures…………………………………………………………………… ix
List of tables……………………………………………………………………. x
List of appendices……………………………………………………………… xi
Abbreviations………………………………………………………………….. xii
CHAPTER ONE: INTRODUCTION……………………………………….. 1
1.1 Background of the study…………………………………………………. 1
1.2 Benefits of coal as a source of power generation to the nation…………. 4
1.3 Statement of research problem…………………………………………… 5
1.4 Aim and Objectives………………………………………………………… 5
1.5 Significance of the Research……………………………………………… 6
1.6 Scope of Research…………………………………………………………. 6
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CHAPTER TWO: LITERATURE REVIEW……………………………… 7
2.1 Availability of coal in Nigeria……………………………………………. 7
2.2 Previous researches on coal……………………….………………………. 9
2.3 Classification of coal……………….………………………….………….. 11
2.4 Clean Coal Technology………………………………………………….. 12
2.4.1 Circulating Fluidized Bed Combustion (CFBC)………………………… 12
2.4.2 Pressurized Fluidized Bed Combustion (PFBC)………………………… 13
2.4.3 Integrated Gasification Combined Cycle (IGCC)………………………. 14
2.4.4 Top Cycles……………………………………………………………….. 16
2.5 Terms and Significance of Various Parameters in Proximate Analysis..18
2.5.1 Fixed carbon……………………………………………………………… 18
2.5.2 Volatile Matter…………………………………………………………… 18
2.5.3 Ash Content……………………………………………………………… 18
2.5.4 Moisture Content………………………………………………………… 18
2.6 Ultimate Analysis………………………………………………………. 19
2.7 Calorific Value…..….………………………………………………….. 19
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2.8 Thermogravimetric analysis…………………………………………… 20
2.9 Fusibility of coal ash…………………………………………………… 21
2.10 Ash Composition Analysis………………………….………………… 22
2.11 Auto-Ignition temperature and coal storage……………………….. 22
2.12 Coal quality requirements for coal-fired plant…………………….. 23
2.13 Power generation from low grade coals…………………………….. 25
2.14 Research Gap…………………………………………………………. 26
CHAPTER THREE: MATERIALS AND METHODS………………… 27
3.1 Coal Samples……………………………………………………………27
3.2 General Sample Preparations…………………………………………. 27
3.3 Proximate Analysis…………………………………………………….. 27
3.4 Ultimate Analysis………………………………………………………. 29
3.5 Determination of Total Sulphur Content…………………….……… 30
3.6 Determination of Calorific Value………………………………….…. 30
3.7 Thermogravimetric and Differential Scanning Calorimetry………. 31
3.8 Determination of Ash Fusion Temperature of Coal Samples….…… 31
3.9 Ash composition analysis………………………………………………. 32
3.10 Experimental procedure for the determination of
auto-ignition temperature……………………………………………………32
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CHAPTER FOUR: RESULTS AND DISCUSSION..……………………. 33
4.1 Introduction……………………………………………………………… 33
4.2 Proximate Analysis………………………………………………………. 33
4.3 Ultimate Analysis…………………………………..…………………….. 34
4.4 Calorific Value………………………………………………………….… 35
4.5Thermogravimetric and Differential Scanning Calorimetry analyses… 35
4.5.1 TG-DSC of Kurumu coal deposit………………………………………. 35
4.5.2 TG-DSC of Garinmaiganga coal deposit…………………………….… 36
4.5.3 TG-DSC of Gindiakwaticoal deposit………………………….……….. 36
4.5.4 TG-DSC of Ogboyoba coal deposit………………………….…………. 37
4.6 Ash Analysis….…………….……………………………….……………… 37
4.7Ash Fusion Temperature…………………………………….…………… 38
4.8 Coal Auto-Ignition Temperature……………………………………….. 38
4.9 Discussion of result……………………………………………………….. 39
4.9.1 Proximate analysis…………………………………………….………… 39
4.9.2 Ultimate analysis…………………………………………….………….. 40
4.9.3 Calorific value…………………………………………….……………… 41
4.9.4 Thermogravimetric and Differential Scanning Calorimetry analyses….. 42
4.9.5 Coal ash analysis………………………………………….…………….. 43
4.9.6 Ash fusion temperature…………………………………….…………… 44
4.9.7 Coal auto-ignition temperature………………………….……………… 44
4.9.8 Ranking of analysed coal samples……………………….…………….. 45
4.9.9 Ash and sulphur classification of the analysed coal samples…….……. 46
4.9.10 Suitability of analysed coal samples for power generation…….……. 46
CHAPTER FIVE: SUMMARY, CONCLUSION AND
RECOMMENDATIONS……………….…………………………………… 51
5.1 Summary…………………………………………………………………. 51
5.2 Conclusion………………………………………………………………… 52
5.3 Recommendations………………………………………………………… 53
REFERENCES……………………………………………………………….. 54
APPENDICES………………………………………………………………… 57
CHAPTER ONE
INTRODUCTION
1.1 Background of the study
Adequate power supply is an unavoidable prerequisite to any nation’s
development. Electricity plays a very important role in the socio-economic and
technological development of every nation. The electricity demand in Nigeria far
outstrips the supply and the little supply is epileptic in nature. The country is
faced with acute electricity problems which is hindering its development
notwithstanding availability of vast energy resources in the country. It is widely
accepted that there is a strong correlation between socioeconomic development
and the availability of electricity in a given country. The energy woes today had
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continued unabated over the years since 60 percent of Nigeria’s electricity –
generating capacity broke down due to decades of neglect by the government.
The remainder serves only 40% of her citizens
(Essien et al., 2013; Sambo et al., 2010) at different degrees of black-outs,
rolling black-outs and brown-outs. Another side to these woes is the fact that for
more than three decades, Nigeria went for gas – fired power stations, in the days
when there was still abundant cheap gas. With the present skyrocket price of gas,
it has become expensive to run those plants when compared to coal – fired and
nuclear plants ( Oodo and Zou, 2009).
In Nigeria presently, 93% of electric power generation is provided by gas, the
remainder is from hydro sources. There are over 8.6GW of installed capacity of
generating plant made of government owned and independent power plant across
Nigeria. Despite the large number of installed power generation capacity, Nigeria
could still not meet the electricity demand of its populace which is estimated at
10GW because of old age of the power plants and lack of new generation plants
addition. Actual electricity generation is only between 2.5 – 3.6GW (Ujam and
Diyoke, 2013).
Even if new power plants addition were to be made, the overdependence of
Nigeria’s electrical system on gas which cannot guarantee longer term
sustainability should be a major concern. The frequent agitation for resource
control from areas with fossil fuel reserves and incessant vandalization of power
plant gas supply infrastructure are threats to the continuous sustainability of the
Nigeria’s power system of today.
Moreover, there is an urgent need for a good energy mix in the nation’s energy
generation infrastructure due to the combined benefits derivable from it.
Globally, the energy industry is driving towards sustainable low carbon emitting,
renewable energy sources.
However, renewable as at now are still in their infant stage of commercialization
and cannot help to meet Nigeria’s base load electricity demand deficit. It is also
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worthy of mention that even in the most envisioned grid of the 21st century
otherwise called the smart grid, traditional large central power plants still form
the ‘nucleus’ of this concept both in Europe and America
( Essien et al., 2013).
Coal is an important energy resource across the world, principally for electricity
generation. It is the world’s most abundant and widely distributed fossil fuel,
with global proven reserves totaling nearly 1 trillion tonnes (Ujam and Diyoke,
2013).
Coal which is spread across Nigerian states with an estimated reserve of 2.734
billion tones
(Sambo et al., 2010; Ujam and Diyoke, 2013) holds the key to Nigeria’s
present and even future energy security. On the average, 40% of the world’s
electricity is generated from coal with a rather higher percentage as you move
from one country to another. For instance, electricity generation in South Africa
derivable from coal fuels is placed at about 93%, it is 92% in Poland, 79% in
china, 69% in India, 49% in the USA (Olayande et al., 2012) etc as shown in
Table 1.1, but most unfortunately it is 0% in Nigeria. Most developed and
developing countries that has coal deposits meet their energy demands through
coal based generation. Nigeria can bridge its energy demand and supply deficit
by leveraging on its abundant coal deposit resources.
Nigeria cannot continue to be in the dark when there is approximately 3 billion
tonnes of coal deposits spread across 22 locations in Nigeria (Kibiya, 2012) that
has not been harnessed. The growing energy needs of the developing world are
likely to ensure that coal remains a key component of the power generation mix
in the foreseeable future, regardless of the climate change policy.
Table 1.1 Top 12 Countries that use Coal for Electricity Generation
S/No. Country Percentages (%)
1 South Africa 93
2 Poland 92
3 China 79
4 Australia 77
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5 Kazakhstan 70
6 India 69
7 Israel 63
8 Czech republic 60
9 Morocco 55
10 Greece 52
11 USA 49
12 Germany 46
Source: Olayande et al., 2012
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 shown in Table 1.2:
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 56 1.0 215 2.0 668 3.9
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Table 1.2: Developing Countries Electricity Generation from Major Fuels, IEA
Reference Scenario
Source: International Energy Agency, 2007
1.2 Benefits of coal as a source of power generation to the nation
The exploitation of coal for electricity generation and the production of coal
briquettes for domestic and industrial heating will bring a number of benefits
including;
i) Increased and more reliable electricity supply
ii) Lower cost electrical energy
iii) Expanded industrialization of the economy
iv) Increased employment and human resource development
v) Increased capacity utilization of existing industries
vi) Increased national income through taxes and
vii) Reduced deforestation and prevention of desert encroachment in the
northern parts of the Country
Despite these benefits, the use of coal for electricity generation also have some
short comings most of which are centered on environmental pollution. However
the development of clean coal technology has considerably reduced these green
house emission effects.
1.3 Statement of research problem
Since the discovery of petroleum in Nigeria, the use of coal for electricity
generation, cooking, heating up houses in the cold period to create warmth, e.t.c,
has been neglected in spite of its abundance in the country. This results to
constant failure in power supplies, political and economical instability due to
insufficiency and increase in price of petroleum product. Therefore, against the
backdrop of abundant proven reserves of coal, analyses of coal properties for
their suitability in power generation can significantly contribute to Nigeria’s
energy mix. The generation of electricity in Nigeria has suffered a major setback
(excluding hydro)
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due to unavailability of data on Nigerian coal for investors. To readily attract
prospective investors, it is pertinent to readily make available the properties of
Nigerian coals that are critical for electricity generation.
1.4 Aim and Objectives
The aim of this research is to determine the properties of coal from four deposits
in Nigeria which include Kurumu (Gombe State), Garin-maiganga (Bauchi
State), Gindi-akwati (Plateau State) and Ogboyoba (Kogi State) thereby
enriching the repository of existing data on properties of Nigerian coals in power
generation.
The specific objectives of the research are:
i) To carry out proximate and ultimate analyses of the coal samples
ii) To determine the calorific values of the coal samples
iii) To carry out thermogravimetric analysis of the coal samples
iv) To determine the ash fusion temperature, auto-ignition temperatures of
coal samples and carry out ash analysis of the coal samples
v) To characterize the coal samples and To compare the results with existing
standards and make recommendations on the use of the coal from each
deposit for power generation
1.5 Significance of the Research
With the world’s industrial giants such as the United States of America, China,
Germany etc, heavily depending on coal for electricity generation, Nigeria
cannot exclude herself from benefitting from this resource which she has in
abundance. This research therefore has helped to determine the suitability of
some of the Nigerian coals for use in coal-fired power plants not only in Nigeria,
but as an export product to other coal-consuming countries around the world.
This will assist potential investors in Nigerian power sector to make a decision
on the profitability of using each deposit as a source for power generation.
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1.6 Scope of research
This research covers analyses of coal samples from four deposits in Nigeria
which include Kurumu (Gombe State), Garin-maiganga (Bauchi State), Gindiakwati
(Plateau State) and Ogboyoba (Kogi State). Analyses carried out were
proximate analysis, ultimate analysis, determination of calorific value,
thermogravimetric analysis, ash composition analysis, ash fusion temperature
and auto-ignition temperature to assess their suitability for electric power
generation. From the analyses carried out, the coal samples were characterized
and the appropriate clean coal technology was recommended.
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