ABSTRACT
This work studied the effect of groundnut shell and maize cob on coal
briquette. The ratio of coal: biomass prepared were 90:10, 85:15, 80:20,
75:25, 70:30, 100:0. The mixture was treated with Ca(OH) which serves
as a desulphurizing agent, before briquetting. The chemical analysis
carried out on the raw materials (i.e. groundnut shell, maize cob and
coal) indicated the presence of Ca, Mg, Al, Na, Fe, Cu, K, Zn, Mn, Pb,
Ni, Cr, As, S. The proximate analysis of the raw materials was also
carried out. Burning and viability tests carried out revealed that maize
cob-coal briquettes ignite and burn faster, smoke less, produce flame
and small quantity of ash after burning, than the other briquettes.
Hardness compressive strength and density test of the briquettes
produced showed that coal briquette has better hardness, compressive
strength, and density results than the other briquettes. Also, the bio-coal
briquette with the highest percentage of biomass (i.e. 30%) gave the
best viability, burning, porosity, porosity index, ash content, calorific
value results than the other briquettes. However, maize cob-coal
briquettes gave the best results compared to the groundnut shell-coal
briquettes and the coal briquette which was used as the standard.
vi
TABLE OF CONTENTS
Title page………………………………………………………………… i
Certification page………………………………………………………… ii
Dedication ………………………………………………………………… iii
Acknowledgements…………………………………………………… iv
Abstract…………………………………………………………………… v
Table of contents………………………………………………………. vi
List of tables………………………………………………………………. x
List of figures……………………………………………………………… xi
List of plates………………………………………………………………. xii
CHAPTER ONE
1.0 INTRODUCTION…………………………………………………… 1
1.1 Coal …………………………………………………………………. 3
1.1.1 Concept of coal…………………………………………………….. 3
1.1.2 Uses of coal…………………………………………………………. 8
1.1.3 Coal as an alternative energy resources ………………………… 11
1.1.4 Nigerians’ overdependence on oil and gas………………………. 12
1.1.5 A forecast of coal demand in Nigeria……………………………… 12
1.1.6 Environmental issues………………………………………………. 13
1.1.7 Coal Analysis………………………………………………………… 14
1.2 Briquetting technology………………………………………………… 15
1.2.1. Advantages of briquette production ……………………………… 16
1.2.2. Types of briquettes ………………………………………………… 16
1.2.2.1 Coal briquetting ………………………………………………….. 17
1.2.2.2 Biomass briquetting ……………………………………………… 22
1.2.2.3 Bio-coal briquetting………………………………………………… 23
1.2.2.3.1 Characteristics of bio-coal briquettes……………………….. 23
vii
1.2.2.3.2 Advantages of bio-coal briquettes…………………………… 25
1.2.2.3.3 Bio-coal briquetting technology……………………………….. 25
1.2.3. Biomass as a feedstock for the production of bio-coal briquette 29
1.2.4 Groundnut shell as an appropriate residue for the production
of bio-coal briquettes……………………………………………… 42
1.2.4.1 Analyses of groundnut shell……………………………………… 43
1.2.4.2. Uses of groundnut shell…………………………………………. 44
1.2.5 Maize/Corn cob as an appropriate residue for the production of
bio- coal
briquettes……………………………………………………….45
1.2.5.1. Analyses of corn cob………………………………………………46
1.2.5.2. Uses of corn cob……………………………………………………47
1.2.6. Binders used in the production of bio-coal briquettes……………47
1.2.6.1 Starches as a binder for the production of bio-coal briquette….48
1.2.6.1.1 Other applications of starch……………………………………..50
1.2.7 Burning process of bio-coal briquette …………………………….51
1.2.8 Characteristics of a good fuel (bio-coal briquette),……………….52
1.3 The aim of the research………………………………………………54
CHAPTER TWO
2.0 EXPERIMENTALS:……………………………………………………55
2.1 Materials and methods. ………………………………………………55
2.1.1 Materials and their sources…………………………………………..55
2.1.2 Apparatus used for the experiment. …………………………………55
2.1.3 Reagents used for the experiment…………………………………..56
2.1.4 Preparation of materials ……………………………………………..57
2.2 Characterization of the raw materials…………………………………58
2.2.1 Determination of the colour and texture of the raw materials…….58
2.2.2 Determination of chemical composition of the raw materials…….58
2.2.3 Proximate analysis of the raw materials…………………………..59
viii
2.2.3.1 Determination of the moisture content of the raw materials……59
2.2.3.2 Determination of the volatile matter in the raw materials……….60
2.2.3.3 Determination of the ash content of the raw materials………….60
2.2.3.4 Determination of the carbon content of the raw materials………61
2.2.3.5 Determination of calorific value of the raw materials ……………61
2.2.3.6 Determination of the fixed carbon content of the raw materials.63
2.3 Bio-coal briquette formulation …………………………………….63
2.4 Characterization of the bio-coal briquette samples…………………65
2.4.1 Determination of the calorific value of the briquette samples……65
2.4.2 Determination of the moisture content of the briquette samples..67
2.4.3 Determination of the ash content of the briquette samples………68
2.4.4 Determination of the porosity of the briquette samples…………..68
2.4.5 Determination of the porosity index of the briquette samples……69
2.4.6 Determination of the density of the briquette samples……………69
2.4.7 Determination of the hardness of the briquette samples…………69
2.4.8 Determination of the compressive strength of the briquette
samples………………………………………………………………..70
2.4.9 Water boiling tests of the briquette samples………………………72
2.4.10 Viability tests of the briquette samples …………………………..72
CHAPTER THREE
3.0 RESULTS AND DISCUSSION………………………………………73
3.1 Colour and texture of the materials………………………………….73
3.2 Chemical composition of the materials…………………………….73
3.3 Analysis of the materials…………………………………………….76
3.4 The effect of biomass on the production of briquettes …………..79
3.5 Characterization of the briquette samples…………………………80
3.5.1 Effect of biomass on the calorific value of the briquette samples.80
3.5.2 Effect of biomass on the moisture content of
the briquette samples………………………………………………82
ix
3.5.3 Effect of biomass on the ash content of the briquette samples….83
3.5.4 Effect of biomass on the porosity of the briquette samples…….85
3.5.5 Effect of biomass on the porosity index of the
briquette samples…………………………………………………..87
3.5.6 Effect of biomass on the density of the briquette samples……..89
3.5.7 Effect of biomass on the hardness of the briquette samples…..90
3.5.8 Effect of biomass on the compressive strength of the
briquette samples…………………………………………………92
3.5.9 Effect of biomass on the water boiling test of the
briquette samples……………………………………………………94
3.5.10 Effect of biomass on the viability tests of the briquette samples.95
3.6 Cost analysis……………………………………………………………99
3.7 Conclusion …………………………………………………………….100
3.8 Recommendation……………………………………………………..101
References…………………………………………………………………103
x
LIST OF TABLES
Table1: Existing potential coal mine sites with reserves in Nigeria.
Table 2: Coal tar chemicals.
Table 3: Chemical analysis on bio-coal briquette ash.
Table 4: Types of biomass feed stocks used for energy purposes.
Table 5: Ash content of different biomass types.
Table 6: The physical and chemical characteristics of biomass feed
stock and their effect on co-firing.
Tables 7: Chemical composition of groundnut shell.
Table 8: Ash analysis of groundnut shell.
Table 9: Proximate analysis of corn cob.
Table 10: Elemental analysis of corn cob.
Table 11: Ash analysis of corn cob.
Table 12: Bio-coal briquettes formulation.
Table 13: Colour and texture of the raw materials.
Table 14: Chemical composition of the raw materials.
Table 15: Proximate analysis of the raw materials.
Table 16: Carbon content of the raw materials.
Table 17: Calorific value of the raw materials.
Table 18: Calorific value results of the briquette samples.
Table 19: Moisture content results of the briquette samples.
Table 20: Ash content results of the briquette samples.
Table 21: Porosity test result of the briquette samples.
Table 22: Porosity index results of the briquette samples.
Table 23: Density test results of the briquette samples.
Table 24: Hardness test results of the briquette samples.
Table 25: Compressive strength test results of the samples.
Table 26: Water boiling test results of the samples.
Table 27: Viability test results of the samples.
xi
List of figures
Fig. 1: Typical uses and the estimated percentage of the world’s coal
reserves for each coal rank.
Fig. 2: Process flow of briquette production
Fig. 3: A cross-sectional view of carbonization furnace.
Fig. 4: Basic process flow for bio-briquette production.
Fig. 5: Schematic manufacturing process of bio-coal briquette.
Fig. 6: Chemical composition of coal.
Fig. 7: Chemical composition of groundnut shell.
Fig. 8: Chemical composition of corn cob.
Fig. 9: Proximate analysis of the raw materials.
Fig. 10: Results of calorific value of the briquette samples.
Fig. 11: Moisture content results of the briquette samples.
Fig. 12: Results of ash content of the briquette samples.
Fig. 13: Porosity test results of the briquette samples.
Fig. 14: Porosity index results of the briquette samples.
Fig. 15: Density test results of the briquette samples.
Fig. 16: Hardness test results of the briquette samples.
Fig. 17: Compressive strength test results of the briquette samples.
Fig. 18: Water boiling test results of the briquette samples.
Fig. 19: Ignition time test results of the briquette samples.
Fig. 20: Burning time of the briquette samples.
xii
List Of Plates
Plate 1: The briquettes produced
Plate 2: The manual hydraulic briquetting machine.
Plate 3: Oxygen bomb calorimeter.
1
CHAPTER ONE
1.0 INTRODUCTION:
Energy is the ability to do work. Sources of energy include
electricity, petroleum, nuclear power, solar energy, tar sand, burning of
coal, wood and biomass, etc. Nigeria is blessed with abundant energy
resources: oil, gas, coal, wood, biomass, solar, wind, nuclear and
hydropower.
Energy availability in Nigeria and its supply has been a source of
constant friction between the people and the government. This however,
should not be so because, among the abundant energy resources
available in Nigeria, only oil and gas sector have so far been well
developed. The industrial and domestic sectors of the Nigerian economy
continue to suffer from perennial shortage of energy. This shortage has
led to accurate energy crisis at the household level. The bulk of the
energy used for cooking at the household level in Nigeria is mainly
derived from wood fuel and fossil fuel (kerosene).
The fossil fuels are produced and delivered at a cost most
Nigerians cannot afford. As a result, a greater percentage of the evergrowing
population of the country have resorted to depend on the
country’s forest waste as a source of fuel for agricultural, domestic and
small-scale industrial activities in semi urban and rural areas. The use of
wood fuel encourages cutting down/felling of trees (deforestation). This
leads to desertification in the Northern part of Nigeria; and flooding, soil
erosion and loss of top soil fertility in the Southern part of Nigeria. In
some cases, it can lead to extinction of wild life.
Energy is the key factor in economic development in most
countries today. In Nigeria, there is overdependence on oil and gas for
energy for industrial and domestic purposes, since it is the only source of
2
energy that is well developed. Hence, there is need to develop the other
sources of energy so that energy supply will be enough and affordable
for industrial and domestic purposes, and our oil and gas be conserved
(and used for transportation). Most advanced countries today are
adapting the concept of preserving and also retaining their natural
resources. As the world adjusts itself to the new millennium and its
technology, the demand for fuel and energy increases, therefore, it
should be conserved.
Of all the available energy resources in Nigeria, coal and coal
derivatives such as smokeless coal briquettes, bio-coal briquettes, and
biomass briquettes have been shown to have the highest potential for
use as suitable alternative to coal/wood fuel in industrial boiler and brick
kiln for thermal application and domestic purposes, therefore, it will serve
as the most direct and effective method of combating deforestation in the
country. Coal and biomass are available, and cheap.
There is a worldwide acceptance of briquettes and growing
demand for the briquetting plants. In June 2009, a workshop on
“Investment Potentials of the Nigerian Coal Industry” was organized by
the Nigerian Coal Coporation. It was clear from the workshop that
substantial progress has been made in briquetting technology and
practice in recent years.
In countries like Japan, China and India, it was observed that
agricultural waste (agro residues) can also be briquetted and used as
substitute for wood fuel. Every year, millions of tons of agricultural waste
are generated. These are either not used or burnt inefficiently in their
loose form causing air pollution to the environment. The major residues
are rice husk, corn cob, coconut shell, jute stick, groundnut shell, cotton
stalk, etc. These wastes provide energy by converting into high-density
fuel briquettes. These briquettes are very cheap, even cheaper than coal
3
briquettes. Adoption of briquette technology will not only create a safe
and hygienic way of disposing the waste, but turn into a cash rich
venture by converting waste into energy and also contributing towards a
better environment.
Coal can be blended with a small quantity of these agricultural
waste (agro residues) to produce briquettes (bio-coal briquettes) which
ignites fast, burn efficiently, producing little or no smoke and are cheaper
than coal briquettes.
Briquetting technology is yet to get a strong foothold in developing
countries including Nigeria, because of the technical constrains involved
and lack of knowledge to adopt the technology to suit local conditions.
Overcoming the many operational problems associated with this
technology and ensuring the quantity of the raw material used are crucial
factors in determining its commercial success. In addition to this
commercial aspect, this technology encourages conservation of wood.
Hence, briquette production technology can prevent flooding and serve
as a global warming countermeasure through the conservation of forest
resources.
1.1 Coal:
1.1.1 Concept of coal:
Coal is a carbon containing, combustible solid, usually stratified which
is formed by debris from the decay of ferns, vines, trees and other plants
which flourished in swamps millions of years ago. Over time, the debris
became buried and the actions of bacteria, heat, and pressure
transformed the debris first into peat (a precursor of coal) and then into
the various types of coal .This process of transformation is referred to as
metamorphosis, coalition or lithification. Coal is composed chiefly of
carbon, hydrogen, oxygen, with a minor amount of nitrogen and sulphur,
and varying amounts of moisture and mineral impurities such as
4
phosphorus. Coal lumps are black or dark brown in colour, its colour,
luster, texture, etc vary with the type, rank and grade [1]
Classification of coal:
There are four main classifications of coal, arising from progressive
variation in their carbon content.
i. Peat: contains about 60% carbon.
ii. Lignite coal: contains about 65% carbon.
iii. Sub bituminous coal: contains about 70% carbon.
iv. Bituminous coal: contains about 85% carbon.
v. Anthracite coal: contains about 94% carbon [2].
Destructive distillation of coal:
This involves heating coal to a very high temperature (600-12000C) in
the absence of air. During this process, the coal decomposes to give
coal gas, coal tar, coke and ammoniacal liquor.
Coal heat coke + coal tar + coal gas + ammoniacal liquor.
i. Coal gas: This is a mixture of hydrogen, carbon(iv) oxide and small
amount of ethane, hydrogen sulphide, and sulphur (iv) oxide. The
main use of coal gas is as fuel.
ii. Coal tar: A thick brownish-black liquid is a mixture of many organic
chemicals including benzene, toluene, phenol, naphthalene and
anthracene. The component can be separated by fractional
distillation and are used for the manufacture of commercial products
including drugs, dyes, paints, insecticides , etc.
iii. Coke: This is non-volatile residue which contains about 90%
amorphous carbon and is chemically similar to hard coal. Coke is
used in the manufacture of carbide as fuel and as reducing agent in
the extraction of metals. Coke is used to make producer gas and
water gas.
5
iv. Ammoniacal liquor: This is an aqueous solution containing mainly
ammonia, and is used in the manufacture of ammonium
tetraoxosulphate (iv) [3].
Coal mining in Nigeria:
Coal was first discovered in Nigeria in 1909 near Udi by the mineral
survey of Southern Nigeria. Between 1909 and 1913, more coal
outcrops were located. Coal is found in the following Nigerian States:
Enugu, Imo, Kogi, Delta, Plateau, Abia , Benue ,Edo, Bauchi, Adamawa,
Gombe, Cross River States. In 1950, the Nigerian Coal Corporation
(NCC) was formed and given the responsibility for exploration,
development and mining of the coal resources [4].
Nigerian coal resources:
Nigerian coal resources has been found suitable for boiler fuel,
production of high calorific gas, domestic heating, briquettes, formed
coke, and the manufacture of a wide range of chemicals including
waxes, resins, adhesives and dyes. The characteristic properties of
Nigerian coal (low sulfur, and ash content and low thermoplastic
properties) make these sub-bituminous coals ideal for coal-fired electric
power plant [4].
Coal deposits of Nigeria:
Coal exploration in Nigeria started as far back as 1916. Available
data show that coal (mainly sub-bituminous steam coals except for the
Lafi-obi bituminous coking coal) occurrences in Nigeria have been
indicated in more than 22 coal field spread over 13 States of the
Federation. The proven coal reserves so far in Nigeria total about 639
million metric tones while the inferred reserves sum up to 2.75 billion
metric tones. In addition, an estimated 400 million tones of coal lie
untapped under the soil of Enugu. [5]
6
Presently, the Nigeria coal industry has four existing mines at Okpara
and Onyeama underground mines in Enugu State, Okaba surface mine
in Kogi State and Owukpa underground mine in Benue state. In addition,
there are more than 13 undeveloped coal fields. The undeveloped coal
fields in Nigeria are of two categories:
The virgin coal fields where further detailed exploration work and/or
access roadways are required and the developing coal fields where
reserved have been proven and mine access roadways developed. The
developed coal fields include Azagba Lignite field in Delta State,
Ogboyoga coal field in Kogi State, Ezimo coal field in Enugu State, Lafiobi
coal field in Nassarawa State and Inyi coal field in Enugu State while
others are located in Amansiodo in Enugu state, Ute in Ondo State,
Lamja area of Adamawa State, Gindi-Akunti in Plateau State, Afuze in
Edo State, Janata-Koji area of Kwara State and extension of Okpara
mine south in Enugu State [6].
Table1: EXISTING POTENTIAL COAL MINE SITES WITH RESERVES IN
1.1.2 Uses of coal:
(a). Cement production: Coal is used for cement manufacture. In
Nigeria, Okaba, Ogboyoga and Owukpa coals are suitable for cement
manufacturing. Their physical properties qualify them for the purpose [6]
(b). Power generation: Coal is one of the two most principal sources of
fuel and energy, the other being petroleum [7]
Power plays a central and crucial role in national development.
Nigeria‘s power supply falls far short of demand. This inadequacy
represents a major constraint on industrial growth, and underscores the
need to make electricity more widely available, and more specifically in
the rural areas. This is in order to encourage the development of cottage
industries in the countryside, ameliorate the living conditions of the rural
dwellers and thus reduce the incidence of flight to the cities in search of
gainful employment, especially by the youth and trained man power. To
ensure a regular and dependable supply of the requisite amount of
power in the country, coal can be used for power generation [8]. In
Nigeria, Okaba, Ogboyoga, and Onyeama coals are suitable for power
generation. Their physical properties which include high calorific value,
low sulphur content (about 0.69%), low ash, low moisture, and high
volatility qualify them for this purpose [6].
(c). Metallurgical purposes: The most important non fuel use of coal is in
smelting of iron ores. The main process for iron production from its ore is
still the blast furnace. The blast furnace process of making iron and steel
employs coke (the solid product from coal carbonization) as a major raw
material [7]. Not all coal can yield the type of coke (metallurgical coke)
that can be utilized in a blast furnace. The Nigerian coals are generally
non–coking, and hence, the coals derived from there are not directly
utilizable in blast furnace [8]. Onyeama mine and Okpara West area
9
mine coals are suitable as the process require very high temperatures
[6].
(d). Coal for export: Onyeama mine and Okpara mine coals have been
mapped out mainly for export.
(e). Industrial fuel: Coke char will also find widespread use in a variety of
industrial enterprises such as cement factories, foundries, ceramics
plants, bakeries, laundries and brick manufacture. Because of the
unreliability of electric supply, coke char and solid briquettes could also
be effectively deployed as non-polluting prime energy resources by rural
cottage industries [8].
(f). Coal is also used in making chemicals: For instance, the solvent
extraction studies of Enugu coals using benzene /methanol
(C6H6/CH3OH) as the extracting solvent system, it was possible to
fractionate the extract into pre-asphaltenes (benzene insoluble, pyridine
soluble), asphaltene (n-hexane insoluble) and oils (n-hexane solubles)
and determine the n-paraffin content of the oils by urea adduction
technique. Also, montan wax has been obtained from brown coal by
solvent extraction. The waxes have immense industrial uses in candle
making, waxing paper, medicinal and cosmetics preparation among
others [9].
Coal Chemicals:-
For about 100 yrs, chemicals obtained as by-product in the primary
processing of coal to metallurgical coke have been the main source of
aromatic compounds used as intermediates in the synthesis of dyes,
drugs, antiseptics and solvent. Although some aromatic hydrocarbons
such as toluene and xylene are now obtained largely from petroleum
refineries, the main sources of others such as benzene, naphthalene,
anthracene, and phenanthrene is still the by-product of coke oven.
10
Heterocyclic nitrogen compounds such as pyridines and quinolines are
also obtained largely from coal tar.
Table 2: Coal tar chemicals:
Compound Use
Naphthalene Phthalic acid
Acenaphthenes Dye intermediates
Fluorene Organic synthesis
Phenanthrene Dyes, explosives
Anthracene Dye intermediates
Carbazole and other similar compounds Dye intermediates
Phenol Plastics
Cresols and xylenols Antiseptics
Pyridine, picolines, Intidines, quinolines, Drugs, dyes,antioxidants
acridine, and other tar bases.
Coal can also be converted to liquid fuels by:
a. Fischer Tropsch process:- Here, coal is heated in the presence of
steam to a temperature of 12000C to give water gas.
C+ H2O 12000C CO + H2
b. Bergius process: Here, coal is heated in the presence of hydrogen
to the temperature of 4500C and pressure of 200 atm to give
gasoline.
C + H2 4500C/ 200 atm gasoline
The use of a particular coal depends on its rank (i.e. peat, lignite,
bituminious, anthracite). The diagram below provides the estimated
percentage of the world’s coal reserves for each coal rank and also the
use of each coal rank.
11
% of world
resources
Carbon and heating value high
High moisture content
Low rank coal (47%) Hard coal (53%)
Lignite (17%) sub bituminious (30%) anthracite (1%)
Bituminious (52%)
Largely power generation domestic industries
Power generation, cement
manufacture, industrial uses .
thermal steam coal
1.3 The aim of the research:
The aim of the research work is to investigate the effect of the use of
different biomass (groundnut shell and corn cob) on the properties of
coal briquettes.
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