ABSTRACT
The decreasing availability of fuel wood, coupled with the ever rising prices of kerosene
and cooking gas in Nigeria draws attention to consider alternative sources of energy for
domestic and cottage level industrial use in the country. This research work was conducted
to design and construct a low cost briquette machine for rural communities in Nigeria. It
involved the modification of the existing CINVA RAM press and evaluation of the
products produced. Selected agricultural residues (i.e. rice straw and rice husk), saw dust
residue of softwood and a combination of 50% rice husk + 50% saw dust by weight with
30% optimum cassava starch by weight as binder were used to produce briquettes.
Performance characteristics were evaluated for the briquettes produced based on average
fuel efficiency, burning rate and specific fuel consumption. Calorific value of 16,577KJ/Kg
was obtained for rice straw briquette, 14,396KJ/Kg for rice husk briquette, 15,547KJ/Kg
for sawdust briquette, 17,529KJ/Kg for 50% rice husk + 50% saw dust briquette and
12,378KJ/Kg for firewood (Parkia biglobosa). The average fuel efficiency, burning rate
and specific fuel consumption values of 10.68%, 1.10Kg/hr, 0.3g/g, 22.42%, 0.83Kg/hr,
0.13g/g, 15.40%, 1.03Kg/hr, 0.26g/g, 18.52%, 0.93Kg/hr, 0.16g/g and 12.29%, 1.62Kg/hr,
0.36g/g were obtained for rice straw briquette, rice husk briquette, saw dust briquette, 50%
rice husk + 50% saw dust briquette and firewood respectively. Statistical analysis using the
least square differences in comparison to each of the fuel samples average performances
showed that rice husk briquette had the most outstanding thermal performance.
TABLE OF CONTENTS
TITLE PAGE . . . . . . . . ii
DECLARAION . . . . . . . . iii
CERTIFICATION . . . . . . . . iv
DEDICATION . . . . . . . . v
ACKNOWLEDGEMENT . . . . . . . vi
NOMENCLATURE . . . . . . . . viii
ABSTRACT . . . . . . . . . xii
TABLE OF CONTENTS . . . . . . . xiii
CHAPTER ONE
1.0 Introduction . . . . . . . . 1
1.1 Problem Statement . . . . . . . 2
1.2 Agricultural and wood Residues . . . . . 3
1.2.1 Particle board and straw board production . . . . 4
1.2.2 Biogas production by anaerobic decay of organic materials . . 4
1.2.3 Gasification . . . . . . . . 5
1.2.4 Biomass Combustion . . . . . . . 6
1.2.5 Briquetting . . . . . . . . 7
1.2.6 Ruminant Feeding . . . . . . . 7
1.2.7 Construction of village level grain storage structure . . . 7
1.2.8 Regulation and reduction of geothermal temperature . . 8
1.3 Justification of Research . . . . . . 8
1.4 Existing Briquetting Techniques . . . . . 10
xiv
1.4.1 Wu-Presser . . . . . . . . 10
1.4.2 Earth Rams . . . . . . . . 10
1.4.3 Tube-Presses . . . . . . . . 11
1.4.4 Screw Presser . . . . . . . . 12
1.4.5 Hydraulic Press . . . . . . . 12
1.4.6 Piston Press . . . . . . . . 13
1.4.7 Pelletizer . . . . . . . . 13
1.4.8 Heat Die Extrusion Screw Press . . . . . 14
1.5 Objectives of study . . . . . . . 15
CHAPTER TWO
2.0 Literature Review . . . . . . . 16
2.1 Research and Development Efforts in the Use of Agricultural Residues
as Energy Source for Cooking Purpose Using Low Cost Technique . 16
2.2 Review of Previous Research Work on Briquette making Raw Materials 22
2.3 Review of Previous Research Work on Residue Energy Potential . 24
2.4 Review of Previous Studies on Binding of Briquettes . . 25
2.5 Review of Research Work on Calorific Values of Some Briquettes . 27
CHAPTER THREE
3.0 Machine Design and Construction Processes. . . . 30
3.1 Material . . . . . . . . 30
3.2 Design Considerations . . . . . . 30
3.3 Description of Parts and Functions . . . . . 31
3.3.1 The Main Frame and Mould . . . . . . 31
xv
3.3.1.1 Function . . . . . . . . 31
3.3.2 The Base Ram. . . . . . . . 32
3.3.2.1 Function . . . . . . . . 32
3.3.3 The Connecting Link Mechanism and Power Screw . . . 32
3.3.3.1 Function . . . . . . . . 32
3.4 Design Analysis . . . . . . . 32
3.4.1 The Handle . . . . . . . . 32
3.4.2 The Thread Shaft (Square Thread) . . . . . 33
3.4.3 Bearings . . . . . . . . 35
3.4.4 Nut . . . . . . . . . 36
3.4.5 The Cover Plate . . . . . . . 36
3.4.6 Coupling Bolt for Installation . . . . . . 37
3.5 Design Calculations . . . . . . . 38
3.6 Construction of Machine . . . . . . 45
3.7 Pallets (Aluminum Foil) . . . . . . 50
3.8 Coupling of Components . . . . . . 50
3.9 Method of Operating the Briquette Press . . . . 51
3.9.1 Filling Mould with Material . . . . . . 51
3.9.2 Compression Stroke . . . . . . . 52
3.9.3 Ejection Stroke . . . . . . . 52
3.9.4 Maintenance and Repair . . . . . . 53
3.10 Briquette Production . . . . . . . 53
3.10.1 Material . . . . . . . . 53
3.10.2 The Binder: Cassava Flour . . . . . 53
xvi
3.10.3 Preparation and Production of Briquettes from Residues . . 54
CHAPTER FOUR
4.0 Tests and Results . . . . . . . 56
4.1 Tests . . . . . . . . . 56
4.2 Determination of Calorific Value . . . . . 56
4.2.1 Equipments used for the Calorific value test . . . . 56
4.2.2 Test Procedure Carried Out . . . . . . 56
4.3 The Water Boiling Test (WBT) . . . . . 59
4.3.1 Introduction . . . . . . . . 59
4.3.2 Equipments used in the Boiling Water Test . . . . 60
4.3.3 Variables . . . . . . . . 60
4.3.3.1 Fuel Samples . . . . . . . . 60
4.3.3.2 Stove . . . . . . . . . 61
4.3.3.3 Pot . . . . . . . . . 61
4.3.3.4 Lid . . . . . . . . . 61
4.3.3.5 Power Control . . . . . . . . 62
4.3.3.6 Environment . . . . . . . . 62
4.4. Experimental Phases Process . . . . . . 62
4.4.1 Phase 1: High Power (Cold start) . . . . . 62
4.4.2 Phase 2: High Power (Hot start) . . . . . 63
4.4.3 Phase 3: Low Power (Simmering) . . . . . 64
4.5 Analysis . . . . . . . . 64
4.5.1 Definition of terms . . . . . . . 64
xvii
4.5.2 Statistical Analysis . . . . . . . 65
4.5.3 Analysis of Variance (ANOVA) . . . . . 66
4.6 Calorific value of fuel samples . . . . . 67
4.6.1 Average Thermal Efficiency ( in %) for Fuel Samples . . 68
4.6.2 Average Burning Rate for Fuel Samples . . . . 68
4.6.3 Average Specific Consumption for Fuel samples . . . 69
4.6.4 Boiling Time . . . . . . . . 70
CHAPTER FIVE
5.0 Discussion of Results . . . . . . . 75
5.1 Introduction . . . . . . . . 75
5.2 Performance of the Briquetting Screw Press . . . . 75
5.3 Performance of Fuel Samples . . . . . . 76
5.3.1 Rice Straw Briquettes . . . . . . . 76
5.3.2 Rice Husk Briquettes . . . . . . . 77
5.3.3 Saw Dust Briquettes . . . . . . . 78
5.3.4 50% Rice Husk + 50%Saw Dust Briquettes . . . . 79
CHAPTER SIX
6.0 Summary, Conclusion and Recommendation. . . . 81
6.1 Summary . . . . . . . . 81
6.2 Conclusion . . . . . . . . 82
6.3 Recommendation . . . . . . . 83
REFERENCES . . . . . . . . 84
APPENDICES . . . . . . . . 88
WORKING DRAWINGS . . . . . . . 114
xviii
CHAPTER ONE
INTRODUCTION
Approximately 2000 million people world wide; most rural people and many urban
as well, all depend on wood fuels as their main or sole source of energy to cook their food
and keep warm. Nine-tenths of all the wood harvested annually is used for energy; “it
accounts for over two-thirds of total energy consumption in 24 tropical countries of which
16 are least-developed countries” (Rodas, 1981).
The demand for fuel wood is expected to have risen to about 213.4×103 metric
tones, while the supply would have decreased to about 28.4×103 metric tones by the year
2030 (Adegbulugbe, 1994).
In Nigeria, the Energy Commission of Nigeria (ECN) recently (2005) reported that
Nigeria’s fossil led economy is under severe pressure and gave data of potential renewable
energy for utilization including crop residue as shown in table 1.1 below.
Table 1.1: Nigeria’s renewable energy resources
Energy Source Capacity
Hydropower, large scale 10,000MW
Hydropower, small scale 734MW
Fuel wood 13,071,464 hectares (forest land)
Animal waste 61 million tones/yr
Crop Residue 83 million tones/yr
Solar Radiation 3.5 – 7.0 kW/m2-day
Wind 2-4 m/s (annual average)
Source: ECN (2005)
2
1.1 Statement of Problem
As wood fuel supplies diminish, the people who depend on wood fuels are
suffering increase in physical or economic burdens in maintaining even a minimal daily
fuel supply. The use of firewood and misuse of the existing energy resources (agricultural
residues) is creating human and environmental crisis in developing countries which is
resulting in deforestation. Traditionally, wood in form of fuel wood, twigs and charcoal
has been the major source of renewable in Nigeria, accounting for about 51% of the total
annual energy consumption; the other sources of energy include natural gas (5.2%),
hydroelectricity (3.1%), and petroleum products (41.3%) (Akinbami, 2001).
In many developed and developing countries, the forest covers at least 25% of the
total land area, the minimum level required by international standard. The first indicative
forest inventory project completed in Nigeria in 1977 put reserved forest at approximately
10% of the total land area. Between 1976 and 1990, deforestation proceeded at an average
rate of 400,000 ha. per annum, in 1981-1985 at 3.48% while in 1986-1990 it was 3.57%
including some forest reserves. The FAO concluded that if this rate was maintained, the
remaining forest in Nigeria would disappear by the year 2020. The degradation and
depletion of the forest reserve base has major effects on other sectors of the economy. The
disappearance of forest cover leads to erosion, soil degradation and unfavorable
hydrological changes (Government of Nigeria, 1997).
The decreasing availability of fuel wood, coupled with the ever rising prices of
kerosene and cooking gas in Nigeria, draw attention to the need to consider alternative
sources of energy for domestic and cottage level industrial use in the country
(Olorunnisola, 2007). Such energy sources should be renewable and should be accessible
3
to the poor. As rightly noted by Stout and Best (2001), a transition to a sustainable energy
system is urgently needed in the developing countries such as Nigeria. This should, of
necessity, be characterized by a departure from the present subsistence energy level usage
which is based on decreasing firewood resources, to a situation where human and farming
activities would be based on sustainable and diversified energy forms.
The realization that deforestation and wood fuel shortages are likely to become
pressing problems in many countries has turned attention to other types of biomass fuel.
Agricultural residues are, in principle, one of the most important of these. They arise in
large volumes and in the rural areas which are often subject to some of the worst pressures
of wood shortage (Eriksson and Prior 1990). If one or more efficient method of using the
abundant agricultural and wood residues could be developed on a large scale the energy
situation could be sustainable and the deforestation problem could be controlled.
The lack of capital among most house holds in the rural communities makes it
difficult to move from either firewood or charcoal, to a more advanced energy sources
where small initial capital investment can be used. Hence, the substitute of these fuels
requires a minimal capital investment, be as cheap and accessible as charcoal and
firewood. At the same time be environmentally sustainable.
1.2 Agricultural and wood residues
Large quantities of agricultural and wood residues are generated yearly in
developing countries but they are neither managed nor utilized efficiently. Agricultural
residues which are freely available are often discarded or burned as wastes. They occur in
large amounts and have the potential to be an important industrial input for fuel production
in briquette forms, particle board and straw board for furniture making, biogas fuel,
4
gasification, biomass combustion, ruminant feeding, absorbent for industrial effluents
treatment, grain storage structure and regulation/reduction of geothermal temperature.
The procedures for manufacturing these products are described briefly below;
1.2.1 Particle board and straw board production.
Wood residues resulting from furniture making industries or stalks like cotton
stalks after harvesting cotton are either grounded into particles for particle board or steam
heated to breakdown the residues into fibers for medium density fiberboard, then dried to
lower moisture content. After the fiber is dried, it is blended with wax, a synthetic resin
such as urea formaldehyde, and other addictives, and formed into mats. The mats are
processed in large presses that use heat and pressure to cure the resin and form the products
into sheets or boards. Primary finishing steps of particle and medium density fiber board
include cooling or hot stacking, grinding, trimming/cutting and sanding. Secondary steps
include fooling, painting, laminating and edge finishing. Straw boards are made from straw
and bagasses, which undergo the same production procedure as particle board production.
They are used for making doors, furniture and cabinets (Gary and Rajiva, 2001).
1.2.2 Biogas production by anaerobic decay of organic materials.
Anaerobic reactors are generally used for the production of methane biogas, from
manure (human and animal waste) and agricultural residues. They utilize mixed
methanogenic bacterial cultures which are characterized by defined optimal temperature
ranges for growth. These mixed cultures allow digesters to be operated over a wide range
i.e. above 0oC up to 60oC. When functioning well, the bacteria convert about 90% of the
feedstock energy content into biogas containing about 55% methane, which is a readily
5
useable energy source for cooking and lighting. Fig.1 below shows the route path of biogas
energy production.
Figure 1: Biogas energy route Source: Elizabeth, et al, (1999)
1.2.3 Gasification.
Gasification is the process involving the burning of biomass fuels (human, animal
and agricultural wastes) at very high temperatures with a limited supply of oxygen so that
the burning process is only partially completed (Elizabeth et al, 1999). High temperatures
and a controlled environment lead to virtually all the raw materials being converted to gas.
This takes place in two stages. In the first stage, the biomass is partially combusted to form
producer gas and charcoal. In the second stage, the carbon dioxide (CO2) and water (H2O)
produced in the first stage is chemically reduced by the charcoal, forming carbon
monoxide (CO) and hydrogen (H2). The composition of the gas is 18% to 20% H2 gas
equal portion of CO, 2% to 3% methane (CH4), 8% to 10% CO2 and the rest nitrogen.
These stages are spatially in the gasifiers. Gasifiers require temperature of about 800oC and
is carried out in closed-top or open top gasifiers. These gasifiers can be operated at
Anaerobic
Digestion
Methane
Digester Sludge Heating and
lighting
Manure/Soil Mechanical power
Conditioner
Animal waste
Human/municipal
wastes
Agricultural or
crop wastes
Industrial
Carbonaceous
waste
Electrical power
6
atmospheric pressure or higher. The producer gas can be burned directly in processes
which normally use oil fired boilers. It can be burned in ovens, kilns and driers to replace
fuels otherwise, used in this equipment. The gas can also be cleaned and used to run an
engine for generating electricity.
Figure 2: Gasification process. Source: Vannbush, (2006)
1.2.4 Biomass Combustion.
Biomass fuel (agricultural residue) is burned in a furnace or boiler. The heat is used
to produce high pressure steam. This steam is introduced into a steam turbine where it
flows over a series of aerodynamic turbine blades, causing the turbine to rotate. The
turbine shares a common shaft with an electric generator so as the steam flows it causes the
turbine to rotate, the electric generator is turned and electricity is produced. Also it can be
used to produce hot water for goods processing.
7
1.2.5 Briquetting.
This involves the densification process of loose organic materials, such as rice
husk, sawdust and coffee husk aiming at improving handling and combustion
characteristics. There are two principal methods of briquetting, with or without a binder.
The binder technology is used where low pressure presses are employed to produce
briquette. Binders are added to this process to improve mechanical strength and also allow
dry materials to be briquetted using low pressure techniques as simple block presses or
extrusion presses. The binderless technology is a high pressure technique which produces
briquettes from fine dry particle size materials without a binder being added. Three types
of press are commonly used. Piston press, pelletizers and screw extrusion presses.
Briquettes are burned the same way as wood and can be used directly in open fires,
gasifiers, boilers, furnaces and kilns.
1.2.6 Ruminant Feeding.
Fibrous agricultural residues such as rice straw, sugarcane tops, cassava leaf,
soyabean-straw, peanut vines and sweet potato vines are important component of the feed
base for ruminant livestock particularly in areas where land grazing is limited and pasture
growth is seasonal (Dixon, 1985).
1.2.7 Construction of village level grain storage structure.
Agricultural residues could be used to construct village level grain storage
structure, called rhumbu which may be thatched, mud or underground pit. Thatched
rhumbus are commonly found in the north-Eastern parts of Nigeria. They are cylindrical in
shape with floors made of wooden grass stems or fibers and overhanging conical roof
made with straws or grass. The structure normally is supported on low wooden structure or
8
by stones. The wall is provided with tension rings in two or three positions using local rope
material. Mud rhumbus are found in Zaria and Sokoto towns in Nigeria. They are circular
in cross section and supported on stone pieces or pillars which are about 25-50cm above
the ground. The floor is made of wood and plastered with mud; the roof is conical and
made of thatch. Underground pits are found in the Sahel part of the Sudan savanna Zone
where water table is low. The pit is either round or square is 2-3m deep and 1.5-3m in
diameter or square. The pit is lined with straw mat (Zare) with corn husk padding or
insulation is provided at the bottom of the pit, it is covered with a polyethylene or metal
sheet, then a layer of husk and finally with layers of laterite (Olumeko and Igbeka, 1996).
1.2.8 Regulation and reduction of geothermal temperature.
In animal structures agricultural residues such as groundnut shells, maize husk or
sawdust of 6mm particles are spread on the floors of poultry houses, horse stables and
goat/sheep pens to serve as an absorbent material to keep the structure dry and the animals
away from cold floors.
1.3 Justification of Research
The abundantly available agricultural and wood residues can efficiently be used for
resolving energy problems to a significant extent by adopting proper measures.
Olorunnisola (2002) states that of the various types of biomass processing technologies
that are being considered, and for which there are currently potentially viable local markets
for in the country, which include biomass combustion, gasification and
briquetting/pelletizing it is evident that none of these alternatives can compete with the low
capital investment that is required; with the briquetting technology. Several kinds of
agricultural residues can be utilized properly by densifying loose residues to produce a
9
compact product of different sizes. Briquetting is essentially a mechanical process
requiring investment in equipment and training to ensure a product of reasonable quality
that will perform the task for which it is intended. Russell, (1997) considered that
briquetting is often seen as a relatively high-cost high-pressure technology, and that it is
possible to use a low-cost low-pressure technique to produce acceptable briquettes.
For rural communities the most suitable briquetting methods are those which are based
on available waste and building materials. The manufacturing should be done in locally
made hand operated presses and the briquettes held together mainly by a binder.
Briquette making saves trees and prevents problems like soil erosion and
desertification by providing an alternative to burning wood for heating and
cooking.
Briquetting substitutes agricultural waste like hulls, husk, corn stocks, grass, leaves
and other garbages for a valuable resource.
Briquetting engenders many micro enterprise opportunities making the presses
from locally available materials, supplying materials, supplying materials and
making the briquettes, selling and delivering the briquettes.
The availability of briquette as an alternative fuel to replace firewood can also
improve the living conditions of the rural women and children, who spend most of
their time collecting firewood instead of engaging in other income generating
activities or attending school.
10
1.4 Existing Briquetting Techniques
1.4.1 Wu-Presser
The Wu-presser was developed by the Washington University. It is constructed
from either metal or wooden parts as shown in figure 3 below.
Figure 3: The Wu-presser Source: Legacy Foundation (2003)
The Wu-presser presses briquettes in three steps shown in the illustration above. Each step
will press with increasing pressure. This takes advantage of the non-linear force to distance
property of briquetting pressing.
1.4.2 Earth Rams
Presses currently in use for making stabilized earth blocks might be modified to
make briquettes. The Combustaram, similar to the CINVA-Ram and Tersaram, is
commercially available or can be manufactured locally, see figure 4 below. The lever arm
is put in the open position, feed stock is poured into the molds and the lever is then quickly
pushed up, over the top of the press, and down. This movement positions the lever over the
top of the press and compresses the briquettes on the downward stroke.
11
Figure 4: Combustaram Source: Davies (1985)
The lever is then moved back to the original position and again pushed down, thus forcing
the briquettes out of the molds. Finished briquettes are set in the sun to dry. The process
requires at least two workers.
1.4.3 Tube-Presses
Metal or plastic pipe provides a good briquetting mould since it produces
cylindrical briquettes. The tube press, illustration shown in Figure 5 below,
Figure 5: Tube Press Source: Davies (1985)
Moulding Box
Roller Fulcrum
for Ejection
Adjustable piston
guide
Handle Latch
Toggle Linkage
Tube with
feed stock
Press
Removable Base
Plate
Hole to
push
finished
briquette
through
Close fitting ram
for hand
compression
Tube partially
filled with
briquetting
feedstock
Frame
Piston
12
consist of a tube mounted vertically on a platform and a close fitting ram used for
compaction. The basic design can be varied considerably, as the figure indicates. Feed
stock is poured into the tube and compressed with the ram. The tube is then positioned
over a hole (or a slide is removed) below the tube exposing a hole and the briquette is
pushed through. Briquettes are then dried in the sun before storage and use.
1.4.4 Screw Presser
The screw presser makes briquettes in upright cylinders. The raw material is
compressed by lowering a metal disc which is moved vertically by a screw that is turned
by hand. The screw press is most commonly made of metal as shown in figure 6 below.
Figure 6: Screw presser in use. Source: Olle and Olof (2006)
1.4.5 Hydraulic Press
These machines operate by hydraulic pressure acting upon a piston that extrudes
the material through a longitudinal die. The machine operates rather slowly which
minimizes the wave rates. However, they operate at much lower pressures and the
briquette quality is of lower density. They are typically used for low outputs of 40kg/hr but
can be made to achieve up to 80kg/hr.
13
1.4.6 Piston Press
These machine works best with dry (15% moisture content maximum) cellulose
material, which is fed into a compression chamber. A reciprocating piston then forces the
material through a tapered die to form a long briquette as shown in figure 7 below.
Typically flywheel drive machines produce between 300kg and 500kg of briquettes per
hour.
Figure 7: Piston Press Source: Bhattacharya et al, (1984)
The machine can achieve a service life of between 500 hours and 1000 hours using
relatively clean material such as sawdust. Use of agricultural wastes containing high levels
of silica (sand) will reduce the operating hours considerably. The initial cost of this type of
machine is high and the briquettes are prone to breaking.
1.4.7 Pelletizer
Pellet presses have dies with small diameter (usually about 30mm). The machine
has a number of dies arranged as holes bored in a thick steel disk or ring. The material is
forced into the dies by means of a ram, perpendicular to the centerline of the dies. The
14
main force applied results in shear stresses in the material which often is favorable to the
final quality of the material. The pellets are cut to lengths normally about one or two times
the diameter (Eriksson and Prior, 1990). Pelletizers can produce up to 1000kg of pellets
per hour but require high initial capital investment and high energy input.
1.4.8 Heat Die Extrusion Screw Press
The heat die extrusion screw press is an industrial machine for producing briquettes
(see figure 8 below). It consists basically of an electric motor, a hopper, a die heater and
muff, and the screw which densifies the raw material.
Figure 8: Heated die extrusion screw press Source: Bhattacharya et al, 1984
The electric motor drives the briquetting screw, which is housed inside the die,
through a V-belt and pulley arrangement. Biomass raw material is fed to the screw through
the hopper. The electric die-heater softens the lignin in the raw material as it passes
through the die which acts as a binding material. A smoke trapping system traps and
removes the smoke from the vicinity during the briquetting process. Besides the cost of the
Electric Motor
Die Heater
Hopper
Muff
15
investment, the machine has a cost for the electricity consumed. Another cost is the screw
that gets worn and has to be replaced frequently.
1.5 Objectives of study
The objective of this project is to:
Design and construct a simple, low cost briquette machine which can be used in
rural communities.
Test the design briquette machine using selected agricultural residues (sawdust, rice
husk, rice straw) with cassava starch as binder.
Evaluate the calorific value of briquetted residues.
Compare calorific value and performance with firewood.
16
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