1.1 INTRODUCTION
Briquettes of Agricultural
by-products like cassava peel, sawdust, rice husks e.t.c. can largely overcome
some of the major problem regarding their utilization for energy because the
rural peoples rely heavily on fuel from wood which is faced with the rapid
depletion of forest resources resulting from excessive exploitation for fuel
and timber, clearing of products for village expansion work and agricultural
activities (Ajueytsi, 2002). Nigeria, even though an oil producing nation has
challenges of energy crisis. According to Adegoke (2002), Nigeria is passing
through an unprecedented energy crisis like non – renewable energy such as
kerosene and gas are outside the reach of the common man, the supply of
electricity another conventional energy source is epileptic where available or
non available at all in most parts of the country.
Agricultural wastes
which cause health and environmental risks are now processed into briquettes
which make agricultural waste into wealth (Bernard,1985), at this present rate
of deforestation, there will soon be a severe shortage of fuel from wood and
its necessary to introduce other sources of cheap and available fuels, increase
in agricultural productivity is associated with increase in agricultural
residues supplies which can be converted into high grade energy source with the
modern technology known as briquettes (Adekunle, 2004). The main domestic and
household fuels Nigeria families use for cooking and business are firewood,
charcoal and kerosene, a greater percentage of Nigerians are still in search of
cheap and affordable fuel for use at home and business (Abdullahi,
2000).
2.1 MATERIALS AND METHODS
2.1.1 Materials
Some of the materials used for this work were
cassava peel, sawdust, butter cake and cassava starch
as a binder
2.1.2 Equipments
The following
equipment was used in this work:
i.
A stopwatch was used during the experiment to
record the timing of the different stages of the test
ii.
Weighing balance to measure the weight
iii.
California bearing ratio testing machine for determination
of the crushing strength
iv.
Water bucket
v.
Electric heater for boiling water
vi.
Stainless pan for proper mix
vii.
Hydraulic briquetting machine for compression
viii.
Coal pot stoves
ix.
Aluminum cooking pot
2.1.3 Working principle of the briquetting
machine
A manually operated
hydraulic briquetting machine fabricated in mechanical engineering department,
Federal University of Technology, Minna was used for the compression of the
mixtures of cassava peels, shea butter cake and sawdust sample into a solid
shaped briquette fuel. The machine is equipped with a pressure gauge, hand
lever with a mould that could produce 15 briquettes at the same time. The
resulting mix of the agricultural by-products known as feed stock is fed into a
mould and compressed at 40KN pressure, after the compaction, the mould is
placed over an appropriate opening and the formed briquette is extracted by
gradual application of pressure at the hydraulic jack.
2.1.4 Production of briquettes
Measured quantity of
cassava starch gotten at temperature between 80oC and 100oC
was added to a mixture of varying composition of cassava peels, sawdust and
shea butter cake and then stirred vigorously to achieve a uniform mix. Tempering
of the mix was ensured by introduction of appropriate cassava starch gel at the
temperature range of 80oC, and 100oC.
The resulting mix known as feed stock was fed into mould and compressed. After
compaction, the mould was placed over an appropriate opening and the formed
briquette by gradual application of pressure at the hydraulic jack. The
extracted briquette was then allowed to dry in the sun, after sun drying the
briquette produced and tested for burning efficiency by varying the quantity of
the mix organic materials.
2.2 Experimental
Design for the Briquette
i.
The crushing strength was determined using
the California bearing ratio (CBR) testing machine.
Crushing
strength = load x 25.5
Where:
25.5
is the proving ring factor or calibrating factor of the CBR testing machine
ii.
The calorific value of a fuel which is the
amount of energy liberated by burning a unit mass
The following must be accomplished; the heat
must be balanced that is,
1
Where:
E = Energy released by fuel (J/kg)
M = Mass of water used (kg) = 0.9kg
Ma = Mass of equivalent apparatus = 42kg
MF = Mass of fuel used (kg)
iii.
The burning test was carried out using
the various briquettes replicate to test for the burning capacity and the burning
efficiency. There are different methods of water boiling test to be carried out;
they are percentage heat utilized (PHU). specific fuel
consumption (SFC). According to Adekunle J.O (2004),
2
3
Where:
Mi = initial mass of briquette before
burning (kg)
Mf = final mass of briquette after burnt
(kg)
Mw = mass of pot and water (kg)
Mp = mass of pot (kg)
iv.
Statistical analysis and model simulation
progressing test was used for the predicted briquette mode
3.1 RESULTS AND DISCUSSIONS
The results of the
effect of the three factors at two levels investigated simultaneously are given
by the fitted models for predicting the quality of briquette developed from
Agricultural by- products from the main experimental values of the eight
experimental runs as shown in Table 1-2.
3.1.1
Crushing strength
The interaction of
cassava peel and shea butter cake have higher positive influence on the
crushing strength while the interaction of sawdust at a lower level have
negative influence on the crushing strength at the experimental runs six as
presented in Table 2. However, the Ymean of the crushing strength at runs six
have Y = (833). The fitted model at the runs have Y = (797) from the predicted
regression coefficient equation.
ϔ = 644.94+41.44X1+64.81X13
– 45.69X123
3.1.2
Calorific value
The interaction of
cassava peel and shea butter cake have lower negative influence on the
calorific value while the interaction of sawdust has a higher positive
influence on the calorific value of the experimental runs. However, the Ymean
of the calorific value at run three have ϔ = (867) as shown in the Table 2
and the fitted model at the same runs have ϔ = (885) from the predicted
regression coefficient.
ϔ = 726.92 –
62.22X3 + 95.41X13
3.1.3
Burning efficiency
The interaction of
cassava peel and sawdust have higher influence on the burning efficiency while
the interaction of the shea butter cake have lower negative influence on the
burning efficiency at the experimental runs four. However, the Ymean of the
burning efficiency model at the runs have ϔ = (0.007875) from the
predicted regression coefficient.
ϔ = 0.06825 +
0.004625X1 – 0.005875X13
4.0 CONCLUSION
Briquettes of several
proportions of cassava peel, sawdust, butter cake and
cassava starch were produced. The crushing strength and calorific value were
determined, also they were burnt to determine the burning efficiency using the
specific fuel consumption (S.F.C), the result obtained from the 23
full factorial design techniques employed in this work have shown that the
briquette produced are of good quality with the following models for predicting
the crushing strength, calorific value and burning efficiency at 5% level of
significance.
ϔcs = 644. 944 + 41.44X1 + 64.81X13
– 45.69X123
ϔcv = 726.92 – 62.22X3
+ 95.41X13
ϔbe = 0.06825 + 0.004625X1
– 0.005875X13
Where:
ϔ = fitted
response
X1 = cassava
peel
X2 = sawdust
X3 = shea butter cake
The result of the
crushing strength, calorific value and burning efficiency of the experiments
and the developed models confirms that cassava peel, sawdust and shea butter
cake are important for characterizing the above mentioned properties of
briquettes i.e. crushing strength, calorific value and burning efficiency
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Adegoke, C.O and Mohammed, T.I (2002). Investigation of
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O.N.A (2002). Evaluation of local briquettes as a source of
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