dc.description.abstract |
Instability in the world’s petroleum is occasioned by perpetual escalation in petroleum
prices, increasing environmental effect from exhaust emissions has prompted the
search for renewable sources of fuel. Currently in Kenya, biomass such as sawdust
from sawmill industries and agro wastes, like banana leaves and pseudo stem, are
potential sources of renewable energy. However, in most cases biomass is normally
discarded in the fields with no value addition and also little information exists on their
use as fuel in blended briquettes. Consequently, this study investigated the use of
carbonized sawdust and banana waste as raw materials for briquettes production as an
alternative energy source. Specifically, the study aimed at characterizing physical
properties of the raw materials, fabricating blended briquettes at varying mix
ratios/particle sizes and characterizing physical and combustion properties of the
blended briquettes. In the study, pseudo stem and banana leaves from Musa
acuminata AAA species and sawdust from Eucalyptus tree species were collected,
dried to 8 % moisture content, hammer milled, sieved and carbonized in muffle
furnace at 400 °C for 5 minutes. Blended briquettes were produced at constant
compaction pressure of 5 MPa at varying blend ratios(1:0,4:1,3:2,1:1,2:3,1:4, 0:1)and
particle sizes(2.5 mm, 5 mm, 7 mm, 9 mm,11 mm)using molasses as a binder. The
briquettes were then characterized in terms of mass density, durability index, ash
content, moisture content, volatile matter and calorific value. Raw materials: sawdust,
banana waste and molasses had moisture contents of 12.52 %, 14.63 % and 22.23 %;
volatile matter of 25.32 %, 31.45 % and 43.25 %; calorific value of 15.92 MJ/kg,
12.35 MJ/kg and 11.24 MJ/kg; ash content of 5.79 %, 6.89 % and 8.00 %,
respectively. The density ranged from 392.54 kg/m 3 to 681.21 kg/m 3 , calorific
value,23.40 MJ/kg to 25.92 MJ/, ash content, 6.89 % to 5.79 %, moisture content,
11.10 % to 7.45 %, durability index,95.35 % to 99.70 % and CO emission, 5.64 ppm
to 1.74 ppm. In addition, as the particle sizes were increased from 2.5 mm to 11 mm,
the briquettes’ moisture content ranged from 7.22 % to 6.98 %, ash content,5.82 % to
5.83 %, CO emission,5.87 ppm to 5.20 ppm, calorific value,26.49 MJ/kg to 25.84
MJ/kg, density,763.33 kg/m 3 to 557.68 kg/m 3 and durability index,97.77 % to 93.43
%. In conclusion, sawdust had better calorific value, lower ash and moisture contents,
lower volatile matter and higher mass density than banana waste. Mix ratio of 1:1
provided optimal durability and moisture content in briquettes while that of 3:1 gave
optimal CO emission. An increase in sawdust content increased both calorific values
and ash content of the briquettes. Lastly, blended briquettes with fine particles have
higher mass density, calorific value, durability index, and CO emission than those
with coarser particles. From the study, it is recommended that briquettes with high
and fine sawdust content (50% above) should be used owing to their good durability,
low moisture content, low CO emission and higher calorific value. Future studies
should determine effects of interaction between variables such as compaction
pressure, blend ratio and particle sizes on combustion properties. |
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