Abstract:
The main focus of this research is to evaluate the combustion characteristics of
biomass fuel, macadamia nut shells. It seeks to determine its optimum combustion
by designing a biomass burner with provision for measurement and then evaluating
the combustion behaviour of the macadamia shells using the burner. The research
also sought to determine the physical and chemical properties of the macadamia
shells as factors that may a ect combustion.
The analysis for the properties of the macadamia nut shells, determined that it
has a higher heating value of 21.12 MJ/kg, 72.1% volatile matter, 13.1% moisture
content, 1.6% ash and 13.1% xed carbon. In addition, further analysis evaluated
the carbon, hydrogen, nitrogen, sulphur and oxygen compositions as 54.5%, 5%,
0.36%, 0.02% and 39.8%, respectively. These analyses show that macadamia shells
has a high heating value with low ash content which are suitable qualities for an
industrial fuel.
An experimental rig was designed, constructed with a special fuel feeding screw
and used in this research to enable the combustion of the macadamia nut shells.
The instruments connected to the rig included thermocouples, ori ce-meter, and
emission gas analyzer. An Adventest TR2724 multichannel temperature recorder
was used to acquire and record temperature data from the thermocouples to and
accuracy of 0.5oC in the system.
The combustion parameters, viz, combustion chamber temperature and gaseous
emissions, were determined by varying the rate of fuel feed rate and the amount of
combustion air per unit time. It was found that an air fuel ratio of 2.4 kg of air
for a unit kg of fuel gives the optimal combustion chamber temperature of 800 oC,
with acceptable gaseous emissions of; Carbon monoxide (CO), Nitrogen monoxide
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(NO), Nitrogen dioxide (NO2) , and Sulphur dioxide (SO2). The results of this study
provides an insight for future design of biomass systems to be used in small scale
industries locally.
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