Browsing by Author "Chaula, Zephania"

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    The Combustion Characteristics of Biomass Syngas from High Temperature Air, Entrained Flow and Circulating Fluidized Bed Gasifiers
    (SSRN Electronic Journal, 2014-02-21) Said, Mahir M.; Chaula, Zephania; John, Geoffrey R.; Mhilu, Cuthbert F.
    The study has been performed to determine fundamental combustion characteristics of syngas. Three technologies were selected to produce the syngas; High Temperature Agent Gasifier (HTAG), Entrained Flow Gasifier (EFG) and Circulating Fluidized Bed Gasifier (CFBG). Although the material used for production of syngas was the same, wood biomass, the compositions of syngas obtained were different. The adiabatic flame temperatures were determined at different air to fuel ratio. The maximum adiabatic temperature for HTAG, EFG and CFBG syngas at stoichiometric condition were 1846 K, 2250 K and 2234 K respectively. It has been observed that combustion of CFBG syngas produces more nitrogen oxide (NOx) than when using syngas of EFG. The high NOx in CFBG is caused by the high methane content, which increases the adiabatic flame temperature to 2200 K at stoicheometric condition. The lowest NOx emission was observed in HTAG syngas. The adiabatic temperature increased linearly with the preheating temperature, whilst oxygen enrichment increased the adiabatic temperature. It has been concluded that syngas produced from EFG and CFBG are better candidate as gaseous fuel in combustion chamber than HTAG syngas.
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    Modelling the Suitability of Pine Sawdust for Energy Production via Biomass Steam Explosion
    (Scientific Research, 2014) Chaula, Zephania; Said, Mahir M.; John, Geoffrey R.; Mhilu, Cuthbert F.
    Biomass material as a source of fuel is difficult to handle, transport, store, and utilize in its original form. To overcome these challenges and make it suitable for energy prodution, the material must be pre-treated. Biomass steam explosion is one of the promising pretreatment methods where moisture and hemicellulose are removed in order to improve biomass storage and fuel properties. This paper is aimed to model the suitability of pine saw dust for energy production through steam explosion process. The peak property method was used to determine the kinetic parameters. The model has shown that suitable operating conditions for steam explosion process to remove moisture and hemicellulose from pine sawdust. The temperature and pressure ranges attained in the current study are 260 -317 ℃ (533 -590 K), 4.7 -10.8 MPa, respectively.
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    Non-Isothermal Degradation and Thermodynamic Properties of Pine Sawdust
    (Scientific Research Publishing, 2018-12-28) Said, Mahir; John, Geoffrey; Chaula, Zephania; Samwel, Manyele; Mhilu, Cuthbert
    The study of non-isothermal kinetics analyzed the reactivity of pine sawdust, while the thermodynamic properties analyzed energy consumed and released from the pine sawdust. The kinetic parameters were determined by analyzing mass loss of pine sawdust components by using Thermogravimeric analyzer. The cellulose has the highest conversion rate of 9.5%/min at 610 K compared to hemicellulose and lignin, which are 5%/min at 600 K and 2%/min at 800 K, respectively. The activation Energy for cellulose, hemicellulose and lignin was 457.644 kJ/mol, 259.876 kJ/mol, and 89.950 kJ/mol, respectively. The thermodynamic properties included the change of Gibbs free energy for cellulose and hemicellulose, which were −214.440 and −30.825 kJ/mol respectively, their degradation was spontaneous in forward direction, while change of Gibbs free energy for lignin was 207.507 kJ/mol, which is non-spontaneous reaction. The positive value of change of entropies for the active complex compounds formed from hemicellulose and cellulose is less stable, while the active complex compounds of lignin are characterized by a much higher degree of arrangement since its change of entropy is negative. The kinetic and thermodynamic properties show that pine sawdust is a good candidate for production of char since it is easier to remove hemicellulose through thermal process.
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    Thermal Characterization of Pine Sawdust as Energy Source Feedstock
    (International knowledge Sharing Platform, 2014) Chaula, Zephania; Said, Mahir M.; John, Geoffrey R.
    Pine sawdust was analyzed for thermal chemical conversion such as combustion, torrefaction, pyrolysis and gasification. The methods used to analyze involved performing proximate analysis, ultimate analysis, heating value and thermal decomposition for determining the biomass characteristics. Based on elemental composition, the pine sawdust exhibited lower energy content of 15.01 MJ/kg than bituminous coal that has about 31.8 MJ /kg. The kinetic parameters of pine sawdust described the individual component decomposition; the easiest component to decompose is hemicelluloses followed by cellulose and lignin. The heat released during thermal degradation of pine sawdust was -4380 J/g under inert condition, this shows pine sawdust potential for production of energy during combustion.