College of Engineering and Technology
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Browsing College of Engineering and Technology by Subject "Activation energy"
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Item Fast Pyrolysis and Kinetics of Sugarcane Bagasse in Energy Recovery(Springer Berlin Heidelberg, 2013-06-05) Said, Mahir M.; John, Geoffrey R.; Mhilu, Cuthbert F.; Manyele, SamwelThe trend for material and energy recovery from biomass-waste along with the need to reduce green house gases has led to an increased interest in the thermal processes applied to biomass. The thermal process applied to biomass produces either liquid fuel (bio-oil) or gaseous fuel. Liquid fuel is more preferred because it is easier to transport from one point to another and also it can be used for production of chemicals. One of the biomass obtained in Tanzania is sugarcane bagasse. The sugarcane bagasse is the fibrous materials that remain after sugarcane is crushed to extract juice. Currently, it is burnt directly in the boilers for production of steam, but it can be used for production of bio-oil. The bio-oil can be optimally obtained by fast pyrolysis, which is a fast thermal decomposition of biomass material at temperature range 523–800 K in the absence of an oxidizing agent. In order to undertake a parametric study on the fast pyrolysis of sugarcane bagasse, it is imperative to establish its thermal characteristics. The paper reports the proximate and ultimate analysis, and thermal degradation of sugarcane bagasse in nitrogen as heating agent. The thermal degradation was conducted in a thermo-gravimetric analyzer from room temperature to 1,000 K at different heating rates of 5, 10, 20 and 40 K min−1. The thermo-gravimetric analyzer was used to study the effect of heating rate on the thermal degradation characteristics and to determine mass loss kinetics. The sugarcane bagasse was observed to be suitable for use in pyrolysis since it contains high volatile level of 80.5 % and fixed carbon of 8.2 %. The peak temperature was observed at 573 K at 10 K min−1 and corresponding activation energy was 387.457 kJ/mol.Item Pyrolysis Kinetics of Rice Hull: Influence of Soda Cooking(SCIENCEDOMAIN International, 2015-01) Ndazi, Bwire S.The effect of soda cooking as an effective defibrillation technique of rice hull on its thermal stability has been investigated in this paper. The goal was to investigate the impact of the decomposition of lignin and silica during soda cooking on the thermal stability and kinetics of pyrolysis of the resulting rice hull products by thermal gravimetric analysis (TGA). Soda cooking was carried out using 2.5, 5, 7.5 and 10% NaOH in the cooking liquor at 170°C for 60 minutes. The resulting crude fiber was heated from 25 to 700°C under N2 environment. The results have demonstrated that the removal of silica and lignin from the bulk structure of rice hull by soda cooking affect the thermal stability and pyrolysis kinetics of the rice hull. The final degradation temperature was reduced by 80°C from around 560°C to around 480°C and peaks of maximum decomposition temperatures of the second and third degradation steps shifted to lower temperatures by at least 50°C. The activation energies ranged from 84 to 202 J/mol. This revealed increasing trend of pyrolysis energies, from lower to higher ecomposition steps. The pyrolysis reaction was a single order reaction since the reaction orders ranged from 0.5 to 0.98. Pyrolysis kinetics can be used to study the effect of chemical treatments of agricultural fibers e.g. by soda cooking.