Browsing by Author "Mengist, Muluken"

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    Briquetting of Sawdust using Waste Paper as a Binder
    (Addis Ababa University, 2015-07) Mengist, Muluken; Woldeyes, Belay (PhD)
    This study explored the possibility of producing sawdust briquettes that could be used for energy supply in small factories and for domestic cooking. A briquetting machine suitable for the production of sawdust briquettes on a small scale was constructed. A portion of sawdust was screened in to average diameter of: A (0.5mm), B (1.5mm), C (3mm), D (4.8mm), E (6.8mm) using standard sieves of 1mm, 2mm, 4mm, 5.6mm and 8mm mesh size. The raw sawdust was characterized for the following properties: moisture content (24.43%), density (91.34 kg/m3), volatile matter (94.92%) and ash content (2.6%). Briquettes were produced by mixing sawdust (both screened and raw) with waste paper in weight percentage ratios of 75:25, 70:30, 65:35, 60:40 and 55:45 respectively at three different die diameters. The computed density, porosity index, shatter resistance, volatile matter, ash content, fixed carbon and calorific value for all sawdust briquettes falls in the range of 218.24-322.62kg/m3, 33.97-312.4%, 98.88-99.95%, 70.24-90.56%, 2.33-7.26%, 6.7-24.26% and 14.5019-18.3832MJ/kg respectively. Further more from the results of the Analysis of Variance (ANOVA) carried out, there were no significant difference (p>0.05) in the quality of briquettes bonded with waste paper at different percentages except for percentage volatile matter, ash content and heating value . The effect of die diameter was found to be significant only on the physical properties of sawdust briquettes. A significant effect of average particle size of sawdust was recorded in density, porosity index and volatile matter of the briquettes. However, it was insignificant on shatter resistance, ash content and fixed carbon of the briquettes. The optimum blend of sawdust particle size - waste paper percentage and die diameter- waste paper percentage was assessed on the basis of the briquette properties: density, porosity index, volatile matter, ash content and gross calorific value. The combination of 0.5mm average particle size of sawdust and 30% waste paper gave the optimal density of 270.658kg/m3, porosity index of 29.782%, volatile matter of 86.496%, ash content of 2.829% and gross calorific values of 16.613 MJ/kg. The optimum blend of die diameter and waste paper was obtained at the combination of 6 cm and 25% with optimal values of density of 306.079 kg/m3, porosity index of 35.92%, volatile matter of 83.90%, ash content of 3.05% and gross calorific value of 17.134MJ/kg. It was concluded that the calorific values of briquettes obtained were sufficient to produce heat required for household cooking. Therefore sawdust briquettes can be a very good alternative source of energy for domestic cooking