Browsing by Author "Yimam, Abubeker (PhD)"

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    Biodiesel from Microalgae Based on Co2 Released from Cement Industries (Case Study: - Dangote Cement Plant)
    (Addis Ababa University, 2016-06) Assefa, Mekonnen; Yimam, Abubeker (PhD)
    Fossil fuels which are recognised as common sources of energy are continuously decreasing in quantity due to increasing demand, Moreover, the increase in atmospheric carbondioxide from chemical industries like cement plants is resulting in global climate change. In order to achieve environmental and economic sustainability, 3rd generation biofuel derived from microalgae are considered to be the best alternative energy resource compared to 1st and 2nd generation biofuels. Mixed species of microalgae was sourced locally from Kilole Lake at Bishoftu district and found suitable feed stock to produce algal biodiesel in the laboratory. Experiments were carried out using PVC jars of 3.5 litre capacity using 0.1 to 4% carbondioxide concentration, air bubbling rate of 0.1 to 7.0 litre per minute and pH ranged between 5 -7. The maximum biomass was obtained 0.44 gm/lt at pH 7, bubbling rate 3.5 lt/min and 2% carbondioxide feed. Oil was extracted from the algal biomass and analysed for water content, acid value, and fatty acid composition and saponification value. Algal oil fatty acid composition was very low and as a result of this no pre-treatment of algal oil was needed. Biodiesel produced by transesterfication of algal oil performed by using sodium methoxide as catalyst, and it was analysed for kinematic viscosity, specific gravity, acid value and sulphated ash. The properties of biodiesel tested were within limits of ASTM standard. Scale up of biodiesel plant in integration with the cement industry facility was studied as a way to mitigate the carbondioxide released from the plant flue gas as well as to address the shortage of fossil fuel in our country. Using the preliminary design of the biodiesel plant, a production capacity of 5,860 ton/year biodiesel was obtained and it was possible to capture 22,893.3 ton per year carbondioxide released from the cement industry. The net energy ratio of the proposed plant is 1.03; meaning 3% of energy can be produced more than required by the process. Key words: - Algal biomass, carbon dioxide, lipid oil, Biodiesel, Raceway pond
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    Bioethanol Production from Waste Paper (Used Office Paper)
    (Addis Ababa University, 2016-06) Berhane, Kiros; Yimam, Abubeker (PhD)
    There is a vested interest in developing alternate sources of fuel to fossil fuel due to lowering stocks, increasing prices and the need for environmentally sustainable energy sources. One major alternative to fossil fuels is bio-ethanol (ethanol from biomass) and waste paper (used office paper) represents a significant source for bioethanol production because of its high cellulose and hemicellulose contents. This study involved ethanol production from waste paper (used office paper) and investigation of process variables (temperature and time) on the yield of bioethanol. The conversion of waste paper to ethanol can be achieved mainly by four process steps: pretreatment of waste paper to remove lignin and hemicellulose, acid hydrolysis of pretreated waste paper to convert cellulose into reducing sugar (glucose), fermentation of the sugars to ethanol using Saccharomyces cerevisiae and finally distillation of the fermented sugar into final product. A three level full factorial design with two factors (time and temperature) was applied to optimize the acid hydrolysis process and study the interaction effects of the factors. The experimental results were analyzed by using Design Expert 7 software, to investigate the effects of hydrolysis parameters on yield of ethanol. High yield of bioethanol 14.5ml/50g (0.23g/g) was obtained at the optimum parameters, temperature of 1400C and time 60 min. ANOVA (statistical analysis) showed that an ethanol yield of 14.2426ml/50ml (0.22g/g) was obtained at a temperature of 1400C and time 63.24 min. Investigation on the preliminary economic analysis of the ethanol production was performed and results from the feasibility study indicated that the proposed work was feasible with rate of return (ROR) of 26% and the payback period of 1.8 year. Keywords: Bioethanol, waste paper, fermentation, Saccharomyces cerevisiae
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    Extraction, Characterization and Optimazation of Essential Oil From Ethiopian Black Cumin Seed Varieties by Solvent Extraction
    (Addis Ababa University, 2016-06) Belay, Alemu; Yimam, Abubeker (PhD)
    Black cumin seed oil has a long history of uses for food flavors, perfumes, medicinal value, cosmetics industry and in production of liquid soap, shampoos and essential ingredient in soup component, sausages, cheese, cakes, candies and for preparation curries, bread, katikala, preservation of butter and flavor food. The objective of this thesis was proximate and mineral analysis, investigation of the effects of extraction time and particle size, identification of the essential oil by GC-MS and FT-IR and extraction of essential oil was from black cumin seed varieties and characterized of psycho-chemical analysis of iodine value, saponification, acid value, pH, kinematics viscosity and specific gravity. The extraction was carried out using Soxhlet method, and determination of proximate compositions, physicochemical and functional properties of two improved black cumin essential oil seed varieties was done, Soxhlet extraction using n-hexane was chosen to investigate the effect of time and particle size on yield and quality of the extracted oil. A general full factorial design was applied to both seed varieties, and 54 experimental runs were performed followed by optimization of the two varieties of essential oil. The values of moisture content, crude protein content, crude fat, crude fiber, total ash and carbohydrate of Eden seed were 5.29 g/100g , 19.83 g/100g, 41.3 g/100g, 18.96 g/100g, 5.10 g/100g and 9.52 g/100g whereas Dirshaye registered 5.43 g/100g , 19.95 g/100g, 40.3 g/100g, 14.28 g/100g, 4.35 g/100g and 14.69 g/100g, respectively. The mineral analysis indicated that potassium is the dominant one (829.11mg/100g, 746.27mg/100mg) followed by phosphorous, calcium, sodium, iron and zinc in Eden and Dirshaye varieties. The results obtained from the experiment were analyzed using Design Expert software. The minimum oil yield was found to be 46.77% in Dirshaye variety whereas Eden contained 49.57%, after the extraction time of 2 hours with a particle size of 1.4-2.5mm. A maximum oil yield of 91.08 and 94.767% was found for Dirshaye seed and Eden Seed, respectively at the extraction time of 6 hours and at a particle size of 0.25-0.5mm. Finally GC-MS and FT-IR analysis has been carried out on the two seed oil varieties contains of linoleic, oleic and palmitic acids were the dominant fractions respectively and both seed varieties of the dominant functional component contain p-cymene but longifoline available only in Dirshaye oil by 0.51 %. Generally due to the presence of Linoleic acid, thymoquinone and high saponification value of oil suggests and guarantees the use of oil for cosmetics industry. Due to the above properties and characteristics Eden varieties have been found to possess higher yield variety and preferable for making cosmetics.
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    Extraction, Characterization and Optimization of Banana Trunk Fiber
    (Addis Ababa University, 2016-11) Dandesa, Milkiyas; Yimam, Abubeker (PhD)
    Banana plants do not only give delicious fruit but it can also provide banana fiber. Production of natural fiber is expected to increase because their production mostly centered on environmental friendly process and renewable. As a result production of natural fiber to satisfy the needs could take advantage over the synthetic fiber production in this regard. This study aimed at production, characterization and optimization of further process ability and mechanical property performance improvement of mechanically extracted banana fiber. So the final outcome of the research is to produce high quality banana trunk fiber which can be used in different sectors. The fiber is extracted manually by mechanical process. This is because of the fiber extracted mechanically was found to be appropriate for yarn spinning and knitting, have better color and tensile properties as well as the process is time conserving. The fiber obtained was treated with 0.1M, 0.3M and 0.5M of NaOH for different treatment time duration of 30min, 45min and 60min at the temperature of 300c, 600c and 900c. The fiber is treated with different concentration of chemical such bleaching agent hydrogen peroxide(5%) and lubricants such as castor oil (10%), sodium silicate(10%), soap(10%) and acetic acid(10%). Three parameters of treatment which are temperature, time and concentration was investigated. The effect of each parameter on the mechanical properties of the fiber was studied carefully by keeping the two other constant during treatment. In this study the obtained fiber is standardized (conditioned) at 200c and relative humidity of 60% for 24hr according to the standard method before the tensile test for textile fiber to ensure environmental equilibrium moisture content. The linear density of the banana fiber is determined for treated and non-treated using ASTM-D-6612 by putting 200mm of or both treated and untreated banana fiber in linear density measuring device. The linear density of untreated banana fiber is found to be 9.00Ne while for treated bleached and lubricated banana fiber is found as 26.80Ne. Finally the fiber was tested for its strength and other properties using yarn testing machine TEXTECHNO STATIMAT ME+ BY using ASTM: D -3822-07(ISO2062-500). It is found that treated banana fiber at a temperature of 900c with 0.3M of NaOH for 60minute produced the best quality and superior property in terms of tensile properties such as elongation, maximum force, work to break tenacity and time to break.
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    Extraction, Optimization and Characterization of Ethiopian Marula (Sclerocarya Birrea) and Zigba (Podocarpus Falcatus) Oils
    (Addis Ababa University, 2014) Hundessa, Gadissa; Yimam, Abubeker (PhD)
    To investigate the potential use of marula (Sclerocarya birrea) and Podocarpus falcatus oil and to recommend the optimum extraction conditions, dried podo and marula seeds were crushed to release the kernels and oil was extracted using n-hexane as a solvent for 2, 3 and 4 hours with moisture content of 9%, 12% and 15%. Main characteristics of optimized oil extract were determined. The average oil content was found to be 61.36% and 58.63 % respectively for S. birrea and P. falcatus with optimum extraction conditions of 12% moisture content and 3 hours of extraction. The saponification value of the oils were 190 mg KOH/g and 189.1 mg KOH/g oil, specific gravity at 150C was 0.899 and 0.90, peroxide value 4.2 and 4.4 mEq/kg, refractive index 1.467 and 1.47 whilst the average acid value was 3.6% and 4.0% respectively for S. birrea and P. falcatus oils. The fatty acid profile of S. birrea and P. falcatus oils were determined using GC-M S. Oleic acid was found to be the predominant fatty acid, 73.60% and 78.94% respectively for S. birrea and P. falcatus oils. Analysis of the main characteristics indicated that both S. birrea and P. falcatus oils have potential use in salad, cooking oils and cosmetics application. Marula juice was extracted and characterized. The result showed 25% of marula fruit can be extracted to juice. The juice is rich in vitamin C, 141.29 mg/100g and potassium 257.2mg/100g. Key words: Sclerocarya birrea, Podocarpus falcatus, Fatty acids profile, Optimum, moisture content, extraction time, effect
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    Investigation of Brewery Spent Grain as Adsorbent for Removal of Heavy Metals from Wastewater
    (Addis Ababa University, 2016-06) baylie, Hunegnaw; Yimam, Abubeker (PhD)
    Heavy metals are considered a major cause for environmental problems. Several conventional treatment methods have been developed for removal of toxic metal ions from wastewaters. Currently biological materials have received attention for heavy metal removal and recovery due to their good performance, low cost and availability. Among the broad lists of biosorbent materials, brewery spent grain has utilized for this study to remove, lead and chromium from wastewater. BSG was modified with 1M NaOH and afterward it was washed, dried and grinded to have particles sizes of 250-500μm. Lead (II) and Chromium (VI) stock solutions were prepared and from which different concentrations were obtained by serial dilution. Batch adsorption of Lead (II) and Chromium (VI) onto BSG was studied. The results indicated that the maximum percentage removal of lead and chromium was found to be 96.53% and 79.47% at pH= 4 and pH=2 respectively. The adsorption data of metal ions have been described by the Freundlich and Langmuir isotherm models. The sorption process conformed to both Langmuir and Freundlich isotherms with maximum sorption capacities of 26.3 and 10.75 mg/g for lead and chromium, respectively. Sorption kinetics for lead and chromium(VI) followed pseudo second order with regression coefficients of 0.9999 and 0.9998 respectively. Optimum operating conditions of 10 g/l adsorbent dose, 120 minutes and pH=2 for Cr(VI) and pH= 4 for Pb(II) solution were applied to remove lead and chromium ions from real electroplating wastewater. The results showed that brewery spent grain reduced lead ions from its initial concentration of 82 mg/l to 38.37 mg/l while chromium ion was reduced from 156.9 mg/l to 88.73 mg/l. Therefore, it can be concluded that modified spent grain as a new effective adsorbent has potential for Pb(II) and Cr(VI) removal from aqueous solutions. Basic terms: Brewer’s Spent Grain, Lead, Chromium (VI), sorption, Isotherm, Kinetics, wastewater
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    Optimization and Characterization of Synthesis Conditions of Adsorbent from Bone for Removal of Fluoride
    (Addis Ababa University, 2015-07) Tadele, Mitiku; Yimam, Abubeker (PhD)
    This work aims to prepare adsorbents based on low cost cattle bones. The bones have sustained pyrolyzation in inert atmosphere at three different temperatures (400°C, 500oC and 600°C), time (60, 90 and 120 minutes) and inlet N2 pressure (1.5, 2 and 2.5bar) in an electric furnace. The charcoals obtained were characterized by its percentage removal of fluoride ion from synthetic fluoride water and naturally fluoridated water. The effect of contact time, adsorbent dosage, pH, temperature in shaker and initial concentration of fluoride was investigated. The adsorption was rapid during the initial one hour. The adsorption efficiency of bone char for fluoride removal was increased with adsorbent dosage. The defluoridation capacity was appreciable at neutral pH. Bone char adsorbents pyrolyzed in the range between 400 to 500oC gave better fluoride removal. The fluoride adsorption efficiency depends directly on initial fluoride concentration. The adsorption data were well fitted to the Freundlich isotherm model. The adsorption capacity and adsorption intensity at equilibrium(qe) are 12.075mg/g and 1.548 respectively.
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    Optimization of Process Parameters for the Extraction of Oil from Mango Seed Kernel (Mangifera indica) for Cosmetics Application
    (2015-06) Kemal, Mustefa; Yimam, Abubeker (PhD)
    The main aim of the study was to determine the optimum operating condition for the extraction of oil from mango seed kernel. For this, particle size range of 0.25 mm - 0.5 mm, 0.5 mm - 1.5 mm and 1.5 mm – 3 mm, solvent type hexane, ethanol and petroleum ether and extraction time of 2 hr, 4 hr and 6 hr were considered for optimization. A general factorial design was applied to investigate the effect of process variables on oil yield. Maximum oil yield of 84.81% was obtained for particle size range of 0.25 mm - 0.5 mm at extraction time of 6 hr and with solvent type hexane followed by a yield of 83.33% at particle size range 0.25 mm - 0.5 mm, solvent type petroleum ether and 6 hour extraction time. And minimum oil yield of 18.88% was obtained for particle size range 1.5 mm – 3 mm at extraction time of 2 hr and with solvent type ethanol. ANOVA analysis was showed significant effect of particle size, solvent type and extraction time on oil yield (P value < 0.05). When the particle size range decreased from 1.5 mm – 3 mm to 0.25 mm - 0.5 mm the oil yield increased from 64.07% to 84.81% for solvent type hexane and for 6 hr extraction time. As extraction time was increased from 2 hr to 6 hr the oil yield increased from 57.41% to 84.81% for solvent type hexane and particle size range 0.25 mm - 0.5 mm. Quadratic regression model equations were obtained to describe the effect of variables on the oil yield. The physicochemical properties (total phenolic content, unsaponifiable matter, iodine value, acid value, saponification value, moisture and volatile matter, pH, viscosity, refractive index and specific gravity) of the oil extracted under optimum condition were determined and compared to those of the commercial available mango kernel oil and Indian standards for mango kernel fat. It was found that the physicochemical properties are within the standard except the acid value which is slightly higher. The result also indicated that there is a presence of high unsaponefiable matter (3.85%) and phenolic content (115mg/g for ethanol extract, 83.2mg/g hexane extract and 79.6mg/g for petroleum extract) in the mango kernel oil (obtained from local variety) which makes the oil suitable for cosmetics application. Key words: Mango seed kernel oil, Total Phenolic content, Unsaponefiable matter, Extraction
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    Production and Optimisation of Carboxymethylcellulose from Waste Cartons
    (Addis Ababa University, 2016-02) Hailu, Abebe; Yimam, Abubeker (PhD)
    Lignocellulosic materials (e.g. Waste cartons) can be utilized to produce carboxymethyl cellulose, a water soluble, biodegradable anionic polymer. This study involved production and optimization of carboxymethyl cellulose from waste cartons. The conversion of waste cartons to CMC can be achieved mainly by three process steps: extraction of cellulose from waste cartons, alkalization of the extracted cellulose and etherification of the alkali cellulose into CMC. The central composite experimental design (CCD) method involving response surface methodology was chosen to optimize the alkalization, etherification reaction and to determine the effect of three operating variables: NaOH concentration, amount of monochloroacetic acid and temperature (T). For the response surface methodology involving CCD, a total of 20 experiments were conducted for three factors at two levels with three replicates at center point. An optimization was carried out to optimize the alkalization and etherification reaction parameters so as to determine the best NaOH concentration, sodium monochloroacetic acid dosage, and etherification temperature that resulted optimum degree of substitution (DS) of the CMC. The statistical analysis showed that the degree of substitution of CMC of 0.767 was obtained at optimised alkalization & etherification variables of 13.53%w/w NaOH conc., 0.4 w/w of monochloroacetic acid to cellulose, and 41.62°C etherification temperature. The value of degree of substitution of CMC obtained from experiment at the optimized conditions of sodium hydroxide concentration of 13%, monochloroacetic acid concentration of 0.4w/w and etherification temperature of 41°C was 0.767. It is concluded that the waste cartons can be a good source of cellulose that can be modified by etherification reaction to carboxymethylcellulose with a medium degree of substitution of about 0.767.
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    “Production, Optimization and Characterization of Ferrous Sulfate from Local Iron Ore”
    (Addis Ababa University, 2017-07) Getachew, Birhan; Yimam, Abubeker (PhD)
    Iron sulfate has a diversified uses in agriculture, chemical industries and waste water treatment plants. Although Ethiopia has a huge deposits of iron ore. Therefore, this study investigates the potential of the country to produce iron sulfate from local iron ore and sulfuric acid. Iron samples has been taken from two ores namely Horu Guduru and Melkasedi in Oromia regional state characterized, 77% and 66% weight based iron oxide composition obtained from Horu Guduru and Melkasedi respectively. The sample from high iron oxide composition ore, Horu Guduru was reacted with sulfuric acid and hydro chloric acid subsequently by varying three process variables: temperature, reaction time and particle size. From the analysis the optimum iron sulfate yield obtained is 97.75% at temperature of (75oC), reaction time 60 min and particle size 1.00(which is <0.125mm) . Lastly, after iron sulfate characterization its production economics evaluated. The total investment cost of the project is estimated to be 1,830,822 birr. The project is financially viable with an internal rate of return (IRR) of 17.68 % and a Net annual profit of Birr 6,144,677.5birr/yr, at discounted rate of 10%. From the result, it is possible to conclude that establishment of such factory in the country saves foreign exchange, contributes for the economy, creates job opportunities, assures product availability and enhances input and output chain in the country
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    Recycling of Used Lubricating Oil Using Acid-Clay Treatment Process
    (Addis Ababa University, 2014-10) Andargachew, Hayalu; Yimam, Abubeker (PhD)
    Numerous industries are emerging in Ethiopia and urban developments are accelerated giving rise to multiple waste generations. As used lubrication oil is one of the hazardous wastes generated at different development sectors, it should not be utilized and/or disposed in ways which are unsafe to the environment hence calling for its proper management. This study primarily focuses on the recycling of used oil by applying acid-clay treatment process. Used engine oil properties gave expected undesired characteristics caused by oil deterioration. The characterization was indicative to the sources of contaminations from conditions during the oils application period. For instance, the lower flash point (132°C) indicated light fuel contamination effect; increased density (0.93 g/ml) and viscosity (kinematic Viscosity @ 40 °C was 126.41 cSt) showed possible oxidation and polymerization products dissolved and suspended in the used oil; and ash content (2.3%) indicated contamination from incombustible solid particles of dirt, dust, grit and metallic fragments. Similarly, deviations of other parameters also referred different contamination sources. Recycling experiments utilized 15, 20 and 25% acid and adsorbent (Bentonite clay) ratios with different combinations. Nine combinations with their respective triplicates were conducted. The experiments showed that the acid-clay treatment process was effective in recovering valuable oil from used oil samples with comparable qualities. From the twenty seven runs performed, yields within the range of 55% to 74.7 % was obtained. The run with acid percentage of 20% and adsorbent percentage of 15% was chosen as the optimum combination using statistical analysis that considered selected quality parameters of recovered oil i.e. density, kinematic viscosity @ 40 °C and ash content. The optimum combination gave a 69% yield; density of 0.886 g/ml; kinematic viscosity @ 40 °C of 94 cSt; and 0.34% ash content. Eight to ten percent of valuable light fuel was also recuperated from the vacuum distillation step of the process. The preliminary cost analysis showed, an estimated sum amount of 22.86 birr is expected to recover a liter of usable oil which is 61.64 birr less, relative to the amount required to import the original fresh oil that costs 84.5 birr/liter.
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    Refining of Used Motor Oil Using Solvent Extraction
    (Addis Ababa University, 2016-07) Negash, Tadele; Yimam, Abubeker (PhD)
    Used lubricating motor oil is a high pollutant material that requires responsible management. It may cause damage to the environment when dumped into the ground or into water streams including sewers. This may result in groundwater and soil contamination. Recycling of such contaminated materials will be beneficial in reducing lubricating motor oil costs. In addition, it will have a significant positive impact on the environment. Used oil can be refined to yield base oils that are blended into lubricating products, thus reducing the consumption of virgin oils. Refining restores the physical and chemical properties of lubricating oil so that it can go back to its original and intended use. This thesis work investigates refining of used lubricating motor oil using solvent extraction method. The laboratory experiment was based on a full factorial design and two categorical factors with two levels were nominated which were solvent to used oil ratio (4:1&6:1) and solvent type (2-Propanol and n-Butanol). First used lubricating motor oil, of two varieties, namely TOTAL Rubia and TOTAL Quartz was collected from TOTAL Ethiopia oil company gas stations and characterized for important properties and contaminates. Then by applying appropriate treatment, i.e. pretreating, dehydration, vacuum distillation, solvent extraction and distillation for solvent recovery, the base oil was obtained. The refined base oil was then characterized and compared with the used and virgin oil. The type of solvent used and the mixing ratio applied for different runs has shown significant effects on the yield of recovered oil. 2-Propanol solvent with mixing ratio of 6:1 gave the best result. A Maximum yield of 72% was obtained for Rubia Tir 7400 using 2-Propanol solvent and mixing ratio of 6:1, whereas minimum recovery yield of 55% was obtained using n-Butanol and 4:1 mixing ratio. For Quartz 20W-50 a maximum yield of 73.4 was obtained using 2-Propanol solvent and mixing ratio of 6:1 whereas minimum recovery yield of 50% was obtained using n-Butanol and 4:1 mixing ratio. The metal contaminants and chlorine are considerably reduced in the base oils for both lubricants. So it can be concluded that used lubricating motor oil can be refined using solvent extraction method and reduces environmental contaminations and decreases foreign currency
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    ―Removal of Lead from Waste Water Using Corn Cob Activated Carbon as An Adsorbent
    (Addis Ababa University, 2016-07) Tesfaye, Debela; Yimam, Abubeker (PhD)
    Industrial development has caused the release of various pollutants including heavy metals into the environment. These toxic compounds are extremely dangerous to living beings and the environment due to their non-biodegradability, severe toxicity, carcinogenicity, the ability to be accumulated in nature and the ability to contaminate groundwater and surface water. The aim of the present research was to provide an appropriate and cost-effective adsorbent to remove one of these heavy metals namely lead from waste water. The activated carbon was produced from the dried corn cob. Batch experiments were performed on synthetic samples at room temperature. The effect of pH, adsorbent dose, initial concentration, and contact time were studied, and the adsorption isotherms of heavy metals were determined. The optimum conditions for corn cobs activated carbon preparation were determined as impregnation ratio of 1.5, carbonization temperature of 450oC, activation time of 120min, and acid concentration 60% by weigh. The result of the characterization showed that the corn cob activated carbon has good properties as compared with other reference activated carbons. The maximum removal efficiency of heavy Pb2+ions by activated carbon adsorbent prepared from corn cobs was obtained optimum pH 5, optimum adsorbent dose of 3g, and the optimum contact time of 120 min; in these optimum conditions the removal efficiency was 96.8%. Greater adsorption amount of 10.7mg/g occurs at smaller adsorbent dose of 1g. The results were also confirmed that the adsorption process follows Langmuir isotherm model with a better sorption fit and supported for the monolayer adsorption of Pb+2ions on corn cobs activated carbon. The kinetic model of this study shows a pseudo-second order kinetic model with good correlation coefficient. Based on the results obtained, the activated carbon produced from corn cob has a good capability in removal of the lead ions from the aqueous solutions. Key words: corn cobs activated carbon; adsorption of lead (Pb2+); optimal conditions.
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    Silver Recovery and Optimization from Waste X-Ray Photographic Film Using Sodium Hydroxide Stripping
    (Addis Ababa University, 2014-12) Demelash, Mekurialem; Yimam, Abubeker (PhD)
    Silver is a depleted precious resource and in the near future it all be used up. In addition to this, our country is not produced the metal at this moment. Extracting silver from enough silver-containing wastes like used X-ray photographic film will considerably save the foreign currency to import this metal. This work reports on a novel, simple, fast and cheap method to utilize waste x-ray film for recovering silver using sodium hydroxide stripping. In this study, the silver recovery was optimized against the stripping temperature, stripping time and sodium hydroxide concentration. Firstly, the film was washed, dried, cut and weighed. Then, the silver was stripped at three different factor’s level i.e. sodium hydroxide concentration (0.5M, 1.5M and 2.5M), temperature (50 oC, 70 oC and 90oC) and time (1 min, 10.5 min and 20 min.). Finally, silver was recovered by precipitation using sodium sulphide. The yield or recovery was then determined using XRF. A maximum silver recovery of 54% w/w and a purity level of 98.02% were obtained. The experimental results were then analyzed using Design Expert Software (version 7.0.0) to determine the optimum operating conditions. The optimum operating conditions found to be a stripping temperature of 70.81oc, stripping time of 10.90 minute and NaOH concentration of 1.46M. It is concluded that waste x-ray photographic film can be stripped by NaOH and precipitated by Na2S successfully and in most economical way. Keywords: Silver recovery, waste photographic film, sodium hydroxide.
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    Simulation of Municipal Solid Waste Gasification in Updraft Fixed Bed Reactors
    (Addis Ababa University, 2017-05) Gesesse, Samuel; Yimam, Abubeker (PhD)
    A steady state simulation of syngas production from municipal solid waste gasification process using fixed bed gasification technology was performed using Aspen Plus. For the simulation, the average proximate and ultimate compositions of municipal solid waste obtained from the koshe open dump site were employed. The simulation was applied to conduct sensitivity analyses in the air to solid fuel feed mass ratio and operating temperature over the key parameters: syngas molar composition, overall carbon conversion in the reactors, syngas lower heating value and heat conversion (thermal) efficiency. The achieved information allows the selection of critical operating conditions leading to improve system efficiency and environmental performance. The results indicate that the air to feed (equivalence) ratio is a key variable as it significantly affects both the syngas composition, lower heating value and thermal efficiency. With huge organic composition of Addis Ababa municipal solid waste, the gasification simulation results are found to be satisfactory compared to gasifier database prepared for simulation purposes. At the optimum conditions of this study (T = 640 oC and equivalence ratio of 0.4), the best results found are 36.32% CO, 3.09% H2, 0.94% CH4 and a lower heating value of 6.819KJ/Nm3.
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    Study on Biogas Energy Production from Cactus Opuntia Ficus-indica (L.) Mill
    (Addis Ababa University, 2016-08) Beshir, Jemal; Yimam, Abubeker (PhD)
    Energy plays a driving role in socio-economic development arena; poverty reduction and improvement of the quality of life. Conversion of animal waste to biogas energy to replace traditional fuel and use of the slurry as a fertilizer is the current focus of the national biogas program of Ethiopia (NBP 2013). This paper presents the experimental results of the anaerobic digestion of cactus (Opuntia ficus-indica) (L.) Mill. The total solid (TS), volatile solid (VS), fixed solid (FS) and the C:N ratio of the feed stock (cactus) had been determined before the anaerobic digestion process began and then estimation of biogas production and methane content of each of the treatments, T1 (<1 year cactus at 27oC), T2 (<1 year cactus at 37oC), T3 (1 year cactus at 27oC), T4 (1 year cactus at 37oC), T5 (2 year cactus at 27oC), T6 (2year cactus at 37oC), T7 (3 year cactus at 27oC) and T8 (3year cactus at 37oC) were performed. From 500g of cactus it was found that the amount of biogas production and quality was highest in T2 (3500ml of biogas and 49% CH4) and T4 was the second highest in the amount of production and quality (3400ml of biogas and 45% CH4). T7 produced the minimum biogas production and quality (2500ml of biogas and 33% CH4). Moreover, compare to other source of energy, cactus produced a good volume of biogas but low in quality due to its C: N ratio. Thus, Cactus can be digested alone or it can be one of the feed stock for co-digestion process. This could give better quality biogas.