Process Engineering

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Adaptive Control Design for a MIMO Chemical Reactor
(Addis Ababa University, 2004-07) Yimam, Abubeker; Venkatanarasaiah, D. (PhD)
The major disadvantage of non-adaptive control systems is that these control systems cannot cope with fluctuation in the parameters of the process. One solution to this problem is to use high levels of feedback gain to decrease the sensitivity of the control system. However high gain controllers have two major problems: large signal magnitude and closed loop instability. The solution to this problem is to develop a control system that adapts to changes in the process. This paper presents the design of adaptive controller to a MIMO chemical reactor. The proposed adaptive controller is tested by using Math lab Simulink program and its performance is compared to a conventional controller for a different situation. The paper demonstrated that while the adaptive controller exhibits superior performance in the presence of noise the convergence time is typically large and there is a large overshoot. To resolve these problems of adaptive controller, the proposed controller is redesigned by modifying the adaptation law. And the results show a significant improvement in the performance of the adaptive controller without excessive increase in the adaptation rate. life of the low and middle income inner-city residents of Addis Ababa. Financial, institutional and legal problems are also seen as the major problems that hinder the implementation of LDPs in Addis Ababa
The Utilization of Indigenous Coal as Energy Substitute in Cement Industry
(Addis Ababa University, 2004-08) Dejene, Yoseph; Kaba, Tassisa (PhD)
Ethiopia spends million of dollars to meet its energy requirement, it is estimated around 20-30 million dollars is spent for the purchase of furnace oil for cement sectors only. In order to change the country’s economic situation and to come-out of poverty it is necessary to develop and utilize the country’s energy potential. For the reason of fuel economy cement plants all over the world are switching over from fuel oil or gas to coal for their kiln operation. Ethiopia has discovered large potential low grade coals at different areas. The development and the utilization of this indigenous coal as an energy source for all energy consuming sectors will be a major issue in this country in near future. The study aims to determine the potential use of one of the indigenous coal as a substitute in place of furnace oil in cement industry. Results from the analysis and comparisons of Yayu coal quality revealed the possibility of using Indigenous coal in place of furnace oil up to a certain percent. Based on the results the study attempts to select the equipments required if Yayu coal is replaced in place of fuel oil in Mugher Cement Enterprise. Substantial investment for additional facilities and equipments are required, and as a consequent considerable saving in production cost in addition to the reduction of foreign currency can be achieved through the switch over to indigenous coal. Additionally the study revealed air pollution, spontaneous coal fires and coal dust explosion are the major concerns of cement plant if this indigenous coal is used in place of furnace oil. In view of this the study recommended cement plants to see this alternative source of energy and to identify their concerns as soon as possible.
Cleaner Production Options for Solid Waste Management in the Leather Industry
(Addis Ababa University, 2005-01) Ayalew, Andualem; W/yes, Belay (PhD)
The leather industry is characterized as an industry that uses moderately large types and quantities of chemicals and water. The wastes generated in tannery processes include wastewater effluent, solid waste, and hazardous waste. These wastes create pollution problems in the environment. Most leather industries in Ethiopia discharge wastes into the environment prior to any proper treatment. An alternative approach to this is to eliminate or reduce the problem at the source using Cleaner Production (CP) approach. In this paper, a study is performed at Addis Ababa Tannery Sh.Co.(AAT) by implementing CP Methodologies. The solid waste inventory of the factory has been carried out. The major problems have been identified. The possible CP options for the existing problems are also suggested. Technical and economic aspects of the best three CP options have been evaluated. Result of the study indicates that the implementation of the suggested CP options gives significant benefit for the factory.
Modeling Chemical Engineering Processes Using Artificial Neural Networks
(Addis Ababa University, 2005-01) Ambaw, Alemayehu; Assefa, Berhanu (PhD); Tefera, Nurelegne (PhD)
In this thesis the application of feed forward type artificial neural networks to model chemical engineering processes are demonstrated with reference to five different problems. Neural network models are constructed and employed to predict vapor-liquid equilibrium (VLE) data of twelve different binary systems having different chemical structures and solution types (azeotrope-nonazeotrope) in various conditions (isothermal or isobaric). It is observed that the data found by neural network model gives an excellent agreement with the experimental data. In fact the neural network model can be treated as a powerful means for VLE data prediction in a fast and reliable way. This study has confirmed the feasibility of using a neural network to capture the nonlinear and interacting relationships between the moisture content and different drying conditions of potato. Simulating time series temperature profiles of adiabatic batch reactor has also investigated. Neural network trained with a limited number of experimental data were capable of predicting fresh data that were not used to train the network. The results obtained in using the developed models are physically sound as expected from experience. Simulating a human operator controlling a chemical plant is also a good instance where the advantage of using artificial neural networks is demonstrated in the thesis. This thesis also describes the use of multilayer feed forward neural networks as a CO2 analyzer. It was proved that MLP-type network of a relatively simple structure made it possible to predict the CO2 effluent from a furnace. Taking in to account the difficulties in experimental conditions, complicated measurements and unavoidable errors of devices used, limit the precision of laboratory measurement results. The accuracy of the results generated by the developed neural network models may be considered satisfactory for engineering calculations.
Intrusion Detection System Using Visualization and Integration Technique
(Addis Ababa University, 2006-08) Denboba, Sisay; Raimond, Kumudha (PhD)
Intrusion detection is an area of ever increasing importance. Currently existing Intrusion Detection Systems (IDS) lack visualization and false alarms detection capabilities. Researchers have proposed integrated systems which may reduce the percentage of false alarms. This work addresses the above stated problems by integrating Self-Organized Map (SOM) with Genetic Algorithm (GA) so as to minimize the false alarms and also to provide visualization capability to the new IDS. SOM is an unsupervised Artificial Neural Network (ANN) learning algorithm that attempts to visualize a large dataset in compact representation. GA is an evolutionary computing type of artificial intelligence algorithm, which is better for optimization, feature selection and clustering problems. The performance of the model is measured using Knowledge Discovery and Data Mining (KDD) Cup 99 dataset, which was prepared for The Third International Knowledge Discovery and Data Mining (DM) Tools Competition for researchers who work on intrusion detection. The work also includes GA based feature selection to further improve the performance of the model. The result shows 94.3 % of intrusion detection rate with 2.93% of false alarm rate.
Selection of Clay Adsorbents and Determination of The Optimum Condition for Defluoridation of Ground Water in Rift Valley Region
(Addis Ababa University, 2007-01) Hassen, Ahmedin; Assefa, Berhanu (PhD); Tefera, Nurelegne (PhD)
People in several regions of the Rift Valley of Ethiopia are suffering from skeletal and non-skeletal fluorosis as result of consuming water containing excessive fluoride. Defluoridation of drinking water using variety of material has been suggested by different researchers. This study assesses the fluoride adsorption characteristics of clays collected from different areas in Ethiopia. Bombawoha clay, Combolcha clay and Muger clay 2 were found to have the better potential as fluoride adsorbents. The effect of contact time, amount of adsorbent dose, pH, particle size, heat treatment of adsorbent and initial concentration of fluoride was investigated. The adsorption was rapid during the first one hour. The adsorption efficiency of fluoride was increased with adsorbent dosage. The defluoridation capacity was appreciable with in acidic pH range. Clay adsorbents treated in the range between 400 to 600oC gave better fluoride removal. The fluoride adsorption efficiency depends directly with initial fluoride concentration. The adsorption data were well fitted to the Langmuir isotherm model with adsorption capacity of 0.136, 0.168, and 0.191 for Bombawoha clay, Combolcha clay and Muger clay 2 respectively. Laboratory scale column were conducted and showed good removal of fluoride. At breakthrough the three clay samples Bombawoha clay, Combolcha clay and Muger clay 2 showed 0.1248, 0.235, 0.239 mg/g of adsorption capacity, 1.64, 1.1, 1.02 mg/L of residual fluoride and 300, 500, 500 mL of breakthrough volume respectively.
Analysis of Fillers for Production of Alternative Building Materials Using Magnesia Cement
(Addis Ababa University, 2008-01) Tadele, Tamrat; Assefa, Berhanu (PhD)
Fillers, which are available in the country, are essential for the production of magnesia cement boards. These include pumice and lignocellulostic fillers such as bagasse, sawdust and coffee husk. While applying these fillers to produce the boards, their nature and performance should be studied. Magnesia cement was used as binding materials; varying boards were produced for different proportion fillers with fixed ratio of magnesium oxide and magnesium chloride. For the board produced, density, water absorption, and setting time as well as mechanical properties such as the compressive strength and the bending strength determined. In addition, the effects of different fillers on the properties of the board and production cost were examined. When the saw dust and coffee husk filler substituted the current used bagasse filler, the water absorption and setting time of the boards reduced. While the density, bending strength and compressive strength of the board increased. The mix ratio of fillers and pumice powder had also influence on the physical and mechanical property of the boards. The test results showed as the proportion of the pumice increased, the mechanical strength of the boards increased and the setting time of the cement paste reduced. The cost analysis showed that the saw dust board production cost was lower than coffee husk and bagasse board cost. While the production cost of the coffee husk board was slightly higher than others. viii In aim of production of filler boards as alternative building materials are, the cost comparison showed in the possibility of producing relatively low price than the hollow concrete blocks included finishing work cost.
Composting of Khat and Related Materials as Solid Waste Management Option in Awaday Town
(Addis Ababa University, 2008-06) Yusuf, Mahabub; kifle, Zebene (PhD)
The huge hip of solid waste has reduced the beauty of the town and became a breeding place of some rodents and vectors. Moreover; the waste encourages some people to dispose more and therefore exacerbates the poor sanitation of the town. The total daily average quantity of solid waste is determined to be approximately 13 tones according to the data obtained for April, 2008 from disposers (i.e. Khat shops or markets) and municipal waste collection department. The waste consists of leaves different plants such as khat, eucalyptus tree, small shrubs and grasses. And since the waste is dumped in an open air it is exposed to the chemical reaction facilitating conditions or factors such as temprature, air and moisture. The process of composting was started by preparing four sites each with 1m3 dimensions at Haramaya town. A track of Khat and related materials waste, which weighs 4 tones, was taken as sample from market center of Awaday. The compostible materials are separate from the waste stream and then shredded to an optimal size. The composing matter is segregate between two groups each with two piles and expose to two different sets of conditions. The piles in the first group are enclosing so as to prevent entry of rodents and exposure to sunlight. The other piles in the second group are left with no enclosure. However, the latter used to be covered with plastic sheets during rainy hours. Moreover, additional conditions and/or factors such as Aeration, moisture, particle size had been maintained and in a pile from each group, manure as facilitator has been used. Besides, temprature measurements have been taken daily till the end. The temperature of the piles was found to pick up to a maximum of 64°c. Then the temperature starts to decline to a daily average of 25°c as the compost in the center of pile is cool or reaches it’s maturity. The analytical results of the Nutrients contents of eight samples of composts taken give values 0.9-1.40 % for nitrogen, 532.00-803.00 ppm for available phosphorus and 6775.72-12445.24 ppm for available potassium. Above all the volume of waste piles have reduced from 1m3 to 0.40 m3 (i.e.60%). x The result of the study indicates that composting has effectively reduced the volume of the waste and can serve as means of removal. Besides, the widely varying nutrients content is significant enough to use the resulting compost as alternative fertilizer.
Biosorption of Selected Heavy Metals by Brewery Derived Yeast Biomass
(Addis Ababa University, 2009-05) Mesfin, Anteneh; Kaba, Tassisa
Waste brewery yeast has been used for biosorption of lead and nickel. The dried, ground and protonated yeast has been contacted with Lead (II) and Nickel (II) solutions so as to investigate impact of PH, Contact time, presence of co-ion, and study equilibrium and kinetics of the sorption process. PH has been found to affect lead sorption considerably in the test range of 3 to 6 where the optimum sorption capacity was found to be PH of 3 to 4. Nickel sorption remained almost unaffected in the PH range 3-7. The higher proportion of the heavy metal ion has been sorbed during 5 to 10 minutes of contacting and equilibrium has been reached within 60 minutes where the optimum sorption time is 30min. Langmuir and Freundlich adsorption models have been used in the equilibrium study in order to fit the equilibrium data procured after 24 hours of contacting. As to the Langmuir isotherm model, maximum adsorption capacity qmax and affinity,b were found to be 312.5 mg/g and 0.237 for lead and 526.3 mg/g and 0.005 for nickel respectively. For Freundlich model Kf and n have been determined to be 0.946 and 0.971 for lead and 0.239 and 1.133 for nickel respectively. Concerning the kinetics of the metal uptake process, rate of metal uptake has been determined for varying metal dose in the range of 10-200mg/l and yeast dose in the range of 0.5 – 4 g/l. the curve fitted better to freundlich model than Langmuir model. The equilibrium uptake capacity (qe) rate constant(k) and initial rate of uptake(h) were calculated for metal doses ranging from 10- 200 mg/l and yeast biomass dose of 0.5-4 g/l. qe shows an increasing trend for increasing metals dose and is inversely related to yeast dose, similarly, K and h also show increasing trend for metal dose. As to the co-ion tests conducted sorption of lead decreased from 576mg/g to 444.5mg/g when nickel concentration was increased from 50 mg/l to 700 mg/l. But to the contrary increasing dose of lead did not affect the sorption of nickel. Based on recovery tests, he recoverability of lead (80%) was significantly higher than that of nickel (38%).
Utilization of Starch from Selected Crops as a Partial Substitute for Barley Malt in Brewing Technology
(Addis Ababa University, 2009-06) Admassu, Habtamu; Zegeye, Adamu (Mr); Gessesse, Amare (PhD)
Brewing process generally involves the steps of malting, mashing and fermentation. The main purpose of malting is the development of amylolytic enzymes in the grain with simultaneous degradation of high molecular substances in the cell walls enabling the achievement of a distinctive character. Barley malt is the principal ingredient in the manufacturing of beer and has traditionally been the grain of choice in the brewing industry. However, it is not always economically feasible to brew with 100% malted barley, and today's breweries are forced to minimize their costs without changing the quality or the character of their beer. Therefore, the present study was initiated to utilize Maize, Potato and Enset starch as a partial substitute for barley malt and to evaluate some physico-chemical quality attributes of the beer. All the experiments were conducted at Addis Ababa University’s laboratories(Science Faculty) and Meta Abo Brewery. The quality parameters of the starch (composition and degradability) were tested. The beer underwent four series of experiments in triplicate involving the starch from the three crops (10%, 20% and 30% starch substitute from each) with full barley malt serving as a control. The major attributes of the beer (alcohol content & flavor) were evaluated for each of the 10%, 20% and 30% substitutes from the three crops with reference to the control beer. Accordingly, the collected data were subjected to statistical analysis using SPSS software with emphasis on alcohol content and sensory attributes (flavor).The results showed that 30% substitution of barley malt with Maize and Enset starch is promising in the beer production. Beer produced using these two crops showed no statistically significant difference from the control barley malt beer (p≤0.05).The present study indicated that it is possible to partially substitute full barley malt up to 30% as it is feasible in many ways. Based on the findings, a production technology involving maize starch as a partial substitute for barley-malt has been suggested. Key words: Barley; Beer; Partial Substitution; Starch
Optimization of Anaerobic Co-Digestion of Sewege Sludge and Brewery Yeast Waste
(Addis Ababa University, 2009-06) Tilahun, Tewodros; Woldeyes, Belay (PhD)
A batch anaerobic digestion experiment was carried out to determine the optimum methane produced from digestion of sewage sludge and brewery yeast waste in different mix, and the fertilizer potential of the sludge after digestion. The maximum methane production from anaerobic digestion of sewage sludge and brewery yeast waste was assessed in batch tests using armfield glass made anaerobic digester in chemical engineering laboratory. The volume of biogas produced and methane composition of different mix of the feed stock were determined by water displacement and geotechnical land fill gas analyzer model GA 45, respectively. It was observed that the independent variable – mix ratio significantly affect (p-value 0.0027) the dependent variable – amount of methane produced since the p-value is less than the chosen α-level usually 0.05. The calculated volume of methane in the biogas produced per gram COD removed were 0.218L, 0.103L, and 0.075L and per gram volatile solid removed were 0.271L, 0.172L and 0.136L for sewage sludge alone, 80:20% mix, and 60:40% mix of sewage sludge to brewery yeast waste respectively. In general From the digestion of sewage sludge alone: 0.44 m3/d/m3 biogas with 57.75% methane was produced; 0.74 m3/d/m3, and 0.91 m3/d/m3 biogas with 19.84% and 19.34% methane produced from 80:20% mix and 60:40% mix of sewage sludge to brewery yeast waste, respectively. The mix ratio significantly affects the biogas production (p-value 1.65*10-9). Totally 83,850 m3 CH4/year can be captured and hence same amount of methane emission into the atmosphere is prevented from the sewage sludge currently managed in Addis Ababa waste water treatment plant if anaerobic digester is used. With regard to the fertilizer potential of the digestate; heavy metal content is not a limiting factor in the use of sewage sludge managed in Addis Ababa waste water treatment as a soil conditioner and fertilizer. Moreover, the nitrogen, phosphorus and potassium content of the sludge satisfy specific plant uptake requirements in many land application systems. Sun drying on drying beds after anaerobically digested sludge is helpful in the viability of land application of treated sludge by completely inactivating the pathogen and reducing the potential risk. Key words: Biogas, Methane, Organic fertilizer, Anaerobic digestion, Digester, Sewage sludge, Brewery yeast waste
Two-Dimensional Conservative Contaminant Transport Modeling of the Akaki Wellfield
(Addis Ababa University, 2009-11) Seid, Jemal; Worku, Teshome (Mr)
This thesis work focuses on non-reactive solute transport modeling of the akaki wellfield for two selected groundwater contaminants (chloride & fluoride) for the 25 operating boreholes administered by Addis Ababa Water & Sewerage Authority (AAWSA). The work is conducted based on laboratory analysis of groundwater samples from selected boreholes and based on historical data of the wellfield boreholes. The widespread use of chemical products, coupled with the disposal of large volumes of waste materials, poses the potential for widely distributed groundwater contamination. Because such contaminations can pose a serious threat to public health, prediction of the degree of contamination by appropriate numerical modeling tools is vital to aware the end user from possible risks. Mathematical models solved numerically are the subject of this thesis work focusing on conservative solute transport in the Akaki well field. Chloride & fluoride ions predictive modeling of the wellfield for the next ten years (2007-2017) is made first by calibrating the model input parameters using the available historical solute concentration data for selected boreholes at various periods. For calibration purpose, initial solute concentration was taken as 3 mg/l for chloride and 0.51 mg/l for fluoride and MATLAB simulation of chloride & fluoride ion concentration is done. The simulation results show that while chloride concentrations in the wellfield get increased; fluoride, however, is getting decreasing through out all of the boreholes in the wellfield. This is in agreement with the actual observed pattern of solute load of the wellfield revealing chloride is being introduced in to the wellfield by one or more mechanisms somewhere in the vicinity of the akaki river catchment (ARC) while fluoride is not. Keywords: aquifers, breakthrough curves, initial conditions, boundary conditions, calibration, prediction, conservative contaminant transport, hydraulic conductivity, porosity.
Production and Quality Evaluation of Spray Dried Fruit Products
(Addis Ababa University, 2010-06) Zeberga, Seifu; Zegey, Adamu (Mr)
Fruits and fruit products are the enigma of food in modern society. Fresh fruits are perishable and have limited shelf life. To prolong shelf life, various processing and preservation methods such as drying, chemical treatments and various packaging methods are used. Spray drying of mango and banana pulp into powder is a challenging operation, mainly due to heat sensitive and hygroscopic nature of the fruits. Identification of the optimum inlet temperature and flow rate is crucial for proper drying to produce powders using spray driers. This study was conducted using a laboratory scale mini spray dryer to develop mango and banana powders and evaluate their sensory qualities. The improved mango (Tommy) variety was obtained from Upper Awash Agroindustry Enterprise and the local Arbaminch mango and banana were purchased from the local market in Addis Ababa. The experiments on spray drying and product quality analysis were carried out in the Food Engineering laboratory of the Department of Chemical Engineering, Addis Ababa University. Laboratory analysis of the proximate composition was conducted at the Ethiopian Health and Nutrition Research Institute (EHNRI). The development of mango and banana powders involved: cleaning, peeling, stone removal, chopping, pulping, dilution, filtration and spray drying. Feed flow rate and inlet temperature were varied at 3.6 and 4.5 ml/min (12 and 15 % of pump rate) and 200,210°C for mango powder and 3.6 and 4.5 ml/min(12 and 15 % of pump rate) and 170,180°C for banana powder, respectively. Physico-chemical properties of the fruits were determined. The mango and banana powders were analyzed for bulk density, particle size, residual moisture content, soluble solids, protein content, fat content, crude fiber content and, vitamin C. Sensory evaluation was conducted for both mango and banana powders. The collected data were subjected to analysis of variance using statistical soft ware SPSS version 17. The inlet temperature and flow rate were found to have significant effect (P< 0.05) on the yield, moisture, solubility and bulk density of mango and banana powders. As inlet temperature increased from 2000 C to 210 0 C for mango pulp and from 170 0 C to 180 0C for banana pulp and flow rate from 3.6 and 4.5 ml/min(12 and 15 % 0f pump rate) , the mango and banana powder yield decreased 24.5 g to 20 g and from 12.5g to 10.35g ,respectively. Sensory evaluation results showed that 75% of the panelists preferred the mango powder produced at inlet temperature of 200oC and 3.6 ml/min flow rate(12% of pump rate), while xiii 62.5% of them preferred the banana powder manufactured at 170 oC and 3.6 ml/min flow rate(12% of pump rate). Processing of mango and banana fruits using spray dryer is capable of producing powder that retains nutritional values, colour, and aroma and is suitable for commercialization. This study clearly indicated that especially there is an opportunity for mango powder production in the country. Based on the findings, an economically feasible processing technology for mango powder production has been suggested. Key words: Banana; Mango Powder; Quality; Sensory Evaluation; Spray drying
Influence of Baking Time and Temperature on the Quality of Kocho Biscuit Enriched with Faba Bean and Wheat
(Addis Ababa University, 2010-06) Yohannes, Kalekristos; Admassu, Shimelis (PhD)
The production of nutritious biscuit from Kocho of low protein and high carbohydrate, mineral and crude fiber; fortified with faba bean of high protein and moderate fat content; and wheat of good glutenin and gliadin; were the bases for enriched biscuit production. The proximate analysis of enriched Kocho biscuit was done using the AOAC, 2003 analytical procedure. The enriched Kocho biscuit showed an upgrade in protein content from 0.96 of whole Kocho biscuit processed at 1700C for 10min to 9.7% of KFWB2 at 1700C for 10min. This also implies that the consumption of 2 pack of 250g each (one pack contain 21 biscuit of each weighing 12g) of enriched Kocho biscuit of blend KFWB2 processed at 1700C for 10min accommodates the daily protein requirement of 39g/day and 50g/day for the age of 1-3 and 4-10; respectively. The mineral content of enriched Kocho biscuit is improved by the presence of Kocho and faba bean. The time and temperature effect of baking the enriched biscuit shows a major change in protein content due to an increase in the faba bean concentration. With increasing temperature and time the value of the protein decreased due to protein denaturation by heat. As can be seen in KFWB3 processed at 1700C when the time increases from 7 to 8, 8 to 9, and 9 to 10min the protein decreases from 9.94%-9.51%, 9.51%-9.08%, and 9.08%-8.99% respectively. Correspondingly, at a fixed time of 10min in KFWB3, an increase in temperature from 1600C to 1700C, and 1700C to 1800C resulted in decrease from 9.56%-9.08%, and 9.08%-8.98% respectively. The result obtained from the SPSS analysis revealed that biscuit KFWB2 processed at 1700C for 10 min. gave best result for protein content of 9.7% on dry basis. This implies that the enriched Koch biscuit is a good source of protein and can support problem solving in protein malnutrition in the country. The farinograph data for various blends of flour revealed that faba bean has 206 FQN which is better than that of wheat of 108FQN. Combination of this faba bean with Kocho flour improves its farinograph quality number from 7 to 200 of KFWF3 and makes it more suitable for biscuit production. The flour property like water and oil adsorption for whole Kocho flour (KF) were 2.29ml/g and 0.93ml/g; respectively which improved to KFWF2 of 2.05 ml/g and 1.15ml/g; respectively which is not significantly different form wheat flour of 2.2ml/g and 1.18ml/g. This makes the enriched Kocho biscuit comparable in terms of farinograph quality number and dough consistency with the standard whole wheat flour biscuit. The water activities of the whole blended flours were in between 0.47% and 0.55% indicating below the minimum water content required by microorganisms. The water activity for the biscuit is also in the range of 3.7% and 6.5%. The moderately high 5 amount of water activity in whole wheat flour biscuit (KFWB5) results in damage by microorganisms. The recommended water activity for the biscuit is in the range of 0.3% and 0.5%.
Production of Biodiesel from Microalgae
(Addis Ababa University, 2010-07) Gebeyehu, Menelik; Tefera, Nurelegne (PhD)
Since petroleum resources are believed to last only for a few decades, alternative sources of biofuel production should be exploited. In order to replace all the fossil fuels consumed in the world, other sources of biodiesel which have higher productivity per unit area of land than vegetable and non edible oilseed feed stocks are required. One of the alternative sources which falls in to relatively higher productivity per unit area of land (10g/m2/day -50g/m2/day) is the production of biodiesel from microalgae. This study focuses on production of biodiesel from microalgae by transesterification reaction. Algal biomass of symbiotic blue green algae were collected from ARARI. After drying the biomass, algae oil was extracted by soxhlet extraction method using solvent, hexane. Then, purification of the oil was performed by degumming, neutralization, and bleaching to facilitate the characterization and biodiesel production process. The characterization test of the oil confirmed that oil can be produced from the algal biomass with the acceptable range of pyiscochemical properties for biodiesel production. Then, biodiesel was produced by base catalyzed transesterification reaction and characterized by determining density, kinematic viscosity, acid value, saponification number, flash point and heating value. HPLC analysis was conducted to determine the conversion of oil to biodiesel. The characteristic test result of the biodiesel showed that the density, kinematic viscosity, acid value, saponification number, flash point and heating value conforms to all the standard specifications of ASTM D 6751 and EN 14214, except for its acid value (0.57mgKOH/g) which is 14 % above the EN 14214 specification. The result showed that the symbiotic blue green algae in ARARI can be used to produce biodiesel with acceptable quality. However, the oil yield of the algal biomass was very low (5.4wt %) when compared with oil contents of algal strains (>15wt %) recommended for biodiesel production. Therefore, three different pure algal strains were selected and assessed based on their oil content and productivity with growth parameter requirements of climatic conditions which conform to the Ethiopian environment particularly to the specific area selected for cultivation. The results of the investigation showed that the strain Bortyococcus braunii gives the best result and recommended for cultivation of algal biomass for biodiesel production in Ethiopia.
Optimum Production of Biogas from Bio-Municipal Solid Wastes Using Two Stages Anaerobic Digester
(2011-06) Assefa, Gizachew; Assefa, Birhanu (PhD)
Various aspects of Anaerobic Digestion (AD) have been became a promising technology for the management of Municipal Solid Waste. Thus, the objective of this study was to optimize the production of biogas from these wastes by using two-stage anaerobic digester. To achieve this, batch anaerobic digestion experiments were conducted to determine the optimum methane produced from the digestion and co-digestion of Organic Fraction of Municipal Solid Waste (OFMSW) and Cow Manure (CM) in different mix operated under ambient condition. Moreover, this study presents several runs of experiment and analysis with the aim of substrate mix and the duration of overall stage of digestion process while optimizing the biogas generation with higher methane content. The physical and chemical characteristic of the sample done by analytical method, volume of biogas produced and methane composition of different mix of the feed stock were determined by water displacement and digital gas (SR2-BIO gas analyzer), respectively. The highest specific gas production observed was 353 L/Kg VS added for the digestions of 1:2 mix of OFMSW: CM. It was observed that the independent variable – mix ratio significantly affect (p-value 4.18*10-9) the dependent variable – amount of methane produced since the p-value is less than the chosen α-level usually 0.05. The calculated volume of methane in the biogas produced per Kg of volatile solid removed were 510L, 355L, 375L, 435L and 600L for OFMSW (100%), 2:1 mix of OFMSW: CM, CM (100%), 1:1 and 1:2 mix of OFMSW: CM, respectively. In general From the digestion of 1:2 mix of OFMSW: CM: 0.47 m3/d/m3 biogas with 51.5% methane content was produced; 0.45 m3/d/m3, 0.35 m3/d/m3, 0.26 m3/d/m3, and 0.23 m3/d/m3, biogas with 31.4%, 42.9%, 20.3% and 33.7 % methane composition is produced from 1:1 mix of OFMSW: CM, CM alone, OFMSW alone and 2:1 1 mix of OFMSW: CM respectively. The mix ratio significantly affects the biogas production (p-value<<0.05).
Extraction and Characterization of Essential Oil from Margosa Seed
(Addis Ababa University, 2011-06) Workneh, Wondesen; Kiflie, Zebene (PhD)
The objective of this study was to develop a process for the extraction of essential oil from Neem seed. The extraction was carried out using soxhlet and agitated mixing vessel extraction units. In the soxhlet extraction a n-hexane was chosen to determine the effect of time and particle size on yield of the extraction oil. In the agitated mixing vessel n-hexane and ethanol were used to investigate the effects of solvents, particle sizes, and temperatures (30, 40 and 50oC) on the quality and yield. A general factorial design was applied to both extraction processes using DESIGN EXPERT software and linear regression model was obtained growing the individual effect of time, particle size, temperature and solvent type as parameter and their interaction in the entire extraction process. For the soxhlet extraction, the minimum oil yield has been determined as 37.625% after the extraction time of 2hours with particle size ranges from 0.85-1.4mm and maximum oil yield 46.545% was found at the extraction time of 6 and 8hours in a particle size ranges from 0.425-0.75mm. Therefore, increasing extraction time and decreasing particle size will increase the amount of oil extracted. In the batch experiment, results showed that the maximum oil yields were 33.19% for ethanol and 47.32% for n-hexane at 50oC, and 0.425-0.71 mm particle size. The Neem oil was found to have a colour of golden yellow due to the presence of Nimbidin. Based on psycho-chemical characteristics, analysis showed that increasing temperature decrease iodine value, but increase saponification, and acid value, which means that higher extraction temperature results in higher oil yield but lower oil quality. The rough profitability evaluation indicates us this project is beneficial as it is clearly observed from the cost estimation, the rate of return on investment was calculated and has 79.45% and the payback period tells us the plant return its total investment cost in one year.
Development of supplementary food from blends of maize and soybean flour with moringa powder
(Addis Ababa University, 2011-06) Massresha, Erkihun; Kumar, Yogesh (Professor); Zegeye, Adamu (Mr)
The objectives of the study were to develop supplementary foods from moringa, maize and soybeans blend for infants. The sample diets were formulated with different proportion and Faffa was used as a control .Material balance method was used to predict the nutrient requirement in order to meet the standards of the final product. Analyses were made for different formulated diets and compared with the control and recommended daily allowance (RDA). The five supplementary blends (Diets 1,2,3,4 and 5) were formulated based on the protein and energy of the food commodities. Standard procedures were used to determine the basic principal in formulated diets. UV-spectrophotometer analyzer was used to detect tannin and phytate content of samples, Viscometer analyzer was used to detect and quantify the gruel concentration, and functional properties. The overall results
Investigation of Biodiesel Production Using Heterogeneous Catalyst
(Addis Ababa University, 2011-06) Mathewos, Temesgen; Tefera, Nurelegne (PhD)
Biodiesel production is a very hot issue within research, politics and investments worldwide. The problem of finding economically viable and environmentally friendly renewable energy sources is an urgent matter. Not only is the world faced with a finite supply of fossil-fuels, but concern is growing over the possibility of climate change caused by greenhouse gas emissions. Biodiesel, a liquid fuel derived from plant oils or animal fats, represents a renewable energy source that could contribute to the solution of both problems; it can be continually produced as long as we are able to grow plants and it can be made in such a way as to release no net addition of greenhouse gases to the environment. However, technical challenges must be overcome before biodiesel can contribute significantly to the world's energy supply; with current technology biodiesel production is profitable only under special circumstances. This thesis research seeks to address this problem by studying the production of biodiesel using heterogeneous catalysts. Heterogeneous catalysts can make biodiesel more energy efficient, and therefore less expensive, by eliminating the need for expensive purification processes that separate the catalyst from reaction products typical in the use of homogeneous catalysts. The experimental design and statistical analysis was done by Design-Expert 7.0.0 program. Fatty acid methyl ester was produced via transesterification process using sodium phosphate as a heterogeneous catalyst and purified jatropha curcas oil which is extracted from the jatropha seed bought from dessie. To obtain a high quality biodiesel fuel that comply the specification of standard methods, some important variables such as reaction temperature, molar ratio of methanol to oil and mass weight of catalyst were selected and studied. At the following conditions; 333K of reaction temperature, methanol to jatropha oil ratio of 4 and 5 mass wt% of catalyst, an optimum fatty acid methyl ester yield of 94.98% was obtained, indicating that sodium phosphate has the potential as a heterogeneous catalyst for the production of fatty acid methyl ester from jatropha oil. Moreover, physico-chemical characterization of the fatty acid methyl ester was performed and compared with the standard biodiesel properties.
Synthesis of Carboxymethyl Cellulose from Sugarcane Bagasse
(Addis Ababa University, 2011-06) Woldeamanuel, Yalew; Kiflie, Zebene (PhD)
Sugar cane bagasse is a potential cellulose source, though usually used as a fuel source for the boiler. This work reports concisely on a method to utilize sugar cane bagasse for preparing sodium carboxymethylcellulose (CMC) and its characteristics. The desirable characteristics that are imparted on the cellulose were the solubility, viscosity and others which are responsible for many applications. Furthermore, in this work the carboxymethylation reaction was optimized against the reaction temperature, reaction time, monochloroacetate concentration and sodium hydroxide concentration. The sugar cane bagasse is obtained shortly after the juice is extracted in the roller mill. Sodium hydroxide, chloroacetic acid and isopropanol were used for the carboxymethylation process. Firstly, the sugarcane bagasse was dried, ground to pass 1mm screen. Then the cellulose was extracted using 4N NaOH at 100oC for 1 hour. Finally, cellulose was converted to carboxymethyl cellulose (CMC) by basification and etherification processes using sodium monochloroacetate and sodium hydroxide. Two reactions were taken place simultaneously during carboxymethylation that were the primary reaction which produces pure carboxymethyl cellulose and side reaction that produce undesired sodium glycolate. The degree of substitution and viscosity were determined and then analyzed with respect to the reaction conditions using design expert statistical software. From the analysis the maximum degree of substitution was 1.92, and the maximum viscosity 25.4 cp. But after optimization of reaction conditions had been carried out, the optimized degree of substitution was 1.79 and viscosity 14.63cp. These were obtained at a reaction temperature of 30oC, reaction time of 2.95 hours, NaOH concentration of 25% w/v and chloroacetic acid concentration of 0.5 w/w. It is concluded that the sugarcane bagasse is a good source of cellulose that can be modified by etherification reaction to carboxymethylcellulose with a medium degree of substitution of about 1.79. Keywords: Degree of substitution, cellulose, carboxymethyl cellulose, sugar cane bagasse.

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