Process Engineering

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Activated Carbon Preparation and Characterization from Flax Straw for Removal of Pb (II) Ions from Aqueous Solution and Industrial Wastewater
(Addis Ababa University, 2021-09) Tayto, Mindahun; Shegaw, Ahmed (PhD)
There are different modern technologies to remove heavy metals from industrial effluent. However, applying these modern technologies is impossible in all situations. Hence, investigating alternative technologies like adsorption by AC for such kinds of problem is very important. Considering this, the aim of this study was to prepare AC from flax straw and investigate its potential for the removal of Pb (II) ions from aqueous solution and paint industry wastewater. AC was prepared by chemical activation method using H3PO4 as activating agent. The effects of activation time, activation temperature and activating agent concentration on yield and iodine number were studied by using RSM. The effects of initial Pb (II) ion concentration, adsorbent dose, contact time and pH on removal efficiency were studied by using synthetic wastewater prepared from lead nitrate on a batch mode. The collected wastewater sample was characterized before and after treatment according to APHA methods. AC was characterized and results showed that the flax straw AC had 8.04% of moisture, 6.04% of ash, 18.615% of volatile matter, 79.421% of fixed carbon, 459.807 mg/g of iodine number and surface area of 489.455 m2/g. Physico-chemical characteristics revealed that raw wastewater had a concentration of 3.95 mg/L Pb (II), 158.52 mg/L BOD5, 2482 mg/L COD, and 652.667 mg/L TSS. The highest removal efficiencies of Pb (II) metal ion which was achieved from aqueous solution and paint wastewater were found to be 95.16% and 78.73%, respectively. The experimental data are fitted with pseudo-second order model and adsorption of Pb (II) on flax straw AC fits the model of Langmuir very well. The results suggested that flax straw AC can be used as adsorbent to remove Pb (II) ion from paint industry wastewater.
Activation of Raw Bentonite (Afar Region) Using Sulfuric Acid for Rapeseed and Niger Seed Oil Bleaching
(Addis Ababa University, 2017-06) Shemsu, Leena; Tekola, Beteley (PhD)
In this study, a two-stage process was conducted. The first one was carrying out the activation process of raw bentonite at different conditions and the optimum parameter was chosen. The second process was bleaching of Niger seed oil and rapeseed oil using the chosen activated bentonite. The raw bentonite collected from Gewane in Afar region was activated by sulfuric acid and the design of various experiments in order to assess and simulate the effects of the acid activation of raw bentonite on the bleaching capacity of Niger seed oil is described. Two key parameters of the acidic activation, namely acid concentration and activation temperature, were considered. The highest bleaching capacity was obtained around 3M acid concentration and at 90oC of activation temperature as optimal activation. The raw and activated bentonite at optimal condition was characterized by XRD, FTIR and SEM with EDS. The results of the XRD showed that the raw bentonite is composed of montmorillonite, quartz, muscovite, hematite, feldspar and cristobalit. X-ray and FTIR data confirmed that acid activation affects both the octahedral and the tetrahedral sheets. The results of the analysis by Energy Dispersive Spectroscopy (EDS), showed that, presence of silica, alumina and iron as major constituents, along with traces of sodium, potassium, magnesium, calcium, and titanium in the form of impurities. These exchangeable cations were removed partially by acid attack. Full factorial experimental design was employed to correlate the bleaching parameters (temperature, time and dosage of clay) to the percentage color reduction for Niger seed and rapeseed oil bleached. The result showed that the optimum condition for the bleaching process was a temperature of 900C, a period of 30 minutes and 4 % clay dosage which resulted in 94.37% bleaching of the Niger seed oil. For rapeseed oil, the maximum bleaching efficiency, which is 96.01%, was obtained at 110 0C, a time period of 45 minutes and 1% clay dosage. The experimental result was in agreement with the model prediction. Generally, the study has shown that the clay is a good adsorbent for the bleaching of both oils. This research has further established that acid activated bentonite has the power to remove not only pigments but also reduce the free fatty acid of unbleached oils. Keywords: Bentonite, Acid activation, Characterization, Bleaching, Niger seed oil, Rapeseed oil
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
Adsorption-Anaerobic Digestion coupling process for molasses vinasse Treating
(Addis Ababa University, 2018-07) Mohammed, Seid; Shemelis, Kebede (PhD)
The production of ethanol from biomass results in the co-current production of acidic material known as distillery spent wash or vinasse. It is generated at a rate of 10 to 15 times greater than the ethanol itself, and is characterized by a high dissolved organic matter content. Anaerobic digestion is the most effective methods for the treatment of such type of wastewater. In this work, a combined adsorption–anaerobic digestion treatment of distillery wastewater was studied in order to develop an effective procedure for increasing the anaerobic biodegradability of vinasse to reduce its environmental impact. The adsorption stage with banana peel as a pretreatment was evaluated for removal of phenolic compound. The removal of phenolic compound with this biosorbent was carried out using Box-Behnken experimental design taking 3 factors, adsorbent dose, contact time, and particle size. The maximum phenol removal recorded was 76.425% at the optimum condition (adsorbent dose of 20 g/L, contact time of 129.98 min, and particle size of 0.53 mm). Removals of 22% in chemical oxygen demand (COD) was obtained in this stage. Among the adsorption isotherm models analyzed, the Langmuir model fitted best to the experimental data with maximum adsorption capacity of 4.12 mg/g, and also the adsorption mechanism follows pseudo-second order model. The pretreated vinasse was undergone to an anaerobic digestion process in the second stage under mesophilic condition. After anaerobic digestion, a global removal of 84% in COD, and over 95% in phenols content were obtained. It was shown that, a combination of treatment method (i.e. banana peel biosorption and anaerobic digestion) is a promising option for simultaneous removal of phenol and COD from molasses vinasse under the stated conditions.
Ammonium Chloride Production and Optimization of Brine Ammoniation for Lime Removal in Leather Processing
(Addis Ababa University, 2014-06) Moreda, Michael; Kaba, Tassisa (PhD)
Leather industry occupies a place of prominence in Ethiopian economy in view of its massive potential for employment, growth and export. The need of import substituting leather processing chemicals from locally available feed stocks is an urgent matter both from economic and environmental point of view. One of the chemicals used in leather processing is ammonium chloride which is a deliming agent in Beam house operation. In this study, the production of ammonium chloride from proven available urea feed stocks ammonia, carbon dioxide and from the cheapest chlorine source sodium chloride which is readily available in Ethiopia, and its use and efficiency as a deliming chemical as compared to standard ammonium chloride is analyzed. A modified Solvay process approach was adopted in search of a route to the production of ammonium chloride locally. The method involves brine purification, ammoniated brine formation, carbonation of ammoniated brine, separation of sodium bicarbonate from ammonium chloride containing mother liquor, evaporation of ammonium chloride filtrate, cooling of the evaporated ammonium chloride filtrate to crystallize, centrifugation and drying of ammonium chloride which is collected as a white solid crystal of 98.5 - 99.5 wt.% NH4Cl. This preparation met the established specification for ammonium chloride of Indian Society for Testing and Materials (ISTM). The maximum yield of ammonium chloride (92.5%) was produced when the brine ammoniation reaction was carried out at a temperature of 100C, ammonium solution to saturated brine molar ratio of 2 and reaction time of 1 hour. Therefore, these values can be considered as optimal for ammonium chloride production using ammonium solution, dry ice and saturated brine in batch reactor. The reaction temperature was varied in the range of 100C - 200C, ammonium solution to saturated brine molar ratio was varied in the range of 1 – 3; and reaction time was varied in the range of 0.5 - 1.5 hours. Testing of the optimal product on leather met the IULTCS standards.
Analysis and Optimization of Para-Xylene Production Process From Sugarcane Bagasse
(AAU, 2018-06) Brhanu, Gebreslassie; Hundessa, Dessalegn (PhD)
Lignocellulosic biomass has a great potential for biofuel and fine chemical productions. This study focused on the effective conversion of the lignocellulosic biomasses, particularly sugarcane bagasse to the most valuable aromatic hydrocarbon called Para-xylene via two-step acid-catalyzed hydrolysis, dehydration, hydrogenation, and Diels-Alder cycloaddition reaction steps. Para-xylene is one of the most important aromatic hydrocarbons, which is used for the production of purified polyethylene terephthalate (PET), in which it is used for the production of world plastics. So, the production of fine chemicals from biomass helps to reduce the dependence of the imported oils as well as used to improve the overall economic and sustainability of the world. In this study, the effect of operating variables on the Diels-Alder cycloaddition reaction between the biomass-derived furan and the suitable dienophile, which is called Maleic anhydride, was investigated and optimized using the most reactive and selective Lewis acid catalyst (AlCl 3 ). In the Diels Alder cycloaddition reaction, the effects of reactant molar ratio, catalyst loading and reaction time on the conversion of DMF and the yield of dimethyl benzoic acid was investigated and optimized using Design expert®7 software. As the result, 41.4% conversion of DMF and 64.6% yield of dimethyl benzoic acid were obtained at the optimum values of the operating variables such as molar ratio of the reactant, catalyst loading and reaction time. And also, the effects of acid concentration and reaction time on the dehydration of dimethyl benzoic acid to Para-xylene were investigated, and 70.36% conversion of dimethyl benzoic acid and 49.66% yield of Para-xylene were obtained. In addition to this, the final product (Para-xylene) was analyzed using FTIR and GC-MS. As the result, the FTIR result is the same with the standard functional group of 1,4-dimethyl benzene, and 30.88% composition of Para-xylene were obtained using GC-MS.
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.
The Assessment of Peanut shell and Chat stem as Alternative Energy Source for Cement Industries
(AAU, 2018-10) Birhan, Gebregziabher; Shimelis, Kebede (PhD)
Cement industries are one of the major energy-intensive industries and heavy polluting process. To reduce the energy cost and environmental impact, cement producers are currently using alternative fuels. This study analyzed the assessment of peanut shell and chat stem as alternative energy source for cement industries. The main objective of this study was to carbonized mixed of a peanut shell and chat stem. The parameters of carbonization process, which affect the calorific value such as temperature (350, 450 and, 450 o C), time (60, 90 and 120min) and mixing ratio (25, 50 and 75%) were optimized via Central Composite Design (CCD). All the necessary analysis that included physiochemical characteristics of peanut shell and chat stem, mixed carbonized and mixed carbonized pellet, then the results were compared with commercial coal. In addition, thermogravimetric analysis were examined the thermal property of peanut shell and chat stem. Based on the result, the optimal conditions were (temperature at 450 o C, time for 60min and mixed ratio 75%) with a maximum calorific value of 6552.6 Cal/g. However, the energy content of sample was comparable with coal, but it needs pellet for suitable storage, handling, transporting. Then the optimum mixed carbonized pellet with 10% of molasses, the calorie develop to 6838.19cal/g. The optimum mixed carbonized pellet showed a decrease in moisture content (2.87%), volatile content (30.75%), Hydrogen (2.95%) and Oxygen (26.19%) while the fixed carbon (57.57%), and carbon (70.86%) increased considerably. Therefore, in this study shows that the mixed carbonized pellet has potential replaced coal as an alternative energy source for cement production due to their calorific value at optimum carbonation condition.
Ayka Addis Textile Wastewater Treatment by the Fenton’s Reagent
(Addis Ababa University, 2011-06) Soresa, Mekibib; Worku, Teshome (Eng)
Treatment of wastewater is one of the biggest challenges faced by textile manufacturers. One of the textile industries in Addis Ababa at Alem Gena, Ayka addis textile and investment group plc, is experiencing high concentration of COD and color in the final effluent, due to the absence of appropriate treatment facility, as a result of this the effluent wastewater exceeds the standard discharge limits. The use of conventional textile wastewater treatment processes becomes drastically challenged to environmental engineers with increasing more and more restrictive effluent quality by water authorities. Conventional treatment such as biological treatment discharges will no longer be tolerated as 53 % of 87 colors are identified as non-biodegradable. The purpose of this study was to investigate the suitability of using Fenton’s reagent for treatment of Ayka Addis textile effluent wastewater and reduction of COD and color from the wastewater. The oxidation experiments was carried out using Fenton’s reagent (hydrogen peroxide (H2O2) and ferrous sulphate (FeSO4.7H2O)), and to adjust the pH of the wastewater sample hydrochloric acid (HCl) and sodium hydroxide (NaOH) were used. In this work, optimum conditions such pH, reaction time and stirrer speed on COD and color removal efficiency were examined and after determination of the appropriate experimental conditions, the optimum dosages of Fenton’s reagent were determined, at the optimal treatment conditions and dosages a satisfactory results were obtained. It is found that the tested Ayka Addis textile wastewater revealed high susceptibility to treatment using a combined action of ferrous salts and hydrogen peroxide. The main characters of the wastewater, such as color and chemical oxygen demand (COD) were reduced by considerable amount. The result of this investigation shows a marked increase in degradation of pollutants by Fenton’s reagent oxidation. Keywords: Fenton’s reagent, textile wastewater treatment, advanced oxidation process
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
Biodiesel Production from Jatropha Oil Using Ethanol with Alkali Catalyst
(Addis Ababa University, 2011-07) Adamu, Esubalew; Sokol, Walter (Prof.)
The jatropha oil was extracted using solvent extraction and mechanical pressing. The extracted oil was refined through degumming and neutralization followed by washing and drying. The acid value, amount of free fatty acid, saponification value and flash point of the extracted jatropha oil were determined. The biodiesel was produced from jatropha oil using anhydrous ethanol (99.4% w/w) anhydrous NaOH catalyst (97% w/w). The experimental design was done in two parts. The first one was done for one factor of four levels to establish the parameters influence independently on biodiesel yield. To determine the temperature effect, experiments were done at temperatures of 35 o o o o C, 55 C, 65 C and 75 C. Similarly, to investigate the effect of amount of catalyst, experiments were done at 0.25% (w/w), 0.5% (w/w), 1% (w/w) and 2% (w/w) of NaOH catalyst. In addition, to determine the influence of molar ratio of alcohol to oil, molar ratios of 6:1, 8:1, 10:1 and 12:1 were used. In the second of the experimental design, the full factorial, was done for the three factors at two levels and two replicas at a temperature of 55 o o C and 65 C, molar ratio of alcohol to oil 6:1 and 8:1, and the amount of catalyst required was 0.5% (w/w) and 1% (w/w), which were used to investigate the effects of the three parameters and their interaction simultaneously on biodiesel yield. It was found that the standardized effect of molar ratio of alcohol to oil had the highest effect whereas the least effect was observed at the interaction of temperature and alcohol. The standardized effect of the interaction of all the three parameters together was greater than the temperature effect alone. The average maximum biodiesel yield was 83.6% (w/w) at 55 o C, 8:1 molar ratio of alcohol to oil and 1% (w/w) NaOH catalyst amount. On the other hand, the average minimum biodiesel yield was 64.9% (w/w) at 65 o C, 6:1 molar ratio and 0.5% (w/w) catalyst amount. The viscosity, density, flash point, acid value, saponification value, moisture content and ash content of the produced biodiesel were determined. These properties were matched with ASTM specifications except viscosity which was slightly higher than ASTM limit.
Biodiesel Production from Tannery Solid Waste
(Addis Ababa University, 2012-11) Mamo, Addisu; Woldeyes, Belay (PhD)
The dwindling resources of fossil fuels coupled with the steady increase in energy consumption have encouraged research interest in alternative and renewable energy sources. Biodiesel is one of the most promising alternatives for fossil fuels. To foster market competitiveness for biodiesel, it is necessary to produce biodiesel from economically viable and environmentally sound feed stocks. This study deals with the biodiesel production from tannery solid waste. The tannery solid wastes, from different sections of processing units, have been characterized for their fat content. The investigation proved that it was the fleshing waste which has a potential fat content (23%) to be used as biodiesel feed stock. The fleshing oil converted to free acid methyl ester (FAME) or biodiesel using a two step acid and base catalyzed esterification and transesterification reactions respectively. The effect of oil to alcohol molar ratio, the amount of catalyst and temperature on biodiesel production was investigated using Design Expert 7.0.0 and optimum reaction conditions were determined. The fuel properties of the biodiesel were also studied according to the ASTM standard. The result showed that fleshing oil can be a very viable and commercially competitive biodiesel feed stock even though some of the properties like cloud point needs further improvement.
Biodiesel production from vernonia galamensis oil using ethanol with alkali catalyst
(Addis Ababa University, 2012-11) Abebe, Enkuahone; Shiferaw, Gizachew (Eng)
This work was done with the aim of producing biodiesel from vernonia galamensis oil by using ethanol with alkali catalyst, sodium hydroxide. Additionally it was investigated the effects of catalyst amount from 0.25 %( w/w) to 2 %( w/w) of weight of oil, molar ratio of ethanol to oil from 6:1 to 12:1 and reaction temperature from 35 oC to 75 oC on biodiesel yield. Vernonia galamensis oil was extracted using solvent extraction and mechanical pressing. The extracted oil was purified through degumming, neutralization, washing and drying sequentially. Acid value, amount of free fatty acid, saponification value and flash point of the extracted oil were determined. Biodiesel was produced from vernonia galamensis oil using anhydrous ethanol 99.5% (w/w) and sodium hydroxide catalyst 97% (w/w). The experimental design was done by using the Design Expert 7.0.0 software three levels; three factor Central Composite Design with full type in the optimization study, requiring 20 experiments. To determine the effect of temperature, amount of catalyst and molar ratio of alcohol to oil experiments were done in the ranges of 35oC to 75oC, 0.25% to 2.0% (w/w) and 6:1 to 12:1 subsequently. The maximum biodiesel yield was 87 % (w/w) at 55oC, 9:1 molar ratio of alcohol to oil and 1.125% (w/w) sodium hydroxide catalyst amount. In contrast, the minimum biodiesel yield was 52% (w/w) at 75oC, 12:1 molar ratio and 2% (w/w) catalyst amount. The viscosity, density, flash point, acid value, saponification value, moisture content and ash content of the produced biodiesel were determined. These properties were matched with ASTM specifications. Based on the preliminary economic analysis evaluation, the suggested project is feasible.
Biodiesel Production from Wado Seed Oil
(Addis Ababa University, 2011-07) Tesfaye, Kalay; Sokol, W. (Professore)
is a renewable, biodegradable, environmentally benign fuel for use in the diesel engines. It can be produced from renewable sources such as vegetable oils or animal fats. Although this fuel has gained worldwide recognition for many years, it is not being widely commercialized mainly because it is more expensive than petroleum diesel. A two-step acid-base catalyzed method was successfully used in the synthesis of biodiesel from wado seed oil. The study satisfies the objective of reducing the high FFA present in the oil, followed by KOH catalyzed transesterification. The variables affecting the acid value and the methyl ester yield, such as molar ratio, catalyst concentration, reaction time and reaction temperature, were investigated to determine the best strategy for producing optimum biodiesel from the oil. Acid value and FAME yield were used to verify the optimization of the ester conversion process. Based on the amount of WSO used, a reduction of acid value from 12.6% to 2.1 % mg KOH/g was obtained. A 94.5% FAME conversion was also obtained using a methanol/oil ratio of 6:1, 1.0% mass KOH and 55°C reaction temperature. The important properties of the biodiesel (density, kinematic viscosity, cloud point, cetane number, iodine value, and high heating value) were compared to those of ASTM and EN standards for biodiesel. The comparison shows that the wado seed oil methyl ester could be used as an alternative to diesel.
Bioethanol Production from Barley- Spent Grain (Breweries Spent Grain)
(Addis Ababa University, 2016-06) Fissha, Amare; Jabasingh, S.Anuradha Asoc (Associate Professor)
The objective of this study was production of bioethanol from Barley spent grain by using two-stage diluted acid hydrolysis. The production process was carried out in four main stage such as pretreatment, hydrolysis (first and second stage), fermentation and distillations. The first stage diluted acid hydrolysis was used as chemical pretreatment stage and the process variables were fixed at the best optimum condition (liquid/solid ratio of 8 g/g, 100 mg H2SO4/g of dry matter, 17 min reaction time and 121oC temperature). Before the first stage hydrolysis process was carried out, the wet Barley spent grain was dried using oven at 70oC temperature for 24 hours. For the second stage hydrolysis, 23 full factorial central composite design (CCD) was applied to investigate the effect of temperature (130-150oC), reaction time (20-30min) and acid concentration (1.5-2%) using Design expert® 6 software. RSM was applied to investigate the interaction effect of hydrolysis process variables and to find the optimum yield of ethanol from BSG. After hydrolysis process sugar content of the hydrolyzate was quantified using quantitative benedict reagent solution. Fermentation of the hydrolyzate was performed using 5g/L Saccharomyces cerevisiae at 30oC temperature, pH 5.0 and 72h fermentation time for all samples. After fermentation the specific gravity of the produced alcohol was measured by pycnometer (specific gravity bottle) and alcohol concentration was obtained from the relationship between the specific gravity and the proportion of ethanol in alcohol solution at 20oC (Perry Chemical Engineering Handbook). Significance of the process variables were analyzed using analysis of variance (ANOVA) and second order polynomial function was fitted to the experimental results. Thus, the influence of all experimental variables, factors and interaction effects on the response was investigated. Hydrolysis temperature, time and interaction between temperature and acid concentration have significance effect on the yield of ethanol. As the result of RSM optimization, the best yield of TRS and bioethanol were found at 144.29oC hydrolysis temperature, 26.26 min reaction time and 1.68% w/w acid concentration. Under these condition 47.60%w/w and 8.33mL per 50 g dry barley spent grain of TRS and bio-ethanol was obtained respectively. Keywords: Bioethanol, Barley spent grains, diluted-acid hydrolysis, and Saccharomyces cerevisiae
Bioethanol Production from Sequential Acidic-Alkaline Pretreated Sorghum Straw Hydrolysate
(Addis Ababa University, 2019-07) Fseha, Gebremichael; Sintayehu, Nibret (PhD)
The depletion and environmental problems associated with fossil fuels as main energy source motivates to look for alternative energy sources that do not compromise both food security and the environment. Sorghum is a fast-growing crop that can be harvested twice a year and produce both food (grain) and straw that can be utilized for ethanol production. The study explores the production of bioethanol from sequential acidic-alkaline pretreated sorghum straw hydrolysate. Sequential acid-alkaline pretreatment method was employed to obtain most intact monosaccharides from cellulose and hemicellulose. Dilute sulfuric acid (1%) pretreatment at 125 ℃ for 10 minutes was used at the first stage mainly for hemicellulose removal. In the second stage pretreatment, dilute sodium hydroxide (1.25 %) at 90 ℃ for 10 minutes was employed for delignification. The residues after the second pretreatment were hydrolyzed using dilute sulfuric acid of concentrations (2 %, 3%, and 4%), at temperatures (110 ℃, 125 ℃, and 140 ℃) and times (20, 40, and 30 minutes). The sugar concentration of the hydrolysates was determined using phenol sulfuric acid method. Three hydrolysates having sugar levels 30.42 g/L, 31.79 g/L, and 32.9875 g/L were selected for fermentation. Response surface methodology, Box-Behnken experimental design with design expert version 11.1.0.1 was applied to randomize and analyze the effects of the variables encountered in fermentation experiments. The experiments were done using the selected hydrolysates, varying size of inoculum (5 %, 10 %, and 15 %), and pH (4.5, 5, and 5.5) at 30 ℃ for 72 hours. The fermented samples were finally centrifuged and evaporated for purifying the ethanol. The yield of ethanol was determined after determining the percentage ethanol using digital density meter. FTIR analysis was done to determine the functional group of the product obtained and the result showed O-H, C-O, and C-H peaks similar to the standard ethanol. The results of the statistical analysis showed that all the three independent factors and the interaction between sugar level and pH affected the ethanol yield and a maximum of 0.617 mL/g yield was obtained at sugar level of 3.29875 g, pH of 5, and 15 % inoculum size. Generally, controlling fermentation parameters during the production of ethanol from sequential acidic-alkaline pretreated sorghum straw is a good choice in view of increasing yields of sugar and ethanol, decreasing dose and cost of chemicals, and minimizing waste generation.
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
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%).
Catalytic Conversion of Sugarcane Bagasse into Furfural
(Addis Ababa University, 2022-04) Negesso, Wakushie; Belay, Woldeyes (Prof.); Hundessa, Dessalegn (PhD)
The production of furfural, high-value-added platform chemicals, is hampered by the typical drawbacks of homogeneous acid catalysts, such as difficulty in separating the catalyst from the reaction mixture. As a result, developing a heterogeneous catalyst to overcome the limitations of current commercial processes is highly desirable. The carbon-based catalysts were synthesized by carbonizing and functionalizing teff-straw as a carbon precursor in concentrated sulfuric acid simultaneously and showed the ability to dehydrate xylan/xylose to generate furfural. As shown by FTIR, the catalyst comprises functional groups such as –SO 3 iv H, –COOH, and –OH, which are extremely beneficial to catalytic performance. The elemental analysis of the samples also confirmed the successful attachment of sulfur to the carbon structure and XRD results, the diffraction peak at 2 from 15 to 30 o , depicted the amorphous nature of the catalyst prepared. Experimental runs, catalytic and thermal, were carried out over the prepared catalyst to investigate catalytic activities such as overall conversion, selectivity, and catalyst stability. Conversion of xylose to furfural was investigated using a Teff straw-based sulfonated catalyst (TSSC) in water/toluene as an extraction medium. A maximum furfural yield of 62.50% was obtained at 190°C for 20 min with 0.2g solid acid. Besides, hydrolysis of sugarcane bagasse to xylose using a dilute sulfuric acid catalyst was investigated. An optimum xylose yield of roughly 0.18g/g of dry bagasse was obtained in 32 minutes with 0.77% sulfuric acid at 143 °C. Model-Based Calibration Toolbox in MATLAB software was used for the design of experiments, statistical modeling, and optimization. Although the combined effect of temperature, acid concentration, and time was positive towards the formation of glucose and furfural, harsher treatment conditions showed negative effects on the yield of xylose. The experimental data were analyzed to create a kinetic model for lignocellulosic biomass conversion to furfural using the synthesized catalyst. The kinetic model for the dehydration of xylose to furfural was developed using experimental data obtained based on the Central composite design. The well-evaluated kinetic model matched well with the experimental data and kinetic parameters. The thermodynamic analysis suggested that the presence of toluene, in the reaction system, as a solvent for instantaneous extraction of furfural enhanced furfural production while decreasing degradation rate as compared to water-only system.
CFD Modeling and Simulation on Hydrodynamics of CFB Biomass Gasifier using FLUENT
(Addis Ababa University, 2011-07) Kebede, Beniyam; Kiflie, Zebene (PhD)
Biomass gasification in Circulating fluidized beds (CFB) is one of the most promising conversion processes in meeting future ecologically compatible and sustainable energy demand, based on a combination of flexibility, efficiency, and environmental acceptability. Widespread industrial use of CFB technology in coal and biomass combustion and gasification depends on improved control of the fluidization process that demands a better understanding of fluidized bed hydrodynamics. However, its application to CFB systems is limited due to the high computational requirements for understanding complex fluid flow behavior. The effect of different operating parameters on the hydrodynamic behavior of a two-phase gas-solid CFB biomass gasifier were studied in this thesis work systematically using computational fluid dynamics (CFD) software FLUENT. Both 2-D and 3-D computational fluid dynamics (CFD) model based on Eulerian-Eulerian approach coupled with granular kinetic theory is developed to simulate the hydrodynamics and flow structures of the CFB under different operating conditions. A parametric analysis is performed to comprehensively investigate the influences of particle properties (Bagasse, sand and its sizes), operating parameters (gas velocity and solid circulation rate) and gasifier geometries (inlet structure/position). The dynamic characteristics obtained from CFD simulation have been compare ed with the some similar conditions experimental data obtained from open literatures and in general a good agreement has been observed. Eulerian-Eulerian granular multiphase flow model approach is capable of predicting the core-annulus structure in CFB. The lower region of the CFB riser is denser than the upper-dilute region. Back-mixing behavior or accumulation of particles near the wall has been perfectly exist in the CFB. Increasing solids flux slows down the flow development, but increasing superficial gas velocity makes the flow development faster. Superficial gas velocity has a strong influence on the axial solids velocity. The volume fraction of big particles is lower in the upper. This hydrodynamics model provides the powerful theoretical basis for next steps on CFB designs. This study proposes that the operating parameters (solid circulation rate and gas velocity) and solid inlet geometry may be the critical consideration in order to reduce non-uniform distribution of gas and solid in CFB gasifier.

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