Process Engineering

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Cultivation of Microalgae for Biofuel Production: Coupling With Sugar Factories
(Addis Ababa University, 2021-06) Deribew, Tefera; Abubeker, Yimam (PhD)
Due to many important characteristics of microalgae including high oil content, ability to overcome harsh conditions and high photosynthetic efficiency the production of biofuels from algal biomass has gained interest. However, large scale production of biofuel from microalgae is still uncertain primarily due to a lack of feasibility of the process and that it proves to be capital and energy-intensive. Therefore, an integration of microalgal cultivation with other processes for achieving an inexpensive nutrient and a reduced energy use has paramount importance. Coupling of microalgal biofuel production with other process such as wastewater treatment, industrial and power plants has been found helpful in increasing feasibility of the process. The main objective of the present study was to evaluate the potential of sugar factories’ wastes to support the growth of microalgae for biofuel production. A case study approach was followed considering a sugar factory, Metahara sugar factory, with annexed distillery plant. Two scenarios were considered. In the first scenario the wastewater from the sugar mill was used as the only nutrient source for the growth of the microalgae. In the second scenario the vinasse from the ethanol production plant was used as an additional nutrient source along with the wastewater from the sugar mill. Economic feasibility was also performed for the second scenario. The first scenario of the study shows that 12 mg of total nitrogen (TN) and 7.4 mg of total phosphorus (TP) per liter of wastewater could be transferred to algal growth ponds, and approximately 121 tons/year algal biomass would be produced from the integrated process. By applying all the underlined assumptions reductions of COD (mg O2/L) from 2200 to 447, BOD5 (mg O2/L) from 1200 to 207, total nitrogen, TN (mg/L) from 15 to 0.6 and total phosphorus, TP (mg/L) from 10 to 1.5 were found from the coupled process. The results from second scenario of the study showed three products: biodiesel production of 188 ton/year, biogas production of 2011000 m3/year, and bio-fertilizer production of 42 tons/year. Economic evaluation of the coupled process for the biofuel production showed that in order for the biodiesel from microalgae to be competitive with the current petroleum its minimum selling price (MBSP) needs to be reduced at least by half. Sensitivity analysis on the MBSP shows that oil content of the microalgae and nitrogen content in the waste effluents are the two dominant factors which significantly affect the feasibility of the process. This study investigated the potential of a future possible bio-refinery and environmental pollution reduction concept by coupling microalgae biomass production with sugarcane-processing factory wastes and by-products. It was found that the factory wastes and by-products have a significant potential for a viable biofuel production from microalgae. Study on the biology of the microalgae to get a robust strain with high oil content, the development of energy-efficient and cost-effective harvesting technology, and study on the development of selective, sensitive and inexpensive control methods, etc. are essential future research works for boosting viability of biofuel production from microalgae.
Extraction, Characterization and Optimization of the Sweet Basil ( Ocimum Basilicum) Essential Oil
(Addis Ababa University, 2021-03) Seblewongel, Gashaw; Abubeker, Yimam (PhD)
Essential oils are aromatic substances that found in the immune system of the plant and it is very interesting natural product in their variety application. Ethiopia has also spending a huge foreign currency to import the essential oil for its different application. This study has been carried out to extraction of essential oil from the leaves of Ocimum basilicum L. by using steam distillation extraction method. The Sweet basil (Ocimum basilicum L.) is a native plant in Ethiopia locally named as “Bessobela’’ (in Amharic). This study is more important in investigation of sweet basil as assume the one of the economy source crop for extraction of essential oil and decreasing a country foreign currency spending to import EO. A general factorial design was applied to in the analysis of results using DESIGN-EXPERT 6.08 software and linear regression model. In this study, the minimum and maximum oil yield are 0.12% and 0.8% respectively. Thus, minimum was obtained at 2hrs in the extraction of fresh sweet basil leaves and maximum oil yield of 0.8 % was obtained at a time of 4hrs in extraction of the sweet basil dried in atmospheric air. Characterization of the oil at the optimum condition yield was also carried out and also the results are shown as 0.8481��/��3 specific gravity, 1.49 refractive index value, 3.5 pH, 6.02 mpas dynamic viscosity, 205oC boiling point temperature, 78oC flash point, 5.04 mgKOH/g acid value, 56 mgKOH/g saponification value, 3.17 ml/g iodine value and 50.93 mgKOH/g ester value. The essential oil was analyzed by using GC-MS and FTIR. Then, Twenty-five components were obtained and it has been reached in monoterpene hydrocarbons, oxygenated monoterpenes, sesquitrpene and alcohol group. Generally , according to its chemical constituents , the sweet basil essential oil exhibits potent antimicrobial activity due to its richness in linalool (oxygenated monoterpene), and the Methyl chavicol (estragol) constituents of O. basilicum oil implies that EO extensively used as a flavoring, antimicrobial, antioxidant and anti-inflammatory agent.
Extraction, Optimization and Characterization of Oil from Ethiopian Jatropha Seed Kernels Using Solvent Extraction Method
(Addis Ababa University, 2017-11) Zinnabu, Tassew; Abubeker, Yimam (PhD)
In this study, the seed of Jatropha curcas was collected from Bati of Amhara Region and it was utilized for determination of proximate and mineral composition analysis of the seed, oil extraction, characterization, and optimization. The Jatropha curcas oil was extracted using normal hexane (62— 78°C) by Soxhlet apparatus. The result showed that the seed kernels consisted of: 55.30% ( w/w) oil, moisture (6.3621% w/w), total ash (5.25 % w/w), crude protein (21.59 % w/w), crude fat (46.57 % w/w), crude fiber (16.77 % w/w) and carbohydrate (3.4%w/w) as its proximate analysis; and Na (31.99 mg/100g), K (1159 mg/100g), Ca (8.65 ppm), Zn (0.308 ppm) and P (0.03g/100g) as the main mineral profile of the seed. After optimization using Design-Expert has been carried out, optimal conditions of temperature (70 C), solvent to solid ratio (10:1), and particle size (0.66mm) have been obtained and an oil yield of 55.28% by wt. was found. After the optimum values have been obtained, an experiment has been conducted and an oil yield of 54.81% by wt. was found which is closely in agreement with the result obtained from the model and the experimental observation and hence validated the findings of the optimization. Physicochemical characterization of the optimized oil yield revealed that it has the following most important properties: moisture and volatile matter (15.4883% w/w), kinematic viscosity (0.014mm o C, specific gravity (0.8567) at 20 2 o ) at 40 o C, acid value (13.0152 mg KOH g-1 oil), free fatty acid value (6.5076 % by wt.), saponification value (140.25 mg KOH g-1 oil), iodine value (104 g I2/100 g), and ash content (0.0811 % by wt.). From the FT-IR result, different functional components like alcohols, phenols, alkanes, easters, aldehydes were identified. The GC-MS analysis result of J. curcas oil showed that the presence of the following major fatty acids: oleic acid (44.61%), palmitic acid (22.55%), linolic acid (13.64%), stearic acid (8.64%), myristic acid (2.63%), 11-Hexadecenoic acid (1.85%) and other acids (6.08%).
Investigation of Heat Recovery Targets for Efficient Use of Energy in Brewery Via Thermal Pinch Analysis
(Addis Ababa University, 2019-12) Selam, Berhe; Abubeker, Yimam (PhD)
Brewing industry is currently expanding in high rate.The rising cost of energy and environmental concerns have led the brewing industry to search for techniques of reducing energy consumption in brewery operations. High energy costs and the need to reduce on CO2 emissions have brought to the fore the importance of reduction of energy usage in beer production. It is important that brewing process be analyzed to identify and evaluate opportunities for saving energy in specific process applications. In this study, pinch analysis was applied to a typical Ethiopian based large scale brewery( Meta Abo Brewery) to target for the minimum energy requirements of the process. It presents a methodology aimed at investgating the energy recovery target for the brewery by applying thermal pinch analysis; and analyzed four cases for different values of a design parameter which is minimum temeparture difference (∆Tmin). The different steps of the analysis are presented. Pinch analysis spreadsheet was used for the analysis. At the chosen minimum temperature differences with in the possible range of 0 - 45 °C, the minimum cooling and heating utility requirements of the brewery were studied and determined to be 1288.8 KW and 188.04 KW respectively and 805.19 KW of total heat recovery by two separate routes is possible for case 1. It was observed that using the technique, significant amount of energy could be recovered through process to process heat exchange in all four cases eventhough the amount of maxiumim energy recovery decreases as the minimum temperature difference increases. Furthermore, the heat exchange network(HEN) for all cases is designed. It is recommended that results from this study could be used in the design or retrofit of a heat exchanger network of the brewery for improved energy efficiency. Considerations can also be made for various values of ΔTmin with in the possible range so as to work on the economic analysis for capital and energy cost tradeoff.
Investigation of the Potential of Sugar Cane Bagasse Ash for Production of Ceramic Material (Wall Tiles)
(2019-07-09) Taresa, Miresa; Abubeker, Yimam (PhD)
Utilization of sugarcane bagasse ash (SCBA) waste as a value added material in industrial process is interested from both environmental and economic perspectives. Hence, this thesis work focused on partial replacement of quartz/silica sand by SCBA which is composed of 72.02% SiO2, 7.96% fluxing compounds (K2O, Na2O and MgO) and other minor components has been investigated to produce ceramic wall tiles, where ceramic raw materials (feldspar, kaolin and clay) have been remained constant. The compositional and mineralogical analysis of materials (SCBA and silica sand) have been performed by using atomic absorption (AA) method and x-ray diffraction (XRD) respectively. This result revealed the suitability of replacement of quartz by SCBA. The experiments have been conducted by replacing quartz with SCBA (20, 35 and 50 wt.%). Correspondingly the effects of pressing pressure at 15, 17, 19MPa and firing temperature at 1000℃, 1100℃, 1200℃ have been investigated. The physico-mechanical properties like: green, dry and fired strength, linear shrinkage, water absorption, LOI and crazing test (for glazed) of the products have been analysed. The experimental results showed that at 1100℃ firing temperature, replacement of quartz by 35% SCBA and at17MPa pressing pressure found the best for ceramic wall tiles production. Thus, from the experimental results, it was concluded that SCBA can be utilized for production of ceramic wall tiles as partial replacement for silica sand/quartz. Hence, minimization of the SCBA environmental impacts and its economic advantages have been realized.
Optimization and Characterization of Essential Oil from Coriander Seed
(Addis Ababa University, 2021-03) Firehiwot, Mola; Abubeker, Yimam (PhD)
Coriander seed (Dimblal) is both an annual and a perennial herb that has been cultivated in Ethiopia and has been used to flavoring, cooking, and fragrance rather than for medical purpose. The goal of this research was to Optimization and characterization of essential oil from coriander seed (Coriandrum sativum L.) using steam distillation method. Umbellifera, a family of coriander seed, was the raw material of experimental work. In this research, the moisture in coriander seed was first dried in an oven at 105oC, then the dried coriander seed were grind in cross beater mill with sieve size of 1mm and the sample was sieved using vibrating shaker. Finally steam distillation was used to complete the extraction. The results from experimental work were analyzed with the aid of DESIGN EXPERT 7.0 software and using general factorial design. The effect of various parameters, such as extraction time and particle size on the extraction yield of coriander oil was investigated. This work was deals with random experimental design consisted of extraction time of 2, 3 and 4hours; particle size of 1, 1.4, 1.8 and 2mm, under constant temperature (85oC), and it was conducted with three replications. In steam distillation, the maximum oil yield of 0.84% was obtained at extraction time of 4 hour and with particle size ranges of 1-1.4mm and at a 2hr of extraction time and range of 1.8-2mm particle size, the minimum oil yield of 0.02% was obtained. This shows that, a higher yield is obtained by increasing the extraction time and decreasing the particle size. Physic-chemical characterization of the oil was carried out. The extracted oil has a refractive index of 1.4699, specific gravity of 0.878, pH value of 6.2, viscosity 35 mpas, boiling point at 131oC and saponification value (16.833ml/g), iodine value (31.725ml/g), acid value (21.0375ml/g). Gas chromatography–Mass spectroscopy was used to determine the composition of coriander oil. The major components were alpha-pinene (13.4253%), Linalyl acetate (54.8565%), gamma-terpinene (4.8523%), Camphor (3.7224%), Limonene (8.3925%), Decanal (1.6571%), and beta-myrcene (4.5846%).
Preparation of Solid Acid Catalyst from Rice Husk and Investigation of Its Catalytic Performance in Esterification
(Addis Ababa University, 2017-10) Abel, Aklilu; Abubeker, Yimam (PhD)
The fundamental reaction in organic synthesis is esterification of carboxylic acid and alcohol which can produce high value of material in the areas of cosmetics, plastics, food, medicines, intermediates, etc. Furthermore, this reaction is used in the pretreatment step for biodiesel production from low cost, lower quality feedstocks (with high free fatty acid content) to improve the economics of production. The cost of utilization of virgin oil (higher feedstock with lower FFA content) as a raw material for biodiesel production constitutes 70% of the total biodiesel production cost. Homogeneous acid catalysts, such as sulfuric acid and phosphoric acid, are conventional catalysts for esterification. However, the uses of these homogeneous acid catalysts are limited in a practical application due to corrosion, environmental pollution, side reactions and a more tedious separation process. Alternatively, a number of prospective heterogeneous acid catalysts, which are easily separated from the reactants and products through suction filtration, get attractive routes for biodiesel production and could eliminate the problems mentioned above. A sulfonated carbon-based solid acid catalyst was prepared by sulfonating rice husk char with concentrated sulphuric acid and the catalytic activity was validated through the esterification of oleic acid with ethanol for biodiesel production. Characterization methods of X-ray diffraction (XRD),Fourier transform infrared spectroscopy(FT-IR), thermogravimetry analysis and acid density tests was carried out to reveal the physical and chemical characteristics of the prepared catalyst. The effects of catalyst preparation conditions and esterification reaction conditions on the performance of the catalyst were investigated using the esterification of oleic acid and ethanol as the probe reaction. The results showed that 4500C and 1100C were suitable carbonization and sulfonation temperatures respectively. The catalyst prepared at these conditions exhibited high catalytic performance and 98% conversion of oleic acid was obtained under the optimal reaction conditions with a catalyst loading of 5.73%, ethanol to oleic acid molar ratio of 10.6:1, and a reaction time of 2.65 hr. The conversion still reached 94.89% after five cycles of successive reuse, which indicated that the catalyst stability was excellent. These results clearly show that the rice husk-derived catalyst is promising, economic and eco-friendly for biodiesel production from low-cost feedstocks and potentially substituted for homogeneous sulfuric acid catalyst for esterification in industries in the near future.
Production and Characterization of Biodiesel from Moringa Stenopetala Seed Oil via Catalytic Transesterification Process
(Addis Ababa University, 2021-07) Gemechu, Yadeta; Abubeker, Yimam (PhD)
The energy demand of the world is increasing from time to time. Depletion of petroleum reserves, the rising price of petroleum fuels and environmental pollution are the major problems of the countries including Ethiopia. These problems pushed the researchers to focus on renewable energy sources such as biodiesel. Biodiesel is a clean and alternative energy source derived from natural fats or vegetable oils. This study investigated production of biodiesel from moringa stenopetala seed oil via catalyzed transesterification process. The optimum process parameters for soxhlet extraction of oil were: 80 °c, 5 hours and 5:1 for temperature, extraction time and hexane to sample ratio respectively. Biodiesel was produced from purified oil by catalyzed transesterification reaction. Experimental design and statistical analysis was done by Design Expert 11.0 software. The optimization of process parameters of transesterification reaction: methanol to oil ratio, temperature and catalyst load was carried out by response surface method (RSM). The experimental result showed that the maximum biodiesel yield was obtained at optimum conditions of temperature 55°c, methanol to oil ratio 6:1 and catalyst loading 1.0 %. The main physicochemical properties of oil and biodiesel were determined according to international ASTM and EN standards. It was found that MSSO biodiesel moisture content 1.4 %, pH 7.9, specific gravity 0.874 g/mole, kinematic viscosity 4.8 mm2/s ,acid value 0.4, saponification value 196 mg KOH/g, free fatty acid 0.2 %, iodine value 104,2 g I2/100 g , calorific value 43 MJ/KG, flash Point 184 °c , fire point 190 °c ,pour point 1 °c ,cloud point 10 °c and cetane number 53. Whereas, moisture content, density, kinematic viscosity, acid value, saponification value and free fatty acid of oil were 6.54%, 840 kg/m3, 9.4 mm2/s, 1.6 mg KOH/g. 189 mg KOH/g and 0.8 % respectively. These results agreed with international standards values and previous research works.
Production of Eco Bricks Using Tannery Sludge as a Partial Substitute for Clay
(Addis Ababa University, 2021-10) Haregewoin, Nida; Abubeker, Yimam (PhD); Lemma, Dendena (PhD) Co-Advisor
Tannery sludge is an unavoidable by-product of waste water treatment plants of leather industries and with no safe disposal options; it has the potential to become a significant environmental burden for Ethiopia in the future. Presently, the sludge generated from the leather industries will be land filled without any kind of treatment. Because sludge contains a high concentration of organic and inorganic components, including heavy metals, its accumulation is a burden on the industry and has negative consequences for the environment and human health. As a result, an alternative sludge disposal strategy is required. The major goal of this research was to see if using TS with certain proportions in the manufacturing of bricks may be a viable alternative to natural clay. In laboratory-controlled conditions, clay bricks were made with various proportions of sludge (10%, 15%, 20%, and 25% by weight) with firing temperature of 800℃, 900℃ and 1000℃and its potential as a construction material was evaluated based on its Compressive strength, water absorption, weight loss on ignition, bulk density, firing shrinkage, electrical conductivity and heavy metal leaching properties. As a result, increasing the sludge content in bricks resulted in a decrease in compressive strength and increase in water absorption. When TS content was increased from 0% to 25%, the compressive strength of TS bricks decreased significantly, from 30.24 MPa to 20.15 MPa. Water absorption increased from7.03% to 16.03% when sludge proportion was increased from 0% to 25% at firing temperature of 1000°C. In addition, total shrinkage and weight loss in burning were compared to raw brick, revealing that total shrinkage did not differ significantly, while weight loss in burning varied from 12.25 % to 30.8 % in raw brick to 25% TS brick at firing temperature of 1000°C. Furthermore, the sludge altered up to a 15% mixing ratio demonstrates minimal heavy metal leachability as analyzed by TCLP and is compatible with the USEPA standard. As a result of the research, tannery sludge has the potential to be used in the production of sludge bricks with sludge proportion of 10% to 15% and firing temperature of 900°C to1000°C.
Production, Optimization and Characterization of Essential Oil From Spearmint Leaves
(Addis Ababa University, 2019-06) Gebremichael, Gebrehiwot; Abubeker, Yimam (PhD)
The national consumption of essential oils in Ethiopia is increasing very fast. Production technology is an essential element to improve the overall yield and quality of essential oil. The objective of this study was the production, optimization and characterization of oil from spearmint leaves using hydro distillation method. The effect of three factors, drying methods (shade, sun and oven drying), drying duration (0, 3 and 7 days) and distillation time (1, 1.5 and 2 hours) on the oil yield was investigated. This paper includes the physical properties of spearmint oil like, density (0.915), refractive index (1.43), pH (6.06) and dynamic viscosity (0.47mPaS).And the chemical properties; saponification value (41.83), acid value (0.045), peroxide value (0.67) and iodine value (17.8) were determined. Design expert software was used to optimize the oil yield and examine the effect of the three factors. General factorial design was chosen for the above mentioned optimization as well as for the data analysis (ANOVA).Then from this study, the best operating conditions are found as drying method (shade), drying time (7 days) and a distillation time of 2 hours. At this condition, a maximum yield of 2.27 % oil is obtained. This research also determined the chemical composition of the oil. From GC/MS result 41 components were obtained.

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