Theses and Dissertations

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Theses and Dissertations (Chemical Engineering)

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Open Access
Citric Acid Production from Cassava Hydrolysates and Molasses Using Aspergillus Niger
(2015-06-18) Alao, Mofoluwake Moronfade
This work investigated the potential of cassava and molasses as feedstocks for the production of citric acid using indigenous Aspergillus niger. This was with the view to developing indigenous biotechnological process for its production. Cassava starch was extracted from freshly harvested tubers and hydrolyzed into glucose and maltose-rich syrups using enzyme hydrolysis method, while molasses was pretreated to serve as sucrose source. The hydrolysates and molasses were used as feedstocks for the cultivation of A. niger. Fermentation was carried out under shake flask culture using the gyratory incubator shaker at a temperature of 30 °C and agitation rate of 100 rpm for ten days. Surface culture fermentation of the hydrolysates and molasses was also carried out using ten sets of 250 ml Erlenmeyer flasks for ten days. The initial pH of 4.0 and 3.0 was employed and for optimum citric acid production, different concentrations (glucose-rich syrup: 140, 180 and 235 g/L; maltose-rich syrup: 140 and 330 g/L and sucrose based molasses: 140 and 180 g/L) were used. Samples were withdrawn at 24 hour intervals and analyzed for citric acid. biomass and reducing sugars. The variation of pH profile of the cultures with time was also monitored. The results showed that the glucose-rich syrup obtained from the hydrolysis of cassava starch was able to support the growth of the microorganism used in this study. Of all the three concentrations investigated, glucose-rich syrup of 180 g/L gave the highest citric acid accumulation (17.6 g/L) on the eight day of fermentation followed by the glucose-rich syrup of 235 g/L with 11.3 g/L of citric acid accumulation on the eighth day of fermentation and lastly, glucose-rich syrup of 140 g/L with 10.1 g/L citric acid production on the fourth day of fermentation. Highest biomass concentrations obtained were 37.1, 36.1, and 32.7 g/L with corresponding glucose-rich syrup of 180, 235 and 140 g/L, respectively. For maltose-rich syrup, the highest citric acid accumulation (2.61 g/L) was obtained from 140 g/L on the third day of shake fermentation which was low when compared with 6.9 g/L obtained from 140 g/L on the seventh day of surface fermentation. These values were lower than any of results obtained for the various concentrations of glucose-rich syrup investigated in this work. The highest production of biomass observed was 29.6 g/L on the tenth day of surface fermentation. It was observed that 330 g/L maltose-rich syrup was not favourable to citric acid and biomass production; the highest accumulation of citric acid recorded on the eighth day of shake fermentation was 2.1 g/L while highest biomass production obtained was 2.6 g/L on the tenth day of fermentation. Investigations on sucrose based molasses showed that 140 g/L gave highest citric acid of 6.5 g/L on the sixth day and 180 g/L gave 11.6 g/L on the tenth day of fermentation under surface culture. The best biomass concentration throughout this work (46.1 g/L) was obtained from 180 g/L sucrose based molasses on the tenth day. The study concluded that glucose-rich syrup obtained from cassava starch hydrolysates favoured the accumulation of citric acid than maltose-rich syrup and sucrose from molasses. In addition, surface culture favoured the production of citric acid than shake culture.
Open Access
Improving Binary Distillation Column Design and Operation Using Exergy Analysis
(2015-05-14) Osuolale, Funmilayo Nihinlola
This study developed methodologies that would improve the design and operation of distillation column by reducing the irreversibility within the column and improving the column efficiency. This was with a view to minimize the consumption of energy in distillation processes. Two binary systems benzene-toluene and methanol-water were considered for this research. The performance parameters for these systems were obtained from McCabe Thiele and 'Ponchon-Savarit methods of designing distillation columns in chemical engineering. The systems were simulated using process simulator software HYSYS with capabilities for generating the thermodynamic and physical data of the components. Different variations were made for the design and simulation of the column. Exergy analysis of the data was carried out using a program developed and written in C++ language. The enthalpy versus exergy factor graph and the temperature versus exergy graph were used to identify the best operating and design variables. Also the total cost (energy and capital) was used to identify the best design variables. Efficiencies and irreversibility calculations were made for each of the design and simulation variation. The results showed that the optimum operating feed temperature for the systems were 95°C and 79°C for benzene-toluene and methanol-water systems respectively. Feed rate of the systems were 260kmol/hr and 84.4kmol/hr for benzene-toluene and methanol water systems respectively and column pressure for the systems was l atm as against feed rate of 350kmol/hr for benzene-toluene system and feed temperature of 53°C for methanol-water system. Also optimum reflux ratio for the systems was 2 for benzenexv toluene and 1.5 for methanol-water from the thermodynamic diagrams as well as from the cost analysis method. It can be concluded that the developed methodologies could be used to know the optimum operating conditions for a distillation column and the methodologies were found to be useful tools in the design and operation of energy efficient distillation column.
Open Access
Artificial Neural Network Modeling of Viscosity and Wax Deposition Potential of Nigerian Crude Oil and Gas Condensate
(2015-05-05) Oladiipo, Abiodun Koyumu
Artificial Neural Network (ANN) based models were developed for predicting viscosity and wax deposition potentials of petroleum reservoir fluids as a preliminary measure to address the problem of loss of production associated with wax deposition. Several ANN architectures were trained using supervised paradigms for viscosity modelling and unsupervised paradigms for wax deposition potentials. Input to the model for viscosity prediction was temperature and pressure data of the reservoir well, while wax deposition potential model regime. For viscosity prediction, Levenberg Marquardt (LM), Bayesian Regularization (BR), Brodyen , Fletcher, Goldfarb and Shano (BFG), Powelle-Beale Conjugate Gradient (CGB), Generalized Regression Neural Network (GRNN), Resilient Back-Propagation (RP), Scaled Conjugate Gradient (SCG), and Adaptive Gradient Descent (GDX) algorithms were used in two layers and three layers architectures with tan-sigmoid transfer function in hidden layer and linear transfer function at the output layer. Competitive layer and Probabilities neural networks algorithm were used in the wax deposition prediction model. Five Nigeria crude oil and gas condensate reservoir data were used to validate the models. The correlation coefficient of viscosity algorithm are: LM (99.84%), CBG (99.76%), SCG (99.72%), BFG (99.75%), GDX (99.71%), GRNN (98.27%), BR (41.10%). The two layer networks trained with LM algorithm for viscosity with twenty six neurons in the hidden layer gave the best performance. The viscosity model developed with ANN has correlation coefficient of 99 81%, while classical regression techniques (CRT), developed had correlation coefficient of 95%, when both techniques were validated with blind data set. ANN competitive wax deposition model developed in this work excellently identified crude oil and gas condensate potential to deposit wax in upstream and down stream facilities compared to CRT based mathematical model, when validated with Nigerian crude oil and Gas condensate. The inherent problems of pipeline blockage by wax deposits would be minimized by the application of the predicting models during well development stage prior to production.
Open Access
Modeling of an Herbivorous Digestive System as a 3-Continuous Stirred Tank Reactor (CSTR) -1-Plug Flow Reactor (Per) Arrangement with Particular Reference to Hippopotamus Amphibious
(2015-04-16) Awolu, Olugbenga Olufemi
Hippopotamus Amphibious has three stomach compartments together with small and large intestines all required in digesting lignocellulosics. It is desirable to model the performance of such a natural (in - vivo) system with the view to designing a physical (in-vitro) system for efficient digestion of lignocellulosics. Each stomach compartment in Hippopotamus Amphibious was modeled as a continuously stirred Tank Reactor (CSTR) and the small and large intestines as Plug Flow Reactor (PFR) arrangement in series in order to determine the performance of the digestive system. Monod Kinetics and Michaelis-Menten equations were used to develop the design equation (-rAM = f(X)) used for the sizing of the reactor, where -rAM is the rate of disappearance of substrate from the reactor(s) and X is the conversion. The equation was at steady state. The solutions from the design equation above are obtained graphically using Levenspiel plot and numerically, using Simpson's Rule to solve the Integrals, in order to determine the efficiency of each reactor at converting the substrates (lignocellulosics) into the final products. The result showed that 3CSTR – 1PFR arrangement in series has reactor volume of 0.5863m3, while ICSTR — 1PFR has 0.6120m3. The model of the whole system as 1PFR has reactor volume of 0.6030m3, The 3CSTR —1PFR which has the lowest value of 0.5863m3 is the best reactor arrangement to achieve efficient digestion of lignocellulosics. It could be concluded that, the Hippopotamus Amphibious digestive system is best modeled, in –vitro as a 3CSTR – 1PFR arrangement in series.
Open Access
Recovery of Heavy Oil from Nigerian Tar Sands.
(Obafemi Awolowo University, 1985) Dawodu, Olukayode Fatai; Oshinowo; Ademodi
Solvent extraction of heavy oil from Nigerian tar sands has been investigated using toluene. Pulverization, followed by sieving of the tar sand resulted in spherical agglomeration of the tar sand particles. The agglomeration was found to beneficiate the tar sands in terms of increased percent oil content to the tune of and 13% for the rich and lean tar sands respectively. The effects of solid/liquid ratio, temperature and agitation on the extraction process were evaluated factorial experimental design. Extraction efficiency was found to increase with increasing agitation speed and cuss transfer driving force, expressed in terms of solid/ liquid ratio, but decreased with increasing temperature. Of the three variables, the solid/liquid ratio the greatest effect on extraction efficiency. The rate of oil extraction, expressed as extractibility showed a great dependence on agitation. Twelve and thirteen fold increases creases in extractibility were obtained at solid/liquid ratios of 1/20 and 1/5 respectively for 2.8 fold increase in agitation (250 r.p.m to 700 r.p.m). The asphaltenes content of the heavy oil extracted at 50C was about 12% lower than that of the heavy oil extracted at 25°C for extraction times below 10 minutes. The implication of this reduction in asphaltenes level could be very significant in terms of the cost of upgrading the heavy oil. Stage-wise extraction gave high extraction efficiency at a low solid/liquid ratio. An efficiency of about 99 was obtained at a total, solid/liquid ratio of 2/3 w/v (43wt% solid loading) and agitation speed of 430 r.p.m in a three stage extraction. From an analysis of the power consumed and time ±or extraction, it was found that 440 r.p.m, 26 minutes and 440 r.p.m, 18 minutes could be the most economical agitation and time levels of operation at solid/liquid ratio- of 1/5 and 1/20 respectively.

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