Browsing by Author "Raphael, Matheo L."
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Item Bubble Size and Gas-Liquid Interfacial Area Measurements Using Molten Paraffin Waxes in Bubble Columns(American Institute of Chemical Engineers, 1987) Bukur, Dragomir B.; Patel, Snehal A.; Daly, James G.; Raphael, Matheo L.Experiments were conducted in 0.05 m ID and 0.23 m ID by 3 m tall bubble columns with different types of molten waxes as the liquid medium and nitrogen as the gas, under processing conditions typical or Fischer-Tropsch synthesis over iron catalysts (i.e. gas velocities up to 0.15 m s, and temperatures between 200 and 270/sup 0/C) to estimate gas liquid interfacial area from measured values of average gas hold-up and Sauter mean bubble diameter. The gas hold-up was estimated from visual observations of the expanded and static liquid heights, and the Sauter was estimated from bubble size measurements obtained by photography and dynamic gas disengagement. The paraffin wax (FT-300) used in the authors' studies is non-coalescing and has a tendency to foam. The amount of foam is greater for runs conducted in the order of increasing gas velocities, than in runs with decreasing velocities. Thus, two values of hold-up are possible and the start-up procedure determines which one will be attained. At higher gas velocities (> 0.05 m/s) the foam disappears and a transition to the slug flow, churn-turbulent regime takes place. Reactor waxes are coalescing in nature and do not produce foam. Despite similar hold-ups for the different waxes at higher gas velocities, the Sauters are significantly different and this is reflected in the specific gas-liquid interfacial areas, with larger values obtained with the paraffin wax compared to values with reactor waxes.Item EOS Model and Black-Oil PVT Table Generation for a Tanzanian Reservoir(International Journal of Applied Science and Technology, 2019) Mkinga, Oras Joseph; Kleppe, Jon; Rwechungura, Richard Wilfred; Raphael, Matheo L.Tuning of an EOS model and generation of Black-oil PVT tables for a gas field in Tanzania, here named R reservoir, are presented. The Soave-Redlich-Kwong equation of state was tuned using experimental data and PhazeComp software to obtain the EOS model which represents fluid behavior change in the R reservoir. A contribution is provided in a relationship between specific gravity and molecular weight, which is a modified form of Soreide equation for C7+ characterization. Constants of the equation are determined using linear regression to fit experimental data. A residual oil in the reservoir is recognized using EOS calculation; PVT data generated in this paper can be used to study its potential to condensate blockage and well deliverability. Gas and oil PVT tables are generated for saturated and undersaturated condition, they can be used in reservoir simulation of R reservoir.Item Hydrodynamics of Fischer-Tropsch Synthesis in Slurry Bubble Column Reactors(1987) Bukur, Dragomir B.; Daly, James G.; Patel, Snehal A.; Raphael, Matheo L.; Tatterson, Garry B.An improved photographic technique was employed to obtain pictures, for bubble size analysis, in experiments conducted in the Unit AMk2G (511 cm ID, 305 cm tall glass column)] During these experiments measurements of the average gas hold-up were made at 200 and 265oc using FTk300 paraffin wax as the liquid medium and nitrogen as the gas. Additional experiments were performed adding oxygenates, stearyl alcohol and stearic acid, (5 - 10 % by weight) to the wax at a temperature of 265°C. The addition of oxygenates did not have a significant effect on the average gas hold'up.Item Isoelectric Precipitation of Sunflower Protein in a Tubular Precipitator(Wiley, 1995) Raphael, Matheo L.; Rohani, S.; Sosulski, F.Isoelectric precipitation of sunflower protein was carried out in a 10-m long, 6-mm internal diameter glass tubular precipitator. The effects of feed flow rate, protein concentration in the feed stream, and volumetric feed ratio of precipitant (HCl aqueous solution) to protein solution on solid protein recovery and particle size distribution were studied. The dispersion range of the tubular precipitator was modelled to predict the experimental results. Calculated initial growth rates of protein particles were found to: increase with increases in feed flow rate and protein concentration in the feed stream, and decrease with increases in volumetric feed ratio.Item Isoelectric Precipitation of Sunflower Protein in an MSMPR Precipitator: Modelling of PSD with Aggregation(Elsevier, 1996) Raphael, Matheo L.; Rohani, S.Isoelectric precipitation of sunflower protein was carried out in a 273 ml MSMPR precipitator. Experimental results showed a bimodal particle-size distribution (PSD) of protein particles when the solids concentration or the mean residence time was low. Increasing the solids concentration and the mean residence time transformed the bimodal PSD to a unimodal PSD. Protein particle growth by turbulent collision mechanism and breakage by shear mechanism were modelled using an approach similar to Glatz et al. A.I.Ch.E. J.32, 1196–1204 (1986). The model results showed that the breakage of large aggregates results in the birth of two daughter fragments. Also at high solids concentrations the particle growth rate was linear with respect to particle size. At low solids concentrations the growth rate constant was larger than the breakage rate constant and vice versa at high solids concentrations.Item On-Line Estimation of Solids Concentrations and Mean Particle Size Using a Turbidimetry Method(Elsevier, 1996) Raphael, Matheo L.; Rohani, S.On-line measurement of solids concentrations was performed using a turbidimetry method. Four different samples (PVC, sand, protein and KCl particles) with solids concentrations up to 10 wt.% were used in this study. At higher solids concentrations the measured light intensity approached zero. The extrapolated Beer-Lambert's equation in polynomial form, ln (transmission) as a function of ln(solids concentration), was found to best fit the experimental data. For protein particles with mean sizes less than 50 μm the fifth or sixth order polynomial equation was required to give the best fit (regression coefficient greater than 0.98). Whereas, larger particles were best fit using Beer-Lambert's equation with the mean particle size as one of the parameters. Transmission data from samples with unimodal particle size distribution (KCl samples) were used to estimate the optical parameters of the KCl suspension. With known optical parameters and on-line turbidity and solids concentrations the mean particle size of the flowing suspension was estimated. The calculated and experimental mean particle sizes are within ± 10%.Item Protein in a Tubular Precipitator(1997) Raphael, Matheo L.Item Recovery and Kinetics Study of Isoelectric Precipitation of Sunflower Protein in a Tubular Precipitator(1997) Raphael, Matheo L.Oilseed sunflower is one of the major vegetable oil sources. The residue after the extraction of oil (defatted meal, DM) contains a substantial amount of nutritious protein which is recoverable by extraction and precipitation methods. For effective recovery of the solid proteins from the solids-liquid suspension, it is imperative to have large particles with a narrow spread in their size distribution and high solids concentration. In this research, up to 97 % w/w and 65 % w/w of the proteins in the laboratory and industrially defatted sunflower meals, respectively, were extracted using aqueous alkaline solutions at pH 10.0. Up to 84 % of these soluble proteins were recovered as solids when the pH was lowered from 10.0 to 4.0 (isoelecmc pH) using aqueous HCI acid. The amount of proteins recovered as solids decreased with decreasing concentrations of the acid.Item Sunflower Protein Precipitation in a Tubular Precipitator(Wiley, 1999) Raphael, Matheo L.; Rohani, SohrabIsoelectric precipitation of sunflower protein was carried out in a 20 m long, 6 mm internal diameter glass tubular precipitator. Effects of feed flow rate, protein concentration in the feed stream, and mean residence time on particle size distribution (PSD) were studied. The population balance equation (PBE) for the tubular precipitator was solved using the orthogonal collocation multiple shooting method. A simulated annealing method was used to determine the precipitation kinetic parameters for the nucleation rate, growth rate, aggregation rate, and breakage rate from the experimental data. Due to the lack of experimental data on the kinetics of sunflower protein precipitation in the literature, the extracted kinetics from our experiments were used to evaluate the predictive capability of the present model for experiments whose results had not been used to derive the kinetics. The model predictions of the particle size distribution along the tubular precipitator showed better agreement with the experimental data for large particles in comparison to the small particles (< 10 μm).