Browsing by Subject "blending"
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Item Application and modeling of near-infrared frequency domain photon migration for monitoring pharmaceutical powder blending operations(Texas A&M University, 2006-10-30) Pan, TianshuFrequency domain photon migration consists of launching an intensitymodulated near-infrared light into the powder medium and measuring the amplitude, mean-intensity, and phase shift of detected intensity modulated light for extracting both the isotropic scattering and absorption coefficients of the powder bed. The dependence of absorption coefficient upon the active pharmaceutical ingredient (API) concentration of powder blend enables FDPM to monitor blending homogeneity. The volume sampled by FDPM in powder blend was investigated through a designed heterogeneity experiments. A model which describes the visitation probability of a local region by migrating photons was developed to theoretically determine the sampled volume of FDPM in terms of signal-to-noise ratio. The applicability of FDPM in monitoring blending homogeneity was directly verified by measuring the API contents in a series of industrial samples, which were retrieved from various locations at various times in an actual pharmaceutical blending process. The FDPM measurement results were consistent with the traditional analysis using high performance liquid chromatography. The homogeneity evolution revealed through FDPM agreed with the well-established first order model of blending. A simulation method was developed which consisted of (i) dynamic simulation for generating the powder structure; (ii) the completely-randommixture model for predicting the spatial distribution of API particles within the powder bed; and (iii) Monte Carlo simulation for tracking photon trajectories within the powder bed. The simulation of photon migration in powder blend revealed that while both the isotropic scattering and absorption coefficients increased with the solid-volume fraction, the ratio of absorption coefficient to the isotropic scattering coefficient is (i) independent of the solid-volume fraction; (ii) linearly dependent upon the API concentration; and (iii) appropriate for monitoring the powder blending homogeneity under simultaneous variations of solid-volume fraction and API content. Finally, a rigorous two-speed diffusion equation for describing photon migration in powders was derived from the two-group radiative transfer equations and the analytical expression of the isotropic scattering coefficient was provided. The theoretical results agreed well with the experimental measurements in resin powder media and resin suspensions.Item Effect of Blending on High-Pressure Laminar Flame Speed Measurements, Markstein Lengths, and Flame Stability of Hydrocarbons(2012-02-14) Lowry, William BaughNatural gas is the primary fuel used in industrial gas turbines for power generation. Hydrocarbon blends of methane, ethane, and propane make up a large portion of natural gas and it has been shown that dimethyl ether can be used as a supplement or in its pure form for gas turbine combustion. Because of this, a fundamental understanding of the physical characteristics such as the laminar flame speed is necessary, especially at elevated pressures to have the most relevance to the gas turbine industry. This thesis discusses the equations governing premixed laminar flames, historical methods used to measure the laminar flame speed, the experimental device used in this study, the procedure for converting the measured data into the flame speed, the results of the measurements, and a discussion of the results. The results presented in this thesis include the flame speeds for binary blends of methane, ethane, propane, and dimethyl ether performed at elevated pressures, up to 10-atm initial pressure, using a spherically expanding flame in a constant-volume vessel. Also included in this thesis is a comparison between the experimental measurements and four chemical kinetic models. The C4 mechanism, developed in part through collaboration between the National University of Ireland Galway and Texas A&M, was improved using the data presented herein, showing good agreement for all cases. The effect of blending ethane, propane, and dimethyl ether with methane in binary form is emphasized in this study, with the resulting Markstein length, Lewis number (Le), and flame stability characterized and discussed. It was noticed in this study, as well as in other studies, that the critical radius of the flame typically decreased as the Le decreased, and that the critical radius of the flame increased as the Le increased. Also, a rigorous uncertainty analysis has been performed, showing a range of 0.3 cm/s to 3.5 cm/s depending on equivalence ratio and initial pressure.Item Process simulation, integration and optimization of blending of petrodiesel with biodiesel(2009-05-15) Wang, TingWith the increasing stringency on sulfur content in petrodiesel, there is a growing tendency of broader usage of ultra low sulfur diesel (ULSD) with sulfur content of 15 ppm. Refineries around the world should develop cost-effective and sustainable strategies to meet these requirements. The primary objective of this work is to analyze alternatives for producing ULSD. In addition to the conventional approach of revamping existing hydrotreating facilities, the option of blending petrodiesel with biodiesel is investigated. Blending petrodiesel with biodiesel is a potentially attractive option because it is naturally low in sulfur, enhances the lubricity of petrodiesel, and is a sustainable energy resource. In order to investigate alternatives for producing ULSD, several research tasks were undertaken in this work. Firstly, base-case designs of petrodiesel and biodiesel production processes were developed using computer-aided tools ASPEN Plus. The simulations were adjusted until the technical criteria and specifications of petrodiesel and biodiesel production were met. Next, process integration techniques were employed to optimize the synthesized processes. Heat integration for petrodiesel and biodiesel was carried out using algebraic, graphical and optimization methods to maximize the integrated heat exchange and minimize the heating and cooling utilities. Additionally, mass integration was applied to conserve material resources. Cost estimation was carried out for both processes. The capital investments were obtained from ASPEN ICARUS Process Evaluator, while operating costs were calculated based on the updated chemical market prices. The total operating costs before and after process integration were calculated and compared. Next, blending optimization was performed for three blending options with the optimum blend for each option identified. Economic comparison (total annualized cost, breakeven analysis, return on investment, and payback period) of the three options indicated that the blending of ULSD with chemical additives was the most profitable. However, the subsequent life-cycle greenhouse gas (GHG) emission and safety comparisons demonstrated that the blending of ULSD with biodiesel was superior.