Chemical and Biomolecular Engineering - Theses
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ItemStudies on modeling and scale-up of ceramic hybrid pulsed column( 2018)Extraction of lithium from chloride brine in salt lakes is a separation process of great importance. It is also a promising industrial field where solvent extraction columns are likely to be used. However, the extraction solution is corrosive to traditional stainless steel column because of its high chloride content, therefore a type of novel anti-corrosive ceramic hybrid pulsed column is designed and tested in order to be considered for industrial applications, as well as a ceramic standard pulsed sieve plate column for comparison. The hydrodynamics of the two columns are tested under pilot plant conditions. For each column, effects of pulsation intensity and two phase velocities on holdup, characteristic velocity and Sauter mean diameter are investigated. Holdup of ceramic hybrid pulsed column is higher by around 50%. Correlations are proposed to predict holdup for both columns with ARD of 5.9% and 9.3% respectively. Characteristic velocity, which is key parameter in calculating column throughput, is investigated and modelled. Results show that characteristic velocities of ceramic pulsed sieve plate column are larger. Sauter mean diameter of ceramic hybrid pulsed column is smaller by around 30%. Correlations are proposed to predict the Sauter mean diameter, d_32, with ARD of 13.6% and 4.2% respectively. The higher holdup and smaller d_32 in the ceramic hybrid pulsed column contribute to larger mass transfer area and hence better mass transfer efficiency. Axial dispersion and mass transfer parameters, which are important to determine column height, are tested with a standard liquid-liquid system with medium interfacial tension, 30% TBP in Shellsol 2046–water with acetic acid as solute. Axial dispersion coefficients, E_c, of the ceramic hybrid pulsed column are less by around 50%. Effects of pulsation and two phase velocities on E_c are investigated. Correlations are proposed to predict E_c with ARD of 6.0% and 6.9% respectively. The height of overall mass transfer unit, H_ocp, of the ceramic hybrid pulsed column is less by around 40%, indicating better mass transfer efficiency. Effects of pulsation and two phase velocities on H_ocp are investigated. Volumetric mass transfer coefficients, K_oc a, for both columns are calculated. K_oc a of the ceramic hybrid pulsed column is higher by around 50%. Correlations are proposed to predict K_ox a with ARD of 12.0% and 7.0% respectively. Under proper operating condition, height of transfer unit of ceramic hybrid pulsed column can reach as low as 0.2m, showing very good efficiency. Two-phase computational fluid dynamics (CFD) models for the two columns are developed with commercial software ANSYS FLUENT. Hydrodynamic performance including two-phase distribution and velocity fields are generated. Holdup and axial dispersion coefficients are studied systematically, and CFD successfully predicts the higher holdup and lower axial dispersion coefficients for the ceramic hybrid pulsed column in experiments. CFD gives reasonable predictions for the trends of holdup and axial dispersion coefficients with pulsation intensity and two phase velocities. Predicted axial dispersion coefficients with this method are accurate. However the breakage and coalescence phenomenon of drop swarms is so complicated that the development of more accurate prediction method for holdup based on population balance model (PBM) still needs further research. A pilot ceramic hybrid pulsed column for lithium extraction from salt lake brine is designed for industrial applications. Physical properties are tested for the real system from Qinghai province, China. A MATLAB program is coded under the framework of design from first principles for the demonstration column, and its applicability is validated with experimental data. Program simulations are performed to investigate the effects of key operating parameters including two phase flow ratio and pulsation intensity. With considerations of volumetric efficiency and solvent reprocessing cost, these two parameters are determined to be V_c:V_d=1:1 and Af=1.0cm/s respectively. The demonstration column diameter and height are determined with the MATLAB program, under the operating conditions determined previously. To reach an annual yield of 10 tons/year and 99% lithium recovery in the extraction section, the demonstration column needs to have an effective height of 1.8m and an internal diameter of 0.36m.
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ItemA fundamental study of emulsions formed in a hexane-based lipid extraction from slurries of ruptured microalgae( 2018)Efficient lipid recovery is a major barrier to economical production of algal biofuels. The use of non-polar solvents is promising, as they can be recovered via centrifugation, avoiding energy-intensive evaporation of the water phase. Emulsions are central to this process. However, there is currently little understanding of the emulsion properties and how they relate to extraction and separation. This thesis investigated the fundamental physical mechanisms underlying the formation and subsequent destablisation of these emulsions in a hexane-based lipid extraction process.