Browsing by Author "Toledo Cayuleo, Felipe Rodrigo"

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    Effect of heat transfer on the pressurization, extraction, and depressurization stages of a supercritical CO2 extraction process. 1. Development and validation of the heat transfer model
    (2023) Toledo Cayuleo, Felipe Rodrigo; Del Valle Lladser Jose Manuel
    We modeled and simulated the heat and mass transfer in the depressurization, pressurization, and extraction stages of a supercritical CO2 extraction process. Parameters of a Nusselt correlation for convective wall-to-fluid heat transfer coefficient were best fitted to experimental temperatures during the depressurization of vessels packed with different materials. Heat transfer in the pressurization and extraction stages was simulated predictively using this correlation and compared with literature laboratory-scale, pressurization, and extraction data. In depressurization, simulated temperature, pressure, and vented mass flow profiles agreed reasonably well with experimental values, as the calculated Mean Absolute Percent Error (MAPE) was 1.8% for the temperature. For pressurization, simulated values of final temperatures and pressures fell within a standard deviation of experimental data, estimating a MAPE of 3.9% for temperature and 5.2% for pressure. In the extraction stage, including radial and axial temperature gradients in the mass transfer model reduced the error (about 2%) of simulated cumulative extraction curves against experimental values compared to those obtained when neglecting radial variations in temperature. These results are significant because they prove that heat transfer phenomena may impact industrial more considerably than laboratory-scale processes.
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    Effect of the heat transfer on supercritical CO2 extraction of solid substrates: Modeling and quantification of the impact at industrial level
    (2024) Toledo Cayuleo, Felipe Rodrigo; Valle Lladser, José Manuel del; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    La modelación y simulación de la extracción de sustratos sólidos con CO2 supercrítico es una herramienta útil para optimizar extracciones, escalar resultados y diseñar plantas industriales. Sin embargo, los modelos de transferencia de masa para este proceso incluyen suposiciones que pueden ajustarse en extracciones de laboratorio, pero que es difícil controlar a grandes escalas. El objetivo de esta tesis fue evaluar el efecto de relajar la suposición de temperatura constante durante el proceso y cuantificar su impacto en extracciones en plantas industriales. Esta tesis presenta un programa de simulación de plantas con múltiples extractores y un modelo de transferencia de masa y calor que estima perfiles de temperaturas durante las etapas de despresurización, presurización y extracción, los cuales son considerados en el cálculo de las curvas de rendimiento de extracción. El simulador de plantas industriales mostró la importancia del número de extractores y el tiempo de ciclo para evaluar la productividad de estas plantas. Un modelo unidimensional para la transferencia de calor en estado estacionario fue ajustado con datos de extracciones (en un extractor de 1 litro) con gradientes de temperaturas impuestos (a 48 MPa, con CO2 a 40 °C con la pared del extractor a 60 °C y viceversa). Al aplicar los perfiles de temperatura calculados en el modelo de transferencia de masa, las curvas de extracción simuladas coinciden con los datos experimentales de la extracción con gradientes impuestos. El modelo de transferencia de calor fue expandido para considerar un sistema transiente y variaciones axiales y radiales de temperatura, junto con las etapas de despresurización y presurización. Una nueva correlación para estimar la transferencia de calor por convección pared-fluido fue ajustada con datos experimentales de despresurización, y su uso fue validado en el modelo por medio de la simulación y comparación con datos experimentales de las etapas de presurización y extracción. Finalmente, este modelo general de transferencia de calor y masa fue aplicado en la simulación de una planta industrial con dos extractores (volumen de 1 m3) para evaluar el efecto de los gradientes de temperatura formados durante las etapas de reacondicionamiento en las curvas de extracción. Para una extracción a 48 MPa, con el CO2 y el fluido de servicio en contacto con la cara externa del extractor a 60 °C, las diferencias entre el caso no isotérmico y el isotérmico no superan un 9%, incluso variando velocidad superficial del CO2 y el tamaño de partícula. Estas diferencias aumentan significativamente hasta un 36% cuando las condiciones del proceso aumentan a 70 MPa y 80 °C, cuando el tiempo de extracción es de 10 minutos.
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    Simulation of a flexible multi-vessel extraction plant with counter-current contacting between a solid substrate and supercritical CO2
    (2023) Toledo Cayuleo, Felipe Rodrigo; García Serna, Juan; Nunez, Gonzalo A.; Valle Lladser, José Manuel del
    This work develops a program (MVSEPS) to simulate a multi-vessel SuperCritical Fluid Extraction (SCFE) plant operating in a counter-current fashion. MVSEPS was applied to an SCFE to extract hemp seed oil using the shrinking core mass transfer model. A microstructural factor was best-fitted to experimental data from literature, to describe the inner mass transfer of the oil within the substrate, that was used as a parameter in subsequent simulations. The oil concentration in the CO2 stream exiting an extraction vessel, and the productivity, and efficiency of the SCFE plant were studied by changing selected parameters of the process and extraction conditions. The number of extraction vessels operating in series and the cycle time were relevant simulation parameters, because they cannot be studied experimentally at a laboratory scale. Using a larger number of extraction vessels and shorter cycle times increase the plant productivity but decrease the extraction efficiency. Other parameters studied, such as the particle size of the milled substrate, superficial CO2 velocity, extraction temperature and pressure, impact the operation of the SCFE plant similarly to at laboratory scales.
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    Supercritical CO2 extraction of pelletized oilseeds : Representation using a linear driving force model with a nonlinear sorption isotherm
    (2021) Toledo Cayuleo, Felipe Rodrigo; Del Valle Lladser, Jose Manuel; Opazo, Álvaro P.; Núñez, Gonzalo A.
    This work develops a general, predictive model for the SuperCritical (SC) CO2 extraction of pelletized oilseeds. Cumulative SC-CO2 extraction curves of small (S, dp = 2.5 mm) and large (L, dp = 4.0 mm) cylindrical evening primrose seed pellets were modeled simultaneously using a Linear Driving Force (LDF) approximation modified to consider the nonlinear oil partition between CO2 and the substrate and extrapolated using the actual solubility of oil in CO2 at extraction conditions (40 °C and 45 MPa). Model best-fitting parameter was a single interparticle porosity (εp) of pellets considering equilibrium conditions after static extraction, and mass transfer kinetics during dynamic extraction. The adaptation of general model to bisized mixtures containing 25–75% S-pellets, predicted experimental results better than a monosized version (same Sauter mean diameters) because of the negative impact on overall cumulative extraction curves of slow-extracting L-pellets. Finally, a simplified version of the general model was developed that neglected the intraparticle porosity (εp = 0) and used a microstructural factor () in the general model as the best-fitting parameter. This simplified model saved 33% of computational time at the expense of overestimating extraction rates, particularly at the beginning of the diffusion-controlled period, which diminished as εp decreased and FM increased.
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    Temperature gradients within the packed bed affect cumulative supercritical CO2 extraction plots for oilseeds
    (Elsevier B.V., 2022) Toledo Cayuleo, Felipe Rodrigo; Lorca Cáceres, Christopher Andrés; Del Valle Lladser, José Manuel; Fiori, Luca
    We studied the effect of temperature gradients within a packed bed on the SuperCritical (SC) CO2 extraction of oil from pelletized cranberry seeds. Temperature gradients were imposed on the extractor by using different temperatures for the SC-CO2 flow and the extractor vessel wall in heating and cooling experiments (60 and 40 °C, and viceversa) for oilseed pellets and glass beads at 48 MPa. A two-phase heat transfer model and a linear-driving-force mass transfer model described temperature profiles and oil extraction curves. Overall, temperatures in the packed bed were more affected by the vessel wall than the SC-CO2 inlet condition. Extraction curves for heating and cooling experiments were between the isothermal extraction curves for 40 and 60 °C, being affected by the vessel wall temperature in the solubility-controlled period of the extraction and approaching each other after 1-h of dynamic extraction. Both heat and mass transfer models allowed a satisfactory prediction of such a behavior and represent a step forward in the prediction of SC-CO2 oil extraction course.