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Santiago Lorenzo, Rubén

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Santiago Lorenzo
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Autor: Lemus, Jesús × Tiene archivos: true ×

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    Publicación
    Assessment of Ionic Liquids as H2S Physical Absorbents by Thermodynamic and Kinetic Analysis based on Process Simulation
    (Elsevier, 2019-09-07) Lemus, Jesús; Xiao Outomuro, Ana; Bedia, Jorge; Palomar Herrero, José Francisco; Santiago Lorenzo, Rubén
    A comprehensive evaluation of ionic liquids (ILs) as potential H2S absorbents was performed using both molecular and process simulation. First, the Conductor-like-Screening MOdel for Real Solvents (COSMO-RS method) was applied to select promising ILs absorbents and to understand the H2S gas solubility from a molecular point of view. The ILs screening more than 700 ionic combinations determines that H2S physical absorption is mainly controlled by the hydrogen-bond acceptor capacity of the anion, due to the easily hydrogen bond formation when mixed with the acidic solute. Based on molecular simulation analysis, 6 ILs of different nature were evaluated in a typical industrial packed absorption column using COSMO-based/Aspen Plus methodology. Equilibrium based simulations demonstrated higher H2S separation efficiency (i.e. lower solvent expenses and smaller equipment sizes) when increasing H2S absorption capacity of the IL solvent. In contrast, rigorous process simulation analysis (including kinetic equations) reveals a strong mass transfer kinetic control in the H2S absorption in commercial packed column, which severely limits the maximum H2S absorption given by thermodynamics. As a result, ILs that present the best performance in the thermodynamic aspect, become worse for the operation. In fact, it was found that H2S recovery at given operating conditions increases when decreasing the viscosity of IL, being 1-ethyl-3-methylimidazolium dicyanamide, the one that presents the best absorbent performance, requiring the lowest operating temperatures and liquid volume flows. Lastly, the absorption operation was designed to achieve fixed H2S recovery using different liquid/gas feed ratios, resulting in column heights and diameters inside the typical range marked by heuristic rules for usual industrial packed columns. In sum, current prospective study based on COSMO-RS and Aspen Plus have been proved as a useful tool to analyze the potential industrial application of ILs in the H2S capture and to select the most adequate ILs, before starting with experimental tests, highly demanding in cost and time.
  • Miniatura
    Publicación
    CO2 Capture by Supported Ionic Liquid Phase: Highlighting the Role of the Particle Size
    (2019-06-27) Lemus, Jesús; Hospital Benito, Daniel; Moya, Cristian; Bedia, Jorge; Alonso Morales, Noelia; Rodríguez Jiménez, Juan J.; Palomar Herrero, José Francisco; Santiago Lorenzo, Rubén
    CO2 capture by fixed-bed sorption has been evaluated using Supported Ionic Liquid Phase (SILP) based on the ionic liquid 1-butyl-3-methylimidazolium acetate ([bmim][acetate]). The SILP sorbent was prepared with three remarkably different mean particle sizes and characterized by porous texture, morphology, thermal stability, and elemental composition. The thermodynamics and kinetics of the CO2 capture process has been studied, testing the effects of SILP particle size, sorption temperature, gas flow rate, and CO2 partial pressure. The CO2 sorption isotherms at different temperatures were obtained by gravimetric measurements, revealing that the equilibrium sorption capacity is only due to the IL incorporated on the silica support of SILP. The experimental isotherms were successfully fitted to the Langmuir−Freundlich model. Fixed-bed experiments of CO2 capture were carried out to evaluate the performance of the SILP sorbents at different operating conditions. All the breakthrough curves were well described by a linear driving force model. The obtained kinetic coefficients revealed that the CO2 sorption rate in fixed-bed linearly increases when decreasing the SILP particle size and increasing the operating temperature. Higher CO2 partial pressure in the inlet gas stream led to a faster mass transfer rate, affecting both the mass transfer driving force and kinetic coefficient. Aspen Adsorption simulator was successfully applied to model the fixed-bed operation, highlighting the role of the particle size on separation efficiency. Simulations results indicate that at very low CO2 partial pressure chemical absorption is the controlling step, while increasing that partial pressure shifts the regime toward diffusion into the SILP. This methodology will allow designing CO2 sorption systems based on SILPs that fulfill the separation requirements at given conditions (CO2 partial pressure and temperature), minimizing the SILP needs by optimizing the particle size and type of IL.