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  • 1.
    Benavente, Martha
    et al.
    Department of Chemical Engineering, National University of Engineering, Managua, Nicaragua.
    Arévalo, Marcos
    Department of Chemical Engineering, National University of Engineering, Managua, Nicaragua.
    Martinez, Joaquin
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Speciation and Removal of Arsenic in column packed with chitosan2006Inngår i: Water Practice & Technology, ISSN 1751-231X, Vol. 1, nr 4, s. 2006-89Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The arsenic speciation and arsenic removal in chitosan packed column were studied. Arsenic removal experiments were carried out with an arsenic standard solution (1.0 mg/l) and drilled well water samples from Limon Mine Community at different pH, water flowrate, and volume of adsorbent material. The simulation of arsenic speciation was carried out at a pH range from 0 to 12, a temperature of 25ºC, a pE equal to 4, and a total arsenic concentration of 1.34 x 10-5 mol kg-1. According to speciation calculations arsenic is found mainly in oxidized form in the conditions of Limon Mine’s drilled well waters, dihydrogen arsenate ion (H2AsO4-), and hydrogen arsenate ion (HAsO42-) being the major species. The experiments showed that arsenic adsorption depends mainly on the pH as well as the activity of functional groups that compose the chitosan structure. At pH 3 and volume of adsorbent material of 337.8 cm3 an adsorption of 94% was obtained from arsenic standard solution, and the arsenic present in the Limon Community’s water was almost totally removed at pH 3 and 7. The use of the results for designing purposes demands the breakthrough curves for chitosan to be determined.

  • 2.
    Benavente, Martha
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Especiación Acuosa de Cianuro y Componentes Derivados en Lavados de Colas de Minerales de Oro2006Inngår i: Nexo, ISSN 1818-6742, Vol. 19, nr 1, s. 1-9Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [es]

    En este trabajo se simuló la especiación del cianuro y componentes relacionados en soluciones de lavado de colas cianuradas de minerales de oro de la Mina El Limón, utilizando el programa geoquímico PHREEQC. Se consideró un modelo de especiación iónica formado por un conjunto de reacciones químicas y de especies principales en fase acuosa (hierro, cobre, cinc, calcio y aluminio, cloruro y cianuro), en distintas condiciones de pH, Eh y concentraciones de cianuro. Las simulaciones muestran que las concentraciones de las especies iónicas y complejas dependen principalmente del pH de la solución y de la concentración de cianuro disponible en el sistema, reproduciéndose en forma satisfactoria los valores de pH y solubilidad de metales medidos en el sistema. El cianuro forma complejos de alta estabilidad química con los metales disueltos, observándose que las especies de Fe-CN son altamente estables incluso a pH ácido donde prácticamente no existe el ión cianuro libre (CN-) producto de la formación del componente gaseoso HCN.

  • 3.
    Benavente, Martha
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära. National University of Engineering (UNI), Nicaragua.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Martinez, Joaquin
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Sorption of heavy metals from gold mining wastewater using chitosan2011Inngår i: Journal of the Taiwan Institute of Chemical Engineers / Elsevier, ISSN 1876-1070, E-ISSN 1876-1089, Vol. 42, nr 6, s. 976-988Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study is concerned with the use of chitosan produced from shrimp shell waste for the removal of Cu(II), Hg(II), Pb(II) and Zn(II) from gold ore tailing solutions containing cyanide. This work involved the study of equilibrium and kinetic adsorption, the physicochemical characterization of mining effluents and desorption using different regenerating solutions. The experimental results showed that the adsorption capacity of chitosan is a function of the solution pH and that the optimum pH for these metallic ions is 6, except for Hg (pH 4). The equilibrium data were described using the Langmuir, Freundlich, Redlich-Peterson and SIPS isotherm models. The Langmuir equation was used to find the maximum adsorption capacity for Cu (79.94 mg/g), Hg (109.55 mg/g), Pb (58.71 mg)g) and Zn (47.15 mg/g). To determine the rate-controlling mechanism for metallic ion adsorption, pseudo-first-order, pseudo-second-order and the Elovich equation kinetic models were tested with experimental adsorption kinetic data. Tests conducted with gold ore tailing solutions indicated that chitosan is effective to remove these metallic ions above 70%. Desorption studies revealed that the regeneration of chitosan saturated with these metallic ions depends on the type and concentration of the regenerating solution ((NH(4))(2)SO(4), H(2)SO(4), HCl, NaOH and NaCl).

  • 4.
    Benavente, Martha
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Adsorption Kinetic of Copper and Zinc from Binary Solutions using Chitosan2010Inngår i: Hydro Process 2010: Proceedings of the 3rd International Workshop on Process Hydrometallurgy / [ed] Marcelo Jo, Juan Patricio Ibáñez, Jesús Casas, Santiago, Chile: GECAMIN, 2010, s. 22-23Konferansepaper (Fagfellevurdert)
  • 5.
    Benavente, Martha
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Biosorption of Lead using Chitosan2009Inngår i: Advances in Chitin Science, Volumen XI: EUCHIS 2009 / [ed] Franco Rustichelli, Carla Caramella, Sevda Senel, Kjell M. Vaarum, Venice, Italy, 2009, s. 487-492Konferansepaper (Fagfellevurdert)
  • 6.
    Benavente, Martha
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Production of Glucosamine Hydrochloride from Crustacean Shell2011Inngår i: Advances in Chitin Science, Volume XIII: EUCHIS 2011 / [ed] Valery Varlamov, Svetlana Bratskaya, Irina Yakovleva, Sevda Senel, SAINT-PETERSBURG, RUSSIA, 2011, s. 29-35Konferansepaper (Fagfellevurdert)
  • 7.
    Benavente, Martha
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Sjörén, Anna
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Remoción de Mercurio de Efluentes Mineros por Biosorción2007Inngår i: Nexo, ISSN 1818-6742, Vol. 20, nr 2, s. 47-55Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [es]

        La minería y la extracción de oro en operaciones a pequeña escala han contribuido a la contaminación de los recursos acuáticos de Nicaragua durante décadas. En este trabajo se investigó un proceso de biosorción a bajo costo para la remoción de iones mercurio (II) de soluciones estándar y de aguas naturales usando quitosano como adsorbente. La regeneración del adsorbente también fue estudiada. Los resultados mostraron que la adsorción de iones mercurio fue independiente del pH en el rango de pH 4-10 y que la capacidad se reduce considerablemente a pH 2. Los estudios de la cinética mostraron una fase inicial rápida de adsorción seguida por una fase más lenta. Por otro lado, se comprobó que los datos experimentales se ajustan al modelo de Langmuir, y se determinó, mediante el uso de este modelo, una capacidad de adsorción de 106 mg Hg/g quitosano. Una solución acuosa de NaCl demostró ser una opción barata y eficiente para la regeneración del adsorbente; además, el adsorbente mostró una capacidad de adsorción alta después de la regeneración. Se encontró que la concentración de mercurio en 4 de las 8 muestras recolectadas cerca de la ciudad de la Libertad, excedían ligeramente los niveles permisibles (1.09-2.25 μg Hg L-1) para agua de consumo humano según las normas CAPRE. Además, se determinó que la capacidad de adsorción de mercurio es menor en aguas naturales que en las soluciones estándares.

  • 8.
    Benavente, Martha
    et al.
    National University of Engineering, Nicaragua.
    Sjörén, Anna
    KTH, Skolan för kemivetenskap (CHE).
    Westergren, Robin
    KTH, Skolan för kemivetenskap (CHE).
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Martinez, Joaquin
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Biosorption of Heavy Metals on Chitosan2007Inngår i: Hydro Copper 2007 / [ed] Jorge M. Menacho and Jesús M. Casas de Prada, Santiago, Chile: GECAMIN Ltda. , 2007, s. 283-290Konferansepaper (Fagfellevurdert)
  • 9.
    Benavente, Martha
    et al.
    National University of Engineering, Nicaragua.
    Álvarez, Erick
    National University of Engineering, Nicaragua.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Martinez, Joaquin
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Removal of Copper and Zinc from Gold Ore Tailings Solutions using Chitosan2008Inngår i: Hydro Process 2008 / [ed] Jorge M. Menacho and Jesús M. Casas de Prada, Santiago, Chile: GECAMIN Ltda. , 2008, s. 139-152Konferansepaper (Fagfellevurdert)
  • 10.
    Espinosa, Rodolfo
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Diagramas de Equilibrio para la Extracción con Solvente de Aceite e Insecticida de Semilla Molida de Nim2006Inngår i: Nexo, ISSN 1818-6742, Vol. 19, nr 1, s. 10-17Artikkel i tidsskrift (Fagfellevurdert)
  • 11.
    Gamero, Rafael
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Luna, Fabio
    Café Soluble, S.A., Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Convective Drying of a Multicomponent Falling Film2006Inngår i: DRYING 2006: IDS 2006 / [ed] István Farkas, 2006, s. 243-250Konferansepaper (Fagfellevurdert)
  • 12.
    Gamero, Rafael
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Determinación de los Coeficientes de Difusión Multicomponente en Capilares no Saturados2006Inngår i: Nexo, ISSN 1818-6742, Vol. 19, nr 1, s. 18-26Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [es]

    Este trabajo consiste en un estudio de transferencia simultánea de calor y masa con la finalidad de determinar la matriz de coeficientes de difusión multicomponente en fase líquida. La literatura reporta una fórmula semi-empírica desarrollada por Bandrowski y Kubaczka para calcular la matriz de coeficientes de difusión multicomponente, método que separa las contribuciones cinética y termodinámica a la transferencia de masa e incluye un exponente empírico para realizar cálculos más precisos. El presente trabajo propone la estimación del exponente empírico en un amplio rango de temperaturas estudiando la redistribución de composición en un capilar no isotérmico y no saturado, tomando en consideración las no idealidades descritas por la matriz de coeficientes de factores termodinámicos. Para tal fin, se ha utilizado el sistema ternario agua-etanol-acetona a dos diferentes rangos de temperaturas y dos diferentes grados de saturación. Los resultados muestran que el método es efectivo ya que se obtuvieron valores consistentes del exponente empírico que modifica la matriz de factores termodinámicos. Además, se evidencia que el exponente es dependiente de la temperatura.

  • 13.
    Gamero, Rafael
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Determination of Multicomponent Diffusion Coefficients by Studying Heat and Mass Transfer in Partially Saturated Capillaries2005Inngår i: HEFAT 2005, Cairo, Egypt, 2005, s. GR-2Konferansepaper (Fagfellevurdert)
  • 14.
    Gamero, Rafael
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UN), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Determination of Multicomponent Diffusion Coefficients in Liquid Phase from the Liquid Composition Distribution in a Partially Filled Non-Isothermal TubeManuskript (preprint) (Annet vitenskapelig)
  • 15.
    Gamero, Rafael
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Internal mass transfer during isothermal drying of a porous solid containing multicomponent liquid mixture2005Inngår i: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 23, nr 9-11, s. 1939-1951Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Internal mass transfer in a porous solid partially saturated with multicomponent liquids has been experimentally and theoretically studied. Isothermal drying experiments were performed using a jacketed wind tunnel where the transient composition profiles and total liquid content of a cylindrical sample were determined. Sand samples wetted with the ternary liquid mixtures watermethanol-ethanol and 2-propanol-methanol-ethanol were dried at two different initial compositions and temperatures. A mathematical model including mass transfer by capillary movement of the liquid and interactive diffusion in both gas and liquid phase was developed. To simulate the capillary movement of liquid mixtures, parameters experimentally determined for single liquids where weighed according to liquid composition. A fairly good agreement between theoretical and experimental liquid composition profiles was obtained provided that axial dispersion is included in the model.

  • 16.
    Gamero, Rafael
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Liquid Transport during Isothermal Drying of a Capillary Porous Solid Containing Multicomponent Liquid Mixtures2004Inngår i: DRYING 2004: IDS 2004 / [ed] M.A. Silva and S.C.S. Rocha, Sao Paulo, Brazil: State University of Campinas , 2004, s. 452-460Konferansepaper (Fagfellevurdert)
  • 17.
    Gamero, Rafael
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Study of Heat and Mass Transfer to Determine Multicomponent Liquid Diffusion Coefficients in Partially Saturated Capillaries2007Inngår i: Experimental heat transfer, ISSN 0891-6152, E-ISSN 1521-0480, Vol. 20, nr 2, s. 147-157Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A study of simultaneous heat and mass transfer in partially saturated capillaries has been performed in order to develop a method that determines the matrix of multicomponent diffusion coefficients in liquid phase. The literature provides a semi-empirical formula developed by Bandrowski and Kubaczka [4] to calculate the matrix of multicomponent diffusion coefficients. The method separates the kinetic and thermodynamic contributions to mass transfer, and it contains an empirical exponent to improve the calculations. The present work attempts an estimation of the empirical exponent by studying the redistribution of compositions in an unsaturated nonisothermal capillary, taking into consideration the nonideality described by the matrix of thermodynamic factors. Two different ternary mixtures were tested at different temperature gradients and saturation degrees. The results reveal that the method is effective since specific values of the empirical exponent that modifies the matrix of thermodynamic factors were obtained for each system. In addition, the exponent seems to be dependent on temperature.

  • 18.
    Gamero, Rafael
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    The Effective Thermal Conductivity in a Solid containing a Liquid Mixture: An Approach from Drying Experiments2010Inngår i: DRYING 2010: IDS 2010 / [ed] E. Tsotsas, T. Metzeger, M. Peglow and A.S. Mujumdar, Magderburg, Germany: DECHEMA e.V. , 2010, s. 101-108Konferansepaper (Fagfellevurdert)
  • 19.
    Gamero, Rafael
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    The use of drying experiments in the study of the effective thermal conductivity in a solid containing a multicomponent liquid mixture2012Inngår i: Chemical engineering research & design, ISSN 0263-8762, E-ISSN 1744-3563, Vol. 90, nr 11, s. 1765-1778Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effective thermal conductivity of a porous solid containing multicomponent liquid mixtures has been studied. To achieve this, the liquid composition, liquid content and temperature distributions have been measured in a cylindrical sample dried by convection from the open upper side and heated by contact with a hot source at the bottom side. A quasi-steady state reached at high source temperatures permits to calculate the total heat flux from temperatures measured on the surface and the gas stream. The simulations performed and compared with experimental data made it possible to estimate the adjusting geometric parameter of Krischer's model for the effective thermal conductivity. The effective thermal conductivity has been widely studied for two-phase systems, mostly with regard to thermal insulation elements. The calculation of this transport parameter includes the contribution to heat transfer of the evaporation–diffusion–condensation mechanism undergone by the multicomponent mixture. The influence of liquid composition and temperature on the thermal conductivity due to the evaporation–diffusion–condensation mechanism and the effective thermal conductivity is described. The results reveal that in this case the resistance to heat transfer seems to correspond to a parallel arrangement between the phases.

  • 20.
    Gamero, Rafael
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Picado, Apolinar
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Luna, Fabio
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    AN ANALYTICAL SOLUTION OF THE CONVECTIVE DRYING OF A MULTICOMPONENT LIQUID FILM2006Inngår i: DRYING 2006 / [ed] I. Farkas, Gödöllo, Hungary: Szent István University Publisher , 2006, s. 516-523Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Analytical solutions of the diffusion and conduction equations applied to liquid-side-controlled convective drying of a multicomponent liquid film are developed. Assuming constant physical properties of the liquid, the equations describing interactive mass transfer are decoupled by a similarity transformation and solved simultaneously with conduction equation by the method of variable separation. Variations of physical properties along the process trajectory are taken into account by a stepwise application of the solution in time intervals with averaged coefficients from previous time steps. Despite simplifications, the analytical solution gives a good insight into the selectivity of the drying process and is computationally fast.

  • 21.
    Intelvi, Marco
    et al.
    University of Padova, Padova, Italy.
    Picado, Apolinar
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Contact Drying Simulation of Particulate Materials: A Comprehensive Approach2011Inngår i: World Academy of Science, Engineering and Technology (WASET) / [ed] J.A. Nelson, Venice, Italy: World Academy of Science, Engineering and Technology (WASET) , 2011, s. 1669-1676Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this work, simulation algorithms for contact drying of agitated particulate materials under vacuum and at atmospheric pressure were developed. The implementation of algorithms gives a predictive estimation of drying rate curves and bulk bed temperature during contact drying. The calculations are based on the penetration model to describe the drying process, where all process parameters such as heat and mass transfer coefficients, effective bed properties, gas and liquid phase properties are estimated with proper correlations. Simulation results were compared with experimental data from the literature. In both cases, simulation results were in good agreement with experimental data. Few deviations were identified and the limitations of the predictive capabilities of the models are discussed. The programs give a good insight of the drying behaviour of the analysed powders.

  • 22.
    Luna, Fabio
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Birgersson, Erik E.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Martinez, Joaquin
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Diffusion equation applied to isothermal drying of a multicomponent liquid film2005Inngår i: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 23, nr 11-sep, s. 1953-1975Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Liquid-side-controlled drying by convection of a multicomponent liquid film is studied. Interactive diffusion in liquid phase is considered the main mechanism for mass transfer. Assuming an isothermal drying process and a constant matrix of multicomponent diffusion coefficients, an analytical solution of the diffusion equation is developed. The equations are decoupled by a similarity transformation and solved by the method of variable separation. The solution is applied to the drying of ternary mixtures, one of them containing a component of negligible volatility. The variation of diffusion coefficients along the process trajectory was taken into account by a piecewise application of the solution in time intervals with averaged coefficients from previous time steps. Despite the simplifications made, the analytical solution gives a god insight into the selectivity of the drying process and is computationally fast. The limitations of the analytical solution and the prospect of applying the solution to the description of a nonisothermal process are discussed. It would introduce an important computational economy since the rigorous treatment of multicomponent drying leads to partial differential equations with variable coefficients, which can only be solved by time-consuming iterative procedures.

  • 23.
    Luna, Fabio
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Isothermal Drying of a Multicomponent Liquid Film2004Inngår i: DRYING 2004: IDS 2004 / [ed] M.A. Silva and S.C.S. Rocha, Sao Paulo, Brazil: State University of Campinas , 2004, s. 461-468Konferansepaper (Fagfellevurdert)
  • 24.
    Mahiques, Joan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Modelling of Leaching of Copper Oxides in Dumps and In-Situ2006Inngår i: Hydro Process 2006 / [ed] Esteban M. Domic & Jesús M. Casas de Prada, Santiago, Chile: GECAMIN Ltda. , 2006, s. 429-441Konferansepaper (Annet vitenskapelig)
  • 25.
    Martínez, J.
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Rodríguez Varela, R.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Forsberg, Kerstin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Rasmuson, Åke C.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Factors Influencing Separation Selectivity of Rare Earth Elements in Flat Sheet Supported Liquid Membranes2018Inngår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 191, s. 134-155Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Separation selectivity of the mixture Yttrium-Neodymium-Dysprosium using Bis (2-ethylhexyl) hydrogen phosphate (D2EHPA) as extractant in a flat sheet supported liquid membrane was studied by simulations. A new definition of selectivity and a diffusional-kinetic transient model were used in the calculations. Resistance distribution between the phases, stripping phase pH, extractant concentration and initial feed concentration have great influence on selectivity and process time and their appropriate management would improve separation. The analysis of selectivity using the present model would be a useful tool to design a multistage process aimed at the separation of a multicomponent mixture of rare earth elements into its constituents.

  • 26.
    Mike, León
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Lozano, Elizabeth
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Gamero, Rafael
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Mass Transfer during the Isothermal Drying of Acetylsalicylic Acid2006Inngår i: XXII Interamerican Congress of Chemical Engineering, CIIQ 2006 and V Argentinian Congress of Chemical Engineering, CAIQ 2006 - Innovation and Management for Sustainable Development 2006 22nd Interamerican Congress of Chemical Engineering, CIIQ 2006 and 5th Argentinian Congress of Chemical Engineering, CAIQ 2006; Buenos Aires; Argentina; 1 October 2006 through 4 October 2006 / [ed] Oscar Pagola, Buenos Aires, Argentina: Argentine Association of Chemical Engineers (AAIQ) , 2006Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The objective of this work is to study theoretically and experimentally the mass transfer during the isothermal drying of acetylsalicylic acid. In the first part, internal mass transfer during isothermal drying of porous bed of acetylsalicylic acid, partially saturated with single solvents has been experimentally and theoretically studied. Drying experiments with water and ethanol as single solvents were performed at different temperatures and transient liquid content profiles were determined. The parameters to describe the retention properties of the solid and the capillary movement of the liquid were determined by comparing experimental data and calculation from a developed mathematical model. In the second part, isothermal drying kinetics of a porous bed of acetylsalicylic acid was examined performing experiments in a tunnel dryer. The Crank solution to the unidirectional mass balance and the model with transport parameters developed in the internal mass transfer part were compared with the experimental drying curves. Particular characteristics reveled during the internal mass transfer experiments demands additional study on the behavior of the solid, probably closely related to dissolution and crystallization processes.

  • 27.
    Mohammadi, Maryam
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Forsberg, Kerstin
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    De La Cruz, Joaquin Martinez
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Rasmuson, Åke
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Separation of ND(III), DY(III) and Y(III) by solvent extraction using D2EHPA and EHEHPA2015Inngår i: Hydrometallurgy, ISSN 0304-386X, E-ISSN 1879-1158, Vol. 156, s. 215-224Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The equilibrium separation of trivalent rare earth elements (Nd(III), Dy(III), and Y(III)) from hydrochloric acid solution by di-(2-ethylhexyl) phosphoric acid (D2EHPA) and 2-ethylhexylphosphonic acid mono-2-ethyl hexyl ester (EHEHPA) separately and in mixtures has been studied. The effect of extractant concentration, extractant mixture composition and solution acidity has been investigated. The results show that a mixture of D2EHPA and EHEHPA provide a better separation of Y(III) from Dy(III) when the total extractant concentration is 0.06 and 0.09 mol/L, while the separation is better using pure EHEHPA at higher extractant concentration (0.15 mol/L). The separation of Nd(III) from Y(III) and Dy(III) is higher using pure D2EHPA (0.06 and 0.15 mol/L). The results show that for the complexation of the Nd(III) ions approx. 1-2 hydrogen ions/rare earth element (REE) ion are released to the aqueous phase upon binding approximately 1 extractant dimer on average. For the complexation of Y(III) and Dy(III) ions 2-3 hydrogen ions are released upon binding approximately two extractant dimers on average. Accordingly, under the conditions of this work the complexation involves not only extractant molecule dimers but also monomers or aggregated REE species to some extent, and a fraction of the REE is extracted as chloride complexes. (C) 2015 Elsevier B.V. All rights reserved.

  • 28.
    Nyberg, Malin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Leiva, José M.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Picado, Apolinar
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Gamero, Rafael
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Leaching and Drying of Neem Flakes (Azadirachta indica) to Obtain a Botanical Insecticide2008Inngår i: Nexo, ISSN 1818-6742, Vol. 21, nr 2, s. 54-64Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The purpose of this work is to experimentally study the feasibility of improving the processing of neem flakes in columns by performing the leaching of insecticide without intermediate removal of the non-polar solvent and by performing simultaneously both leaching steps. The drying of the solvents remaining in the neem flakes is also experimentally studied. The parameters chosen to be studied in the leaching part of this work is leaching time, thickness of the flakes, volume ratio of solvents, and total volume of solvents. They were all shown to have a great influence on the yield of insecticide components, but the influence of solvent ratio was the most important one. It was shown that more methanol than hexane had to be used to obtain a large yield of insecticide compounds. The yield of oil was mainly influenced of the flake thickness. In the drying part obvious conclusions are difficult to make. What can be said is that the temperature of the incoming airflow has influence on the process. Conclusions about the drying time or the drying rate are not possible to make from the results of the experiments. The variations in drying time are too large and the drying rate seems to be independent of the conditions of the previous leaching step.

  • 29.
    Picado, Apolinar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Drying of Granular Food Materials in a Continuous Vibrated Fluidised Bed Dryer2011Inngår i: IACChE 2011 / [ed] Ricardo Pérez, Santiago, Chile: Chilean Institute of Chemical Engineers , 2011, s. S4-55Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A mathematical model for the drying of grain in a continuous vibrated fluidised bed dryer was developed. A plug-flow equipment model in which, a thin layer of particles moving forward and well mixed in the direction of the gas flow was applied. Mass and heat transfer within a single wet particle was described by effective transport coefficients. Assuming constant effective mass transport coefficient and thermal conductivity, analytical solutions of the mass and energy balances were obtained. The variation of both transport coefficients along the dryer was taken into account by a stepwise application of the analytical solution in space intervals with averaged coefficients from previous locations in the dryer. Calculation results were in fairly good agreement with experimental data from the literature. The effects of operational parameters on moisture content and temperature profiles along the dryer were studied.

  • 30.
    Picado, Apolinar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Mathematical Modeling of a Continuous Vibrating Fluidized Bed Dryer for Grain2012Inngår i: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 30, nr 13, s. 1469-1481Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A mathematical model for the drying of grain in a continuous vibrating fluidized bed dryer was developed. Simple equipment and material models were applied to describe the process. In the plug-flow equipment model, a thin layer of particles moving forward and well mixed in the direction of the gas flow was examined. Mass and heat transfer within a single wet particle was described by effective transport coefficients. Assuming constant effective mass transport coefficient and thermal conductivity, analytical solutions of the mass and energy balances were obtained. The variation in both transport coefficients along the dryer was taken into account by a stepwise application of the analytical solution in space intervals with averaged coefficients from previous locations in the dryer. Calculation results were in fairly good agreement with experimental data from the literature. However, the results depend strongly on relationships used to determine heat and mass transfer coefficients; because the results from correlations found in the literature vary considerably, the correlations should be adapted to the specific equipment in order to obtain reliable results.

  • 31.
    Picado, Apolinar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Modelling and Simulation of a Vibrofluidised Bed Dryer for Solids containing Solvent Mixtures2007Inngår i: Nexo, ISSN 1818-6742, Vol. 20, nr 2, s. 56-68Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The drying of solids in a continuously worked vibrated fluidised bed dryer is studied by simulations. A model considering the drying of a thin layer of particles wetted with a multicomponent mixture is developed. Particles are assumed well mixed in the direction of the airflow and only the longitudinal changes of liquid content, liquid composition and particle temperature are considered. Interactive diffusion and heat conduction are considered the main mechanisms for mass and heat transfer within the particles. Assuming a constant matrix of effective diffusion coefficients analytical solutions of the diffusion and conduction equations are obtained. The variation of both the diffusion coefficients and the effective thermal conductivity of the particles along the dryer is taken into account by a stepwise application of the analytical solution in space intervals with averaged coefficients from previous locations in the dryer. The analytical solution represents a suitable method to study the selectivity and aroma retention during drying of foodstuffs. The solution is computationally fast; therefore, the experimental verification of this approximate model would be very useful since the rigorous treatment of multicomponent drying involves tedious and time-consuming calculations.

  • 32.
    Picado, Apolinar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Simulation of a Continuous Plug Flow Vibrated Fluidised Bed Drier2010Inngår i: COMCAPLA 2010 / [ed] Manuela Cruz-Díaz, Mexico City, Mexico: National Polytechnic Institute (IPN) , 2010, s. SIM-106Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The drying of solids in a continuous plug flow vibrated fluidised bed drier was studied by simulations. A simple equipment model described the process. The model considered the drying of a thin layer of particles wetted with a multicomponent mixture. Particles were assumed to move forward, well mixed in the direction of the airflow and only the longitudinal changes of liquid content, liquid composition and particle temperature along the drier were considered. The changes of gas composition and temperature after passing through the bed of particles were calculated by global balances in each volume element defined by a space step along the drier. Solids wetted with a liquid mixture: ethanol-2-propanol-water was used in the calculations. Simulations using the present model gave a good insight into the selectivity of the drying process and predicted correctly volatile retention during drying. The model was then used to examine the effect of the vibration intensity on the volatile retention.

  • 33.
    Picado, Apolinar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Simulation of a Two-Stage Drying System in Closed-Cycle for Aroma Retention2011Inngår i: IACChE 2011 / [ed] Ricardo Pérez, Santiago, Chile: Chilean Institute of Chemical Engineers , 2011, s. S4-56Konferansepaper (Fagfellevurdert)
    Abstract [en]

    During the drying of liquid foods, volatile substances that are present at low concentrations, which contribute to aroma and flavour of the final product, are removed together with water. Consequently, the quality of the final product depends on the amount of volatile substances that is retained during the drying process. Independently of the drying method used, it seems to be impossible to avoid completely the losses of volatile compounds when water is removed. A potential method for improving aroma retention is to dry foods in a closed-cycle dryer since a part of the volatiles should be kept within the system. With the purpose of testing this alternative, a two-stage drying system consisting of a spray dryer and a vibrated fluidised bed dryer has been studied by simulations. As moisture model, a mixture of water and organic solvents of low molecular weights was used. The process units have been divided into modules and solved sequentially to determine process variables in both gas and solid phases. Simulations showed that to keep volatile compounds circulating inside the drying system improve the retention of volatiles by the product and condensing temperature in the recovery system is the variable with main influence on the process.

  • 34.
    Picado, Apolinar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Simulation of a Vibrated Fluidised Bed Dryer for Solids containing a Multicomponent Moisture2006Inngår i: XXII Interamerican Congress of Chemical Engineering, CIIQ 2006 and V Argentinian Congress of Chemical Engineering, CAIQ 2006 - Innovation and Management for Sustainable Development 2006 22nd Interamerican Congress of Chemical Engineering, CIIQ 2006 and 5th Argentinian Congress of Chemical Engineering, CAIQ 2006, Buenos Aires, Argentina, 1 October 2006 through 4 October 2006 / [ed] Oscar Pagola, Buenos Aires, Argentina: Argentine Association of Chemical Engineers (AAIQ) , 2006, s. 01d-301Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The drying of solids in a continuously worked vibrated fluidised bed dryer is studied by simulations. A model considering the drying of a thin layer of particles wetted with a multicomponent mixture is developed. Particles are assumed well mixed in the direction of the airflow and only the longitudinal changes of liquid content, liquid composition and particle temperature are considered. Interactive diffusion and heat conduction are considered the main mechanisms for mass and heat transfer within the particles. Assuming a constant matrix of effective multicomponent diffusion coefficients and thermal conductivity of the wet particles analytical solutions of the diffusion and conduction equations are obtained. The variation of both the diffusion coefficients and the effective thermal conductivity of the particles along the dryer is taken into account by a stepwise application of the analytical solution in space intervals with averaged coefficients from previous locations in the dryer. The analytical solution gives a good insight into the selectivity of the drying process and can be used to estimate aroma retention during drying. The solution is computationally fast; therefore, the experimental verification of this approximate model would introduce an important computational economy since the rigorous treatment of multicomponent drying involves tedious and time-consuming calculations.

  • 35.
    Picado, Apolinar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Mendieta, Rolando
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Drying Kinetics of Brewer's Yeast (Saccharomyces cerevisiae)2006Inngår i: Nexo, ISSN 1818-6742, Vol. 19, nr 1, s. 49-56Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, the drying kinetics of the brewer's yeast was studied taking into account the shrinkage effect. The experimental data were obtained using three different temperatures. The volumetric and thickness shrinkage was evaluated by direct measurement. It was found that yeast shrinkage is almost isotropic and has a considerable effect on the drying rate. In addition, during the drying the yeast shows only one falling rate period and does not exhibit a characteristic drying curve.

  • 36.
    Ramírez, Javier
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Determinación de Propiedades Físicas y Parámetros de Transporte a Colas Auríferas de mina El Limón2006Inngår i: Nexo, ISSN 1818-6742, Vol. 19, nr 1, s. 57-63Artikkel i tidsskrift (Fagfellevurdert)
  • 37.
    Sidborn, Magnus
    et al.
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Casas, Jesus
    Martínez, Joaquín
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Moreno, Luis
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Two-dimensional Dynamic Model of a Copper Sulphide Ore Bed2003Inngår i: Hydrometallurgy, ISSN 0304-386X, E-ISSN 1879-1158, Vol. 71, s. 67-74Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A two-dimensional dynamic model for bioleaching of secondary copper minerals from a pile has been developed. In the model. aeration of the pile is considered to be due to natural convection caused by the density gradient in the air within the bed. The rate of sulphide mineral dissolution is modelled according to the unreacted core model. The transport of ferric ions from the particle surface to the reaction zone is calculated considering film diffusion, diffusion within the particle and reaction kinetics. The rate of oxidation of the ferrous ion by bacteria attached to the ore surface is modelled using the Michaelis-Menten relationship. The influences of temperature, dissolved ferric iron and dissolved oxygen in the leaching solution are considered in the kinetic formulation. The set of partial differential equations is solved using the FEMLAB(R) software. The model was used to study the influence of process variables on copper recovery in the bed with time. This model is a useful tool to aid the design and optimisation of industrial operations.

  • 38.
    Vargas, Marcia
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Influencia de un Sólido sobre el Secado de Mezclas Líquidas Parcialmente Miscibles2006Inngår i: Nexo, ISSN 1818-6742, Vol. 19, nr 1, s. 64-72Artikkel i tidsskrift (Fagfellevurdert)
  • 39.
    Villanueva, Melina
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Gamero, Rafael
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Instant Beans Obtained from Simultaneous Processes of Drying and Size Reduction2006Inngår i: IACChE 2006 / [ed] Oscar Pagola, Buenos Aires, Argentina: Argentine Association of Chemical Engineers (AAIQ) , 2006, s. 01d-425Konferansepaper (Fagfellevurdert)
  • 40.
    Vílchez, José F.
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Retención de Aroma durante el Secado de Extracto de Café en un Sistema Cerrado2006Inngår i: Nexo, ISSN 1818-6742, Vol. 19, nr 1, s. 73-77Artikkel i tidsskrift (Fagfellevurdert)
1 - 40 of 40
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