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Papers by Ricardo Lobo-Oehmichen
Hydrodynamics has a strong influence on substrate elimination capacity in trickle-bed bioreactors... more Hydrodynamics has a strong influence on substrate elimination capacity in trickle-bed bioreactors (TBB). The present study reports the influence of liquid mass flow rate and bed void fraction on the TBB liquid residence time distribution (RTD), gas-liquid pressure drop, liquid hold-up, and biofilm wetting efficiency. Most RTD are well represented by a dispersion model. It is also shown that the hydrodynamic parameters increase as superficial liquid mass flow rate increases and as bed void fraction diminishes. The TBB isopropyl alcohol (IPA) mineralization capacity reach its largest values at a bed void fraction of 0.6, and the lowest are obtained when it is 0.44, when the TBB turns anaerobic due to excessive biomass growth. Overall, it is shown that the TBB performance is strongly dependent on hydrodynamics.
Educación Química, 2018
No es necesario argumentar la importancia que tiene contar con una visión lo más amplia posible p... more No es necesario argumentar la importancia que tiene contar con una visión lo más amplia posible para abordar los retos que enfrenta la educación de los ingenieros químicos (o de cualquier otro profesional). Uno de estos retos consiste en esbozar los atributos (el perfil) idealmente deseables en la persona que será el futuro profesional. La definición del perfil es un aspecto muy importante, porque concreta una visión de la persona y de los conceptos educativos de una institución de educación superior que aspira a formarla.
Computers & Chemical Engineering, 2017
A co-hydrotreating RD process for production of green diesel is proposed Thermodynamic analys... more A co-hydrotreating RD process for production of green diesel is proposed Thermodynamic analysis of the reactive mixtures was performed by PC-SAFT EoS Effect of the triglycerides and FFA content on the RD performance is investigated Simulations reveal that bio-oils with high FFA content are suitable to be hydrotreated.
Computer Aided Chemical Engineering, 2016
Abstract A systematic approach for the hydrotreating of vegetable oils and “sulfured” petroleum d... more Abstract A systematic approach for the hydrotreating of vegetable oils and “sulfured” petroleum diesel is proposed. The conceptual design of a reactive separation process that combines both, the hydrodeoxigenation (HDO) of triglycerides, free fatty acids (FFA), and biodiesel (methyl esters) and hydrodesulfurization (HDS) of petroleum diesel reactions is carried out. The systematic approach considers a thermodynamic analysis of model mixtures of triglycerides and fatty acids with hexadecane and hydrogen to determine the appropriate operating conditions (temperature, pressure and compositions blends) of the reactive separation process. The results of the thermodynamic analysis are used to propose two different reactive distillation processes to obtain the improved diesel fuel. Simulations of the reactive processes in Aspen-Plus environment were performed using the PC-SAFT equation of state. Simulation results show that the performance of the combined HDO-HDS hydrotreating process is more efficient when a pre-hydrogenation step of the triglycerides to produce free fatty acids is included.
Computer Aided Chemical Engineering, 2015
Computers & Chemical Engineering, 2010
A systematic study of the operating conditions and parameter sensibility under which multiple ste... more A systematic study of the operating conditions and parameter sensibility under which multiple steady states may occur in a reactive distillation column (RDC) for diesel deep hydrodesulfurization is presented. The multiplicity analysis is performed through ...
Computers & Chemical Engineering, 2012
The catalytic esterification of n-propyl propionate using propionic acid and n-propyl alcohol as ... more The catalytic esterification of n-propyl propionate using propionic acid and n-propyl alcohol as reactants via a conventional pilot plant reactive distillation column was carried-out. The strongly acidic ion-exchange resin Amberlyst46 TM was used as the solid acid catalyst. The influence of the reflux ratio (from 2.0 to 2.5), the molar feed ratio (from 2.0 to 2.5), and total feed (from 3.0 to 4.0 kg/h) on the purity and conversion of the species and on the composition and temperature profiles along the column was analyzed. A 2 3 experimental design with six actual and two simulated experiments was carried-out. With the experimental conditions obtained from the simulation results, the experiments showed that a reflux ratio of 2.0, a molar feed ratio of 2.0 and a total feed of 4 kg/h, yielded the largest propyl propionate production (1.60 kg/h). The simulated experiments were carried out using a non-equilibrium model implemented into the simulation environment Aspen Custom Modeler TM .
Chemical Engineering Journal, 2005
Based on a thermodynamic analysis in terms of reaction-separation feasibility, a conceptual desig... more Based on a thermodynamic analysis in terms of reaction-separation feasibility, a conceptual design of a reactive distillation column for ultra-low sulfur diesel production has been developed. The thermodynamic analysis considers the computation of reactive and non-reactive residue curve maps for a mixture that models the sulfured diesel fuel. The visualization of the reactive residue curves is posed in terms of elements. From the reactive residue curve maps, it is found that there is a high temperature region where the vaporization of hydrogen sulfide favors the elimination of the heavier organo-sulfur compounds. Considering the differences in volatility and reactivity of the organosulfur compounds and the phase behavior through the residue curve maps, a conceptual reactive distillation column design was developed. The reactive distillation column considers two reactive zones: In reactive zone I, located above the hydrocarbon feed stream, thiophene and benzothiophene are preferentially eliminated. In reactive zone II, located below the feed stream, dibenzothiophene and 4,6-dimethyldibenzothiophene (4,6-DMDBT) are mostly consumed. To validate the conceptual design, rigorous steady state simulations were performed. The design goal was stated to produce 4000 bbl/day of ultra-low sulfur diesel with a 99% conversion of 4,6-DMDBT. It is shown that reactive distillation may be considered a viable technological alternative for deep HDS of diesel.
Chemical Engineering Journal, 2005
This paper reports the effect of superficial liquid mass flow rate and bed void fraction on the p... more This paper reports the effect of superficial liquid mass flow rate and bed void fraction on the pressure drop, dynamic liquid holdup , mean liquid residence time and biofilm wetting, in a co-current down-flow xylene-removing trickle bed air biofilter (TBAB). The gas-liquid pressure drop increased with liquid mass flow rate and it also increased with diminishing bed void fraction, the effect being larger at bed void fraction of 0.41. Dynamic liquid holdup was higher with increasing liquid mass flow rate, and showed a maximum when the bed void fraction was 0.69. The same pattern was observed for the mean liquid residence time and the wetting efficiency. Liquid residence time distribution curves indicate stagnant regions, channeling, and recirculation within the TBAB, whose effects were larger at a bed void fraction of 0.41. A maximum elimination capacity of 30 g/m 3 h, with 78% removal efficiency, was reached when the bed void fraction was 0.8 and the liquid mass rate 14.1 kg/m 2 s. An average minimum elimination capacity of 6 g/m 3 h was observed at a bed void fraction of 0.41. Xylene isomers were preferentially removed in the order of o > m > p.
Chemical Engineering Journal, 2012
A simple computational procedure to determine reactive critical points of kinetically controlled ... more A simple computational procedure to determine reactive critical points of kinetically controlled reacting mixtures was developed. The thermodynamic analysis considers the simultaneous calculation of the reactive and non-reactive residue curve maps using the Peng-Robinson equation of state and the Heidemann and Khalil method for the computation of critical points. Two kinetically controlled reactive systems were considered: (i) the reversible esterification reaction of acetic acid with ethanol in the presence of CO 2 and, (ii) the irreversible hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene with tetralin as solvent for the production of ultra low sulfur diesel. It was found that the amount of catalyst loaded (˛) into the reacting vessel plays a key role for the existence of the reactive critical points for the deep HDS of diesel while for the esterification reactions has little significance. Also, results showed that, while the catalyst loaded does not have any influence on the existence of the reactive critical point for the esterification reactive system (T C ∼ 566 K; P C ∼ 68 atm; x HAc ∼ 0.39, x EtOH ∼ 0.26, x EtAc ∼ 0.15, x H 2 O ∼0.19, and x CO 2 ∼0.01), it moves the range of temperature where a maximum liquid composition of ethyl acetate can be obtained. Several critical points for the hydrodesulfurization of 4,6-DMDBT were found with different ˛ values.
Biotechnology and Bioengineering, 1999
An analysis of the local processes occurring in a trickle-bed bioreactor (TBB) with a first-order... more An analysis of the local processes occurring in a trickle-bed bioreactor (TBB) with a first-order bioreaction shows that the identification of the TBB operating regime requires knowledge of the substrate concentration in the liquid phase. If the substrate liquid concentration is close to 0, the rate-controlling step is mass transfer at the gas-liquid interface; when it is close to the value in equilibrium with the gas phase, the controlling step is the phenomena occurring in the biofilm. CS 2 removal rate data obtained in a TBB with a Thiobacilii consortia biofilm are analyzed to obtain the mass transfer and kinetic parameters, and to show that the bioreactor operates in a regime mainly controlled by mass transfer. A TBB model with two experimentally determined parameters is developed and used to show how the bioreactor size depends on the rate-limiting step, the absorption factor, the substrate fractional conversion, and on the gas and liquid contact pattern. Under certain conditions, the TBB size is independent of the flowing phases' contact pattern. The model effectively describes substrate gas and liquid concentration data for mass transfer and biodegradation rate controlled processes.
Chemical Engineering Science, 2000
A model for non-isothermal absorption with chemical reaction based on Toor and Marchello's "lm-pe... more A model for non-isothermal absorption with chemical reaction based on Toor and Marchello's "lm-penetration concept was developed for "rst-and second-order irreversible reactions. Enhancement factor predictions are discussed in terms of the gas reactant solubility, reaction activation energy, solution and reaction heats, reactant concentrations and di!usivities. Results are compared with those of non-isothermal "lm and penetration models. For "rst-and second-order reactions, the predictions of non-isothermal "lm-penetration model di!er from both non-isothermal "lm and penetration results, but are closer to the former. Also, predictions for non-isothermal "lm-penetration model are similar to the corresponding isothermal ones when the process is limited by liquid-phase reactant. Results of non-isothermal "lm-penetration model presented here provide quantitative support to the long used assumption that the "lm theory results represent conservative estimates for most systems. : S 0 0 0 9 -2 5 0 9 ( 0 0 ) 0 0 1 5 9 -7
Hydrodynamics has a strong influence on substrate elimination capacity in trickle-bed bioreactors... more Hydrodynamics has a strong influence on substrate elimination capacity in trickle-bed bioreactors (TBB). The present study reports the influence of liquid mass flow rate and bed void fraction on the TBB liquid residence time distribution (RTD), gas-liquid pressure drop, liquid hold-up, and biofilm wetting efficiency. Most RTD are well represented by a dispersion model. It is also shown that the hydrodynamic parameters increase as superficial liquid mass flow rate increases and as bed void fraction diminishes. The TBB isopropyl alcohol (IPA) mineralization capacity reach its largest values at a bed void fraction of 0.6, and the lowest are obtained when it is 0.44, when the TBB turns anaerobic due to excessive biomass growth. Overall, it is shown that the TBB performance is strongly dependent on hydrodynamics.
Educación Química, 2018
No es necesario argumentar la importancia que tiene contar con una visión lo más amplia posible p... more No es necesario argumentar la importancia que tiene contar con una visión lo más amplia posible para abordar los retos que enfrenta la educación de los ingenieros químicos (o de cualquier otro profesional). Uno de estos retos consiste en esbozar los atributos (el perfil) idealmente deseables en la persona que será el futuro profesional. La definición del perfil es un aspecto muy importante, porque concreta una visión de la persona y de los conceptos educativos de una institución de educación superior que aspira a formarla.
Computers & Chemical Engineering, 2017
A co-hydrotreating RD process for production of green diesel is proposed Thermodynamic analys... more A co-hydrotreating RD process for production of green diesel is proposed Thermodynamic analysis of the reactive mixtures was performed by PC-SAFT EoS Effect of the triglycerides and FFA content on the RD performance is investigated Simulations reveal that bio-oils with high FFA content are suitable to be hydrotreated.
Computer Aided Chemical Engineering, 2016
Abstract A systematic approach for the hydrotreating of vegetable oils and “sulfured” petroleum d... more Abstract A systematic approach for the hydrotreating of vegetable oils and “sulfured” petroleum diesel is proposed. The conceptual design of a reactive separation process that combines both, the hydrodeoxigenation (HDO) of triglycerides, free fatty acids (FFA), and biodiesel (methyl esters) and hydrodesulfurization (HDS) of petroleum diesel reactions is carried out. The systematic approach considers a thermodynamic analysis of model mixtures of triglycerides and fatty acids with hexadecane and hydrogen to determine the appropriate operating conditions (temperature, pressure and compositions blends) of the reactive separation process. The results of the thermodynamic analysis are used to propose two different reactive distillation processes to obtain the improved diesel fuel. Simulations of the reactive processes in Aspen-Plus environment were performed using the PC-SAFT equation of state. Simulation results show that the performance of the combined HDO-HDS hydrotreating process is more efficient when a pre-hydrogenation step of the triglycerides to produce free fatty acids is included.
Computer Aided Chemical Engineering, 2015
Computers & Chemical Engineering, 2010
A systematic study of the operating conditions and parameter sensibility under which multiple ste... more A systematic study of the operating conditions and parameter sensibility under which multiple steady states may occur in a reactive distillation column (RDC) for diesel deep hydrodesulfurization is presented. The multiplicity analysis is performed through ...
Computers & Chemical Engineering, 2012
The catalytic esterification of n-propyl propionate using propionic acid and n-propyl alcohol as ... more The catalytic esterification of n-propyl propionate using propionic acid and n-propyl alcohol as reactants via a conventional pilot plant reactive distillation column was carried-out. The strongly acidic ion-exchange resin Amberlyst46 TM was used as the solid acid catalyst. The influence of the reflux ratio (from 2.0 to 2.5), the molar feed ratio (from 2.0 to 2.5), and total feed (from 3.0 to 4.0 kg/h) on the purity and conversion of the species and on the composition and temperature profiles along the column was analyzed. A 2 3 experimental design with six actual and two simulated experiments was carried-out. With the experimental conditions obtained from the simulation results, the experiments showed that a reflux ratio of 2.0, a molar feed ratio of 2.0 and a total feed of 4 kg/h, yielded the largest propyl propionate production (1.60 kg/h). The simulated experiments were carried out using a non-equilibrium model implemented into the simulation environment Aspen Custom Modeler TM .
Chemical Engineering Journal, 2005
Based on a thermodynamic analysis in terms of reaction-separation feasibility, a conceptual desig... more Based on a thermodynamic analysis in terms of reaction-separation feasibility, a conceptual design of a reactive distillation column for ultra-low sulfur diesel production has been developed. The thermodynamic analysis considers the computation of reactive and non-reactive residue curve maps for a mixture that models the sulfured diesel fuel. The visualization of the reactive residue curves is posed in terms of elements. From the reactive residue curve maps, it is found that there is a high temperature region where the vaporization of hydrogen sulfide favors the elimination of the heavier organo-sulfur compounds. Considering the differences in volatility and reactivity of the organosulfur compounds and the phase behavior through the residue curve maps, a conceptual reactive distillation column design was developed. The reactive distillation column considers two reactive zones: In reactive zone I, located above the hydrocarbon feed stream, thiophene and benzothiophene are preferentially eliminated. In reactive zone II, located below the feed stream, dibenzothiophene and 4,6-dimethyldibenzothiophene (4,6-DMDBT) are mostly consumed. To validate the conceptual design, rigorous steady state simulations were performed. The design goal was stated to produce 4000 bbl/day of ultra-low sulfur diesel with a 99% conversion of 4,6-DMDBT. It is shown that reactive distillation may be considered a viable technological alternative for deep HDS of diesel.
Chemical Engineering Journal, 2005
This paper reports the effect of superficial liquid mass flow rate and bed void fraction on the p... more This paper reports the effect of superficial liquid mass flow rate and bed void fraction on the pressure drop, dynamic liquid holdup , mean liquid residence time and biofilm wetting, in a co-current down-flow xylene-removing trickle bed air biofilter (TBAB). The gas-liquid pressure drop increased with liquid mass flow rate and it also increased with diminishing bed void fraction, the effect being larger at bed void fraction of 0.41. Dynamic liquid holdup was higher with increasing liquid mass flow rate, and showed a maximum when the bed void fraction was 0.69. The same pattern was observed for the mean liquid residence time and the wetting efficiency. Liquid residence time distribution curves indicate stagnant regions, channeling, and recirculation within the TBAB, whose effects were larger at a bed void fraction of 0.41. A maximum elimination capacity of 30 g/m 3 h, with 78% removal efficiency, was reached when the bed void fraction was 0.8 and the liquid mass rate 14.1 kg/m 2 s. An average minimum elimination capacity of 6 g/m 3 h was observed at a bed void fraction of 0.41. Xylene isomers were preferentially removed in the order of o > m > p.
Chemical Engineering Journal, 2012
A simple computational procedure to determine reactive critical points of kinetically controlled ... more A simple computational procedure to determine reactive critical points of kinetically controlled reacting mixtures was developed. The thermodynamic analysis considers the simultaneous calculation of the reactive and non-reactive residue curve maps using the Peng-Robinson equation of state and the Heidemann and Khalil method for the computation of critical points. Two kinetically controlled reactive systems were considered: (i) the reversible esterification reaction of acetic acid with ethanol in the presence of CO 2 and, (ii) the irreversible hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene with tetralin as solvent for the production of ultra low sulfur diesel. It was found that the amount of catalyst loaded (˛) into the reacting vessel plays a key role for the existence of the reactive critical points for the deep HDS of diesel while for the esterification reactions has little significance. Also, results showed that, while the catalyst loaded does not have any influence on the existence of the reactive critical point for the esterification reactive system (T C ∼ 566 K; P C ∼ 68 atm; x HAc ∼ 0.39, x EtOH ∼ 0.26, x EtAc ∼ 0.15, x H 2 O ∼0.19, and x CO 2 ∼0.01), it moves the range of temperature where a maximum liquid composition of ethyl acetate can be obtained. Several critical points for the hydrodesulfurization of 4,6-DMDBT were found with different ˛ values.
Biotechnology and Bioengineering, 1999
An analysis of the local processes occurring in a trickle-bed bioreactor (TBB) with a first-order... more An analysis of the local processes occurring in a trickle-bed bioreactor (TBB) with a first-order bioreaction shows that the identification of the TBB operating regime requires knowledge of the substrate concentration in the liquid phase. If the substrate liquid concentration is close to 0, the rate-controlling step is mass transfer at the gas-liquid interface; when it is close to the value in equilibrium with the gas phase, the controlling step is the phenomena occurring in the biofilm. CS 2 removal rate data obtained in a TBB with a Thiobacilii consortia biofilm are analyzed to obtain the mass transfer and kinetic parameters, and to show that the bioreactor operates in a regime mainly controlled by mass transfer. A TBB model with two experimentally determined parameters is developed and used to show how the bioreactor size depends on the rate-limiting step, the absorption factor, the substrate fractional conversion, and on the gas and liquid contact pattern. Under certain conditions, the TBB size is independent of the flowing phases' contact pattern. The model effectively describes substrate gas and liquid concentration data for mass transfer and biodegradation rate controlled processes.
Chemical Engineering Science, 2000
A model for non-isothermal absorption with chemical reaction based on Toor and Marchello's "lm-pe... more A model for non-isothermal absorption with chemical reaction based on Toor and Marchello's "lm-penetration concept was developed for "rst-and second-order irreversible reactions. Enhancement factor predictions are discussed in terms of the gas reactant solubility, reaction activation energy, solution and reaction heats, reactant concentrations and di!usivities. Results are compared with those of non-isothermal "lm and penetration models. For "rst-and second-order reactions, the predictions of non-isothermal "lm-penetration model di!er from both non-isothermal "lm and penetration results, but are closer to the former. Also, predictions for non-isothermal "lm-penetration model are similar to the corresponding isothermal ones when the process is limited by liquid-phase reactant. Results of non-isothermal "lm-penetration model presented here provide quantitative support to the long used assumption that the "lm theory results represent conservative estimates for most systems. : S 0 0 0 9 -2 5 0 9 ( 0 0 ) 0 0 1 5 9 -7