Artículos (Ingeniería Química y Ambiental)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/11382

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Advances in research project IBUMECO2: project and process description, methodology, and goals expected
(Society of Chemical Industry and John Wiley & Sons Ltd., 2023) Gallego Fernández, Luz Marina; Portillo Estévez, Esmeralda; Baena Moreno, Francisco Manuel; Vilches Arenas, Luis Francisco; Navarrete Rubia, Benito; Ingeniería Química y Ambiental; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; TEP135: Ingeniería Ambiental y de Procesos
In this work, the research project IBUMECO 2 is presented for the first time. This project risesas a need to implement negative emissions technologies and circular economy approaches in ourcurrent energy production system. The overall goal of the project is the integration of CO 2 capture andutilization in biogas upgrading plants in combination with membrane technology for solventregeneration. The integration of CO2 capture and utilization in biogas upgrading plants is pivotal for twomain reasons: (1) it allows to obtain biomethane, a potential substitute of natural gas; (2) the utilizationof the CO2 contained in biogas makes the idea a negative emission technology. The implementation ofmembrane technology for solvent regeneration makes the process affordable and includes it in acircular economy framework. In this paper, the project and the process are deeply described, includingpotential technological improvements identified by a state-of-the-art, the methodology and goalsexpected.
Implementation of a continuous assessment system through the creation of a problem book using DOCTUS in general chemistry subjects
(Elsevier, 2025) Leiva Fernández, Carlos; Arroyo Torralvo, Fátima; Luna Galiano, Yolanda; Ronda Gálvez, Alicia; Muñoz de la Peña Sequedo, David; Ingeniería Química y Ambiental; Ingeniería de Sistemas y Automática
A continuous evaluation system, integrating both formative and summative assessments has been implemented in a Chemistry subject with a high number of students. This system employs a personalized problem notebook developed through an application (DOCTUS), enabling the generation of individualized complex problem statements, easy correction, and multiple submission opportunities. This approach facilitates effective feedback, promotes autonomous and cooperative learning, accelerates the learning process, and enhances activity achievement levels. The experience has been carried out with a group of 91 students enrolled per year in the subject 'Chemistry' corresponding to the first academic year in degree of Chemical Engineering at the Higher Technical School of Engineering (University of Seville), although only 71 have participated in the activity. The platform used, which offers free access, was utilized to create personalized problem notebooks for each student. It assigns identical problems with personalized data and corrects submissions via Excel files in under 10 s. An improvement in the results has been observed; since the students have obtained a numerical grade for their work instantly after delivery of the problem, and they can redo it at a short time (hours), when the students still have the problem in their mind, where they want and with the material that they consider, and without a large increase in the amount of time spent by the teacher. The final qualification was on average 1.2 points higher than previous years. Compared to other subjects in the same academic year, Chemistry had a lower percentage of students who did not participated in the subject (22 % compared to 30–54 % in other subjects from the same course). The number of approved students has increased, reflected in the number of repeaters, which decreased in the next year from 42 % to 29 %.
Evaluation of Spent Catalyst from Fluid Catalytic Cracking in Fly Ash and Blast Furnace Slag Based Alkali Activated Materials
(Multidisciplinary Digital Publishing Institute (MDPI), 2025) Luna Galiano, Yolanda; Cabrera Gallardo, Domingo; Rodríguez Galán, Mónica; Novais, Rui M.; Labrincha, J.A.; Leiva Fernández, Carlos; Ingeniería Química y Ambiental
The objective of this work is to evaluate how spent catalyst from fluid catalytic cracking (SCFCC) affects the physical, mechanical and durability properties of fly ash (FA) and blast furnace slag (BFS)-based alkali-activated materials (AAMs). Recycling of SCFCC by integrating it in a AAM matrix offers several advantages: valorization of the material, reducing its disposal in landfills and the landfill cost, and minimizing the environmental impact. Mineralogical, physical and mechanical characterization were carried out. The durability of the specimens was studied by performing acid attack and thermal stability tests. Mass variation, compressive strength and porosity parameters were determined to assess the durability. BFS- and FA-based AAMs have a different chemical composition, which contribute to variations in microstructure and physical and mechanical properties. Acid neutralization capacity was also determined to analyse the acid attack results. Porosity, including the pore size distribution, and the acid neutralization capacity are crucial in explaining the resistance of the AAMs to sulfuric acid attack and thermal degradation. Herein, a novel route was explored, the use of SCFCC to enhance the durability of AAMs under harsh operating conditions since results show that the compositions containing SCFCC showed lower strength decay due to the lower macroporosity proportions in these compositions.
Anaerobic Digestion as an Alternative to Improve the Industrial Production of MnP Economically and Environmentally Using Olive Mill Solid Waste as the Substrate
(Multidisciplinary Digital Publishing Institute (MDPI), 2025) Araneda, Michael; Pinto Ibieta, Fernanda; Alonso-Fariñas, Bernabé; Fermoso, Fernando G.; Ciudad, Gustavo; Ingeniería Química y Ambiental; Agencia Nacional de Investigación y Desarrollo (ANID). Chile
Manganese peroxidase (MnP) is widely studied for its potential in bioremediation, although its production typically relies on costly synthetic culture media (SCM). This study evaluates olive mill solid waste (OMSW) as a sustainable substrate for MnP production. Three alternatives were evaluated: (1) using SCM; (2) using OMSW; and (3) using OMSW, followed by anaerobic digestion (AD). The alternatives were evaluated by both an economic and life cycle assessment (LCA). The economic analysis considered indicators such as net present value (NPV), internal rate of return (IRR), and payback period. The LCA methodology was conducted according to ISO 14040/44 standards, with a cradle-to-gate system boundary, using SimaPro v9.4 software. Replacing SCM with OMSW improved economic performance, though environmental impacts showed no significant improvement and, in some cases, worsened. In contrast, combining OMSW with anaerobic digestion enhanced both dimensions: Alternative 3 reached the highest NPV (USD 984,464), a 20.9% IRR, and a 4.1-year payback, while reducing impacts by 275% (Stratospheric ozone depletion), 89% (terrestrial ecotoxicity), 78% (freshwater ecotoxicity), and 50% (marine eutrophication) compared to Alternative 1. Finally, the use of OMSW combined with AD reduces economic costs and environmental impact, contributing to the field of sustainable enzyme production.
Numerical and experimental study of the optimal specimen geometry for direct tension strength tests in high tensile strength fiber reinforced concrete
(Nature Research, 2025-03-28) Vicente Cabrera, Miguel Ángel; Mena Alonso, Álvaro; González Cabrera, Dorys Carmen; Ruiz López, Gonzalo; Cifuentes-Bulté, Héctor; Leiva Fernández, Carlos; Yu, Rena C.; Mínguez Algarra, Jesús; Mecánica de Medios Continuos y Teoría de Estructuras; Ingeniería Química y Ambiental; Ministerio de Economía y Competitividad (MINECO). España; TEP972: Mecánica de Materiales y Estructuras; TEP142: Ingeniería de Residuos
The accurate determination of the tensile strength of concrete is a topic of growing interest, especially driven by the new ultra-high tensile strength fiber-reinforced concretes. However, this is a complex task, as traditional methods provide inconsistent results (both splitting tensile test and 3-point bending test). The most robust method is the direct tensile test. However, in concrete, it poses a technical challenge that has not yet been satisfactorily solved. The aim of this study is the design of a test specimen that maximizes the percentage of successful failure and also allows a viable anchorage solution to the load application equipment, especially for high and ultra-high tensile strength concretes. An optimized geometry of a bone-shaped specimen that maximizes the probability of collapse occurring at the central neck is presented. First, a mathematical function of the generatrix of the bone-shape specimen is presented. The behavior of the solution is also analyzed numerically and statistically, comparing it with other commonly used solutions for direct tensile tests. Additionally, the design, fabrication, and calibration of a tailored cardan joint for load centering, thus minimizing its eccentricity and the dispersion of the results. Finally, the results of a static test campaign carried out on six carbon-fiber reinforced high tensile strength concrete specimens. The proposed bone-shaped specimen shows a much higher percentage of successful failures than the other specimen geometries commonly used for tensile testing, which improves the quality of tensile characterization test campaigns for high and ultra-high tensile strength concretes.
Properties and Optimization Process Using Machine Learning for Recycling of Fly and Bottom Ashes in Fire-Resistant Materials
(MDPI, 2025-04) Guirado Albeira, Elena; Ruíz Martínez, Jaime Delfino; Campoy Naranjo, Manuel; Leiva Fernández, Carlos; Ingeniería Química y Ambiental; Ministerio de Ciencia e Innovación (MICIN). España
Significant amounts of coal fly and bottom ash are generated globally each year, with especially large quantities of bottom ash accumulating in landfills. In this study, fly ash and bottom ash were used to create fire-resistant materials. A mix of 30 wt% gypsum, 9.5 wt% vermiculite, and 0.5 wt% polypropylene fibers was used, maintaining a constant water-to-solid ratio, with varying fly ash/bottom ash ratios (40/20, 30/30, and 20/40). The density, as well as various mechanical properties (compressive strength, flexural strength, and surface hardness), fire insulation capacity, and leaching behavior of both ashes were evaluated. When comparing the 40/20 and 20/40 compositions, a slight decrease in density was observed; however, compressive strength dropped drastically by 80%, while flexural strength decreased slightly due to the action of the polypropylene fibers, and fire resistance dropped by 8%. Neither of the ashes presented any environmental concerns from a leaching standpoint. Additionally, historical data from various materials with different wastes in previous works were used to train different machine learning models (random forest, gradient boosting, artificial neural networks, etc.). Compressive strength and fire resistance were predicted. Simple parameters (density, water/solid ratio and composition for compressive strength and thickness and the composition for fire resistance) were used as input in the models. Both regression and classification algorithms were applied to evaluate the models’ ability to predict compressive strength. Regression models for fire resistance reached r2 up to about 0.85. The classification results for the fire resistance rating (FRR) showed high accuracy (96%). The prediction of compressive strength is not as good as the fire resistance prediction, but compressive strength classification reached up to 99% accuracy for some models.
Multi-scale toughening of UHPC: synergistic effects of carbon microfibers and nanotubes
(MDPI, 2025-04-21) Ruiz Martínez, Jaime Delfino; Ríos Jiménez, José David; Cifuentes-Bulté, Héctor; Leiva Fernández, Carlos; Ingeniería Química y Ambiental; Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Ciencia e Innovación (MICIN). España; TEP972: Mecánica de Materiales y Estructuras; TEP142: Ingeniería de Residuos
This study investigates multi-scale reinforcement of Ultra-High-Performance Concrete through targeted modifications of its mechanical and fracture-resistant properties via carbon microfibers and carbon nanotubes. The research employed comprehensive characterization techniques including workability tests, mercury porosimetry for microscale porosity analysis, and X-ray tomography for macro-scale pore evaluation. Mechanical performance was assessed through compression strength, tensile strength, and fracture energy measurements. Results demonstrated significant performance enhancements testing UHPC samples with 6 mm carbon microfibers (9 kg/m3) and varying carbon nanotubes dosages (0.11–0.54 wt%). The addition of carbon microfibres improved compressive strength by 12%, while incorporating 0.54 wt% carbon nanotubes further increased strength by 24%. Remarkably, the combined reinforcement strategy yielded a 313% increase in tensile strength compared to the reference mixture. The synergistic effect of carbon fibers and carbon nanotubes proved particularly effective in enhancing concrete performance. This multi-scale reinforcement approach presents a promising alternative to traditional steel fiber reinforcement, offering superior mechanical properties and potential advantages in corrosive environments.
Hydrogen production from supercritical water reforming of acetic acid, acetol, 1-butanol and glucose over Ni-based catalyst
(Elsevier, 2018-08) Gutiérrez Ortiz, Francisco Javier; Campanario Canales, Francisco Javier; Ingeniería Química y Ambiental
Supercritical water reforming (SCWR) of four main constituents of bio-oil aqueous phase (acetic acid, acetol, 1-butanol and glucose) to produce hydrogen was studied in a tubular fixed-bed reactor using commercial Ni/Al2O3-SiO2 catalyst. The process was carried out under different operating conditions at 240 bar (500–800 °C, 5.0–22.5 wt.% of organic compounds and values of weight-hourly space velocity (WSHV) of 2.5–22.5 gorg-comp h−1 gcat−1). The data were reported as reaction rates, expressed as turnover frequencies (TOF), and the Arrhenius parameters (pre-exponential factor and apparent activation energy) were obtained. The process performance was compared to that without using any catalyst and that regarding equilibrium condition. Hydrogen yields were very close to those values predicted by equilibrium within the operating window tested in this study.
Understanding the evolution of particle size dispersion with time in a fluidised bed granulation process
(Elsevier, 2023-06) Cronin, Kevin; Gutiérrez Ortiz, Francisco Javier; Ingeniería Química y Ambiental; TEP135: Ingeniería Ambiental y de Procesos
Minimisation of final size dispersion remains an important objective of fluidised bed granulation. Some of the factors that control the evolution of the granule size distribution with time in such a process are examined using a validated aggregation model. The aim is to understand the intrinsic behaviour of size dispersion versus time with an approach that is not specific to a particular system of fluidised granulation. Because relative size dispersion (size dispersion compared to the mean size) is also important, the study also examines the evolution of mean granule size versus time. The model includes an aggregation rate that is time and size dependent and a granule kinetic energy dissipation mechanism. The relative importance of these components of the model is quantified in terms of how they control the output and it is shown that the action of the energy absorption mechanism (implemented using the viscous Stokes criterion) makes the dominant contribution although the interplay with the other effects is also significant. Mean granule volume monotonically approaches a quasi-stable asymptotic value while standard deviation in granule volume passes through a peak value before falling to a lower, quasi-stable asymptotic value. The reasons underlying such behaviour are outlined. Two new temporal parameters, an equivalent aggregation time constant and a Stokes time constant, are developed and can be employed to predict and interpret system behaviour. Such knowledge can then be applied to suggest how dispersion in size can be controlled within certain intrinsic limits, which will be of interest to the industry.
Techno-economic assessment of biogas plant upgrading by adsorption of hydrogen sulfide on treated sewage–sludge
(Elsevier, 2016-10) González Aguilera, Paloma; Gutiérrez Ortiz, Francisco Javier; Ingeniería Química y Ambiental; TEP135: Ingeniería Ambiental y de Procesos
Biogas plant upgrading by adsorption of hydrogen sulfide on treated sewage–sludge was techno-economically assessed. Three different processes were included in the study: the desulfurization of biogas by adsorption, the in-situ regeneration of the adsorbent and its production from sewage-sludge. Biogas plant upgrading was performed for a flow rate of 1000 Nm3/h of biogas with a H2S concentration of 2000 ppmv and a breakthrough concentration of 200 ppmv, which is the technical limit value for internal combustion engines. The cost due to the steam required for the in-situ regeneration was evaluated in two different scenarios: as a bought external utility and as an in-situ produced utility, installing an electric or a biogas steam boiler. According to the cash flow analysis carried out, all the options require a similar minimum selling price for the upgraded biogas (about 0.27–0.29 €/Nm3), with a cost of the overall desulfurization process between 2.5 and 4.0 c€/Nm3.
Life cycle assessment of the Fischer-Tropsch biofuels production by supercritical water reforming of the bio-oil aqueous phase
(Elsevier, 2020-11) Gutiérrez Ortiz, Francisco Javier; Alonso-Fariñas, Bernabé; Campanario Canales, Francisco Javier; Kruse, Andrea; Ingeniería Química y Ambiental; TEP135: Ingeniería Ambiental y de Procesos
This paper is aimed at performing an environmental evaluation regarding biofuel production. The process combines four sections: biomass fast pyrolysis to bio-oil with two phases, oil-phase upgrading by hydrotreating, using H2 obtained by steam reforming, and a new process to produce Fischer-Tropsch biofuels from supercritical water reforming of the aqueous phase. This phase can be valorised in the latter process entirely so natural gas is reformed to H2 (case-study 1), or partially so a fraction of this aqueous phase is reformed (case-study 2), or all this phase is reformed to H2 (case-study 3). The two former can include CO2 storage and aqueous phase concentrations were 15, 25 and 35 wt% organic compounds. At 25 wt%, the global warming potential is 11 g CO2-eq/MJ-biofuel for the case 2 with CO2 storage, while it was 11.3, 12.6, 27.7 and 34 g CO2-eq/MJ-biofuel for the cases 3, 2 without CO2 storage, 1 with and without CO2 storage, respectively. Thus, the case-study 2 with CO2 storage gives the minimum global warming potential, allowing significant reductions with respect to the use of fossil fuels. For the other categories, the case-study1 presents the lowest impacts. Similar trends are found at 15 and 35 wt%.
Assessing sediment toxicity risks with bioavailable metal fractions: new factors and index applied to the Colombian tropical Andes hotspot
(Springer, 2025-06) Rincon-Vasquez, Ingrid Vanessa; Fohrer, Nicola; Rosado Alcarria, Daniel; Ingeniería Química y Ambiental; TEP218: Biotecnología Ambiental
Heavy metal toxicity risk assessments in sediments often rely on pseudototal concentrations, despite the higher theoretical predictive potential of bioavailable fractions. This study introduces the Bioavailable Fraction Toxicity Factor (BTf) and the Bioavailable Fraction Toxicity Index (BTI) to evaluate metal toxicity risks using a bioavailable fraction calculated as the sum of the first two steps of the Tessier sequential extraction procedure. Investigating heavy metal pollution (Cd, Cr, Cu, Mn, Ni, Pb, Zn) in the Vetas River catchment, a critical freshwater source in the Santurbán Páramo within the Tropical Andes biodiversity hotspot, the study identified artisanal and small-scale mining as the primary driver of contamination. Water and sediment of mining areas, particularly La Baja Creek and El Volcán Village, exhibited the highest concentrations of metals, with some sediment levels being categorized as strongly contaminated by the Geoaccumulation Index and Pollution Load Index and exceeding the Probable Effect Concentration threshold. Bioavailable fraction of metals in sediments were measured. Bioavailable fractions were higher in mining-affected areas, suggesting greater potential for metal release under acidic conditions. The BTf and BTI provided a more nuanced understanding of metal toxicity risks compared to pseudototal concentrations, with higher BTI values in mining-influenced sites. These findings underscore the need for mitigation measures to address heavy metal pollution and highlight the ecological importance of the Santurbán Páramo. Further research into bioremediation potential using local flora is recommended to support sustainable management practices.
A new time-dependent rate constant of the coalescence kernel for the modelling of fluidised bed granulation
(Elsevier, 2021-02) Cronin, Kevin; Gutiérrez Ortiz, Francisco Javier; Ring, Denis; Zhang, Fuweng; Ingeniería Química y Ambiental; TEP135: Ingeniería Ambiental y de Procesos
This paper presents a novel approach to the determination of the coalescence kernel for population balance modelling of a general class of batch fluidised bed aggregation systems, using a continuous sprayed-in liquid binder. Coalescence requires inter-particle collisions, the wetting of the contact surfaces and the dissipation of particle kinetic energy by the viscous squeezing of the binder film. These three sub-processes in principle depend both on the size of the contacting particles and on time. A new time-dependent aggregation rate constant of the coalescence kernel has been formulated by considering the general evolution of inter-particle collision behaviour with time. The model is implemented in MATLAB and its numerical output compared to two sets of experimental data: the granulation of glass beads with polyethylene glycol as a binder and the granulation of semolina with water. The evolution of mean and standard deviation in diameter versus time are examined as is the state of the size distribution at different stages in the process. The time-averaged aggregation rate for the glass beads evaluated as 7.59 × 10−9 m-0.5 s−1 while for the semolina it was 3.86 × 10−9 m-0.5 s−1. The agreement between numerical predictions and experiment is shown to be good, demonstrating the validity of the approach. Whilst conceptually simple, the model generates realistic output and provides a powerful insight into the underlying mechanisms of granulation.
A pilot-scale laboratory experience for an inductive learning of hydrodynamics in a sieve-tray tower
(Elsevier, 2019-10) Gutiérrez Ortiz, Francisco Javier; Ingeniería Química y Ambiental; TEP135: Ingeniería Ambiental y de Procesos
A specific inductive teaching approach for undergraduate students of Chemical Engineering bachelor’s degree based on a laboratory experience is presented. Thus, the simple experiment performed to show an aspect of theory previously taught in a classroom is overcome. The specific laboratory experience involves a sieve-tray tower whereby a binary distillation is carried out. However, the focus is not on this separation operation but in the hydrodynamics associated with the start-up of the process, which needs a boiler as an ancillary system to supply the required energy. All these process units are usually taught operating under stationary conditions, which are achieved quickly if small laboratory units are used. In this paper, the hands-on experience is performed in a pilot plant, which makes students feel closer to industry and allows them to visualize different physical phenomena. Students work with their teammates, and they can acquire technical knowledge and develop transferable skills that prepare them for their future profession in a more engaged and motivational way. From their feedback, students feel that their mood increase, because they understand the phenomena shown in the experience better when it is performed first and then explained. Therefore, the approach is very well received by the students, so this new teaching scaffolding should be more and more developed and implemented in the chemical engineering curriculum. It is rewarding for the teaching staff because the laboratory experience helps students construct meaning by themselves in a more active and efficient way. This approach makes it possible to find and correct misconceptions in the students, to demonstrate procedures and methods used in the chemical engineering and to explain particular concepts within the knowledge area. But what is more important, it makes students protagonists of their own learning and gives them more confidence.
The use of process simulation in supercritical fluids applications
(Royal Society of Chemistry, 2020-03) Gutiérrez Ortiz, Francisco Javier; Kruse, Andrea; Ingeniería Química y Ambiental; TEP135: Ingeniería Ambiental y de Procesos
The use of supercritical fluids is spreading more and more throughout the world. The interest in them and their applications is clear from the increasing number of papers and patents in the last few years, as well as by the number of new research groups and facilities. When applied to process engineering, mathematical modelling is a powerful tool to gain insight into the impact of the process parameters under a large variety of conditions, which reduces the required experimentation and, hence, the economic and time resources. This review deals with modelling at molecule scale (molecular dynamics) and, more specifically, at macroscale (thermodynamic methods) in order to estimate thermodynamic and transport properties as well as the kinetic parameters needed for the subsequent process simulation. This latter is usually performed for chemical and energy processes, such as supercritical water gasification, supercritical water oxidation, biodiesel production using supercritical methanol and different applications of supercritical carbon dioxide, among others. As a further step, this type of simulation can be refined using computational fluid dynamics, thus optimizing the design of process units involved in specific processes in a rigorous way. Many recent papers are discussed in the context of simulation and modelling related to supercritical fluids applications, taking into account the software used to perform this type of study.
Integral energy valorization of municipal solid waste reject fraction to biofuels
(Elsevier, 2019-01) Gutiérrez Ortiz, Francisco Javier; Kruse, Andrea; Ramos, F.; Ollero de Castro, Pedro Antonio; Ingeniería Química y Ambiental
Nowadays, the waste generation increases more and more, especially of the municipal solid waste. The municipal solid waste reject fraction may be valorized from an energy point of view. With this aim, a conceptual design of a process was developed by considering material and energy integration, which mainly consists of three sub-processes: fast pyrolysis of municipal solid waste to produce bio-oil, supercritical water reforming of the bio-oil aqueous phase to produce hydrogen to be used in the third section, which is the upgrading of the organic phase of the bio-oil by hydrodeoxygenation. The overall system was simulated using Aspen Plus software to achieve the highest process performance and the lowest utilities requirement. The former was assessed by the biofuel production (liquefied fuel gas, gasoline and diesel) and the net electrical power. In addition, the potential economic profitability of the plant was performed by specifying the main process units. Thus, for a feeding of 50 t/h of municipal solid waste reject fraction, a generation of a net electric power equal to 10.65 MWe and a production of 5.2 t/h biofuels (21.1% of the carbon present in the municipal solid waste) may be achieved, thus obtaining a very low gate fee (16.7 €/t) using the same industrial selling prices that those of fossil fuels and electricity in a full plant. Therefore, the process seems to be technically and economically feasible.
Modeling of fixed-bed columns for gas physical adsorption
(Elsevier, 2019-12) Gutiérrez Ortiz, Francisco Javier; Barragán Rodríguez, Manuel; Yang, Ralph T.; Ingeniería Química y Ambiental
Adsorption processes may be classified as purification or bulk separation, depending on the feed concentration of the compounds to be adsorbed (adsorbates). The adsorption dynamics of a fixed-bed is crucial for a well-designed adsorption process. This work focuses on physical adsorption and provides a modeling to predict the breakthrough curves using a minimum set of experimental data. The modeling does not require one to obtain key parameters from the experiment unlike other modeling found in the literature. In addition, boundary conditions, thermal effects, correlations to be used, and the homogeneous/heterogeneous modelings are discussed for 1-D modeling, after verifying that it provides the same output as 2-D modeling does. Moreover, it is demonstrated that pseudo-homogeneous modeling is realistic, so a more complex heterogeneous modeling is not necessary. The modeling has been tested against five sets of experimental data: three cases of bulk separation and two cases for purification. The simulation was carried out by Comsol Multiphysics software, and a good match between the experimental data and the simulation output was achieved, which demonstrates the applicability of the modeling, so it may be used with confidence. Purification can be modeled as an isothermal process, and no energy balance equation is needed. However, for bulk separation, noticeable thermal effects may take place due to the relatively high adsorbed gas that consequently releases a higher amount of heat; at the same time, the superficial fluid velocity is reduced due to the decrease in the flow-rate, and the gas properties change, affecting the breakthrough curves.
Hydrogen production from supercritical water reforming of glycerol over Ni/Al2O3–SiO2 catalyst
(Elsevier, 2015-05) Gutiérrez Ortiz, Francisco Javier; Campanario Canales, Francisco Javier; González Aguilera, Paloma; Ollero de Castro, Pedro Antonio; Ingeniería Química y Ambiental; Ministerio de Ciencia y Tecnología (MCYT). España
Hydrogen production from the supercritical water reforming of glycerol was studied in a tubular fixed-bed reactor by using a Ni-based catalyst supported on Al2O3 and SiO2. Tests were carried out at a pressure of 240 bar, temperatures of 500–800 °C, glycerol feed concentrations of 5–30 wt.%, and weight hourly space velocity from 1.25 to 22.5 gGly h−1 gCat−1 (residence time from 1.6 to 4.8 s through the bed). The dry gas is mainly composed of H2, CO2, CO, CH4. The results showed that the glycerol conversion was almost complete, except at the highest glycerol feed concentration and lowest temperature. Hydrogen yields were very close to those values predicted by equilibrium at a short residence time. Nickel on catalyst was completely reduced, and structured carbon nanotubes were encountered at glycerol concentrations higher than 20 wt.%. This study illustrates that the reforming of glycerol using supercritical water over a Ni catalyst makes it possible to reduce the reforming temperature needed when no catalyst is used (from 800 °C to 600 °C), achieving a high-yield hydrogen production, very close to equilibrium, and requiring less energy.
Effect of mixing bio-oil aqueous phase model compounds on hydrogen production in non-catalytic supercritical reforming
(Royal Society of Chemistry, 2017-10) Gutiérrez Ortiz, Francisco Javier; Campanario Canales, Francisco Javier; Ollero de Castro, Pedro Antonio; Ingeniería Química y Ambiental
Bio-oil derived from biomass fast pyrolysis can be processed into fuel or some chemical products, but it has a waste aqueous phase that, however, may be valorized. Supercritical reforming of this stream, simulated using mixtures of model compounds (acetic acid, acetol, 1-butanol and glucose), was experimentally studied in a tubular reactor without using a catalyst. The effect of mixing the model compounds at different operating parameters (temperature, feed composition, and residence time) on the process performance was investigated, thus addressing an important chemical aspect of biomass-based renewable energy. The experimental dry gas composition consisted of H2, CO2, CO and CH4, although the gas yields were far from equilibrium. Hydrogen yields were normally less than 2.0 moles of H2 per mole of organic feed, which are lower than those obtained for pure compounds with the same concentration. Based on the analyzed liquid samples, a series of probable reaction pathways were proposed to explain the experimental results by considering the interactions among the compounds and their formed intermediates. Thus, under tested supercritical conditions, the residence time was insufficient to reform the formed methane into hydrogen, thus leading to lower hydrogen production.
Techno-economic assessment of an energy self-sufficient process to produce biodiesel under supercritical conditions
(Elsevier, 2017-10) Gutiérrez Ortiz, Francisco Javier; Santa-Ana, P. de; Ingeniería Química y Ambiental
This paper presents a conceptual design, simulation and techno-economic assessment of an energy self-sufficient process to produce 10,000 t per year of biodiesel using supercritical methanol and propane as cosolvent. A suitable heat-integrated design of the process was performed using a part of the produced biodiesel (7.4 wt.%) to achieve the energy self-sufficiency for the plant. The simulations were performed by Aspen Plus considering a continuous multitubular reactor operating at 280 °C, 128 bar, methanol-to-oil molar ratio of 24, propane-to-methanol molar ratio of 0.05, and a residence time of 9.7 min. The use of flash separators instead of distillation columns for methanol and propane separation contribute significantly to reduce the energy requirement, with respect to other studies. Final products are high purity of methyl esters (99.8%) and glycerol (96.4%). The economic analysis of the biodiesel plant resulted in a break-even point for the biodiesel selling price of 0.479 €/kg (at 10% rate of return), so the process can compete with the existing alkali and acid catalyzed processes.

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