Artículos (Ingeniería Química y Ambiental)

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

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Optimization of power and hydrogen production from glycerol by supercritical water reforming
(Elsevier, 2013-02) Gutiérrez Ortiz, Francisco Javier; Ollero de Castro, Pedro Antonio; Serrera, Ana; Galera, Sebastián; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Ministerio de Ciencia y Tecnología (MCYT). España
A process design is proposed and simulated for reforming glycerol using supercritical water aimed to produce maximum power and hydrogen in an energy self-sufficient system. The selected route takes advantage of the huge pressure energy of product gas just at the outlet of the reformer converting that into power by a turbine. The expanded product gas is conditioned by two water gas shift reactors and a pressure swing adsorption unit, so a hydrogen-rich gas stream is sent to a proton exchange membrane fuel cell to be converted into electrical energy and the pressure swing adsorption off-gas stream is used as fuel gas to provide the thermal energy required by the reforming process. The evaluation of the global efficiency of the process is carried out by energy and exergy analysis. Required glycerol feed concentration in aqueous solution was obtained for a self-sufficient process, both for pure and pretreated crude glycerol, at reforming temperatures from 600 to 1000 °C and 240 atm. Thus, reforming and preheating at 800 °C and 240 atm, it was obtained a power of 1592 kW per ton/h of glycerol, with exergy and energy efficiencies of 33.8% and 35.8%, respectively.
Methanol synthesis from syngas obtained by supercritical water reforming of glycerol
(Elsevier, 2013-03) Gutiérrez Ortiz, Francisco Javier; Serrera, Ana; Galera, Sebastián; Ollero de Castro, Pedro Antonio; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Ministerio de Ciencia y Tecnología (MCYT). España
A process for producing methanol from the synthesis gas obtained by reforming of glycerol using supercritical water is studied. The process also produces power from the huge pressure energy of product gas just at the outlet of the reformer by a turbine. The expanded product gas is conditioned in a PSA system, which has three sections so as to produce a H2-rich gas stream, a CO-rich gas stream and CO2 for sequestration. Thus, it can be achieved the feed required for the methanol synthesis. The surplus hydrogen is sent to a fuel cell to generate power, and the PSA off-gas, purge from the methanol loop and gases separated from the crude methanol are burnt in a furnace to achieve an energy self-sufficient process. By changing the reforming temperature, the water-to-glycerol mass ratio and the purge from the methanol loop, the conditions for optimizing the overall process relative to methanol and power productions were achieved. Thus, by reforming at 1000 °C and 240 atm, and performing the methanol synthesis at 250 °C and 85 atm, the optimal conditions were a water-to-glycerol mass ratio of 1.68 with a purge ratio of 0.2. Under these conditions 0.270 kg MeOH/kg glycerol and overall energy efficiency of 38.0% were obtained. The separated CO2 for sequestration is 0.38 kg/kg of glycerol.
Experimental study of the supercritical water reforming of glycerol without the addition of a catalyst
(Elsevier, 2013-07) Gutiérrez Ortiz, Francisco Javier; Serrera, Ana; Galera, Sebastián; Ollero de Castro, Pedro Antonio; Universidad de Sevilla. Departamento de 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 reactor without adding a catalyst. Experiments were carried out at a pressure of 240 bar, temperatures of 750–850 °C, and glycerol feed concentrations of 5–30 wt.%. Likewise, the residence time was changed from 12 to 160 s, by handling the feed flow-rate. The dry gas is mainly consisted of H2, CO2, CO, CH4. In addition, small concentrations of glycerol were measured in the liquid phase analysis, but barely traces of others like glycolaldehyde, glyceraldehyde, dihydroxyacetone and lactic acid were detected. Thus, two probable reaction pathways are discussed, which makes it possible to explain the experimental results by using a method applicable to other similar processes. The results showed that the glycerol conversion was almost complete, except at the highest glycerol feed concentration, in which the conversion was of 88%. Hydrogen yields from 2 to 4 mol H2/mol glycerol were obtained at high and low glycerol feed concentrations, respectively, when operating at high temperature and residence time. Besides, it was verified the catalytic effect of the reactor material (Inconel 625) from the trend of the gas product yields with time and the structured carbon nanotubes encountered. The catalytic activity of the reactor material was decreasing to reach a steady state after a few tens of operating hours. This study illustrates that the reforming of glycerol using supercritical water without added catalyst is feasible to achieve a high-yield hydrogen production, and it encourages to continue the research line, to obtain a process economically interesting.
Syngas methanation from the supercritical water reforming of glycerol
(Elsevier, 2014-11) Serrera, Ana; Gutiérrez Ortiz, Francisco Javier; Ollero de Castro, Pedro Antonio; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Ministerio de Ciencia y Tecnología (MCYT). España
An overall heat-integrated process of SCW (supercritical water) reforming of glycerol for methanation of the syngas obtained and power generation is proposed and analyzed. Methanation is the methane synthesis from the hydrogenation of CO and CO2. The SCW reforming is performed at 240 bars. Reforming temperatures from 700 °C to 900 °C and glycerol feed concentrations between 25 wt.% and 50 wt.%, needed to reach an energy self-sufficient process, are studied. For methanation, three adiabatic, fixed-bed reactors are connected in series with intermediate gas cooling, operating at 30 bars. The exit temperatures of these reactors range from 600 °C to 300 °C, respectively. The feed for the methanation section is previously conditioned by a Pressure Swing Adsorption unit to achieve a stoichiometric number of 3. The recommended operating conditions are a reforming temperature of 800 °C and a glycerol concentration of 33 wt.% to obtain 0.166 kg CH4/kg glycerol, 0.433 kWe/kg glycerol and an overall energy efficiency of 61.6%, which may increase up to 76.1% if the hot water leaving the process at 90 °C is considered (cogeneration water). The results of this process were compared to those of the methanol synthesis, previously published, resulting in a better performance, because the carbon proportion converted into methane is higher than into methanol from SCW reforming of glycerol, and the higher specific overall value for the methane production, which considers the price of the product and the electricity jointly.
Modeling and simulation of the adsorption of biogas hydrogen sulfide on treated sewage–sludge
(Elsevier, 2014-10) Gutiérrez Ortiz, Francisco Javier; González Aguilera, Paloma; Ollero de Castro, Pedro Antonio; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental
For the design of a fixed-bed adsorber, it is essential to know the prediction of the column breakthrough. This paper compares two modeling approaches of the dynamic behavior of a fixed bed that contains treated sewage–sludge for biogas desulfurization. The first approach is based on the simple model by Bohart and Adams, which has been widely used to describe the adsorption dynamics when chemical reaction takes place, and the second one uses the linear driving force model (LDF), solving it analytically by Klinkenberg equation and numerically with the aid of Aspen Adsorption. While the Bohart–Adams model uses rectangular isotherm to describe the equilibrium, the LDF model is solved with a more realistic and suitable isotherm. The Klinkenberg solution implies a linear isotherm, and the prediction is not good enough, although better than that of the approach of Bohart–Adams. The trouble is that the linear isotherm used in the analytical solution is not realistic and a nonlinear isotherm is required. This paper presents a methodology to estimate the overall mass transfer coefficient dynamically as well as the isotherm that best fits. Thus, the LDF model with the Freundlich isotherm provide a breakthrough curve that match the experimental results much better than the Bohart–Adams approach. In order to apply the prediction obtained, a scaling up of the lab scale was performed, discussed and assessed.
Biogas desulfurization by adsorption on thermally treated sewage-sludge
(Elsevier, 2014-02) Gutiérrez Ortiz, Francisco Javier; González Aguilera, Paloma; Ollero de Castro, Pedro Antonio; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental
Biogas is a renewable source for power production, but the H2S present must be removed because it is very corrosive and may damage the combustion engines. The adsorption using activated carbon is one of the most used desulfurization methods. The operational life of the activated carbon could be extended if the H2S concentration was reduced prior entering the activated carbon bed by using other cheaper adsorbent. Sewage sludge is a possible inexpensive precursor to obtain adsorbents, and thus it would be valorized. An experimental study was performed using three types of sludge from three Spanish locations, which were activated to increase their adsorption capacity. Two thermal treatments were tested using nitrogen (pyrolysis) and air (calcination), as well as three heating temperatures. The adsorption dynamics of the prepared adsorbents were investigated in a fixed-bed column, determining the breakthrough curves and adsorption capacity of adsorbents. Besides, both their surface properties and their chemical properties were analyzed to get more insight about the adsorbent behavior. In addition, the effect of the oxygen content, relative humidity and the chemical impregnation, using different procedures, were also studied. As a relevant result, the adsorbent obtained by calcination at 700 °C of one of the three kinds of sludge showed a capacity twice of that of a commercial activated carbon without impregnation, although somewhat lower than that of a commercial activated carbon impregnated with a NaOH solution. The results showed that the use of this kind of precursors is very attractive to achieve adsorbents with a relative high adsorption capacity valuable to apply them in an economically feasible pretreatment.
Techno-economic assessment of hydrogen and power production from supercritical water reforming of glycerol
(Elsevier, 2015-03) Galera, Sebastián; Gutiérrez Ortiz, Francisco Javier; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental
Hydrogen and power production from supercritical water reforming of glycerol was techno-economically assessed, considering future states of technology because there is no demonstration plant using this technology. Two different configurations were proposed: supercritical water reforming (SCWR) and autothermal supercritical water reforming (ASCWR). A plant size of 1000 kg/h of glycerol was considered on a process flow-sheet simulated by Aspen Plus with the criterion of being energy self-sufficient. The results reveal that, although ASCWR presents better performance than SCWR in terms of energy efficiency, the investment capital and operational difficulties of ASCWR process leads to higher hydrogen production costs. The levelized production cost of hydrogen was evaluated using a discounted cash flow analysis with a discount rate of 10% and 100% equity financing. Thus, the minimum hydrogen selling price (achieved when net present value is zero) is 5.36 $/kg for SCWR and 5.75 $/kg for ASCWR. These values are somewhat higher than in a few conventional technologies, such as steam methane reforming, although lower than other renewable processes, such as wood gasification. In a future scenario, possible improvements in SCW reforming performance may lead to a decrease in the estimation of renewable hydrogen price.
Thermodynamic analysis of the autothermal reforming of glycerol using supercritical water
(Elsevier, 2011-09) Gutiérrez Ortiz, Francisco Javier; Ollero de Castro, Pedro Antonio; Serrera, Ana; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Ministerio de Ciencia y Tecnología (MCYT). España
Hydrogen can be produced by autothermal reforming of glycerol using supercritical water (SCW). With the aid of AspenPlus™, a systematic thermodynamic analysis of this process has been carried out by the total Gibbs free energy minimization method, which computes the equilibrium composition of synthesis gas (syngas). The predictive Soave-Redlich-Kwong equation of state (EOS) has been used as thermodynamic method in the simulation of the supercritical region. A sensitivity analysis has been conducted both for a pure glycerol feed and pretreated crude glycerol feed coming from biodiesel production. Simulations run so as to calculate the O2 needed to enter the Gibbs reactor (reformer) for achieving the thermoneutral condition (no external heat to sustain the reformer operation is required). Thus, the effect of the main operating parameters (reforming temperature, water to glycerol mole ratio, glycerol purity in the feed of crude glycerol, oxygen to glycerol mole ratio and the inlet feed temperature) aimed to the hydrogen production has been investigated, by obtaining the mole fraction and molar flow-rate of components in syngas, as well as the hydrogen yield. By this way, the most thermodynamic favorable operating conditions at which glycerol may be converted into hydrogen by autothermal reforming using SCW have been identified. As a second part of the study, a conceptual design and an energy and exergy analysis of the overall process will be performed later.
Assessment of plate–wire electrostatic precipitators based on dimensional and similarity analyses
(Elsevier, 2011-09) Gutiérrez Ortiz, Francisco Javier; Navarrete Rubia, Benito; Cañadas Serrano, Luis; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Ministerio de Ciencia y Tecnología (MCYT). España
This paper is focused towards dimensional analysis in ESP model building, showing both the reduction in effort and more effective modeling that can result. Electrostatic precipitators (ESP) are widely used in industry today and much research has been carried out during the last decades. However, dimensional analysis is still an unsettled matter, in spite of it allows to reduce the number of parameters necessary for defining the ESP performance, provides a reliable scaling-up of the desired operating conditions from the pilot-scale to full-scale plant (based on the invariance of the pi-space) as well as a consistent extrapolation within the range covered by dimensionless numbers, and gives a greater flexibility in choice of parameters. This analysis together with the similarity analysis is presented in this work, in order to obtain a functional dependence between a target number and a set of few dimensionless numbers. The target selected has been the ratio of particle dust concentration at the outlet of the ESP and that at the inlet of the ESP. Thus, after doing these analyses, several quite reduced models have been formulated theoretically and later tested and validated with experimental data obtained in a pilot ESP, in order to show an application of the study. By this way, a non-linear regression model matches well with experimental data from a pilot plant.
Process integration and exergy analysis of the autothermal reforming of glycerol using supercritical water
(Elsevier, 2012-06) Gutiérrez Ortiz, Francisco Javier; Ollero de Castro, Pedro Antonio; Serrera, Ana; Galera, Sebastián; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Ministerio de Ciencia y Tecnología (MCYT). España
The most thermodynamically favorable operating conditions at which glycerol can be converted into hydrogen with maximum hydrogen yield by autothermal reforming using supercritical water were identified in a previous paper. As a second part of the study, a conceptual design based on energy integration and exergy analysis of the whole process has been performed. In the proposed scheme, the huge pressure energy of the gas product just at the outlet of the reforming reactor is converted into electrical power and a fraction of the expanded gas used to provide energy support for the process by burning it in a furnace, if needed. By using the optimal conditions found in the previous work, a severe deficit of energy arises in the process. Thus, both water-to-glycerol and oxygen-to-glycerol mole ratios at which thermoneutral conditions are achieved in the reformer are computed by burning all the product gas from the reformer, both for pure and pretreated crude glycerol, at different reforming and preheating temperatures. The pressure used is 240 atm. The effects of the main operating parameters are investigated by sensitivity analysis to identify optimal conditions to maximize power production under autothermal conditions, evaluating the results by energy and exergy analyses. The computations are made with the aid of AspenPlus™, using the predictive Soave–Redlich–Kwong equation of state as the thermodynamic method in the simulation of the supercritical region
An energy and exergy analysis of the supercritical water reforming of glycerol for power production
(Elsevier, 2012-01) Gutiérrez Ortiz, Francisco Javier; Ollero de Castro, Pedro Antonio; Serrera, Ana; Galera, Sebastián; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Ministerio de Ciencia y Tecnología (MCYT). España
As a continuation of a previous work, a conceptual design is proposed for reforming glycerol using supercritical water to produce maximum electrical power in an energy self-sufficient system. The scheme of the process is simulated after discussing some routes to achieve the aim. The selected way takes advantage of the huge pressure energy of reformate products just at the outlet of the reforming process. The expanded product gas is used as a fuel gas to provide the thermal energy required by the reforming process. The evaluation of the thermodynamic performance of the process is carried out by an energy and exergy analysis. As relevant outputs measurements of the process performance, the net work and exergetic efficiencies as well as the mole fraction and molar flow-rates of hydrogen obtained. Glycerol feed concentration in aqueous solution at which no external heat source is needed was obtained, both for pure and pretreated crude glycerol, at 800 °C and 240 atm. The effect of the main operating parameters has been investigated by sensitivity analysis to identify optimal conditions that maximize power production. In the exergy analysis, the thermodynamic efficiencies used for the overall process and for its individual units are suitably discussed. The computation has been made with the aid of AspenPlus™, using the predictive Soave-Redlich-Kwong equation of state as thermodynamic method in the simulation of the supercritical region. The next study in this series of glycerol reforming using SCW will aim to maximize hydrogen production, including the syngas purification, to generate electricity via fuel cells.
Enhancing the matrix-fiber bond in ultra-high-performance fiber-reinforced concrete using a high performance plasticizer. Impact on the flowability, physical and mechanical properties
(Elsevier, 2025) Ruiz Martínez, Jaime D.; Ríos Jiménez, José David; Pérez-Soriano, Eva María; Cifuentes Bulté, Héctor; Leiva Fernández, Carlos; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP972: Mecánica de Materiales y Estructuras; Universidad de Sevilla. TEP118: Ingeniería de los Transportes; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales; Universidad de Sevilla. TEP142: Ingeniería de Residuos
One of the main problems in the use of ultra-high-performance fiber-reinforced concrete (UHPFRC) with steel fibers is low flowability. The addition of 2,3,4,5,6-Pentahydroxycaproic acid sodium salt (SPS) in small amounts (0.05, 0.1 and 0.15 %wt of the cement content) can significantly increase the flowability and setting time. The effects on porosity, matrix chemical composition and fiber-matrix interaction were examined, as well as its influence on strength. Improving the flowability, pores larger than 50 μm show a significant decrease, while those smaller than 0.1 μm show a significant increase. According to the results of thermo-gravimetric analysis, the production of ettringite with finer grains and staggered symbiosis improves the pore structure of the UHPFRC matrix. An improvement of the adhesion of the steel fibers to the matrix was determined by stereomicroscope images, showing evidence of a relationship between SPS dosage and the expanded concrete area surrounding the fiber. The flexural and compressive strength increased by 10 % and 8 %, respectively, when the plasticizer/cement ratio was 0.15 %.
Efect of nano silicon nitride on the microstructural characteristics and mechanical properties of ultra‑high‑performance steel fber reinforced concrete
(Springer Nature, 2025) Ruiz Martínez, Jaime D.; Ríos Jiménez, José David; Pérez-Soriano, Eva María; Cifuentes-Bulté, Héctor; Leiva Fernández, Carlos; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP142: Ingeniería de Residuos; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales; Universidad de Sevilla. TEP972: Mecánica de Materiales y Estructuras
This study investigates the incorporation of an innovative nano-reinforcement, nano silicon nitride (NSIN), to enhance the workability and mechanical performance of ultra-high-performance fber reinforced concrete. The addition of NSIN at dosages of 0.25, 0.5, 0.75, and 1.5 wt% of cement was analyzed to evaluate its impact on the distribution and interaction between steel fbers and the cementitious matrix. Experimental analyses, including thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), were conducted to establish a relationship between the microstructural modifcations, fber-matrix interactions, and the resulting mechanical behavior. The fndings revealed that NSIN increased workability and extended setting time, enabling improved steel fber dispersion and interaction
Supercritical water reforming of model compounds of bio-oil aqueous phase: Acetic acid, acetol, butanol and glucose
(Elsevier, 2016-08) Gutiérrez Ortiz, Francisco Javier; Campanario Canales, Francisco Javier; Ollero de Castro, Pedro Antonio; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental
An experimental study of the supercritical water reforming of model compounds (acetic acid, acetol, 1-butanol and glucose) of the aqueous phase of bio-oil was performed in a tubular reactor without using a catalyst, aimed at maximizing hydrogen yield. In addition, a systematic thermodynamic analysis was carried out using two thermodynamic approaches by simulation in AspenPlus™ (non-stoichiometric approach) and modelling in Matlab™ (stoichiometric approach), selecting first the thermodynamic method that describes the supercritical state more suitably. The effect of the main operating parameters (temperature, organic feed concentration and residence time) on the process performance was investigated thermodynamically and experimentally for each feedstock. Experimental and theoretical results were compared with each other, arising that experimental gas yields were far from equilibrium. However, a better agreement was achieved using an equilibrium approach temperature ranged from 125 to 225 °C.
Life cycle assessment of hydrogen and power production by supercritical water reforming of glycerol
(Elsevier, 2015-05) Galera, Sebastián; Gutiérrez Ortiz, Francisco Javier; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental
The environmental performance of hydrogen and electricity production by supercritical water reforming (SCWR) of glycerol was evaluated following a Life Cycle Assessment (LCA) approach. The heat-integrated process was designed to be energy self-sufficient. Mass and energy balances needed for the study were performed using Aspen Plus 8.4, and the environmental assessment was carried out through SimaPro 8.0. CML 2000 was selected as the life cycle impact assessment method, considering as impact categories the global warming, ozone layer depletion, abiotic depletion, photochemical oxidant formation, eutrophication, acidification, and cumulative energy demand. A distinction between biogenic and fossil CO2 emissions was done to quantify a more realistic GHG inventory of 3.77 kg CO2-eq per kg H2 produced. Additionally, the environmental profile of SCWR process was compared to other H2 production technologies such as steam methane reforming, carbon gasification, water electrolysis and dark fermentation among others. This way, it is shown that SCWR of glycerol allows reducing greenhouse gas emissions and obtaining a favorable positive life cycle energy balance, achieving a good environmental performance of H2 and power production by SCWR of glycerol.
Autothermal Reforming of Glycerol with Supercritical Water for Maximum Power through a Turbine Plus a Fuel Cell
(ACS Publications, 2013-01) Gutiérrez Ortiz, Francisco Javier; Ollero de Castro, Pedro Antonio; Serrera, Ana; Galera, Sebastián; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Ministerio de Ciencia y Tecnología (MCYT). España
An autothermal reforming of glycerol process using supercritical water was proposed to produce maximum power by means of a turbine, from the huge pressure energy of product gas just at the outlet of the reformer, and a proton exchange membrane (PEM) fuel cell, which is fed by a hydrogen-rich stream. The reformate gas is upgraded to hydrogen using serially two water–gas shift reactors and a pressure swing adsorption unit. To achieve the energy self-sufficiency condition, all of the pressure swing adsorption (PSA) off-gas, which mainly consists of methane and non-recovered hydrogen, is used as fuel gas to provide a fraction of the thermal energy required by the overall process, and thus, the oxygen needed within the supercritical autothermal reformer is reduced. The system analysis was performed by simulation using AspenPlus, and simulation results are presented. Different reforming and preheating temperatures were taken, and the best values of both water/glycerol and oxygen/glycerol mole ratios to maximize power production were identified. Thus, by reforming and preheating at 800 °C and 240 atm, a specific power of 1.60 kW/kg of glycerol with exergy and energy efficiencies of 33.5 and 36.0%, respectively, was obtained. In addition, a comparison with the use of glycerol as a fuel in a combined Brayton–Rankine cycle showed a lower overall energy efficiency.
Modeling of fire-tube boilers
(Elsevier, 2011-11) Gutiérrez Ortiz, Francisco Javier; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental
In fire-tube boilers, the flue gas passes inside boiler tubes, and heat is transferred to water on the shell side. A dynamic model has been developed for the analysis of boiler performance, and Matlab has been applied for integrating it. The mathematical model developed is based on the first principles of mass, energy and momentum conservations. In the model, the two parts of the boiler (fire/gas and water/steam sides), the economizer, the superheater and the heat recovery are considered. The model developed can capture the dynamics of the boiler level and boiler pressure with confidence, and it is adequate to approach the boiler performance and, hence, to design and test a control strategy for such boilers. Furthermore, it gives insight of dynamics performance not only during nominal operating conditions, or transient behavior when a parameter is changed, but also for the start-up. The model proposed can be easily implemented and thus, it is useful to assist plant engineers and even for training future operators. A case study of an 800 HP fire-tube boiler burning fuel-oil has been simulated to test the boiler performance by varying operating conditions using a pulse and a step change in fuel and steam flow-rate as well as simulating a start-up form the beginning up to achieve the steady state. The results match qualitatively well when compared to results from the literature.
Thermodynamic Study of the Supercritical Water Reforming of Glycerol
(Elsevier, 2011-07) Gutiérrez Ortiz, Francisco Javier; Ollero de Castro, Pedro Antonio; Serrera, Ana; Sanz, A.; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Ministerio de Ciencia y Tecnología (MCYT). España
Hydrogen can be produced by steam reforming, partial oxidation, autothermal, or aqueous-phase reforming processes using various noble metal based catalysts, but also by supercritical water (SCW) reforming. Using AspenPlus™, a systematic thermodynamic analysis of glycerol reforming using supercritical water has been carried out by the total Gibbs free energy minimization method, which computes the equilibrium composition of synthesis gas (syngas). The predictive Soave–Redlich–Kwong equation of state (EOS) has been used as thermodynamic method in the simulation of the supercritical region, after evaluating it against other EOS methods. A sensitivity analysis has been conducted on supercritical water reforming of pure and pretreated crude glycerol, as obtained from biodiesel production. The effect of the main operating parameters (temperature, concentration of glycerol feed, glycerol purity in the feed of crude glycerol, and pressure) aimed to the hydrogen production has been investigated in the reforming process, by obtaining the mole fraction and molar flow-rate of components in syngas, as well as the hydrogen yield. Selectivity to the different compounds has been also calculated. By this way, the thermodynamic favorable operating conditions at which glycerol may be converted into hydrogen by SCW reforming have been identified. The simulation results agree well with some few experimental data from the literature. This study is the first of a series addressed to glycerol reforming using SCW.
Determinación de la actividad biológica y de la biomasa en sistemas de depuración: Aplicación en la detección de estados de inhibición o toxicidad
(Instituto Químico de Sarriá, 2005) Isac Oria, Laura; Arnáiz Franco, Carmen; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental
Los ensayos de detección de la toxicidad en el fango activo que son realizados sobre los propios microorganismos del sistema están basados en la estimación de la viabilidad y niveles de actividad biológica de dichos microorganismos en respuesta al impacto, ambiental recibido. Viabilidad y actividad de la biomasa microbiana son de por si parámetros de control del proceso cuyas determinaciones pueden ser adaptadas a los procedimientos de evaluación de Ia inhibición o toxicidad ejercidos por determinados compuestos presentes en los influentes de las estaciones depuradoras. En este trabajo se realiza una revisión de los principales métodos de determinación de la actividad biológica y de la biomasa, así como de sus aplicaciones a la detección de estados de inhibición/toxicidad sobre una muestra de fango activo.
Anaerobic digestion of dairy wastewater by inverse fluidization: The inverse fluidized bed and the inverse turbulent bed reactors
(Taylor & Francis, 2003) Arnáiz Franco, Carmen; Buffière, Pierre; Elmaleh, Samuel; Lebrato Martínez, Julián; Moletta, Renè; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Universidad de Sevilla. Departamento de Ingeniería Química; Ministerio de Educación y Cultura (MEC). España
This paper describes the application of the inverse fluidization technology to the anaerobic digestion of dairy wastewater. Two reactors were investigated: the inverse fluidized bed reactor and the inverse turbulent reactor. In these reactors, a granular floating solid is expanded by a down-flow current of effluent or an up-flow current of gas, respectively. The carrier particles (Extendospheres(™)) were chosen for their large specific surface area (20,000 m2m−3) and their low energy requirements for fluidization (gas velocity of 1.5 mm s−1, 5.4 m h−1). Organic load was increased stepwise by reducing hydraulic retention time from more than 60 days to 3 days, while maintaining constant the feed COD concentration. Both reactors achieved more than 90% of COD removal, at an organic loading rate of 10–12 kgCOD m−3d−1, respectively. The performances observed were similar or even higher than that of other previously tested fluidized bed technologies treating the same wastewater. It was found that the main advantages of this system are: low energy requirement, because of the low fluidization velocities required; there is no need of a settling device, because solids accumulate at the bottom of the reactor, so they can be easily drawn out and particles with high-biomass content can be easily recovered. Lipid phosphate concentration has been revealed as a good method for biomass estimation in biofilms since it only includes living biomass.

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