Sustainable construction materials and technologies, 2019
In this work, the possibility of reusing ashes issued by an oxyfuel combustion process (OC) as a ... more In this work, the possibility of reusing ashes issued by an oxyfuel combustion process (OC) as a source of material in the production of belite calcium sulfoaluminate BCSA cements has been investigated. OF process is one of the most promising combustion technologies for CO2 reduction from power plants. Combustion tests were carried out in an oxyfuel bubbling fluidized bed pilot plant. Four BCSA clinker-generating raw mixes were heated in a laboratory electric oven in the temperatures range 1150°-1350°C: one included only natural materials (limestone, clay, bauxite and gypsum), the others contained OC ashes as total substitute for clay. X-ray diffraction (XRD) analysis on the burning products showed high conversion of reactants toward the main BCSA clinker components (C2S and C4A3$), especially at 1200° or 1250°C. Moreover, physical-mechanical tests associated with XRD and differential thermal-thermogravimetric analyses accomplished on all the cements (obtained by adding natural gypsum to the clinkers produced at the best synthesis temperatures) generally displayed a similar hydration behaviour.
The improvement of specific energy consumption and the reduction of steam temperature to drive th... more The improvement of specific energy consumption and the reduction of steam temperature to drive the system are two of the main challenges to improve the performance of distillation processes in desalination plants, especially for multi-effect distillation technique. The low temperature requirement is a suitable characteristic to integrate multi-effect distillation units as bottom system. Obviously, one of the best options is to use low-grade heat from power plants or gas turbines as a cogeneration system. Mitigation of CO 2 emissions from power plants will be a priority for most of power companies in a near future, one of the most promising techniques is carbon capture and storage. Nevertheless, energy requirements and efficiency penalties in the overall system are some of their disadvantages. They are largely caused by CO 2 compression above both its critical temperature and pressure prior storage. There are a huge low-grade heat coming from condensing water in the CO 2 stream and from compressors intercooling that is suitable to reduce energy penalties in CO 2 capture process and to produce desalted water. With the aim of analyzing these combined systems (desalination unit, power plant and CO 2 capture), five different integration configurations have been proposed and simulated. Three aspects have been analyzed: the energy penalty in the steam cycle, the water costs associated to thermal energy and their environmental impact. Results show that although CO 2 capture systems reduce power generation and therefore increases its costs, available heat from those systems could produce distilled water at affordable costs.
ABSTRACT Air-staged combustion is a known, successful way to reduce NOx emission in solid-fired s... more ABSTRACT Air-staged combustion is a known, successful way to reduce NOx emission in solid-fired systems. Despite this measure has been more frequently applied in pulverized fuel units, it can also be found in fluidized bed boilers. In this case, air-staging affects the fluid dynamics and other closely related issues, like combustion efficiency or desulphurization. The extent of these effects is still to be completely determined in oxy-fired boilers. This paper discusses the influence of gas-staging on CO, NOx and SO2 emissions in fluidized bed oxy-firing. An experimental plan was carried out in a 90 kWth bubbling fluidized bed with two secondary gas inlets located at different heights. The tests were conducted firing two Spanish coals (anthracite and lignite) for a variety of O2/CO2 atmospheres and secondary flow rates. The secondary gas ratio has been revealed as the key variable, since solid mixing and particle conversion in the dense zone are directly affected. While gas-staging is shown to be an effective measure to reduce NOx emissions for all the coals and atmospheres tested, SO2 is however penalized, so finally a trade-off solution is needed. These trends are deepened for the higher values of CO2 concentration.
The objective of this work is to reflect on the main methodological aspects to take into account ... more The objective of this work is to reflect on the main methodological aspects to take into account in the development of video teaching for use as modular and reusable learning objects. This reflection is one of the results of the work carried out by the authors in a teaching innovation project funded by the University of Zaragoza during the academic years 2015-16, 2016-17 and 2017-18. In this project, 25 educational videos under licenses have been created to improve the learning outcomes of five subjects in the field of thermodynamics and thermal engineering, currently taught at three different qualifications. Preparing educational videos requires different strategies compared with an in real time session and aspects such as the approach of the contents, the adaptation to the environment and technical quality influence the effectiveness as a learning tool by what must be taken into account in its development phase.
In order to improve the operational behavior (efficiency and stability) of the cyclone separator ... more In order to improve the operational behavior (efficiency and stability) of the cyclone separator system in Escatron PFBC power plant, a laboratory-scale cold model has been built. Scaling laws have been applied to simulate the hydrodynamics and performance of the systems, in order to obtain valuable and relevant results for commercial PFBC technology. It has been demonstrated that the filtration effect of the cyclones in a PFBC power plant is extended down to the dipleg. Previous studies in a laboratory-scale cold model have pointed out the importance of the vortex inside the dipleg and its influence in the separation efficiency. It is due to the fact that the cyclone effect is still active in the dipleg. These studies are based in pressure drop dipleg measurements. Thermal anemometry has been used to measure the gas velocity and turbulence of several installations. In this case it has been used in order to check the vortex activity in the upper section of the dipleg of a cyclone separator system for a PFBC power plant. This paper deals with the results and conclusions of the research about the velocity field inside the dipleg. The possibility of improving cyclone efficiency by means of extending the more » vortex, the study of the variables affecting the vortex (and also the cyclone efficiency) and the establishment of a flow-pattern in the dipleg are the main objectives of the research and the paper. « less
Prevención, trabajo y salud: Revista del Instituto Nacional de Seguridad e Higiene en el Trabajo, 2004
El comportamiento termico del ser humano tiene importantes implicaciones sobre la vida cotidiana.... more El comportamiento termico del ser humano tiene importantes implicaciones sobre la vida cotidiana. En la evaluacion de puestos de trabajo, donde resulta fundamental conocer la respuesta y adaptacion del cuerpo humano a distintas situaciones. Esta respuesta dependera tanto del funcionamiento termorregulador de la persona como de las condiciones externas, temperatura, humedad, influencia de la indumentaria, la radiacion solar directa (o de otro foco) o el trabajo realizado entre otras variables. La necesidad de realizar una simulacion del comportamiento termico del ser humano y de la ropa que utiliza es obvia, cuanto mejor se conozcan las variables de las que depende, como y cuanto afectan a la respuesta termica obtenida, mejor se podra hacer frente a situaciones extremas, se podran establecer una serie de limites saludables y de confort en diferentes situaciones cotidianas o e incluso disenar tejidos especiales para resistir las condiciones atmosfericas mas adversas. En cualquier caso la disponibilidad de una herramienta informatica que sirva para simular el comportamiento termico del ser humano permitira ahorrar mucho tiempo y coste en experimentacion. Con el nuevo modelo desarrollado se pretende calcular, para cada parte del cuerpo, todas las variables que intervienen en la transferencia de calor en el ser humano, teniendo en cuenta la ropa que lleva el individuo en cada zona y las caracteristicas de esta (aislamiento termico, espesor y permeabilidad al vapor de agua). El objetivo es realizar un modelo util para realizar comparaciones y obtener, para un determinado puesto de trabajo y unas condiciones ambientales dadas, tendencias de la evolucion de las temperaturas de distintas partes del cuerpo, y otras variables de interes como sudoracion, vasodilatacion o vasoconstriccion.
ABSTRACT The external heat exchanger (EHE) plays an essential role in the adequate control of the... more ABSTRACT The external heat exchanger (EHE) plays an essential role in the adequate control of the heat balance in large-scale oxy-fuel circulating fluidized bed (CFB) boilers. However, the EHE of an oxy-fuel CFB presents two particularities compared to the known air-combustion case: the composition of the fluidizing gas and the higher flow of recycled solids. Both these issues are addressed in this paper: Firstly, heat transfer coefficients are measured in a 90 kW bubbling fluidized bed, operated at different temperatures, with air and with a wide range of O2/CO2 mixtures. Thereafter, experiments are also carried out in a cold scaled-down EHE in order to assess the influence of an increment in the solids flow across the EHE on heat transfer. Based on the results of these experiments, an expression for the heat transfer coefficient is proposed which accounts for gas composition and solids flow rate. Finally, a model for the EHE is integrated into a large oxy-fuel CFB model in order to quantify the influence of oxy-fuel operation mode on the heat transfer surfaces required in the EHE
Due to security, sustainability of supply, strategic and energetic dependence reasons, it is well... more Due to security, sustainability of supply, strategic and energetic dependence reasons, it is well accepted the necessity to continue using coal as main fuel for producing electricity from power plants. In order to reduce CO 2 concentrations in the atmosphere, it is essential to ...
Some remarkable hybridizations to enhance Power to Gas are those that avoid carbon capture penalt... more Some remarkable hybridizations to enhance Power to Gas are those that avoid carbon capture penalties. A suitable option to this end is the hybridization of PtG with an oxy-fuel combustion process. In oxy-fuel combustion, pure oxygen is used as comburent instead of air. Conventionally, requiring an air separation unit to produce the oxygen leads to a strong penalty. However, electrolysis in PtG by-produces oxygen, which can be supplied to the oxy-fuel combustion thus avoiding the penalty. Three case studies of this integration are presented in the chapter: a small oxy-fuel combined cycle, a district heating system and a cogeneration system for large urban buildings.
Sustainable construction materials and technologies, 2019
In this work, the possibility of reusing ashes issued by an oxyfuel combustion process (OC) as a ... more In this work, the possibility of reusing ashes issued by an oxyfuel combustion process (OC) as a source of material in the production of belite calcium sulfoaluminate BCSA cements has been investigated. OF process is one of the most promising combustion technologies for CO2 reduction from power plants. Combustion tests were carried out in an oxyfuel bubbling fluidized bed pilot plant. Four BCSA clinker-generating raw mixes were heated in a laboratory electric oven in the temperatures range 1150°-1350°C: one included only natural materials (limestone, clay, bauxite and gypsum), the others contained OC ashes as total substitute for clay. X-ray diffraction (XRD) analysis on the burning products showed high conversion of reactants toward the main BCSA clinker components (C2S and C4A3$), especially at 1200° or 1250°C. Moreover, physical-mechanical tests associated with XRD and differential thermal-thermogravimetric analyses accomplished on all the cements (obtained by adding natural gypsum to the clinkers produced at the best synthesis temperatures) generally displayed a similar hydration behaviour.
The improvement of specific energy consumption and the reduction of steam temperature to drive th... more The improvement of specific energy consumption and the reduction of steam temperature to drive the system are two of the main challenges to improve the performance of distillation processes in desalination plants, especially for multi-effect distillation technique. The low temperature requirement is a suitable characteristic to integrate multi-effect distillation units as bottom system. Obviously, one of the best options is to use low-grade heat from power plants or gas turbines as a cogeneration system. Mitigation of CO 2 emissions from power plants will be a priority for most of power companies in a near future, one of the most promising techniques is carbon capture and storage. Nevertheless, energy requirements and efficiency penalties in the overall system are some of their disadvantages. They are largely caused by CO 2 compression above both its critical temperature and pressure prior storage. There are a huge low-grade heat coming from condensing water in the CO 2 stream and from compressors intercooling that is suitable to reduce energy penalties in CO 2 capture process and to produce desalted water. With the aim of analyzing these combined systems (desalination unit, power plant and CO 2 capture), five different integration configurations have been proposed and simulated. Three aspects have been analyzed: the energy penalty in the steam cycle, the water costs associated to thermal energy and their environmental impact. Results show that although CO 2 capture systems reduce power generation and therefore increases its costs, available heat from those systems could produce distilled water at affordable costs.
ABSTRACT Air-staged combustion is a known, successful way to reduce NOx emission in solid-fired s... more ABSTRACT Air-staged combustion is a known, successful way to reduce NOx emission in solid-fired systems. Despite this measure has been more frequently applied in pulverized fuel units, it can also be found in fluidized bed boilers. In this case, air-staging affects the fluid dynamics and other closely related issues, like combustion efficiency or desulphurization. The extent of these effects is still to be completely determined in oxy-fired boilers. This paper discusses the influence of gas-staging on CO, NOx and SO2 emissions in fluidized bed oxy-firing. An experimental plan was carried out in a 90 kWth bubbling fluidized bed with two secondary gas inlets located at different heights. The tests were conducted firing two Spanish coals (anthracite and lignite) for a variety of O2/CO2 atmospheres and secondary flow rates. The secondary gas ratio has been revealed as the key variable, since solid mixing and particle conversion in the dense zone are directly affected. While gas-staging is shown to be an effective measure to reduce NOx emissions for all the coals and atmospheres tested, SO2 is however penalized, so finally a trade-off solution is needed. These trends are deepened for the higher values of CO2 concentration.
The objective of this work is to reflect on the main methodological aspects to take into account ... more The objective of this work is to reflect on the main methodological aspects to take into account in the development of video teaching for use as modular and reusable learning objects. This reflection is one of the results of the work carried out by the authors in a teaching innovation project funded by the University of Zaragoza during the academic years 2015-16, 2016-17 and 2017-18. In this project, 25 educational videos under licenses have been created to improve the learning outcomes of five subjects in the field of thermodynamics and thermal engineering, currently taught at three different qualifications. Preparing educational videos requires different strategies compared with an in real time session and aspects such as the approach of the contents, the adaptation to the environment and technical quality influence the effectiveness as a learning tool by what must be taken into account in its development phase.
In order to improve the operational behavior (efficiency and stability) of the cyclone separator ... more In order to improve the operational behavior (efficiency and stability) of the cyclone separator system in Escatron PFBC power plant, a laboratory-scale cold model has been built. Scaling laws have been applied to simulate the hydrodynamics and performance of the systems, in order to obtain valuable and relevant results for commercial PFBC technology. It has been demonstrated that the filtration effect of the cyclones in a PFBC power plant is extended down to the dipleg. Previous studies in a laboratory-scale cold model have pointed out the importance of the vortex inside the dipleg and its influence in the separation efficiency. It is due to the fact that the cyclone effect is still active in the dipleg. These studies are based in pressure drop dipleg measurements. Thermal anemometry has been used to measure the gas velocity and turbulence of several installations. In this case it has been used in order to check the vortex activity in the upper section of the dipleg of a cyclone separator system for a PFBC power plant. This paper deals with the results and conclusions of the research about the velocity field inside the dipleg. The possibility of improving cyclone efficiency by means of extending the more » vortex, the study of the variables affecting the vortex (and also the cyclone efficiency) and the establishment of a flow-pattern in the dipleg are the main objectives of the research and the paper. « less
Prevención, trabajo y salud: Revista del Instituto Nacional de Seguridad e Higiene en el Trabajo, 2004
El comportamiento termico del ser humano tiene importantes implicaciones sobre la vida cotidiana.... more El comportamiento termico del ser humano tiene importantes implicaciones sobre la vida cotidiana. En la evaluacion de puestos de trabajo, donde resulta fundamental conocer la respuesta y adaptacion del cuerpo humano a distintas situaciones. Esta respuesta dependera tanto del funcionamiento termorregulador de la persona como de las condiciones externas, temperatura, humedad, influencia de la indumentaria, la radiacion solar directa (o de otro foco) o el trabajo realizado entre otras variables. La necesidad de realizar una simulacion del comportamiento termico del ser humano y de la ropa que utiliza es obvia, cuanto mejor se conozcan las variables de las que depende, como y cuanto afectan a la respuesta termica obtenida, mejor se podra hacer frente a situaciones extremas, se podran establecer una serie de limites saludables y de confort en diferentes situaciones cotidianas o e incluso disenar tejidos especiales para resistir las condiciones atmosfericas mas adversas. En cualquier caso la disponibilidad de una herramienta informatica que sirva para simular el comportamiento termico del ser humano permitira ahorrar mucho tiempo y coste en experimentacion. Con el nuevo modelo desarrollado se pretende calcular, para cada parte del cuerpo, todas las variables que intervienen en la transferencia de calor en el ser humano, teniendo en cuenta la ropa que lleva el individuo en cada zona y las caracteristicas de esta (aislamiento termico, espesor y permeabilidad al vapor de agua). El objetivo es realizar un modelo util para realizar comparaciones y obtener, para un determinado puesto de trabajo y unas condiciones ambientales dadas, tendencias de la evolucion de las temperaturas de distintas partes del cuerpo, y otras variables de interes como sudoracion, vasodilatacion o vasoconstriccion.
ABSTRACT The external heat exchanger (EHE) plays an essential role in the adequate control of the... more ABSTRACT The external heat exchanger (EHE) plays an essential role in the adequate control of the heat balance in large-scale oxy-fuel circulating fluidized bed (CFB) boilers. However, the EHE of an oxy-fuel CFB presents two particularities compared to the known air-combustion case: the composition of the fluidizing gas and the higher flow of recycled solids. Both these issues are addressed in this paper: Firstly, heat transfer coefficients are measured in a 90 kW bubbling fluidized bed, operated at different temperatures, with air and with a wide range of O2/CO2 mixtures. Thereafter, experiments are also carried out in a cold scaled-down EHE in order to assess the influence of an increment in the solids flow across the EHE on heat transfer. Based on the results of these experiments, an expression for the heat transfer coefficient is proposed which accounts for gas composition and solids flow rate. Finally, a model for the EHE is integrated into a large oxy-fuel CFB model in order to quantify the influence of oxy-fuel operation mode on the heat transfer surfaces required in the EHE
Due to security, sustainability of supply, strategic and energetic dependence reasons, it is well... more Due to security, sustainability of supply, strategic and energetic dependence reasons, it is well accepted the necessity to continue using coal as main fuel for producing electricity from power plants. In order to reduce CO 2 concentrations in the atmosphere, it is essential to ...
Some remarkable hybridizations to enhance Power to Gas are those that avoid carbon capture penalt... more Some remarkable hybridizations to enhance Power to Gas are those that avoid carbon capture penalties. A suitable option to this end is the hybridization of PtG with an oxy-fuel combustion process. In oxy-fuel combustion, pure oxygen is used as comburent instead of air. Conventionally, requiring an air separation unit to produce the oxygen leads to a strong penalty. However, electrolysis in PtG by-produces oxygen, which can be supplied to the oxy-fuel combustion thus avoiding the penalty. Three case studies of this integration are presented in the chapter: a small oxy-fuel combined cycle, a district heating system and a cogeneration system for large urban buildings.
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Papers by Luis M Romeo