Luis M. Romeo

Operation of a cyclonic preheater in the Ca-looping for CO2 capture.

Calcium looping is an emerging technology for CO2 capture that makes use of the calcium oxide as a sorbent. One of its main issues is the significant energy consumption in the calciner, where the regeneration of the sorbent takes place. Nevertheless, as a high temperature looping technology, the surplus heat flows may be used to reduce the energy needs in this reactor. The addition of a cyclonic preheater similar to those used in the cement industry is proposed in this work. A calcium looping system was modeled and simulated to assess the advantages and disadvantages of the inclusion of a cyclonic preheater. Despite the negative effect on the maximum average capture capacity of the sorbent, a reduction on the coal and oxygen consumptions and on the extra CO2 generated in the calciner is obtained.

Gas-particle flow inside cyclone diplegs with pneumatic extraction

This paper presents a detailed flow analysis inside cyclone diplegs equipped with bottom gas extraction. Up to now, little experimental work has been done related with these devices, specially used for hot gas cleaning applications, such as pressurized fluidized bed combustion (PFBC). Tests varying inlet solid loading and gas extraction flow rate were carried out in a one-fifth cold-flow model of a PFBC cyclone. Velocity and pressure measurements along cyclone dipleg have been carried out. Results from experimental measurements reveal that the swirling flow penetrates inside the dipleg, deeper than can be anticipated by literature predictions on conventional cyclone designs. This effect is caused by the high inlet velocities of this kind of cyclones and the gas suction at dipleg bottom. Dipleg pressure coefficient is shown to be a function of the inlet solid loading and the tangential to axial velocity ratio. Although for standard cyclone designs it has been claimed that underneath the vortex end there is a stagnant region where solid recirculation and reentrainment can occur, it has been experimentally verified that even with a small percent of gas extracted at the bottom a substantial tangential velocity component is induced at dipleg bottom. This velocity assures solids conveyance to the extraction device. As solid loading is increased, an upward movement of the vortex end is detected from wall pressure measurements. The solid loading causes an important decrease of the vortex energy and, consequently, a weakening of the dipleg tangential velocity. A new method for measuring the vortex penetration in dipleg is presented.

Effect of the Solid Loading on a PFBC Cyclone with Pneumatic Extraction of Solids

This paper presents the effects of solid loading on the performance of a cyclone with pneumatic extraction of solids. The cyclone is a non-conventional design, especially used for hot-gas cleaning applications such as pressurized fluidized bed combustors (PFBC). A scaled-down cold-flow model was employed for the research. Experiments were conducted at 9–14 m/s inlet gas velocities, inlet solid loadings ranging from 30 to 230 g/kg gas, and bottom gas extraction percentages from 0.3 to 1.5%. Experimental results of pressure drop resistance coefficients and collection efficiency were compared with literature predictions. At PFBC operating conditions, cyclone geometry and solid concentration are the main parameters influencing cyclone pressure drop and collection efficiency. The vortex penetration in dipleg causes lower pressure drop values and higher collection efficiencies than predicted. These parameters can be suitably predicted for PFBC cyclones by introducing a modified penetration length in Muschelknautzs model [1]. For the present cyclone design, a new correlation of pressure drop, including the influence of solid loading, is proposed. A new method for detecting cyclone fouling, not previously addressed, is also presented, based on the evolution of the pressure drop resistance coefficient. An enhanced separation efficiency has been found, related to collection efficiency, which is especially important for particle sizes below 10 μm revealing agglomeration effects.

Policies for the setting up of alternative energy systems in European SMEs: a case study

Abstract SMEs—which provide two-thirds of all jobs in the European Union—have proven to be particularly dynamic vehicles for innovation so they must be given easy access to available advanced energy systems. In this scenario, renewable energies represent the most adequate resource to supply SMEs, included in rural areas, assuring continuity and without dependence to the fluctuations of energy market. SMEnergy project results have to be taken into account because the project, specially designed for the Spanish Region of Aragon, can be implemented to specific European Areas needs and integrated at a wider key synergy’s project.

Simulation of a full-scale pressurized fluidized bed combustor by using semi-empirical pilot plant correlations

Abstract A model, based on semi-empirical correlations, was developed to simulate the behavior of a pressurized fluidized bed combustor (PFBC) under various operating conditions. This paper presents the results of a comprehensive survey of one-dimensional empirical correlations applicable to a PFBC and which were used to assemble a 1-D predictive model of the complete performance of a pressurized fluidized bed combustor. The model was adjusted in order to reproduce process and in-bed data taken at Escatron PFBC power station (Spain) under a wide range of operating conditions. The novelty of this approach lies in the use of full-scale information to validate empirical correlations, the objective being to draw specific conclusions on the reliability of empirical PFBC modeling. The model was validated using experimental power plant data. Good agreement was found between the computed results and actual plant data of bed temperature profiles, bed density, char and sorbent elutriation, fuel feed rate, in-bed and entrainment particle size distributions, oxygen and carbon dioxide concentrations, heat transfer coefficients along the combustor height and heat transfer to the tube bundles under different operational regimes. This paper describes the model, as well as its results, validation and prospects for future work.

Energy and exergy pertaining to solid looping cycles

Abstract This chapter describes why calcium looping and chemical looping combustion technologies are more efficient than their rivals, particularly when the aim is to produce a stream of CO2 for storage or utilization. The focus is on causes of inefficiency, and the development of solid looping cycle energy and exergy analyses as key tools to achieving designs with low efficiency penalties. The chapter concludes with a discussion of other CO2 capture technologies, and makes comparisons to highlight the advantages of solid looping processes. Future trends, especially in advanced process layouts of solid looping cycles, are also summarized.

Repowering of Fossil Fuel Power Plants and Reversible Carbonation/Calcination Cycle for CO2 Abatement

Fossil fuel power plants account for about a third of global carbon dioxide emissions. Coal is the major power-generation fuel, being used twice as extensively as natural gas (IEA, 2003). Moreover, on a global scale, coal demand is expected to double over the period to 2030; IEA estimates that 4500 GWe of new installed power will be required. Coal is expected to provide 40% of this figure. It is thus obvious that coal power plants must be operative to provide such amount of energy in the short term, at the same time reducing their CO2 emissions in a feasible manner and increasing their efficiency and capacity. However, the main technologies currently considered to effect CO2 capture, both post-and pre-combustion, introduce a great economic penalty and largely reduce the capacity and efficiency. One of these technologies involves the separation of CO2 from high temperature flue gases using the reversible carbonation reaction of CaO and the calcination of CaCO3 . The process is able to simultaneously capture sulfur dioxide. The major disadvantage of this well-known concept is the great amount of energy consumption in the calcinator and auxiliary equipment. This paper proposes a new, feasible approach to supply this energy which leads to an optimal integration of the process within a conventional coal power plant. Calcination is accomplished in a kiln fired by natural gas, whereas a gas turbine is used to supply all the auxiliary power. Flue gases from the kiln and the gas turbine can substitute a significant part of the heat duty of the steam cycle heaters, thus accomplishing feed water repowering of the steam turbine. This novel CO2 -capture cycle is proposed to be integrated with aging coal-fired power plants. The paper shows that an optimal integration of both elements represents one of the best methods to simultaneously achieve: a) an increase of specific generating capacity in a very short period of time, b) a significant abatement of CO2 emissions, and c) an increase of plant efficiency in a cost-effective way.Copyright

Experiencia piloto de aula invertida para mejorar el proceso de enseñanza-aprendizaje en la asignatura de Termodinámica Técnica

Este trabajo ha sido financiado por medio de los proyectos de innovacion docente PIIDUZ_16_032 y PIIDUZ_16_165 (Programa de Proyectos de Innovacion Docente para Grupos de Profesores del Vicerrectorado de Politica Academica de la Universidad de Zaragoza).

Evaluación de la mejora del proceso de enseñanza-aprendizaje mediante la integración de objetos de aprendizaje reutilizables en un curso abierto OCW

En un contexto de Recursos Educativos Abiertos (REA), el concepto de Objetos de Aprendizaje Reutilizables (OAR), en formato digital y de caracter independiente y autonomo, resulta de gran interes para su uso en contextos educativos multiples como los cursos abiertos (OCW, por sus siglas en ingles). El objetivo de este trabajo es presentar los principales resultados obtenidos hasta la fecha en un proyecto de innovacion docente financiado por la Universidad de Zaragoza durante los cursos academicos 2015-16 y 2016-17 (Ref. PIIDUZ_15_079, 16_165 y 16_032). En este proyecto, se han creado 25 OARs en forma de videos docentes bajo licencias Creative Commons para mejorar los resultados de aprendizaje de cinco asignaturas en el campo de la Termodinamica y la Ingenieria Termica, que actualmente se imparten en tres titulaciones distintas. Para evaluar la mejora del proceso de ensenanza-aprendizaje obtenida mediante los videos, se han preparado y lanzado diferentes cuestionarios para los estudiantes. Hasta el momento, los resultados muestran que la mayoria de los estudiantes estan satisfechos con esta experiencia de innovacion. En este sentido, consideran que el uso de videos docentes ha mejorado su proceso de aprendizaje, aumentando su motivacion para estudiar y ayudandoles a entender los conceptos mas complejos. Keywords: OAR, OCW, REA, videos docentes, innovacion docente.

Energy Intensity Reduction of Ca-Looping CO2 Capture by Applying Mixing Loop Seals and Cyclonic Systems

Abstract This work faces the challenge of cutting the specific energy demand in the CO2 capture process based on Ca-looping technology. The use of high-temperature sorbents allows an efficient integration of the excess heat flows. Up to now, several investigations studied the Ca-looping integration with external systems such as a steam cycle. In this research, a further step is done by comparing technological solutions for the internal heat integration with the aim of reducing the energy needs. Particles preheating before entering the regeneration reactor appears as an opportunity for energy saving since solids have to be heated up around 250–300°C from one reactor to another. Two different internal heat integration possibilities making use of a particle separation device and a mixing valve are presented and compared. The former consists of the inclusion of a cyclonic preheater. This configuration presents the a priori advantage of a more developed technology since it is widely used in the cement industry but the drawback of a worse gas–solid heat exchange. Although there is a lack of practical experience regarding the use of a single seal valve to feed two reactors, this configuration presents a promising prospective related to the excellent heat exchange features of the solid flows. The aim is to obtain comparative results by means of implementing advanced thermochemical models, in order to make progress on the development of less energy-intensive configurations of the calcium looping.