Ca-looping for postcombustion CO2 capture: A comparative analysis on the performances of dolomite and limestone

The low cost and wide availability of natural limestone (CaCO3) is at the basis of the industrial competitiveness of the Ca-looping (CaL) technology for postcombustion CO2 capture as already demonstrated by ~1Mwt scale pilot projects. A major focus of studies oriented towards further improving the efficiency of the CaL technology is how to prevent the gradual loss of capture capacity of limestone derived CaO as the number of carbonation/calcination cycles is increased. Natural dolomite (MgCa(CO3)2) has been proposed as an alternative sorbent precursor to limestone. Yet, carbonation of MgO is not thermodynamically favorable at CaL conditions, which may hinder the capture performance of dolomite. In the work described in this paper we carried out a thermogravimetric analysis on the multicyclic capture performance of natural dolomite under realistic regeneration conditions necessarily implying high calcination temperature, high CO2 concentration and fast transitions between the carbonation and calcination stages. Our study demonstrates that the sorbent derived from dolomite has a greater capture capacity as compared to limestone. SEM analysis shows that MgO grains in the decomposed dolomite are resistant to sintering under severe calcination conditions and segregate from CaO acting as a thermally stable support which mitigates the multicyclic loss of CaO conversion. Moreover, full decomposition of dolomite is achieved at significantly lower calcination temperatures as compared to limestone, which would help improving further the industrial competitiveness of the technology.Junta de Andalucía FQM-5735, TEP-7858, TEP-1900Ministerio de Economía y Competitividad FIS2011-25161, CTQ2011- 2762

«A Baptism of Fire»: Towards a Practical Hybrid Approach for the Lexicographic Indexation of Phraseological Units with Religious Lexical Components in English and Spanish

Traditionally, researchers have had a particular interest in the study of the relationship between phraseology and lexicography [e.g., Alonso Ramos (2006); Mellado Blanco (2008); Buendía Castro and Faber (2015); Paquot (2015); Nuccorini (2020)] to the point of having labeled it a «scientific marriage» (Leroyer 2006). In addition, scholars have been increasingly interested in the semantic analysis of phraseological units (henceforth PUs) [e.g., Grčić Simeunović and de Santiago (2016) and Torijano and Recio (2019)]. Among the problems that these and several other studies have pointed out, there is the recurrent reference to inaccuracy and difficulty in indexing PUs in lexicographic resources. Although some scholars consider onomasiological approaches as an interesting starting point [e.g., Bosque (2017) and Siepmann (2008)], a systematic methodology in phraseology that includes both the semantical analysis of the entries and their indexation is still needed./nWe intend to address that need here through the analysis of 242 idioms (199 in Spanish and 43 in English) extracted from a 21,045-idiom database that was compiled from two phraseological dictionaries: the Diccionario fraseológico documentado del español actual (henceforth DFDEA) (Seco, Andrés et al., 2004), and the Collins COBUILD Dictionary of Idioms (henceforth CCDOI) (Sinclair and Moon 1997). The criteria employed to select the resulting analysis units were: (i) they had to include at least one lexical component related to religion, and (ii) the idiom had to be nominal or verbal. The religious component was identified semi-automatically by using the UCREL's Semantic Analysis System (USAS) (Archer et al., 2002)./nThe contributions of this paper are as follows: (i) it presents a lexicographic analysis of the macrostructure and microstructure of the two phraseological resources previously mentioned, (ii) it offers a model of semantic analysis for PUs with religion-related components, (iii) it proposes an alternative indexation method of PUs in lexicographic resources involving semasiological and onomasiological approaches; and finally, (iv) it shows a systematic way to use semantic and pragmatic information in order to create semantic entries for PUs./nIn conclusion, by closely examining said set of phraseological entries, this study sheds light on the semantic composition of Pus. It also suggests a systematic hybrid approach for their lexicographic indexation in English and Spanish.Tradicionalmente, los investigadores han demostrado un particular interés por el estudio de la relación entre fraseología y lexicografía [p. ej. Alonso Ramos (2006); Mellado Blanco (2008); Buendía Castro y Faber (2015); Paquot (2015); Nuccorini (2020)] hasta el punto de denominarlo «matrimonio científico» (Leroyer 2006). De igual manera, los académicos se han interesado de manera creciente por el análisis semántico de las unidades fraseológicas (en nuestro texto, PUs, por sus siglas en inglés) [e.g., Grčić Simeunović y de Santiago (2016) y Torijano y Recio (2019)]. Entre los problemas que estos y otros estudios han señalado se encuentra la recurrente referencia a la inexactitud y la dificultad para indexar las PUs en los recursos lexicográficos. Aunque algunos investigadores consideran los enfoques onomasiológicos como un interesante punto de partida [e.g., Bosque (2017) y Siepmann (2008)], sigue siendo necesario establecer una metodología sistemática respecto a la fraseología que incluya tanto el análisis semántico de las entradas como su indexación./nNos proponemos abordar esta necesidad analizando 242 modismos (199 en español y 43 en inglés) extraídos de una base de datos con 21.045 modismos que ha sido compilada a partir de dos diccionarios fraseológicos: el Diccionario fraseológico documentado del español actual (en adelante DFDEA) (Seco, Andrés et al., 2004), y el Collins COBUILD Dictionary of Idioms (en adelante CCDOI) (Sinclair y Moon 1997). Los criterios empleados para seleccionar las unidades resultantes con vistas a su análisis han sido: (i) debían incluir al menos un componente léxico relacionado con la religión, y (ii) el modismo tenía que ser nominal o verbal. El componente religioso fue identificado de manera semi-automática utilizando el UCREL's Semantic Analysis System (USAS) (Archer et al., 2002)./nLas aportaciones de este artículo son las siguientes: (i) presenta un análisis lexicográfico de la macroestructura y la microestructura de los dos recursos fraseológicos antes mencionados, (ii) ofrece un modelo de análisis semántico para las PUs con componentes relacionados con la religión, (iii) propone un método de indexación alternativa de las PUs en recursos lexicográficos que implican enfoques semasiológicos y onomasiológicos; y finalmente, (iv) propone una manera sistemática de utilizar la información semántica y pragmática para crear entradas semánticas para las PUs./nEn conclusión, al examinar dicha serie de entradas fraseológicas, este estudio arroja luz sobre la composición semántica de las PUs. También sugiere un enfoque híbrido sistemático para su indexación lexicográfica en inglés y español

CO2 multicyclic capture of pretreated/doped CaO in the Ca-looping process. Theory and experiments

We study in this paper the conversion of CaO-based CO2 sorbents when subjected to repeated carbonation/calcination cycles with a focus on thermally pretreated/doped sorbents. Analytical equations are derived to describe the evolution of conversion with the cycle number from a unifying model based on the balance between surface area loss due to sintering in the loopingcalcination stage and surface area regeneration as a consequence of solid-state diffusion during the looping-carbonation stage. Multicyclic CaO conversion is governed by the evolution of surface area loss/regeneration that strongly depends on the initial state of the pore skeleton. In the case of thermally pretreated sorbents, the initial pore skeleton is highly sintered and regeneration is relevant whereas, for nonpretreated sorbents, the initial pore skeleton is soft and regeneration is negligible. Experimental results are obtained for sorbents subjected to a preheating controlled rate thermal analysis (CRTA) program. By applying this preheating program in a CO2 enriched atmosphere, CaO can be subjected to a rapid carbonation followed by a slow rate controlled decarbonation, which yields a highly sintered skeleton displaying a small conversion in the first cycle and self-reactivation in the next ones. Conversely, carbonation of the sorbent at a slow controlled rate enhances CO2 solid-state diffusion, which gives rise, after a quick decarbonation, to a highly porous skeleton. In this case, CaO conversion in the first cycle is very large but it decays abruptly in subsequent cycles. Data on CaO conversion retrieved from the literature and from further experimental measurements performed in our work are analyzed as influenced by a variety of experimental variables such as preheating temperature program, preheating exposition time, atmosphere composition, presence of additives, and carbonation/calcination conditions. Conversion data are well fitted by the proposed model equations, which are of help for a quantitative interpretation on the effect of experimental conditions on the multicyclic sorbent performance as a function of sintering/ regeneration parameters inferred from the fittings and allow foreseeing the critical conditions to promote reactivation. The peculiar behavior of some pretreated sorbents, showing a maximum of conversion at a small number of cycles, is explained in the light of the mode

Constant rate thermal analysis for thermal stability studies of polymers

This paper explores the relationship between the shapes of temperature-time curves obtained from experimental data recorded by means of constant rate thermal analysis (CRTA) and the kinetic model followed by the thermal degradation reaction. A detailed shape analysis of CRTA curves has been performed as a function of the most common kinetic models. The analysis has been validated with simulated data, and with experimental data recorded from the thermal degradation of polytetrafluoroethylene (PTFE), poly(1,4-butylene terephthalate) (PBT), polyethylene (PE) and poly(vinyl chloride) (PVC). The resulting temperature-time profiles indicate that the studied polymers decompose through phase boundary, random scission, diffusion and nucleation mechanisms respectively. The results here presented demonstrate that the strong dependence of the temperature-time profile on the reaction mechanism would allow the real kinetic model obeyed by a reaction to be discerned from a single CRTA curve.Junta de Andalucía TEP-03002Ministerio de Ciencia e Innovación MAT 2008-06619/MA

Bootstrap method for calculating technical provisions for claims

[ES] La adecuada gestión del riesgo es uno de los objetivos fundamentales en las compañías aseguradoras, la buena valoración de la incertidumbre es una de las claves de éxito en este sector empresarial, por ello, abarca el objeto de nuestro estudio. La clave para gestionar la incertidumbre es poder prever los posibles siniestros y así estimar las provisiones técnicas a constituir por la empresa para el pago de estos. La Directiva Europea Solvencia II, que entra en vigor en 2016, modificó sustancialmente la metodología a emplear para la estimación de las provisiones técnicas utilizada con anterioridad. Esta normativa establece una mejor valoración del riesgo para poder afrontar los pagos por siniestros sin tener problemas de insolvencia o escasa liquidez. Adaptándonos a dicha normativa, procedemos a estimar las provisiones técnicas mediante el método Chain Ladder aplicado mediante el formato triangulo, el cual se adapta a la directiva y tiene en cuenta el comportamiento de los pagos por siniestros en diferentes años. Para reducir la incertidumbre en nuestras estimaciones, utilizamos el método Bootstrap con el que determinaremos la fiabilidad de los datos estimando el error. Mediante los datos obtenidos de una compañía aseguradora en su ramo de autos, realizamos hipótesis para determinar la fiabilidad del método de estimación Chain Ladder con Bootstrap, obteniendo que dicha metodología se adecua a la nueva normativa además de demostrar su eficiencia en la estimación de las provisiones técnicas, siendo el percentil 50 el estadístico más adecuado para dicha estimación.[EN] Proper risk management is one of the main objectives in the insurance companies, the good assessment of uncertainty is one of the keys to success in this business sector, therefore, covers the object of our study. The key to managing uncertainty is to foresee the possible claims and thus estimate the technical provisions to set up by the company for the payment of these. The European directive Solvency II, which came into force in 2016, substantially modified the methodology to be used for the estimation of technical provisions used previously. This regulation establishes a better assessment of the risk to meet payments for claims without having problems of low liquidity or insolvency. Adapting ourselves to this norm, we proceed to estimate technical provisions through the Chain Ladder method implemented by the triangle format, which adapts to the directive and takes into account the behaviour of the payments for claims in different years. To reduce uncertainty in our estimates, we use the Bootstrap method which we will determine the reliability of the data estimating the error. Using the data obtained from an insurance company in its area of cars, we carry out hypothesis to determine the reliability of the Chain Ladder with Bootstrap estimation method

Optical router for optical fiber sensor networks based on a liquid crystal cell

Optical fiber sensor networks are evolving rapidly. They are used because of the inert nature of optical fibers allowing no electromagnetic interference and safe applications in inflammable atmospheres; other relevant characteristics are their low weights and wide bandwidths as a transmission medium. In any case, it is very interesting to have specific components such as optical routers for selecting a certain path in a network with no optical to electrical and electrical to optical conversions. In this paper, we propose an all-optical router based on liquid crystals, polarizers, and a spatial split polarization beam splitter. The implemented device is designed to operate with visible light and it has been tested with plastic optical fibers. It has a crosstalk of 14 dB between selected ON channels and nonoperative OFF channels and 11-dB insertion losses. An average switch time of 100 ms is measured. The device checks the optical power level in each channel and, in case of failure, automatically switches to an operative channel while an alarm is activated.Publicad

Multicyclic conversion of limestone at Ca-looping conditions: The role of solid-sate diffusion controlled carbonation

Limestone derived CaO conversion when subjected to multiple carbonation/calcination cycles is a subject of interest currently fueled by several industrial applications of the so-called Ca-looping (CaL) technology. The multicyclic CaO conversion at Ca-looping conditions exhibits two main features as demonstrated by thermogravimetric analysis (TGA). On one hand, carbonation occurs by two well differentiated phases: a first kinetically-driven fast phase and a subsequent much slower solid-state diffusion controlled phase. On the other, carbonation in the fast phase usually shows a drastic decay with the cycle number along the first carbonation/calcination cycles. This trend can be reversed by means of heat pretreatment, which induces a marked loss of fast conversion in the first carbonation but enhances diffusion of CO2 in the solid. Upon decarbonation the regenerated CaO skeleton displays an increased conversion in the fast carbonation phase of the next cycle, a phenomenon which has been referred to as reactivation. Nonetheless, sorbent reactivation is hampered by looping carbonation/calcination conditions as those to be likely found in practice such as carbonation stages characterized by low CO2 concentrations and short duration and calcination stages at high temperatures in a CO2 enriched atmosphere, which causes a sintering and loss of activity of the regenerated CaO skeleton. We analyze in this work sorbent reactivation as affected by heat pretreatment and carbonation/calcination conditions. Aimed at shedding light on the role played by these conditions on reactivation we look separately at the multicyclic evolution of conversion in the kinetic and diffusive phases. Generally, the evolution of multicyclic conversion after the first cycle can be described by a balance between the surface area gain due to diffusive carbonation and the surface area loss as caused by sintering in the calcination stage. A significant gain of relative surface area after the first cycle, which is favored by harshening the heat pretreatment conditions, leads however to a marked decay of it during subsequent cycles, which precludes reactivation for an extended interval of cycles. On the other hand, sorbent grinding, if performed before heat pretreatment, leads to a less marked but more sustainable reactivation along the cycles. A novel observation reported in our work is that pretreatment of limestone in a CO 2 atmosphere leads upon a subsequent quick decarbonation to a CaO skeleton with extraordinarily enhanced reactivity in the kinetically-driven carbonation phase and with a high resistance to solid-state diffusion, which can be attributed to annealing of the crystal structure as reported by independent studies

Critical study of the isoconversional methods of kinetic analysis

A critical study of the use of isoconversional methods for the kinetic analysis of non-isothermal data corresponding to processes with either a real or an apparent variation of the activation energy, E, with the reacted fraction, α, has been carried out using for the first time simulated curves. It has been shown that the activation energies obtained from model-free methods are independent of the heating rate. However, the activation energy shows a very strong dependence of the range of heating rates used for simulating the curves if the apparent change of E with α is caused by overlapping processes with different individual activation energies. This criterion perhaps could be used for determining if a real dependence between E and α is really occurringEspaña Ministerio de Educación y Ciencia No. MAT2004-0264

Kissinger kinetic analysis of data obtained under different heating schedules

The dynamic heating rate method developed by TA Instruments ( Hi-Res ™ ) is a kind of sample controlled thermal analysis in which a linear relati onship between the logarith m of the heating rate and the rate of weight change is imposed. It is s hown in this paper that the reacted fraction at the maximum reaction rate strongly depends on the parameters selected for the Hi-Res heating algorithm, what invalidates the use of the Kissinger method for analysing Hi-Res data unless that the reaction fits a first order kinetic law. Only in this latter case, it has been demonstrated that it is not required that a constant value of the reacted fr action at the maximum reaction rate is fulfilled for determining the activation energy from the Kissi nger method. In such a case the Kissinger plot gives the real activation energy, independently of both the heating schedule used and the value of the reacted fraction, α m , at the maximum

Calcium-looping for post-combustion CO2 capture. On the adverse effect of sorbent regeneration under CO2

The multicyclic carbonation/calcination (c/c) of CaO solid particles at high temperature is at the basis of the recently emerged Calcium-looping (CaL) technology, which has been shown to be potentially suitable for achieving high and sustainable post-combustion CO2 capture efficiency. Despite the success of pilot plant projects at the MWth scale, a matter of concern for scaling-up the CaL technology to a commercial level (to the GWth scale) is that the CaO carbonation reactivity can be recovered only partially when the sorbent is regenerated by calcination at high temperatures (around 950 °C) as required by the CO2 high concentration in the calciner. In order to reactivate the sorbent, a novel CaL concept has been proposed wherein a recarbonator reactor operated at high temperature/high CO2 concentration leads to further carbonation of the solids before entering into the calciner for regeneration. Multicyclic thermogravimetric analysis (TGA) tests demonstrate the feasibility of recarbonation to reactivate the sorbent regenerated at high calcination temperatures yet at unrealistically low CO2 partial pressure mainly because of technical limitations concerning low heating/cooling rates. We report results from multicyclic c/c and carbonation/recarbonation/calcination (c/r/c) TGA tests at high heating/coling rates and in which the sorbent is regenerated in a dry atmosphere at high CO2 partial pressure. It is shown that at these conditions there is a drastic drop of CaO conversion to a very small residual value in just a few cycles. Moreover, the introduction of a recarbonation stage has actually an adverse effect. Arguably, CaCO3 decomposition in a CO2 rich atmosphere is ruled by CO2 dynamic adsorption/desorption in reactive CaO (1 1 1) surfaces as suggested by theoretical studies, which would preclude the growth of the regenerated CaO crystal structure along these reactive surfaces, and this effect would be intensified by recarbonation. Nevertheless, the presence of H2O in the calciner, which is also adsorbed/desorbed dynamically in CaO reactive planes, would shield CO2 adsorption/desorption thus mitigating the deeply detrimental effect of CO2 on the carbonation reactivity of the regenerated CaO structure. Oxy-combustion, which produces a significant amount of H2O, is currently used in pilot-scale plants to raise the temperature in the calciner. Auxiliary techniques are being explored to help heating the partially carbonated solids since oxyxombustion represents an important penalty to the CaL technology. Our study suggests that steam injection would be necessary in a dry calciner environment to avoid a sharp loss of CaO conversion if the sorbent is regenerated at high CO2 partial pressure.Junta de Andalucía FQM-5735 TEP-7858España Mineco Feder FIS2011-25161 CTQ2011-2762