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This work presents a new design of a solar particle receiver. Opposite to current technologies, the receiver is placed at the ground level, and thus, no tower is needed. To concentrate the solar radiation on the solar receiver, Fresnel and Beam-down optics are employed. The receiver consists on a multistage fluidized bed in which the gas flows consecutively through the different fluidized beds, which are connected horizontally. The receiver presents modular design, which allows the installation of several units in series configuration to achieve a gradual increase of the gas and particles temperature. As an example of the proposed design, a Fresnel field of heliostats and a beam-down reflector are sized following the common dimensions of Fresnel technology. A well-mixed fluidized bed model is used to estimate the temperatures of gas and particles. The temperature of gas and particles reach T ≈ 800 °C for a reflective Fresnel area of 9072 m2, a beam-down mirror placed 18 m above the Fresnel reflectors and total length of Ltotal = 140 m.

A severe maldistribution problem was induced with a half-covered gas distributor plate. Videos of the bed surface were recorded and analyzed to study how the boundary between maldistribution and stable fluidization is affected by the gas velocity and the bed aspect ratio. It was observed that the visual inspection of the bed surface reports no information about the maldistribution at the bottom bed. Several cases of moderate maldistribution (i.e. different distributions of open orifices) were investigated by means of pressure fluctuation signal analysis to provide a criterion for maldistribution detection. The effect of the measurement position on maldistribution detection was also investigated. The attractor comparison test, the S-test, as well as the statistical process control of the standard deviation and wide band energy regions, were applied to test their capability of online detecting and monitoring gas maldistribution. The statistical process control methodology, based on standard deviation of pressure fluctuation signals, can be successfully applied to online detection of maldistribution when the pressure probe is located between 50% and 75% the total bed height. Finally, the rotation of the distributor was studied as a counteracting mechanism, showing good results overcoming maldistribution problems in fluidized beds.

Humidity and temperature measurements, together with pressure fluctuation signals, were employed to analyze a drying process in a lab-scale bubbling fluidized bed. The experimental facility was equipped with a rotating distributor. The operational conditions reported in sludge, paste, and granular drying processes were reproduced using silica sand as wet material and as inert medium. Experiments were performed by changing the bed aspect ratio and the water-sand content in the bed operated at ambient conditions. Four drying periods were found when analyzing humidity and temperature signals. The multi-resolution approach of the pressure fluctuation signals showed the effect of the sample drop over the bed surface on the fluidization conditions, by relating the drying periods with the bed dynamics. The drying process can affect the low- and high-frequency details of the pressure signal when the bed state changes towards defluidization, or just the high-frequency detail if the bed was at the maldistributed regime. The drying conditions needed to use the pressure signals to control the drying process are defined by means of a statistical monitoring approach. A comparison between the static and the rotating distributor tests showed clear benefits for the operation with the rotating distributor for shallow and deep beds. When the distributor was rotating, the average improvement of the drying rate was 11%, whereas the drying time was reduced by 40% for the tests of the maldistributed and defluidized regimes.

This paper presents a methodology to guide the design of heat exchangers for a steam generator in a solar power tower plant. The low terminal temperature difference, the high fluid temperatures and the high heat duty, compared to other typical shell and tube heat exchanger applications, made the design of the steam generator for molten-salt solar power towers a challenge from the thermomechanical point of view. Both the heat transfer and the thermal stress problems are considered to size the preheater, evaporator, superheater and reheater according to the TEMA standards and ASME Pressure Vessel code. An integral cost analysis on the steam generator design effects on the power plant performance reveals an extremely low value for the optimum evaporator pinch point temperature difference. Furthermore, an optimization using genetic algorithms is performed for each heat exchanger, which leads to economical and feasible designs. A 110 MWe solar power tower plant is studied. Two configurations of the steam generator are proposed: with one or two trains of heat exchangers. The results show that the optimum pinch point temperature differences are very close to 2.6 degrees C and 3 degrees C for the steam generator with one and two trains, respectively. The proposed design of the steam generator consists of a U-shell type for superheater and reheater, a TEMA E shell forced circulation evaporator and a TEMA-F shell preheater. Also, the approach point temperature difference analysis is performed to avoid subcooled flow boiling in the pre-heater. An economic study to compare forced and natural circulation evaporator designs is carried out.

Since the operation of a concentrating solar power plant depends on the intermittent character of solar energy, the steam generator is subject to daily start-ups, stops and load variations. Faster start-up and load changes increase the plant flexibility and the daily energy production. However, it involves high thermal stresses on thick-walled components. Continuous operational conditions may eventually lead to a material failure. For these reasons, it is important to evaluate the transient behavior of the proposed designs in order to assure the reliability. The aim of this work is to analyze different steam generator designs for solar power tower plants using molten salt as heat transfer fluid. A conceptual steam generator design is proposed and associated heat transfer areas and steam drum size are calculated. Then, dynamic models for the main parts of the steam generator are developed to represent its transient performance. A temperature change rate that ensures safe hot start-up conditions is studied ...

In this research the use of a feedback PID-like fuzzy controller scheme for pH control is presented to deal with instability problems near the equivalence point in neutralization processes. State space analysis of the titration curves and a fuzzy clustering algorithm based on calculating a measure of potential derived from the square distance of the pH data are complementary applied to define the membership structure and the fuzzy sets of the controller. To test the performance of the controller, both simulated and experimental runs were used. The fuzzy controller was tested for compensating step-change perturbations of propionic acidic flow rates, propionic acid concentration, and buffering conditions. Stationary cycling behavior has been observed for large loads of acidic flow rates. It was found that though the rejection time was strongly dependent on the mean residence time of the liquid solutions, the proposed controller keep the neutralization process operating close to the specified set point of pH = 7.

This paper revisits the basic hypothesis underlying the measurement of flow-induced vibration in fluidized beds. A novel theoretical approach based on the standing pressure field characterizing the bed dynamics is proposed to link the pressure fluctuations to the measured accelerometer signals. The model provides a reliable prediction of the carrying frequency band and helps in designing the accelerometer measurement process. The model was tested with previous results reported in the literature as well as with piezoelectric accelerometer measurements collected from a lab-scale experimental facility. A study on accelerometer measurements was conducted to identify the main limitations expected for measuring flow-induced vibrations in a gas-solid fluidized bed. The structural response of the vessel to flow-induced vibration was mostly determined by the "bed acoustics" that can be dominated by either elastic or compression waves. Finally, the survival of an envelope process on the measured accelerometer signal guaranteed the quality of the flow dynamical information collected during the measurement process. Financial support from projects DPI2009-10518 (MICINN) and CARDENER-CM (S2009ENE-1660). Publicado

While fresh water resources are increasingly limited, efforts are taken aiming at a more efficient use of those resources and the value of water reuse, not only due to environmental but also due to economic aspects. This is especially true for the industrial sector, with a high potential to save water by reuse. This is expected to be even more critical in the coming future as the price of the water increases and the access to good quality water sources near the industries decreases. Reverse osmosis (RO) technology has been used in the industrial sector for decades for various purposes such as softening, ultra pure water production, or water reuse. But like in other applications such as desalination, in industrial applications, membrane fouling remains as one of the main causes for poor RO plant performance. This implies frequent downtime for cleaning and maintenance and shorter membrane life time, leading to significant operational costs. Therefore, the selection of a proper pretreatment is essen...

The present work considers the use of the two-fluid (Euler-Euler) CFD approach for the continuum description of vibrated fluidized beds as a less computationally demanding alternative to the discrete description given by Lagrangian-Eulerian methods such as DEM. In particular, a novel simulation strategy consisting on solving the two-fluid model equations in a coordinate reference system that moves with the vibrating walls of a gas-solid fluidized bed is proposed. By this way, vibration is transformed into simple alternating acceleration terms that are introduced through body forces in both the gas and the particle phase equations. The results of a series of two-fluid model simulations compare well with discrete particle simulations as well as with experimental data reported for beds containing Geldart group B particles. In general, the results of a series of two-fluid model simulations show similar trends to those seen in discrete particle simulations as well as in experimental data reported for beds containing Geldart group B particles. Exception of that is the velocity of bubbles, for which the two-fluid simulations compare less satisfactorily with the available experimental data. The two-fluid model simulations are also able to reproduce expected phenomena like the bubble growth with the vibration amplitude and the dependence of the pressure drop fluctuation on the vibration strength. In view of these promising results, the proposed two-fluid model formulation opens the possibility of increasing the scale of the vibrated fluidized beds currently simulated. The present work has been funded by the Spanish Ministerio de Ciencia e Innovación through the Project DPI2009-10518. The Authors gratefully appreciate this support. Publicado

Low frequency accelerometry signals have been applied for detecting regime transitions in a gas solid fluidized bed. Three solids have been fluidized to promote bubbling, churn and slugging regime. The Kolmogorov entropy and the power spectral density have been used to determine the regime transitions as well as to analyze the dynamical features characterizing the different regimes. Pressure and external acceleration measurements have been taken simultaneously. The accelerometry signal was sampled at 10 kHz; then, the envelope was extracted and resampled at 400 Hz. Pressure signal was sampled at 10 kHz and resampled at 400 Hz. Two problems were found during the work: the colored noise present in the envelope and the lack of low frequency information for one of the tested solids. FIR, wavelet and EMD filter strategies have been applied to remove the noise present in the envelope. It is concluded that the envelope of the accelerometry signal might be used to detect regime transition in the same way as the pressure fluctuation signals. Both Kolmogorov and spectral analysis exhibit common features to those obtained from pressure signal analysis, supporting the hypothesis of using low frequency accelerometry instead of conventional pressure measurements for monitoring fluidized beds The authors would like to especially thank Prof. María C. Palancar for her contribution to this work and the useful guiding during those years. Moreover, the financial support from the Spanish Ministry of Research, project CTQ2006 15525 C02 01 is kindly acknowledged Publicado

A phenomenological discrete bubble model is proposed to help in the design and dynamic diagnosis of bubbling fluidized beds. An activation region mechanism is presented for bubble formation, making it possible to model large beds in a timely manner. The bubbles are modeled as spherical-cap discrete elements that rise through the emulsion phase that is considered as a continuum. The model accounts for the simultaneous interaction of neighboring bubbles by including the trailing effects due to the wake acceleration force. The coalescence process is not irreversible and therefore, the coalescing bubble pair is free to interact with other rising bubbles originating the splitting phenomena. To validate the model, the simulated dynamics are compared with both experimental and literature data. Time, frequency, and state space analysis are complementarily used with a multiresolution approach based on the empirical method of decomposition to explore the different dynamic scales appearing in both the simulated time series and those obtained from experimental runs. It is concluded that the bubble dynamics interactions play the main role as the driver of the resulting bed dynamics, matching the main features of measured bubble dynamics. Exploding bubble phenomena have been identified by establishing a direct relation between the bubble generation, interaction and eruption, and the measured signals Projects DPI2009-10518 (MICINN) and CARDENER-CM (S2009ENE-1660) Publicado

En los últimos años, el funcionalismo sistémico o normativo se ha asentado y desplegado en la doctrina y jurisprudencia del derecho penal peruano, instaurando con claridad, precisión y coherencia, soluciones a problemas concretos que anteriormente quedaban rezagados a las respuestas dadas por las doctrinas naturalistas, ontologistas y finalistas. Así, acogiendo una visión avanzada del funcionalismo, nos ocupamos de explicitar su evolución anterior y la postura asumida por el maestro de la Universidad de Bonn, Günther Jakobs, autor que plantea la relación funcional entre la sociedad y la dogmática jurídico penal, la cual debe ser refundamentada en su planteamiento central, de cara a salvaguardar el sistema social y estatal mediante la estabilidad de la norma penal, en procura de garantizar las mínimas expectativas del ciudadano en el adecuado funcionamiento de la vida social

… because you can confess with me as with God for I am a comisario of the Holy Office … (Lorenzo de Torquemada 1641) Nihil occultum quod non reveletur [There is nothing hidden that will not be ma...

The dimension of interaction dynamics, d 2 int , is used to study the nonlinear interactions in a fluidized bed between the local bubble, “bulk” bed and particle dynamic components. The different timescales are obtained by a multi-resolution analysis based on the Hilbert–Huang Transform Method (HHTM). The state space analysis is used to study the time–space structure of the fluidized bed dynamics. A method for constructing Poincare projections based on the join probability matrix computation is provided. The Kolmogorov entropy, K , and the correlation dimension, D 2 , are used to compute the invariant properties of the corresponding attractor. It is concluded that the local bubble dynamics has chaotic features and is responsible for the determinism found in pressure fluctuation signals. It has been found that, as expected, the bubble component is the driver of the gas–solid fluidized bed hydrodynamics.

A novel approach to estimate the size of stagnant regions in large-scale fluidized beds by means of experimental data obtained from images recorded on the bed surface was presented. For this purpose, the internal structure of an induced maldistributed pseudo-2D fluidized bed was first studied. Half of the total distributor area was covered to generate an induced stagnant region. The size and shape of this area was studied for several relative gas velocities and bed aspect ratios. The defluidized area was found to be almost independent of the bed aspect ratio, however, it was found to decrease for higher relative gas velocities. A solids recirculation zone was also found above the defluidized zone. The size of this zone increases with relative gas velocity, suggesting that it is strongly related to bubble motion. A correlation was developed to relate the visible bubble flow to the size of the defluidized zone. The results obtained in the 2D bed were extrapolated to a 3D cylindrical fluidized bed with a half-covered distributor plate to estimate the volume of the defluidized zone. The visible bubble flow in the 3D facility was estimated. Using the proposed correlation for the defluidized volume in the 2D bed was used to estimate the defluidized volume in the 3D bed. Finally, the calculated values of the defluidized volume were compared with the experimental values in the 3D facility, obtaining a maximum relative error of 20% in the estimations.

The Cuerpo de Hombre paleoglacier occupies the upper sector of the Cuerpo de Hombre river basin, located on the northwest slope of the Sierra de Bejar Mountains (Iberian Central System). At the stage of the maximum ice extent during the last glacial cycle, this paleoglacier was one of the longest tongues emerging from the Sierra de Bejar plateau glacier. The study of the morphostratigraphic succession and the geometric and genetic relations between the geomorphological indicators of this paleoglacier has revealed its evolutionary sequence during the last glacial cycle. The comparison between this sequence and the one previously established by a regional evolutionary pattern shows that although they both coincide in general terms, some stages/substages of this pattern must be corrected or more clearly defined. The absolute chronology of the different stages was obtained using terrestrial cosmogenic nuclides (10Be). The maximum ice extent of Cuerpo de Hombre paleoglacier has been dated to ∼25.0 ka (MIS2 and concurrent with the LGM). This chronology coincides with date obtained for other paleoglaciers in the Iberian Central System, but is slightly more modern than the regional chronology estimated as most likely for the maximum ice extent in these areas. Subsequent to reaching the maximum extent, the glacier had a retreat (minimum age ∼20.6 ka), followed by another stage of expansion or readvance, after which it stabilised until the start of the deglaciation stage (∼17.8 ka). In all previous work, the deglaciation stages in the Iberian Central System have been described as one continuous recession process. However, in the Cuerpo de Hombre paleoglacier, all the data point to stabilisations of considerable magnitude, and particularly to another stage of readvance of the glacier. Based on its chronology (minimum age ∼11.1 ka) and its evolutionary significance, this new readvance has been correlated with the Older Dryas stadial. Finally, the evolutionary context marked by the indicators and its chronology confirm that the whole of the Late Glacial sequence identified in Cuerpo de Hombre can be correlated with the traditionally established in northern Europe (climatic periods or stadials and interstadials): Oldest Dryas-Bolling-Older Dryas-Allerod-Younger Dryas. The minimum ages obtained for the cold periods (stadials) in this sequence in the Cuerpo de Hombre paleoglacier are (respectively): ∼17.5 ka, ∼13.9 ka and ∼11.1 ka. This complete sequence of the Late Glacial Period, including the stadials Older and Younger Dryas, had not been previously identified in any of the paleoglaciers in the Iberian Central System.

The Hilbert–Huang transform method, HHTM, is applied to perform a multi-resolution analysis by means of the empirical mode decomposition, EMD, of noisy pressure signals collected from a gas–solid fluidized bed operating in slugging regime. Several important dynamic components, such as local bubble, “bulk” and particle dynamics, are identified. The bulk dynamic component is used to estimate the bed expansion ratio and bed height. The Kolmogorov entropy, K , and the correlation dimension, D 2 , are used for monitoring slugging dynamics from the resulting bubble, particle and bulk time scales. To study the attractor structure, a method for elaborating return-maps, based on the join probability matrix, is used. It has been found that the bulk dynamics provides information of the global behavior of the dense phase and allows characterizing the slugging dynamics with correlation dimension 2.2 D 2 2.6 . In contrast, the local bubble dynamics is characterized by a correlation dimension that ranges from 1.8 to 2.

The purpose of this research is to show that measurements of low frequency out-bed passive acoustic emissions are useful for monitoring gas–solid fluidised bed hydrodynamics. A methodology is proposed to develop portable measurement systems (PMS) feasible for both laboratory scale optimisations and, later, for process diagnosis within industrial facilities. The methodology includes a multirate technique where the first sampling frequency used was about 11 kHz that was successfully later reduced to 500 Hz, which is far from the most common used for sampling ultrasonic ranges. The acoustic frequency range of interest (0–200 Hz) allows the use of a commercial jukebox and two low cost condenser microphones to record the out-bed acoustic emissions. The underlying bed dynamic process was studied by monitoring both acoustic and pressure fluctuation signals and by applying time, frequency and state space analysis over the measured time series. The crude acoustic signals exhibit marked random behaviour due to a high content of background noise. This is detected by the mutual information function. The power spectral density of the acoustic time series shows high complexity and claims for reducing the acoustic frequency range to be evaluated (initially 0–5.5 kHz). To decide an optimal frequency range and, consequently, a better sampling frequency, the acoustic pressure was estimated from a numerical simulation based on the well-known particle array model. From the results of the simulations, and in agreement to the literature, it is concluded that the bed dynamic acoustic information mainly lies within the range 0–200 Hz. According to that, the signals were subsequently re-sampled at a sampling frequency of 500 Hz. Finally, by comparing the pressure time series monitoring to the analysis of the mesoscale bed acoustic region (mainly due to bubbles, 0–20 Hz), it is concluded that from out-bed acoustic time series monitoring, only the state space analysis is able to fully characterize the slugging dynamics by means of a correlation dimension in the range 2.5–3.5 for the experimental conditions covered.

We present a new method of scaling hydrodynamic data obtained from a 2D gas–solid fluidized bed, establishing links between 2D and 3D geometries. The methodology proposed may also be useful for verifying 3D–3D dynamic scaling. According to the chaos scale-up methodology proposed by Van den Bleek and Schouten [1993. Chemical Engineering Science 48, 2367–2373], the information balance is taken into account. The complexity shown by these systems is measured as the Kolmogorov entropy. Fluidized beds of different geometry (2D, 3D) performing under the bubbling regime were operated at different bed height and bed aspect ratios by fluidizing several particle groups belonging to Geldart groups B and D. Finally, an empirical correlation is proposed to compare fluidized bed hydrodynamics. This correlation relates the global information flow of the system K G = KFr r to the relative Reynolds particle number.

The use of free surface fluctuations in three-dimensional (3-D) fluidized bed dynamic characterization is addressed. This technique provides a noninvasive global measure of the quality of fluidization by measuring at one position in the bed. The well-known effect of particle size on fluidized bed hydrodynamics was explored using a 3D fluidized bed operated with four different particle groups. The analytical methods used were mutual information functions, frequency, and state space analysis of time series collected from bed surface fluctuations. Turbulent, multiple, and noninteracting bubble flow patterns, occurring during bubble regimes, have been characterized. Kolmogorov entropy for the reconstructed attractor is very sensitive to the transition between fluidization regimes. Moreover, correlation dimension estimates ranging between 3 < D2 < 5 indicate apparent low-dimensional dynamics. Additionally for larger particle groups, D2 reaches a value close to 3, indicating slow bubbling controlled by large bubbles before the transition between different bubble flow patterns takes place. Finally, particle size has been found to have strong influence on signal persistence. © 2004 American Institute of Chemical Engineers AIChE J, 50: 3060–3067, 2004

We present a novel method of extracting hydrodynamic information from a gas–solid fluidized bed. The proposed method involves measuring the fluctuations produced in a laser sheet that perpendicularly crosses the free bed surface. This non-local, non-intrusive technique can be applied to 2D and 3D gas–solid fluidized bed systems. Frequency domain and state space analysis were used in a complementary manner to characterize the fluidization regimes of these systems by monitoring EWB, μ, D2, λmax, and K. Finally, we evaluated the influence of H/L on attractor invariants in 3D fluidized beds.

A statistical method based on approximation of the cumulative energy distribution by Student's t-distribution is proposed for the unbiased frequency domain division. The proposed method fixes the number of samples needed to estimate the power spectrum and its corresponding cumulative energy distribution using the Kolmogorov&-Smirnov test. The reliability of the method to divide the frequency domain was shown for different fluidization velocities by changing the bed aspect ratio and using different pressure probes. Water-induced defluidization tests were conducted to illustrate the use of wide band energy as a monitoring tool. The Student's t-distribution results are compared with an analysis performed using the traditional visual inspection method. The energy of the power spectrum contained within the frequency regions obtained by the visual method is not able to detect changes in the bed aspect ratio or the start of the rotating distributor. No meaningful differences could be observed in the frequency regions using different quality pressure sensors because the approach using Student's t-distribution focuses on the sharp energy increase produced by the primary frequencies of the power spectrum. The sensitivity exhibited by the proposed frequency division approach for the range of fluidization conditions tested improves the use of the energy contained in these regions as a diagnostic tool in fluidized bed processes. The author would like to express appreciation for the financial support from Projects DPI2009-10518 (MICINN) and CARDENER-CM (S2009ENE-1660). Publicado

Pretende destacar y difundir, tambien, los avances jurídicos y las nuevas doctrinas que renuevan al derecho haciendo que la justicia no sea una mera declaración, sino en el aspecto funcional del Estado y la sociedad