CFD analysis of co-firing of coke and biomass in a parallel flow regenerative lime kiln

The lime industry is a highly energy intensive industry, with a huge presence worldwide. To reduce both production costs and pollutants emissions, some lime production plants are introducing more environmentally-friendly energy sources, such as local agro-industry residues. In this paper, a numerical tool is presented, which simulates a large-scale Parallel Flow Regenerative (PFR) kiln that currently uses coke as main fuel. The developed tool aims at investigating the combustion process under conditions of co-firing of coke and biomass and to assist the plant operators in the optimization of such operating conditions. To achieve this goal, a two-way coupling Euler–Lagrange approach is used to model the dynamics of the particulate phase and their interaction with the gas phase. Pyrolysis, volatiles oxidation and char oxidation are modelled by kinetics/diffusion-limited model (for heterogeneous reactions) and mixture fraction approach (for homogeneous reactions). Moreover, two methods are investigated for representing the limestone bed: a porous medium (PM) approach and a “solid blocks” (BM) tridimensional mesh. Comparison of the results for the case of 100% coke showed that the ideal “blocks” method is more accurate as it adequately simulates the scattering of fuel particles through the PFR kiln anchor, which is limited with the PM approach. Moreover, the temperature profile, maximum and minimum temperatures, as well as CO2 and O2 concentrations at outlet, are comprised in the expected range for this technology, according to available literature. Finally, the predicted results of a co-firing case with 60% biomass (in mass) were validated with measurements in an industrial facility, with production capacity of 440 calcium oxide tons per day. The results suggest that the model is fairly accurate to predict gas temperature, as well as O2 and NOX concentrations at the kiln outlet. Although some improvements are recommended to refine the CFD predictions, these promising results and the high computational efficiency laid the foundation for future modelling of co-firing of coke and biomass, as well as the modelling of the lime calcination process. It also paves the way for facilitating the reduction of pollutant emissions thus contributing to a more sustainable lime production

Experimental evidence of the role of non-gyrotropy in magnetopause equilibrium

Is the magnetosphere closed or open? This is one of the oldest questions in space physics still at the basis of the hottest topics in the field today. With respect to the magnetopause boundary, this translates into: "is this boundary a tangential discontinuity or not?". We revisit this question, and show that the small thickness of the magnetopause escapes classic theory, from which comes the notion of tangential discontinuity. For such "quasi-tangential" discontinuities, both compressive and rotational properties coexist as observed, without requiring strictly null normal fluxes, while they are mutually exclusive when Finite Larmor radius effects are ignored. This change is similar to the change from a shear Alfven wave to a Kinetic Alfven wave for linear modes. We present a typical example of MMS data from a magnetopause crossing. We show that the non-gyrotropic pressure tensor does indeed play a very important role in the boundary equilibrium

A comparison of wave mode identification techniques

The four point measurements available from the Cluster mission enable spatiotemporal effects in data sets to be resolved. One application of these multipoint measurements is the determination of the wave vectors and hence the identification of wave modes that exist within the plasma. Prior to multi-satellite missions, wave identification techniques were based upon the interpretation of observational data using theoretically defined relations. However, such techniques are limited by the quality of the data and the type of plasma model employed. With multipoint measurements, wave modes can be identified and their wave directions determined purely from the available observations. This paper takes two such methods, a phase differencing technique and k-filtering and compares their results. It is shown that both methods can resolve the k vector for the dominant mirror mode present in the data. The phase differencing method shows that the nature of the wave environment is constantly changing and as such both methods result in an average picture of the wave environment in the period analysed. The k-filtering method is able to identify other modes that are present

BV technique for investigating 1-D interfaces

To investigate the internal structure of the magnetopause with spacecraft data, it is crucial to be able to determine its normal direction and to convert the measured time series into spatial profiles. We propose here a new single-spacecraft method, called the BV method, to reach these two objectives. Its name indicates that the method uses a combination of the magnetic field (B) and velocity (V) data. The method is tested on simulation and Cluster data, and a short overview of the possible products is given. We discuss its assumptions and show that it can bring a valuable improvement with respect to previous methods.Comment: submitted to JG

Experimental study on the ash behaviour in combustion of pelletized residual agricultural biomass

Agricultural residual biomass presents a high potential for energy use around the world, often not utilized to a large extent due to its significant differences with respect to other biomass types, such as the one of forest origin. These differences are mainly related to the characteristics of its ashes (quantity and composition) which increase certain problematic phenomena during combustion, among them bottom ash sintering and fly ash deposition. The main goal of this paper is the experimental study of these issues for four different agropellets made of residual agricultural biomass (one woody -vineyard pruning- and three blended with an herbaceous component -corn stover and/or barley straw-) and a forest wood pellet (used as a reference), evaluated under different operating conditions in a laboratory fixed bed reactor. The influence of inlet air flow and temperature on the sintering degree and deposition ratio has been analyzed in a systematic way. For the five biofuels, under tested conditions, a clear relation inversely proportional between air excess ratio and deposition ratio has been determined. Deposition was more substantial for the four agropellets; meanwhile the sintering degree was more important for the three with an herbaceous component. The information obtained in this research work is intended to help researchers and technologists to make choices regarding the design and operation of conversion systems adapted for agricultural residual biomass, enhancing its market penetration

Módulos habitables de consumo de energía casi nulo para bases militares en entorno NATO

Con la finalidad de disminuir la dependencia de combustibles fósiles así como reducir las emisiones de CO2 en las Bases, Acuartelamientos y establecimientos militares (BAEs) de las Fuerzas Armadas Europeas, a través de un proyecto europeo (LIFE 19 CCM/ES/001327), el consorcio compuesto por el Centro Universitario de la Defensa de Zaragoza, B+HAUS, ARPA Equipos Móviles de Campaña y la Fundación de Hidrógeno de Aragón, ha diseñado y construido un prototipo habitable construido en base a contenedores de 20 pies, desmontable, modular y autosuficiente energéticamente. Para alcanzar la auto-suficiencia energética, se han modificado substancialmente los módulos existentes según dos grandes líneas: 1) minimizar la demanda de energía, construyendo bajo el estándar Passivhaus que permite una reducción de la misma en torno al 90%; 2) producción de energía in situ con energías limpias (paneles fotovoltaicos y aerogenerador) y almacenamiento de la energía sobrante en forma de hidrógeno. Además, estos módulos eliminan la huella térmica, ya que además de poseer unas pérdidas energéticas por la envolvente muy bajas, no tienen puentes térmicos y sus infiltraciones de aire a través de la envolvente mínimas. En la actualidad, gracias a la colaboración de la Brigada Aragón I en la Base San Jorge, con el apoyo técnico y de personal del Batallón de Zapadores I, dicho prototipo se ha montado en sus instalaciones para monitorizar y estudiar en detalle su funcionamiento. El prototipo se va a probar en clima extremo árido en Zaragoza y en clima extremo frío en la Antártida, donde se ubicará definitivamente en la Base Gabriel de Castilla

ULF waves in the low‐latitude boundary layer and their relationship to magnetospheric pulsations: A multisatellite observation

On April 30 (day 120), 1985, the magnetosphere was compressed at 0923 UT and the subsolar magnetopause remained near 7 REgeocentric for ∼2 hours, during which the four spacecraft Spacecraft Charging At High Altitude (SCATHA), GOES 5, GOES 6, and Active Magnetospheric Particle Tracer Explorers (AMPTE) CCE were all in the magnetosphere on the morning side. SCATHA was in the low-latitude boundary layer (LLBL) in the second half of this period. The interplanetary magnetic field was inferred to be northward from the characteristics of precipitating particle fluxes as observed by the low-altitude satellite Defense Meteorological Satellite Program (DMSP) F7 and also from absence of substorms. We used magnetic field and particle data from this unique interval to study ULF waves in the LLBL and their relationship to magnetic pulsations in the magnetosphere. The LLBL was identified from the properties of particles, including bidirectional field-aligned electron beams at ∼200 eV. In the boundary layer the magnetic field exhibited both a 5–10 min irregular compressional oscillation and a broadband (Δƒ/ƒ ∼ 1) primarily transverse oscillations with a mean period of ∼50 s and a left-hand sense of polarization about the mean field. The former can be observed by other satellites and is likely due to pressure variations in the solar wind, while the latter is likely due to a Kelvin-Helmholtz (K.-H.) instability occurring in the LLBL or on the magnetopause. Also, a strongly transverse ∼3-s oscillation was observed in the LLBL. The magnetospheric pulsations, which exhibited position dependent frequencies, may be explained in terms of field line resonance with a broadband source wave, that is, either the pressure-induced compressional wave or the K.-H. wave generated in or near the boundary layer

The STAFF-DWP wave instrument on the DSP equatorial spacecraft: description and first results

The STAFF-DWP wave instrument on board the equatorial spacecraft (TC1) of the Double Star Project consists of a combination of 2 instruments which are a heritage of the Cluster mission: the Spatio-Temporal Analysis of Field Fluctuations (STAFF) experiment and the Digital Wave-Processing experiment (DWP). On DSP-TC1 STAFF consists of a three-axis search coil magnetometer, used to measure magnetic fluctuations at frequencies up to 4 kHz and a waveform unit, up to 10 Hz, plus snapshots up to 180 Hz. DWP provides several onboard analysis tools: a complex FFT to fully characterise electromagnetic waves in the frequency range 10 Hz-4 kHz, a particle correlator linked to the PEACE electron experiment, and compression of the STAFF waveform data. The complementary Cluster and TC1 orbits, together with the similarity of the instruments, permits new multi-point studies. The first results show the capabilities of the experiment, with examples in the different regions of the magnetosphere-solar wind system that have been encountered by DSP-TC1 at the beginning of its operational phase. An overview of the different kinds of electromagnetic waves observed on the dayside from perigee to apogee is given, including the different whistler mode waves (hiss, chorus, lion roars) and broad-band ULF emissions. The polarisation and propagation characteristics of intense waves in the vicinity of a bow shock crossing are analysed using the dedicated PRASSADCO tool, giving results compatible with previous studies: the broad-band ULF waves consist of a superimposition of different wave modes, whereas the magnetosheath lion roars are right-handed and propagate close to the magnetic field. An example of a combined Cluster DSP-TC1 magnetopause crossing is given. This first case study shows that the ULF wave power intensity is higher at low latitude (DSP) than at high latitude (Cluster). On the nightside in the tail, a first wave event comparison - in a rather quiet time interval - is shown. It opens the doors to future studies, such as event timing during substorms, to possibly determine their onset location

Two-Dimensional Velocity of the Magnetic Structure Observed on July 11, 2017 by the Magnetospheric Multiscale Spacecraft

In order to determine particle velocities and electric field in the frame of the magnetic structure, one first needs to determine the velocity of the magnetic structure in the frame of the spacecraft observations. Here, we demonstrate two methods to determine a two-dimensional magnetic structure velocity for the magnetic reconnection event observed in the magnetotail by the Magnetospheric Multiscale (MMS) spacecraft on July 11, 2017, Spatio-Temporal Difference (STD) and the recently developed polynomial reconstruction method. Both of these methods use the magnetic field measurements; the reconstruction technique also uses the current density measured by the particle instrument. We find rough agreement between the results of our methods and with other velocity determinations previously published. We also explain a number of features of STD and show that the polynomial reconstruction technique is most likely to be valid within a distance of 2 spacecraft spacings from the centroid of the MMS spacecraft. Both of these methods are susceptible to contamination by magnetometer calibration errors