Data reconstruction and homogenization for reducing uncertainties in high-resolution climate analysis in Alpine regions

Analysis of climatic series needs pre-processing to attain spatial- and time-consistent homogeneity. The latter, in high-resolution investigations, can rely on the strong correlations among series, which in turn requires a strict fulfilment of the quality standard in terms of completeness. Fifty-nine daily precipitation and temperature series of 50 years from Trentino, northern Italy, were pre-processed for climatic analysis. This study describes: (1) the preliminary gap-filling protocol for daily series, based on geostatistical correlations on both horizontal and vertical domains; (2) an algorithm to reduce inhomogeneity owing to the systematic snowfall underestimation of rain gauges; and (3) the processing protocol to take into account any source of undocumented inhomogeneity in series. This was performed by application of the t test and F-test of R code RHtestV2. This pre-processing shows straightforward results; correction of snowfall measurements re-evaluates attribution of patterns of altitudinal trends in time trends; homogenization increases the strength of the climatic signal and reduces the scattering of time trends, assessed over a few decades, of a factor of 2

The role of thermophoretic effect in the formation of soot from liquid fuels

In order to rationalize soot formation in two-phase combustion, the related dynamics can be conveniently studied in simpler systems. In the latest twenty years, experimental activity in drop towers and in the outer space have allowed to investigate the combustion of isolated droplets in microgravity conditions, i.e. spherically symmetric systems where buoyancy effects and slip velocity are absent, yet still containing the major phenomena affecting real combustion (unsteady evolution, convection, gas and soot radiation, heterogeneous properties and so on). In such conditions, it had been speculated [1] that a key role in soot formation is played by thermophoretic effect, because of which solid particles are transported towards the droplet surface, thus increasing their residence times in the fuel-rich area, where soot growth is kinetically favoured. The spherical symmetry also allows to numerically study these systems with a relatively low computational weight. The importance of thermophoresis in the dynamics of soot formation can thus be investigated in a variety of operating conditions (droplet size, pressure, composition, etc.), which is the subject of this work. Starting from a description of the constitutive parts of the isolated-droplet model, the transient dynamics of soot formation in n-heptane droplets is analysed. The impact of the submodel describing thermophoresis is considered in detail, and indications about its possible refinements are provided

Novel coal gasification process: Improvement of syngas yield and reduction of emissions

This article is intended to propose and model an innovative process layout for coal gasification that improves the production of syngas and also reduces the sulfur and CO2emissions. The typical coal gasification process uses Sulfur Recovery Units to convert H2S to sulfur, but these have some disadvantage, e.g low sulfur price, coal charge with low sulfur flow rate, use of Tail Gas Treatment unit. Compared to the Claus process, this solution converts H2S and CO2into syngas (economically appealing), reduces emission of H2S and CO2and allows the use of coal charge with high sulfur flow rate, e.g. 9.5% mol/mol. The novel process takes advantage of a double amine wash, a thermal regenerative furnace and considers the recycle of the acid gases coming from the catalytic reactor to further promote the H2S conversion. In particular, the double amine wash is useful to purify the H2S stream to be sent to the thermal furnace from the syngas and CO2, in order to reduce the reactor inlet flow rate. The regenerative furnace is simulated using a large detailed kinetic scheme to appropriately describe the minor species (among them, pollutants like CS2 and COS). As a result, the recycle appears to substantially reduce the pollutant emissions. In addition, the conversion of the Claus process into the novel process doesn't require any change in the main equipment, just needing for a variation in the layout and the operating conditions

Devolatilization of organo-sulfur compounds in coal gasification

Coal gasification is a thermo-chemical process aiming at the production of high heating value syngas. The coal charges present, typically, a low quantity of sulfur compounds for prevent the formation of a large amount of sulfuric acid (H2S), that is a pollutant and a poison for catalysts, in syngas stream. However, in the world there are a lot of coals that cannot be used for gasification because of their high sulfur content (e.g. Sulcis Italian coal or Inner Mongolia Chinese coal). The interest on these types of coal is increasing due to a novel technology that allows to convert H2S and CO2into syngas (AG2S\u2122). The aim of this work is to propose a predictive kinetic model of the release of sulfur compounds (e.g H2S) from coal. This kinetic scheme is implement into GASDS, a package that includes a gasifier mathematical model, which accurately describes the inter-phase mass and heat transfer. The first complexity relies in the characterization of the coal, in particular the relative amount of the different forms of sulfur components (e.g. inorganic such as pyritic and sulfates, and organic sulfur such as aliphatic, aromatic and thiophenic) and their pyrolysis and devolatilization process. The kinetic model, with the related rate parameters, is validated through comparison with experimental data from the literature and obtained during several experimental campaigns at the Sotacarbo S.p.A. pilot platform. Finally, different operating conditions of gasification are analyzed in order to obtain the best yield in the downstream process, with special reference to the novel Acid Gas to Syngas (AG2STM) process

Long-term changes of hydrological variables in a small Lowland watershed in Central Poland

Climate-induced changes in small watersheds are still not well researched because long-term datasets are usually missing for these watersheds. Such studies can, however, improve our understanding of the watershed response to climatic changes at such a small scale being transparent. In this study, we investigate trends in temperature, precipitation and river-flow characteristics in a small watershed, typical for Central Poland, with 53 years of observations (1963–2015) using the Mann-Kendall test. Particularly, we examine whether any trends in hydro-meteorological variables can be identified, and if any associated changes in water resources in this region can already be observed. We found that this short period already allows for detecting some changes in hydro-meteorological variables. These changes could be characterized by a significant increase in the mean annual air temperature on a daily basis, and a significant decrease in the mean annual discharge on a daily basis and in the minimum annual discharge on a daily basis. Yet, no significant trend could be detected for the total annual precipitation, the maximum summer rainfall, and the maximum annual discharge on a daily basis. These findings indicate that water resources are decreasing in this region, which affects natural habitats, agriculture and local communities

GLIMS-IT: contributo italiano al progetto GLIMS di monitoraggio satellitare dei ghiacciai del globo

Si illustra lo stato di avanzamento del contributo italiano al progetto GLIMS-Global Land Ice Measurements from Space che consiste nella redazione di un Atlante satellitare dei ghiacciai italiani. Dall'analisi di cinque immagini rilevate dal sensore ASTER installato sul satellite TERRA sono stati delineati i limiti dei ghiacciai nei gruppi montuosi delle Alpi Lepontine, Pusteresi, delle Dolomiti venete, del versante trentino del Cevedale e dell'Adamello-Presanella. Dal punto di vista metodologico si sono sfruttate, tra l'altro, le informazioni desumibili dai canali spettrali dell'infrarosso termico per il riconoscimento di alcuni ghiacciai coperti da detrito e, una volta delineata l'estensione del ghiacciaio, i parametri geomorfologici vengono estratti in modo automatico con un codice di calcolo che implementa i requisiti del progetto GLIMS. I risultati delle elaborazioni sono stati trasmessi al data base gestito dal National Snow and Ice Data Center ed al Comitato Glaciologico Italiano, che collabora all'iniziativa per l'aggiornamento del catasto dei ghiacciai italiani. Le informazioni per i gruppi montuosi del Cevedale e dell'Adamello-Presanella sono state organizzate in un sistema informativo territoriale in formato KML. Mediamente, nelle aree sinora investigate, è stata rilevata una diminuzione dell'estensione dei ghiacciai, dagli anni '80 al 2007, compresa tra il 34% ed il 50%, una marcata frammentazione di diversi ghiacciai e la scomparsa di alcune unità glaciologiche, confermando l'accelerazione del ritiro iniziato al termine della Piccola Età Glaciale. Si presentano i risultati dell'elaborazione di un'immagine del gruppo dell'Adamello-Presanella la cui estensione dei ghiacciai si è ridotta del 36% dagli anni '80 al 2007

A CFD model for biomass flame-combustion analysis

The present work addresses the study of the combustion of individual biomass particle surrounded by a gas stream of N2/O2 under the operating conditions encountered in a drop tube reactor. The aim of this analysis is to give a better insight into the chemical and physical processes that occur both at particle and reactor scale where the volatiles, generated by the biomass pyrolysis, burn in a fuel particle enveloped flame. A comprehensive CFD model was developed within the open-source OpenFOAM® framework in order to properly handle the computational mesh and the discretization of the characteristic governing equations. At the reactor scale, the reactive flow was described by the equations for continuous, multicomponent, compressible and thermally-perfect mixtures of gases. At the particle scale, instead, the solid particle was considered as a porous media with isotropic and uniform morphological properties

Upstream Operations in the Oil Industry: Rigorous Modeling of an Electrostatic Coalescer

This paper deals with a first-principle mathematical model that describes the electrostatic coalescer units devoted to the separation of water from oil in water-in-oil emulsions, which are typical of the upstream operations in oil fields. The main phenomena governing the behavior of the electrostatic coalescer are described, starting from fundamental laws. In addition, the gradual coalescence of the emulsion droplets is considered in the mathematical modeling in a dynamic fashion, as the phenomenon is identified as a key step in the overall yield of the unit operation. The resulting differential system with boundary conditions is then integrated via performing numerical libraries, and the simulation results confirm the available literature and the industrial data. A sensitivity analysis is provided with respect to the main parameters. The mathematical model results in a flexible tool that is useful for the purposes of design, unit behavior prediction, performance monitoring, and optimization