Giacobbe Braccio

Techno-economic evaluation of a solar powered water desalination plant

for the countries located within the Southern Mediterranean belt, generally characterized by vast arid and isolated areas with practically no access to electric power from the national grid. Economic factors being one of the main barriers to the diffusion of solar devices so far, an attempt was made to estimate water production cost for two different solar desalination systems: reverse osmosis and multiple effect evaporation process driven by photovoltaic and solar thermal energy, respectively. The results, obtained for plants with a capacity varying between 500 and 5,000 m3/d, were compared to the values relevant to a conventional desalination system.

Efficiency test of solar collectors: uncertainty in the estimation of regression parameters and sensitivity analysis

The results obtained from efficiency tests conducted on a flat plate solar collector, according to the ISO 9806/1 test procedure, have been used to determine the uncertainty in the curve fitting parameters. The said standard, though requiring certain levels of accuracy in the measuring process, doesnot provide any method to determine the uncertainty of the efficiency curve parameters. The methodology used in the present paper (not provided by the ISO standard) allows solving the above mentioned problem and evaluating not only the parameters and their uncertainties but also the reliability of the test procedure and its goodness toward fitness. In order to evaluate the effects of measurement errors on the values of the uncertainty in estimated parameters, a sensitivity analysis has also been conducted. Strong dependence of some uncertainties, involving a larger accuracy level in the estimation of the measured parameters, is a clear indication of the present investigations.

Ethanol production in immobilized-cell bioreactors from mixed sugar syrups and enzymatic hydrolysates of steam-exploded biomass

We investigated ethanol production from mixed sugar syrups. Hydrolysates were prepared from enzymatic saccharification of steam-pretreated aspen chips. Syrups containing 45 g/L of glucose and 12 g/L of xylose were detoxified through two ion-exchange resins and then fermented with Pichia stipitis and Saccharomyces cerevisiae immobilized in Ca-alginate gel beads. Combinations of different gel fractions in the fermentation volume, amount of yeast cells, and ratios of P. stipitis vs S. cerevisiae within each bead were compared. In the best conditions, by using a total beads volume corresponding to 25% of the working volume, we obtained a yield of 0.39 gethanol/ginitial sugars. This amount of gel entrapped an initial cell concentration of 6×1012cells/L with ratio of S. cerevisiae/P. stipitis of 0.25 g/g. Modified stirredtank reactors were obtained either by adding marbles or by inserting a perforated metal cylinder, which reduced considerably the rupture of beads while visibly improving oxygenation of the medium.

Dataset of working conditions and thermo-economic performances for hybrid organic Rankine plants fed by solar and low-grade energy sources.

This article provides the dataset of operating conditions of a hybrid organic Rankine plant generated by the optimization procedure employed in the research article “A genetic optimization of a hybrid organic Rankine plant for solar and low-grade energy sources” (Scardigno et al., 2015) [1]. The methodology used to obtain the data is described. The operating conditions are subdivided into two separate groups: feasible and unfeasible solutions. In both groups, the values of the design variables are given. Besides, the subset of feasible solutions is described in details, by providing the thermodynamic and economic performances, the temperatures at some characteristic sections of the thermodynamic cycle, the net power, the absorbed powers and the area of the heat exchange surfaces.

Study of a Synergistic Solvent Extracting System to Separate Yttrium and Heavy Rare Earths: A Deep Investigation on System Behavior

Yttrium is a strategical material for its several usages in a wide range of industrial production. For this reason, improving the recovery of Yttrium has become a crucial focus for international research. In this scientific activity, the utilization of two extractants, 2-ethylhexyl-mono 2-ethylhexyl ester phosphonic acid (P-507) and sec-octylphenoxy acetic acid (CA-12), working in a synergistic extracting system, has been tested. A series of trials have been carried out to optimize the experimental conditions in order to separate yttrium from a mix of heavy rare earths in chloride media. Tests with different relative concentrations of extractants and a phase modifier (TPB, trybutyl phosphate), with different presaponification rate, have been performed to evaluate the behavior of the synergistic system. Results are very promising to recover and separate yttrium with a high purity.

Behavior of Sec-Octylphenoxy Acetic Acid (CA-12) in Yttrium Recovery from High Concentrated Heavy Rare Earths Mixture

The solvent extraction technique is the only industrial way used to separate and purificate yttrium from other rare earths. In order to improve this process several extractants have been tested during last years. In this work, the behavior of sec-octylphenoxy acetic acid (CA-12) in Yttrium recovery from high concentrated heavy rare earth mixture was investigated. Sodium hydroxide solution was used in order to presaponify organic phase composed by CA-12 and Tributyl phosphate (TBP) diluted in kerosene. In the investigated condition, TBP confirmed its role of phase modifier not significantly altering the extraction behavior of CA-12. The CA-12-TBP system showed a high affinity in extraction for lighter rare earths such as Sm, Eu, and Gd, leaving yttrium in aqueous phase. Using a feed concentration (∑ [RE]) of 1 M, organic mixture is capable to extract around the 70% of metals in a single extraction test showing this extraction sequence Y < Lu < Yb < Tm < Er < Ho < Dy < Tb < Gd < Eu < Sm. Moreover for [CA-12] = 1.79 M and [RE] = 2 M the instability of extraction system occurs.