Learning distillation by a combined experimental and simulation approach in a three steps laboratory : Vapor pressure, vapor-liquid equilibria and distillation column

Distillation is one of the most important separation process in industrial chemistry. This operation isbased on a deep knowledge of the fluid phase equilibria involved in the mixture to be separated. In par-ticular, the most important aspects are the determination of the vapor pressures of the single compoundsand the correct representation of the eventual not ideality of the mixture. Simulation science is a fun-damental tool for managing these complex topics and chemical engineers students have to learn andto use it on real case-studies. To give to the students a complete overview of these complex aspects, alaboratory experience is proposed. Three different work stations were set up: i) determination of vaporpressure of two pure compounds; ii) the study of vapor-liquid equilibria of a binary mixture; iii) the useof a continuous multistage distillation column in dynamic and steady-state conditions. The simulation ofall these activities by a commercial software, PRO II by AVEVA, allows to propose and verify the thermo-dynamic characteristics of the mixture and to correctly interpret the distillation column data. Moreover,the experimental plants and the data elaboration by classical equations are presented. The students arerequest to prepare a final report in which the description of the experimental plants and experimentalprocedure, the interpretation of the results and the simulation study are critically discussed in order toencourage them to reason and to acquire the concepts of the course.Two different questionnaires each with 7 questions, for the course and for the laboratory, are proposedand analyzed. The final evaluation of the students was strongly positive both for the course as a wholeand for the proposed laboratory activities

Biogas upgrading by physical water washing in a micro-pilot absorption column conducted at low temperature and pressure

The European Energy Policy has currently two main goals to reach: to minimize exposure to volatility of fossil fuel prices and to reduce of greenhouse gas (GHG) emissions. To reach these targets a practical way, among the others is represented by the biogas production by anaerobic digestion (Bonoli et al., 2014) (AD) and its upgrading to biomethane. In this work the absorption of CO2is studied using a column working at atmospheric pressure and low temperature (599%) and a stream of methane (>99.9 %) in order to reproduce a typical raw biogas composition, i.e. molar fraction of methane of about 0.6. The internal temperature was monitored by a thermocouple and the inlet and outlet flow of biogas (G) was measured using a mass flowmeter while the water flow rate (L) was monitored using a magnetic induction flowmeter. The compositions were determined using a 3000A micro-Gas Chromatograph Agilent, previously calibrated. The temperature was varied between 6.5 and 20 °C and the water flow rate between about 0.5 and 5 L/h. The composition of the gas exiting the micro-pilot plant was monitored every 5 minutes until the stationary condition

Compact GaN-based Stacked Cells for 5G Applications at 26 GHz

This work presents the development of two 2-FET stacked cells at 26 GHz in the WIN Semiconductors 150 nm power GaN/SiC technology. Two different compact layouts, based on the same circuit scheme, are designed targeting similar performance in the FR2 5G frequency band. One version favoring distance between components, to relieve electromagnetic cross-talk, and the other favoring instead symmetry. The cells have been conceived as basic building blocks for the development of high-power 5G amplifiers, rather than as stand-alone amplifiers, hence including only input matching and stabilization networks. Based on large-signal simulations on the optimum load, the cells are expected to deliver around 34 dBm with an efficiency higher than 35% at 26 GHz, and a linear gain of 10 dB. The output power performance is maintained from 24.5 GHz to 27.5 GHz, where the saturated efficiency is above 30 % for both cells. The small-signal experimental characterization results are in very good agreement with the simulations, proving the effectiveness of the electromagnetic simulation setup adopted for all the passive structures, despite the challenges posed by the compact layouts

On the dimension of Voisin sets in the moduli space of abelian varieties

We study the subsets $V_k(A)$ of a complex abelian variety $A$ consisting in the collection of points $x\in A$ such that the zero-cycle $\{x\}-\{0_A\}$ is $k$-nilpotent with respect to the Pontryagin product in the Chow group. These sets were introduced recently by Voisin and she showed that $\dim V_k(A) \leq k-1$ and $V_k(A)$ is countable for a very general abelian variety of dimension at least $2k-1$. We study in particular the locus $\mathcal V_{g,2}$ in the moduli space of abelian varieties of dimension $g$ with a fixed polarization, where $V_2(A)$ is positive dimensional. We prove that an irreducible subvariety $\mathcal Y \subset \mathcal V_{g,2}$, $g\ge 3$, such that for a very general $y \in \mathcal Y$ there is a curve in $V_2(A_y)$ generating $A$ satisfies $\dim \mathcal Y \le 2g - 1.$ The hyperelliptic locus shows that this bound is sharp.Comment: Final version to appear in Mathematische Annale

Use of a sol-gel hybrid coating composed by a fluoropolymer and silica for the mitigation of mineral fouling in heat exchangers

The technology of the organic/inorganic hybrid coating was employed in the preparation of a hydrophobic coating (contact angle higher than 140\ub0) for fouling mitigation on stainless steel heat transfer surfaces. A commercial triethoxysilane perfluoropolyethers was combined with a sol-gel silica network with the aim to increase the mechanical and thermal resistance of the films when exposed to aggressive liquid environments as the heat exchanging fluids. The experimentation on a shell and tube heat exchanger pilot plant confirmed the ability of the hybrid coating to prolong the crystallization fouling induction period of 200 h in respect to an uncoated heat exchanger, operating in the same conditions. Moreover, the fouling particles deposited on the coated heat transfer surfaces had only slight adhesion strength toward the coated surfaces and were easily removed by inducing higher wall shear stresses inside the tubes of the plant

Ka-band 4 W GaN/Si MMIC power amplifier for CW radar applications

In this contribution it is reported the design, implementation and characterization of a 4-stage single-ended Ka-band power amplifier based on 100 nm GaN/Si commercial process. The amplifier, designed for CW radar applications, has been measured under small-signal and pulsed large-signal conditions. The amplifier exhibits an output power above 4W, together with power added efficiency in excess of 28 % and operative gain larger than 25dB over the 34GHz-38GHz frequency range