A level set approach for computation of bubble dynamics in airlift reactors.

In this work, we employ the so-called level set approach to simulate the rising of gas bubbles in a pilot-scale external loop airlift photobioreactor in which microalgae are used to capture CO2from flue gas and to treat wastewater. A coupled level set and finite difference method is adopted in this work to track the moving gas-liquid interfaces in the ALR riser. Level set methods implicitly represent dynamic fronts by solving an Hamilton-Jacobi partial differential equation such as the normal flow equation, in turn dependent on a flow function that can be regarded as a speed vector field. This latter, for the case at hand, is obtained by solving the non-dimensional Navier-Stokes equations through a Chorin type projection technique on a staggered gri

Analytical Solutions of One-Dimensional Contaminant Transport in Soils with Source Production-Decay

An analytical solution in closed form of the advection-dispersion equation in one-dimensional contaminated soils is proposed in this paper. This is valid for non-conservative solutes with first order reaction, linear equilibrium sorption, and a time-dependent Robin boundary condition. The Robin boundary condition is expressed as a combined production-decay function representing a realistic description of the source release phenomena in time. The proposed model is particularly useful to describe sources as the contaminant release due to the failure in underground tanks or pipelines, Non Aqueous Phase Liquid pools, or radioactive decay series. The developed analytical model tends towards the known analytical solutions for particular values of the rate constants

A Low-Cost Monitoring System and Operating Database for Quality Control in Small Food Processing Industry

The use of completely automated systems for collecting sensor data with the aim of monitoring and controlling the quality of small-scale food processes is not widespread. Small and micro-enterprises usually do not carry out their own precompetitive research or prototype development as regards to automation technologies. This study proposes a web-based, low-cost monitoring and supervisory control and data acquisition (SCADA) system whose kernel is available for free, as a possible solution that could be adopted by these food producers. It is mainly based on open SW/HW so as its configuration is adaptable to the application and type of plant. It presents a modular architecture and its main functionalities encompass the acquisition, management, aggregation and visualization of process data, providing an operating database. It also provides food tracking and process quality control: The time series are browsable due to QR-Code generation and different early warning detection strategies are implemented. A tool for solving migration problems based on Fick\u2019s equation is offered as a packaging decision support system

Adhesion of sea-urchin living cells on nano-patterned anodic porous alumina

In this work we investigated the possibility of using living cells as stress sensing material in biosensors, in the light of the three Rs principle \u2013 Replacement, Reduction and Refinement . This approach requires the necessity to cultivate them on biocompatible electrical conducting substrate and to insert the circuit into a culture chamber that must assure both the transport of oxygen and the diffusion of the medium containing the potential stressor to the cells, without modifying their response and the structure of the culture. To this aim we fabricated nano-patterned substrates of anodic porous alumina to be used for enhancing cell adhesion, and culture chambers made in polylactic acid. Sea-urchin cells (coelomocytes) were cultured on these substrates at different times of 1, 3 and 5 days in vitro. Since these cells are progenitors of immune cells in vertebrate systems (blood cells), they carry out similar functions. For this reason, although they can differ considerably from vertebrates, they have been proved to be very promising sentinels of environmental water qualit

A novel method for Ion Exchange Capacity characterization applied to Anion Exchange Membranes for Water Electrolysers

Hydrogen production from water electrolysis, hydrogen fuel cells and redox flow batteries are the right approach for the renewable energy sector because the electricity generated by solar, wind, photovoltaic, hydroelectric can be managed with a carbon-free approach. These technologies all have in common one fundamental component: the membrane. Different types of membranes have been developed for both cationic and anionic exchange, and recently, research activity focalized on improving their performances is very fervent. One fundamental characteristic of a membrane is its Ion Exchange Capacity (IEC), i.e. the density of charged functionalizing groups. Within our research project NEMESI, funded by EU-PNRR (ID: RSH2B_000002), and dedicated to Anion Exchange Membrane Water Electrolysis, we studied and validated a novel alternative method to measure IEC. The present titration methods have limitations for the need of dedicated hardware or qualitative inspection of their color-turning endpoint. The proposed method, based on the redox titration of potassium ferricyanide with ascorbic acid, allows a quantitative and independent assessment based on both potentiometric and spectrophotometric measurements, along with the usually adopted visual observation, as the yellow-colored ferricyanide is reduced to colorless ferrocyanide. Moreover, if compared to the classical Mohr titration with silver nitrate, the new method can be carried out at variable ferricyanide concentrations during the addition of the ascorbic acid, so a complete curve of the redox reaction can be constructed: the initial ferricyanide ion load of the membrane (IEC) can thus be derived in a more precise way than with a single-point evaluation. Only one Ag/AgCl reference electrode and a platinum working electrode are required without any power supply/potentiostat. The proposed method was validated using Anion Exchange Membranes with known IEC

Design of the experiments for the selection of potential electrocatalysts for both AEM Electrolyzers and Redox Flow Batteries

Both hydrogen production by anion exchange membrane water electrolysis (AEMWE) and energy storage by redox flow batteries (RFB) are promising technologies for dealing with the intermittency of green electricity generation. We investigated on the possibility of using the same electrocatalyst in both the systems in order to reduce production costs if industrial scale electrochemical devices are to be constructed. In this work we selected spinel-based nanostructures as promising catalysts for both oxygen evolution reaction (OER) in AEMWE and positive electrode improvement in Vanadium RFB, and design a complete experimental campaign to choose the best material

Data Driven Modelling and Control Strategies to Improve Biogas Quality and Production from High Solids Anaerobic Digestion: A Mini Review

Anaerobic Digestion (AD) is one of the oldest processes for producing biofuels from organic waste. Approximately 180 years have passed since the construction of the first modern plant, however, large prospects for improvement are still feasible, especially in regards to the quality and uniformity of the biogas produced. This work focalizes on the main quality issues and the available post-production treatment processes for biogas; subsequently, a mini-review on data-driven models and control strategies for biogas and bio-methane production plants is presented. Attention is focused on High Solids Anaerobic Digesters (HSADs), since these reactors present many interesting advantages, including a high number of operating variables which enable process optimization, high methane concentration in exit, reduced reactor volume and low water requirements. HSADs are the reactors with which Europe is aiming to rapidly increase the production of biogas and bio-methane, in order to carry out de-carbonization and reduce dependence on external methane imports. Crucial points for achieving these objectives include qualitative leaps in process operation and management, which, contrary to current practice in existing plants, require a significant increase in process automation, with control of product quality and reduction of stops due to death of bacteria at changing process parameters (such as temperature and pH). The most significant papers related to biogas quality, data-driven models and control strategies are briefly analyzed

Treatment of qualitative geographic information in monitoring environmental pollution

The inverse problem of material sources identification, with particular reference to air polluting sources and their detection from experimental data, is a difficult task to solve and it is classified as a typical ill- posed problem. The traditional approach to these problems uses the additional information available on the system in order to limit the number of solutions consistent with the data by means of regularization techniques. In this paper we propose a method that allows to fund reliable solutions by treating qualitative spatial and geographic information. It is shown how to code in a general fuzzy optimization algorithm the experimental knowledge, quantitative models and the a-priori knowledge about territory configuration such as urban areas, lakes, parks and high-traffic motorways. The architecture of an automatic system that allows to handle the coupled qualitative and quantitative knowledge about the system is presented

Set-up of operating conditions in airlift photo-bioreactors for microalgae cultivation in integrated energy production processes

A set of external loop airlift photobioreactors for Chlorella Vulgaris production has been designed and constructed in order to be integrated into a closed-loop plant in which both biodiesel by transesterification and syngas by gasification are produced. In airlift reactors energy consumption for mixing is low, mixing is guaranteed by gas sparging that assures correct mass transfer between the three phases. However, elimination of pumps means more operating difficulty: residence times into the different zones of the reactor must contemporary guarantee good mass transfer, best CO2 distribution and oxygen release and best light/dark cycles if part of the airlift reactor is made of not-transparent material. A method for correctly set-up and tune process variables before the final plant installation is here described

Sustainable Biodiesel Production by Transesterification of Waste Cooking Oil and Recycling of Wastewater Rich in Glycerol as a Feed to Microalgae

none2The amount of solid and liquid organic waste and wastewater is continuously increasing all over the world. The necessity of their reuse and recycling is, therefore, becoming more and more pressing. Furthermore, the limited fossil fuel resources, in conjunction with the need to reduce greenhouse gas emissions, advocate the production of renewable fuels. In this work, we analyze a sustainable second-generation process to produce biodiesel by transesterification of waste cooking oil, coupled with a third-generation process in cascade for recycling the incoming wastewater. Since this latter is rich in glycerol, it is used as a feed for microalgae, from which oil can be extracted and added to the waste cooking oil to further produce biodiesel and close the cycle. We studied the influence of different factors like temperature, catalyst load, and reactants ratio on the kinetics of transesterification of the waste oil and estimated the kinetic parameters by different kinetic schemes. The obtained values of activation energies and pre-exponential factors at chosen conditions of T = 60 °C and catalyst load of 0.6% w/w in methanol are: Ea,direct = 35,661 J mol−1, Ea,reverse = 72,989 J mol−1, k0,direct = 9.7708 [dm3 mol−1]3 min−1, and k0,reverse = 24,810 [dm3 mol−1]3 min−1 for the global fourth-order reversible reaction scheme and Ea = 67,348 J mol−1 and k0 = 2.157 × 109 min−1 for the simplified pseudo-first-order irreversible reaction scheme; both in strong agreement with literature data. Furthermore, we designed very efficient conditions for discontinuous and continuous operating mode, both at lab-scale and pilot-scale. The quality of the biodiesel produced from waste cooking sunflower oil is compared with that of biodiesel produced by different kinds of virgin vegetable oils, showing that the former possesses acceptable quality standards (Cetane number = 48 and LHV = 36,600 kJ kg−1). Finally, the recycling of wastewater rich in glycerol as a nutrient for mixotrophic microalgae nurturing is discussed, and microalgae growing kinetics are evaluated (k1 about 0.5 day−1), endorsing the possibility of algae extraction each 4–5 days in a semi-continuous operating mode. The experimental results at the pilot scale finally confirm the quality of biodiesel, and the obtained yields for a two-stage process prove the competitiveness of this sustainable process on the global market.nonePaladino, Ombretta; Neviani, MatteoPaladino, Ombretta; Neviani, Matte