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Modelling and energy efficiency analysis of the microwave continuous processing of limestone
Publication . Gonçalves, Sofia N.; Albuquerque, Duarte M.S.; Pereira, José C.F.; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; Faculdade de Ciências e Tecnologia (FCT); Elsevier
Our numerical investigation is oriented to the energy efficiency of the microwave heating technology for the continuous production of cement clinker. Simulations of the novel microwave continuous processing of limestone are performed using the COMSOL Multiphysics® Software. The proposed mathematical model couples Maxwell's equations with energy and chemical equations, and numerical verification and validation are undertaken to support the accuracy of the results in this work. This approach includes automatic control actions regulating energy input and cavity impedance. A rectangular waveguide, operating as a single-mode cavity at 2.45 GHz, is utilized. The impact of various fill ratios of material on the system's efficiency unveiled an intriguing heat transfer mechanism responsible for optimal operational conditions, with microwave efficiency up to 75% and thermal efficiency exceeding 90%. Notably, the potential of microwave technology in reducing greenhouse gas emissions is contingent upon establishing clean energy sources for electricity production.
Surface Morphology and Electrochemical Behavior of Microstructured Cu Electrodes in All-Solid-State Sodium Batteries
Publication . Prior, Tomás; Figueira, Joana; Freitas, Ângela; Carvalho, David; Gomes, Beatriz Moura; Baptista, Manuela C.; Lebre, Hugo; Martins, Rodrigo; Pereira, Luís; Pinto, Joana Vaz; Braga, M. Helena; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; MDPI - Multidisciplinary Digital Publishing Institute
The integration of microstructured current collectors offers a potential pathway to enhance interface properties in solid-state battery architectures. In this work, we investigate the influence of surface morphology on the electrochemical performance of Zn/Na2.99Ba0.005OCl/Cu electrodeless pouch cells by fabricating copper thin films on microstructured parylene-C substrates using a combination of colloidal lithography and reactive ion etching. O2 plasma etching times ranging from 0 to 15 min were used to tune the surface topography, resulting in a systematic increase in root-mean-square roughness and a surface area enhancement of up to ~30% for the longest etching duration, measured via AFM. Kelvin probe force microscopy-analyzed surface potential showed maximum differences of 270 mV between non-etched and 12-minute-etched Cu collectors. The results revealed that the chemical potential is the property that relates the surface of the Cu current collector/electrode with the cell’s ionic transport performance, including the bulk ionic conductivity, while four-point sheet resistance measurements confirmed that the copper layers’ resistivity maintained values close to those of bulk copper (1.96–4.5 µΩ.cm), which are in agreement with electronic mobilities (−6 and −18 cm2V−1s−1). Conversely, the charge carrier concentrations (−1.6 to −2.6 × 1023 cm−3) are indirectly correlated with the performance of the cell, with the samples with lower CCCbulk (fewer free electrons) performing better and showing higher maximum discharge currents, interfacial capacitance, and first-cycle discharge plateau voltage and capacity. The data were further consolidated with Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy analyses. These results highlight that the correlation between the surface morphology and the cell is not straightforward, with the microstructured current collectors’ surface chemical potential and the charge carriers’ concentration being determinant in the performance of all-solid-state electrodeless sodium battery systems.
Housekeeping System for Suborbital Vehicles
Publication . Rodrigues, Geraldo; Arribas, Beltran; Melicio, Rui; Gordo, Paulo; Valério, Duarte; Casaleiro, João; Silva, André; UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; CTS - Centro de Tecnologia e Sistemas; MDPI - Multidisciplinary Digital Publishing Institute
The work presented in this paper regards the improvement of a housekeeping system for data acquisition of a suborbital vehicle (VIRIATO rocket or launcher). The specifications regarding the vehicle are presented and hardware is chosen accordingly, considering commercial off-the-shelf components. Mechanical and thermal simulations are performed regarding the designed system and a physical prototype is manufactured, assembled and programmed. Functional and field test results resorting to unmanned aerial vehicles, as well as the system’s integration within VIRIATO project’s mock-up vehicle, are presented. These tests demonstrate the viability of this system as an independent data acquisition system, and simulation results show that commercial off-the-shelf components have the capability of surviving expected launch environments.
Enhancing the efficiency of Brown 24 pigment production through continuous microwave heating in conveyor belt and rotary kiln systems
Publication . Ramos, Pedro A.V.; Albuquerque, Duarte M.S.; Pereira, José C.F.; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; DEMI - Departamento de Engenharia Mecânica e Industrial; Faculdade de Ciências e Tecnologia (FCT); Elsevier Science B.V., Amsterdam.
In energy intensive industries, the continuous production with microwave technology presents several challenges in achieving high energy efficiency and heating uniformity. In the ceramic pigments sector, the Brown 24 is the ideal candidate for this study due to its susceptibility to thermal runaways and its high temperature to reach total conversion, higher than 1000 K. By another hand, most literature related to this field focus on static systems while ignoring the continuous ones which are required by the industry. A coupled model that integrates thermal, electromagnetic and chemical phenomena within an energy system was implemented in COMSOL Multiphysics. Additionally, a MATLAB controller was employed to dynamically adjust the cavity length through a moving plunger, which maximizes the electrical efficiency. The required power is also managed to guarantee a total chemical conversion of the material. The proposed optimization methodology reduces computational costs, and it is applicable to any continuous microwave system processing moving solid materials. In this work, two microwave configurations were optimized. The first one, based on a conveyor belt, achieved a global efficiency close to 70%. While the second one, based on a rotary kiln, achieved a global efficiency of 85% and a production rate of 4.66 kg/h, significantly outperforming a previous study by factors of 1.57 and 2.06, respectively. These findings show the potential for substantial improvements in continuous microwave systems.
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Fundação para a Ciência e a Tecnologia
Programa de financiamento
Concurso de avaliação no âmbito do Programa Plurianual de Financiamento de Unidades de I&D (2017/2018) - Financiamento Programático
Número da atribuição
UIDP/50022/2020