Associate Laboratory of Energy, Transports and Aeronautics

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Publications

Promoting sustainability: wastewater treatment plants as a source of biomethane in regions far from a high-pressure grid: a real portuguese case study

Publication . Baena Moreno, Francisco Manuel; Malico, Isabel; Marques, Isabel Paula

ABSTRACT: Wastewater treatment plants (WWTP) located in regions far from a high-pressure grid can produce renewable biomethane, which can partially substitute the natural gas locally consumed. However, the economic viability of implementing biomethane plants in WWTP has to be guaranteed. This paper uses the discount cash flow method to analyze the economic viability of producing biomethane in a WWTP located in evora (Portugal). The results show that, under the current conditions, it is unprofitable to produce biomethane in this WWTP. Since selling the CO2 separated from biogas may result in an additional income, this option was also considered. In this case, a price of 46 EUR/t CO2 has to be paid to make the project viable. Finally, the impact of potential government incentives in the form of feed-in premia was investigated. Without selling CO2, the project would only be profitable for feed-in premia above 55.5 EUR/MWh. If all the CO2 produced was sold at 30 EUR/t CO2, a premium price of 20 EUR/MWh would make the project profitable. This study shows that the economic attractiveness of producing biomethane in small WWTP is only secured through sufficient financial incentives, which are vital for developing the biomethane market with all its associated advantages.

2021-08Journal article

Open access

Electrochemical assessment of corrosion-fatigue degradation stages

Publication . Simões, Alda Maria Pereira; Canut, Felipe; Reis, Luis; Napoleão Bastos, Ivan; Mamiya, Edgar

ABSTRACT: The study is focussed on the joint effect of corrosion and mechanical cyclic stresses observed on mooring chains of Floating Production Storage and Offloading (FPSO) units. The tests were performed using grade R4 steel in artificial sea water, under stress-controlled and fully reversed loading. The corrosion-fatigue degradation was monitored using open circuit potential measurements simultaneously with the cyclic mechanical load. The open circuit potential response varies during the corrosion-fatigue test, depending on the stage of degradation of the material. This technique has proven to be capable of identifying important phenomena, such as crack initiation and crack propagation, on the material under corrosion-fatigue loading condition.

2022-11Conference object

Open access

Synthesis of Non-Cubic Nitride Phases of Va-Group Metals (V, Nb, and Ta) from Metal Powders in Stream of NH3 Gas under Concentrated Solar Radiation

Publication . Shohoji, Nobumitsu; Oliveira, Fernando Almeida Costa; Galindo, José; Rodriguez, Jose; Cañadas, Inmaculada; Fernandes, Jorge Cruz; Rosa, Luís Guerra

ABSTRACT: Using a high-flux solar furnace, loosely compacted powders of Va-group transition metal (V, Nb, and Ta) were reacted with stream of NH3 gas (uncracked NH3 gas) being heated by concentrated solar beam to a temperature (T) range between 600 and 1000 degrees C. From V, sub-nitride V2N (gamma phase) and hypo-stoichiometric mono-nitride VN possessing fcc (face-centered cubic) crystal lattice structure (delta phase) were synthesized. On the other hand, in the reaction product from Nb and Ta, hexagonal mono-nitride phase with N/M atom ratio close to 1 (epsilon phase) was detected. The reaction duration was normalized to be 60 min. In a conventional industrial or laboratory electric furnace, the synthesis of mono-nitride phase with high degree of crystallinity that yield sharp XRD peaks for Va-group metal might take a quite long duration even at T exceeding 1000 degrees C. In contrast, mono-nitride phase MN of Va-group metal was synthesized for a relatively short duration of 60 min at T lower than 1000 degrees C being co-existed with lower nitride phases.

2021-06Journal article

Open access

A New Insight into the Role of Silicate-Type Binders on the Crushing Strength of Alumina Foams

Publication . Oliveira, Fernando Almeida Costa; Pommier, Stéphane; Fernandes, Jorge Cruz; Dias, Diamantino

ABSTRACT: Semi-closed cell macroporous alumina foams with relative densities ranging from 0.26 to 0.35 have been produced by the well-established replication method based on the coating of a polyurethane (PU) template foam by a ceramic slurry, followed by burnout of the PU template, and sintering of the ceramic skeleton. Collapse of the three-dimensional structure upon the volatilisation of the PU sponge can only be prevented using appropriate binders. Scarce data are available on the slurry formulations of commercial alumina foams. The aim of this study was to investigate the influence of silicate-type binders, namely kaolin and bentonite additives, on the crushing strength of alumina foams. The highest crushing strength of around 10 MPa was observed at a porosity of 66 +/- 2%. The open-cell model is inadequate to fit the crushing strength data of such semi-closed cell type structures. Both microscopic and macroscopic flaws resulting from the foam processing method contribute to the wide scatter of the strength, thereby explaining the Weibull modulus ranging from 4 to 7. Both flaw populations require further improvement to maximise the crushing strength of these foams with high potential for the design of structured catalyst carriers and molten aluminium filters.

2022-10Journal article

Open access

Análise do comportamento de lentes em vidro de sílica perante a utilização de radiação solar concentrada

Publication . De Almeida, G.; Guerra Rosa, L.; Pereira, J.C.G.; Bravo Gonzalo, I.; Franco, P.; Fernandes, J.C.; González-Aguilar, J.

RESUMO: Este trabalho descreve os ensaios realizados com um simulador laboratorial de radiação solar concentrada com o objectivo de avaliar o comportamento de lentes em vidro de sílica quando sujeitas a elevados fluxos de radiação, e permitiu comparar o seu comportamento com o que foi demonstrado por lentes idênticas, mas fabricadas em vidro de borossilicato (BK-7) cujo preço é muito inferior. Os ensaios de irradiação das lentes atingiram durações de 60 minutos, durante os quais se procedeu à monitorização contínua da potência da radiação aplicada sobre cada lente e da temperatura nela gerada. Todas as lentes em vidro de sílica se comportaram bem, mas o mesmo não ocorreu com as lentes em vidro de borossilicato. No trabalho é aventada a hipótese de o comportamento negativo registado nas lentes em borossilicato ser provocado pelo facto de se ter usado a radiação emitida por uma lâmpada de arco de xénon que pode conter comprimentos de onda que estão ausentes na radiação solar, pelo que é proposto que nos futuros testes não se use um simulador de radiação solar.

2020-11Conference object

Open access