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- Preliminary study on the use of biodiesel obtained from waste vegetable oils for blending with hydrotreated kerosene fossil fuel using Calcium Oxide (CaO) from natural waste materials as heterogeneous catalystPublication . Ozkan, Sila; Puna, Jaime; Gomes, João; Cabrita, T.; Palmeira, José; Santos, Maria TeresaIn this experimental work, calcium from natural seafood wastes was used as a heterogeneous catalyst separately or in a blend of "shell mix" for producing biodiesel. Several chemical reaction runs were conducted at varied reaction times ranging from 30 min to 8 h, at 60 degrees C, with a mass content of 5% (W-cat./W-oil) and a methanol/oil molar ratio of 12. After the purification process, the biodiesel with fatty acid methyl ester (FAME) weight content measured was higher than 99%, which indicated that it was a pure biodiesel. This work also showed that the inorganic solid waste shell mixture used as the heterogeneous catalyst can be reused three times and the reused mixture still resulted in a FAME content higher than 99%. After 40 different transesterification reactions were performed using liquid (waste cooking oils) and solid (calcium seafood shells) wastes for producing biodiesel, under the specific conditions stated above, we found a successful, innovative, and promising way to produce biodiesel. In addition, blends prepared with jet fuel A1 and biodiesel were recorded with no invalid results after certain tests, at 25 degrees C. In this case, except for the 10% blend, the added biodiesel had no significant effect on the viscosity (fluidity) of the biojet fuel.
- Synthesis gas production from water electrolysis, using the Electrocracking conceptPublication . Guerra, Luís; Moura, K.; Rodrigues, J.; Gomes, João; Puna, Jaime; Bordado, João; Santos, Maria TeresaThe present research work is focused on the production of synthesis gas by water electrolysis, using renewable electric energy and, further on, liquefied biomass as a carbon source necessary for obtaining carbon monoxide and carbon dioxide. In order to demonstrate and also optimize this process, this study comprised the influence of the electrolyte concentration, liquefied cork concentration, temperature and pressure and the main process outputs, such as: the flow rate of the produced gas, carbon monoxide, carbon dioxide and oxygen composition, as well as the energy consumed in the process. This gas can further on, be used for producing renewable synthetic fuels, such as: methane, methanol, dimethyl ether (DME), diesel, etc. The optimum operational conditions thus determined for this process, at laboratory scale, comprised the use of NaOH 1.2 M mixed with 20% (v/v) liquefied cork, as electrolyte. Applying these operating conditions a synthesis gas composed of 66.67% H2, 25.32% CO, 0.00% CO2 and 8.01% O2 was obtained at a flow rate of 8.31 L/h, consuming a power of 7.75 Wh/L. Also, the analysis of the residual biomass deposited in the electrodes showed some changes in the initial structure, as expected.
- Methane production by a combined Sabatier reaction/water electrolysis processPublication . Guerra, Luís; Rossi, S.; Rodrigues, J.; Gomes, João; Puna, Jaime; Santos, Maria TeresaThis paper describes production of synthesis gas (syngas) and its optimization through a one-step innovative 1 kW prototype of alkaline water electrolysis (patented), using graphite electrodes and without gas separation (containing CO, CO2, H2 and small amounts of O2). The behavior of the syngas composition and flow rate has been studied and optimized, changing operational parameters such as temperature, pressure and current intensity, and testing two different kinds of electrodes. Afterwards, the best syngas composition has been sent into a catalytic reactor (filled with a bed of Ni/CaO-Al2O3 catalyst) in order to achieve methane production, at 1 bar and different temperatures. The main competitive advantage of this process lies in the built-in of an innovative technology product, from renewable energy (RE) power in remote locations, such as islands, villages in mountains as an alternative for energy storage for mobility constraints. In the catalytic reactor it was possible to achieve a CH4 yield of 25.5 %, a CO2 conversion into CH4 of 44.2% and a CH4 selectivity of 96.5%.
- Management options for construction and demolition wastes from residential recuperationPublication . Santos, Maria Teresa; Lamego, Paula; Frade, P.Nowadays, the construction, remodelling and demolition operations can cause serious environment impacts. These activities produce materials defined as construction and demolition wastes (CDW). The CDW generated in Europe represents around 25-30 % of total waste. In EU 28 CDW production is about 821,160,000 t, but there is a significant difference among the European countries, mainly because of the variation of construction and demolition activity. In 2011, the total production of CDW in Portugal was around 930,000 t, but regional production is not homogeneous. The substantial inert fraction from the CDW makes them suitable for reuse. The present study aims to quantify and characterize CDW from residential recuperation of small constructions in Portugal and then propose mitigating measures to improve CDW management. The results obtained by bibliographic research revealed that the construction and demolition activity has decreased significantly in the last years and consequently CDW production. In addition, it was observed a big number of entities were involved in CDW management. Therefore, it was necessary to select a specific area from Portugal (Setubal region) which has thirteen City Halls. The surveys had scarce response. This can be explained by the lack of obligation of enterprises with less than ten employees to register CDW production and because in some regions the CDW are mixed with municipal solid waste. Most of the CDW collected from Setubal region was disposed in landfill. In order to reduce CDW production it is necessary to promote and make available recycled materials for small works at low cost.
- Tratamento de águas residuais: processos de tratamento biológicoPublication . Monte, Helena Marecos do; Santos, Maria Teresa; Barreiros, Ana MariaO objetivo principal dos processos de tratamento biológico de AR consiste na remoção de poluentes orgânicos biodegradáveis, por meio da repro dução intensiva dos fenómenos de autodepuração naturais, em reatores biológicos projetados de forma a proporcionar aos microrganismos as con dições favoráveis à sua ação de degradação da matéria orgânica (MO), nomeadamente o fornecimento de oxigénio, por arejamento mecanizado. A degradação bioquímica da MO processa-se em meio aquoso, pela ação de microrganismos sobre a MO dissolvida e particulada em suspensão coloidal, o que pressupõe a prévia remoção de sólidos grosseiros e de SST nos níveis de tratamento designadas por tratamento preliminar e tratamento primá rio, respetivamente (Capítulo 2 do Curso Técnico 5). Esta é a razão pela qual o tratamento biológico é frequentemente designado por tratamento secundário, o que não é totalmente rigoroso, pois, o tratamento secundário também pode ser conseguido por processos de tratamento físico-químico. Além da remoção de MO biodegradável, geralmente quantificada pela Carência Bioquímica de Oxigénio (CBO), os processos biológicos ainda per mitem a remoção de nutrientes (compostos de N e de P) das AR. Também o tratamento de lamas se efetua, em larga medida, através de processos biológicos.
- Tratamento de águas residuais: operações e processos de tratamento físico e químicoPublication . Monte, Helena Marecos do; Santos, Maria Teresa; Barreiros, Ana Maria; Albuquerque, AntonioA história do tratamento de águas residuais (AR) é bem recente, tem pouco mais do que cem anos, datando dos primeiros anos do século XX, quando entraram em operação as primeiras estações de tratamento de águas residuais (ETAR), de que Stahnsdorf, na Alemanha é um exemplo (Müller, 1907 citado por Wiesmann, 2007). O facto de o tratamento de AR ser uma questão tão recente é devido à circunstância de, durante quase toda a história da Humanidade, a evacuação dos excreta humanos ter sido feita por deposição a seco, nos pátios domésticos ou nas ruas dos centros urbanos. Não obstante, existem casos de evacuação dos excreta por via hídrica na Antiguidade, na Idade Média e na Idade Moderna, que constituem exemplos notáveis para a sua época.
- Coal fly ash waste, a low-cost adsorbent for the removal of Mordant Orange dye from aqueous mediaPublication . Rosa, Teresa; Martins, Angela; Santos, Maria Teresa; Trindade, Teodoro; Nunes, NelsonIn this study, a coal fly ash material generated in a Portuguese coal thermal powerplant was tested as a low-cost adsorbent to remove dye molecules. Pre-treatment of the coal fly ash samples was not performed in order to reduce end use cost. Physical and chemical characterization revealed their inert nature and low effects lixiviation in aqueous media. Preliminary adsorption studies include adsorbent quantity, and adsorption kinetics. The adsorption studies focused on Mordant Orange 1 (Mo1) dye, but two other molecules, Rhodamine B (RhB) and Methylene Blue (MeB) were also included for comparison reasons. The adsorption isotherms were tested with different models including Langmuir, Freundlich and modified Langmuir-Freundlich. The effect of temperature, pH and unburn carbon in the adsorption process were also studied. The results show that adsorption capacity of the coal fly ash occurs mainly due to electroestatic interactions between the adsorbent surface and the adsorbate, which depends on the pH of the aqueous media and the surface chemistry of the material, quantified by the point of zero charge, pHpzc. These joint effects are responsible for the higher retention of Mo1 that is about 16 times higher, when compared to the other two molecules tested.
- Production of synthesis gas obtained via alkaline water electrolysis and added biomassPublication . Gomes, João; Puna, Jaime; Santos, Maria TeresaThis paper presents the results of the research currently being carried out at ISEL with the objective of developing new electrochemistry-based processes to obtain renewable synthetic fuels from alkaline water electrolysis using a carbon source. In the developed process, the gas mixture obtained from alkaline water electrolysis and a carbon source is not separated into their components but rather is introduced into a catalyzed reactor, in order to achieve conversion to synthetic 2nd generation biofuels, such as biomethane, biomethanol, bio-dimethyl ether, etc. Tests have been previously executed in a pilot electrolyzer and reactor of 1 kW, and are now being scaled up to a pilot electrolyzer and reactor of 5 kW, producing 250 l/h CH4, as an intermediate step to a pilot of 100 kW.
- Calcium rich food wastes based catalysts for biodiesel productionPublication . Catarino, Maria Alice; Ramos, M.; Soares Dias, A. P.; Santos, Maria Teresa; Puna, Jaime; Gomes, JoãoBiodiesel produced from food wastes can help to solve several environmental issues: anthropogenic carbon emissions due to fossil fuels combustion and waste management. Biodiesel was produced using waste frying oils (WFO) and calcium rich food wastes such as mollusk, shrimp, eggs shells and cuttlebone to produce calcium based heterogeneous catalysts by calcination. The characterization of chalky white calcined powders by XRD showed diffraction lines typical of lime but some samples were slightly contaminated with calcite. The powders with low crystallinity showed high hydration rate presenting XRD features ascribable to nanocrystals of calcium hydroxide. The post reaction samples presented mainly lines due to calcium diglyceroxide and methoxide. Thermograms of used catalysts showed some weight loss of these calcium compounds, confirming the presence of such phases. All prepared catalysts were effective in catalyzing the methanolysis of soybean oil. A FAME yield around 96% was obtained after 2.5 h of reaction. When using WFO, the FAME yield was only 65% with simultaneous production of soap. The use of WFO and soybean oil mixtures attenuates the loss of catalytic performances. The obtained glycerin's presented a light color characteristic of heterogeneous catalyzed processes. FTIR spectra of glycerin's showed some features belonging to matter organic non glycerin and methanol. The catalyst reutilization without intermediate reactivation indicated that catalysts are somewhat stable. When WFO was used, the reused catalysts showed improved performance probably due to the formation of calcium diglyceroxide. Nevertheless, calcium diglyceroxide is bound to promote homogeneous catalysis and consequent deactivation.
- Sludge recovery from industrial wastewater treatmentPublication . Santos, Maria Teresa; Lopes, Pedro AndréIndustry is a fundamental sector that allows mass production to support a large population. As population grows, many industries produce large amounts of industrial effluents with different pollutants, that must be removed at the industrial wastewater treatment plants, with the consequent production of large amounts of sludge. The present study was conducted to identify and evaluate different sludge treatment/valorisation methodologies, being given priority to the valorisation in detriment of the elimination operations, like incineration or landfill. Therefore, sludges from the wastewater treatment plant of a resin industry, after dehydration operation by a press, were submitted to several valorisation methodologies, such as: application in anaerobic digestion aiming the production of biogas and allowing energy recovery, use in the preparation of adsorbents for the treatment of industrial wastewater, use as cement replacement in mortar production, and application of heterogeneous catalysts to produce biodiesel. The results revealed that all methodologies can be applied as sludge recovery. However, it is possible to conclude that the most promising industrial sludge treatment/recovery hypothesis is anaerobic co-digestion followed by the production of heterogeneous catalysts for biodiesel production.