Browsing by Author "Ribeiro, A.M."
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- Co-gasification of glycerol/fat mixtures in a downflow fixed bed reactor: Preliminary resultsPublication . Almeida, A.; Pilão, Rosa Maria; Ramalho, Elisa; Ribeiro, A.M.; Pinho, CarlosThe aim of this work was to assess the technical viability of glycerol/fat co-gasification. The gasification performance was studied in a downflow fixed bed reactor using steam as oxidizing agent. Tests were performed with a mixture of 10% of fat and 52% of water, and the effect of temperature was evaluated in the 800 ºC to 950 ºC range. Samples of dry gas from the gasifier were collected and analysed by gas chromatography in order to determine the CO, CO2, CH4 and H2 content. The results revealed that the co-gasification of glycerol/fat mixtures seems to be a feasible technical option. Best results of the gasification parameters were obtained at the highest tested temperature, 950 °C.
- Co-pyrolysis of brown macroalgae and pinecones in a fixed bed reactorPublication . Silva, F.T.; Nascimento, M.; Pilão, R. M.; Neto, M.P.; Ribeiro, A.M.This study presents results on the slow co-pyrolysis of Laminaria digitata (LD) and pinecones (PC), at an average temperature of 560 °C, for mass ratios LD/PC of 100/0, 50/50, 30/70, 10/90 and 0/100. The biochar yields varied from 35.3 to 31.2 %, for bio-oils, the yields were in the range of 23.3 to 39.9 %, and for the gas phase, between 41.4 to 28.9 %, as the amount of PC increased in the feeding mixture. The biochars were characterized in terms of proximate analysis and higher heating value (HHV). The properties of bio-oils that were determined included pH, density and HHV, as well as identification of compounds by infrared analysis. CO2, CO, CH4 and H2 were identified in the gas phase of all the experiments by gaschromatography, but the most produced gas was CO2, followed by CO.
- Gasification of animal fat using dolomite as particle bed in a downdraft fixed bed reactorPublication . Pilão, R.; Araujo, A.L.; Silva, F.T.; Ribeiro, A.M.; Campos, J.B.L.M.One of the wastes generated in the tanning industry is hide fleshings, which contains 40% of animal fat, currently being deposited in landfills. The objective of this work was to study the catalytic capacity of dolomite in the gasification of this waste. The tests were carried out in a downflow fixed bed reactor using steam as gasification agent and used as bed of particles, alumina, dolomite and a mixture of the two mate-rials. Tests were caried out at 750 ºC and 800 ºC and the gas obtained was quantified and analyzed by gas chromatography. The results obtained showed that dolomite improves the performance of the gasification process, with an increase in carbon and hydrogen conversion efficiencies, cold gas efficiency and dry gas yield with the use of dolomite. It was also possible to verify the catalytic capacity of this material in the cracking of hydrocarbons and its potential in promoting the production of H2. In addition, the use of the mixed bed allowed to improve the results of the gasification parameters obtained at 800 ºC without compromising the degradation of the dolomite verified at higher temperatures.
- Gasification of Cork Wastes in a Fluidized Bed ReactorPublication . Rodrigues, Sara; Almeida, Ana F.; Ribeiro, A.M.; Neto, Paula; Ramalho, Elisa; Pilão, Rosa MariaBiomass gasification has been identified as an option for energetic valorisation of organic wastes. This work aimed to study the gasification of cork industry wastes using a semi-batch fluidized bed reactor. The experimental tests were performed using air as oxidizing agent and sand particles as bed material. The heating was performed with an electrical resistance of 3 kW. The effect of biomass load (2–5.6 g), and bed temperature (780–900 °C) on gasification performance was evaluated using an air flow rate of 0.092 g/s. Samples of producer gas were analysed by a gas chromatograph fitted with a thermal conductivity detector. The detected and quantified compounds on producer gas were H2, CO, CH4 and CO2. Temperature and mass load had a predominant role in gasification performance and all gasification parameters increased with the temperature rise. The increase of mass resulted in a decrease of carbon conversion efficiency, cold gas efficiency and dry gas yield. Best results were obtained with mass load at a range of of 2–4 g, working at 850 °C. The results showed that cork particles are a sustainable raw material for gasification processes.
- Gasification of crude glycerol after salt removalPublication . Almeida, Ana; Pilão, Rosa; Ribeiro, A.M.; Ramalho, Elisa; Pinho, CarlosThe increase in the amount of crude glycerol available on the market, as well as the decrease in its purity due to the use of waste materials in the production of biodiesel, has forced producers to look for alternative ways of valuing this byproduct. In this research work, crude glycerol of a Portuguese biodiesel producer was pretreated using an ion exchange process in order to reduce its salt content. The gasification process was performed using steam as the oxidizing agent in a down-flow fixed-bed reactor using alumina particles as bed material. After the gasification process, the producer gas flowed through a condensing and cleaning system, in order to remove the condensable fraction. Dry gas samples were collected and analyzed by GC in order to quantify the CO, CO2, CH4, and H2 content. Three different feed mixtures were studied with 35%, 39%, and 59% (w/w) water, and the tests were performed at 850, 900, and 950 °C. The results showed that the increase of the water content in the feed mixture led to higher values of H2 and CO2, and lower values for CO and CH4, on the producer gas composition. A slight increase of dry gas yield and hydrogen conversion efficiency with the increase of water content in the feed was observed, while the lower heating value of producer gas decreased. No significant influence of water content was detected in the carbon conversion efficiency and cold gas efficiency. The increase of temperature resulted in the increase of four gasification parameters with maximum mean values of 90% for carbon conversion efficiency, 100% for hydrogen conversion efficiency, 107% for cold gas efficiency, and 1.3 m3/kg raw material. The maximum lower heating value of 14.5 MJ/m3 was obtained at 850 °C.
- Influence of the operating temperature on the slow pyrolysis of pineconesPublication . Nascimento, M.; Silva, F.; Pilão, R.M.; Neto, M.P.; Ribeiro, A.M.This study investigated the production of biochars, bio-oils and non-condensable gas from pinecones through pyrolysis. The effect of temperature on the yields of the three phases and their characterization was studied. Char yield varied from 39.7 to 29.5 % and gas yield increased from 22.1 to 33.9 % as temperature rose from 408 to 661 ºC. Bio-oil yield increased from 38.3% at 408 ºC to 39.9 % at 562 ºC and then decreased to 36.6 % at 661 ºC. The chars obtained had an ash content between 1.38 and 2.20 %, volatiles in the range of 3.90 to 22.99 %, fixed carbon from 75.23 to 94.72 % and a higher heating value (HHV) in the range of 28.81 to 31.63 MJ.kg-1. The gas phase was mainly composed of carbon dioxide (CO2), carbon monoxide (CO), methane (CH4) and hydrogen (H2).
- Pirólise de agulhas de pinheiro: resultados preliminaresPublication . Nascimento, M.; Silva, F.; Pilão, R.; Neto, M.P.; Ribeiro, A.M.(Introdução) As florestas em Portugal ocupam uma área aproximada de 3 224 200 ha, apresentando como espécies predominantes o sobreiro, o pinheiro e o eucalipto (ICNF, 2021). Os pinheiros ocupam cerca de 28 % desta área e geram diversos resíduos, entre os quais as agulhas, que se não forem retiradas das florestas podem agravar o problema dos incêndios florestais (Omvesh et al., 2023). A energia proveniente de resíduos florestais pode ser transformada em combustíveis ou em outros produtos químicos através de processos termoquímicos, como a pirólise, onde há a formação de três fases distintas: o carbonizado, o bio-óleo e o gás (Basu, 2018).
- Pyrolysis of leather wastes from the footwear industry –preliminary resultsPublication . Direito, D.; Pilão, Rosa Maria; Crispim, Alfredo; Ribeiro, A.M.Most of the leather used by the footwear industry (more than 70%) is produced from skins and hides tanned with chromium sulphate [1]. The production of leather goods, especially shoes, gives rise to wastes that amount to 15 – 20% of the entry leather [2]. As an example, the European footwear industry generates between 1x105 to 2x105 tons per year of leather wastes [1]. In the last few years, various investigations have been carried out in order to find alternatives to the disposal of these residues in landfills. Several processes have been developed to treat the leather residues that include, among others, combustion, pyrolysis, chemical treatment (oxidation and hydrolysis) or direct application of the wastes [2]. Pyrolysis is the thermal degradation of wastes, in the presence of an inert atmosphere, producing a solid phase (biochar), a liquid phase (bio-oil) and a gas phase composed mainly of CO2, CO, CH4 and H2 [3]. Several authors have reported work on the pyrolysis of chromium tanned leather wastes [4, 5, 6]. [...]
- Thermogravimetric analysis of high-density cork granules using isoconversional methodsPublication . Ribeiro, A.M.; Ramalho, Elisa; Pimenta, Maria Paula; Pilão, Rosa MariaIn the present work thermogravimetric techniques were used to study the thermal degradation of high-density cork granules. Pyrolysis experiments were carried out for four heating ramps (10, 15, 20 and 25 °C.min−1), using nitrogen as the carrier gas. From the differential thermogravimetric (DTG) curves it was seen that degradation mainly occurs from 220 °C to 525 °C for the main components of cork (suberin, lignin, cellulose, and hemicellulose). It was also observed that for temperatures higher than 525 °C and up to 900 °C, lignin continued to decompose. Activation energies were calculated using the data obtained and the two isoconversional methods Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO). For the KAS method, and for degrees of conversion between 0.10 and 0.85, the activation energies varied between 232.2 and 353.0 kJ.mol−1. Using the FWO method and for the same degrees of conversion, the activation energies were in the range of 230.0 to 346.6 kJ.mol−1. These values agree with data provided by other authors, for different lignocellulosic biomass.
- Valorisation of leather wastes from footwear industry via pyrolysis: Product yields and characterisationPublication . Silva, F.; Direito, D.; Pilão, R.; Ribeiro, A.M.(Objectives) The influence of temperature on the pyrolysis of leather trimmings from the footwear industry; Characterization of leather waste used in the pyrolysis process; The physical-chemical characterizations of biochar, bio-oil and non-condensable gases.