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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.
- 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).
- 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 the Footwear Industry via Pyrolysis: Product Yields and CharacterisationPublication . Silva, F.; Direito, D.; Pilão, R.; Ribeiro, A.M.; Silva, Felipe; Direito, Daniel; Pilão, Rosa Maria; Ribeiro, AlbinaThe footwear industry, although contributing positively to the Portuguese economy, generates a lot of residues including chromium tanned leather wastes. This study presents results on the slow pyrolysis of these residues at particle sizes between 5 and 6.3 mm and temperatures inside the reactor ranging from 444 to 875 °C. For this range of temperatures, char yield decreased from 36.2 to 28.1% and gas yield increased between 33.2 and 47.6%. The liquid phase yield was highest at 444 °C (30.6%) and then decreased to 24.3% at 875 °C. As the operating temperature increased, there was an increase in the ash content (15.8 to 21.6%) and a decrease in volatiles content (20.9–3.7%) of biochars. The higher heating values (HHV) of the chars were between 21.9 and 23.1 MJ/kg. Preliminary results show that an increase in particle size leads to a rise in char yield. The infrared analysis of the liquid phase indicated the presence of water, alcohols, phenols, carboxylic acids, alkanes, alkenes, and aromatics. The liquid phases had an average water content of 43%, densities between 1110 and 1120 kg/m3 and the HHV between 12.7 and 15.1 MJ/kg. The gases produced were analysed by gas chromatography. For 538 °C, the production of H2, CO, CH4 and CO2 was, respectively, 1.00, 0.37, 0.18 and 1.37 mol/kg of leather. At 875 °C, H2 was the most produced gas (2.74 mol/kg leather), followed by CO, CO2 and CH4 with quantities of 1.40, 1.26 and 0.42 mol/kg leather.
- 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.
- Co-Gasification of Crude Glycerol/Animal Fat MixturesPublication . Almeida, Ana F.; Pilão, Rosa Maria; Ribeiro, Albina; Ramalho, Elisa; 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 activated alumina particles as bed material and steam as oxidizing agent. The effect of gasification temperature, from 800 to 950 °C was studied with a feed mixture with 10% (w/w) of animal fat. The influence of fat incorporation on the feedstock in the overall gasification process was also performed, using 3% (w/w) and 5% (w/w) of fat in feed mixtures. Samples of dry gas from the gasifier were collected and analyzed by gas chromatography in order to determine the CO, CO2, CH4, and H2 content. The best results were obtained using the highest tested temperature, 950 °C, and using 3% (w/w) of animal fat in the feed mixture. The overall results revealed that the co-gasification of glycerol/animal fat mixtures seems to be a feasible technical option
- 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]. [...]
- 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.
- Thermodynamic equilibrium modelling of glycerol gasificationPublication . Almeida, Ana; Ramalho, Elisa; Ribeiro, Albina; Pinho, Carlos; Pilão, RosaThe modeling of the gasification process using the thermodynamic chemical equilibrium of the process is an important tool when it is intended to obtain preliminary results or to scale-up an experimental installation. In this work, the gasification process of crude glycerol using steam as the gasification agent was modeled using stoichiometric and non-stoichiometric chemical equi librium models. The effect of the gasification temperature on the equilibrium composition of the producer gas was evaluated. The simulation results were com pared with the experimental results obtained in a downdraft fixed bed reactor. The results obtained showed that the two models predict the equilibrium compo sition in a similar way. They also showed that the gasification reactor is operating under conditions deviating from chemical equilibrium.
- 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.