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Porriño, Spain

Pascual A.,University of La Coruna | de la Varga D.,University of La Coruna | Arias C.A.,University of Aarhus | Van Oirschot D.,Rietland bvba | And 2 more authors.
Environmental Technology (United Kingdom) | Year: 2016

The HIGHWET project combines the hydrolytic up-flow sludge bed (HUSB) anaerobic digester and constructed wetlands (CWs) with forced aeration for decreasing the footprint and improving effluent quality. The HIGHWET plant in A Coruña (NW of Spain) treating municipal wastewater consists of a HUSB and four parallel subsurface horizontal flow (HF) CWs. HF1, HF2 and HF3 units are fitted with forced aeration, while the control HF4 is not aerated. All the HF units are provided with effluent recirculation, but different heights of gravel bed (0.8 m in HF1 and HF2, and 0.5 m in HF3 and HF4) are implemented. Besides, a tobermorite-enriched material was added in the HF2 unit in order to improve phosphorus removal. The HUSB 76–89% of total suspended solids (TSS) and about 40% of chemical oxygen demand (COD) and biological oxygen demand (BOD). Aerated HF units reached above 96% of TSS, COD and BOD at a surface loading rate of 29–47 g BOD5/m2·d. An aeration regime ranging from 5 h on/3 h off to 3 h on/5 h off was found to be adequate to optimize nitrogen removal, which ranged from 53% to 81%. Average removal rates of 3.4 ± 0.4 g total nitrogen (TN)/m2·d and 12.8 ± 3.7 g TN/m3·d were found in the aerated units, being 5.5 and 4.1 times higher than those of the non-aerated system. The tobermorite-enriched HF2 unit showed a distinct higher phosphate (60–67%) and total phosphorus (54%) removal. © 2016 Informa UK Limited, trading as Taylor & Francis Group Source

Pellizzari M.,University of Trento | Caliskanoglu D.,Bohler Edelstahl Gmbh | Fernandez A.,AIMEN | Barbero J.I.,Fundacion Labein | And 5 more authors.
HTM - Haerterei-Technische Mitteilungen | Year: 2012

An intensive research work was carried out in the frame of a RFCS (Research Found for Coal and Steel) project, to investigate the influence of different deep cryogenic treatments (DCT) on hardness, strength, toughness and wear resistance of AISI M2. Short and a long classical DCT, providing the soaking at temperature close to the boiling point of liquid nitrogen (-196 °C) for 6 h and 20 h, respectively, were carried out prior to and after tempering. Furthermore, a third short DC route, providing temperature cycling between RT and low temperature was also considered. Care was taken to avoid stabilization of retained austenite or self tempering due to wait at room temperature prior to DCT and/or tempering. All treatments were calibrated to get 840 HV 10, in order to compare the properties of steel with the same reference hardness. DCT does not allow the complete transformation of retained austenite in the investigated high speed steel, due to the stabilizing effect of alloying elements. Tempering is necessary to completely transform this phase and to allow proper secondary hardening. If carried out after quenching, DCT shits the secondary hardness peak to lower temperature, evidencing the need to adjust the tempering parameters to avoid overtempering. The microstructure didn't show any signiicant influence of DCT in terms of carbides distribution, due to the conditioning of martensite at low temperature. The same can be also concluded for the other properties (toughness, tensile strength and wear resistance), which are practically the same for samples having the same hardness.© 2012 Carl Hanser Verlag, München. Source

Mira-Aguiar T.,University of Coimbra | Verdera D.,AIMEN | Leitao C.,University of Coimbra | Rodrigues D.M.,University of Coimbra
Journal of Materials Processing Technology | Year: 2016

A Friction Stir Welding (FSW) related technique, which will be labelled Tool Assisted Friction Welding (TAFW), is presented in the current paper. Using this technique, linear lap welding of very thin steel plates is obtained by using a non-consumable columnar tool, with a featureless shoulder, to generate heat by friction with the components to be welded, as in FSW, and also to promote the joining of the plates, under pressure, as in Friction Welding (FW). The joining mechanisms, as well as the thermomechanical conditions developed during welding, will be discussed based on the metallurgical analysis of similar welds produced in two steels: a galvanised low carbon steel (DX51D) and a mild steel (DC01). Mechanical testing, using Digital Image Correlation (DIC) for strain data acquisition, enabled to assess welds strength and plastic properties. The results obtained prove that the TAFW technique enables to obtain very good quality welds, for both base materials, at a very high welding speed and low tool wear/damage. An important influence of the galvanised coating of the DX51D steel on the welding conditions and weld microstructure was also observed. © 2016 Elsevier B.V. Source

Casal J.M.,University of Vigo | Porteiro J.,University of Vigo | Miguez J.L.,University of Vigo | Vazquez A.,AIMEN
Applied Thermal Engineering | Year: 2015

Abstract This study presents a new modelling methodology for three-dimensional simulation of a reheating furnace of steel billets with natural gas burners. The movement of the billets inside the furnace is a periodically transient phenomenon. A modification in the energy transport equation is introduced through source terms in the billet region to convert the transient movements of the billets into a steady-state simulation, which significantly reduces the computational time without any loss of information. The combustion simulation inside the burners is performed using a global combustion mechanism that takes into account the combustion of the main gaseous species present in natural gas following a kinetic and turbulent control of the reaction through the Eddy Dissipation Concept (EDC). The results are contrasted and validated with the data obtained in a real facility though the SCADA of the plant. Some parameters, such as the surface temperatures of billets at the outlet and the distribution of power supplied by the fuel inside the furnace are reasonably close to the real case data obtained in temperature fields of both billets and the gas phase as well as the energy balance, leading to the conclusion that the proposed methodology is adequate for the purpose of simulating this system. © 2015 Elsevier Ltd. Source

Costa M.I.,University of Coimbra | Verdera D.,AIMEN | Costa J.D.,University of Coimbra | Leitao C.,University of Coimbra | Rodrigues D.M.,University of Coimbra
Journal of Materials Processing Technology | Year: 2015

The influence of pin geometry and process parameters on the morphology and strength of friction stir lap welds, in very thin sheets, is analysed. The base material is the AA5754-H22 work hardened aluminium alloy. Three different pin geometries were tested, one cylindrical and two conical, with different taper angles. For each pin geometry, varying welding speeds, ranging from 350 to 1000 mm/min, were tested in order to simultaneously weld properties and process productivity. Weld defects assessment was performed using metallographic analyses. strength was by performing mechanical tests both monotonic and cyclic loading conditions. Monotonic tests included performing transverse and lap tensile-shear tests. Strain data acquisition using Digital Image Correlation (DIC) enabled to determine local weld properties as the joints failure mode monotonic loading. The results show that the use of unthreaded conical pin tools, with a low shoulder/pin diameter relation, is the more suitable solution for the production of good quality welds. Irrespective of the pin geometry, very high joint strength efficiencies (close to 90%) were obtained when loading the retreating side of the welds. It is also shown that good quality welds may be produced at very high welding speeds. © 2015 Elsevier B.V. All rights reserved. Source

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