56 research outputs found

    Comprehensive analysis of the combustion of low carbon fuels (hydrogen, methane and coke oven gas) in a spark ignition engine through CFD modeling

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    The use of low carbon fuels (LCFs) in internal combustion engines is a promising alternative to reduce pollution while achieving high performance through the conversion of the high energy content of the fuels into mechanical energy. However, optimizing the engine design requires deep knowledge of the complex phenomena involved in combustion that depend on the operating conditions and the fuel employed. In this work, computational fluid dynamics (CFD) simulation tools have been used to get insight into the performance of a Volkswagen Polo 1.4L port-fuel injection spark ignition engine that has been fueled with three different LCFs, coke oven gas (COG), a gaseous by-product of coke manufacture, H2 and CH4. The comparison is made in terms of power, pressure, temperature, heat release, flame growth speed, emissions and volumetric efficiency. Simulations in Ansys® Forte® were validated with experiments at the same operating conditions with optimal spark advance, wide open throttle, a wide range of engine speed (2000–5000 rpm) and air-fuel ratio (λ) between 1 and 2. A sensitivity analysis of spark timing has been added to assess its impact on combustion variables. COG, with intermediate flame growth speed, produced the greatest power values but with lower pressure and temperature values at λ = 1.5, reducing the emissions of NO and the wall heat transfer. The useful energy released with COG was up to 16.5% and 5.1% higher than CH4 and H2, respectively. At richer and leaner mixtures (λ = 1 and λ = 2), similar performances were obtained compared to CH4 and H2, combining advantages of both pure fuels and widening the λ operation range without abnormal combustion. Therefore, suitable management of the operating conditions maximizes the conversion of the waste stream fuel energy into useful energy while limiting emissions.This research was supported by the Project, “HYLANTIC”- EAPA_204/2016, co-financed by the European Regional Development Fund within the framework of the Interreg Atlantic program and the Spanish Ministry of Science, Innovation and Universities (Project: RTI2018-093310-B-I00). Rafael Ortiz-Imedio thanks the Concepción Arenal postgraduate research grant from the University of Cantabria. The authors acknowledge Santander Supercomputación support group at the University of Cantabria who provided access to the supercomputer Altamira Supercomputer at the Institute of Physics of Cantabria (IFCA-CSIC), member of the Spanish Supercomputing Network, for performing simulations. The authors also acknowledge the help provided for the model development by the Engineering Department from the Public University of Navarre in Pamplona

    Design of novel adsorption processes for the removal of arsenic from polluted groundwater employing functionalized magnetic nanoparticles

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    For many developing countries, groundwater is the main source for water consumption in rural and urban areas. The occurrence of arsenic in groundwater is an environmental problem due to its high toxicity. Although the removal of arsenic by different technologies has been proven, adsorption is one of the best alternatives due to its simplicity and low cost. In particular, nanoadsorbents incorporating magnetic properties are promising separation agents because of their advantageous and efficient potential recovery in a magnetic field, characteristic that is very attractive and of utmost relevance in the development of low cost technologies to provide drinking water in developing countries. In this work, Fe3O4 and Fe3O4/SiO2 magnetic nanoparticles functionalized by amino derivatives coordinated with Fe3+ were synthesized and characterized and further evaluated as adsorbents to remove arsenate from groundwater. The adsorption equilibrium of As5+ was satisfactorily described at 298 K by the Langmuir model with the following parameters: a) Fe3O4: qm=20.4±0.3 mg g-1 and KL=0.373±0.003 L mg-1 and b) Fe3O4/SiO2: qm=121±4.1 mg g-1 and KL=0.383±0.066 L mg-1. At low arsenate concentrations, 50-1000 µg L-1, the adsorption equilibrium As5+-Fe3O4/SiO2 was described by linear isotherms with equilibrium parameters KH=278.8 L g-1 in monocomponent systems and KH=1.80 L g-1 in the presence of competing ions, being carbonate and especially phosphate the main species affecting the process with contributions to the loss of efficacy around 70%. Finally, the material reuse after regeneration with NaOH 10-3 mol L-1 d was assessed under several composition scenarios reaching adsorption yields similar to those obtained with fresh materials.Financial support from the Spanish Ministry of Economy and Competitiveness under the project CTQ2012-31639 (FEDER 2007-2013) is gratefully acknowledged

    Resistance of ion exchange membranes in aqueous mixtures of monovalent and divalent ions and the effect on reverse electrodialysis

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    Salinity gradient energy has gained attention in recent years as a renewable energy source, especially employing reverse electrodialysis technology (RED), which is based on the role of ion exchange membranes. In this context, many efforts have been developed by researchers from all over the world to advance the knowledge of this green source of energy. However, the influence of divalent ions on the performance of the technology has not been deeply studied. Basically, divalent ions are responsible for an increased membrane resistance and, therefore, for a decrease in voltage. This work focuses on the estimation of the resistance of the RED membrane working with water flows containing divalent ions, both theoretically by combining the one-thread model with the Donnan exclusion theory for the gel phase, as well as the experimental evaluation with Fumatech membranes FAS-50, FKS-50, FAS-PET-75, and FKS-PET-75. Furthermore, simulated results have been compared to data recently reported with different membranes. Besides, the influence of membrane resistance on the overall performance of reverse electrodialysis technology is evaluated to understand the impact of divalent ions in energy generation. Results reflect a minor effect of sulfate on the gross power in comparison to the effect of calcium and magnesium ions. Thus, this work takes a step forward in the knowledge of reverse electrodialysis technology and the extraction of salinity gradient energy by advancing the influence of divalent ions on energy recovery.The authors of this work would like to acknowledge the financial support from the LIFE program (LIFE19 ENV/ES/000143). The UC team wants to thank J.A. Abarca and F.J. Rodríguez-Oria for their help in impedance measurements and SGP-RED experiences. This work was also facilitated by REDstack BV in the Netherlands. REDstack BV aims to develop and market the ED and the RED technology. J.V. would like to thank his colleagues from the REDstack company for the fruitful discussions
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