Design, construction, and operation of the first industrial salinity-gradient solar pond in Europe: An efficiency analysis perspective

A 500 m2 industrial salinity-gradient solar pond (SGSP) was constructed in a mineral processing plant (Solvay Minerales) in Granada (Spain). This renewable energy technology was designed to supply a low-temperature heat (up to 60 °C) to achieve the temperature requirements of the flotation mineral purification stage. The low-temperature source was integrated to partially replace the fuel oil boiler used to heat the water used in the flotation stage. Theoretical calculations based on solar radiation indicated that the use of the SGSP would reduce the annual fuel consumption by more than 50%, thus providing a significant improvement at both economic and environmental levels. Two months after the SGSP was established, in August 2014, the temperature in the storage zone of the SGSP reached approximately 90 °C. The overall performance was evaluated in two periods (2014 and 2015) in terms of the retrofitting of mining facility with a solar pond and a new method to assess the thermal efficiency of the solar pond in a long-term perspective has been proposed. The overall efficiencies obtained after the first and second operation periods were 10 and 12%, respectively, with maximum values of 28 and 24% obtained during the first operation months. Regarding the economic savings, the fuel oil cost of the flotation unit was reduced by a higher percentage than the fuel oil consumption, due to the decreasing tendency of fuel oil prices during 2014 and 2015. Reductions of 52 and 68% were obtained in the first and second periods of operation, respectively, when compared to 2013. In addition, not only does the SGSP have considerably reduced operating costs but also the environmental costs are clearly reduced when considering the reduction of CO2 emissions.Peer ReviewedPostprint (author's final draft

Enhancing the efficiency of solar pond heat extraction by using both lateral and bottom heat exchangers

In this study, heat extraction from both the gradient and heat storage zones of a salinity-gradient solar pond (SGSP) has been evaluated. For this purpose, an experimental solar pond pilot plant was constructed in 2009 in Barcelona (Spain). The structure of the pond is a cylindrical tank of 3-m height and 8 m diameter with a total area of 50 m(2). The main objective was to evaluate a heat-extraction system from the SGSP designed to enhance the system efficiency under different conditions. Thus, an in-pond heat exchanger covering all of the lateral wall area of the pond was installed, and its performance was compared with the traditional in-pond heat exchanger situated on the bottom of the pond. Heat extraction experiments were performed using both heat exchangers individually or both at the same time. The study covers the experiments performed at three different seasonal temperature conditions: winter (December), summer (July) and autumn (October and November). The variations of the temperature inside the pond during the heat extraction were measured and analyzed. The results demonstrated that the efficiency of the pond increases when the heat is removed from the lateral heat exchanger alone compared to either using the bottom heat exchanger or using both heat exchangers simultaneouslyPostprint (author's final draft

Increasing the storage capacity of a solar pond by using solar thermal collectors: heat extraction and heat supply processes using in-pond heat exchangers

In this study, an experimental investigation of the performance of a salinity gradient solar pond (SGSP) integrating solar collectors is presented. The SGSP is located in Barcelona (Spain) and has a cylindrical tank 3¿m in height and 8¿m in diameter with a total area of 50¿m2. For this purpose, four solar thermal collectors (10¿m2) are integrated, as an external source of heat, with the solar pond pilot plant in order to increase the storage capacity and its overall efficiency. The aim of this study is to evaluate heat extraction and heat supply processes from and to the SGSP under different seasonal conditions. Two in-pond heat exchangers are used, a conventional one situated on the bottom of the pond and a second one covering the lateral wall area of the pond. Heat extraction and supply experiments are performed using both heat exchangers individually or both at the same time. The experiments are conducted under two different seasonal temperature conditions: winter (February and March) and summer (July). The variations of the temperature inside the pond during the heat extraction/supply tests are monitored and analyzed. The results have indicated that the use of solar collectors as an extra source of heat for the solar pond led to a 50% increase in the daily efficiency during the cold season tests, while heat extraction only appeared as the best option during the warm season tests. Higher daily efficiency and heat supply results can only be obtained if large amounts of heat are extracted, otherwise, the daily efficiency of the solar pond could decrease. Finally, the solar collectors can be considered a good alternative for avoiding a significant decrease in solar pond temperatures (especially during the cold season), which would not only result in a significant energy storage efficiency improvement but also increase the capacity of the solar pond to supply heat to an external application.Peer ReviewedPostprint (author's final draft

Simultaneous phosphate and ammonium removal from aqueous solution by a hydrated aluminum oxide modified natural zeolite

A natural zeolite (Z-N), rich in clinoptilolite, was modified (Z-Al) by incorporation of hydrated aluminium oxide (HAlO) for the simultaneous phosphate and ammonium removal. The incorporation of surface hydroxyl groups (ffiAl-OH) into the zeolite structure, as active groups for phosphate removal, was characterized by acid–base titrations (pHPZC= 4.5 ± 0.2). The phosphate sorption increases from 0.6 mg-P/g for Z-N up to 7.0 mg-P/g while only a slight decrease on the ammonium sorption capacity from 33 mg-N/g of Z-N to 30 mg-N/g for Z-Al was observed. The HAlO modified zeolite sorption capacity for both phosphate and ammonium was slightly reduced by common ions typically present in secondary waste water effluents. Column experiments revealed higher enrichment factor for ammonium (120) than for phosphate (50) using 1 M NaOH as elution solution. A reduction of zeolite phosphate capacity with regeneration cycles was observedPostprint (author’s final draft

Thermal performance of 500m2 salinity gradient solar pond in Granada, Spain under strong weather conditions

In this study, an experimental investigation of temperature performance and efficiency of an industrial solar pond during strong winter conditions is presented. Several temperature sensors connected to a data logger were used to measure the temperature gradient in a 500¿m2 solar pond. During the winter 2015 there was a snowfall in the solar pond of Granada (Spain), reaching a minimum air ambient temperature of -2.4¿°C. The temperature of the storage zone in Granada solar pond remained constant (around 40¿°C) indicating the system responds positively to weather variations and confirming the fundamental role of the salinity gradient as a thermal insulation layer. The stored energy during January 2015 was 13.3¿GJ, the weekly efficiency reached 10% and finally, the solar pond was able to provide 247.1¿MJ to the flotation unit during the week of the snowfall.Peer ReviewedPostprint (author's final draft

Aproximació química al tractament de residus

En aquesta comunicació es resumeixen alguns dels treballs realitzats en la caracterització, tractament i estudi de propietats fisicoquímiques de diferent tipus de residus industrials: orgànics, metàl·lics i radioactius

Como usar Atenea en la gestión de grupos en una asignatura de laboratorio de Química

En esta propuesta se presenta la experiencia de utilización del campus virtual ATENEA como herramienta de comunicación y de gestión de la interacción tanto profesorado-alumnado como alumnado-alumnado en la asignatura de Experimentación en Química II de segundo curso de la titulación de Ingeniería Química, que se imparte en la ETSEIB. Atenea ha demostrado ser una herramienta eficaz que ha permitido, durante el curso 2009-10, facilitar la información general y la planificación temporal de todas las actividades de la asignatura, además de gestionar el seguimiento y retroacción de las tareas de los grupos de trabajo cooperativo.Peer Reviewe

Recovery of natural polyphenols from spinach and orange by-products by pressure-driven membrane processes

Spinach and orange by-products are well recognized for their health benefits due to the presence of natural polyphenols with antioxidant activity. Therefore, the demand to produce functional products containing polyphenols recovered from vegetables and fruits has increased in the last decade. This work aims to use the integrated membrane process for the recovery of polyphenols from spinach and orange wastes, implemented on a laboratory scale. The clarification (microfiltration and ultrafiltration, i.e., MF and UF), pre-concentration (nanofiltration, NF), and concentration (reverse osmosis, RO) of the spinach and orange extracts were performed using membrane technology. Membrane experiments were carried out by collecting 1 mL of the permeate stream after increasing the flow rate in 1 mL/min steps. The separation and concentration factors were determined by HPLC-DAD in terms of total polyphenol content and by polyphenol families: hydroxybenzoic acids, hydroxycinnamic acids, and flavonoids. The results show that the transmembrane flux depended on the feed flow rate for MF, UF, NF, and RO techniques. For the spinach and orange matrices, MF (0.22 μm) could be used to remove suspended solids; UF membranes (30 kDa) for clarification; NF membranes (TFCS) to pre-concentrate; and RO membranes (XLE for spinach and BW30 for orange) to concentrate. A treatment sequence is proposed for the two extracts using a selective membrane train (UF, NF, and RO) to obtain polyphenol-rich streams for food, pharmaceutical, and cosmetic applications, and also to recover clean water streams

Producciones digitales para la fase pre-laboratorio de experimentación en química

Postprint (published version

The contribution of HIV point-of-care tests in early HIV diagnosis: community-based HIV testing monitoring in Catalonia, 1995 to 2018

Infeccions per VIH; Serveis de salut; DiagnòsticInfecciones por VIH; Servicios de salud; DiagnósticoVIH infections; Health services; DiagnosisBackground: Community-based HIV testing services combined with the use of point-of-care tests (POCT) have the potential to improve early diagnosis through increasing availability, accessibility and uptake of HIV testing. Aim: To describe community-based HIV testing activity in Catalonia, Spain, from 1995 to 2018, and to evaluate the impact of HIV POCT on the HIV continuum of care.Methods: A community-based network of voluntary counselling and testing services in Catalonia, Spain has been collecting systematic data on activity, process and results since 1995. A descriptive analysis was performed on pooled data, describing the data in terms of people tested and reactive screening test results. Results: Between 1995 and 2018, 125,876 HIV tests were performed (2.1% reactive). Since the introduction of HIV POCT in 2007, a large increase in the number of tests performed was observed, reaching 14,537 tests alone in 2018 (1.3% reactive). Men who have sex with men (MSM), as a proportion of all people tested, has increased greatly over time reaching 74.7% in 2018. The highest percentage of reactive tests was found in people who inject drugs followed by MSM. The contribution of community-based HIV testing to the overall total notified cases in the Catalonia HIV registry has gradually increased, reaching 37.9% in 2018, and 70% of all MSM cases. In 2018, the percentage of individuals with a reactive screening test who were linked to care was 89.0%. Conclusion: Our study reinforces the important role that community-based HIV POCT has on the diagnosis of HIV in key populations