Producción de salmuera saturada a partir de rechazo de desaladora o residuo de actividad minera

Access to drinking water is one of the challenges of the 21st century for an increasing number of countries in the world. In Spain, a desalination plant providing between 20% and 30% of Barcelona¿s drinking water has been in operation since summer 2009. The desalination plant¿s Reverse-Osmosis (RO) system processes sea water to produce drinking water and a waste product, concentrated brine, which has a negative impact on the flora and fauna (coral) around the plant outlet pipe. It would be a shame for this waste product with such a high salt concentration (60 g to 80 g of salt per litre, compared to about 30 g per litre in the sea) to go unused. This research explores the possibility to reduce the amount of brine discharged into the sea by the desalination plants by using it in an industrial process. By means of an Electrodialysis (ED) process, the concentration of the discharge from the Reverse- Osmosis process can be increased up to 250 g per litre so the brine can then be purified and used as a raw material in the chlor-alkali industry. Taking these challenges into account, an ED pilot plant using CIMS and ACS Neosepta membranes was built in Barcelona to test concentration of RO brine solutions. The ED pilot was dimensioned to concentrate 500L/h of brine coming from two different configured RO pilot plants. As the ED plant had unlimited access to the feed brine and it did not pretend to desalt this brine, the circuits of diluate and electrolyte were designed in one-single pass. This allowed operating the plant with high current densities, as limiting current density was never achieved. Consequently, higher NaCl concentrations on the concentrate stream were obtained. The results obtained during the start-up and preliminary operation of the pilot plant aredescribed in the current thesis. These experiences showed the concentration feasibility of this technology when reaching 258 g NaCl/L after 35h of operation at 0.4kA/m2 with a power consumption of 0.24 kWh/kg NaCl at 10ºC. Moreover, as the membranes used (Neosepta CIMS and ACS) were mainly selective for univalent ions, polyvalent ions such as calcium and magnesium were partially removed from the brine which represented an advantage for its final reuse in the chlor-alkali industry. However further treatments would be needed to meet the electrolysis requirements. A mathematical model was also developed based on Nernst-Planck equations to predict NaCl concentration performance of the ED pilot plant. Several of the model parameters were obtained experimentally and others were taken from the literature. The model was able to accurately predict the NaCl concentration reached in the concentrate tank along the experiment, as well as the time required to reach maximum concentration and production overflow as a function of the operation conditions such as electrical current intensity and NaCl feed concentration. In this work, the results of the mathematical model are compared with the preliminary experimental results obtained at the pilot plant in order to validate the model. Finally, this pHd aims at evaluating the possibility to use an alternative source of brine in a cost effective way compared to current sources of salt. At the same time it provides a technical solution for the optimal use of natural resources since it minimizes environmental impact of the desalinization process. To meet this challenge, our brine and electrolysis specialists in Italy are collaborating on the project with the Barcelona water company (Aguas de Barcelona - AGBAR) and the Universitat Politècnica de Catalunya (UPC). Finally this thesis brings an interesting step forward in reducing environmental impact of the desalinization process transforming the RO waste into raw material for the Chlor- Alkali Industry. Besides, it helps develop future applications for existing Technologies as the Electrodyalisis.Para hacer frente al problema de la escasez de agua para el consumo, actualmente se plantea la necesidad de recurrir a recursos no naturales como la desalación por ósmosis inversa, que permite garantizar el suministro de caudales constantes con una alta calidad, independientemente de la climatología. Sin embargo la desalación produce un rechazo salino en cuantía similar a la producción de agua potable. El objetivo de esta tesis es explorar el valor del residuo salino procedente de rechazo de desalación como materia prima para la industria electroquímica, teniendo en consideración que esta salmuera rechazo presenta una concentración de 70 g NaCl/kg, lejos de la concentración de saturación (250 g/kg) necesaria para el proceso electrolítico de la industria cloro-álcali. Tras un análisis de las tecnologías de concentración existentes, la investigación se ha llevado a cabo utilizando la tecnología de la Electrodiálisis (ED) como sistema más eficiente para concentrar la salmuera de rechazo de desaladora. Así, se ha diseñado y construido una planta piloto experimental, necesaria para confirmar la viabilidad técnica y económica de la electrodiálisis como sistema de concentración de salmuera. Dicha planta piloto se ubicó en el Prat de Llobregat (Barcelona), en el centro de investigación de desalación del proyecto SOSTAQUA (www.sostaqua.com) donde DOW y DEGREMONT tienen instaladas sus plantas piloto de Ósmosis Inversa (OI). Los principales hallazgos de la investigación doctoral confirman que la conexión de la planta de electrodiálisis al rechazo de OI para la producción de salmuera destinada a una electrolisis de Cloro-Sosa ofrece las siguientes ventajas competitivas: 1. El acceso ilimitado de salmuera ya pre-concentrada permite trabajar en la configuración de paso directo (One Single Pass). Esto significa que la corriente de diluido no se llega a desconcentrar (pierde 6 g NaCl) en iones Na+ y Cl-, por lo que la resistividad del stack de membranas se mantiene constante (y baja), incluso cuando se aplican densidades de corriente elevadas. 2. Los pre-tratamientos realizados al agua de mar previos a la OI, como la eliminación de materia orgánica, ahorran la etapa de depuración previa a la EDI. Además, el uso de anti-escalantes retrasa la precipitación de sulfatos en la superficie de las membranas. 3. Al ser un proceso de arrastre electroquímico, la EDI no añade reactivos nocivos a la salmuera rechazo de OI; sino todo lo contrario, el rechazo de la EDI es salmuera diluida y el concentrado es el residuo que se pretende valorizar como materia prima para un proceso industrial. 4. La selectividad de las membranas de electrodiálisis consigue una primera etapa de depuración de los iones bivalentes nocivos para el posterior proceso industrial durante el propio proceso de concentración. Al no concentrar los iones Mg2+ y Ca2+ la electrodiálisis resulta una tecnología interesante pues integra una etapa de depuración en iones bivalentes para la aplicación industrial de producción de Cl2 -NaOH. 5. Finalmente, la ventaja competitiva de la electrodiálisis viene por el lado del consumo energético Los resultados experimentales sitúan el consumo energético en torno a 0,2 kWh/kg sal frente a los 8,5 kWh/kg de los sistemas tradicionales de concentración de salmuera por evaporación. Por otra parte, se ha desarrollado un modelo teórico basado en las ecuaciones de Nernst-Planck, que se ha podido validar con resultados experimentales obtenidos en la planta piloto. El modelo resulta ser válido para predecir la evolución temporal de la concentración en NaCl de la solución. Finalmente, en el aspecto ambiental, esta tesis aporta aspectos muy interesantes ya que da salida al rechazo producido en los procesos de desalación de OI como materia prima para la industria y sienta bases para ayudar a desarrollar futuras nuevas aplicaciones a tecnologías existentes.Postprint (published version

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

Computer simulation of ion-exchange membrane electrodialysis for salt concentration and reduction of RO discharged brine for salt production and marine environment conservation

The salt discharged from reverse osmosis is concentrated by ion-exchange membrane electrodialysis to produce salt for industrial use and the salt concentration is reduced to seawater level for preventing environmental impact on marine ecosystems. The technology was evaluated experimentally and discussed with a computer simulation program of the electrodialysis system incorporated with U shape cells. The algorithm computes mass transport, energy consumption, electric current leakage, concentrate NaCl purity, pressure drop and limiting current density. The seawater reverse osmosis discharged brine was supplied to the electrodialysis pilot plant and it was operated changing current density and temperature taking benefit of seasoning variations. The computed energy consumption E-Nacl and NaCl concentration in concentrated solutions C-NaCl '' using developing algorithms provided a good description of the experimentally measured values with correlation coefficients of R(r) = 0.9 for E-NaCl and R(r) = 0.6 for C-NaCl ''. Then the reasonability of the developed algorithms is supported by the experimental set of data. The current leakage is nearly 3% for any electric current. The pump driving force is very low. The limiting current density is very high. In order to decrease salt concentration at the outlets of desalting cells to seawater level, it is necessary to increase desalting ratio to 0.5. This technique however increases Emu and decrease C-NaCl ''. In spite of this operating circumstance, E-NaCl and C-NaCl '' are comparable to the data in the salt manufacturing plant operation to produce edible salt. NaCl produced from in the reverse osmosis discharged brine electrodialysis is competitive in the edible salt market. (C) 2015 Elsevier B.V. All rights reserved.Peer ReviewedPostprint (author's final draft

Producción de salmuera saturada a partir de rechazo de desaladora o residuo de actividad minera

Access to drinking water is one of the challenges of the 21st century for an increasing number of countries in the world. In Spain, a desalination plant providing between 20% and 30% of Barcelona¿s drinking water has been in operation since summer 2009. The desalination plant¿s Reverse-Osmosis (RO) system processes sea water to produce drinking water and a waste product, concentrated brine, which has a negative impact on the flora and fauna (coral) around the plant outlet pipe. It would be a shame for this waste product with such a high salt concentration (60 g to 80 g of salt per litre, compared to about 30 g per litre in the sea) to go unused. This research explores the possibility to reduce the amount of brine discharged into the sea by the desalination plants by using it in an industrial process. By means of an Electrodialysis (ED) process, the concentration of the discharge from the Reverse- Osmosis process can be increased up to 250 g per litre so the brine can then be purified and used as a raw material in the chlor-alkali industry. Taking these challenges into account, an ED pilot plant using CIMS and ACS Neosepta membranes was built in Barcelona to test concentration of RO brine solutions. The ED pilot was dimensioned to concentrate 500L/h of brine coming from two different configured RO pilot plants. As the ED plant had unlimited access to the feed brine and it did not pretend to desalt this brine, the circuits of diluate and electrolyte were designed in one-single pass. This allowed operating the plant with high current densities, as limiting current density was never achieved. Consequently, higher NaCl concentrations on the concentrate stream were obtained. The results obtained during the start-up and preliminary operation of the pilot plant aredescribed in the current thesis. These experiences showed the concentration feasibility of this technology when reaching 258 g NaCl/L after 35h of operation at 0.4kA/m2 with a power consumption of 0.24 kWh/kg NaCl at 10ºC. Moreover, as the membranes used (Neosepta CIMS and ACS) were mainly selective for univalent ions, polyvalent ions such as calcium and magnesium were partially removed from the brine which represented an advantage for its final reuse in the chlor-alkali industry. However further treatments would be needed to meet the electrolysis requirements. A mathematical model was also developed based on Nernst-Planck equations to predict NaCl concentration performance of the ED pilot plant. Several of the model parameters were obtained experimentally and others were taken from the literature. The model was able to accurately predict the NaCl concentration reached in the concentrate tank along the experiment, as well as the time required to reach maximum concentration and production overflow as a function of the operation conditions such as electrical current intensity and NaCl feed concentration. In this work, the results of the mathematical model are compared with the preliminary experimental results obtained at the pilot plant in order to validate the model. Finally, this pHd aims at evaluating the possibility to use an alternative source of brine in a cost effective way compared to current sources of salt. At the same time it provides a technical solution for the optimal use of natural resources since it minimizes environmental impact of the desalinization process. To meet this challenge, our brine and electrolysis specialists in Italy are collaborating on the project with the Barcelona water company (Aguas de Barcelona - AGBAR) and the Universitat Politècnica de Catalunya (UPC). Finally this thesis brings an interesting step forward in reducing environmental impact of the desalinization process transforming the RO waste into raw material for the Chlor- Alkali Industry. Besides, it helps develop future applications for existing Technologies as the Electrodyalisis.Para hacer frente al problema de la escasez de agua para el consumo, actualmente se plantea la necesidad de recurrir a recursos no naturales como la desalación por ósmosis inversa, que permite garantizar el suministro de caudales constantes con una alta calidad, independientemente de la climatología. Sin embargo la desalación produce un rechazo salino en cuantía similar a la producción de agua potable. El objetivo de esta tesis es explorar el valor del residuo salino procedente de rechazo de desalación como materia prima para la industria electroquímica, teniendo en consideración que esta salmuera rechazo presenta una concentración de 70 g NaCl/kg, lejos de la concentración de saturación (250 g/kg) necesaria para el proceso electrolítico de la industria cloro-álcali. Tras un análisis de las tecnologías de concentración existentes, la investigación se ha llevado a cabo utilizando la tecnología de la Electrodiálisis (ED) como sistema más eficiente para concentrar la salmuera de rechazo de desaladora. Así, se ha diseñado y construido una planta piloto experimental, necesaria para confirmar la viabilidad técnica y económica de la electrodiálisis como sistema de concentración de salmuera. Dicha planta piloto se ubicó en el Prat de Llobregat (Barcelona), en el centro de investigación de desalación del proyecto SOSTAQUA (www.sostaqua.com) donde DOW y DEGREMONT tienen instaladas sus plantas piloto de Ósmosis Inversa (OI). Los principales hallazgos de la investigación doctoral confirman que la conexión de la planta de electrodiálisis al rechazo de OI para la producción de salmuera destinada a una electrolisis de Cloro-Sosa ofrece las siguientes ventajas competitivas: 1. El acceso ilimitado de salmuera ya pre-concentrada permite trabajar en la configuración de paso directo (One Single Pass). Esto significa que la corriente de diluido no se llega a desconcentrar (pierde 6 g NaCl) en iones Na+ y Cl-, por lo que la resistividad del stack de membranas se mantiene constante (y baja), incluso cuando se aplican densidades de corriente elevadas. 2. Los pre-tratamientos realizados al agua de mar previos a la OI, como la eliminación de materia orgánica, ahorran la etapa de depuración previa a la EDI. Además, el uso de anti-escalantes retrasa la precipitación de sulfatos en la superficie de las membranas. 3. Al ser un proceso de arrastre electroquímico, la EDI no añade reactivos nocivos a la salmuera rechazo de OI; sino todo lo contrario, el rechazo de la EDI es salmuera diluida y el concentrado es el residuo que se pretende valorizar como materia prima para un proceso industrial. 4. La selectividad de las membranas de electrodiálisis consigue una primera etapa de depuración de los iones bivalentes nocivos para el posterior proceso industrial durante el propio proceso de concentración. Al no concentrar los iones Mg2+ y Ca2+ la electrodiálisis resulta una tecnología interesante pues integra una etapa de depuración en iones bivalentes para la aplicación industrial de producción de Cl2 -NaOH. 5. Finalmente, la ventaja competitiva de la electrodiálisis viene por el lado del consumo energético Los resultados experimentales sitúan el consumo energético en torno a 0,2 kWh/kg sal frente a los 8,5 kWh/kg de los sistemas tradicionales de concentración de salmuera por evaporación. Por otra parte, se ha desarrollado un modelo teórico basado en las ecuaciones de Nernst-Planck, que se ha podido validar con resultados experimentales obtenidos en la planta piloto. El modelo resulta ser válido para predecir la evolución temporal de la concentración en NaCl de la solución. Finalmente, en el aspecto ambiental, esta tesis aporta aspectos muy interesantes ya que da salida al rechazo producido en los procesos de desalación de OI como materia prima para la industria y sienta bases para ayudar a desarrollar futuras nuevas aplicaciones a tecnologías existentes

Concentration of seawater reverse osmosis brines using electrodialysis for a zero discharge system

Seawater RO brines have been identified as an alternative to common NaCl sources for the chlor-alkali industry. Electrodialysis (ED) has been evaluated as a preliminary step of NaCl concentration for these brines.Postprint (author's final draft

Concentration of seawater reverse osmosis brines using electrodialysis for a zero discharge system

Seawater RO brines have been identified as an alternative to common NaCl sources for the chlor-alkali industry. Electrodialysis (ED) has been evaluated as a preliminary step of NaCl concentration for these brines

Valorisation of Ca and Mg by-products from mining and seawater desalination brines for water treatment applications

BACKGROUNDBrines from the drainage of potash mine tailings and from seawater reverse osmosis (SWRO) desalination were previously evaluated as sources of NaCl for the chlor-alkali industry. Valorisation of NaCl as raw material is required to meet the membrane electrolysis specifications of NaCl saturation and control of interferences (Ca, Mg and sulphate). Brines concentration in NaCl was previously achieved for SWRO brines using electrodialysis (ED). In this work, valorisation of Ca and Mg by-products via selective recovery was evaluated.; RESULTSRecovery of Ca(II) and Mg(II) using chemical precipitation with Na2CO3 and NaOH was evaluated at 25 degrees C and 65 degrees C using one single reagent and mixtures of reagents. The excess of reactants needed to achieve the maximum removal efficiency ranged from 0.35 to 14 g L-1 Na2CO3 and 0.85 g L-1 NaOH. Selective concentration of SWRO brines by ED benefited the purification, as it slightly diluted the antiscalants. The increase of temperatures also benefited their removal process.; CONCLUSIONSTotal chemical analysis of Ca and Mg by-products showed the presence of mixed salts of Ca and Mg when Na2CO3 was used and more pure precipitates of Mg when NaOH was used. In both cases, small amounts of minor traces initially present in the brines were found. (c) 2014 Society of Chemical Industry.Peer ReviewedPostprint (published version

Valorisation of Ca and Mg by-products from mining and seawater desalination brines for water treatment applications

BACKGROUNDBrines from the drainage of potash mine tailings and from seawater reverse osmosis (SWRO) desalination were previously evaluated as sources of NaCl for the chlor-alkali industry. Valorisation of NaCl as raw material is required to meet the membrane electrolysis specifications of NaCl saturation and control of interferences (Ca, Mg and sulphate). Brines concentration in NaCl was previously achieved for SWRO brines using electrodialysis (ED). In this work, valorisation of Ca and Mg by-products via selective recovery was evaluated.; RESULTSRecovery of Ca(II) and Mg(II) using chemical precipitation with Na2CO3 and NaOH was evaluated at 25 degrees C and 65 degrees C using one single reagent and mixtures of reagents. The excess of reactants needed to achieve the maximum removal efficiency ranged from 0.35 to 14 g L-1 Na2CO3 and 0.85 g L-1 NaOH. Selective concentration of SWRO brines by ED benefited the purification, as it slightly diluted the antiscalants. The increase of temperatures also benefited their removal process.; CONCLUSIONSTotal chemical analysis of Ca and Mg by-products showed the presence of mixed salts of Ca and Mg when Na2CO3 was used and more pure precipitates of Mg when NaOH was used. In both cases, small amounts of minor traces initially present in the brines were found. (c) 2014 Society of Chemical Industry.Peer Reviewe

Concentration of NaCl from seawater reverse osmosis brines for the chlor-alkali industry by electrodialysis

Currently, numerous studies are focused on the valorisation of seawater desalination reverse osmosis brines. Electrodialysis can be used to concentrate one of the primary components (NaCI) and obtain a suitable raw material for industrial applications, such as the chlor-alkali industry. An electrodialysis pilot plant was used to evaluate the efficiency of concentrating a seawater reverse osmosis (SWRO) brine under representative full-scale operational conditions covering the temperature range of a semiarid climate. The results indicate that electrodialysis is a technology that can concentrate SVVRO brines from approximately 70 to 245 g/L NaCl, achieving an additional intrinsic purification of major multivalent ions (Ca2+, Mg2+, SO42-) due to the selectivity patterns of ion exchange membranes and the ion-complexation reactions in the concentrated brines. However, minor components, such as Ni and Cu, are concentrated due to the formation of Cu and Ni complexes with chloride ions to form monocharged species (e.g., NiCl+ and CuCl+). Energy consumption values of 0.12 kWh/kg NaCl for 185 g NaCl/l at 27 degrees C and 0.35 kA/m(2) or 0.19 kWh/kg NaCl for 203 g NaCl/l at 27 degrees C and 0.50 kA/m(2) were reached. These results were compared with the data obtained from the literature for salt production by electrodialysers. (C) 2013 Elsevier B.V. All rights reserved.Peer ReviewedPostprint (published version

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 Reviewe