Estudio de los procesos de oxidación y gasificación en agua supercrítica aplicado al tratamiento de vertidos industriales

En las últimas décadas, el tratamiento de residuos industriales ha adquirido una gran importancia en todo el mundo, y la necesidad de establecer métodos efectivos que permitan la eliminación de los residuos, transformando los componentes tóxicos y peligrosos en productos finales inocuos. En este sentido, los procesos de oxidación hidrotérmica han despertado un gran interés por su eficacia en el tratamiento y depuración de los vertidos industriales de alta carga orgánica. A nivel experimental, esta tecnología ha demostrado una enorme capacidad para transformar gran variedad de residuos en efluentes no contaminantes. Sin embargo, existe una falta de datos experimentales a escala de planta piloto necesarios para el escalamiento del proceso a nivel industrial. Por su parte, el proceso de gasificación, en condiciones subcríticas y supercríticas, se presenta como una posible vía de aprovechamiento energético de residuos mediante su transformación en un gas combustible de gran poder calorífico por su alto contenido en hidrógeno e hidrocarburos ligeros. Ello permite la aplicación de dicho proceso a residuos industriales con un alto porcentaje de agua en su composición, los cuales no resultan aptos para su tratamiento mediante los métodos convencionales de gasificación térmica. El presente trabajo se ha desarrollado en tres frentes: por una parte se ha ampliado los estudios de oxidación en agua supercrítica a escala de laboratorio a un nuevo residuo: las vinazas. Además, se ha estudiado el proceso de gasificación hidrotérmica a escala de laboratorio de un compuesto modelo como es la glucosa y dos residuos industriales: vinazas y taladrinas. Y por último, ambos procesos, oxidación y gasificación supercrítica, se han escalado a planta piloto. Dicha planta se ha validado con fenol. Finalmente, se ha desarrollado una simulación del proceso de oxidación que pueda servir de base para posteriores estudios de escalamiento de la tecnología a escala industrial

Analysis of the Supercritical Water Gasification of Cellulose in a Continuous System Using Short Residence Times

Supercritical Water Gasification (SCWG) has the capacity to generate fuel gas effluent from wet biomass without previously having to dry the biomass. However, substantial efforts are still required to make it a feasible and competitive technology for hydrogen production. Biomass contains cellulose, hemicellulose and lignin, so it is essential to understand their behavior in high-pressure systems in order to optimize hydrogen production. As the main component of biomass, cellulose has been extensively studied, and its decomposition has been carried out at both subcritical and supercritical conditions. Most previous works of this model compound were carried out in batch reactors, where reaction times normally take place in a few minutes. However, the present study demonstrates that gasification reactions can achieve efficiency levels of up to 100% in less than ten seconds. The effect of temperature (450-560 degrees C), the amount of oxidant (from no addition of oxidant to an excess over stoichiometric of 10%, n = 1.1), the initial concentration of organic matter (0.25-2 wt.%) and the addition of a catalyst on the SCWG of cellulose in a continuous tubular reactor at short residence times (from 6 to 10 s) have been studied in this work. Hydrogen yields close to 100% in the gas phase were obtained when operating under optimal conditions. Moreover, a validation of the experimental data has been conducted based on the theoretical data obtained from its kinetics

Applications of Supercritical Water in Waste Treatment and Valorization: A Review

The present review deals with water applications in sub and supercritical conditions with a focus on supercritical water oxidation process (SCWO) as an example of high temperature and pressure technologies. It starts by presenting the advantages of water properties near and beyond the critical point and the major applications exploiting them. Then, it presents a review on SCWO from the description of the process, the reaction mechanism and kinetics to reactor design and modeling. It also presents the main problems and difficulties that delay the SCWO industrial application, and summarizes the main efforts and research to overcome them for a safe, efficient and economic process

Effect of the Heating Rate to Prevent the Generation of Iron Oxides during the Hydrothermal Synthesis of LiFePO4

Lithium-ion batteries (LIBs) have gained much interest in recent years because of the increasing energy demand and the relentless progression of climate change. About 30% of the manufacturing cost for LIBs is spent on cathode materials, and its level of development is lower than the negative electrode, separator diaphragm and electrolyte, therefore becoming the "controlling step". Numerous cathodic materials have been employed, LiFePO4 being the most relevant one mainly because of its excellent performance, as well as its rated capacity (170 mA center dot h center dot g(-1)) and practical operating voltage (3.5 V vs. Li+/Li). Nevertheless, producing micro and nanoparticles with high purity levels, avoiding the formation of iron oxides, and reducing the operating cost are still some of the aspects still to be improved. In this work, we have applied two heating rates (slow and fast) to the same hydrothermal synthesis process with the main objective of obtaining, without any reducing agents, the purest possible LiFePO4 in the shortest time and with the lowest proportion of magnetite impurities. The reagents initially used were: FeSO4, H3PO4, and LiOH, and a crucial phenomenon has been observed in the temperature range between 130 and 150 degrees C, being verified with various techniques such as XRD and SEM.A. Benitez thanks the financial support from the European Social Fund and Junta de Andalucia. Finally, the authors wish to acknowledge the technical staff from the University Institute of Nanochemistry (IUNAN) of the University of Cordoba. This research received no external funding

Energy Production by Hydrothermal Treatment of Liquid and Solid Waste from Industrial Olive Oil Production

This work studies the use of olive oil mill waste (OMW) treated as subcritical or supercritical water to produceboth, a biofuel by liquefaction and a gas fuel by gasification. The increasing amount of OMW, both liquid and solid, isbecoming a serious environmental problem. This wastewater is highly resistant to biodegradation and contains a widevariety of compounds such as polyphenols, polyoils, organic acids, etc, that require depuration treatments to remove theodour and pollutant load before being discharged.This work studies both, liquefaction and gasification of OMW streams in subcritical and supercritical water in differentbatch reactors at temperatures between 200 and 530 ºC and pressures between 150 and 250 bar. This study also teststhe effectiveness of various types of homogeneous (KOH 0.01 g/gsample dry) and heterogeneous catalysts (TiO2, V2O5 andAu-Pd 0.1-0.5 g/gsample dry) for supercritical water gasification (SCWG) and studied the way they affect biomassconversion yields. It also covers the effect that the use of different organic compound concentrations (23, 35, and 80 gO2/l of chemical oxygen demand concentration (COD)) and compositions (mixtures of solid and liquid OMW) has onenergy production results. A maximum of 82% oil yield was obtained from the hydrothermal liquefaction of OMW underoptimum conditions (330 ºC, 150 bar, 23 g O2/l as initial concentration and 30 minutes reaction time). Meanwhile, a yieldof 88.6 mol H2/kgOMW dry was obtained when Au-Pd was used as a catalyst for the gasification of OMW supercritical water.Fil: Casademont Lanzat, Pau. Universidad de Cadiz. Facultad de Ciencias; EspañaFil: García Jarana, Belén. Universidad de Cadiz. Facultad de Ciencias; EspañaFil: Chen, Xiaowei. Universidad de Cadiz. Facultad de Ciencias; EspañaFil: Olmos Carreno, Carol Maritza. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Cadiz. Facultad de Ciencias; EspañaFil: Sánchez Oneto, Jezabel. Universidad de Cadiz. Facultad de Ciencias; EspañaFil: Portela, Juan R.. Universidad de Cadiz. Facultad de Ciencias; EspañaFil: Martínez de la Ossa, Enrique J.. Universidad de Cadiz. Facultad de Ciencias; Españ