Use of alternative fuels obtained from renewable sources in brayton cycles

Analysis and simulation of the behaviour of gas turbines for power generation using different nonconventional fuels obtained from different renewable sources are presented. Three biomass-tobiofuel processes are considered: anaerobic digestion of biomass (biogas), biomass gasification (synthesis gas) and alcoholic fermentation of biomass and dehydration (bioethanol), each of them with two different biomass substrates (energy crops and municipal solid waste) as input. The gas turbine behaviour in a Brayton cycle is simulated both in an isolated operation and in combined cycle. The differences in gas turbine performance when fired with the considered biofuels compared to natural gas are studied from different points of view related with the current complex energetic context: energetic and exergetic efficiency of the simple/combined cycle and CO2 emissions. Two different tools have been used for the simulations, each one with a different approach: while PATITUG (own software) analyses the behaviour of a generic gas turbine allowing a total variability of parameters, GT-PRO (commercial software) is more rigid, albeit more precise in the prediction of real gas turbine behaviour. Different potentially interesting configurations and its thermodynamic parameters have been simulated in order to obtain the optimal range for all of them and its variation for each fuel.

Analysis of the Behaviour of Biofuel-Fired Gas Turbine Power Plants

The utilisation of biofuels in gas turbines is a promising alternative to fossil fuels for power generation. It would lead to significant reduction of CO2 emissions using an existing combustion technology, although significant changes seem to be needed and further technological development is necessary. The goal of this work is to perform energy and exergy analyses of the behaviour of gas turbines fired with biogas, ethanol and synthesis gas (bio-syngas), compared with natural gas. The global energy transformation process (i.e. from biomass to electricity) has also been studied. Furthermore, the potential reduction of CO2 emissions attained by the use of biofuels has been determined, considering the restrictions regarding biomass availability. Two different simulation tools have been used to accomplish the aims of this work. The results suggest a high interest and the technical viability of the use of Biomass Integrated Gasification Combined Cycle (BIGCC) systems for large scale power generation.

Optimización de la metodología de contratación de carbones térmicos con destino a la generación eléctrica

En los últimos quince años se ha producido una liberalización de los mercados eléctricos en los distintos países de ámbito occidental que ha ido acompañado de un incremento por la preocupación por la incidencia de las distintas tecnologías de generación en el entorno medioambiental. Ello se ha traducido en la aparición de un marco regulatorio más restrictivo sobre las tecnologías de generación fósiles, con mayor incidencia en las derivadas de productos petrolíferos y carbón. A nivel mundial han ido apareciendo cambios normativos relativos a las emisiones de distintos elementos contaminantes (CO2, SO2, NOx…), que hacen que en particular las centrales térmicas de carbón vean muy afectadas su rentabilidad y funcionamiento. Esta situación ha supuesto que la tecnología de generación eléctrica con carbón haya avanzado considerablemente en los últimos años (calderas supercríticas, sistemas de desulfuración, gasificación del carbón…). No obstante, el desarrollo de la generación con energías renovables, la generación con gas mediante centrales de ciclo combinado y la opinión social relativa a la generación con carbón, principalmente en Europa, suponen un serio obstáculo a la generación con carbón. Por consiguiente, se hace necesario buscar vías para optimizar la competitividad de las centrales de carbón y el camino más razonable es mejorar el margen esperado de estas plantas y en particular el coste de adquisición del carbón. Ello se hace aún más importante por el hecho de existir numerosas centrales de carbón y un elevado número de nuevos proyectos constructivos de centrales de carbón en países asiáticos. Por consiguiente, el objeto de la presente tesis doctoral se centra en definir una metodología para optimizar la compra de carbón, desde el punto de vista económico y técnico, con destino a su consumo en una central térmica, con ello reducir el coste del carbón consumido y mejorar su competitividad. También se enfoca a determinar que herramientas pueden ser utilizadas para optimizar la gestión del carbón después de su compra y con ello abrir la posibilidad de obtener márgenes adicionales para dicho carbón. De acuerdo con este objetivo, el autor de la presente Tesis Doctoral realiza tres aportaciones novedosas en el ámbito de la contratación de carbón térmico y su optimización posterior: - Evaluación de carbones para su adquisición considerando el efecto de la calidad del carbón en el coste de generación asociado a cada carbón ofertado. - Creación, desarrollo, implantación y utilización de una potente herramienta de planificación de Combustibles. Esta herramienta, está diseñada con el objeto de determinar la solución económica óptima de aprovisionamientos, consumos y niveles de existencias para un parque de generación con centrales de carbón y fuelóleo. - La extensión de una metodología contractual habitual en el mercado spot de Gas Natural Licuado, a la contratación spot de Carbón de Importación. Esta se basa en el desarrollo de Acuerdos Marcos de Compra/Venta de carbón, que por su flexibilidad permitan obtener resultados económicos adicionales después de la compra de un carbón. Abstract In the last fifteen years, a liberalization of the electrical markets has occurred in the western countries. This process has been accompanied by an increasing concern of the impact of the different generation technologies towards the environment. This has motivated a regulated framework restricting the use of fossil fuels, impacting a great deal in coal and oil based products. Worldwide, new legal changes have been arising related to the emissions of the different pollutants (CO2, SO2, NOx…). These changes have had a deep impact in the feasibility, profit and running of coal fired power plants. This situation has motivated the coal electrical generation technologies to move forward in an important way in the last few years (supercritical furnaces, desulphuration plants, coal gasification…). Nevertheless, the development of the renewable generation, the gas combined cycle generation and the social opinion related to the coal electrical generation, mainly in Europe, have created a serious obstacle to the generation of electricity by coal. Therefore it is necessary to look for new paths in order to optimize the competitiveness of the coal fired power plants and the most reasonable way is to improve the expected margin of these plants and particularly the coal purchase cost. All of the above needs to be taken into context with the large number of existing coal fired power plants and an important number of new projects in Asian countries. Therefore, the goal of the current doctoral dissertation is focused to define a methodology to be considered in order to optimize the coal purchase, from an economical and a technical point of view. This coal, destined for power plant consumption, permits the reduction of consumption coal cost and improves the plant’s competitiveness. This document is also focused to define what tools we can use to optimize the coal management after deal closing and therefore open the possibility to get further margins. According to this goal, the author of this doctoral dissertation provides three important new ideas in the ambit of contracting steam coal and the posterior optimization: - Evaluation of coal purchases, considering the effect of coal quality on the cost of generation associated with each type of coal offered. - The creation, development, deployment and use of a strong planning tool of fuels. This tool is designed for the purpose of determining the optimal economic solution of fuel supply, consumption and stock levels for a power generation portfolio using coal and fuel oil fired power plants. - The application of a common contractual methodology in the spot market of Liquid Natural Gas, for the contracting spot imported coal. This is based on the development of Framework Agreements for the Purchasing / Sale of coal, which because of its flexibility allows for the gain of additional financial results after the purchase of coal.

Estudio energético comparativo de diferentes configuraciones de ciclo combinado

El objetivo del presente proyecto consiste en la modelización y optimización de una planta de gasificación integrada en ciclo combinado de 400 MW de potencia neta, mediante el uso del programa Cycle-Tempo, desarrollado por la Universidad de Delft. Para la modelización de la planta, se ha dividido en sus dos unidades principales: la isla de gasificación y el ciclo combinado. Para la validación del modelo de la isla de gasificación, se ha utilizado una composición de referencia de un combustible gasificable y se ha obtenido la composición del gas de síntesis esperada. Se han modelado y optimizado varias configuraciones de ciclo combinado, variando los parámetros característicos de la caldera de recuperación de calor. Se ha realizado la integración de las dos unidades para maximizar la potencia entregada por la planta. Finalmente, se ha estimado el balance anual de energía del ciclo combinado alimentado con gas natural y con el gas de síntesis, con el fin de comparar las rentabilidades económicas obtenidas. Mediante el estudio realizado, se deduce que la forma más eficiente de producir energía, a partir del uso del carbón, es la tecnología de gasificación integrada en ciclo combinado, pese a que su rendimiento sea inferior al ciclo combinado alimentado con gas natural. ABSTRACT The aim of this project is the modeling and optimization of an integrated gasification combined cycle plant of 400 MW net power, using the Cycle-Tempo program, developed by the University of Delft. For the modeling of the plant, it has been divided into its two main units: the island of gasification and the combined cycle. For the model validation of the gasification island, a reference composition of a gasifiable fuel has been used and the expected synthesis gas composition was obtained. Several configurations of combined cycle have been modeled and optimized by varying the characteristic parameters of the heat recovery steam generator. It has made the integration of the two units to reach maximum optimization of power, which has been delivered by the plant. Finally, it has been estimated the annual energy balance for the combined cycle plant fueled with natural gas and with syngas, in order to compare the profitability obtained with each one. Through the study, it is deduced that the most efficient way to produce energy from the use of coal, is the integrated gasification combined cycle technology, although their performance is lower than that obtained from the combined cycle fueled with natural gas.

Use of alternative fuels obtained from renowable sources in Brayton cycles

Analysis and simulation of the behaviour of gas turbines for power generation using different nonconventional fuels obtained from different renewable sources are presented. Three biomass-tobiofuel processes are considered: anaerobic digestion of biomass (biogas), biomass gasification (synthesis gas) and alcoholic fermentation of biomass and dehydration (bioethanol), each of them with two different biomass substrates (energy crops and municipal solid waste) as input. The gas turbine behaviour in a Brayton cycle is simulated both in an isolated operation and in combined cycle. The differences in gas turbine performance when fired with the considered biofuels compared to natural gas are studied from different points of view related with the current complex energetic context: energetic and exergetic efficiency of the simple/combined cycle and CO2 emissions. Two different tools have been used for the simulations, each one with a different approach: while PATITUG (own software) analyses the behaviour of a generic gas turbine allowing a total variability of parameters, GT-PRO (commercial software) is more rigid, albeit more precise in the prediction of real gas turbine behaviour. Different potentially interesting configurations and its thermodynamic parameters have been simulated in order to obtain the optimal range for all of them and its variation for each fuel.

Numerical simulation of group combustion of pulverized coal

A mathematical model for the group combustion of pulverized coal particles was developed in a previous work. It includes the Lagrangian description of the dehumidification, devolatilization and char gasification reactions of the coal particles in the homogenized gaseous environment resulting from the three fuels, CO, H2 and volatiles, supplied by the gasification of the particles and their simultaneous group combustion by the gas phase oxidation reactions, which are considered to be very fast. This model is complemented here with an analysis of the particle dynamics, determined principally by the effects of aerodynamic drag and gravity, and its dispersion based on a stochastic model. It is also extended to include two other simpler models for the gasification of the particles: the first one for particles small enough to extinguish the surrounding diffusion flames, and a second one for particles with small ash content when the porous shell of ashes remaining after gasification of the char, non structurally stable, is disrupted. As an example of the applicability of the models, they are used in the numerical simulation of an experiment of a non-swirling pulverized coal jet with a nearly stagnant air at ambient temperature, with an initial region of interaction with a small annular methane flame. Computational algorithms for solving the different stages undergone by a coal particle during its combustion are proposed. For the partial differential equations modeling the gas phase, a second order finite element method combined with a semi-Lagrangian characteristics method are used. The results obtained with the three versions of the model are compared among them and show how the first of the simpler models fits better the experimental results.

Optimización de la gasificación de lodos de estaciones depuradoras de aguas residuales urbanas para minimizar la formación de alquitranes

La gasificación de lodos de depuración es una alternativa atractiva para generar gases combustibles como H2 y CO. A su vez, estos gases pueden emplearse como materias primas para la obtención de productos químicos orgánicos y combustibles líquidos. Sin embargo, la gasificación no está exenta de problemas como el ligado a la generación de residuos sólidos y alquitrán. El alquitrán en el gas puede ser un inconveniente para emplear el gas como combustible por las obstrucciones y corrosión en los equipos. Dado que las condiciones de gasificación influyen en la producción de alquitrán, este trabajo de investigación se ha centrado en analizar la influencia de parámetros como la temperatura, la carga de alimentación, el tamaño de partícula, el agente gasificante y la utilización de catalizadores en la gasificación en lecho fluidizado de lodos de depuración. Adicionalmente a la medición del efecto de los anteriores parámetros en la producción y composición del alquitrán, también se ha cuantificado su influencia en la producción y composición del gas y en producción del residuo carbonoso. Los resultados muestran que el incremento de la carga de alimentación (kg/h.m2) provoca el descenso de la producción de gas combustible y el incremento del residuo carbonoso y del alquitrán debido a la reducción del tiempo de residencia del gas lo que supone un menor tiempo disponible para las reacciones gas-gas y gas-sólido ligadas a la conversión del alquitrán y del residuo carbonoso en gases combustibles. También se ha comprobado que, el aumento del tamaño de partícula, al incrementar el tiempo de calentamiento de ésta, tiene un efecto similar en los productos de la gasificación que el derivado del incremento en la carga de alimentación. La utilización de una temperatura de gasificación alta (850 ºC), el empleo de aire-vapor como agente gasificante y/o catalizadores primarios como la dolomía consiguen reducir la producción de alquitrán. ABSTRACT Gasification of sewage sludge is an attractive alternative for generating of fuel gases such as H2 and CO. These gases, in turn, can be used as raw materials for the production of organic chemicals and liquid fuel. However, gasification is not without problems as the linked ones to production of char and tar. The tar in the gas can be an inconvenience for to use it as fuel by the problems of blockage and corrosion in the equipments. Since the gasification conditions affect the production of tar, this research has focused on analysing the influence of parameters such as temperature, throughput, the particle size, the gasifying agent and the use of catalysts in the fluidized bed gasification of sewage sludge. In addition to measuring the effect of the above parameters on the production and composition of the tar, it has also been quantified their influence on the yield and composition of the gas and char production. The results show that higher throughput (kg/h.m2) leads to a reduction of fuel gas production and an increase in the production of char and tar, this owes to a lower of gas residence time or what is the same thing less time available for gas-solid and gas-gas reactions attached to the conversion of tar and char to fuel gases. There has also been proven that the rising in particle size, by the increasing heating time of it, has a similar effect in the products of gasification that the results by the rise in the throughput. The applications a high gasification temperature (850 ° C), the use of air-steam as gasifying agent and/or dolomite as primary catalysts are able to reduce the production of tar.

Análisis energético de las centrales de ciclo combinado con gasificación integrada y combustión mediante lazo químico

La combustión mediante lazo químico permite una integración de captura de CO2 en una planta térmica de potencia sin penalización energética. Se alcanza una menor destrucción exergética, alcanzándose un rendimiento térmico idóneo. Este proyecto se centra en el estudio del rendimiento energético en una planta de potencia con gasificación integrada cuando la cámara de combustión de las turbinas de gas se sustituye por un sistema de combustión CLC. Después del diseño termodinámico y optimización de algunos parámetros del ciclo, el rendimiento de la planta de potencia es evaluado bajo distintas condiciones de trabajo y comparado con el que se obtendría en una planta de ciclo combinado convencional con gasificación integrada y captura pre-combustión. Abstract Chemical-looping combustion allows an integration of CO2 capture in a thermal power plant without energy penalty. A less exergy destruction in the combustion chemical transformation is achieved, leading to a greater overall thermal efficiency. This Project focus on the study of the energetic performance in a cycle power plant with integrated gasification when the chamber combustion is supplied by a combustion system CLC. After thermodynamic modeling and optimization of some cycle parameters, the power plant performance is evaluated under diverse working conditions and compared to a conventional integrated gasification combined cycle with pre-combustion capture.

Aprovechamiento térmico de residuos estériles de carbón para generación eléctrica mediante tecnologías de combustión y gasificación eficientes y con mínimo impacto ambiental

La presente tesis doctoral, “Aprovechamiento térmico de residuos estériles de carbón para generación eléctrica mediante tecnologías de combustión y gasificación eficientes y con mínimo impacto ambiental”, desarrolla la valorización energética de los residuos del carbón, estériles de carbón, producidos durante las etapas de extracción y lavado del carbón. El sistema energético se encuentra en una encrucijada, estamos asistiendo a un cambio en el paradigma energético y, en concreto, en el sector de la generación eléctrica. Se precipita un cambio en la generación y el consumo eléctricos. Una mayor concienciación por la salud está forzando la contención y eliminación de agentes contaminantes que se generan por la utilización de combustibles fósiles de la forma en la que se viene haciendo. Aumenta la preocupación por el cambio climático y por contener en 2°C el aumento de la temperatura de la Tierra para final de este siglo, circunstancia que está impulsando el desarrollo e implantación definitiva de tecnología de control y reducción de emisiones CO2. Generar electricidad de una manera sostenible se está convirtiendo en una obligación. Esto se materializa en generar electricidad respetando el medioambiente, de una forma eficiente en la utilización de los recursos naturales y a un coste competitivo, pensando en el desarrollo de la sociedad y en el beneficio de las personas. En la actualidad, el carbón es la principal fuente de energía utilizada para generar electricidad, y su empleo presenta la forma de energía más barata para mejorar el nivel de vida de cualquier grupo y sociedad. Además, se espera que el carbón siga presente en el mix de generación eléctrica, manteniendo una significativa presencia y extrayéndose en elevadas cantidades. Pero la producción de carbón lleva asociada la generación de un residuo, estéril, que se produce durante la extracción y el lavado del mineral de carbón. Durante décadas se ha estudiado la posibilidad de utilizar el estéril y actualmente se utiliza, en un limitado porcentaje, en la construcción de carreteras, terraplenes y rellenos, y en la producción de algunos materiales de construcción. Esta tesis doctoral aborda la valorización energética del estéril, y analiza el potencial aprovechamiento del residuo para generar electricidad, en una instalación que integre tecnología disponible para minimizar el impacto medioambiental. Además, persigue aprovechar el significativo contenido en azufre que presenta el estéril para producir ácido sulfúrico (H2SO4) como subproducto de la instalación, un compuesto químico muy demandado por la industria de los fertilizantes y con multitud de aplicaciones en otros mercados. Se ha realizado el análisis de caracterización del estéril, los parámetros significativos y los valores de referencia para su empleo como combustible, encontrándose que su empleo como combustible para generar electricidad es posible. Aunque en España se lleva extrayendo carbón desde principios del siglo XVIII, se ha evaluado para un período más reciente la disponibilidad del recurso en España y la normativa existente que condiciona su aplicación en el territorio nacional. Para el período evaluado, se ha calculado que podrían estar disponibles más de 68 millones de toneladas de estéril susceptibles de ser valorizados energéticamente. Una vez realizado el análisis de la tecnología disponible y que podría considerarse para emplear el estéril como combustible, se proponen cuatro configuraciones posibles de planta, tres de ellas basadas en un proceso de combustión y una de ellas en un proceso de gasificación. Tras evaluar las cuatro configuraciones por su interés tecnológico, innovador y económico, se desarrolla el análisis conceptual de una de ellas, basada en un proceso de combustión. La instalación propuesta tiene una capacidad de 65 MW y emplea como combustible una mezcla de carbón y estéril en relación 20/80 en peso. La instalación integra tecnología para eliminar en un 99,8% el SO2 presente en el gas de combustión y en más de un 99% las partículas generadas. La instalación incorpora una unidad de producción de H2SO4, capaz de producir 18,5 t/h de producto, y otra unidad de captura para retirar un 60% del CO2 presente en la corriente de gases de combustión, produciendo 48 tCO2/h. La potencia neta de la planta es 49,7 MW. Se ha calculado el coste de inversión de la instalación, y su cálculo resulta en un coste de inversión unitario de 3.685 €/kW. ABSTRACT The present doctoral thesis, “Thermal utilisation of waste coal for electricity generation by deployment of efficient combustion and gasification technologies with minimum environmental impact”, develops an innovative waste-to-energy concept of waste coals produced during coal mining and washing. The energy system is at a dilemma, we are witnessing a shift in the energy paradigm and specifically in the field of electricity generation. A change in the generation and electrical consumption is foreseen. An increased health consciousness is forcing the containment and elimination of pollutants that are generated by the use of fossil fuels in the way that is being done. Increasing concern about climate change and to contain the rise of global temperature by 2°C by the end of this century, is promoting the development and final implementation of technology to control and reduce the CO2 emission. Electricity generation in a sustainable manner is becoming an obligation. This concept materialised in generating electricity while protecting the environment and deployment of natural resources at a competitive cost, considering the development of society and people´s benefit. Currently, coal is the main source of energy employ to generate electricity, and its use represents the most cost competitive form of energy to increase the standard of living of any group or society. Moreover, coal will keep playing a key role in the global electricity generation mix, maintaining a significant presence and being extracting in large amounts. However, coal production implies the production of waste, termed waste coal or culm in Pennsylvania anthracite extraction, produced during coal mining and coal washing activities. During the last decades, the potential use of waste coal has been studied, and currently, in a limited amount, waste coal is used in roads construction, embankments and fillings, and to produce some construction materials. This doctoral thesis evaluates the waste to energy of waste coals and assesses its potential use to generate electricity, implementing available technology to minimise the environment impact. Additionally, it pursues the significant advantage that presents sulphur content in waste coal to produce sulphuric acid (H2SO4) as a byproduct of the waste-to-energy process, a chemical compound highly demanded by the fertiliser industry and many applications in other markets. It analyses the characteristics of waste coal, and assesses the significant parameters and reference values for its use as fuel, being its fuel use for electricity generation very possible. While mining coal is taking place in Spain since the 1700s, it has been evaluated for a more recent period the waste coal available in Spain and the existing legislation that affects its application and deploy to generate electricity in the country. For the evaluation period has been calculated that may be available more than 68 million tons of waste coal that can be waste-toenergy. The potential available technology to deploy waste coal as fuel has been evaluated and assessed. After considering this, the doctoral thesis proposes four innovative alternatives of facility configuration, three of them based on a combustion process and one in a gasification process. After evaluating the four configurations for its technological, innovative and economic interest, the conceptual analysis of one of alternatives, based on a combustion process, takes place. The proposed alternative facility developed has a capacity of 65 MW, using as fuel a mixture of coal and waste coal 80/20 by weight. The facility comprises technology to remove 99.8% SO2 present in the flue gas and more than 99% of the particles. The facility includes a unit capable of producing 18.5 t/h of H2SO4, and another capture facility, removing 60% of CO2 present in the flue gas stream, producing 48 tCO2/h. The net capacity of the power station is 49.7 MW. The facility unitary cost of investment is 3,685 €/kW.

Gaseificação de microalgas: estudo termogravimétrico e modelagem matemática do processo em reator solar.

Devido ao esgotamento de recursos não renováveis e o aumento das preocupações sobre as alterações climáticas, a produção de combustível renovável a partir de microalgas continua a atrair muita a atenção devido ao seu potencial para taxas rápidas de crescimento, alto teor de óleo, capacidade de crescer em cenários não convencionais e a neutralidade de carbono, além de eliminar a preocupação da disputa com as culturas alimentares. Em virtude disso, torna-se importante o desenvolvimento de um processo de conversão das microalgas em gás combustível, em destaque o gás de síntese. Visando essa importância, estudou-se a reação de gaseificação da microalga Chlorella vulgaris através de experimentos de análise termogravimétrica para estimar os parâmetros cinéticos das reações e através da simulação de um modelo matemático dinâmico termoquímico do processo usando equações de conservação de massa e energia acoplados a cinética de reação. Análises termogravimétricas isotérmicas e dinâmicas foram realizadas usando dois diferentes tipos de modelos cinéticos: isoconversionais e reações paralelas independentes (RPI). Em ambos os modelos, os valores dos parâmetros cinéticos estimados apresentaram bons ajustes e permaneceram dentro daqueles encontrados na literatura. Também foram analisados os efeitos dos parâmetros cinéticos do modelo RPI sobre a conversão da microalga no intuito de observar quais mais se pronunciavam diante a variação de valores. Na etapa de simulação do sistema controlado pelo reator solar, o modelo matemático desenvolvido foi validado por meio da comparação dos valores de temperatura e concentrações de produtos obtidos medidos experimentalmente pela literatura, apresentando boa aproximação nos valores e viabilizando, juntamente com a etapa experimental de termogravimetria, a produção de gás de síntese através da gaseificação da microalga Chlorella vulgaris.

Gaseificação de vinhaça em água supercrítica.

A gaseificação utiliza o conteúdo intrínseco de carbonos e hidrogênios das matérias primas sólidas ou líquidas na geração de uma mistura de hidrogênio (H2), monóxido de carbono (CO), dióxido de carbono (CO2) e metano (CH4). Tal mistura pode ser utilizada como matéria prima na síntese de novos produtos ou como combustível. A gaseificação pode ser utilizada no processamento de uma gama variada de produtos, independentemente de suas características ou estado físico. A utilização de biomassa como insumo da gaseificação vem sendo cada vez mais explorada e estudada, já que apresenta benefícios não somente na esfera ambiental, mas também em âmbitos econômicos e sociais. A vinhaça é um subproduto do processo de produção de álcool, que contém grandes concentrações de nutrientes e matéria orgânica em sua composição. A sua utilização hoje está limitada a fertirrigação e a aplicações isoladas em biodigestão e outros, que não são suficientes para o consumo da produção anual crescente do resíduo. Seu uso na gaseificação permitiria o aproveitamento do conteúdo orgânico da mesma e a produção de gases de alto valor agregado. Como a umidade do insumo interfere negativamente na eficiência da gaseificação clássica, a aplicação da mesma para matérias primas com alto teor de líquidos não é recomendada. Uma alternativa viável seria a utilização do meio gaseificante supercrítico, que resulta em rendimentos constantes, independentemente da umidade da corrente de entrada do reator. O presente trabalho consiste no projeto de um módulo de gaseificação de vinhaça em água supercrítica, a ser instalado como uma unidade anexa a usinas de açúcar e álcool. Ele compreende o projeto conceitual e análise de viabilidade deste módulo, incluindo estimativas de CAPEX (Capital Expenditure) e OPEX (Operation Expenditure) e uma análise de sensibilidade dos mesmos. O estudo apresenta ainda o estado da arte do conhecimento e da tecnologia de gaseificação com água supercrítica (SCWG), relacionando os gargalos a serem resolvidos, assim como os ganhos intrínsecos da definição conceitual do projeto.

Synthesis gas production from various biomass feedstocks

The decomposition of five different biomass samples was studied in a horizontal laboratory reactor. The samples consisted of esparto grass, straw, Posidonea Oceanic seaweed, waste from urban and agricultural pruning and waste from forest pruning. Both pyrolysis in inert atmosphere and combustion in the presence of oxygen were studied. Different heating rates were used by varying the input speed. Major gas compounds were analyzed. The experimental results show that the amount of CO formed is lower in less dense species. It is also found that there is an increase of hydrocarbons formed at increasing feeding rates, in particular methane, while there is a decrease in the production of hydrogen.

Preparation of high metal content nanoporous carbon

Activated carbons with high metal content have been prepared by the pyrolysis of ethylene tar with dissolved metal acetylacetonates (Ti, V, Fe, Co, Ni and Cu) and subsequent activation with KOH of the pitch obtained in pyrolysis. These metal compounds decompose during the pyrolysis of ethylene tar yielding metal nanoparticles formed by metal and/or oxide which are homogeneously distributed in the pitch and remain in the activated carbon, so that the concentration of metal is, in most cases, 4–5 times higher than in the pristine ethylene tar. Since KOH is an effective activating agent, all activated carbons combine a high porosity development with a high metal content. In some of the carbons, such as P2FeA (3.3% Fe, pore volume 1.84 cm3/g, BET surface area 3270 m2/g), there is even an increase in the pore volume when compared to the activated carbon prepared in the same way without metal, in spite of the fact that the metal increases the weight of carbon without contributing to the adsorptive capacity. It seems that iron, on the one hand modifies the pyrolysis to give a pitch with larger mesophase content and on the other hand it locally catalyzes carbon gasification with the CO2 produced along the synthesis of the carbon. In addition to its influence on activation, iron promotes the formation of graphitic carbon fibers.

Enhanced electro-oxidation resistance of carbon electrodes induced by phosphorus surface groups

The electro-oxidation of carbon materials enormously degrades their performance and limits their wider utilization in multiple electrochemical applications. In this work, the positive influence of phosphorus functionalities on the overall electrochemical stability of carbon materials has been demonstrated under different conditions. We show that the extent and selectivity of electroxidation in P-containing carbons are completely different to those observed in conventional carbons without P. The electro-oxidation of P-containing carbons involves the active participation of phosphorus surface groups, which are gradually transformed at high potentials from less-to more-oxidized species to slow down the introduction of oxygen groups on the carbon surface (oxidation) and the subsequent generation of (C*OOH)-like unstable promoters of electro-gasification. The highest-oxidized P groups (–C–O–P-like species) seem to distribute the gained oxygen to neighboring carbon sites, which finally suffer oxidation and/or gasification. So it is thought that P-groups could act as mediators of carbon oxidation although including various steps and intermediates compared to electroxidation in P-free materials.

Symposium proceedings : Environmental Aspects of Fuel Conversion Technology, II, December 1975, Hollywood, Florida /

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