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.

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.

Energía renovable a partir de los lodos de depuradoras urbanas

El lodo de depuradora es el residuo líquido o semilíquido procedente de las Estaciones Depuradoras de Aguas Residuales (EDARs) del que puede obtenerse una energía renovable empleando la tecnología de la gasificación. Esta tecnología consiste en la oxidación parcial del sustrato carbonoso del lodo a altas temperaturas bajo condiciones subestequiométricas de aire, oxígeno u otros agentes gasificantes. Los productos obtenidos mediante gasificación son: un gas de síntesis (SYNGAS, con composición variable de H2, CO) un residuo carbonizado (char) y una fracción líquida de compuestos orgánicos de distinto peso molecular denominados alquitranes. El gas de síntesis tiene aplicaciones como son la generación de energía eléctrica/térmica o la síntesis de compuestos químicos. Sin embargo, la presencia de alquitranes imposibilita su uso en buena parte de las aplicaciones. El trabajo realizado que aquí se presenta estudia la posibilidad de tratar los lodos de depuradora mediante gasificación. Para ello, se han realizado las siguientes tareas: - Caracterización del lodo incluyendo la determinación de su humedad, materia orgánica, análisis elemental (C, N, H, S) y contenido de metales pesados (Cd, Cu, Ni, Pb, Zn, Hg y Cr). - Estudios de termogravimetría (TGA) del lodo para conocer su comportamiento térmico y la temperatura a la que se producen las principales reacciones en la gasificación. - Gasificación en un equipo de lecho fluido burbujeante y alimentación en continuo a escala de laboratorio. Con dicho gasificador se ha experimentado a distintas temperaturas y cargas para conocer las condiciones de proceso más favorables para aumentar la producción y el poder calorífico del SYNGAS obteniendo, a la vez, una baja producción en alquitranes. Para ello se ha analizado la composición de los gases obtenidos, la producción de alquitranes, la conversión del carbón y la eficiencia en la gasificación. Los alquitranes fueron analizados mediante cromatografía de gases y espectrometría de masas, para conocer y cuantificar sus diferentes componentes. - Determinación de la capacidad adsorbente de carbones activos producidos mediante gasificación, utilizando azul de metileno como adsorbato. Las conclusiones obtenidas permiten considerar la viabilidad técnica de la gasificación de lodos como fuente de energía renovable.

Gasification technology assessment of sterile coal to clean electrical power generation.

Sterile coal is a low-value residue associated to the coal extraction and mining activity. According to the type and origin of the coal bed configuration, sterile coal production can mainly vary on quantity, calorific value and presence of sulphur compounds. In addition, the potential availability of sterile coal within Spain is apparently high and its contribution to the local power generation would be of interest playing a significant role. The proposed study evaluates the availability and deployment of gasification technologies to drive clean electricity generation from waste coal and sterile rock coal, incorporating greenhouse gas emission mitigation systems, like CO2, H2S and NOx removal systems. It establishes the target facility and its conceptual basic design proposal. The syngas obtained after the gasification of sterile coal is processed through specific conditioning units before entering into the combustion chamber of a gas turbine. Flue gas leaving the gas turbine is ducted to a heat recovery steam generation boiler; the steam produced within the boilerdrives a steam turbine. The target facility resembles a singular Integrated Gasification in Combined Cycle (IGCC) power station. The evaluation of the conceptual basic design according to the power output set for a maximum sterile contribution, established that rates over 95% H2S and 90% CO2 removal can be achieved. Noticeable decrease of NOx compounds can be also achieved by the use of commercial technology. A techno-economic approach of the conceptual basic design is made evaluating the integration of potential unitsand their implementation within the target facility aiming toachieve clean power generation. The criterion to be compliant with the most restrictive regulation regarding environmental emissions is setting to carry out this analysis.

Simulation of an Integrated Gasification Combined Cycle with Chemical-Looping Combustion and CO2 sequestration

Chemical-looping combustion allows an integration of CO2 capture in a thermal power plant without energy penalty; secondly, a less exergy destruction in the combustion chemical transformation is achieved, leading to a greater overall thermal efficiency. This paper focus on the study of the energetic performance of this concept of combustion in an integrated gasification combined cycle power plant when synthesis gas is used as fuel for the gas turbines. After thermodynamic modelling 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 precombustion capture. Energy savings in CO2 capture and storage has been quantified. The overall efficiency increase is found to be significant and even notable, reaching values of around 7%. In order to analyze the influence of syngas composition on the results, different H2-content fuels are considered.

Biomass Gasification in a Fluidized Bed Reactor: Effect of Temperature, Stoichiometric Ratio and Biomass Type

This paper investigates the gasification of two biomass types (pine wood and olive stones) in a laboratory scale bubbling fluidized bed reactor, in order to evaluate comparatively their potential in the production of syngas.