Polygeneration based on an integrated biomass gasifier and an alkaline electrolyzer for district energy networks
- Autores: Jimmy Barco Burgos
- Directores de la Tesis: Juan Carlos Bruno Argilaguet (dir. tes.)
- Lectura: En la Universitat Rovira i Virgili ( España ) en 2022
- Idioma: español
- Número de páginas: 199
- Tribunal Calificador de la Tesis: Manuel Felipe Rosa Iglesias (presid.), Alberto Gómez-Barea (secret.), Farid Farid Janna (voc.)
- Programa de doctorado: Programa de Doctorado en Ingeniería Termodinámica de Fluidos por la Universidad de Burgos; la Universidad de Santiago de Compostela; la Universidad de Valladolid y la Universidad Rovira i Virgili
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
- español
Se desarrollaron seis capítulos de tesis; El Capítulo 1 proporciona información de antecedentes y posibles escenarios para los sistemas de poligeneración, específicamente, la integración de la gasificación de biomasa y la electrólisis de agua impulsada por energías renovables para la producción de gas de síntesis rico en hidrógeno. El Capítulo 2 proporciona un estudio de revisión de la integración de bombas de calor en redes DHC (District Heating and Cooling) y cómo puede ser una solución innovadora y rentable para diferentes sectores de descarbonización. El Capítulo 3 desarrolló un modelo de gasificación riguroso pero sencillo para diseñar y simular una planta de gasificación de biomasa utilizando el programa de resolución de ecuaciones Engineering Equation Solver (EES). El Capítulo 4 incluyó una investigación experimental de la gasificación con vapor de cáscaras de palmiste (PKS) para la producción de gas de síntesis libre de N_2 rico en hidrógeno en un gasificador alotérmico atmosférico de corriente descendente a escala piloto. El capítulo 5 incluyó el diseño y caracterización térmica de una celda de electrólisis alcalina para la generación de hidrógeno a presión atmosférica.
- català
Es van desenvolupar sis capítols de tesi; El capítol 1 proporciona informació de fons i possibles escenaris per als sistemes de poligeneració, concretament, la integració de la gasificació de biomassa i l'electròlisi de l'aigua impulsada per energies renovables per a la producció de gas de síntesi ric en hidrogen. El capítol 2 ofereix un estudi de revisió de la integració de les bombes de calor a les xarxes DHC (District Heating and Cooling) i com és una solució innovadora i rendible per a diferents sectors de descarbonització. El capítol 3 va desenvolupar un model de gasificació rigorós però senzill per dissenyar i simular una planta de gasificació de biomassa mitjançant el programa de resolució d'equacions Engineering Equation Solver (EES). El capítol 4 incloïa una investigació experimental de la gasificació amb vapor de closques de nucli de palma (PKS) per a la producció de gas de síntesi lliure de N_2 rica en hidrogen en un gasificador alotèrmic de corrent descendent atmosfèric a escala pilot. El capítol 5 incloïa el disseny i la caracterització tèrmica d'una pila d'electròlisi alcalina per a la generació d'hidrogen a pressió atmosfèrica. Finalment, en l'últim capítol, s'integren tots els models desenvolupats prèviament i les dades experimentals per analitzar sistemes de poligeneració en xarxes de calefacció i refrigeració de districte de baixa temperatura a Lachine Est a Mont-real.
- English
Polygeneration systems allow producing four or more useful commodities by using the same input or system increasing energy efficiency and conserves the resource. Despite increases system complexity, properly designed polygeneration enhances energy efficiency, reduces emission, waste, and increases the economic benefit. There are several advantages to polygeneration. For example, gasification-electrolyzer-based polygenerations systems reduce carbon footprint, resolves the problem of fossil resource scarcity, and increases energy efficiency compared to stand-alone units. Likewise, decentralized polygeneration in remote areas also increases energy access to rural people, and for waste-based systems, polygeneration with carbon capture and utilization is beneficial from environmental and economic viewpoints.
With little experimental data in this integrated gasification/electrolysis energy system available, it is necessary to improve system modeling and design, operate, monitor, and optimize the performance of pilot-scale systems. This study investigates a proposed polygeneration concept that can produce or consume power, heat, cold and store electricity as biofuels. The concept consists of a joint platform of thermal waste-gasification, electrolyzer technologies with district heating network that form a very efficient and flexible system. This system has two operational states: 1) The gasifier operates with air and/or steam as the gasifying agent.
The resulting product gas is fed to heat recovery units, a clean-up section, and a turbine coupled with a chiller to generate power, heat, and cold; 2) The system is operated with a gasifier integrated with electrolysis cells. The electrolyzer converts electricity and water into H_2 and O_2, water electrolysis is used to provide the O_2 as the gasifying agent. At the same time, H_2 is directly sent to the syngas stream to improve the heating value of syngas generated that produces an N_2-free gas suited for biofuel synthesis, electricity, heat, and cold production.
Six thesis chapters were developed; Chapter 1 provides background information and possible scenarios for polygeneration systems—specifically, the integration of biomass gasification and renewable-energies-driven water electrolysis for hydrogen-rich syngas production. Chapter 2 provides a review study of the integration of heat pumps into DHC (District Heating and Cooling) networks and how it be an innovative and profitable solution for different decarbonizing sectors. Chapter 3 developed a rigorous but straightforward gasification model for designing and simulating a biomass gasification plant using the equation solver program Engineering Equation Solver (EES). Chapter 4 included an experimental investigation of the steam gasification of palm kernel shells (PKS) for hydrogen-rich N_2- free syngas production in a pilot-scale atmospheric downdraft allothermal gasifier.
Chapter 5 included the design and thermal characterization of an alkaline electrolysis cell for hydrogen generation at atmospheric pressure. Finally, in the last chapter, all previously developed models and experimental data are integrated to analyze polygeneration systems in low-temperature district heating and cooling networks in Lachine Est in Montreal, Canada.
The literature review showed that the main problems related to the integration of waste gasification syngas and renewable-energies-driven water electrolysis for hydrogen-rich syngas production are: (i) the alkaline electrolyzer hydrogen production had not been fully explored under different operating environments. Specifically, the challenges of reducing energy consumption, cost, and maintenance persist. Simultaneously, an increase in reliability, durability, and safety is required by integrating renewable energy; (ii) the necessity exists to continue advancing in gasification technology to develop, optimize and implement this technology for the alternative use of residual biomass from many of our industries’ (wood, brick, solid urban waste, coal, and agro-industrial) waste. Specifically, hydrogen production from a separation of syngas produced by allothermal gasification of biomass has not been fully explored under different operating environments. Finally, (iii) the necessity in field trials using waste-based flexible energy plants to prove the polygeneration concept that can alter operation based on the current state of the grids and convert power into practical and easily storable energy carriers.
The integration of heat pumps into DHC (District Heating and Cooling) networks provides significant environmental and performance improvements, an innovative and profitable solution for different decarbonizing sectors. Chapter 2 reviews different district heating and cooling networks and the integration of high-temperature commercial heat pumps. Likewise, it describes placement options and connection modes of a heat pump unit in DHC networks, identifying twelve generic configurations of heat pumps and how they can be integrated into DHC systems, where four (4) of them have not been studied in the literature. The 3G, and 4G, are the most common district heating and cooling network generations for reference conditions reviewed. When considering a case where a central heat pump and CHP plant were located in the DHC network, the resulting coefficient of system performance (COSP) was in the range of 3 to 4 for commercial equipment with a range of coefficients of performance (COP) between 2 to 6. Using local HPs in the fourth and fifth-generation district heating networks, the resulting COSP was in the range of 0.95 to 1.5 for commercial equipment with a range of coefficients of performance (COP) between 2 to 6. Finally, for individual HPs in the district heating and cooling network, the resulting COSP was in the range 3 to 4 for commercial equipment with a range of coefficients of performance (COP) between 2 to 8.
The main contribution of the Chapter 3 consists of developing a rigorous but straightforward gasification model for designing and simulating a biomass gasification plant using the equation solver program Engineering Equation Solver (EES). The model includes some modifications for adaptation to real processes, in which only a partial approach to chemical equilibrium is achieved. The model developed, which has been validated with other authors' experimental data, provides the opportunity to evaluate different gasification processes and variations in fuel and operating conditions. The data was obtained to confirm a variation of less than 10% when comparing the proposed model's compositions with the experimental results reported in the literature. The model has also been used to evaluate the influence of temperature and the oxidizing agents in the syngas' hydrogen production and Lower heating value (LHV). Comparing the three oxidizing agents, steam showed a higher capacity to generate hydrogen than air + steam and air by 52% and 63%, respectively. Likewise, a higher capacity to generate syngas with superior LHV than air + steam and air by 44 % and 51%, respectively.
The main contribution of the Chapter 4 consists of investigating of the steam gasification of palm kernel shells (PKS) for hydrogen-rich N_2-free syngas production in a pilot-scale atmospheric downdraft allothermal gasifier. The feedstock material characterization, description of the gasifier design, auxiliary systems, operating conditions, and evaluation of the operating methodology for obtaining fuel gas are presented. The gasification equipment was tested under gasification temperatures between 800 and 950 and steam-biomass mass ratios between 0,2 and 1,2. The maximum H_2 generation is achieved with a gasification temperature of 850 , steam/biomass ratio of 0,85, particle sizes of 2 - 3 mm, and biomass feed of 57,1 kg?h. The volume fraction of H_2+ CO can reach 80,4 %, and maximum cold gas efficiency of 80 % with an average lower calorific value of (11,5 MJ)?Nm^3 .
The main contribution of the Chapter 5 consists of the design and thermal characterization of an alkaline electrolysis cell for hydrogen generation at atmospheric pressure. The electrolytic cell was manufactured from acrylic, using 316 L stainless steel electrodes, and considering a membrane separation for gases. The effect of current conditions, the distance between electrodes on the production efficiency of hydrogen and the distribution and variation of temperatures on the surface of the electrodes in operation were evaluated. Maximum hydrogen generation was achieved with a separation between electrodes (anode and cathode) of 3 mm and a current of 30 A at 12 V. Furthermore, the thermoelectric effects on the electrodes were analyzed, and the presence of areas of higher activity was discussed for oxidation and reduction reactions.
Finally, the results indicated in Chapter 6 shows that the electricity, heat, cooling, and hydrogen demand by the Lachine-Est area can be covered by the plant concept planted. The combination of biomass gasification and electrolyzer can be a potential solution to the emission problem and replace fossil fuels. The electrolyzer converts water into chemical products (i.e., O_2 or H_2) with the help of electricity from gasification. The gasification produces syngas and electricity from biomass, and at the same time provides heat for the heating demand. In this scheme, biomass plays a key role as a CO_2 capture system as it grows by consuming CO_2 from the air. The overall efficiency ranges from about 10 – 88 %, depending on the oxidizing agent and operating conditions used.
- español
