Publication: Experimental optimization of Cynara cardunculus L. and sewage sludge pyrolysis in a fluidized bed reactor
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Publication date
2020-01
Defense date
2020-07-03
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Abstract
La presente tesis doctoral recoge un estudio experimental acerca de la pirólisis de lodos de depuradora y de Cynara cardunculus L. en reactores de lecho fluido. La composición de ambas biomasas fue determinada con un analizador elemental, mientras la cinética química de sus reacciones de pirólisis se estudió por medio de ensayos no isotermos realizados en un analizador termogravimétrico.
Se empleó una novedosa técnica de medida para investigar el proceso de pirólisis tanto de lodos de depuradora como de C. cardunculus L. Dicha técnica de medida consistió en colocar un reactor de lecho fluido a escala de laboratorio, dentro del cual se movía libremente la muestra de biomasa a convertir, para detectar la masa liberada durante el proceso de pirólisis. Por medio de la señal monitorizada por la balanza, se obtuvieron medidas precisas de la evolución temporal de la conversión de las muestras para distintas condiciones de operación. De este modo, se investigaron los efectos de la temperatura del lecho y la velocidad del gas inerte, y por lo tanto, el régimen del lecho, sobre el proceso de pirolisis para ambos biocombustibles. La influencia del tamaño de partícula en el proceso de pirólisis también se cuantificó para los ensayos en los que se emplearon muestras de C. cardunculus L. Además, se desarrolló un modelo de cinética química aparente capaz de estimar la evolución del grado de conversión durante el proceso de conversión para los casos en que los efectos de transferencia de calor son despreciables, es decir, aquellos casos en los que la pirólisis se lleva a cabo para pequeñas partículas de biomasa en un lecho fluido burbujeante.
La pirólisis de C. cardunculus L. fue estudiada también mediante ensayos en una nueva instalación experimental, diseñada para obtener y analizar todos los productos provenientes del proceso de pirólisis. Los productos sólidos y líquidos se recogieron tras cada ensayo, mientras la cantidad y composición de los gases no condensables se determinó en tiempo real mediante analizadores de gases permanentes. El líquido obtenido se sometió a posteriores análisis para determinar su porcentaje de bio-oil y agua, la cual fue generada en su totalidad a través del proceso de pirólisis. Los efectos de la temperatura del lecho, la velocidad del gas inerte y el régimen del lecho sobre los productos de la pirólisis de C. cardunculus L. fueron evaluados. Además, los porcentajes de retención de carbono, oxígeno y azufre en los gases permanentes se determinaron para todas las condiciones de operación empleadas.
In this PhD thesis the pyrolysis of sewage sludge and Cynara cardunculus L. in fluidized bed reactors is investigated experimentally. The composition of both biomass species was determined using an elemental analyzer and their pyrolysis kinetics was studied by means of non-isothermal pyrolysis measurements conducted in a thermogravimetric analyzer. A novel experimental technique was used to analyze the pyrolysis of sewage sludge and C. cardunculus L. The procedure consisted in placing a lab-scale fluidized bed over a scale capable of detecting the mass released during the pyrolysis of a batch sample of biomass, while moving freely inside the bed. Based on the evolution of the mass monitored by the scale, accurate measurements of the time evolution of the pyrolysis conversion were obtained as a function of the operating conditions. The effect of bed temperature, inert gas velocity, and therefore the bed regime, on the pyrolysis process of both biomasses was evaluated. In the case of the C. cardunculus L. samples, the particle size was also varied to quantify its effect on the pyrolysis performance in the bed. An apparent kinetic model was also used to estimate the evolution of the reacted fraction during pyrolysis for the cases where heat transfer effects are negligible, i.e., for the pyrolysis of small biomass particles in a bubbling fluidized bed. The pyrolysis of C. cardunculus L. was also analyzed using a different experimental facility where the products obtained from the pyrolysis process can be collected and analyzed. The solid and liquid yields were collected, whereas the composition of the non-condensable gases was determined by online permanent gas analyzers. The liquid yield was further analyzed to distinguish between the bio-oil and the water generated during pyrolysis. The effect of bed temperature, inert gas velocity, and bed regime on the yields obtained from C. cardunculus L. pyrolysis was evaluated. The retention percentages of C, O, and S in the permanent gases were also measured for all the operating conditions tested.
In this PhD thesis the pyrolysis of sewage sludge and Cynara cardunculus L. in fluidized bed reactors is investigated experimentally. The composition of both biomass species was determined using an elemental analyzer and their pyrolysis kinetics was studied by means of non-isothermal pyrolysis measurements conducted in a thermogravimetric analyzer. A novel experimental technique was used to analyze the pyrolysis of sewage sludge and C. cardunculus L. The procedure consisted in placing a lab-scale fluidized bed over a scale capable of detecting the mass released during the pyrolysis of a batch sample of biomass, while moving freely inside the bed. Based on the evolution of the mass monitored by the scale, accurate measurements of the time evolution of the pyrolysis conversion were obtained as a function of the operating conditions. The effect of bed temperature, inert gas velocity, and therefore the bed regime, on the pyrolysis process of both biomasses was evaluated. In the case of the C. cardunculus L. samples, the particle size was also varied to quantify its effect on the pyrolysis performance in the bed. An apparent kinetic model was also used to estimate the evolution of the reacted fraction during pyrolysis for the cases where heat transfer effects are negligible, i.e., for the pyrolysis of small biomass particles in a bubbling fluidized bed. The pyrolysis of C. cardunculus L. was also analyzed using a different experimental facility where the products obtained from the pyrolysis process can be collected and analyzed. The solid and liquid yields were collected, whereas the composition of the non-condensable gases was determined by online permanent gas analyzers. The liquid yield was further analyzed to distinguish between the bio-oil and the water generated during pyrolysis. The effect of bed temperature, inert gas velocity, and bed regime on the yields obtained from C. cardunculus L. pyrolysis was evaluated. The retention percentages of C, O, and S in the permanent gases were also measured for all the operating conditions tested.
Description
Mención Internacional en el título de doctor
Keywords
Biomass pyrolysis, Cynara cardunculus L., Sewage sludge, Distributed Activation Energy Model (DAEM), Fluidized bed