This study has the aim to develop a simulation model able to predict the production of a biomass pyrolysis plant, which allows to define right working parameters for optimizing the process. Moreover, an analysis regarding an energy recovery line has been performed to maximize the valorization of products and reduce the utilization of external energy sources. Biomass is a general name that includes a great number of organic substances with very different composition as well as physical and chemical properties; for this reason, in the library of the simulation software there is not a standard material suitable for this kind of processes. Nevertheless, there is the possibility to create non-conventional components starting from known characteristics, so a solid “biomass” determined by values derived from previous experimentation and literature researches has been defined. The scheme of thermo-chemical process used in this work is based on layout of a pyrolysis pilot plant located in Sicily, fed by 30 kg/h of olive pits and agricultural residues and worked between 600 °C and 800°C. In accordance to plant feedstock specification, fraction of C, O2 and H used to model the biomass has been chosen crossing standard ligno-cellulosic composition and average values of ultimate analysis of these considered materials. The decomposition of organic matter is idealized as a two-stage process: firstly, in the reactor, it is decomposed in a residual solid fraction (char) and a gaseous mixture. Then, this mixture is directed in the cooling section in which condensable part is divided from permanent gas generating the pyro-oil. To reproduce the degradation of biomass and the resulting evolution of chemical species, a new mathematical model, based on operative temperature (considered in a range between 500°C and 900°C) and kinetic of reaction involved during the process, was developed. Kinetic parameters are obtained performing all the reactions of decomposition of cellulose, hemicellulose and lignin. The conversion process is simulated by a R-yield reactor supported by a calculator block set with the proposed model calculated for each component involved in considered reactions. Permanent gas fraction was firstly characterized and then used to feed a micro-CHP system in order to produce electrical power and a thermal power. This latter is recirculated toward the pyrolysis plant to support drying or conversion process. Simulations were developed at 600°C and 800°C and thus the obtained results were compared to highlight: - Yield of each compound and differences during each section of the process; - Characteristics, composition and energetic content of pyro-gas; - Efficiency of micro-CHP system in terms of both electric and thermal power and respectively possibility to support the main process.
Il presente studio ha lo scopo di sviluppare un modello in grado di prevedere la distribuzione e le caratteristiche dei prodotti derivanti da un impianto pilota per la pirolisi delle biomasse, permettendo un’adeguata scelta dei parametri operativi e una conseguente ottimizzazione del processo. Inoltre è stata svolta un’analisi riguardo una linea di recupero energetico in grado di valorizzare i prodotti ottenuti e ridurre l’apporto di energia da fonti esterne. Nella definizione di “Biomassa” sono incluse una grande varietà di specie diverse sia dal punto di vista chimico che fisico; per questo motivo nella maggior parte dei database presenti nei software di simulazione non è presente una biomassa adatta a questo tipo di processo. Ciononostante, è presente una funzione che permette di creare nuovi componenti “non-convezionali” inserendo le caratteristiche del materiale desiderato. Grazie a questa possibilità, è stato creato un solido denominato “biomass”, modellato sulla base delle analisi ricavate da lavori precedenti e da una ricerca di letteratura. Lo schema del sistema di conversione termo-chimica proposto in questo lavoro è ispirato al layout di un impianto pilota presente in Sicilia. Tale impianto è alimentato da 30 kg/h di nocciolino di oliva e altri residui agricoli e lavora a temperature comprese tra 600°C e 800°C. Per modellare il feedstock sono stati incrociati dati ricavati dalle analisi elementari (percentuali di C, O2 e H) e dalla composizione lignocellulosica di questi materiali. Per descrivere la decomposizione del materiale organico è stato utilizzato un modello che si divide in due fasi: - la prima avviene nel reattore e porta alla degradazione del feedstock in una frazione solida (char) e una miscela gassosa. - durante la seconda fase, questa miscela viene diretta verso una sezione di raffreddamento e lavaggio gas, durante la quale avviene la condensazione e la separazione della frazione liquida (prevalentemente bio-oil + acqua) dal permanent gas residuo. Per riprodurre questa decomposizione e la conseguente evoluzione delle specie chimiche risultanti da questo processo, è stato proposto un nuovo modello matematico dipendente da due fattori: - la temperatura alla quale viene svolto il processo (è stato considerato un range compreso tra 500°C e 900°C); - la cinetica delle reazioni che coinvolte durante la decomposizione della cellulosa, dell’emicellulosa e della lignina. La pirolisi è stata simulata mediante un reattore “R-yield” supportato da un “Calculator block” nel quale è stato applicato il modello ideato alle singole reazioni di conversione e ai vari componenti chimici presenti durante il processo. La frazione di permanent gas ricavata è stata utilizzata per alimentare un sistema micro-CHP con lo scopo di produrre energia termica ed elettrica che verrà ricircolata verso l’impianto per fornire energia all’essicatore e al reattore. Le simulazioni sono state svolte a 600°C e 800°C per confrontare: - la diversa distribuzione dei prodotti al variare della temperatura; - le caratteristiche e la composizione della frazione gassosa prodotta; - l’efficienza del sistema micro-CHP.
Modeling, Software Simulation and Preliminary Test of a Biomass Pyrolysis Pilot Plant / Agrifoglio, Antonio. - (2020 Jan 17).
Modeling, Software Simulation and Preliminary Test of a Biomass Pyrolysis Pilot Plant
AGRIFOGLIO, ANTONIO
2020-01-17
Abstract
This study has the aim to develop a simulation model able to predict the production of a biomass pyrolysis plant, which allows to define right working parameters for optimizing the process. Moreover, an analysis regarding an energy recovery line has been performed to maximize the valorization of products and reduce the utilization of external energy sources. Biomass is a general name that includes a great number of organic substances with very different composition as well as physical and chemical properties; for this reason, in the library of the simulation software there is not a standard material suitable for this kind of processes. Nevertheless, there is the possibility to create non-conventional components starting from known characteristics, so a solid “biomass” determined by values derived from previous experimentation and literature researches has been defined. The scheme of thermo-chemical process used in this work is based on layout of a pyrolysis pilot plant located in Sicily, fed by 30 kg/h of olive pits and agricultural residues and worked between 600 °C and 800°C. In accordance to plant feedstock specification, fraction of C, O2 and H used to model the biomass has been chosen crossing standard ligno-cellulosic composition and average values of ultimate analysis of these considered materials. The decomposition of organic matter is idealized as a two-stage process: firstly, in the reactor, it is decomposed in a residual solid fraction (char) and a gaseous mixture. Then, this mixture is directed in the cooling section in which condensable part is divided from permanent gas generating the pyro-oil. To reproduce the degradation of biomass and the resulting evolution of chemical species, a new mathematical model, based on operative temperature (considered in a range between 500°C and 900°C) and kinetic of reaction involved during the process, was developed. Kinetic parameters are obtained performing all the reactions of decomposition of cellulose, hemicellulose and lignin. The conversion process is simulated by a R-yield reactor supported by a calculator block set with the proposed model calculated for each component involved in considered reactions. Permanent gas fraction was firstly characterized and then used to feed a micro-CHP system in order to produce electrical power and a thermal power. This latter is recirculated toward the pyrolysis plant to support drying or conversion process. Simulations were developed at 600°C and 800°C and thus the obtained results were compared to highlight: - Yield of each compound and differences during each section of the process; - Characteristics, composition and energetic content of pyro-gas; - Efficiency of micro-CHP system in terms of both electric and thermal power and respectively possibility to support the main process.File | Dimensione | Formato | |
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