Coal gasification by indirect heating in a single moving bed reactor: Process development & simulation

In this work, the development and simulation of a new coal gasification process with indirect heat supply is performed. In this way, the need of pure oxygen production as in a conventional gasification process is avoided. The feasibility and energetic self-sufficiency of the proposed processes are addressed. To avoid the need of Air Separation Unit, the heat required by gasification reactions is supplied by the combustion flue gases, and transferred to the reacting mixture through a bayonet heat exchanger installed inside the gasifier. Two alternatives for the flue gas generation have been investigated and compared. The proposed processes are modeled using chemical kinetics validated on experimental gasification data by means of a standard process simulator (Aspen PlusTM), integrated with a spreadsheet for the modeling of a special type of heat exchanger. Simulation results are presented and discussed for proposed integrated process schemes. It is shown that they do not need external energy supply and ensure overall efficiencies comparable to conventional processes while producing syngas with lower content of carbon dioxide

Petcoke & Coal Exploitation: Development of Environment Friendly Processes

In view of the current and projected gap of the supply and demand of energy in the world, especially in countries like Pakistan, of the growing threat of the impacts of greenhouse gas emissions with respect to climate change, and of the current rate of development of the renewable and sustainable energy resources, responsible and efficient use of fossil fuels stands with utmost importance in the priorities of today’s industrial and scientific community. With this idea, development and optimization of efficient gasification systems and downstream processes is the core objective of this thesis. Simulation-based and experimental approaches have been taken in the course of this work. Aspen Plus™ is employed as the core simulation tool for the modelling, analysis, and comparison of three novel indirect gasification schemes proposed in this work. These schemes appear to be compatible with the conventional gasification processes in terms of syngas quality and overall process efficiency. Aspen Plus™ has also been utilized for the simulation of proposed downstream processes needed for the treatment of syngas to remove contaminants such as tars and trace species. Another downstream process studied and optimized is the biodegradation of phenol absorbed in the wastewater streams originating in the syngas wet treatment units. Samples of lignite from Pakistan and petcoke from Italy have been experimentally studied for their pyrolysis and combustion characteristics using thermogravimetric analyses. These fuels and their mixture exhibit a high potential to be used in the gasification process to produce power or synthesis chemicals. Their kinetic behavior is measured, analyzed using the Arrhenius law, and compared, with the aim to provide kinetic data helpful for pyrolysis and gasification process development.Considerato l’attuale divario e le future tendenze dell'offerta e della domanda di energia nel mondo, la minaccia degli impatti dovuti alle crescenti emissioni di gas serra e l'attuale diffusione delle fonti di energia rinnovabili e sostenibili, l'uso responsabile ed efficiente dei combustibili fossili rappresenta oggi una delle principali priorità per la comunità industriale e scientifica. Alla luce di ciò, lo sviluppo e l'ottimizzazione di efficienti sistemi di gassificazione e di processi ausiliari è il principale obiettivo di questo lavoro di tesi. Esso è stato sviluppato secondo un approccio sia sperimentale che di tipo simulation-based. Aspen Plus™ è stato impiegato come strumento di simulazione di base per la modellazione, l'analisi e il confronto di tre nuovi sistemi di gassificazione indiretti. Sono stati dunque sviluppati e simulati tre schemi di processo di gassificazione indiretti originali. Questi schemi sembrano essere compatibili con i processi di gassificazione convenzionali in termini sia di qualità del syngas e che dell'efficienza complessiva del processo. Aspen Plus™ è stato anche utilizzato per la simulazione di processi a valle richiesti per il trattamento del syngas allo scopo di rimuovere contaminanti come catrami ed elementi presenti in tracce. In aggiunta, un altro trattamento studiato e dunque ottimizzato è stato quello di biodegradazione del fenolo che è presente nelle acque reflue prodotte dai trattamenti di lavaggio ad umido del syngas. In aggiunta, l'utilizzo nella gassificazione di materie prime di bassa qualità come la lignite e coke di petrolio è stato considerato. Entrambi questi combustibili sono legati a processi di combustione poveri, sono altamente inquinanti anche se sono relativamente economici rispetto ad altre materie prime quali carbone bituminoso e oli di fornace. Sono stati sottoposti a test sperimentali campioni di lignite provenienti dal Pakistan e coke di petrolio italiano specialmente per quanto riguarda le loro proprietà in regime di pirolisi e combustione. I test sono stati condotti mediante analisi termogravimetrica. Questi combustibili e le loro miscele mostrano un alto potenziale d’uso nel processo di gassificazione per produrre energia o dare sintesi. Il loro comportamento cinetico è stato dunque analizzato mediante un approccio secondo legge di Arrhenius e infine confrontato con lo scopo di fornire dati cinetici utili allo sviluppo del processo di pirolisi e di gassificazione

Coal gasification by indirect heating in a single moving bed reactor: Process development & simulation

In this work, the development and simulation of a new coal gasification process with indirect heat supply is performed. In this way, the need of pure oxygen production as in a conventional gasification process is avoided. The feasibility and energetic self-sufficiency of the proposed processes are addressed. To avoid the need of Air Separation Unit, the heat required by gasification reactions is supplied by the combustion flue gases, and transferred to the reacting mixture through a bayonet heat exchanger installed inside the gasifier. Two alternatives for the flue gas generation have been investigated and compared. The proposed processes are modeled using chemical kinetics validated on experimental gasification data by means of a standard process simulator (Aspen PlusTM), integrated with a spreadsheet for the modeling of a special type of heat exchanger. Simulation results are presented and discussed for proposed integrated process schemes. It is shown that they do not need external energy supply and ensure overall efficiencies comparable to conventional processes while producing syngas with lower content of carbon dioxide