This thesis focuses on the study of an innovative configuration of WtE plant, based on a reheated steam cycle. The preliminary design of the boilers has been carried out by considering both the on-design and off-design working conditions. For the sake of comparison, a traditional waste-to-energy incineration plant without reheat has also been designed and is used as a benchmark in the comparison of costs and efficiency. The design has been simulated and validated using the commercial ThermoFlow® software. The complexity arising out of the introduction of reheat section in the boiler has been overcome by the innovative concept of Gas Quenching, which makes possible the manufacturing of the critical sections of the boiler, namely Superheater and Reheater (due to the excessive tendency of corrosion) based on the use of conventional materials and techniques. Both the considered plants are large-size grate-based three-line installations, with combustion power of 200 MWth. The design of each boiler has been made in order to achieve the desired steam outlet temperature of 450°C at the outlet of both the superheater and reheater at all conditions of loads. The performances were evaluated at part load conditions ensuring to reach the same operational parameters for optimum efficiency. After the preliminary design of the two types of boiler, the associated investment costs for WtE plants comprising three incineration lines (i.e. plant size of 200 MWLHV) were evaluated, by considering also the different sizing of the steam cycles and of the other equipment. Therefore, the costs of electricity for the conventional and the innovative configurations have been evaluated as function of the gate fee. The innovative configuration appears to be superior not only in terms of energy efficiency, but also from the economic point of view: at a gate fee of 70 € per ton of treated waste, the innovative configuration achieves a cost of electricity of 45.62 € per MWhe, which compares with the 51.45 € per MWhe of the conventional configuration. Furthermore, from an environmental point of view, the extra electricity generated by the innovative configuration replaces the burden of fossil fuel fired power plants to compensate for the reduced power generated by the traditional power plant, thus contributing to the reduction of Green House Gas (GHG) emissions resulting from the production and consumption of fossil fuels.
Questa tesi si concentra sullo studio di una configurazione innovativa di impianto WtE, basato su un ciclo a vapore risurriscaldato. È stato effettuato il progetto preliminare delle caldaie considerando sia le condizioni di lavoro on-design che off-design. Come termine di confronto è stato considerato un impianto WtE convenzionale senza risurriscaldamento, progettato con le medesime metodologie e con le stesse assunzioni dell’impianto innovativo. I due progetti sono stati simulati e validati utilizzando il software commerciale ThermFlow®. La complessità derivante dall'introduzione della sezione di risurriscaldamento in caldaia è stata superata introducendo l’innovativo concetto del “Gas Quench”, che permette la realizzazione delle sezioni critiche della caldaia, cioè surriscaldatore e risurriscaldatore (a causa dell'eccessiva tendenza alla corrosione), utilizzando materiali e tecniche convenzionali. Entrambe gli impianti considerati sono installazioni di grande taglia, basate su tre linee di trattamento, con combustori a griglia, potenza di combustione complessiva di 200 MWTH e un ciclo a vapore comune. La progettazione di ogni caldaia è stata realizzata per ottenere la temperatura del vapore prodotto di 450 °C sia all'uscita del surriscaldatore che del risurriscaldatore, in ogni condizione di carico. Le prestazioni sono state valutate a condizioni di carico parziale per assicurare il raggiungimento degli stessi parametri operativi per un'efficienza ottimale. Dopo la progettazione preliminare dei due tipi di caldaia, i costi di investimento associati ai due impianti WtE sono stati valutati considerando anche il diverso dimensionamento dei cicli a vapore e delle altre apparecchiature. Pertanto, i costi di elettricità per le configurazioni convenzionali e innovative sono stati calcolati in funzione della tariffa di conferimento. La configurazione innovativa sembra essere superiore non solo in termini di efficienza energetica, ma anche dal punto di vista economico: alla tariffa di conferimento di 70 € per tonnellata di rifiuti trattati, la configurazione innovativa raggiunge un costo dell’elettricità di 45.62 € per MegaWattora, che si confronta con il costo di 51.45 € per MegaWattora della configurazione convenzionale. Inoltre, da un punto di vista ambientale, l'energia elettrica addizionale generata dalla configurazione innovativa sostituisce elettricità altrimenti prodotta da centrali elettriche a combustibili fossili, così contribuendo alla riduzione delle emissioni di gas serra derivanti dalla produzione e dall’uso di combustibili fossili.
Innovative boiler design for waste-to-energy incinerator with reheat for optimum design and off-design performance
SRIDHARAN, SRIRAM
2016/2017
Abstract
This thesis focuses on the study of an innovative configuration of WtE plant, based on a reheated steam cycle. The preliminary design of the boilers has been carried out by considering both the on-design and off-design working conditions. For the sake of comparison, a traditional waste-to-energy incineration plant without reheat has also been designed and is used as a benchmark in the comparison of costs and efficiency. The design has been simulated and validated using the commercial ThermoFlow® software. The complexity arising out of the introduction of reheat section in the boiler has been overcome by the innovative concept of Gas Quenching, which makes possible the manufacturing of the critical sections of the boiler, namely Superheater and Reheater (due to the excessive tendency of corrosion) based on the use of conventional materials and techniques. Both the considered plants are large-size grate-based three-line installations, with combustion power of 200 MWth. The design of each boiler has been made in order to achieve the desired steam outlet temperature of 450°C at the outlet of both the superheater and reheater at all conditions of loads. The performances were evaluated at part load conditions ensuring to reach the same operational parameters for optimum efficiency. After the preliminary design of the two types of boiler, the associated investment costs for WtE plants comprising three incineration lines (i.e. plant size of 200 MWLHV) were evaluated, by considering also the different sizing of the steam cycles and of the other equipment. Therefore, the costs of electricity for the conventional and the innovative configurations have been evaluated as function of the gate fee. The innovative configuration appears to be superior not only in terms of energy efficiency, but also from the economic point of view: at a gate fee of 70 € per ton of treated waste, the innovative configuration achieves a cost of electricity of 45.62 € per MWhe, which compares with the 51.45 € per MWhe of the conventional configuration. Furthermore, from an environmental point of view, the extra electricity generated by the innovative configuration replaces the burden of fossil fuel fired power plants to compensate for the reduced power generated by the traditional power plant, thus contributing to the reduction of Green House Gas (GHG) emissions resulting from the production and consumption of fossil fuels.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/138829