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Definition of validated membrane reactor model for 5 kW power output CHP system under different natural gas composition
No full textDefinition of validated membrane reactor model for 5 kW power output CHP system for different natural gas compositions
Full text linkOver the last years, many studies focused on the development of membrane reactors for micro-cogeneration systems based on PEM fuel cells, thanks to its unique feature of separating pure hydrogen. This work deals with (i) the design of a fluidized bed membrane reactor flexible towards different natural gas (NG) qualities and (ii) its integration in PEM based systems of 5 kW power output. Four typical NG compositions from reference European countries have been identified in this study featuring an average condition and three extreme cases. Two different membrane reactor models were developed: a 1D phenomenological model and a quasi-lumped model inside the overall system implemented in Aspen Plus. Results show the importance of taking into account the natural gas composition in the design phase: only assuming the NG with the highest inert content as base case, the target electric efficiency of 39% can be reached for any other case
Recent Progress of the Ca-Cu Technology for Decarbonization of Ammonia, Iron and Steel and Hydrogen Industries
No full textPre-combustion packed bed chemical looping (PCCL) technology for efficient H2-rich gas production processes
Full text linkA novel reactor system is presented and investigated for the production of a hydrogen rich gas stream for power or ammonia production, based on pre-combustion chemical looping (PCCL) technology using dynamically operated packed bed reactors. In this process, the oxygen carrier (OC) is alternately oxidized with a gas mixture of air and steam to produce a H2/N2 product gas stream combining oxidation by air and water-splitting, and subsequently reduced with syngas producing a concentrated CO2 stream. The process is carried out at elevated pressure, but at intermediate temperature (in the range of 600-900 °C), which allows circumventing the extremely high temperatures required in chemical-looping combustion. In addition, the N2/H2 gas stream can be produced at the required composition for ammonia production, rendering this process also competitive with the conventional ammonia production. A preliminary experimental study has been carried out in a 2 kWth packed bed reactor using an iron-based oxygen carrier. The influence of the operating temperature and the initial solid composition during the oxidation cycle on the H2-rich gas yield has been investigated. The complete reduction to pure iron reduces the reactivity of the material due to sintering, whereas a controlled reduction to wüstite (FeO) allows to maintain a higher stability of the material, although the oxygen capacity is decreased.A preliminary thermodynamic assessment of the integrated PCCL plant for power production with natural gas has been carried out reaching an electrical efficiency of 49-51.5% (depending on the plant arrangement) with a carbon capture rate above 95%. The main parameter affecting the plant performance was found to be the steam requirement during the oxidation cycle. The comparison with benchmark technologies has confirmed the potential of the PCCL system
Modelling of 3D-printed catalyst structures : influence of the solid phase on heat transfer performance and steam methane reforming reaction
No full textLAUREA MAGISTRALEIl processo di manifattura additiva, conosciuto come "Additive Manufacturing", promette di offrire un'ampia libertà a livello di design e modellazione di materiale catalitico mediante la produzione di strutture personalizzate. Queste strutture catalitiche innovative possono quindi essere modificate per ottenere proprietà ottimali in termini di quantità di catalizzatore, perdite di carico e trasporto di massa ed energia. In questo studio, vengono proposte 9 strutture come alternativa alla tradizionale configurazione di reattore a letto impaccato, conosciuto anche come "Packed-Bed reactor". Due di esse rappresentano la comune e già studiata configurazione "Log-Pile", mentre le restanti strutture rappresentano una versione migliorata delle prime due già menzionate, grazie all'introduzione di setti porosi che agiscono come miscelatore statico, generando un flusso trasversale. Inoltre, il supporto catalitico è stato studiato come via valida per trasferire energia all'interno delle strutture, tramite conduzione termica.
Studi di fluidodinamica computazionale tramite Open-FOAM sono stati eseguiti sulle strutture stampate in 3D per studiare le interazioni a livello di trasferimento di calore tra fluido e solido, mappando il calore fornito e le perdite di carico ottenute in funzione della conduttività termica del catalizzatore solido.
Si osserva che l'introduzione di deflettori porosi in sinergia con la presenza di un supporto catalitico termicamente conduttivo porta prestazioni ottimali in termini di trasferimento di calore, superando un tradizionale reattore a letto impaccato nella gestione del calore e nella caduta di pressione. Il miglioramento delle prestazioni in termini di calore introdotto si ottiene anche a bassi valori di conducibilità termica del solido, coerenti con i supporti catalitici comunemente adottati come Allumina o Silice.
I risultati sulle strutture sono quindi stati testati tramite l'introduzione della reazione di "Steam Methane Reforming", nella quale si è osservato un aumento della conversione del metano grazie alla migliore distribuzione di calore e un migliore grado di miscelazione.
Mentre simulazioni su scala reale, convalidate dagli esperimenti, devono ancora essere svolte per completare l'analisi, il lavoro attuale illustra il potenziale di queste nuove classi di catalizzatori strutturati per i reattori chimici intensificati.Additive manufacturing promises to unlock large design freedom in designing and shaping catalytic material by means of custom structures. Those novel structures can be altered in order to achieve optimal properties in terms of catalytic holdup, transport properties and pressure drop.
In this modelling study, 9 structures are proposed as an alternative to a common Packed-Bed reactor configuration. Two of them represent the so called Log-Pile configuration, while the remaining structures represent an improved version of the first two already mentioned thanks to the introduction of porous baffles acting as a static mixer, generating cross-flow. Additionally, the catalytic support was studied as a viable way to transfer heat inside the structures by means of solid thermal conduction.
An Open-FOAM Computational Fluid Dynamics study was performed on the 3D-printed structures to investigate the fluid-solid heat transfer interactions by mapping the heat provided and pressure drop obtained as a function of the solid catalyst thermal conductivity.
It is observed that the introduction of porous baffles in synergy with the presence of a thermally conductive catalytic support provides optimal heat transfer performance, outperforming a traditional Packed-Bed in heat management and pressure drop. Moreover, the tested structures were able to perform better than a Packed-Bed also in absence of the conductive catalytic support. Enhancements in heat management are also reached at low values of solid thermal conductivity, which are coherent with the commonly adopted catalytic supports such as Alumina or Silica. This is exemplified by the Steam Methane Reforming reaction test on the structures, which resulted in increased methane conversion thanks to the improved heat and mixing management.
Whilst full scale 3D simulations validated by experiments remain to be assessed, this works shows the potential of the novel 3D-printed structures in terms of heat management, pressure drop and reactants conversion
Real time determination of optimal switching times for a new H2 production process with CO2 capture: a supervised learning approach
Full text linkThe Ca-Cu looping process combines H2 production via reforming of natural gas with inherent CO2 capture, using CaO as CO2 sorbent and a Cu/CuO chemical looping for sorbent regeneration. The process comprises three dynamic stages, conducted sequentially in a packed bed reactor. This thesis addresses the determination of the optimal duration of each stage via a real-time approach. For the purpose, GPR models, a relatively recent method employed in machine learning, are used as soft-sensors.ope
Fluidized bed membrane reactors for water gas shift: mass transfer, hydrodynamics and experimental demonstration
Full text linkFeasibility of a catalytic membrane reactor for ethylene production via oxidative coupling of methane
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