Paola Ammendola

Hydrogen production by catalytic methane decomposition and catalyst regeneration by oxygen mixtures in fluidised and fixed bed reactors

In the present paper, the Thermo-Catalytic Decomposition (TCD) of methane has been investigated in a laboratory-scale bubbling fluidised bed reactor using copper dispersed on γ-alumina as a catalyst. The usefulness of a fluidised bed operation instead of a fixed bed operation has been assessed in terms of methane-to-hydrogen conversion and the amount of carbon accumulated on the catalyst. The possibility of carrying out a two-stage operation for hydrogen production from methane TCD in fluidised bed reactors, which consists of operating the fluidised bed as a reactor for methane decomposition until a defined catalyst deactivation degree is achieved and then operating the fluidised bed as a combustor for catalyst regeneration by carbon oxidation, has also been investigated. The typical behaviours of fluidised bed reactors contribute to the opportunity to adopt such a regeneration strategy on the basis of the performances obtained with catalyst regeneration by means of carbon combustion in fixed and fluidised bed reactors.

Controlling thermal properties of dense gas fluidized beds for concentrated solar power by internal and external solids circulation

Fluidization technology displays a long record of success stories, mostly related to applications to thermal and thermochemical processes, which are fostering extension to novel and relatively unexplored fields. Application of fluidized beds to collection and thermal storage of solar radiation in Concentrated Solar Power (CSP) is one of the most promising, a field which poses challenging issues and great opportunities to fluidization scientists and technologists. The potential of this growing field calls for reconsideration of some of the typical design and operation guidelines and criteria, with the goal of exploiting the inherently good thermal performances of gas-fluidized beds at their best. “Creative” and non-conventional design and operation of fluidized beds, like those based on internal and external solids circulation, may be beneficial to the enhancement of thermal diffusivity and surface-to-bed heat transfer, improving the potential for application in the very demanding context of CSP with thermal energy storage. This paper investigated: i) a fluidized bed configuration with an uneven distribution of the fluidizing gas to promote vortices in the scale of bed height (internal solids circulation); ii) a dual fluidized bed configuration characterized by an external solids circulation achieved by the operation of a riser and a bubbling fluidized bed. CFD simulations showed the hydrodynamics conditions under which the internal solids circulation was established. The hydrodynamic characterization of the external solids circulation was achieved by an experimental study carried out with different cold models. The dual fluidized bed system was optimized in terms of operating conditions and geometrical features of the connections between two fluidized beds.Fluidization technology displays a long record of success stories, mostly related to applications to thermal and thermochemical processes, which are fostering extension to novel and relatively unexplored fields. Application of fluidized beds to collection and thermal storage of solar radiation in Concentrated Solar Power (CSP) is one of the most promising, a field which poses challenging issues and great opportunities to fluidization scientists and technologists. The potential of this growing field calls for reconsideration of some of the typical design and operation guidelines and criteria, with the goal of exploiting the inherently good thermal performances of gas-fluidized beds at their best. “Creative” and non-conventional design and operation of fluidized beds, like those based on internal and external solids circulation, may be beneficial to the enhancement of thermal diffusivity and surface-to-bed heat transfer, improving the potential for application in the very demanding context of CSP with therm...