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Reimpiego di residui idratati della combustione del carbone in letto fluido come materiali desolforanti a base di ettringite
No full textFluidized bed combustion wastes, whose disposal and utilization is made difficult by their high quantity and low quality, can be conveniently re-introduced in the reactor and employed as desulphurizing agents, when submitted to a previous controlled hydration treatment. It has been found that ettringite, one of the hydration products, can give an important contribution to the desulphurizing ability of such hydrated wastes. Sulphation tests, made in a laboratory scale fluidized bed reactor, have shown that the desulphurizing action of a synthetic ettringite is better than that of a commercial limestone: the relative activity index is always favourable to ettringite and it is varying from 4.7 to 1.9, respectively between the start and the end of the sulphation tests. During hydration tests, carried out at 70°C up to 4 days, on industrial fluidized bed combustion wastes, ettringite has been obtained as main hydration product. Conversion degrees towards ettringite, comprised between 0.35 and 1.00, have been reache
Char-wall Interaction and Properties of Slag Waste in Entrained-Flow Gasification of coal
No full textThe aim of this paper is to investigate the properties of solid wastes coming from an industrial-scale pressurized
entrained-flow gasifier, by means of a combination of techniques: elemental, granulometric and X-ray diffraction
analyses, scanning electron microscopy and energy dispersive X-ray analysis. The results are critically discussed in
the light of the different regimes of char-slag micromechanical interaction and of the different phases that are
established in the gasification chamber. The discussion allows to give useful insights concerning the properties and
partitioning of carbon among the three main sources (coarse slag, slag fines, fly ash) of solid residues coming from
the gasifier: in particular, differences between coarse slag and slag fines are highlighted, though these wastes are
generated from the same main-stream. Furthermore, it is observed that residual carbon in slag granules is present in
a segregated embedded form, while slag fines are composed of both porous (high-carbon) and compact (low-carbon)
material. Altogether, the properties of the three residues are consistent with a mechanistic framework of the bulk-towall
transfer and partitioning of solids during entrained-flow gasification of coal developed in a recently-published
theoretical paper
Fluidized Bed Combustion Wastes as a Potential Source of Ettringite for Recycling Purposes – A Hydration Study
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Use of atmospheric fluidised bed combustion and desulphurisation residues for the manufacture of non traditional binders.
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Impiego di ettringite come materiale desolforante e sua generazione per idratazione di residui della combustione in letto fluido
No full textCalcium sulphoaluminate cements made from fluidized bed combustion wastes
No full textWastes generated in a bench-scale atmospheric fluidized bed combustor, using two different coals and a high-lime limestone, sorbent, were employed as raw materials for the synthesis of calcium sulphoaluminate (4 CaO•3 Al2O3•SO3)-based cements, which can be utilized for a wide range of applications. Raw mixes containing the bed material were heated in an electric oven in the temperature range 1000°–1200°C. The best results in terms of reactants conversion, and selectivity towards 4 CaO•3 Al2O3•SO3 were obtained at 1200°C with the addition of an external source of alumina which was required to avoid melting phenomena or integrate the Al2O3 content, necessary for the 4 CaO•3 Al2O3•SO3 formation
Il recupero in qualità di fonti di materie prime dei residui della combustione desolforante del carbone in letto fluido
No full textTHE INFLUENCE OF THE HYDRATION TIME ON SPENT SORBENTS REACTIVATION FOR FLUIDIZED -BED DESULPHURIZATION PROCESSES. PROCEEDINGS OF COMBUSTION AND SUSTAINABLE DEVELOPMENT
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