Sulphation of limestones in a fluidized bed combustor: The relationship between particle attrition and microstructure

Authors

  • Fabrizio Scala,

    1. Istituto di Ricerche sulla Combustione, CNR, Piazzale Tecchio 80, 80125 Napoli, Italy
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  • Fabio Montagnaro,

    1. Dipartimento di Chimica, Università degli Studi di Napoli Federico II, Complesso Universitario del Monte di Sant'Angelo, 80126 Napoli, Italy
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  • Piero Salatino

    Corresponding author
    1. Dipartimento di Ingegneria Chimica, Università degli Studi di Napoli Federico II, Piazzale Tecchio 80, 80125 Napoli, Italy
    • Dipartimento di Ingegneria Chimica, Università degli Studi di Napoli Federico II, Piazzale Tecchio 80, 80125 Napoli, Italy.
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Abstract

Sulphation of two limestones in a fluidized bed combustor has been investigated. One limestone (coarse-grained) was characterized by a significant population of relatively large pores after calcination; the other (fine-grained) presented a finer and fairly unimodal pore size distribution. Differences in the microstructure were reflected by different thickness of the sulphate shell formed upon sulphation and ultimate calcium conversion degree. Particle attrition/fragmentation were fairly small under moderately bubbling fluidization conditions. Fragmentation upon impact was significant. The fine-grained limestone, characterized by a thinner sulphate shell, was more susceptible to fragmentation than the other. Particle fragmentation discloses unreacted CaO enabling secondary sulphation of exhausted particles.

Abstract

On a étudié la sulfatation de deux calcaires dans un combusteur à lit fluidisé. Un calcaire (à grains épais) a été caractérisé par une population significative de pores relativement larges après calcination; l'autre (à grains fins) présente une distribution de tailles de pores plus fine et assez unimodale. Les différences de microstructure se reflètent par l'épaisseur différente de la coque de sulphate formée par sulfatation et le degré ultime de conversion du calcium. L'attrition et/ou fragmentation des particules sont relativement faibles dans des conditions de fluidisation par bullage modéré. La fragmentation lors de l'impact est significative. Le calcaire à grains fins, caractérisé par une coque de sulphate plus fine, est davantage sujet à la fragmentation que l'autre. La fragmentation des particules révèle du CaO non réagi permettant la sulfatation secondaire des particules traitées.

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