In Situ Desulphurisation in Fluidised Bed Combustors

The possibility of performing in situ desulphurisation during fluidised bed combustion is one of the main advantages of this technology for energy production. The process is presented in its general characteristics and, with specific reference to limestone-based sorbent particles, the main attrition and fragmentation phenomena are discussed. Then follows a more detailed description of the reactive process which involves the capture of sulphur dioxide by calcium oxide. First of all, the grain model is presented, with the identification of the main degrees of conversion, the expressions for the sulphation rate, and the constitutive equations. Then we focus on the random pore model and its main equations. Finally, the concepts of fractal-like dynamics for the study of heterogeneous processes are presented, then applied to the case of the sulphation reaction, with the introduction of a time-dependent expression for the diffusion coefficient.