Kinetics of oxidation of CaS particles in the regime of high SO2 release

Citation
G. Marban et al., Kinetics of oxidation of CaS particles in the regime of high SO2 release, CHEM ENG SC, 54(4), 1999, pp. 495-506
Citations number
34
Categorie Soggetti
Chemical Engineering
Journal title
CHEMICAL ENGINEERING SCIENCE
ISSN journal
00092509 → ACNP
Volume
54
Issue
4
Year of publication
1999
Pages
495 - 506
Database
ISI
SICI code
0009-2509(199902)54:4<495:KOOOCP>2.0.ZU;2-L
Abstract
Oxidation experiments of pure CaS particles (18.6 mu m size) in the regime of high SO2 release (890 degrees C < T < 1175 degrees C at P-O2,P-O = 0.21 atm) were carried out in a thermogravimetric analyser. Additionally, the ev olution of SO2 liberation during oxidation was followed by experiments carr ied out in a quartz microreactor. SEM-EDX analyses of oxidised CaS pellets allowed the structural changes during oxidation to be disclosed. Air oxidat ion of the CaS particles used in this work, consisting of agglomerates of C aS crystallites, takes place via oxidation of the CaS surfaces to CaSO4. Th e product so formed rapidly reacts with the contiguous CaS via a solid-soli d reaction to form small CaO grains of a rounded shape. These grains are su lphated by the SO2 released in the solid-solid reaction, thus growing in si ze and eventually plugging the pore structure of the particle. The growing of the CaO grains involves crystallisation towards a cubic-like shaped CaSO 4 phase. A fraction of the SO2 formed via the solid-solid reaction is relea sed to the bulk gas phase during the first stage of reaction, before closur e of the pore network of the particles takes place. Afterwards, the gases d iffuse inside the particles via a solid-state mechanism. A kinetic model fo r CaS oxidation, which takes into account the above consideration, was deve loped. (C) 1999 Elsevier Science Ltd. All rights reserved.