Steam gasification of tars using a CaO catalyst

Catalytic gasification of three tars from different sources (oil refinery, Petrox; coking, Huachipato; coal gasification, Gasco) was carried out at a laboratory scale fixed bed reactor using CaO as catalyst, obtained by limes tone calcination. Gasification runs were performed keeping constant the tar feed flow rate, as well as the steam concentration. The residence time, ta u, was regulated through the carrier gas (argon) flow. For steam to tar rat ios, R-V(o) (g/g) equal to, or larger than 3.5 and temperatures over 750 de grees C, total conversion to gaseous products was obtained; solid carbon de position was observed at lower values of R-V(o). Gas yields and product dis tribution can be explained and partially predicted by extensive tar charact erization, reported elsewhere. A kinetic model is proposed, which coupled w ith mass balances in a flowing reactor led to an expression of carbon conve rsion to gaseous products as a function of the operating variables, R-V(o) and tau. The data for the catalytic gasification of these tars corroborate the mechanisms proposed at earlier studies of catalytic gasification, using naphthalene as a model compound. (C) 1999 Elsevier Science B.V. All rights reserved.