L. Alonso et al., The performance of some ZnO-based regenerable sorbents in hot coal gas desulfurization long-term tests using graphite as a pore-modifier additive, ENERG FUEL, 15(6), 2001, pp. 1396-1402
In a previous study it was shown that the overall reactivity in thermobalan
ce tests and the efficiency at breakthrough in 2-cycle tests in a fixed bed
reactor of a sorbent used for hot coal gas desulfurization increased subst
antially by the addition of a 5 wt % concentration of graphite during the p
reparation of sorbent ZT(0.8:1). In this paper, the study of the graphite e
ffect as a pore forming additive is extended to other types of sorbents who
se performance is investigated through the sulfidation breakthrough curves
obtained in 20-cycle tests in a fixed bed reactor. Experiments show that th
e efficiency of the studied sorbents, ZFC, ZFT, and ZT, a zinc oxide, and a
zinc ferrite doped with TiO2 or CuO, respectively, are dramatically increa
sed by the addition of a 5 wt % graphite concentration as compared with the
efficiency shown by the same sorbents prepared without graphite. The graph
ite effect is also evidenced by the achievement of a substantial delay of s
palling appearance, a detrimental process consisting in the appearance and
development of a crack network in the extrudate, decreasing the mechanical
strength of the sorbent progressively down to excessively low values, after
enough number of successive sulfidation-regeneration cycles. A first study
trying to recover the reactivity of a sorbent, that became inactive after
20-cycles operation in a fixed bed reactor, by graphite addition is also in
cluded.