M. Pineda et al., Performance of zinc oxide based sorbents for hot coal gas desulfurization in multicycle tests in a fixed-bed reactor, FUEL, 79(8), 2000, pp. 885-895
Zinc oxide based sorbents doped with CuO or TiO2 have been studied in 5-cyc
les tests in a fixed-bed reactor, as regenerable sorbents for desulfurizati
on of coal gas at high temperature (600 degrees C). TiO2 increases the stab
ility of ZnO and zinc ferrite, under the reducing power of coal gas, and th
e sorbent porosity. However, it also increases the H2S concentration in the
outlet gas before breakthrough, and the sorbent reactivity is not substant
ially modified. in addition, the presence of TiO2 makes more difficult the
formation of mixed oxides and the behaviour of the fresh sorbents is usuall
y different than that of the first regenerated samples. The presence of CuO
increases sorbent reactivity and the efficiency for the first 1-3 cycles i
s excellent. Unfortunately, neither CuO nor TiO2 can prevent the excessive
decay in performance of the studied sorbents as the number of cycles increa
ses. This feature appears correlated, not with structural changes as shown
by XRD, but with a decrease of the sorbent porosity due to progressive ther
mal sintering. The presence of iron oxides in the sorbent composition cause
s different behaviour with the appearance, after breakthrough, of COS in su
lfidation and H2S and elemental sulphur in regeneration. (C) 2000 Elsevier
Science Ltd. All rights reserved.