Attrition of Calcining Limestones in Circulating Fluidized-Bed Systems

Abstract

Limestone attrition in circulating fluidized-bed combustors (CFBCs) has received limited attention. Although there are a number of early studies on attrition in bubbling-bed systems, most current studies focus on simultaneous calcination and sulfation. However, this subject is increasing in importance as CO 2 looping cycles are proposed. CO 2 looping cycles involve repeatedly calcining the CaCO 3 component of the limestone to drive off a pure stream of CO 2 for storage or sequestration. Here, we have looked at five limestones from across Canada, the United States, and Mexico to determine the extent of their attrition under calcining conditions in fluidized-bed systems. This work shows that attrition varies very significantly from limestone to limestone, and even among different batches. It is clear, therefore, that each limestone will have to be carefully categorized to determine its potential for use in such cycles. Also, since limestones crush differently, even those limestones that are double-sieved may have very different initial size distributions. This will affect the results seen in tests carried out under realistic conditions. This work shows that most of the material loss in multiple calcination/ carbonation cycles is in the first few cycles, and that even a very low level of sulfation can be a very effective means of reducing that material loss.

The calcium looping cycle for CO2 capture from power generation, cement manufacture and hydrogen production

“…The reactor used is the adaptation of a system previously used by Anthony and co-workers (Salvador et al, 2003;Abanades et al, 2004;Jia et al, 2007); reviews by Anthony and coworkers (Anthony and Granatstein, 2001;Anthony et al, 2007;Anthony, 2008). Salvador et al (2003) and Abanades et al (2004) Cadomin and Havelock (both Canadian) limestones with most of the attrition occurring over the first couple of calcinations; the authors also reported a marked decrease in attrition rates of partially sulphated sorbent at the expense of sorbent reactivity, though sulphation extent would have to be carefully controlled to limit deactivation of the sorbent for CO 2 capture ).…”

Investigation of SO2 Capture in a Circulating Fluidized Bed Carbonator of a Ca Looping Cycle

“…Different trends have been reported in the literature. Some authors 29 have found that the presence of SO2…”

HCl absorption by CaO/Ca 3 Al 2 O 6 sorbent from CO 2 capture cycles using calcium looping

“…Therefore, as the sorbent consumption decreases, both equipment cost and energy consumption would be reduced significantly. Besides, as opposed to the fragile natural calcium-based sorbents [54], Pacciani et al [55] found that the formation of calcium aluminates due to the reaction of CaO and Al 2 O 3 could strengthen the synthetic sorbent structure. Thus the synthetic CO 2 sorbent may mitigate the severe attrition problem under the fluidized bed operation conditions.…”