(24d) High Temperature CO2 Capture with Modified CaO-Based Pellet Sorbents

High temperature CO₂ capture with modified
CaO-based pellet sorbents

Yinghai Wu,
Ian He, Vasilije Manovic
and Edward J. Anthony

CanmetENERGY, Natural Resources
Canada

K1A1M1

Abstract

It is
generally accepted that increasing greenhouse gases, in particular CO₂,
contribute to global warming. Currently, one third of all anthropogenic CO₂
emissions come from fossil fuel combustion for power generation. CO₂
capture from large stationary sources is therefore necessary to stabilize the
atmospheric concentration of CO₂ in order to prevent more severe
climate change effects in the future. CaO-based
sorbent looping cycles, which utilises reversible carbonation and calcination
reactions, offer a promising technology to separate CO₂ from flue or
syngas to produce a high purity CO₂ stream
suitable for sequestration or use and in the case of syngas
application, for sorption enhanced H₂ production. Naturally occurring
limestones (mostly calcitic)
have so far been the subject of intensive research. However, natural sorbents
lose their CO₂ carrying capacity quickly with increasing numbers of
reaction cycles. Hence, hydration of the spent sorbents has been proposed as a
method to recover the lost carrying capacity, but the resulting reactivated
sorbents tend to be fragile and are unsuitable for fluidized bed conditions. To
overcome this drawback with natural sorbents, a novel method using pelletization
of the sorbents is proposed here. In this study, the performance of the
pelletized sorbents was tested in a small bubbling fluidized bed reactor. Calcium
aluminate cements and bentonite
were investigated as different types of binders for pelletization. It was shown
that pelletized sorbent can maintain their capacity over many cycles. The
effect of sintering and attrition of the pellet sorbents are also discussed and
the morphology changes of these sorbents during carbonation and calcination
cycles are examined by SEM.