The impact of calcium sulfate and inert solids accumulation in post-combustion calcium looping systems

Abstract

Postcombustion CO 2 capture by calcium looping (CaL) is being rapidly developed for coal combustion applications. This work discusses the impact of the accumulation of CaSO 4 and other inert solids on CO 2 capture efficiency and the overall CaL process performance. Several process configurations are considered, and the mass and energy balances and an updated carbonator reactor model are solved for each configuration.The minimum fresh sorbent requirements for sustaining a certain level of CO 2 capture efficiency are quantified as well as the effects of an increase in the make-up flow. It was found that the main effect on the CaL process is produced by the sulfur present in the coal fed to the calciner and in the flue gas entering the carbonator. For a typical set of operating conditions it was calculated that the deactivating effect caused by an increase of 0.5% in the sulfur content with respect to a reference coal (low ash content) fed to the calciner is similar to the effect caused by the accumulation of inerts when using a coal with 15% more ash.

Effect of dolomite decomposition under CO2 on its multicycle CO2 capture behaviour under calcium looping conditions

“…The second inconvenient is the progressive deactivation of the sorbent along the successive carb/calc cycles that makes necessary to periodically introduce a fresh limestone makeup into the calciner. CaO deactivation may occur due to the screening effect of external agents such as ash or SO 2 produced during oxycombustion, which leads to the irreversible sulphation of the CaO particles [9,13,19,20]. Yet, deactivation is mostly caused by the drastic loss of surface area of the CaO grains when calcination takes place under high CO 2 partial pressure and high temperatures, which enhances aggregation and subsequent sintering of the nascent CaO nanocrystals during the CaCO 3 /CaO transformation [21].…”

Modelling of the kinetics of sulphation of CaO particles under CaL reactor conditions

“…A recent paper [20] illustrates with mass and energy balances the operational and fuel composition windows that make this synergy possible. SO 2 is produced in the CFBC as well as in the oxy CFB calciner due to the combustion of coal.…”

Economic evaluations of coal-based combustion and gasification power plants with post-combustion CO 2 capture using calcium looping cycle

“…For instance, sorbent make-up rate is a technical parameter having major influence on plant economics. The sorbent used in CaL unit has to be continuously renew due to two important factors: solid attrition caused by high operating temperature which produce the degradation of sorbent capacity to capture CO 2 and sorbent contamination with ash from additional coal used in the calciner [32,33]. As an illustrative example, Fig.…”