Effect of Sodium Bromide on CaO-Based Sorbents Derived from Three Kinds of Sources for CO₂ Capture

Abstract

The calcium looping (CaL), which applies carbonation/calcination cyclic reactions of a CaO sorbent, has received extensive attention for postcombustion CO 2 capture. However, as the number of cyclic reactions increased, the capture efficiency of regenerated CaO decreased rapidly. Sodium doping was proposed for modification of a CaO sorbent, but there was little research on whether sodium doping had a good effect on different kinds of sorbents. In this paper, three different kinds of calcium-based sorbents, i.e., CaCO 3 , dolomite, and SG-CaO, were modified by NaBr to explore the effect of sodium on CO 2 capture performance. The results showed that the modification effects of sodium on three kinds of precursors were different. For CaCO 3 , the modification effect of sodium doping was the best. After 50 cycles, the sorption capacity of CaO/NaBr was over 3.5 times that of an unmodified sorbent; for dolomite, sodium had a moderate effect during initial cycles and then showed obvious improvement in the stability of the sorbent, the sorption capacity of the modified dolomite increased by over 30% after 50 cycles; for the SG-CaO, sodium had a negative effect, the sorption capacity of the modified sorbent decreased by about 30% after 50 cycles. When the atmosphere contained SO 2 , the doping of an alkali metal also showed a certain effect.

Inhibitory Effect of Na and Al on the Sintering Phenomenon of Calcium-Based Sorbents during Calcium Looping

“…Therefore, the CO 2 capture performance of the 70Ca−30Al−Na sorbent was less effective after a 64 h cycle experiment. However, despite this, compared with the pure CaO (the carbon capture capacity was reduced to 0.05 g of CO 2 /g of sorbent after 50 cycles), 29 the CO 2 capture performance of the 70Ca−30Al− Na sorbent still had advantages.…”

“…A small amount of Na can obviously slow down the sintering of CaO and increase the pores of the sorbent, 29 thus promoting more CO 2 through the pores to come in contact with CaO for adsorption reaction. To better explain the effect of Na and Al on the cyclic CO 2 capture performance of the sorbent, the effective CaO conversion rate of the modified sorbents with different Al 2 O 3 doping ratios in the presence of a small amount of Na was investigated, and the results are shown in Figure 4.…”

“…However, as one of the most basic sample preparation methods, the mechanical mixing method has the disadvantages of uneven particle mixing and severe abrasion, which affect the cyclic CO 2 capture performance of modified sorbents. In previous studies, it was found that NaBr can greatly increase the carbon capture capacity of calcium-based sorbents . However, the calcium-based sorbent directly modified with NaBr has poor mechanical properties and cannot meet the requirements of fluidized-bed reactors.…”

“…In previous studies, it was found that NaBr can greatly increase the carbon capture capacity of calcium-based sorbents. 29 However, the calcium-based sorbent directly modified with NaBr has poor mechanical properties and cannot meet the requirements of fluidized-bed reactors.…”

CO2 capture using solid sorbents: Fundamental aspects, mechanistic insights and recent advances

“…Alkali metal halides (e.g. NaCl or KCl) appear to enhance sintering more than do alkali metal carbonates [306], [340], [341]. Al-Jeboori et al [342], [343] Generally, the immobilization of dopants in the sorbent is difficult and the choice of dopants should thus consider the possibility of the formation of harmful by-products (e.g.…”