Stabilization Of Ca-based CO₂ Sorbents And Application In Fluidized Bed For Cyclic CO₂ Capture

There is an urgent need to propagate carbon capture and storage in order to constrict the global temperature increment within 2°C.With low cost and energy penalty,calcium looping has been demonstrated to be very prospective in industrial carbon capture.However,CaO sorbents are vulnerable to deactivation due to sintering under high temperature,hindering the further industrial propagation.In view of this problem,this work tried to improve sorbent's cyclic stability via the incorporation of inert stabilizers?Al or Si?.Meanwhile,cyclic CO₂ capture in a bench-scale fluidized bed has been investigated.The concisions are as follows:Calcium acetate and aluminum nitrate as precursor,a series of Al stabilized CaO sorbents(CaO-Ca₉Al₆O₁₈)were synthesized with heat drying,freeze drying and spray drying.According to the cyclic test in TGA,SD70?with an active CaO loading of 70 wt.%and prepared by spray drying?showed the best CO₂ capture performance.In detail,this sorbent maintains a high sorption capacity of 0.44 g-CO₂ g-sorbent^-1 at the 30^th cycle and the total CO₂ uptake in 30 cycles is 14.0 g-CO₂ g-sorbent^-1?sorption:650°C,15 vol.%CO₂,30 min;regeneration:850°C,pure N₂,no dwell time?.Moreover,under the severe condition?sorption:650°C,90 vol.%CO₂,5 min;regeneration:950°C,90 vol.%CO₂,no dwell time?,SD70 still maintains 0.33 g-CO₂ g-sorbent^-1 of CO₂ uptake at the 30^thh cycle and 11.9 g-CO₂ g-sorbent^-1 for the total CO₂ uptake in 30 cycles.Calcium acetate and sodium silicate as precursor,a series of Si stabilized CaO sorbents?CaO-Ca₂SiO₄?were prepared with the same method above.The cyclic test in TGA showed that FD90?with an active CaO loading of 90 wt.%and prepared by freeze drying?was the best sorbent.In detail,this sorbent maintains a high sorption capacity of 0.41 g-CO₂ g-sorbent^-1 at the 30^th cycle and the total CO₂ uptake in 30 cycles is 14.0 g-CO₂ g-sorbent^-1?sorption:700°C,15 vol.%CO₂,20 min;regeneration:850°C,pure N₂,5 min?.Under the severe condition?sorption:700°C,15 vol.%CO₂,20 min;regeneration:920°C,pure CO₂,5 min?,FD90 still maintains 0.21 g-CO₂ g-sorbent^-1 of CO₂ uptake at the 30^thh cycle and 8.0 g-CO₂ g-sorbent^-1 for the total CO₂ uptake in 30 cycles.The Euler-Euler two fluid model?TFM?was applied to simulate the fluidization of sorbent particles under room temperature,showing that the flow rate of 1.5 L min^-1 could fluidize the sorbent particles well.According to the cyclic test in the fluidized bed reactor?10 cycles in total?,Al-SD90 and Si-FD90 present much better carbon capture property than the natural lime from Wukuang Corporation,Sichuan.Kinetic analysis indicates that the three sorbents above follow the same“two stage”principle in fluidized bed reactor as in TGA.In terms of the resistance to attrition,the three samples follow the order:Al-SD90>Si-FD90>natural lime.