Synthesis Of High-active Calcium-based Sorbent And Its CO₂ Capture And HCl Removal Performance

The increasing CO₂ emissions caused by power plant and mankind activities have become a huge problem,and it is an urgent problem for all countries in the world.Calcium looping has been regarded as a common technology for CO₂ post-combustion capture,and the sorbents have advantages in wide resource and low price.However,the CO₂ capture capacities of natural sorbents decrease rapidly with the increase of cycle number.Therefore,how to improve the CO₂ capture performance of the sorbents is one of the main problems of calcium looping.This paper focuses on this problem and studies on synthesizing the high-active calcium-based sorbent and its CO₂ capture performance.A novel method that CaO modified with the by-product of biodiesel?BPB?by the combustion was proposed to improve its CO₂ capture capacity.The effects of preparation conditions on CO₂ capture performance of BPB modified sorbent had been studied,and the optimum conditions have been obtained.CO₂ capture capacity of BPB modified CaO retains 0.5 g CO₂/g sorbent after 20 cycles.This method is beneficial to the CO₂ capture performances of CaO and calcium-based waste?carbide slag?.Moreover,the cyclic CO₂ capture capacity of the deactivated CaO is significantly reactivated after the by-product of biodiesel modification.Compared to others organic solvent modified sorbents in the references,BPB modified CaO has better CO₂ capture capacity and cyclic stability.According to microstructure analysis,BPB modified CaO exhibits porous structure,especially the pores in the range of 20-1 00nm in diameter,which is useful for CO₂ capture.The main mechanism of BPB modified method to improve the CO₂ capture performance of CaO is pore-forming in the combustion process.This paper proposes the absorbent cotton used as a template,calcium acetate and aluminium nitrate used as carrier materials,to synthesize modified calcium-based sorbent.The effect of synthesis route of synthetic sorbent on CO₂ capture capacity had been discussed and concluded the optimum preparation conditions.The modified sorbent achieves the highest CO₂ capture capacity when the mass ratio of CaO/Al₂O₃ is 80/20 in the preparation process of the synthetic sorbent,and the CO₂ uptake exhibits 0.48 g?CO₂?/g?sorbent?after 10 cycles under 70%CO₂/30%N2 calcination condition.The synthetic sorbent has the porous structure with many hollow tubes just like the pyrolyzed absorbent cotton,and the tube wall is united with CaO and Cai2Ali4O33.Ca₁₂Al₁₄O₃₃ has strong anti-sintering capacity,and CO₂ can diffuse into the surfaces of modified sorbent by all directions,which is beneficial to CO₂ capture.The modified sorbent has high specific surface area and pore volume,and then the CO₂ capture performance of synthetic sorbent is improved.To solve the escape problem of calcium-based sorbent because of particle abrasion in the fluidized bed,the influences of binder,proppant and pore forming material on CO₂ capture capacity of sorbents were studied in this paper.And porous Al₂O₃ power is firstly used as the proppant.It is shown that PVP is the optimum binder and the addition ratio is 2%.High-Aluminium cement and porous Al₂O₃ power are suitable for pelletization,and the addition ratio is 10%.The pelletization sample using porous Al₂O₃ power showes higher CO₂ capture capacity than that using high-aluminium cement.The CO₂ uptake of the pelleted sorbent is 0.23 g?CO₂?/g?sorbent?after 10 cycles,which is 1.35 times higher than high-aluminium cement.Microcrystalline cellulose as the pore forming material can effectively improve the CO₂ capture capacity of sorbent,but the compressive strength is slightly reduced.The compressive strength of sample pelleted by porous Al₂O₃ power is higher than that of pelleted by high-Aluminium cement.Although the specific surface area of sample pelleted by porous Al₂O₃ power is not very high,the pore volume is higher than sample pelleted by high-Aluminium cement,especially the accumulated pore volume of pores over 30nm in diameter.The HCl capture performances of BPB modified CaO,Mg-stabilized carbide slag?MSCS?and template modified calcium-based sorbent MAC-Al-CaO which had experienced repetitive CO₂ capture cycles using calcium looping were studied.The effects of the chlorination temperature,the number of CO₂ capture cycles,the HCl concentration and the presence of CO₂ in the chlorination atmosphere on HCl removal by the cycled sorbents from calcium looping cycles were discussed.MAC-Al-CaO modified by template method achieves the highest HCl capture capacity due to its developed pore structure.MgO and Ca₁₂Al₁₄O₃₃ are inert supports,and HCl capture capacities of the cycled MSCS and MAC-Al-CaO drop slightly with the number of CO₂ capture cycles.The cycled sorbents reach the highest HCl capture capacity at 750?.The presence of CO₂ leads to a reduction in the HCl capture capacity of the cycled sorbents.And the HCl capture capacities of the sorbents increase with increasing the HCl concentration in the chlorination atmosphere.