Scale-up Production And Pelletization Of CaO-based Sorbents For CO₂ Capture

CO₂,one of the main components of greenhouse gases,increased rapidly because of the growing use of fossil fuels and has accelerated global warming and climate change.CaO-based solid sorbents could efficiently separate and removal CO₂from high-temperature flue gas.Herein,the scale-up production and pelletization of CaO-based sorbents were carried out.In addition,the effects of technological conditions on CO₂sorption performance,texture properties and mechanical reliabilities of sorbents were also investigated.In this work,Zr-doped CaO-based sorbents were synthesized at kilograms per batch using a simple and facile sol-gel method,in which the CO₂adsorption performance and cycling stability were significantly improved in consequence of the incorporation of Zr component.Technological conditions of the scale-up production were optimized based on 300 g samples prepared per batch,including precursor concentration of calcium,amount of citric acid,gelification temperature and time,which played important roles in the sol-gel preparation process.The factors affecting the carbonation/calcination process of sorbent（volume fraction of CO₂and calcination temperature）were also investigated.A 4-kg CaO-based sorbents,with appropriate nano-size CaO crystallite,loose and porous structure and uniform distribution of Ca and Zr,have been synthesized successfully at one batch,which exhibited a final CO₂adsorption capacity of 5.9 mol-CO₂/kg-ads under a lower volume fraction of CO₂（15%）and a higher calcination temperature（900°C）after 45adsorption/desorption cycles.A series of Al-doped CaO-based sorbents were prepared via co-precipitation methods using a 50-liter glass kettle,in which Al serves as an inert support and can effectively obstruct the sintering of adsorbents,achieving an improvement on thermal stability.Preparation conditions of the mass-produced sorbents were optimized on 400g powder prepared per batch,including Ca/Al molar ratio,precursor concentration of calcium,coprecipitating temperature and time,which act critical roles in co-precipitation process.Scale-up production of the CaO-based adsorbents were implemented step by step（400 g,1500 g and 6000 g）using the optimum preparation conditions through a 200-liter enamel-lined reactor.In addition,pelletization of the kilogram-scale produced sorbents were also executed utilizing extrusion-spheronized granulation methods.And a typical binder material（pseudo boehmite,10 wt%）with peptizing agent（nitric acid,10 wt%）was incorporated to ameliorate nano-porous structure and mechanical reliability of sorbent pellets.The sorbent pellets,fabricated using the kg-scale produced powder,exhibit a final CO₂adsorption capacity of 5.4mol-CO₂/kg-ads and great anti-attrition resistance（0.14 wt%/h）after 30adsorption/desorption cycles in fluid bed.