Study On Composite Modification Of CaO-based Sorbent

It's well known that carbon dioxide (CO2) is the main responsible for global warming. Statistics indicate that 33% CO2 in industry comes from high temperature flue gas produced by the combustion of fossil. Therefore, the exploitation of an efficient high temperature CO2 sorbent is very important. As a cheap high temperature CO2 sorbent, CaO widely used in industrial processes, however, it could be sintered easily and had low cycling efficiency. In this work, a composite modified CaO-based sorbent (Code:SMV-CaO) was developed by doping with V2O5 and calcium aluminates cement in CaO. The properties and kinetics of carbonation-regeneration of modified CaO were studied by a fixed bed reactor. The results showed that the optimal doping amount of V2O5 was 2%wt, a vanadate (Ca2V2O7) generated by the reaction of CaO with V2O5 could significantly improve the carbonation-regeneration rate of CaO, and reduce its regeneration temperature. However, additive V2O5 accelerated the sintering of CaO. Calcium aluminates cement could inhibit CaO sintering effectively, its optimum adding amount was 5%wt when cycle stability, absorption capacity and the decay rate of carbonation were regarded as research targets. XRD and SEM were used to study the structure of SMV-CaO. The results presented that Ca12Al14O33 produced by the reaction of CaO with calcium aluminates cement could support the microstructure of CaO effectively, as well as improve the cycle stability of CaO. In this experiment system, the optimum carbonation and regeneration temperature of SMV-CaO was 600℃,800℃respectively. Carbonation conversion of SMV-CaO was influenced significantly in the atmosphere of 15%-3O% CO2, while the effect was weaken when CO2 concentration was raised to 100%. Avrami—Erofeev equations was selected to simulate kinetics of SMV-CaO in rapid reaction phase under the temperature of 450-600℃and atmosphere of 15%-100%CO2. The carbonation activation energy is 27.16 kJ/mol, with the average deviation of 8.97%. The shrinking core model was adopted to correlate regeneration kinetics of SMV-CaO under the temperature of 750-850℃and atmosphere of 50ml/min N2.The regeneration activation energy is 165.71kJ/mol, with the average deviation of 5.60%.