Study On CaO-Ca₁₂Al₁₄O₃₃ Based Sorbents For CO₂Capture And Hydrogen Production

With the development of global economy, more and more fossil energy are needed,and thus produced large amount of CO2. It’s the main reason for greenhouse and causedtremendous damage to the environment. So CO2capture and storage technology andhydrogen production technology has attracted much more attention. After analyzing andsummarizing the research work on solid sorbents for CCS and hydrogen production,CaO-Ca12Al14O33based materials were tested systematically, then they were used for thehydrogen production.CaO-Ca12Al14O33based solid sorbents doped with K,Na,Ce were prepared bysol-gel method. The samples were characterized by X-ray diffraction and BET methods.The experimental study of CO2sorption was performed by fixed-bed reactor andthermogravimetric analysis. The effect of different factors which influence the CO2sorption such as reaction temperature, CO2partial pressure and cyclic times have beenanalyzed. The experimental results showed that the sorbents doped with K and Ce have abetter capacity for CO2sorption, while Na have a bad effect on the CO2capture. With theamount of doped K increases, the capacity for CO2sorption decreased. When a properamount of Ce(8%) was doped into the sorbents, the capacity can reach to the best, whichis63.4wt%. In the range of550℃-700℃,the capacity increases with the temperatureincreases. When the CO2concentration changes between10%and20%,the capacities ofthe sorbents change little. K can improve the stability of the sorbents, while Ce have theopposite effect. But before28cycles, the sorbent still remains better capacity for CO2sorption than sorbents doped with nothing.Double exponential model was used to fitting the process of the CO2absorption bysorbents doped with Ce. The results show that k1(chemisorption) values are10timeshigher than those of k2(diffusion), which means that the chemisorption process is moredependent on the temperature, and diffusion is the limiting step of the total process.The experiment study of steam methane reforming and hydrogen production viacoal gasification were performed in a self-made test bench. CaO-Ca12Al14O33sorbentscan enhance the results of steam methane reforming for hydrogen production. K and Cecan further improve the concentration of H2in the gas products, which can reach85.5% and92.6%respectively. With the increasing of temperature, the hydrogen concentrationproduced by steam methane reforming via the sorbents doped with three kind ofelements increases first and then decreases, it reaches highest at650℃. Steam methanereforming can still happen under relatively low temperature when using the sorbentdoped with Ce but no catalyst.