Study On Capture CO₂Using Lithium Silicate Sorbents At High Temperature Enhanced Steam Methane Reforming For Hydrogen Production

Sorption enhanced steam methane reforming(SE-SMR) technology for hydrogenproduction is an efficient and low-cost technology which combining reaction withseparation. Suitable sorbent which can effectively remove CO2plays an important role inSE-SMR technology. Currently, lithium silicate is widely used as CO2sorbent. However,considering the high cost of its preparation, it is of great importance to find cheap lithiumsilicate sorbent for the development of SE-SMR technology.To solve the high-cost problem of lithium silicate preparation, the dealuminized fly ash,kaolin and rice husk (RH) were used for preparing high-performance lithium silicatematerial. Thermogravimetry (TG), X-Ray Diffraction (XRD), scanning electron microscope(SEM), and BET analysis were performed to characterize the materials. The CO2removalperformance of these materials were compared and analyzed, and the preparation conditionwas also studied. The results indicated that lithium silicate derived from RH performs bestin the process of CO2adsorption. The preparation temperature of acid-washed RH(ARH)can influent the performance of sorbent. SiO2in the ARH transformed from amorphousform into quartz crystal at higher calcining temperature (950℃), which is beneficial for thesynthesis of lithium silicate. Appropriate temperature and time of calcination are importantfactors which affect the synthesis of lithium silicate. K, Ca and Al in the RHA derivedlithium silicate can improve the morphology features of the material, which contributes toits better adsorption performance.K, Ca and Al were used to study the influence of doped elements on the adsorptionperformance of ARH-Li4SiO4. Detailed researches were carried out to figure out the bestdoping content of K, and dynamics analysis was also performed. The results indicated thatthe doped K is beneficial for both the enhancement of the adsorption capacity and thedecrease of adsorption temperature. The addition of Ca and Al also lowers the adsorptiontemperature, but barely affects the adsorption capacity. The study on doping content of K demonstrated that the best ratio of K2CO3and ARH-Li4SiO4is0.02, and the modifiedsorbents show larger adsorption capacity, better cycling stability and dynamicsperformance.The potential of RH-Li4SiO4in SE-SMR was investigated, and the influence ofexperimental conditions was also discussed. The results showed that the adsorptiontemperature of RH-Li4SiO4agrees well with the catalytic reaction temperature ofnickel-based catalyst, which means that RH-Li4SiO4can perform well in SE-SMR system.Considering the hydrogen-producing efficiency and the productivity, the most appropriatereaction conditions can be derived (temperature:650℃, gas flow rate:0.5L/min, H2O/CH4ratio:4:1), and the hydrogen-producing efficiency can be high as98%.