Browsing by Author "Qin, Changlei"

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    Compatibility of NiO/CuO in Ca‐Cu chemical looping for high‐purity H2 production with CO2 capture
    (Wiley, 2018-02-04) Tan, Lili; Qin, Changlei; Zhang, Zhonghui; Ran, Jingyu; Manovic, Vasilije
    Ca‐Cu chemical looping is a novel and promising approach in converting methane into pure H2 following the principle of sorption‐enhanced reforming. Its operational efficiency is largely determined by an appropriate coexistence of Cu‐based oxygen carriers and Ni‐based catalysts. In this work, NiO/CuO composites were synthesized and their catalytic activity for H2 production was measured using a fixed‐bed reactor system equipped with an online gas analyzer. It is reported for the first time that the presence of CuO could hinder the activity of Ni‐based catalysts in H2 production, and experimental results show that the negative effect of CuO is strengthened with increasing CuO content and calcination temperature during sample preparation. With the help of a series of specific test and characterization techniques (SEM‐EDS, BET, XRD, TPR and XPS), interaction rules between NiO and CuO was further investigated and understood, and based on that an action mechanism model was proposed. Furthermore, an arrangement of mixed particles that avoiding the intimate contact of CuO/NiO was suggested and tested, and a superior performance was demonstrated while observing no restrictions of CuO on Ni‐based catalysts in sorption‐enhanced steam‐methane reforming under the conditions of Ca‐Cu chemical looping.
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    Efficient-and-Stable CH4 Reforming with Integrated CO2 Capture and Utilization using Li4SiO4 Sorbent
    (Elsevier, 2021-08-16) Lv, Zongze; Qin, Changlei; Chen, Shuzhen; Hanak, Dawid P.; Wu, Chunfei
    CO2 capture and utilization has been considered as an up-and-coming short- to mid-term approach to mitigate the excessive CO2 emission. Comparing to the conventional separate capture, transportation and conversion arrangement, the integrated CO2 capture and utilization (ICCU) could largely simplify the complex process and reduce the energy consumption. However, the poor stability of high-temperature CO2 sorption/desorption severely limit the potential of ICCU. Therefore, it is indispensable to develop a new sorbent/catalyst system ensuring the high-efficiency and long-term operation of the ICCU. In this paper, we propose and demonstrate the feasibility and performance of using K2CO3-doped Li4SiO4 as an efficient CO2 sorbent for ICCU operating at a relatively low temperature by dry reforming of methane. Results show that the ratio of H2/CO produced is stabilized at 1±0.05 in the pre-breakthrough stage, and the duration extends to be 1.6 times of the original value in the cyclic operations, displaying an excellent performance in reaction matching and process stability.
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    Kinetic study and modeling on the regeneration of Li4SiO4-based sorbents for high-temperature CO2 capture
    (Elsevier, 2021-08-06) Chen, Shuzhen; Qin, Changlei; Yuan, Weiyang; Hanak, Dawid P.; Ran, Jingyu
    Li4SiO4 is acknowledged as a promising sorbent candidate in high-temperature CO2 adsorption. However, reaction kinetics for the regeneration process of Li4SiO4, especially its dependence on CO2 pressure is lack of understanding. This work designed and carried out a series of isothermal tests on the regeneration of pure Li4SiO4 and K-Li4SiO4 under CO2 partial pressure of 0–0.5 atm and temperature of 625–725 °C. For the first time, the expression of (Peq − PCO2)n is introduced into the regeneration rate equation so as to reveal its dependence on CO2 pressure. The reaction order (n) is found to grade according to the value of (Peq − PCO2), and the apparent activation energy is calculated as 284.42 kJ•mol−1 and 146.31 kJ•mol−1 for the regeneration of Li4SiO4 and K-Li4SiO4, respectively. Furthermore, this work proposes that power law model with m = 4/3 is the most probable mechanism function for the regeneration of Li4SiO4-based sorbents.
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    Reaction mechanism and kinetics of the sulfation of Li4SiO4 for high-temperature CO2 adsorption
    (American Chemical Society, 2021-07-02) Yuan, Weiyang; Chen, huzhen; Qin, Changlei; Hanak, Dawid P.; Zhou, Xu
    CO2 adsorption is an important approach to control the excessive CO2 emission from energy and industrial plants and mitigating the greenhouse effect. As an acknowledged high-temperature adsorbent, Li4SiO4 shows advantages in capturing a large amount of CO2 with a fast reaction rate and excellent cyclic stability. However, its CO2 adsorption capacity would be significantly affected by the flue gas impurities, such as SO2 and O2. The underlying reaction mechanism of such impurities and Li4SiO4 is still unclear. For this reason, this work studied the reaction path and kinetics between Li4SiO4 and SO2 through experiments, thermodynamic calculations, and characterizations. The results showed that Li4SiO4 reacts with SO2 to produce Li2SiO3 and Li2SO4 in the presence of O2 at 500–700 °C and forms Li2SiO3 and Li2SO3 in the absence of O2 at 500–682 °C. Furthermore, this study revealed a very low activation energy of 7.47 kJ/mol for Li4SiO4 sulfation in the presence of O2 in the kinetic-controlled stage, and the value goes up to 249.7 kJ/mol in the diffusion-controlled stage. These results will provide valuable references for the industrial applications of CO2 adsorption by Li4SiO4.
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    Simulation of the calcination of a core-in-shell CuO/CaCO 3 particle for Ca–Cu chemical looping
    (Elsevier, 2016-05-12) Qin, Changlei; Manovic, Vasilije; Ran, Jingyu; Feng, Bo
    The internal heat balance through heat generation due to CuO reduction and its consumption by CaCO3 decomposition makes calcination a critical step in a novel Ca–Cu chemical looping process (CaL–CLC). Thus, the calcination behaviour of composite Ca/Cu particles needs to be well understood, especially taking into account that mismatching of heat generation and consumption in the particles can lead to local superheating, agglomeration and loss of activity due to enhanced sintering. In this work, a composite particle model was developed to study the calcination behaviour within a spherical core-in-shell type of particle containing grains of CuO and CaCO3. Simulation results showed that ambient temperature, shell porosity, particle size, and CaCO3 grain size significantly affected the CuO and CaCO3 reaction processes, while the impact of initial particle temperature and CuO grain size can be ignored in the range of parameters considered in the study. By comparison of different types of particles, it was concluded that the core-in-shell pattern was more advantageous if such particles are being applied in CaL–CLC cycles due to better matching in reaction kinetics resulting in more stable and uniform particle temperature distribution during the calcination stage.