Browsing by Author "De La Hoz Siegler, Hector"

Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Investigation of Mixed Support Oxides in Methane Fueled Chemical Looping Combustion
    (2020-10-28) Elgarni, Moheddin Mohamed; Mahinpey, Nader; De La Hoz Siegler, Hector; Hu, Jinguang
    Fossil fuels constitutes the main sources of energy as greenhouse gases emissions (GHGs) continue to rise which is the cause of climate change. In addition to alternative sources of energy, carbon capture is a necessary tool in mitigating the rise of CO2 (the major GHG contributor) emissions. The desire for efficient technology in power generation with CO2 capture led to a growing interest in chemical looping combustion (CLC). This alternative technology provides a pure CO2 stream without the energy penalty to capture it as an oxygen carrier allows for the combustion of the fuel in a N2 free environment. In this study, CH4 fueled CLC was investigated for Ni- and Cu-based oxygen carriers supported by Al2O3, CeO2, ZrO2 and their combinations. The oxygen carriers were synthesized using the incipient wetness impregnation technique and the mixed oxide supports were prepared using co-precipitation method. The testing of oxygen carriers was carried out using a Thermogravimetric Analyzer (TGA) to evaluate the reactivity and chemical stability of the samples. The oxygen carriers underwent 10 cycles of reduction and oxidation at 750°C, 850°C and 950°C. The following characterization tests were conducted on the samples: XRD, SEM/EDX and BET surface area analysis. The characterization tests were conducted on the samples after the final calcination of the oxygen carriers and after CLC tests. The XRD profiles led to the observation of the different phases from the active site-support interactions: NiAl2O4 and support-support interactions: CeAlO3. A positive correlation was observed between the oxygen capacity and the temperature in all Ni-based samples and most of Cu-based samples. The oxygen capacity of CuO/ZrO2 and CuO/CeO2 increased from 750°C to 850°C but decreased at 950°C. In some of the samples (such as NiO/CeO2, NiO/Al2O3-CeO2, NiO/Al2O3-CeO2-ZrO2, CuO/CeO2), the oxygen capacity exceeded the theoretical value for active site loading of 30% which was attributed to the partial reduction of NiAl2O4, CeO2 and ZrO2. In addition, in the samples with CeO2 and Al2O3 supports, NiAl2O4 was further reduced as promoted by the formation of CeAlO3. The kinetic parameters for the oxidation and reduction reactions were determined where the nucleation and nuclei growth model (NNG) and shrinking core model (SCM) were compared for the oxidation reaction. NNG model was found to be a better representative of the experimental data. The activation energy for NiO/Al2O3-ZrO2-CeO2 (11.3 kJ∙ mol-1) was found to be lower than NiO/Al2O3 (17.2 kJ∙ mol-1) and NiO/ZrO2 (36.6 kJ∙ mol-1) but higher than NiO/CeO2 (6.8 kJ∙ mol-1). This indicates the positive impact of the addition of CeO2 to Al2O3 and ZrO2 in the case of NiO/Al2O3-CeO2-ZrO2.
  • Thumbnail Image
    ItemOpen Access
    Rheological Properties of Bitumen and Bitumen-Heptane and Bitumen-Heptanol Mixtures
    (2021-01-25) Park, In Young; Gates, Ian Donald; Benneker, Anne M.; Lu, Qingye; De La Hoz Siegler, Hector
    The rheological changes and high viscosity of bitumen, arising from high molecular weight molecules in bitumen, are the main challenges for its production to the surface and its transportation in pipelines. To solve the environmental issues associated with bitumen recovery, such as greenhouse gas emissions from steam-based recovery processes, solvent injection has been a strong alternative given their ability to reduce the viscosity of bitumen. Among solvent options, the ability of alcohol solvents has not been clearly studied. In this study, two sets of experiments were conducted on the rheology of bitumen and solvent-bitumen mixtures. The first set of experiments demonstrates that the rheological behaviour of bitumen is complex since its viscosity varies with both shear rate and time. In the experiment, the rheology of bitumen and bitumen-heptanol mixtures were examined. Their viscosities and shear stress were measured with increasing and decreasing shear at 24C. The results showed that non-Newtonian behaviour was observed in all samples. Additionally, hysteresis and ramp test of the viscosity profiles revealed that the bitumen and its mixtures are time-dependent (anti-thixotropic) fluids. In the second set of experiments, the viscosity of bitumen in contact with heptanol was examined and compared to bitumen-heptane mixtures. The results show that the effects of heptanol on viscosity reduction were less than that of heptane. The literature values of Hansen Solubility Parameters (HSP) of bitumen, asphaltenes, heptanol and heptane were used to explain the reason for the lower viscosity reduction effect of heptanol on bitumen. The relatively high viscosity of heptanol and deviation of the fractional HSP between bitumen and heptanol is also consistent with the results.