| The traditional solution for the problem of energy utilization and environmental pollution often follows the way of'treatment after pollution', where the chemical energy of the fossil fuel is converted into thermal energy through direct combustion with air to drive the thermal cycle, and the produced pollutants are treated with chemical separation method independent of the energy conversion process. This direct combustion of fossil fuel causes CO2diluted by N2, resulting in a large amount of flue gas to be treated, and leading to the increase in the energy penalty and the cost for CO2reduction.This dissertation focuses on the research of CO2control with multi-energy input, and originally integrates the mid-temperature solar thermochemical process with the chemical-looping combustion (CLC) to simultaneously achieve a high net solar-to-electric efficiency and zero energy penalty for CO2separation in the power cycle. The research work was carried out from three aspects including the mechanism study, the experimental validation and the system integration.Based on the principle of the chemical energy cascade utilization integrated CO2capture, the correlationship among the Gibbs free energy change△G, the degree of chemical energy cascade utilization k and the relative enrichment of CO2concentration λ was built, and the mechanism of fuel chemical energy release in CLC was explored. By comparing with the energy conversion process with CO2separation before combustion, it was proved that the CLC process can realize the cascade utilization of fuel chemical energy integrated CO2separation with minus energy penalty. The coupling of mid-temperature solar thermal chemical process and CLC was also explored, a phenomenon of the upgrade of the energy level of the mid-temperature solar thermal energy was found, and the synthetic effect of CO2control with hybridization of solar thermal energy and fossil fuel was revealed. Experiments on the CLC process were carried out on the TGA reactor. Oxygen carriers, with Fe2O3, NiO, and CoO as solid reactants and Al2O3, MgAl2O4, and YSZ as binders, were prepared by dissolution method. The reactivity of the oxygen carriers was compared, and the effects of the reaction temperature, the gas composition and the particle size were studied. Carbon deposition in the reduction process of DME with CoO/CoAl2O4was completely suppressed by adding water vapor to the gaseous reactant, and the optimal value of H2O/DEM is around2.0. These research findings validate the feasibility of the integration of mid-temperature solar thermochemical process and CLC, and bring the CLC technology into utilization of renewable energy and alternative fuel for CO2mitigation.The effects of different additives on the reactivity of the oxygen carrier CoO/CoAl2O4were studied, and a new kind of oxygen carrier (CoO+1.0%PtO2)CoAl2O4was developed. Compared with CoO/CoAl2O4, the activation energy of the reduction of (CoO+1.0%PtO2)/CoAl2O4with DME was lowered by about43kJ/mol, and the reaction rate was dramatically improved by about4times. The effect of PtO2content on reactivity showed that the suitable PtO2content was1.0%. By adding water vapor into the fuel reactor, carbon deposition was completely avoided, and the appropriate mole ratio of H2O/DEM was around1.0. This value was lower than that of CoO/CoAl2O4, which can significantly reduce the water consumption, as well as the energy consumption of the CLC process.Based on the synthetic utization of the solar thermal energy and the chemical energy of fossil fuel, a new solar-hybrid thermal cycle, integrating CLC with mid-and-low temperature solar thermal energy has been proposed. The thermodynamic performance of the proposed cycle was evaluated, the characteristics were identified with the aid of graphical exergy methodology, and the effects of the key parameters on the system performance were analysed. The results showed that, the exergy efficiency of the proposed solar thermal cycle would be expected to be58.4%at a turbine inlet temperature (TIT) of1673K, and the net solar-to-electric efficiency can reach as high as30.1%. The promising results obtained here indicate that this solar-hybrid combined cycle not only offers a new approach for highly efficient use of middle-and-low temperature solar thermal energy to generate electricity, but also provides the possibility of simultaneously utilizing renewable energy and alternative fuel for CO2capture with low energy penalty. The research work of this dissertation offers both theoretical and experimental support for CO2control with the synthetic cascade utilization of multi-energy.
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