In this paper, a new neuro-fuzzy approach for complex dynamical systems identification is proposed. The approach combines the merits of fuzzy logic theory, radial basis function neural networks, and differential evolution algorithm. The structure of the proposed algorithm model is a four-layer radial basis function fuzzy neural network (RBFFNN). The differential evolution algorithm is used for network optimization. A parameter called contribution factor is introduced to find out unimportant rules, and delete them. Both the fuzzy network structure and parameter learning can be performed automatically from input-output samples without a priori knowledge. Finally, examples of thermal processes identification are given to illustrate the effectiveness of the proposed approach.
Combined with Intra3D, the virtual demonstration of the temperature field in a fluidized bed combustor is discussed. Eulerian models to describe the gas-solid two phase flow in the fluidized bed combustor(FBC), and the combustion models of volatile release and char combustion are presented. Combined with self-defined functions, the FLEUNT CFD software is selected to simulate the process in CFB. The result data are kept as a database. Based on the simulation result of the temperature field in the fiuidized bed combustor and computer graphic technology,the iso-temperature profile is set up in CFB through Marching Cube method and particle system-based fire model. The virtual combustion fire is built. The virtual demonstration technique can be used to study and simulate the properties of thermal systems instead of experimental methods.
CeO2 is a typical fluorite oxide with desirable lattice oxygen conductivity and can be applied as an active support for the Fe-based oxygen carrier in chemical looping hydrogen generation (CLHG). However, Fe2O3/CeO2 always suffers from low thermal stability and sintering. Doping foreign cations could be a proper way to improve its reactivity and cyclic stability. In this work, Zr4+ and Sm3+, with a smaller ionic radius and lower valence than Ce4+, respectively, were doped into Fe2O3/CeO2 using the co-precipitation method, and the doping effects on the reactivity and redox stability of Fe2O3/CeO2 in CLHG were investigated. Fe2O3/Ce0.6Sm0.15Zr0.25O1.925 provided the best redox reactivity, and the purity of generated hydrogen for all oxygen carriers reached nearly 100% (the detection limit of CO/CO2 was 0.01% in volume). The reactivity followed the sequence Fe2O3/Ce0.6Sm0.15Zr0.25O1.925 > Fe2O3/Ce0.8Sm0.2O1.9 > Fe2O3/Ce0.75Zr0.25O2 > Fe2O3/CeO2. However, the concentration of oxygen vacancy was ranked as Fe2O3/Ce0.8Sm0.2O1.9 > Fe2O3/Ce0.6Sm0.15Zr0.25O1.925 > Fe2O3/Ce0.75Zr0.25O2 > Fe2O3/CeO2. The Zr doping boosted the reactivity of Fe2O3/CeO2 mainly by enhancing its sintering resistance, whereas the Sm doping achieved it mainly by promoting the oxygen conductivity, whose ability to improve the thermal stability of Fe2O3/CeO2 was rather limited. Both Zr and Sm doping could suppress the outward migration of Fe cations in the particles, resulting in higher sintering resistance. Furthermore, Zr and Sm could dissolve into CeO2 for prepared Fe2O3/Ce0.6Sm0.15Zr0.25O1.925; however, the bleeding out of both dopants was observed with Sm0.5Zr0.5O1.75 formation, which could be detrimental to the redox stability of the oxygen carrier.
Fe2O3 is an excellent active metal oxide for chemical looping hydrogen generation (CLHG) with high conversion of CO to CO2 in the reduction stage, and high H2 mole fractions in the subsequent steam oxidation stage, especially for its low cost and abundance in nature. However, supports are generally used to improve its reactivity and stability and to eliminate its carbon deposition. In this paper, Fe-based oxygen carriers are prepared by a coprecipitation method with three supports, i.e., CeO2, ZrO2, and Al2O3. The reactivity, carbon deposition, redox stability, and sintering characteristics of the oxygen carriers are analyzed to investigate the effects of supports as well as the fundamental mechanism. The results show that the properties of the oxygen carriers highly rely on the support and its interaction with iron oxide. The oxygen carrier supported on Al2O3 exhibits poor reactivity and stability, and the oxygen carrier supported on ZrO2 leads to much carbon deposition, decreasing H2 purity, despite its high reactivity and stability. Nevertheless, the oxygen carrier supported on CeO2 demonstrates good reactivity and stability with no carbon deposition observed, and the reducible support CeO2 counteracts the negative effect originating from sintering and guarantees the reactivity and stability of Fe2O3/CeO2 due to its oxygen mobility property and the oxygen mobility enhancement originating from the formation of Fe–Ce solid solution and perovskite-type CeFeO3. Overall, the reducible CeO2 is a potential support to improve the redox characteristics of iron oxygen carrier in CLHG, and the Fe2O3/CeO2 exhibits the highest reactivity at 850 °C. In addition, all three oxygen carriers are characterized by scanning electron microscopy images, energy dispersive X-ray spectrometer analysis, and X-ray diffraction patterns before and after the redox cycles.
This paper focuses on the design of decentralized PID control scheme for the ALSTOM gasifier based on online coal quality analyzing technique. Taking into account characteristics changing with coal quality variations during gasifier operation, corresponding control strategies were added into the decentralized PID control scheme. Simulation results show good control performance for the ALSTOM gasifier benchmark test with fine coal quality signal. The proposed control scheme adopted the traditional PID control algorithm which could be easily implemented. Thus, provides good guidelines for practical control system design for gasifiers that are subject to coal quality variations.
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