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A fluidized bed gasification system was built to investigate the biomass steam gasification performance in different conditions. Medium heating value syngas with 34% H2 content and no more than 20 g/Nm3 tar content could be obtained under 800°C with a S/B (steam vs. biomass ratio) of 0.9 by using olivine as bed material. The results indicated that syngas quality (including H2 content, gasification efficiency, tar reduction, etc.) is in a positive correlation with temperature and S/B, but has a negative correlation with fluidization number (FN). Compared with quartz sand and dolomite, olivine is more suitable for fluidized bed because of its catalytic ability and good abrasion performance for fluidized bed gasifier. As a result, a set of optimum parameters is recommended with S/B of 0.9~1.0, FN of 1.4, and temperature of 800°C in this study. Tar is a by-product from the gasification process, which will cause the pipeline congestion, reduce the gasification efficiency, and deteriorate the working condition. According to this experiment, the temperature and S/B both have a negative effect on tar content, while tar content increased with increase in the FN. Dolomite and olivine both have an inhibition function on tar, and the olivine is considered the best choice of bed material because of its good anti-wear properties. [ABSTRACT FROM AUTHOR]

Abstract: In China, the conventional utilization of oil shale is concentrated mainly on retorting oil shale to produce shale oil and fuel gas, and burning oil shale to generate electricity. The growth of petroleum price, and the development in heavy industry, make these conventional utilization facilities become unavailable on the energy market. In this paper, a new comprehensive utilization system is recommended for the future use of Huadian oil shale, based on the current status of energy and the characteristics of oil shale. The system involves three subsystems: retort subsystem, where coarse oil shale (8–80mm) is retorted to shale oil, hydrocarbon gases and oil shale semicoke; combustion subsystem, where the mixture fuel of oil-shale semicoke and fine oil shale (0–8mm) is fed to a circulating fluidized bed (CFB) furnace to burn, in order to generate high-pressure steam which is used to supply heat and generate electricity via a traditional steam-electric power mode; and ash processing subsystem, where oil shale ash from the CFB furnace is utilized to produce building materials. A comprehensive utilization system with handling capacity of 2.6×106 t/a Huadian oil shale is economically analyzed, showing that it can advantage oil shale utilization in the economic efficiency and the product type. [Copyright &y& Elsevier]

Abstract: A self-consistent calculation of the subband energy levels of n-doped quantum wells is studied. A comparison is made between theoretical results and experimental data. In order to account for the deviations between them, the ground-state electron–electron exchange interactions, the ground-state direct Coulomb interactions, the depolarization effect, and the exciton-like effect are considered in the simulations. The agreement between theory and experiment is greatly improved when all these aspects are taken into account. The ground-to-excited-state energy difference increases by 8meV from its self-consistent value if one considers the depolarization effect and the exciton-like effect only. It appears that the electron–electron exchange interactions account for most of the observed residual blueshift for the infrared intersubband absorbance in N/GaN multiple quantum wells. It seems that electrons on the surface of the k-space Fermi gas make the main contribution to the electron–electron exchange interactions, while for electrons further inside the Fermi gas it is difficult to exchange their positions. [Copyright &y& Elsevier]