Cotton Stalk Combustion in a Circulating Fluidized Bed

The basic properties of cotton stalk (CS) of length 10–100 mm and its ash were investigated. Studies concerning the combustion characteristics of CS were performed in a circulating fluidized bed (CFB) test facility with a heat input of 0.5 MW. According to previous cold tests, there is very little segregation during the mixing of CS with this size profile and bed material at a fluidization number of N > 7, but the hot experimental results indicate that slight segregation has a small effect on the steady combustion of the dense region. Experiments were carried out with the aim of investigating the effects of operating conditions on the axial temperature and gas concentration profiles along the combustor height, as well as the emission performance and combustion efficiency of the CFB. The experimental results indicate it is difficult to react alumina bed material with alkali metals from CS ash following 26 h of combustion. The overall conclusions appear to indicate that the application of circulating fluidized bed boilers to fire pure CS of length 10–100 mm, is feasible.     

HEAT TRANSFER MEASUREMENTS OF A 1·0 TON-STEAM/HR CIRCULATING FLUIDIZED-BED COMBUSTOR BURNING TAIWAN COALS

The circulating fluidized-bed combustor (CFBC) recently has its commercial breakthrough as a viable technology to burn solid fuels with high efficiencies and low emissions. A 1·0 ton-steam/hr CFBC test facility has been designed, built, and systematically tested with Taiwan coals. The CFBC test chamber of 0·4 m square cross-section and 10 m high has built-in flexibility in thermal and combustion measurements. This paper presents the results of local heat transfer between bulk solids and the combustor wall. Effects of superficial fluidizing velocity, bed density, bed temperature, and solid recycle rate on heat transfer coefficient were measured and delineated.     

SK-PAM特种抗冲磨树脂砂浆材料工程特性研究

本文针对目前常用的薄层抗冲磨防护材料难以抵抗高速水流推移质磨蚀破坏难题,以柔性氨基树脂材料和特种固化剂为胶结体系,添加抗冲磨填料,研发了一种新型抗冲磨树脂砂浆材料。并对新型树脂砂浆进行了力学性能、冲磨能力和环境适应性试验,试验结果表明砂浆伸长率在5%以上,与基面黏接强度大于2.5MPa,表明其具有良好的抗裂能力和适应变形的能力;水下钢球法冲磨试验3个周期质量基本没有损失,同等条件下圆环法冲磨对比试验证明其抗冲磨强度是高强环氧砂浆的5倍以上,证明新型抗冲磨树脂砂浆具有高弹韧性的材料特性,适用于泄水建筑物的抗冲磨、特别是推移质破坏的防护和修复。     

Vertical distribution of fauna in the bed sediment of three running water sites: Influence of physical and trophic factors

Relationships between invertebrates, substrate characteristics and trophic factors were investigated, with special emphasis on the hyporheic habitat, in order to characterize the functioning of different running waters ecosystems. Three contrasting study sites were chosen in catchments exhibiting different features: (1) a meandering reach of the Loire River in its alluvial floodplain, upstream of the ‘Bec d'Allier’; (2) a reach of the Galaure with a fairly developed riparian corridor, a small sinuous foothill river; and (3) a braided reach of the Drac, an alpine torrential stream. Each site was sampled once using the freezing-core technique with previous electro-positioning of the invertebrates. In each site, four 60 cm cores were extracted, each one from different morphodynamic units. In the Loire and Galaure rivers, most invertebrates are found in the first 15 cm of the sediment, with the exception of some particular taxa or morphodynamic units (riffle head). Conversely, in the Drac lotic units, maximum density of invertebrates occurs between 15 and 30 cm and more than 75 per cent of all organisms are found at a depth > 15 cm. The vertical distribution of organisms does not follow a uniform pattern in different streams. In the substrate, the vertical distribution of macroinvertebrates is very closely related to porosity in contrast with trophic parameters that always decrease with depth. The porosity is negatively correlated with the percentage of sand in the sediment and seems to be important in determining the vertical distribution of fauna, and should be integrated in a functional typology of running waters. The trophic parameters and the structure of invertebrate community with its dominant feeding groups allow discrimination of the different sites.     

国外地质勘探报告解读要点

对国内外地质勘探报告中确定地基容许承载力的方法进行了对比，并对地基承栽力的修正系数进行了分析。     

The impact of tidal stream turbines on large-scale sediment dynamics

Tidal stream turbines are exploited in regions of high tidal currents. Such energy extraction will alter the hydrodynamics of a tidal region, analogous to increasing the bed friction in the region of extraction. In addition, this study demonstrates that energy extracted with respect to tidal asymmetries due to interactions between quarter (M₄) and semi-diurnal (M₂) currents will have important implications for large-scale sediment dynamics. Model simulations show that energy extracted from regions of strong tidal asymmetry will have a much more pronounced effect on sediment dynamics than energy extracted from regions of tidal symmetry. The results show that energy extracted from regions of strong tidal asymmetry led to a 20% increase in the magnitude of bed level change averaged over the length of a large estuarine system, compared with energy extracted from regions of tidal symmetry. However, regardless of the location of a tidal stream farm within a tidal system, energy extraction reduces the overall magnitude of bed level change in comparison with non-extraction cases. This has practical application to many areas surrounding the UK, including the Irish Sea and the Bristol Channel, that exhibit strong tidal currents suitable for exploitation of the tidal stream resource, but where large variations in tidal asymmetry occur.     

循环流化床锅炉的燃烧及传热特性

燃烧和传热特性是循环流化床锅炉的燃烧技术基础.循环流化床锅炉的燃烧有三大特点,其传热方式独特,并可调节传热效果.     

Why the two-fluid model fails to predict the bed expansion characteristics of Geldart A particles in gas-fluidized beds: A tentative answer

It is well known that two-fluid models (TFMs) can successfully predict the hydrodynamics of Geldart B and D particles. However, up to now, TFM have failed to accurately describe the hydrodynamics of Geldart A particles inside bubbling gas-fluidized beds: Researchers have reported that bed expansions are over-predicted by as much as 70%. In this work we show—for the first time—that TFM can predict the correct bed expansion, without any artificial modifications, provided that a sufficiently fine grid size and small time step is used. This suggests that the previously reported failure of TFM is mainly due to the lack of scale resolution, and that from a modeling point of view there is no fundamental difference between Geldart A particles and Geldart B and D particles.