Study on extracting alumina from fly ash by compound additive activation method

According to the chemical and mineral composition characteristics of the fly ash, alumina can be extracted from fly ash through the calcining method by using sodium carbonate and calcium carbonate additives. The effects on leaching rate of alumina have been investigated. The results showed that the fly ash can be activated effectively and the leaching rate of alumina can be improved to more than 92% through this method. The best process parameters were the ratio of raw materials, i.e. the material weight ratio of fly ash, calcium carbonate and sodium carbonate was 1.0：1.2：0.9. The activating temperature was 850℃-900℃, activating time was 3 h. This process has a potential application prospect and improves the value of comprehensive utilization of fly ash.     

免烧粉煤灰滤料的制备及其性能的研究

为了扩大粉煤灰的应用范围,减少其对环境的污染,并且寻求一种新的水处理滤料的配方与制备方法,以粉煤灰、粘土为主要原料,以生石灰、石膏、水泥为激发剂,以H₂O₂（双氧水）、NaHCO₃为发泡剂,经搅拌、成型、自然冷却等工艺在实验室制备了免烧粉煤灰滤料.结果表明,如果以孔隙率作为主要的性能评价指标,制备免烧粉煤灰滤料的最佳质量配比为：粉煤灰46.30%,粘土13.89%,生石灰18.52%,水泥13.89%,石膏1.85%,纯H₂O₂ 5.55%,此时所制滤料的孔隙率为72.24%.     

Chemical composition and leaching characteristics of granules made of wood ash and dolomite

 In 1995, the central heating plant Draken in Kalmar, Sweden, started manufacturing a granular ash product for nutrient recycling to forest soil, instead of dumping the ash in landfills. Chemical composition, leaching and dissolution characteristics were determined for the Draken wood ash, the dolomite used in granule manufacturing and the final granule product. The heavy metal concentrations in fly ash were within the limit values recommended by the Swedish National Board of Forestry for ash recycling, except for Cd and As levels which occasionally exceeded the limit values. The Ca, Mn and P levels were too low for nutrient recycling at the time. Adding dolomite insures that the levels of the important nutrients Ca and Mg are sufficient in the granules. After 7 months in the field, about 60 % of Na and K was leached out from granules. Between 20 and 60% of trace elements Mo, Sc, V, Y and Zr were leached out after 7 months. The release of Ca and Mg was low, 1–5% during 7 months. Received: 12 July 1999 · Accepted: 31 August 1999     

快速数论变换的一种算法

本文构造了一种快速数论变换算法,该算法是一种以数论为基础,有效高速的数论变换算法,并且这种算法易于在计算机上实现。     

氢化物发生—原子荧光光谱法快速测定粉煤灰中微量硒

随着环境科学与人体健康研究的深入,硒作为人体必需的15种微量元素之一,尤为科技工作者所重视。硒属于一种稀散微量元素,主要用于电子和电器工业以及导弹,高空通讯设备等。在半导体﹑橡胶﹑石油工业中,硒也有着广泛的用途。人体硒水平偏低,可致老年期衰减速度加快,合理地补充硒可以预防和治疗心血管疾病,增强体液的免疫力,并能有效地防止肿瘤的扩展,起到预防和治疗癌症的作用。本文应用专属性强的AFS方法分析证实,对测定粉煤灰中的硒,具有简单快速﹑准确灵敏、取样量少、测定范围宽等优点。其加标回收率在:90.0%~101.0%之间,RSD为:3.36%~6.02%。     

复杂背景下的仿蝇视觉遥感异常检测

本文针对遥感影像复杂背景下,背景地物光谱特征与目标光谱特征之间存在较强相关性的问题,提出一种基于仿蝇视觉的复杂背景下遥感异常检测算法。首先构建并行多孔径背景模型,实现对复杂背景特征的自适应描述;然后基于异常目标的光谱特征相对异常性,采用相对马氏距离区分异常区域、不确定区域与无目标区域,消除背景与目标光谱相关性对检测结果干扰的同时,弥补了传统假设检验无法区分无目标和不确定问题的不足;最后融合多个背景模型的检测结果,实现异常目标检测。仿真实验将围绕多种背景地物并存复杂区域的异常检测验证本文算法的有效性。     

Effects of Volcanic Ash on Computers and Electronic Equipment

Computers and electronic equipment are an important component of the infrastructure of our modern environment. It is therefore essential that we know the effects of volcanic ash on such equipment. This paper presents the results of a pilot study to test computers and cooling fans in an ash-charged environment to assess their vulnerability. In the experiment, ash was poured on to computers and cooling fans in a sealed 0.216 m³ perspex box, with the effects on both the ash and the equipment monitored. Three different types of ash (1996 Ruapehu andesitic ash, Sakurajima andesitic ash and Kaharoa rhyolitic ash) were used in the experiments.In the first experiment each type of ash was photographed by Scanning Electron Microscope (SEM), then passed through the bearing unit of a cooling fan and photographed again afterwards. The bearings within the cooling fan continued to work even after 720 h of testing and there was no significant abrasion of the fan-shaft bearing. The ash was however fragmented, suggesting that the brittle ash shattered to fine dust, which caused significantly less abrasion to the bearings or shaft than expected. Three computers were then tested in the sealed box. Ash was introduced at increasing rates to simulate catastrophic entry of ash into a work environment, and computers were tested throughout using the BURNIN^® testing programme. Failure times ranged from 100 to 150 h; most failures occurring when humidity was increased by spraying water mist into the airflow. If dried out the computers continued to operate again if failure was not catastrophic. Card slot edge connectors proved to be one of the weakest links, as a bridge of ash formed across the gap. They were also subject to abrasion with some of the gold plating being removed. This did not however cause operating difficulties.The conclusions are that computers are more resilient than originally thought, unless the ash is moist. Simple low-tech procedures should be adequate to protect computers from small amounts of dry and moist ash contamination.     

Surface area, porosity and water adsorption properties of fine volcanic ash particles

Our understanding on how ash particles in volcanic plumes react with coexisting gases and aerosols is still rudimentary, despite the importance of these reactions in influencing the chemistry and dynamics of a plume. In this study, six samples of fine ash (<100 m) from different volcanoes were measured for their specific surface area, a_s, porosity and water adsorption properties with the aim to provide insights into the capacity of silicate ash particles to react with gases, including water vapour. To do so, we performed high-resolution nitrogen and water vapour adsorption/desorption experiments at 77 K and 303 K, respectively. The nitrogen data indicated a_s values in the range 1.1–2.1 m²/g, except in one case where a a_s of 10 m²/g was measured. This high value is attributed to incorporation of hydrothermal phases, such as clay minerals, in the ash surface composition. The data also revealed that the ash samples are essentially non-porous, or have a porosity dominated by macropores with widths >500 Å. All the specimens had similar pore size distributions, with a small peak centered around 50 Å. These findings suggest that fine ash particles have relatively undifferentiated surface textures, irrespective of the chemical composition and eruption type. Adsorption isotherms for water vapour revealed that the capacity of the ash samples for water adsorption is systematically larger than predicted from the nitrogen adsorption a_s values. Enhanced reactivity of the ash surface towards water may result from (i) hydration of bulk ash constituents; (ii) hydration of surface compounds; and/or (iii) hydroxylation of the surface of the ash. The later mechanism may lead to irreversible retention of water. Based on these experiments, we predict that volcanic ash is covered by a complete monolayer of water under ambient atmospheric conditions. In addition, capillary condensation within ash pores should allow for deposition of condensed water on to ash particles before water reaches saturation in the plume. The total mass of water vapour retained by 1 g of fine ash at 0.95 relative water vapour pressure is calculated to be ~10^–2 g. Some volcanic implications of this study are discussed.Editorial responsibility: J. Gilbert     

粉煤灰湿陷变形的三轴试验和计算

采用双压力室三轴仪对粉煤灰试样进行了单线法湿陷试验,研究了在静水压力作用以及在不同应力状态和应力水平下粉煤灰湿陷变形的规律,得出了粉煤灰湿陷变形的经验计算公式.提出了计算粉煤灰地基湿陷变形的"全应变曲线"增量有限元法.基于本文的试验结果,对一个粉煤灰地基的湿陷变形进行了有限元计算.