Removal of NAPLs from the unsaturated zone using steam: prevention of downward migration by injecting mixtures of steam and air

Steam injection for remediation of porous media contaminated by nonaqueous phase liquids has been shown to be a potentially efficient technology. There is, however, concern that the technique may lead to downward migration of separate phase contaminant. In this work, a modification of the steam injection technology is presented, where a mixture of steam and air was injected. In two-dimensional experiments with unsaturated porous medium contaminated with nonaqueous phase liquids, it was demonstrated how injection of pure steam lead to severe downward migration. Similar experiments, where steam and air were injected simultaneously, resulted in practically no downward migration and still rapid cleanup was achieved. The processes responsible for the prevention of downward migration when injecting steam-air mixtures were analyzed using a nonisothermal multiphase flow and transport model. Hereby, three mechanisms were identified and it was demonstrated how the effectiveness of these mechanisms depended on the air-to-steam mixing ratio.     

Mechanical performance of woodfibre–waste plastic composite materials

Plastic products used for packaging are often discarded after a single use resulting in an inexhaustible supply of waste polymeric materials. The stiffness and strength of polymeric materials have been known to improve with the addition of lignocellulosic fibres available in abundance in nature. Hence, composite materials containing natural fibres and waste plastics would result in the reduction of solid wastes and the use of cheap, renewable resources. Composite specimens, consisting of waste plastics obtained from a Kerbside collection (high density polyethylene (HDPE) waste, Janitorial waste, Kerbside waste I and Kerbside waste II) and Pinus radiata woodfibres (medium density fibres (MDF)), have been produced through melt blending and injection moulding. The effects of fibre content, matrix type and interfacial bonding on the tensile and flexural properties of these composite materials have been determined through extensive testing at various conditions. The mechanical properties of these composites at room temperature and humidity depend on the amount of woodfibres, the mechanical properties of the waste plastics used and the presence of a suitable coupling agent. The tensile strengths of MDF/waste plastic composites do not generally change with fibre content except for 40% MDF/HDPE waste and 40% MDF/Kerbside waste II (plus 1% Epolene™) composites, where the tensile strengths increase by about 25% compared to those of the corresponding waste plastics. Flexural strengths of MDF/waste plastic composites increase with the addition of medium density fibres with the exception of MDF/Kerbside waste I composites. The tensile and flexural moduli of MDF/waste plastic composites mostly increase with increasing fibre content.     

SIMULATING THE EFFECTS OF REDUCED PRECIPITATION ON GROUND WATER AND STREAMFLOW IN THE NEBRASKA SAND HILLS1

ABSTRACT: The Nebraska Sand Hills have a unique hydrologic system with very little runoff and thick aquifers that constantly supply water to rivers, lakes, and wetlands. A ground water flow model was developed to determine the interactions between ground water and streamflow and to simulate the changes in ground water systems by reduced precipitation. The numerical modeling method includes a water balance model for the vadose zone and MOD‐FLOW for the saturated zone. The modeling results indicated that, between 1979 and 1990, 13 percent of the annual precipitation recharged to the aquifer and annual ground water loss by evapotranspiration (ET) was only about one‐fourth of this recharge. Ground water discharge to rivers accounts for about 96 percent of the streamflow in the Dismal and Middle Loup rivers. When precipitation decreased by half the average amount of the 1979 to 1990 period, the average decline of water table over the study area was 0.89 m, and the streamflow was about 87 percent of the present rate. This decline of the water table results in significant reductions in ET directly from ground water and so a significant portion of the streamflow is maintained by capture of the salvaged ET.     

饮用水絮凝剂的应用现状与发展趋势

针对饮用水絮凝剂存在的问题，本文就国内外饮用水絮凝剂的研究，发展及应用情况进行了概述，并对絮凝剂今后的研究工作提出了建议。     

固体微粒气溶胶灭火剂产物腐蚀性研究

固体微粒气溶胶灭火剂是一种新型灭火材料，具有良好的抑制火灾的能力。研究了气溶液灭火剂的固体产物对四种金属材料的腐蚀情况，对其腐蚀性做了定性及定量分析，评价了不同灭火剂的固体产物对四种金属材料的腐蚀性级别。结果表明，在相对湿度小于55%时，气溶胶灭火剂的固体产物在短时间（≤8h)内，其腐蚀性非常小；随着时间的延长、湿度的增加，气溶胶对金属的腐蚀会加剧。     

提高水基热气溶胶灭火剂燃速途径的研究

水基热气溶胶灭火剂是以替代哈龙为目的而研制的新一代气溶胶灭火剂；因为其燃烧速度对灭火效率有重大影响，故本文在理论分析的基础上，采用加入金属粉提高导热系数，增加反应放热量；加入正催化剂降低反应活化能；在反应器中采用导流管除去燃烧表面的液态产物，加强燃烧反应的热反馈等方式提高灭火剂燃速。     

渤海埕北油田生产污水处理

1987年底埕北油田排海生产污水含油严重超标，为解决这一问题，采取了一系列措施，如：调整改进聚结器、浮选器，砂滤器添加滤网，清洁水缓冲罐增设污油回收装置。之后，进行了加药实验，实验表明：选择适用子处理埕北油田生产污水的化学药剂和其合适的加药浓度，使排海生产污水含油达到了规定的标准。从根本上解决了排海污水超标问题。     

场地液化危害的概率分析

为使场地液化危害程度的估计建立在以概率论为基础的可靠性分析之上,本文提出二种估计场地液化危害程度的概率方法,二种方法分别采用不同的途径处理地震和岩土的不确定性,不仅分析了一点液化的概率,而且提供了估计整个土层住状液化概率的方法,文中最后通过算例简要讨论了液化概率分析结果的工程应用。     

THE STABILITY IN WATER OF A NEW CHLORAMINE DISINFECTANT1

ABSTRACT: The stability in water of a novel new chloramine agent, 3-chloro-4, 4-dimethyl-2-oxazolidinone (agent I), which is an excellent water disinfectant, has been compared to the stabilities of several other water disinfectants. The agents tested in addition to agent I included N-chlorosuccinimide, 2, 4-dichloro-5, 5-dimethylhydantoin, tichloroisocyanuric acid, calcium hypochlorite, commercial grade HTH, and household bleach. The total chlorine content of a water solution of agent I in a demand free environment remains constant over a period of at least eight weeks, while that for all of the other agents declines markedly over that time period. An explanation for these observations will be offered. Prior work in these laboratories concerning use of agent I as a disinfectant for lake water in a laboratory scale treatment plant had shown that agent I has considerable potential for use as an alternative to chlorine gas for water disinfection.     

新型气体灭火技术在海上平台的应用可行性分析

根据海上油气生产平台的特点及灭火需求,分析了海上平台现有灭火系统及灭火剂的综合性能及缺陷,对新型灭火系统的安全性、环保特性、灭火剂的毒性及灭火效能等方面进行对比和分析,对采用新灭火技术替代平台现有灭火装置的应用可行性进行探讨,分析显示:新型灭火剂Novec1230比目前海上平台应用的其他气体灭火剂在安全环保灭火性能上更具优势。