Thermally induced biological effects caused by once-through cooling systems: A rationale for evaluation

The thermally induced biological effects of power plants with once-through cooling systems can be evaluated in a logical, scientifically defensible manner. First, we combined a near-field integral model (the Shirazi-Davis model) with a far-field model (the Okubo-Pritchard model) to predict the fields of excess temperature and velocity associated with a hypothetical power plant sited on a river and an estuary, and to establish the time-excess temperature exposure histories resulting from the interaction of an assumed distribution of organisms with these fields. Next, we developed a new thermal response model to assess the thermal effects of these exposures on these organisms.Our thermal response model can be used with data from existing and proposed power plants to estimate what fraction of plankton in waters contiguous to the plant will be exposed to thermal doses greater than those that cause death at any stated level. The model can also be used to aid in the design of once-through cooling systems to keep the mortality rate caused by thermal stresses below any designated threshold. The inputs to the model are the frequency distribution of time-excess temperature histories experienced by particular plankton (the Representative Important Species), thermal resistance curves for those organisms, and the spatial and temporal variations of the natural temperature of the receiving waters.To illustrate, we applied our thermal response model to three important aquatic environments of New York State, Long Island Sound, the lower Hudson River, and Lake Ontario. The Representative Important Species were identified for each of these environments and the thermal resistance data for their early (entrainable) life stages were reviewed. Fromall of the thermal resistance data available for any of the entrainable species composing these three communities, we constructed community thermal resistance curves and showed how they could be combined in graphic form with the distribution of thermal doses computed from the physical models and an assumed distribution of organisms in the receiving waters. For each community it appeared that the most sensitive organisms were the ichthyoplankton and juvenile fish; therefore, protection of these organisms from thermal stress should protect the entrainable populations as a whole.Finally, we made several recommendations for future research so that the full management potential of our approach can be achieved.     

Studies on the pyrolysis behavior of gasification and melting systems for municipal solid waste

 It is important to investigate the pyrolysis processes of municipal solid waste (MSW) in the same way as for any mixture comprised of multiple substances. In this article, a two-reaction model for a variety of MSW mixtures is proposed to predict mass changes due to pyrolysis. In order to formulate the model based on pyrolysis kinetics, we conducted experiments to determine the kinetic model parameters. By thermal analysis of the typical components of MSW, mass changes attributable to the pyrolysis reaction were found at about 350°C for paper, 400°–500°C for plastics, and 200°–400°C for garbage (dry condition). Activation energies were obtained by the Ozawa method based on the mass changes in pyrolysis. Thus, the pyrolysis behavior is formulated as a function of temperature. Then the pyrolysis mass change of the mixture can be predicted by using a weighted sum of the individual components. The model proved useful in experiments with real waste (refuse-derived fuels). Furthermore, the weight yields (pyrolysis gas, tars, solid residues) of the mixture can be calculated by their additive property after measuring the mass balance of each component. Received: May 11, 2001 / Accepted: November 16, 2001     

生物法治理燃煤电厂高pH值灰坝水

采用加丰、，接种驯化的微生物产酸和种养水生生物等技术降低燃煤电厂灰坝水的ｐＨ值。该技术经过一年多实际运行考察，说明处理后灰坝水的ｐＨ值，ＳＳ和ＣＯＤｃｒ等指标均符合ＧＢ８９７８－９６《污水综合排放标准》的要求，并且可用于养殖和农灌。     

热排放对水库溶解氧的影响

报道了电厂热排放对水库溶解氧的影响。结果表明,溶解氧含量随水温而变化,建立了T-DO回归方程.除深水库底层外,溶解氧含量通常不小于5.0mg/L.大伙房水库的自然生态环境特征是湖水的季节性分层和夏季底层贫氧.电厂热排放,表层水温增加,使湖水分层更加明显,热成层和化学成层的延长将导致夏季极端气象条件下湖下层氧的耗竭加强.     

Effect of silica additive on the thermal stability of catalysts for NOx abatement

The aim of the plesent investigation was to study the effect of SiO₂ addition on the thermal deactivation of V₂O₅/WO₃/TiO₂ catalysts used for NOx pollution abatement. The results suggest that the degradation of the catalytic properties is strongly correlated to the structural ageing which is, in turn, mainly related to the anatase–rutile phase transformation and to the WO₃ phase segregation. The addition of SiO₂ strongly influences the temperature at which these phenomena occur. In fact, it was found that the introduction of this oxide stabilizes the material, retarding the collapse of surface area, and increases the temperature of the anatase to rutile phase transition.     

以苛性法软化油田采出水用作锅炉给水的处理新工艺

在应用蒸汽开采重油（稠油）生产中，常因采出水不需回注而带来环境保护上的问题。较适宜的处置方法是将采出水处理后作为发生蒸汽的锅炉给水。而软化具高矿化度的采出水使其符合硬度指标要求极为严格的锅炉用水，是处理工艺中关键技术之一。本文对美国当前在这方面的一般处置方法作了综合性介绍，着重介绍了Belridge油田水软化处理厂采用苛性法和弱离子交换法这一新工艺的成功经验。     

Variations in surface functional groups, carbon chemical state and graphitization degree during thermal deactivation of diesel soot particles

The thermal deactivation of diesel soot particles exerts a significant influence on the control strategy for the regeneration of diesel particulate filters (DPFs). This work focused on the changes in the surface functional groups, carbon chemical state, and graphitization degree during thermal treatment in an inert gas environment at intermediate temperatures of 600°C, 800°C, and 1000°C and explore the chemical species that were desorbed from the diesel soot surface during thermal treatment using a thermogravimetric analyser coupled with a gas-chromatograph mass spectrometer (TGA-GC/MS). The surface functional groups and carbon chemical state were characterized using Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The graphitization degree was evaluated by means of Raman spectroscopy (RS). The concentrations of aliphatic C–H, C–OH, C=O, and O–C=O groups are reduced for diesel soot and carbon black when increasing the thermal treatment temperature, while the sp²/sp³ hybridized ratio and graphitization degree enhance. These results provide comprehensive evidence of the decreased reactivity of soot samples. Among oxygenated functional groups, the percentage reduction during thermal treatment is the largest for the O–C=O groups owing to its worst thermodynamic stability. TGA-GC/MS results show that the aliphatic and aromatic chains and oxygenated species would be desorbed from the soot surface during 1000°C thermal treatment of diesel soot.     

Characteristics of mercury desorption from sorbents at elevated temperatures

This study investigated the dynamic desorption characteristics of mercury during the thermal treatment of mercury-loaded sorbents at elevated temperatures under fixed-bed operations. Experiments were carried out in a 25.4 mm ID quartz bed enclosed in an electric furnace. Elemental mercury and mercuric chloride were tested with activated carbon and bauxite. The experimental results indicated that mercury desoption from sorbents was strongly affected by the desorption temperature and the mercury–sorbent pair. Elemental mercury was observed to desorb faster than mercuric chloride and activated carbon appeared to have higher desorption limits than bauxite at low temperatures. A kinetic model considering the mechanisms of surface equilibrium, pore diffusion and external mass transfer was proposed to simulate the observed desorption profiles. The model was found to describe reasonably well the experimental results.     

粉尘云最小点火温度测试实验系统设计

通过对Godbert -Greenwald恒温炉分析与改造 ,设计了粉尘云最小点火温度实验装置 ,并建立了相应的测试系统。调试结果表明 ,该实验系统扬尘均匀性、温控精度及结果可重复性能良好