Characteristics of eccentric bubble plumes in liquids

The hydrodynamics of air/water plumes in a large scale model of a metallurgical ladle was investigated. The dimensions of the cylindrical vessel were 1600 mm i.d. and 2250 mm total height. The air was injected through an eccentric nozzle positioned halfway between the center and the wall of the vessel. The gas concentration, bubble frequency, and liquid and gas velocities were measured using electrical resistivity probes and a propeller flowmeter. Particular attention was paid to the liquid velocity. Its field is complex and nonstationary. Light scattering experiments on a small scale model were carried out to supplement the velocity data measured in the large vessel. From the analysis of the data, it was found that the maximum values of the gas fraction (time average), the upward liquid velocity, and the gas velocity can be described with the same dimensionless correlations derived previously for the centered plume.     

Application of pure oxygen for the passivation of mild steel in high temperature and pressure Bayer liquor under conditions of disturbed flow

The passivation characteristics of sulfuric acid cleaned mild steel in spent Bayer liquor (pH 14.4 and 160 °C) are examined using a high pressure nickel flow loop. An entrained atmosphere of 99.90% v/v oxygen gas is incorporated as an experimental variable along with Reynolds number (141,700 and 50,950) and intensity of fluid flow disturbance. State of passivation has been defined using criteria derived from transient polarisation resistance measurements and large-scale polarisation, linear sweep voltammetry. In the majority of cases, oxygenation introduces instantaneous passivation of the mild steel on contact with the Bayer liquor. In comparison to de-oxygenated and aerated electrolytes, this rapid rate of passivation can lead to up to an order of magnitude reduction in the quantity of charge associated with metal dissolution over 20 h. Although relative rates of corrosion when passive are low and largely independent of the level of flow disturbance, dissolution rates when passive are somewhat larger at the higher Reynolds number.     

The high temperature reactor - an important tool in meeting the challenge of world energy supply

A growing and, in its majority, poor mankind will need increasing amounts of energy at moderate prices. At the same time, ecological stresses on our environment, on the forests of the Third World (firewood crisis), and on the climate must be limited. The High Temperature Reactor (HTR) is a well-suited answer to all challenges, as it can supply eletricity safely and economically, be built close to process steam and district heat consumers, procure more hydrocarbons from coal relative to a given release of CO₂, and has the potential of splitting water with high efficiency. At times of affluent fossile fuels, however, and not yet apparent need to restrict their use for reasons of climate, individual companies cannot bear the development and introduction of HTRs all by themselves. Therefore governments are called upon for support.     

Digitale Simulation des Stofftransports in hintereinander aufsteigenden Gasblasen unter Berücksichtigung ihrer Entstehungsphase

Ein früher entwickeltes digitales Simulationsmodell für Entstehung, Ablösung und Aufsteigen einzelner Blasen an Düsen in flüssigen Metallen wird um den Stoffaustausch erweitert und ausgewertet. Die Modellrechnungen zeigen die Notwendigkeit der Berücksichtigung der Blasenentstehungsphase bei quantitativen Berechnungen der Gasbehandlungen; beispielsweise erhöhen alle Maßnahmen wie kleine Badhöhen, kleine Gasdurchsätze, kleine Düsen, die die Verweilzeit der Blasen an der Düse im Vergleich zu ihrer Aufstiegszeit verlängern, den Anteil des Stoffaustauschs während der Blasenbildung im Vergleich zum Blasenaufstieg. Die Modellrechnungen simulieren erstaunlich gut auch den Stoffaustausch in flüssigen Metallen, soweit die bekannten, spärlichen experimentellen Daten einen Vergleich erlauben.     

Computing partial expectations from tables

Many applications in inventory control, reliability engineering and preventive maintenance involve frequent calculations of probabilities and partial expectations. In the design of high-volume computer-based applications recourse to internal tables may therefore be preferable to an import of statistical packages. While interpolation in tabulated cdf’s will often prove sufficiently accurate from the point of view of statistical representation of the underlying problem, tables of compatible (partial) expectations need to be constructed with regard to the method of interpolation employed. The mathematics for establishing such tables differ from standard textbook procedures. This paper develops appropriate expressions in general terms and gives explicit results for the Gamma family of distributions, which is of particular interest in the areas of application mentioned.     

Tracking River Plumes with Volatile Halocarbon Contaminants: The Niagara River—Lake Ontario Example

The concentrations of six predominant volatile halocarbon contaminants CCl₄, total and industrial CHCl₃, CHBrCl₂, CH₂Cl₂, CFCl₃, and C₂Cl₄ in epi- and hypolimnetic lake waters are used to demonstrate tributary plumes and nearshore currents on the Lake Ontario/Niagara River example. The relative speed and sensitivity of the analysis for volatile halocarbons provides for a synoptic view of the major currents at the time of sampling. For example, the individual distributions of several contaminants indicate the existence of a Niagara River surface water plume in northerly direction for approximately 8 km into the lake. In contrast, the predominantly east-west isostats of the contaminant concentrations in the hypolimnetic water indicate little direct influence by the Niagara River and show the existence of other contaminant sources in these areas.     

Sicherung chemischer Produktionsanlagen mit Mitteln der Elektro-/Meß-, Steuerungs- und Regelungstechnik

Safeguarding of chemical production plant by means of control engineering . Control equipment is becoming increasingly important for safeguarding of plant. According to VDI/VDE 2180, sheet 3, control equipment is classified as operational equipment, as monitoring equipment, or as protective equipment. Operational and monitoring control equipment serves the proper operation of plant in its correct state or in a faulty but still acceptable state. Protective control equipment is intended to prevent occurrence of an unacceptable faulty state of the plant. It is helpful if the control equipment is classified at an early stage of planning. Preferably the protective control equipment should be considered separately from the other control equipment. It is then possible to design it in such a way that its behaviour in the event of faults can be clearly defined. A distinction is made between active faults (or functiontriggering faults) and passive faults (or function-inhibiting or blocking faults). An active fault reduces the availability of chemical plant for production by inadvertent shut-down. Passive faults of protective equipment prevent triggering of the protective function, even though the conditions for triggering are fulfilled. They adversely affect the safety of the plant. Passive faults of control equipment must therefore by prevented or kept under control. A selection of appropriate measures for achieving this is presented.