Microbial desulphurization of coal – development and application of a slurry reactor

Microbial desulphurization of coal by pyrite oxidizing enrichment cultures containing predominantly Thiobacillus ferrooxidans was performed in an air-agitated slurry reactor, 20 l in volume. A model of microbiological and chemical reactions, occurring at various points within the coal, was set up taking into account the pore structure of the coal. The influence of parameters relevant to industrial processes, such as superficial gas velocity, particle size, initial pyrite concentration, and slurry density of the coal, on the conversion of pyrite was examined. Variation of the superficial gas velocity in the range of 0.01 to 0.04 m/s confirmed that the reaction is not controlled by oxygen transfer from gaseous to liquid phase. The rate of pyrite oxidation depends mainly on the accessibility of pyrite to micro-organisms which is determined by the particle size of the coal as well as the distribution of pyrite crystals in the coal matrix. The accessibility of pyrite to the micro-organisms is described by the ratio of effective to maximum microbial activity, measured as oxygen consumption. Starting with higher initial concentration of pyrite in the coal increases the oxidation rate, according to first order kinetics. Enhanced slurry densities lead to a decrease of pyrite conversion, in spite of higher pyrite concentration. The maximum pyrite oxidation rate was measured at 15% (v/v) slurry density and 25°C as 1800 mg S_pyr/kg coal per day, or 360 mg S_pyr/l reactor volume per day.     

Fundamental principles for a nuclear design and structural analysis code for HTR components operating at temperatures above 800°C

With reference to the special characteristics of an HTR plant for the supply of nuclear process heat, the investigation of the fundamental principles to form the basis for a high temperature nuclear structural design code has been described. As examples, preliminary design values are proposed for the creep rupture and fatigue-behaviour. The linear damage accumulation rule is for practical reasons proposed for the determination of service life, and the difficulties in using this rule are discussed. Finally, using the data obtained in structural analysis, the main areas of investigation which will lead to improvements in the utilization of the materials are discussed. Based on the current information, the working group “Design Code” believes that a service life of 70 000 h for the heat-exchanging components operating at above 800°C can be.     

Lossless handover for wireless ATM

Handover is one of the key research topics for the emerging wireless ATM networks. This paper describes a handover mechanism for intra-switch handovers for wireless ATM. The handover procedure is simple enough to be implementable as a limited enhancement to ATM switch platforms for fixed network, yet provides low delay and lossless handover when used together with a suitable radio interface. The paper also reports on initial simulation result.     

On point-based temporal disjointness

We address the problems of determining consistency and of finding a solution for sets of three-point relations expressing exclusion of a point from an interval, and for sets of four-point relations expressing interval disjointness. Availability of these relations is an important requirement for dealing with the sorts of temporal constraints encountered in many AI applications such as plan reasoning. We prove that consistency testing is NP-complete and finding a solution is NP-hard.     

Measuring of the quenching effect of liquid hardening agents on the basis of synthetics

To judge liquids for steel hardening, normally special test specimens are quenched by means of immersion. Characteristics are taken from temperature-time curves, which are picked up in the sample center. These characteristics (i.e. temperature of transition from filmboiling to nucleate boiling – LEIDENFROST-Temperature – and cooling rates) serve as criterions for the judgement of quenching effect. The effect of sample characteristics (geometry and material) upon characteristic values of the cooling curve was determined. Hence a proposal to design a test specimen was derived. This specimen (Chromenickel-steel-cylinder, diameter 15 mm, length 45 mm, rounded edges) presents of all examined configurations a very good possibility to a precise judgement of quenching media as well as chances to estimate the quenching process in case of steel hardening. As common quenching tests (with a single – central – hot junction) do not allow to draw conclusions referring to steel hardening, an additional method was developed to calculate the surface-temperature dependent heatflux density (respectively heattransfer coefficient) from three temperature-time-curves, measured on different radii of the sample cylinder. The reliability of this method was proved (differential method according to Binder-Schmidt).     

Erfahrungen mit der lonenchromatographie in einem Laboratorium der Eisen- und Stahlindustrie

Beschreibung des Prinzips der lonenchromatographie und der Arbeitsweise eines lonenchromatographen. Mitteilung der Erfahrungen anhand von Anionenanalysen, die aus dem routinemäßig durchgeführten Programm der Wasseranalysen ausgewählt wurden.