Polymernetzwerke zum Einschluß von Mikroorganismen

Different network formation processes, applicable to obtain biocatalytic systems by entrapment of whole microbial cells are described. Properly chosen suspension techniques can be used to prepare copolymer beads from water soluble or water insoluble monovinyl divinylmonomer systems. Inclusion of small NaCI crystallites during the curing process leads to epoxy resins which possess a macroporous as well as a highly microporous structure. Crosslinking of natural, seminatural and synthetic polyelectrolytes with multivalent cations (?ionotropic gels”?) proves to be a very gentle entrapment procedure. Networks of nonspecific bonding character are obtained by precipitation of linear water insoluble or poorly water-soluble polymers.     

Effect of deformation conditions on the transformation of micro-alloyed medium-carbon forging steels

The CCT diagrams of three medium-carbon steels without and with microalloying by vanadium and titanium were constructed by applying direct cooling of as-deformed austenite. Deformation parameters corresponding to those of industrial forging were varied with a laboratory simulation technique by using the plane strain hot compression test. The effect of microalloying, deformation, and deformation temperature on the amount of structural substituents was quantified. For practical application of the study the as-forged controlled cooling conditions were determined to achieve the desired bainite-free ferritic-pearlitic microstructure with beneficial mechanical properties.     

Steam gasification of German hard coal using alkaline catalysts: Effects of carbon burn-off and ash content

Laboratory-scale experiments were performed on chars from German hard coals with potassium carbonate addition. The steam gasification rate at 4 MPa and 700 °C as a function of the amount of catalyst added is described for a low-and high-ash char. From the burn-off behaviour the reaction order relative to carbon was determined. For the low-ash char a uniform reaction order was found but the high-ash char indicated a complex interaction of catalytic gasification, catalyst deactivation, and the development of the reacting surface.     

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.