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The burn-off in coal dust flames is mainly determined by the mass transfer of the oxygen for the maximum grain. The particles were assumed as spheres and the minimal value of the Sherwood number of two are used for the calculation of the mass transfer. However, the real shape of the particle differs considerably from the sphere. Therefore the mass transfer was calculated by defined model bodies numerically. Accordingly the Sherwood number formed with the sieve diameter deviate considerably from the value two. The influence of the particle shape can be characterised approximately by the length-diameter ratio of L/d. The burn-off time of the model bodies with equal sieve diameter but a length-diameter-ratio of 0.2 L/d 5 vary around the factor 3. The range of this burn-off times was compared with a multitude of measurements from the literature. Some measurements lie below the line for the burnoff time determined by mass transfer with Sh=2. The introduced results show that the considerable scattering of the measurements can be led back partly to the shape of the particle. 312*Kinetic Modeling of the Hydrochlorination of Silicon with SiCl 4 and H 2 F r a n k B e c k e r 1 S i g u r d B u c h h o l z 2 L e s l a w M l e c z k o 2 A kinetic model describing the hydrochlorination of silicon with SiCl 4 and H 2 was employed in the analysis of the influence of main reaction conditions and mode of operation (pressure, hydrogen/chlorine-ratio in the feed, reaction temperature, presence of a copper catalyst) on the yield to trichlorosilane. The investigations aimed at the elucidation of optimal conditions with respect to maximum space-time yield. 313*Complex Response to Perturbations in the CSTR with pH-Oscillating Reaction Z a g o r a J . S c h r e i b e r o v a  L . S c h r e i b e r I .Pulsed perturbations changing H + ions concentration are delivered to a CSTR with the oscillatory bromate±sulphite-ferrocyanide (BSF) reaction. Response to periodic forcing of weakly acidic steady state by sodium hydroxide and phase shifts of periodic oscillations due to single pulse perturbations by sodium hydroxide and by sulphuric acid are measured and modelled. The phase shifts are characterised by phase transition curves (PTCs) [4]. A detailed mechanism of the BSF system is used for construction of a model. Good agreement with experiments in all compared features such as bifurcation diagrams and PTCs is found .

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