Milan Carsky

Physical properties of bagasse

Bagasse is a by-product of sugar milling and important fuel resource for that industry. It is a fibrous, low density material with a very wide range of particle sizes and high moisture content. It is difficult to characterize properties of bagasse particles in the usual ways (i.e. by particle density, size, drag co-efficient, etc.). These properties are necessary to apply normal design procedures to, for example, pneumatic conveying, fluidization, drying, combustion, etc. In this paper techniques to determine some physical properties of the three major components of bagasse, namely pith, fibre and rind, are demonstrated. Average material properties may then be obtained based on the weight proportions of the components constituting the bagasse.

Segregation potential in binary gas fluidized beds

Some smoothly fluidized binary mixtures exhibit no tendency to segregate under a particular combination of solids and fluid volume fractions. In these cases the equilibrium mixture remains stable, even in the absence of mixing forces. The conditions corresponding to segregation potential free mixtures can be theoretically predicted from the physical properties of the system, and have been validated for liquid fluidized systems. This paper shows that the same approach may be applied to gas fluidized beds of fine particles. Experimental results of different binary mixtures in gas fluidized beds are reported to support the theory.

Segregation in binary and ternary liquid fluidized beds

The mechanism underlying segregation in liquid fluidized beds is investigated in this paper, A binary fluidized bed system not at a stable equilibrium condition. is modelled in the literature as forming a mixed part-corresponding to stable mixture-at the bottom of the bed and a pure layer of excess components always floating on the mixed part. On the basis of this model: (0 comprehensive criteria for binary particles of any type to mix/segregate, and (ii) mixing, segregation regime map in terms of size ratio and density ratio of the particles for a given fluidizing medium, are established in this work. Therefore, knowing the properties of given particles, a second type of particles can be chosen in order to avoid or to promote segregation according to the particular process requirements. The model is then advanced for multicomponent fluidized beds and validated against experimental results observed for ternary fluidized beds

Binary system fluidized bed equilibrium

Abstract A concentration profile is generated in fluidized bed binary system during a time interval. The resulting profile of the measured system was found to be very little affected by the initial arrangement. This phenomenon is analogous to phase equilibria and it is strongly affected by superficial velocity, especially at higher jetsam concentration. The best segregation was achieved at gas velocities close to the minimum fluidization velocities of the binary system. A simple criterion indicating segregated or mixed fluidized bed has been found for the binary systems of type 3 and type 6.

Neural network modelling of coal pyrolysis

Yields of coal pyrolysis products obtained by four different techniques of pyrolysis were modelled using neural network analysis. Coals from five different sources were considered in this study. The modelling focused on effects as diverse as holding time of particles in bed, residence time of volatiles in freeboard, peak reaction zone temperature, pressure, pre-heating time of coal particles, rate of heating, secondary reactions in freeboard and bed, type of reactor, particle size, concentration of coal particles, bed depth, sample size, coal type, type of inert and type of carrier and its flow rate. A neural network model was trained and tested using the published experimental data. Even for the limited number of data points the network model was capable of approximating the experimental data precisely.

Preparation of iron oxide nanocatalysts and application in the liquid phase oxidation of benzene

Abstract A series of iron oxide nanocatalysts were prepared using an ultrasonically assisted co-precipitation technique. Molybdenum promoted Fe3O4 and Fe2O3 were prepared from the original materials by wet impregnation using a solution of ammonium molybdate. The catalysts were tested in the liquid phase oxidation of benzene at atmospheric pressure and at 60°C using molecular oxygen. Phenol yields between 7% and 14.5% were obtained. The major products were pyrogallol and catechol.

Thermal Resonance in Hyperbolic Heat Conduction in Porous Media due to Periodic Ohm’s Heating

The effect of periodic Ohm’s heating on hyperbolic heat conduction in porous media is studied analytically with the objective of identifying the thermal resonance conditions. Local thermal equilibrium conditions are assumed to apply. The paper focuses initially on the temperature solution and looks at the conditions required for resonating the temperature signal. The heat flux solution is then evaluated. While a discrete infinite set of modes can be resonated, it is shown that in practice the resonance in the temperature signal is felt starting from moderately small values of Fourier numbers and becomes too small to be noticed if the Fourier number is extremely small. The temperature solution is shown to represent a standing wave the amplitude of which is strongly affected by the Fourier number. While the heat flux solution is shown to differ from the one obtained for the temperature, it also shows similar features such as the standing wave behavior the amplitude of which is strongly affected by the Fourier number.

WEAK NONLINEAR ANALYSIS OF THE NEOCLASSICAL GROWTH MODEL AT SPATIALLY HOMOGENEOUS CONDITIONS

The neoclassical growth model is being analyzed subject to spatially homogeneous perturbations by using the weak nonlinear method of solution and comparing its results to the numerical solution. The latter expands the analytical tools beyond the investigation of Turing instability. The results identify a Hopf bifurcation at a critical value of a controlling parameter, and their comparison to direct numerical solutions show an excellent match in the neighborhood of this critical value and for amplitudes of oscillations that are not too large.

LINEAR STABILITY ANALYSIS OF THE NEOCLASSICAL GROWTH MODEL TO SPATIALLY HOMOGENEOUS PERTURBATIONS

A linear stability analysis of the stationary solutions for growth of populations with respect to Spatially Homogeneous Perturbations (SHoP) is presented. The Neoclassical growth theory is extended to apply to spatially heterogeneous populations. The latter includes the metabolic mass transfer effects and allows for the recovery of substantial and distinct phenomena observed experimentally, such as the mechanism controlling the LAG phase, a result that holds impressive future potential in diverse applications. The stability conditions are expressed explicitly in terms of the primitive parameters of the original nonlinear system. The results are necessary when undertaking a corresponding linear stability analysis for growth of populations with respect to Spatially Heterogeneous Perturbations (SHeP).