Miloslav Hartman

Predicting the free-fall velocities of spheres

Etude de differentes expressions de prediction de la vitesse de chute libre de spheres. Proposition dune nouvelle expression empirique et explicite. Comparaison des predictions avec les resultats experimentaux

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.

Formation of NOx in fluidized bed combustion of model mixtures of liquid organic compounds containing nitrogen

Abstract Model liquid mixtures of organic compounds containing nitrogen were burned in a laboratory fluidized bed reactor at temperatures ranging from 700 to 900 °C and oxygen concentrations ranging from 2 to 15 vol%. The model solutions included binary mixtures of toluene with pyridine, quinoline, aniline, 1-aminonaphthalene, nitrobenzene and benzonitrile. Several ternary mixtures containing propanol, ethanol, pyridine, thiophene, toluene and urea were also employed. The nitrogen concentrations in the model mixtures varied within the range 0.5–5 wt%. The results showed that the dependence of the NO x emissions on temperature was influenced by the gas phase oxygen concentration. The conversion of the fuel nitrogen to NO x was less dependent on nitrogen compound type than on other factors. The conversions to NO x increased with increasing air excess for combustion and with decreasing organic nitrogen concentrations. Only a weak influence of SO 2 and in situ desulphurization on NO x emissions in the fluidized bed was observed. Addition of water, propanol or ethanol to a model burned mixture caused a significant reduction of NO x emissions.

Reaction of sulphur dioxide with magnesia in a fluidised bed

With the aid of simplified models for the fluidised bed behaviour, the experimental breakthrough curves and transient characteristics of sulphur dioxide are employed in educing the kinetics of the desulphurization reaction. The rate of reaction is a nonlinear function of both the concentration of SO2 in the gas and the conversion of magnesium oxide to sulphate. Using a differential reactor with a thin, fixed bed of sorbent, the rate of reaction was also measured as weight gain. The final rate equation is in reasonable agreement with the experimental data amassed in this entirely different manner.

Predicting voidage particulate fluidization of spheres by liquids

Presentation de donnees experimentales sur lexpansion particulaire de particules spheriques, en verre, fluidisees dans un liquide visqueux. Comparaison de differentes correlations pour les fractions de vide de lits fluidises particulaires

Numerical solution of the model for sulphur dioxide removal in a fluidized bed of sorbent

Abstract The model is represented by a set of nonlinear, variable-coefficient partial differential equations of the parabolic type. Approximating the time derivative with backward differences leads to a semi-implicit scheme, which was solved by the iteration procedure with a variable time step. The character of the solved set necessitates the use of an extremely small increment of time. In order to make the computations feasible, the method of pseudo-steady states was employed. The pseudo-steady states are detected as an approximate balance of large forces which bring about the motion of the solution in the phase space.