V. Veselý

Predicting the rate of thermal decomposition of dolomite

This communication presents experimental data on the thermal decomposition of a high-grade dolomite. The objective is to determine and describe the rate of thermal dissociation of dolomite at moderate temperatures as a function of temperature and conversion

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.

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.

THERMAL DEHYDRATION OF THE SODIUM CARBONATE HYDRATES

A thermal gravimetric method was employed to explore the course of dehydration of Na2CO3 · 10 H2O, and Na3CO3 · H2O particles. Experimental data were amassed both in the temperature-increasing and constant temperature mode. Very small sample masses were used in an effort to eliminate an effect of heat and mass transfer processes on the rate of reaction. Kinetic equations of Arrhenius type were proposed for two stages of the dehydration and tested against the results collected by experiment.

Kinetic investigation of the oxidation of bromide ions by cobalt(III). Part 2.—The influence of pyridine and hydrocarbon on the reaction in acetic acid solvent

The kinetics of cobalt(III) acetate reduction in acetic acid have been studied under nitrogen at 60–93 °C in the presence of bromide, p-xylene and pyridine. At high p-xylene concentration the initial rate of reaction obeys the rate law [graphic omitted] =kc[CoIII]2[HBr]2//[CoII][Py]2 with kc= 0.057 s–1 at 80 °C and an apparent activation enthalpy of 59.8 ± 5.0 kJ mol–1. The value of the apparent reaction order with respect to hydrocarbon tends to one at low concentrations. The overall stoichiometry of reduced CoIII and oxidized Br– ions, ΔCoIII/ΔBr–, is close to two. The mechanism of reaction involves attack of hydrocarbon by bromine species coordinated to cobalt.

Kinetic investigation of the oxidation of bromide ions by cobalt(III). Part 1.—The influence of pyridine in acetic acid solvent

A kinetic investigation of the reduction of cobalt(III) acetate by bromide ions in acetic acid and in the presence of pyridine at 60–93 °C has shown that the initial rate obeys the rate law –(d[CoIII]//dt)0=–(d[Br–]//dt)0=kobs[CoIII]2[HBr]2//[CoII][Py]2. A mechanism is proposed involving the formation of bromine anion radicals as intermediates. Pyridine or other amines influence mainly (i) the actual concentration of bromide ions, (ii) the dissociation of active dimeric CoIII species and (iii) the exchange of bromide ligands.

Performance of an afterburner chamber with a natural gas burner

The axial temperature and concentration profiles of CH4, O2, CO2 and CO in a pilot-plant refractory afterburner chamber fitted with a natural gas burner were measured as functions of the throughput and excess air ratio. The performance of the afterburner is strongly related to the overall temperature regime, concentration of oxygen and gas residence time.