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  • Author or Editor: A. Mianowski x
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Abstract  

It was proved on the basis of Holba-Šesták equation (1972) that the one is very interesting point of view to define the relative rate of reaction/process. Thereby, the assumption about interconnection between three-parametric equation and thermodynamic condition determined by equilibrium conversion degree in given temperature, is strengthened. Further considerations, still based on analysis of the inequality, made possible proposition of thesis about maximal rate of reaction/process in dynamic conditions in relation to modified van’t Hoff’s isobar (equation).

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Abstract  

A novel parameter of the relative rate of thermal decomposition has been defined on the basis of an analysis of equation relating the logarithm of the conversion degree on the temperature. The dependence of this parameter on temperature in the dynamic conditions has been analyzed and discussed. The dependence of the relative rate of thermal decomposition is a linear relationship involving two coefficients. These coefficients can be related to the enthalpy and activation energy. The parameter developed has been used for the analysis of a series of consecutive reactions of thermal decomposition of calcium oxalate monohydrate.

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Abstract  

We performed the analysis of the thermokinetic equations taking into account Kissinger law. The formulas obtained were verified by the use of the so-called isokinetic effect. It was shown that the thermokinetic equation, g(α)=(AT/q)exp(-E/RT), appeared to connect both laws analyzed. Moreover, this approach validates equation km=q/T m which takes a form of Kissinger law, i.e. ln(q/T m) vs. 1/T m.

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Abstract  

The dependence of conversion degree estimated from the (TG) curve of the mass loss on heating of temperature has been analyzed. It has been shown that dynamic TG curve can be modeled by an equation relating to the logarithm of conversion degree as a function of temperature. A coefficient in the equation developed provides information on the distance from the equilibrium, therefore, the coefficient a 2=0–50 implies equilibrium, while a 2>50 informs about some distance from the equilibrium. Further possibilities for the use of the models of lnα vs. 1/T in the analyses of thermodynamics and kinetics of thermal dissociation of solids has been shown.

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Abstract  

The idea of the generation of thermokinetic models on the basis of the analysis of kinetic equations (isothermal conditions) and thermokinetic equations (dynamic conditions) is presented. The method resembles that used in polisothermal conditions, which consists in analysis of the relation of the equilibrium conversion degree vs. temperature. The interpretation of the coincidence of mass integrals g(α) in the relation α vs. temperature has been attempted.

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Abstract  

Further considerations concerning thermal decomposition of reference material — CaCO3, described by three-parametric equation in version (3), have been presented. It was established that in linear relationship between coefficients of Eq. (3) a 2 is the argument of a 1, which reaches minimal value of thermodynamic character (δH/vR) when a 2=0 (equilibrium relationship). During thermal decomposition connection between system atmosphere — rich in CO2 or vacuum, caused by fast evacuation of gaseous products — and activation energy value, as well as maximal temperature of reaction process. Conditions of this kind may be explained by Zawadzki-Bretsznajder law.

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Abstract  

The present paper contains theoretical analysis and a thorough discussion of the applicability of Fick’s approach to modelling CO2 and CH4 diffusion in heterogeneous coal, especially with regard to the estimation of a single diffusion coefficient from the dependence defined by a number series. The computations were performed for high rank coal depending on the grain size of coal samples and within a narrow range of temperature − 293 and 303 K. The results of the model’s application to the experimental data show that the method of estimation of the diffusion coefficient is very important. Our results also show that the diffusion coefficient changes are closely related with the one-parameter analysis of coal grain size distribution. It was shown that for the investigated grain size distribution the diffusion coefficient as expressed by Fick’s law may only be determined as a value which is directly proportional to the diffusion parameter. Hence, the estimation of D/r 2 is recommended.

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Abstract  

Using the earlier theoretical achievements, it was possible to elaborate a full description of adequate transport properties, including the determination of activation energy for the sorption of such gases as CO2 and CH4 on coal, as well as the formulation of model solutions. The interrelation of the kinetic-diffusion parameters was also demonstrated. We then analyse the experimental kinetic curve over the entire time range with a constant of a kinetic character and with the application of two typical solutions of Fick’s law, for fast and slow processes. These three constants may be compared with one another, since they are expressed using the same unit, and, in effect, may be used to determine the isokinetic effect. Finally, we suggest a new approach to the estimation of the activation energy, despite the fact that the measurements were performed at two close temperatures, 293 and 303 K. In the presented investigations, the isokinetic effect for sorption process has been found to be statistically less significant when compared with that of chemical reactions/processes.

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Abstract  

Thermogravimetric analyses of thermal decomposition (pyrolysis, thermal dissociation and combustion) of 9 different samples were carried out in dynamic conditions at different heating rates. The kinetic parameters (E, A and k m) of thermal decomposition were determined and interrelations between the parameters and heating rate q were analyzed. There were also relations between Arrhenius and Eyring equations analyzed for thermal decomposition of solid phase. It was concluded that Eyring theory is an element, which interconnects used thermokinetic equations containing Arrhenius law and suggests considering kinetic quantities in way relative to 3 kinetic constants (E, A and k m). Analysis of quantities other than km (i.e. E, A, Δ+ H, Δ+ S) in relation to heating rate is an incomplete method and does not lead to unambiguous conclusions. It was ascertained that in ideal case, assuming constant values of kinetic parameters (E and A) towards heating rate and satisfying both Kissinger equations, reaction rate constant k m should take on values intermediate between constants (k m)1 and (k m)2 determined from these equations. Whereas behavior of parameters E and A towards q were not subjected to any rule, then plotting relation k m vs. q in the background of (k m)1 and (k m)2 made possible classification of differences between thermal decomposition processes taking place in oxidizing and oxygen-free atmosphere.

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Abstract  

The investigations of interactions between polyolefins and test solutes at temperatures 58–122�C were carried out in the work. The test solutes were intentionally selected as representatives of the most important groups of compounds occurring in technological oils, which may be used as additives in conditions of industrial decomposition of polyolefins in Poland. For this purpose both the Flory-Huggins theory and inverse gas chromatography (IGC) were used. On the basis of retention data the values of both interaction and solubility parameters of analyzed polymers were determined. Solubility parameter δ and interaction parameter χ are related to some heat quantities e.g. excess free energy of mixing. It was observed influence of molecular mass and existence of chain branches on the values of the parameters. The obtained values allowed determination of influence of composition change of typical technological oils on their interactions with polymers and, at the same time, on course of charge preparation in these processes.

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