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Abstract  

Combustion of brick-shaped carbonaceous materials (carbon deposits from coke oven, coke and electrographite) was carried out in thermobalance in static air. Analysis of kinetics of the process was carried out using both classical (Arrhenius law) and newer (three-parametric equation) methods. In classical approach two types of kinetic equations were used in calculations: differential and integral. The results obtained show that, independently on kinetic variables (α – conversion degree or m – mass of sample) used in differential equations, kinetics of combustion of brick-shaped carbonaceous materials is characterized by only one pair of Arrhenius coefficients: activation energy (E) and pre-exponential constant (A). At the same time the integral equation demonstrates distinction in relation to methods based on differential equations, generating higher activation energies and separate isokinetic effect (IE). Parallel IE shows that kinetic analysis has to encompass activation energy in connection to second coefficient, pre-exponential constant A, depending on assumptions made for kinetic equations. On the other hand three-parametric equation allows describing kinetic of combustion in alternative way using only one experimental value – initial temperature in form of point of initial oxidation (PIO) – and also offers new methods of interpretation of the process.

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Summary The aim of this work is to develop a simplified, though rigorously based thermogravimetric analysis (TG) method to estimate intrinsic reactivity parameters (activation energy, E, and pre-exponential factor, A) for the oxidation in air of engineering carbonaceous materials. To achieve this aim, a modified Coats-Redfern method for analysing linear curves has been devised. The new method assumes first-order reaction kinetics with respect to carbon, and uses a statistical criterion to estimate an ‘optimum’ heating rate. For the oxidation in air of a model carbon, an optimum rate of 27 K min-1 was determined, at which E=125.8 kJ mol-1. This is in good agreement with activation energies obtained using established, though more limited model-free or isoconversional methods.

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powder design. It is known that the melting rate increases with increasing carbon reactivity [ 7 ]. The reactivity of powder can be determined by knowing the decomposition kinetic of carbonaceous material; in this way, lower activation energy should be

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Abstract  

The combustion of two different sewage sludges and a semianthracite coal was studied and compared by thermogravimetric analysis. Non-isothermal thermogravimetric data were used to evaluate the Arrhenius parameters (activation energy and the pre-exponential factor) of the combustion of these carbonaceous materials. The paper reports on the application of model-free isoconversional methods for evaluating and comparing the corresponding activation energy of the combustion process.

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Summary Non-isothermal thermogravimetric data were used to evaluate the Arrhenius parameters (activation energy and the pre-exponential factor) of the combustion of two carbonaceous materials, selected as diesel soot surrogates. The paper reports on the application of model-free isoconversional methods (Flynn-Wall-Ozawa and Kissinger methods) for evaluating the activation energy of the combustion process. On the other hand, by means of the compensation relation between E and lnA, which was established by the model-dependent Coats-Redfern method, the value of the pre-exponential factor was estimated from the known value of the model-independent activation energy.

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Abstract  

Decomposition and removal of carbonizate was performed over platinum catalysts supported on two types of alumina differing in the surface area: low surface area one (LSA) and high surface one (HSA). For the sake of comparison, the performance of platinum catalyst supported on silica and bimetallic platinum-rhenium catalysts was analyzed. It has been shown that all platinum catalysts examined caused an increase in the removal of carbonizate. The activity of these catalysts was independent of the kind of support applied or addition of rhenium as a second component.

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Decomposition and removal of carbonizate was performed over platinum catalysts supported on two types of alumina differing in the surface area: low surface area one (LSA) and high surface one (HSA). For the sake of comparison, the performance of platinum catalyst supported on silica and bimetallic platinum-rhenium catalysts was analyzed. It has been shown that all platinum catalysts examined caused an increase in the removal of carbonizate. The activity of these catalysts was independent of the kind of support applied or addition of rhenium as a second component.

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performance in composite materials [ 8 – 19 ]. The preparation of carbon material involves two main steps. First, the raw materials are pre-carbonized in an inert atmosphere to produce carbonaceous materials, and then the carbonized carbon is carried

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industrially in blast furnaces. Proximate analysis of the materials used is given in Table 1 . Table 1 Proximate analysis of the carbonaceous materials used

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