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Pyrolysis conditions have a substantial impact on the properties of the resulting char and, consequently, on the kinetics of the gasification process. The aim of this study was to determine the impact of coal pyrolysis on the gasification stage. By applying the thermogravimetric method, kinetic analyses of CO 2 gasification of chars derived from Polish "Janina" coal were conducted. Gasification examinations were performed for chars prepared earlier in an argon atmosphere at various heating rates, which, after cooling, were subjected to CO 2 gasification (indirect char gasification). Examinations were also carried out in the case of chars formed during heating of coal samples in a CO 2 atmosphere (direct char gasification). Samples of chars were gasified in non-isothermal conditions of up to 1100 °C under 0.1 MPa pressure at various heating rates. The char gasification reaction order with CO 2 was determined with the use of the Coats−Redfern method, and it can be assumed that it is a first-order reaction. The activation energy and pre-exponential factor were calculated using two first-order models: Coats−Redfern method and Senum−Yang method. The results were subsequently compared to kinetic parameters calculated on the basis of the modelfree isoconversional method combined with the model-dependent Coats−Redfern method. Despite the differences in values of kinetic parameters obtained from the use of a given model, all results confirmed that the method of char preparation has an influence on the gasification stage and direct char gasification is more favorable. Activation energy obtained from the use of models based on the first-order reaction ranged between 275 and 296 kJ/mol for direct gasification of chars, while the chars gasified indirectly between 307 and 342 kJ/mol, depending upon the heating rate that was used. The model-free isoconversional method confirmed these results. The values for chars gasified directly amounted to E a = 257−277 kJ/mol, and the values for indirect char gasification obtained by the pyrolysis process at heating rates of 3, 10, and 20 K/min amounted to E a = 280−291, 287−309, and 289−305 kJ/mol, respectively.

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One-component catalysts based on alkali and alkaline earth metals (sodium, potassium, and calcium) as well as their composites were applied to the surface of coal samples used in the gasification process. The aim of this work was to compare the impact of these catalysts on the steam gasification of coal by analyzing the results of catalytic and noncatalytic measurements. The use of composites was intended to check whether it is possible to accomplish the synergistic effects (an effect arising between two or more substances interacting together to produce an effect greater than the sum of their individual effects) and overcome the shortcomings of individual metal catalysts. Measurements of steam gasification were conducted by a thermovolumetric method under isothermal conditions at an elevated pressure of 1 × 106 Pa and at four temperatures ranging from 1073 to 1273 K. On the basis of the obtained results, curves of the formation rate of gasification products were developed and yields of main products (hydrogen and carbon monoxide) were evaluated. The influence of the temperature and type of catalyst on the kinetics of H2 and CO formation was determined, and kinetic parameters (activation energy and pre-exponential factor) were calculated on the basis of three models (isoconversional method, grain model, and random pore model). The obtained results showed the effectiveness of the catalysts tested, especially at low temperatures (1073–1173 K). In this temperature range, the one-component catalyst based on Na (3 wt %) was the most effective. Other single-component catalysts (3 wt % K and 3 wt % Ca) were less catalytically active at 1073 K than composite catalysts consisting of 1 wt % Na and 1 wt % K or 1 wt % Na, 1 wt % K, and 1 wt % Ca, although the former composite contained a smaller amount of catalytically active material. These results indicate that at low temperatures the type of catalyst is more important than the quantity. However, the addition of a catalyst, regardless of type, caused a decrease in the activation energy of CO and H2 formation reactions by nearly half in comparison with that seen for the noncatalytic process.