The non-isothermal thermogravimetric tests of animal bones combustion. Part. I. Kinetic analysis |
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Authors: | Bojan Jankovi Ljiljana Kolar-Ani Ivana Smi
iklas Slavko Dimovi Dragana Aranelovi |
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Institution: | aFaculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16, P.O. Box 137, 11001 Belgrade, Serbia;bVinča Institute of Nuclear Sciences, Mike Petrovića Alasa, P.O. Box 522, 11001 Belgrade, Serbia;cInstitute of General and Physical Chemistry, Studentski trg 12-16, 11001 Belgrade, Serbia |
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Abstract: | The non-isothermal combustion of animal bones was investigated by simultaneous thermogravimetric and differential thermal analysis (TG–DTA), in the temperature range ΔT = 20–650 °C. The full kinetic triplet (A, Ea and f(α)) for the investigated process was established, using different calculation procedures: isoconversional (model-free) and the Kissinger's methods. The non-isothermal process occured through three reaction stages (I, II and III). Stage I was described by a reaction model, which contains two competing reactions with different values of the apparent activation energy. The autocatalytic two-parameter Šesták–Berggren (SB) model (conversion function f(α) = α0.62(1 − α)3.22), best described the second (II) reaction stage of bone samples. This stage, which corresponds to the degradation process of organic components (mainly collagen), exhibited the autocatalytic branching effect, with increasing complexity. Stage III, attributed to the combustion process of organic components, was best described by an n-th reaction order model with parameter n = 1.5 (f(α) = (1 − α)1.5). The appearance of compensation effect clearly showed the existence of three characteristic branches attributed to the dehydration, degradation and combustion processes, respectively, without noticable changes in mineral phase. The isothermal predictions of bone combustion process, at four different temperatures (Tiso = 200, 300, 400 and 450 °C) were established in this paper. It was concluded that the shapes of the isothermal conversion curves at lower temperatures (200–300 °C) were similar, whereas became more complex with further temperature increase due to organic phase degradation. |
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Keywords: | Bone Combustion Differential thermal analysis Thermogravimetric analysis Kinetic analysis Autocatalytic |
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