A global kinetic model for the pyrolysis of pretreated second generation biofuels

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A global kinetic model for the pyrolysis of pretreated

second generation biofuels

Relatori

Candidato

Prof. Ing. Leonardo Tognotti

Rosanna Paradiso

Ing. Enrico Biagini

matr. 429061

Anno Accademico 2012/2013

Appello di Laurea: 5 maggio 2014

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ABSTRACT

The use of biomasses in thermochemical conversion processes has been further enhanced in recent years and special attention has been paid to pretreatments aiming to improve the characteristics of the raw materials.

In order to make quantitative predictions and comparison about the combustion behavior, devolatilization should be accurately described. In this work, kinetic models have been considered using dataset out of tests performed on different virgin and pretreated biomasses at low heating rate and in an Isothermal Plug Flow Reactor in which the heating rate is evaluated to be on the order of 104 – 105 K/s. The characteristic kinetic parameters of each model have been obtained by minimizing the residuals between the modeled and experimental results based on a least-squares objective function. An attempt to model together low and high heating rate tests also combining isothermal and non-isothermal runs has been presented trying to point out the relation between kinetic parameters and operating conditions. The model results show that the heating rate and the temperature play a ‘resistance’ role on the biofuel reactivity.

Aiming to evaluate the reliability of the considered models, expressed by mean of a tolerance range of the found kinetic parameters, the accuracy of the considered datasets has been quantified also identifying the main sources of errors.

Finally, a review of the effects of the operating conditions and of the pretreatments on the volatile matter content and on the gaseous species in volatiles is presented and by comparing the devolatilization behavior of the considered biofuels it can be stated that the pretreatments improve the biomass combustion characteristics but increase the operating costs so that through modeling, supported also by CFD simulations, an optimum can be found.

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