Thermoanalytical investigation of selected fuel during isothermal heating

I. Vitázek¹,*, T. Ondro², I. Sunitrová³, R. Majdan¹ and M. Šotnar²

¹Slovak University of Agriculture in Nitra, Faculty of Engineering, Department of
Transport and Handling, Tr. A. Hlinku 2, SK949 76 Nitra, Slovakia
²Mendel University in Brno, Faculty of Agronomy, Department of Agricultural, Food and Environmental Engineering, Zemědělská 1, CZ61300 Brno, Czech Republic
³Constantine the Philosopher University in Nitra, Faculty of Natural Sciences,
Department of Physics, Tr. A. Hlinku 1, SK94974 Nitra, Slovakia
*Correspondence: ivan.vitazek@uniag.sk

Abstract:

The thermal decomposition of woody biomass was studied using pellets made from residual processing spruce wood (Picea abies). The samples were studied using thermogravimetric analysis in the isothermal regime at the temperatures 275 °C, 300 °C, 325 °C, and 350 °C, which corresponds to the main decomposition region. The results show that the main decomposition region can be described as a volatilisation of the main constituents at a temperature higher than 300 °C. Otherwise, the results indicate, that the lignin does not decompose at lower temperatures. Therefore, it can be concluded that the heating rate is one of the most important parameters that affect the thermal decomposition of lignin and could lead to different interpretations if non-isothermal measurements are used.

Key words:

Determination of activation energy of the pellets and sawdust using thermal analysis

D. Kunecová and P. Hlaváč

Slovak University of Agriculture in Nitra, Faculty of Engineering, Tr. A. Hlinku 2, SK-949 76 Nitra, Slovak Republic
Correspondence: kunecova@uniag.sk; peter.hlavac@uniag.sk

Abstract:

The aim of this study is to describe the thermophysical properties of pellets and sawdust. Samples were chosen with regard to sustainability and environmental friendliness of materials. The main object of this paper was the investigation of thermal degradation of selected samples. Industrial pellets from Slovakia and sawdust from household source were compared. Materials suitable for pyrolysis are organic materials that degrade at increased temperature. Cellulose, hemicellulose and lignin are main components of biomass (wood) in varying proportions. Thermal processes were carried out from 25 °C to 850 °C using inert nitrogen atmosphere. Heating rate was linear from 5 °C min^-1, 10 °C min^-1 to 20 °C min^-1. Mass decrease to 150 °C corresponds to release of water and other lighter unbound hydrocarbons. Samples lose 6–8% of their mass due to the temperature. At main decrease the mass loss was between 62% and 69%. In some cases this decrease is in two drops that end at the temperature around 500 °C. Pyrolysis can be considered to consist of independent parallel reactions. In order to make theoretical groundwork for biomass pyrolysis available, activation energies were calculated with the help of two kinetic models (Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa model). The residuals from pyrolysed samples are determined and temperature dependent profiles of the materials were obtained.

Key words:

activation energy, biomass-waste, pyrolysis, thermogravimetric analysis