Effect of alkaline hydrolyse pretreatment on the thermal decomposition kinetics of sunflower seed husk

Due to the fact that fossil fuels are about to run out, the need for energy is increasing and the trend towards alternative energy sources is increasing. This situation has led to the increasing importance of biomass energy, which is the fourth largest energy source after coal, oil ans natural gas. A wide variety of biomass sources can be used to produce biofuels with high energy content. Sunflower husks are annual herbaceous plant grown for its oil. Sunfower plants are frequently grown in Turkey and large amounts of husks are produced as waste. As a thermochemical conversion process, pyrolysis is a common method used to generate energy from biomass waste materials. In this study, the effect of alkaline hydrolysis application on the pyrolysis kinetics of sunflower seed hulls, which is an agricultural product with high production capacity, before the pyrolysis process was investigated. Thermogravimetric analysis of sunflower seed husk was carried out at three different heating rates (10, 20 ve 40 ºC/dk) and from ambient temperature to 800 ºC. 1%, 3% and 10% NaOH solutions were used for alkaline hydrolysis. As a result of the thermal characterization, it was concluded that the solution containing %3 alkali concentration is sufficient for an effective pretreatment. In order to determine the kinetic parameters, the activation energies were calculated with three (KAS, FWO, Friedman), then the reaction models were determined with the Criado's master curves method, and finally pre-exponantial factors were calculated. Accordingly all three methods used in the calculation of activation energies support each other, and the activation energy values decreased from approximately 172 kJ/mol to 145 kJ/mol when pretreatment was applied. The reaction models started with the diffusion reaction model in the untreated state, then n. continued with the second-order reaction model. In the study where %3 alkali concentration was applied, only n. order pyrolysis reaction was observed. Pre exponential factors are calculated approximately in the range of 1,0E+12-9,9E+13. Finally, the accuracy of the models was proven by comparing the results of the kinetic validation study with the experimental and kinetic model studies.