Study on the synergistic co-pyrolysis behaviors of mixed rice husk and two types of seaweed by a combined TG-FTIR technique

Abstract

An investigation by TG-FTIR analysis was undertaken of the pyrolysis of five samples, three pure samples; Enteromorpha clathrata(EN), Sargassum fusiforme(SA) and rice husk(HU), and two blended 50/50 by weight of Enteromorpha clathrata with rice husk and Sargassum fusiforme with rice husk. The pyrolysis of each pure and each blended sample was divided into four stages; evaporation, depolymerization, devolatilization and carbonization. Differential calorimetry analysis showed that pyrolysis of the rice husk was mainly endothermic, pyrolysis of the blended seaweed and rice husk was exothermic and that the seaweed and rice husk were syergistic coupled during pyrolysis. Comparison of experimental data and theoretical data for calculated DTG curves in the pyrolysis of the blended sample of seaweed and rice husk showed that during the process of the main volatiles being precipitated, the thermal weight-loss rate was improved. The components of the blended sample pyrolised synergistically. The FTIR analysis of volatile gases in the pyrolysis process indicated that oxysulfide and nitrogen gases were released from Enteromorpha clathrata and Sargassum fusiforme, the main components in seaweed being protein and soluble polysaccharides. Due to the blending, some differences were found. The strength of CO and SO precipitation peaks were enhanced in the FTIR spectrum of the blend of EN and HU. However, the precipitated carbonyl peaks were weaked in the FTIR spectrum of the mixture of SA and HU. Kinetic analysis using the Coats-Redfern integral method showed that the pyrolysis activation energy in the blended sample was lower than in the seaweed biomass. Kinetic model functions for the blended samples at high temperature and at low temperature respectively, conformed to the second order rate equation and the Avrami–Erofeev (n=1) equation.