Torrefaction of rice straw

Abstract

Torrefaction of rice straw was performed in a fixed bed reactor under nitrogen flowrate of 150ml/min from room temperature of 200-300°C at holding time of 20, 40 and 60 mins. It was observed that mass yield of torrefied rice straw decreased upon increasing torrefaction temperature. This was due to the contribution of lignocellulosic removal during devolatilization stage as Carbon dioxide (CO2), Carbon monoxide (CO) via decarboxylation and decarbonylation reactions respectively. The proximate analysis, predicted Carbon (C), Hydrogen (H), and Oxygen (O) as well as predicted heating values were performed on raw and torrefied rice straw. It was determined that from proximate analysis, the moisture content and volatile matter decreased upon increasing torreffaction temperature. The predicted CHO analysis showed that the C content increased but O and H content decreased upon increasing temperature. The predicted high heating value of torrefied rice straw also increased with increasing torrefaction temperature. The removal of volatile gaseous product contributed to these phenomena. Obviously, torrefaction process had improved the moisture content and heating value of rice straw. The kinetics parameter for torrefaction of rice straw was evaluated by Coats-Redfern method. The value of activation energy (Ea) for torrefaction of rice straw were in the range of 28.18 – 29.94 kJ/mol for holding time 20,40 and 60 mins. The value of pre-exponential factor (Ln A) is 1.13 – 1.55.