Thermal degradation of rice husk: Effect of pre-treatment on kinetic and thermodynamic parameters

Abstract

Pyrolysis of untreated, acid treated and alkali treated rice husk (URH, ARH and ALRH, respectively) was investigated. Pre-treatment resulted in change in values of proximate and ultimate analyses parameters, gross calorific values and cellulose, hemi-cellulose and lignin contents. Thermal degradation experiments were carried out from ambient to 800 °C at heating rates of 5, 10 and 15 °C/min in presence of nitrogen (flow rate 50 mL/min). Analysis of the pyrolysis data was carried out using, Flynn – Wall – Ozawa (FWO), Kissinger – Akahira – Sunose (KAS) and Starink iso-conversional models. The activation energy was estimated to be 219.67, 220.09 and 218.83 kJ/mol using FWO model; 222.18, 222.69 and 227.98 kJ/mol using KAS model and 222.19, 223.57 and 228.38 kJ/mol using Starink model for URH, ARH and ALRH, respectively. Thermodynamic parameters (ΔH, ΔG, ΔS) were also evaluated in each case. Effect of pre-treatment on the pyrolysis reaction mechanism was predicted using Criado method. The results indicated that pre-treatment of RH improved its thermal degradation process.