Pyrolysis of torrefied rice straw from gas-pressurized and oxidative torrefaction: Pyrolysis kinetic analysis and the properties of biochars

Abstract

In this work, the pyrolysis of torrefied rice straw (RS) from oxidative/non-oxidative torrefaction were carried out, in order to investigate the effects of torrefaction pressure such as rotary tube reactor (AP) and gas-pressurized autoclave (GP) on the pyrolysis behavior and biochars’ properties. The pyrolysis kinetic parameters were determined using four model-free (Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), Friedman and Kissinger) methods. The results revealed that the pyrolysis kinetics of torrefied RS were significantly influenced by the torrefaction pressure. The experimental results were best fit by the FWO method, and the Eα values obtained by the KAS and Friedman methods were similar to that obtained by the FWO method. The pyrolysis of GP-torrefied RS was safer and more stable than that of AP-torrefied RS. The parameters of AP-180 °C sample calculated by the Kissinger method were highly correlated (R2 > 0.9), although it was not applicable for the AP/GP-270 °C samples. The biochars derived from AP-torrefied RS had a higher specific surface area and higher O/C and (O + N)/C ratios than those derived from GP-torrefied RS. Adsorption capacity of the biochar derived from AP-torrefied RS (P-A3, 68.97 mg/g) for tetracycline was higher than that of the biochar derived from GP-torrefied RS (P-G3, 39.68 mg/g).