Title
Eco-friendly pulping of rice stem by twin-screw extruder: Optimization of cooking time and NaOH concentration
Authors
H. PIRMAHBOUB A. TALEBIZADEH-RAFSANJANI P. REZAYATI CHARANI and R. MORVARIDI

Received July 15, 2013
Published Volume 49 Issue 5-6 May-June
Keywords twin-screw extruder, rice stem, papermaking, process optimization, nanocellulose

Abstract
In this study, rice stem pulping was performed using a co-rotating intermeshing twin-screw extruder as an eco-friendly method. The effects of NaOH concentration and cooking time during alkali pre-treatment on the chemical compositions and contents of the resulting pulp, and handsheet physical characteristics were investigated. Using a two level factorial design and the Minitab software suite, equations relating each dependent variable to the independent variables were obtained. These equations predicted the experimental results for the dependent variables with errors of less than 30% for cooking times and NaOH concentrations in the ranges of 15-75 min and 1-2%, respectively. The results showed that the NaOH concentration had a greater effect on pulp and handsheet properties compared to cooking time. The rice stem could be pulped at a low NaOH concentration (1%) and low cooking time (15 minutes) using the twin-screw extruder at atmospheric boiling point, generating a pulp with a Kappa number of approximately57, which is suitable for fluting paper, linerboard and nanocellulose production. A pulp with a lower Kappa number was also produced under intensified process conditions (75 min cooking time and 2% NaOH concentration).