Application of Twin-Screw Extruder for Production of Pulp from Rice Stalk

Twin-screw extruder has been attractive with many efficient benefits as one of developing pulping technology from non-wood feedstocks in recent decades. Extrusion pulping is a chemi-mechanical pulping method in which fibers are processed by means of compression and shear forces. In this research, application of this technology was introduced in pulp and paper industries and the extrusion pulping of rice stalk was investigated. Extrusion pulping of rice stalk was conducted following a central composite design using a two-level factorial plan involving three process variables (pretreatment NaOH concentration: 0.4, 0.8 and 1.2%, extrusion temperature: 40, 60 and 80 ^oC, extruder rotational speed: 55, 70 and 85 rpm). Responses of pulp properties to the process variables were analyzed using statistical software (MINITAB 15). As the results show, a more content of initial ash of rice stalk was remained in the obtained pulp. Also, because of high freeness of obtained pulps, it is necessary to retransfer the obtained pulp from extruder or refine it for fluting paper and linerboard production. Moreover, analysis of the results reveales that this process can be used to obtain a pulp with low kappa number under a relatively long pretreatment time, high NaOH concentration, high extrusion temperature and moderate extruder rotational speed.