Fluid Dynamics Study Of Lignocellulosic Pretreatment Reactor

As the first step in the biochemical conversion process to produce bioethanol, pretreatment plays a critical role in preparing biomass for enzymatic conversion to C5 and C6 sugars. The high solids loading in the pretreatment resulted in the significant reduction on steam consumption and waste water generation. Therefore, it’s an urgent task to develop the reactor that can handle this kind of material. It is necessary to use mechanical mixing to enhance the heat and mass transer. Helical impeller is prefered in this study because of its good performance in the mixing of high solid content and high viscosity materials. Firstly, we carried out the pre-mixed experiment to find optimal impeller geometry (d/D=0.9). Secondly, the mock-up experiments were carried out in three different scale stirred vessels, the results shows that, rotation speed, particle size distribution and moisture content are the factors that effect on the mixing process. Both mixing time and power consumption depends on the collision frequency and the friction among the particles of CS. Thirdly, the power-law model parameters of CS/PCS in different moisture content were measured using the impeller method., all of them shows shear-thinning properties, the index number decrease with the increase of the moisture content; Finally, this study established CFD model that contains the power-law model was validated according to the power and mixing time data in different scale stirred vessels, the results are in good agreement.