生物质物料热压成型工艺参数的探讨

Exploration on the Technological Parameters of Hot Extruding of Biomass Materials

通过对挤压部件的试验研究,论述了压力、温度和成型过程的滞留时间对螺杆式挤压成型机工作性能和制品质量的影响。在Darnell和Mol公式的基础上,分析了物料塞与螺杆槽壁间的滑动对压力建立的影响。研究指出,压力随滑动量的增加而减少。滑动的存在将减少最大的质量流率,如果已知滑动时的质量流率,则可估算出压力。在螺杆的输送—压缩段对最大轴向压力的测试结果表明,理论估算值与实测值间具有良好的一致性。文中引入了5元素Maxwell模型,阐述了农业废弃物在加热的机筒内压缩时的流变行为及压力分布。借助应力松驰曲线,确定了物料在机筒内的滞留时间。

The influences of three main parameters, i. e, the forming pressure, the heating temperature and the residence time of materials within the barrel on the working performance of the screw extruder and the quality of product, were studied. Based on Darnell and Mol' s equation, the effect of the slippage between the plug and the screw channel wall on the forming pressure build up was analysed. The study indicated that the pressure decreases with the increase of slip. The presence of slippage would reduce the maximum mass flow rate. If mass flow rate taking into account the slip is known, the pressure build up may be evaluated. The maximum axial pressure at the conveying-compacting section of the screw was measured with results very mach consistent with the theoretical evaluations. To introduce the 5-element Maxwell model, the rheological properties of agricultural waste materials compressed in a heated barrel and the pressure distribution were clarified. The residence time was determined by means of the curve of stress-relaxation. Besides, a simple method to evaluate the required quantity of thermal energy in the hot extruding process was given.