生物质基磁性固体酸催化玉米秸秆液化工艺的研究

通过热化学液化法,以乙二醇、聚乙二醇、丙三醇的混合比例、催化剂种类、催化剂量、液化温度、液化时间为影响因素,液化率为指标,采用单因素试验和正交试验优化生物质基磁性固体酸催化玉米秸秆多组分溶剂液化工艺条件.利用最佳工艺条件下制备的玉米秸秆液化油替代多元醇制备聚氨酯发泡材料,对发泡体进行观察.结果表明,7个因素对玉米秸秆液化率影响的主次顺序为乙二醇量>聚乙二醇量>液化温度>液化时间>催化剂种类>丙三醇量>催化剂量,即最佳工艺条件为液化剂V(乙二醇)∶V(聚乙二醇)∶V(丙三醇)为1∶1.5∶1.5.在玉米秸秆基磁性固体酸作为催化剂,催化剂量为12 g,液化温度135℃,液化时间70 min的条件下,液化玉米秸秆得到最高液化率为72.3%;玉米秸秆液化油替代多元醇能够制备均匀的聚氨酯发泡材料.

Variation of drought over northern China during 1950-2000

Based on China's monthly precipitation data of 629 stations during 1950-2000, we calculated Z indices and separated them into seven Dryness and Wetness grades. Further, a drought area index was proposed to study changes in drought severity in northern China. The results revealed that the different severity of droughts all showed expanding trends in northern China's main agricultural area. Moreover, the area coverage of droughts in different seasons and different regions displayed different trends.

螺旋叶片温度场有限元分析

螺旋出料机叶片寿命是影响转底炉运转效率的关键因素。利用ANSYS软件对螺旋叶片温度场进行分析计算,计算结果表明:直接焊接式及二段式结构形式的叶片,叶片两侧边缘温度较高,均超过1000℃,并且大于三分之一叶片工作温度高于800℃;采用水冷式结构,85%部分叶片温度为300℃左右,且随叶片厚度增加,叶片最高温度逐渐降低。研究结果为设计更经济合理的螺旋出料机叶片提供了理论依据。