单螺杆挤出机物料停留时间分布的在线检测

On-line detection of residence time distribution of single screw extruder

挤出机停留时间分布(Residence time distribution,RTD)反映物料在挤出过程中所受的热历史,可以表征其轴向混合能力。基于荧光原理,借助转矩流变仪的单螺杆挤出平台搭建一套挤出机RTD在线检测装置。利用荧光分光光度计确定不同示踪剂的最佳测量波长,进一步探明示踪剂浓度和光信号的线性关系;在优选蒽(EN)为示踪剂的基础上,通过重复实验考察此荧光在线检测装置的可靠性,并确定示踪剂用量同时也考察螺杆转速对聚苯乙烯(Polystyrene,PS)在单螺杆挤出过程RTD的影响。结果表明:该荧光在线检测装置可以成功检测到PS在单螺杆挤出机中的停留时间分布且稳定性良好;螺杆转速越快、最小停留时间越小、停留时间分布变窄,表明挤出机的轴向混合能力减小。

The residence time distribution（RTD）of extruder indicated the thermal history of the material during the extrusion process,which could characterize its axial mixing capacity.Based on the principle of fluorescence,a set of on-line detection device of RTD was built with the help of single screw extrusion platform of torque rheometer.And the maximum excitation wavelengths of different tracers were determined and further analyzed the linear relationship between tracer concentration and optical signal by fluorescence spectrophotometer.Repeated experiment showed that the detection device was reliable with choosing EN as the tracer.Meanwhile the amount of tracer was determined to study the effect of screw speed on RTD of PS.The results showed that the device with good stability could successfully detect the RTD of PS.At the same time,the RTD of PS became narrow as the screw speed increased,which indicating the axial capacity of single screw extruder decreased when screw speed increased.