聚酯切片流态化特性的研究

聚酯切片的含水量和结晶度明显影响后续的固相缩聚过程,采用特殊流化床进行干燥和结晶处理是发展方向。在内径为85 mm的流化床中对聚酯切片的流态化特性进行了冷态模拟实验研究,测定了聚酯切片的起始流化速度和床层膨胀比,并通过对床层的压力脉动进行功率谱分析,考察了聚酯切片的流态化动力学特性和流型转变。实验结果表明,所研究的聚酯切片属于Geldart D类颗粒,起始流化速度为0.66 m/s。对床层压力脉动进行快速傅里叶变换分析的结果表明,聚酯切片的流化状态不稳定,首先形成节涌流态化;当流化气速大于3 m/s时,形成湍动流态化。当流化床处于湍动流态化状态时,气体与聚酯切片间传热传质效率高,可实现快速干燥和结晶。

Fluidization Characteristics of Polyester Pellets

The drying and crystallizing of polyester(PET)pellets in fluidized bed were trends of development for PET solid state polycondensation.The fluidization process of PET pellets was studied experimentally in a fluidized bed with an inner diameter of 0.085m.The minimum fluidization velocity and expansion ratio in the fluidized bed were measured and pressure fluctuation signals at different gas velocities were analyzed by means of power spectrum analysis.The PET pellets belonged to Geldart D type powder and the minimum fluidization velocity of PET pellets was 0.66m/s.According to results of fast Fourier transform analysis,the fluidization process was unstable and turned gradually from slugging fluidization into turbulent fluidization with gas velocity increasing.The fast drying and crystallizing of PET pellets could become a reality,due to heat transfer and mass transfer between gas and solid were of high efficiency in turbulent fluidization.