Monitoring the Fluidization Characteristics of Polyolefin Resins Using X-Ray Computer Assisted Tomography Scanning

ABSTRACT

Flow visualization of chemical reactor phenomena was given a new direction with the implementation of process tomography techniques. These techniques can provide valuable information on flow phenomena in heterogeneous reactors. In particular, visualization and understanding of flow phenomena in gas phase polymerization reactors can aid us in achieving a better temperature distribution in the reactor and higher quality of products. In this study, the fluidization characteristics of a series of commercially available LLDPE, HDPE and IPP resins were investigated. The experiments were run in a small column of 10 cm in diameter (D) and variable bed heights (L), at L/D ratios of one, two and three. The fluidization velocities were varied between one and three times the minimum fluidization velocity of each sample. The particle size distributions varied from very narrow mesh sizes to full particle size distributions as they came out of commercial gas phase polymerization reactors. The resins also varied in sphericity. In several samples, there was some rubber present in the particles resulting in a “stickiness” characteristic of the resin. All experiments were performed at ambient conditions and inside the x-ray Computer Assisted Tomography (CAT) scanner facility. The CAT scanner images provided areal gas voidage distributions as a function of position and operating conditions at a resolution of 400 μm by 400 μm in cross section and 3 mm in thickness. A large number of images were collected and analyzed.

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