The electrostatic charge that is generated when two materials are contacted or rubbed and then separated is a well-known physical process that has been studied for more than 2500 years Contact electrification occurs in many contexts, both natural and technological For example, in dust storms the collisions between particles lead to electrostatic charging and in extreme cases, extraordinary lightning displays In electrophotography, toner particles are intentionally charged to guide their deposition in well-defined patterns Despite such a long history and so many important consequences, a fundamental understanding of the mechanism behind contact electrification remains elusive An open question is what type of species are transferred between the surfaces to generate charge—experiments suggest various species ranging from electrons to ions to nanoscopic bits of material, and theoretical work suggests that non-equilibrium states may play an important role Another open question is the contact electrification that occurs when two insulating materials with identical physical properties touch—since there is no apparent driving force, it is not clear why charge transfer occurs A third open question involves granular systems—models and experiments have shown that a particle-size dependence for the charging often exists In this review, we discuss the fundamental aspects of contact electrification and highlight recent research efforts aimed at understanding these open questions

https://iopscience.iop.org/article/10.1088/0022-3727/44/45/453001/pdf

Contact electrification of insulating materials

Experiments are carried out to examine triboelectric charging in granular systems composed of particles that are chemically identical but differ in size. A methodology is developed so that only particle-particle interactions (but not particle-wall interactions) contribute to the charging. Since all particles are chemically identical, there is no apparent driving force for charge transfer, but charging occurs nonetheless, such that smaller particles tend to charge negatively while larger particles tend to charge positively. For bimodal systems, a model for the frequency of collisions of particles with different size predicts the concentrations for which the observed charge segregation is maximized.

Charge segregation depends on particle size in triboelectrically charged granular materials.

Investigation of electrostatic charge distribution in gas–solid fluidized beds

Computational fluid dynamics and electrostatic modeling of polymerization fluidized-bed reactors

CFD simulation of fluidized bed reactors for polyolefin production – A review

Electrostatics and gas phase fluidized bed polymerization reactor wall sheeting

Disclosed herein is a method of operating a polymerization reactor for a polymerization reaction comprising modifying a recycle gas composition to increase the heat capacity of the recycle gas wherein the recycle gas composition is modified by reducing or eliminating the nitrogen concentration in the recycle gas. In an embodiment, the nitrogen concentration is reduced or eliminated by reducing or eliminating one or more nitrogen input sources to the polymerization reactor and replacing the nitrogen with an alternate inert fluid (a gas or liquid that is inert to the catalyst and reactants). The alternate inert fluid has a higher heat capacity and a higher molecular weight than nitrogen. In an embodiment, the nitrogen utilized to convey a catalyst into the polymerization reactor is replaced with an alternate inert fluid. In an embodiment, the alternate inert fluid is ethane, propane, isobutane, or combinations thereof.

Method for operating a gas phase polymerization reactor

A method for transferring polymer within a polymerization system, comprising continuously withdrawing the polymer from the reactor and conveying the polymer from a reactor to a flash chamber via a pressure differential between the reactor and the flash chamber. A method for transferring polymer within a polymerization system comprising conveying the polymer from a reactor to a flash chamber via a pressure differential between the reactor and the flash chamber and purging interstitial gases from the polymer prior to conveying the polymer from the flash chamber to a purge column. A method for transferring polymer within a polymerization system comprising conveying the polymer from a flash chamber directly to a purge column via a pressure differential between the flash chamber and the purge column.

Polymer transfer within a polymerization system

Techniques are provided for producing polymer particles of a size just slightly larger than the size of polymer fines. The technique may prevent or limit the occurrence of reactor fouls associated with large polymer particles. The technique also may provide a greater weight percentage of solids in the reactor. The desired polymer particle size may be achieved by employing a catalyst having particles of a size determined based on the expected catalyst productivity. In certain embodiments, the catalyst particle size may be determined based on the expected catalyst productivity, the polymer particle density, the catalyst particle density, and/or the polymer particle size.

Methods and systems for controlling polymer particle size

Techniques and systems for the prevention of reactor fouls in polymerization reactors are described. Described embodiments include techniques and systems for performing analyses on reactor data collected over time for the detection of incipient reactor fouling. Techniques are provided for monitoring the state of the reactor as well as for monitoring individual system parameters, including rates of change, for predicting the onset of a reactor foul. In particular, the techniques may be implemented such that predictive proactive control systems may be integrated into polymerization reactor systems to prevent reactor fouling.

Gregory G. Hendrickson

Papers

Electrostatics and gas phase fluidized bed polymerization reactor wall sheeting

Method for operating a gas phase polymerization reactor

Polymer transfer within a polymerization system

Methods and systems for controlling polymer particle size

Prediction and control solution for polymerization reactor operation