Pilot Plants For Polyolefin Research And Development

This report discusses the choices of reactor engineering and sizing to be used in pilot plants for producing polyolefin resins in applications of research and development. By virtue of the collaboration between Oakwood Consulting, Inc. and Xytel Corporation, versatile and reliable continuous pilot plants are designed and constructed for the polyolefin industry. These are used to produce ethylene- and propylene-based resins, i.e., homopolymers, random copolymers, and impact ethylene-propylene (EP) copolymers, as well as a few others, such as terpolymers. The resin output capacity may be tailored to range from 2.0 to over 200 kg/hr. The small-scale continuous units may be models of world-scale commercial facilities--models that may optionally include catalyst mixing, prepolymerization, and metering into a train of multiple polymerization reactors. Design flexibility also permits one to create a unique configuration for a conceptual process, if desired.

The primary focus of this presentation is on suspension types of polymerization reaction environments. Some common examples are the following: polyethylene (PE) made in diluent hydrocarbon slurry, polypropylene (PP) made in bulk (liquid-pool) monomer, and both polymers made in powder-gas phase reactors of various designs. Depending on the application to be emphasized, the size is chosen: catalyst evaluation tending to be smaller units and market evaluation lots tending to be very large units.

The scale-down and scale-up guidelines are discussed and tabulated quantitatively for some common examples of reaction environments, using scale factors ranging from 5 to over 4000. Principles used in scaling include geometric factors, dimensional factors, and dimensionless factors. Issues and guidelines for heat and mass transfer are included in these tables. Some examples of pilot plant operating data are included to demonstrate the application of these units to measurements of Melt Index response to the reactor concentration of hydrogen and the resin density response to the concentration of comonomer used. The pilot data are extrapolated to include the application to fullscale operation.