In this paper, a model for an ethylene slurry polymerization system using supercritical propane as a solvent is developed by adopting a set of thermodynamic and kinetic parameters Using fundamental chemical engineering principles and Polymers Plus software. The Ziegler-Natta catalyst is characterized by assuming the existence of multiple types of catalyst sites and deconvolution data from gel permeation chromatography to determine the most probable chain-length distribution and relative amounts of polymer produced at each site type. A set of suitable reaction subclasses and kinetic constants for different site types that fit plant conditions is developed, validating our model. The values calculated for production rate, ethylene conversion, residence time, H-2/C2H4 molar ratio in the reactor, number-average molecular weight, and polydispersity index are all close to actual values, verifying that our model accurately describes plant conditions.